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Linear Accelerator Quality Control | The increasing complexity of radiation therapy has rendered the traditionally accepted approach to ensuring accurate treatment development and delivery less effective. The goal of quality assurance (QA) is to evaluate a particular process. The specifications of the QA procedure are set such that when the process is operating within these specifications the result or outcome is acceptable. In our case the goal is accurate dose delivery. Traditionally, QA has centered on determining if the various equipment involved is working within specifications. This paradigm suggests that properly functioning systems equals accurate treatment delivery. The inherit flaw is that the systematic errors in the treatment delivery process are not evaluated by quality assurance procedures.
| Quality Control of Linear Accelerators Presentation QC of Linear Accelerators Abstract | 
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Quality control (QC) implements an overall system of technical activities that measures the attributes and performance of a process against defined standards to verify that they meet the stated requirements. Quality control also seeks to minimize variability, detect and resolve sources of systematic error to ensure the process is on target. In radiotherapy we need a QC system that evaluates the entire process of treatment delivery on an ongoing basis. It ideally would frequently test the treatment delivery process during each treatment day. This is a paradigm shift from traditional QA procedures.
One method of quality control is Statistical Process Control (SPC) introduced by Walter A. Shewart at Bell Labs in 1924. It applies probability and statistics to quality control of mass production of products utilizing the control chart. This technique was most recently applied to radiation therapy by Pawlicki and Boyer (Med Phys 32(9), 2777-2786(2005)).
| I have taken SPC and applied it to external beam treatment delivery in which a linear accelerator is utilized. In the initial work I wanted to determine if the application of SPC could in fact detect anomalies in treatment delivery resulting from errors introduced in the mechanical operating specifications of the linear accelerator as defined by Task Group 40 of the AAPM. The results were recently presented at the 2008 International Congress on Medical Physics held in Beijing, China. You can review the presentation and the abstract published in the proceedings by clicking on the links below.
The QC technique is being expanded to evaluate not only mechanical attributes but also dosimetric performance of treatment delivery. I hope to publish the results by the autumn of 2009. | 
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