Genetic algorithm‐based optimization of pulse sequences.
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| Title: | Genetic algorithm‐based optimization of pulse sequences. |
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| Authors: | Somai, Vencel1,2 (AUTHOR) Vencel.Somai@cruk.cam.ac.uk, Kreis, Felix3 (AUTHOR), Gaunt, Adam1 (AUTHOR), Tsyben, Anastasia1 (AUTHOR), Chia, Ming Li1 (AUTHOR), Hesse, Friederike1 (AUTHOR), Wright, Alan J.1 (AUTHOR), Brindle, Kevin M.1,4 (AUTHOR) |
| Source: | Magnetic Resonance in Medicine. May2022, Vol. 87 Issue 5, p2130-2144. 15p. |
| Subjects: | Spin excitations, Cost functions, Magnetic fields, Protons, Uniformity |
| Abstract: | Purpose: The performance of pulse sequences in vivo can be limited by fast relaxation rates, magnetic field inhomogeneity, and nonuniform spin excitation. We describe here a method for pulse sequence optimization that uses a stochastic numerical solver that in principle is capable of finding a global optimum. The method provides a simple framework for incorporating any constraint and implementing arbitrarily complex cost functions. Efficient methods for simulating spin dynamics and incorporating frequency selectivity are also described. Methods: Optimized pulse sequences for polarization transfer between protons and X‐nuclei and excitation pulses that eliminate J‐coupling modulation were evaluated experimentally using a surface coil on phantoms, and also the detection of hyperpolarized [2‐13C]lactate in vivo in the case of J‐coupling modulation‐free excitation. Results: The optimized polarization transfer pulses improved the SNR by ~50% with a more than twofold reduction in the B1 field, and J‐coupling modulation‐free excitation was achieved with a more than threefold reduction in pulse length. Conclusion: This process could be used to optimize any pulse when there is a need to improve the uniformity and frequency selectivity of excitation as well as to design new pulses to steer the spin system to any desired achievable state. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Purpose: The performance of pulse sequences in vivo can be limited by fast relaxation rates, magnetic field inhomogeneity, and nonuniform spin excitation. We describe here a method for pulse sequence optimization that uses a stochastic numerical solver that in principle is capable of finding a global optimum. The method provides a simple framework for incorporating any constraint and implementing arbitrarily complex cost functions. Efficient methods for simulating spin dynamics and incorporating frequency selectivity are also described. Methods: Optimized pulse sequences for polarization transfer between protons and X‐nuclei and excitation pulses that eliminate J‐coupling modulation were evaluated experimentally using a surface coil on phantoms, and also the detection of hyperpolarized [2‐13C]lactate in vivo in the case of J‐coupling modulation‐free excitation. Results: The optimized polarization transfer pulses improved the SNR by ~50% with a more than twofold reduction in the B1 field, and J‐coupling modulation‐free excitation was achieved with a more than threefold reduction in pulse length. Conclusion: This process could be used to optimize any pulse when there is a need to improve the uniformity and frequency selectivity of excitation as well as to design new pulses to steer the spin system to any desired achievable state. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 07403194 |
| DOI: | 10.1002/mrm.29110 |
