The search for cavitation in vivo

Until the mid 1970s, it was generally assumed that, with the short pulses o f ultrasound (US) used in medical diagnosis, there was little need for conc ern about the possibility of inertial cavitation in vivo. This assumption c ame into question when experimental evidence indicated that killing of frui t fly larvae by diagnostically relevant US was associated with the presence of gas in the respiratory apparatus of the organisms. Independent theoreti cal contributions by Flynn and Apfel in the early 1980s made it clear that complacency in regard to cavitation was not warranted. Later, the mammalian lung, as with larva, was shown to be particularly vulnerable when it conta ined air. Yet, overall evidence suggests that lung hemorrhage is not consis tent with the classical picture of inertial cavitation. Most recently, howe ver, hemolysis and hemorrhage associated with the use of contrast agents ha ve provided nearly incontrovertible evidence of the occurrence of cavitatio n in vivo. (C) 2001 World Federation for Ultrasound in Medicine & Biology.