相关函数法用于监控脉冲高强度聚焦超声治疗的准确性研究

摘要

目的 探讨脉冲高强度聚焦超声(PHIFU)治疗过程中超声监控的准确性,提高PHIFU治疗中超声判断组织坏死的灵敏度.方法 采用定点辐照牛肝组织的方法,按治疗剂量设定为A组(2000 J)和B组(1440 J),A、B两组再根据占空比不同分为A1组:100W连续波辐照20 s,A2组:100W占空比50％的脉冲波辐照40 s,A3组:100W占空比40％的脉冲波辐照50 s;B1组:120W连续波辐照12s,B2组:120W占空比50％的脉冲波辐照24 s,B3组:120W占空比40％的脉冲波辐照30 s.观察各组辐照后超声图像出现灰度变化,并对辐照前后图像进行相关函数分析,比较灰度变化与相关函数二者对坏死判断的准确性.结果 超声图像灰度增强用于判断PHIFU辐照后损伤的判对率仅为51％,相关函数法判对率可达到85％,明显高于超声灰度增强的方法.结论 PHIFU辐照损伤的监控不能仅依赖于超声图像灰度变化,相关函数法能够更为准确、灵敏的判断PHIFU所致的组织损伤.%Objective To investigate the accuracy of ultrasound monitoring during pulsed high intensity focused ultrasound (PHIFU) treatment and improve the sensitivity of ultrasound monitoring of tissue necrosis caused by PHIFU treatment. Methods Bovine liver ex vivo was dot-exposed with HIFU at the therapeutic doses of 2000 J (group A) and 1440 J (group B). The two groups were further divided into groups A1 (power 100 W, duty cycle 100%, irradiate 20 s) A2 (power 100 W, duty cycle 50%, irradiate 40 s), A3 (power 100 W, duty cycle 40%, irradiate 50 s), B1 (power 120 W, duty cycle 100%, irradiate 12 s), B2 (power 100 W, duty cycle 50%, irradiate 24 s), and B3 (power 100 W, duty cycle 40%, irradiate 30 s). The gray scale changes in the ultrasonic images after the exposures were observed, and the correlation function of the image was calculated before and after the exposure. The accuracy of evaluations based on the correlation function and gray-scale changes was compared. Results The correct rate of gray scale-based evaluation of tissue necrosis caused by PHIFU was only 51%, while that by correlation function-based evaluation reached 85%. Conclusion Monitoring of tissue necrosis caused by PHIFU treatment can not rely solely on evaluation of gray-scale change of the ultrasound images, and the correlation function-based evaluation can be more accurate and sensitive for that purpose.