Direct in vivo observation of microbubble destruction with ultrasound

Abstract

Background: It has been reported that microbubbles (MB) can be destroyed by ultrasound (US), resulting in a bioeffect, such as angiogenesis. Objective: Our aim is to observe the effect of MB destruction with US on capillary by our intravital CCD videomicroscope. Methods: The superficial capillaries (n=317) of spinotrapezius muscle from 46 WKY rats were exposed to US (2.5 MHz) at mechanical indexes (MI) of 0.1, 1.0, and, 1.9 for 3 min after intraarterial MB injection (Optison). The capillary flow was monitored by the microscope before, during and after US application. Results: We succeeded in capturing real time images of capillary rupture with destruction of MB in 3 capillaries at MI 1.9. The MB destruction with US resulted in flow in which individual RBC halted within capillaries. No-flow after initiation of US irradiation was detected in 6.9%, 21.3%, and 57.6% of all observed capillaries at MI 0.1, 1.0, and 1.9, respectively. In most of capillaries (77.8%) the flow was improved at 15min, while in other fraction of capillaries (22.2%) flow disturbance remained at that time, followed by slow flow recovery. Exposure to US alone did not induce no-flow. Conclusions: US exposure to MB in capillaries transiently resulted in MI-dependent microvascular damage including land-mine like capillary rupture. [Jpn J Physiol 54 Suppl:S101 (2004)]