Neuroimaging

Question 1

Pros and cons of MRI

Answer 1

Pros: Best resolution for seeing brain and spinal cord, can see multiple views, no radiation
Cons: Takes a long time, sensitive to patient movement, metallic pacemakers/implants cannot be scanned, claustrophobia risk

Question 2

Pros and cons of CT

Answer 2

Pros: Short scanning time
Cons: poorer resolution than MI, only axial views, radiation exposure

Question 3

What are the 2 major MRI modalities and how do they differ?

Answer 3

T1-weighted and T2 weighted
T1: good for seeing anatomy, CSF is dark
T2: good for pathology, CSF is bright, most lesions appear bright

Question 4

Describe the CT scan changes of a cerebral hemorrhage over time

Answer 4

Initially, acute hemorrhages are hyperdense on CT. As time passes, subacute hemorrhages appeare isodense, and chronic appear hypodense.

Question 5

What biochemical substance within hemorrhages dictates the MRI appearance?

Answer 5

Iron content of hematomas/bleeds changes from hemoglobin to methemoglobin to hemosiderin.

Question 6

What is the best imaging for acute infarction?

Answer 6

MRI
DWI MRI provides earliest detection. T2W or FLAIR images show infarctions as high signal.
CT may not show early subtle changes or small lacunar infarcts.

Question 7

How does edema appear on CT? T2W/FLAIR MRI?

Answer 7

On CT, edema is hypodense
On T2W/FLAIR, edema is hyperintensity

*Often involves white matter, sparing gyri

Question 8

How does an abscess appear on a contrast CT?

Answer 8

Ring-enhancing lesions

Question 9

What is the best imaging modality for seeing herniated discs?

Answer 9

T2W MRI gives the best view of CSF around the spinal cord and how the disc is impinging on the cord.