Abstract: An arrangement for radiation of a radio-frequency field into an examination subject has a local coil unit with a housing. An insulating dielectric material is embodied at least at one part of the housing in order to passively compensate an inhomogeneity of the B1 field that occurs in the examination subject. An adjustment arrangement allows for fixed but detachable provision of the insulating dielectric material at the housing part.

Abstract: A detector unit for arrangement in a field generating unit of a magnetic resonance device has an RF transmission/reception system for transmitting RF pulses into, or receiving magnetic resonance signals from, an examination volume of the field generation unit. The RF transmission/reception system surrounds a patient tunnel at a radial distance from a tunnel axis thereof, and is divided into two sub-systems located at a distance from each other along the direction of the tunnel axis, so as to form a substantially annular cavity or interstice therebetween.

Abstract: In an MR imaging method and apparatus which MR images with improved signal intensity, improved signal-noise ratio, improved contrast and improved image homogeneity can be acquired, the polarization state of the magnetic field of the RF pulses radiated into the measurement subject and of the resonance signals emitted by the measurement subject are distorted by the interaction with electrically-active materials of the measurement subject. In the transmission branch of the RF system the RF pulses emitted by a transmission coil are pre-distorted with regard to their polarization state. The sensitivity of the reception branch is optimized such that it is capable of detecting resonance signals independent of their polarization state.

Abstract: In an MR imaging method and apparatus which MR images with improved signal intensity, improved signal-noise ratio, improved contrast and improved image homogeneity can be acquired, the polarization state of the magnetic field of the RF pulses radiated into the measurement subject and of the resonance signals emitted by the measurement subject are distorted by the interaction with electrically-active materials of the measurement subject. In the transmission branch of the RF system the RF pulses emitted by a transmission coil are pre-distorted with regard to their polarization state. The sensitivity of the reception branch is optimized such that it is capable of detecting resonance signals independent of their polarization state.

Abstract: A dielectric element is formed of a dielectric material exhibiting a magnetic resonance relaxation time, with a relaxation agent incorporated in the dielectric material that reduces the relaxation time of the dielectric material. The dielectric element is adapted for placement on a subject while magnetic resonance data are acquired from the subject, and locally influences the B1 field distribution in the subject during the acquisition of magnetic resonance data.

Abstract: A transmission antenna for magnetic resonance applications has a birdcage-like structure that includes antenna rods proceeding between first and second terminating elements respectively located at opposite ends of the antenna rods. A detuning circuit is located at the second terminating element. Either the second terminating element is formed as a completely continuous short circuit ring and the detuning circuit is arranged between the ends of the antenna rods and the second terminating element, or the second terminating element has a number of ferrule segments, between which the detuning circuit is arranged. The second terminating element has a larger cross-section than a the first terminating element.

Abstract: A detection unit is disclosed for arrangement in the main magnet of an MR device, which has both an RF transceiver system and a PET detector. In at least one embodiment the RF transceiver system is divided into two parts and the two parts are arranged upstream and downstream of the PET detector in the longitudinal direction of the patient tunnel. The RF transceiver system and PET detector are applied to the same image volume. In at least one other embodiment, an MR device is equipped with the detection unit, and in at least one other embodiment, a method operates the detection unit.

Abstract: A dielectric element is formed of a dielectric material exhibiting a magnetic resonance relaxation time, with a relaxation agent incorporated in the dielectric material that reduces the relaxation time of the dielectric material. The dielectric element is adapted for placement on a subject while magnetic resonance data are acquired from the subject, and locally influences the B1 field distribution in the subject during the acquisition of magnetic resonance data.

Abstract: An arrangement for radiation of a radio-frequency field into an examination subject has a local coil unit with a housing. An insulating dielectric material is embodied at least at one part of the housing in order to passively compensate an inhomogeneity of the B1 field that occurs in the examination subject. An adjustment arrangement allows for fixed but detachable provision of the insulating dielectric material at the housing part.

Abstract: A device for superposed magnetic resonance tomography and positron emission tomography imaging is disclosed. In at least one embodiment, the device includes a magnetic resonance tomography magnet, which defines a longitudinal axis; a magnetic resonance tomography gradient coil, arranged radially within the magnetic resonance tomography magnet; a magnetic resonance tomography RF coil, arranged radially within the magnetic resonance tomography gradient coil; and a multiplicity of positron emission tomography detection units, arranged in pairs lying opposite to one another about the longitudinal axis. In at least one embodiment, the many positron emission tomography detection units are arranged radially within the magnetic resonance tomography gradient coil and are arranged along the longitudinal axis next to the magnetic resonance tomography RF coil.

Abstract: An RF antenna arrangement of a combined MR/PET system is disclosed. In at least one embodiment, the RF antenna arrangement includes a first part installed in the examination tunnel in a fashion fixed to the system such that it is arranged underneath the couch board when the latter is introduced, and a second part, which can be placed onto the couch board and be introduced into and withdrawn from the examination tunnel together with the couch board. In at least one embodiment, the second part is of dimensionally stable design and has a clear cross section that is adapted to the object to be examined. Consequently, the time outlay for applying the RF antenna is reduced, and the fixed position of the RF antenna enables a correction of the attenuation of gamma rays. Furthermore, a number of second parts having various diameters can be provided.

Abstract: Detection unit is disclosed for arrangement inside a cylindrical patient receptacle of a magnetic resonance apparatus. In at least one embodiment, the detection unit includes an annular PET detector arrangement with PET detector blocks, and a radiofrequency coil arrangement, arranged coaxially inside the PET detector arrangement and including longitudinal conductors, the longitudinal conductors being guided at least in sections along interspaces between mutually spaced apart detector blocks.

Abstract: A dielectric element is formed of a dielectric material exhibiting a magnetic resonance relaxation time, with a relaxation agent incorporated in the dielectric material that reduces the relaxation time of the dielectric material. The dielectric element is adapted for placement on a subject while magnetic resonance data are acquired from the subject, and locally influences the B1 field distribution in the subject during the acquisition of magnetic resonance data.

Abstract: A magnetic resonance apparatus has an RF antenna unit, a gradient coil unit and an RF shield, the conductor structures of which are independent of one another. The RF shield is arranged between the RF antenna unit and the gradient coil unit, a first RF field return volume is arranged between RF the antenna unit (1, 29, 55A, and the gradient coil unit, the RF field return volume closes RF magnetic field lines of the RF antenna unit and is bordered by the RF shield on the side of the gradient coil unit. The conductor structure of the gradient coil unit occupies a first region. A second conductor-free region is within the first region, on the side facing the RF antenna unit, between a primary gradient coil unit and a secondary shim gradient coil unit of the gradient coil unit. The second conductor-free region is at least partially surrounded by the conductor structure of the gradient coil unit and is fashioned as a second RF field return volume in connection with the first RF field return volume.

Abstract: In a method and magnetic resonance system for homogenization of the B1 field for a magnetic resonance data acquisition with a number of iteration steps. An iteration step includes the following sub-steps: Measurement data are acquired that represent a B1 field distribution in at least one part of the examination volume of the magnetic resonance system. A B1 homogeneity analysis based on the acquired measurement data is automatically implemented. A specific homogenization action is automatically selected from among a number of possible homogenization actions based on the B1 homogeneity analysis, or the iterative homogenization method is ended if the diagnosed homogeneity is sufficient for an intended magnetic resonance measurement. The selected homogenization action is implemented.

Abstract: A magnetic resonance system has a primary RF transmitting antenna and at least one secondary RF transmitting antenna. Both antennas generate RF excitation fields in an examination volume. At least one of the primary and secondary transmitting antennas has a control element connected thereto, which allows an amplitude ratio and/or a phase difference of the respective excitation currents in the antennas to be set by a control and evaluation device. The control and evaluation device causes the excitation current in the secondary transmitting antenna to have a smaller amplitude than the excitation current in the primary transmitting antenna, so that the excitation field generated by the secondary transmitting antenna has a smaller spatial extent in the examination volume than the excitation field generated by the primary transmitting antenna.

Abstract: A magnetic resonance apparatus has an RF antenna unit, a gradient coil unit and an RF shield, the conductor structures of which are independent of one another. The RF shield is arranged between the RF antenna unit and the gradient coil unit, a first RF field return volume is arranged between RF the antenna unit (1, 29, 55A, and the gradient coil unit, the RF field return volume closes RF magnetic field lines of the RF antenna unit and is bordered by the RF shield on the side of the gradient coil unit. The conductor structure of the gradient coil unit occupies a first region. A second conductor-free region is within the first region, on the side facing the RF antenna unit, between a primary gradient coil unit and a secondary shim gradient coil unit of the gradient coil unit. The second conductor-free region is at least partially surrounded by the conductor structure of the gradient coil unit and is fashioned as a second RF field return volume in connection with the first RF field return volume.

Abstract: A local coil unit for a magnetic resonance apparatus, which radiates a radio-frequency field into an examination subject, has a housing and at least a part of the housing is formed of an insulating dielectric material that passively compensates for an inhomogeneity in the high-frequency field in the subject. The material has a relative dielectric value ?r of greater than 50, preferably greater than 100, and a dielectric loss factor tan ? of less than 2.5×10?2, preferably less than 1×10?3. In the dielectric material displacement currents are generated which create an additional magnetic field that compensates for the minima in the B1 field as a result of the eddy currents arising in the patient due to the radio-frequency radiation.

Abstract: A dielectric element is formed of a dielectric material exhibiting a magnetic resonance relaxation time, with a relaxation agent incorporated in the dielectric material that reduces the relaxation time of the dielectric material. The dielectric element is adapted for placement on a subject while magnetic resonance data are acquired from the subject, and locally influences the B1 field distribution in the subject during the acquisition of magnetic resonance data.

Abstract: In a method and magnetic resonance system for homogenization of the B1 field for a magnetic resonance data acquisition with a number of iteration steps. An iteration step includes the following sub-steps: Measurement data are acquired that represent a B1 field distribution in at least one part of the examination volume of the magnetic resonance system. A B1 homogeneity analysis based on the acquired measurement data is automatically implemented. A specific homogenization action is automatically selected from among a number of possible homogenization actions based on the B1 homogeneity analysis, or the iterative homogenization method is ended if the diagnosed homogeneity is sufficient for an intended magnetic resonance measurement. The selected homogenization action is implemented.