Prostate brachytherapy with iodine-125 seeds: radiation protection issues

Brachytherapy for prostate cancer by means of permanently implanted 125I sources is a well established procedure. An increasing number of patients all over the world are treated with this modality. When the technique was introduced at our institution, radiation protection issues relative to this technique were investigated in order to comply with international recommendations and national regulations. Particular attention was paid to the need for patient shielding after discharge from hospital.

The effective and equivalent doses to personnel related to implantation, the effective dose to patient relatives as computed by a developed algorithm, the air kerma strength values for the radioactive sources certified by the manufacturer compared with those measured by a well chamber, and the effectiveness of lead gloves in shielding the hands were evaluated.

The effective dose to the bodies of personnel protected by a lead apron proved to be negligible. The mean equivalent doses to the physician's hands was 420 microSv for one implant; the technician's hands received 65 microSv. The mean air kerma rate measured at the anterior skin surface of the patient who had received an implant was 55 microGy/h (range, 10-115) and was negligible with lead protection. The measured and certified air kerma strength for125I seeds in RAPID Strand corresponded within a margin of +/- 5%. The measured attenuation by lead gloves in operative conditions was about 80%. We also defined the recommendations to be given to the patient at discharge.

The exposure risks related to brachytherapy with 125I to operators and public are limited. However, alternation of operators should be considered to minimize exposure. Patient-related measurements should verify the dose rate around the patient to evaluate the need for shielding and to define appropriate radiation protection recommendations.