SU‐FF‐T‐232: IMRT QA Using a Hybrid Mapcheck / Electronic Portal Dosimetry Environment

• Published in: Medical Physics 2009-06, Vol.36 (6), p.2574-2574
• Main Authors: Malhotra, H, Bakhtiari, M, Kumaraswamy, L, Bailey, D, Liu, J, Tran, T, Podgorsak, M
• Format: Article
• Language: English
• Subjects: Brain; Dosimetry; Image analysis; Image detection systems; Image guided radiation therapy; Image sensors; Intensity modulated radiation therapy; Linear accelerators; Medical treatment planning; Quality assurance
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.3181708

Purpose 2D array detector planar dose verification systems play an important role in pre‐treatment quality assurance of IMRT plans. In the present study, we are demonstrating a hybrid IMRT pretreatment QA environment using Varian's aS500 & aS1000 electronic portal imaging devices (EPID) in conjunction with Sun Nuclear analysis tools. Materials & Methods 5 patients for prostate [minimally modulated], brain [moderately modulated] and head and neck [heavily modulated], each with IMRT plans generated with Eclipse Treatment Planning system were used in this study. The plans were designed for sliding‐window IMRT dose delivery technique on a Varian 6 MV linear accelerator fitted with millennium MLC. An individual verification plan per field was generated from the clinically approved plans. Portal dosimetry treatment plans were also generated in a standard manner assuming 1 CU = 100 cGy. The results were compared with Mapcheck measurements. Results The percentage of detectors passing 3%/3mm criterion as well as the CAX dose measured by the system and the computed plan in absolute dose values were determined for evaluation purposes. For minimal or moderately modulated IMRT plans, both the planar dose verification systems gave comparable results in terms of passing rates [3%/3mm >90%] as well as CAX deviations [