The application of statistical process control in linac quality assurance

Objective To improving linac quality assurance (QA) program with statistical process control (SPC) method. Methods SPC is applied to set the control limit of QA data, draw charts and differentiate the random and systematic errors. A SPC quality assurance software named QA_MANAGER has been developed by VB programming for clinical use. Two clinical cases are analyzed with SPC to study daily output QA of a 6MV photon beam. Results In the clinical case, the SPC is able to identify the systematic errors. Conclusion The SPC application may be assistant to detect systematic errors in linac quality assurance thus it alarms the abnormal trend to eliminate the systematic errors and improves quality control.