A novel sequence to improve auditory functional MRI with variable silent delays

  • Purpose: Auditory functional MRI (fMRI) often uses silent inter-volume delays for stimulus presentation. However, maintaining the steady-state of the magnetization usually requires constant delays. Here, a novel acquisition scheme dubbed “pre-Saturated EPI using Multiple delays in Steady-state” (SEPIMS) is proposed, using spin saturation at a fixed delay before each volume to maintain steady-state conditions, independent of previous spin history. This concept allows for variable inter-volume delays and thus for flexible stimulus design in auditory fMRI. The purpose was to compare the signal stability of SEPIMS and conventional sparse EPI (CS-EPI). Methods: The saturation module comprises two non-selective adiabatic saturation pulses. The efficiency of the saturation and its effect on the SEPIMS signal stability is tested in vitro and in vivo. Results: Data show that SEPIMS yields the same signal stability as CS-EPI, even for extreme variations between inter-volume delay durations. However, dual saturation pulses are required to achieve sufficiently high saturation efficiency in compartments with long T1 values. Importantly, spoiler gradient pulses after the EPI readout have to be optimized to avoid eddy-current-induced image distortions. Conclusion: The proposed SEPIMS sequence maintains high signal stability in the presence of variable inter-volume durations, thus allowing for flexible stimulus design.

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Author:Manoj ShresthaORCiD, H. Sean Lee, Ulrike Nöth, Ralf DeichmannORCiD
Parent Title (English):Magnetic resonance in medicine
Place of publication:New York, NY [u.a.]
Document Type:Article
Date of Publication (online):2020/09/04
Date of first Publication:2020/09/04
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2022/03/09
Tag:adiabatic saturation; auditory fMRI; scanner noise; sparse imaging; steady-state condition; variable silent delay
Page Number:14
First Page:883
Last Page:896
Open access funding enabled and organized by Projekt DEAL.
Dewey Decimal Classification:6 Technik, Medizin, angewandte Wissenschaften / 61 Medizin und Gesundheit / 610 Medizin und Gesundheit
Licence (German):License LogoCreative Commons - Namensnennung 4.0