Dosimetric Evaluation of Surgically Targeted Radiation Therapy (STaRT) Brain Implants with GammaTile
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PO-GePV-T-45 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: With the advent of GammaTile® (GT), a device with Cs-131 seeds embedded in a resorbable collagen-based tile has significantly lowered the technical barrier to radiation planning and ease of surgical application providing a more modular system than previously available. GT based surgically targeted radiation therapy (STaRT) can be utilized, against a spectrum of CNS tumors, including recurrent meningiomas, high grade gliomas and brain metastases. In this study we evaluated post implant dosimetry who received STaRT with GammaTiles for Brain metastasis.
Methods: Six patients were selected who received STaRT implants using GammaTiles. Gammatiles were implanted in intraoperatively by the neurosurgeon. A post implant dosimetry was performed using Varian Eclipse and VariSeed TPS after the 1-2 days of the implant. CT and MR were fused in Eclipse and tumor cavity were drawn for each patient and then data set were exported to VariSeed TPS for post planning purposes. Nominal dose prescription for these implants were 60Gy to the tumor cavity. Volumes of the cavity, number of tiles/seeds implanted, V90%, V150%, V200, D90%, D1cc%, D2cc% were collected and analyzed. All doses and volumes were normalized to the prescription and cavity volume respectively.
Results: The Average Volume of the cavities were 13.5cc (SD 4.7,range 8.9-22.6). The Mean values of cavity volumes V90%, V150%, V200% were 99.7 (SD 1.7, range 95.6-100), 83.7 (SD 6.8, range 71.8-92.3), and 67.4 (SD 9.9, range 50.2-82.4) respectively. The mean dose values for the cavity D90%, D1cc% and D2cc% were 132.9 (SD 18.4, range 109-162.1), 524.5 (SD 51.9, range 478.0-633.4), and 408.6(SD 42.5, range 375-498.7) respectively.
Conclusion: Treating tumor bed with Cs-131 seeds embedded in GammaTiles is an effective and safe treatment for recurrent as well as new brain metastatic lesions with good clinical outcome. Our implant procedure found to be satisfactory based on our post implant dosimetric analysis.
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