MR imaging in the presence of vascular stents: A systematic assessment of artifacts, for various stent orientations, sequence types, and field strengths

A systematic evaluation of the potential quality of magnetic resonance imag es recorded in the presence of metallic stents was performed on a low-field open imager operating at 0.2 T and on a high-field closed unit operating a t 1.0 T. Eight different stent types were examined by two-dimensional gradi ent-echo sequences with echo times of 4 and 10 msec and by a fast spin-echo technique. In addition, a three-dimensional gradient-echo sequence was app lied with an echo time of 2.4 msec. A set of sequence and slice parameters was used on both scanners, Thus, artifacts due to susceptibility effects de pending on the magnetic field strength could be distinguished from radiofre quency shielding effects in the lumen of the stents (independent of the fie ld strength). Nine different orthogonal orientations of the stent axis and the image (in terms of slice, read, and phase-encoding direction) were test ed, and the artifacts (extension of signal void and visibility of the lumen ) were compared. The optimal strategy for visualization of vascular and per ivascular regions outside the stents was fast spin-echo imaging with the st ent axis and read direction parallel to the static field. Susceptibility in duced signal void In gradient-echo images was minimal using the three-dimen sional approach. Increased transmitter amplitudes above usual values provid ed clearly improved insight in the lumen using gradient-echo sequences. (C) 2000 Wiley-Liss, Inc.