Rapidarc

The diode detector array ArcCHECK was used for measurement of the real dose distribution of IMRT and VMAT. After acquiring a CT image of the ArcCHECK, virtual treatment plans were prepared for head-neck, lung and prostate cases based on the CT images. In each cancer cases, the IMRT and RapidArc (Varian, Palo Alto, CA, USA) plans were made using photons of 6 MV and 10 MV, respectively, and 12 plans were prepared. The virtual tumor target and OARs were contoured as shown in Fig 1. All of the plans were created using an Eclipse (Varian, Palo Alto, CA, USA) planning system and prepared according to the dose prescription, as shown in Table 1. A clinical linear accelerator (LINAC), Trilogy Tx (Varian, Palo Alto, CA, USA), was used in this study.

Treatment was delivered at a TrueBeam linac (Varian Medical Systems, Palo Alto, USA) equipped with a 6-degrees-of-freedom couch. Cone-beam computed tomography (CBCT) can be acquired by a gantry mounted X-ray line. All patients were treated with 6 or 8 MV photons using static field IMRT or volumetric modulated arc therapy technique (RapidArc, Varian Medical Systems, Palo Alto, USA), which enables favorable gradients around the target volume (28 (link)).
Free breathing gated delivery during the exhalation phase was provided with the help of real-time position management (RPM) respiratory gating system (Varian). Daily low-dose kV-CBCT scans also gated during the exhalation phase served for the online setup and online adaptation with the help of a 6D-positioning table at TrueBeam (Varian) and were used for the determination of interfractional CTV deformations (CTV_i) compared to the planning CT (CTV_plan). Further tools used for online image guidance were set up with anterior/posterior kV radiographs, breathing coaching to a flat stable respiration at the expiration plateau, and anterior/posterior fluoroscopy with delineation of the diaphragm for documentation of the respiration amplitude relative to the RPM marker.

All patients underwent surgical intervention after imaging and discussion in our center’s neuro-oncology multidisciplinary meeting, either in the form of maximal safe resection or biopsy. All the patients with IDH-WT tumors were offered post-operative RT with or without concurrent and adjuvant chemotherapy (temozolomide). All patients received 3D planning using CT data with pre-operative and post-operative MRI images. RapidArc (Varian Medical Systems, Inc. Palo Alto, CA, USA) intensity-modulated radiotherapy (IMRT) planning was routinely performed for all patients. In patients with good performance status, long-course radical radiotherapy was commonly delivered to a dose of ≥54 Gy in ≥30 daily fractions over 6 weeks. Alternative short-course radiation of 30 Gy in 6 fractions on alternate days over 2 weeks was used for older patients or patients with limited performance status.
The decision for concurrent temozolomide (TMZ) was taken on an individual basis under consideration of the patient’s performance status and presence of disease high-risk features, consistent with standard-of-care treatment protocols at the time of diagnosis. The Stupp regimen was followed for administering concurrent and adjuvant TMZ [8 (link)].

All HNC plans were created with a simultaneous integrated boost (SIB) technique using 6MV photons and 2 full RapidArc™ (Varian Medical Systems, Palo Alto, USA) arcs. In 35 fractions, plans aimed to deliver 95 % of the prescribed dose of 54.25Gy/70.0Gy to 98 %/99 % of the elective/boost PTV (PTV_E/PTV_B), while limiting the volume of each PTV receiving >107 % of the prescribed dose. A 5mm transition zone (PTV_T) was created between PTV_E and PTV_B to facilitate dose fall-off between them. The optimization goals and included OARs have been outlined in detail previously [7 (link), 19 (link)–21 (link)].

Twenty-one consecutive liver SBRT patients were selected with prescription doses ranging from 30 to 60 Gy in five fractions. Liver volumes ranged from 550 to 3346 cc and PTV volumes from 2 to 222 cc. The patient cohort includes a pediatric patient with a small liver volume and a patient with enlarged liver due to cancer infiltration. The patients were clinically treated using VMAT (RapidArc, Eclipse Treatment Planning System version 10, Varian) with either 2 coplanar full arcs or 2–3 coplanar partial arcs entering the body proximal to the tumor, depending on the tumor laterality. The VMAT optimization and dose calculation in Eclipse used the Progressive Resolution Optimizer (PRO, version 10.0.28) and anisotropic analytical algorithm (AAA, version 10.0.28) with 2.5x2.5x2.5 mm³ grid resolution, respectively. Collimator rotations were used between arcs. All plans were normalized to cover 95% of the PTV by the prescription dose. For the OARs, plan objectives are liver volume receiving less than 15 Gy > 700 cc, stomach and bowel volumes receiving more than 20 Gy < 20 cc, maximal dose to kidney and spinal cord <12Gy. The same objectives were applied to all prescription doses.