Re-Evaluation of Patient-Sourced Radiation Doses in PET/CT.

BACKGROUND: New generation PET/CT devices provide quality images using low radiopharmaceutical activities. Dose monitoring is carried out for nuclear medicine personnel, other health personnel, and companions by determining the radiation dose emitted from low-activity patients to the environment. In particular, it is necessary to revise the working conditions of the personnel according to the radiation dose exposed. AIM: It was aimed to reevaluate the radiation dose rate transmitted to the environment from patients injected with 18F-FDG. MATERIALS AND METHODS: A total of 31 patients (14F, 17M) who underwent 18F-FDG PET/CT imaging were included. The mean 18F-FDG activity of 7.26 ± 1.29 mCi was used for injection. After injection, radiation dose rates (mR/h) were measured at distances of 25, 50, 100, 150, and 200cm for 3 different periods from the level of the head, thorax, abdomen, and pelvis by using a GM counter. Additionally, biological samples such as urine and sweat were taken during 3 different periods. The activity amounts (µCi) in the samples were measured with a well-type counter. RESULTS: Strong correlations were calculated between normalized dose rates obtained by all regions and time. Considering the nuclear medicine staff handling time with a PET/CT patient, the average dose received by staff was calculated between a range of 0.002-0.004 mSv/pt. The radiation dose exposed to the porter and nurse was calculated as 0.049 mSv/pt for the 2nd hour and 0.001-0.007 mSv/pt for the 4th hour, respectively. The companion was exposed to a dose between 0.073-0.147 mSv and 0.024-0.048 mSv for public transport and private car transportation after 4-6 hours of injection (for 30-60 min of travel duration), respectively. For inpatients, the received dose for porters, serving 20min from a distance of 30cm for the 2nd and 4th hours after the PET/CT scan, was 0.049 mSv/pt and 0.048 mSv/pt, respectively. And for nurses serving from a 50cm distance between 1-5 minutes, these values were found to be 0.001-0.007mSv/pt, 0.001-0.007mSv/pt, and 0.001-0.006mSv/pt, respectively. CONCLUSION: The radiation dose of nuclear medicine staff, porters, nurses, and companions are found to be below the recommended dose limit by the ICRP. According to our results, there is no need for any restrictions for patients, companions, or healthcare personnel in PET/CT units.

Evaluation in Terms of Dosimetry and Fertility of F18-FDG and Ga68- PSMA in Prostate Cancer Imaging: A Simulation with GATE.

INTRODUCTION: F18 and Ga68 radioisotopes are used in PET imaging for prostate cancer. It was aimed to calculate the prostate, testicle and bladder effective doses (ED) caused by F18 and Ga68 used in prostate cancer imaging with PET/CT via simulation with the GATE toolkit and evaluate the ED in terms of fertility. METHODS: The prostate, testicle and bladder were defined together with their geometric properties and densities in GATE simulation. F18 and Ga68 with activity of 277.5 MBq and 151.7 MBq were identified in the prostate as a source organ. The ED, uncertainties, and S values were taken as an output file in the TXT format with the DoseActors command. S values were used for validation of the simulation. RESULTS: The ED of the prostate, total testicle and bladder for F18 were found to be 6.627E-04 ± 1.799E-06, 12.74E-07 ± 4.11E-08 and 1.617E-05 ± 4.317E-09 (Gy/s), respectively. The ED of the prostate, total testicle, and bladder for Ga68 were found to be 9.195E-04 ± 2.660E-06, 6.54E-07 ± 2.93E-08 and 4.290E-05 ± 6.936E-09 (Gy/s), respectively. CONCLUSION: It was found that Ga68 produced high prostate and bladder ED, and F18 produced high testicular ED. In terms of male fertility, Ga68 seems to be a good alternative because it produces low testicular doses. The ED of the testicle both F18 and Ga68 were below the reported spermatogonia and azoospermia dose.

Dosimetric Comparison of Different Radionuclides Used in Metastatic Bone Disease Treatment.

INTRODUCTION: This study aimed to determine the critical organ doses in 223Ra, 89Sr, 153Sm, and 32P treatments via dosimetry using the phantoms. MATERIAL AND METHODS: The OpenDose was used to calculate S values (mGy MBq-1s-1) for bone surface, red bone marrow, urinary bladder wall, testes, ovaries, uterus, and kidneys using male (ICRP110AM) and female (ICRP110AF) phantoms. The cortical thoracic spine was modeled as metastasis. Moreover, the absorbed doses were computed via MIRD formalism according to the activities of 3.3, 148, 2220, and 370 MBq for ICRP110AM and 4.015, 148, 2701, and 370 MBq for ICRP110AF in 223Ra, 89Sr, 153Sm, and 32P treatments, respectively. RESULTS: Whilst the maximum bone surface doses were found as 1.22E+02 and 8.51E+01 mGy at 32P treatment, the minimum bone surface doses were calculated as 8.42E-02 and 8.26E-02 mGy at 223Ra. In terms of the comparison of red bone marrow, urinary bladder wall, and kidney doses, 153Sm and 89Sr treatments showed maximum doses of 2.45E-03, 1.50E-03, 3.23E-07, 5.45E-06, 1.20E-01, 1.49E-01 mGy and the minimum doses with 3.46E-05, 1.99E-05, 6.33E-09, 8.77E-09, 1.19E-04, 1.15E-04 mGy, respectively. The maximum testes and ovaries-uterus doses were found as 6.17E-08, 7.40E-06, 3.46E-07 mGy in 153Sm treatment, and minimum testes and ovaries doses as 1.70E-09, 1.34E-07 mGy in 223Ra. The minimum uterus dose with 7.03E-09 mGy was determined in 89Sr treatment. CONCLUSION: It is observed that 223Ra produces low critical organ doses in the treatment of painful bone metastasis. Among the beta-emitting radionuclides, 89Sr stands out by showing optimal dosimetric results.

Comparison of Y-90 and Ho-166 Dosimetry Using Liver Phantom: A Monte Carlo Study7.

BACKGROUND: It is estimated that more than 1 million people are diagnosed with liver malignancy each year and one of the treatments is radioembolization with Y-90 and Ho-166. OBJECTIVE: The aim of this study is to calculate the absorbed doses caused by Y-90 and Ho-166 in tumor and liver parenchyma using a phantom via Monte Carlo method. METHODS: A liver model phantom including a tumor imitation of sphere (r =1.5cm) was defined in GATE. The total activity of 40 mCi Y-90 and Ho-166 was prescribed into tumor imitation as source and 2x2x2 mm3 voxel-sized Dose- Actors were identified at 30 locations. The simulation, performed to calculate the absorbed doses left by particles during 1 second for Y-90 and Ho-166, was run for a total of 10 days and 11 days, respectively. Total doses were calculated by taking the doses occurring in 1 second as a reference. RESULTS: The maximum absorbed doses were found to be 2.334E+03±1.576E+01 Gy for Y-90 and 7.006E+02±6.013E- 01 Gy for Ho-166 at the center of tumor imitation. The minimum absorbed doses were found to be 2.133E-03±1.883E- 01 Gy for Y-90 and 1.152E-02±1.036E-03 Gy for Ho-166 at the farthest location from source. The mean absorbed doses in tumor imitation were found to be 1.50E+03±1.36E+00 Gy and 4.58E+02±4.75E-01 Gy for Y-90 and Ho-166, respectively. And, the mean absorbed doses in normal parenchymal tissue were found to be2.07E+01±9.58E-02 Gy and 3.79E+00±2.63E-02 Gy for Y-90 and Ho-166, respectively. CONCLUSION: Based on the results, Ho-166 is a good alternative to Y-90 according to dosimetric evaluation.