BEST IN PHYSICS (JOINT IMAGING-THERAPY)- A Novel 4D CT Acquisition and Analysis Technique to Generate Low Noise Artifact-Free Images at User Selected Breathing Phases
D Thomas*, B White, S Gaudio, S Jani, P Lee, J Lamb, D Low, University of California, Los Angeles, Los Angeles, CATU-G-141-1 Tuesday 4:30PM - 6:00PM Room: 141
Purpose: To develop a novel 4DCT technique that exploits standard fast helical acquisition, a simultaneous breathing surrogate measurement, deformable image registration, and a breathing motion model to remove motion-induced artifacts.
Methods: Five patients were imaged under free breathing conditions 25 successive times 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. The lungs were segmented from each image. Deformable registration was used to register the first to the subsequent 24 segmented images. Voxel-based motion model parameters were determined using a published breathing motion model. A low-noise image was created by averaging the 25 images deformed to the first image geometry, reducing statistical noise by a factor of 5. The motion model was used to deform the low noise image to any user-selected breathing phase. Accurate HU values were assigned to each voxel in the reconstructed images.
Results: Images produced using the model at user-selected breathing phases did not suffer from motion artifacts. The mean discrepancy between the breathing motion model results and the measured positions corresponding to each scan was determined to be 0.7mm (standard deviation of 0.4mm). In each patient, regions near to the myocardium exhibited mean discrepancies greater than 1 mm, which were likely due to uncompensated cardiac motion.
Conclusion: The proposed technique can be employed as a clinical 4DCT technique providing motion artifact free images at user-selected breathing phases. It is robust in the presence of irregular breathing, and allows the entire imaging dose to contribute to the resulting image quality, providing motion artifact free images at a patient dose similar to or less than current 4DCT techniques. We are currently modifying the protocol to work on 16-slice CT scanners.
Funding Support, Disclosures, and Conflict of Interest: This work supported in part by NIH R01CA096679