Effect of diagnostic radioisotopes and radiographic contrast media on measurements of lumbar spine bone mineral density and body composition by dual-energy x-ray absorptiometry.

Since there is almost no information on whether the concomitant use of diagnostic radioisotopes and radiographic contrast media interferes with dual-energy X-ray absorptiometry (DXA), we investigated these potentially confounding effects. At routine scheduled radiographic follow-up, 40 patients previously treated for malignant lymphomas or solid tumors in Hamilton and Ottawa, Canada were evaluated, 10 in each of the following 4 categories of diagnostic procedure: (1) computed tomography (CT) with intravenous, iodine-based contrast (+/-oral contrast), (2) magnetic resonance imaging (MRI) with gadolinium-based contrast, (3) gallium scan (GS), and (4) technetium bone scan (TBS). Whole body bone mineral content (WB-BMC) and lumbar spine bone mineral density (LS-BMD), total fat mass (TFM), and lean body mass (LBM) were measured by DXA immediately before and after the other radiological studies (on the same day) and then 7 days later. No statistically significant differences were found among WB-BMC, LS-BMD, TFM, and LBM Z-scores immediately before and after MRI, GS, TBS, and 7 days later. The DXA measurements performed immediately before and after CT showed statistically significant differences in WB-BMC (100% vs 124.5%, p<0.001), TFM (100% vs 75.4%, p<0.001), and LBM (100% vs 110%, p<0.001), resulting from the CT contrast agents compromising the precision of the DXA. The DXA results after 7 days were not statistically different from those at baseline. Dual-energy X-ray absorptiometry can be performed in association with other radiological techniques, with the exception of CT conducted with contrast within 1 week. This study provides information that applies not only to patients with cancer but to the general population undergoing diagnostic procedures.