Inner-volume imaging in vivo using three-dimensional parallel spatially selective excitation
Johannes T Schneider1, Raffi Kalayciyan, Martin Haas
1Bruker BioSpin MRI GmbH, Ettlingen, Germany. Johannes.Schneider@Bruker-BioSpin.de
Magnetic Resonance in Medicine
|June 26, 2012
Summary
Researchers achieved the first in vivo 3D spatially selective excitation using parallel transmission. This technique enables rapid, high-resolution imaging by precisely targeting specific regions within the body.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Biomedical Engineering
- Physics
Background:
- Three-dimensional (3D) spatially selective excitation is crucial for advanced MRI techniques like inner-volume imaging.
- Achieving short, accurate 3D excitation pulses in vivo is challenging due to hardware imperfections and off-resonance effects.
- Parallel transmission (pTx) offers potential for faster and more precise excitation but requires careful pulse design.
Purpose of the Study:
- To experimentally realize 3D spatially selective excitation using parallel transmission in vivo.
- To investigate the impact of transmit k-space trajectories on pulse performance.
- To demonstrate the feasibility of this technique for accelerated, high-resolution MRI in realistic applications.
Main Methods:
- Simulation study comparing stack-of-spirals and concentric-shells k-space trajectories for 3D parallel excitation.
- In vivo MR inner-volume imaging experiments using optimized 3D parallel excitation pulses.
- Consideration of experimental parameters like transmit-coil geometry and off-resonance conditions.
- Temporal optimization and real-time path measurement of k-space trajectories during pulse calculation.
Main Results:
- Identified critical influence of experimental parameters on trajectory suitability, especially with undersampling.
- Demonstrated that temporally optimized and measured trajectories yield short (3.2 ms) and robust 3D selective pulses.
- Successfully excited arbitrarily shaped volumes in vivo (corn cob, rat).
- Achieved high spatial resolution and significantly reduced scan times using reduced field-of-view imaging.
Conclusions:
- The first experimental realization of 3D spatially selective excitation using parallel transmission in vivo was achieved.
- Optimized k-space trajectories, considering real-world experimental conditions, are essential for robust and efficient 3D parallel excitation.
- This technique holds significant promise for accelerating realistic MRI applications, enabling high-resolution imaging of targeted regions.
