Abstract:
An antenna for a magnetic resonance apparatus has an antenna conductor that can be adapted to examination regions of different sizes, with one region of the antenna conductor divided into conductor sections. The conductor sections are connected to one another via capacitive elements, with the conductor sections and the capacitive elements connected alternating in series. The conductor sections are connectable to the remaining antenna conductor via releasable electrical connections.
Abstract:
A radio-frequency antenna for a magnetic resonance apparatus has an antenna conductor in the form of a ribbon conductor. The ribbon antenna conductor has interconnects arranged side-by-side. Neighboring interconnects are connected to one another via bridges that conduct radio-frequency currents.
Abstract:
A resonator for use in a magnetic resonance imaging apparatus for transmitting and receiving high frequency signals is formed by a combination of two antenna sub-systems, which generate respective magnetic fields which are perpendicular to each other, with the currents in the sub-system being phase-shifted by 90.degree. relative to each other, and each sub-system includes a capacitance which defines the resonant frequency. Each of the sub-systems forms a current loop, the current loops containing a common current network and a common base plate, which serves as a return path for both current loops. The junctions of the current network are connected via the resonant capacitances to the base plate, which consists of electrically conductive material. A circularly polarizing resonator is achieved for the transversal, fundamental field of the imaging apparatus, with the resonator also being capable of use as a surface resonator if the spacing between the current network and the base plate is small.
Abstract:
A head antenna for nuclear magnetic resonance examinations has an examination chamber, formed so as to accept the head, and an antenna conductor, formed as a frame antenna, that surrounds the examination chamber in an examination position. The antenna conductor is divided into two curved sub-conductors that respectively have electrical contacts at their ends for detachably electrically connecting the sub-contractors together. The first sub-conductor arrangement is fastened to a holding part which is arranged outside the examination chamber and which is made of an electrically non-conductive, non-ferromagnetic material. For fastening the holding part to a patient support, a first fastening assembly is arranged on the holding part. For fixing the position of the head, a second fastening assembly is arranged on the holding part.
Abstract:
A radio frequency antenna for a nuclear magnetic resonance tomography apparatus has interior conductors which form a transmission line resonator with at least one shortening capacitor. The transmission line resonator can resonate at a plurality of resonator frequencies, and a trap circuit is provided for decoupling the interior conductors from the other conductors. The antenna can be operated at a number of different resonate frequencies, for example, at frequency f.sub.1 =170 MHz for protons (hydrogen) and F.sub.2 =69 MHz for phosphorous.
Abstract:
A method and apparatus for measuring electrical or magnetic fields, such as high-frequency alternating fields in a nuclear magnetic resonance tomography device, convert a test signal into a corresponding ultrasound signal, and transmit the ultrasound signal to a receiver, where the received signal is converted back into an electrical signal. The transmission path contains no metallic components and thus does not cause any disturbance in the field being measured.
Abstract:
An antenna structure for exciting a substantially homogeneous magnetic RF field and/or for receiving RF signals in a nuclear magnetic resonance tomography apparatus includes a hollow cylindrical conductor sheath which is substantially transmissive at low frequencies for gradient magnetic fields, a number of conductor units within the conductor sheath, each conductor unit including at least one conductor element, and RF reflector disposed at the end faces of the antenna structure and an external energy feed or reception device. In this antenna structure, the current drop which increasingly occurs toward the end faces of the antenna structure is largely compensatable by shaping the electrically conductive cross-section of the conductor units so as to decrease symmetrically from an axial center of the antenna structure moving toward the end faces of the structure. The conductor units thus have a largest cross-section at a center of the antenna structure, and a smallest cross-section at the end faces.
Abstract:
A heat radiation shield has an electrically insulating support on which a mosaic of electrically conductive elementary layers is arranged on at least one side.
Abstract:
A transmission/reception arrangement for a diagnostic magnetic resonance apparatus has an antenna, a matching and tuning circuit and a signal transmission line. The antenna together with the matching and tuning circuit is fashioned for exciting and/or receiving proton magnetic resonance signals having a first frequency. A reactance circuit is connected between the matching and tuning circuit and the signal transmission line. The reactance circuit is fashioned such that a reflection factor to the second transmission line substantially disappears at a second frequency. The apparatus is thus provided with the capability of conducting examinations using hyperpolarized gases, while still preserving the capability of conducting imaging with conventional proton (.sup.1 H) signals without modification.
Abstract:
For operating the radio-frequency antenna of a nuclear magnetic resonance tomography apparatus, the antenna being connected to an asymmetrical line, a sheath wave trap is provided between the antenna and the line, with the inductor of the sheath wave trap being a toroid. A low-scatter sheath wave trap is obtained in this manner, particularly suitable for circularly polarized resonators. The trap suppresses difference currents caused by asymmetries, and thus simultaneously functions as a balanced-to-unbalanced transformer (balun).