Sofie Rahbek1, Tim Schakel2, Faisal Mahmood3,4, Kristoffer H. Madsen5,6, Marielle E.P. Philippens2, and Lars G. Hanson1,5
1Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark, 2Department of Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands, 3Laboratory of Radiation Physics, Odense University Hospital, Odense, Denmark, 4Department of Clinical Research, University of Southern Denmark, Odense, Denmark, 5Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark, 6Department of Applied Mathematics and Computer Science, Technical University of Denmark, Kgs. Lyngby, Denmark
1Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark, 2Department of Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands, 3Laboratory of Radiation Physics, Odense University Hospital, Odense, Denmark, 4Department of Clinical Research, University of Southern Denmark, Odense, Denmark, 5Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark, 6Department of Applied Mathematics and Computer Science, Technical University of Denmark, Kgs. Lyngby, Denmark
The diffusion-weighted SPLICE sequence was improved using the proposed framework for optimization of individual refocusing flip-angles in the echo-train. This provides optimal SNR for a given spatial point spread function representing a desired resolution and acceptable Gibbs ringing.
Brain images for the reference scheme (constant FA of 120°) and optimized FA scheme, respectively. (a-b): Data sampled with linear phase-encoding order before and after applying calculated filters. (c-d): Data sampled with center-out phase-encoding order before and after applying calculated filters.
The Hanning target function (a) and corresponding PSF (b) having a low FWHM and limited ripples. The optimized FAs (c) together with the reference scheme of 120° flips. The first four echoes are marked as “transients” and discarded for improved robustness. The resulting filters for both echo families, E1 and E2, normalized with the coefficient used for the center of k-space.