Improvement of the diffusion-weighted images acquired with radial trajectories using projection data regeneration.

PURPOSE To reduce the artifacts due to pulsatile motion artifacts in diffusion-weighted imaging (DWI) with radial trajectories and to improve the image quality using projection data regeneration. MATERIALS AND METHODS The projection data is obtained by a radial spin-echo DWI (rSE-DWI) sequence, from which a temporary image is generated using the inverse Radon transform (IRT). The projection data include some degraded data due to cardiac pulsatile motion. The degraded data are then replaced with data that are regenerated using the Radon transform (RT) of the temporary image. The proposed method for image quality improvement is demonstrated through a computer simulation and in vivo images obtained by rSE-DWI. RESULTS In general, electrocardiograph (ECG) triggering is used to reduce the degradation of projection data in the DWI with radial trajectories, where the amount of degradation depends on the cardiac phase. Cardiac gating reduces the artifacts resulting from the cardiac pulsatile motion to a certain extent only. The proposed projection data regeneration method successfully improves image quality. CONCLUSION The regeneration method based on back-projection reconstruction effectively uses the features of the degraded projections having lower signal intensity than the normal projections, resulting in image quality improvement without acquisition of additional data.