Dosimetric validation and clinical implementation of two 3D dose verification systems for quality assurance in volumetric‐modulated arc therapy techniques

Abstract

A pretreatment quality assurance program for volumetric techniques should include redundant calculations and measurement‐based verifications. The patient‐specific quality assurance process must be based in clinically relevant metrics. The aim of this study was to show the commission, clinical implementation, and comparison of two systems that allow performing a 3D redundant dose calculation. In addition, one of them is capable of reconstructing the dose on patient anatomy from measurements taken with a 2D ion chamber array. Both systems were compared in terms of reference calibration data (absolute dose, output factors, percentage depth‐dose curves, and profiles). Results were in good agreement for absolute dose values (discrepancies were below 0.5%) and output factors (mean differences were below 1%). Maximum mean discrepancies were located between 10 and 20 cm of depth for PDDs (‐2.7%) and in the penumbra region for profiles (mean DTA of 1.5 mm). Validation of the systems was performed by comparing point‐dose measurements with values obtained by the two systems for static, dynamic fields from AAPM TG‐119 report, and 12 real VMAT plans for different anatomical sites (differences better than 1.2%). Comparisons between measurements taken with a 2D ion chamber array and results obtained by both systems for real VMAT plans were also performed (mean global gamma passing rates better than 87.0% and 97.9% for the 2%/2 mm and 3%/3 mm criteria). Clinical implementation of the systems was evaluated by comparing dose‐volume parameters for all TG‐119 tests and real VMAT plans with TPS values (mean differences were below 1%). In addition, comparisons between dose distributions calculated by TPS and those extracted by the two systems for real VMAT plans were also performed (mean global gamma passing rates better than 86.0% and 93.0% for the 2%/2 mm and 3%/3 mm criteria). The clinical use of both systems was successfully evaluated.PACS numbers: 87.56.Fc, 87.56.‐v, 87.55.dk, 87.55.Qr, 87.55.‐x, 07.57.Kp, 85.25.Pb

Commissioning of the Mobius3D independent dose verification system for TomoTherapy

“…Mobius3D has only three parameters, but significant differences were not observed in point dose and planar dose comparisons for measurements and calculations in our phantom study. These results are similar to previous study using ion chamber and water‐equivalent phantom for C‐arm linear accelerator . Conversely, point dose using Planning Station was underestimated compared to measurement for prostate cases with NFW 5.0 cm as listed in Table .…”

“…In addition to treatment planning process verification using Mobius3D, data transfer from TPS to linear accelerator control system and hardware malfunction during irradiation must be verified. In recent research, new approach was opposed that the system verifies the dose distribution between TPS and reconstructed dose from information generated from linear accelerator after irradiation . In addition to Mobius3D, Mobius has a system using these new approaches named MobiusFX for C‐arm linear accelerators, but it does not deal with TomoTherapy now .…”

Clinical implementation of Dosimetry Check™ for TomoTherapy® delivery quality assurance

“…For TomoTherapy ® ‐based intensity‐modulated radiotherapy (IMRT), the current delivery quality assurance (DQA) process consists of comparing measured versus calculated doses in a phantom using an ionization chamber and a film or using detector array devices . These devices have generally provided such accurate DQA results in terms of low absolute dose difference or high gamma pass rate.…”

“…Recently, various new systems have been commercially released for DQA of patient treatment plans using modern radiotherapy modalities . These systems use log‐files of the beam irradiation or measured beam fluence to reconstruct the dose distribution on the CT images of patients, thereby reconstructing the dose to the target and surrounding normal structures.…”

Evaluation of targeted image-guided radiation therapy treatment planning system by use of american association of physicists in medicine task group-119 test cases

“…[567] Recently, researchers have done TG-119 protocol on different planning systems, different detectors, and LINAC machines with different photon energies and obtained different gamma criteria. [8910111213141516]…”