Radiotechnologists and Radiation Exposure from PET and PET/CT Systems / 대한산업의학회지

OBJECTIVES: In this study, radiotechnologists who work performing PET and PET/CT methodologies were analyzed in order to find the cause for the differences in radiation exposure as they applied to general characteristics, work characteristics, knowledge, and exposure recognition or conduct. METHODS: From April 15th, 2010 to May 14th, 2010, we conducted a retrospective analysis on 80 radiotechnologists using data garnered from their individual general characteristics, work characteristics, knowledge, and exposure recognition or conduct. Their average annual radiation exposure dosages were measured using a thermoluminescence dosimeter. A multiple regression analysis was performed as a statistical tool. RESULTS: Regarding the general PET and PET/CT characteristics, when the work experience was short, the exposure dose was higher. The factors of age, marriage, work experience in nuclear medicine, PET, PET/CT, and sex were found to have statistically significant effects. The knowledge, recognition, and conduct factors for the radiotechnologists were affected by unsecure radiation exposure at the moment of carrying, unsecure radiation exposure at the moment of injection, the application of protection at the moment of injection, and the use of auto distributor. It was found that, the use of an auto distributor, efforts in reducing the radiation exposure, unsecure exposure when with a patient, and the application of protective procedures at the moment of injection affected the overall factor of radiotechnologists radiation exposure dose. CONCLUSIONS: We believe that if radiotechnologists would reduce their radiation exposure by using auto distributors, make efforts to reduce the chance of exposure, and be conscious of radiation, they would be able to reduce the radiation exposure dose even during unavoidable circumstances.

Comparison of F-18 FDG Radioacitivity to Determine Accurate Dose Calibrator Activity Measurements / 의학물리

Obviously, the administration of the prescribed amount of activity to the patient requires proper operation of the dose calibrator, which shall be verified by implementing the required quality control on the instrument. This investigation examined the accuracy and precision of dose calibrator activity measurement of the radiopharmaceutical F-18 FDG. To investigate the status of the nuclear medicine centers in Korea for the performance of dose calibrators, 10 centers providing PET/CT system services in Korea were inspected in 2008. We measured accuracy and precision in 10 equipments in consideration of PET/CT model, installation area, and installation time. According to the results of comparative analysis of 10 dose calibrators used to measure radioactivity of F-18 FDG, accuracy was -5.00~4.50% and precision was 0.05~0.45%, satisfying the international standards, which are accuracy +/-10% and precision +/-5%. This study demonstrated that, for accurate measurements, no adjustment is necessary for a dose calibrator setting when measuring different dose calibrators of F-18 FDG activity prescriptions.

Comparison of F-18 FDG Radioacitivity to Determine Accurate Dose Calibrator Activity Measurements / 의학물리

Obviously, the administration of the prescribed amount of activity to the patient requires proper operation of the dose calibrator, which shall be verified by implementing the required quality control on the instrument. This investigation examined the accuracy and precision of dose calibrator activity measurement of the radiopharmaceutical F-18 FDG. To investigate the status of the nuclear medicine centers in Korea for the performance of dose calibrators, 10 centers providing PET/CT system services in Korea were inspected in 2008. We measured accuracy and precision in 10 equipments in consideration of PET/CT model, installation area, and installation time. According to the results of comparative analysis of 10 dose calibrators used to measure radioactivity of F-18 FDG, accuracy was -5.00~4.50% and precision was 0.05~0.45%, satisfying the international standards, which are accuracy +/-10% and precision +/-5%. This study demonstrated that, for accurate measurements, no adjustment is necessary for a dose calibrator setting when measuring different dose calibrators of F-18 FDG activity prescriptions.

The Evaluation for Attenuation Map using Low Dose in PET/CT System / 의학물리

The current PET/CT system with high quality CT images not only increases diagnostic value by providing anatomic localization, but also shortens the acquisition time for attenuation correction than primary PET system. All commercially available PET/CT system uses the CT scan for attenuation correction instead of the transmission scan using radioactive source such as 137Cs, 68Ge. However the CT scan may substantially increase the patient dose. The purpose of this study was to evaluate quality of PET images reconstructed by CT attenuation map using various tube currents. In this study, images were acquired for 3D Hoffman brain phantom and cylindrical phantom using GE DSTe PET/CT system. The emission data were acquired for 10 min using phantoms after injecting 44.03 MBq of 18F-FDG. The CT images for attenuation map were acquired by changing tube current from 10 mA to 95 mA with fixed exposure time of 8 sec and fixed tube voltage of 140 kVp. The PET images were reconstructed using these CT attenuation maps. Image quality of CT images was evaluated by measuring SD (standard deviation) of cylindrical phantom which was filled with water and 18F-FDG solution. The PET images were evaluated by measuring the activity ratio between gray matter and white matter in Hoffman phantom images. SDs of CT images decrease by increasing tube current. When PET images were reconstructed using CT attenuation maps with various tube currents, the activity ratios between gray matter and white matter of PET images were almost same. These results indicated that the quality of the PET images using low dose CT data were comparable to the PET images using general dose CT data. Therefore, the use of low dose CT is recommended than the use of general dose CT, when the diagnostic high quality CT is not required. Further studies may need to be performed for other system, since this study is limited to the GE DSTe system used in this study.