ABSTRACT
Objective: To purpose an effective solution of reducing MRI time when rapid change and gradient switching rate of gradient magnetic field are restrained by eddy current caused by self induction and mutual inductance of gradient coil in MR system. Methods: With the constraints of gradient inductance minimization and gradient magnetic field self-shielding, a mathematical model was established by combining the target field point method to solve the winding distribution of the double-plane gradient coil, so as to reduce the magnetic field energy of the gradient coil and the eddy current on the performance of the gradient coil. At the same time, in order to shorten the operation time of solving the above complex mathematical model matrix by MATLAB software, graphic processing unit (GPU) acceleration algorithm was used to realize the calculation of gradient coil. Results: By minimizing gradient inductance, eddy current effect could be effectively reduced, the magnetic field self-shielding could be realized, the gradient switching rate was good, and the overall performance of the gradient coil could be improved. Conclusion: The new target field point method for biplane gradient coil is effective and feasible, which can realize minimization of gradient inductance and designing self-shielding gradient coil of gradient magnetic field.
ABSTRACT
Dual-energy computed tomography (CT) reconstruction imaging technology is an important development direction in the field of CT imaging. The mainstream model of dual-energy CT reconstruction algorithm is the basis material decomposition model, and the projection decomposition is the crucial technique. The projection decomposition algorithm based on projection matching was a general method. With establishing the energy spectrum lookup table, we can obtain the stable solution by the least squares matching method. But the computation cost will increase dramatically when size of lookup table enlarges and it will slow down the computer. In this paper, an acceleration algorithm based on projection matching is proposed. The proposed algorithm makes use of linear equations and plane equations to fit the lookup table data, so that the projection value of the decomposition coefficients can be calculated quickly. As the result of simulation experiment, the acceleration algorithm can greatly shorten the running time of the program to get the stable and correct solution.