Room: AAPM ePoster Library
Purpose: purpose of this study is to use image reject analysis methods, common in diagnostic radiology, to inform imaging practice in a radiation therapy program.
Methods: were retrospectively reviewed from three CT simulators in a large radiation therapy department. The reject/repeat rate was calculated as the ratio of repeated images to the total number of scans acquired. The reason for the repeat image was categorized into one of the following bins: patient preparation, patient motion, scan protocol, image quality and other. A secondary stratification was the location of the CT simulator, since the department is dispersed geographically.
Results: overall repeat rate was determined to be 2.2%, which is lower than for typical diagnostic installations. This is largely due to the fact that images are rarely rejected on the basis of image quality at the time of CT simulation. Given the different goal of CT simulation from diagnostic imaging, the standard reject reasons suggested for diagnostic departments do not generally apply in the radiation therapy context. The data show that most repeat scans (80%), are caused by inadequate patient preparation, mostly due to inappropriate rectal or bladder filling. There was an observed difference in repeat rate between different simulators, with one machine reporting a repeat rate of 1% and the highest being 3.5%. This is due in part to differences in treatment techniques at the different sites.
Conclusion: reject analysis is commonly used in diagnostic imaging to assess image quality, optimize exam protocols and identify gaps in clinical processes. The use of reject analysis in radiation therapy can similarly lead to improvements in process by identifying gaps in patient education, staff training and performance drift. This can lead to a lower rate of repeat scans and a reduction in unnecessary patient exposure.