MRIgHIFU治疗的热损伤阈值研究  

Research on the Threshold of Thermal Tissue Damage for MRIgHIFU

作　　者：刘莉莉[1] 李发琪[1] 龚晓波[1] 刘映江[1] 胡晓[1] 

机构地区：[1]重庆医科大学生物医学工程系,重庆市超声医学工程重点实验室,重庆400016

出　　处：《科技导报》2009年第4期50-53,共4页Science & Technology Review

基　　金：国家"十一五"科技支撑计划项目(2006BAI03A02);国家自然科学基金重点项目(30830040);重庆市科技攻关项目(2007AA5020)

摘　　要：研究基于磁共振T-Map的等效热剂量积分法监控高强度聚焦超声治疗的可行性,并筛选出高强度聚焦超声损伤组织的热剂量阈值。运用磁共振导航高强度聚焦超声治疗系统,使用1MHz、焦距为150mm、直径150mm的聚焦超声换能器,用不同辐照声功率和辐照时间定点辐照深度为20mm的新鲜离体牛肝脏,辐照过程中用磁共振的测温序列采集各体素随时间变化的温度值并计算各体素的Eq43值,比较计算结果与发生凝固性坏死的Eq43参考阈值,判断该体素是否发生坏死,得到发生凝固性坏死的热剂量区域轮廓和面积。辐照结束后沿凝固性坏死最大面剖开牛肝组织,测量凝固性坏死的面积。选择不同的Eq43参考阈值,并将热剂量计算得到的坏死面积与实际坏死面积进行比较,筛选出离体牛肝组织发生凝固性坏死的最佳热剂量参考阈值。结果表明,基于磁共振T-Map的等效热剂量积分法得到的凝固性坏死的面积值能很好地反应实际发生凝固性坏死的情况,当Eq43参考阈值选为31.2min时,各辐照声功率和辐照时间下两者大小均无统计学差异。热剂量法为HIFU治疗提供了一种新的判断凝固性坏死发生的方法,这种方法可以实时地反馈控制超声辐照剂量,提高了治疗的安全性和有效性。This paper explores in vitro the feasibility of using the T-mapping of MRI-derived temperature and thermal dose measurements to determine the threshold of thermal tissue damage. The MR imaging guided HIFU system was used, the parameters of therapeutic transducer were： frequency-1 MHz, diameter-150 mm, focal length-150 mm. Sonications were delivered in fresh beef liver tissue in vitro at a fixed depth of 20 mm and at varying powers and times. Temperature-sensitive MR images obtained during the sonications were used to estimate the temperature and the thermal dosage of each voxel in the target region was calculated. The thermal dosage of each voxel is compared with the reference threshold thermal dosage, so as to determine the boundary and area of the coagulated tissue. After the exposure, the tissue was dissected along the maximal section of the coagulation necrosis, and the area of the biological focal region was measured. Comparing results of different reference threshold thermal dosage, the best dosage in fresh beef liver tissue is obtained. The results show that the occurrence of tissue damage correlates well with the equivalent thermal dose calculation based on the T-mapping of MRI, and there were no statistical differences when the reference threshold thermal dosage was 31.2 min. The equivalent thermal dose calculation based on the T-mapping of MRI provides an index to predict the threshold for tissue damage in vivo, which may be used to improve the online control over minimally invasive thermal treatments and increase the safety and effectiveness of the therapy.

关 键 词：磁共振引导的高强度聚焦超声 磁共振测温 热剂量 

分 类 号：R730.5[医药卫生—肿瘤]