INITIAL EXPERIENCE USING BRAINLAB ELEMENTS CRANIAL SRS

Purpose: Cranial SRS uses non-coplanar fixed IMRT beams or arc to reach clinically acceptable radiosurgery plans. Elements cranial SRS software uses a 4Pi optimization algorithm and clinical Protocols for couch angle selection, start /stop gantry angle and trajectory optimization. The objective of this work was to evaluate the initial experience using Elements cranial SRS software v1.5. Methods: The first 39 SRS treatment plans were selected. The pathologies associated were acoustic neurinomas (#7, 13Gy - 1 fraction, #2, 25Gy - 5 fractions and #5, 18Gy - 3 fraction), pituitary macroadenoma (#1, 25Gy - 1 fraction and #4, 27Gy - 5 fractions), meningioma (#1, 13Gy - 1 fractions; #1, 16Gy - 1 fraction; #1, 18Gy - 3 fraction and #2, 30Gy - 5 fractions), cavernoma (#2, 16Gy - 1 fraction), hamartoma (#2, 22Gy - 1 fraction), metastasis (#1, 25Gy - 1 fraction, #2, 30Gy - 3 fractions and #2, 27Gy - 3 fractions), craniopharyngioma (#1, 27Gy - 5 fractions and #1, 21Gy - 3 fractions), capillary hemangioma (#1, 21Gy - 3 fractions) and glioblastoma (#3, 36/25Gy - 5 fractions). Clinical protocols were created for each treatment. Plans were evaluated by monitor units (MU), conformity index (CI) and gradient index (GI). Patient specific QA was done by EBT3 film (global gamma, 2%- 2mm analyzed by RIT software v6.7), Delta4 (local and global gamma, 2%-2mm, ScandiDos), ion chamber measurement (PinPoint chamber within and in-house head phantom) and independent MU calculation (RadCalc v6.3). Results: All plans fulfil the clinical plan quality and OARs dose constraints. The average PTV volume was 6.0cc [0.5, 33.2], MU needed to deliver 10 Gy was 2756MU [1682, 6092], CI 1.2 [1.1, 1.7] and GI 3.0 [2.1, 5.2]. EBT3 film global gamma was better than 97.6% and for 88% of the plans better than 99.4%. Delta4 local gamma was better than 92.7% and global gamma better than 96.2%. The average ion chamber dose variation was 1.2% [-3.5, 5.4] and independent MU calculation variation was 3.1% [0.1, 8]. Conclusion: The implementation of Elements Cranial SRS present good results for CI, GI and patient specific QA. According to the previous results, it is concluded that Elements Cranial SRS is a tool that comply the requirements for its continuous use in the clinic.