Dosimetric and Radiobiological Impact of Flattening Filter‐Free Beam and Dose Calculation Algorithm Using RapidArc Plans for Cervical Cancer Treatment

Abstract

PurposeThe aim of this study is to quantify the potential benefits of a flattening filter‐free (FFF) beam and implement a dose‐computation algorithm for cervical radiotherapy through dosimetric and radiobiological analyses using RapidArc.MethodsThirty‐three patients were enrolled, and four RapidArc plans were created for each patient using a dual‐arc flattening filter and 6‐MV FFF photon beams for the two calculation algorithms. Homogeneity index (HI), conformity index (CI), target coverage, monitor units (MUs), and organ‐at‐risk (OAR) dosimetric characteristics were compared between the plans. Radiobiological characteristics and normal tissue complication probability (NTCP) scores were computed for the OAR using different biological models.ResultsNo significant differences were observed in the Dmax, D98%, and CI in the planning target volume (PTV). Both computations estimated a significant difference in V95%, D2%, and HI for the PTV. Furthermore, the FFF beam showed a significant increase in the MUs and a significant reduction in V30% for the femoral heads. The NTCP score showed a significant increase in the late effects on the bladder, rectum, and bowel with FFF beams.ConclusionThe current study recommends FFF beams for better conformity, comparable dose coverage for the target, and OAR sparing invariable to the dose computation algorithm. The difference in the NTCP score for OAR was minimal with the FFF beam.

Assessment of normal tissue objectives in RapidArc treatment for cervical cancer

“…Achieving this dose fall-off and optimizing the protection of normal tissues involves employing techniques such as eliminating the body from targets or inserting multiple rings radially around the target. 9,10 Although it is effective, the use of ring structures increases planning time. Creating a ring structure is time-consuming and creates the additional challenge of choosing the number of rings, ring width, gaps or overlaps, and the associated penalty priorities.…”