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The BOLD sensitivity of rapid steady-state sequences.
Klaus Scheffler1,2, Rahel Heule1, Mario G Báez-Yánez1,3
1High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
Magnetic Resonance in Medicine
|November 30, 2018
Summary
Steady-state sequences are sensitive to microvessels, offering a BOLD (blood-oxygen-level-dependent) signal potentially closer to neuronal activity. This contrasts with gradient echo sequences, which are less sensitive to smaller vessels.
Area of Science:
- Magnetic Resonance Imaging
- Biophysics
Background:
- Blood-oxygen-level-dependent (BOLD) contrast in MRI arises from magnetic field inhomogeneities near deoxygenated blood vessels.
- These inhomogeneities affect water proton relaxation and dephasing, influenced by vessel size and imaging parameters.
Purpose of the Study:
- Analyze the BOLD sensitivity of steady-state MRI sequences.
- Investigate the dependence on vessel size, magnetic field strength, and sequence parameters.
Main Methods:
- Simulated steady-state magnetization in artificial vascular networks using Monte Carlo methods.
- Performed experimental measurements on microspheres to validate simulation results.
Main Results:
- Demonstrated a vessel size-dependent signal attenuation across all simulated coherence pathways.
- Observed that FID and ECHO pathways in steady-state sequences suppress the signal from larger vessels, similar to spin echo sequences in the static dephasing regime.
Conclusions:
- Steady-state sequences exhibit heightened sensitivity to microvessels.
- This microvessel sensitivity may provide BOLD signals more closely aligned with underlying neuronal activity compared to conventional gradient echo sequences.
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