A Clinical Objective IMRT QA Method Based on Portal Dosimetry and Electronic Portal Imager Device (EPID) Measurement

Clinical objective IMRT QA is a new approach to conduct patient specific IMRT QA by evaluating the QA result based on metrics like the structure dose volume histograms (DVH) on the planning CT image. Different from traditional 2D planar dose based IMRT QA in which all the measurements and evaluations were based on a phantom, clinical objective IMRT QA reveals the direct clinical impact of any measured variation based on the predicted delivered dose to the patient target volumes and critical organs. In this study, we proposed a method to implement the clinical objective IMRT QA procedure by using generally available dosimetry equipment in a radiation oncology clinic. The proposed procedure was tested and validated on five IMRT plans by using a solid water phantom, which served as a test patient, along with total 30 ion chamber measurements. The result showed that the proposed QA procedure successfully achieved the goal of clinical objective IMRT QA. Based on the ion chamber measurements, the QA procedure predicted that the average variations between the planned and the delivered doses were within 1.9%. This method may hold potentials to help radiation oncology clinics to move from the traditional IMRT QA to the clinical objective IMRT QA.