Room: Exhibit Hall
Purpose: The aim of this research was to introduce and evaluate a respiratory-guided slow gantry rotation 4D digital tomosynthesis (DTS).
Methods: For each of 10 volunteers, 2 breathing patterns were obtained for 3 minutes, one under free breathing condition and the other with visual respiratory-guidance using an in-house developed respiratory monitoring system based on pressure sensing. Visual guidance was performed using a 4s cycle sine wave with an amplitude corresponding to the average of end-inhalation peaks and end-exhalation valleys from the free-breathing pattern. The scan range was 40 degrees for each simulation, and the frame rate (FR) and gantry rotation speed (GRS) were determined so that one projection per phase should be included. Both acquisition time (AT) and the number of total projections to be acquired (NPA) were calculated. Applying the obtained respiration pattern and the corresponding sequence, virtual projections were acquired under a typical geometry of Varian on-board imager for two virtual phantoms, modified Shepp-Logan (mSL) and XCAT (extended Cardiac-Torso). For the XCAT, two different orientations were considered, anterior-posterior (i.e., coronal) and left-right (i.e., sagittal). Projections were sorted to 10 phases and image reconstruction was made using a modified filtered back-projection. Reconstructed images were compared with the planned breathing data (i.e., ideal situation) by SSIM (Structural Similarity) and NRMSE (Normalized Root-mean-square Error).
Results: For each case, simulation with guidance (SwG) showed motion-related artifact reduction compared to that under free-breathing (SuFB). SwG required less NPA but provided slightly higher SSIM and lower NRMSE values in all phantom images than SuFB did. In addition, the distribution of projections per phase was more regular in SwG.
Conclusion: Through the proposed respiratory-guided 4D DTS, it is possible to reduce imaging dose while improving image quality.
Funding Support, Disclosures, and Conflict of Interest: This research was supported by the Mid-career Researcher Program (NRF-2018R1A2B2005343) through the National Research Foundation (NRF) funded by the Ministry of Science and ICT (MSIT) of Korea.