An automated Monte Carlo QC system for volumetric modulated arc therapy: Possibilities and challenges

作者：Chakarova R^*; Cronholm R^*; Krantz M; Andersson P; Hallqvist A

来源：Physica Medica, 2018, 51: 32-37.

DOI：10.1016/j.ejmp.2018.03.010

• Monte Carlo
• Patient specific VMAT QC
• Normalized dose difference

Purpose: To develop and implement an automated Monte Carlo (MC) system for patient specific VMAT quality control in a patient geometry that generates treatment planning system (TPS) compliant DICOM objects and includes a module for 3D analysis of dose deviations. Also, the aims were to recommend diagnose specific tolerance criteria and an evaluation procedure.
Methods: The EGSnrc code package formed the basis for development of the MC system. The workflow consists of a number of modules connected to a TPS by means of manual DICOM exports and imports which were executed sequentially without user interaction. DVH comparison was performed in the TPS. In addition, MC-and TPS dose distributions were analysed by applying the normalized dose difference (NDD) formalism. NDD failure maps and a pass rate for a certain threshold were obtained. 170 clinical plans (prostate, thorax, head-and-neck and gynecological) were selected for analysis.
Results: Agreement within 1.5% was found between clinical-and MC data for the mean dose to the target volumes and within 3% for parameters more sensitive to the shape of the DVH e.g. D-98% PTV. Regarding the NDD analysis, tolerance criteria 2%/3 mm were established for prostate plans and 3%/3 mm for the rest of the cases.
Conclusions: An automated MC system was developed and implemented. Evaluation procedure is recommended with NDD-analysis as a first step. For pass rate < 95%, the evaluation continues with comparison of DVH parameters. For deviations larger than 2%, a visual inspection of the clinical-and MC dose distributions is performed.

• 出版日期2018-7