Ex vivo evaluation of ferromagnetism, heating, and artifacts produced by heart valve prostheses exposed to a 1.5‐T MR system

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Abstract
Ex vivo testing techniques were used to determine the ferromagnetic qualities of, presence of heating in, and artifacts produced by 13 different heart valve prostheses exposed to a 1.5‐T (64‐MHz) magnetic resonance (MR) system. None of the heart valve prostheses showed a measurable deflection in the 1.5‐T static magnetic field. Only minimal artifacts were produced during MR imaging with a fast spoiled GRASS (gradient‐recalled acquisition in the steady state) pulse sequence. The largest temperature changes measured during a “worst case” MR imaging sequence (estimated average specific absorption rate, 2.5 W/kg; estimated spatial peak specific absorption rate, 7.6 W/kg) were +0.2°C with the implant imaged “in air” and +0.3°C with the implant imaged in normal saline. Therefore, MR procedures performed with a 1.5‐T (64‐MHz) MR system may be performed safely in patients with any of the 13 different heart valve prostheses evaluated in this study.