Dalecki D, Raeman C H, Child S Z, Carstensen E L
Department of Electrical Engineering, University of Rochester, NY 14627, USA.
Ultrasound Med Biol. 1995;21(8):1067-72. doi: 10.1016/0301-5629(95)00041-o.
Threshold exposures for producing intestinal hemorrhage in mice were determined using focused sources operating at 0.7, 1.1, 2.4 and 3.6 MHz. The choice of pulse length (10 microseconds) and pulse repetition frequency (100 Hz) made the exposures diagnostically relevant, while at the same time, minimized possible thermal contributions to the mechanism of action of the ultrasound. Each animal was irradiated at four to five abdominal sites for 5 min per site. Suprathreshold lesions ranged from small petechiae to hemorrhagic regions extending 4 mm or more along the intestine, depending upon the exposure levels. Higher frequencies were less effective in producing intestinal hemorrhage than lower frequencies. Thermocouple measurements of temperature rise in the intestine during ultrasound exposure revealed temperature increments between 1 degrees and 2 degrees C at the highest exposure levels. The frequency dependence of the production of intestinal hemorrhage together with the observed limited heating is consistent with a cavitation-related mechanism of action of pulsed ultrasound.
使用工作频率为0.7、1.1、2.4和3.6兆赫兹的聚焦源，测定了小鼠产生肠道出血的阈暴露量。脉冲长度（10微秒）和脉冲重复频率（100赫兹）的选择使这些暴露具有诊断相关性，同时将超声作用机制中可能的热贡献降至最低。每只动物在四到五个腹部部位接受照射，每个部位照射5分钟。超阈值损伤范围从小的瘀点到沿肠道延伸4毫米或更长的出血区域，这取决于暴露水平。高频产生肠道出血的效果不如低频。超声暴露期间肠道温度上升的热电偶测量显示，在最高暴露水平下，温度升高了1摄氏度至2摄氏度。肠道出血产生的频率依赖性以及观察到的有限加热与脉冲超声的空化相关作用机制一致。
