CORTICAL THICKNESS ASSESSED BY PERIPHERAL QUANTITATIVE COMPUTED-TOMOGRAPHY - ACCURACY EVALUATED ON RADIUS SPECIMENS

The purpose of the present study was to evaluate the accuracy of perip heral quantitative computed tomography (pQCT) in measuring the thickne ss of the radial cortex. Thirty left forearm specimens were scanned on an XCT 960 Stratec pQCT device using a 2.5 mm thick slice at the junc tion of the middle and the distal third of the radius. Cortical and tr abecular areas were assessed using a threshold procedure; cortical thi ckness was subsequently calculated assuming a circular ring model for the radius. Cortical thickness was also measured on the true shape of bone using an iterative contour detection procedure. Subsequently 2.5 mm thick resin-embedded cylindrical radial specimens, matched with the site of pQCT examination, were obtained and contact radiographs were performed. After tenfold magnification, the cortical and trabecular ar eas of the specimens were measured using computerized planimetry and c ortical thickness was calculated assuming a circular ring model. The c ortical thickness could be assessed by pQCT in all cases using the thr eshold algorithm (mean (SD) 2.51 (0.58) mm) and in 21 cases could be d irectly measured on the true shape of bone (2.62 (0.32) mm). The corti cal thickness of the specimens showed good correlation and high propor tionality with that measured using pQCT with either the threshold algo rithm (r = 0.941, slope = 0.976) or the iterative contour detection pr ocedure (r = 0.883, slope = 0.987). In conclusion, pQCT is able to ass ess the thickness of the radial cortex, at the junction of the middle and the distal third, with high accuracy.