MR imaging of tissue near aneurysm clips using short- and zero time MR sequences

This study shows how 3D ultra-short (UTE) and zero echo time (ZTE) experiments could be used to minimize susceptibility artifacts caused by MR-compatible aneurysm clips. Aneurysm clips are used to stop or prevent an aneurysm from bleeding. Postoperative imaging is needed to detect incomplete clipping, de novo aneurysm formation or multiple aneurysms. MRI is a non-invasive, radiation-free, technique to diagnose aneurysms. Unfortunately, treatment assessment by MRI after surgical placement of an aneurysm clip is complicated due to the presence of the metal clip, resulting in susceptibility artifacts. The clip's high magnetic susceptibility causes severe, orientation dependent, variations in the local magnetic field. Often this results in pronounced MR image distortions, including signal voids and pile-ups. We show that ZTE and 3D-UTE experiments, using radial sampling, provide MR images with less distortions than sequences using slice selection. Due to the minimal delay after RF-excitation and a significant reduction in signal time evolution during acquisition, susceptibility artifacts can be reduced.