To determine the relationship between muscle echo intensity (EI) and fractal dimension (FD), and the diagnostic performance of both ultrasound parameters for the identification of frailty phenotype. A retrospective interpretation of ultrasound scans from a previous cohort (November 2014–February 2015) was performed. The sample included healthy participants <60 years old, and participants ≥60 divided into robust, pre-frail, and frail groups according to Fried frailty criteria. A region of interest of the rectus femoris from the ultrasound scan was segmented, and histogram function was applied to obtain EI. For fractal analysis, images were processed using two-dimensional box-counting techniques to calculate FD. Statistical analyses were performed with diagnostic performance tests. A total of 102 participants (mean age 63 ± 16, 57 men) were evaluated. Muscle fractal dimension correlated with EI (r = .38, p < .01) and showed different pattern in the scatter plots when participants were grouped by non-frail (control + robust) and frail (pre-frail + frail). The diagnostic accuracy for EI to categorize frailty was of 0.69 (95%CI: 0.59–0.78, p = .001), with high intra-rater (ICC: 0.98, 95%CI: 0.98–0.99); p < .001) and inter-rater (ICC: 0.89, 95%CI: 0.75–0.95; p < .001) reliability and low measurement error for both parameters (EI: −0.18, LOA95%: −10.8 to 10.5; FD: 0.00, LOA95%: −0.09 to 0.10) in arbitrary units. The ROC curve combining both parameters was not better than EI alone (p = .18). Muscle FD correlated with EI and showed different patterns according to frailty phenotype, with EI outperforming FD as a possible diagnostic tool for frailty.

确定肌肉回声强度 (EI) 和分形维数 (FD) 之间的关系，以及用于识别虚弱表型的两种超声参数的诊断性能。对先前队列（2014 年 11 月至 2015 年 2 月）的超声扫描进行了回顾性解释。样本包括<60岁的健康参与者，60岁以上的参与者根据Fried虚弱标准分为健壮组、体弱前组和虚弱组。对来自超声扫描的股直肌感兴趣区域进行分割，并应用直方图函数来获得 EI。对于分形分析，使用二维盒计数技术处理图像以计算 FD。使用诊断性能测试进行统计分析。共有 102 名参与者（平均年龄 63 ± 16，57 名男性）进行了评估。肌肉分形维数与 EI 相关（r  = .38, p  < .01) 并且当参与者按非虚弱（对照组 + 健壮）和虚弱（体弱前 + 虚弱）分组时，散点图中显示出不同的模式。EI 对虚弱进行分类的诊断准确性为 0.69 (95%CI: 0.59–0.78, p  = .001)，内部评分者较高 (ICC: 0.98, 95%CI: 0.98–0.99)；p  < .001）和评分者间（ICC：0.89，95%CI：0.75–0.95；p  < .001）两个参数的可靠性和低测量误差（EI：-0.18，LOA95%：-10.8 至 10.5；FD : 0.00, LOA95%: -0.09 to 0.10) 任意单位。结合这两个参数的 ROC 曲线并不优于单独的 EI ( p = .18）。肌肉 FD 与 EI 相关并根据虚弱表型显示不同的模式，EI 优于 FD 作为虚弱的可能诊断工具。