Method and device for monitoring a radio-frequency transmitter device in a magnetic resonance tomography system

A radio-frequency transmitter device for a magnetic resonance tomography apparatus, comprising:

• a transmitter antenna system comprising a plurality of transmitter channels;
• and
• a monitoring device that monitors transmission by said transmitter antenna system during acquisition of magnetic resonance data, said monitoring device comprising a processor configured to open at said transmission antenna system prior to introducing an examination subject into the magnetic resonance apparatus, to determine a reference scattering parameter matrix of the transmitter antenna system in an unloaded state, and to operate said transmission antenna system after introduction of an examination subject into the magnetic resonance apparatus, to determine a subject-specific scattering parameter matrix of the transmitter antenna system in a state loaded by the examination subject, and to automatically determine time-dependent transmitter amplitude vectors for each of said transmitter channels that represent radio-frequency voltage amplitudes in the respective transmitter channels, and to use said subject-specific scattering parameter matrix and said reference scattering parameter matrix and said transmitter amplitude vectors to determine radio-frequency power values that are absorbed by the examination subject at respective transmit times, and to form a plurality of monitoring values based on the determined radio-frequency power values, and to limit operation of said radio-frequency transmitter device during the acquisition of said magnetic resonance data when one of said monitoring values equals or exceeds a predetermined boundary monitoring value.

A radio-frequency monitoring device for monitoring a radio-frequency transmitter device in a magnetic resonance tomography apparatus, during acquisition of magnetic resonance data, involving the transmitter device, in the magnetic resonance system, said radio-frequency transmitter device comprising a transmitter antenna system comprising a plurality of transmitter channels, said monitoring device comprising:

• a measurement device that, prior to introducing an examination subject into the magnetic resonance apparatus, determines a reference scattering parameter matrix of the transmitter antenna system in an unloaded state;
• said measurement device, after introduction of an examination subject into the magnetic resonance apparatus, determining a subject-specific scattering parameter matrix of the transmitter antenna system in a state loaded by the examination subject;
• a processor that automatically determines time-dependent transmitter amplitude vectors for each of said transmitter channels that represent radio-frequency voltage amplitudes in the respective transmitter channels;
• said processor, using said subject-specific scattering parameter matrix and said reference scattering parameter matrix and said transmitter amplitude vectors, determining radio-frequency power values that are absorbed by the examination subject at respective transmit times;
• said processor forming a plurality of monitoring values based on the determined radio-frequency power values;
• and
• said processor limiting operation of said radio-frequency transmitter device during the acquisition of said magnetic resonance data when one of said monitoring values equals or exceeds a predetermined boundary monitoring value.

A magnetic resonance tomography system comprising:

• a magnetic resonance data acquisition unit;
• a radio-frequency transmitter device in said magnetic resonance data acquisition unit, comprising a transmitter antenna system comprising a plurality of transmitter channels;
• and
• a monitoring device that monitors transmission by said transmitter antenna system during acquisition of magnetic resonance data, said monitoring device comprising a processor configured to open at said transmission antenna system prior to introducing an examination subject into the magnetic resonance data acquisition unit, to determine a reference scattering parameter matrix of the transmitter antenna system in an unloaded state, and to operate said transmission antenna system after introduction of an examination subject into the magnetic resonance data acquisition unit, to determine a subject-specific scattering parameter matrix of the transmitter antenna system in a state loaded by the examination subject, and to automatically determine time-dependent transmitter amplitude vectors for each of said transmitter channels that represent radio-frequency voltage amplitudes in the respective transmitter channels, and to use said subject-specific scattering parameter matrix and said reference scattering parameter matrix and said transmitter amplitude vectors to determine radio-frequency power values that are absorbed by the examination subject at respective transmit times, and to form a plurality of monitoring values based on the determined radio-frequency power values, and to limit operation of said radio-frequency transmitter device during the acquisition of said magnetic resonance data when one of said monitoring values equals or exceeds a predetermined boundary monitoring value.