Shielding effect of a customized intraoral mold including lead material in high-dose-rate 192-Ir brachytherapy for oral cavity cancer.
A high-dose-rate (HDR) 192-Ir brachytherapy using a customized intraoral mold is effective for superficial oral cavity cancer, and the surrounding normal tissue is kept away from the radioactive source with gauze pads and/or mouth piece for reducing the dose on the normal tissues. In the Tokushima university hospital, the mold has a lead shield which utilizes the space prepared with sufficient border-molding by a specific dental technique using modeling compound. In HDR 192-Ir brachytherapy using a lead shielded customized intraoral mold, there are no reports measuring the absorbed dose. The purpose of the present study is to measure the absorbed dose and discuss the optimum thickness of lead in HDR 192-Ir brachytherapy using a customized intraoral mold with lead shield using a 1 cm thickness mimic mold. The thickness of lead in the mold could be changed by varying the arrangement of 0.1 cm thickness sheet of the acrylic resin plate and lead. The measured doses at the lateral surface of the mold with thermo-luminescence dosimeter were reduced to 1.12, 0.79, 0.57, 0.41, 0.31, 0.24 and 0.19 Gy and the ratios to the prescription dose were reduced to 56, 40, 29, 21, 16, 12 and 10 percent as lead thickness increased from 0 to 0.6 cm in 0.1 cm increments, respectively. A 0.3 cm thickness lead was considered to be required for a 1 cm thickness mold, and it was necessary to thicken the lead as much as possible with the constraint of limited space in the oral cavity, especially at the fornix vestibule.
Department of Oral and Maxillofacial Radiology, Institute of Health Biosciences, University of Tokushima Graduate School, Japan. kudoh@dent.tokushima-u.ac.jp
Takaharu
T
Kudoh
Hitoshi
H
Ikushima
Eiichi
E
Honda
D000042:Absorption; D000180:Acrylic Resins; D000362:Agar; D001918:Brachytherapy / Q000009:adverse effects / Q000295:instrumentation*; D003760:Dental Impression Materials; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D004867:Equipment Design; D006801:Humans; D007496:Iridium Radioisotopes / Q000008:administration & dosage / Q000009:adverse effects*; D007854:Lead; D008422:Materials Testing; D009062:Mouth Neoplasms / Q000532:radiotherapy*; D009064:Mouth Protectors; D058958:Organs at Risk; D011832:Radiation Injuries / Q000517:prevention & control*; D011835:Radiation Protection / Q000295:instrumentation*; D011874:Radiometry; D011879:Radiotherapy Dosage
D000180:Acrylic Resins; D003760:Dental Impression Materials; D007496:Iridium Radioisotopes; D007854:Lead; D000362:Agar