目的 以CT肝脾衰减比值（CT_L/S）为参考标准，评估超声衰减分析（ultrasound attenuation analysis， USAT）技术在代谢相关脂肪性肝病（metabolic dysfunction-associated steatotic liver disease， MASLD）肝脂肪变性定量分析中的诊断效能。 方法 前瞻性纳入拟诊MASLD患者及健康成年人。所有受试者于同日完成USAT成像及CT检查。通过Bland-Altman检验、组内相关系数（interclass correlation coefficient，ICC）评估USAT稳定性。Spearman分析USAT值与肝脂肪变性分级的相关性。通过线性回归分析确定USAT值的影响因素。采用受试者工作特征（receiver operating characteristic，ROC）曲线评估USAT在肝脂肪变性定量分析中的诊断效能，并与临床预测模型对比（DeLong检验）。 结果 共纳入268例受试者，基于CT_L/S分级肝脂肪变性程度分布如下：正常肝脏组64例，MASLD组204例（轻度脂肪肝：78例，中度脂肪肝：69例，重度脂肪肝：57例）。Bland-Altman检验及ICC分析显示USAT测值一致性优异。USAT值与CT_L/S相关性良好（r = -0.850，95%CI：-0.880 ~ -0.813），且与肝脂肪变性分级存在强相关性（r = 0.846，95%CI：0.807 ~ 0.878），均P < 0.001。随着肝内脂肪含量增加，USAT值递增，USAT在无、轻、中、重度脂肪肝的中位数分别为0.55、0.67、0.77、0.86 dB/（cm·MHz），组间差异有统计学意义，均P < 0.001。经简单线性回归、多元线性回归分析，肝脂肪变性分级为USAT值的决定性因素。USAT检测轻、中、重度肝脂肪变性分级的截断值分别为0.61、0.71、0.82 dB/（cm·MHz），对应的ROC曲线下面积（area under the curve， AUC）分别为0.90、0.88、0.87，显著高于临床预测模型（DeLong检验P < 0.01）。 结论 USAT为一种可定性观察、定量分析MASLD患者肝脂肪变性程度的无创、便捷新技术，未来或将广泛应用于肝内脂肪定量的筛查。

Objective To evaluate the diagnostic performance of ultrasound attenuation analysis （USAT） for quantifying hepatic steatosis in metabolic dysfunction-associated steatotic liver disease （MASLD）， the CT liver-to-spleen attenuation ratio （CT_L/S） was used as the reference standard. Methods In this prospective study， we consecutively enrolled adult participants who were clinically suspected of having MASLD and healthy control volunteers. All participants underwent both USAT imaging and non-contrast CT during the same visit. The repeatability of USAT measurements was evaluated using Bland-Altman analysis and the intraclass correlation coefficient （ICC）. The association between USAT values and the grade of hepatic steatosis was analyzed by means of Spearman′s rank correlation. Factors influencing USAT values were explored through linear regression analysis. The diagnostic accuracy of USAT was determined via receiver operating characteristic （ROC） curve analysis and compared with a clinical prediction model using the DeLong test. Results Among the 268 enrolled participants， CTL/S grading identified 64 individuals with normal liver and 204 with MASLD， which included 78 cases of mild， 69 cases of moderate， and 57 cases of severe steatosis. Bland-Altman analysis and ICC assessment demonstrated excellent agreement for USAT measurements. USAT values were strongly inversely correlated with CTL/S （r = -0.850， 95%CI： -0.880 - -0.813） and strongly positively correlated with steatosis grade （r = 0.846， 95%CI： 0.807 - 0.878； both P < 0.001）. The median USAT value increased progressively as the severity of steatosis increased： 0.55 dB/cm/MHz （normal liver）， 0.67 dB/cm/MHz （mild steatosis）， 0.77 dB/cm/MHz （moderate steatosis）， and 0.86 dB/cm/MHz （severe steatosis）， with significant inter-group differences （all P < 0.001）. Based on simple and multiple linear regression analyses， fatty liver grading was found to be the determining factor for USAT. The optimal USAT cut-off values for detecting mild， moderate， and severe steatosis were 0.61， 0.71， and 0.82 dB/cm/MHz， respectively， yielding areas under the curve （AUCs） of 0.90， 0.88， and 0.87， which were significantly superior to those of the clinical prediction model （DeLong test， all P < 0.01）. Conclusions USAT， a non-invasive， practical， and novel technique， offers both qualitative and quantitative assessment of hepatic steatosis in MASLD. It has significant potential for broad adoption in screening and quantifying hepatic fat content.