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

2a. CT - Head Radiology Flashcards

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

A

bacteria
viruses
parasites
fungi

25
Q

what are 4 examples of non-infectious diseases

A

trauma
malignancy
inflammatory
degenerative

26
Q

what is intra-vascular contrast media

A

compounds injected to increase the contrast of structures or fluids on imaging

27
Q

does contrast media cross the blood brain barrier

A

usually dont cross the BBB unless it is not intact

28
Q

what xrays need contrast media and what type of contrast media do CT use

A 
xray = angiography
CT = iodinated media
29
Q

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

A

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
Q

iodinated media can do what to poor renal function and what is the rate of contrast reaction

A

exacerbate poor renal function

rate is high

31
Q

what can gadolinium based media rarely cause and why

A

nephrogenic systemic fibrosis when used in large dose in patients with poor renal function due to gadolinium deposition in tissues

32
Q

if non hemorrhagic the stroke can be treated wiht what 2 ways

A

tissue plasminogen activator/TPA

neuro-radiological intervention/clot removal

33
Q

if the stroke is haemorrhagic what does the image look like and is TPA used

A

blood seen on bright signal on CT

TPA withheld as will likely cause more haemorrhage

34
Q

what are the 2 disadvantages of CT

A

uses high ionising radiation

intermediate cost

35
Q

what is an early sign of ischemia on CT

3 signs

A

loss of definition between grey and white matter

ill-defined internal capsule

hyperdense middle cerebral artery not always seen

36
Q

are acute signs of ischaemia seen on CT

A

sometimes changes take 24hrs to develop

37
Q

what are acute signs of acute bleed on CT

A

hyperintensity

38
Q

if concern of bleeding and CT doesnt show anything what happens next

A

patient may go to MRI for diffusion weighted imaging (DWI)

39
Q

which is more sensitive to ischemic changes - CT, MRI, DWI

A

DWI

40
Q

what is epidural bleed in terms of where the blood is between what structures of the head/skull

A

traumatic collection of blood between the inner aspect of the skull and the stripped of dura

41
Q

what is epidural bleed in terms of the bleeding is from what vessel

A

usually trauma and bleeding from the middle meningeal artery

42
Q

what is subdural bleed in terms of shape and edge of bleed shape

A

lentiform shape

clean edge of bleed

43
Q

what is subdural bleed in terms of where the blood is between what structures of the head/skull

what vessel type is injured

A

traumatic injury to veins between dura mater and arachnoid mater leading to collection of blood in subdural space

44
Q

what is epidural bleed in terms of shape and edge of bleed shape

A

crescent shape

jagged, irregualr edge of bleed

45
Q

what do chronic bleeds in the head do to the brain

A

squishes material of the brain itself

46
Q

for a sub arachnoid bleed where is the blood collection in the brain

A

between arachnoid mater and pia mater

47
Q

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

A

bright signal

seen in basal cisterns immediately after bleed

48
Q

what is the basal cisterns in the brain in terms of location and shape

what is the blood intensity on the image

A

circle structure with projections like a star

seen in the center of the brain in a axial scan

bright blood/high intensity

49
Q

what 2 things causes subarachnoid hemorrhages

A

hypertension

rupture of aneurysms of cerebral vessels

50
Q

what are meningiomas and how fast does it grow and is it dangerous

A

tumors arising from meninges

slow growing

90% benign

51
Q

on a CT scan what does a lesion look like before and after the contrast is applied

A

before = grey circle similar to surrounding healthy brain tissue

after = high intensity very bright

52
Q

what is a glioblastoma tumor in terms of appearance when contrast is applied and what other injury is associated with it

A

most common malignant brain tumor

enhancing lesion associated with surrounding oedema (doesnt enhance very well)

53
Q

what is a glioblastoma tumor and is it dangerous, how fast does it grow

A

most common malignant brain tumor

slow growing less aggressive

54
Q

what are vessels of aggressive tumors like compared to slow growing tumors and what does this mean for contrast uptake

A

aggressive tumors = vessels are more leaky

blood leaks and contrast gets into it so more bright

55
Q

what are the key characteristics of abscess on CT

A

rim enhancing lesion with oedema

middle of lesion has pretty dark intensity

56
Q

what is the rim like in appearance of abscess on CT images

A

very thin uniform enhancing edge

57
Q

what is the oedema like in appearance of abscess on CT images

A

slightly darker area outside rim enhancement

slightly darker than normal tissue

58
Q

Why is CT good for imaging facial trauma

3 reasons

A

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
Q

when there is a fracture of the infraorbital wall what happens to the contents of the orbit

what is clinically significant about this

A

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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