[en] When the ¹¹C-, ¹⁵O- and ¹⁸F-labeled radiopharmaceuticals are intravenously injected or inhalated into human subjects for the PET studies, the activities cumulated in source organs and the absorbed doses in target organs are estimated by the whole-body PET scanning method and the TLD method. In the TLD method a number of TLDs (BeO) were attached during the PET study on nine points of the skin surface close to nine source organs (brain, heart, right lung, left lung, lever, kidney, pancreas, bladder and rest of the body) which accumulated the radiopharmaceuticals. The TLD doses measured on the body surface were converted to the activities cumulated in the source organs through the mathematical inverse transformation (unfolding) method, using the response matrix which represented the absorbed dose at each TLD position per unit cumulated activity in a source organ. The response matrix was calculated by using the MIRD mathematical phantom. The accuracy of the TLD method was first investigated by using a water phantom in which several gamma-ray volume sources of known activity were placed to simulate source organs. For ¹⁸F-labeled FDG (Fluoro-Deoxy-Glucose) which is most commonly used in PET, the accuracy of the cumulated activities obtained by the TLD method was also investigated by comparison with those by the whole-body PET on the same six normal volunteers. Both results show good agreement within 50% for all source organs. The TLD method was then applied to estimate the organ absorbed doses and effective doses to the individuals using the MIRD method for intakes of ¹¹C-labeled Methionine, Doxepin, Benzotropin, YM09151-2, and ¹⁵O-labeled CO, O₂, CO₂ gases. This TLD method has great advantages, in that cumulated activities in several organs can be obtained easily with a single procedure, and the measurements of body surface doses are performed simultaneously with the nuclear medicine procedure, as TLDs are too small to interfere with other medical measurements. (author)