Author: Bhuvaneswari Narayanan, Niko Papanikolaou, Daniel L. Saenz 👨🔬
Affiliation: UT Health San Antonio, University of Texas HSC San Antonio 🌍
Purpose: To evaluate dosimetric accuracy of Brainlab Elements (BLE) 4.0 treatment planning system (TPS) for linac based SRS and Spine SBRT treatment.
Methods: RT Safe cranial and thorax phantoms with inhomogeneities built in were used for end-to-end testing. The phantoms were imaged on CT and treatment plans were generated on BLE TPS to simulate SRS and Spinal SBRT treatments. For the cranial SRS, two distinct plan geometries were created with differences in the target sizes. For Spinal SBRT three distinct plans were generated: uniform irradiation, simultaneous boost and avoidance structure plan. Each of these plans were generated with 6MV and 6FFF beam and calculated with pencil beam (PB) and Monte Carlo (MC) dose calculation algorithm. These plans were delivered on Elekta Versa HD Linac equipped with Agility MLC. Exradin A16 ion-chamber was used to measure the dose in each of these geometries. A comparison was made between the calculated dose and measured dose for these different configurations.
Results: For the cranial irradiation, the discrepancies between the PB and MC methods are noticeable in the smaller target sizes. PB shows larger difference in 6FFF configuration and MC showed higher discrepancy than PB for 6MV beam with both calculation methods tending to overestimate the dose. For larger target sizes, the differences between PB and MC calculation methods are minimal for both 6MV and 6FFF beams, indicating that the methods perform similarly under these conditions. For the Spinal irradiation, a similar trend is noticed with PB method showing higher percentage difference than MC in all scenarios. The differences between PB and MC is more pronounced for avoidance setting with PB overestimating the dose significantly.
Conclusion: BLE TPS supports high dosimetric accuracy for SRS and Spine SBRT deliveries and MC appears to provide more accurate dose prediction in the geometries considered in this study.