Development of a 3D printed phantom for commissioning and quality assurance of multiple brain targets stereotactic radiosurgery

Single plan techniques for multiple brain targets (MBT) stereotactic radiosurgery (SRS) are now routine. Patient specifc quality assurance (QA) for MBT poses challenges due to the limited capabilities of existing QA tools which necessitates several plan redeliveries. This study sought to develop an SRS QA phantom that enables fexible MBT patient specifc QA in a single delivery, along with complex SRS commissioning. PLA marble and PLA StoneFil materials were selected based on the literature and previous research conducted in our department. The HU numbers were investigated to determine the appropriate percentage infll for skull and soft-tissue equivalence. A Prusa MK3S printer in conjunction with the abovementioned flaments were used to print the SRS QA phantom. Quality control (QC) was performed on the printed skull, flm inserts and plugs for point dose measurements. EBT3 flm and point dose measurements were performed using a CC04 ionisation chamber. QC demonstrated that the SRS QA phantom transverse, coronal and sagittal flm planes were orthogonal within 0.5°. HU numbers for the skull, flm inserts and plugs were 858±20 and 35±12 respectively. Point and EBT3 flm dose measurements were within 2.5% and 3%/2 mm 95% gamma pass rate, respectively except one Gross Tumour Volume (GTV) that had a slightly lower gamma pass rate. Dose distributions to fve GTVs were measured with EBT3 flm in a single plan delivery on CyberKnife. In conclusion, an SRS QA phantom was designed, and 3D printed and its use for performing complex MBT patient specifc QA in a single delivery was demonstrated.