Neuroimaging

Question 1

Event-related potentials

Answer 1

Brief changes in slow-wave EEG signal in response to a discrete sensory stimulus

Question 2

Appearance of CT

Answer 2

White = dense (bone)
Black = less dense (air)
Dark gray (CSF)
Nearly black (fat tissue just outside skull)

Hyperdense = brighter areas
Hypodense = darker areas
Grey/isodense = intermediate density similar to brain tissue

Question 3

Appearance of hemorrhage on CT

Answer 3

Hyperdense when fresh, becomes isodense after ~ a week, hypodense after ~ 2-3 weeks

Question 4

MRI is better than CT in what situations?

Answer 4

Subtle tumor/infarct, brainstem lesion, old hemorrhage, anatomical detail

Question 5

CT is better than MRI in what situations?

Answer 5

Head trauma, lower cost, fresh hemorrhage, speed, skull fracture, pacemaker

Question 6

Appearance of MRI scans

Answer 6

Hyperintense = brighter areas

Hypointense = darker areas

Question 7

Neuroangiography

Answer 7

The study of central nervous blood vessels & related cervicocerebral vasculature using radiographs during injection of IV contrast medium

Question 8

UBO

Answer 8

Unidentifiable bright object

Refers to hyperintense white matter foci on MRIs (T2-weighted)

Question 9

What might UBOs represent?

Answer 9

May be due to white matter pallor, infarction, ischemia, plaques or other causes

Question 10

What is the differences between T1 and T2 MRI images?

Answer 10

T1 - white matter is brighter than gray matter

T2 = CSF is brighter than gray matter

Question 11

Magnetic resonance spetroscopy (MRS)

Answer 11

Noninvasive technique used to measure chemical makeup of tissue (e.g., levels of neurotransmitters in the brain)

Question 12

EEG changes in dementia

Answer 12

Nonspecific slowing is most common

Question 13

Limitations of EEG

Answer 13

Unable to detect activity from deep cortical & subcortical structures

Uncertain localization

Question 14

EEG - coherence

Answer 14

Degree to which respective regions’ frequencies are correlated; often interpreted as a measure of “connectivity” between regions

Question 15

What neuroimaging findings are most strongly related to AD severity?

Answer 15

Volumetric measures of medial temporal lobe & other cortical structures

Also has prognostic value for IDing progression from MCI to AD

Question 16

How does IV contrast dye affect the appearance of CTs?

Answer 16

Contains iodine which is denser than brain & will appear hyperdense in areas of increased vascularity or breakdown of BBB

Question 17

Myelography

Answer 17

Iodinated contrast dye is introduced into CSF, allows better visual of nerve roots & abnormal impingement on spinal CSF

Question 18

Describe the appearance of intracranial hemorrhage on MRI

Answer 18

Acute may be hard to see b/c resembles CSF
Subacute contains hemosiderin & appears white
Chronic contains dark areas resulting from hemosiderin deposits

Question 19

Which MRI sequence is better for identifying anatomy: T1 or T2?

Answer 19

T1

Question 20

Which MRI sequence is better for clear differentiation of fluid: T1 or T2?

Answer 20

T2

Question 21

Diffusion tensor imaging

Answer 21

Depicts the directionality of water diffusion which is associated with meylin integrity

Question 22

How do brain tumors appear on PET?

Answer 22

High-grade neoplasms demonstrated increased metabolism, low-grade neoplasms demonstrate decreased activity; radiation necrosis shows decreased activity & tumor recurrence shows increased

Question 23

Magnetic resonance spectroscopy (MRS)

Answer 23

Detects local concentrations of certain chemicals in the brain