Room: Room 202
Purpose: We propose 4D digital tomosynthesis (DTS) based on slow gantry rotation technique with respiratory guiding to reduce imaging dose and time.
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. Then, we used the respiratory patterns to determine the frame rate and gantry rotation speed for scanning 40 degrees so that one projection per phase should be included. Lastly, we calculated acquisition time (AT) and the number of total projections (NP). Applying the obtained respiration pattern and the corresponding sequence, virtual projections were acquired for modified Shepp-Logan (SL), anterior-posterior (i.e., coronal) and left-right (i.e., sagittal) 4D XCAT (extended Cardiac-Torso) phantoms under a typical geometry of Varian on-board imager. 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 RMSE (Root-mean-square Error).
Results: Simulation with guidance (SwG) showed motion-related artifact reduction compared to simulation under free-breathing (SuFB). SwG required less AT and NP but provided slightly higher SSIM and lower RMSE characteristics 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 and scanning time while improving image quality.