Compensation of concomitant field effects in double diffusion encoding by means of added oscillating gradients

• Verfasst von: Rauch, Julian [VerfasserIn]
• Verfasst von: Laun, Frederik B. [VerfasserIn]
• Verfasst von: Bachert, Peter [VerfasserIn]
• Verfasst von: Ladd, Mark E. [VerfasserIn]
• Verfasst von: Kuder, Tristan Anselm [VerfasserIn]
• Titel: Compensation of concomitant field effects in double diffusion encoding by means of added oscillating gradients
• Verf.angabe: Julian Rauch, Frederik B. Laun, Peter Bachert, Mark E. Ladd, Tristan A. Kuder
• E-Jahr: 2024
• Jahr: January 2024
• Umfang: 9 S.
• Fussnoten: Gesehen am 05.03.2024 ; Onlineversion: 7 November 2023, Artikelversion: Januar 2024
• Titel Quelle: Enthalten in: Magnetic resonance imaging
• Ort Quelle: Amsterdam [u.a.] : Elsevier Science, 1982
• Jahr Quelle: 2024
• Band/Heft Quelle: 105(2024) vom: Jan., Seite 133-141
• ISSN Quelle: 1873-5894
• DOI: doi:10.1016/j.mri.2023.11.006
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: ALGORITHM
• Sach-SW: ANISOTROPY
• Sach-SW: ARTIFACTS
• Sach-SW: Concomitant fields
• Sach-SW: CONSTRAINTS
• Sach-SW: CONTRAST
• Sach-SW: Diffusion weighting
• Sach-SW: Double diffusion encoding
• Sach-SW: K-SPACE
• Sach-SW: MR
• Sach-SW: Optimization
• Sach-SW: OPTIMIZATION
• Sach-SW: Oscillating gradients
• Sach-SW: Sequence design
• Sach-SW: SYSTEM CHARACTERIZATION
• Sach-SW: TERMS
• K10plus-PPN: 1882514130

Abstract

Maxwell or concomitant fields imprint additional phases on the transverse magnetization. This concomitant phase may cause severe image artifacts like signal voids or distort the quantitative parameters due to the induced intravoxel dephasing. In particular, double diffusion encoding (DDE) schemes with two pairs of bipolar diffusion-weighting gradients separated by a refocusing radiofrequency (RF) pulse are prone to concomitant field-induced artifacts. In this work, a method for reducing concomitant field effects in these DDE sequences based on addi-tional oscillating gradients is presented. These oscillating gradient pulses obtained by constrained optimization were added to the original gradient waveforms. The modified sequences reduced the accumulated concomitant phase without significant changes in the original sequence characteristics. The proposed method was applied to a DDE acquisition scheme consisting of 60 pairs of diffusion wave vectors. For phantom as well as for in vivo experiments, a considerable increase in the signal-to-noise ratio (SNR) was obtained. For phantom measurements with a diffusion weighting of b = 2000 s/mm2 for each of the gradient pairs, an SNR increase of up to 40% was observed for a transversal slice that had a distance of 5 cm from the isocenter. For equivalent slice parameters, in vivo measurements in the brain of a healthy volunteer exhibited an increase in SNR of up to 35% for b = 750 s/ mm2 for each weighting. These findings are supported by corresponding simulations, which also predict a positive effect on the SNR. In summary, the presented method leads to an SNR gain without additional RF refocusing pulses.