In Vitro Evaluation of MR Imaging Issues at 3T for Aneurysm Clips Made from MP35N: Findings and Information Applied to 155 Additional Aneurysm Clips

Abstract

BACKGROUND AND PURPOSE:Aneurysm clips need to be tested at 3T to characterize MR imaging concerns, including magnetic field interactions, MR imagingϪrelated heating, and artifacts. Therefore, we evaluated these risks for aneurysm clips.

A next-generation, flow-diverting implant used to treat brain aneurysms: in vitro evaluation of magnetic field interactions, heating and artifacts at 3-T

“…The test apparatus was a flat plastic material with a grid on the bottom. The implant was placed on the apparatus at a 45°o rientation relative to the static magnetic field of the 3-T MR system [8][9][10]. The implant was positioned in the center of the MR system where the effect of torque from the static magnetic field is greatest based on well-known characteristics of the 3-T MR system used for this assessment.…”

“…Measurements of deflection angles for the implant were obtained at the location in the 3-T MR system that produced the greatest magnetically induced angle. The highest "patient accessible" spatial gradient magnetic field for the 3-T MR scanner used in this investigation is 720 gauss/cm and occurs at an off-axis position that is 74 cm from isocenter of the MR system [8][9][10][11]. This point was determined for the MR system using gauss line plots, measurements using a gauss meter (Extech 480823 Electromagnetic Field and Extremely Low Frequency Meter; Extech, Nashua, NH, USA) and visual inspection to identify the location where the spatial magnetic field gradient was the greatest.…”

“…Magnetic field-induced torque was assessed qualitatively for the implant as previously described [8][9][10]. The test apparatus was a flat plastic material with a grid on the bottom.…”

“…Translational attraction was assessed using the deflection angle method as previously described [8][9][10]. The implant was attached to a test fixture to measure the deflection angle in the 3-T MR system.…”

“…This point was determined for the MR system using gauss line plots, measurements using a gauss meter (Extech 480823 Electromagnetic Field and Extremely Low Frequency Meter; Extech, Nashua, NH, USA) and visual inspection to identify the location where the spatial magnetic field gradient was the greatest. The Surpass NeuroEndoGraft was held vertically from the test fixture and then released; the deflection angle from the vertical position to the nearest 1°w as measured three times, and the mean value was calculated [8][9][10].…”