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Purpose: Patient exposure rate measurements verify published patient dose rate data and characterize dose rates near 2-18-fluorodeoxyglucose ({sup 18}F-FDG) patients. A specific dose rate constant based on patient exposure rate measurements is a convenient quantity that can be applied to the desired distance, injection activity, and time postinjection to obtain an accurate calculation of cumulative external radiation dose. This study reports exposure rates measured at various locations near positron emission tomography (PET) {sup 18}F-FDG patients prior to PET scanning. These measurements are normalized for the amount of administered activity, measurement distance, and time postinjection and are compared with other published data. Methods: Exposure rates were measured using a calibrated ionization chamber at various body locations from 152 adult oncology patients postvoid after a mean uptake time of 76 min following injection with a mean activity of 490 MBq {sup 18}F-FDG. Data were obtained at nine measurement locations for each patient: three near the head, four near the chest, and two near the feet. Results: On contact with, 30 cm superior to and 30 cm lateral to the head, the mean (75th percentile) dose rates per unit injected activity at 60 min postinjection were 0.482 (0.511), 0.135 (0.155), and 0.193 (0.223)more » {mu}Sv/MBq h, respectively. On contact with, 30 cm anterior to, 30 cm lateral to and 1 m anterior to the chest, the mean (75th percentile) dose rates per unit injected activity at 60 min postinjection were 0.623 (0.709), 0.254 (0.283), 0.190 (0.218), and 0.067 (0.081) {mu}Sv/MBq h respectively. 30 cm inferior and 30 cm lateral to the feet, the mean (75th percentile) dose rates per unit injected activity at 60 min postinjection were 0.024 (0.022) and 0.039 (0.044) {mu}Sv/MBq h, respectively. Conclusions: The measurements for this study support the use of 0.092 {mu}Sv m{sup 2}/MBq h as a reasonable representation of the dose rate anterior from the chest of patients immediately following injection. This value can then be reliably scaled to the desired time and distance for planning and staff dose evaluation purposes. At distances closer than 1 m, a distance-specific dose rate constant of 0.367 {mu}Sv/MBq h at 30 cm is recommended for accurate calculations. An accurate patient-specific dose rate constant that accounts for patient-specific variables (e.g., distribution and attenuation) will allow an accurate evaluation of the dose rate from a patient injected with an isotope rather than simply utilizing a physical constant.« less

Purpose: Effective dose ( E ) is useful as a dose index for patient exposures in interventional radiology; therefore, the authors estimated E from the kerma-area product ( P K A ) utilized during hepatic embolization interventional radiology cases performed at a cancer center and determined the variation of such doses over a representative patient population. Methods: A single-center, IRB-approved retrospective study was performed to estimate doses from consecutive hepatic embolization procedures performed during 2006. Organdoses E and E / P K A were determined from patient height, weight, P K A , procedure geometry factors, beam quality, the PCXMC Monte Carlo model, and the International Commission on Radiological Protection organ weighting factors. Results: One hundred thirteen patients were included in the study population, 72 males and 41 females, with a median age of 63 yr (29–89 yr), weight of 79 kg (42–111 kg), height of 170 cm (147–188 cm), and P K A of 233 Gy cm 2 ( 9 – 1020 Gy cm 2 ) . E was directly correlated with P K A r 2 = 0.8 ( p 0.01 ) , with a median E / P K A of 0.18 mSv Gy − 1 cm − 2 ( 0.12 – 0.33 mSv Gy − 1 cm − 2 ) . The E / P K A ratio was inversely and exponentially correlated with weight r 2 = 0.9 ( p 0.001 ) . The median E (mSv) for the study patient population was 44 mSv (2.0–255 mSv). Conclusions: Values of E can be estimated utilizing patient-specific and procedure-specific parameters. The strong inverse correlation of E / P K A with patient weight allows simple estimation of E from P K A and patient weight. There is a wide variation in effective dose in oncologic hepatic embolizations with doses up to an order of magnitude higher than diagnostic imaging of the abdomen by CT radiology. Variation is likely due to patient geometry, clinical technique factors, and procedure complexity.