Journal of magnetic resonance imaging : JMRI
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To establish image parameters for some routine clinical brain MRI pulse sequences at 3.0 T with the goal of maintaining, as much as possible, the well-characterized 1.5-T image contrast characteristics for daily clinical diagnosis, while benefiting from the increased signal to noise at higher field. ⋯ When parameters are adjusted for changes in relaxation rates, routine clinical scans at 3.0 T can provide similar image appearance as 1.5 T, but with superior image quality and/or increased speed.
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J Magn Reson Imaging · Jul 2005
Apparent diffusion coefficient and fractional anisotropy in spinal cord: age and cervical spondylosis-related changes.
To present the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) change with age in the normal spinal cord and in cervical spondylosis. ⋯ ADC increases and FA decreases with age in the normal spinal cord. Elevated ADC and reduced FA were measured in the spinal cord of spondylosis cases with clinical symptoms of myelopathy.
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J Magn Reson Imaging · Jul 2005
Cardiac CINE imaging with IDEAL water-fat separation and steady-state free precession.
To decompose multicoil CINE steady-state free precession (SSFP) cardiac images acquired at short echo time (TE) increments into separate water and fat images, using an iterative least-squares "Dixon" (IDEAL) method. ⋯ Multicoil IDEAL-SSFP imaging can produce high quality CINE cardiac images with uniform water-fat separation, insensitive to Bo inhomogeneities. This approach provides a new method for reliable fat-suppression in cardiac imaging.
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J Magn Reson Imaging · Jun 2005
Relationship between contrast enhancement on fluid-attenuated inversion recovery MR sequences and signal intensity on T2-weighted MR images: visual evaluation of brain tumors.
To investigate the relationship between the degree of contrast enhancement in fluid-attenuated inversion recovery (FLAIR) sequences and tumor signal intensity on T2-weighted images. ⋯ The signal intensity in FLAIR sequences is largely influenced by both T1 and T2 relaxation time; there is a close relationship between the signal intensity of brain tumors on T2-weighted images and the degree of contrast enhancement on FLAIR sequences. When tumors have higher signal intensity than normal cortex on T2-weighted images, additional postcontrast FLAIR imaging may improve their depiction.
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In view of recent applications in cardiovascular and functional brain imaging, this work revisits the basic performance characteristics of spiral imaging in direct comparison to echo-planar imaging (EPI) and conventional rapid gradient-echo imaging. Using both computer simulations and experiments on phantoms and human subjects at 2.9 T, the study emphasizes single-shot applications and addresses the design of a suitable trajectory, the choice of a gridding algorithm, and the sensitivity to experimental inadequacies. ⋯ Moreover, when ignoring parallel imaging strategies that are also applicable to EPI, improvements of image quality via reduced acquisition periods are only achievable by interleaved multishot spirals because partial Fourier sampling and rectangular fields of view (FOVs) cannot be exploited for non-Cartesian trajectories. Taken together, while spiral imaging may find its niche applications, most high-speed imaging needs are more easily served by EPI.