Measuring Radiation-Induced Changes in Perfusion with Dynamic Contrast-Enhanced 4DCT and Non-Contrast Lung Density Analysis in a Novel Swine Model
A Wuschner1*, E Wallat1, M Flakus1, J Reinhardt2, G Christensen2, A Baschnagel1, J Bayouth1, (1)University of Wisconsin, Madison, WI,(2)Iowa City, IA
Presentations
WE-F-TRACK 6-4 (Wednesday, 7/28/2021) 4:30 PM - 5:30 PM [Eastern Time (GMT-4)]
Purpose: To measure radiation-induced changes in perfusion using dynamic contrast-enhanced CT and correlate these changes to a non-contrast imaging biomarker in a novel swine population.
Methods: Five Wisconsin Mini-Swine(WMS™) received 60 Gy in 5 fractions following a clinical SBRT schedule using an MRI-guided LINAC. A dynamic contrast-enhanced 4DCT was taken prior to and 3 months post-RT. Vasculature was masked to enable the analysis of the non-vessel lung parenchyma and the vessels separately. All post-RT scans were deformably registered to the pre-RT scan using B-spline registration to allow voxel-wise comparisons. Analysis was performed in 10 Gy dose bins. Dose contours were copied onto the contralateral lung which received <5Gy for comparison. In each contour, measurements of the baseline HU measurement in the non-vessels and the max HU value of the vessels were obtained at pre and 3 months post-RT.
Results: Statistically significant(p=0.001) increases in the mean HU value in the non-vessel lung parenchyma were observed in the ipsilateral lung. The percent increases depended linearly with EQD2 dose (R=0.989). Additionally, statistically significant decreases (p<0.05) in the peak mean HU inside vessels were observed in each dose bin of the ipsilateral and contralateral lungs. The HU-increases outside the vessels strongly correlated (R2=0.85) to HU-reductions inside the vessels suggesting radiation-induced vasculature leakage. The slope of the HU increase outside vessels vs. HU decrease inside vessels curve was -0.87. Additionally, there was an apparent threshold dose above which this leakage occurred of approximately 25Gy.
Conclusion: This work suggests there is radiation-induced vessel leakage that occurs above a threshold dose of 25Gy. Additionally, this leakage can be predicted using a non-contrast biomarker (HU change outside vasculature). This presents the potential to develop non-contrast imaging bio-markers for radiation-induced change in perfusion to guide functional avoidance treatment planning.
Funding Support, Disclosures, and Conflict of Interest: Joseph M. Reinhardt is a shareholder in VIDA Diagnos-tics, Inc John E. Bayouth is a co-owner of MR Guidance, LLC (MRG), which has performed business with vendors of technologies used in this publication
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