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Session: Functional Imaging in Radiation Therapy [Return to Session]

Investigating the Feasibility of CT Ventilation Imaging On Fast, Low-Dose 4DCBCT to Enable Daily Adaptive Lung Function Sparing

H Byrne1*, O Dillon1, S Blake1, J Kipritidis2, R O'Brien1, P Keall1, (1) ACRF Image X Institute, The University of Sydney, Sydney, AU (2) Northern Sydney Cancer Centre, Royal North Shore, Sydney, AU


WE-C1000-IePD-F6-3 (Wednesday, 7/13/2022) 10:00 AM - 10:30 AM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 6

Purpose: CT ventilation imaging (CTVI) creates a 3D map of lung ventilation from 4DCT images. CTVI enables functional lung sparing during planning leading to lower treatment toxicity. Applying CTVI to 4DCBCT could enable daily adaptive lung function sparing. Advances in 4DCBCT include faster acquisition with lower dose. This lower dose results in lower 4DCBCT image quality, that affects the CTVI quality. Therefore, the purpose of this work is to investigate the feasibility of CTVI on low-dose 4DCBCT to enable daily adaptive lung function sparing.

Methods: In the ADAPT clinical trial (NCT04070586), 4DCT scans and fast (1-minute) low-dose (200-projection) 4DCBCT scans were acquired per patient for two treatment fractions. For five patients selected from the trial, CTVI was generated from the 4DCT and the two 4DCBCTs. The peak inhale image was deformably registered to the peak exhale image. Ventilation was calculated from the Jacobian determinant of the deformation vector field. CTVI generated from each 4DCBCT was compared to the CTVI generated from the planning 4DCT. The difference between the images was quantified using voxel-to-voxel Spearman correlation.

Results: Spearman correlations between the CBCT ventilation maps at fraction 1 and the planning CTVI had a mean (range) of 0.54 (0.32 – 0.71) while fraction 2 had a mean (range) of 0.42 (0.25 – 0.54). The patients showing the highest and lowest correlations at fraction 1 also showed the highest and lowest correlations at fraction 2.

Conclusion: Ventilation images from high quality, low dose 4DCBCT at two treatment fractions were positively correlated to planning 4DCT ventilation. Improvements in low dose 4DCBCT image quality and CTVI methods should increase the correlation. These findings encourage further investigation of the role of CT ventilation imaging with low-dose 4DCBCT to enable daily adaptive lung function sparing.

Funding Support, Disclosures, and Conflict of Interest: The CT ventilation IP has been licenced to a commercial company.


Ventilation/perfusion, Registration, Cone-beam CT


IM/TH- Cone Beam CT: 4DCBCT

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