Abstract: A transmission path (13) for transmitting high frequency (RF) signals is disclosed, which comprises a plurality of lead segments (20, 21, 22) which are coupled to one another on one end by a capacitive coupling element (30) and on the other end by an inductive coupling element (31) and which each have an effective length of approximately ?i/4, wherein ?i is the wavelength of a differential mode signal to be transmitted over the path (13). By providing these element (30, 31) in the form of distributed elements which electrically extend over at least a part of adjacent lead segments (20, 21; 21, 22) a very thin transmission path (13) can be realized, which is especially suitable for use with invasive catheters. Furthermore, this path (13) can be guided through RF fields of a magnetic resonance (MR) imaging system because common mode resonances are effectively suppressed.

Abstract: The present invention relates to a magnetic resonance imaging system (1) comprising a plurality of RF coils (4) forming a multi-coil array and furthermore to a magnetic resonance imaging method for such a system. In order to provide an MR imaging system and method in which a desired excitation pattern is achieved in a simple way, it is suggested to utilize an analytical procedure how to combine the single coil elements to obtain the most homogeneous B1 excitation possible with a given coil array. In other words, the homogeneity of the B1 field is improved in a very simple way. The sensitivity of each RF coil (4) of the coil array is scaled or weighted by a complex factor, i.e. phase and amplitude of each coil drive signal is adjusted accordingly. These complex factors are determined analytically utilizing the sensitivities S(8) of the coil elements (4) and the desired excitation pattern P (IO, 11). The invention allows an optimized control of the field distribution (RF shimming) for arbitrary RF coil arrays.

Abstract: Methods and circuit arrangements for operating a multi-channel transmit/receive antenna device or arrangement, especially for use in a magnetic resonance imaging (MRI) system, are disclosed by which RF amplifiers can be used to their full peak power capability without running the risk that the RF amplifier is damaged due to excessive reflected power at its output. Furthermore by evaluating certain forward and reflected power signals patient safety is achieved with respect to monitoring the limits of the specific absorption rate.

Abstract: A radio frequency coil system (34) used in the context of electric properties tomography (EPT, electrical impedance tomography, EIT, applied potential tomography, APT) generates radio frequency excitation pulses in an examination region (14). The radio frequency coil system (34) includes N coil elements (38) which generate magnetic (H) and electric (E) fields. A weight setting device (54) sets weight factors for input signals for the coil elements (38). A transmitting system (52) creates RF pulses, at least two sets of each with differently weighted input signals, and transmits the at least two sets of RF pulses to the coil elements (38) such that each of the transmitted RF pulse sets generates shifted electric fields (110, 112) having a shifted zero crossing point (120, 122) from each other. An image processor (62) computes electric permittivity maps from resonance induced by the at least two sets of RF pulses with different weighting.

Abstract: An electrically conductive link (connection lead) or transmission line (13) comprising at least one transformer (41, 42; 83) for coupling at least two lead segments (51, 52; 81, 82) of the line (13) and for providing safety of the line when guided through a RF field is disclosed. Furthermore, an electrical device (10) in combination with such a conductive link or transmission line (13) and a method for manufacturing thereof are disclosed. These lines are especially provided for use with a magnetic resonance (MR) imaging system and for connecting an electrical device (10), especially a catheter or another invasive device for the examination of a human body, to a connection unit (12) such as, for example, a power supply or control unit outside the examination zone (1) without imposing the risk of disturbances and/or destruction of the electrical device and/or the connection unit and of burning a patient (P) by a heating of the line when guided through RF fields.

Abstract: A magnetic resonance imaging system includes a coupling compensation processor (70) for compensating induced magnetic coupling between n individual coil segments (38) of a coil arrangement (36). An adjusted signal determining device (74) determines an adjusted input signal for each of the n individual coil segments of the coil arrangement (36). A transmitting system (54) creates RF pulses in accordance with the determined adjusted input signals and transmits the RF pulses to corresponding coil segments such that the transmitted RF pulses compensate for coupling between the coil segments (38) in the digital domain.

Abstract: Methods and circuit arrangements for operating multi-channel transmit/receive antenna devices or arrangements especially for use in magnetic resonance imaging (MRI) systems are disclosed, by which a fully independent control of complete multi-channel RF transmit and receive chains can be conducted in a flexible way and new options like RF shimming, transmit sensitivity encoding (TransmitSENSE), RF encoding, determination of S- or Z-matrix prior to spin echo measurements, calibration, SAR (specific absorption rate) reduction etc. can be utilized or improved.

Abstract: Methods and circuit arrangements for operating a multi-channel transmit/receive antenna device or arrangement, comprising a power monitoring unit, especially for use in a magnetic resonance imaging (MRI) system are disclosed. These methods and circuit arrangements are especially provided for ensuring that a specific absorption rate of a patient is not exceeded in the case in which antenna devices or arrangements are used which comprise a plurality of coils and/or coil segments which are independently supplied with RF transmit signals with different amplitudes and/or phases and/or waveforms and/or power levels. A maximum power level is set for at least one of the transmit channels. An alarm state is activated if the supplied power level or the reflected power for that channel exceeds the maximum power level. A maximum sum power level is set for a plurality of transmit channels.

Abstract: The arrangement 10 according to the invention is suited for transmitting an informative signal S1, generated by suitable signal generator 1 at a first electrical site 7a to a second electrical site 7b. The first electrical site 7a is electrically connected to the second electrical site 7b by means of a capacitively coupled transmission line 5a, 5b. In order to enable such capacitively coupled transmission line distributed or lumped capacitors 4a, 4b, 4c, 4d can be used. The arrangement is connectable to an accessory device 6, which may comprise a spectrometer, a further signal generator, tuning means, etc. The further signal S2 is conceived to be generated by the accessory device 6 and to be transported via the capacitively coupled transmission line 5a, 5b in a direction from the second electrical site 7b to the first electrical site 7a. The further signal S2 can be used for feeding the amplifier 2, or for carrying the signal S1.

Abstract: A magnetic resonance imaging system is provided with one or more electrical accessory devices, for example, catheters (10) or RF surface coils (6), which are intended for use during the examination of an object, as well as with a connection lead (13) which is arranged so as to extend through an examination zone (1) of the magnetic resonance imaging apparatus, which zone can be exposed to an RF field, and to connect the accessory device to a connection unit (12). In order to avoid heating of the connection lead (13) due to common mode currents induced in the connection lead by the RF field, which currents could lead to injury of a patient or damage of the accessory device or the connection unit (12), the connection lead (13) comprises at least two lead segment (131, 132, . . .