Program Information
Elevated Patient Exposure Due to Bariatric Table Construction and Dose Modulation in Computed Tomography
R Lamoureux*, T Slauter , D Sandoval , G Chambers , R Selwyn , University of New Mexico, Albuquerque, NM
Presentations
TU-RPM-GePD-I-4 (Tuesday, August 1, 2017) 3:45 PM - 4:15 PM Room: Imaging ePoster Lounge
Purpose: To demonstrate elevated patient exposure due to flat top bariatric table construction in CT modulated head exams and the impact technologist training has had on the number of scans above threshold dose, on the max, 75th percentile, and median CTDIvol.
Methods: Dose monitoring of modulated head CT scans provides thumbnails of scouts overlaid with dose modulation plots. This allowed for pattern recognition of a highly attenuating reinforcement section within the CT bariatric table that was elevating patient exposures. The extent of the issue was investigated through the use of the ACR CT image quality phantom. The CT dose modulation system dictated mAs over and not over the reinforcement and the CTDIvol and CNR for both were compared. Training sessions were held for the technologists on positioning to avoid the reinforcement in clinical scans. The number of alerts above dose threshold due to table construction were quantified along with comparing the maximum, 75th percentile, and median CTDIvol values for pre/post-training for 3 month periods.
Results: The resulting effective mAs, CTDIvol, and measured CNR are 360 mAs, 58.72 mGy, and 1.58 over the reinforcement; 192 mAs, 31.14 mGy, and 1.49 not over the reinforcement. Three months pre-training, 75 scans were above threshold due to the highly attenuating reinforcement. Post-training, there are no scans above threshold due to the reinforcement. The max, 75th percentile, and median CTDIvol pre-training are 98.2 mGy, 48.5 mGy, and 37.3 mGy. Post training they are 73.8 mGy, 39.4 mGy, and 35.6 mGy.
Conclusion: Dose monitoring identified elevated patient exposure due to the construction of the bariatric table and dose modulation. Investigation and technologist training decreased dose and eliminated exams over threshold from this issue. Overall, dose monitoring software helps the clinical team with quality oversight by allowing monitoring of clinical parameters that are otherwise not available.
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