Patent ID: 8082127
Filing Date: 2011-12-20
Classification: G01R

Abstract:
1. A method for determining the spatial distribution of magnetic resonance signals from a predetermined imaging area, which consists of at least one extended region within a volume of investigation of a nuclear magnetic resonance apparatus, wherein a transverse magnetization of nuclear spins is excited through multi-dimensional RF (radio frequency) pulses using magnetic field gradients and RF transmitting antenna means, said antenna means comprising at least one transmitting element, wherein in a definition step, a k-space trajectory which is to be generated through magnetic field gradient switching and which must be followed during excitation, as well as a phase encoding scheme with phase encoding steps are determined for spatial encoding using a computer or controller, in a preparatory step, the amplitude and phase behavior with time of the RF pulses to be irradiated for exciting the transverse magnetization of the nuclear spins is calculated for each transmitting element of the transmitting antenna means for the selected k-space trajectory using the computer or controller, in an execution step, transverse magnetization of nuclear spins within the volume of investigation is excited during each phase encoding step by a multi-dimensional RF pulse, phase encoding takes place according to the phase encoding scheme, and magnetic resonance signals are acquired using receiver antenna means, in a reconstruction step, a two- or three-dimensional spatial distribution and/or spatial allocation of the magnetic resonance signals and/or values derived therefrom are calculated from the magnetic resonance signals acquired in all phase encoding steps using the computer or controller, and in a display/storage step, the results of reconstruction and/or the one or more values derived therefrom are stored and/or displayed, wherein further in the definition step, a two- or three-dimensional resolution grid with resolution grid cells that covers the object under investigation is predetermined, an at least two-dimensional grid of directly neighboring encoding cells is determined for each region of the imaging area, wherein each encoding cell consists of one or more resolution grid cells of the imaging area, for which the same spatial encoding is to be performed, and for each phase encoding step, a complex excitation pattern is defined which is given by amplitudes and phases of the transverse magnetization to be excited in all resolution grid cells, in which the amplitudes assigned to the resolution grid cells are set within the imaging area in correspondence with a predetermined distribution identically for each phase encoding step, the amplitudes assigned to the remaining resolution grid cells are set to zero, and the phases assigned to the resolution grid cells within the imaging area are set in accordance with the defined phase encoding scheme, in the preparatory step, the amplitude and phase behavior of the RF pulses to be irradiated is calculated for each defined complex excitation pattern of the phase encoding steps and for each transmitting element, in the execution step, the transverse magnetization of the nuclear spins is repeatedly excited, wherein for each phase encoding step, the RF pulse(s) calculated for the transmitting element(s) is/are applied during passage of the predetermined k-space trajectory, such that phase encoding is performed within the imaging area during excitation of the transverse magnetization of the nuclear spins.