COMPARATIVE MEASUREMENTS OF BONE-MARROW DOSE IN QUANTITATIVE COMPUTED-TOMOGRAPHY (QCT), DUAL PHOTON X-RAY (DPX) AND CONVENTIONAL LUMBAR SPINE X-RAY

One of the issues in the discussion on the best method for measuring the bone mineral content is the relevance of the applied dose. We used highly sensitive thermoluminescent dosimeters (TLD) to directly compare bone marrow doses in a human phantom. DPX gave a bone marrow dose in the lumbar spine of 4-mu-Gy, in QCT the dose corrected to the same amount of irradiated marrow was about 1 mGy. This value is in the same range as conentional a.p. plus lateral view x-rays of the lumbar spine. Corrected to the total body dose, the QCT dose is as low as 10% of the yearly background irradiation. It should therefore be radiobiologically irrelevant.