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Design of adiabatic selective pulses using optimal control theory
1School of Physics and Astronomy, Tel-Aviv University, Israel.
Magnetic Resonance in Medicine
|September 1, 1996
Summary
This study integrates adiabaticity into optimal control for magnetic resonance imaging (MRI) RF pulse design. Researchers can now balance slice resolution with pulse adiabaticity for improved selective excitation and fat suppression.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Optimal Control Theory
- Radiofrequency (RF) Pulse Design
Background:
- Optimal control theory is established for selective excitation in MRI, often using "minimum distance" formulations.
- Adiabatic pulses are crucial for robust spin inversion and excitation, especially in inhomogeneous RF fields.
Purpose of the Study:
- To develop a method for incorporating adiabaticity into optimal control problems for RF pulse design.
- To enhance the cost functional with specific adiabatic terms.
- To explore the trade-off between slice resolution and pulse adiabaticity.
Main Methods:
- Enhancing the cost functional with adiabatic terms.
- Solving the optimal control problem using the Hamiltonian approach and mathematical programming.
- Designing frequency-selective fat suppression pulses and regular inversion pulses.
Main Results:
- A novel method for incorporating adiabaticity into optimal control for RF pulse design is presented.
- Two distinct adiabatic terms and two solution methods (Hamiltonian, mathematical programming) were employed.
- Design examples demonstrate the ability to adjust slice resolution versus adiabaticity.
Conclusions:
- The proposed method effectively integrates adiabaticity into optimal control for RF pulse design.
- Pulse designers can now strategically balance slice resolution and adiabaticity.
- This offers enhanced control over selective excitation and inversion pulses in MRI.