Truebeam linear accelerator linac

kV radiation experiments were performed using a 160 kVp X-ray source (Faxitron CP-160 Arizona USA) with a 0.8 mm Be filter. All doses stated are the absorbed dose in water 33 cm from the radiation source, at a dose rate of 0.77 Gy/min. MV irradiations were performed using a Varian TrueBeam™ linear accelerator (LINAC) in the North West Cancer Centre’s Radiotherapy Facility (Altnagelvin Hospital, Western Health and Social Care Trust). To achieve dosimetric accuracy, an in-house phantom was produced for irradiation purposes and treatment plans generated using Eclipse™ treatment planning system (Additional file 1: Figure S3).

Seven-field IMRT plans using the SW technique were created on the Eclipse™ 10 treatment planning system [Varian Medical Systems, Palo Alto USA]. All plans were generated for the Varian True Beam linear accelerator (LINAC) using beam energies of 15 MV photons and beam angles of 0°, 51°, 102°, 153°, 204°, 255° and 306°. The VMAT plans were created using the same treatment planning system as for SW. Two incomplete arcs from 200° to 160° for the protection of the posterior rectum wall were used. The plans were created using 15 MV photons with a 0.5 cm leaf width. A maximum dose rate of 600 MU/min as well as MLC motion of 2.5 cm/s was applied. The MLC-leakage was at 1.8%. The HT plans were assessed using Tomo planning system version 5 (Accuray® Inc., Sunnyvale, USA). The plans were created for the High Art HDII HT system that uses a helical slice 6 MV photon beam modulated by 64 binary multileaf collimators. The Multiplan® planning system version 5.2 was used to generate the CK plans (Accuray®, Sunnyvale, USA). The CK robotic arm moves in six different axes with a specific positioning accuracy of 0,2 mm. It delivers a 6 MV photon beam with a dose rate of 850 MU/min. The collimator system consists of 12 fixed cones with a size of 5 mm to 60 mm (at 800 mm SAD).