Radiology Flashcards

Question

What is phase wrap around? How is it prevented?

Answer 1

MRI artifact that occurs when the dimensions of an object exceed the defined FOV * A type of aliasing where large phase shifts in the periphery of an object are mismapped into lower phase shifts near the center * More severe along the phase-encoding axis Prevented: * FOV in the PE direction needs to be larger than the area of anatomy being imaged * Phase oversampling MRI Q&A

Answer 2

For a given gradient strength: smaller bandwidth --\> smaller FOV Fixed bandwidth: increased gradient strength --\> smaller FOV \*\* in practice the technician specifies the FOV desired in the frequenting encoding direction and has no access to gradient strength Bandwitch can be modified at the control station in order to improve SNR (decreasing bandwitch) The machine automatically adjusts the frequency encoding gradient strength to maintain the specified FOV

Answer 3

For a given sampling frequency, there is a risk that high frequencies may not be sampled and represented accurately in the MR signal leading to aliasing or wraparound artifact Mai

Answer 4

Slice selectin gradient is applied simultaneously with the RF pulses so that these pulses are selective of the slice of interest Phase encoding gradient applied between the 90° and 180 degree pulses Frequency encoding gradients applied during the application of phase-encoding gradients, and at the same time the echo is formed (during readout of the MRI signal) Mai

Answer 5

T1W imaging: short TR, short TE T2W imaging: long TR, long TE PDW: long TR (minimizes T1 differences of various tissues); short TE (minimizes differences of T2 of various tissues) - only proton density determines the signal of the image Mai

Answer 6

MRI sources of noise: 1. Patient's body (emits RF energy due to thermal motion) 2. Receiver chain (preamplifier, RF receive coil) Noncontrollable factors influence SNR: 1. Magnetic field strength (B0 increases, increase signal to read) 2. Relaxation times of tissues (determines the amount of signal available for readout) Controllable factors that influence SNR: 1. Volume of voxels (larger voxels = more protons = more signal, less resolution) 2. Receiver bandwidth 3. Number of exitations 4. Number of PE steps (number of pixels in the PE direction) Mai

Answer 7

TR: longer TR --\> more longitudinal magnetization has recovered --\> more magnetization available for next pulse --\> more signal TE: Longer TE --\> less transverse magnetization remains --\> lower signal Flip angle: Flip angle \< 90, lower amplitude of transverse magnetization, less signal Type of receiver coil Mai

Answer 8

Number of phase encoding steps = number of pixels in the phase encoding direction NEX = number of excitations TR = time to repetition Mai

Answer 9

T0: 90 degree RF pulse (shifts net magnetization into the transverse plane) TE/2: 180 degree RF pulse tuned to the slice of interest TE: progressive rephasing of the protons, signal readout (while FE gradient is turned on for a period of time that depends on chosen rBW) TR: after readout, new 90 degree RF pulse is applied One echo is obtained per TR, filling 1 line of K space at a time Mai

Answer 10

Shortens the T1 relaxation time of protons --\> longitudinal magnetization recovers much faster --\> more measurable transverse magnetization Mai

Answer 11

Fast spin-echo uses separate phase-encodings for each echo, allowing accelerated imaging * in conventional spin echo, all echoes are recorded with the same TE * in FSE, pulse sequences are collected at various TEs with 1 TR * "if we use shallow gradients for the echoes within the echo train that occur at the desired TE, we maximize signal contrast for these echoes, and thus obtain an appropriately weighted image * FAT tends to be BRIGHTER on TW FSE images * Susceptibility artifacts (ex/ metal implants) are reduced with FSE MRI Q&A

Answer 12

Single-shot fast spin-echo * short acquisition time = low SNR * long echo train after single excitation --\> severe T2 blurring artifacts in the PE direction --\> significantly degrades image quality * Clinical applications: * used to image tissues with long T2 relaxation times * myelogram effect on sagittal images of the spine - quick snapshot of the subarachnoid space in a short time, rapid detection of spinal cord compressive lesions and areas of dilation of the subarachnoid space Mai

Answer 13

Inversion recovery * STIR - TI is short (matching the nulling time of fat) * Nulling of fat with STIR is more efficient than with the fat saturation techniques as STIR is not sensitive to magnetic field inhomogeneities * Cannot be used with gadolinium contrast because the T1 of enhancing tissue is shortened, closer to that of fat --\> enhancing tissues will be suppressed on STIR images * FLAIR - TI is calculated so that signal from fluid is nulled * relatively pure fluids (CSF) have long relaxation times * FLAIR can be made with T1 or T2 images depending on TR and TE values Mai

Answer 14

Gradient echo imaging - reversal gradient * Smaller flip angles * Shorter TR and TE --\> faster acquisition times * Echo is created by biphasic gradient (dephasing/rephasing) * Transverse magnetization decays according to T2\* (does not compensate for dephasing of spins caused by tissue magnetic susceptibilities) Mai

Answer 15

SNR tends to be reduced compared with spin-echo sequences due to smaller flip angle and decreased TR Image weighting of gradient echo: depends on TR, TE and flip angle * TR is always short - main determinants are TE and flip angle * A significant degree of T2\* weighting is always present * T1 weighting: flip angle \> 70°, short TE * T2\* weighting: flip \< 20°, long TE * PDW: flip angle \< 20°, short TE Mai

Answer 16

1. High sensitivity to magnetic susceptibility - used to identify hemorrhage (low flip angle, long TR, long TE) 2. single slice breath hold image for abdominal scanning for dynamic contrast enhancement studies 3. MR angiography Mai

Answer 17

Steady state gadient echo/rewound gradient echo/coherent gradient echo * The signal is T2\* and T1W because it is contributed to by transverse coherence and longitudinal magnetization tilted by the RF pulse * Steady state gradient echo imaging, TR is very short, tissue with longer T2 do not loose their transverse magnetization between 2 excitation RF pulses. There is a permanent longitudinal and transverse magnetization * Image contrast depends on the ratio of T2/T1 Mai

Answer 18

Spoiled gradient echo = incoherent gradient echo * because transverse magnetization is spoiled, the residual signal depends less on T2/T2\*, and more heavily on T1 * Spoiling done in 2 ways: * Application of spoiled gradient --\> dephases transverse magnetization * Excitation RF pulses of variable phase in a pseudo random fashion (called RF spoiling) * Excellent T1 contrast, fast imaging, sensitivity to flow make them suitable for MRI angiography Mai

Answer 19

Time reversed gradient echo * Represents a T2 contrast enhanced approach * Gradients are applied prior to the RF excitation pulses (as opposed to simultaneous to them) --\> no gradient echo from the pure FID is recorded * Signal is more T2W because it is generated in the form of a spin echo Mai

Answer 20

Neoplasia with high cellular density - compresses the extracellular space and restricts free diffusion of water in the EC space Cytotoxic edema - water molecules move in the intracellular compartment where their movement is impaired by cell membranes and intracellular organelles Mai

Answer 21

Classic DWI * Duration and amplitude of the 2 gradients are identical * First diffusion gradient --\> phase to be acquired by protons in water molecules in the voxel * If protons move out of the voxel prior to the application of the second diffusion gradient - that phase is not reversed by the second diffusion gradient --\> drop in signal in the voxel * If the water molecule has restricted motion and remains in the voxel between the 2 diffusion gradients, the phase acquired during the first diffusion gradient and inverted by 180 pulse is completely reversed by the second diffusion gradient --\> high signal in the voxel * Typically this is repeated 3x by applying the diffusion gradients in the slice selection, frequency encoding and phase encoding gradients - assessment of movement of restriction of water is performed in all 3 directions of space Mai

Answer 22

B-value * An image is obtained with a B value of 0 = no diffusion = T2W * An image is obtained with a b value of \> 0 (typically around 1000) = DWI * From that information, an ADC can be determined within each voxel that measures the absolute diffusion of water between the 2 images * This is displayed on an ADC map - restricted motion appears black and unrestricted motion has a brighter signal Mai

Answer 23

Block vertebrae result from a failure of segmentation in the developing vertebrae * can involve fusion of the vertebral bodies, arches, or entire vertebrae * Often incidental BUT there may be instability and an increased likelihood of intervertebral disc herniation at the site adjacent to block vertebrae * Results from fusion of 2+ vertebral bodies +/- vertebral arches * Disc space seen as radiolucent line * Most common in the cervical region * Fused sacral vertebrae = normal block vertebrae (BSAVA Manual, Thrall)

Answer 24

Myelograph induced seizures have been reported to occur in **10-20%** of patients and are more likely to occur in **large** patients Myelograph contrast medium induces mild meningitis that makes csf interpretation within a WEEK of myelography difficult (BSAVA Manual)

Answer 25

Extradural - displacement of at least one contrast column is seen in at least one projection Brain Camp

Answer 26

Sacral OCD * Arrow - multiple small but highly attenuating osseous fragments are seen within the vertebral canal at the level of the lumbosacral junction * large arrowhead - there is a defect of the craniodorsal margin of the first sacral body (angular flattening of the bone) * small arrowhead - lumbosacral intervertebral disc space is widened and a soft tissue mass containing the fragmented bone protrudes into the vertebral canal, indicative of intervertebral disc herniation and possible dorsal ligamentous hypertrophy (Atlas of Small Animal MRI and CT)

Answer 27

Prevalence of seizures was 21.4% (dog had at least 1 generalized seizure during or after myelography) Risk factors: * injection site (cerebellomedullary injection 7x \> lumbar) * Mean total volume higher in dogs that developed seizures * Dogs weighing \> 20kg \*dogs that did NOT have surgery were more likely to have a seizure Barone et al 1998

Answer 28

T1W - hypointense as compared to brain, not as hypointense as CSF PDW and T2 images - hypointense as compared to brain with central hyperintensities T1WI+C - 2/3 dogs had rim of contrast enhancement, areas of uniform enhancement interspersed with nonenhancing regions 1/3 dog had uniform enhancement Lipsitz et al 2001

Answer 29

False - definite meningeal enhancement was not observed in any dog in this study MRI features of intracranial extension or orbital disease: 1. Structures within and in continuity with the skull foramina had increased T2, STIR, and FLAIR signal 2. Contrast enhancement at the skull base in continuity with the orbital lesion 3. Hyperintensity and thickening of the periorbita after contrast medium injection Kneissl et al 2007

Answer 30

28% Lamb 2005

Answer 31

1. Diffuse **enlargement of the trigeminal nerve** within the calvarium and trigeminal canal 2. Affected nerves are isointense on T1W, iso-to-hyperintense on T2W images, and have homogeneous or heterogeneous contrast enhancement after gadolinium injection 3. +/- concurrent atrophy of the **masticatory muscles** Mai

Answer 32

Contrast enhancement of the entire trigeminal nerve in 39/42 dogs Contrast enhancement in the region of the trigeminal ganglion in all 42 dogs (Intensity of contrast enhancemet was subjectively less than or equal to that of the pituitary gland) Retrospective - 42 dogs w/ normal MRI images, no trigeminal disease

Answer 33

False (Boroffka et al 2008)

Answer 34

1. Single cysts/ Intratumoral fluid accumulations 2. Moderate or severe contrast-enhancement 3. Some or all tumor situated in the diencephalon or any part of the internal capsule (deeper location)

Answer 35

1. caudal fossa location - astrocytoma 2. contact surface - oligodendroglioma 3. ventricular distortion - oligodendrogliomas have been reported to be more likely to cause ventricular than astrocytomas, however others found no difference between astrocytomas and oligodendrogliomas regarding relationship to the lateral ventricles 4. Intraventricular location - oligodendrogliomas. CSF drop metastases have been reported Mai

Answer 36

1. Significantly associated with presence of moderate to extensive peri-tumoral edema 2. Lack of ventricular distortion 3. Isointense to hyperintense T1W signal

Answer 37

astrocytoma Mai

Answer 38

Glioblastoma multiforme MRI findings: * focal or multifocal ill-defined T2/FLAIR hyperintense areas associated with brain and/or spinal cord * typically not contrast enhancing; however mild parenchymal enhancement and meningeal enhancement is possible * several adjacent cerebral lobes are typically simultaneously affected * Focal mass-like changes are possible in the midst of diffuse lesions, and concurrent astrocytoma or oligodendroglioma may be identified * Normal MRI is possible (?) Mai

Answer 39

in 73% of the lesions, the histomorphologic features explained the contrast enhancement pattern * vascular proliferation and dilated vessels occurred significantly more often in areas with enhancement than in areas without enhancement In 15/81 lesions, there was no association between MR images and histologic findings * contrast enhancement was found within necrotic areas * ring enhancement was seen in lesions w/o central necrosis "These findings imply that necrosis cannot be differentiated reliably from viable tissue based on postcontrast images" Brunner-Sing et al 2011

Answer 40

56% benign 43% atypical 1% malignant Sturges 2008

Answer 41

injection into the central canal Brain Camp

Answer 42

70% of french bulldogs 84% of english bulldogs 97% of pugs retrospective study of 271 dogs presenting for problems unrelated to spinal disease Bertram et al 2017

Answer 43

2 headed arrow - foramen magnum is larger than normal and elongated in the dorsal-ventral axis OAA malformation arrowhead - the rostral margin of the dorsal arch of the atlas extends into the dorsal part of the foramen resulting in atlantooccipital overlapping arrows/arrowheads - occipital condyles are hypoplastic but appear to articulate well with the articular fovea of the atlas marked rotational subluxation of the atlantoaxial joint is evident. the odontoid process of the axis is hypoplastic (Atlas of Small Animal MRI and CT)

Answer 44

Arrows - multiple T1 isointense and T2 hyperintense ovoid extradural masses that uniformly enhance following intraveneous contrast administration Masses = confirmed extradural nephroblastoma presumably resulting from residual disease or surgical seeding (Atlas of Small Animal MRI and CT)

Answer 45

Asterisk - A large, ovoid, T2 hyperintense, T1 isointense mass is present in the caudal cranial fossa, causing rostrodorsal displacement and compression of the cerebellum and dorsal compression of the brainstem Arrow - There is a complex, sessile mixed‐intensity “cap” on the dorsal margin of the mass, best seen on T2 images The mass nonuniformly and peripherally contrast enhances \*confirmed **epidermoid cyst**, ruptured causing lipogranulomatous encephalitis surrounding the cyst (Atlas of Small Animal CT and MRI)

Answer 46

Covnentional scintigraphy (BSAVA Manual)

Answer 47

arrowheads (a) - comminuted fractures of the pedicles and the cranial body white arrow - comminuted fractures of the cranial body of the 11th thoracic vertebra Arrowhead (b) - T10-11 intervertebral disc space narrowing and subluxation black arrow - contrast medium has absorbed into the spinal cord marenchyma indicative of myelomalacia (Atlas of Small Animal MRI and CT)

Answer 48

A) 2y pug with dilation of the quadrigeminal cistern B) 4y male chihuahua w/ moderate dorsocaudal dilation of the 3rd ventricle C) 1y mix with large dorsocaudal expansion of the 3rd ventricle. Enlargement of the quadrigeminal cistern leads to the dorsoventral compression of the cerebellum D) 11y shih tzu with dilation of the quadrigeminal cistern E) 2y Chihuahua with dorsocaudal out pocketing of the 3rd ventricle F) 8m Yorkie with supracollicular dilation of the 3rd ventricle and displacement of the quadrigeminal plate \*large dilations of quadrigeminal cistern and 3rd ventricle lead to displacement of the occipital lobes and interthalamic adhesion Bertolini et al 2016

Answer 49

T4/5 A - anatomically correct articular process joint ventral = cranial articular process dorsal = caudal articular process B - right-sided unilateral caudal articular process aplasia Bertram et al 2017

Answer 50

arrow - Well-delineated, contrast-enhancing mass within the horizontal part of the right external ear canal arrowhead - fluid is entrapped between the tympanic membrane and the mass in the proximal part of the canal Thickening of the ipsilateral tympanic bulla and a small volume of exudate adherent to the bulla wall are suggestive of previous otitis media. \*biopsy = ceruminous adenoma of the external ear canal, chronic otitis externa (Atlas of Small Animal MRI and CT)

Answer 51

well demarcated expansile mass emanating from the left tympanic bulla which has eroded the petrous temporal bone and adjacent occipital bone, extends into the cranial vault and has resulted in brainstem deformation. Mass is heterogeneously but T1 hypointense, and moderately T2 hyperintense. There is irregular peripheral contrast enhancement (small arrows) and adjacent meningeal enhancement (large arrow) Similar changes in the R tympanic bulla, confined within the bulla cavity Pronounced left-sided temporal, masseter, and pterygoid muscle atrophy is evident \*biopsy = cholesteatoma (Atlas of Small Animal MRI and CT)

Answer 52

High sensitivity (94%)/specificity (95%) for detecting neoplastic and inflammatory brain disease Low sensitivity (38%) for detecting cerebrovascular disease (Wolf et al 2012)

Answer 53

Located on either side of the sella turcica 1. internal carotid arteries 2. sympathetic plexus associated w/ internal carotid artery 3. CN 3, 4, 5, 6 (Atlas of Small Animal CT and MRI)

Answer 54

mild left-sided displacement of the spinal cord and a split contrast column on the right, indicative of an intradural-extramedullary mass The mass homogeneously enhances following intraveneous contrast administration \*post-mortem confirmed meningioma (Atlas of Small Animal MRI and CT)

Answer 55

A partially and diffusely mineralized mass arises from the right frontal bone and extends around the right zygomatic arch The mineralized component of the mass has a coarse, granular appearance characteristic of MLO Arrow - mass is osteodestructive and displaces normal soft tissue structures Arrowhead - right globe \*\* approximately 50% of dogs experience local recurrence after treatment, approximately half develop metastatic disease (Atlas of Small Animal MRI and CT)

Answer 56

Diffuse brachial plexus nerve thickening Circumscribed brachial plexus mass +/- additional brachial plexus thickening Kraft et al 2007

Answer 57

injection of gas Brain Camp

Answer 58

arrowheads - multiple extradural T2 isointense, mildly T1 hyperintense masses are widely distributed within the vertebral canal and uniformly enhance following intraveneous contrast administration \*B-cell lymphoma (Atlas of Small Animal MRI and CT)

Answer 59

Cerebellum is small and the surface contours appear unusually well defined because of increased CSF volume. 4th ventricle and cerebellomedullary cistern are larger than expected 3.5m MI Cocker Spaniel w/ presumptive cerebellar hypoplasia (Atlas of Small Animal CT and MRI)

Answer 60

4% Bertram et al 2017

Answer 61

gadolinium contrast enhancement (71%) T2 hyperintense foci (50%) Negrin et al 2006

Answer 62

arrowhead - a large mass of partially mineralized disc material has been extruded into the right side of the vertebral canal extradural space, causing lateralized spinal cord compression some disc material has migrated cranially and can be seen within the mid body of T12 Arrow - the T12/13 intervertebral disc space contains residual mineralized disc material (Atlas of Small Animal MRI and CT)

Answer 63

T2 shine through (Brain Camp)

Answer 64

Arrowhead - dorsal subluxation of C7 relative to C6 and narrowing of the C6/7 intervertebral disc space Arrow - highly comminuted and displaced fracture of the right cranial articular process of C7 (Atlas of Small Animal MRI and CT)

Answer 65

contrast enhancement 83% (20/24) - uniform or heterogeneous enhancement with hypoechoic central area well defined margins (13/24) muscle atrophy in 83% (20/24) - most apparent in the region of the scapula

Answer 66

Arrows - T2 hyperintensity in the caudal lumbar spinal cord and cauda equina that enhances following intraveneous contrast administration the enhancement is plaque-like and appears to be contained by the dura matter \*postmortem confirmed widely disseminated intradural-extramedullary histiocytic sarcoma (Atlas of Small Animal MRI and CT)

Answer 67

Uniformly contrast enhancing and symmetrical pituitary gland is evident The gland is considered within normal limits for size, but the dorsal margin is convex and extends beyond the dorsal extend of the sella turcica \*pituitary macroadenoma (Atlas of Small Animal CT and MRI)

Answer 68

1. acute nonhemorrhagic infarcts 2. meningiomas 3. glial cell tumor 4. granulomatous meningoencephalitis Sutherland-Smith et al 2011

Answer 69

R optic nerve is enlarged and has a nonuniform diameter Meningeal sheath of R optic nerve intensely enhances. R orbital exenteration was performed and a R optic nerve meningioma was confirmed histologically The dog returned 2y later with clinical signs referrable to intracranial dz - proximal remnant of the right optic nerve is enlarged, irregularly margined, and nonuniformly contrast enhances (Atlas of Small Animal CT and MRI)

Answer 70

Arrowheads - Ill‐defined bilateral T1 hyperintensity in the lentiform nuclei is seen There is no corresponding change on T2 images and no evidence of enhancement following contrast administration. These lesions are consistent with those described in dogs with liver insufficiency due to portosystemic shunting. The T1 hyperintensity is due to **_manganese_** accumulation (Atlas of Small Animal CT and MRI)

Answer 71

Arrow - ill-defined, ovoid mass within the left thalamic region which is heterogeneously T1 hypointense and heterogeneously FLAIR hyperintense Arrow - similar but larger mass is seen in the right occipital lobe Arrowheads - extensive, bihemispheric white matter edema associated with both masses Arrow - masses markedly contrast enhance, revealing ill-defined and irregular margins Arrowhead - excessive meningeal enhancement evident adjacent to the masses \*Post-mortem examination confirmed granulomatous encephalitis from systemic aspergillosis (Atlas of Small Animal CT and MRI)

Answer 72

Survey spinal radiographs - widespread focal and coalescing osteodestructive lesions involving the ribs, vertebrae and scapulae. CT/myelogram - multifocal osteolytic lesions in the ribs and scapular cortices the subarachnoid contrast column is circumferentially attenuated at the level of T5 Multiple myeloma confirmed on post mortem exam (Atlas of Small Animal MRI and CT)

Answer 73

Dorsal column = lamina, pedicles, and articular processes Middle column = dorsal half of the vertebral body and intervertebral disc ventral column = ventral half of the vertebral body (Atlas of Small Animal MRI and CT)

Answer 74

artifact that occurs when the dimensions of an object exceed the field of view Generally more severe along the phase-encode axis mitigated by * increase FOV * phase oversampling * applying saturation bands

Answer 75

Black arrow - hyperattenuating new bone of the lamina and articular processes (arrow heads) results in reduction of the vertebral canal cross-sectional area and change in shape White arrow - osseous fragment associated with the distal margin of the right caudal aspect of the 4th cervical articular process - consistent with OSTEOCHONDROSIS The spinal cord is grossly distorted by bilateral compression from hypertrophied articular facets. (Atlas of Small Animal MRI and CT)

Answer 76

rads arrow - vertebral end plate osteolysis, surrounding bone sclerosis, and narrowing of the L3-4 intervertebral disc space CT arrow - endplate destruction is more apparent CT arrow - loss of normally fat attenuating ventral epidural space CT arrowhead - regional enhancement adjacent to the vertebral column and within the ventral epidural space (Atlas of Small Animal MRI and CT)

Answer 77

White arrow - right occipital condyle is axially subluxated in relation to the cranial articular fovea of C1 Asterisk - cranial articular fovea of C1 arrowhead - left occipital condyle is ventrally luxated (Atlas of Small Animal MRI and CT)

Answer 78

small arrowhead - an in situ mineralized nucleus pulposus is present at the T11-12 intervertebral disc space arrow - mineralized disc material from the T12-13 intervertebral disc space has herniated into the ventral subdural space of the spinal canal causing spinal cord compression with attenuation of the contrast columns. large arrowhead - the T12/13 disc space is narrow and contains residual mineralized disc material (Atlas of Small Animal MRI and CT)

Answer 79

arrow - hyperattenuating new bone of the lamina arrow head - hyperattenuating new bone of the articular processes reduction of vertebral canal cross‐sectional area and change in shape, with greatest narrowing occurring in the horizontal axis. Remodeled articular facet margins impinge on the spinal cord to the greatest extent at C4–5, although a thin subarachnoid contrast column is retained (Atlas of Small Animal MRI and CT)

Answer 80

The contrast medium has been injected into the epidural space, causing opacification of the intervertebral foramina (short arrow) and an undulating appearance to the contrast medium column due to opacification of the venous sinuses (long arrow). (BSAVA Manual)

Answer 81

TRUE Especially for lesions of the leptomeninges Keenihan et al 2013

Answer 82

There is ill‐defined, bihemispheric, white‐matter T2 hyperintensity and T1 hypointensity There are multiple focal signal voids in the deep gray matter and at the cerebral cortical gray–white matter interface, best seen on T2\* images The residual pituitary tumor is best seen on the contrast‐enhanced T1 image The signal voids represent susceptibility effect from multiple lacunar infarcts from the vascular effects of irradiation. The white matter T2 hyperintensity is consistent with necrotizing leukoencephalopathy. (Atlas of Small Animal CT and MRI)

Answer 83

50% (BSAVA Manual)

Answer 84

True (Atlas of Small Animal CT and MRI)

Answer 85

Arrowheads - T1 and T2 hyperintense mass involving the entire right cerebral cortex, causing a pronounced midline shift Arrowheads - the mass intensely and uniformly enhances following contrast administration \*confirmed granular cell tumor (Atlas of Small Animal CT and MRI)

Answer 86

Arrow - large, well-defined mass present within the 3rd ventricle arrowheads - generalized hydrocephalus Solitary 3rd ventricle choroid plexus carcinoma was confirmed on post mortem examination w/o evidence of overt obstruction --\> diagnosis of overproduction hydrocephalus (Atlas of Small Animal MRI and CT)

Answer 87

There are focal regions of T2 and FLAIR hyperintensity involving the lateral geniculate nuclei, the caudal colliculi, and vestibular nuclei Other thalamic nuclei were similarly affected (not shown). There is also ill‐defined T2 and FLAIR hyperintensity of the axial regions of the parietal and occipital cortex, which enhance following contrast administration. These MR features are characteristic of multifocal polioencephalopathy due to thiamine deficiency. Further questioning of the owner revealed the cat had been fed an almost exclusively meat diet. Clinical signs resolved with dietary change and thiamine supplementation (Atlas of Small Animal CT and MRI)

Answer 88

arrowhead - well-defined, uniformly enhancing caudal fossa mass T2 hyperintense, variably contrast enhancing nodules widely distributed in the periphery of the spinal cord, intradural in location \*post mortem confirmed a choroid plexus carcinoma arising from the right lateral aperature with widespread CSF disseminated metastasis (Atlas of Small Animal MRI and CT)

Answer 89

Asterisk - large, encapsulated soft tissue attenuating mass adjacent to the third lumbar vertebra. heterogeneously enhances following intraveneous contrast administration arrowhead - tissue within the vertebral canal is uniformly soft tissue attenuating without evidence of epidural fat arrowhead (c) - CT image cranial to the mass shows clearly defined spinal cord surrounded by lower attenuating epidural fat \*Postmortem - infiltrative left paralumbar myxosarcoma with invasion of the spinal cord (Atlas of Small Animal MRI and CT)

Answer 90

The transverse plane image reveals a unilateral regional nasal turbinate destruction. The fluid-attenuating mass represents a combination of remaining turbinates, mucosa and accumulated exudate. The fragmented gas pattern suggests this is not a solid mass. A plant awn (foxtail foreign body) was removed via rhinoscopy. (Atlas of Small Animal MRI and CT)

Answer 91

A well‐delineated, T1 isointense, T2 hypointense intraaxial cerebral mass is present in the region of the right piriform lobe. There is moderate edema surrounding the mass as well as a thin peripheral rim of contrast enhancement There is uniform susceptibility effect within the lesion Acute intracranial hemorrhage (Atlas of Small Animal CT and MRI)

Answer 92

regions of hyperintensity on DWI images that conforms to regions of T2 hyperintensity on T2WI does NOT indicate cytotoxic edema (Brain Camp)

Answer 93

high sensitiity, low specificity for detecting specific brain diseases (Wolf et al 2012)

Answer 94

T2W hyperintense (13/18) T1WI isointense (14/18) T1WI+C heterogeneously contrast enhancing (13/18), uniform (4/18) Kraft et al 2007

Answer 95

epidurogram with complete obstruction of cranial flow of contrast media over the LS junction epidurogram with dorsal deviation of the ventral epidural space epidurogram with epidural space deviation/attenuation recognized on dorsoventral views (Roberts, Selcer 1993)

Answer 96

Black arrow - T1 and T2 hyperintense mass dorsal to the caudal thoracic vertebral column that has caused osteolysis of the vertebral lamina and pedicles White arrow/arrowhead - the mass extends into the vertebral canal producing spinal cord compression. The mass is hypointense on a fat suppressed contrast-enhanced sequence and has minimal peripheral enhancement CT - mass is predominantly fat attenuating \*confirmed liposarcoma (Atlas of Small Animal MRI and CT)

Answer 97

highly aggressive mass extends from the ethmoid bone to the retropharyngeal region Mass margins are ill defined on the contrast enhanced images with enhancement extending along fascial planes and invading temporal and pterygoid musculature marked destruction of ethmoid, frontal, palatine, pterygoid, and sphenoidal bones is evident The mass extends into the cranial vault \*cytology = aggressive, anaplastic adenocarcinoma (Atlas of Small Animal MRI and CT)

Answer 98

rad arrowheads - ill defined new bone formation on the ventral aspect of the L1 and L2 vertebral bodies arrow - right sublumbar musculature is focally enlarged at the level of the first lumbar vertebra, which is peripherally contrast enhancing following contrast administration CT arrowhead - an additional tract is seen extending toward the right lateral paraspinal region \*migrating foxtail was removed (Atlas of Small Animal MRI and CT)

Answer 99

Intradural - spinal cord enlargement and subsequent divergence and thinning of the contrast columns visible on all radiographic projections Brain Camp

Answer 100

Arrowheads - Multiple foci of marked T2/FLAIR hyperintensity and T1 hypointensity involving the cerebral cortex Arrow - Regional T2 hyperintensity of the white matter and caudate nucleus on the right Arrowheads - mild amorphous contrast ehancement of the right caudate nucleus Arrowheads - mild amorphous contrast enhancement of the meninges overlying the cerebral cortical lesions \*confirmed NME (extensive cortical necrosis and encephalomalacia) (Atlas of Small Animal CT and MRI)

Answer 101

white arrowheads - complex tubular contrast-filling defect is seen within the cervical subarachnoid space black arrowhead - A complex of dilated, coiled blood vessels is seen in the cervical region on a CT myelogram following intraveneous contrast administration White arrow - postmortem examination documented the extent of vascular dilation and impingement on the cervical spinal cord (Atlas of Small Animal MRI and CT)

Answer 102

Arrow - mineralized disc material from the C5/6 intervertebral disc space has herniated into the right ventral extradural space of the vertebral canal causing focal spinal cord impingement with attenuation of the contrast column large arrowhead - part of the herniated disc material also extends into the right intevertebral foramen, potentially compressing the origin of the right 6th cervical spinal nerve small arrowhead - the C5/6 disc space contains residual mineralized disc material (Atlas of Small Animal MRI and CT)

Answer 103

Arrow - Communuted fracture of the right wing of the atlas with moderate displacement of fracture fragments (Atlas of Small Animal MRI and CT)

Answer 104

Subdural injection of contrast "Dural drape sign." Brain Camp

Answer 105

basilar artery the resistance index can be calculated for the basilar artery and has been shown to be related to intracranial pressure and neurological status (Fukushima, Saito et al) (BSAVA Manual)

Answer 106

measures the total diffusion within a voxel the measurement that is used to produce DWI images (Brain Camp)

Answer 107

There is diffuse T2/FLAIR white matter hyperintensity in both cerebral hemispheres, consistent with vasogenic edema. Arrow - There is focal right hemispheric subcortical T2 hyperintensity, FLAIR mixed intensity, and T1 hypointensity consistent with a focal fluid collection Arrow - an additional T2 hyperintense mass is present within the pons Arrowhead - diffuse meningeal enhancement is also evident \*confirmed NLE (multifocal lymphohistiocytic leukencephalitis with cystic malacia and necrosis, consistent with necrotizing leukoencephalitis) (Atlas of Small Animal CT and MRI)

Answer 108

Current neurologic signs include nystagmus and rolling. arrowheads - symmetrical T2 and FLAIR hyperintensity of the dentate nuclei is present There is no visible abnormality on the unenhanced T1 image and no evidence of contrast enhancement MR features are consistent with metronidazole neurotoxicity, and both serum and cerebrospinal fluid were positive for metronidazole on liquid chromatography/mass spectrometry analysis. (Atlas of Small Animal CT and MRI)

Answer 109

Arrowheads - comminuted compression fracture of L3 that results in marked reduction of the vertebral canal diameter arrow - sharp fracture margin from one of the larger fragments is displaced dorsally into the canal and impinges on the ventral margin of the spinal cord (Atlas of Small Animal MRI and CT)

Answer 110

There is a mass in the left dorsal thalamic region causing a midline shift and compression o the third and left lateral ventricles Arrow - The mass is characterized by T1 hypointensity with heterogeneous T2 intensity arrowheads - extensive perilesional edema \*similar lesion also present in the L occipital lobe Arrow - the mass intensely and heterogeneously enhances following contrast administration and mass margins are poorly defined and irregular \*Confirmed granulomatous encephalitis from systemic aspergillosis (Atlas of Small Animal CT and MRI)

Answer 111

Marked expansion and osseous remodeling of the right tympanic bulla Soft-tissue attenuating material fills the bulla and the horizontal ear canal Bulla contents and soft tissues adjacent to the bulla are mildly contrast enhancing Histologic features of biopsy material were consistent with cholesteatoma (Atlas of Small Animal MRI and CT)

Answer 112

The external ear canals are occluded because of stenosis and exudates. Contrast-enhanced images show marked enhancement and redundancy of the external ear canal walls Gas and fluid within the canal lumen can be distinguished from adjacent enhancing epithelium Biopsy revealed severe diffuse chronic lymphoplasmacytic otitis externa with epithelial hyperplasia and ceruminous and sebaceous gland hyperplasia (Atlas of Small Animal MRI and CT)

Answer 113

arrow - reduced opacity of the body of C5 on survey radiographs MR - osteodestructive soft tissue mass arising from the C5 vertebral body that is T2 hyperintense and mildly T1 hyperintense (compared to adjacent muscle) and also involves the right pedicle and invades the transverse foramen lg arrowhead - the mass breaches the dorsal cortex and extends into the floor of the vertebral canal causing spinal cord compression small arrowhead - mass involves the right pedicle and invades the transverse foramen Arrowhead (g) - spinal cord compression (Atlas of Small Animal MRI and CT)

Answer 114

Inter-rater agreement was very good for overall detection of structural brain lesions and neoplastic lesions MRI inter-rater agreement was only fair for cerebrovascular lesions (Wolf et al 2012)

Answer 115

HASTE = half-Fourier-acquisition single-shot turbo spin-echo Mankin et al 2012

Answer 116

There is generalized reduction in cerebral and cerebellar volume with concomitant generalized ventriculomegaly and prominence of the subarachnoid space due to gyral atrophy and sulcal widening There is also loss of white and gray matter definition on the proton density image Postmortem examination revealed neuronal accumulation of eosinophilic granular intracytoplasmic material. The material was autofluorescent and stained positive with PAS, LFB, and Sudan black B, all of which supported the diagnosis of neuronal ceroid lipofuscinosis 2y MC Border Collie cross with 4‐month history of progressive behavior changes, ataxia, and incoordination. (Atlas of Small Animal CT and MRI)

Answer 117

1. Pituitary macroadenoms and adenocarcinomas are \> 10mm in height and arise from the sellar region 2. Invasive adenomas are on average, larger than noninvasive adenomas 3. Both macroadenomas and adenocarcinomas can have smooth or irregular margins, can contain cysts or hemorrhage, and can occasionally be mineralized (Atlas of Small Animal CT and MRI)

Answer 118

arrow - There is evidence of noncompressive increased spinal cord diameter and parenchymal update of contrast medium at T13/L1 arrowhead - the T13/L1 intervertebral disc width is also slightly narrower than those of the adjacent disc spaces (Atlas of Small Animal MRI and CT)

Answer 119

L5/6 injection in which the contrast medium has entered the subdural space causing a characteristic spindle-shaped end to the contrast medium column caudally (BSAVA Manual)

Answer 120

Smooth, dense production of bone centered on the parietal bone and expanding both intracranially and extracranially. The mass is hyperattenuating and uniform on CT images. MR - mass effect compressing the brain, lateral ventricle and displacement of the falx cerebri to the right T2 hyperintensity of white matter next to the mass - edema OSTEOMA (Atlas of Small Animal MRI and CT)

Answer 121

water shift from intracellular to extracellular space with a consecutive widening of the extracellular space Bendszus et al 2001 (human paper)

Answer 122

Well-demarcated ovoid mass within the 3rd ventricle which is predominantly T1, T2 and FLAIR hyperintense. The mass deforms the lateral ventricles, but there is minimal hydrocephalus and no peritumoral edema The mass intensely and nonuniformly enhances following contrast administration Confirmed ependymoma within the 3rd ventricle post-mortem \*an unrelated diagnosis of lymphoplasmacytic meningitis explains the meningeal enhancement (Atlas of Small Animal CT and MRI)

Answer 123

Hypopituitarism --\> dwarfism HASEGAWA et al 2008

Answer 124

Suspected to be the dorsal longitudinal ligament Olby et al 2000

Answer 125

between 1st and 2nd caudal vertebrae or at the sacral-caudal vertebral junction Roberts, Selcer 1993

Answer 126

Arrow - mixed pattern of osteoproduction and osteolysis of the first cervical vertebra arrow - predominantly right-sided osteoproductive and destructive expansile mass that extends into the vertebral canal causing spinal cord compression \*confirmed osteosarcoma (Atlas of Small Animal MRI and CT)

Answer 127

Bilateral tympanic bulla effusion is seen associated with mild bulla wall thickening Arrow - large polyp completely occludes the naropharyngeal lumen. The nasopharyngeal mass likely occludes the auditory canals resulting in obstructive bulla effusion (Atlas of Small Animal MRI and CT)

Answer 128

T1 spinal nerve

Answer 129

Pugs "When compared to French and English bulldogs, Pugs showed a significantly higher prevalence of caudal articular process dysplasia, a significantly higher number of affected vertebrae per dog, Pugs had significantly more often caudal articular process aplasia, significantly less often hypoplasia, demonstrated significantly more frequently a generalized spatial pattern, and vertebra being affected bilaterally. Furthermore, Pugs showed a significantly different anatomical distribution of caudal articular process dysplasia along the vertebral column, with a high prevalence of articular process aplasia between T10 and T13. This area was almost completely spared in the two other breeds" Bertram et al 2017

Answer 130

R vestibular noncontrast - right tympanic bulla is filled with fluid-attenuating material and there is partial osteolysis of the bulla wall laterally contrast - enhancement of tissues surrounding the tympanic bulla consistent with a clinically confirmed abscess. There is also focal intracranial contrast enhancement in the location of the cochlear branch of the vestibulocochlear nerve suggesting extension of disease through the internal acoustic meatus. (Atlas of Small Animal MRI and CT)

Answer 131

Arrow - displaced odontoid process fracture arrowhead (a)- mildly displaced left C1 wing fracture arrowhead (b) - focal region of T2 hyperintensity within the ventral aspect of the spinal cord immediately dorsal to the fractured odontoid process (Atlas of Small Animal MRI and CT)

Answer 132

Arrowhead - apical fracture of the odontoid process is not seen on survey radiographs, but easily detected on CT White/black arrowheads - transverse images through C1 ordered from cranial to caudal show the apical fracture fragment positioned on midline with the basilar part of the dens positioned to the left of midline - indicative of fracture displacement and atlantoaxial instability (Atlas of Small Animal MRI and CT)

Answer 133

ADC - calculated by the MRI system on a voxel-by-voxel basis from multiple diffusion weighted images. Used to identify restricted diffusion and differentiate cytotoxic edema from T2 shine through (Brain Camp)

Answer 134

intradural extramedullary - focal widening of the contrast column adjacent to the lesion = golf tee Brain Camp

Answer 135

Arrowhead - Salter Harris type 1 fracture of the caudal body of physis of T5 with concurrent ventral displacement of T6 relative to T5 Arrow (a, c) - T5/6 vertebral articulations are subluxated Arrow (b) - vertebral canal diameter is reduced (Atlas of Small Animal MRI and CT)

Answer 136

Signs of epidural, subdural, and subarachnoid hemorrhage are evident. Arrowheads - epidural hemorrhage is seen as a T1 isointense and T2 hyperintense contrast‐enhancing crescent dissecting between the right hemispheric dura and parietal bone Large arrow - Focal subdural hemorrhage is seen in the right dorsal parietal region and is T1 hyperintense and of mixed T2 intensity Small arrows - There is T1 hyperintensity and prominence of the sulci margins indicative of subarachnoid hemorrhage. (Atlas of Small Animal CT and MRI)

Answer 137

arrows - hyperattenuating hemorrhage in the lateral and 3rd ventricles. Arrowheads - additional hyperattenuating parenchymal hemorrhage and associated hypoattenuating edema are seen in the right and left parietal lobes (Atlas of Small Animal CT and MRI)

Answer 138

Bilateral lateral ventriculomegaly CSF in the right lateral ventricle is moderately intense compared to the low-intensity signal within the left lateral ventricle on FLAIR Thickening and intense enhancement of the right lateral ependymal lining is evident on the contrast enhanced T1 image FIP (Atlas of Small Animal MRI and CT)

Answer 139

Spina bifida * Results from lack of development of the vertebral arch, may be associated neural tube defects too * Cleft in the dorsal part of the vertebral arch, absence or splitting of the spinous process * There is rarely a neural tube defect in dogs with spinal bifida occurring in the thoracic spine * At the lumbosacral junction - more severe NTD * Bulldogs + Manx cats (Atlas of Small Animal MRI and CT, Thrall)

Answer 140

arrowheads (ABDE) - regional T2 hyperintensity and T1 hypointensity surrounding the spinal cord consistent with a fluid collection, causes cord deformation and compression. Appears to be both extradural and intradural arrow/arrowhead (f) - extradural and extramedullary intradural enhancement on the transverse T1+C image arrow (a) - diffuse parenchymal T2 hyperintensity with increased spinal cord diameter at the level of C2 Meningioma (Atlas of Small Animal MRI and CT)

Answer 141

Arrowheads - FLAIR images reveal ill-defined areas of mildly increased signal intensity, primarily in the cerebrum and thalamic regions Mild asymmetrical hyperintensity of the parietal and temporal lobes. Arrowhead -These areas do not contrast enhance with the exception of one focal lesion in the right thalamic region. \*post-mortem: severe generalized neuronal loss, axonal necrosis, and demyelination \*immunohistochemical staining documented abundant intralesional CANINE DISTEMPER VIRUS antigen \*symmetrical parietal and temporal lobe changes were thought to be associated with recent seizures (Atlas of Small Animal CT and MRI)

Answer 142

False Sutherland-Smith et al 2011

Answer 143

AV = vestibular aqueduct (extension of the membranous labyrinth and connects with the meninges of the brain) C = cochlea I = incus, M = malleolus TC = tympanic cavity. TB = tympanic bulla (Atlas of Small Animal MRI and CT)

Answer 144

q - quadrigeminal cistern tv - 3rd ventricle short arrow - thin membrane isoattenuatting to the soft tissue separates the quadrigeminal cistern from the overlying 3rd ventricle long arrow - on parasagittal image, the rostral extensions of the quadrigeminal cistern reach the middle-rostral part of the interthalamic adhesion p - quadrigeminal plate The quadrigeminal cistern is visible on mid sagittal image as a short linear cavity on the roof of the midbrain Bertolini et al 2016

Answer 145

Large ovoid mass with mixed T1, T2 and FLAIR intensity in the left cerebrum. Mass margins are well-defined on T2 and FLAIR images, and the halo of hyperintensity surrounding the mass on these sequences is indicative of vasogenic edema The mass nonuniformly enhances following contrast administration, with more intense enhancement peripherally Post-mortem examination confirmed glioblastoma multiforme There was extensive intratumoral hemorrhage consistent with the complex, mixed signal intensity seen on unenhanced images. (Atlas of Small Animal CT and MRI)

Answer 146

5y MC DSH. Trauma of unknown cause a - fracture-luxation involving the nasal and maxillary bones b - mandibular symphyseal fracture c - fractures of the perpendicular processes of the palatine bones and separation of the palating symphysis d - fractures of the pterygoid bones e - caudal luxation of the condyloid process (arrowhead) and fracture through the zygomatic process of the left temporal bone (arrow) (Atlas of Small Animal MRI and CT)

Answer 147

Comminuted fracture of the sacrum with displacement of major fragments large arrowhead - the fracture disrupts the ventral margin of the vertebral canal small arrowheads - fracture fissures involve the drosal and pelvic sacral foramina arrow - mildly displaced left sacroiliac luxation (Atlas of Small Animal MRI and CT)

Answer 148

arrow - well-defined, bone-attenuating mass arising from the caudal lamina of T6 that appears continuous with more normal adjacent bone of the basilar part of the T6 spinous process arrowhead - encroachment into the spinal canal implies spinal cord compression \*surgical excision confirmed solitary osteochondroma (Atlas of Small Animal MRI and CT)

Answer 149

An open, comminuted depression fracture of the right frontal bone is evident on unenhanced, wide‐windowed images Arrow - A focal hyperattenuating epidural hemorrhage is evident on the same unenhanced images (narrow window) adjacent to the internal surface of the largest fracture fragment arrowhead - A smaller hyperattenuating lesion is present within the right frontal lobe, consistent with acute intraparenchymal hemorrhage arrows - Regional hypoattenuation in the right frontal lobe is consistent with parenchymal edema (Atlas of Small Animal CT and MRI)

Answer 150

False Barthez et al 1994 (BSAVA Manual)

Answer 151

There is moderate ill‐defined T2 and FLAIR hyperintensity and T1 hypointensity involving both piriform lobes No other abnormalities were seen on this examination, and the dog responded to medical management of seizures (Atlas of Small Animal CT and MRI)

Answer 152

Arrowheads - regional marked T2/FLAIR hyperintensity and T1 hypointensity involving the frontoparietal cerebral cortex Arrow - transtentorial herniation Arrowhead - cerebellar herniation Arrows - interstitial edema Arrows - widespread meningeal enhancement is seen following contrast administration \*Confirmed NME (meningitis and necrotizing encephalitis of gray and white matter predominantly in the cerebral hemispheres) (Atlas of Small Animal CT and MRI)

Answer 153

Nasopharyngeal stenosis arrow - Focal occlusion of the nasopharyngeal lumen near the level of the pterygoid processes and 1cm caudal to the caudal margin of the hard palate arrow - the pharyngeal lumen rostral and caudal to this focal lesion appears normal The soft tissues associated with the occlusive lesion mildly contrast enhance \*biopsy - moderate chronic active neutrophilic eosinophilic and lymphoplasmacytic pharyngitis and rhinitis (Atlas of Small Animal MRI and CT)

Answer 154

T11/12 A - anatomically correct articular process joint cranial articular process (lateral) caudal articular process (medial) B - bilateral caudal articular process aplasia Bertram et al 2017

Answer 155

Precontrast - fluid/soft tissue opacity withinthe right external ear canal and tympanic bulla is indicative of otitis externa and otitis media Post contrast/arrow - well-delineated contrast enhancing mass is seen within the horizontal part of the right external ear canal and the bulla. The mass is distinguished from nonenhancing fluid in the bulla Excisional bx revealed inflammatory polyp and suppurative otitis externa (Atlas of Small Animal MRI and CT)

Answer 156

C2/3 marked hypertrophy and remodeling of the C2 and 3 articular processes is seen on the CT image Arrowheads - subchondral bone defects Arrows - encroachment of new bone into the vertebral canal (Atlas of Small Animal MRI and CT)

Answer 157

Enhancement of dura was evident in multiple contiguous subtraction images (arrowheads), hence a pachymeningeal lesion was suspected. Leptomeningeal enhancement was considered within normal limits. Histopathologically there is infiltration of the leptomeninges over the gyri and into the sulci with invasion of the brain by lymphoid cells Keenihan et al 2013

Answer 158

Arrow - a crescent-shaped T1 hyperintense, right-sided subdural hematoma arrow - the hemorrhage has central T2 hypointensity consistent with subacute hemorrhage Arrowhead - A focal, nonenhancing, T1 hyperintense lesion is also present in the left pyriform lobe associated with regional edema and consistent with subacute parenchymal hemorrhage. Given the location of this second lesion in relation to the subdural hematoma, it is thought to represent a contrecoup brain contusion. (Atlas of Small Animal CT and MRI)

Answer 159

Dose: 0.3 - 0.5mL/kg Iohexol 240 Given over 1-2 minutes HEAD ELEVATED "When CT myelography is performed alone, one- fifth to one-third of the regular iohexol dose is injected at the cisterna manga" - RE CSM CT myelogram (BSAVA Manual)

Answer 160

arrowheads - pronounced increase in spinal cord diameter centered at C6. The magnitude of the diameter change is abnormal, and causes annular attenuation of the subarachnoid contrast medium FCE (Atlas of Small Animal MRI and CT)

Answer 161

arrow - large, irregularly shaped osteodestructive and expansile mass arises from the left side of the second thoracic vertebra and rib head arrow - mass is heterogeneous T1 and T2 hyperintensity compared to adjacent paraspinal muscle and intense and nonuniformly enhances following intraveneous contrast administration. arrowhead - Axially, it extends into the vertebral canal causing right-sided spinal cord displacement and compression The complex intensity pattern seen in all sequences suggests a hemorrhagic component \*confirmed hemangiosarcoma (along w/ splenic mass) (Atlas of Small Animal MRI and CT)

Answer 162

Large arrow - large T1 and T2 hyperintense ovoid mass in the left lateral recess Mass that encroaches on the 4th ventricle, distends the contralateral lateral recess, and displaces and compresses the brainstem and cerebellum Smaller mass is seen ventral to the brainstem Both masses intensely and uniformly enhance following contrast administration Distention of the 3rd ventricle and infundibular recess is indicative of obstructive hydrocephalus The large mass in the left lateral recess was confirmed to be a choroid plexus carcinoma and the small mass confirmed local metastatic lesion. the 4th ventricle and right lateral aperature were somewhat distended (Atlas of Small Animal CT and MRI)

Answer 163

Expansile mass that is T1 and T2 hyperintense compared to adjacent muscle arises from the body of the 7th lumbar vertebra. There is extensive cortical osteolysis and the mass extends into the vertebral canal elevating and enveloping the cauda equina The mass uniformly enhances following intraveneous contrast biopsy - plasma cell neoplasia (Atlas of Small Animal MRI and CT)

Answer 164

Large, well-defined T1 isointense, T2 hyperintense ovoid mass arising from the pituitary fossa Carotid arteries are identified in cross-section and appear to be surrounded by the mass Following administration of contrast, the mass uniformly and intensely enhances, and the basilar part of the mass can be seen to invade into the cavernous sinus bilaterally Carotid arteries are confirmed to be incorporated into the mass bilaterally (arrowheads) \*cavernous sinus syndrome (Atlas of Small Animal CT and MRI)

Answer 165

A lateral view of a myelogram in a dog with ascending myelomalacia precipitated by an intervertebral disc herniation (arrowed). There is contrast medium in the subarachnoid space and within the spinal cord parenchyma. (BSAVA Manual)

Answer 166

white arrow - dorsal deviation of the dural sac white arrowhead - neural elements within the dural sac black arrowhead - thin stalk extends from the dorsum of the myelomeningocele to the skin surface, which is dimpled. (Atlas of Small Animal MRI and CT)

Answer 167

The pituitary gland has nonuniform mixed T1 intensity and T2 signal that is isointense Hyperintense secretory granules within the neurohypophysis are displaced to the right The pituitary enhances nonuniformly following contrast administration Dorsal pituitary margin is irregular, convex, and extends beyond the dorsal extent of the sella turcica \*Consistent w/ Pituitary Microadenoma (Atlas of Small Animal CT and MRI)

Answer 168

the axillary artery and vein lie ventromedial and caudal to the plexus The external jugular vein and superficial cervical artery cross the ventral surfaces of the 7th and 8th cervical spinal nerves laterally Kraft et al 2007

Answer 169

Epidural hemorrhage of the left parietal region (Atlas of Small Animal CT and MRI)

Answer 170

Motion related artifacts (phase mismapping) * most severe in PE direction * Avoid by: * Swap PE and FE * Apply saturation bands over lg blood vessels/GI tract * Gating * Increase NEX Mai

Answer 171

1. Time of flight 2. Entry slice phenomenon 3. Intravoxel dephasing Mai

Answer 172

Time of flight flow artifact * Stationary fluid experience both 90 and 180 pulses (in spin echo sequence) --\> generates a signal * Faster fluids, either all or only part of the blood experiences both RF pulses so partial or no signal is generated * Gradient echo: no flow-related loss of signal, instead show flow-related enhancement because whole body receives the refocusing gradient and flowing fluid is rephased irrespective of its slice position Mai

Answer 173

Entry slice phenomenon (vascular flow artifact) * Nuclear spins of blood flowing perpendicularly become progressively more saturated as protons move through a stack of slices * Nuclear spins of blood within the center will have experienced more excitation * Blood within the entry slice may show greater signal than blood in the image slices further away from the entry slice * Varies with TR, slice thickness, and direction/velocity of the flow Mai

Answer 174

Flow-related intravoxel dephasing * Occurs when nuclei having different velocities are present in the same voxel * Due to their different velocities - these nuclei will have traveled different distances to reach that voxel between the 90RF pulse and signal readout - therefore will have accumulated variable amounts of phase during their travel * When they arrive in the voxel, these differences in phase accrued will cause destructive interference in amplitude of the signal that is recorded from that voxel - signal drop in affected voxels * This can be reduced using gradient moment rephasing (nulling) = flow compensation Mai

Answer 175

CSF flow artifact * Most commonly seen on T2 and T2W FLAIR * T2 - signal drouput * T2 FLAIR - failure of suppression of high CSF signal Mai

Answer 176

Phase-encoded motion artifact (Pulsatility artifact) * Usually associated with the pulsing of larger blood vessels --\> ghost images in the PE direction * They are only visible in one imaging plane and inconsistent * Brighter moving structure --\> brighter ghost images * Usually more marked on post-contrast images - should not be mistaken for abnormal contrast enhancement Mai

Answer 177

Zipper artifact * caused by leakage of external RF signals into the MRI scanning room * in the FREQUENCY ENCODING direction Mai

Answer 178

Spike or Herringbone artifact * Only occurs during certain sequences when there is a loose electrical connection - most likely to occur when the gradients are applied at a very high duty cycle Mai

Answer 179

Coil artifact * correction via filtering of the image * correct FOV Mai

Answer 180

Cross excitation * Occurs if there is no gap between slices * Worst on inversion recovery sequences * Can be avoided by having an interslice gap of at least 1/3 of the slice thickness, using an interleaved acquisition technique, or 3D acquisition Mai

Answer 181

Slice overlap/cross talk * results in dark bands across the images Mai

Answer 182

Technique used to prevent phase wrap artifact * FOV is enlarged in the PE direction in order to cover a wider area of anatomy and to preserve spatial resolution * Results in longer acquisition time Mai

Answer 183

Gibb's artifact * occurs due to phase undersampling - causes high frequency signal from a high contrast sharp interface not to be represented accurately * occurs most often in the PE direction * Correction - increase size of image matrix and voxel size Mai

Answer 184

Chemical shift artifact - misregistration of signal * Occurs in the FE direction * Worsens at increasing magnetic field strength Minimized by: * Increase receiver bandwidth * Fat suppression technique Mai

Answer 185

Phase cancellation artifact (chemical shift) * Differences in the resonant frequencies of fat and water --\> phase cancellation or 2nd order chemical shift artifact * Occurs on gradient echo sequences, not spin echo sequences * results in black lines at the boundaries of tissues when voxels along the periphery of the object contain both water and fatty tissues * At specific TEs when the spins of fat and water are exactly 180 out of phase, they cancel each other out --\> signal loss * Can be avoided by choosing a TE when fat and water are in phase Mai

Answer 186

Susceptibility artifact * at these boundaries, there is microscopic variation in local magnetic field --\> focal distortion of the image * largest around ferromagnetic objects - hemorrhage, suture material, foreign body, gas * Larger with increasing field strength * Causes spectral fat suppression not to be homogeneous Mai

Answer 187

1. Avoid gradient echo pulse sequences 2. Avoid parallel imaging if metal artifacts are present 3. Parallel imaging reduces artifacts due to air in the sinuses and tympanic bullae 4. Short-echo spacing – allows collection of more echoes during the echo-train before the signal decays, and less time for dephasing of spins 5. Use longer echo train 6. Shorter TE – less time for dephasing of spins 7. High receiver bandwidth 8. Thin slices 9. Avoid spectral fat saturation – if suppression of fat signal is desired, use sequences that do not rely on frequency-specific fat saturation (STIR) 10. Maintain adequate SNR 11. Swap PE and FE directions 12. Change alignment of metallic implants relative to B0 – change limb or body position Mai

Answer 188

Partial volume averaging * occurs with large voxels at the boundaries of different structures * more severe with increasing slice thickness Mai

Answer 189

66% of cats with focal rostro-tentorial lesions and concurrent brain herniation showed signs of brainstem dysfunction 48% of these cats presented with nystagmus ACVIM Proceedings

Answer 190

Palliative: 97 days Surgery: 144 days SRT: 371 days ACVIM Proceedings

Answer 191

incompletely penetrant or polygenic trait clinical findings - if a genetically susceptible horse receives enough dietary vitamin E during the first year of life, they are unlikely to develop a moderate to severe ataxia Autosomal dominant mode of inheritance suggested in Morgan horses ACVIM Proceedings

Answer 192

Transitional vertebrae * Usually involve vertebral arch rather than body * Occur at cervicothoracic, thoracolumbar and lumbosacra junctions * Increased incidence of lumbosacral disc disease and nerve root compression occurs in dogs with a lumbosacral transitional malformation (Thrall)

Answer 193

Left 15 - 30 degree ventral/ right dorsal radiograph * VD projections can be made, there is risk of exacerbating the spinal cord compression. VD is not necessary to confirm a diagnosis of AA subluxation Normal linear relationship between dorsal lamina of atlas and axis - if this becomes angular luxation is present (Thrall)

Answer 194

Disc-associated 1. Changes in shape of the vertebral body 2. Narrowing of the intervertebral disc space 3. Vertebral canal stenosis * Approximately 20 - 25% of clinically normal dogs have radiographic changes comparable with those seen in dogs with CSM * "cervical vertebral ratios may be useful as a screening test for dogs with CSM" Osseous 1. Osteoarthritis, sclerotic changes of articular facets (DeCosta VCNASAP)

Answer 195

Diffuse brain atrophy resulting in enlargement of the ventricular system and subarachnoid space. The pituitary fossa is filled and appears T1 hypointense and T2 hyperintense. This fluid accumulation appears to communicate with the 3rd ventricle by way of the infundibular recess (lg arrow) The interpeduncular (small arrow) and chiasmic (arrowhead) cisterns are also prominent \*Empty sella syndrome (Atlas of Small Animal CT and MRI

Answer 196

Large arrow - nonuniformly T1 hypointense, T2 mixed intensity mass that distends the 3rd ventricle and results in lateral ventriculomegaly (arrowheads) Small arrows - mass has an extraventricular component involving the falx cerebri CT - mass is mineralized Post-contrast - marked nonuniform enhancement following contrast administration Arrows - post-mortem examination confirmed the presence of a predominantly intraventricular **psammomatous meningioma** (Atlas of Small Animal CT and MRI)

Answer 197

Low kVp High mA Brain Camp

Answer 198

Prominent, well-delineated, T1 hypointense, T2 hyperintense extraaxial masses are present on either side of the brainstem, causing axial compression bilaterally The masses are moderately and uniformly contrast enhancing CSF/postmortem - **lymphoma** (Atlas of Small Animal CT and MRI)

Answer 199

Arrow - elongated tear drop-shaped dilation of the dorsal subarachnoid space at the level of the 2nd cervical vertebra arrowhead - pronounced spinal cord compression (Atlas of Small Animal MRI and CT)

Answer 200

Arrowhead - meningeal lining of the pituitary fossa is T2 hyperintense Arrrowhead - the meninges of the fossa and dural septum intensely contrast enhance arrows - more diffuse meningeal enhancement is evident involving the meninges of the falx cerebri and the basilar regions of the piriform obes \*postmortem - diffuse meningoencephalitis with marked **chronic granulomatous and lymphoplasmacytic hypophysitis** (Atlas of Small Animal CT and MRI)

Answer 201

Spinous processes and pedicle margins of the caudal-most lumbar vartebra are missing, consistent with spina bifida (Atlas of Small Animal MRI and CT)

Answer 202

1. Tilting of the craniodorsal edge of the vertebral body dorsally - site of spinal cord compression may NOT be related to the tilt 2. Abnormal vertebral body shape (flattened cranioventral epiphysis, triangular shape) 3. Spondylosis deformans ventral to the intervertebral space 4. Stenosis of the vertebral canal - cranial orifice narrower than the caudal * Suggested that - normal dobermans, difference between diameter of cranial orifice and caudal orifice is \< 3mm 5. Increased opacity, loss of joint space of articular processes +/- new bone 6. Intervertebral disc space - narrowing, mineralization of the disc Plain film changes do not always correlate with myelographic evidence of cord compression Lewis et al 1991 - 28 dogs that had marked changes indicative of CCSM (stepping \> 3mm, vertebral malformation, canal stenosis, ventral spondylosis) - 20 developed signs of CCSM \*\* Dogs without such changes did not go on to develop CCSM during the period of the study (Sharp)

Answer 203

1. Ventral extradural compression is the most common findings - usually related to the intervertebral disc. Splitting of the contrast column is seen if the compression is asymmetrical 2. Dorsal extradural compression from ligamentum flavum or articular processes 3. Articular process hypertrophy - best seen on VD

Answer 204

* Fat: **-100 to -50** * CSF: **0-15** * Brain/spinal cord: **25 - 50** * Recent hemorrhage (\<24 hours): **55 - 95** * Recently herniated mineralized disc: **100 - 500** * Chronically herniated mineralized disc material: **450 - 1000** * Bone: **600 - 1000** 100 - 200HU (this is because differences in physical density and anatomic number are not markedly different) (BSAVA Manual)

Answer 205

1. Vertebral body malformation 2. Stenosis 3. Malalignment 4. Vertebral tipping 5. Articular process remodeling 6. Disc degeneration/prolapse 7. Spinal cord compression 8. Ligamentum flavum hypertrophy, interarcuate ligament or joint capsule hypertrophy (can only be assessed with MRI) (Thrall)

Answer 206

Sensitivity 72%, specificity 77% CT is superior to radiography for identifying and characterizing vertebral fractures (Thrall)

Answer 207

1. Narrowing of the intervertebral disc space 2. Narrowing of the intervertebral articular process joint 3. Small intervertebral foramen 4. Increased opacity within the intervertebral foramen 5. Mineralized disc material within the vertebral canal (Thrall)

Answer 208

Spondylitis (nonspecific term referring to inflammation of the vertebrae) 1. Microbial infection 2. Plant awn migration 3. Spirocerca lupi 4. Paraspinal abscess Radiographic changes: 1. Increased opacity over the vertebral body 2. Periosteal response of the vertebral body 3. Osteomyelitis - aggressive bone response with patchy lysis of the vertebral bodies and irregular periosteal response 4. S. lupi infection results in osseous proliferation of the ventral aspect of the vertebral bodies of T8-11 Metastatic neoplasia can cause similar periosteal lesions

Answer 209

Sharpey fibers - connect annulus fibrosus to vertebral end plate Annulus fibrosus is anchored to the dorsal longitudinal ligament by short fibers Presently - accepted theory states that disruption of sharpeys fibers is the initiator --\> radiographic evident osseous proliferation (or enthesopathy) of the margins of the end plate * These enthesophytes are variably sized ventrolateral spurs that have been referred to as osteophytes incorrectly * osteophytes occur at osteochondral junctions of synova joints * Eventually, ventral vertebral enthesophytes can bridge the intervertebral disc space at single or multiple sites --\> fusion * When this occurs in the thoracolumbar junction, adjacent vertebral junctions are at risk for disc degeneration * Other radiographic findings: * End plate thickening * Narrowing of the intervertebral disc space * Whether or not disc degeneration is a factor in the development of spondylosis deformans is unclear * In dogs, type II intervertebral disc disease may be part of the pathogenesis of spondylosis deformans * Type II IVD is often seen in dogs at sites of spondylosis deformans, cause and effect are not clearly established * Most agree that spondylosis deformans is insignificant clinically, unless a concurrent prolapsed disc is present or if there is bony impingement on the spinal cord or spinal nerve roots * Nerve root compression from spondylosis is rare except in lumbosacral instability where foraminal impingement results from dorsal extension of enthesophytes (Thrall)

Answer 210

1. Remodeling of the articular processes 2. Osteophytosis 3. Thinning of the joint space No clinical signs unless causing spinal cord compression (Thrall)

Answer 211

1. Intervertebral disc disease 2. Instability of the lumbosacrum 3. Stenosis from remodeling changes associated with spondylosis deformans 4. Impingement from osteoarthritis of the articular process joints 5. Osteochondrosis-like lesion of the sacral end plate (GSD) (Thrall)

Answer 212

Sarcomas (osteosarcoma, chondrosarcoma, hemangiosarcoma, fibrosarcoma) Other ddx: lymphoma, multiple myeloma In 61 canine vertebral tumors, the most common site for primary neoplasia was the **thoracic** area Most metastatic lesions were found in the **lumbar** area *_Metastatic neoplasia is more common than primary vertebral_* neoplasia - **carcinomas and sarcomas** most common metastatic neoplasias (Thrall)

Answer 213

Multiple myeloma and lymphoma - these changes are not pathognomic Textbook of veterinary diagnostic radiology

Answer 214

1. Bridging ossification along ventral and lateral aspects of three contiguous vertebral bodies 2. Relative preservation of disc space width within involved areas, absence of changes of degenerative disc disease 3. Osteoarthritis of the dorsal intervertebral process joints 4. Pseudoarthrosis of the spinous processes 5. Enthesopathy of soft tissue attachments (axial and appendicular skeleton) 6. Osteophytes, sclerosis and ankylosis of the sacroiliac joints 7. Bony ankylosis of the symphysis pubis Suggested that 4/7 criteria be present for confirmation of DISH in the dog Likely a separate entity than spondylosis deformans - predominant excessive ventral distribution supports this

Answer 215

1. Remodeling and shape change of the vertebra, 2. Spondylosis deformans 3. Abnormal development of the dens These changes are primarily a manifestation of vertebral epiphyseal dysplasia Skull 1. Shortened nasal conchae 2. Aplasia and hypoplasia of the frontal and sphenoid sinuses 3. Shortened dimensions of the incisive and maxillary bones 4. Changes in appendicular skeleton * Epiphyseal dysphasia of long bones * Abnormal nasal choncal development * Coxofemoral luxation (Thrall) (picture) severe degenerative shoulder changes (arrows), and short cervical vertebrae with irregular epiphysis

Answer 216

Cysts associated with the articular processes are extradural fluid-filled round or oval, well defined structures that develop as a result of degeneration of the articular process joint 1. Synovial cysts - lined by synovium-like epithelial cells resulting from outpouching of synovial membrane through weakened capsular tissue 2. Ganglion cysts - result of mucinous degeneration of periarticular connective tissue and which do not have a synovial lining From clinical and imaging perspectives, the 2 entities are indistinguishable and can be grouped together Giant breed dogs, cysts tend to be multiple and located in the cervical spine in young dogs Large breed dogs, cysts more commonly found in the thoracolumbar or lumbosacral area in young adults and older dogs (Thrall)

Answer 217

Dogs: osteosarcoma, chondrosarcoma 1. Solitary/disseminated histiocytic sarcoma 2. Lymphosarcoma 3. Multiple myeloma 4. Metastatic vertebral tumors - prostatic carcinoma, transitional cell carcinoma 5. Sarcoma 6. Infiltrative lymphoma Cats: lymphosarcoma

Answer 218

CT - infiltrative lipomas characteristically hypoattenuating, similar to normal fat MRI - infiltrating lipomas are T1 and T2 hyperintense, and suppress with fat suppression (Thrall)

Answer 219

1. Soft tissue asymmetry - tumor often has attenuating properties similar to muscle 2. Unilateral muscle atrophy 3. Soft tissue mass that is isoattenuating to surrounding muscles and contrast-enhancement that is uniform, patchy or rim-like 4. Occasionally tracks in a linear fashion into a neighboring intervertebral foramen, can invade the vertebral canal 5. Invasion into the thoracic cavity can also be seen Approximately 45% are located in the nerve roots proximal to the spinal cord, while 55% are located in the plexus area or peripheral nerves Masses as small as 1cm can be identified on CT

Answer 220

1. Focal mass or diffuse thickening of affected nerves 2. Proximal extension into the intervertebral foramen and vertebral canal is possible 3. T2 hyperintense or mixed signal intensity, T1 isointense (or hyperintense/mixed) 4. STIR and T1WI+C fat suppressed useful in increasing conspicuity of the tumor * homogenous/inhomogenous contrast enhancement 5. Ipsilateral muscle atrophy - T1 and T2 hyperintense and mildly contrast-enhancing (neurogenic atrophy, edema, fat infiltration, fibrosis) (Thrall)

Answer 221

Occasionally frow in the epidural space, most lesions are intradural extramedullary Usually single, multifocal meningiomas seen occasionally CT - golf tee sign!! - best seen on sagittal and dorsal images * May be IV contrast-enhancement of the mass (Thrall)

Answer 222

1. Focal masses 2. T2 hyperintense 3. T1 isointense/hypointense * T2 hypointensity and T1 hyperintensity have also been reported 4. T1WI+C - meningiomas usually have moderate to strong, well-defined contrast enhancement 5. Dural tail often present (Thrall)

Answer 223

CT: swelling of the spinal cord with obliteration of the epidural fat observed in the affected area * Intradural/extramedullary pattern with myelography MRI: 1. T2 isointense (may have heterogeneous signal), T1 isointense 2. Widening of SAS cranial and caudal to the mass (Thrall)

Answer 224

1. Spinal cord swelling (loss of SAS, loss of epidural fat 2. Diffuse patchy T2 hyperintensity that extends over the length of several vertebral bodies * Focal regions of T2 hypointensity - hemorrhagic foci 3. T1 isointense to hypointense 4. Regions of T2\* hypointensity (presumed hemorrhage) (Thrall)

Answer 225

20% have normal MRI * Usually happens when dogs are imaged \< 72 hrs after onset of clinical signs * Higher in ambulatory dogs A lesion-length-to-vertebral-length ratio \> **2.0** has a sensitivity of 100% in predicting a poor clinical outcome * On average - length of the spinal cord T2 hyperintensity observed on sagittal MRI images in dogs with ischemic myelopathy is approximately 1.8 x length of C6 for cervical/cervicothoracic lesions * 2.2 x length of L2 for thoracolumbar and lumbosacral lesions A % cross-sectional area of the lesion \> **67%** has a sensitivity of 100% in predicting poor clinical outcome (Thrall)

Answer 226

CT: epidural mass suspected based on lack of visualization of hypoattenuating epidural fat around the spinal cord. Epidural mass best identified with myelography. MRI: 1. Well defined epidural mass in the dorsal or ventral vertebral canal 2. T2 hyperintense or mixed signal 3. T1 hypointense 4. Peripheral, rim-like contrast enhancement or a diffuse enhancement pattern 5. T2\* - focal hypointense areas in the epidural mass may be present 6. T2 hyperintense gray matter lesions within the spinal cord - secondary to compression or vascular compromise (Thrall)

Answer 227

CT: 1. Spinal cord swelling 2. Spinal cord hypoattenuation 3. Occasionally intramedullary or meningeal contrast enhancement MRI 1. Irregular areas of T2 intramedullary hyperintensity 2. Precontrast T1 weighted images - isointense or hypointense to the spinal cord, various contrast enhancement \*\* MRI findings are not specific for meningomyelitis - ddx myelomalacia or ischemic myelopathy (Thrall)

Answer 228

Signs of pain Scratching behavior Scoliosis 95% of CKCS with max syrinx width of 0.64cm or more will have associated clinical signs (Thrall)

Answer 229

MRI: 1. Heterogeneous signal intensity with large regions of contrast enhancement 2. Well-delineated invasion of soft tissues and brain CT: 1. Well defined margins 2. Limited lysis of bone 3. Central cord of the tumor appears granular (Thrall)

Answer 230

MRI Epidermoid 1. Hypointense on T1WI, 2. Hyperintense on T2WI/FLAIR 3. Peripherally enhancing CT epidermoid 1. Hypoattenuating on CT images Dermoid cyst MRI 1. Hyperintense on T1 and T2WI due to fat content

Answer 231

1. Chemical fat suppression of T1W images 2. Delayed acquisition time following gadolinium administration reported to provide marginal improvement of contrast enhancement **Subtraction images** - Normal dogs have been shown to have consistently identifiable contrast enhancement of the meninges when dynamic subtraction is applied to the images, attributable mainly to the pachymeningeal vessels. In dogs with confirmed inflammatory conditions of the brain, *dynamic subtraction does not appear to increase sensitivity of detection of meningeal enhancement (compared with standard pre post contrast images)* *\*\** Dynamic subtraction images appear to increase the sensitivity of MRI to detect intra-axial inflammatory lesions in dogs, therefore may still be recommended when meningoencephalitis is suspected (Mai)

Answer 232

In general, when compared with neoplasia, the MRI appearance of meningoencephalitis is more likely to: 1. Be multifocal 2. Involve both supratentorial and infratentorial regions of the brain 3. Irregular lesion shape with ill-defined margins 4. Uniform T2W and T2 FLAIR signal hyperintensity 5. Meningeal contrast enhancement In general, when compared with neoplasia, the MRI appearance of meningoencephalitis is LESS likely to 1. Have strong contrast enhancement (contrast enhancement is still common) 2. Have heterogeneous T2W or T2 FLAIR signal intensity 3. Have mass effect (still frequently seen) (Mai)

Answer 233

Diffuse GME (Mai)

Answer 234

Focal GME vs. neoplasia (Mai)

Answer 235

Necrotizing meningoencephalitis (Mai)

Answer 236

Necrotizing leukoencephalitis (Mai)

Answer 237

Idiopathic eosinophilic meningoencephalitis (Mai)

Answer 238

Idiopathic hypertrophic pachymeningitis (Mai)

Answer 239

Acute distemper encephalitis (Mai)

Answer 240

Cuneiform vertebra * The base of the wedge in most cases is oriented dorsally * Incorrectly called hemivertebra * A true hemivertebrae is one where half of the vertebra (centrum and neural arch) fails to form * This would lead to scoliosis rather than kyphosis Butterfly vertebra = Ventral and median aplasia of the vertebra (Dewey et al)

Answer 241

Most dogs with neurologic dysfunction had a Cobb angle associated with the kyphotic vertebral segment \> 35 degrees (Vet Clin N America)

Answer 242

2mm slice thickness Transverse T2 best T1 can be helpful for bony landmarks (Mai)

Answer 243

Cranial nerves 2. 3. 5 (and divisions), 8 - consistently visualized Cranial nerves 4, 7, and group of 9, 10, and 11 - better visualized on thin slices CN 6 and 12 - poorly visualized or not visualized 2mm thick slices allowed accurate visualization of most CN emergencies - 2, 3, 4, 5, 7, 8 and 9/10/11 Course of 2, 3, and 5 could be followed on several slices Main branches of CN V seen well on thin-slice studies (Couturier et al)

Answer 244

Cranial nerves II, V and its divisions, VII and VIII are typically visualized The emergency of CN IX, X, XI, XII, and the common path of nerves IX, X, and XI through the TOF can be visualized as an ill-defined HYPERINTENSE structure CN III - inconsistently visualized CN IV and VI - not visualized (Couturier et al)

Answer 245

A1 - Vermis 2 - Accessory n 3 - Basilar artery B1 - Lateral recess of the 4th ventricle 2 - Caudal cerebellar peduncle 3 - Emergence of CN IX, X, XI C1 - 4th ventricle 2 - paraflocculus of the cerebellum 3 - cochlear nucleus D1 - Culmen 2 - Lingula 3 - Perilymph and endolymph (within vestibule of inner ear) 4 - CN VIII Couturier et al.

Answer 246

E1 - culmen 2 - fourth ventricle 3 - middle cerebellar peduncle 4 - facial nerve 5 - perilymph and endolymph of the cochlea F1 - facial canal 2 - rostral part of the cochlea 3 - tympanic bulla of the middle ear G1 - rostral part of cerebellum 2 - caudal colliculus 3 - area of emergence of the trochlear nerve 4 - emergence of trigeminal nerve H1 - optic chiasm 2 - orbital fissure (Couturier et al)

Answer 247

G - 1 oculomotor nerve 2 - ophthalmic branch of trigeminal nerve 3 - maxillary branch of trigeminal nerve in round foramen H1 - optic chiasm 2 - maxillary branch of trigeminal nerve in rostral alar foramen I1 - optic nerves 2 - oculomotor, trochlear, and abducent nerves in orbital fissure 3 - ophthalmic branch of the trigeminal nerve in orbital fissure 4 - retractor bulbi muscle (Couturier et al)

Answer 248

J - 1, optic nerves 2 - oculomotor nerve in orbital fissure 3 - ophthalmic branch of trigeminal nerve in orbital fissure 4 - maxillary artery 5 - maxillary branch of trigeminal nerve K1 - optic nerve 2 - ophthalmic branch of the trigeminal nerve with associated vessels, oculomotor nerve, trochlear nerve, and abducent nerve. These structures cannot be differentiated here L1 - optic nerve Couturier et al

Answer 249

A1 - caudal colliculus 2 - mesencephalic aqueduct 3 - periaqueductal gray matter 4 - trigeminal nerve B1 - rostral colliculus 2 - brachium (white matter) of the caudal colliculus 3 - mesencephalic aqueduct 4 - trigeminal nerve and ganglion C1 - lateral geniculate nucleus 2 - medial geniculate nucleus 3 - area of oculomotor nucleus 4 - trigeminal nerve and ganglion Couturier et al

Answer 250

D1 - thalamus 2 - trigeminal nerve E1 - thalamus 2 - interthalamic adhesion 3 - third ventricle 4 - ophthalmic and maxillary branches of trigeminal nerve F1 - thalamus 2 - interthalamic adhesion 3 - third ventricle 4 - pituitary gland 5 - ophthalmic and maxillary branches of trigeminal nerve 6 - mandibular branch of trigeminal nerve in the oval foramen. (Couturier et al)

Answer 251

(A) Dorsal T1W image through the brain of a normal medium-sized dog showing the optic nerves (white arrow). (B) Dorsal T2W image through the brain of a normal medium-sized dog showing the maxillary branch of the trigeminal nerve (small white arrow) and the zygomatic salivary gland (large white arrow) Couturier et al

Answer 252

(A) Parasagittal T2W image through the brain of a normal Afghan hound showing the emergence of the trigeminal nerve (small white arrows)

Answer 253

A1 - vermis 2 - fourth ventricle 3 - hypoglossal nerve 4 - pyramid B1 - vermis 2 - fourth ventricle 3 - CN IX, X, XI, and XII 4 - pyramid C1 - occipital lobe of telencephalon 2 - rostral vermis of cerebellum 3 - cerebellar peduncle 4 - vestibulocochlear nerve 5 - fourth ventricle 6 - myelencephalon D1 - occipital lobe of telencephalon 2 - rostral vermis of cerebellum 3 - caudal colliculus 4 - facial nerve 5 - cochlea 6 - transverse pontine fibers E1 - longitudinal cerebral fissure 2 - hippocampus 3 - cerebral cortex 4 - periaqueducal gray matter 5 - mesencephalic aqueduct 6 - brachium of the caudal colliculus 7 - trigeminal nerve F1 - rostral colliculus 2 - mesencephalic aqueduct 3 - medial geniculate body 4 - trigeminal nerve ganglion (Gomes et al)

Answer 254

G1 - temporal lobe of telencephalon 2 - third ventricle 3 - lateral geniculate body 4 - thalamus 5 - pituitary gland 6 - oval foramen with mandibular branch of trigeminal nerve H1 - dorsal part of the third ventricle 2 - interthalamic adhesion 3 - pituitary gland 4 - oculomotor nerve 5 - round foramen with maxillary branch of trigeminal nerve I1 - lateral ventricle 2 - interthalamic adhesion 3 - third ventricle 4 - orbital fissure nerve group (III, IV, VI, and ophthalmic branch of V) J1 - longitudinal cerebral fissure 2 - lateral ventricle 3 - hypothalamus 4 - optic chiasm 5 - orbital fissure (CNIII, IV, V, and VI) K1 - corpus callosum 2 - internal capsule 3 - caudate nucleus 4 - optic nerve 5 - sphenoid sinus L1 - optic nerve 2 - ophthalmic branch (trigeminal nerve), oculomotor, abducent, and trochlear nerves. CN, cranial nerve. (Gomes et al)

Answer 255

(A): Thin copper wire in thehypoglossal canal (arrow) (B) 1, hypoglossal canal and 2, tympano-occipital fissure (C) internal acoustic meatus (arrow) (D) facial canal (arrow) (E) ovalforamen (arrow) (F) round foramen (arrow) (Gomes et al)

Answer 256

(A) through the optic nerve: 1, optic nerve, 2,optic chiasm (B) through the vestibulocochlear nerve (arrow) (Gomes et al)

Answer 257

Ischemic penumbra * Surrounding the penumbra, there is an area of tissue with mild reduction in blood flow, which is more likely to survive called the 'oligemic region' (Mai)

Answer 258

Underestimates the size DWI is significantly more sensitive, especially in peracute stage (Mai)

Answer 259

The exponential ADC map is calculated from the ADC values, leads to an inverted scale more similar to the DW images, where restricted diffusion appears bright, but again eliminating T2 shine-through effects like the regular ADC map These exponential ADC maps may be more sensitive than ADC images for recognizing restricted diffusion in periventricular areas, as bright signal adjacent to the dark CSF (Mai)

Answer 260

24 hours Chronic stroke - ADC elevated (after 10d in human) (Mai)

Answer 261

T2FLAIR T1W post contrast T2\*W GRE (or other susceptibility weighted imaging) DWI (Mai)

Answer 262

1. Resolution of edema 2. Resorption of necrotic tissue 3. Restoration of the BBB Usually takes 6 weeks Serial imaging of infarcts has shown that: * Chronic infarcts are smaller and more sharply marginated than acute infarcts * Often parenchymal volume loss * Areas of cavitation * Absence of parenchymal contrast enhancement * Secondary changes (atrophy due to wallerian degeneration) may be seen downstream of the areas of infarction (Mai)

Answer 263

* Medial striate arteries which arise form the circle of willie at the junction of the ethmoidal and middle cerebral artery * Number varies, usually symmetric and there is no association between the number and the dog's size * Lateral striate arteries - arise from the middle cerebral artery * The distribution and number of lateral striate arteries is more variable (usually 2 on each site) * Origin of these arteries is variable - may arise from the communicating arteries, rostral or middle cerebral arteries * Some anastomoses and small overlap of vascular territories occur (Mai)

Answer 264

Peracute (Mai)

Answer 265

Acute (Mai)

Answer 266

Subacute (Mai)

Answer 267

Chronic arterial infarct (Mai)

Answer 268

Rostral choroidal artery Branch of middle cerebral artery or directly from arterial circle @ the level of MCA (Mai)

Answer 269

Medial striate arteries/lenticulostriate arteries (arise from the circle of willis @ level of MCA) (Mai)

Answer 270

Lateral striate arteries/lenticulostriate arteries Branches of MCA (Mai)

Answer 271

Proximal perforating artery Arises from the caudal communicating branch (Mai)

Answer 272

Distal perforating artery Arises from the caudolateral aspect of the thalamus and subthalamus (Mai)

Answer 273

Caudal perforating artery arising from the basilar bifurcation Paramedian branches arising from the proximal portion of the caudal cerebral artery (Mai)

Answer 274

Acute lacunar infarcts In dog 1 (a), the transverse T2-FLAIR image shows an infarct within the territory of the right striate arteries (solid arrow). In dog 2 (b, c), transverse and dorsal T2W images show an infarct within the territories of the perforating arteries (dotted arrows). In dog 3 (d), there is an infarct also in the territories of the perforating arteries (open arrow). Acute lacunar infarcts have variable shapes. Often on one imaging plane lacunar infarcts have an angular appearance and are relatively sharply marginated with minimal or no mass effect. Note the difference in shape of the infarct on the transverse (b) and dorsal (c) images in dog 2. Small lacunar infarcts adjacent to the lateral ventricles are often best seen on dorsal plane T2W images. Clinical history, CSF analysis, and DWI may be required to differentiate some lacunar infarcts from inflammatory disease. The distribution of lacunar infarcts depends on which arteries are involved. It is not uncommon for there to be multiple lacunar infarcts in different vascular territories, in contrast to large territorial infarcts, which are usually solitary (Mai)

Answer 275

Lacunar infarct * Multiple infarcts in differing vascular territories are suggestive of an embolic disease * DWI pulse sequences may show restricted diffusion in the early stages, but due to small size lesions may not be visible * In chronic stages, cavitation and loss of volume are common * Hemorrhagic transformation is uncommon (Mai)

Answer 276

1. Artifactual (T2 shine through) 2. Lesions containing viscious/proteinaceous fluid (early abscessation) 3. Cytotoxic edema * Infarction/ischemia * Post-ictal edema * Some metabolic diseases and toxicosis * Hypertensive encephalopathy * Viral encephalitis/Encephalitis * Leukodystrophy 4. Densely cellular mass * Lymphoma * Some gliomas * Granulomas (Mai)

Answer 277

Glioma: * Not confined to vascular territory * Tend to be larger * More pronounced mass effect * More pronounced perilesional edema * More often bright on DWI and ADC Infarct * Confined to vascular territory * Smaller * Less mass effect, less perilesional edema * Bright on DWI, dark on ADC * Wedge-shaped (Mai)

Answer 278

Seizure induced post-ictal changes have hyperperfusion (acute infarcts are underperfused)

Answer 279

1. T2W, T2FLAIR hyperintensity within the cortical gray matter of the parieto-occipital lobes 2. T2W and T2 FLAIR hyperintensity within the caudate nuclei 3. Bilateral distribution, most commonly symmetric but may be asymmetric 4. Mild or no involvement of subcortical white matter 5. Mild diffuse cortical and caudate nucleus contrast enhancement in some cases Follow up MRI - may show reduced size and severity of lesions, gray matter hyperintensities may persist permanently (Mai)

Answer 280

Transverse T2W (a) and T2-FLAIR (b) images in an 8-year-old Maltese who had general anesthesia the day prior for a dental procedure. The dog was previously healthy but was slow to recover from anesthesia and then developed generalized tremor with altered mentation; he became stuporous and non-ambulatory tetraplegic. There is increased signal intensity in the gray matter of both frontoparietal lobes, symmetric but worse on the left. The changes together with the history are consistent with **global brain ischemia**. (Mai)

Answer 281

DSS = dorsal sagittal sinus TR = transverse sinus TE = temporal sinus MV = maxillary vein ST = straight sinus SI = sigmoid sinus DCV = dorsal cerebral vein (Mai)

Answer 282

Abnormal signal within a sinus Corresponding absence of flow on MRV (Mai)

Answer 283

1. T2 hyperintensities within the white matter (vasogenic edema) 2. Isoitnense T2W, noncontrast-enhancing (or mild contrast enhancement) 3. Lesions preferentially involve the mid-caudal cerebrum (parietal and occipital lobes), although lesions can be extensive within the cerebrum and involve the frontal regions 4. Caudate nuclei/thalamus are less commonly affected 5. Lesions may be bilaterally symmetric or asymmetric 6. Clear differentiation between white and gray matter in affected areas 7. DWI show increased signal on ADC maps - increased diffusion due to vasogenic edema Diagnosis is based on documenting hypertension and resolution of the neurologic signs following control of the hypertension (Mai)

Answer 284

Hypertensive encephalopathy (Mai)

Answer 285

1. Absence or hypoplasia of normal vessels 2. Persistent transient embryonic vessels 3. Vessels with abnormal morphology 4. Arteriovenous malformations 5. Dural arteriovenous fistulas 6. Aneurysms 7. Cavernous malformatin (Mai)

Answer 286

1. Feeding arteries 2. Draining veins 3. Nidus of abnormal vessels between the 2 * Differs histologically from capillaries * Functions as an arteriovenous shunt (Mai)

Answer 287

Cavernous malformations * they may occur anywhere in the brain, most commonly found within the subcortical white matter (and may be multiple) (Mai)

Answer 288

Accelerate both longitudinal and transverse proton relaxation = decrease the T1 and T2 relaxation time The effects are most obvious on T2W --\> results in increased signal For paramagnetic effects of Fe and heme to be recognized, water molecules must be in close proximity to the Fe atoms Although the Fe in deoxyhemoglobin, and hemosiderin/ferritin is paramagnetic/superparamagnetic, the molecular configuration of these molecules shields the Fe from water molecules --\> no or minimal effects on relativity (T1 signal) are seen on the image (Mai)

Answer 289

Hemorrhage: Fe creates a local magnetic field distortion --\> shortened T2 relaxation and rapid loss of neighboring protons' phase coherence Fe within cell (compartmentalization) --\> local heterogeneity in magnetic field --\> acceleration of spin dephasing Weaker paramagnetic substances (methemoglobin) may not cause significant magnetic field heterogeneity When noncompartmentalized, this will be even weaker (Mai)

Answer 290

Oxyhemoglobin (Mai)

Answer 291

Deoxyhemoglobin (Mai)

Answer 292

Methemoglobin (Mai)

Answer 293

Ferritin and hemosiderin (Mai)

Answer 294

Relaxivity effects are greatest on T1 relaxation Susceptibility effects are greatest on T2 relaxation (especially T2\*) (Mai)

Answer 295

T1W images Acute - isointense Subacute - hyperintense (Mai)

Answer 296

T2W in people (this may not apply to dogs).... Early subacute - T2 hypointense Late subacute - T2 hyperintense (Mai)

Answer 297

T1 and T2 hyperintensity suggests late subacute/chronic (Mai)

Answer 298

1. Melanin (melanoma mets, melanosis) 2. Flow artifacts 3. Lipis (dermoid cyst, lipoma) 4. Protein effects (colloid cysts, rathke's cleft cyst, epidermoid cyst, laminar cortical necrosis) 5. Magnanese/Fe/gadolinium/Cu deposition 6. Calcification 7. Vasopressin in the pituitary gland 8. Hemorrhage (methemoglobin) (Mai)

Answer 299

* MRI appearance is predominantly a solid mass * Hemorrhagic tumors are often complex masses with solid, contrast-enhancing parts * Lack of a distinct, complete T2/T2\* hypointense rim * Bleeding of different ages within the lesion * Humans - there is a trend for tumors to have more severe perilesional edema (remains present on repeat imaging) (Mai)

Answer 300

Early subacute hematoma (Mai)

Answer 301

Hyperacute-acute lesion The large amount of perilesional edema, absence of contrast enhancement, narrow complete hypointense rim of T2\* - consistent with benign etiolog (Mai)

Answer 302

Higher oxygen tension in the dura/CSF/subarachnoid space - progression between stages is slower (especially for subarachnoid and intraventricular hemorrhage) The appearance of very chronic hemorrhage in the extra-axial spaces differs due to the formation of non-paramagnetic hemichromes when methemoglobin undergoes oxidative denaturation (due to greater oxygen levels) Chronic extra-axial hemorrhage - absence of a hemosiderin rim (unless there is repeated bleeding) (Mai)

Answer 303

Subarachnoid hemorrhage * Focal/diffuse hemorrhage confined to the subarachnoid space within the basal cisternae and/or adjacent to the cerebral hemispheres * Variable signal intensity dependent on age but T1 hyperintensity, T2 hypointensity, or T2\* gradient echo hypointensity +/- susceptibility artifact is suggestive * Chronic cases (in humans) - superficial siderosis (subpial accumulation of hemosiderin) is reported - appears as linear T2/T2\* gradient echo hypointensity following the cortex and in later stages, cyst formation and brain atrophy (Mai)

Answer 304

Subdural hemorrhage * Signal intensity varies with chronicity - main component is usually hyperintense or of mixed signal intensity on T2W images, and low signal intensity on T1W images in the chronic stages * Acutesubacute stages - similar to intraparenchymal hemorrhages * In chronic cases, meninges may be markedly thickened and show diffuse increased contrast enhancement * Repeated bleeding may result in low signal periphery due to hemosiderin deposits - overwhelm normal clearance mechanisms (Mai)

Answer 305

Fig. 5.7.16 Acute traumatic brain injury and **extra-axial (probable subarachnoid) hemorrhage and small skull fracture** in a 3-year-old Cavalier King Charles Spaniel hit by a car 3 days previously and showing signs of mild ataxia. Dorsal (a) and transverse T2W (b), T2-FLAIR (c), and T2\*W gradient echo (d) images showing a small fracture in the left temporal bone on the dorsal plane image (solid arrow, a) and linear T2 hyperintensity conforming to the surface of the left cerebrum consistent with an acute small subarachnoid hemorrhage (dotted arrows, a and c). The fluid accumulation is best seen on the T2-FLAIR image (c). The presence of corresponding reduced signal within the fluid on the T2\*W image (d) is difficult to visualize due to the small size of the lesion and adjacent bone. (Mai)

Answer 306

Epidural hemorrhage * Occurs within the space between the inner cortex of the cranium, and the dura mater * Most commonly arterial in origin * Rare * Low signal from the fibrous dura may be visible between the hematoma and surface of the cerebral cortex (Mai)

Answer 307

**Acute epidural hematoma** in a 1-year-old Labrador Retriever secondary to Angiostrongylus vasorum infection. Sagittal (to the left of midline, a) and transverse T2W (b), T2\*W gradient echo (c), and T1W (d) images showing a biconvex (‘lenticular’) extra-axial fluid accumulation, which does not cross the frontoparietal suture line (arrow, a). Within the hematoma, there is dependent fluid-fluid level (arrow, b). The presence of peripheral T1 hyperintensity (dotted arrow, d) and low signal on the T2\*W (c) image is consistent with an acute hemorrhage (Mai)

Answer 308

Acute stage - isointense on T1 and T2 but will be hyperintense on FLAIR (and can be noted on T2\*) (Mai)

Answer 309

Diffuse axonal injury * This results in disruption of axons (especially at the gray-white matter junction of the cerebrum, corpus callosum, basal nuclei, and rostral aspect of the brainstem) * DAI is poorly documented in animals (Mai)

Answer 310

1. Diffuse cerebral swelling (effacement of cerebral sulci, ventricular compression, vasogenic edema ect.) 2. Herniation 3. Ischemia/infarct 4. Infection 5. Pneumocephalus (Mai)

Answer 311

1. Degree of midline shift 2. Extent of intraparenchymal lesions 3. Brain herniation 4. Skull fractures 5. Injuries affecting the caudal fossa, or both rostral and caudal fossa (Mai)

Answer 312

* Expansion of lateral ventricles - first detected at 3-4 weeks of age * Changes in gray and white matter signal intensity due to progressive myelination of the brain * Occur from caudal to rostral in the brainstem * And from central to peripheral in the cerebellum * MRI maturation of the cerebellum and brainstem reached at 4 weeks on T1W images, 6 weeks on T2W and STIR images, 12 weeks on FLAIR images * MRI maturation of the corpus callosum is reached at 6 weeks on T1 images, 8 weeks on T2W and STIR images, and 12 weeks on FLAIR images * Maturation of cerebral gyri and sulci continues after birth, complete by 14 days postpartum * Sequence and time course of gyrification are identical for all breeds studied * Symmetry of gyri is maintained during this development (Mai)

Answer 313

1-3 weeks: white matter isointense or hyperintense to gray matter 3-4 weeks: Isointense transition 16+ weeks: White matter hypointense to gray matter (mature) (Mai)

Answer 314

* 1-4 weeks - juvenile, white matter isointense or hyperintense to gray matter * 4-8 weeks - isointense transition * 16+ weeks - white matter hypointense to gray matter (mature) (Mai)

Answer 315

* 1-2 weeks - White matter hypointense to gray matter (pseudomature) * 3 weeks - 1st isointense transition * 4-6 weeks - White matter hyperintense to gray matter (Juvenile) * 6-12 weeks - 2nd isointense transition * 36 weeks - white matter hypointense to gray matter (mature) (Mai)

Answer 316

a) 1-4 weeks - subcortical white matter is T2 hyperintense to gray matter during the juvenile phase b) 6 weeks - subcortical white matter is isointense during the transition phase c) 8-36 weeks - subcortical white matter is hypointense during maturation phase and into adulthood The relative decrease in white matter intensity is predominantly due to a decrease in water content during myelination (Mai)

Answer 317

Male - larger loss of prefrontal cortex, reduction in white matter tract volume of the optic nerve bundle Female - larger loss of temporal cortex, greater atrophy of hippocampal white matter Male/female - equivalent atrophy of the internal capsule Cerebral atrophy is most pronounced in mesaticephalic and brachycephalic breeds (Mai)

Answer 318

1. Smaller frontal lobe volume 2. Larger A-beta load 3. Smaller interthalamic adhesion (Mai)

Answer 319

Unclear - Hippocampal volume in dogs \> 11 years was significantly smaller than younger animals (study of 66 beagles) No correlation between hippocampus size and age was observed in a study of 19 beagles (Mai)

Answer 320

* Chronic ischemia --\> perivascular demyelination and axonal loss * BBB compromise * Amyloid angiopathy These seem to correspond to age-related white matter changes and leukoariosis originally reported in elderly people, more recently in dogs In people, they are known to contribute to dementia while their significance in dogs is undetermined to date (Mai)

Answer 321

1. Cerebral atrophy with increased ventricular size and widening of sulci (less marked than dog) 2. Small multifocal T2 hypointensity, predominantly in the piriform lobes (Mai)

Answer 322

Increased value of: Intraorbital optic nerve sheath diamteer (measured on transverse T2W images) : body weight (Mai)

Answer 323

Idiopathic oculomotor neuropathy Transverse MR images obtained at the level of the pituitary gland (asterisk, c) in a 6-year-old male neutered Beagle presented with internal ophthalmoplegia and external ophthalmoparesis of the right eye. There is marked enlargement of the right oculomotor nerve with isointensity on T2W (arrow, a), hypointensity on T2-FLAIR (arrow, b), and isointensity on T1W pre-contrast (arrow, c) with marked focal homogeneous enhancement following contrast administration (arrow, d). (Mai)

Answer 324

\*\* most common \*\* Neoplastic: Meningioma, lymphoma, metastatic carcinoma, pituitary tumors, GCT, glial cell tumors, PNET\< retropharyngeal neuroendocrine tumors Trauma Vascular anomalies Infectious - cryptococcosis, FIP (Mai)

Answer 325

Facial neuritis (secondary to otitis media/interna)

Answer 326

Beam hardening artifact After passing through a particularly dense bone (petrous temporal bone) from a variety of angles, the reconstruction algorithm does not allow for the unpredicted increase in energy --\> formation of white and black lines superimposed on the image The reconstruction algorithm falsely interprets the transmitted high energy beam as the result of low attenuation (BSAVA)

Answer 327

1. Shift highly attenuating structures (bones, metal) away from the area of interest (not feasible....) 2. Change slice angle 3. Use high kVp and high filtration to increase the average beam energy (CT PPT)

Answer 328

Normal white matter 25 - 35, normal gray matter 35-50 Immediately: 40 - 60HU (Hematoma forms heterogeneous mass of RBCs + WBCs + platelets + serum) Early hours: 60 - 80HU (Formation of meshwork of fibrin fibrils + globin molecules; clot retraction) Days 80 - 100HU center, hypodense halo (Further clot retraction, serum extrusion, vasogenic edema) Weeks - density decreases 0.7 - 1.5HU/day from the periphery to the center (Breakdown of globin molecules) Weeks/months - Resolution of hematoma or persistence of hypodense area (Digestion of blood degradation products by macrophages) "Acute and subacute hemorrhage is hyperattenuating to the normal brain parenchyma (40 - 100HU) and is readily depicted on CT. Over time, density of intracranial hemorrhage decreases until it becomes hypoattenuating to brain parenchyma" (Hecht)

Answer 329

Myelin = mostly phospholipids (as compared to triglycerides in adipose) Phospholipids - very fast T2 relaxation = ~\*MRI invisible\*~ White matter contains 12% less water than grey matter which makes them T2 hypointense Demyelinating lesions are T2 hyperintense due to increased water (Tidwell)

Answer 330

Time of flight vascular flow-related artifact Transverse T2W (a) and T2\*W gradient echo (b) images of the normal cervical spine in a dog. There is absence of signal within the carotid arteries (solid arrows) and jugular veins (dashed arrows) on the T2W image (a) but high signal on the T2\*W image (b) due to ‘time of flight’ effects. Blood within the ventral vertebral venous sinuses (Mai)

Answer 331

Entry slice phenomenon - vascular flow-related artifact Transverse T1W images of the cranial abdomen showing entry slice phenomenon. Blood flowing into the aorta (solid arrows) is highest in signal in the entry (cranial) slice (a) and is low signal at the exit (caudal) slice (b). The reverse is seen in the caudal vena cava (dashed arrows), where the entry slice is caudal and the exit slice is cranial. (Mai)

Answer 332

Intravoxel dephasing - vascular flow-related artifact Transverse T2\*W gradient-echo images with (a) and without (b) flow compensation of the cervical spine in a French Bulldog with syringomyelia. Without flow compensation (b) there is low signal within the carotid arteries (solid arrows, b) due to intravoxel dephasing. With flow compensation (a), the altered phase shifts of the flowing blood are corrected and the vessels appear higher in signal (solid arrows, a). In addition to correcting for signal changes due to intravoxel dephasing, flow compensation can reduce other flow-related artifacts ( (Mai)

Answer 333

Pulsatility artifact (a type of flow-related artifact) Matched post-contrast transverse T1W images of the canine brain at the level of the thalamus. (a) With the phaseencoding gradient applied in a ventral to dorsal direction, vascular pulsations (dashed arrows) create ghosts superimposed on brain parenchyma (solid arrows). (b) **When the phase-encoding direction is changed** to a horizontal orientation (left to right), the artifact is no longer superimposed on the brain. (Mai)

Answer 334

Pulsatility artifact (a type of flow artifact) Transverse T1W post-contrast (a), T2W (b), and dorsal T1W post-contrast images in a normal 10-year-old Boxer. In (a) a pulsatility artifact originating from the venous sinuses (arrowhead) overlies the cerebellum and appears a curvilinear hyperintensity (solid arrow) on the transverse T1W post-contrast image. Smaller pulsatility artifacts (dashed arrows) are present overlying the digastricus muscles. Pulsatility artifacts occur in the phase-encoding direction, which in this case is right to left. The pseudolesion can be recognized as artifactual as it is not visible on other pulse sequences or imaging planes (b, c). (Mai)

Answer 335

Intensity nonuniformity Transverse T2W image of the brain (a) and sagittal T2W image of the lumbar spine in a dog (b) obtained with a spine surface coil. There is variation in signal intensity across the images with greatest signal intensity in the tissues closest to the coil (circle in a; arrow in b). Filtering of the image (c) to correct for the non-uniformity of signal results in more uniform signal intensity across the image (Mai)

Answer 336

Gibbs artifact (truncation/ringing artifact) Sagittal T2W images in a dog with C4-C5 disc extrusion with images acquired with 302 (a) and 476 (b) phase-encoding steps. The linear T2 hyperintensities (arrows) within the spinal cord, which mimic the central canal, are artifactual and occur due to truncation (Gibbs) artifact. The severity of the artifact can be reduced by increasing resolution in the phase encoding direction. Note that the artifact is reduced with an increased number of phase-encoding steps (b). (Mai)

Answer 337

B₀-sensitive (‘off-resonance’) banding artifact Transverse bFFE image of the cervical spine of a normal dog. The curved black bands (arrows) are due to B0-sensitive banding artifact (Mai)

Answer 338

Chemical shift - misregistration of signal Dorsal T2W images of the normal lumbar spine in a dog showing the effect of frequency-encoding direction on chemical shift artifact. With frequency encoding right to left (a) the artifact is asymmetrical lateral to the spinal cord and lumbar nerves and results in apparent thickening of the meninges and lumbar nerves (arrows). When frequency encoding is craniocaudal, the fat/cord interface is parallel to the direction of frequency-encoding, and the dark bands from the chemical shift artifact are no longer visible, making interpretation easier. (Mai)

Answer 339

Chemical shift - phase cancellation Transverse T2\*W gradient echo images of the lumbar spine of a normal dog acquired in-phase with TE of 13.8 ms (a) and out-of-phase (b) with TE of 20.7 ms showing phase cancellation artifact. The black boundary (arrows, b) along the margins of the bladder and intestines is due to voxels containing fat and water and is most severe in the phase-encoding direction (right to left). (Mai)

Answer 340

Alpha mannosidosis * Reported in Persian, long-hair and shorthair cats * Affected animals present as early as 8 weeks of age * MRI - morphologic/signal intensity changes have not been reported * DWI - increase in ADC values of white and gray matter * T2 mapping - increase in T2 values of white matter - corresponds to neuronal swelling, abnormal myelin, astrogliosis (Mai)

Answer 341

* Widening of cerebral sulci and cerebellar fissures * Ventriculomegaly * Abnormally small corpus callosum * Less common MRI findings include: * Enhancement and thickening of meninges * Subdural hematoma formation * Lack of gray and white distinction on T2W images (Mai)

Answer 342

L-2-hydroxyglutaric aciduria MRI 1. Bilaterally symmetric gray matter abnormalities (polioencephalopathy) affecting the cerebrum, cerebellum, diencephalon, mesencephalon, and metencephalon * T2 hyperintensity and T1 hypointensity of gray matter with no contrast enhancement * Cerebral cortex, thalamus, caudal colliculi, and dorsomedian tegmentum commonly affected * Symmetric changes to gray matter nuclei 2. T2 hyperintensity of peripheral subcortical white matter (Mai)

Answer 343

1. Bilaterally symmetric abnormalities (T2 hyperintensity, T1 iso-or-hypointensity) without evidence of contrast enhancement of various brain and brainstem nuclei 2. Symmetric spinal cord lesions affecting gray matter (same signal characteristics as brain lesions) (Mai)

Answer 344

Significantly higher concentration of glutamine-glutamate complex and significantly lower concentration of myoinositol on magnetic resonance spectroscopy MRI findings: * Brain atrophy * Bilaterally symmetric T2 hyperintensity of the lentiform nuclei attributed to increased concentration of manganese * This decreases with treatment of the underlying cause * Bilaterally extensive T2 hyperintense lesions along the cerebral cortex (Mai)

Answer 345

Dogs: 1. T2/FLAIR hyperintensity and contrast-enhancement in: * Red nuclei * Caudal colliculi * Vestibular nuclei of the brainstem * Cerebellar nodulus 2. T2 hyperintensity in the: * Caudate nuclei * Rostral colliculi Cats: 1. T2, FLAIR hyperintensity in the: * Lateral geniculate nuclei * Caudal colliculi * Periaqueductal gray matter * Medial vestibular nuclei * Cerebellar nodulus * Facial nuclei 2. T1 hyperintensity of the: * Caudal colliculi * Medial vestibular nuclei * Facial nucleus Abnormalities improve with thiamine supplementation (Mai)

Answer 346

1. Bilaterally symmetric, T2/FLAIR hyperintense, nonenhancing lesions of the: * Thalamus * Caudate nuclei * Cerebrocortical gray-white matter junction (Mai)

Answer 347

Bilaterally symmetric lesions in the caudate nuclei * Strongly hyperintense on T2W and T2 FLAIR images * Hyperintense rim with a hypointense center on T2WI images * No evidence of contrast enhancement * Improvement of lesions after treatment (Mai)

Answer 348

1. Bilaterally symmetric abnormalities mostly affecting gray matter 2. T2 hyperintense lesions in the thalamus, mesencephalon, pons, caudal cerebellar peduncle, and interposital nuclei Signs improvement with supplementation (Mai)

Answer 349

1. Normal MRI 2. Progressive, generalized brain atrophy (Mai)

Answer 350

* Bilaterally symmetric, T2/T2\*/T2FLAIR hyperintense, T1 isointense, and nonenhancing intra-axial lesions in the pyramids and ventral aspect of the crus cerebri (Mai)

Radiology Flashcards

(382 cards)