WO2024026520A1

WO2024026520A1 - Circuit for the signal processing of a signal from an rf antenna

Info

Publication number: WO2024026520A1
Application number: PCT/AT2023/060255
Authority: WO
Inventors: Bernhard Gruber
Original assignee: Bernhard Gruber
Priority date: 2022-08-01
Filing date: 2023-07-31
Publication date: 2024-02-08
Also published as: AT526399A1; AT526399B1

Abstract

The invention relates to a circuit for the signal processing of a signal from at least one RF antenna (20) of a local RF coil (9) of a magnetic resonance imaging system (1), comprising one preamplifier (31) per RF antenna (20), which preamplifier amplifies the signal from the RF antenna (20), wherein a digitization unit (33) is connected to the preamplifier (31) and digitizes the amplified signal from the preamplifier (31), and wherein the preamplifier (31) is present in an integrated component (IC) and is a preamplifier (31) having a selectable working frequency since the preamplifier (31) comprises a plurality of different amplification circuits (32).

Description

CIRCUIT FOR SIGNAL PROCESSING OF A SIGNAL FROM AN RF ANTENNA

The invention relates to a circuit for signal processing of a signal from at least one RF antenna of a local RF coil of a magnetic resonance tomography system.

The currently most important diagnostic procedures in the health sector are non-invasive imaging procedures, which enable (early) detection of diseases and form the basis for sustainable therapeutic decisions. However, the possibilities of imaging procedures go far beyond the diagnostic area in clinical or veterinary medicine and are used in a wide variety of areas of research (e.g. materials research, neuroscience, etc.). At this point in time, magnetic resonance imaging (MRI) can be viewed as the gold standard in imaging procedures, as complex processes and structures can be understood through the precise representation of the material being examined, especially soft matter.

Magnetic resonance tomography uses strong external magnetic fields to align the core spins of the object to be examined and stimulates them to precess around this alignment using alternating electromagnetic fields. The precession or return from this higher energy, excited state to a state of lower energy, in turn creates an alternating electromagnetic field, which is received via radio frequency antennas (RF antennas). For local coding of the detected signals, magnetic gradient fields are applied, which retroactively allow a volume element assignment. The image reconstruction is carried out by evaluating (e.g. Fourier transformation) the signals received from the RF antennas and creates an imaging, tomographic representation of the examination object.

A decisive factor for the quality of MR scans is the signal-to-noise ratio (SNR), which significantly influences the quality and duration of an MR scan, but is itself influenced by various factors. These include factors such as the field strength of the MRI, the antenna design used, the length of electrical signal lines or the electronics used to amplify and process the received MR signal. The signal received by local coil arrangements (local coils, coils, coil arrays) or antenna systems is a voltage signal induced by the MR measurement, which is then transmitted using a low-noise preamplifier (e.g. LNA) within the field of view or field-of-view ( FoV) in the magnetic field, amplified and finally transmitted to the receiving electronics with as little loss as possible. An antenna system is generally referred to as a receiving coil arrangement, which can consist, for example, of one or more antenna elements (coil elements). Multiple antenna elements are called array coils. These individual antenna elements are resonant high-frequency circuits, which are available in various designs (e.g. loop antenna, flex PCB coil, saddle coils, butterfly). Following the array system are various setting, adaptation and decoupling networks (tuning, matching, decoupling), the preamplifier, other electronics (e.g. standing wave filters for common mode suppression) and a connector system for connection to the MR system. The sooner you get through it The MR signal received by individual antennas is amplified, the less disruptive influences can negatively influence the signal quality, the SNR and thus also the image quality and scan duration.

Currently, these preamplifiers and the associated complementary circuits are constructed with discrete components and, especially with multi-channel local coil arrangements (coil arrays), take up a relatively large amount of space in the already cramped environment of the MRI tube or on or near the coil arrays. The signal transmission to the internal technical interface of the MRT OEM (Original Equipment Manufacturer) egg tray and the subsequent reconstruction system is usually carried out in analog form via coaxial cable. The lossy transmission via a coaxial line itself can in turn lead to negative influences (common-mode interference signals) on the SNR due to the radiation of energy required within the MRI tube to excite the core spins through the transmitting antenna.

Due to the limited diameter of the MRI tube (physical or technical limits due to a necessary homogeneous field of view (FOV)), the use of multi-channel local coils and the lack of whole-body transmitting and receiving coils (body coils). Some MR devices and the increasingly important use or combination of other imaging or functional applications within the MRI result in a significant lack of space within the MRI. In addition, patient comfort decreases as the space within the MRI tube becomes smaller, which in turn can lead to problems ranging from discomfort to complete cancellations or inability to perform examinations. On the other hand, there is a desire for the highest possible SNR in order to create an image that is as error-free and detailed as possible and not to lose a significant part of the signal along the signal chain or through other components. In addition, there is the problem that all instruments (receiving or transmitting coils, etc.) only work at a certain frequency, which is determined by the main magnetic field. This means that every MRI device has several transmitting or receiving coils that only work there or on similar devices with the same field strength and configuration.

In MRI, hydrogen atoms (1H) are mostly measured. However, other nuclides can also be measured (multi-nuclear MRI), for example to show the metabolism of organs or tumors. This requires the amplification of the received MR signal away from the primarily used MR frequency (Larmor frequency).

So far, the space problem has only been partially solved by reducing the size of the discrete components or placing components outside the MR tube, although signal transmission still takes place in analog form. Installing more than 100 of these conventional preamplifiers involves considerable technical challenges and often does not produce the desired result.

An attempt has already been made to realize a preamplifier in integrated form (e.g. CMOS). Please refer:

• Cao, X., et al. Design of a 3T preamplifier which stability is insensitive to coil loading. Journal of Magnetic Resonance #265 (2016), p. 215-223, https://doi.org/10.1016/jjmr.2016.02.012.

• Homeff, A., et al. A new CMOS broadband, high impedance LNA for MRI achieving an input referred voltage noise spectral density of 200pV/sqrt(Hz). IEEE International Symposium on Circuits and Systems, (ISCAS) 2019, Sapporo, Japan, May 26-29, 2019, p. 1-5, https://10.1109/ISCAS.2019.8702445

However, a modular multi-frequency amplifier for different discrete MR frequencies has not yet been developed. The realization of this concept as an extremely broadband, discretely constructed variant in the most compact possible design would result in very high parasitic impedances, which would mean that the necessary amplification with very low noise amplification would not be possible. In addition, such a variant would require a lot of space.

The problem of using MR transmitting and receiving coils across MRI devices has not yet been solved.

In order to solve all of these problems, a circuit according to claim 1 is proposed.

A circuit for signal processing of a signal from at least one RF antenna of a local RF coil of a magnetic resonance tomography system is therefore proposed, comprising a preamplifier for each RF antenna, which amplifies the signal of the RF antenna, with a digitization unit connected to the preamplifier, which does this amplified signal of the preamplifier is digitized, the preamplifier being present as an integrated component (IC), the preamplifier being a preamplifier with a selectable working frequency, in that the preamplifier comprises several different amplification circuits.

The preamplifier is preferably extremely low-noise with a noise figure of less than 1 dB, in particular less than or equal to 0.7 dB.

The digitization unit includes at least one analog-to-digital converter.

The preamplifier and the digitization unit can be present together in an integrated module. The preamplifier and the digitization unit can be present in or as two separate integrated components.

An integrated module comprising the preamplifier and/or the digitization unit, and can optionally include additional components such as mixers or filters, which can preferably be switched on and off. The mixers and filters can be controllable; in particular, the parameters of the mixers and filters can be adjusted based on a selected working frequency of the preamplifier.

Several preamplifiers, as described above, can also be combined in a group, i.e. an array, and designed in an integrated version. Therefore, an integrated component can include several preamplifiers, each of the several preamplifiers being a preamplifier with a selectable operating frequency, in that each preamplifier has several different ones Amplification circuits include. The multiple preamplifiers can be identical, i.e. with identical amplification circuits (number and frequency ranges of the amplification circuits) or with different amplification circuits (number and/or frequency ranges of the amplification circuits). The signal from one RF antenna can be applied to each of the several preamplifiers of the integrated module. In one variant, the multiple preamplifiers of the integrated component can be controlled together by selecting the amplification circuit identically for all preamplifiers of the integrated component. The multiple preamplifiers of the integrated component can be controlled individually in a different variant, so that the choice of the amplification circuit can be made differently for each preamplifier of the integrated component.

The circuit preferably comprises several RF antennas, with each RF antenna being assigned a preamplifier of an integrated component. In one variant, there is an integrated component per RF antenna. In another variant, at least one integrated component includes several preamplifiers in order to be able to amplify the signals from several RF antennas.

In one variant, the preamplifier and/or the analog-to-digital converter are designed as an ASIC (application-specific integrated circuit).

In one variant, the preamplifier and the analog-to-digital converter are designed using CMOS technology.

CMOS stands for Complementary metal-oxide-semiconductor and is a name for semiconductor devices that use both p-channel MOSFETs and n-channel MOSFETs on a common substrate . MOSFET stands for metal-oxide-semiconductor field effect transistor.

It is preferred that there are several RF antennas, with one of several preamplifiers amplifying the signal of an RF antenna, with at least one analog-to-digital converter receiving the amplified signal of a preamplifier at one of several of its inputs.

It is preferred that the analog-to-digital converter converts the amplified signal of the preamplifier from an analog electrical signal into an optical digital signal.

In another embodiment variant, the digitized signal from the analog-to-digital converter can be transmitted wirelessly.

It is preferred that the circuit comprises a control unit which communicates with a transmitting and receiving antenna control unit of the magnetic resonance tomography system.

It is preferred that the circuit comprises a control unit which controls the selection of the amplification circuit of each preamplifier. It is preferred that the control unit communicates with a transmitting and receiving antenna control unit of the magnetic resonance imaging system and controls the selection of the amplification circuit of each preamplifier.

The control unit preferably also controls or switches on or off the optional additional components such as mixers and filters.

It can also be provided that at least one setting, adaptation and decoupling network (tuning, matching and detuning network) is set via the control unit, in particular in that the control unit receives setting values for the setting from the transmitting and receiving antenna control unit of the magnetic resonance tomography system -, adaptation and decoupling network receives at least one RF antenna and can preferably change it.

In one embodiment variant it is provided that the communication between the control unit and the transmitting and receiving antenna control unit preferably takes place via an optical line and the signal transmission of the amplified and digitized signal also preferably takes place via the optical line.

In one embodiment variant it is provided that the signal transmission of the amplified and digitized signal takes place via an optical line and the communication between the control unit and the transmitting and receiving antenna control unit takes place via an additional analog control line.

The inventive design that the preamplifier is a preamplifier with a selectable working frequency, in that the preamplifier comprises several different low-noise amplification circuits, ensures that all working frequencies including multi-core applications in MR and other complementary applications can be covered.

Low-noise is defined here as an amplifier or an amplification circuit that has a noise figure (NF) of less than 1.5 dB. However, a noise figure (NF) of less than 1 dB is preferred. The typical gain of a low noise amplifier is between 10 and 20 dB with single stage gain or between 10 and 40 dB depending on the number of amplifier stages.

The amplifying circuits may be single-stage amplifying circuits or multi-stage amplifying circuits.

It is preferred that the selection of the working frequency, i.e. the selection of the required amplifier circuit, takes place via the control unit.

It is preferred that the circuit comprises at least one preamplifier, at least one digitization unit and at least one control unit, the components mentioned being present in integrated form or as separate components on a common socket PCB, or the components mentioned being present individually or in any combination on separate socket PCBs. PCBs are available, whereby the socket PCBs are specifically adapted to the system requirements of devices from different MRI manufacturers. The setting, adaptation and decoupling network (tuning, matching and detuning network) can also be present on a separate socket PCB or, in addition to one or more of the components mentioned, on a common socket PCB.

It is preferred that the circuit is present within a local RF coil element. The circuit can be present, for example, in a rigid housing of a local RF coil, for example a head coil, or in a flexible local RF coil, which can be designed, for example, in the form of a blanket or other flexible structure and adapts to the contour of a person's body can adapt.

It is preferred that the preamplifier in the form of an amplifier chip comprises at least three different amplification circuits, the input signal of which comes from a single RF antenna and the output signal of which is present at a single input of the digitization unit, the amplifier chip comprising at least one additional input for selecting the working frequency by selectively using one of the amplification circuits.

It is preferred that each of the amplifier circuits of a preamplifier has a bandwidth predetermined by its circuit components, the amplifier circuits together covering a larger bandwidth than the respective individual amplifier circuit, each amplifier circuit being assigned a definable working area, the selection of that amplifier circuit taking place in its working area the determined or expected signal frequency to be amplified.

In one embodiment variant, the circuit can also be present on the outside of the local RF coil. In one embodiment variant, parts of the circuit can be present on the inside and other parts on the outside of the local RF coil.

In one embodiment variant it is provided that the preamplifier is provided with an on-board analog-to-digital converter.

In one embodiment variant it is provided that one preamplifier is connected to one analog-to-digital converter.

In one embodiment variant it is provided that a preamplifier is combined with an analog-to-digital converter in a common integrated module.

In one embodiment variant it is provided that a preamplifier and an analog-to-digital converter are present as separate modular components that are combined to implement the circuit.

In another embodiment variant it is provided that several preamplifiers are connected to a common analog-to-digital converter.

The integrated amplifier is preferably programmable for different MR frequencies via an optical or analog connection by a monitoring and control unit. This allows it to be used at various relevant MR field strengths and resonances (multi-core) with optimal performance (frequency modularity).

In order to be able to implement the invention on different MRI platforms from different manufacturers, a programmable interface on the integrated preamplifier is preferably used to switch additional integrated optional modules or features (such as filters, mixers, etc.) on or off in order to achieve the greatest possible flexibility in the MRI To enable conditions specified by platforms.

In order to be able to implement the invention on different MRI platforms from different manufacturers, it is proposed in another embodiment that socket PCBs adapted to the MRI manufacturer are used, which also allow modular additional modules or features (such as mixers, filters, etc.) to be integrated thereon .) to switch on or off. In one design variant, these socket PCBs also have a modular structure.

These socket PCBs supply (with power and control signals) the preamplifier and the analog-to-digital converter, as well as all other components such as an RF antenna and a matching and decoupling network. Control signals for frequency adjustment of the RF antenna and the adjustment and decoupling network are routed via the socket PCBs. The socket PCBs provide any additional manufacturer-specific functions via an optical, analog or wireless connection to a control unit, in particular a radio frequency antenna control unit, for better integration.

The integrated form, especially in CMOS technology, makes it possible to transfer the previously discrete and extremely noise-sensitive topology of the preamplifier into a robust and much smaller integrated component (IC) without losing amplification performance. At the same time, it is possible to directly digitize the received signals and advance the digital device interface (frontend). Furthermore, the CMOS integration allows a significantly more energy-saving implementation and also a more electromagnetically compatible solution than previous discrete preamplifiers for magnetic resonance imaging (MRI).

The frequency modularity of the integrated amplifier is a significant advantage and allows the use of a single amplifier chip for different MR device field strengths (e.g. 0.55 Tesla, 1.5 Tesla, 3 Tesla, 4 Tesla, 7 Tesla, 10.5 Tesla, 11.4 Tesla, 14 Tesla, etc.) and thus saves the production of several analog amplifiers designed for the applicable field strength. A conventional implementation of an extremely low-noise multi-frequency amplifier covering bandwidths of up to/above 1 GHz, which should be extremely compact, would result in significant parasitic impedances, meaning that the desired properties would not be achievable. Such an implementation is therefore only possible in an integrated form (e.g. CMOS).

Miniaturization not only enables the electrical benefits mentioned above, but also enables system-wide benefits. Smaller amplifiers enable a higher antenna density within an MRI receiving coil (the more receiving channels that can be used, the faster or higher resolution MR scans are made possible; Currently the standard is 32 channels; tested so far: 128 channels; Simulations showed advantages when using up to 256 channels) as the size can be drastically reduced, thus creating more space within the housing. The additional space can be used for further applications, such as magnetic field monitoring/influencing, transcranial magnetic field stimulation (TMS), electroencephalography (EEG), etc. or for further improvements in the area of methodology or diagnostics, or even more in terms of design Space and comfort are provided for the patients/subjects.

Digitalizing the MR signal locally as early as possible also has the advantage of eliminating disruptive interactions between signal transfer lines (common mode rejection), which influence the stability of discrete amplifiers and can themselves drastically worsen the signal-to-noise ratio. The modular design of the system based on a building block principle makes it possible to adapt the front end of MR transmitting and receiving coils to the respective needs and conditions. Depending on the transmitting or receiving system, the output signal of one or more integrated amplifiers can be sent to an ADC. This ADC can be located inside or outside the local MR transmitter or receiver coil/unit. From there, the digitized MR signal can preferably be forwarded optically to the MR backend.

The modular combination of integrated amplifier and analog-digital converter (ADC) can be implemented on individually adapted, manufacturer- or customer-specific motherboards/carriers (PCB-Printed Circuit Board). Preferably, certain features or modules that are integrated in the integrated amplifier can be switched on or off electronically.

The combination of modular design of the integrated component or PCBs and frequency modularity makes it possible to upgrade existing MR systems and thus bring the systems up to the latest technical standards. This allows older MR scanner systems to be cost-effectively upgraded or converted and contributes to the more sustainable use of this expensive technology.

In addition, the integrated design of the amplifier makes it easier to add or switch on and off integrated, optionally necessary features or elements in order to ensure the highest possible compatibility. Optionally necessary is a feature or element that is required for at least one MRI system and is not required for at least one other MRI system. So that the amplifier can be used on both MRI systems, it contains the feature or element, which is switchable and/or adjustable. Adjustability can be provided for features or elements that are required on at least two MRI systems but are used with different parameters.

The invention is illustrated using drawings:

Fig. 1: Shows the basic structure of a magnetic resonance imaging system (MRI system).

Fig. 2: shows a schematic representation of the system components according to the invention. Fig. 3: shows schematically the use of several different amplifier blocks to amplify the individually received and adapted MR signals from radio frequency coils.

Fig. 4: Shows schematically the use of modular receiving units on a head coil system.

Fig. 5: illustrates an exemplary classification of specific modular amplifier bandwidths and working ranges.

1 illustrates a magnetic resonance imaging system (MRI system) 1, which has a tunnel 2 in which a person 3 located on a couch 8 can be placed for imaging. The MRI system 1 includes a superconducting magnetic coil 4, several gradient coils 5 and shim coils 6. Optionally, a transmitting and receiving body coil 7 can be present integrally in the MRI device together with the aforementioned coils. If there is a transmitting and receiving body coil 7, the MRI device can be used for imaging with the coils integrated in the housing. If there is no receiving body coil 7, an additional local receiving coil, which is referred to herein as a radio frequency coil or local RF coil 9, is required, which is present on the person 3. An additional local RF coil 9 can also be used if a receiving body coil 7 is present, since this is advantageously closer to the body of the person 3. The RF coil 9 can be present as a pure receiving coil or as a transmitting and receiving coil (transceiver coil).

As illustrated, the local RF coil 9 is located on or around a part of the body of the person 3 and is located in the tunnel 2 during imaging with the person 3.

Also illustrated is an MRI control unit 10, which can include subunits 11-14, which can be used to control the subsystem of the MRI device. In addition, the MRI control unit 10 has a data memory 15 or is connected to one via a network. The MRI device is arranged in a shielded room 16, with the MRI control unit 10 or at least most components of the MRI control unit 10 being outside of the shielded room 16.

The data transmission between the MRI device and the MRI control unit 10 takes place via data lines, which usually include analog and digital signal lines. This is particularly the case with the data from the local RF coil 9. Wireless transmission has already been proposed, at least in the patent literature.

The individual subunits 11-14 of the MRI control unit 10 are a general control 11, a gradient control 13, a shim coil control 14 and a radio frequency transmitting and receiving antenna control unit 12. The signal line between gradient coils 5 and the gradient control 13 takes place via a signal line 18 of the gradient subsystem. The signal line between shim coils 6 and the shim coil control 14 takes place via a signal line 19 of the shim coil subsystem. The signal line between the transmitting and receiving body coil 7 and the local RF coil 9 and the transmitting and receiving antenna control unit 12 takes place via signal lines 17. If a local RF coil 9 is present, the transmitting and receiving body coil 7 can be operated as a transmitting coil become. If the local RF coil 9 is a transceiver coil, the transmitting and receiving body coil 7 is not needed.

According to the prior art, the transmitting and receiving antenna control unit 12 is located in the shielded room 16, since an analog signal is routed via a coaxial cable from the local RF coil 9 to the transmitting and receiving antenna control unit 12. With this type of transmission, the transmission path must be kept short, so that the transmitting and receiving antenna control unit 12 is located on the side of the MRI device. Wireless transmission of data through the shield is not possible.

In the present invention, the transmitting and receiving antenna control unit 12 can also be located outside the shielded room 16 because the signal is digitized in the front end, i.e. before the signal is routed to the transmitting and receiving antenna control unit 12.

The present invention relates to the signal processing of receiving coils, in particular local RF coils 9, and is illustrated in Figures 2-4.

In the upper part of FIG. 2, a single RF antenna 20 is shown, which can be referred to as a coil and can be in different designs, such as a loop coil.

The signal from the RF antenna 20 is, as is known in the art, connected to the preamplifier 31 through a tuning, matching and detuning network 21. Tuning is the adjustment of the coil electronics to the person's resonance frequency. Matching is the adjustment of the coil impedance to reduce feedback.

Detuning is the deactivation (decoupling) of the individual receiving elements 20 or 28 during the irradiation of the RF pulse by the transmitting antenna in order to excite the protons (generation of the MR signal). This also protects the preamplifier 31 and other electronics from overload, and also provides one of several patient safety layers that protect against RF accidents. Since these processes and the circuits required for them are known from the prior art, they will not be discussed in more detail here.

The invention relates to the digital front end 22 comprising a low-noise amplifier (preamplifier - PA) 31 and a digitization unit 33, both of which are in integrated form, in particular in CMOS technology. The digitization unit 33 includes at least one analog-to-digital converter (ADC).

The data transmission from the digital front end 22 to the transmitting and receiving antenna control unit 12 preferably takes place via an optical or a coaxial line 23. Wireless transmission would also be conceivable. The digitization unit 33 can include one or more optical outputs and therefore convert the previously analog electrical signal into a digital optical signal. Alternatively, an additional converter can follow the digitization unit 33, which converts the electrical digital signal into an optical digital signal. The digitization unit can include a signal mixer for combining or modulating the digital signal and/or a filter for removing interfering, unwanted sidebands by having the digitization unit and these functionalities in a common integrated module. The signal mixer and/or the filter can also follow the digitization unit 33.

The optical digital signal can be transmitted to the transmitting and receiving antenna control unit 12 via one or more optical fibers.

As a less preferred alternative to optical transmission, the digital signal can also be transmitted via a coaxial cable or wirelessly by radio, although these types of transmission are already documented in the prior art.

The digital front end 22 can be controlled via the optical line 23 and/or an optional analog control line 24 or wirelessly. The digital front end 22 and the setting, adaptation and decoupling networks 21 are supplied with power via a direct current power supply 27. Alternatively or optionally, this can also be done using energy harvesting systems or circuits, whereby depending on availability and strength, this energy comes from the radiated electromagnetic fields.

To process the data of the digital front end 22, the transmitting and receiving antenna control unit 12 includes filter, modulation and amplification modules 25, which can alternatively or optionally also be brought forward or integrated into the digitization unit 33 and/or can be optionally switched on. The control signals for this come from a monitoring and control unit 26 of the transmitting and receiving antenna control unit 12.

As a modification of the upper illustration, the lower illustration in FIG. 2 illustrates an RF antenna array 28. The array can be in the form of a parallel array or, as illustrated, as a phased array. Each RF antenna 20 of the RF antenna array 28 is provided with a setting, matching and decoupling network 21 of an array 29 of a plurality of setting, matching and decoupling networks 21. For each RF antenna of the RF antenna array 28, a preamplifier 31 is present in integrated form in the digital front end 22, i.e. a preamplifier array 30. Each preamplifier of the preamplifier array is preferably present as one or in its own integrated module. The digital front end 22 includes at least one digitization unit 33. The digitization unit 33 includes an integrated analog-to-digital converter (ADC) and preferably mixers, filters and/or other optional modules or components. A digitization unit 33 can digitize and optionally modulate, filter and/or manipulate the amplified signals of all preamplifiers 31 of the digital front end 22. The digital front end 22 can also include several digitization units 33, depending on the number of RF antennas of the RF antenna array 28 and the number of inputs of the digitization units 33. The remaining structure is identical to the upper part of Fig. 2.

The amplified signal from one of several preamplifiers is present at its own input of a digitization unit 33, so that a parallel or simultaneous digitization and optional manipulation of the amplified signals from several preamplifiers takes place. The number of outputs of the digitization unit 33 can correspond to the number of inputs. The digitization unit 33 can also provide the analog signals from several inputs at a digital output as a digital signal.

It is advantageous that the transmission of the MR signal from the digital front end 22 to the MR backend (i.e. to the transmitting and receiving antenna control unit 12) can be carried out optically and digitally, so that it is insensitive to interference and can also overcome the electromagnetic shielding if necessary.

Fig. 3 illustrates an embodiment variant of a digital front end 22, which is suitable for frequency-modular and extremely low-noise operation. There is a preamplifier 31 with a selectable working frequency for the RF antenna 20. The preamplifier 31 is an extremely low-noise broadband amplifier in an integrated design (e.g. CMOS). The preamplifier 31 with a selectable operating frequency includes several different amplification circuits 32, the selective use of which enables a frequency to be preselected. The individual amplification circuits 32 have a narrow band, so that in combination they cover a wide band.

5 shows a schematic representation of an exemplary arrangement of modular frequency bands of several preamplifier circuits or amplification circuits 32. Each amplification circuit 32 has a defined operating point (AP,1; AP, 2; AP, 3; AP, 4 ... AP,n ) around which the amplification circuit 32, within the preamplifier 31, works. Each amplification circuit 32 therefore has a defined working range 40, 41, 42, 43, with the selection of the amplification circuit 32 depending on the expected signal frequency of the next signal cycle of the MRI. The respectively selected amplification circuit 32 amplifies the signal received by the RF antenna 20 and forwarded through an adjustment, adaptation and decoupling network 21, within the frequency band or frequency range of its working range 40, 41, 42, 43, which is each determined by a lower limit frequency fL,l to fL,4 or fL,n and an upper limit frequency fH,l to fH,4 or fH,n is defined. The required frequency band and the operating point fvp can be selected and adjusted by selecting an amplification circuit 32, in particular automatically by the control unit 34.

In one embodiment variant, the working frequency is set automatically in such a way that the resonance frequency of the signal applied to the integrated component is used to select the preamplifier circuit 32 in this signal cycle or in the subsequent signal cycle depending on the resonance frequency. This can be done in particular through an internal Feedback loop and magnetic field sensors that detect the resonance frequency take place. The recognition of the resonance frequency can take place in the integrated component, which includes the at least one preamplifier 31, or through an additional part of the circuit.

In each individual preamplifier 31, only one amplifier circuit 32 can be activated per MRI signal cycle. However, different frequency ranges and operating points can be provided and set for several amplifiers 31. The gain is shown linearly in FIG. 5 over the frequency range of the working range 40, 41, 42, 43 as an ideal. The amplifier circuits are preferably in the form of bandpass amplifiers, which means that they have a gain maximum at the operating point, which can be at least approximately constant over a certain bandwidth and then has a falling edge at lower and higher frequencies. The working areas 40, 41, 42, 43 are preferably located so that they are within the bandwidth of the bandpass amplifier. In other words, each of the amplifier circuits 31 has a bandwidth predetermined by its circuit components, with each amplifier circuit 31 being assigned a definable working area 40, 41, 42, 43, the selection of the respective amplifier circuit 31 being carried out in its working area 40, 41, 42, 43 is the expected signal frequency or the signal frequency to be amplified. The bandwidths of the amplifier circuits 31 can therefore overlap, but the defined working areas 40, 41, 42, 43 cannot. A purely exemplary amplification curve is shown for the amplifier circuit 31 with the assigned working area 42 with a dotted line.

3, the preamplifier 31 (in the form of an amplifier chip as disclosed above) comprises at least three different amplification circuits 32, the input signal of which comes from a single RF antenna 20 and the output signal of which corresponds to a single input of the analog to Digital converter 33 is present, the amplifier chip comprising at least one additional input for selecting the working frequency by selectively using one of the amplification circuits.

The front end 22 preferably includes a control unit 34, which controls the setting of the amplifier working frequency point. The front end 22 preferably includes any other integrated circuits for signal processing or improvement, which can be activated or deactivated. The front end 22 preferably includes optionally necessary modules for better system integration on different MR systems from different manufacturers, in particular communication modules. In addition, the control unit 34 can carry out the setting of noise suppression parameters, the reception coil tuning and detuning and/or system clock control. The connection of the control unit 34 to the MR backend, in particular to the transmitting and receiving antenna control unit 12, can take place via an optical, wireless or analog connection.

The type of communication between the control unit 34 of the circuit in question and the MRI system or the transmitting and receiving antenna control unit 12 depends on the MRI system on which the invention in question is implemented and can therefore be viewed as predetermined become. The control signals can be provided in analog or digital form by the transmitting and receiving antenna control unit 12. The control signals are signals that are required to control the system components and are therefore different from the MRT signals of the RF antennas 20. However, the control signals can be transmitted on the same transmission path as the digitized MRT signals of the RF antennas 20. However, the control signals are not amplified by the preamplifier 31.

The front end 22 includes a digitization unit 33, which sends the amplified and digitized and optionally mixed and filtered or otherwise processed MRI signal from the RF antenna 20 to the backend via the preferably optical data line 23. Because the preamplifier 31 has a selectable working frequency, the gain can be adapted to the reception frequency of the RF antenna 20 or the transmission frequency of the MRI device used.

The frequency modularity of the preamplifier 31 also results in the need to adjust the setting, adaptation and decoupling network 21. Since frequency adjustment of the adjustment, adaptation and decoupling network 21 is known from the prior art and is not the object of the present invention, this will not be discussed further here.

In a preferred embodiment variant, the front end 22 is designed completely in an integrated design, in particular as an ASIC (application-specific integrated circuit). What is to be understood as complete is that the integrated module includes at least one preamplifier 31 with several amplifier circuits 32, at least one digitization unit 33 and at least one control unit 34. In addition, the components of the front end 22 described as optional can be integrated into the integrated module.

In Fig. 4, not completely integrated embodiment variants are illustrated in order to be able to adapt the invention to different MRI platforms. For this purpose, a socket PCB 36 (slot element) adapted to the MRI manufacturer is preferably used. In one embodiment variant, these socket PCBs 36 are also modular.

In one embodiment variant (illustrated with reference numeral 35), at least one preamplifier 31 or at least one preamplifier array 30, at least one digitization unit 33 and at least one control unit 34 are placed on a common socket PCB 36.

The socket PCB 36 may also include an adjustment, matching and decoupling network 21 and/or a network array 29.

This socket PCB 36 supplies (with power and control signals) the preamplifier 31 and the digitization unit 33, as well as all other components, such as an RF antenna 20 and the setting, adaptation and decoupling network 21. The energy supply can also be achieved by means of integrated, switchable Energy harvesting infrastructure (e.g. induction of scattered electromagnetic fields). Control signals for frequency adjustment of one or more RF antennas 20 and the setting, adaptation and decoupling network 21 are routed via the socket PCB 36.

The socket PCBs 36 provide any additional manufacturer-specific functions via an optical, wireless or analog connection to a control unit, in particular to the transmitting and receiving antenna control unit 12, for better integration.

The number of socket PCBs 36 required for a local RF coil 9 depends on how many RF antennas 20 it includes and how many preamplifiers 31 are installed on a socket PCB 36. Because each preamplifier 31 is preferably present as a preamplifier 31 with a selectable working frequency, the circuit can be identical for different socket PCBs 36. The socket PCBs 36 therefore preferably differ in their physical form, such as size and type and arrangement of the connections or interfaces.

In one embodiment variant (illustrated with reference numeral 37), functionally separate socket PCBs 38, 39 are present, with the previously mentioned components of one socket PCB 36 being divided into several socket PCBs 38, 39 in any combination.

A socket PCB 38, 39 can, for example, comprise a digitization and transmission unit, i.e. at least one digitization unit 33 and an optical interface to the optical line 23.

A socket PCB 38, 39 can include one or more preamplifiers 31, for example.

A socket PCB 38, 39 can include a control unit 34, for example.

In the embodiment variant illustrated under 37, a socket PCB 38 is illustrated, which includes a digitization unit 33 and a control unit 34.

In the embodiment variant illustrated under 37, a socket PCB 39 is illustrated, which includes a preamplifier 31.

Claims

Patent claims

1. Circuit for signal processing of a signal of at least one RF antenna (20) of a local RF coil (9) of a magnetic resonance tomography system (1) comprising a preamplifier (31) for each RF antenna (20), which receives the signal from the RF antenna ( 20) amplified, characterized in that a digitization unit (33) is connected to the preamplifier (31), which digitizes the amplified signal of the preamplifier (31), the preamplifier (31) being present in an integrated module (IC) and a preamplifier ( 31) with a selectable working frequency in that the preamplifier (31) comprises several different amplification circuits (32).

2. Circuit according to claim 1, characterized in that there are several RF antennas (20), one of several preamplifiers (31) amplifying the signal of an RF antenna (20), the digitization unit (33) being connected to one of each receives the amplified signal of a preamplifier (31) from several of its inputs.

3. Circuit according to claim 1 or 2, characterized in that the digitization unit (33) converts the amplified signal of the preamplifier (31) from an analog electrical signal into an optical digital signal.

4. Circuit according to one of claims 1 to 3, characterized in that the digitization unit (33) carries out manipulation of the amplified signal and/or the already digitized signal, in particular modulation, mixing and/or filtering.

5. Circuit according to one of claims 1 to 4, characterized in that the circuit comprises a control unit (34) which communicates with a transmitting and receiving antenna control unit (12) of the magnetic resonance tomography system (1) and / or which selects the amplification circuit (32 ) of each preamplifier (31) vomimmt..

6. Circuit according to claim 5, characterized in that the communication between the control unit (34) and the transmitting and receiving antenna control unit (12) takes place via an optical line (23) and the signal transmission of the amplified and digitized signal also takes place via the optical line (23 ) he follows.

7. Circuit according to claim 5, characterized in that the signal transmission of the amplified and digitized signal takes place via an optical line (23) and the communication between the control unit (34) and the transmitting and receiving antenna control unit (12) via an additional control line (24). he follows.

8. Circuit according to one of claims 1 to 7, characterized in that the selection of the working frequency is carried out by selecting an amplification circuit (32) via the control unit (34), or the resonance frequency of the signal applied to the integrated module is used by the circuit automatically select the amplification circuit (32) based on this resonance frequency. Circuit according to one of claims 1 to 8, characterized in that it comprises at least one preamplifier (31), at least one digitization unit (33) and at least one control unit (34), said components being in integrated form or as separate components on a common socket -PCB (36) or the components mentioned are present individually or in any combination on separate socket PCBs (38, 39), the socket PCBs (36, 38, 39) being specifically adapted to the system requirements of devices from different MRI manufacturers . Circuit according to one of claims 1 to 9, characterized in that it comprises at least one preamplifier (31), at least one digitization unit (33) and at least one control unit (34), the said components being in a common integrated module, in particular as an ASIC, present. Circuit according to one of claims 1 to 10, characterized in that a plurality of preamplifiers (31) are integrated in the integrated module, each of which comprises a plurality of amplification circuits (32), the integrated module having its own input for each of the preamplifiers (31). which has a signal coming from an RF antenna (20). Circuit according to claim 10 or 11, characterized in that additional optionally necessary modules or features are integrated in the integrated module, which can be switched on and off for better adaptation to different MR systems. Circuit according to one of claims 1 to 12, characterized in that the circuit is present within the housing of a local RF coil (9). Circuit according to one of claims 1 to 13, characterized in that the preamplifier (31) in the form of an amplifier chip comprises at least three different amplification circuits (32), whose input signal comes from a single RF antenna (20) and whose output signal comes from a single input the digitization unit (33), the amplifier chip comprising at least one additional input for selecting the working frequency by selectively using one of the amplification circuits (32). Circuit according to one of claims 1 to 14, characterized in that each of the amplifier circuits (31) of a preamplifier (31) has a bandwidth predetermined by its circuit components, the amplifier circuits (31) together covering a larger bandwidth than the respective individual amplifier circuit (31 ), each amplifier circuit (31) being assigned a definable working area (40, 41, 42, 43), the selection of that amplifier circuit (31) taking place in whose working area (40, 41, 42, 43) the determined or expected one amplifying signal frequency.