(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: To present the commissioning aspects of the first commercial use of the Cs-131 GammaTile permanent brain implant after FDA approval.
Methods: The GammaTile is a collagen tile containing four embedded Cs-131 seeds and is permanently implanted in the brain resection cavity. Each three tiles are delivered with a check source from the batch. Metal shielding trays for transport of tiles are provided by the vendor. Patient survey was done using a calibrated survey meter. Eclipse Brachytherapy Treatment Planning System (TPS) was commissioned by entering published TG-43 parameters and running several checks for dose calculation accuracy. A tile autoradioagraph using EBT3 Gafchromic film was also obtained and compared with TPS. Post-surgery planning was done using the CT scan acquired within 24h of implant. The resection cavity serves as the GTV. PTV is created by adding a 5 mm expansion around GTV. The plan is evaluated based on the PTV coverage (D90) of the prescription dose (usually ranging from 60 to 80 Gy).
Results: Air Kerma Strengths of the check source was within 0.1% of the vendor-specified strength. Film and TPS measurements were in agreement. Dose rate immediately after implant at 1m from ipsilateral and contralateral sides of the implant cavity were 2.5mR/h and 0.1mR/h, respectively. The exposure rates were within tolerance for patient release (NUREG 1556).
Conclusion: The first experience with a GammaTile implant is presented, including source position verification, TPS commissioning, and radiation safety aspects of the procedure.
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