Program Information
Effects of Dose Reduction On Emphysema Score
P Lo1 , S Young2*, J Hoffman3 , M Wahi-Anwar4 , H Kim5 , M McNitt-Gray6 , (1) University of California, Los Angeles, Los Angeles, CA, (2) UCLA, Los Angeles, CA,(3) UCLA, Los Angeles, CA, (4) University of California, Los Angeles, Los Angeles, CA, (5) University of California, Los Angeles, Los Angeles, CA, (6) UCLA School of Medicine, Los Angeles, CA
Presentations
SU-G-206-15 (Sunday, July 31, 2016) 4:00 PM - 6:00 PM Room: 206
Purpose: The purpose of this study was to investigate the effects of reducing radiation dose levels on emphysema scores from lung cancer screening CT exams.
Methods: 52 cases were selected from the National Lung Screening Trial (NLST) patients for which we had both the image series and the raw CT data. All scans were acquired with fixed effective mAs (25 for standard-sized patients, 40 for large patients) on a 64-slice scanner (Sensation 64, Siemens Healthcare) using 120kV, 64x0.6mm collimation and pitch 1.0. All images were reconstructed with 1mm slice thickness, B50 kernel. Based on a previously-published technique, we added noise to the raw data to simulate reduced-dose versions at 50% and 25% of the original dose (approximately 1.0- and 0.5-mGy CTDIvol). Lung segmentations were obtained via region growing from manual seed point at a threshold of 600HU followed by manual removal of trachea and major airways. Lung segmentations were only performed on original dose scans, and mapped to simulated reduced-dose scans. Emphysema scores based on relative area of lung with attenuation values lower than -950HU (RA950) were computed for all cases.
Results: Average RA950 of all 50 cases were 31.6 (±5.5), 32.5 (±4.9) and 32.8 (±4.6) for 100%, 50% and 25% dose level respectively. The average absolute difference in RA950 between simulated and original dose scans were 1.0 (±0.7) and 1.4 (±1.1) for 50% and 25% dose level respectively.
Conclusion: RA950 is relatively robust to dose level, with a difference of no more than 5 from the original dose scans. The average RA950 of this population was high for a two reasons: This was a high risk population of patients with substantial smoking history; The use of B50 kernel, which may be biased towards high emphysema scores. Further exploration with smoother kernels will be conducted in the future.
Funding Support, Disclosures, and Conflict of Interest: Institutional research agreement, Siemens Healthcare
Past recipient, research grant support, Siemens Healthcare
Consultant, Toshiba America Medical Systems
Consultant, Samsung Electronics
NIH grant support from U01 CA181156
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