DUAL-ENERGY X-RAY ABSORPTIOMETRY IS ALSO AN ACCURATE AND PRECISE METHOD TO MEASURE THE DIMENSIONS OF HUMAN LONG BONES

The accuracy, as well as the in vitro and in vivo precision of width a nd length measurements of human humerus and femur from dual energy X-r ay absorptiometry (DXA) images, was investigated. The measurement was based on the bone area inside a specified region determined by the bon e edge detection software of the scanner. The accuracy and in vitro pr ecision studies were performed using a bane-simulating aluminum phanto m embedded in different amounts of water. The in vivo precision was de termined by measuring both limbs twice in 10 subjects (for humerus) an d in 9 subjects (for femur). The accuracy was not significantly affect ed by the amount of water, and varied from 0.6 to 1.2%. Similarly, the in vitro precision varied from 0.4 to 0.6%. The average in vivo preci sion of the width measurement ranged from 0.4% (humeral and femoral mi dshaft) to 0.9% (proximal humerus), not depending on the size of the m easured bone. The precision of the length measurement was 0.3% for the humerus and 3.7% for the femoral neck. In conclusion, the standard DX A technique provides a reliable measurement of the width and length in human humerus and femur in vivo, and thus may be useful in evaluating the properties of these bones in conjunction with the standard bone m ineral measurements. Specifically, studies evaluating the effects of v arious types of mechanical loading (exercise) on bone may greatly bene fit from this possibility because not only the bone mineral content an d density but also the bone geometry change due to loading.