QC in CT by Automated Monitoring of Key Performance Indicators: A Ten Month Study
P Nowik*, R Bujila, H Andersson, C Jonsson, Karolinska University Hospital, Stockholm, SwedenSU-E-I-33 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Purpose: To develop a method of performing routine periodical QC of CT systems by automatically analyzing key performance indicators (KPI) obtainable from scanning manufacturers' QC phantoms making it possible to follow a CT scanners performance between annual tests (e.g., on a daily basis).
Methods: A KPI pertains to a measurable or determinable parameter that is influenced by other underlying parameters, where a stable KPI implies that the underlying parameters are stable as well. KPIs were identified and verified by studying and mapping out the relationship between established QC parameters used in annual testing. The KPIs include positioning, noise, uniformity, homogeneity, CT number of water and CT number of air. An application that automatically analyzes phantom images sent to a DICOM receiver was developed (MonitorCT). CT technologists send scans of a QC phantom to the developed application on a daily basis.
Results: 290 daily QC scans, from two CT scanners, have been collected and analyzed during ten months. A systematic offset of circa 3mm from the scanner isocenter has been observed in the positioning test, which is under investigation. Noise, uniformity and homogeneity tests have been within specified tolerances during the data collection period. The CT numbers have trended outside of both MonitorCT and vendor tolerances which was caught using the developed method, which would not have been noticed otherwise until annual tests were performed. Consequently, actions could be taken promptly (water calibration).
Conclusion: Automated monitoring of KPIs is a powerful tool that can, with little effort, be used to supplement established QC methodologies. Medical physicists, or other concerned parties, are able to obtain an indication of the current and historical (trends) status of a CT system so that actions can be taken directly to ensure the quality of CT examinations and patient safety.