Magnetic resonance imaging
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Replacement of the aortic heart valve typically requires open-heart surgery. A new transcatheter aortic valve replacement (TAVR) bioprosthesis made from metallic material was recently developed that is an advantageous alternative insofar as it is implanted using a minimally invasive procedure. Because of the presence of metal, there are safety issues related to MRI. Therefore, the purpose of this study was to use standardized testing techniques to evaluate MRI issues for this TAVR bioprosthesis in association with a 3-Tesla MR system. ⋯ The TAVR bioprosthesis that was evaluated in this investigation is acceptable, or using current MRI terminology "MR Conditional", for a patient undergoing MRI at 3-Tesla or less.
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The purposes of this study were (1) to compare single-echo PETRA with dual-echo PETRA using in vivo MR imaging, (2) to compare non-fat-saturated PETRA with fat-saturated PETRA using a 3-T clinical MR scanner, and (3) to determine the effect of the adequate sequence and post-processing method. ⋯ We demonstrated that there was significantly lower signal intensity on ultrashort TE PETRA images in the patients with meniscal pathologies. In addition, the single-echo of the ultrashort TE PETRA images echo time could be a more sensitive indicator between normal and pathologic meniscus conditions in patients.
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To evaluate the performance of diffusion tensor imaging (DTI) of the cervical spinal cord by comparing 2-dimensional standard single-shot interleaved multisection inner volume diffusion-weighted echo-planar imaging (2D ss-IMIV-DWEPI) and conventional 2D ss-DWEPI in a clinical population, focusing on the lower cervical spinal cord. ⋯ 2D rFOV ss-IMIV-DWEPI demonstrated higher performance than conventional 2D rFOV ss-DWEPI in terms of improving image quality, even in the lower segment of the cervical spinal cord.
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When using radial MR image acquisition techniques gradient or sampling delays due to hardware imperfections can cause mismatch between the expected and the actual k-space trajectory along the readout direction. To provide a robust and simple correction of such system delays we developed a new calibration method which is independent of using any reference data or applying sequence modifications. ⋯ We have demonstrated that radial data acquired with a 360° or golden-angle ordering scheme can be used for reliable intrinsic correction of system delays. The proposed technique enables a per-scan correction of system delays without the need for additional calibration data or modifications of the radial imaging sequence.
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A novel method for improving the accuracy of diffusion tensor imaging (DTI) is proposed. It takes into account the b matrix spatial variations, which can be easily determined using a simple anisotropic diffusion phantom. ⋯ The proposed technique was demonstrated on the Bruker Biospec 94/20USR system, using the spin echo diffusion sequence to image an isotropic water phantom and an anisotropic capillary phantom. The accuracy of the diffusion tensor determination was improved by an overall factor of about 8 for the isotropic water phantom.