Cadaver validation of skeletal muscle measurement by magnetic resonance imaging and computerized tomography

TLDR

MRI and CT are promising reference methods for quantifying skeletal muscle mass, yet previous validation studies used outdated techniques, assessed anatomic rather than adipose‑tissue‑free muscle, focused only on the thigh, or reported large estimation errors. This study aimed to compare arm and leg adipose‑tissue‑free skeletal muscle cross‑sectional area estimates from standard MRI and CT with cadaver measurements, and to validate MRI and CT assessments of interstitial and subcutaneous adipose tissue. Standard MRI and CT acquisition and image‑analysis protocols were applied to measure cross‑sectional areas of arm and leg ATFSM and adipose tissue, with results compared to cadaver estimates. ATFSM areas measured by MRI (38.9 ± 22.3 cm²), CT (39.7 ± 22.8 cm²), and cadaver (39.5 ± 23.0 cm²) were not different (P > 0.001) and highly correlated (r = 0.99), with similar agreement for interstitial and subcutaneous adipose tissue, supporting MRI and CT as reliable reference methods for appendicular muscle and adipose tissue measurement in vivo.

Abstract

Magnetic resonance imaging (MRI) and computerized tomography (CT) are promising reference methods for quantifying whole body and regional skeletal muscle mass. Earlier MRI and CT validation studies used data-acquisition techniques and data-analysis procedures now outdated, evaluated anatomic rather than adipose tissue-free skeletal muscle (ATFSM), studied only the relatively large thigh, or found unduly large estimation errors. The aim of the present study was to compare arm and leg ATFSM cross-sectional area estimates (cm 2 ) by using standard MRI and CT acquisition and image-analysis methods with corresponding cadaver estimates. A second objective was to validate MRI and CT measurements of adipose tissue embedded within muscle (interstitial adipose tissue) and surrounding muscle (subcutaneous adipose tissue). ATFSM area ( n = 119) by MRI [38.9 ± 22.3 (SD) cm 2 ], CT (39.7 ± 22.8 cm 2 ), and cadaver (39.5 ± 23.0 cm 2 ) were not different ( P > 0.001), and both MRI and CT estimates of ATFSM were highly correlated with corresponding cadaver values [MRI: r = 0.99, SE of estimate (SEE) 3.9 cm 2 , P < 0.001; and CT: r = 0.99, SEE = 3.8 cm 2 , P < 0.001]. Similarly good results were observed between MRI- and CT-measured vs. cadaver-measured interstitial and subcutaneous adipose tissue. For MRI-ATFSM the intraobserver correlation for duplicate measurements in vivo was 0.99 [SEE = 8.7 cm 2 (2.9%), P < 0.001]. These findings strongly support the use of MRI and CT as reference methods for appendicular skeletal muscle, interstitial and subcutaneous adipose tissue measurement in vivo.