Avaliação das características musculares por imagem de tomografia computadorizada: comparação entre sítios anatômicos

Abstract

Studies evaluating low muscle mass (or sarcopenia) by computed tomography (CT) images often evaluate the third lumbar vertebrae (L3). However, lower limbs appendicular muscles are more involved in balance, physical function, locomotion, and daily activities. This study aimed to compare the assessment of skeletal muscle area (SMA in cm²), skeletal muscle index (SMI in cm²/m²) and skeletal muscle density (SMD in HU) between third lumbar vertebra (L3) and thigh landmarks, and the agreement in diagnosing low muscle mass and low SMD (L3 as the reference method). This was multicenter cross-sectional study including healthy individuals (≥ 18 years old) of both sexes, who had an elective CT exam including abdominal and pelvic regions. CT images were analyzed to evaluate SMA, SMI and SMD. Muscle abnormalities (low SMA, SMI, and SMD) were defined as values below the 5th percentile from a subsample of healthy young individuals (n=111; 18-39 years; 55,9% female). Correlation coefficients, Bland-Altman graphs and receiver operating characteristic (ROC) curves were calculated for the total sample and stratified by sex and age. A total of 268 individuals (44.3 ± 15.2 years) were evaluated (53% female). Significant (p <0.001 for all analysis) and strong correlations between SMA (rho = 0.896), SMI (rho = 0.853), and SMD (rho = 0.864) compared to L3 and thigh landmarks were observed. For the ROC curves, similar AUC values were obtained for males (0.981), females (0.895), younger (0.902) and older adults (0.894). Muscle characteristics between L3 and thigh landmarks have a strong correlation. This suggests that images of the thigh can be used to characterize muscle characteristics. Image acquisition and analysis of thigh region is simpler, with less radiation exposure, and consequently more appropriate for longitudinal analysis.