Bone texture analysis on direct digital radiographic images: precision study and relationship with bone mineral density at the os calcis.

Assessment of bone microarchitecture in complement to bone mineral density (BMD) exam could improve prediction of osteoporotic fractures. A high-resolution X-ray prototype was developed to assess microarchitecture quality. Images were obtained on os calcis; then, three texture parameters were calculated on the same region of interest (ROI): a fractal parameter, a run-length parameter, and a co-occurrence parameter. This work describes the reproducibility of this method. We also examine the relationship between texture parameters and BMD at a site-matched ROI. Measurements on the left heel were performed on 30 healthy women, on the same day, with repositioning for short-term precision error. An additional measurement was done at 1 week to evaluate mid-term precision error on 14 subjects. Os calcis images from 10 healthy women were used to evaluate both intra- and interobserver reproducibility. Thirty other healthy patients were measured successively on two similar devices for interprototype comparison. BMD and texture analyses of the left heel were obtained from 57 women. Short-term precision errors ranged 1.16-1.24% according to the texture parameter. Mid-term precision error was slightly higher than short-term precision for the mean Hurst exponent parameter. Comparisons of texture parameters and BMD at a site-matched ROI on the os calcis showed no significant relationships. The results also show that the use of this high-resolution digital X-ray device improves the reproducibility of parameter measurement compared to the indirect digitization of radiologic films previously used.