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

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 I-125 or Pd-103 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 mu Gy/h (range: 0.1-31.5) for I-125 and 1.5 mu Gy/h (range: 0.02-14.9) for Pd-103. 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 Pd-103 patient, no radiation safety precautions are required. For the typical I-125 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 I-125 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. (C) 2010 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.