Imaging

Question 1

Does CT or MRI have better spatial and contrast resolution?

Answer 1

CT has better spatial resolution, MRI has better contrast resolution

Question 2

What is contrast resolution?

Answer 2

The ability to discriminate tissues of differing composition

Question 3

What is spatial resolution?

Answer 3

The ability to resolve fine detail

Question 4

Which imaging modality has the highest spatial resolution?

Answer 4

Radiographs

Question 5

Is bone hypointense or hyperintense on MRI?

Answer 5

Hypointense (black) due to the absence of hydrogen protons

Question 6

What contrast medium is typically used in MRI studies?

Answer 6

Gadolinium based contrast media

Question 7

What is functional MRI

Answer 7

The provision of physiologic information through the use of specialized pulse sequences

Question 8

What are the Hounsfield units for various structures viewed on CT scan?

Answer 8

Question 9

What terms are used to describe image brightness on various modalities?

Answer 9

Radiography: Opacity
CT: Attenuation or density
MRI: Intensity

Question 10

What are MRI FLAIR sequences typically used for?

Answer 10

Suppression of fluid signal.

Question 11

What are MRI STIR sequences typically used for?

Answer 11

Suppression of fat signal.

Question 12

How can T2 FLAIR sequences distinguish fluid types?

Answer 12

Pure fluid with little to no protein content such as cerebrospinal fluid is nulled, whereas edema is hyperattenuated

Question 13

What is the primary difference between spin echo and gradient echo MRI sequences?

Answer 13

Spin echo corrects for signal loss caused by static inhomogeneities in the field, whereas gradient echo does not.

Question 14

What is the main difference between T1W and T2W MRI images?

Answer 14

T1W images provide good anatomic detail, T2W images are considered to be more sensitive to pathology

Question 15

What are gradient echo (T2*W) sequences most useful in detecting?

Answer 15

Hemorrhage - shown as signal voids

Question 16

What is spectral fat saturation?

Answer 16

Suppression of the MRI fat signal. Can be used to better delineate lesions within the fatty cancellous bone, lesions involving the meninges, and in discriminating between structures that may be hyperintense on T1W and T2W images

Question 17

Describe the substances that are hyperintense on T1W and T2W images

Answer 17

Question 18

Is cerebrospinal fluid hypointense or hyerintense on T1W and T2W images?

Answer 18

Hyperintense on T2W, hypointense on T1W

Question 19

Is white or gray matter more or less hyperintense on T1W and T2W images?

Answer 19

White matter more hyperintense than gray matter on T1W images, reverse for T2W

Question 20

Are protein bound fluids such as in mucin or cerebrospinal fluid inflammation more or less hyperintense on T1W and T2W images?

Answer 20

More hyperintense on T1W images (as compared to edema which is more hyperintense on T2 images)

Question 21

What CNS structures are normally enhanced on MRI with the administration of contrast?

Answer 21

Meninges, choroid plexus, pituitary

Question 22

Is T1W or T2W more useful for evaluation post-contrast images?

Answer 22

T1W. Contrast will be seen as hyperintense. Lesion may be surrounded by hypointense region if associated vasogenic edema

Question 23

What are some signs on MRI that suggest an extraparenchymal intracranial lesion?

Answer 23

Displacement of subadjacent neural tissue, broad base, contiguous dural enhancement, or dural tail, hyperostosis/remodelling of the skull, CSF between the mass and brain

Question 24

What are the classifications of abnormalities involving the spinal cord based MRI/CT?

Answer 24

Extradural, intradural-extramedullary, intramedullary

Question 25

What does the ‘golf tee sign’ indicate on spinal MRI imaging?

Answer 25

Extramedullary location of mass (see image pg 384 Tobias)