Ventricular Assist Device implant (AB 5000) prototype cannula: In vitro assessment of MRI issues at 3-Tesla

Abstract

Purpose: To evaluate MRI issues at 3-Tesla for a ventricular assist device (VAD). Methods:The AB5000 Ventricle with a prototype Nitinol wire-reinforced In-Flow Cannula and Out-Flow Cannula attached (Abiomed, Inc., Danvers, MA) was evaluated for magnetic field interactions, heating, and artifacts at 3-Tesla. MRI-related heating was assessed with the device in a gelled-saline-filled, head/torso phantom using a transmit/received RF body coil while performing MRI at a whole body averaged SAR of 3-W/kg for 15-min. Artifacts were assessed for the main metallic component of this VAD (atrial cannula) using T1-weighted, spin echo and gradient echo pulse sequences.

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

“…17,[20][21][22][23] Translational Attraction. To evaluate translational attraction for each aneurysm clip, the deflection-angle technique was used according to a previously described methodology.…”

“…The test fixture incorporated a protractor with 1°graduated markings. 17,[20][21][22][23] The test sample was suspended on the apparatus by a lightweight string (20 cm in length; weight, Ͻ1% of the weight of each clip), which was fixed at the 0°i ndicator of the protractor. Deflection angles for each aneurysm clip were assessed at the point of the highest spatial magnetic gradient for the 3T MR system.…”

“…17,[20][21][22][23] The highest spatial magnetic gradient for the 3T scanner used in this investigation is 720 G/cm and occurs at an off-axis position 74-cm from the isocenter. 22 The maximum deflection angle from the vertical direction to the nearest 1°was measured 3 times for each aneurysm clip, and an average value was calculated. 17,[20][21][22][23] Torque.…”

“…22 The maximum deflection angle from the vertical direction to the nearest 1°was measured 3 times for each aneurysm clip, and an average value was calculated. 17,[20][21][22][23] Torque. Torque for each aneurysm clip in association with exposure to the 3T MR system was determined by using a previously described qualitative assessment technique.…”

“…Torque for each aneurysm clip in association with exposure to the 3T MR system was determined by using a previously described qualitative assessment technique. [20][21][22][23] This involved the use of a flat plastic device with a millimeter grid. [20][21][22][23] Each aneurysm clip was placed on the test apparatus in an orientation that was 45°relative to the static magnetic field of the 3T MR system.…”