超声射频信号时域分析大鼠脂肪肝的初步研究

Ultrasound Tissue Characterization of Hepatic Fat in Rats Using Radiofrequency Signal Analysis

目的探讨超声射频信号多参数诊断SD大鼠脂肪肝价值。方法 32只大鼠分为对照组(n=8)和脂肪肝组(n=24),采用高脂饮食喂养建立大鼠脂肪肝模型。用高频超声探头以40 MHz的采样频率获取肝脏的16位超声数字射频信号,再在MATLAB7.0软件上计算感兴趣区域内射频信号包络的均值(Mean)、均值/标准差(MSR)、偏态量(SK)、峰态量(KU)4个参数,以病理结果为金标准,计算这些参数诊断脂肪肝的准确性,并与常规超声诊断的准确性比较。结果脂肪肝组Mean、MSR高于对照组(P<0.05),SK、KU低于对照组(P<0.05)。Mean、MSR、SK、KU诊断脂肪肝的ROC曲线下面积分别为0.85、0.96、0.98、0.98,临界值为38.67,1.75,1.08,1.43,诊断脂肪肝的灵敏度和特异度分别为70.8%和88.9%、87.5%和100%、95.8%和100%、95.8%和100%,而常规超声诊断的灵敏度和特异度为68.2%和66.7%。结论与常规超声相比,基于超声射频信号包络的参数MSR、SK、KU诊断脂肪肝准确性更高,可用于脂肪肝的辅助定量分析。

Objective To investigate the significance of multi-parameter quantitative evaluation of hepatic fat using ultrasound radiofrequency signal analysis.Methods Thirty two SD rats were divided into two groups,with 24 having fatty livers and 8 serving as normal controls.Radiofrequency signals were sampled with a 13-MHz ultrasound probe and digitized at 40 MHz in 16-bit resolution.Four statistical parameters of the radiofrequency envelope（Mean,Mean/SD ratio（MSR）,skewness（SK）,and kurtosis（KU）） within the ROI were calculated offline,and their ability to diagnose fatty liver was analyzed.Results The rats with fatty livers had greater Mean and MSR but lower skewness and kurtosis than the controls.The areas under the ROC curve of Mean,MSR,skewness and kurtosis for diagnosing fatty livers were 0.85,0.96, 0.98,and 0.98 respectively.The sensitivity and specificity of Mean,MSR,skewness and kurtosis for diagnosing fatty livers were 70.8%/88.9%,87.5%/100%,95.8%/100% and 95.8%/100% respectively,whereas conventional ultrasound achieved only 68.2% in sensitivity and 66.7% in specificity.Conclusion Compared with conventional ultrasound,radiofrequency signal analysis is more accurate in diagnosing fatty livers.