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Comparison of multi-echo spiral and echo planar imaging in functional MRI
Markus Klarhöfer1, Markus Barth, Ewald Moser
1Arbeitsgruppe NMR, Institut für Medizinische Physik, Universität Wien, Vienna, Austria.
Magnetic Resonance Imaging
|August 8, 2002
Summary
Multi-echo spiral and echo-planar imaging (EPI) accurately measure T(2)* in the brain. Both functional magnetic resonance imaging (fMRI) sequences yield comparable results, with spiral imaging offering higher spatial resolution.
Area of Science:
- Magnetic Resonance Imaging
- Neuroimaging
- Biophysics
Background:
- Functional magnetic resonance imaging (fMRI) relies on detecting brain activity through blood-oxygen-level-dependent (BOLD) signals.
- Accurate quantification of signal changes, particularly T(2)* (effective transversal relaxation time), is crucial for understanding vascular contributions and inflow effects in fMRI.
- Comparing different imaging sequences is essential for optimizing fMRI data acquisition and interpretation.
Purpose of the Study:
- To compare the performance of multi-echo spiral and echo-planar imaging (EPI) sequences at 3 Tesla for fMRI.
- To evaluate the ability of both sequences to measure T(2)* and I(0) parameters.
- To assess the comparability of functional activation results obtained with both sequences.
Main Methods:
- Multi-echo spiral and EPI sequences were employed for fMRI experiments at 3 Tesla.
- T(2)* and I(0) values were measured in the human brain using single- and multi-echo FLASH, EPI, and spiral sequences.
- Motor stimulation was used to elicit functional brain responses, and changes in T(2)* were analyzed in activated areas.
Main Results:
- Both multi-echo EPI and spiral imaging allowed for the calculation of T(2)* and I(0) values.
- T(2)* measurements in a prefrontal region ranged from 42.9 to 53.8 ms, validating fast single-shot techniques.
- Functional experiments showed comparable absolute T(2)* increases (1.1 +/- 0.6 ms for EPI, 1.4 +/- 0.9 ms for spiral) and activated area sizes.
- Spiral imaging achieved higher spatial resolution due to efficient gradient performance.
Conclusions:
- Multi-echo spiral and EPI sequences are suitable for quantitative fMRI analysis at 3 Tesla.
- Both sequences provide comparable results for T(2)* measurements and functional activation detection.
- Spiral imaging offers an advantage in spatial resolution, potentially enhancing the sensitivity and specificity of fMRI studies.