Investigation of Treatment Planning and Dose Verification Procedures Using Unflat Linac Photon Beams

Abstract

The current research work was carried out in order to investigate the appropriate detectors for small field dosimetry; the optimised methods of treatment planning techniques for lung and spinal SBRT; and the suitability of pretreatment dose verification tools for a 6 MV FFF photon beam. The results of this study suggest that all three treatment techniques, i.e., FFF-VMAT, FFF-IMRT, and FFF-3DCRT were able to deliver conformal SBRT plans while meeting the RTOG dose constraints. On the other hand, based on the comparison of dosimetric indices, such as CI, D2cm, HI, and HDV, FFF-VMAT provides a superior treatment plan to FFF-IMRT and FFF-3DCRT in the treatment of peripheral and central lung PTVs. Dosimetric indices, such as R50% and GI, were improved for FFF-3DCRT compared with those of FFF-VMAT. It is also clear that despite the requirement for higher MUs in the FFF-VMAT plans compared to FFF-3DCRT, the treatment delivery time is much shorter because of the superior gantry speed of the VMAT technique. The study suggests that the treatment dose calculated using Acuros XB is more accurate than that of AAA in a heterogeneous medium, such as the lung. The outcome of these studies provided some insight about the selection of appropriate detector to be used for dosimetry of small FFF photon field, the optimized method of the treatment planning of SBRT treatment plans and appropriateness of dose verification procedures in FFF photon beam.