高强度聚焦超声治疗剂量对组织温升影响的研究

Effects of Therapeutic Dose on Temperature Rise Induced by High Intensity Focused Ultrasound in Tissue

测量了高强度聚焦超声 (HIFU)定点辐照新鲜离体牛肝脏时 ,不同声强和辐照时间下的组织焦点温升。根据 Pennes传热方程 ,从理论上分析了高强度聚焦超声定点辐照生物组织前后组织温度变化的规律 ,研究结果表明 :一定的声强下 ,总有一个辐照阈值时间存在 ,当辐照时间超过辐照阈值时间后 ,温升缓慢 ,声强越大 ,辐照阈值时间出现得更早 ;组织焦点温升、相对累积热剂量随声强、辐照时间的增加而增大 ;当治疗剂量一定时 ,声强对组织焦点温升的影响大于辐照时间对组织焦点温升的影响。因此 ,HIFU最适治疗剂量应满足 :适度的声强、辐照时间为该声强下的辐照阈值时间。

Based on the well-known Pennes' bioheat equation, we analyzed theoretically the temperature rise in tissue during high intensity focused ultrasound(HIFU) irradiation, and measured the focal temperature rise induced by HIFU in the treatment of freshly excised cow liver with different acoustic intensity and exposure time. The results showed that a threshold exposure time always existed under a certain acoustic intensity. Temperature rise was slow when exposure time exceeded the threshold exposure time.The greater the acoustic intensity was, the earlier the threshold time appeared. The focal temperature rise and the relative cumulative thermal dose (RCTD) increased with the increasement of acoustic intensity and exposure time. For a certain therapeutic dose, the effects of acoustic intensity on focal temperature rise were more distinct than the effects of exposure time on focal temperature rise. Therefore, the optimal HIFU therapeutic dose should meet the need, i.e. moderate acoustic intensity, and the exposure time be the threshold exposure time under this acoustic intensity.