[Imaging Parameter Optimization of 3D Phase Contrast-MRA to Reduce Susceptibility-artifact and Radiofrequency-shielding around the Intracranial Stent].

The purpose of this study was to evaluate the degree of signal attenuation generated around the stent by the susceptibility artifacts and radiofrequency (RF) shielding in phase contrast-magnetic resonance angiography (PCA) images and construct optimal PCA imaging parameters for intracranial stent lumen images. The two types of PCA images of stents (Neuroform, Enterpraise II) placed in the vascular flow phantom were imaged with different the flip angle (FA) and echo time (TE). Each original image of the vascular flow phantom was reconstructed into a coronal multiplanar reconstruction (MPR) image and a profile curve along the long axis of the stent was calculated. The reduction of in-stent signal was assessed by relative in-stent signal (RIS) calculated by comparing intra-stent signal intensity to the reference tube in the original images. When the TE was 2.3 ms, the profile curve was the highest signal intensity. However, RIS had not changed by the extension of TE. When the FA was high, the RIS showed a high value, but when it exceeded 25 degrees, the signal attenuated in the distal part of the slab.The susceptibility artifacts and RF shielding generated around the stent can be reduced by the shortest TbE (2.3 ms) and 20 degrees of FA in the PCA imaging.