Three-dimensional surface imaging for clinical trials: Improved precision and reproducibility in circumference measurements of thighs and abdomens

Background and Objectives: Numerous body contouring and laser-assisted liposuction devices have recently obtained or are seeking FDA clearance, and assessment of efficacy of these devices is largely based upon qualitative comparisons of before and after photographs and measurable changes in patient circumference. The current standard for measuring body circumference in clinical trials involves the use of a standard measuring tape. These manual measurements introduce human error and may incorrectly support or refute a device or procedure's efficacy. A promising alternative to manual measurements is three-dimensional (3D) photography. This technology allows circumference measurements to be performed on 3D digital models. Our objective is to compare the precision and reproducibility of manual versus 3D photographic measurement of body circumference. Study Design/Materials and Methods: Thirty subjects completed this IRB approved study. Each subject's thighs and abdomen were measured twice by each of two blinded investigators and twice by the 3D system. Results: For right and left thigh circumference, the variance of the replication errors [measurement 1-measurement 2] for the human investigators was 20.5% larger than the variance for the 3D photography system. For abdominal circumference, the variance for the human investigators was 231.3% larger than the variance for the 3D system. Conclusions: 3D photography is a valuable tool that enables investigators to reliably detect minute changes in body shape; consequently, 3D photography reduces the number of subjects needed to sufficiently power a clinical study. For studies involving abdominal circumference, utilizing 3D photography reduces the number of subjects needed by 1/2 to 2/3.