Detection and measurement of simulated early rheumatoid lesions of the hand using digital subtraction radiography

The ability of digital subtraction radiography, a new technique to detect and quantify small bone lesions, is demonstrated. Discrete lesions in the metacarpals of cadaver hands simulated erosive bone loss. Radiographs made before and after removal of bone were digitized and subtracted. Density changes on subtraction images were determined, and bone loss was estimated by an automatic procedure that compared changes in radiographic density with a calibration wedge included in the radiographs. Comparison of estimated bone loss with the weight of bone removed showed reproducible detection and measurement of bone lesions as small as 4.6 mg, a size undetectable using current radiographic methods. Subtraction radiographs of bone chips overlaid on the hand of a volunteer indicated detection limits were similar in vivo. This technique enhanced the radiographic visibility of erosive lesions and thus has the potential to improve the detection of subtle bone changes in clinical settings.