Abstract: Magnetic resonance apparatus includes an RF measuring coil system (12) for detection of magnetic resonance signals to be generated in an object to be examined, which measuring coil system includes an at least one-dimensional array (33) of contiguous surface coils (33a, . . . 33f) and means for decoupling the surface coils from one another, and a signal processing circuit (15) which is connected to the surface coils and includes a number of processing channels (49a, 49b, 49c) for processing RF signals generated by the surface coils. Between the surface coils (33a, . . . ,) and the signal processing circuit (15) there is arranged a combination circuit (13) which includes at least two adder units (45a, 45b, 45c), each adder unit having at least two inputs and one output (47a, 47b, 47c) and being arranged to add signals, presented to its input, with a predetermined mutual phase shift, and to make the signal resulting from the addition available on the output. Each input of the adder unit (45a, . . .

Abstract: A quadrature coil system which includes the following elements. (1) First and second electric main conductors which are situated at a distance from one another in a first plane and a second plane, respectively, and each of which is formed as a loop with an opening, the main conductors having mainly the same orientation. (2) First and second connection conductors, each of which constitutes an electric connection between the free ends of the first and second main conductors, which free ends are situated to corresponding sides of the opening. (3) An electric connection device which is connected to the conductors so that first and second sets of turns are formed which are suitable to generate and/or receive first and second magnetic fields, respectively, which are mutually orthogonally directed.

Abstract: In magnetic resonance apparatus in a magnet system (1) for generating a steady magnetic field, a coil system (3) for generating gradient fields, and at least one RF coil (9) which is tuned to a predetermined frequency and connected to first and second input terminals (53, 55) of an input amplifier circuit (43) of a receiving device (13) for RF order to enable simulation of the loading of the RF coil (9) by a patient during installation and testing of the operation of the apparatus without utilizing a load phantom, the circuit formed by the RF coil (9) and the input amplifier circuit (43) comprises a load network (61 ). In one embodiments first and second input terminals (53, 55) of the input amplifier circuit (43) are interconnected via the load network (61) which comprises a series connection of a switch (63) and a resistor (65).

Abstract: A phantom which simulates the electric load in a magnetic resonance apparatus includes a loop which can be inductively coupled to the RF coil of the MRI apparatus and which has a predetermined electric resistance. The phantom has a simple, rugged and light construction in that the loop includes a member having a shape that corresponds mainly to the shape of the RF coil and which is made of a solid material having a specific electric resistance and a thickness chosen so that the square resistance measured on a surface of the member is between predetermined limits. The member is preferably formed as a layer of an electric resistive material provided on an electrically insulating support having a suitably shaped surface.

Abstract: A magnetic resource apparatus includes a mainly cylindrical RF coil (9) having a longitudinal directed central axis (33) and symmetry plane (35) which contains the central axis and a reference plane (37). The reference plane extends perpendicularly to the symmetry plane and also contains the central axis. The coil (9) has a number of rod conductors (39) which extend, parallel to the central axis (33), across a mainly cylindrical surface, and loop conductors (41) which extend around the central axis near the ends of the rod conductors, the length of the rod conductors (39) situated near the symmetry plane (35) being greater than that of the rod conductors situated near the reference plane (37).

Abstract: Magnetic resonance apparatus includes a main magnet system (1) for generating a steady magnetic field, a magnet system (3) for generating gradient fields, an RF transmitter coil (9) and an RF receiver coil system (13) which includes first and second RF coil systems (47, 49) for detecting resonance signals generated in respective first and second regions of an object to be arranged on a supporting face (43), said regions being adjacently situated in a first direction (57), each of the first and second RF coil systems comprising at least a surface coil. The apparatus is intended notably for the examination of the spine of a patient arranged on the supporting face (43), the first region containing the thoracic segment of the spine (T-spine) and the second region containing the lumbar segment (L-spine).

Abstract: In a magnetic resonance imaging apparatus comprising a surface coil, the circuit in which the surface coil is included is interrupted by means of a PIN diode in the non-active state of the coil. In addition to the PIN diode in the resonant circuit of the surface coil, PIN diodes are included in all supply leads of the resonant circuit. An advantage thereof consists in that no RF currents will flow in the supply leads and that the induction voltages generated in the surface coil in the active state of the transmitter coil of the device are actually rectified by the diodes and themselves form a blocking voltage for the PIN diodes included in the circuit. As a result, the biasing of the PIN diodes is increased, so that they remain blocked.

Abstract: In magnetic resonance imaging apparatus in which bird-cage coils are used in combination with other coils, a capacitance is bridged by means of an inductive element. Substantial detuning and hence adequate uncoupling of the bird-cage coil from the other (receiving) coil is achieved. Use can be made of the already present coaxial transmission line via which the RF energy is applied to the bird-cage coil. Connecting the core and the jacket of the coaxial transmission line there is arranged a diode switch so that the bird-cage coil circuit can be electronically detuned, thus enabling fast switching on and off of the bird-cage coil.

Abstract: In a magnetic resonance imaging apparatus an RF rotating field is generated by applying RF energy to two mutually perpendicular coil systems, a 1/4.lambda. lead being provided between the connection points of the systems. In that case the drive points and the detection signal output points are not the same, so that in the case of a change-over from transmission to reception, the connection between the transmitter and the receiver must be switched over. In the magnetic resonance imaging apparatus in accordance with the invention, a phase difference of 180.degree. is created between two junctions by means of 1/4.lambda. leads so that an intermediate junction will actually not carry a voltage. This point (for transmission and reception, two different points) is connected to ground by means of a PIN diode. A simplification enables connection of the transmitter as well as the receiver to the transmitter/receiver coil system via a single coaxial cable.

Abstract: For increasing the sensitivity of an MR apparatus when measuring comparatively high frequencies, the radio frequency excitation measurement coil (10, 30) is divided into two individual symmetrically drivable and readable coil halves (32, 34), respectively. The mutual connection of central connections of the coil halves can be realized by means of a balun (54) but for this purpose any other symmetrical form of coupling, for example using a strip-line transformer (70) or suitably dimensioned coaxial cables (60, 62) may alternatively be used.

Abstract: The transmitter comprises an array of electro-acoustic transducers (1), each of which is connected to an oscillator circuit (9) which has a start input (11). The start inputs (11) successively receive start signals from a start signal generator (13) which comprises a number of comparators (15), each of which comprises a first input (17) and a second input (19). The first inputs (17) are together connected to an output of a sawtooth generator (21), the second input (19) of each comparator (15) are connected to a direct voltage source (23). A direct voltage source (23) is provided for each start signal to be successively generated at least some of the direct voltage sources being controllable in common.

Abstract: A method of and a device for ultrasonic examination of an object by means of a row of N electroacoustic transducers. Each time a group of M transducers (M.gtoreq.N) thereof is selected by means of a switching member. These M transducers are first included in transmission networks, transmission signals then being applied to the converters; subsequently, they are included in receive networks, receive signals then being applied to a display device. The transmission and/or receive signals are multiplied by weighting factors between 0 and 1. The sum of the weighting factors during transmission may deviate from that during reception. During transmission and/or reception, at least two different combinations of weighting factors are used, the sum thereof being each time the same. The scanning line density can thus be substantially increased.