Room: Exhibit Hall | Forum 4
Purpose: Brainlabâ€™s Multimet Elements (MME) software was commissioned for single-isocenter multi-target frameless treatment on a VersaHD. Commissioning and initial clinical experience is presented and categorized by target size, number, and shape.
Methods: Commissioning was performed for a 6FFF beam following TG53 guidelines. Test cases were taken from previously treated GammaKnife patients. Single and multi-target cases were created using two to five couch angles to achieve Paddick Gradient Indices < 5 and Inverse Paddick Conformity Indices < 1.43. A microDiamond and SRSMapcheck placed in a StereoPhan were used to validate absolute and planar dose, respectively. Planar dose was evaluated with relative Gamma analysis (2%/1mm/10% threshold). Clinical treatment plans were generated, tested, and delivered to patients using the same procedures as commissioning.
Results: Fourteen commissioning and seventeen clinical targets between 0.03 cc to 17.11 cc have been studied. Clinically acceptable plans were created for target sizes down to 1 cm (0.32 cc), before index metrics became unacceptable. Plan quality was especially dependent on target shape, with spherical targets producing the best results. For multi-target cases, mean measured-calculated dose deviation was 0.31% (max 2.84%) and average gamma pass rate was 98.9% (min 95.4%). For single-targets, dose difference grew quadratically with decreasing target size and was 4% for a 1cm target; average pass rates for planar relative dose analysis remained high at 99.8%.
Conclusion: MME produces highly conformal multi-target single-isocenter plans for targets > 1cm, below which conformity is compromised in part due to the limited 5mm y-jaw step size that is especially problematic for non-spherical targets. Caution should be taken when using MME for single target lesion, especially for target size smaller than 2cm.
Not Applicable / None Entered.