OBJECTIVE: We evaluated the influence of surrounding anatomical structures on the registration accuracy of a diagnostically important region, by varying the ROI (region of interest) window used in an automatic ROI-based digital subtraction method. STUDY DESIGN: Pairs of radiographs were taken at 2 molar regions using paralleling techniques of XCP devices (Rinn Co., Elgin, Ill) attached with and without a bite block. The global and local registration accuracies were measured by the RMS (root mean square) of subtraction images for various ROIs. RESULTS: No significant differences were found in global registration accuracies among various ROI sizes in all the paralleling techniques. The local registration accuracies decreased with extension of the ROI size. CONCLUSION: Registration using an ROI restricted to the anatomical region of diagnostic interest provides higher accuracy than using a larger ROI.
OBJECTIVE: We evaluated the influence of surrounding anatomical structures on the registration accuracy of a diagnostically important region, by varying the ROI (region of interest) window used in an automatic ROI-based digital subtraction method. STUDY DESIGN: Pairs of radiographs were taken at 2 molar regions using paralleling techniques of XCP devices (Rinn Co., Elgin, Ill) attached with and without a bite block. The global and local registration accuracies were measured by the RMS (root mean square) of subtraction images for various ROIs. RESULTS: No significant differences were found in global registration accuracies among various ROI sizes in all the paralleling techniques. The local registration accuracies decreased with extension of the ROI size. CONCLUSION: Registration using an ROI restricted to the anatomical region of diagnostic interest provides higher accuracy than using a larger ROI.