Impact of shield location on staff and caregiver dose rates for I-131 radiopharmaceutical therapy patients.

The goal of this study is to investigate the effect of the location and width of a single lead shield on the dose rate of staff and caregivers in a hospital room with an I-131 patient. The best orientation of the patient and caregiver relative to the shield was determined based on minimizing staff and caregiver radiation dose rates. Shielded and unshielded dose rates were simulated using a Monte Carlo computer simulation and validated using real-world ionisation chamber measurements. Based on a radiation transport analysis using an adult voxel phantom published by the International Commission on Radiological Protection, placing the shield near the caregiver yielded the lowest dose rates. However, this strategy reduced the dose rate in only a tiny area of the room. Furthermore, positioning the shield near the patient in the caudal direction provided a modest dose rate reduction while shielding a large room area. Finally, increased shield width was associated with decreasing dose rates, but only a four-fold dose-rate reduction was observed for standard width shields. The recommendations of this case study may be considered as potential candidate room configurations where radiation dose rates are minimized, however these findings must be weighed against additional clinical, safety, and comfort considerations.

SUBSTANTIAL EXTERNAL DOSE RATE VARIABILITY OBSERVED IN A COHORT OF LU-177 PATIENTS INDEPENDENT OF BMI AND SEX.

External dose rates were measured 1 m away from 230 Lu-177 patients to characterise the variability in normalised dose rates as a function of administered activity, body mass index (BMI) and sex. The largest dose rate observed was 0.07 mSv/h associated with an administered activity of 7.2 GBq. Substantial variability was found in the distribution of the normalised dose rate associated that had an average of 0.0037 mSv/h per GBq and a 95% confidence interval of 0.0024-0.0058 mSv/h per GBq. Based on this study, estimating the patient dose rate based on the Lu-177 gamma exposure factor overestimates the dose rate by a factor of 2. A statistically significant inverse relationship was found between the patient dose rate and patient BMI and an empirically derived equation relating these two quantities was reported. On average, male patient dose rates were 3.5% lower than female dose rates, which may be attributed to the larger average BMI of the male patient group.