Journal of magnetic resonance imaging : JMRI
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J Magn Reson Imaging · Apr 2006
Calculation of cerebral perfusion parameters using regional arterial input functions identified by factor analysis.
To calculate regional cerebral blood volume (rCBV), regional cerebral blood flow (rCBF), and regional mean transit time (rMTT) accurately, an arterial input function (AIF) is required. In this study we identified a number of AIFs using factor analysis of dynamic studies (FADS), and performed the cerebral perfusion calculation pixel by pixel using the AIF that was located geometrically closest to a certain voxel. ⋯ This study indicates that the use of FADS and the nearest-AIF method is preferable to manual selection of one single AIF.
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J Magn Reson Imaging · Apr 2006
EPI distortion correction from a simultaneously acquired distortion map using TRAIL.
To develop a method for shot-by-shot distortion correction of single-shot echo-planar imaging (EPI) that is capable of correcting each image individually using a distortion measurement performed during acquisition of the image itself. ⋯ Shot-by-shot distortion correction may be performed for EPI images acquired using an extension of the TRAIL technique, ensuring that the correction reflects the actual distortion pattern and not merely a previously measured, but possibly no longer valid, distortion field. This avoids errors due to changes in the distortion field or misregistration of a previously measured distortion map resulting from subject motion.
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To develop a novel pulse sequence called spin-locked echo planar imaging (EPI), or (SLEPI), to perform rapid T1rho-weighted MRI. ⋯ We demonstrate the feasibility of the SLEPI pulse sequence to perform rapid T1rho MRI. The sequence produced images of higher quality than a gradient-echo EPI sequence for the same contrast evolution times. We also discuss applications and limitations of the pulse sequence.