Analysis and Improvement of Radial Spin-Echo Diffusion-Weighted Images

The pulsatile motion artifacts in the radial spin-echo diffusion-weighted-imaging (rSE-DWI) are analyzed and a method to improve the image quality of the rSE-DWI using the projection data regeneration method is proposed in this work. In general, ECG-triggering is used together with the rSE-DWI in order to prevent the loss of projection data, where the amount of loss depends on the data acquisition timing in the cardiac cycle. The ECG-triggering reduces the artifacts related to the cardiac pulse to some extent, but still leaves some degraded projection data while increasing the data acquisition time. Thus, the projection data regeneration method is proposed in order to improve the image quality. In the proposed method, the projection data is acquired by the rSE-DWI from which a temporary image is generated by an inverse Radon transform (IRT). The projection data acquired at each view angle is tested to figure out whether it is damaged by the pulsatile motion, and then the degraded data are replaced with the data that are regenerated by the Radon transform (RT) of the temporary image. The regeneration process is repeated until the image gains reasonable quality. In the meanwhile, the thermal noise of the signal is removed using the mask generated by thresholding the intensity of the projection data. In order to demonstrate the efficiency, the proposed method for the improvement of image quality is applied to a phantom and in-vivo images. The quality of the DW images acquired by either ECG-triggered or non-triggered rSE-DWI can be improved using the proposed method without increasing the imaging time. Keywords—radial spin-echo diffusion-weighted images (rSE-DWI), ECG-triggering, Projection data regeneration.