摘要目的：离体实验研究高强度聚焦超声（HIFU）焦域处温度场的分布及变化，为HIFU治疗的安全性和可靠性提供理论依据。方法对重约1000 g猪里脊肌肉块（长10 cm×宽8 cm ×厚6 cm）在一个矢状面进行间隔5 mm平行连续的5个辐照点行单层HIFU辐照，以MRI成像系统内置质子频率共振位移测温序列进行实时温度图成像，研究HIFU辐照过程中组织温度场的分布变化，分析60℃以上辐照区域大小、位置及其变化。结果在HIFU辐照第五点时平均最高温度大于前4点，差异有统计学意义（P<0.05）。辐照点2、3、4和5焦域60℃以上区域近场边缘到焦点中心的各个平均距离均大于焦域60℃以上区域远场边缘到焦点中心的平均距离，差异有统计学意义（P<0.05）。随着每点超声辐照能量的累积，温度图显示60℃以上区域呈锥形向焦域近场明显扩展，而焦域远场则呈逐渐减弱。结论随着HIFU辐照时间增加，焦域温度场的最高温度增高，60℃以上区域面积呈锥形向声源方向逐渐扩展，而焦域远场显著减弱。

abstractsObjectiveTo investigate the distribution and variation of focal regional temperature field of the high intensity focused ultrasound (HIFU) in vitro for assessing the safety and reliability of focused ultrasound ablation.MethodsMRgHIFU (acoustic power of 150w, intensity: 1s of sonication time /1s of cooling time) were applied for 30s at one spot and total 150s at five spots to produce lesions in porcine muscle tissue (width 8 cm, length 10 cm, thickness 6 cm, n=3), respectively. The dynamic changes of tissue temperatures at far field (post-focal field) and near field (pre-focal field) of the focal region were detected and measured by using MRI real-time temperature mapping.ResultsThe average maximum temperature of the 5th point was higher than other four points (P<0.05). For all five points except the 1st point , the mean ranges between the fringe of ≥60℃temperature field and focal regional center at the near field were greater than that of the far field (P<0.05). With the accumulation of sonication energy, the temperature map showed that the ≥60℃temperature region had been conically extended at the near field and shrunk at the far field. ConclusionThe accumulation of sonication energy made the maximum temperature of focal region rise and the ≥60℃ temperature region conically extend to the acoustic source at the near field and fade at the far field gradually.