Author: Timothy J Allen, Clara Ferreira 👨🔬
Affiliation: University of Minnesota, Department of Radiation Oncology, University of Minnesota, Minneapolis 🌍
Purpose: Presurgical treatment planning for GammaTile cranial implants is limited to estimates of required tiles and provides no positioning information. Existing tools are intended for tile estimation of roughly spherical glioblastomas and brain metastasis but not for irregular meningiomas. This work introduces a novel pre-planning technique to improve tile quantity estimate accuracy and to provide tile position and dose information in the pre-planning phase.
Methods: Full and half tiles were modelled as applicators in BrachyVision v11.0.47. The applicators are geometrically representative of the physical size and shape of the tiles. Source dwell positions corresponding to the tile seed locations provided seed positioning relative to the tile applicators. Dose was calculated using a 3.5 U source strength and permanent dwell times. The Cs-131 (Model CS-1, Rev 2) TG-43 consensus data was used to model the source. The number of tiles was estimated using this method for a meningioma case and compared to conventional estimation methods and to the number of tiles implanted.
Results: Both the full and half tile applicators were successfully implemented. The applicators can be moved translationally and rotationally with dose being updated in real time. Use of this method in the meningioma case resulted in a predicted 16 tiles compared to 24 tiles resulting from conventional estimation methods. The actual number implanted was 13.5.
Conclusion: Use of a pre-planning tool may better estimate the number of required tiles and allow for pre-operative planning of tile positioning and orientation. This could prevent ordering of excess tiles and serve as a guide to intraoperative tile placement. The proposed technique may be especially helpful for complex cases such as meningiomas where tile placement is particularly challenging. The real time dose updating allows the surgeon and radiation oncologist to immediately see the impact of tile positioning and orientation.