Program Information
Correlating Image Quality and Reduced Radiation Exposure From Low-Dose CT Scanning in a Lung Cancer Screening Program
I Lipnharski*, A Mench , C Carranza , R Lamoureux , S Gyapong , L Rill , T Mohammed , M Arreola , University of Florida, Gainesville, FL
Presentations
PO-BPC-Exhibit Hall-3 (Saturday, March 7, 2015) Room: Exhibit Hall
Purpose: To correlate acceptable image quality and reduced radiation doses by employing iterative reconstruction and manipulating exam parameters in low-dose computed tomography (LDCT) for routine lung cancer screening.
Methods: Three post-mortem subjects were scanned on a commercial 320-slice CT scanner using a lung cancer screening protocol, reconstructed with an iterative algorithm (AIDR-3D). The minimum tube current was decreased from a default setting of 100 mA to 30 mA, with tube current modulation employed. Further dose savings were attained by increasing noise target levels from a standard deviation of 12.5 to 17.5, 20, and 25. The dose length product (DLP) reported by the scanner was recorded for each scan. Organ doses were directly measured in one of the post-mortem subjects using in-vivo dosimetry methods utilizing optically stimulated luminescent dosimeters. Eleven radiologists were recruited to perform a blinded observer study, grading the images with a score of (1) for non-diagnostic, (2) for sub-optimal, or (3) for diagnostically acceptable.
Results: With the reduced tube current employed, increasing the noise tolerance index achieved significant dose savings of 40%, 49%, and 66%, for standard deviations of 17.5, 20, and 25, respectively. The majority of readers found all images to be acceptable. It was not until very high dose savings of 66% that one of the readers found the image to be unacceptable.
Conclusion: With the nationwide acceptance of the lung cancer LDCT initiative, it is imperative that these scans be performed using very low dose protocols. Due to the high likelihood of repeat scans and elevated cumulative radiation dose, the consideration of this at-risk population must focus on low dose. Together with AIDR-3D, which offers dose savings in the range of 20-40%, employing reduced tube current and increased noise tolerance can offer substantial dose reduction of 75%, while still maintaining acceptable image quality.
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