Magnetic resonance imaging device with magnetic assembly

Abstract

The present invention relates to an imaging device (1), comprising at least one first module (36), the first module comprising a trolley (38) provided on one side with a plate (39) on which rests a magnetic assembly (1A) intended to apply a main magnetic field in an analysis zone (22) of a main housing (16) of the magnetic assembly (1A), the trolley (38) further comprising two side walls (40, 41) supporting the plate (39) via one of their edges designated as the upper edge, and a second module (37) of substantially parallelepiped shape supporting a set of electronic control elements, the second module (37) being configured in particular for a console to be inserted between the side walls of the trolley (38), the console and the first module comprising means for identifying, by the console, the geometrical and magnetic characteristics of the magnetic assembly (1A) of the first module, the identifying means being integrated in the connecting means.

Description

[Technical Field]

[0001] The present invention relates to the field of magnetic resonance imaging, more particularly to a magnetic resonance imaging device, in particular a magnetic resonance imaging device provided with a magnetic assembly capable of applying a main magnetic field to an analysis zone. [Background technology]

[0002] Magnetic resonance imaging (MRI) is now widely used to non-invasively image the interior of the body, especially the human body. In particular, MRI makes it possible to examine the hydrogen nuclei of water molecules that form part of the body, in particular their nuclear spin.

[0003] In this regard, an MRI device comprises a magnet intended to apply a static magnetic field (called the "main magnetic field") to the body, under the influence of which the nuclear spins associated with the hydrogen nuclei contained in the water molecules forming part of this body become polarized.

[0004] In particular, the magnetic moments associated with these spins are preferentially aligned along an axis called the z-axis, which is determined by the orientation of the main magnetic field to produce the magnetization of the body.

[0005] The MRI device also includes gradient coils configured to generate small-amplitude, spatially varying magnetic fields when current is applied to the gradient coils. More specifically, the gradient coils are aligned parallel to the main magnetic field and are designed to generate magnetic field components whose amplitudes vary linearly with position along one of the x, y, or z axes (each pair of x, y, and z axes is perpendicular).

[0006] The combined effect of the magnetic fields provided by the gradient coils therefore makes it possible to spatially encode each of the body locations intended to be probed.

[0007] The MRI device also comprises at least one radiofrequency (RF) coil intended to function as a RF receiver-transmitter, in particular configured to emit RF energy pulses at a frequency equal to or close to the resonance frequency of hydrogen atomic nuclei spins and at a frequency that is at least partially absorbed by these atomic nuclei.

[0008] As soon as the RF emission is discontinued, the nuclear spins relax to return to their initial energy state and then emit RF signals that can be collected by at least one RF coil, which are then processed using a computer and reconstruction algorithms to obtain an image of the body.

[0009] A main magnetic field generally comprised between 1.5 and 3 Tesla makes it possible to achieve a relatively reasonable signal-to-noise ratio, and consequently to form images of the human body of sufficient quality with durations of the order of one minute or more.

[0010] However, there are situations in which it is not possible to achieve such a main magnetic field strength, such as portable MRI devices, which generally contain permanent magnets or electromagnets with limited capacity and are unable to apply a main magnetic field with a strength greater than 60 mT or even greater than 200 mT without adversely affecting the mass or volume of the MRI device under consideration.

[0011] This limitation on the main magnetic field strength directly affects the performance of the MRI system, and therefore improving the homogeneity of the main magnetic field can be essential.

[0012] One object of the invention is to propose a magnetic resonance imaging device that allows the analysis of different parts of the body, regardless of their size, without reducing the quality of the images obtained for these parts.

[0013] The object of the invention is to propose a magnetic resonance imaging device which advantageously implements a low-intensity main magnetic field, provided with a magnetic assembly in which the homogeneity of the generated magnetic field is improved with respect to the assemblies known from the prior art. Summary of the Invention

[0014] The object of the present invention is achieved by a magnetic resonance imaging apparatus, the magnetic resonance imaging apparatus comprising: at least one first module, each first module of the at least one first module comprising a trolley with a plate on whose face, called the top face, a magnetic assembly is placed, the magnetic assembly intended to apply a main magnetic field to an analysis zone of a main recess of the magnetic assembly, the trolley further comprising two side walls supported by one of the edges, called the top edge; a second module (37) provided with a substantially parallelepiped console supporting a set of electronic control elements of the device, the console comprises, in particular, a second module configured to be inserted between the side walls of the trolley of each first module of the at least one first module by means of a sliding connection, Both the console module and at least the first module are provided with means for identifying the geometric and magnetic characteristics of the magnetic assembly of the first module by the console, the identification means being incorporated into the connecting means of the console and the first module.

[0015] According to one embodiment, the magnetic assembly comprises: a plurality of support plates each having an annular section defining an opening, referred to as the support aperture, the support plates being assembled together by alignment means along a major axis such that the support apertures aligned along the major axis define a generally cylindrically shaped main recess, each support plate further comprising a first plurality of permanent magnets housed in a first housing provided within the annular section along at least one annular Halbach array about the major axis, the set of magnets of the first plurality of magnets generating a primary magnetic field in a zone, referred to as the analysis zone, of the main housing exhibiting a first uniformity; The set of annular sections comprises a plurality of annular sections assembled coaxially with the annular section and rigidly connected to the support plate, each annular section comprising a second plurality of magnets housed in a second recess provided in the annular section, the set of annular sections being arranged to generate a secondary magnetic field in the analysis zone such that a resultant magnetic field of the primary and secondary magnetic fields, called the main magnetic field, in the analysis zone has a second improved uniformity relative to the first uniformity.

[0016] According to one embodiment, the magnetic assembly comprises a main part inserted between two secondary parts, the main part being formed from a support plate called the main support plate, and both secondary parts being formed from support plates called the secondary support plate, the opening in the main support plate called the first opening having a first diameter and the opening in the secondary support plate called the second opening having a second diameter smaller than the first diameter.

[0017] According to one embodiment, the support plate comprises a non-magnetic material, advantageously the non-magnetic material comprises aluminum, a plastic material, for example PMMA plexiglass.

[0018] According to one embodiment, the alignment means comprise threaded rods essentially parallel to the main axis and here fixed to each other, i.e. to the support plate.

[0019] According to one embodiment, each support plate is enclosed between two cover plates by means of gripping means configured to hold a magnet of the first plurality of magnets in a first cavity of the support plate under consideration, the gripping means advantageously comprising a nut cooperating with a threaded rod.

[0020] According to one embodiment, each support plate comprises an opening called an alignment opening, whereby the magnetic assembly comprises at least one alignment passage of square or rectangular cross section formed by the alignment opening, the alignment passage extending parallel to the main axis, the magnetic assembly further comprising at least one alignment tube passing through the alignment passage and having a shape according to the cross section of the passage, the at least one alignment tube intended to fix the magnetic assembly to the trolley.

[0021] According to one embodiment, each support plate comprises a first plate and a second plate assembled to each other by contact surfaces, and each first recess comprises two cavities formed from one and / or the other contact surfaces of the first plate and the second plate.

[0022] According to one embodiment, the alignment means comprises at least one rail provided with alignment notches, each alignment notch holding a support plate, the notches being configured to maintain a predetermined spacing between two adjacent support plates.

[0023] According to one embodiment, the alignment means comprises an alignment element having a base covered by a cradle hole on a cylindrical portion having a groove formed on its inner surface, and each of the support plates is held in its own groove.

[0024] According to one embodiment, each support plate comprises an outer tongue extending radially relative to the annular section and inserted into a cavity formed in the bottom of the groove holding the support plate.

[0025] According to one embodiment, the annular portion is held together with the support plates by threaded rods, called threaded rods.

[0026] According to one embodiment, the support plate is provided with internal or external tabs to form a housing capable of accommodating one or several permanent magnets.

[0027] According to one embodiment, the annular portion is disposed within the main housing.

[0028] According to one embodiment, the annular portions are arranged outside the main housing, and each annular portion is inserted between two support plates.

[0029] According to one embodiment, the magnetic assembly further comprises a radio frequency coil and a magnetic field gradient coil disposed within the main housing and mechanically integrated with the magnetic assembly.

[0030] According to one embodiment, the radio frequency coil and the gradient coil are removable. [Brief explanation of the drawings]

[0031] Other features and advantages of the present invention will become apparent from the following detailed description of the invention which refers to the accompanying drawings. [Figure 1] 3 is a photograph of a magnetic assembly of the imaging device according to the first embodiment of the present invention. [Figure 2] 1 is a photograph of a support plate that can be implemented in the context of a first embodiment of the invention. [Figure 3] FIG. 10 is a cross-sectional view taken along a cutting plane passing through a main axis of a magnetic assembly according to a first modified example of the first embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view taken along a cutting plane passing through the main axis of a magnetic assembly according to a second modified example of the first embodiment of the present invention. [Figure 5] This is an enlarged version of the photograph in [Figure 1]. [Figure 6]1 is a photograph of a piston that can be implemented within the scope of the present invention. [Figure 7] 1 is a photograph of a piston that can be implemented within the scope of the present invention. [Figure 8] FIG. 10 is a side view (a view perpendicular to the main surface) of a support plate according to a second embodiment of the present invention. [Figure 9] FIG. 10 is a view taken along a cross section of a first recess according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a perspective view of the alignment means formed by the rails; [Figure 11] FIG. 1 is a view along a section perpendicular to the main axis AA′ of a magnetic assembly provided with alignment means formed by eight rails. [Figure 12] FIG. 10 is a perspective view of the alignment means formed by the cradle. [Figure 13] FIG. 1 is a diagram of a magnetic assembly with an RF coil and a gradient coil. [Figure 14] FIG. 2 is an explanatory diagram of a first module and a second module. [Figure 15] 1 is a schematic diagram of a male plug and a female plug. [Figure 16] FIG. 10 is another schematic diagram of a male plug and a female plug. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention relates to a magnetic resonance imaging apparatus, at least one first module, each first module of the at least one first module comprising a trolley with a plate on whose face, called the top face, a magnetic assembly is placed, the magnetic assembly intended to apply a main magnetic field to an analysis zone of a main recess of the magnetic assembly, the trolley further comprising two side walls supported by one of the edges, called the top edge; a second module provided with an essentially parallelepiped console supporting a set of electronic control elements of the device, the console being adapted in particular to be inserted between the side walls of the trolley of each first module from at least one first module by means of a sliding connection, Both the console module and at least the first module comprise means for identifying by the console the geometric and magnetic characteristics of the magnetic assembly of the first module, the identification means being incorporated into the connecting means of the console and the first module.

[0033] The magnetic assembly is intended in particular to apply a static magnetic field to the body, under the influence of which the nuclear spins associated with the hydrogen nuclei contained in the water molecules that partly form this body become polarized.

[0034] In particular, the magnetic assembly includes a plurality of support plates, each having an annular section defining an opening, referred to as a support opening. More specifically, the support plates are integrally assembled to one another by alignment means along a main axis, such that the aligned support openings define a generally cylindrical main housing. Each support plate further includes a first plurality of permanent magnets housed in a first housing provided in the annular section according to at least one annular Halbach array about the main axis. The assembly of support plates is particularly arranged to generate a primary magnetic field in a zone, referred to as an analysis zone, of the main housing exhibiting a first uniformity.

[0035] The magnetic assembly also includes annular sections disposed coaxially with the annular section and secured to the support plate. Each annular section includes a second plurality of magnets housed in a second housing disposed within the annular section. In this regard, the annular sections are configured to generate a secondary magnetic field within the analysis zone, such that a resultant magnetic field of the primary and secondary magnetic fields, referred to as a main magnetic field, within the analysis zone has a second uniformity that is improved relative to the first uniformity.

[0036] In accordance with the terminology of the present invention, the analysis zone is understood to include the central section of the main housing, and also to be defined at least by annular portions positioned at opposite ends along the major axis of the assembly formed by the annular portions.

[0037] "Magnetic field homogeneity" is understood to mean the spatial variation of the magnetic field in the analysis zone. According to the invention, the spatial variation of the magnetic field can be characterized in particular by the difference between the maximum and minimum magnetic fields observed in the analysis zone. Therefore, according to the principles of the invention, the smaller this difference, the better the homogeneity.

[0038] The modular nature of the imaging device according to the invention allows for the consideration of different first modules, each first module being adapted to the analysis of a particular part of the body: in particular, one first module can be considered for the analysis of the skull, while another first module is suitable for the analysis of the limbs, in particular the legs.

[0039] FIG. 1 shows a magnetic assembly 1A of a magnetic resonance imaging device 1 (not shown) according to a first embodiment of the present invention.

[0040] The magnetic assembly 1A particularly comprises a plurality of support plates 10. Each support plate 10 is generally flat and comprises two main surfaces that are essentially parallel to one another. The support plates 10 may comprise a non-magnetic material, in particular aluminium, or a plastic material, for example PMMA plexiglass.

[0041] As shown in FIG. 2, the support plate 10 has an annular section 11 that defines openings, called support openings 12, on each of its two main faces.

[0042] The support plate 12 also has a plurality of through openings on each of its two main faces, which form housings called first recesses 14. More specifically, the first recesses 14 are formed on the annular section 11 of the support plate 10. In particular, as shown in FIG. 2, the first recesses 14 are arranged in the form of two concentric rings.

[0043] The magnetic assembly 1A also includes a first plurality of permanent magnets 13. The selection of these magnets is left to the discretion of those skilled in the art.

[0044] The magnets 13 are individually housed in the first recesses to form an annular Halbach array. More specifically, referring to FIG. 2, the annular Halbach array includes two sets of magnets 13 forming two concentric rings. However, the present invention is not limited to these embodiments, and other solutions may be considered by those skilled in the art.

[0045] According to the present invention, the support plates 10 are integrally assembled with one another by alignment means. More specifically, the support plates 10 are assembled so that each support plate 10 has one of its major surfaces facing the major surface of the support plate 10 immediately adjacent to it. Furthermore, a spacing E may be provided between two adjacent support plates.

[0046] According to this configuration, the annular portion 11 defines a housing, referred to as a main recess 16, having a generally cylindrical shape centered about a major axis AA' (see FIG. 3). More specifically, the support openings 12 are aligned along the major axis AA' and are parallel to one another to form the main recess 16.

[0047] All magnets of the first plurality of magnets 13 in an annular Halbach array generate a primary magnetic field in a zone of the main housing, referred to as the analysis zone, that exhibits a first uniformity.

[0048] Furthermore, according to this first embodiment, the magnetic assembly 1A also comprises a cover plate 17 of generally planar shape, which also comprises an opening, referred to as a cover opening, which may be circular.

[0049] In particular, each support plate 10 is associated with two specific cover plates 17. In particular, each support plate 10 is clamped between the two cover plates 17. More particularly, when the cover plates 17 surround a given support plate 10, the cover plates 17 are configured to hold the magnets 13 in the first recesses 14 of the support plate 10 under consideration.

[0050] The cover plate 17 may comprise a non-magnetic material, in particular aluminium, or a plastic material, for example PMMA plexiglass.

[0051] The cover opening is understood to have a shape and size similar to that of the main opening, but need not be specified, in other words, the shape and size of the cover opening do not define the main housing as contemplated in this invention.

[0052] The magnetic assembly 1A can comprise a main part 2 interposed between two secondary parts 3 and 4 (FIG. 3). In this regard, the main part 2 is formed by a support plate 11 (main support plate 11A), while both secondary parts 3 and 4 are formed from a support plate 11, referred to as a secondary support plate 11B. More specifically, the opening 12 in the main support plate 11A, referred to as the first opening, has a first diameter, while the opening 12 in the secondary support plate 11B, referred to as the second opening, has a second diameter smaller than the first diameter.

[0053] Further according to this first embodiment, the alignment means are essentially parallel to the main axis AA' and comprise threaded rods 15 which hold the support plates 10 (Fig. 1) together. In this regard, the support plates 10 and the cover plates may comprise holes through which the threaded rods 15 pass. Advantageously, each support plate 10 is therefore enclosed between two cover plates by clamping means, which advantageously comprise nuts 18 cooperating with the threaded rods (Fig. 5). The nuts 18 may in particular be configured to maintain the spacing E between adjacent support plates.

[0054] The magnetic assembly 1A may also comprise at least one alignment passage, for example two alignment passages, extending parallel to the main axis AA' and having a rectangular cross section (in a plane parallel to the main axis AA'). The alignment passage may in particular be formed by a series of openings, called alignment openings, passing through the side of the support plate 10. It will be understood that the cover plate 17 also comprises alignment openings.

[0055] The magnetic assembly 1A may also include at least one alignment tube 50 passing through the alignment passage and having a shape according to the cross section of the passage (see FIG. 1). The at least one alignment tube 50 allows the magnetic assembly 1A to be fixed to the trolley 38 of the imaging device 1 by magnetic resonance (see FIG. 6).

[0056] The magnetic assembly 1A also includes a plurality of annular portions 19 arranged coaxially with the annular section 11 and fixed to the support plate 10. For example, the annular portions 19 are held together with the plurality of support plates by threaded rods called auxiliary threaded rods 21 (FIG. 3).

[0057] According to a first variant of the first embodiment, the annular portion 19 is arranged in the main housing 16 (FIG. 3).

[0058] According to a second variant of the first embodiment shown in FIG. 4, the annular portions 19 are arranged outside the main housing 16. In particular, each annular portion 19 is inserted between two support plates 10.

[0059] Each annular portion 19 comprises two faces, called auxiliary faces, parallel to the main faces of the support plate 10. Second recesses 20 are formed in the annular portions 19. More specifically, the second recesses 20 of the annular portions 19 are opened by one and the other of the auxiliary faces of the annular portion under consideration.

[0060] The magnetic assembly 1A also includes a second plurality of permanent magnets, the selection of which is left to the discretion of one skilled in the art.

[0061] Each permanent magnet of the second plurality of permanent magnets is individually housed within a second housing.

[0062] Furthermore, according to the present invention, the annular portion 19 is arranged to generate a secondary magnetic field within the analysis zone 22, so that the resultant magnetic field of the primary and secondary magnetic fields, referred to as the main magnetic field within the analysis zone, has a second improved homogeneity relative to the first homogeneity.

[0063] The analysis zone 22 corresponds to the interior volume defined by the annular portion 19 .

[0064] The arrangement of the magnets in the second plurality of permanent magnets can be determined by implementing a digital simulation method, more particularly by implementing a genetic algorithm. Those skilled in the art who wish to implement a genetic algorithm can refer in particular to the principles described in the following article: S. Binia and SS Sathya, "SurveyBio Inspire Optimization Algorithms," International Journal of Soft Computing and Engineering, vol. 2, issue 2, pp. 137-151, May 2012.

[0065] According to an advantageous variant, the support plate 10 is provided with internal tabs 23 or external tabs (not shown) to form a housing capable of accommodating one or several permanent magnets (FIG. 2J).

[0066] The latter aspect also makes it possible to reduce the inhomogeneity of the main magnetic field in the analysis zone.

[0067] 8 is a schematic representation of a support plate 10 that can be implemented in a second embodiment of the present invention. This second embodiment essentially picks up the principles and terminology of the first embodiment.

[0068] More specifically, this second embodiment differs from the first embodiment in that the implementation of cover plates is not taken into account, whereas the spacing E between two adjacent support plates 10 is always taken into account in this second embodiment.

[0069] Therefore, according to this second embodiment, the support plate 10 comprises a first plate 25 and a second plate 26, as shown in FIG.

[0070] In particular, the first plate 25 and the second plate 26 are assembled together by contact surfaces, in particular the first plate 25 comprises a first contact surface 25A and the second plate 26 comprises a second contact surface 26A in contact with the first contact surface 25A.

[0071] The assembly of the first plate 25 and the second plate 26 can in particular implement a set of screws.

[0072] According to this second embodiment, each first recess 14 is formed by a first cavity 14A and a second cavity 14B formed in a first plate 25 and a second plate 26, respectively (FIG. 9).

[0073] More specifically, the first cavity 14A is exposed by a first contact surface 25A, and the second cavity 14B is exposed by a second contact surface 26A.

[0074] It will be understood that the surface of the first plate 25 facing the first contact surface 25A forms one of the main surfaces of the support plate, and the surface of the second plate 26 facing the second contact surface 26A forms the other of the main surfaces of the support plate.

[0075] According to a variant of the embodiment described above, the alignment means comprise at least one rail 27 provided with alignment notches 28 (FIG. 10). Each alignment notch 28 is configured in particular to hold a support plate 10. In this respect, the support plate 10 may also comprise a notch, called alignment notch 29, configured to cooperate with the alignment notches 28.

[0076] Advantageously, the alignment notches 28 are configured to maintain a predetermined spacing between two adjacent support plates 10. The rails 27 may also be secured to the support plates 10 with screws.

[0077] As shown in [Figure 11], it is also possible to consider several rails 27, distributed around the magnetic assembly 1A, where all the support plates 10 are at different angular positions around the main axis AA'.

[0078] [Figure 12] shows another alternative alignment means. In particular, the alignment means according to this other variant comprises a base 30 covered by a cradle 31. In this respect, the cradle comprises a cylindrical portion having grooves 32 formed on its inner surface. In particular, each groove 32 is intended to receive a support plate 10.

[0079] Advantageously, each support plate 10 comprises an external tongue 33 extending radially relative to the annular section, the external tongue 33 being inserted into a cavity 34 formed in the bottom of the groove holding the support plate.

[0080] The arrangement proposed in the present invention makes it possible to ensure the overall coupling of the magnetic assembly 1A. Indeed, the first plurality of magnets as well as the second plurality of magnets generate magnetic forces that are likely to lead to mechanical instability of the magnetic assembly. The implementation of the holding means described in the present invention makes it possible to compensate for these effects.

[0081] Furthermore, by taking into account the annular portion 19 it is possible to at least partially compensate for inhomogeneities in the main magnetic field applied to the analysis zone.

[0082] Regardless of the embodiment considered, as shown by way of example in FIG. 13, the magnetic assembly 1A can also comprise a radio frequency (RF) coil 34 and a gradient coil 33 carried by a support 35. More specifically, the RF coil 34 and the gradient coil 33 are carried by a support 35 within the main housing. Advantageously, the RF coil 34 and the gradient coil 33 are interchangeable, also giving the magnetic assembly 1A a modular character.

[0083] The gradient coils are configured to generate small amplitude magnetic fields that vary in space when a current is applied. More specifically, the gradient coils are aligned parallel to the main magnetic field and are designed to generate magnetic field components whose amplitudes vary linearly with position along one of the x, y, or z axes (each pair of x, y, and z axes is perpendicular). Thus, the combined effect of the magnetic fields imparted by the gradient coils makes it possible to spatially encode each of the body locations intended to be probed.

[0084] The RF coil is intended to function as an RF transceiver. In particular, the RF coil is configured to emit RF energy pulses at a frequency equal to or close to the resonance frequency of hydrogen atomic nuclear spins, and at a frequency that is at least partially absorbed by these atomic nuclei. As soon as the RF emission is discontinued, the nuclear spins relax to return to their initial energy state and then emit RF signals that can be collected by at least one RF coil. This RF signal is then processed using a computer and a reconstruction algorithm to obtain an image of the body.

[0085] The imaging device 1 according to the present invention constitutes a modular system. More specifically, the imaging device 1 can include at least a first module 36 and a second module 37.

[0086] Each first module 36 of the at least first modules F is formed in particular by a magnetic assembly 1A and a trolley 38. The trolley 38 may include casters.

[0087] The trolley 38 is provided, in particular, on its surface, called the top surface, with a plate 39 on which the magnetic assembly 1A is mounted. The trolley has two side walls 40 and 41 which support the plate 39 by one of their edges, called the top edge.

[0088] The two side walls 40 and 41 together with the plate 39 define a receiving space 42 .

[0089] The second module 37 comprises an essentially parallelepiped-shaped console supporting a set of electronic control elements of the device, the console being configured in particular to be inserted into the receiving space 42. In this regard, the console may be equipped with castors that enable it to be inserted into the receiving space.

[0090] In particular, the side surfaces 43 and 44 are in sliding connection with the side walls 40 and 41, respectively. In this respect, the device can comprise a system of sliding guides for sliding and locking the side surfaces 43 and 44 relative to the side walls 40 and 41, respectively. The sliding system may in particular comprise one or two slides 45a, 45b. In this respect, the one or two slides 45a, 45b are intended to cooperate with rails 46a and 46b arranged on the side walls 40 and 41. The rails 46a and 46b can also be provided with locking means making it possible to block the second module in the receiving space 42. The locking means may comprise shims 47a and 47b.

[0091] Finally, the imaging device 1 also comprises connection means making it possible to connect the first module 36 and the second module 37. The connection means are in particular plug-in means comprising a male plug 48 and a female plug 49 (FIGS. 14 and 15). In particular, the male plug 48 is associated with the second module 37 and the female plug 36 is associated with the first module 36.

[0092] Both the console module and at least the first module include means for identifying the geometric and magnetic characteristics of the magnetic assembly of the first module by the console, the identification means being incorporated into the connecting means of the console and the first module. The identification means refers to a means that allows the console to recognize the geometric and magnetic characteristics of the magnetic assembly. According to this aspect, in particular, the console can recognize the configuration of the imaging device.

[0093] The complementary male and female plugs 48, 49 may each have a star shape (see FIG. 16). The latter may also comprise ports, called identification ports 48a and 49a, that allow the type of a first module connected to a second module to be identified (the identification ports are specifically associated with the identification means).

[0094] The identification function may involve digital means (e.g., a chip ID, e.g., an RFID in the female plug and an ID reader in the second module), or analog means (e.g., a combination of a resistor in the female plug and an ammeter in the second module).

[0095] Male plug 48 and female plug 49 contain other ports associated with RF coil control and gradient coils.

[0096] Such a configuration makes the imaging device 1 modular and allows for different specific magnetic assemblies to be considered, in particular according to the invention it is possible to consider different magnetic assemblies, each magnetic assembly intended to image a specific part of the body.

[0097] The invention relates to a method for manufacturing a magnetic assembly of an imaging device 1 by magnetic resonance according to the invention, said method comprising the steps of: forming a support plate; forming an annular portion; and assembling the support plate and the annular portion; The method is characterized in that the number and positioning of the annular portions and the amount of magnets forming each second plurality of magnets are determined by implementing a genetic algorithm configured so that the resultant magnetic field of the primary magnetic field, called the main magnetic field, and the secondary magnetic field in the analysis zone has a second homogeneity that is improved with respect to the first homogeneity.

[0098] Naturally, the invention is not limited to the described embodiments, and variant embodiments can be added thereto without departing from the scope of the invention as defined by the claims.

Claims

1. at least one first module (36), each of said at least one first module comprising a trolley (38) provided on its body, referred to as the top surface, with a plate (39) on which a magnetic assembly (1A) rests, said magnetic assembly (1A) intended to apply a main magnetic field in an analysis zone (22) of a main housing (16) of said magnetic assembly (1A), said trolley (38) further comprising two side walls (40, 41) supporting said plate (39) by one of its edges, referred to as the top edge; a second module (37) provided with an essentially parallelepiped console supporting a set of electronic control elements of the device, said console being adapted in particular to be inserted between the side walls of the trolley (38) of each of the at least one first module by means of a sliding connection, A magnetic resonance imaging device (1), wherein both the console module and the at least one first module comprise means for identifying, by the console, the geometric and magnetic characteristics of the magnetic assembly (1A) of the first module, the means for identifying being integrated into the connecting means of the console and the first module.

2. The magnetic assembly (1A) comprises: a plurality of support plates (10) each having an annular section (11) defining an opening referred to as a support opening (12), said support plates (10) being assembled together by alignment means along a major axis such that said support openings aligned along said major axis define a generally cylindrical main housing (16), each support plate (10) further comprising a first plurality of permanent magnets (13) housed in a first housing (14) provided in said annular section (11) according to at least one annular Halbach array about said major axis, said magnet set of said first plurality of permanent magnets generating a primary magnetic field in a zone referred to as an analysis zone (22) of said main housing (16) having a first uniformity; 2. The magnetic resonance imaging device (1) of claim 1, further comprising: a plurality of annular portions (19) assembled coaxially with the annular section and integral with the support plate (10), each annular portion comprising a second plurality of magnets housed in a second recess (20) provided in the annular portion, the set of annular portions (19) being arranged to generate a secondary magnetic field in the analysis zone (22), the resultant magnetic field of the primary magnetic field and the secondary magnetic field, referred to as the main magnetic field in the analysis zone (22), having a second improved homogeneity with respect to the first homogeneity.

3. 3. The magnetic resonance imaging device of claim 2, wherein the magnetic assembly comprises a main part (2) inserted between two secondary parts (3, 4), the main part (2) being formed from a support plate (10) called the main support plate (11A), and one and the other of the secondary parts (3, 4) being formed from a support plate called the secondary support plate (11B), the opening in the main support plate (11A) called the first opening having a first diameter and the opening in the secondary support plate (11B) called the second opening having a second diameter smaller than the first diameter.

4. 4. A magnetic resonance imaging device (1) according to claim 2 or 3, wherein the support plate (10) comprises a non-magnetic material, the non-magnetic material comprising aluminum or a plastic material.

5. 4. Magnetic resonance imaging device (1) according to claim 2 or 3, wherein the alignment means comprise threaded rods (15) which are essentially parallel to the main axis and hereby rigidly connected to the support plates (10) and to each other.

6. 6. The magnetic resonance imaging device (1) of claim 5, wherein each support plate (10) is enclosed between two cover plates (17) by gripping means configured to hold the magnets of the first plurality of permanent magnets in a first recess of the support plate (10) under consideration, the gripping means comprising a nut (18) cooperating with the threaded rod (15).

7. 7. The magnetic resonance imaging device (1) according to claim 6, wherein each support plate (10) comprises an opening called an alignment opening, whereby the magnetic assembly (1A) comprises at least one alignment passage of square or rectangular cross section formed by the alignment opening, the alignment passage extending parallel to the main axis, and the magnetic assembly (1A) further comprises at least one alignment tube (50) passing through the alignment passage and having a shape according to the cross section of the passage, the at least one alignment tube (50) intended to fix the magnetic assembly (1A) to the trolley (38).

8. 4. A magnetic resonance imaging device (1) according to claim 2 or 3, wherein each support plate (10) comprises a first plate (25) and a second plate (26) assembled to each other by contact surfaces, and each first recess (14) comprises two cavities formed from the contact surfaces of one and / or the other of the first plate (25) and the second plate (26).

9. 9. The magnetic resonance imaging device (1) of claim 8, wherein the alignment means comprises at least one rail (27) provided with alignment notches (28), each of which holds a support plate (10), the notches being configured to maintain a predetermined spacing between two adjacent support plates (10).

10. 9. The magnetic resonance imaging device (1) of claim 8, wherein the alignment means comprises an alignment element having a base (30) on which a cradle (31) is mounted, the cradle forming a cylindrical portion having a groove (32) formed on its inner surface, each of the support plates (10) being held in its own groove.

11. 11. The magnetic resonance imaging device (1) of claim 10, wherein each support plate (10) has an outer tongue extending radially relative to the annular section (11) and inserted into a cavity formed in the bottom of the groove that holds the support plate (10).

12. 4. A magnetic resonance imaging device (1) according to claim 2 or 3, wherein the annular portion (19) is held together with the plurality of support plates (10) by threaded rods (15), called threaded rods (15).

13. 4. Magnetic resonance imaging device (1) according to claim 2 or 3, wherein the support plate (10) is provided with internal or external tabs to form a housing capable of accommodating one or several permanent magnets.

14. 4. A magnetic resonance imaging device (1) according to claim 2 or 3, wherein the annular portion (19) is arranged within the main housing (16).

15. 4. A magnetic resonance imaging device (1) according to claim 2 or 3, wherein the annular portions (19) are arranged outside the main housing (16), each annular portion being inserted between two support plates (10).

16. 4. A magnetic resonance imaging device (1) according to any one of claims 1 to 3, wherein the magnetic assembly (1A) is arranged within the main housing (16) and further comprises a radio frequency coil (34) and a gradient magnetic field coil (33) mechanically integrated with the magnetic assembly (1A).

17. 17. Magnetic resonance imaging device (1) according to claim 16, wherein the radio frequency coil and the gradient coil are detachable.

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