Answers to the Questions on Page 53

Question 1

Answer = A

In patients with allergy to sulfonamides, there is significant risk of serious allergic reaction, even life-threatening, with the administration of acetazolamide (1,2). Acetazolamide is a carbonic anhydrase inhibitor, which produces a vasodilatory effect on the cerebral circulation. Similar to pharmacologic myocardial perfusion scintigraphy, a significantly stenosed cerebral vessel is not able to dilate in proportion to the nonstenosed vessels, resulting in a relative low flow state and a relative underperfusion.

Question 2

Answer = D

There is a 30% decrease in radiotracer distribution to the entire left hemisphere on challenge imaging. This decrease is interpreted as a significant perfusion defect. Examples of SPECT images of regional cerebral blood flow in healthy subjects are available for review at http://brainscans.indd.org.

Question 3

Answer = A

The decreased radiotracer distribution, on challenge imaging, suggests a vascular involvement within the left cerebral hemisphere only.