Journal article
Optimized flip angle schemes for the split acquisition of fast spin-echo signals (SPLICE) sequence and application to diffusion-weighted imaging
MRI Acquisition, Magnetic Resonance, Department of Health Technology, Technical University of Denmark1
Magnetic Resonance, Department of Health Technology, Technical University of Denmark2
Department of Health Technology, Technical University of Denmark3
Utrecht University4
University of Southern Denmark5
Cognitive Systems, Department of Applied Mathematics and Computer Science, Technical University of Denmark6
Department of Applied Mathematics and Computer Science, Technical University of Denmark7
Hyperpolarization & Metabolism, Magnetic Resonance, Department of Health Technology, Technical University of Denmark8
Purpose : The diffusion-weighted SPLICE (split acquisition of fast spin-echo signals) sequence employs split-echo rapid acquisition with relaxation enhancement (RARE) readout to provide images almost free of geometric distortions. However, due to the varying T (Formula presented.) -weighting during k-space traversal, SPLICE suffers from blurring.
This work extends a method for controlling the spatial point spread function (PSF) while optimizing the signal-to-noise ratio (SNR) achieved by adjusting the flip angles in the refocusing pulse train of SPLICE. Methods : An algorithm based on extended phase graph (EPG) simulations optimizes the flip angles by maximizing SNR for a flexibly chosen predefined target PSF that describes the desired k-space density weighting and spatial resolution.
An optimized flip angle scheme and a corresponding post-processing correction filter which together achieve the target PSF was tested by healthy subject brain imaging using a clinical 1.5 T scanner. Results : Brain images showed a clear and consistent improvement over those obtained with a standard constant flip angle scheme.
SNR was increased and apparent diffusion coefficient estimates were more accurate. For a modified Hann k-space weighting example, considerable benefits resulted from acquisition weighting by flip angle control. Conclusion : The presented flexible method for optimizing SPLICE flip angle schemes offers improved MR image quality of geometrically accurate diffusion-weighted images that makes the sequence a strong candidate for radiotherapy planning or stereotactic surgery.
Language: | English |
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Publisher: | John Wiley and Sons Inc. |
Year: | 2023 |
Pages: | 1469-1480 |
ISSN: | 15222594 and 07403194 |
Types: | Journal article |
DOI: | 10.1002/mrm.29545 |
ORCIDs: | Rahbek, Sofie , 0000-0002-1234-3479 , 0000-0002-7270-7967 , Madsen, Kristoffer H. and Hanson, Lars G. |
Diffusion-weighted magnetic resonance imaging Point spread function SNR SPLICE Sequence optimization Variable flip angle
Algorithms Brain Diffusion Magnetic Resonance Imaging Image Enhancement Imaging, Three-Dimensional Magnetic Resonance Imaging Signal-To-Noise Ratio diffusion-weighted magnetic resonance imaging diffusion‐weighted magnetic resonance imaging point spread function sequence optimization variable flip angle