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302 MEDIMAGE > 2a. CT - Head Radiology > Flashcards

2a. CT - Head Radiology Flashcards

(59 cards)

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1
Q

in a imaging studies the patients left side is my ___ side

A

right

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2
Q

how do your know an image is a CT scan and not another modality

A

bones of skull is white (high intensity) in CT

opposite of MRI where bones of skull would be black

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3
Q

on CT what colour/intensity would bone be

A

high intensity - white

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4
Q

on CT what colour/intensity would white matter of the brain be

A

darker grey

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5
Q

on CT what colour/intensity would CSF be

A

hypointense (black/dark)

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6
Q

on CT what colour/intensity would fat be

A

very dark - hypointense

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7
Q

on CT what colour/intensity would muscle be

A

mid grey

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8
Q

on CT what colour/intensity would blood be

A

high-low intensity depending on freshness of blood

fresh blood = bright/intense
old blood = dark/hypointense

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9
Q

what are the 4 things to describe in terms of a lesion on a CT scan

A

which side the lesion is on
lesion appearance
location of lesion
other features of lesion

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10
Q

what are the components in your description of a lesion

x6 things

A

shape of lesion (eg biconvex)
intensity (hyper/hypo)
size (eyeball cmxcm)
where in the brain structures is the lesion located (eg ant cranial fossa)
where the lesion borders are extending to (eg extends to midline)
is it compressing the brain/is the midline skewed - what side is it displacing the midline to

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11
Q

what are the 3 cross sectional imaging modalities

A

CT, MRI, ultrasound

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12
Q

which of the 3 cross sectional imaging modalities can be used with contrast?

A

all of the 3

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13
Q

what are the 5 advantages of CT scans

A

fast (1-20min)
relatively widely avail
3D reformatting and reconstruction
intermediate cost

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14
Q

what are 3 uses of CT scans

A

acute trauma
stroke to rule out bleed
angiography with contrast media

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15
Q

how does the CT work

A

CT anode produces a narrow continuous fan shaped stream of xrays as it rotates around the head

anode is paired with a detector array which also rotates at a constant 180* to the anode

the image is reconstructed into stack of 2D images using a number of algorithms

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16
Q

is the CT scan technique quantitative or qualitative why

A

quantitative as the scale is a linear transformation of the original tissue attenuation

Quantative as intensity on screen can give a number to it - Hounsfield unit

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17
Q

what is the hounsfield unit

A

can give it a number to the intensity on screen

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18
Q

what is the hounsfield unit for water and air

A 
water = 1
air = -1000
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19
Q

what can the hounsfield unit used for

A

density quantifications

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20
Q

does the hounsfield number change with windowing

A

no

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21
Q

calcium has what hounsfield unit relative to bone

A

high value sim to bone

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22
Q

what are the 2 main types of disease

A

congenital and acquired

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23
Q

what are the 2 types of acquired disease

A

infectious and non-infectious

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24
Q

what are 4 examples of infectious diseases

Study These Flashcards
A

bacteria
viruses
parasites
fungi

25
what are 4 examples of non-infectious diseases
trauma malignancy inflammatory degenerative
26
what is intra-vascular contrast media
compounds injected to increase the contrast of structures or fluids on imaging
27
does contrast media cross the blood brain barrier
usually dont cross the BBB unless it is not intact
28
what xrays need contrast media and what type of contrast media do CT use
``` xray = angiography CT = iodinated media ```
29
what does the image look like when there is a pathology that allows the contrast media to enter the tissues/vessels, how does this happen what is the wash out rate
in areas of apthology eg tumour/stroke leaky vessels means contrast agent enters the abnormal tissue wash out is slow visualized as high signal - bright
30
iodinated media can do what to poor renal function and what is the rate of contrast reaction
exacerbate poor renal function rate is high
31
what can gadolinium based media rarely cause and why
nephrogenic systemic fibrosis when used in large dose in patients with poor renal function due to gadolinium deposition in tissues
32
if non hemorrhagic the stroke can be treated wiht what 2 ways
tissue plasminogen activator/TPA neuro-radiological intervention/clot removal
33
if the stroke is haemorrhagic what does the image look like and is TPA used
blood seen on bright signal on CT TPA withheld as will likely cause more haemorrhage
34
what are the 2 disadvantages of CT
uses high ionising radiation | intermediate cost
35
what is an early sign of ischemia on CT 3 signs
loss of definition between grey and white matter ill-defined internal capsule hyperdense middle cerebral artery not always seen
36
are acute signs of ischaemia seen on CT
sometimes changes take 24hrs to develop
37
what are acute signs of acute bleed on CT
hyperintensity
38
if concern of bleeding and CT doesnt show anything what happens next
patient may go to MRI for diffusion weighted imaging (DWI)
39
which is more sensitive to ischemic changes - CT, MRI, DWI
DWI
40
what is epidural bleed in terms of where the blood is between what structures of the head/skull
traumatic collection of blood between the inner aspect of the skull and the stripped of dura
41
what is epidural bleed in terms of the bleeding is from what vessel
usually trauma and bleeding from the middle meningeal artery
42
what is subdural bleed in terms of shape and edge of bleed shape
lentiform shape | clean edge of bleed
43
what is subdural bleed in terms of where the blood is between what structures of the head/skull what vessel type is injured
traumatic injury to veins between dura mater and arachnoid mater leading to collection of blood in subdural space
44
what is epidural bleed in terms of shape and edge of bleed shape
crescent shape jagged, irregualr edge of bleed
45
what do chronic bleeds in the head do to the brain
squishes material of the brain itself
46
for a sub arachnoid bleed where is the blood collection in the brain
between arachnoid mater and pia mater
47
for a sub arachnoid bleed what does the blood look like on the surface of the brain in images and where is the blood also seen after bleed
bright signal seen in basal cisterns immediately after bleed
48
what is the basal cisterns in the brain in terms of location and shape what is the blood intensity on the image
circle structure with projections like a star seen in the center of the brain in a axial scan bright blood/high intensity
49
what 2 things causes subarachnoid hemorrhages
hypertension rupture of aneurysms of cerebral vessels
50
what are meningiomas and how fast does it grow and is it dangerous
tumors arising from meninges slow growing 90% benign
51
on a CT scan what does a lesion look like before and after the contrast is applied
before = grey circle similar to surrounding healthy brain tissue after = high intensity very bright
52
what is a glioblastoma tumor in terms of appearance when contrast is applied and what other injury is associated with it
most common malignant brain tumor enhancing lesion associated with surrounding oedema (doesnt enhance very well)
53
what is a glioblastoma tumor and is it dangerous, how fast does it grow
most common malignant brain tumor slow growing less aggressive
54
what are vessels of aggressive tumors like compared to slow growing tumors and what does this mean for contrast uptake
aggressive tumors = vessels are more leaky blood leaks and contrast gets into it so more bright
55
what are the key characteristics of abscess on CT
rim enhancing lesion with oedema | middle of lesion has pretty dark intensity
56
what is the rim like in appearance of abscess on CT images
very thin uniform enhancing edge
57
what is the oedema like in appearance of abscess on CT images
slightly darker area outside rim enhancement slightly darker than normal tissue
58
Why is CT good for imaging facial trauma 3 reasons
CT scan avoids superimposing of bones so can see structure really well high contrast between bone and soft tissue enables easy segmentation and 3D reconstruction good visualization for surgeon when planning surgery
59
when there is a fracture of the infraorbital wall what happens to the contents of the orbit what is clinically significant about this
contents of orbit pushed down may have bit of blood in maxillary sinus and fat in orbit gets trapped and eye muscles trapped in sinus so eyes dont work together as well so get double vision clinically

302 MEDIMAGE (20 decks)

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