Optimized flip angle schemes for the split acquisition of fast spin‐echo signals (SPLICE) sequence and application to diffusion‐weighted imaging

Autor: Sofie Rahbek, Tim Schakel, Faisal Mahmood, Kristoffer H. Madsen, Marielle E.P. Philippens, Lars G. Hanson
Rok vydání: 2022
Předmět:
Zdroj: Rahbek, S, Schakel, T, Mahmood, F, Madsen, K H, Philippens, M E P & Hanson, L G 2023, ' Optimized flip angle schemes for the split acquisition of fast spin-echo signals (SPLICE) sequence and application to diffusion-weighted imaging ', Magnetic Resonance in Medicine, vol. 89, no. 4, pp. 1469-1480 . https://doi.org/10.1002/mrm.29545
ISSN: 1522-2594
0740-3194
DOI: 10.1002/mrm.29545
Popis: 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.
Databáze: OpenAIRE
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