ESTIMATION OF ABSORBED DOSE FOR 2-[F-18]FLUORO-2-DEOXY-D-GLUCOSE USING WHOLE-BODY POSITRON-EMISSION-TOMOGRAPHY AND MAGNETIC-RESONANCE-IMAGING

The purpose of this study was to measure the cumulated activity and ab sorbed dose in organs after intravenous administration of 2-[F-18]fluo ro-2-deoxy-D-glucose (F-18-FDG) using whole-body positron emission tom ography (PET) and magnetic resonance imaging (MRI). Whole-body dynamic emission scans for F-18-FDG were performed in six normal volunteers a fter transmission scans. The total activity of a source organ was obta ined from the activity concentration of the organ measured by whole-bo dy PET and the volume of that organ measured by whole-body T1-weighted MRI. The cumulated activity of each source organ was calculated from the time-activity curve. Absorbed doses to the individuals were estima ted by the MIRD (medical internal radiation dosimetry) method using S- values adjusted to the individuals. Another calculation of cumulated a ctivities and absorbed doses was performed using the organ volumes fro m the MIRD phantom and the ''Japanese reference man'' to investigate t he discrepancy of actual individual results against the phantom result s. The cumulated activities of 18 source organs were calculated, and a bsorbed doses of 27 target organs estimated. Among the target organs, bladder wall, brain and kidney received the highest doses for the abov e three sets of organ volumes. Using measured individual organ volumes , the average absorbed doses for those organs were found to be 3.1x10( -1), 3.7x10(-2) and 2.8x10(-2) mGy/MBq. respectively. The mean effecti ve doses in this study for individuals of average body weight (64.5 kg ) and the MIRD phantom of 70 kg were the same, i.e. 2.9x10(-2) mSv/MBq , while for the Japanese reference man of 60 kg the effective dose was 2.1x10(-2) mSv/MBq, The results for measured organ volumes derived fr om MRI were comparable to those obtained for organ volumes from the MI RD phantom. Although this study considered F-18-FDG, combined use of w hole-body PET and MRI might be quite effective for improving the accur acy of estimations of the cumulated activity and absorbed dose of posi tron-labelled radiopharmaceuticals.