BackgroundSeveral comparison studies have shown the capability of VMAT to achieve similar or better plan quality as IMRT, while reducing the treatment time. The experience of VMAT in a multi vendor environment is limited. We compared the plan quality and performance of VMAT to IMRT and we investigate the effects of varying various user-selectable parameters.MethodsIMRT, single arc VMAT and dual arc VMAT were compared for four different head-and-neck tumors. For VMAT, the effect of varying gantry angle spacing and treatment time on the plan quality was investigated. A comparison of monitor units and treatment time was performed.ResultsIMRT and dual arc VMAT achieved a similar plan quality, while single arc could not provide an acceptable plan quality. Increasing the number of control points does not improve the plan quality. Dual arc VMAT delivery time is about 30% of IMRT delivery time.ConclusionsDual arc VMAT is a fast and accurate technique for the treatment of head and neck cancer. It applies similar number of MUs as IMRT, but the treatment time is strongly reduced, maintaining similar or better dose conformity to the PTV and OAR sparing.

Methods and results for commissioning of the complete VMAT delivery chain are presented for the combination of Nucletron's Oncentra MasterPlan® v3.3 with Elekta's Mosaiq® v1.6 and SynergyS® linac. VMAT specific linac commissioning included determination of the size of the minimal dynamic leaf gap. Dosimetric validation of the complete treatment chain was performed using a 2D-ionization-chamber-array and showed excellent dosimetric results. [30]. Clinical implementation of VMAT, however, requires not only sufficient plan quality but also commissioning of the complete delivery chain including treatment planning, data transfer to the record and verify system, and delivery on the linear accelerator (linac). Ling et al. [19] and Bedford and Warrington Keywords

Although qIMAT uses a large number of fields and therefore the volume of normal tissue that receives low-dose radiation is larger than for IMRT, the total OED (by considering primary and secondary contributions of radiation) does not increase the risk of developing a secondary cancer compared to a conventional IMRT plan.

No abstract

: The study showed that qIMAT improves the sparing of OARs while keeping the uniformity within the PTV, when compared with conventional IMRT. The more concave the PTV, the more noticeable is this behavior. The qIMAT technique has the advantage that it can be realized with a conventional equipment. The plan quality is high even with a single gantry arc and one segment per beam direction.