Activating a magnetic resonance system

1. A method for activating a magnetic resonance system having a transmit antenna arrangement, the transmit antenna arrangement comprising a plurality of independent high-frequency transmit channels with a respectively assigned transmit antenna, each high-frequency transmit channel of the plurality of independent high-frequency transmit channels having a controllable oscillator, the method comprising:

activating individual high-frequency transmit channels of the plurality of independent high-frequency transmit channels with independent transmit pulses;

controlling a frequency of the controllable oscillators independently so that at least two of the controllable oscillators oscillate in different frequencies; and

transforming the transmit pulses calculated for a predefined target magnetization with the magnetic resonance system to a complex transmit pulse amplitude component and a frequency-modulating component, the frequency-modulating component being taken into account in controlling the controllable oscillators.

2. The method as claimed in claim 1 , wherein at least one of the controllable oscillators is controlled such that the frequency during a transmit pulse changes over time.

3. The method as claimed in claim 2 , wherein the transmit antennae irradiate different spatial regions, and

wherein a time-dependency of the frequency results from a time-dependency of a current gradient vector multiplied by a vector marking a mean value of the respective spatial region to be irradiated.

4. The method as claimed in claim 1 , wherein the transmit antennae irradiate different spatial regions, and

wherein a time-dependency of the frequency results from a time-dependency of a current gradient vector multiplied by a vector marking a mean value of the respective spatial region to be irradiated.

5. A control system for activating a magnetic resonance system having a plurality of independent high-frequency transmit channels with a respectively assigned transmit antenna, the control system comprising:

a controllable oscillator for each high-frequency transmit channel of the plurality of independent high-frequency transmit channels; and

a processor configured to:

activate individual high-frequency transmit channels of the plurality of independent high-frequency transmit channels with independent transmit pulses;

activate frequencies of the controllable oscillators independently, so that at least two of the controllable oscillators oscillate in different frequencies; and

transform the transmit pulses into a complex transmit pulse amplitude component and a frequency-modulating component, the frequency-modulating component controlling the frequencies of the controllable oscillators.

6. The control system as claimed in claim 5 , wherein the processor is further configured to activate the frequency of at least one of the controllable oscillators as a function of time during a pulse.

7. A magnetic resonance tomography system having a plurality of independent high-frequency transmit channels with a respectively assigned transmit antenna, each high-frequency transmit channel of the plurality of independent high-frequency transmit channels having a controllable oscillator, the magnetic resonance tomography system comprising:

a control system configured to:

activate individual high-frequency transmit channels of the plurality of independent high-frequency transmit channels with independent transmit pulses;

control frequencies of the controllable oscillators independently, so that at least two of the controllable oscillators oscillate in different frequencies; and

transform the transmit pulses calculated for a predefined target magnetization with the magnetic resonance system to a complex transmit pulse amplitude component and a frequency-modulating component, the frequency-modulating component being taken into account in controlling the controllable oscillators.

8. A magnetic resonance system comprising:

different high-frequency transmit channels configured to emit a multichannel pulse train having a plurality of individual HF-pulse trains, the plurality of individual HF pulse trains containing information about a complex transmit amplitude and information about an oscillator frequency to be used for the different high-frequency transmit channels.

9. In a non-transitory computer-readable storage medium that stores instructions executable by a processor of a programmable control system of a medical imaging unit to activate a magnetic resonance system having a transmit antenna arrangement, the transmit antenna arrangement comprising a plurality of independent high-frequency transmit channels with a respectively assigned transmit antenna, each high-frequency transmit channel of the plurality of independent high-frequency transmit channels having a controllable oscillator, the instructions comprising:

activating individual high-frequency transmit channels of the plurality of independent high-frequency transmit channels with independent transmit pulses;

controlling a frequency of the controllable oscillators independently so that at least two of the controllable oscillators oscillate in different frequencies, and

transforming transmit pulses calculated for a predefined target magnetization with the magnetic resonance system to a complex transmit pulse amplitude component and a frequency-modulating component, the frequency-modulating component being taken into account in activation of the controllable oscillators.

10. The method as claimed in claim 9 , wherein at least one of the controllable oscillators is controlled such that the frequency during a transmit pulse changes over time.