Magnetic resonance imaging device comprising a magnetic enclosure comprising a detachable end module

Abstract

The invention relates to a magnetic resonance imaging device comprising a magnetic enclosure (1) having a tubular enclosure body (2) comprising a main part (2A) interposed between two end parts (2B, 2C), a first series of permanent magnet support plates (20) forming the main part (2A) of the enclosure body (2), a second series of permanent magnet support plates (21) forming at least one of the two end parts (2B, 2C), means for assembling the support plates (20, 21) of the first and second series to one another, the assembly means comprising a first arrangement of one or more rails comprising at least one alignment rail (3) having a main rail segment provided with notches for retaining the support plates (20) of the first series and at least one end rail segment, adjacent to the main rail segment (30), comprising a flat surface (33) on which the support plates (21) of the second series are fixed.

Description

Magnetic resonance imaging device comprising a magnetic enclosure including a removable end module TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of magnetic resonance imaging.

[0002] The invention relates more particularly to a magnetic resonance imaging device comprising a magnetic enclosure having a tubular enclosure body comprising a main part interposed between two end parts, a first series of permanent magnet support plates forming the main part of the enclosure body, a second series of permanent magnet support plates, of annular section, forming at least one of the two end parts, and means for assembling the support plates of the first and second series together, arranged to allow coaxial assembly of the support plates together.

[0003] The magnetic resonance imaging device according to the invention is, in particular, but not exclusively, a portable MRI device. By portable, we mean a movable (mobile) MRI device. STATE OF THE ART

[0004] Magnetic resonance imaging (MRI) is now widely recognized as a non-invasive imaging technique for the internal structures of bodies, particularly human bodies. This technique allows, in particular, the examination of hydrogen nuclei, and especially their nuclear spin, within water molecules that make up part of the body.

[0005] Typically, a device employing this technique (an MRI scanner) is equipped with a magnet designed to impose a static magnetic field (called the "primary magnetic field") on the body. Under the influence of this field, the nuclear spins associated with the hydrogen nuclei contained in the water molecules that partially compose the body become polarized. An MRI scanner also includes gradient coils configured to produce small-amplitude magnetic fields that vary in space when a current is applied to them. The combined effects of the magnetic fields imposed by the gradient coils allow for the spatial encoding of each position of the body being scanned. The MRI scanner further includes at least one radio frequency (RF) coil designed to act as an RF transmitter / receiver.The radio frequency coil is configured to emit RF energy pulses at a frequency equal to or close to the resonant frequency of hydrogen nuclei's spins, a frequency at least partially absorbed by these nuclei. As soon as the RF emission is interrupted, the nuclear spins relax to return to their initial energy state and, in turn, emit an RF signal that can be collected by at least one RF coil. This RF signal is then processed using a computer and reconstruction algorithms to obtain an image of the body.

[0006] While the benefits of MRI scanners are undeniable, they do have the drawback of being quite bulky and heavy. They are therefore permanently installed, requiring substantial dedicated space and necessitating patient transfers within these facilities.

[0007] To overcome this drawback, portable MRI devices have been developed. By portable, we mean MRI devices that can be moved (mobile).

[0008] Among portable MRI devices, the one described in international application WO2023 / 104948 filed by the Applicant is known. The MRI imaging device described in this application comprises a magnetic assembly designed to impose a primary magnetic field in an scanning area of ​​a primary patient room, said magnetic assembly being mounted on a trolley. The magnetic assembly includes, in particular, a plurality of annular-section permanent magnet support plates, joined together by alignment means in the form of alignment rails. The alignment means include at least one rail having alignment notches, each alignment notch retaining a support plate, the notches being configured to maintain a predetermined spacing between two adjacent support plates.The magnetic assembly further includes a radio frequency coil and gradient coils arranged inside the main housing and assembled to the support plates. Advantageously, the radio frequency and gradient coils are removable.

[0009] While the MRI device described above allows for examination of all parts of the body, offering satisfactory image quality and improved uniformity of the magnetic field compared to known prior art assemblies, access to the magnetic assembly housing for mounting and dismounting the gradient coils remains difficult. The support plates at the ends of the magnetic assembly have narrower openings than the support plates at the center, in order to confine the magnetic field to each end and thus achieve greater homogeneity in the central area to be imaged.Due to this arrangement, gradient coils forming a tubular gradient assembly are preferred, having two end sections connected by a central section whose external diameter is larger than both the external diameter of the end sections and the diameter of the openings in the end support plates. Given the arrangement of the support plates and the gradient assembly, it is necessary to remove the end support plates at one end to insert (or remove) the gradient assembly into (or out of) the magnetic assembly housing.To do this, several alignment rails must be disassembled to disengage the support plates located at one end of the magnetic assembly. Then, the end support plates must be removed one by one to allow, once removed, the insertion (or removal) of the gradient coils into (or out of) the magnetic assembly housing. Furthermore, mounting the alignment rails onto the support plates remains difficult due to the mass of the support plates and the magnetization exerted between the plates and adjacent plates by the magnets on the relevant support plates.

[0010] The invention aims to remedy these problems by proposing a magnetic resonance imaging device comprising a magnetic assembly offering simple and quick access within it so as to allow the mounting and dismounting of the coils placed inside it. SUBJECT OF THE INVENTION

[0011] To this end, and according to a first aspect, the invention proposes a magnetic resonance imaging device comprising a magnetic enclosure having a tubular enclosure body comprising a main part interposed between two end parts, a first series of permanent magnet support plates forming the main part of the enclosure body, a second series of permanent magnet support plates forming at least one of the two end parts, each support plate of the first and second series having an annular section delimiting an opening, the opening of the support plates of the second series having a diameter smaller than that of the opening of the support plates of the first series, means for assembling the support plates of the first and second series together, arranged to allow coaxial assembly of the support plates,The imaging device is notable in that the assembly means comprise a first arrangement of rail(s) including at least one alignment rail having a main rail segment provided with notches for retaining the support plates of the first series and at least one end rail segment, adjacent to the main rail segment, comprising a flat surface on which the support plates of the second series are fixed.

[0012] Thus, thanks to the assembly of the support plates with an arrangement of alignment rail(s) as defined above, it can be easily and quickly accessed within the magnetic enclosure by removing the support plates fixed on the flat of the rail(s) without it being necessary to remove the alignment rail(s), their reassembly being just as easy.

[0013] Advantageously, the flat surface includes indexing means allowing the support plates of the second series to be indexed relative to each other on the flat surface according to a predetermined spacing.

[0014] Advantageously, the flat includes transverse slots for the passage of fixing screws for fixing the alignment rail of the first arrangement onto the support plates of the second series, the slots forming with the fixing screws, the means for indexing the support plates of the second series.

[0015] Advantageously, the notches are arranged to hold the support plates of the first series at a predetermined spacing relative to each other.

[0016] Advantageously, the spacing defined by the notches and that defined by the lights are repetitive and constant. The spacing between the support plates received in the notches or fixed to the flat surface is thus maintained and remains reproducible when a support plate is removed and reinstalled. Maintaining this spacing improves the homogeneity of the magnetic field within the enclosure.

[0017] Advantageously, the magnetic enclosure includes a third series of permanent magnet support plates forming the other of the two end parts, the main segment of the alignment rail of the first arrangement being dimensioned to assemble the support plates of the first series and the support plates of the third series.

[0018] Advantageously, the assembly means include a second arrangement of rail(s) comprising at least one alignment rail having notches distributed along the length of said rail and configured for retaining the support plates of the second series. A module of support plates of the second series is thus formed.

[0019] Advantageously, the assembly means include a third arrangement of rail(s) comprising at least one alignment rail provided with notches distributed along the length of said rail and configured for retaining the support plates of the second series forming the other end part of the enclosure.

[0020] Advantageously, the alignment rail of the third arrangement is located in alignment with the alignment rail of the second rail arrangement(s).

[0021] Advantageously, the alignment rails of the first rail arrangement(s) are distributed around the circumference of the enclosure body alternately with the alignment rails of the second rail arrangement(s).

[0022] Advantageously, the alignment rails of the first, second and third arrangements are respectively external rails (rails mounted on the outer circumference of the enclosure body).

[0023] Advantageously, the assembly means include a fourth arrangement of rail(s) formed of reinforcing rails assembling the support plates of the main part by their internal circumference.

[0024] The rail arrangements just described, whether used alone or in combination, also have the advantage of preventing the support plates they assemble from deforming under the force of the magnetic field, and in particular the attraction or repulsion of the plates relative to each other. The alignment rails arranged on the outer circumference of the support plates, and comprising a main rail segment with an indentation defining notches for retaining the support plates, and a segment without an indentation (flat), structure the enclosure body and allow for the disassembly and reassembly of only the end support plates thanks to the toothless area.Furthermore, joining multiple end support plates together using dedicated additional rails—preferably two or three support plates—creates a removable magnetic "cap" and, in conjunction with the alignment rails, reinforces the speaker enclosure to prevent deformation. The internal rails, for their part, reinforce the structure's rigidity to prevent plastic deformation of the support plates in the central part of the speaker enclosure. BRIEF DESCRIPTION OF THE FIGURES

[0025] Other features and advantages of the invention will become apparent from the detailed description of the invention that follows, given by way of example and with reference to the accompanying figures in which:

[0026] Lare represents a perspective view of a magnetic enclosure of a magnetic resonance imaging device according to an example of an embodiment of the invention;

[0027] Lare represents a cross-sectional view of the enclosure showing the insertion of the gradient coils;

[0028] The image represents a view of the enclosure, after the gradient coils have been installed and before the end module is assembled on the main part of the enclosure body;

[0029] The representation shows a view of the enclosure, with the end module assembled to the main part of the enclosure body;

[0030] Lare represents a perspective view of an alignment rail of a first arrangement of rail(s);

[0031] Lare represents a perspective view of an alignment rail of a second arrangement of rail(s);

[0032] Lare represents a perspective view of a reinforcement rail of another rail arrangement(s). DETAILED DESCRIPTION OF THE INVENTION

[0033] In relation to figures 1 to 7, a magnetic resonance imaging device comprising a magnetic enclosure 1 is described.

[0034] The magnetic enclosure 1 has a tubular enclosure body 2 formed of plates 20, 21 supporting permanent magnets 6. The plates 20, 21 will be referred to hereafter as "support plate 20, 21".

[0035] More specifically, the speaker enclosure 2 comprises a first set of support plates 20 and a second set of support plates 21. Each support plate 20, 21 has an annular cross-section defining an opening, the opening of the support plates 21 of the second set having a smaller diameter than that of the opening of the support plates 20 of the first set. The support plates 20 of the first set define a portion called the main part 2A of the speaker enclosure, while the support plates 21 of the second set define the end parts 2B, 2C of the speaker enclosure, the main part being interposed between the end parts and advantageously adjacent to them. In the illustrated example (Figures 2 and 3), and as will be seen later, the end part 2B forms a removable part, similar to a lid, which, once removed, allows for the mounting and dismounting of gradient coils 8.The end part 2C, opposite the end part 2B, forms the patient entry part into the enclosure body 2.

[0036] The magnetic enclosure 1 further includes means for assembling the support plates of the first and second series together, said support plates being assembled together in a coaxial manner.

[0037] According to the invention, the assembly means comprise a first arrangement of rail(s) including at least one alignment rail 3, in the illustrated example eight alignment rails (only four rails are shown in Figure 1). The alignment rail 3 of the first arrangement, illustrated in Figure 1, comprises a main rail segment 30 and an end rail segment 31, adjacent to the main rail segment 30.

[0038] The main rail segment 30 is provided with notches (indentations) 32 for retaining the support plates 20 of the first series. The notches 32 are arranged to hold the support plates 20 of the first series at a predetermined spacing (gap) relative to each other. In the example shown, the spacing of the notches 32 is constant. This allows for a repeatable spacing between the support plates 20 of the first series.

[0039] The end rail segment 31 is not notched. More specifically, the end rail segment 31 includes a flat 33 to which the support plates 21 of the second series are attached. The support plates 21 of the second series are attached to the flat 33 by means of fixing screws mounted through slots 34 extending transversely across the flat 33 and fixed respectively in an insert 210 housed in a bore provided for this purpose on the peripheral edge of the associated support plate 21. Advantageously, the flat 33 includes a number of slots 34 at least equal to the number of support plates 21 to be fixed. In the illustrated example, there are three support plates 21 of the second series. This is, of course, a non-limiting example; the end portion 2B of the enclosure body 2 may be formed of a different number than illustrated.Preferably, however, the end portion 2B comprises at least three support plates.

[0040] The flat surface 33 also advantageously includes indexing means for indexing the support plates 21 of the second series relative to each other on the flat surface 33 according to a predetermined spacing. In the illustrated example, the indexing means are formed by the transverse slots 34 receiving the fixing screws for attaching the alignment rail 3 of the first arrangement to the support plates 21 of the second series.

[0041] Advantageously, the assembly means include a second rail arrangement comprising at least one alignment rail 4. This alignment rail 4 is dimensioned to assemble only the support plates 21 of the second series forming the end portion 2B of the enclosure (the portion opposite the patient entrance), in the illustrated example three support plates 21. The alignment rail has a length corresponding to the length of the end portion. The support plates 21 thus assembled by this "short" rail form a single support plate module. The alignment rail 4 is provided with notches 42, in the example three, distributed along its entire length. As with the rail of the arrangement described above, the notches 42 are equally spaced to ensure regular spacing of the support plates. An example of a rail of the second arrangement is illustrated in Figure 1.

[0042] In the illustrated embodiment, the assembly means include a third rail arrangement comprising at least one alignment rail 5 dimensioned to assemble only the support plates 21 of the second series forming the other end portion 2C of the enclosure (patient entry portion). In the illustrated example, this rail is identical to the alignment rail 4 of the second arrangement described previously. The alignment rail, whose length corresponds to the length of the end portion to be assembled, is thus provided with three notches distributed along its entire length. As shown in the figure, the support plates 21 are assembled to each other by the alignment rails 5 of the second arrangement and to the alignment rail 3 of the first arrangement extending along the entire length of the magnetic enclosure.The presence of alignment rails 5, which assemble only the support plates of part 2C of the enclosure body 2, in addition to the alignment rails 3, has the advantage of reinforcing the support and spacing of the support plates 21 relative to each other, thus eliminating the constraints related to magnetism generated by the magnets carried by the support plates, which tend to move closer together or further apart. This limits the deformations exerted on the support plates and therefore ensures a homogeneous magnetic field at the input of the magnetic enclosure.

[0043] In the illustrated example, only one end of the alignment rail 3 of the first arrangement includes a flat surface 33. According to an alternative embodiment not shown, the guide rail of the first arrangement may have a main segment with notches interposed between two end segments without notches. The end segments thus form a flat surface 33. Therefore, the enclosure body will comprise two end modules consisting of a set of support plates that can be individually disassembled (i.e., all the support plates of the end portion being removed at once) or assembled by simply placing them onto the relevant flat surface 33.The advantage of this configuration with two detachable end modules is to optimize access to the support plates 20 of the first series composing the main part 2A of the enclosure body 2 in case of maintenance of support plates 20 of the main part 2A of the enclosure body 2.

[0044] As shown in the figure, the rails of each arrangement are positioned such that the alignment rails 3 of the first arrangement alternate with the alignment rails 4, 5 of the second and third arrangements around the entire outer circumference of the enclosure body. This arrangement of alignment rails has the advantage of limiting the deformation of the support plates 20, 21. It should be noted that the deformation will be further limited at the entrance of the enclosure because the support plates 21 of the end section 2C are kept apart from each other not only by the alignment rail 4, which joins only these support plates, but also by the alignment rails 3, which extend along the entire length of the enclosure body. The support plates 21 of the end section 2B are joined to each other only by the alignment rails 4.The deformations of the support plates 21 at the end part 2B will however remain limited thanks to the assembly of the support plates 21 by the alignment rails 3 on the one hand and the fixing of each of the plates on the flat of each of the alignment rails 3 on the other hand.

[0045] In the illustrated example, the assembly means include a fourth rail arrangement formed by reinforcing rails 7 that join the support plates 20 of the main part 2A by their inner circumference (Figures 2 and 7). The reinforcing rails 7, whose length corresponds to the length of the main part, are housed respectively in a longitudinal slot extending along the entire length of the main part of the enclosure body 2. More specifically, each support plate 20 of the main part 2A has notches distributed along its inner peripheral edge, said support plates being arranged relative to each other so that the notches of each support plate 20 form longitudinal slots extending along the entire length of the main part of the enclosure body 2, each slot forming a slot for receiving an internal reinforcing rail 7.Each reinforcing rail 7 comprises a rail body with a rectangular cross-section and an axial longitudinal axis, having two opposing longitudinal walls with notches arranged symmetrically with respect to the axial axis. Advantageously, the reinforcing rails 7 are arranged opposite the alignment rails 3 of the first rail arrangement(s).

[0046] Thanks to the configuration of the alignment rails 3 that join the support plates 20, 21 together, and in particular the flat surface of said rails, the support plates 21 forming the removable part 2B of the speaker enclosure 2 can be removed without having to dismantle the alignment rails to allow the insertion of an assembly of gradient coils 8 as illustrated in the figure. The support plates 21 of part 2B are advantageously removed simultaneously, being joined together by alignment rails 4. Once the gradient coils 8 are in place within the speaker enclosure 2, the support plates 21 are repositioned and fixed onto the alignment rails 3. In the example described, the magnetic enclosure 1 comprises eight alignment rails 3 relating to the first rail arrangement, seven alignment rails 4 relating to the second rail arrangement, and seven alignment rails 5 relating to the third rail arrangement.This is of course an example of implementation, it being understood that the number of rails relating to each of the rail arrangements may be different and that the presence of alignment rails relating to the second and third arrangements is optional.

[0047] The invention is described above by way of example. It is understood that a person skilled in the art is able to carry out different embodiments of the invention without departing from the scope of the invention.

Claims

Magnetic resonance imaging device comprising a magnetic enclosure (1) having a tubular enclosure body (2) comprising: a main part (2A) interposed between two end parts (2B, 2C), a first series of support plates (20) for permanent magnets (6) forming the main part (2A) of the enclosure body (2), a second series of support plates (21) for permanent magnets (6) forming at least one of the two end parts (2B, 2C), each support plate (20, 21) of the first and second series having an annular section delimiting an opening, the opening of the support plates (21) of the second series having a diameter smaller than that of the opening of the support plates (20) of the first series, means for assembling the support plates (20, 21) of the first and second series together arranged to allow coaxial assembly of said support plates,characterized in that the assembly means comprise a first arrangement of rail(s) including at least one alignment rail (3) having a main rail segment (30) provided with notches (32) for retaining the support plates (20) of the first series and at least one end rail segment (31), adjacent to the main rail segment (30), including a flat (33) on which the support plates (21) of the second series are fixed. Imaging device according to claim 1, characterized in that the flat (33) has indexing means allowing the support plates (21) of the second series to be indexed relative to each other on the flat (33) according to a predetermined spacing. Imaging device according to claim 1 or claim 2, characterized in that the flat (33) includes transverse slots (34) for the passage of fixing screws for fixing the alignment rail (3) of the first arrangement on the support plates (21) of the second series, the slots (34) forming with the fixing screws, the indexing means of the support plates of the second series. Imaging device according to any one of claims 1 to 3, characterized in that the notches (32) are arranged to hold the support plates (20) of the first series at a predetermined spacing relative to each other. Imaging device according to any one of claims 1 to 4, characterized in that the magnetic enclosure (1) comprises a third series of support plates (21) of permanent magnets (6) forming the other of the two end parts (2B, 2C), the main segment (30) of the alignment rail (3) of the first arrangement being dimensioned to assemble the support plates (20) of the first series and the support plates (21) of the third series. Imaging device according to any one of claims 1 to 5, characterized in that the assembly means comprise a second arrangement of rail(s) including at least one alignment rail (4) provided with notches (42) distributed along the entire length of said rail and configured for holding the support plates (21) of the second series together according to a predetermined spacing. Imaging device according to any one of claims 1 to 6, characterized in that the assembly means comprise a third arrangement of rail(s) including at least one alignment rail (5) provided with notches distributed along the entire length of said rail and configured for retaining the support plates (21) of the second series forming the other end part of the enclosure. Imaging device according to claim 7 when it depends on claim 6, characterized in that the alignment rail (5) of the third arrangement is located in alignment with the alignment rail (4) of the second rail arrangement(s). Imaging device according to claim 6, claim 7 when it depends on claim 6 or claim 8, characterized in that the alignment rails (3) of the first rail arrangement(s) are distributed over the circumference of the enclosure body (2) alternately with the alignment rails (4) of the second rail arrangement(s). Imaging device according to any one of claims 1 to 9, characterized in that the assembly means comprise a fourth arrangement of rail(s) formed of reinforcing rails (7) assembling the support plates (20) of the main part (2A) by their internal circumference.

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