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Flow sensitivity and coherence in steady-state free spin precession.
R B de Vasconcellos Azeredo1, M Engelsberg, L A Colnago
1Instituto de Química de São Carlos, Universidade de São Paulo, Avenida Dr. Carlos Botelho 1465, 13560-970 São Carlos, São Paulo, Brazil.
Summary
This study introduces a continuous wave free precession (CWFP) regime for nuclear spin imaging. CWFP exhibits unique flow sensitivity, even with weak gradients, due to preserved coherence.
Area of Science:
- Magnetic Resonance Imaging
- Nuclear Spin Physics
Background:
- Steady-state free precession (SSFP) is sensitive to flow.
- Standard SSFP can lose coherence rapidly.
Purpose of the Study:
- Investigate flow sensitivity in a novel continuous wave free precession (CWFP) regime.
- Explore the impact of short radio-frequency pulse spacing on coherence and flow effects.
Main Methods:
- Theoretical modeling of nuclear spin dynamics.
- Experimental validation of predicted flow sensitivity.
- Analysis of CWFP under conditions of short pulse repetition times.
Main Results:
- A CWFP regime was established with preserved coherence, unlike standard SSFP.
- Significant flow sensitivity was observed even with minimal magnetic field gradients.
- Experimental results confirmed predicted flow effects due to unspoiled coherence.
Conclusions:
- CWFP offers a distinct and tunable flow sensitivity.
- Adjusting frequency offset is key to tailoring flow sensitivity in CWFP.
- Preserved coherence in CWFP leads to novel flow-related phenomena in MRI.