Relationship of magnetic moment of metallic alloys to image artifact during magnetic resonance imaging

摘要

Abstract: The embryonic area of interventional MRI, i.e. interstitial therapy under MR guidance, includes deep tissue laser ablation of lesions. Laser fibers can be located inside lesions by first inserting an MR-compatible cannula into the lesion and then inserting the laser fiber through the cannula into the lesion. Two factors are critical in selecting alloys for cannulae: the material should exhibit so little magnetic susceptibility that it will neither distort the MR image nor torque even at high field strengths, yet it should exhibit enough susceptibility defect that the cannula can be visualized by MR during positioning. Wires of metals and alloys were tested in a magnetometer to measure their magnetic moment, and imaged with spin echo and gradient echo MRI. Direct measurement of magnetic moment was a good indicator of MR- compatibility. Artifacts visualized with spin echo pulse sequences were smaller than those produced with gradient echo sequences.!9