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Published on: November 29, 2012
Velocity sensitivity of slice-selective excitation
D P Lewis1, B M Tsui, P R Moran
1Department of Biomedical Engineering, University of North Carolina, Chapel Hill 27599-7575, USA. lewis@bme.unc.edu
Magnetic Resonance Imaging
|November 14, 1998
Summary
Flow significantly impacts magnetic resonance imaging slice profiles, degrading excitation quality for certain radiofrequency (rf) pulses. Pulse design is crucial for accurate imaging of flowing materials.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Biophysics
- Medical Physics
Background:
- Slice-selective excitation is fundamental in MRI, defining the imaging region.
- Flowing materials can distort slice profiles, impacting image quality and diagnostic accuracy.
- Existing radiofrequency (rf) pulses are often optimized for stationary tissues.
Purpose of the Study:
- To investigate the impact of material flow on slice-selective excitation.
- To evaluate how different radiofrequency (rf) pulse designs perform under flow conditions.
- To compare simulation predictions with experimental results for flowing materials in MRI.
Main Methods:
- Utilized simulation methods to compute slice profiles for various flow velocities.
- Employed four distinct rf pulse types: Shinnar-LeRoux (linear-phase and inversion), self-refocusing, and SPINCALC.
- Validated simulation findings against experimental data acquired on a clinical MRI system.
Main Results:
- Slice profile degradation due to flow is dependent on gradient amplitude, velocity, and rf pulse duration.
- Shinnar-LeRoux pulses exhibited robustness against flow effects.
- Self-refocusing and SPINCALC pulses showed significant slice profile distortion with increasing velocity.
Conclusions:
- Flow significantly degrades slice-selective excitation in MRI, contingent on velocity and pulse characteristics.
- RF pulse design plays a critical role in maintaining image quality for flowing substances.
- Findings inform the development of optimized rf pulses for imaging dynamic physiological processes.
