Dosimetric evaluation of radiation exposure during I-125 vicryl mesh implants: implications for ACOSOG z4032

Segmentectomy or wedge resection along with brachytherapy delivered via a vicryl mesh implant imbedded with 125I is a novel therapeutic modality to treat early stage lung cancer. This modality is being evaluated in a large national prospective randomized trial (ACOSOG Z4032). There has been concern that this method exposes physicians and staff to unacceptable amounts of radiation. In this prospective study, we measured the exposure to health care professionals during such a procedure.

Dosimetric readings using Special Microdosimeter thermoluminescent detectors (TLDs) (Landauer, Inc) were performed during 22 125I vicryl mesh implantations. Diodes were placed on the back of the each hand of the primary radiation oncologist and primary surgeon during the creation and implantation of the mesh. In addition, diodes were placed on the posterior shoulder of the patient to obtain a control reading.

Patients had 40-60 125I seeds placed. Median activity per seed was 0.511 milli Curie (mCi), with a median total activity implanted of 23.0 mCi. Median radiation dose to the radiation oncologist was 1 milli rem (mrem), and that to the surgeon was 2 mrem. Median dose to the control diode on the patient was a median radiation dose to the outside of the patient of 5.4 mrem/h.

There is very little radiation exposure to physicians and staff during a segmentectomy and 125I vicryl mesh implantation. This is a safe method of lung cancer treatment with respect to health care professionals, although the ALARA (As Low As Reasonably Achievable) principle should still be followed.