Less-restrictive, patient-specific radiation safety precautions can be safely prescribed after permanent seed implantation

Abstract

Purpose To use radiation exposure rate measurements to determine patient-specific radiation safety instructions with the aim of reducing unnecessary precaution times and to evaluate potential doses to members of the public. Methods and Materials Radiation exposure rate measurements were obtained from 1279 patients with Stage T1-2 prostate cancer who underwent transperineal 125I or 103Pd seed implantation from January 1995 through July 2008. An algorithm was developed from these measurements to determine the required precaution times to maintain public effective doses below 50% of the limits for specific exposure situations. Results The median air kerma rates at 30 cm from the anterior skin surface were 4.9 μGy/h (range: 0.1–31.5) for 125I and 1.5 μGy/h (range: 0.02–14.9) for 103Pd. The derived algorithms depended primarily on the half-life T p , the measured exposure rate at 30 cm, and specific exposure situation factors. For the typical 103Pd patient, no radiation safety precautions are required. For the typical 125I patient, no precautions are required for coworkers, nonpregnant adults who do not sleep with the patient, or nonpregnant adults who sleep with the patient. Typical 125I patients should only avoid sleeping in the “spoon” position (i.e., in contact) with pregnant adults and avoid holding a child for long periods of time in the lap for about 2 months. Conclusions The large number of cases available for this study permitted the development of an algorithm to simply determine patient-specific radiation safety instructions. The resulting precaution times are significantly less restrictive than those generally prescribed currently.