Magnetic resonance imaging
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The objective of this study was to determine imaging features that may help predict the presence of placenta accreta, placenta increta or placenta percreta on prenatal MRI scanning. ⋯ MRI can be a useful adjunct to ultrasound in diagnosing placenta accreta prenatally. Three features that are seen on MRI in patients with placental invasion appear to be useful for diagnosis: uterine bulging; heterogeneous signal intensity within the placenta; and the presence of dark intraplacental bands on T2W imaging.
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Temporal clustering analysis (TCA) has been proposed as a method to detect the brain responses of an fMRI time series when the time and location of the activation are completely unknown. But TCA is still incompetent in dealing with the time series of the whole brain due to the existence of many inactive pixels. ⋯ Based on the time series of the modified TCA, activations of the whole brain corresponding to the visual stimulation were detected. Compared with the previous TCA, the modified TCA method shows a significant improvement in the sensitivity to detect activation peaks of the whole brain.
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Microscopic magnetic resonance elastography is a high-resolution method for visualizing shear waves and assessing the biomechanical viscoelastic properties of small biological samples. In this work, we used error propagation to develop a simple analytical model that relates the signal-to-noise ratio of MR magnitude images to the variance in shear-wave maps collected using gradient-echo and spin-echo phase-contrast pulse sequences. Our model predicts results for shear-wave images in phantoms, which match the experimentally observed phase variance within 8%. This model can be used to optimize MR pulse sequences for elastography studies, as well as other phase-difference techniques in MRI.