Improvement of water saturation shift referencing by sequence and analysis optimization to enhance chemical exchange saturation transfer imaging

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• 作者：Anja Mü ; ller-Lutz^a ; Felix Matuschke^a ; Christoph Schleich^a ; ^{Christoph.Schleich@med.uni-duesseldorf.de" class="auth_mail" title="E-mail the corresponding author} ; Frithjof Wickrath^a ; Johannes Boos^a ; Benjamin Schmitt^b ; Hans-Jö ; rg Wittsack^a
• 关键词：Chemical exchange saturation transfer ; Water saturation shift referencing ; Monte-Carlo-simulations ; Field inhomogeneity correction ; Brain ; Intervertebral disks
• 刊名：Magnetic Resonance Imaging
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：34
• 期：6
• 页码：771-778
• 全文大小：1096 K

文摘

To optimize B₀-field inhomogeneity correction for chemical exchange saturation transfer (CEST) imaging by investigating different water saturation shift referencing (WASSR) Z-spectrum shapes and different frequency correction techniques.

Methods

WASSR Z-spectra were simulated for different B₁-fields and pulse durations (PD). Two parameter settings were used for further simulations and experiments (WASSR1: B₁ = 0.1 μT, PD = 50 ms; WASSR2: B₁ = 0.3 μT, PD = 40 ms). Four frequency correction techniques were investigated: 1) MinW: Minimum of the spline-interpolated WASSR-spectrum; 2) MSCF: maximum symmetry center frequency algorithm; 3) PMSCF: further development of MSCF algorithm; 4) BFit: fit with Bloch equations. Performance of frequency correction was assessed with Monte-Carlo simulations and in-vivo MR examinations in the brain and intervertebral disks.

Results

Different shapes of WASSR-Z-spectra were obtained by changing B₁ and PD including spectra with one (1-Peak) or two (2-Peak) minima. WASSR1 resulted in 1-Peak WASSR-spectrum, whereas WASSR2 resulted in 2-Peak WASSR-spectrum. Both Monte-Carlo simulations and in-vivo MR examinations revealed highest accuracy of field-inhomogeneity correction with WASSR1 combined with PMSCF or BFit.

Conclusion

Using a WASSR sequence, which results in a Z-spectrum with a single absorption peak, in combination with advanced postprocessing algorithms enables improved B₀-field inhomogeneity correction for CEST imaging.