Journal of magnetic resonance imaging : JMRI
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J Magn Reson Imaging · Apr 2012
Improving the performance of diffusion-weighted inner field-of-view echo-planar imaging based on 2D-selective radiofrequency excitations by tilting the excitation plane.
To improve the performance and flexibility of diffusion-weighted inner field-of-view (FOV) echo-planar imaging (EPI) based on 2D-selective radiofrequency (RF) excitations by 1) using higher gradient amplitudes for outer excitation lines, and 2) tilting the excitation plane such that the unwanted side excitations do not overlap with the current image slice or other slices to be acquired. ⋯ Tilting the excitation plane and applying variable gradient amplitudes improves the applicability of inner FOV EPI based on 2D-selective RF excitations.
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J Magn Reson Imaging · Apr 2012
Segmentation of carotid plaque using multicontrast 3D gradient echo MRI.
To evaluate the performance of automatic segmentation of atherosclerotic plaque components using solely multicontrast 3D gradient echo (GRE) magnetic resonance imaging (MRI). ⋯ The combination of 3D imaging sequences (TOF, MP-RAGE, and MERGE) can provide sufficient contrast to distinguish NC, CA, and LM. Automatic segmentation using 3D sequences and traditional multicontrast protocol produced highly similar results.
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J Magn Reson Imaging · Apr 2012
Radiofrequency heating induced by 7T head MRI: thermal assessment using discrete vasculature or Pennes' bioheat equation.
To evaluate and compare the maximum temperature (T(max) ) in the head after exposure to a 300 MHz radiofrequency (RF) field induced by a magnetic resonance imaging (MRI) coil using two thermal simulation methods: Pennes' bioheat equation (PBHE) and discrete vasculature (DIVA). ⋯ In some situations, RF exposure limited to SAR(max,10g) led to a T(max) higher than allowed by International Electrotechnical Commission (IEC) regulations. Therefore, it is advisable to use thermal simulations to evaluate RF safety of MRI. The simulation method used only slightly influenced the observed maximum temperature; the observed temperature with PBHE was higher in all situations. So PBHE is an appropriate method for RF safety assessment of MRI in the head. Using DIVA simulations, it was found unlikely that the body temperature increases significantly due to energy deposited by a head coil under normal circumstances.
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J Magn Reson Imaging · Apr 2012
Hadamard-encoding combined with two-dimensional-selective radiofrequency excitations for flexible and efficient acquisitions of multiple voxels in MR spectroscopy.
To improve the efficiency and flexibility of acquisitions of multiple voxels in MR spectroscopy by combining two-dimensional-selective radiofrequency (2DRF) excitations and Hadamard encoding. ⋯ The presented approach improves the flexibility and efficiency of acquisitions of multiple voxels, i.e., can shorten acquisition times accordingly, and can help to reduce partial volume effects.