Answer #33

The correct answer is A: It is the best determinant of the likelihood of cavitation. The mechanical index (MI) is in fact the best indicator of cavitation. It is related to the peak rarefactional pressure divided by the transducer frequency, so it is inversely proportional to the frequency, making Choice B incorrect.

Cavitation is more likely to occur with a higher MI so Choice C is not correct. Typically the MI has to be reduced during contrast studies, since with contrast agents there is significant impedance mismatch between blood and the contrast agent, a lower MI transducer can produce significant signal. A high MI can cause bubble destruction and cavitation.