(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: To examine the radiation safety aspects of GammaTile brachytherapy for brain tumors by measuring the exposure rates of implanted patients and equivalent doses received by medical physicists, radiation oncologists, neurosurgeons, and nurses.
Methods: GammaTile is a collagen tile containing four embedded Cs-131 seeds and is permanently implanted in the resection cavity immediately after tumor resection. This study prospectively analyzed exposure rate for 13 patients who were treated with GammaTile. Exposure rates were measured immediately after implant at 1m from the ipsilateral and contralateral sides of the resection cavity. Patient survey was performed using a calibrated ionization chamber survey meter. A G-M counter was used to survey the operating room after implant. Throughout the implant procedure, the neurosurgeon, radiation oncologist, and medical physicist wore dosimeter badges. No shielding was used during surgery. A radiation safety officer was charged with educating nurses in the unit on how to care for implanted patients. NRC NUREG 1556 Vol. 9, Rev.2, Equation U-2 guidelines were followed, i.e. patient could be released from hospital if exposure rates at 1m were below 6mR/hr. Radiation safety procedures were reviewed with patients and their families.
Results: Immediately following implantation, the mean, maximum, and minimum dose rates at 1m were ipsilaterally: 1.83mR/hr, 3.5mR/hr, and 0.5mR/hr, respectively; and contralaterally: 0.2mR/hr, 0.5mR/hr, and 0.1mR/hr, respectively. Ring badges readings integrated over implant procedures for maximum and minimum were: for neurosurgeon 0.97mSv and 0.59mSv, for radiation oncologist 0.45mSv and 0.25mSv, and for medical physicist 0.60mSv and 0.55mSv. For nurses, badge readings ranged from 0.01mSv to 0.05mSv. operating room was within background levels after patient was sent to recovery.
Conclusion: The results showed that exposure rates for GammaTile implanted patients were below the NRC guidelines and that GammaTile therapy provides limited radiation exposure to both medical staff and family members.
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