LOW NOISE SQUID-BASED RF DETECTION AND CATCHING SYSTEM AND EQUIPMENT WITH THIS SYSTEM

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a low-noise RF detection and acquisition system based on SQUID. It also relates to equipment integrating this system, in particular magnetic resonance imaging equipment. STATE OF THE ART

[0002] It is well known to use SQUID (for "Superconducting QUantum Interference Device") based detection systems: superconducting quantum interference device ) in magnetic resonance imaging (MRI) equipment.

[0003] In an MRI experiment, the subject is placed in a stationary and homogeneous magnetic field B 0 . The sample is then subjected to an RF signal of frequency ω tuned to the Larmor frequency ω 0 = γB 0 protons in the field B 0, with γ / (2 π) = 42.6 MHz.T -1< the gyromagnetic ratio of the proton. Following this excitation, the sample emits a signal of frequency ω 0 captured by a detection system, the principle of which in modern commercial equipment is based on a cooled inductive antenna.

[0004] The usual paradigm in MRI is to choose the highest possible magnetic field, for two reasons: The first is that a higher field allows more protons to be polarized, which leads to more signal, thus reduced experiment time and finer image resolution. The second is that conventional RF detection is done with an inductive antenna, whose sensitivity is proportional to ω .

[0005] Taking into account the thermal noise level in ω 1 / 4< , the detection threshold of the Faraday antenna follows a law in ω -3 / 4< . Since ω is proportional to the working field B 0 , working at high field allows to lower the threshold of detectivity. Typical clinical MRI equipment works at 1.5 or 3 T. Some models go up to 7 T, and experiments aim to reach 11.7 T.

[0006] However, increasing the field produces ionic noise in the sample, degrades image quality due to differences in magnetic susceptibility of tissues, and tends to level out contrasts, not to mention the usual constraints linked to high fields: superconducting coils that are expensive to produce and maintain, magnetically shielded MRI rooms, no MRI for people with pacemakers, or for soldiers wounded by bullets.

[0007] Document CN105137374A discloses an MRI apparatus with nanometer resolution SQUID detection, implementing a magnetic resonance imaging method and an ultra-high resolution device. This method comprises at least a step of placing a test sample within the working range of a magnetic field gradient source and a nano superconducting quantum interference device, a step of using a static magnetic field source to apply a static magnetic field to the test sample, and using a radio frequency source to apply a nuclear magnetic resonance radio frequency pulse to the test sample to excite the test sample to generate nuclear magnetic resonance,a step of using the nano superconducting quantum interference device to directly couple the tested sample to detect the nuclear magnetic resonance spectrum signal generated by the tested sample, and a step of establishing the image of the tested sample according to the detected nuclear magnetic resonance spectrum signal and the spatial distribution information of the magnetic field gradient source. The nano superconducting quantum interference device is used as a detector, magnetic resonance imaging with nanometer-level resolution can be realized, the measurement is not disturbed by vibration and electric field signal, the sample can be directly coupled with the detector at a close distance, the image range is increased, and the work in a strong magnetic field is realized.,

[0008] JP2010256318A discloses high-resolution proton nuclear magnetic resonance and imaging (NMR / MRI) equipment using a high critical temperature (high Tc) superconducting quantum interference device (SQUID) magnetometer via a magnetic flux transformer in a micro Tesla magnetic field. A method and apparatus are provided. The SQUID and the input coil are installed in a superconducting tank that shields ambient noise and puts the SQUID in a stable operating state. The NMR signal can be maintained even when the sample is far away from the SQUID detector.

[0009] CN1287160C discloses a pre-biased SQUID-based NMR and MRI apparatus in which nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Pre-biasing in millitesla fields is followed by detection with an untuned direct current superconducting quantum interference device (SQUID) magnetometer.

[0010] WO2006052236A1 discloses a SQUID-based NMR and MRI device with prepolarization and a Faraday primary antenna. MR imaging in a very weak magnetic field is based on very weak field NMR. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

[0011] These SQUID-based detection and acquisition devices have the disadvantage of requiring prepolarization methods and use high-Tc SQUIDS.

[0012] The document Chen Hsin-Hsien et al: "A compact SQUID-detected magnetic resonance imaging system under microtesla field in a magnetically unshielded environment", Journal of Applied Physics, American Institute of Physics, vol. 110, no. 9, November 1, 2011 (2011-11-01), discloses a SQUID-based radiofrequency detection and acquisition system, intended in particular to be integrated into a nuclear magnetic resonance apparatus, this detection system comprising a primary detection antenna, a flux transformer having a primary winding connected to the primary detection antenna, a SQUID device, a cryogenic device intended to cool the SQUID device and the flux transformer, a stage for processing the secondary detection signal emitted by the SQUID device, this processing stage comprising a flux-locked loop and being intended to deliver an analog acquisition signal.US2013271142A1 discloses low-field SQUID MRI devices, components, and methods. They include a portable low-field MRI (SQUID) instrument and a portable SQUID-based low-field MRI system for use under a bed. This MRI instrument implements a second-order superconducting gradiometer adapted for use with a SQUID low-field MRI device.

[0013] The aim of the invention is to propose a low-noise RF detection and acquisition system based on SQUID which is of simpler and less expensive design than the aforementioned systems of the prior art, and which improves their performance, particularly in terms of signal-to-noise ratio. STATEMENT OF THE INVENTION

[0014] This objective is achieved with a SQUID-based radiofrequency (RF) detection and acquisition system, designed in particular to be integrated into a nuclear magnetic resonance (MRI or NMR) device, comprising: a primary volume type detection antenna, a flux transformer having a primary winding connected to the primary detection antenna, a SQUID device, arranged to capture the magnetic flux captured by the primary antenna and reproduced by an input winding within said SQUID device via the flux transformer, and deliver a secondary detection signal, a cryogenic device provided to cool the SQUID device, a stage for processing the secondary detection signal emitted by the SQUID device, to deliver an analog acquisition signal, comprising a flux-locked loop (FLL) provided to linearize the response of the SQUID device.

[0015] According to the invention, the SQUID device is of the low critical temperature type, the cryogenic device is further provided for cooling the flux transformer, and the primary detection antenna comprises Helmholtz or saddle coils. These volume antennas can be tuned to the signal to be detected, or not tuned.

[0016] Working at low magnetic fields, around 1 mT or less, also allows for a drastic increase in T1 contrasts, opening the way to unique imaging possibilities in the low-field regime. This fact is detailed in the publication "SQUID-detected MRI at 132 µT with Ti-weighted contrast established at 10 µT-300 mT" by SK Lee et al, published in the Journal "Magnetic Resonance in Medicine" Volume 53-1, January 2005, pages 9-14.

[0017] The flux-locked loop (FLL) may advantageously comprise a low-noise amplifier (LNA) which may include a semiconductor heterostructure amplifier or a SQUID-based amplification system. The SQUID-based amplification system is presented in document US2013271142A1. For the implementation of these technologies within the framework of the present invention, reference may usefully be made to the work "The SQUID handbook: Fundamentals of Technology and Applications of SQUIDs and SQUID systems" by John Clarke, Wiley-VCH 2004.

[0018] The detection and acquisition system according to the invention may further comprise one or more active noise compensation coils external to this system.

[0019] The detection and acquisition system according to the invention may further comprise one or more passive shielding screens of the system. This passive shielding may be magnetic in nature, in particular via ferrites, mu-metal, Cryoperm ®< , Metglas ®< , or any other materials or alloys of high magnetic permeability. This shielding may also be made of metal, for example copper or aluminum.

[0020] In a preferred version of the invention, the primary detection antenna cooperates with the flux transformer to concentrate the flux captured by the SQUID device.

[0021] It may also be provided that the detection and acquisition system according to the invention further comprises within the flux transformer an inductance feedback coil arranged to react to variations in the incoming flux, so as to maintain the SQUID device at its maximum flux sensitivity level.

[0022] According to another aspect of the invention, there is provided a magnetic resonance imaging (MRI) equipment comprising a SQUID-based radiofrequency (RF) detection and acquisition system (B) according to the invention, an antenna holder device (A), integrating the primary volume-type detection antenna and connected to said detection and acquisition system (B), and an analog-digital conversion stage (C), provided for converting the analog acquisition signal into digital data suitable for post-processing in order to generate and display an MRI image.

[0023] This MRI equipment can, for example, be coupled with a magnetoencephalography (MEG) device.

[0024] The SQUID-based RF detection and acquisition system may be implemented in nuclear magnetic resonance (NMR) equipment, or in SQUID-based magnetic sensor equipment for metal prospecting, to detect a radiofrequency (RF) wave emitted by a metal vein in response to an emission of a radiofrequency (RF) wave in a ground.

[0025] It is also possible to provide ultra-sensitive radiofrequency sensor equipment including a detection and acquisition system according to the invention, or even radio astronomy equipment operating in the radiofrequency (RF) domain including a SQUID-based RF detection and acquisition system according to the invention. DESCRIPTION OF FIGURES

[0026] The invention is better understood with reference to the figures described below: There Figure 1 is a schematic of the SQUID-based RF detection and signal processing circuit. The figure 2is a schematic diagram of an MRI acquisition from our RF detection invention. The figure 3 illustrates several primary detection antenna geometries. DETAILED DESCRIPTION

[0027] We will now describe, with reference to the figure 1 , an exemplary embodiment of a SQUID-based RF detection and acquisition system 1 according to the invention.

[0028] This SQUID-based RF detection and acquisition system 1 comprises a primary inductive antenna 5 of volume type, produced in the form of Helmholtz coils or horse saddles, or of any other volume type, in particular gradiometric, which is connected, in the case where the antenna is resonant, via a coupling capacitor 9 of capacitance C a to a primary winding 6, of inductance L 1 , of a flux transformer 2 having a secondary winding 7, of inductance L 2 , in series with an input coil 8 of inductance Li generating a flux captured by a SQUID device 3.

[0029] If the antenna is not resonant, the capacitance is not present and the antenna 5 is directly connected to the primary winding 6.

[0030] The flux transformer 2 and the SQUID device 3 are maintained at low temperature in a cryogenic device (not shown) comprising a pulse tube(pulsed tube) such as the PT403 product marketed by CryoMech ®< .

[0031] A stage 4 for processing the secondary detection signal comprises a pre-amplifier 40 (LNA) of the voltage measured at the terminals of the SQUID device 3. This voltage measurement represents a detection signal which is applied to the input of a flux-locked loop circuit 41 FLL including a low-noise amplifier and connected to a feedback coil 10 of inductance L feed intended to react to variations in incoming flux in order to maintain the SQUID device 3 at its maximum flux sensitivity level. The flux-locked loop method is disclosed in document US20120206136A1.

[0032] An example of quantitative characteristics of the SQUID-based RF detection and acquisition system 1 is given below: Typical temporal width of the wave train to be detected: T 2 *~ 50 ms Center frequency of the primary antenna ω 0 - 40 kHz Primary bandwidth Δ ω - 20 kHz Primary quality factor Q - 2 (if resonant antenna) Intensity of the magnetic field at the primary antenna B p , of the order of hundreds of fT to pT Inductance of the SQUID input coil L i = 720 nH Self-inductance of the primary antenna There - 0.1 mH Primary antenna resistance R a = 1Ω Resonant capacity of the primary antenna That = 6 µF Inductive antenna

[0033] Considering the intended applications, a volumetric geometry is chosen for the antenna 5. Examples of this geometry include Helmholtz coils, saddle coils, or other more complex geometries, including gradiometric geometries. This geometry allows for maximum signal collection while, due to its open geometry, providing relative comfort for the patient. The primary Faraday antenna 5 must be tuned to the MRI signal. This antenna 5 has a self-inductance of La, and a resistance of R a , which we will try to reduce as much as possible, in order to minimize the Johnson-Nyquist noise in the antenna.

[0034] The parameters L a , R a are fixed by the chosen antenna geometry and the type of material constituting the antenna. We then have the possibility of making the antenna resonant, which allows two things: The quality factor Q of the resonant antenna allows the captured signal to be naturally amplified, the bandwidth Δω of the antenna allows the captured signals to be filtered and the electromagnetic noise to be rejected outside the band of interest Δω.

[0035] This implementation works for both resonant and non-resonant antennas. The case of the resonant antenna is discussed below.

[0036] The capacitance is adjusted so that the natural frequency of the antenna ω a = 1 / LaCa be tuned to the frequency ω 0 ≈ 40 kHz of the received signal. Furthermore, the antenna design must take into account its bandwidth Δ ω a = R a / There that we wish to have of the same order of magnitude as the bandwidth Δ ω of the RF signal, so as not to lose information while limiting the detected noise. It is therefore the value of the self-inductance Thereof the antenna 5 which will dictate the resistance and capacity to be chosen, depending on the desired frequency characteristics. The primary inductive antenna 5 is a volume antenna. For example, we could choose an antenna with Helmholtz geometry, a saddle antenna, or any other more complex volume geometry, particularly gradiometric.

[0037] There figure 3 presents two of these geometries for a volume antenna implemented in an RF detection and acquisition system according to the invention.

[0038] The first geometry (a) is of the saddle antenna type, well known to those skilled in the art for its performance, particularly in terms of spatial homogeneity. The diameter of the saddle antenna is equal to 1.5 times its length.

[0039] The other geometry (b) is the first-order gradiometric version of the saddle. This 5' volume antenna consists of two sub-antennas 51, 52 connected in series with each other. The first, internal antenna 51, is of saddle geometry and in this example has two turns of wire. The second, external and larger antenna 52, also of saddle geometry, has a single turn of wire. The dimensions of the system and the orientation of the wires are chosen such that: The outer and inner parts of the antenna have the same inductance. This is achieved by the two turns of wire in the inner antenna. The current in the inner part flows in the opposite direction to the current in the outer part.

[0040] With this configuration, the 5' saddle gradiometric antenna can reject noise from sources located at a large distance in front of the dimensions of the 5' antenna, while benefiting from the homogeneity properties of the saddle geometry. A detailed description of the principle of gradiometric antennas can be found in the article by RL Fagaly, "Superconducting quantum interference device instruments and applications", Review of scientific instruments 77, 101101 (2006). Flux concentration and optimal inductance

[0041] To determine the inductance of the antenna, the rest of the detection system is studied with reference to the figure 1 . The SQUID 3 device used (e.g. StarCryo's SQ680 model) is coupled to an 8-inductance input coil L i = 720 nH which achieves current coupling with the primary antenna 5, via a flux transformation system 2 materialized by the coils L 1 and L2, inductively coupled. We note i 1 (resp. i 2) the current flowing in the antenna 5 (resp. the coil L 2) and Φ a the flow captured by antenna 5. We also note M is = k LiLs the input coil-SQUID mutual inductance, and M 12 = k ′ L 1 L 2 the mutual between the coils L 1 and L 2 .

[0042] k And k !< are dimensionless factors and L s is the self-inductance of the SQUID device 3. We are looking for a relationship between the external flux captured by the antenna, Φ a , and Φ sq the flow captured by the SQUID 3.

[0043] The inductive coupling relations in the circuit are written

[0044] Combining these equations, we obtain

[0045] This last equation establishes a link between the external excitation, given by Φ a , and the response level of SQUID 3, quantified by Φ sq . We then understand why such an assembly is called a "flux concentrator": the main role of the Faraday 5 antenna is to increase the flux captured by SQUID 3.

[0046] The maximum sensitivity level of the device, giving the highest response in Φ s for a Φ a given, is reached for

[0047] We set the resistance of the primary antenna 5 to a reasonable value, for example R a = 1 Ω. To respect the bandwidth value of the order of tens of kH, we must therefore ensure There =0.1 mH. This value of There sets a value for the capacity:

[0048] The ratio of inductances L 1 and L 2 is therefore imposed: either L 1 1390 L 2. The precise values ​​of L 1 and of L2 are fixed by the coupling constant k !< , which we try to have as close as possible to 1 in order to ensure the maximum sensitivity of the device. Need for flow transformation

[0049] One might wonder why inductive coupling via coils was introduced. L 1 and L 2. It would have been simpler to connect the antenna directly with the input coil of the SQUID 3. It is assumed that the flux transformer 2 comprising the coils ( L 1 ) and ( L 2) is absent, and that the inductive antenna of inductance There is in series with the input coil ( L i ) of the SQUID. The magnetic coupling is then written Φ a = L a + L i i 1 hence, by introducing the coupling to the SQUID Φ sq = M is i 1 Φ a = L a + L i k L i L s Φ s

[0050] The previous equation shows that the maximum sensitivity is achieved for an inductance of antenna 5 by equalizing the inductance of antenna 5 to that of the input coil 8 of SQUID 3: There = L i .

[0051] For example, we can adjust the inductance of antenna 5 by adjusting the number of turns in the loop, or by adjusting its geometry.

[0052] We then understand the need to introduce a flux transformer. Indeed, without it, the inductance of the antenna is imposed at the value There = L i = 720 nH. This inductance value imposes a resistance for the antenna R a = L Δ ω = 0,72 mΩ and a capacity to plug into the valuable antenna C a = 1 Lω 0 2 = 0,87 mF

[0053] These results are not satisfactory for two reasons. On the one hand, the capacity found is extremely high, at these values ​​we will have to use chemical capacities that may not be suitable for the cold of the cryostat. On the other hand, the resistance value is very low, which will have an impact on the noise intensity in the antenna. δi a = 4 k B T R or, with an antenna cooled to 100 K, δi a ≈ 3 nA / √Hz. This noise is much too high compared to the very low noise level at the SQUID input of the order of pA Hz .

[0054] One solution is to increase the resistance of the primary antenna 5, which requires using a flux transformer 2 to adapt the inductance in order to maintain the same bandwidth. SQUID current reader

[0055] The SQUID 3 device used is a low-Tc SQUID (e.g. SQ680 from STARCryo ®< ) cooled by cryocooler(for "cryorefrigerator", for example the PT 403 from CryoMech ®< , and polarized by a current ip .

[0056] Unlike its high-Tc counterparts, the low-Tc SQUID has a much lower thermal noise level, which allows for a drastic increase in the signal-to-noise ratio and ultimately the quality of the final image. Its role is to read the current generated in the input coil, with a noise level of 0.8 pA / √ Hz This noise level is therefore the objective to be achieved for thermal noise in the inductive antenna. Low-noise amplifier - FLL

[0057] The SQUID device exhibits a non-linear, periodic captured flux-current response of period the flux quantum Φ 0 = h / 2 e. To linearize this response in order to avoid artifacts degrading image quality, the SQUID 3 is coupled to a flux-locked loop (FLL), an example of whose operation is described below.

[0058] This loop first presents a pre-amplifier 40 (LNA) of the voltage measured at the terminals of the SQUID.

[0059] Two choices are possible for the amplification system: either opt for SQUID amplification as is the case for example in document US2013271142A, or use ASIC type semiconductor heterostructure amplification, which is potentially more interesting but also poses more constraints, particularly in the maximum level of amplitude excursion in voltage of the incoming signal.

[0060] The 10 inductance feedback coil L feed allows you to react to incoming flow variations to maintain the SQUID 3 at its maximum flow sensitivity level. The signal is read at the output of the flow-locked loop. MRI equipment

[0061] An ultrasensitive detection and RF acquisition system based on SQUID can be integrated into MRI equipment using a working magnetic field of the order of B0 = 1 mT (which corresponds to a frequency ω0 40 kHz), while maintaining an acquisition time and image quality in accordance with current clinical standards. The reduction of the working magnetic field by several orders of magnitude makes it possible to overcome the constraints preventing on the one hand a massive adoption of MRI as an imaging standard and on the other hand the opening of applications that do not yet exist such as MRI on board a truck to diagnose the type of stroke (vascular-cerebral accident): ischemic or hemorrhagic, 100% MRI breast cancer screening (performed on a scanner today), or intra-operative MRI, thanks to lightweight equipment, without magnetic shielding, and inexpensive.

[0062] There figure 2presents a schematic diagram of an MRI experiment carried out with the detection system according to the invention. We chose to present an MRI of the knee, osteoarticular imaging being one of the first probable cases of application of the invention. The patient's knee is inserted into a cylinder A which includes a solenoid ensuring a permanent field B 0 ≈ 1 mT homogeneous at approximately 10 ppm over a volume of approximately 10x10x10 cm 3< , gradients, and the receiving antenna described previously. The receiving antenna is cooled to a temperature of approximately 60 K using a custom-made cryogenic system derived from the pulse-tube ensuring the cooling of the SQUID system of part B.

[0063] Part B includes the SQUID ensuring the reading of the current coming from the inductive antenna, as well as the signal processing electronics described above, the pre-amplification system, as well as the flux-locked loop FLL composed of an integrating amplifier, a reading resistor, and a looping coil. L feed . This entire stage is cooled using a cryogenic machine, for example the PT403 pulse tube from CryoMech, to a temperature of around 4.2 K.

[0064] Part C provides analog-to-digital conversion of the signal for computer post-processing to drive the equipment and display the resulting MRI image. Medical applications

[0065] The sensitivity and portability of the device make it primarily interesting for magnetic resonance imaging (MRI). The high contrast levels achieved at low fields make the technology interesting for diagnostics where contrast is currently insufficient, with high-field technologies.

[0066] Furthermore, equipment according to the invention could easily be placed in an ambulance truck in order to quickly diagnose, at the scene of the accident, an ischemic or hemorrhagic stroke, in order to treat the patient more quickly and avoid irreparable damage to cognitive faculties.

[0067] Due to its low cost and ease of use, the imaging equipment according to the invention could also be widely used in cases where it is currently underused: screening for breast cancer in women over 50, use in neurology and psychiatry: early screening for diseases such as schizophrenia, depression, or epilepsy; screening for prostate cancer.

[0068] Finally, many SQUID-based low-field MRI projects also aim to design a hybrid MRI-magnetoencephalography (MEG) device. This is the case, for example, of the work of the team at Aalto University in Finland, with reference to the source https: / / www.aalto.fi / en / department-of-neuroscience-and-biomedical-engineering / meg-mri-brain-imaging-group.

[0069] SQUID-based MRI equipment according to the invention may be adapted to integrate an MEG device within it. Nuclear magnetic resonance

[0070] NMR devices used in particular for chemical characterization can also benefit from our detection system to design lighter and less expensive equipment, for reasons similar to those put forward in the context of MRI. Mining industry

[0071] SQUID-based magnetic sensors for metal prospecting already exist in the mining industry, as illustrated in US 7,394,250. Our detection system can also be integrated into such a device for mineral prospecting, thanks to its very low noise level. The principle is as follows: an RF wave is emitted into the ground, if a metal vein is present, eddy currents are induced in the vein which in turn emits an RF wave, this wave is detected by our device integrating the SQUID detection system. Military domain

[0072] Ultrasensitive radiofrequency sensors are well-known elements of electronic warfare systems: they are used, for example, to detect communication signals. Another interesting application is the detection of submerged submersibles: since the submersible is made of ferromagnetic materials, our device is capable of detecting its presence by emitting RF waves and detecting waves produced by induced eddy currents, on the same principle as mineral prospecting. Other systems detect the disturbance of the local Earth field caused by the passage of the submarine, as illustrated in the document "Magnetic detection of a surface ship by an airborne LTS SQUID MAD" by Megumi Hirota et al., April 2001, IEEE Transactions on Applied Superconductivity 11(1):884 - 887. Radio astronomy

[0073] SQUID-based systems are already widely used in the field of radio astronomy, for example integrated into superconducting bolometers for reading and / or amplifying very weak currents. Due to its very high sensitivity, our system could find interesting integration in a telescope calibrated in the RF domain.

[0074] Of course, the present invention is not limited to the embodiments which have just been described and numerous other variant embodiments can be envisaged within the framework of the invention.

Claims

1. System (1) for radio frequency (RF) detection and acquisition based on SQUID, provided in particular to be integrated into a nuclear magnetic resonance apparatus (S), for example a magnetic resonance imaging (MRI) apparatus, comprising: - a volume-type primary detection antenna (5), - a flux transformer (2), - a SQUID device (3), arranged to capture the magnetic flux captured by the primary antenna (5) and reproduced by an input winding (8) within said SQUID device via the flux transformer (2), and to deliver a secondary detection signal, - a cryogenic device designed to cool the SQUID device (3), - a stage (4) of processing the secondary detection signal emitted by the SQUID device (3) to deliver an analog acquisition signal, comprising a flux-locked loop (FLL) provided to linearize the response of the SQUID device (3), characterized in that the SQUID device is a low critical temperature device, the flux transformer (2) has a primary winding (6) connected to the primary detection antenna (5), the cryogenic device is further provided for cooling the flux transformer, and in that the primary detection antenna (5) comprises Helmholtz or saddle coils.

2. Detection and acquisition system according to claim 1, characterized in that the primary detection antenna has a gradiometric geometry.

3. Detection and acquisition system (1) according to claim 1, characterized in that the flux-locked loop (FLL) comprises a low-noise amplifier (LNA).

4. Detection and acquisition system (1) according to claim 3, characterized in that the low-noise amplifier comprises a semiconductor heterostructure amplifier.

5. Detection and acquisition system according to one of claims 3 or 4, characterized in that the low-noise amplifier comprises a SQUID-based amplification system.

6. Detection and acquisition system according to any of the preceding claims, characterized in that it further comprises one or more active noise compensation coils for noise external to said system.

7. Detection and acquisition system (1) according to any of the preceding claims, characterized in that the primary detection antenna (5) cooperates with the flux transformer (2) to concentrate the flux captured by the SQUID device.

8. Detection and acquisition system (1) according to any of the preceding claims, characterized in that it further comprises within the flux transformer (2) an inductance feedback coil (10) arranged to react to the variations of the incoming flux, so as to keep the SQUID device (3) at its maximum flux sensitivity level.

9. Magnetic resonance imaging (MRI) equipment item (S) comprising: - a SQUID-based radio frequency (RF) detection and acquisition system (B) according to any of the preceding claims, - an antenna holder device (A), integrating the volume primary detection antenna and connected to said detection and acquisition system (B), - an analog-to-digital conversion stage (C), designed to convert the analog acquisition signal into digital data suitable for post-processing to generate and display an MRI image.

10. MRI equipment item according to the preceding claim, characterized in that it is coupled to a magnetoencephalography (MEG) device.

11. Nuclear magnetic resonance (NMR) equipment item including a SQUID-based RF detection and acquisition system according to any of claims 1 to 8.

12. SQUID-based magnetic sensor equipment item for the prospecting of metals, including an RF detection and acquisition system according to any of claims 1 to 8, for detecting a radio frequency (RF) wave emitted by a metal vein in response to an emission of a radio frequency (RF) wave in a ground.

13. Ultra-sensitive radio frequency sensor equipment item including a detection and acquisition system according to any of claims 1 to 8.

14. Radio astronomy equipment item operating in the radio frequency (RF) domain including a SQUID-based RF detection and acquisition system according to any of claims 1 to 8.