Abstract: The Magnetic Resonance Imaging (MRI) system includes a radio-frequency transmitter with multiple transmit channels. The MRI system includes an impedance matching network (320, 1402, 1502, 1602) for matching the radio-frequency transmitter to a remotely adjustable radio-frequency antenna (310, 1504, 1602) with multiple antenna elements (312, 314, 316, 318, 1404). The MRI system includes a processor (336) for controlling the MRI system. The execution of the instructions by the processor causes it to: measure (100, 200) a set of radio-frequency properties (352) of the radio-frequency antenna, calculate (102, 202) a matching network command (354) using the set of radio-frequency properties and a radio frequency model (366), and adjust (104, 204) the impedance matching network by sending the matching network command to the impedance matching network, thereby enabling automatic remote impedance matching.

Abstract: The invention relates to a method of characterizing the RF transmit chain of a magnetic resonance imaging scanner (1) using a local transmit/receive coil system (204; 210), comprising a first local NMR probe and a first local magnetic resonance coil, the first NMR probe being spatially located in immediate neighborhood to the first coil, a local receive coil system (206; 208), comprising a second local NMR probe and a second local magnetic resonance coil, the second NMR probe being spatially located in immediate neighborhood to the second coil, wherein the transmit chain comprises an external MR coil (9; 11; 12; 13), the method comprising: determining with the first magnetic resonance coil, a first MR signal phase evolution of the local RF transmit field generated by MR excitation of the first probe using the first magnetic resonance coil by measuring the RF response of the first probe upon said excitation, determining with the second magnetic resonance coil a second MR signal phase evolution of the local RF

Abstract: A multi-channel RF transmitter arrangement comprising a plurality of RF transmitter elements like RE antennas, antenna elements, coils or coil elements, for generating an RF field, especially for use in a magnetic resonance imaging system for exciting nuclear magnetic resonances, and a method for generating such an RF field wherein the RF transmitter elements are segmented in a plurality of segments at least along the direction of one or more of the main magnetic field of the MRI system, the z-direction or the longitudinal direction.

Abstract: A magnetic resonance imaging apparatus produces calculations of local specific energy absorption rates (SAR) by calculating an electrical permittivity map of a subject. The electric permittivity is calculated by measuring the components of the B1 field induced by a radio frequency (RF) coil (16). The Hx and Hy components of the B1 field can be directly measured. The Hz component is measured by encoding it into the phase of the resonance signals. Alternately, Hz can be calculated by solving Gauss's law for magnetism. Hz can also be estimated by finding the z component of the electric field. In the specific case of a birdcage RF coil, Hz can be estimated by using a model of the RF coil and a subject, a model of the RF coil alone, or setting Hz to a constant.

Abstract: The present invention relates to an apparatus (100) for determining at least one electromagnetic quantity characterizing an electromagnetic property of an object, in particular a human body, wherein said object contains magnetic particles. The apparatus (100) applying the known principle of Magnetic Particle Imaging (MPI) comprises selection means for generating a magnetic selection field (50) having the known field pattern showing a field free point (FFP), drive means for changing the position in space of the FFP by means of a magnetic drive field, receiving means for acquiring detection signals depending on the magnetization of the magnetic particles within a field of view (28) and a reconstruction unit (152) for reconstructing a particle distribution quantity depending on the detection signals.

Abstract: A multi-channel transmit/receive antenna device or arrangement for use in a magnetic resonance imaging (MRI) system includes a power monitoring unit. To ensure that a specific absorption rate of a patient is not exceeded, transmitted power levels and reflected power levels on channels for a plurality of coils and/or coil segments are monitored. Each coil/coil segment is supplied with RF transmit signals with different amplitudes and/or phases and/or waveforms and/or power levels.

Abstract: A common method of RF encoding assumes that the B1 field generated by the RF coils is linear, which is likely not the case in many situations. It is therefore desirable to have a method of operating an MR system to reconstruct an image of a subject, wherein the method is capable of also handling arbitrary B1 fields used for RF encoding. Accordingly, such an MR system employing one or more RF coils is disclosed herein. The method comprises obtaining transmit sensitivities and weighting factors for individual RF coils. Each RF coil is activated based on its respective weighting factor to apply RF excitation to a subject under examination in the MR system. MR signals—such as free induction decays (FID) signals or echo signals—generated from the subject in response to the RF excitation are received and processed based on the transmit sensitivities to generate an MR image or spectrum representative of the subject.

Abstract: A method and a monitoring device for performing an RF-safe MIT scan is disclosed in which it is prevented that an RF exposure, especially a specific absorption rate (SAR), imposed on an examination object, especially a patient, exceeds certain limit values during a magnetic induction tomography (MIT) scan. This is achieved on the one hand by an RF simulation method for simulating intended MIT operating parameters and calculating a resulting RF exposure of the object, and on the other hand by a monitoring device for monitoring the RF power which is applied to the object.

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: 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 arrangement (10) 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 generated by the accessory device (6) and 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 an amplifier (2), or for carrying the signal (S1).

Abstract: An electrically conductive link (connection lead) or transmission line (13) including 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. 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 multi-channel RF transmitter arrangement comprising a plurality of RF transmitter elements (e) like RF antennas, antenna elements, coils or coil elements, for generating an RF field, especially for use in a magnetic resonance imaging (MRI) system for exciting nuclear magnetic resonances (NMR), and a method for generating such an RF field is disclosed. The RF transmitter elements (e) are segmented in a plurality of segments (s1, s2, s3, . . . ) at least along the direction of the main magnetic field of the MRI system (or the z-direction or the longitudinal direction.

Abstract: A method and an RF transmit system for generating RF transmit signals for feeding an RF transmitter (14) in the form of, or comprising, one or more antenna device(s), coil(s), coil elements, or coil array(s) is disclosed. Furthermore, a multi-channel RF transmit system for feeding a plurality of such RF transmitters, especially for use as an RF excitation system in a magnetic resonance imaging (MRI) system for exciting nuclear magnetic resonances (NMR) is disclosed. A demand RF transmit signal is compared in the digital domain with an RF transmit signal and digitally corrected with respect to differences or errors between both by means of a complex predistorter (11), an adaption unit (17) and a look-up table unit (18).

Abstract: A multi-channel RF transmitter arrangement in the form of, or comprising, a plurality RF antennas, antenna elements, coils or coil elements (11 to 16), for generating an RF field, especially for use in a magnetic resonance imaging (MRI) system for exciting nuclear magnetic resonances (NMR), and a method for generating such an RF field is disclosed. Furthermore, a multi-channel RF transmit system comprising a plurality of RF waveform generators (31, 32, . . . 3n) and RF amplifiers (21, 22, . . . 2n) for generating RF transmit signals for feeding such a multi-channel RF transmitter arrangement, especially for use as an RF excitation system in an MRI system is disclosed.

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, . . .

Abstract: A method and circuit arrangement for operating multi-channel transmit/receive antenna devices or arrangements is used in magnetic resonance imaging (MRI) systems. Full 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: 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: 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 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.