Related Experiment Videos
MR angiography using velocity-selective preparation pulses and segmented gradient-echo acquisition
F R Korosec1, T M Grist, J A Polzin
1Department of Medical Physics, University of Wisconsin-Madison.
Abstract:
We describe a cardiac-gated MR angiographic imaging method that employs velocity-selective preparation (VSP) pulses in conjunction with segmented gradient-echo acquisition and subtraction to produce images that, ideally, contain no signal from stationary tissues and display vessels with a signal intensity that is dependent on the velocity of the blood in the vessels. The novel features of this method are a) it acquires several phase-encoding values/application of a single VSP pulse, b) it uses subtraction to eliminate signal that is not sufficiently suppressed by the VSP pulses, and c) it uses VSP pulses that are synchronized with the cardiac cycle so it can be used to produce ghost-free images of pulsatile blood. An advantage of this sequence is that it detects a signal that, after preparation, is relatively unaffected by changes in blood velocity. This leads to a large signal-to-noise ratio for all the phase-encoding values, a reduction of ghosting artifacts, and the ability to visualize blood that is in motion for only a short time during the cardiac cycle. Because the signal is prepared during peak flow, venous signal can be suppressed by making the sequence sensitive to high velocities. An additional advantage of this sequence is that it permits sampling with a short TE because the velocity-encoding gradient can be applied in a preparatory interval. Signal loss that results from dephasing during the longer TE preparation interval can be reduced or eliminated by allowing the dephased spins to flow out of the region of complex flow, and perhaps out of the field-of-view, by introducing a delay between the finish of the VSP pulse and the beginning of data acquisition.
Insights
This study introduces a cardiac-gated MR angiography technique using velocity-selective preparation (VSP) pulses. The method enhances blood vessel visualization by minimizing stationary tissue signals and reducing ghosting artifacts for clearer imaging.
Area of Science:
- Medical Imaging
- Cardiovascular Imaging
- Magnetic Resonance Imaging
Background:
- Magnetic Resonance (MR) angiography is crucial for visualizing blood vessels.
- Existing techniques face challenges with stationary tissue signals and motion artifacts.
- Velocity-selective preparation (VSP) pulses offer potential for improved image contrast.
Purpose of the Study:
- To develop and describe a novel cardiac-gated MR angiography method using VSP pulses.
- To achieve images with minimal stationary tissue signal and velocity-dependent vessel intensity.
- To produce ghost-free images of pulsatile blood flow.
Main Methods:
- Employs velocity-selective preparation (VSP) pulses synchronized with the cardiac cycle.
- Utilizes segmented gradient-echo acquisition with subtraction to remove residual signals.
- Acquires multiple phase-encoding values per VSP pulse application.
- Incorporates a delay between VSP pulse and data acquisition to mitigate signal loss.
Main Results:
- Ideally produces images with no signal from stationary tissues.
- Vessel signal intensity is dependent on blood velocity.
- Achieves significant reduction in ghosting artifacts.
- Enables visualization of blood in motion for short durations.
- Allows for suppression of venous signal by tuning velocity sensitivity.
Conclusions:
- The described cardiac-gated MR angiography method with VSP pulses offers enhanced visualization of blood vessels.
- Novel features, including subtraction and cardiac synchronization, improve image quality and reduce artifacts.
- The technique provides a robust approach for cardiovascular imaging with improved signal-to-noise ratio and reduced motion sensitivity.