MAGNETIC-FIELD GRADIENTS IN THE MRI SUITE AND THEIR EFFECTS ON ANEURYSM CLIPS

We studied magnetic field intensity in the magnetic resonance imaging suite at our hospital and its possible effect on several different typ es of aneurysm clips, including one Heifetz 17-7 PH, six Heifetz Elgil oy, one Mayfield, six Perneczky, fifteen Sugita, one Sundt-Kees Varian gle, four Variangle-McFadden and fifteen Yasargil clips. We carefully observed the clips for any translational or rotational movements along the path from the door towards the magnetic resonance imaging gantry. The magnetic field strength was 0.04 kiloGauss at the entrance of the room, with an acute increase of magnetic strength at 310 cm away from the entrance to the room, 90 cm to the entrance of the gantry. The ma gnetic strength continued to increase at a rate of 1.0-1.5 kiloGauss f or every 20 cm up to the entrance to the gantry. No movement was obser ved in any of the clips at the entrance to the suite except for the He ifetz 17-7 PH clip, which showed small movement in the longitudinal pl ane of the clip. At the entrance to the gantry, the Heifetz 17-7 PH, S undt-Kees Variangle, and Mayfield clips were aligned on the walls of t he test container perpendicular to the magnetic bore. The, Heifetz Elg iloy, Perneczky, Sugita, Variangle-McFadden, and Yasargil clips showed no movement throughout the path of the stretcher or near the gantry.