U.S. Philips Corporation

Peter K Roschmann

Roland Proksa

Volker Rasche

Howard E Simon

Noel J Van Den Berg

A MR method determines nuclear magnetic resonance distribution in an examination area and the position of at least one microcoil which is located in the examination area in or on an examination object. In the presence of a homogeneous stationary magnetic field acting on the examination area, sequences are carried out in which at least one high-frequency pulse acting on the examination area is generated, and after the high-frequency pulse an MR signal induced in the microcoil is detected under the influence of a gradient magnetic field that acts on the examination area. Then the position of the microcoil in the gradient direction defined by the gradient field is derived from the detected MR signal. The aforementioned sequences are repeated for another gradient direction, and MR signals are detected by a further receiving coil arrangement to determine the nuclear distribution. Without additional measuring sequences, a position is detected in a manner that the sequences are continuously repeated while the gradient direction is varied, and that the position of the microcoil and the nuclear magnetic distribution are derived from MR signals detected simultaneously by the microcoil and the receiving coil arrangement.

MR method and MR device for implementing the method

A dielectric resonator is used in a magnetic resonance examination apparatus comprising a magnet system (31, 32) for generating a steady magnetic field in an examination space (2), a transmitter device (12, 13, 18, 28) for generating an RF field to be superposed on the steady magnetic field in an object (30) to be examined, a device for producing a resonance step-up of the RF field active in the object (30) to be examined, and a device for detecting magnetic resonance signals generated in the object (30) to be examined. Stronger B.sub.1 fields are created by at least one dielectric resonator (1, 5, 10, 16, 17, 20, 21) which neighbors the object (24) to be examined and which comprises a dielectric having a relative dielectric constant .epsilon..sub.r &gt;20, the dimensions of the resonator being chosen so that therein, using a neighboring transmitter device, (12, 13, 18) there can be generated at least one resonant mode with a frequency which is in the vicinity of the Larmor frequencies to be detected of the nuclei to be excited in the object (24) to be examined, for example, protons.

Magnetic resonance examination apparatus using a dielectric resonator

The invention relates to a circuit arrangement for generating rf signals for MR examinations, comprising a read-only memory in which a signal is stored in the form of a series of data words, an address generator for reading data words from the read-only memory with a clock frequency, and a digital-to-analog converter which succeeds the read-only memory. In order to reduce the required storage capacity, a sinusoidal signal in the form of a series of data words is stored in the memory.

Circuit arrangement for generating rf signals for MR examinations

A surface coil for magnetic resonance examinations which serves to generate or receive high-frequency magnetic fields. The loop forming the surface coil is divided into at least two, preferably equal loop sections. At least the loop section to be coupled to the high-frequency receiver or high-frequency generator comprises two inner conductors which are accommodated in an outer conductor arrangement and one part of which extends (at the center of this loop section) to the high-frequency generator or high-frequency receiver, its other part being connected to the other loop section. A capacitive coupling is obtained between the loop sections so that a high-frequency alternating current can flow in the loop formed by the loop sections, said current producing a high-frequency magnetic field.

Surface coil for high-frequency magnetic fields for magnetic resonance

The invention relates to a high-frequency coil system for a magnetic resonance imaging apparatus, which coil system is formed by one or more systems of conductors. The system of conductors includes an outer conductor in which there is arranged a dielectric. Two inner conductors are arranged, in the dielectric. At least one of the inner conductors is displaceable and they are interconnected at least for high-frequency. The system of conductors is tuned or readjusted by displacement of one of the inner conductors.

High-frequency coil system for a magnetic resonance imaging apparatus

The invention relates to a coil arrangement for nuclear magnetic resonance examinations. The coil arrangement has conductors surrounded by a cylindrical shield. It is achieved by additional shields enclosing the openings of the coil arrangement for partly or entirely introducing the patient that the magnetic field in the longitudinal direction of the coil is highly constant.

Coil arrangement for nuclear magnetic resonance examinations

An R.F. coil system is described for generating and/or receiving at least substantially homogeneous alternating magnetic fields, notably in nuclear magnetic resonance apparatus. The system is arranged about an essentially cylindrical examination space and comprises at least four conductor segments which are oriented essentially parallel to the longitudinal central axis of the examination space. The conductor segments are arranged about the circumference of the examination space symmetrically with respect to at least one plane which extends through the longitudinal central axis and are interconnected so as to form a closed loop. The conductor segments which receive a current of the same sense with respect to the longitudinal axis, are interconnected at neighboring ends by conductor elements which are oriented essentially in the circumferential direction of the examination space so as to form conductor groups. The conductor groups are, in turn, interconnected by connection leads which are connected to the conductor elements. The length (LO) of the connection leads are chosen so that an amplitude maximum of the R.F. currents is formed at the center of each conductor segment while at least one amplitude minimum of the R.F. currents is present on each connection lead.

R.F. coil system for generating and/or receiving alternating magnetic

The invention relates to a drive mechanism for adjusting an element by means of which the resonance frequency in an NMR-apparatus can be varied. The mechanism comprises a coil which is exposed to the main magnetic field off the NMR-apparatus. The coil is connected to a current-pulse supply and is deflected out of its rest position by the current pulses. The reciprocating movement of the coil is converted by a stepping mechanism into a stepwise rotary or translational movement of the adjusting element which tunes or matches the RF coil to the RF generator.

NMR-apparatus with an adjustable RF tuning circuit

A method is described for adjusting the temperature coefficient of the ferrimagnetic resonant frequency in gallium or aluminium substituted YIG disc resonators. At the compensation temperature, T.sub.o, the temperature coefficient of the resonant frequency, f.sub.r, in a given frequency range is approximately zero. Where this range lies, depends, inter alia, on the substitution value. By annealing the discs, T.sub.o can be moved into the desired temperature range. When the manufactured disc has a compensation temperature above the desired temperature range, annealing must be carried out at approximately 850.degree. to 1400.degree. C. When the manufactured disc has a compensation temperature below the desired temperature range, annealing is performed at approximately 400.degree. to 850.degree. C.

Method of manufacturing a disc resonator

A magnet system for compensating the frequency difference between the oscillator frequency f.sub.o of a YIG oscillator and the central filter frequency f.sub.mi of a YIG filter to be independent of the oscillator frequency in which two pole-pieces are provided having opposing surfaces, one which has a raised portion, and one of which has a plate of magnetic material having a saturation magnetization smaller than the smallest field strength desired. The raised surface portion of the pole-piece has a height at which the frequency f.sub.o -f.sub.mi is independent of f.sub.o.

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Hamburg, Germany

Peter K Roschmann