Quantifying Robustness of CT-Ventilation Biomarkers to Image Noise
M Flakus1*, A Wuschner2, E Wallat3, J Meudt4, D Shanmuganayagam5, G Christensen6, J Reinhardt7, J Bayouth8, (1) University of Wisconsin, Madison, WI, (2) University of Wisconsin, Madison, WI, (3) University of Wisconsin, Madison, WI, (4) ,Madison, WI, (5) ,Madison, WI, (6) University of Iowa, Iowa City, IA, (7) University of Iowa, Iowa City, IA, (8) University of Wisconsin-Madison, Madison, WI
Presentations
TH-A-206-4 (Thursday, 7/14/2022) 7:30 AM - 8:30 AM [Eastern Time (GMT-4)]
Room 206
Purpose: To quantify the impact of image noise on CT-based lung ventilation biomarkers calculated using Jacobian-based techniques.
Methods: Five mechanically ventilated swine were imaged on a multi-row CT scanner with acquisition parameters of 120kVp and 0.6mm slice thickness in static and 4-dimensional computed tomography (4DCT) modes with respective pitches of 1 and 0.09. A range of tube current time product (mAs) values were used to vary image dose. On two dates, subjects received two 4DCTs: one with scanner minimum 10 mAs/rotation (low-dose, high-noise) and one with CT simulation standard of care 100 mAs/rotation (high-dose, low-noise). Additionally, ten intermediate noise level breath-hold (BHCT) scans were acquired with inspiratory and expiratory lung volumes. Images were reconstructed with and without iterative reconstruction (IR) using 1mm slice thickness. The Jacobian determinant of a B-spline deformable image registration was used to create CT-ventilation biomarkers estimating lung tissue expansion. Biomarkers derived from reduced dose scans were registered to the reference full dose scan for comparison using metrics of gamma pass rate (Γ) with 2mm/6% criterion, voxel-wise Spearman correlation (ρ) and coefficient of variation (CoV).
Results: By comparing biomarkers derived from low (CTDIvol=6.07mGy) and high (CTDIvol=60.7mGy) dose 4DCT scans, mean Γ, ρ and CoV values were 93%±3%, 0.88±0.03 and 0.04±0.009, respectively. With IR applied, those values were 93%±4%, 0.90±0.04 and 0.03±0.003. Similarly, comparisons between BHCT-based biomarkers with variable dose (CTDIvol=1.35-7.95mGy) had mean Γ, ρ and CoV of 93%±4%, 0.97±0.02 and 0.03±0.006 without IR and 93%±4%, 0.97±0.03 and 0.03±0.007 with IR. IR did not significantly change any metrics (p>0.05).
Conclusion: This work demonstrated that CT-ventilation, calculated using the Jacobian determinant of a B-spline registration, is invariant to Hounsfield Unit (HU) variation caused by image noise. This finding indicates potential for dose reduction, which may broaden CT-ventilation imaging applications and/or allow repeated low-dose acquisitions to improve ventilation variance characterization.
Funding Support, Disclosures, and Conflict of Interest: Joseph M. Reinhardt is a shareholder in VIDA Diagnostics, Inc John E. Bayouth has ownership interest in MR Guidance, LLC, which has business activity with technology used in this study ViewRay, Inc.
Keywords
Noise, Ventilation/perfusion, Radiation Therapy
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