HETEROGENEITY OF TRABECULAR BONE-STRUCTURE IN THE CALCANEUS USING MAGNETIC-RESONANCE-IMAGING

The purpose of this study was to quantify the heterogeneity in the tra becular bone structure in the calcaneus. Magnetic resonance (MR) image s of the calcaneus were obtained in the sagittal plane at an inplane r esolution of 195 mu m and a slice thickness of 1000 mu m in 12 young n ormal subjects. Regions of interest (ROI) were selected to cover the c alcaneus using a grid of square boxes (10 mm per side), A thresholding technique based on the regional intensity histogram was used to segme nt the images into trabecular bone and marrow phases and to calculate measures such as apparent trabecular bone area fraction, apparent trab ecular spacing, apparent trabecular thickness and apparent trabecular number, Bone mineral density (BMD) of the calcaneus was assessed using dual-energy X-ray absorptiometry (DXA), Histological sections of thre e calcanei were also analyzed using transmission light illumination, a nd the results used to calibrate our computational software. For a rel atively narrow intersubject variation in posterior BMD, a significant intersubject variation was seen in MRI-derived structural parameters. Furthermore, the spatial heterogeneity of the structural parameters in the posterior region was as high as 40%. Thus, the posterior tuberosi ty of the calcaneus, a typical site for BMD and single-point ultrasoun d assessments, can demonstrate significant regional variation in trabe cular bone structure.