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Updated: May 2, 2026
High-resolution Functional Magnetic Resonance Imaging Methods for Human Midbrain
Published on: May 10, 2012
Steady-state functional MRI using spoiled small-tip fast recovery imaging
Hao Sun1, Jeffrey A Fessler, Douglas C Noll
1Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, USA.
Purpose:
To determine whether a recently proposed steady-state magnetic resonance imaging (MRI) sequence, "small-tip fast recovery" (STFR), can be used for functional brain imaging. Compared to existing functional MRI (fMRI) based on T2*-contrast and long echo time, STFR has the potential for high-resolution imaging with reduced B0 artifacts such as geometric distortions, blurring, or local signal dropout.
Methods:
We used Monte Carlo Bloch simulations to calculate the voxel-averaged steady-state signal during rest and activation, for blood oxygen level dependent (BOLD) and STFR. STFR relies on a tailored "tip-up" radiofrequency pulse to align the spins with the longitudinal axis after each data readout segment, and here we performed proof-of-concept in vivo STFR fMRI experiments using a tip-up pulse tailored to a two-dimensional region-of-interest in motor cortex. Experiments were performed on multiple subjects to test reliability of the functional activation maps.
Results:
Bloch simulations predict a detectable functional signal that depends mainly on intravoxel dephasing, and only weakly on spin diffusion. STFR produces similar activation maps and signal change as BOLD in finger-tapping experiments, and shows reliability comparable to BOLD.
Conclusion:
STFR can produce functional contrast (even with short TE), and is a potential alternative to long-TE ( T2*) fMRI. The functional contrast arises primarily from the interaction between T2*-like dephasing and the tailored tip-up pulse, and not from spin diffusion.
Insights
Small-tip fast recovery (STFR) magnetic resonance imaging (MRI) shows promise as an alternative to traditional functional MRI (fMRI). This new technique offers comparable functional activation maps and reliability, potentially reducing artifacts in brain imaging.
Area of Science:
- Neuroimaging
- Magnetic Resonance Imaging
Background:
- Functional MRI (fMRI) typically relies on T2*-contrast and long echo times.
- Existing fMRI methods are susceptible to B0 artifacts like geometric distortions and signal dropout.
- A new steady-state sequence, small-tip fast recovery (STFR), has been proposed to address these limitations.
Purpose of the Study:
- To evaluate the efficacy of the STFR sequence for functional brain imaging.
- To compare STFR performance against established blood oxygen level dependent (BOLD) fMRI techniques.
- To assess STFR's potential for high-resolution imaging with reduced artifacts.
Main Methods:
- Monte Carlo Bloch simulations were employed to model steady-state signals for both BOLD and STFR during rest and activation.
- In vivo STFR fMRI experiments were conducted using a tailored tip-up radiofrequency pulse in the motor cortex of multiple subjects.
- Functional activation maps were generated and analyzed for reliability.
Main Results:
- Simulations predicted a functional signal in STFR primarily driven by intravoxel dephasing, with minimal influence from spin diffusion.
- STFR demonstrated comparable activation maps and signal changes to BOLD fMRI during finger-tapping tasks.
- The reliability of STFR functional activation maps was found to be comparable to BOLD fMRI.
Conclusions:
- STFR can generate functional contrast effectively, even with a short echo time (TE).
- This sequence presents a viable alternative to conventional long-TE T2*-based fMRI.
- The observed functional contrast in STFR is attributed to the interplay between T2*-like dephasing and the specific tip-up pulse design.
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