Breathing Motion Model Comparison Inside and Outside the Lung
S Gaudio*, D Thomas, B White, S Jani, P Lee, J Lamb, D Low, University of California, Los Angeles, Los Angeles, CASU-E-J-138 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Purpose: To compare the results of our deformable image registration algorithm inside and outside the lungs for our novel fast 4DCT technique in order to quantify the sliding motion between the lung and other organs in the thorax.
Methods:: Data was acquired with a fast helical protocol. We used a 64-slice CT scanner. 25 low dose whole-lung scans were obtained in alternating directions for five patients. Images were obtained continuously under free breathing conditions. A pneumatic bellows was placed around the abdomen as a respiratory surrogate. Each image slice was assigned a unique bellows voltage signal. The lungs were segmented in each scan and, all scans were deformably registered, and were then deformed to the first scan geometry.
The motion model was fit to the breathing surrogate to obtain the model parameters at each voxel inside the lung. Separately, all tissue outside the lungs was segmented, registered and fit to the motion model. Separate segmentation and registration of tissues inside and outside the lung boundary is necessary to properly treat the sliding motion that occurs at the interface of lung and chest wall. The object of this study was to determine if the separately treated inside and outside regions could be matched at the lung boundary.
Results:Discontinuity in the superior-inferior motion vectors was observed at the edges of the lungs, as expected, due to shear motion. Motion vectors in the left-right and anterior-posterior directions were continuous across the lung border, due to the lack of shear motion in those directions. Two masks representing the lung surface were deformed separately using the interior and the exterior motion models and found to be consistent.
Conclusion: : We obtain a validation of the lung motion model and demonstrated that it can be used to reproduce accurate images for tissues outside the lung
Funding Support, Disclosures, and Conflict of Interest: NIH grant number: ROI CA096679