A Novel Method for Assessing Leg Compartmental Body Composition Using Dual Energy X-ray Absorptiometry

Purpose: Manual segmentation using dual energy X-ray absorptiometry (DXA) is a valid method for quantifying contralateral tissue asymmetries of the body, but has not been used to quantify body composition in the ipsilateral upper leg compartments. The purpose of this study was to examine the validity and reliability of DXA to quantify fat and lean tissue composition in the anterior and posterior thigh compartments. Methods: Twenty-one (10 male/11 female) college athletes (X¯age = 20.3+/-1.3 yrs) were assessed for total and regional body composition. Segmentation of the anterior and posterior thigh compartments was accomplished by scanning participants lying on their right and left sides using DXA (iDXA, General Electric Medical Systems, Madison, WI, USA). Each scan was manually segmented and analyzed by three technicians using enCore(TM) software (platform version 16.0, General Electric Medical Systems, Madison, WI, USA). Custom regions of interest (ROIs) were created from bony landmarks on the femur. In Analysis 1, the proximal border of the custom ROI on the frontal and lateral scans was placed at 40% of the length from the lateral epicondyle to the greater trochanter. The distal border was placed at 40% of the length from the lateral epicondyle to the distal end of the lateral malleolus. Lateral and medial borders were placed outside the leg area. To validate the segmentation method, lateral and frontal scan ROI measures of equal leg area for total, fat, and lean masses for each person and each leg were compared. In Analysis 2, proximal and distal ROI borders were placed at 80% of the length from the lateral epicondyle to the greater trochanter. Lateral and medial ROI borders were placed along the centerline of the shaft of the femur and outside of the leg area, respectively, for the anterior ROI compartment and the opposite for the posterior compartment using the custom area drawing tool to quantify compartmental tissue composition. For Analysis 1 we used paired t-tests to assess differences between the measurement methods for each leg (lateral vs. standard position). To assess intra- and inter-rater reliability for Analysis 2, we used intra-class correlation coefficients (ICC) and coefficients of variation (CV) and compared the lateral segmented technique for measures of total, fat, and lean masses. Results: All comparisons of total, fat, and lean masses between the frontal and lateral DXA scans were non-significant (mean differences in right leg: 0.015+/-0.12 kg, 0.041+/-0.19 kg, -0.0734+/-0.22 kg; mean differences in left leg: 0.041+/-0.12 kg, -0.023+/-0.17 kg, 0.017+/-0.23 kg, respectively; p-value range: 0.15 to 0.74). ICCs were high for all composition measures between- and within-raters, ranging from 0.983 to 0.999 and 0.954 to 0.999, respectively, with low variation across measures (all CVs: <5%). Conclusion: This study suggests that DXA measures using lateral subject positioning and custom ROIs to assess upper leg total, fat, and lean masses are valid and reliable compared with total-body frontal subject positioning. This novel method allows for anterior/posterior compartmental examination of the aforementioned measures using custom ROIs. Future studies are needed to determine the performance and clinical usefulness of lateral position measures regarding prevention or rehabilitation of injury.;Key Words: Dual-Energy X-ray Absorptiometry, Body Composition, Validity, Reliability.