Room: AAPM ePoster Library
Purpose: Intracranial arteriovenous malformations (AVM) can be effectively treated with stereotactic radiosurgery (SRS). However, for large-volume AVMs, the dose is reduced to avoid toxicity. In Volume-staged SRS (VS-SRS) the target is divided into 2 - 3 treatment volumes that are treated in separate sessions with a 3 to 6 month interval. This allows to maintain adequate prescription doses while reducing toxicity and dose to the normal brain. Reports on VS-SRS have been limited to treatments using the Gamma Knife system. The purpose of this study was to implement VS-SRS on a conventional linac-based SRS system.
Methods: Our radiosurgery technique for treatments of AVMs utilizes TrueBeam STx, frame-based immobilization and volumetric dose planning with Brainlab iPlan treatment planning system (TPS). For treatment of large-volume AVMs, the total treatment volume is divided into 2 to 3 volumes under 12 mL each that are treated at 4-6 month intervals. Each stage is treated with one isocenter and four dynamic arcs. Prospective planning is done at the beginning of treatment that shows the composite result of all stages.
Results: So far 3 patients were treated using the VS-SRS for the treatment or large volume AVMs. The range of total target volume was from 17 to 33 mL. The prescription dose was 16 Gy, with a maximum dose under 34 Gy.
Conclusion: VS-SRS was successfully implemented on a conventional linac-based SRS system utilizing TrueBeam STx.