Radiology Flashcards
(303 cards)
1
Q
Outline how you would interpret a chest XR.
A
DRIPE ABCDE
Details/ Date and time
Rotation
Inspiration
Projection (often PA)
Exposure
Airways (trachea, carina, bronchi, hilar, diaphragm)
Breathing (lungs and pleura)
Circulation (heart size and borders)
Disability (bones)
Everything else
2
Q
What is the width of the carina supposed to be?
A
<100 degrees
3
Q
How many ribs should be able to be counted posteriorly?
A
10 posterior ribs bilaterally
4
Q
Outline how you would review the airways in a CXR.
A
Trace down the trachea, check trachea is straight and narrow
Check the carina bifurcates at <100 degrees
Check for foreign bodies/obstructions
5
Q
Outline how you would do the ‘B’ section of a CXR.
A
Check both lungs are expanded and symmetrical in all 3 zones
Can you see posterior 10 ribs
Check density
Check lung vessels branch out progressively and uniformly
Check costophrenic angles
Check hemidiaphragms
Check cardiac borders
6
Q
Outline circulation in a CXR.
A
Check position (1/3 R: 2/3 L)
Check size (CTR <50%)
Check the aortic arch and pulmonary trunk
Check mediastinal width
Look at hilar vessels
7
Q
Outline how you would assess Disability in a CXR.
A
Check each posterior (horizontal) rib on one side of chest, compare to other side
Check each lateral and anterior rib on both sides
Check clavicles and shoulders
Check vertebral bodies (pedicles x2 and disc spaces)
8
Q
What else is there to check in ‘everything’ in a CXR?
A
Pneumoperitoneum
Subcutaneous emphysema
Gastric bubble
Hiatus hernia
Surgical clips
Check lung apices
Retrocardiac/retrodiaphragmatic pathology
9
Q
What is Falciform ligament sign?
A
Aka Silver sign - falciform ligament outlined in a large pneumoperitoneum
10
Q
What is football sign?
A
Massive pneumoperitoneum where abdominal cavity outlined by gas from perforated viscus
11
Q
Give 3 potential causes of Football Sign
A
Bowel obstruction with secondary perforation
Volvulus
Hirschsprung disease
Meconium ileus
Intestinal atresia
Iatrogenic (endoscopic perforation)
Trauma
12
Q
What is Rigler sign?
A
Double-wall sign - sign of pneumoperitoneum on AXR when gas outlining both sides of bowel wall
Seen in a large pneumoperitoneum (>1000mL)
13
Q
What are the 5 basic densities?
A
Air
Fat
Fluid
Bones
Metal
14
Q
What two forms of X-ray generation are there?
A
1) Characteristic X Ray generation: electron fired fast into W anode with electron ejected and outer shell electron replacing inner electron with loss of energy emitted as a photon
2) Bremsstrahlung (braking radiation): electron fired near nucleus which slows down and deflected with energy lost, emitted as a bremsstrahlung X-ray photon
15
Q
How do X rays travel?
A
X-rays travel in straight lines with body parts further away from the detector magnified as these are struck first.
Area closer to the detector is least magnified
Object in patient struck first is magnified most.
16
Q
How might you use magnification in an X-Ray to your advantage?
A
If someone had a pathology in the right side of the posterior mediastinum, below the level of the diaphragm, can take a left lateral image which magnifies the right ribs, displacing them posteriorly and revealing the previously hidden pathology
17
Q
The denser the tissue, the more the X-ray beam is…
A
Attenuated
18
Q
What are the 5 X-ray densities?
A
Air
Fat
Soft tissue
Bone
Metal
19
Q
What is the average radiation dose per person in the UK?
A
2.6mSv per year (2.2 is background, 0.4 is medical exposure)
20
Q
What is the dose of radiation involved in a chest X-Ray?
A
0.02mSv
21
Q
What is the amount of radiation involved in a CT-abdomen?
A
10mSv (=4.5 years of background radiation)
22
Q
What is the inverse square law?
A
Strength of the X-ray beam is inversely proportional to the square of the distance from the source (X).
Thus, increase distance = reduced intensity
23
Q
What is the density of a CT image measured in?
A
Density of each pixel measured in Hounsfield Units (HU)
Air is -1000 HU, water is 0 HU and bone is 500 HU
24
Q
What is ‘windowing’?
A
Windowing is the range of Hounsfield units included in a study thus may allow identification of different pathologies without having to re-image the patient.
25
How are tissue densities described in US?
Based on echogenicity, derived from high-frequency sound waves penetrating tissue and bouncing back internal structures, with echogenicity determined by how much should is reflected.
Bone = hyperechoic (shows as white)
Fluid = hypoechoic (shows as black)
26
How does MRI work?
MRI manipulated energy of a proton (hydrogen nuclei) with positive charge and makes protons align with own magnetic field, releasing energy to be collected and turned into an image
27
What are the indications for a CT head?
Altered mental status
Head trauma (penetrating trauma/GCS <13/ GCS<15 2 hours/ vomiting 2+ times/focal neurological deficit)
CSF leak
Headache (thunderclap/papilloedema/deficit/cancer/known triggers e.g position, sex, activity)
Dangerous mechanism of injury
Amnesia (lasting more than 5 minutes)
Loss of consciousness (lasting more than 5 minutes)
28
When might you want a contrast-enhanced CT?
Suspicion of:
Brain metastases
Meningioma
Brain abscesses
Meningitis
Multiple sclerosis
Lymphoma
29
What are the indications for an MRI head?
Confirmation of intracranial tumour
Chronic headache
Seizure disorder
Focal neurological deficit (MS?)
30
What are the benefits of an MRI head?
No radiation
Multiplayer assessment of brain
Detailed images of the brain
Different sequences allow assessment of different pathology
31
What are the limitations of MRI head?
Longer (20-40 minutes)
Less available
Patients may be claustrophobic
32
How are MRI images described?
Described by signal intensity - hyper intense or hypo intense
33
What is the difference between T1 and T2 imaging?
T1 timing of radiofrequency pulse sequences highlight fat tissue within the body
T2 timing of radiofrequency pulse sequences highlight fat AND water within the body
T1 = 1 tissue type bright = fat
T2 = 2 tissue types bright = fat and water
34
What are the two types of relaxation occurring following radiofrequency impulses in MRI?
Realignment of protons with magnetic field
Dephasing of spinning protons (loss of resonance)
T1 correlates to speed of realignment
T2 correlates to speed of proton spin dephasing
35
What is midline shift?
Finding observed in axial slices when midline of intracranial anatomy has shifted due to pushing/pulling forces either side of the intracranial compartment
36
What is mass effect?
Effect of a tumour on the surrounding brain
A lesion within the skull will compress and/or displace adjacent structures
37
What may cause mass effect?
Tumours
Cerebral abscess
Infarction/oedema
Haemorrhage
38
What is hydrocephalus?
Intracranial ventricular system enlarged due to increased pressure
May be obstructed CSF flow or increased CSF
39
What radiographic feature is shown in hydrocephalus?
Midline shift/mass effect
Dilatation of ventricular system - lateral ventricles dilate first
40
What is a brain mass lesion?
Umbrella term for pathological processes changing the brain when imaged
These may range from an abscess to a brain tumour.
41
What is cerebral oedema?
Additional fluid within the brain parenchyma as a response to injury
Takes two forms:
Vasogenic (white matter, surrounds a mass - abscess/tumour)
Cytotoxic (grey and white matter, ischaemia/infarction)
42
How would cerebral oedema appear in T2 images?
High signal on T2-weighted images (MRI)
43
What is an intracranial haemorrhage?
Bleeding within intracranial cavity including intra-axial and extra-axial haemorrhage
44
What are the radiographic features of an intracranial haemorrhage?
Acute haemorrhage is hyper dense on CT
Chronic blood approaches density of CSF thus density decreases
Sizeable haemorrhage may cause mass effect and midline shift
45
What is an extra-axial collection?
Collection of fluid within the skull, outside the brain
May be CSF, blood or pus and may exist in the extradural, subdural or subarachnoid space.
46
What is a Hounsfield unit?
Dimensionless unit used in CT, deduced from a linear transformation of measured attenuation coefficients
Transformation based on arbitrarily assigned densities of air and pure water
Water = 0HU
Air = -1000HU
at STP
47
What is STP?
Standard temperature (=0 degrees) and pressure (10^5)
48
What is the spectrum of hounsfield units?
air = -1000 HU
water = 0
very dense bone = +2000 HU
49
What is STIR imaging?
Short Tau Inversion Recovery - highly water sensitive and timing of pulse sequence acts to suppress signal from fatty tissues thus only water is bright
50
What approach would you use to interpret an MRI?
Details
Planes (MRI): axial; coronal; sagittal; oblique
Sequences (MRI): T1 and compare to other sequences
Abnormalities: Use DSCAM - distribution; shape; colour (intensity); associated changes; morphology)
Clinical question: relate findings to original question
51
What are the two types of relaxation of a proton following radiofrequency pulses?
Realignment (of protons with magnetic field)
Dephasing (loss of resonance)
52
Which form of proton relaxation predominantly relates to T1 signal?
T1 signal relates to the speed of realignment with the magnetic field
Greater speed of realignment = higher T1 signal
T1 = fat
53
Which form of proton relaxation is related to T2 signal?
T2 signal is related to the speed of proton spin dephasing - the slower the dephasing, the greater the T2 signal
54
What specialised MRI sequences are there? Name one
STIR image (Short Tau Inversion Recovery)
FLAIR (Fluid Attenuation Inversion Recovery)
T2* (gradient echo)
DWI (Diffusion Weighted images)
55
What is a STIR image?
Short Tau Inversion Recovery is where signal is suppressed from fatty tissues in T1 thus water will appear bright
Abnormal low signal in T1 but high in STIR = fluid
56
What is a FLAIR image?
Fluid attenuation inversion recovery
This is where free fluid suppressed and compared with the T2 image thus high signal on T2 suppressed and still high on FLAIR, suggests a lesion e.g. Demyelination
57
What is T2* (gradient echo) images?
Highlights the presence of blood
58
What is DWI?
Diffusion weighted images - increased signal means reduced diffusion (in DWI) which suggests cell death
Possibilities may be infarction, cancer, abscess
59
What is contrast used for?
May enhance a lesion if more vascular; do pre and post-contrast to compare
60
How may you determine where an extra-axial collection is?
Determine location by...
Subarachnoid - extends into sulci and into basal cisterns
Subdural - crescentic (banana)
Extradural - lens-like (egg)
61
What shape is produced by an extradural haemorrhage?
convex shape
62
What is the best initial investigation for a suspected extradural haemorrhage?
CT head non-contrast
63
Why do extradural haematomas have such a classical shape?
Dura tightly adheres to intracranial bony sutures therefore does not travel between and cross suture lines
64
What is a subdural haemorrhage?
Collection of blood between the dura and arachnoid layers of the meninges - usually related to head trauma.
A subdural haemorrhage moves freely in the cranial cavity hence the crescentic shape
65
What is the shape of a subdural haemorrhage?
Crescentic
66
How may a subdural haemorrhage present?
Head injury
Vascular malformations
Confusion
67
What is the best initial investigation for a suspected extra-axial haemorrhage?
Non-contrast CT head
68
What is the presentation of a SAH?
Headache - thunderclap
Neck stiffness
Confusion
Reduced consciousness
69
What radiographic features might be seen on a CT non-contrast?
Hyperdense (bright) on CT
blood in basal cisterns and sulci
CT angiogram should identify and characterise any aneurysm
70
What is the gold standard test to assess the extent of an aneurysm in a SAH?
DSA (digital subtraction angiography)
Allows better visualisation of blood vessels by acquiring a mask image (image of the same area pre-contrast). Same area has images produced at a set rate, with the subsequent image getting the mask image subtracted out. Smaller structures require less contrast to fill the vessel than others thus images appear in the presence of a very pale grey background which produces a high contrast to blood vessels (appearing dark grey)
71
What is the most important MRI sequence in a stroke?
DWI - diffusion restriction is highly sensitive for ischaemia
72
Should a patient present with Broca's aphasia, where is the occlusion?
MCA, superior division
Superior division supplies the frontal lobe which is most likely affected in Broca's aphasia.
73
Which cancers are most likely to metastasise to brain?
Lung
Breast
Melanoma
Renal cell
Colorectal
74
What is the initial test in a suspicion of an intracranial mass?
CT head - pre and post-contrast
75
What is a cerebral abscess?
Focal area of infection within brain parenchyma usually containing pus and having a thick capsule
76
What is the role of imaging in a brain abscess?
Diagnostic
Assess mass-effect and other lesions
Surgical/MDT plan
77
What are the radiographic features of a brain abscess?
CT is first line - low density lesion with peripheral enhancement; surrounding low-density white-matter oedema
MRI is more sensitive with pus being bright on T2 image; wall of abscess will increase in signal following contrast; DWI may provide diagnostic clarity
78
What is the gold-standard investigation for suspected Multiple Sclerosis?
MRI
79
Which MRI sequence best reveals MS?
Fluid-sensitive sequence e.g. T2, FLAIR
80
What is the first line investigation for a suspected skull fracture?
CT head
81
A young adult male, previously well, dove into a shallow pool striking their head on the bottom. They were brought to the emergency department and underwent the non-contrast CT shown...
This shows a vertex extradural haematoma
What does this abnormality represent?
Extradural haematoma due to venous bleeding
Damage to superior sagittal sinus and associated with diastasis of sagittal suture with/without concurrent skull fracture
Thus, this extradural haematoma can cross a suture line
82
What is the vertebral level of the conus medullaris?
L1
83
What is the pathophysiology involved in a spinal cord compression?
Mechanical (herniation; fractures)
Malignancy (primary or secondary metastasis)
Infection (discitis; epidural abscesses)
84
What is the gold-standard investigation in a suspected spinal cord compression?
MRI whole spine
85
What are the two divisions of traumatic brain injury by aetiology?
Closed head injury (blunt trauma/blast/NAI)
Penetrating head injury (high-velocity injury/low-velocity injury)
86
Which group of patients account for the majority of traumatic brain injuries?
75% are males, more common in young patients
87
How may a patient present with a traumatic brain injury?
N/V
Confusion
GCS 14-15 = mild
GCS 9-13 = moderate
GCS 3-8 = severe
88
Outline the Ottawa CT head injury rules.
GCS <15 2 hours post-injury
GCS <13
?Skull fracture
2+ episodes vomiting
Age ≥65
Retrograde amnesia ≥30 minutes
Dangerous mechanism
89
How may you classify a skull fracture?
Anatomical (base of skull vs skull vault)
Open vs Closed
Displaced vs non-displaced
Fracture type (linear vs comminuted)
90
What is the best form of imaging modality for a suspected skull fracture?
CT head - sensitive to detection of fractures
91
How will a skull fracture appear on CT-head?
Appear as a discontinuity - may be displaced or non-displaced.
Must be distinguished from suture lines - fractures do not have corticated margins
Furthermore, fractures may be accompanied by fluid collection, surrounding soft tissue swelling
92
What are the red flags of a headache?
Positional change/Early morning
N/V
Photophobia
Neck stiffness
Temporal artery tenderness
Facial neurological deficit
New headache in ≥50 years old
93
What investigations should be conducted prior to
Cranial nerve examination
Fundoscopy
Visual field assessment
Obs
Bloods
94
What are Dawson's fingers?
White matter changes seen near the ventricles. Usually perpendicular or in a radial distribution.
Phenomenon seen in MS
95
What criteria is used to diagnose MS?
McDonald criteria - dissemination in time and space
96
Which areas are common areas to check for contusions on CT head?
Areas contacting bone at most risk
Anterior horns of temporal lobes almost encased in bone between anterior and middle cranial fossae
97
What are the predominant symptoms of cauda equina syndrome?
Saddle paraesthesia
Bilateral leg weakness
Bladder/bowel/sexual dysfunction
98
What is the best imaging modality for suspected CES?
MRI whole spine
99
Where should an ETT sit in the trachea?
3-5cm
100
What shape should the AP window be on a CXR?
Concave
101
What is silhouette sign?
Two adjacent structures with same density thus loss of normal cardiac silhouette
"loss of silhouette sign"
102
Loss of normal silhouette at the right paratracheal stripe indicates pathology at?
Right upper lobe
103
Loss of normal silhouette at the left paratracheal stripe indicates pathology at?
Left upper lobe
104
Loss of normal silhouette at the right hemidiaphragm indicates pathology at?
right lower lobe
105
Loss of normal silhouette at the left hemidiaphragm indicates pathology at?
Left lower lobe
106
Loss of normal silhouette at the aortic knuckle indicates pathology at?
Left upper lobe
107
Loss of normal silhouette at the right heart border indicates pathology at?
right middle lobe or medial right lower lobe
108
Loss of normal silhouette at the left hemidiaphragm indicates pathology at?
Left lower lobe
109
Loss of normal silhouette on a lateral CXR at the anterior right hemidiaphragm indicates pathology at?
right middle lobe
110
Loss of normal silhouette on a lateral CXR at the posterior right hemidiaphragm indicates pathology at?
right lower lobe
111
What is an air brocnhogram?
Visible bronchioles due to air in bronchioles surrounded by consolidation which results in bronchioles appearing as a translucent tube against hazy opacity
112
What is deep sulcus sign?
Air in pleural space from a pneumothorax collects in locations such as apices if WB or bases
113
What is continuous diaphragm sign?
Chest radiograph sign of free air in the thorax or peritoneum.
May be pneumomediastinum or pneumopericardium if lucency above diaphragm
May be pneumoperitoneum if lucency is below the diaphragm
114
What is the most common accessory fissure?
Azygous fissure is the most common accessory fissure (2% of individuals)
115
What is the point at which the diaphragm meets the heart on XR?
Cardiophrenic angles
116
What is the difference between the costophrenic angle and costophrenic recess?
Costophrenic recess is the area prior to the angle which is the sharp point inferior to the recess
117
How do you calculate CTR?
Cardiac width / Thoracic width
Should be less than 50%
118
What mediastinal contours should you be aware of on CXR?
Aortic knuckle
Left PA
AP window (should be concave)
Paratracheal stripes
119
How many ribs on an AP CXR suggests hyperinflation?
>7 ribs
120
What is the Ginkgo leaf sign?
Surgical emphysema whereby subcutaneous air outlines fibres of pec major
121
What is Chilaiditi's sign?
Interposition of the bowel, usually colon, between the inferior surface of the right hemidiaphragm and the superior surface of the liver.
122
Outline how you would interpret an AXR.
ABDO X
Details: Patient; Data; Indication; Other views/imaging modalities
Air (check for air)
Bowel (position; structure; size)
3:6:9 rule
Densities (examine all bones)
Organs (all organs that can be seen)
eXtra objects
123
When may hepatomegaly be inferred on AXR?
Extension of right lobe inferior to lobe of right kidney
124
When looking for air in the abdomen in an AXR, what should be checked?
Diaphragm
Wall of bowel
Falciform ligament (outlined by gas?)
Liver look less lucent?
125
What is Cupola sign?
Radiographic feature seen in Pneumoperitoneum on AXR in a supine patient whereby air accumulates underneath central tendon of diaphragm in midline
Lucency seen over lower thoracic vertebral bodies
126
What is Doge cap sign?
Sign of pneumoperitoneum seen on AXR as triangular-shaped gas lucency in the RUQ (Morison's pouch; Hepato-renal fossa)
Also called Morrison's pouch sign
127
What is air space opacification?
Descriptive term for filling of lung parenchyma with material attenuating XR more than unaffected tissue. Radiological correlate of pulmonary consolidation
128
What are the distributions of air-space opacification?
Patchy (non-contiguous)
Lobar (fills a lobe)
Multifocal (multiple points/areas)
- Symmetrical vs asymmetrical
- Perihilar vs Peripheral
129
What is atelectasis?
Area of lung collapse
130
What may cause atelectasis?
Direct compression (tumour; aneurysm; osteophyte; consolidation)
Passive (lung relaxes from parietal pleura - pleural effusion; pneumothorax)
Dependent (posterior regions where patients not fully expanding lungs whilst lying for long periods)
131
How does atelectasis usually appear?
Small volume linear shadows
May also be able to see the cause
132
what is an air bronchogram?
Gas-filled bronchi surrounded by alveoli filled with fluid/pus/debris (air-space opacification)
133
What is a pneumothorax?
Air in the pleural space
134
What radiographic sign may show pneumothorax?
Region of radiolucency on CXR/AXR
Lung margins observed
135
What is the criteria for a large vs small pneumothorax?
>2cm = large
<2cm = small
136
Which artefacts may mimic a pneumothorax?
Skin fold artefact (apparent pleural edge is darker cf true pneumothorax which is white)
Clothing
Blankets
Oxygen bags/masks
Pulmonary bullae
Air in other locations (pneumomediastinum; pneumopericardium)
137
What may accumulate in the pleura?
Air
Fluid (blood/pus/simple fluid)
138
What are the two types of simple pleural fluid which may accumulate in the pleural space?
Pleural effusion may be exudate (high protein) or low protein (transudate)
139
Give 3 causes of a pleural effusion.
Lung cancer
Pneumonia
Rheumatoid
TB
140
Give 3 causes of a transudative pleural effusion.
CCF
Hypoalbuminaemia
Hypothyroidism
Meig's syndrome
141
What radiographic features may be seen in a CXR with pleural effusion?
Unilateral air-space opacification - usually basal
Blunted costophrenic angles
142
In what CXR view can heart size be assessed accurately?
PA
143
What method can be used to assess for an increased cardiothoracic ratio?
Measure heart at widest point
Measure thorax at widest point
CTR > 50% = increased cardiothoracic ratio
144
What is pneumomediastinum?
Air within the mediastinum
145
What is surgical emphysema?
Air/gas located in subcutaneous tissues
146
What radiographic features may be seen on CXR in pneumonia?
Air space opacification
Air bronchograms
Complications: cavitation; pleural collections
147
What may cause lobar collapse?
Inflammation
Infection
Neoplasm
Iatrogenic
Mechanical
148
What are the radiographic features of a lobar collapse on CXR?
Complete collapse of lobe with structures into different places due to volume loss
Mediastinal shift
Increased lung density thus radio-opaque
149
What is pulmonary oedema?
Accumulation of fluid in the extravascular compartments of the lung
150
What are the radiographic features of heart failure on CXR?
ABCDE
Alveolar opacification
Batwing sign (bilateral perihilar lung shadowing)
Cardiomegaly
Diffuse interstitial thickening/Upper lobe diversion
Effusion (pleural)
151
What are the three main features of a pneumothorax on CXR?
Peripheral lucency
Visible lung edge
Absence of lung markings peripheral to lung edge
152
What are the radiographic features of a tension pneumothorax on CXR?
Relative lucency of entire hemithorax
Mass effect on ribs, diaphragm and mediastinum - increased rib spacing and depression of the diaphragm to the contralateral side of the chest
153
What are the radiographic features of a pleural effusion on CXR?
Opacification with meniscus at the costophrenic angles
Lung collapse (if large)
Mediastinal shift potentially
154
What radiographic signs may be observed on CXR in COPD?
Flattened diaphragm due to hyper expansion
Increased lung lucency due to parenchymal loss
Decreased peripheral bronchovascular markings
Bulla
Prominence of hilar vessels (in pulmonary hypertension
155
What types of emphysema may you see when conducting a CT-Chest?
Categorised by pattern and extent of emphysema.
Centrilobular (most common) - destruction of parenchyma around terminal bronchiole (which is centre of secondary pulmonary lobule)
Panlobular (A1AT deficiency) -affects all areas of lung lobule
Paraseptal emphysema - emphysema lesions in parenchyma adjacent to pleural surfaces
156
What radiographic signs may be seen in an asthma patient on CXR?
Non-specific
May be normal
Possible to see bronchial wall thickening and hyperinflation
CT can show stuff if ABPA, eosinophilic pneumonia or vasculitis
157
What radiographic features may be seen on CXR in a PE?
Used to look for alternative causes for symptoms
Westermark sign (sharp pulmonary vessel with distal hypoperfusion)
Hampton hump (shallow wedge-shaped opacity in lung periphery)
158
What radiographic signs are present in a lung cancer on CXR?
Enlarged focal lesion
Widened mediastinum
Pleural effusion
Atelectasis
Opacification
159
Which radiographic features are present in mesothelioma on CXR?
Opacification in lateral aspect
White out appearance with trachea shifting potentially
Pleural effusion and mediastinal lymphodenopathy may be seen
160
What is the hallmark feature of bronchiectasis on CXR?
Tram-track sign (dilated bronchi with thickened walls)
161
What is the hallmark feature of bronchiectasis on CT-Chest?
Signet ring sign (enlarged airway with accompanying pulmonary artery)
162
What radiographic features may be present in TB on CXR?
Consolidation
Lymphadenopathy
Pleural effusion
Cavitation
Ghon complex (caseating granuloma)
163
What is Nutcracker syndrome?
Rare vein compression disorder whereby abdominal aorta and SMA squeeze Left Renal Vein - may cause renal symptoms such as flank pain and haematuria
164
What is SMA syndrome?
Duodenum compressed by SMA against abdominal aorta causing blockage and prevention of food into distal SI
165
What is pelvic congestion syndrome?
Condition of chronic pain due to enlarged veins in the lower abdomen
This is caused by venous outflow obstruction
Causes may be:
- Tumour
- Fibroids
- Endometriosis
- Budd-Chiari Syndrome
- Nutcracker Syndrome
- May-Turner Syndrome (iliac vein compression syndrome)
166
What is May-Turner Syndrome?
Compression of common venous outflow of left lower extremity in the iliofemoral veins (left common iliac vein compression by overlying Right common iliac artery)
Blood stasis occurs which predisposes to blood clots (hypercoagulability)
167
What is a sabre sheath trachea?
Diffuse coronal narrowing of intrathoracic portion of trachea with widening of sagittal diameter
Seen in COPD
- Reduced coronal diameter of intrathoracic trachea
- Increased sagittal diameter
168
What differences may an AP film produce in a CXR?
enhanced cardiac shadow
higher diaphragm
reduced lung volumes
169
How is a 3DCT constructed?
CT slices are stacked up as a reformation and provides a 3D image which gives position and orientation of the fracture
170
How does ultrasound work?
Probe directs beam of high-frequency sound waves into the body and measures the manner in which sound is reflected back to the transducer from organs and their interfaces
171
What is acoustic impedance in US?
Degree of which US is reflected back by different tissues with varying physical density of the tissue and the subsequent velocity of the sound
172
How do you calculate acoustic impedance?
Z = pV
Z = acoustic impedance
p = density
V = acoustic velocity
173
What are the benefits of US?
Cheap
Quick
Bedside
Internal
Multiple planes
174
What is the unit of measurement to define magnetic flux density?
Tesla
1 Tesla = 10,000 Gauss
175
What is relaxation time?
Time taken for hydrogen atoms to regain equilibrium state following radiofrequency wave pulsation
176
What are the main differences between T1 and T2 regarding echo time and repetition time?
Repetition time is the time taken between RF pulses
Echo time is the time taken between RF pulses exciting hydrogen atoms and the arrival of return signal at the detector
T2 has longer TR and TE cf T1 has shorter TR and TE
177
How does nuclear imaging work?
Radionuclide (radioactive isotope) injected into body which is labelled to a substance involved in metabolism of the organ/cancer thus remains their to be imaged.
Radionuclide emits gamma rays which are recorded by a gamma camera for a period of time
178
How does PET scanning work?
Positron-producing isotope administered, combined with substance (e.g. glucose) travelling to target organ
Radioactive substance decays, producing positive electrons (positrons) which travel 1-2mm prior to colliding with an electron which results in conversion from mass to energy releasing two gamma rays in opposite directions.
Gamma rays are detected within the ring-shaped PET scanner and a computer produces an image of where radioactive substance has accumulated
179
What may create a false negative in PET scanning?
Raised serum glucose
Some cancer types (RCC; BAC; NHL; mucinous GI tumours)
180
What may cause a false positive in a PET scan?
Patient discomfort + anxiety
Talking
Injected clot
Injected artefact
Sites of high physiological uptake (renal, spleen, liver, GI, salivary glands)
Uterine/ovarian uptake in a cyclical manner (premenopausal)
Infection
Sarcoidosis (autoimmune conditions)
Flare phenomenon
Osteonecrosis
Malunion fractures
Post-operative
Radiation pneumonitis
181
What is meant by the interspace?
Space between posterior segments of adjoining ribs (unless anterior specified)
182
How can you easily identify the first rib on CXR?
Find manubriosternal angle and trace back posteriorly
183
How do you check for rotation on a CXR?
Look at distance between clavicles and spinous process
184
When increasing the penetration of deep structures by increasing exposure, what method may be used to reduce scattered radiation?
Bucky grid
185
How does a bucky grid work to reduce scattered radiation?
Alternating beam of strips with varied radiolucent and radio-opaque material.
When X-rays are perpendicular, the rays pass through radiolucent portions fine but when oblique rays strike radio-opaque regions, these are absorbed thus reduced scattered radiation and reduced blackening of the film
186
What is a Bq?
Becquerel is the measurement of radioactivity
One disintegration per second
187
Which lung hilum is typically higher and why?
Left hilum is higher than the right hilum due to the LPA arching over the left main bronchus
188
In a patient with COPD with a suspected pneumothorax, what investigation should be ordered and why?
Must order a CT-Chest in addition to CXR in case 'pneumothorax' is an emphysematous bullae - chest drain of a bullae may cause lung collapse
189
How many lobes does the right lung have?
3
190
What are the bronchopulmonary segments of the right lung?
Superior lobe: 3
Apical, posterior, anterior
Middle lobe: 2
Medial and lateral
Inferior lobe: 5
Superior; lateral basal, medial basal; posterior basal; anterior basal
Mnemonic: A PALM Seed Makes Another Little Palm
191
How many bronchopulmonary segments are present in the left lung?
8 bronchopulmonary segments
Superior lobe: 4
Anterior; apical posterior; superior (lingula); inferior (lingula)
Inferior lobe: 4
Superior; Posterior basal; Anteromedial basal; Lateral basal
Mnemonic: ASIA ALPS
192
What are the indications for carotid stenting?
Symptomatic with >50% stenosis
193
What might the contraindications of carotid stenting be?
Complete occlusion
Major disabling stroke on same side
ICH/SOL
Unstable plaque
Extremely tortuous vessel
194
What are the complications of carotid stent insertion?
CVA
Hyperperfusion syndrome
195
How is an intra-aortic balloon pump inserted?
Inserted via femoral artery, extend retrogradely to proximal descending thoracic aorta.
Inflate the end of the balloon at diastole and deflate at end of diastole thus provide forward momentum to blood in distal descending aorta but also increased perfusion to vessels arising from aortic arch and ascending aorta
196
What are the two main physiological functions of an intra-aortic balloon pump?
Reduces LV afterload through a vacuum effect (pushed blood further along descending aorta)
Increases myocardial perfusion (whilst reducing myocardial oxygen requirements)
197
Where should the intra-aortic balloon pump be located in the arterial system?
Proximal descending aorta
Just inferior to the origin of the Left Subclavian artery (level of the AP window)
198
What complications may occur with insertion of an intra-aortic balloon pump?
Malpositioning: aortic dissection; too high thus obstructing LSCA; too low thus obstructing splanchnic arteries
Functioning: platelet/RBC destruction; distal embolisation
199
What is endocrine venous sampling?
Sampling venous blood from specific endocrine organs used for diagnostic purposes
200
What is inferior petrosal sinus sampling?
Evaluate for ACTH-secreting pituitary adenoma
201
What is adrenal venous sampling?
Sampling venous blood for identification of primary aldosteronism (Conn syndrome) or Bilateral adrenal hyperplasia
202
Which organs may endocrine venous sampling be used in?
Inferior petrosal sinus sampling (ACTH)
Selective venous sampling for primary hyperparathyroidism
Pancreas
Adrenal venous sampling
Ovarian venous sampling
203
Why would you perform a CT-guided thoracic biopsy?
Diagnose suspicious lung, pleural or mediastinal lesions
204
What are the indications for a CT-thoracic biopsy?
Pulmonary lesion inaccessible to bronchoscopy
Mediastinal/pleural mass
205
What are the contraindications to a CT-guided thoracic biopsy?
Poor respiratory function/reserve
Uncooperative patient
Lack of safe access
Uncorrectable bleeding diathesis (disease)
206
How is a CT-biopsy procedure conducted?
Complete blood count: platelets >50 000/mm^3
Coagulation profile: INR ≤1.5; normal PT and PTT
207
How is a CT-guided biopsy procedure conducted?
Pre-procedure evaluation:
- Complete blood count (platelets >50,000/mm3)
- Coagulation profile (INR, PT, PTT)
- Review diagnostic CT (check relation to structures - vessels, bleb, bullae, central bronchi, fissures)
Positioning (decubitus preferred - limits respiratory motion, minimises local aeration, comfortable)
Biopsy:
- Radiopaque marker utilised to focus optimal access point, mark this with a pen
- Antiseptic and anaesthetic
- Incision (skin orifice made)
- Biopsy needle introduced
- Activate biopsy gun
Post-procedure care:
- XR (4 hours post-procedure)
- Monitoring
- Document procedure appropriately
208
What are the benefits of a decubitus position for a CT-guided lung biopsy?
Reduced respiratory motion
Comfort
Minimises local aeration (reduces pneumothoraces)
209
What are the complications of CT-guided lung biopsy?
Pneumothorax (8-64%)
Alveolar haemorrhage (5-16.9%)
Air embolism (0.2%)
210
How does a preoperative pulmonary nodule localisation work?
CT-guided procedure where marker applied to small lung lesion to assist in surgical identification and resection
Preprocedural evaluation:
- Platelets
- INR/PT/APTT
- Positioning
- Confirm CT
- Introduce marker (metalic/methylene blue/Tc99m/indocyanine green)
211
What is a thoracentesis?
Pleural tap (chest drain) - pleural fluid drained from pleural space for diagnostic ± therapeutic reasons
212
What are the indications for a thoracentesis?
Symptomatic pleural effusion
Investigation of cause of pleural effusion
213
How may you determine a pleural effusion is exudative or transudative?
Determine protein content of the pleural fluid
>3g/dL = exudative
<3g/dL = transudative
214
What are some exudative causes of pleural effusion?
Lung Ca
Pneumonia
Rheumatoid
TB
215
What are some transudative causes of pleural effusion?
CCF
Hypoalbuminaemia
Hypothyroidism
Meig's syndrome
216
Outline the procedure for a US-guided thoracentesis.
Note: May be performed blindly, US-guided or CT-guided
Pre-procedure evaluation:
- History; indication; pathology; prior imaging
- Bloods: Coagulation profile; blood count
Gather equipment:
- US
- Sterile surgical pack
- Long hypodermic needle, syringe and lidocaine
- Scalpel
- 3 way tap
- Dressings
Position:
- Lean forward
- Monitoring
- Access from behind the patient
Insert drain:
- DON
- Subcutaneous and deep infiltrate of local anaesthetic
- Small skin incision with scalpel
- Introduction of thoracentesis needle under US-guidance; travel along superior margin of rib , aspirating whilst advancing until pleural fluid is aspirated
- Connect 3-way tap and drainage bag with airtight dressing
- 50mL fluid required for diagnostic procedure
Post-procedure care:
- Drain until content (either diagnostic or symptoms reduce)
- CXR to confirm absence of pneumothorax
- Safety net with patient
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What are the potential complications of a thoracentesis?
Pain
Cough
Vasovagal reaction
Re-expansion pulmonary oedema
Pneumothorax
Haemothorax
Iatrogenic damage of viscera
Air embolism
Pleural infection/empyema
Trapped lung (non-expanding lung after fluid removal)
218
What is percutaneous transhepatic cholangiography (PTC)?
Radiographic visualisation of biliary tree and can be used as the primary step in numerous percutaneous biliary intervention e.g. stent placement
219
What are the indications of PTC?
Failed ERCP
Biliary system delineation in presence of intra- and extrahepatic biliary calculi
Identify bile leaks
Percutaneous biliary stent placement
Post-operative stricture dilatation
Stone removal
220
What are the contraindications to PTC?
Bleeding diathesis
Gross ascites
221
How is a PTC conducted?
Preprocedural evaluation:
- History
- Indication
- Previous imaging
- Coagulation profile
- Blood count
Positioning:
- Supine
- Anaesthetic (LA vs GA)
Procedure:
- US-guidance to guide point of entry of needle
- Long two part 22G needle inserted into peripheral duct, observe bile reflux at needle hub or inject contrast to confirm duct puncture on fluoroscopy
- Inject sufficient dye and identify obstructive pathology
- Images taken in PA, RAO and LAO views
Post-procedural care:
- Routine observations
222
What are the potential complications of a PTC?
Bile leakage
Biliary peritonitis
Bleeding
Cholangitis
223
What is a percutaneous transhepatic biliary drainage?
PTCG is an IR procedure done on those with biliary obstruction such as cholangiocarcinoma when ERCP is not amenable
Undertaken as part of palliative biliary stent insertion
224
What is a percutaneous cholecystostomy?
Insertion of a drainage catheter into the gallbladder lumen via image-guidance
225
When is a percutaneous cholecystostomy indicated?
Poor surgical candidate
High risk patients with acute calculous/acalculous cholecystitis
Sepsis of unknown origin in critically ill patients
Access or drainage of biliary tree following failed ERCP/PTC
226
How is a percutaneous cholecystostomy conducted?
Preprocedural evaluation:
- History
- Indication
- Previous imaging
- Coagulation profile; Bloods
- Administer prophylactic broad-spectrum ABX 1-4 hours pre-procedure
- Arrange analgesia and sedation according to local protocols
Positioning and set-up:
- Supine position
- Regular monitoring of vital signs
- Clean skin with antiseptic solution and drape
Equipment:
- US machine
- Sterile US probe cover and US gel
- Local anaesthetic
- Relevant needles, guide wires and catheters
Procedure:
- Clean field
- Place sterile drape
- Anaesthetise patient
- Insert catheter using Trocar or Seldinger technique
- Secure catheter to skin
- Attach gravity drainage bag to catheter
- Send bile for Gram stain, culture and count
Post-procedure care:
- Bed rest
- Observations
- Catheter flushed and aspirated
- Cholecystogram performed to help establish satisfactory catheter position
- Catheter removed once tract is mature (3-4 weeks)
227
What is the Seldinger technique used for percutaneous cholecystostomy?
Gallbladder punctured with 18/19 gauge needle under US-guidance and 0.035 guide wire used to change needle for a dilator and drain placed within gallbladder
Aspiration of bile/pus from drain confirms satisfactory position
228
What is the Trocar technique used in percutaneous cholecystostomy?
Load 8 French locking pigtail catheter over trocar
Advance catheter assembly into Gallbladder lumen under image-guidance
Aspirate bile/pus
Unscrew trocar from catheter and advance catheter over trocar into gallbladder
Remove trocar and lock pigtail
229
What are the complications of a percutaneous cholecystostomy?
Catheter displacement
Bile leakage
Biliary peritonitis
Bleeding
Bowel injury
Bradycardia and hypotension from gallbladder manipulation
230
What are the two types of percutaneous liver biopsy?
Use of US/CT-guided for accurate
Focal (directed to focal parenchymal lesion)
Non-focal (used in assessment/staging of parenchymal lesion)
231
What are the indications for a image-guided liver biopsy?
Cirrhosis
NAFLD (NASH/NAFL)
PBC
Wilson disease
Haemochromatosis
Focal liver lesion assessment
232
What are the contraindications to a liver biopsy?
Uncorrectable bleeding diathesis
Ascites
Extrahepatic biliary obstruction
233
How is a percutaneous liver biopsy undertaken?
Pre-procedure preparation: history; indication; consent; equipment; prior imaging; blood counts
Position patient:
- Supine
- Oblique
- LLD
Procedure:
- Aseptic technique
- Entrance created with scalpel
- Needle advanced under US guidance
- Documentation of needle position prior to firing
- Identify if sufficient material obtained
Post-procedure:
- Documentation of procedure
- Check if patient is ok
- Inspection of the site
- Observations
234
What are the complications of a liver biopsy?
Post-procedural pain
Severe haemorrhage (1%)
Death
235
What are the advantages of US-guided percutaneous drainage?
Dynamic study- controls needle insertion
No exposure to ionising radiation
Does not require wide range of stage
236
What are the disadvantages of US-guided percutaneous drainage?
Poor visualisation of deeper structures
Bowel gas can obscure visualisation
Large patients may attenuate the sound beam
237
What are the indications for a percutaneous drainage?
Diverticular abscess
Crohn's disease related abscess
Appendicular abscess
Hepatic abscess
Renal abscess
Splenic abscess
238
Outline the technique for the procedure of a US-guided percutaneous drainage?
US-guided
May be singe stage (direct entry with catheter) or multiple step
Multiple step requires introducer needle with stiff wire passed then track expanded with dilator and catheter passed over stiff guide wire to penetrate abscess
Locking drain used to secure position and catheter connected to external drainage bag
239
What are the advantages of CT-guided percutaneous drainage?
Access areas poorly visualised on US
Vision not obscured by gas
Better vision in large patients
CT table offers more stable positioning
Better in critically-ill patients (intubated patient can be monitored and positioned better)
240
What are the disadvantages of CT-guided percutaneous drainage in a patient?
Not truly dynamic like US
Exposes patient to ionising radiation
Wider range of staff required
Harder in uncooperative patient
241
Which vessels are connected in a TIPS?
Direct communication formed between hepatic vein and portal vein allowing portal flow to bypass the liver
242
What is the target portosystemic gradient following TIPS formation?
<12mmHg
243
What are the indications of a TIPS?
Acute variceal bleeding (refractory to medical therapy)
Recurrent variceal bleeding
Ascites (refractory to medical management)
Portal hypertensive gastropathy
Hepatorenal syndrome
Malignant compression of hepatic or portal veins
Budd-Chiari syndrome
244
What are the absolute contraindications to TIPS?
Severe chronic liver disease (injured liver may not tolerant nutrient diversion)
Severe encephalopathy (diversion of unfiltered blood will worsen it)
Severe right HF (flow diversion increases pre-load)
245
How is a TIPS procedure conducted?
US-guided vascular access to right internal jugular vein
Angigraphic catheter passed into chosen hepatic vein - confirmed with hepatic venography
Curved TIPS puncture needle advanced into hepatic vein
TIPS puncture needle rotated anteriorly and advanced inferiorly through liver parenchyma to location of portal vein branch
Portal venogram performed through TIPS puncture needle to confirm portal vein cannulation
Guidewire advanced through needle and manipulated into splenic or mesenteric vein to ensure portal vein access not lost as liver moves craniocaudally with respiration
Angiographic catheter advanced into portal vein to measure pressure
Track created through liver parenchyma dilated via balloon catheter
Stent deployed over vascular sheath (which is in the portal vein branch)
Portal pressures measured to assess desired reduction into portosystemic gradient
Venography repeated to confirm variceal bleeding ceased with portal pressure reduction
246
Why would the guide wire be advanced all the way into the splenic or mesenteric vein during a TIPS?
Liver moves craniocaudally (inferiorly) with respiration therefore portal vein access will not be lost
247
What are the potential complications of a TIPS procedure?
Haemorrhage
Hepatic infarction
Gallbladder puncture
Sepsis
Vascular site haematoma
Unintentional arterial access
AKI
Uncontrollable hepatic encephalopathy
Hepatic venous stenosis
Stent occlusion
Stent migration
Stent infection
248
What are the approaches for a liver biopsy?
Transjugular
Percutaneous
249
What are the indications for a trans jugular liver biopsy?
Massive ascites
Coagulopathy
Hepatic peliosis
Morbid obesity
Failed percutaneous liver biopsy
250
How is the procedure of a trans jugular hepatic biopsy undertaken?
US-guided needle into IJV
Wire inserted into SVC and sheath placed over wire
Venous puncture conducted.
Guidewire and catheter used to gain entry into right hepatic vein
Venogram obtained to confirm position in right hepatic vein
Catheter exchanged with sheath over stiff wire
Once sheath is in mid RHV, biopsy needle inserted and 2-3 cores of liver tissue obtained following entering liver parenchyma
251
What are the potential complications of a transjugular liver biopsy?
Haemorrhage
Liver capsule rupture
Haemoperitoneum
Pneumothorax
Haemobilia
Fistulisation between hepatic artery and portal vein
252
What is a percutaneous nephrostomy?
Kidney drain under image-guidance through the skin
253
What are the indications for a percutaneous nephrostomy?
Used when retrograde approaches unsuccessful
Urinary tract obstruction
Urinary diversion
Access for percutaneous procedures e.g. stone treatment; ureteric stenting
Diagnostic testing
254
What are the contraindications to a percutaneous nephrostomy?
Uncorrectable bleeding diathesis
Uncooperative patient
Severe respiratory disease
Uncorrected electrolyte abnormality
255
How is a percutaneous nephrostomy procedure undertaken?
Aseptic technique
Infiltration of local anaesthetic
Use image-guidance to puncture the calyx at the mid/lower pole
Urine drains freely on removal of stylet from needle
Contrast injected to confirm needle position
Guidewire advanced and pigtail drain placed in renal pelvis over the guide wire
256
What are the potential complications of a percutaneous nephrostomy insertion?
Bleeding
Pneumothorax
Bowel injury
Urine leak
Splenic/liver injury
Catheter obstruction
Catheter displacement
257
What are the benefits of ultrasound?
Non-ionising
Readily available
Cheap
Straight forward
Few medical staff required
Few contraindications
Real-time imaging
Doppler modality adds physiological data
258
What are the disadvantages to US?
Training required
Ultrasound subject to objects of acoustic impedance
US artifacts may degrade image
May be limited by body habitus
259
What is acoustic enhancement in US?
Increased echoes deep to structures which transmit sound well
This can be seen in fluid-filled structures e.g. cysts
Fluid only attenuates sound less than surrounding tissue thus time gain compensation overcompensates through the fluid-filled structures causing deeper tissues to be brighter
This shoes as increased echogenicity posterior to the cystic area.
260
What is time gain compensation (TGC)?
Compensatory mechanism for attenuation of ultrasound energy with depth.
Allows fine tuning of image which corresponds to a differing depth which reduces the altered time gain which may produce artefacts
261
What is attenuation?
Concept that US wave amplitude reduces as it penetrates a tissue
Thus echoes from deep layers have smaller amplitudes, even if same echogenicity
262
What is acoustic shadowing?
Imaging artefact with signal reduction posterior to a structure absorbing/reflecting ultrasonic waves
263
What is anisotropy in US?
US beam is on a fibrillar structure (e.g. tendon/ligament), organised fibrils may reflect most of the beam away.
Thus the transducer does not receive the returning echo and assumes area will be hypoechoic.
This is dependent upon the angle of beam, perpendicular means maximal return (therefore increase the insonating angle)
264
What impact does the insonating angle have on the level of return in US?
Increasing the insonating angle (perpendicular) will yield maximal return of echo and reduce anisotropy
265
What is beam width artefact?
Reflective object beyond widened ultrasound beam, after focal zone, creates falsely detected echoes which are displayed as overlapping structure of interest.
E.g. echoes generated by object located in peripheral field are perceived as overlapping object of interest.
266
What is mirror image artefact?
Artefact whereby highly reflective surface (e.g. diaphragm) receives primary beam which is reflected once again by another structure (e.g. nodular lesion) then to be reflected again by the diaphragm which is detected by the transducer.
This gives a false assumption that the echo is coming from a deeper structure thus giving a mirror artefact on the other side of the reflective surface
267
How is an ultrasound image generated?
Electric current applied to crystal which vibrates and sends off sound wave which is reflected off a structure, then transduced and generates electrical current (Piezoelectric effect)
Thus acts as a speaker and a microphone
268
What are the best Windows in US?
Areas where fluid or fluid-dense tissues are in contact with skin:
- Liver
- Heart
- Bladder
- Spleen
269
How do you decide which probe to use on ultrasound?
Transducer depends on what you wish to see
Frequency is associated with a transducer
Therefore, high frequency = better resolution but less penetration
low frequency = more penetration but better resolution
270
What radiographic features are seen in a pneumothorax?
Visible visceral pleural edge
No lung markings peripheral to this line (radiolucent cf adjacent lung)
Additional features:
- mediastinal shift
- lung collapse
- subcutaneous emphysema
271
What method can be used to estimate percentage volume of pneumothorax from an AP erect radiograph?
Collins Method:
% = 4.2 + 4.7 (A+B+C)
272
How does a lateral decubitus radiograph increase chance of observing a pneumothorax?
Positioned on 'well side', lung will fall away from Cx wall
273
How does an expiratory chest radiograph enable visualisation of a pneumothorax?
Lung becomes smaller and denser
Pneumothorax remains same size thus more identifiable
274
What radiographic features may be seen on CXR in PE?
Linear/patchy atelectasis
Westermark sign (peripheral oligaemia with proximal dilation of pulmonary arteries)
Air space opacification (pulmonary infarction)
Hampton's hump (pleura based opacification due to PE and lung infection)
Pleural effusion
Palla sign (enlarged right descending PA)
Elevated diaphragm (due to loss of lung volume)
275
How does a V:Q scan work?
IV injection of serum albumin tagged with Technetium-99m which are slightly larger than RBCs and same lumen diameter (>8um) than pulmonary capillaries.
They perfuse the lung and are trapped in capillary branches where they emit gamma radiation - recorded by gamma camera.
Identification of reduced uptake which shows a 'defect' highlights area of reduced perfusion.
If this is abnormal, a ventilation scan is performed by inhalation of Xenon-133 however if normal V scan but abnormal Q scan ≈ PE
276
What process can you use to recognise the ages of carpal bone maturity?
Start at the capitate, rotate anti-clockwise, omitting the pisiform.
277
What age does the capitate appear on radiograph?
2 months
278
What age does the hamate bone develop?
4 months
279
What age does the pisiform develop?
12 years
280
What age does the triquetrum develop?
2 years
281
What age does the lunate develop?
4 years
282
What age does the hamate develop?
4 months
283
What age does the trapezium develop?
6 years
284
What age does the trapezoid develop?
6 years
285
What age does the trapezium develop?
6 years
286
What age does the lunate develop?
4 months
287
What age does the scaphoid develop?
6 years old
288
When does the distal radius develop?
1 years old
289
What age does the distal ulnar develop?
6 years
290
What is the difference between an Os and a Sesamoid bone?
An os trigonometry is an accessory bone developing behind another bone connected by a fibrous band
A sesamoid bone is a bone embedded within a tendon/muscle
291
What is the name of the bone embedded within the lateral head of gastrocnemius?
What type of bone is this?
Fabella
A sesamoid bone
292
What type of injury is a Segond fracture?
Avulsion injury of the lateral tibial plateau and mid-lateral capsule which accompanies ACL rupture
293
Which blood test should be avoided in a pregnant woman query PE? Why?
D-dimer should not be ordered.
Order a form of imaging.
D-dimer will be elevated in pregnancy
294
When does the early arterial phase occur?
15-20 seconds, contrast still in arteries
295
When does the late arterial phase occur?
35-40 seconds
All structures perfused by arteries show optimal enhancement
296
When does the hepatic or late portal phase occur?
70-80 seconds
Liver parenchyma enhances through PV
297
When does the nephrogenic phase occur?
100 seconds
Renal parenchyma enhances
298
When does the delayed phase occur?
6-10 minutes
Washout (equilibrium) phase - washout of contrast in all abdominal structures apart from fibrotic tissue
299
How much contrast is used for someone weighing <75kg in a CT scan?
100cc
300
How much contrast is used for someone weighing 75-90kg in a CT scan?
120cc
301
How much contrast is used for someone weighing >90kg in a CT scan?
150cc
302
What provides optimal enhancement of the liver parenchyma in a CT-Liver (with contrast)?
Portal venous phase (70-80 seconds) is ideal for liver parenchyma as 80% blood supply comes from portal vein
Note: A hypervascular tumour is seen best in the late arterial phase as all liver tumours get 100% blood supply from hepatic artery
A hypovascular tumour enhances poorly in the late arterial phase due to being hypovascular and surrounding liver does also enhance poorly in that phase - seen best when surrounding tissue enhances in the hepatic phase.
303
Which CT phase is a pancreatic carcinoma best visualised in?
This is a hypovascular tumour therefore best seen in late arterial phase 35-40 seconds p.i. when normal glandular tissue enhances and hypovascular tumour does not
