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Does a Breathing Surrogate From a Point On the Abdominal Skin Represent the Organ Motion in Thorax for Phase-Based 4D CT Sorting?

M Lin

M Lin*, W D'Souza , G Lasio , W Lu , K Prado , S Feigenberg , B Yi , University of Maryland School of Medicine, Baltimore, MD

Presentations

SU-E-J-50 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: This work aims (1) to determine the validity of the current practice of the phase-based 4DCT sorting (abdomen signal) for thorax scans; (2) to assess the potential benefit of utilizing the 3D surface breathing surrogate of chest area for phase-based 4DCT sorting.

Methods: Dynamic 3D surface images over the chest and abdomen were acquired using 3D-suface-camera-system (VisionRT Ltd., London, UK) for a total of 10 patients. The vertical motions of five regions-of-interest (ROIs): abdomen, mid-sternum, lower-, middle-, and upper- ipsilateral-chest were tracked. Based on our previous work, the main source of motion artifact is the variation-of-phase-differences (VPD) between the breathing surrogate and the organ motion during scanning. Thus, we utilize VPD as a quantitative index of the variation of the resulting 4DCT images. The average VPD over a 60 second time-period was calculated for each of the abdomen and ROI combination. A simulation study with a wire phantom was designed to demonstrate the resulting 4DCT images.

Results: Simulation showed significant image distortion or motion artifacts when VPD is larger than 5% of breathing period. The average VPDs of individual ROIs of each patient indicates that 75%, 59% and 22% cases have VPD larger than 5%, 10% and 15% of period each cycle between the selected ROI and the abdominal motions patterns, respectively (10.1±6.0 %, minimum 1.0% to maximum 23.9 %). Overall, patients with less 3-second breathing-period present VPD larger than 10%. The correlations between the abdomen and individual chest ROIs motions as well as the motions among chest ROIs are highly case-dependent.

Conclusion: Abdominal motion does not represent the chest motions for some of the patients. This results in motion artifacts in the phase-based 4DCT. Utilizing the surface surrogate of the chest region can potentially improve phase-based 4DCT sorting for thorax 4DCT scan, especially for fast breathing patients.


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