Total body skeletal muscle and adipose tissue volumes: estimation from a single abdominal cross-sectional image

TLDR

A single abdominal cross‑sectional CT or MRI scan routinely acquired in adipose tissue studies can also yield estimates of total body skeletal muscle and adipose tissue volumes. The study examined how abdominal muscle and fat areas measured on a single slice predict whole‑body muscle and fat volumes in a large, diverse cohort of healthy adults. Whole‑body muscle and fat volumes were obtained by multislice MRI in 328 subjects (123 men, 205 women) and used to build and validate predictive models from single‑slice areas, with an additional 49 subjects for validation. The models showed strong correlations (r = 0.71–0.96) and only modest gains in R² with demographic covariates; to match power, studies using a single slice would need 17–24 % more participants for muscle and 6–12 % more for fat, yet the slice still provides useful group‑level estimates.

Abstract

A single abdominal cross-sectional computerized axial tomography and magnetic resonance image is often obtained in studies examining adipose tissue (AT) distribution. An abdominal image might also provide additional useful information on total body skeletal muscle (SM) and AT volumes with related physiological insights. We therefore investigated the relationships between abdominal SM and AT areas from single images and total body component volumes in a large and diverse sample of healthy adult subjects. Total body SM and AT volumes were derived by whole body multislice magnetic resonance imaging in 123 men [age (mean ± SD) of 41.6 ± 15.8 yr; body mass index of 25.9 ± 3.4 kg/m 2 ] and 205 women (age of 47.8 ± 18.7 yr; body mass index of 26.7 ± 5.6 kg/m 2 ). Single abdominal SM and AT slice areas were highly correlated with total body SM ( r = 0.71–0.92; r = 0.90 at L 4 –L 5 intervertebral space) and AT ( r = 0.84–0.96; r = 0.94 at L 4 –L 5 intervertebral space) volumes, respectively. R 2 increased by only 5.7–6.1% for SM and 2.7–4.4% for AT with the inclusion of subject sex, age, ethnicity, scanning position, body mass index, and waist circumference in the model. The developed SM and AT models were validated in an additional 49 subjects. To achieve equivalent power to a study measuring total body SM or AT volumes, a study using a single abdominal image would require 17–24% more subjects for SM and 6–12% more subjects for AT. Measurement of a single abdominal image can thus provide estimates of total body SM and AT for group studies of healthy adults.