Abstract
In this study a simple method using standard flood-field corrected Electronic Portal Imaging Device (EPID) images for routine Intensity Modulated Radiation Therapy (IMRT) Quality Assurance (QA) was investigated. The EPID QA system was designed and tested on a Siemens Oncor Impression linear accelerator with an OptiVue 1000ST EPID panel (Siemens Medical Solutions USA, Inc, USA) and an Elekta Axesse linear accelerator with an iViewGT EPID (Elekta AB, Sweden) for 6 and 10 MV IMRT fields with Step-and-Shoot and dynamic-MLC delivery. Two different planning systems were used for patient IMRT field generation for comparison with the measured EPID fluences. All measured IMRT plans had >95% agreement to the planning fluences (using 3 cGy / 3 mm Gamma Criteria) and were comparable to the pass-rates calculated using a 2-D diode array dosimeter.
Highlights
Intensity Modulated Radiation Therapy (IMRT) is used routinely for prostate, head and neck, and abdominal treatment sites at the Prince of Wales Hospital (POWH)
Electronic Portal Imaging Device (EPID) have many characteristics that make them well suited for IMRT dosimetry [4,5,6,7,8] and the reduced equipment set-up time compared to other dosimeters has the potential to improve efficiencies
EPID vendor-type, beam energy, and the percentage of pixels passing the Gamma criteria of 3 cGy / 3mm with EPID and MapCHECK systems is presented in table 2 for 6 and 10 MV IMRT fields
Summary
Intensity Modulated Radiation Therapy (IMRT) is used routinely for prostate, head and neck, and abdominal treatment sites at the Prince of Wales Hospital (POWH). All IMRT treatments at the POWH have QA performed with the MapCHECK (Sun Nuclear Corporation, Fl, USA) two-dimensional diode array dosimeter for a perfield comparison with treatment planning system (TPS) planar dose fluences. Ongoing increases in IMRT patient workload puts pressure on physics resources and has led to investigations for alternatives to the standard diode array based method. Amorphous silicon (a-Si) Electronic Portal Imaging Devices (EPIDs) have been implemented for two-dimensional dosimetry in many departments globally. EPIDs have many characteristics that make them well suited for IMRT dosimetry [4,5,6,7,8] and the reduced equipment set-up time compared to other dosimeters has the potential to improve efficiencies. Many approaches have been implemented for portal dosimetry as described in a review paper by Van Elmpt [9]. Despite numerous research papers on the topic, and several commercial products being available, portal dosimetry is not yet widespread across all vendor equipment
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