Neurologic CT and MRI basics

Question 1

On an unenhanced CT scan of the head, anything that appears “white”
generally represents ____

Answer 1

either bone (calcified) or acute blood

Question 2

CT is better at detecting _____ than MRI

Answer 2

acute hemorrhage

Question 3

____ is better at detecting fractures (ability to look at bone windows)

Answer 3

CT

Question 4

____ is the imaging modality of choice for trauma

Answer 4

CT

Question 5

CTs are available in two basic forms or “windows”- _____

Answer 5

Bone and Brain

Question 6

Brain volume is assessed by subjectively estimating the relative
volume of the ______.

Answer 6

cerebrospinal fluid (CSF) spaces

Question 7

How to tell suture lines rom fractures on head CTs

Answer 7

● Sutures are well corticated, while acute fractures are not corticated.

Question 8

CT findings after a stroke

Answer 8

● Very early after the onset of stroke-like symptoms, the CT of the head may remain normal.
○ May remain normal for the first few hours
● Within a few hours after the stroke occurs, the appearance of the infarcted brain tissue will
become an area of “low density.”

Question 8

CT Findings for an epidural hematoma (EDH)

Answer 8

● EDHs are lens-shaped and
generally the hemorrhage does
not cross suture lines in the skull

Question 9

CT findings for a subdural hematoma (SDH)

Answer 9

● SDHs are Crescent-shaped and can cross
suture lines or be along the falx or tentorium

Question 10

CT findings for a subarachnoid hemorrhage (SAH)

Answer 10

● Subarachnoid Hemorrhages (SAH) can be either aneurysmal or traumatic.
○ Location of the subarachnoid blood can be diagnostic
● A star pattern of blood in the basal
cisterns suggests rupture of an aneurysm from the Circle of Willis

Question 11

A _____ can technically occur anywhere

Answer 11

traumatic subarachnoid hemorrhage

Question 12

CT findings for hemorrhagic strokes or intracranial hemorrhages

Answer 12

● Hemorrhagic Strokes or other Intracranial Hemorrhages, which can be caused by
trauma or mass lesions, are easily seen.
● These types of bleeds are often surrounded
by edema and sulcal effacement

Question 13

Any swelling or mass lesion that
takes up space can increase the
intracranial pressure and cause
shifting of the brain, which is
referred to as ______

Answer 13

“Mass Effect.”

Question 14

Several types of “sequences” are available for viewing MRI, including ______

Answer 14

T1, T2,
STIR, FLAIR, ADC, and DWI

Question 15

Tumors on CT scans

Answer 15

Tumors can be identified on CT scans, especially if it is
a contrasted study. Edema is often seen as well.

Question 16

_____ is better at visualizing edema

Answer 16

MRI
● This kind of edema can be
from ischemic injury, trauma,
tumors, hydrocephalus with
vasogenic edema, etc.

Question 17

_____ are available as a sequence that reveals
evidence of acute ischemia, even when a CT scan does not reveal evidence of a stroke

Answer 17

Diffusion-Weighted MR images (DWI)

Question 18

_____ images are the negative
image of DWI

Answer 18

Apparent Diffusion Coefficient
(ADC)