Abstract: Sensitivity matrices are determined for hotspots, the sensitivity matrices being used in the determination of control signal sequences for individually-controllable antenna elements of a radio-frequency transmit system of a magnetic resonance tomography device. For each hotspot, an SAR element may be established by summing the products of the elements of the respective sensitivity matrix with the corresponding elements of a cross-correlation matrix. A computer groups voxels of an object defined by a plurality of voxels into clusters. The computer assigns each cluster to one of the hotspots. For each hotspot, the computer establishes the respective sensitivity matrix such that in relation to each voxel of the cluster assigned to the respective hotspot, the difference between the sensitivity matrix established for the respective hotspot and a sensitivity matrix given for the respective voxel is positive semi-definite.

Abstract: A method for determining a magnetic resonance system control sequence that includes a multichannel pulse with a plurality of individual RF pulses to be transmitted in parallel by a magnetic resonance system via different independent RF transmit channels is provided. Using a predefined target magnetization, a multichannel pulse is determined in an RF pulse optimization method. Pulse shapes of the RF pulses for the different RF transmit channels are each described by a linear combination of trial functions. Coefficients of the linear combinations of trial functions are determined in the RF pulse optimization method.

Abstract: Sensitivity matrices are determined for hotspots, the sensitivity matrices being used in the determination of control signal sequences for individually-controllable antenna elements of a radio-frequency transmit system of a magnetic resonance tomography device. For each hotspot, an SAR element may be established by summing the products of the elements of the respective sensitivity matrix with the corresponding elements of a cross-correlation matrix. A computer groups voxels of an object defined by a plurality of voxels into clusters. The computer assigns each cluster to one of the hotspots. For each hotspot, the computer establishes the respective sensitivity matrix such that in relation to each voxel of the cluster assigned to the respective hotspot, the difference between the sensitivity matrix established for the respective hotspot and a sensitivity matrix given for the respective voxel is positive semi-definite.