A pose-independent method for accurate and precise body composition from 3D optical scans

Abstract

Objective: The aim of this study was to investigate whether digitally re-posing three-dimensional optical (3DO) whole-body scans to a standardized pose would improve body composition accuracy and precision regardless of the initial pose.

Methods: Healthy adults (n = 540), stratified by sex, BMI, and age, completed whole-body 3DO and dual-energy X-ray absorptiometry (DXA) scans in the Shape Up! Adults study. The 3DO mesh vertices were represented with standardized templates and a low-dimensional space by principal component analysis (stratified by sex). The total sample was split into a training (80%) and test (20%) set for both males and females. Stepwise linear regression was used to build prediction models for body composition and anthropometry outputs using 3DO principal components (PCs).

Results: The analysis included 472 participants after exclusions. After re-posing, three PCs described 95% of the shape variance in the male and female training sets. 3DO body composition accuracy compared with DXA was as follows: fat mass R² = 0.91 male, 0.94 female; fat-free mass R² = 0.95 male, 0.92 female; visceral fat mass R² = 0.77 male, 0.79 female.

Conclusions: Re-posed 3DO body shape PCs produced more accurate and precise body composition models that may be used in clinical or nonclinical settings when DXA is unavailable or when frequent ionizing radiation exposure is unwanted.

Figure 1.

A) Standard A-pose stance on Fit3D. B-D) Alternate A-pose stances on Fit3D. E-H) Reposed meshes A-D. Images A, B, C, and D was a person in different poses. Images, E, F, G, H showed them reposed.

Figure 2.

(Top) The mean body shape of males and females in the study sample. These are 110,000-vertex 3D meshes. (Below) The first five principal components of shape variance in males (left) and females (right). Each PC has an according −3 SD (left) and +3 SD (right).

Figure 3.

Box and whisker plots. N=8 (male = 4). Each subject had four scans (one with standard protocol and three in various poses). Body composition and anthropometric estimates from the three various poses were subtracted from the standard protocol scan. A-pose and T-pose methods were both used to test the stability of both methods. P-values [FM=0.05, FFM=0.05, %Fat=0.04, VAT=0.09, total surface area=0.99, total volume=0.23].

Figure 4.

Bland-Altman plots of female and male DXA vs. 3DO T-pose body composition values.