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AAPM TG-218 provides recommendations for standard IMRT pre-treatment QA without giving specifics for stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). In light of this, our purpose is to report our experience with applying TG-218 recommendations to a large multicenter clinical SRS and SBRT program for a range of diverse clinical pre-treatment QA systems. Pre-treatment QA systems included Delta4 (Scandidos), Portal Dosimetry (Varian Medical Systems), ArcCHECK (SunNuclear), and SRS MapCHECK (SunNuclear). Plans were stratified by technique for each QA system, and included intracranial and extracranial IMRT and VMAT (total QA cases n=275). Gamma analysis was re-analyzed with spatial/dose criteria combinations ranging from 1 to 3 mm and 1% to 4%, and action and tolerance limits were calculated per plan type and compared to the “universal” TG-218 action limit of 90%. The analysis indicated that spatial tolerance criteria could be tightened to 1 mm while still maintaining an in-control QA process for all QA systems evaluated.The Elekta Unity MR-Linac (MRL) is expected to benefit spine stereotactic body radiotherapy (SBRT) due to the improved soft tissue contrast available with onboard MR imaging. However, the irradiation geometry and beam configuration of the MRL deviates from the conventional linear accelerator (Linac). The purpose of the study was to investigate the feasibility of spine SBRT on the MRL. Treatment plans were generated for lumbar and thoracic spines. Target and spinal cord doses were measured with two cylindrical ion chambers inserted into an anthropomorphic spine phantom. Our study indicated that the Monaco treatment planning system (TPS) could generate clinical treatment plans for the MRL that were of comparable quality to the RayStation TPS with a conventional Linac. For both Linacs the planned dose within the gross tumor volume agreed with measurements within ±3%. For the spinal cord, while the measured doses from the TrueBeam were 1.8% higher for the lumbar spine plan and 6.9% higher for thoracic spine plan, the measured doses from MRL were 0.6% lower for the lumbar spine plan and 3.9% higher for the thoracic spine plan. In conclusion, the feasibility of spine SBRT in Elekta Unity MRL has been demonstrated, however, more effort is needed for such as optimizing the online plan adaptation method.This risk analysis describes our Failure Mode and Effects Analysis (FMEA) for Gamma Knife stereotactic radiosurgery at our community hospital. During bi-monthly meetings over 5 months, our FMEA team mapped a detailed Gamma Knife process tree and identified potential failure modes, each were scored a Risk Priority Number (RPN) for severity, occurrence, detectability. In our process tree of 14 subprocesses and 177 steps, we identified 31 potential failure modes 7 high scoring (RPN o150) and 3 modes ( less then 150) selected by clinicians for mitigation strategies. Eighteen months later, rescoring of high-risk failure modes showed significant reduction in RPN scores, thus confirming the benefit of our FMEA mitigation strategies. Our study provides a roadmap to achieve high-quality Gamma Knife radiosurgery that can be utilized by new centers as a starting point for their quality management program. Five quality control documents were developed that can be customized by any Gamma Knife center.Introduction Two-staged stereotactic radiosurgery (SRS) has been shown as an effective treatment for brain metastases that are too large for single fraction SRS. Methods Patients with large brain metastases (>4 cm3) treated with two-staged SRS from January 2017 to December 2019 at our institution were retrospectively identified. Results There were 23 brain metastases treated. The normal brain volume receiving equivalent 12Gy-in-single-fraction was defined as V12E. The V12E for original single-fraction GKS plan (mean of 41.4 cm3, range 5.6-146.1 cm3) was significantly higher compared to that of the second stage (mean of 23.7 cm3, range 2.8-92.7 cm3). The median tumor volume measured at the second stage (4.30 cm3) was reduced by an average of 52.2% compared to the first stage (9.58 cm3). Three patients (27.3%) showed local tumor progression in 4 tumors (20%). check details The median time to progression was 152 days. Conclusions Two-staged SRS is an effective treatment technique for large brain metastasis that results in significant reduction of tumor volume at the second stage SRS. Optimal treatment dose has not yet been defined.Background This study compares the outcomes of stereotactic body radiation therapy (SBRT) for sacral and thoracolumbar spine metastases. Methods This analysis considered each sacral spine SBRT treatment at a single institution and a cohort of consecutive thoracolumbar treatments. Results 28 patients with 35 sacral treatments and 41 patients with 49 thoracolumbar treatments were included. Local control was 63% and 90%, respectively. The sacral cohort contained more lesions with ≥2 vertebrae and epidural and paraspinal involvement. Sacral patients had larger treatment volumes, increased rates of subsequent SBRT, decreased propensity for pain improvement, and decreased local control (p=0.02 on Kaplan-Meier analysis). Multivariate analysis demonstrated that PTV > 50 cc and epidural involvement were correlated with decreased local control. No cases had grade ≥3 toxicity. Conclusion SBRT for sacral spine metastases is a distinct disease process than metastases to the thoracolumbar spine, resulting in lower rates of local control and pain improvement.We sought to evaluate the association between larynx dose and risk of severe late laryngeal toxicity in patients undergoing re-irradiation SBRT for recurrent HNC. Fifty-five patients with an intact larynx underwent re-irradiation SBRT to a median dose of 44 Gy in 5 fractions. Five (41.7%) patients treated for a laryngeal/hypopharyngeal recurrence experienced late grade ≥3 laryngeal toxicity, compared to 0.0-7.1% for other sites. Logistic dose-response models were created to predict risk of severe late laryngeal toxicity, including dysphagia and airway compromise. According to the model, the risk of severe laryngeal toxicity with a larynx D5cc of 5 Gy is 5.8% (95% CI 2.9-9.9%) and rises to 11.4% with a D5cc of 20 Gy and 25.3% with a D5cc of 40 Gy. In patients with a laryngeal/hypopharyngeal recurrence, SBRT planning should carefully assess the dose to laryngeal structures given these dose findings, and SBRT should be approached with significant caution in such patients.