High Quality Clinical Stereotactic Radiosurgery Planning and Delivery with Standard Resolution (5mm) Multileaf Collimation and Multiple Isocentres.

Abstract Aims To demonstrate the use of novel planning techniques in producing high quality stereotactic radiosurgery (SRS) plans using standard 5mm multileaf collimator (MLC) delivered clinically at local institution using multiple isocenters. Methods Novel planning techniques consisted of offset isocentre, variable asymmetric jaws and dicom edits to reduce leaf tip transmission, all with the aim of maximising dose conformity. A local institution clinical cohort was planned (1-4 targets) and plan conformity metrics common to SRS were compared against conformity metrics from selected previous publications comparing gamma knife (GK) to Linac SRS using HD-MLC (2.5mm). Additionally, local institution plan conformity metrics for two benchmark SRS planning cases (3 and 7 targets) are compared to metrics from other centres treating SRS clinically in England. Finally, pre-treatment QA results, both point dose measurement and film analysis, are presented to demonstrate plan deliverability. Results Clinical conformity metrics are shown to be comparable to previously published results using either GK or Linac with HD-MLC. Metrics from benchmark planning cases are shown to be comparable and have better prescription dose conformity than average nationally in England. Pre-treatment QA results demonstrate suitable plan deliverability. Conclusions SRS planning using standard 5 mm MLC and multiple isocentres produces high quality treatment plans for a limited number of targets with a high degree of dose conformity and dose fall off when employing novel planning techniques to compensate for MLC leaf size and multiple isocentres.