Objective: Recent incidents concerning the over exposure of patients undergoing imaging procedures underscores the need for increased vigilance in practices involving the use of ionising radiation. To address this issue we propose the implementation of an ongoing monitoring process utilizing procedural data to detect unexpected variations in radiation exposures for individual patients and detect persistent changes in radiation output of imaging equipment.
Methods: A procedure for monitoring radiation use in coronary angiography was developed and tested in the cardiac catheterization facility at St Andrew’s War Memorial Hospital. The process employs two control charts, an individual chart to filter case data and an exponentially weighted moving average chart to identify temporal changes in radiation delivery. To increase sensitivity of the charts we account for variation in dose area product (DAP) values due to other measured factors (patient weight, fluoroscopy time, digital acquisition frame count) using multiple linear regression. Control charts are then constructed using residual values from this linear regression.
Results: Retrospective application of this technique identified a number of cases in which the DAP recorded could be considered unexpected. Most of these, upon review, were attributed to data entry errors. When these cases were taken into account, the charts monitoring case radiation delivery exhibited characteristics that suggest they could be used in routine monitoring of the overall imaging process.
Conclusion: This technique offers a valuable enhancement to existing quality assurance programs in radiology that rely upon the testing of equipment radiation output at discrete time frames to ensure performance security.