ABILITY OF HIGH-INTENSITY ULTRASOUND TO ABLATE HUMAN ATHEROSCLEROTIC PLAQUES AND MINIMIZE DEBRIS SIZE

To investigate whether high-intensity ultrasound can destroy atherosclerotic plaques while sparing the normal arterial wall, 279 normal human aortic sites and 119 fibrous and 193 calcified plaques, obtained from 24 necropsies, were insonified in a water tank, at 20 kHz and at 5 different power intensities, ranging from 68 W/cm2 (P1) to 150 W/cm2 (P5). These intensities were associated with a total excursion of the ultrasound irradiation apparatus tip from 90 to 268-mu-m, respectively. Time to perforate normal aortic sites and fibrous and calcified plaques was recorded at each intensity. There was no difference in perforation time between normal aortic sites and fibrous and calcified plaques when high-power levels (P2 to P5) were used. However, at the lowest power (P1), perforation time for the normal aortic wall was significantly longer than for fibrous and calcified plaques: 30 +/- 18 seconds (166 observations), 14 +/- 7 seconds (p < 0.001) (78 observations) and 12 +/- 8 seconds (p < 0.001) (115 observations), respectively. When perforation times for normal vessel wall versus fibrous plaque and normal vessel wall versus calcified plaque from the same necropsy specimen were compared in a pairwise manner, the results were: 29 +/- 13 vs 16 +/- 7 (p < 0.001) (48 paired observations) and 26 +/- 9 vs 10 +/- 5 seconds (p < 0.001) (55 paired observations), respectively. Regardless of whether paired or unpaired comparison was applied, no significant difference was found in perforation time between fibrous and calcified plaques. The debris did not differ in size as measured separately for normal sites and fibrous and calcified plaques by a computer-interfaced Channelizer(R) and Coulter(R) Counter system. A total of 57,863 particles were counted and measured. The mean particle diameter was 7.0 +/- 5-mu-m (range 4.8 to 15.8). Thus, ultrasound may selectively ablate human atherosclerotic plaques at power intensities less-than-or-equal-to 68 W/cm2.