目的：本研究旨在应用多模态超声测量股直肌相关参数，评估多模态超声测量指标与金标准人体生物电阻抗分析法（bio-electrical impedance analysis, BIA）测量结果的相关性，探究多模态超声测量股直肌诊断外科老年住院患者肌肉质量降低的临床应用价值。

方法：本研究依照亚洲肌肉衰减症工作组（Asian Working Group on Sarcopenia, AWGS）诊断标准，将纳入的146例外科老年住院患者分为低肌肉质量组和正常肌肉质量组，其中低肌肉质量组共60例，正常肌肉质量组共86例。上述患者均在入院后完善BIA检查，收集相关临床资料，得到四肢骨骼肌质量指数（appendicular skeletal muscle mass index, ASMI），使用多模态超声测量股直肌厚度、横截面积、剪切波速度和弹性模量。比较两组患者超声测量指标差异性，分析超声测量指标与ASMI相关性，选取相关性良好的指标绘制受试者工作特征（receiver operator characteristic, ROC）曲线，探索多模态超声诊断肌肉质量降低的特异度、灵敏度及最佳阈值，并基于综合参数构建临床预测模型。

结果：低肌肉质量组与正常肌肉质量组患者在年龄、性别分布上均无统计学差异，低肌肉质量组患者体重、BMI、ASM、ASMI、肌肉厚度、横截面积、剪切波速度、弹性模量均显著低于正常肌肉质量组（P＜0.001）。肌肉厚度、横截面积、剪切波速度、弹性模量均与ASMI呈显著正相关，其中横截面积相关性最显著（r=0.798，P＜0.001）。基于本研究样本利用ROC曲线分析多模态超声测量指标诊断肌肉质量降低的效能，四项指标曲线下面积均大于0.7，其中横截面积诊断效能最佳，ROC曲线下面积0.905，特异度94.2%，灵敏度78.3%，诊断阈值3.125cm²。

结论：多模态超声测量股直肌各项参数与金标准相关性良好，诊断肌肉质量降低效能较高，在老年肌肉衰减症患者早期评估及诊断方面具有临床应用价值。

Objective: The study aims to use multimodal ultrasound to measure the related parameters of rectus femoris and to evaluate the correlation between multimodal ultrasound measurement and gold standard bioelectrical impedance analysis (BIA), so as to explore the clinical value of multimodal ultrasound measurement of rectus femoris in the diagnosis of low muscle mass in elderly surgical inpatients.

Methods: In this study, according to the diagnostic criteria of Asian working group on sarcopenia (AWGS), the elderly surgical inpatients were divided into two groups: low muscle mass group (n = 60) and normal muscle mass group (n = 86). All the above patients were examined by BIA after admission, and the relevant clinical data were collected to obtain the appendicular skeletal muscle mass index (ASMI). The thickness, cross-sectional area, shear wave velocity and elastic modulus of rectus femoris were measured by multimodal ultrasound. By comparing the differences of ultrasonic measurement indexes between the two groups, analyzing the correlation between ultrasound measurement indexes and ASMI, selecting the indexes with good correlation to draw ROC curve, to explore the specificity, sensitivity and cut-off value of multimodal ultrasound in the diagnosis of muscle mass decline, and construct a clinical prediction model based on comprehensive parameters.

Results: There was no significant difference in age and sex between the low muscle mass group and the normal muscle mass group. The body weight, BMI, ASM, ASMI, muscle thickness, cross-sectional area, shear wave velocity and elastic modulus in the low muscle mass group were significantly lower than those in the normal muscle mass group (P < 0.001). Muscle thickness, cross-sectional area, shear wave velocity and elastic modulus were positively correlated with ASMI, among which the cross-sectional area was the most significant (r = 0.798, P < 0.001). Based on the samples of this study, the efficiency of multimodal ultrasound measurement in the diagnosis of low muscle mass was analyzed by ROC curve. The area under the curve of the four indexes was more than 0.7. The diagnostic efficiency of cross-sectional area was the best, the area under the curve was 0.905, the specificity was 94.2%, the sensitivity was 78.3%, and the cut-off value was 3.125cm².

Conclusion: The indexes of rectus femoris by multimodal ultrasound has a good correlation with the gold standard, and has a high efficiency in the diagnosis of low muscle mass, which has clinical application value in early evaluation and diagnosis of elderly patients with sarcopenia.