Abstract:
A method and apparatus for diagnostic imaging of a body part, by nuclear magnetic resonance, which method includes the steps of positioning the body part in a detection volume of a nuclear magnetic resonance imaging apparatus, inside a dedicated receiving coil; selecting the section or sections of said body part that has to be imaged and carrying out image detection by nuclear magnetic resonance; identifying and storing the detected images; and carrying out at intervals one or more subsequent image detections with nuclear magnetic resonance of the same body part and of the same section thereof as in the preceding image detections with nuclear magnetic resonance, positioning each time the body part in the same relative position with respect to the imaging volume of the nuclear magnetic resonance imaging apparatus.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the priority of Italian Patent Application No. SV2003A000033, filed in Italy on Sep. 9, 2003, the entire content of which is incorporated herein by reference. 
     BACKGROUND OF THE APPLICATION 
     1. Field of the Invention 
     The present invention relates to a diagnostic imaging apparatus and method for limbs, particularly the hand, by means of nuclear magnetic resonance, which method comprises the steps of positioning the hand in a detection volume of a nuclear magnetic resonance imaging apparatus, inside a dedicated coil, of selecting the section or sections of the hand or wrist of which the image has to be detected and of carrying out the image detection by means of nuclear magnetic resonance. 
     2. Discussion of Related Art 
     At present it has been found that in the evaluation of rheumatoid arthritis the images detected by nuclear magnetic resonance allow one to visualize pathological damages caused by rheumatoid arthritis in a better way than radiograph images, particularly the so called erosion. However these damages are at an advanced phase of the pathology. Recent analysis have shown that due to the image detection with nuclear magnetic resonance it is possible to find damages caused by rheumatoid arthritis in the initial phases of the pathology, such as the damage of soft tissues for example synovium, tendons and meniscus. 
     The synovial membrane is the main inflammation site in the precocious phases of rheumatoid arthritis. During these phases the inflammatory action involves an increase of the vascularization that can be highlighted in the nuclear magnetic resonance images by means of proper contrast agents, such as Gadolinium-di ethylentriamine of pentacetic acid (Gd-DTPA). Recording time sequences of nuclear magnetic resonance images of the synovial membrane with the above contrast agents shows changes of the signal intensity as a function of time that can be considered as indicators of the synovial inflammation and of the pathological activity. This has been shown by analysis regarding the intensity changes of MRI signal in the synovial membrane of the wrist. 
     OBJECTS AND SUMMARY 
     On the basis of the analysis carried out on different patient groups having different pathology activities and patient groups in the recovery phase, at least one embodiment of the present invention provides a method for the progressive evaluation of the pathology course. The method comprises the imaging steps disclosed hereinbefore and one or more subsequent nuclear magnetic resonance image detections of the same part and of the same section thereof as in a preceding nuclear magnetic resonance image detection, each time repositioning the anatomic part, particularly the limbs and especially of the hand in the same relative position with respect to the imaging volume of the nuclear magnetic resonance imaging apparatus. 
     The method provides also a storage of nuclear magnetic resonance image detection sequences used in the preceding detecting sessions, of doses and administration modes of the contrast agents and particularly the definition of the section plane or planes along which the nuclear magnetic resonance images are detected. 
     The method provides that the repositioning is carried out by using means that assure a millimetric and even sub-millimetric positioning repeatability. 
     The invention relates also to an apparatus that allows said repeated positioning. 
     Repositioning means may be an electronic type, i.e., it can use the capability of the nuclear magnetic resonance apparatus or it can be different electronic means such as telecamera or space sensor of markers applied on the limb in positions anatomically sure. 
     According to a preferred example that is very economical, user-friendly and of sure length and efficacy and that allows an extremely precise positioning, said means are composed of a receiving coil to which a cast of the patient limb, particularly the hand, is coupled. 
     The cast is advantageously of the cylindrical type and encloses the hand and the wrist and at least part of the forearm on all sides and is of the type that can be opened. 
     As regards the register repositioning of at least two cast portions, it is possible to use the repositioning means typical of casts and well known. 
     The cast has precise positioning and centering means at least with respect to a supporting bracket having precise positioning means in the apparatus for nuclear resonance magnetic imaging apparatus. 
     According to an advantageous feature, the bracket is composed of the bracket of the receiving coil and the receiving coil itself. 
     Particularly, the cast can be made in a die having a shape exactly identical to the shape of the bracket and the receiving coil outside the nuclear magnetic resonance apparatus. 
     Otherwise, the bracket itself and the receiving coil can form the die making the cast that can be directly made with the coil positioned inside the nuclear magnetic resonance imaging apparatus and preferably after having properly positioned the hand with respect to the image detection volume of the apparatus itself. 
     For the above aims it is advantageous to use a receiving coil of cylindrical annular or elliptical type associated to a coaxial or concentric bracket that together with the annular coil forms a box or case that can be opened and tight closed functioning as a die. 
     The cast portions may be made detachable to the bracket and the receiving coil, reciprocal centering means being provided of movable type and that are generated and incorporated inside the cast walls when it is moulded. 
     In an alternative example, the coil and the bracket are made by at least two portions hinged one with respect to the other along the same axis, said two portions being associable each to one of two cast portions and said cast portions being attached in place by means of movable fastening means, while due to the hinging means of said two bracket and receiving coil portions it is possible to bring said two bracket and coil portions and the associated cast portions from an opened position of the cast and an introduction position of the limb to a closed position of said two portions and to a clamping position without substantial compressive force but with a sure clamping in place of the limb simultaneously inside the cast and inside the receiving coil and/or also inside the bracket. 
     As regards the material that is used to form the cast, it can be any suitable material having the required features of permeability to the excitation and receiving RF signal without generating substantial changes on the same and/or without generating noises to the nuclear resonance magnetic imaging apparatus. 
     Systematic and constant noises or aberrations may be tolerated if they do not involve decadences of the image quality due to systematic adjustments implementable in the nuclear magnetic resonance imaging apparatus. 
     On the basis of what is set out above it is possible to follow analytically and with objective quantitative and precise means the course of the rheumatoid arthritis in end limbs or in extremities and particularly in the hand or in the wrist. That can occur starting from young phases of the pathology before the damages caused by it can be of considerable level. 
     Therefore the methods according to the present invention allows one to evaluate objectively and in a sure scientific way the course itself allowing to intervene in a proper manner to correct the course itself that due to the repositioning of the limb at time intervals in the same image detection position with respect to the preceding detection positions. 
     The precise positioning means can be of any type. The preferred embodiments shown herein are characterized by a simple construction but really efficient in guaranteeing the precise repositioning position. Possible not traumatic changes in time of the hand anatomy have been analyzed and unexpectedly it has been found that their effect is almost of no value on the proper positioning and that therefore such effects are not important. 
     One embodiment according to the present invention combines the receiving coil with its supporting bracket with the repositioning means composed of a cast. The cast is obtained by means of simple casting manufacture in a die that has contact surfaces with the cast having the same shape and size as the ones provided on the receiving coil and on the relative supporting bracket. 
     Advantageously the construction of the coil and of the supporting bracket can be such to form themselves the casting die for making the cast, improving the positioning accuracy and above all knocking down prices and making the operations even simpler and faster. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The characteristics of the invention and the advantages derived therefrom will appear more clearly from the following description of a few nonlimiting embodiments illustrated in the annexed drawings. In which: 
         FIG. 1  is a part section top plan view of an apparatus for repositioning the hand and the wrist according to an embodiment of the present invention. 
         FIG. 2  is a variant of the apparatus of  FIG. 1 . 
         FIG. 3  is a front view with the cast in transverse section of the apparatus according to the preceding figures. 
         FIGS. 4 and 5  are trasverse sections of a further varying embodiment wherein the bracket, receiving coil and cast assembly is realized in two parts hinged one with respect to the other, in closed and opened position, respectively. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the figures, a device for properly positioning the hand according to a preferred embodiment of the present invention includes the combination of a hand supporting bracket and a receiving coil assembly generally indicated by  1  and the cast of the hand itself indicated by  2  and shown in axial section. A bracket  101  is composed of a lower part  101 ′ bearing the hand that can extend in the direction of the forearm to such extent up to the wrist and beyond it in the direction of the elbow. Said lower part  101 ′ is made with a concave surface with an arched section, particularly a circular one and extending for such angular width substantially of 180° C. 
     The bracket  101  extends inside an annular receiving coil  201  closed on itself and extending only for a partial axial length of the total length of the bracket  101 . 
     The hand cast  2  is in the interior for the total length of the bearing lower part  101 ′ or for only a part thereof, preferably for the part substantially coincident with the receiving coil  201 . The hand cast  2  is preferably divided into two halves along an axial plane that is coincident or parallel to a central axial section plane and which plane is parallely oriented to the plane defined by the extension of the hand. The cast  2  can have predetermined centering means with the bearing lower part  101 ′ of the bracket  101  of the limb and of the receiving coil  201  and with the annular receiving coil itself. 
     In this case, in the supporting lower part  101 ′ along the internal contact side with the cast, one or more coaxial ribs  301  are provided engaging with corresponding grooves  102  of the cast. Alternatively, the opposite arrangement may be provided. 
     A coupling and centering means of the cast with the receiving coil can be composed of radial holes in said annular coil that are coincident with radial dead holes  202  provided in coincident and predetermined positions in the cast portions and of fastening and centering pins, screws or bolts  4  engaging the holes of the cast through the annular wall of the receiving coil. It is possible to provide several such pins and holes distributed along the coil circumference as highlighted with discontinuous lines. 
     In this embodiment, the cast may be made outside the receiving coil, i.e., of the supporting means and receiving coil assembly, in a device that is shaped in an identical way to the structure of the coil and supporting bracket. 
     In this case, movable walls are provided completing the lower part with a top part and therefore enclosing on all sides a chamber necessary for containing the plaster, resin or other casting material. At least one of the two head sides obviously can not be closed with a wall because the forearm comes out therefrom. In this case it can be assumed a closing by means of a resilient relatively soft seal or by means of an annular seal that can be swollen fitting the annular gap that is free between the forearm and the delimitating wall of the chamber for the casting. The opposite head side can be closed in a similar manner if the hand projects beyond the bracket or it can be simply closed by a head wall when the hand ends before the corresponding head edge of the bracket  101 . 
       FIG. 2  shows another embodiment wherein further abutment surfaces are provided for the proper reciprocal positioning between the cast  2  and the assembly  1  composed of the bracket and the receiving coil. In this case the cast portion projecting on the introduction side of the forearm is realized with a larger diameter with respect to the inner diameter of the annular receiving coil  201  and it forms a step  302  with an axial annular abutment surface  402  against the faced annular head side of the receiving coil  201  itself. 
     Such surface is highlighted also in  FIG. 3 , the same being indicated with a circular discontinuous line. Within the radial width of the axial abutment surface  402  axial centering means  5  may be provided which can be composed of one or more axial pins  5  arranged along the circumference. In the illustrated example, the axial pins  5  pass through the axial thickness of the coil  201 , but this is only one of the many construction arrangements that a person skilled in the art can adopt or not making a free choice within the base knowledge. 
     Still according to another variation, the centering means can be at the same time also fastening means being composed of bolts engaging threaded bushings incorporated in the cast when it is made. In this case, the casting box constituted by a perfect copy of the bracket and receiving coil assembly  1  must properly have even holes for bolts upon which the internal threaded bushings are screwed before the casting of the cast to incorporate them in the cast in the correct relative position with the bolts. Such bushings may be provided externally with a thread having a direction opposite to the one of the internal thread of the bushings or with a plurality of external radial flaps that are not illustrated in details. 
     In an alternative to the provision of a casting box separated by the bracket and receiving coil assembly  1 , which box is made as a perfect copy of said assembly  1 , it is possible that said bracket and receiving coil assembly  1  is itself a part of the casting box. In this case, further wall portions will be provided that can be coupled in a movable way to the supporting bracket and to the receiving coil to complete the casting box enclosing on all sides of the forearm and the hand even in the inner area of the receiving coil. As regards the head sides one can take into consideration what has been said before with regard to the presence on at least a head side of a tight seal quite soft and resilient or a seal as a tight ring that can be swollen and eventually on at least on a side of a head wall that can be tightly coupled with the shell wall. 
     In this way the casting for forming the cast is made directly on the assembly  1  formed by the supporting bracket and the receiving coil making even more precise the fitting of the complementary contact and reciprocal positioning walls between said assembly and said cast. 
     Again according to another embodiment not illustrated in detail, the cast that is divided into two halves according to a separation plane parallel to the substantially median plane of the hand that is parallel to the plane defined by the extension of the palm of the hand in wide condition, can be even firmly attachable to a bracket and coil assembly. In this case the supporting bracket can be composed of a shell surface closed on itself similarly to the coil and both said supporting bracket and the coil can be composed of at least two portions having an angular extension of 180° or of three portions having an angular extension of 210° that are hinged one with respect to the other and simultaneously movable to an opened position and to a closed position. 
     The cast in two or three portions that are complementary and corresponding to said portions hinged one with respect to the other of the supporting bracket and of the coil can be attached in and with each cast portions to the corresponding portions of the supporting bracket and of the coil in a steady manner by means of fastening means such as screws, bolts or the like. Therefore for a patient having a long pathology it is possible to maintain for some time a supporting bracket and receiving coil assembly anatomically dedicated to said patient, without loosing the possibility once the patient is recovered to use again the bracket and the receiving coil for another patient and moreover without loosing the possibility to restore the cast on the bracket and on the receiving coil for the discharged patient when that could be unfortunately necessary. 
     The above is shown in  FIGS. 4 and 5 . In this embodiment the circular ring of the receiving coil  201  is divided into two halves hinged one with respect to the other at a hinge  401 . The ends diametrically opposed may be provided with mechanical engaging means of the two halves of the receiving coil. At said two halves also automatic electric connectors are provided connecting the individual turns of the receiving coil that have been cut off to allow its opening and that can be constituted also by the mechanical connectors connecting the ends of the two coil portions opposite the hinge  401 . A tubular shell wall divided into two halves by an axial plane coinciding with the separation axial plane of the two halves of the receiving coil constitutes the housing chamber of the two halves of the cast separated by a separation plane extending at least not fully transversally to the separation planes of the receiving coil and of the tubular member. One of the two halves of the tubular element constitutes the support for the forearm and for the hand indicated with  101  in the preceding figures. The two said halves of the tubular member  101 ,  101 ′ are attached to the corresponding two halves of the receiving coil  201 , while the two cast halves are attached to the receiving coil  201  and to said two halves  101 ,  101 ′ of the tubular wall. The above fastening is realized by means of bolts or radial pins  7  according to the modes already disclosed.  FIG. 4  shows the assembly of the receiving coil of the bracket for the limb and of the cast in the closed condition, while  FIG. 5  shows said portions in the opened condition. 
     The above clearly shows the simplicity and the cheapness and the versatility of the repositioning apparatus according to the present invention. 
     Even if the described embodiment has been indicated at present as the preferred one, it has not to be considered limitative as regards the general scope of the present invention. 
     Although only preferred embodiments are specifically illustrated and described herein, it will be appreciated that many modifications and variations of the present invention are possible in light of the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.