Background/purpose: The use and cost of computed tomography (CT) and magnetic resonance imaging (MRI) are both very high. The purpose of this study was to evaluate the relation between physicians' characteristics and the CT and MRI repeated within 90 days, using a nationwide population-based data set from Taiwan's National Health Insurance system. Methods: All physicians who ordered CT and MRI examinations in 2004-2005 were identified. We analyzed the total number of CT and MRI scans, the number of repeat scans, and the repeat scan rate, according to physician characteristics (specialty, age, sex, and type of practice hospital). A multivariate logistic regression analysis was performed to explore the adjusted relationship between physician characteristics and their rate of ordering repeat CT and MRI. Results: A total of 16,307 physicians were responsible for a total of 2,152,292 CT and MRI scans during 2004-2005 in Taiwan. The repeat scans accounted for 21.5% of the total scans. Male physicians and physicians aged 41-50 years ordered more repeat scans. Internal medicine physicians ordered 44.3% of all scans and 50.6% of all repeat scans. Surgeons ordered 40.4% of the total scans and 38.5% of repeat scans. Internal medicine physicians were the most frequent users of CT/MRI scans. Family doctors, obstetricians/gynecologists, and pediatricians ranked last among the specialists. Physicians who practiced in medical centers ordered the most CT/MRI scans. Conclusion: Our study shows that repeat use of CT and MRI scans is related to physicians' characteristics. We recommend that different monitoring standards should be set for CT and MRI repeat use by physicians of different specialties and in hospitals of different accreditation levels.
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