Design And Application Of Optimal Pulse In Magnetic Resonance

Pulse sequence plays a key role in the field of nuclear magnetic resonance, thestate of the spin system can be changed by pulse sequence, resulting in the desiredNMR signal, and thus achieve spectral analysis or imaging of the sample. Comparedwith the traditional pulse, the optimal pulse based on the optimal control theory canwithstand the main magnetic field and pulses of radio frequency(RF) fieldinhomogeneity and other minus factor, which has born a series of fruit in the fieldsof MR. However，when using optimal pulse for further applications, we found thepulse intensity is too large for small MR spectrometer and MRI. This paper focusesthe application of optimal pulse，mainly to complete the work in the following twoaspects:On the one hand, two methods are proposed from two different aspects of thepulse optimization model to optimize pulse with amplitude limits. One is based onL-BFGS-B algorithms, and the other one is using variance assessment. Thensimulation algorithm and experiment are designed to test the excitation effect of theoptimal pulse by comparing with traditional pulse.On the other hand, the idea of pulse optimization is applied to optimize thepulse sequence, in order to enhance image contrast of two similar organizations, andcorresponding simulation imaging has accomplished.The simulation and experiment result demonstrates that the proposed methodsin this paper can expand the optimal pulse application area.