Nakagami-Gamma统计模型参数成像表征高强度聚焦超声致热损伤:体外研究

Nakagami-Gamma statistical model parameter imaging for characterizing thermal injury induced by high intensity focused ultrasound:In vitro study

目的观察基于Nakagami-Gamma统计模型参数成像表征高强度聚焦超声(HIFU)致热损伤的效果。方法对离体猪里脊组织行HIFU热消融,于辐照间隙采集超声射频数据,以Nakagami-Gamma统计模型估计β参数并形成参数图,计算其与参考帧的对数差分;同步构建传统灰阶声像图和灰阶超声差分图,与Nakagami-Gamma对数差分图对比,根据热损伤区与周围组织的对比度噪声比(CNR)评价模型性能。结果利用Nakagami-Gamma模型可在灰阶声像图无明显相应表现时监测热损伤,且能明显提高消融区对比度。Nakagami-Gamma对数差分图的CNR[(1.04±0.60)dB]明显高于灰阶超声差分图[(0.35±0.18)dB](t=18.189,P<0.001),整体相对提升49.64%。结论Nakagami-Gamma统计模型可用于表征HIFU致热损伤。

Objective To explore the effect of Nakagami-Gamma statistical model parameter imaging for characterizing thermal injury induced by high intensity focused ultrasound(HIFU).Methods In vitro HIFU thermal ablation of porcine loin tissue was performed.Data of ultrasound radiofrequency were acquired in intervals of HIFU radiation and applied in a Nakagami-Gamma statistical model to estimateβparameters for forming parameter images,and the logarithmic differences compared with reference frame were calculated.Then conventional ultrasonic gray-scale images and gray-scale difference maps were constructed simultaneously and compared with Nakagami-Gamma logarithmic difference maps.The contrast-to-noise ratio(CNR)between thermally damaged area and the surrounding tissue was used to evaluate the performance of this model.Results The proposed method detected the occurrence of thermal damage when no apparent manifestation of thermal damage was shown om gray-scale images,and the contrast of ablation area was significantly improved.CNR of Nakagami-Gamma logarithmic difference maps([1.04±0.60]dB)were significantly higher than that of gray-scale difference maps([0.35±0.18]dB,t=18.189,P<0.001),with an overall relative increase of 49.64%.Conclusion Nakagami-Gamma statistical model could be used to characterize thermal injury induced by HIFU.