| Abstrakt: |
Introduction: The technological evolution of SRS equipment, where the demands of conformity, gradient and accuracy are at its highest, is significant. Six years on from the 2016 UK benchmarking study [Eaton et al], new technology poses the question “have technological improvements led to a corresponding improvement in treatment plans?”. This benchmarking study assesses the capabilities of the following platforms which were selected as ‘state of the art’ in 2022: Gamma Knife Icon with Lightning inverse planning (GK), Cyberknife S7 with M6 MLC, BrainLab Elements (Elekta VersaHD and Varian TrueBeam), Varian Edge with HyperArc (both 6X-FFF and 10X-FFF), Zap-X. Methods and materials: Six cases (two multiple metastasis cases, four benign targets) were used from the previous study. In order to reflect the evolution of the increased number of metastases treated per patient, a case with 14 targets was added. 28 targets amongst the seven patients ranged from 0.02cc to 7.2cc in volume. Participating centres were sent DICOMRT files containing images, target contours and potential OARs for each treatment plan. They were asked to plan each treatment to the best of their ability using experienced staff (defined as at least two years’ experience with the relevant platform). While some variation in local practice was allowed (eg. the use of margins), groups were asked to prescribe a specified dose to each target and tolerance doses to organs at risk were agreed in advance. Parameters used for comparison between the plans, included coverage, selectivity, Paddick Conformity Index (PCI), Gradient Index (GI), R50%, Efficiency Index, doses to OARs, estimated planning and estimated treatment time. Results: Mean coverage for all targets ranged from 98.2% (Brainlab/Elekta) to 99.7% (Hyperarc 6X). PCI values ranged from 0.722 (Zap-X) to 0.900 (CyberKnife). GI ranged from a mean of 3.15 (Zap-X), representing the steepest dose gradient to 5.08 (HyperArc 10X). The GI appeared to follow a trend with beam energy, with the lowest values from the lower energy platforms (Zap-X; 3MV, GK; 1.25MeV) and the highest value from the highest energy (HyperArc 10X). R50% values (excluding case 7), which are combination of conformity and gradient indices, had a minimum mean value of 3.65 (GK) and a maximum mean value of 4.76 (Hyperarc 10X). Treatment times were lowest with modified linacs. Conclusion: Compared with earlier studies, newer equipment appears to deliver higher quality treatments. CyberKnife and Linac platforms appear to give better conformity while lower energy platforms give better dose gradient. [ABSTRACT FROM AUTHOR] |
