Department of Kinesiology, Michigan State University, East Lansing, MI, USA.
College of Osteopathic Medicine, Michigan State University, East Lansing, MI, USA.
Ultrasound Med Biol. 2023 Dec;49(12):2590-2595. doi: 10.1016/j.ultrasmedbio.2023.08.027. Epub 2023 Sep 27.
The aim of the work described here was to evaluate quadriceps muscle ultrasound metrics and common demographic variables to create a conversion equation that validly predicts magnetic resonance imaging (MRI) percent intramuscular fat after anterior cruciate ligament reconstruction (ACLR).
We recruited 15 participants between the ages of 18 and 35 y who were 1-5 y post-ACLR. For the MRI assessment, we used an iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) sequence to assess the mid-thigh. A single reader manually segmented the rectus femoris on two consecutive MRI slices using ITK-Snap to estimate the percent intramuscular fat. For the ultrasound assessment, a single investigator captured transverse panoramic ultrasound images of the mid-thigh with the participant positioned supine and the knee flexed to 30°. A separate single reader used ImageJ to manually segment the rectus femoris ultrasound images. Ultrasound metrics included muscle cross-sectional area, echo intensity and subcutaneous fat thickness. A stepwise linear multiple regression was used to develop an equation to predict MRI percent intramuscular fat using the ultrasound metrics and common demographics (i.e., age, sex, height, mass). Additionally, intraclass correlation coefficients (ICC) and Bland-Altman plots were used to assess the agreement between true and estimated percent intramuscular fat.
Echo intensity and age significantly predicted MRI intramuscular fat percent (p = 0.003, r = 0.62). When using the conversion equation, there was high agreement (ICC = 0.87, 95% confidence interval: 0.62-0.96) between the estimated and true percent intramuscular fat.
Our patient population-specific conversion equation that uses quadriceps muscle ultrasound echo intensity and age is a valid estimate of MRI percent intramuscular fat.
本研究旨在评估股四头肌超声测量指标和常见人口统计学变量，以创建一个转换方程，该方程可有效预测前交叉韧带重建（ACLR）后磁共振成像（MRI）的肌肉内脂肪百分比。
我们招募了 15 名年龄在 18 岁至 35 岁之间、ACL 重建后 1 至 5 年的参与者。对于 MRI 评估，我们使用迭代水脂分解与回波不对称和最小二乘法估计（IDEAL）序列来评估大腿中段。一位读者使用 ITK-Snap 在连续两个 MRI 切片上手动分割股直肌，以估计肌肉内脂肪百分比。对于超声评估，一名研究人员让参与者仰卧位，膝关节弯曲至 30°，在大腿中段采集横向全景超声图像。一位独立的读者使用 ImageJ 手动分割股直肌的超声图像。超声指标包括肌肉横截面积、回声强度和皮下脂肪厚度。使用逐步线性多元回归建立一个方程，使用超声指标和常见人口统计学（即年龄、性别、身高、体重）来预测 MRI 的肌肉内脂肪百分比。此外，还使用组内相关系数（ICC）和 Bland-Altman 图评估真实和估计的肌肉内脂肪百分比之间的一致性。
回声强度和年龄显著预测了 MRI 肌肉内脂肪百分比（p=0.003，r=0.62）。当使用转换方程时，估计和真实的肌肉内脂肪百分比之间具有高度一致性（ICC=0.87，95%置信区间：0.62-0.96）。
我们的患者人群特定的转换方程，使用股四头肌超声回声强度和年龄，是 MRI 肌肉内脂肪百分比的有效估计值。
