MRI监控高强度聚焦超声辐照升温的有效性和准确性研究

Efficacy and accuracy study of MRI thermometry monitor in high intensity focused ultrasound exposure

目的探讨高强度聚焦超声(HIFU)辐照过程中,MRI靶区温度监控的有效性和准确性。方法 HIFU辐照离体牛肝组织,对比MRI的温度图(T-Map)显示坏死区域与实际解剖坏死区域面积,以检验T-Map监控的有效性;HIFU辐照仿组织透明体模,对比MRI所测温度与光纤传感器所测温度。结果 T-Map所示的坏死区面积和实际坏死区面积出现统计学差异(P>0.05)的概率约为25%;对小于1℃/s的缓慢温度变化,MRI和光纤的测温结果较为一致,二者的平均差异在2.6℃以内;而对于剧烈的温度变化,二者的平均差异达到5℃以上。结论 MRI的T-Map可对靶区坏死情况提供一定的参考信息,但结果并不完全可靠,同时MRI测温的精确性还有待进一步加强。

ABSTRACT Objective To investigate the accuracy and efficacy of MRI thermometry during high intensity focused ultrasound （HIFU） exposure. Methods HIFU was applied on bovine liver tissue in vitro, and then the necrosis square of MRI T-Map and practical tissue was compared, HIFU was also applied to expose the tissue-mimicking phantom, and then the temperature measured by MRI and optical fiber temperature sensor was compared to verify the accuracy of MRI thermometry. Results The probability for necrosis square of T-Map statistically different from the necrosis square of the practical tissue was 25% （P 〉 0.05）; When the temperature change was less than 1℃/s, the result of MRI thermometry was comparatively consistent with the optical fiber sensor, their mean difference was less than 2.6℃ , while for the rapid temperature change, the mean difference was more than 5.0℃. Conclusion T-map of MRI can provide some information for necrosis of target area, but the result is not reliable enough, and the accuracy of MRI thermometry is need to be improved.