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"One-shot" velocity microscopy: NMR imaging of motion using a single phase-encoding step
1Department of Physics and Biophysics, Massey University, Palmerston North, New Zealand.
Magnetic Resonance in Medicine
|January 1, 1992
Summary
Dynamic NMR microscopy measures molecular motion using pulsed gradient spin-echo. This technique can create velocity images alone, aiding studies of capillary flow and plant vascular transport.
Area of Science:
- Magnetic Resonance Imaging
- Biophysics
- Fluid Dynamics
Background:
- Pulsed gradient spin-echo (PGSE) in NMR microscopy allows measurement of molecular motion.
- Dynamic NMR microscopy typically requires complex multi-dimensional data acquisition.
- Acquiring velocity and self-diffusion images simultaneously can be inefficient.
Purpose of the Study:
- To develop a simplified method for generating velocity images in NMR microscopy.
- To demonstrate the utility of this simplified method in biological systems.
- To improve the efficiency of dynamic NMR microscopy for flow measurements.
Main Methods:
- Utilizing a single PGSE phase-encoding step to construct velocity images, sacrificing some multi-dimensional information.
- Employing gradient phase cycling and a "z-storage" radiofrequency pulse to null signals from stationary spins.
- Applying a four-quadrant analysis method to extend the measurable velocity range.
Main Results:
- Achieved velocity resolution limits of approximately 10 microns s-1 in free water.
- Demonstrated water capillary flow imaging at 12 microns transverse pixel resolution.
- Measured vascular transport in a living plant, revealing flow rates around 45 microns s-1.
Conclusions:
- A simplified PGSE approach enables efficient velocity imaging in NMR microscopy.
- This method is effective for studying fluid dynamics in biological samples, including capillary flow and plant vascular transport.
- The technique offers valuable insights into molecular motion and transport processes.