Abstract
The purpose of this work is to evaluate the volumetric‐modulated arc therapy (VMAT) multicriteria optimization (MCO) algorithm clinically available in the RayStation treatment planning system (TPS) and its ability to reduce treatment planning time while providing high dosimetric plan quality. Nine patients with localized prostate cancer who were previously treated with 78 Gy in 39 fractions using VMAT plans and rayArc system based on the direct machine parameter optimization (DMPO) algorithm were selected and replanned using the VMAT‐MCO system. First, the dosimetric quality of the plans was evaluated using multiple conformity metrics that account for target coverage and sparing of healthy tissue, used in our departmental clinical protocols. The conformity and homogeneity index, number of monitor units, and treatment planning time for both modalities were assessed. Next, the effects of the technical plan parameters, such as constraint leaf motion CLM (cm/°) and maximum arc delivery time T (s), on the accuracy of delivered dose were evaluated using quality assurance passing rates (QAs) measured using the Delta4 phantom from ScandiDos. For the dosimetric plan's quality analysis, the results show that the VMAT‐MCO system provides plans comparable to the rayArc system with no statistical difference for V95% (p<0.01), D1% (p<0.01), CI (p<0.01), and HI (p<0.01) of the PTV, bladder (p<0.01), and rectum (p<0.01) constraints, except for the femoral heads and healthy tissues, for which a dose reduction was observed using MCO compared with rayArc (p<0.01). The technical parameter study showed that a combination of CLM equal to 0.5 cm/degree and a maximum delivery time of 72 s allowed the accurate delivery of the VMAT‐MCO plan on the Elekta Versa HD linear accelerator. Planning evaluation and dosimetric measurements showed that VMAT‐MCO can be used clinically with the advantage of enhanced planning process efficiency by reducing the treatment planning time without impairing dosimetric quality.PACS numbers: 87.55.D, 87.55.de, 87.55.Qr
Highlights
259 Ghandour et al.: volumetric-modulated arc therapy (VMAT) multicriteria optimization (Philips, Inc., Andover, MA), and rayArc (RaySearch Laboratories, Stockholm, Sweden), allow for the creation and optimization of dynamic arc plans that meet the clinical goals
All VMAT-multicriteria optimization algorithm (MCO) plans achieved the required planning target volume (PTV) coverage; on average, 99.6% of the PTV received more than 74.1 Gy (95% of the prescription dose), and the average D1% was 80.2 Gy (< 81 Gy)
The results show that, for the rectum and bladder, no large differences in the high-dose regions were detected and slightly better sparing was observed in the low-dose regions for VMAT-MCO
Summary
259 Ghandour et al.: VMAT multicriteria optimization (Philips, Inc., Andover, MA), and rayArc (RaySearch Laboratories, Stockholm, Sweden), allow for the creation and optimization of dynamic arc plans that meet the clinical goals. These systems provide high-quality plans, the optimal solution generally depends on the planner’s time commitment and experience[4,5] to translate the clinical goals into an optimization problem accounting for the relation between the planning target volume (PTV) coverage and the sparing of the organs at risk (OAR). A review of the Pareto optimality optimization concept can be found in Craft.[10]
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