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Purpose: Cardiac radioablation is a novel treatment option for patients with refractory ventricular tachycardia unsuitable for catheter ablation. The quality of treatment planning depends on dose specifications, platform capabilities, and experience of the treating staff. To harmonize the treatment planning, benchmarking of this process is necessary for multicenter clinical studies such as the RAdiosurgery for VENtricular TAchycardia trial., Methods and Materials: Planning computed tomography data and consensus structures from 3 patients were sent to 5 academic centers for independent plan development using a variety of platforms and techniques with the RAdiosurgery for VENtricular TAchycardia study protocol serving as guideline. Three-dimensional dose distributions and treatment plan details were collected and analyzed. In addition, an objective relative plan quality ranking system for ventricular tachycardia treatments was established., Results: For each case, 3 coplanar volumetric modulated arc (VMAT) plans for C-arm linear accelerators (LINAC) and 3 noncoplanar treatment plans for robotic arm LINAC were generated. All plans were suitable for clinical applications with minor deviations from study guidelines in most centers. Eleven of 18 treatment plans showed maximal one minor deviation each for target and cardiac substructures. However, dose-volume histograms showed substantial differences: in one case, the planning target volume ≥30 Gy ranged from 0.0% to 79.9% and the ramus interventricularis anterior V 14Gy ranged from 4.0% to 45.4%. Overall, the VMAT plans had steeper dose gradients in the high-dose region, while the plans for the robotic arm LINAC had smaller low-dose regions. Thereby, VMAT plans required only about half as many monitor units, resulting in shorter delivery times, possibly an important factor in treatment outcome., Conclusions: Cardiac radioablation is feasible with robotic arm and C-arm LINAC systems with comparable plan quality. Although cross-center training and best practice guidelines have been provided, further recommendations, especially for cardiac substructures, and ranking of dose guidelines will be helpful to optimize cardiac radioablation outcomes., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: Our purpose was to investigate whether liver stereotactic body radiation therapy treatment planning can be harmonized across different treatment planning systems, delivery techniques, and institutions by using a specific prescription method and to minimize the knowledge gap concerning intersystem and interuser differences. We provide best practice guidelines for all used techniques., Methods and Materials: A multiparametric specification of target dose (gross target volume [GTV] D50% , GTV D0.1cc , GTV V90% , planning target volume [PTV] V70% ) with a prescription dose of GTV D50%  = 3 × 20 Gy and organ-at-risk (OAR) limits were distributed with computed tomography and structure sets from 3 patients with liver metastases. Thirty-five institutions provided 132 treatment plans using different irradiation techniques. These plans were first analyzed for target and OAR doses. Four different renormalization methods were performed (PTV Dmin , PTV D98% , PTV D2% , PTV Dmax ). The resulting 660 treatments plans were evaluated regarding target doses to study the effect of dose renormalization to different prescription methods. A relative scoring system was used for comparisons., Results: GTV D50% prescription can be performed in all systems. Treatment plan harmonization was overall successful, with standard deviations for D max , PTV D98% , GTV D98% , and PTV Dmean of 1.6, 3.3, 1.9, and 1.5 Gy, respectively. Primary analysis showed 55 major deviations from clinical goals in 132 plans, whereas in only <20% of deviations GTV/PTV dose was traded for meeting OAR limits. GTV D50% prescription produced the smallest deviation from target planning objectives and between techniques, followed by the PTV Dmax , PTV D98% , PTV D2% , and PTV Dmin prescription. Deviations were significant for all combinations but for the PTV Dmax prescription compared with GTV D50% and PTV D98% . Based on the various dose prescription methods, all systems significantly differed from each other, whereas GTV D50% and PTV D98% prescription showed the least difference between the systems., Conclusions: This study showed the feasibility of harmonizing liver stereotactic body radiation therapy treatment plans across different treatment planning systems and delivery techniques when a sufficient set of clinical goals is given., (Copyright © 2022 Elsevier Inc. All rights reserved.)