Room: ePoster Forums
Purpose: To investigate the effect of the embolic material image artifacts on dose calculations for AVM Treatments.
Methods: 33 AVM patients that were administered embolic agents Onyx and Phil embolic agents prior to undergoing SRS. Treatment planning was carried out on BrainLab iPlan TPS and delivered using a linear accelerator with a high definition MLC. Three methods were used to evaluate the dosimetric accuracy, first using planning CT with original patients' treatment plan. The second, same plans were recalculated using diagnostic CT that was acquired prior to the administration of the embolic material. The third, the artefact in the planning CT images were masked and their CT number was set to zero. In addition, known volumes of the two embolic materials and water were used in an anthropomorphic phantom to evaluate the attenuation of each material. The treatments included static conformal fields and dynamic arcs.
Results: Calculated MU to deliver the same dose for all plans were within 1.0 % among the three methods. The maximum dose difference was found to be 4.1% corresponding to patient with the largest embolic structure. The minimum dose difference was 0.8 % for the patient with the smallest embolic structure. Anthropomorphic phantom plans evaluation using Water, Onyx, and Phil revealed a Gamma index of 98.7%, and 98% for Water vs Onyx, and Water vs Phil respectively for conformal beams, and 99.9% with Dynamic arcs.
Conclusion: Artifacts appeared as significant distortion on CT images, yet its effect on the dose calculation was not significant. In addition, Phil material resulted in less artifacts compared to Onyx. Dynamic arcs reduced the effect of CT numbers distortion on dose calculation. The artifact-free diagnostic CT images could be utilized to calculate the magnitude of the attention caused by embolic materials.