AUTOMATIC DETECTION OF THE BOUNDARY OF THE CALCANEUS FROM ULTRASOUND PARAMETRIC IMAGES USING AN ACTIVE CONTOUR MODEL - CLINICAL-ASSESSMENT

This paper presents a computerized method for automated detection of t he boundary of the os calcis on in vivo ultrasound parametric images, using an active dynamic contour model. The initial contour, defined wi thout user interaction, is an iso-contour extracted from the textural feature space. The contour is deformed through the action of internal and external forces, until stability is reached. The external forces, which characterize image features, are a combination of gray-level inf ormation and second-order textural features arising from local cooccur rence matrices. The broadband ultrasound attenuation (BUA) value is th en averaged within the contour obtained. The method was applied to 381 clinical images. The contour was correctly detected in the great majo rity of the cases, For the short-term reproducibility study, the mean coefficient of variation was equal to 1.81% for BUA values and 4.95% f or areas in the detected region. Women with osteoporosis had a lower B UA than age-matched controls (p = 0.0005). In healthy women, the age-r elated decline was -0.45 dB/MHz/yr. In the group of healthy post-menop ausal women, years since menopause, weight and age were significant pr edictors of BUA, These results are comparable to those obtained when a veraging BUA values in a small region of interest.