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A Novel 4D CT Acquisition and Analysis Technique to Account for the Effect of Cardiac Induced Lung Tissue Motion During Free Breathing

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D Thomas

D Thomas*, B White, S Gaudio, S Jani, P Lee, J Lamb, D Low, University of California, Los Angeles, Los Angeles, CA

MO-F-WAB-7 Monday 4:30PM - 6:00PM Room: Wabash Ballroom

Purpose:
To develop a new motion modeling technique to account for internal lung tissue displacement due to cardiac motion during free breathing CT scans.

Methods:
Five patients were imaged 25 successive times under free breathing conditions in alternating directions with a 64-slice CT scanner using a low dose fast helical protocol. A pneumatic bellows around the abdomen was used to as a breathing surrogate and a 3-lead ECG monitor simultaneously measured heart rate. The lungs were segmented from each image and deformable registration was used to register the first image to the subsequent 24 segmented images. The registered voxel locations were fitted to a linear motion model, relating the internal lung tissue deformation to the tidal volume v, airflow f and cardiac phase h. The time dependence of cardiac induced tissue displacement was characterized by a periodic function synchronized to the cardiac cycle, optimized to reduce model error, and was patient specific. The magnitude of cardiac induced motion was evaluated by comparing the discrepancies between fitted and measured motion with and without the cardiac term applied.

Results:
The magnitude of cardiac induced lung tissue displacement was determined to be up to 2.5mm in the lung for regions close to the myocardium. The addition of the cardiac term reduced the total number of voxels with mean errors above 1mm by 33%.

Conclusion:
Application of the cardiac term in the motion model reduces large errors in motion modeling in regions close to the myocardium.

Funding Support, Disclosures, and Conflict of Interest: This work supported in part by NIH R01CA096679

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