Author: Jacob Gooslin, Ellis Lee Johnson, Damodar Pokhrel 👨🔬
Affiliation: University of Kentucky, Department of Radiation Medicine, University of Kentucky, University of Kentucky, Radiation Medicine 🌍
Purpose: HyperArc radiosurgery permits treatment of multiple brain lesions using a single-isocenter improving treatment planning efficiency and workflow. A key stereotactic planning aspect is an independent monitor unit (MU) second check. Commercial products can be costly in the community practice setting and a TMR based methodology implemented in the Eclipse Scripting interface could be useful in this environment. To this end, we’ve developed a simple, clinically useful TMR-based MU second check method for conformal-arc HyperArc brain radiosurgery plans.
Methods: For validation and testing, stereotactic HyperArc plans were developed for seven test patients each having a single brain lesion, using dynamic conformal arcs, and a 6FFF beam. Lesions were planned to 27Gy/3 fractions using HyperArc geometry and AcurosXB. Average planning target volume was 3.7+/-3.0cc. Clinical TMR TrueBeam data were used to calculate MUs. An Eclipse script was used to perform a TMR-based MU second check arc-by-arc and compared to AcurosXB results. The TMR MUs were also compared to our in-house Monte-Carlo (MC) second check system.
Results: Across seven test patients, 27 arcs were analyzed. MUs obtained using the TMR script agreed well (<=5%) with those obtained from AcurosXB. Average percent difference between planned and calculated was 1.98+/-1.0 (0.28–4.92)% with statistically insignificant difference (p=0.121). Average percent difference between TMR script and MC was 2.25+/-0.69 (1.39-3.18)%(p<0.010). MC calculation time is approximately 20 minutes per case, whereas TMR-based script calculation time is only few seconds.
Conclusion: TMR-based Eclipse script for MU second check is feasible for dynamic conformal arc-based, HyperArc geometry and has been independently validated with MC. This script can be implemented without cost to the clinic, requires less computational time and physics resources and can be used for academic teaching for medical physics learners. An advanced TMR-based MU check script for highly modulated HyperArc VMAT brain SRS/SRT plans is currently under investigation.