| 摘要 |
In a method for examination subject-specific determination of parameters for activating gradient coils and radio-frequency of a coil array of a magnetic resonance device to generate a radio-frequency pulse with which nuclear spins in an examination region of an examination subject are moved out of a rest state by an arbitrary angle, a control unit activates phases and amplitudes of currents in the radio-frequency coils and respective currents in the gradient coils in a time-dependent manner in discrete steps to generate gradient fields. In a processor in communication with the control unit, parameters for the activation are automatically calculated dependent on measured sensitivity maps of the radio-frequency coils at the examination subject. The processor optimizes a non-linear equation system within the numerical calculation of the parameters involving a desired magnetization and a theoretical calculated real magnetization. The Jacobian matrix of the real magnetization is calculated in the determination of the parameters dependent on the direction of decline of the magnetization. The matrix elements of the Jacobian matrix consist of products of individual rotations that are determined from the optimized parameters. In the calculation of each matrix element, only factors in which the corresponding parameter is associated with the time step of the matrix element are determined.
|
