Journal of magnetic resonance imaging : JMRI
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J Magn Reson Imaging · Jan 2009
Increased SNR and reduced distortions by averaging multiple gradient echo signals in 3D FLASH imaging of the human brain at 3T.
To demonstrate how averaging of multiple gradient echoes can improve high-resolution FLASH (fast low angle shot) magnetic resonance imaging (MRI) of the human brain. ⋯ SNR is gained efficiently by acquiring additional echoes and increasing TR (and flip angle accordingly to maintain contrast) until the associated T(2) (*) loss in the averaged signal consumes the sqrt(TR) increase in the steady state. A bandwidth of 350 Hz/pixel or higher and echo trains shorter than T(2) (*) are recommended.
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J Magn Reson Imaging · Jan 2009
Diffusion measurements and diffusion tensor imaging with noisy magnitude data.
To compare an unbiased method for estimation of the diffusion coefficient to the quick, but biased, log-linear (LL) method in the presence of noisy magnitude data. ⋯ In the presence of noisy magnitude data, unbiased estimation is essential in diffusion measurements and diffusion tensor imaging.
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J Magn Reson Imaging · Jan 2009
Combination of Mn(2+)-enhanced and diffusion tensor MR imaging gives complementary information about injury and regeneration in the adult rat optic nerve.
To evaluate manganese (Mn(2+))-enhanced MRI (MEMRI) and diffusion tensor imaging (DTI) as tools for detection of axonal injury and regeneration after intravitreal peripheral nerve graft (PNG) implantation in the rat optic nerve (ON). ⋯ MEMRI and DTI enabled detection of functional and structural degradation after rat ON injury, and there was correlation between the MRI-derived and immunohistochemical measures of axon regeneration.
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J Magn Reson Imaging · Jan 2009
Imaging age-related cognitive decline: A comparison of diffusion tensor and magnetization transfer MRI.
To determine which MR technique was the most sensitive to age-related white matter damage. We compared both diffusion tensor imaging (DTI) and magnetization transfer (MT) maps to determine which technique correlated most strongly with cognitive function in a middle-aged and elderly community population. ⋯ DTI appears the most sensitive imaging parameter to determine age-related white matter damage. The stronger relationship with FA suggests that axonal damage is important in age-related cognitive decline.
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J Magn Reson Imaging · Jan 2009
Cerebral blood flow estimation in vivo using local tissue reference functions.
To evaluate the use of bolus signals obtained from tissue as reference functions (or local reference functions [LRFs]) rather than arterial input functions (AIFs) when deriving cross-calibrated cerebral blood flow (CBF(CC)) estimates via deconvolution. ⋯ If CBF is quantified using a patient-specific cross-calibration factor, then LRF CBF estimates are at least as accurate as those from AIFs. Therefore, until AIF quantification is achievable in vivo, perfusion protocols tailored for LRFs would simplify the methodology and provide more reliable perfusion information.