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Impact of Volumetric 4D-CT Motion Artifact Reduction On Ventilation Imaging

H Young1,3,4*, T Lee2,3,4, S Gaede1,2, (1) London Regional Cancer Program, London, ON, CA, (2) Lawson Health Research Institute, London, ON, CA, (3) Robarts Research Institute, London, ON, CA, (4) University of Western Ontario, London, ON, CA


(Wednesday, 7/15/2020) 1:00 PM - 2:00 PM [Eastern Time (GMT-4)]

Room: Track 1

Purpose: To characterize the impact of motion artifacts on ventilation maps generated from clinical 4-dimensional computed tomography (4D-CT) images and compare them to ventilation maps generated from volumetric 4D-CT (v4D-CT).

Methods: Four patients with non-small cell lung cancer who received a clinical helical 4D-CT scan for treatment planning on a Philips Brilliance Big Bore CT scanner were also imaged using a research protocol on a GE Revolution volumetric CT scanner. Clinical 4D-CT images were acquired using: helical mode, 0.5s/revolution, 120kV, 45-60mA, pitch=0.056-0.075, and 24mm axial field-of-view (aFOV). On the volumetric scanner, images were acquired at a single couch position using the following parameters: cine mode, 0.28s/revolution, 100kV, 100mA, and 160mm aFOV for 45-50s. The end-inhale and end-exhale phases were selected from each image set, and the lung volume was semi-automatically segmented in 3DSlicer using a fast-marching technique to aid in registration. The images were non-rigidly registered in Elastix using a b-splines transformation and Mattes mutual information. Specific ventilation was then calculated using an existing density-based method. Finally, the v4D-CT and conventional 4D-CT ventilation maps were registered using Elastix, and the maps were compared visually.

Results: Motion artifacts were visible in all clinical 4D-CT images, while none were visible in the v4D-CT images. For all patients, ventilation measured by clinical 4D-CT differed from v4D-CT in regions where motion artifacts were present. For two patients, motion artifacts led to mis-registration of the inhale and exhale phases, which resulted in visually obvious artifacts in the final ventilation image.

Conclusion: The motion artifacts and resulting ventilation artifacts that are known to exist using conventional 4D-CT may be eliminated by v4D-CT. Artifact reduction with v4D-CT may enable the wider application of CT ventilation in clinical decision making.


Ventilation/perfusion, CT, Motion Artifacts



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