高强度聚焦超声形成生物学焦域的剂量学研究

Study on dosimetry of high intensity focused ultrasound to produce biological focal region

目的 研究辐照剂量对高强度聚焦超声生物学焦域形状、大小的影响 ,探讨高强度聚焦超声 (highintensityfo cusedultrasound ,HIFU)形成生物学焦域的剂量学。方法 运用JC A型Haifu聚焦超声肿瘤治疗系统 ,使用 1.6MHz、焦距12 0mm聚焦超声换能器 ,以 7× 10 3～ 2 7.7× 10 3W cm2 、辐照时间 1～ 2 0s的剂量定点辐照深度为 2 0mm的新鲜离体牛肝脏 ,辐照结束后沿凝固性坏死最大面剖开 ,测量生物学焦域的长、短轴和体积。结果 HIFU生物学焦域不等于声焦域。随着声强和辐照时间的增加 ,HIFU生物学焦域体积增加 ,其形态亦由椭圆体演变成圆锥体 ,且当声强增加时 ,圆锥体HIFU生物学焦域出现的更早。当声强一定 ,随着辐照时间的增加 ,HIFU生物学焦域形态指数 (K)逐渐减小。结论 辐照剂量影响HIFU生物学焦域的形状和大小 。

Objective To explore the influence of exposure dose on the shape and size of biological focal region (BFR) of high intensity focused ultrasound (HIFU) and the dosimetry to produce BFR. Methods A JC A Haifu Focused Ultrasound Tumor Therapeutic System (transducer: 1.6 MHz, focal length: 120 mm) was used in this study. The ultrasound intensity ranged from 7×10 3 W/cm 2 to 27.7×10 3 W/cm 2 and exposure time lasted for 1-20 s. Such doses were used to irradiate the fresh bovine liver tissue in vitro at a fixed depth of 20 mm. After the exposure, the tissue was dissected along the maximal section of the coagulative necrosis, and the long and short axes and the volume of the biological focal region were measured. Results BFR of HIFU was not equal to acoustic focal region. With the increase of acoustic intensity and exposure time, the volume of BFR increased, and its shape changed from an ellipsoid to a cone. When the intensity increased, the cone emerged earlier than an ellipsoid. When the intensity was constant, the shape index (K) of the BFR decreased gradually. Conclusion The exposure dose has influence on the shape and size of a BFR of HIFU, which has provided evidence for the study of dosimetry of HIFU.