EXCISION OF A TRABECULAR ROI FROM RESIN-EMBEDDED VERTEBRAE - REPORT ON A COMPUTER-ASSISTED METHOD

A major problem when evaluating the accuracy of quantitative computed tomography (QCT) against chemical analysis of bone mineral is to ensur e that the same region of interest (ROI) is measured with two techniqu es. The method described here attempts to reach this objective. Forty- nine lumbar vertebrae were scanned. The mid-vertebral portion was sawe d and embedded in a polyester resin. The ROI defined with an automated contour detection was transmitted, using a Hewlett-Packard scanjet, t o a computer-assisted milling machine which excised a trabecular ROI S ample. The volume of each trabecular sample was determined using an Ar chimedian method. ROI volumes assessed on QCT were highly correlated w ith those obtained with the Archimedian method (r = 0.98). The standar d error of the estimate was 170 mm3 (4.5%). These results suggest that trabecular samples obtained with this method optimally agree with the ROIS selected on QCT examination.