97 Magnetic Resonance Imaging Using the Hybridtm Fast-Scan Technique

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

“…The type and extent of various artifacts caused by metallic implants, materials, and devices have also been described and are typically well recognized on MRimages (1,20,21). The distortion of the image by a metallic object is caused by disruption of the local magnetic field, perturbing the relationship between position and frequency, which is crucial for accurate image reconstruction (1.20.2 1).…”

“…The degree of image distortion depends on the magnetic susceptibility, quantity, shape, orientation, and position of the object and the technique used for imaging (ie, the pulse sequence parameters) and image processing (ie, twodimensional Fourier transform reconstruction, back-projection. etc) (1,20,21).…”

“…Nonferromagnetic objects tend to produce artifacts that are less severe than those caused by ferromagnetic objects (1.20.21). A r tfacts caused by nonferromagnetic implants, materials, or devices result from eddy currents generated in the objects by the gradient magnetic fields used for MR imaging, which, in turn, disrupt the local magnetic field and distort the image (1,20,21). different heart valve prostheses produced only a mild or subtle degree of distortion of the MR image, despite the use of a gradient-echo pulse sequence that is typically more likely to produce substantial changes in image quality.…”