Quality control test for electronic portal imaging device using QC-3 phantom with PIPSpro
Purpose:A Quality control (QC) test suitable for routinely daily use has been established for electronic portal imaging device (EPID) using PIPSpro software version 4.4 (Standard Imaging, Middleton, WI). It provides an objective and quantitative test for tolerable image quality on the basis of the high contrast spatial resolution, the contrast-to-noise ratio (CNR) and noise.
Methods: The test uses a QC-3 phantom consisting of five sets of high contrast rectangular bar patterns with spatial frequeinces of 0.10, 0.20, 0.25, 0.43 and 0.75 lp/mm using 6MV and 15MV photon energy for accquiring high quality images. A “base line” value for the relative square wave modulation transfer function (RMTF), CNR and Noise data was obtained during a one week calibration period and one month test period.
Results: Subsequent measurements shows significant deviations from baseline values, resulting in warning messages “potential problems in system performance”. The QC test uses high contrast spatial resolution and CNR for the system with acceptable performance.
Conclusion: The method provides an automatic, objective, and sensitive measure of the system's imaging performance. This is a useful implementation during acceptance testing, commissioning, and routine quality control.
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