Radiation dose to small infants from single-photon absorptiometry.

The radiation dose to the patient resulting from single-photon absorptiometry (SPA), now a widely used method for measuring bone mineral content (BMC) in vivo in infants and children, was evaluated. Lithium fluoride chips were placed on a phantom with a BMC in the small infant range (60 and 145 mg/cm). Measurement procedures mimicked the actual clinical sequence. The radiation exposure for a single BMC measurement is 46-70 mrad (460-700 microGy) to the forearm surface and 25-38 mrad (250-380 microGy) and 125-190 mrad (1,250-1,900 microGy) to the bone marrow and the bone, respectively. When eight repeated measurements are performed over a 1-year period, the radiation dose is about 368-560 mrad (3,680-5,600 microGy) to the forearm surface and 200-305 mrad (2,000-3,050 microGy) and 1,000-1,525 mrad (10.0-15.25 mGy) to the bone marrow and the bone, respectively. Even though the radiation dose is small, this method should be used only in well-designed clinical studies.