Computerised tomography skeletal muscle and adipose surface area values in a healthy Caucasian population

The analysis of computerised tomography (CT) images to provide body composition data has grown exponentially. Despite this, there remains limited published data defining the normal range of skeletal muscle area and adipose tissue area using CT. The aim of this study was to determine age- and sex-specific body composition values using CT at the level of the third lumbar vertebrae, in a Caucasian population with a healthy body mass index (BMI). In addition, we sought to develop threshold values for low skeletal muscle mass using these data.

We included 107 healthy Caucasian patients (46 males; 61 females) with a healthy BMI (18-25 kg/m²) for analysis. Body composition data were obtained from a single transverse CT image at the mid-third lumbar vertebrae using ImageJ software. Tissue segmentation was performed using Hounsfield unit thresholds of -29 to +150 for muscle and -190 to -30 for adipose tissue.

The mean age of the study cohort was 47.8 ± 11.0 years (range 21-73) with a median BMI of 23.7 kg/m² (interquartile range 22.3-24.8). Patients were sub-divided into age above or below 50 years. Cut-offs for low muscle quantity, representing two standard deviations below the young healthy population mean values, were 43.5 cm²/m² for males and 30.0 cm²/m² for females.

Our data provide an insight into the distribution of skeletal muscle and adipose tissue surface area values measured on CT from a healthy Caucasian population. Our CT-derived cut-offs for low muscle quantity, based on international guidelines, are much lower than those previously suggested.