The apparent diffusion coefficient (ADC) ----?T2 EFFECT

Q.All are true regarding the apparent diffusion coefficient (ADC) except

a. ADC requires sequences with at least two different b-values

b. ADC maps are solely based on differences of tissue diffusion

c. The ADC in the normal brain ranges from 2.94 × 10³mm

d. Areas with a decreased ADC appear dark on ADC maps

e. ADC maps are  dependent on  T2 effects

ANS.---e

ADC maps are solely based on differences of tissue diffusion,

 independent of any T2 effects. The ADC in the normal brain

 ranges from 2.94 × 10³mm² s¹ for CSF to 0.22 × 10³mm² s¹ for

 white matter; grey matter lies in between with a ADC of 0.76 × 

10³mm² s. Areas with a decreased ADC appear dark on ADC 

maps, which is the converse to diffusion-weighted images where 

areas of decreased diffusion appear bright.

ALEXANDER DISEASE

Q.All are true regarding Alexander disease except

a.enlarged  brain

b. substantial accumulation of Rosenthal fibers

c. The basal ganglia and cortex  usually relatively preserved

d. sparing of the subcortical U fibers

e. Cavitation  common

ANS.---d

There is no sparing of the subcortical U fibers  in Alexander disease. The cerebellum is less often affected than in other leukodystrophies. MR findings classically demonstrate increased signal intensity on the T2-weighted images in the frontal white matter .The occipital white matter and cerebellum are usually spared.

ureterocele