Test object for use in orthopaedic surgery, and associated evaluation and monitoring methods

Abstract

The present invention relates to a test object (100) for use in orthopaedic surgery, in particular for imaging a lumbar spine of a subject, the test object comprising a receiving volume (5) that accommodates: - a first vertebra element (10a) having properties similar to those of a first vertebra of a subject; - a second vertebra element (10b) having properties similar to those of a second vertebra of the subject, adjacent to the first vertebra of the subject; - at least one orthopaedic implant (20a, 20b, 21a, 21b, 25a, 25b) connecting the first vertebra element to the second vertebra element; and - a scattering medium (30) surrounding the first vertebra element, the second vertebra element and the orthopaedic implant, the scattering medium having scattering properties similar to those of a portion of a body of the subject located near the first vertebra and the second vertebra.

Description

DESCRIPTION TITLE: Test object intended for use in orthopedic surgery and associated evaluation and control procedures TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of medical imaging.

[0002] The invention relates more particularly to test objects used in the medical field, more particularly here in orthopedic surgery. The invention is particularly advantageous for medical applications concerning the lumbar spine.

[0003] The present invention relates to a test object intended to be used in orthopedic surgery, a method for evaluating a quality of an image acquired by a medical imaging system and a method for controlling a setting parameter of a medical imaging system. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0004] Test objects (also called "phantoms") are objects that simulate specific clinical situations. They are commonly used in medical imaging to monitor the quality of images provided by different equipment.

[0005] In orthopedic surgery, it is common to place orthopedic implants, such as screws, plates or rods, during surgical procedures.

[0006] To verify the correct positioning of these orthopedic implants, a control image is acquired at the end of the procedure. This image is generally acquired by an imaging system using X-rays. This image is essential for post-operative monitoring.

[0007] However, the quality of this acquired image is often very heterogeneous. Indeed, this image quality is very dependent on the acquisition parameters used for the imaging system but also very dependent on the morphology of the patient. It is therefore necessary to successfully optimize the acquisition parameters of the imaging system before acquiring the post-operative image in order to ensure the quality of the latter. SUMMARY OF THE INVENTION

[0008] The present invention then proposes to make it possible to improve the optimization of the acquisition parameters of an imaging system to improve the quality of the control images acquired after a surgical intervention (and which must be interpreted by medical personnel in order to ensure, for example, the correct positioning of an orthopedic implant).

[0009] More particularly, the invention relates to a test object intended to be used in orthopedic surgery, the test object comprising a receiving volume housing: - a first vertebra element having properties similar to those of a first vertebra of a subject, the first vertebra element comprising a polymer material, - a second vertebra element having properties similar to those of a second vertebra of the subject adjacent to the first vertebra of the subject, the second vertebra element comprising the polymer material, - at least one orthopedic implant connecting the first vertebra element and the second vertebra element, the orthopedic implant comprising a metallic material, and - a diffusing medium surrounding the first vertebra element, the second vertebra element and the orthopedic implant, the diffusing medium having diffusion properties similar to those of a portion of a subject's body located near the first vertebra and the second vertebra.

[0010] Thus, advantageously according to the invention, the test object presents the shape, dimensions, structure, anatomical details (with or without pathologies) of a portion of the subject's spinal column and the adjacent environment so as to reproduce as much as possible the clinical conditions encountered during the acquisition of post-operative images in orthopedic surgery.

[0011] This test object is particularly suitable for assessing the quality of images acquired by a medical imaging system used in orthopedic surgery (and in particular for imaging a subject's lumbar spine).

[0012] It is also particularly suitable for enabling the adjustment parameters of the medical imaging system to be checked in order to check that the medical imaging system is properly adjusted before it is actually used to acquire post-operative images on patients. This then ensures better post-operative monitoring of patients who have undergone orthopedic surgery. In particular, this will allow effective monitoring of the positioning of orthopedic implants following surgery.

[0013] In addition to the characteristics which have just been mentioned in the preceding paragraph, the test object according to one aspect of the invention may have one or more additional characteristics among the following, considered individually or according to all technically possible combinations: - the polymer material comprises a polyepoxide; - the orthopedic implant comprises a titanium alloy; - the orthopedic implant is in the form of a screw of a length less than or equal to 50 millimeters and a diameter between 4 and 7 millimeters; - the orthopedic implant is in the form of a rod with a diameter less than or equal to 7 millimeters; - a plurality of orthopedic implants are provided connecting the first vertebra element and the second vertebra element; - the plurality of orthopedic implants comprises four screws and two rods connecting the first vertebra element and the second vertebra element, two screws being positioned in the first vertebra element, two other screws being positioned in the second vertebra element, each rod connecting a screw positioned in the first vertebra element and another screw positioned in the second vertebra element; - the diffusing medium comprises a polymer material; - the diffusing medium comprises a hydrogel; - the receiving volume is surrounded by an external wall comprising an elastomeric polymer material; - at least one positioning marker is provided located on the external wall of the receiving volume; - the reception volume has a parallelepiped shape; - the first vertebra element, the second vertebra element and the orthopedic implant forming a vertebra assembly, said vertebra assembly is positioned at a predetermined distance from a first face of the shape parallelepiped of the receiving volume and at another predetermined distance from a second face of the parallelepiped shape of the receiving volume, the second face being orthogonal to the first face; - a disc element is provided positioned between the first vertebra element and the second vertebra element, the disc element having properties similar to those of an intervertebral disc positioned between the first vertebra and the second vertebra of the subject; - a plurality of vertebral elements are provided having properties similar to those of a plurality of vertebrae of the subject, each vertebral element of the plurality of vertebral elements comprising a polymeric material, two adjacent vertebral elements of the plurality of vertebral elements being connected by at least one orthopedic implant; and - the plurality of vertebral elements is associated with a Cobb angle less than 35 degrees.

[0014] The invention also relates to a computer data medium comprising data executable by a three-dimensional printing system to generate the printing of a test object as defined previously.

[0015] The invention also relates to a method for evaluating the quality of an image acquired by a medical imaging system, the evaluation method comprising steps of: - provision of a test object as defined previously, - acquisition, by the medical imaging system, of an image of the test object, - determination, in the acquired image, of a first area of ​​interest associated with a first part of the test object and of a second area of ​​interest associated with a second part of the test object, and - determination of a parameter for evaluating the quality of the acquired image by comparing the first area of ​​interest and the second area of ​​interest.

[0016] In addition to the characteristics which have just been mentioned in the preceding paragraph, the evaluation method according to another aspect of the invention may have one or more additional characteristics among the following, considered individually or according to all technically possible combinations: - the first part of the test object is the first vertebra element and the second part of the test object is the second vertebra element; - the first part of the test object is the first vertebral element or the second vertebral element and the second part of the test object is the orthopedic implant; - the evaluation parameter is a signal-to-noise ratio; and - the evaluation parameter is a contrast-to-noise ratio.

[0017] The invention also relates to a method for controlling a setting parameter of a medical imaging system, the control method comprising steps of: - provision of a test object as defined previously, - acquisition, by the medical imaging system, of an image of the test object, - determination, on the acquired image, of data associated with the test object, - comparison of the determined data with a corresponding reference data by determining a difference between the determined data and the corresponding reference data, and - control of the adjustment parameter of the medical imaging system by comparing the determined difference to a predetermined threshold.

[0018] In addition to the characteristics which have just been mentioned in the preceding paragraph, the control method according to another aspect of the invention may have one or more additional characteristics among the following, considered individually or according to all technically possible combinations: - the determined data is a Cobb angle; and - the data determined is an implantation angle of the orthopedic implant.

[0019] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0020] The figures are presented for information purposes only and in no way limit the invention.

[0021] Figure 1 schematically represents a first example of a test object in accordance with the invention,

[0022] Figure 2a represents a schematic top view of a second example of a test object according to the invention;

[0023] Figure 2b represents a schematic side view of the second example of a test object according to the invention;

[0024] Figure 2c shows another schematic side view of the second example of a test object according to the invention;

[0025] Figure 3 schematically represents a set of vertebrae included in the test object of Figure 1;

[0026] Figure 4 represents, in the form of a flowchart, an example of an evaluation method in accordance with the present invention;

[0027] Figure 5 represents an image of a test object in accordance with the invention acquired by a medical imaging system;

[0028] Figure 6 represents an image of a test object as used during a step E8 of the evaluation method of Figure 4; and

[0029] Figure 7 represents, in the form of a flowchart, an example of a control method in accordance with the present invention.

[0030] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED DESCRIPTION

[0031] The present invention falls within the context of medical imaging. It aims more particularly to enable the improvement of the quality of postoperative images acquired after an intervention, particularly in orthopedic surgery.

[0032] The invention finds a particular application in the case of a medical imaging system adapted to imaging the lumbar spine of a subject. This is for example an imaging system using X-rays, such as radiography, or scanners for example. It is also a medical imaging system using magnetic resonance or ultrasound.

[0033] For this purpose, the present invention relates to a test object specifically designed to meet the quality requirements of post-operative images. These post-operative images are, for example, acquired after a surgical intervention in orthopedic surgery.

[0034] In the present description, a test object, also commonly referred to as a "phantom", relates to an object intended to simulate clinical situations encountered in orthopedic surgery. This test object is used to control the quality of post-operative images acquired by imaging systems, particularly suitable for imaging the subject's lumbar spine.

[0035] More particularly, here, the test object 1; 100 according to the invention is associated with the spine of a subject. In other words, the test object 1; 100 has an anthropomorphic shape, reproducing, in part, the spine of the subject and the environment surrounding the spine of the subject.

[0036] Figures 1 to 3 schematically represent a test object 1; 100 according to the invention. This test object 1; 100 here comprises a receiving volume 5, at least one first vertebra element 10a, a second vertebra element 10b, at least one orthopedic implant 20a, 20b, 21a, 21b, 25a, 25b and a diffusing medium 30.

[0037] The receiving volume 5 comprises an external wall 6 delimiting a receiving housing 7. This receiving housing 7 is adapted to accommodate the first vertebra element 10a, the second vertebra element 10b, the orthopedic implant 20a, 20b, 21a, 21b, 25a, 25b and the diffusing medium 30.

[0038] Here, the receiving volume 5 has a generally parallelepiped shape delimited by the external wall 6. The external wall 6 therefore comprises six rectangular side walls (or faces of the parallelepiped shape) making it possible to define the receiving volume 5 (only three side walls 6A, 6B, 6C are visible in FIG. 1). The dimensions of each rectangular side wall are for example the following: a width of between 20 and 40 centimeters (cm) and a length of between 10 and 30 cm. Preferably, each side wall has a width of the order of 30 cm and a length of 20 cm.

[0039] Alternatively, the receiving volume may have any other shape that allows it to contain the other elements of the test object, to simulate clinical situations encountered in orthopedic surgery and to control the quality of the post-operative images acquired by the imaging systems adapted to imaging the subject's lumbar spine.

[0040] In order to best reproduce the tissues of the subject's human body, the external wall 6 of the receiving volume 5 comprises an elastomeric polymer material.

[0041] As can be seen in Figure 1, the external wall 6 of the receiving volume 5 comprises at least one positioning marker M1, M2, M3. This positioning marker M1, M2, M3 allows precise and reproducible positioning of the test object 1; 100 when used for image acquisition (in particular to control the adjustment parameters of an imaging system as described below).

[0042] The positioning marker M1, M2, M3 is for example in the form of a cross “+” (corresponding to the “plus” sign usually used). Alternatively, it may be another cross “x” (corresponding to the “multiplication” sign usually used). Alternatively, the positioning marker may have any other shape suitable for forming a reference mark.

[0043] Here, in the case of a parallelepiped-shaped receiving volume 5, a positioning marker M1, M2, M3 is positioned at the center of each side wall 6A, 6B, 6C of the external wall 6 (given that only three side walls 6A, 6B, 6C are visible in FIG. 1, only three positioning markers M1, M2, M3 are also visible in FIG. 1).

[0044] In practice, each positioning marker M1, M2, M3 is formed in a radio-transparent material so as not to obstruct the path of rays (for example X-rays) involved by the imaging system concerned.

[0045] The other elements (first vertebra element 10a, second vertebra element 10b, orthopedic implant 20a, 20b, 21a, 21b, 25a, 25b, diffusing medium 30) of the test object 1; 100 are housed in the receiving volume 5. In other words, these other elements are positioned in the receiving housing 7 defined inside the receiving volume 5.

[0046] In this description, a vertebra element corresponds to a manufactured element having properties similar to the properties of a vertebra of a subject. By "similar properties" is meant properties of shapes, dimensions and structures equivalent to those of a vertebra of a subject in order to simulate relevant clinical conditions (in particular for the acquisition of control images after a surgical intervention).

[0047] The vertebrae concerned in the present invention are for example the lumbar vertebrae L1, L2, L3, L4, L5 and the dorsal vertebrae such as the dorsal vertebra Th12. It can also be the vertebrae of the sacrum such as the vertebra S1.

[0048] In other words, each vertebra element 10a, 10b, 10c, 10d, 10e, 10f has a shape modeling the anatomy of a vertebra as well as inclusions representing the anatomical details present in the vertebrae of a subject. Each vertebra element makes it possible to represent a healthy vertebra of a subject or a vertebra presenting a pathology. In particular, the vertebra elements 10a, 10b, 10c, 10d, 10e, 10f may comprise artifacts simulating the presence of pathologies on the vertebrae such as lesions or compressions for example. The vertebra elements 10a, 10b, 10c, 10d, 10e, 10f may also have a structure simulating the presence of osteoporosis as can be observed in the vertebra of a subject.

[0049] In the example shown in Figures 2a to 2c, the test object 1 comprises the first vertebra element 10a and the second vertebra element 10b. This example therefore reproduces only two vertebrae of the subject's spine. These are, for example, the lumbar vertebrae L4 and L5.

[0050] In the example shown in Figures 1 and 3, the test object 100 comprises a plurality of vertebral elements 10a, 10b, 10c, 10d, 10e, 10f, 10g. This example therefore reproduces a larger portion of the subject's spine. The vertebral elements 10a, 10b, 10c, 10d, 10e, 10f, 10g correspond, for example, here to the five lumbar vertebrae L1, L2, L3, L4, L5, to a dorsal vertebra Th12 and to a sacral vertebra S1.

[0051] Thus, as can be seen in Figures 1 to 3, the vertebra elements 10a, 10b, 10c, 10d, 10e, 10f, 10g are arranged one after the other so as to reproduce as accurately as possible the relevant portion of the subject's spinal column.

[0052] In particular, in the example shown in Figures 2a to 2c, the first vertebra element 10a and the second vertebra element 10b have properties similar to those of two adjacent vertebrae of the subject's spine. For example, here, the first vertebra element 10a and the second vertebra element 10b have properties similar to those of two vertebrae L4, L5.

[0053] In the example shown in Figures 1 and 3, the plurality of vertebral elements 10a, 10b, 10c, 10d, 10e, 10f, 10g have properties similar to those of the plurality of adjacent vertebrae of the relevant portion of the spinal column. of the subject. For example here, the plurality of vertebral elements 10a, 10b, 10c, 10d, 10e, 10f, 10g have properties similar to those of the lumbar vertebrae L1, L2, L3, L4, L5 and the dorsal vertebra Th12.

[0054] In particular, the plurality of vertebral elements 10a, 10b, 10c, 10d, 10e, 10f, 10g exhibits a flexion such as that observed on the subject's spine. This flexion is characterized by a Cobb angle [3 (visible in FIG. 3). Conventionally, this Cobb angle is defined from the directions respectively associated with the vertebral elements exhibiting the greatest inclination (here these are the vertebral elements 10b and 10f). The Cobb angle [3 is measured between an upper endplate of the proximal vertebra (i.e. located closest to the center of the spine) most inclined in a coronal plane (i.e. the plane perpendicular to the median plane and the transverse plane, which separates the body into a ventral part and a dorsal part), and an inferior endplate of the caudal vertebra (i.e. located in a posterior part of the spine) most inclined.

[0055] Preferably here, the Cobb angle [3 is less than or equal to 35 degrees. This then indicates a slight scoliosis. Preferably again, the Cobb angle [3 is here of the order of 30 degrees.

[0056] Alternatively, if the test object is associated with a clinical situation with more pronounced scoliosis, the Cobb angle may be greater than 35 degrees.

[0057] Each vertebra element 10a, 10b, 10c, 10d, 10e, 10f, 10g here comprises a polymer material. Preferably, the polymer material comprises a polyepoxide. This is for example an epoxy resin to represent the bony portions of each vertebra. It is for example a polyurethane to represent the flexible portions (such as the spinal cord) of the subject's spine.

[0058] Finally, vertebra elements 10a, 10b, 10c, 10d, 10e, 10f, 10g reproduce the shape, texture and absorption characteristics of a subject's vertebrae.

[0059] In order to reproduce the result of an orthopedic surgery, the test object 1; 100 also comprises at least one orthopedic implant 20a, 20b, 21a, 21b, 25a, 25b.

[0060] In this description, an “orthopedic implant” corresponds to a material used in orthopedic surgery to maintain bone portions in order to to avoid the risk of rotation or displacement of these bone portions. This then ensures better stability of the joint concerned.

[0061] As can be seen in Figures 2a to 2c and 3, the orthopedic implant 20, 25 here makes it possible to connect two adjacent vertebral elements 10a, 10b. More particularly, the orthopedic implant 20a, 20b, 21a, 21b, 25a, 25b here makes it possible to secure the first vertebral element 10a and the second vertebral element 10b. The orthopedic implant 20a, 20b, 21a, 21b, 25a, 25b therefore makes it possible to reproduce the positioning of orthopedic material carried out for example during a vertebral arthrodesis operation so as to secure several vertebrae together so that they can no longer move relative to each other.

[0062] The orthopedic implant 20a, 20b, 21a, 21b, 25a, 25b comprises a metallic material. This metallic material comprises, for example, titanium, chromium or cobalt. Preferably, the orthopedic implant 20, 25 comprises a titanium alloy. This is, for example, the titanium alloy known as “TI6AI4V” (defined according to ISO 5832-3). The orthopedic implant may also comprise an alloy of chromium and cobalt.

[0063] In practice, the orthopedic implant 20a, 20b, 21a, 21b is in the form of a screw. This screw has, for example, a length less than or equal to 50 millimeters (mm) and a diameter between 4 and 7 mm. Preferably, this screw has a length of the order of 40 mm and a diameter of the order of 5.5 mm or 6.5 mm.

[0064] The orthopedic implant 25a, 25b may also be in the form of a rod with a diameter less than or equal to 7 mm. Preferably, this rod has a diameter of the order of 5.5 mm. The length of the rod is here greater than 25 mm. For example, it is between 35 and 40 mm when the vertebrae concerned are the L4-L5 vertebrae. For other vertebrae, the length of the rod may be greater than a hundred millimeters.

[0065] Preferably according to the invention, the test object 1; 100 comprises a plurality of orthopedic implants 20a, 20b, 21a, 21b, 25a, 25b connecting two adjacent vertebra elements. More particularly, as shown in Figures 2a to 2c and 3, several orthopedic implants 20a, 20b, 21a, 21b, 25a, 25b are used to secure the first vertebra element 10a and the second vertebra element 10a. vertebra 10b. This allows the first vertebra element 10a and the second vertebra element 10b to be fixed in such a way as to ensure better locking of each vertebra element in a predefined position.

[0066] In a preferred embodiment of the present invention (shown in Figures 2a to 2c and 3), the test object 1; 100 comprises four screws 20a, 20b, 21a, 21b and two rods 25a, 25b (as a plurality of orthopedic implants). Two screws 20a, 20b are implanted in the first vertebra element 10a. Two screws 21a, 21b are implanted in the second vertebra element 10b.

[0067] In practice, the screws 20a, 20b positioned in the first vertebra element 10a are positioned so as to observe a predetermined implantation angle a (figure 2a). More particularly, by defining a first implantation direction Z1 associated with a first screw 20a implanted in the first vertebra element 10a and a second implantation direction Z2 associated with a second screw 20b implanted in the first vertebra element 10a, the implantation angle a is the angle formed between the first implantation direction Z1 and the second implantation direction Z2.

[0068] Similarly, the screws 21a, 21b positioned in the second vertebra element 10a are positioned so as to observe the predetermined implantation angle a (the same angle as the implantation angle between the screws 20a, 20b in the first vertebra element 10a).

[0069] The first screw 20a implanted in the first vertebra element 10a is positioned opposite another first screw 21a implanted in the second vertebra element 10b. Similarly, the second screw 20b implanted in the first vertebra element 10a is positioned opposite another second screw 21b implanted in the second vertebra element 10b.

[0070] Furthermore, here, the first screw 20a and the second screw 20b are implanted, in the first vertebra element 10a, in a first plane P1 (figure 2c). Similarly, the other first screw 21a and the other second screw 21b are implanted, in the second vertebra element 10b, in a second plane P2 (figure 2c). In a preferred embodiment, the first plane P1 and the second plane P2 are substantially parallel to each other.

[0071] In order to block the movement of the first vertebra element 10a and the second vertebra element 10b, the implanted screws 20a, 20b, 21a, 21b are connected two by two by a rod 25a, 25b. More particularly, as can be seen in FIGS. 2c and 3, a first rod 25a connects the first screw 20a implanted in the first vertebra element 10a and the other first screw 21a implanted in the second vertebra element 10b. Similarly, a second rod 25b connects the second screw 20b implanted in the first vertebra element 10a and the other second screw 21b implanted in the second vertebra element 10b. In practice, the test object also comprises four locking screws (not shown in the figures) for fixing the rods 25a, 25b to the screws 20a, 20b, 21a, 21b concerned in order to ensure locking of the entire structure.

[0072] The positioning of the orthopedic implants in the present invention is carried out according to the Magerl spinal fixation technique. More details concerning this fixation technique can be found in the article by Magerl, FP, "Stabilization of the lower thoractic and lumbar spine with external skeletal fixation", Clin. Orthop. 189, 125-130 (1984).

[0073] Alternatively, other spinal fixation techniques can be used, such as the Krag or Roy-Camille techniques. More details on these other fixation techniques can be found in the following articles: - Roy-Camille, R., Saillant, G. & Mazel, C, “Internai fixation of the lumbar spine with pedicle screw plating”, Clin. Orthop. Relat. Res, 203, 7-17 (1986) and - Krag, MH, Van Hal, ME & Beynnon, BD, “Placement of transpedicular vertebral screws close to anterior vertebral cortex: Description of methods”, Spine (Phila Pa 1976), 14, 879-883 (1989).

[0074] In particular as a variant, the first plane (containing the screws 20a, 20b) and the second plane (containing the screws 21a, 21b) may form a non-zero angle between them.

[0075] Alternatively, the first implantation direction and the second implantation direction may be substantially parallel.

[0076] Alternatively, the test object may include orthopedic implants for which implantation has not been performed properly. Implantation problems are, for example, an orthopedic implant that is not strictly in the vertebral element (corresponding to a situation where the implant orthopedic is not strictly intraosseous) or poor positioning or alignment of orthopedic implants in the vertebral elements.

[0077] The first vertebra element 10a, the second vertebra element 10b and the orthopedic implants 20a, 20b, 21a, 21b, 25a, 25b form a vertebra assembly 2. Similarly, the plurality of vertebra elements 10a, 10b, 10c, 10d, 10e, 10f and the orthopedic implants 20a, 20b, 21a, 21b, 25a, 25b form a vertebra assembly 200.

[0078] This set 2; 200 of vertebrae is positioned in the receiving housing 7 defined in the receiving volume 5. In practice, the set 2; 200 of vertebrae is positioned at a predetermined distance from the external wall 6 of the receiving volume 5.

[0079] More particularly, in the case of the parallelepiped-shaped receiving volume 5, the vertebra assembly 2; 200 is positioned at a predetermined distance from a lateral wall 6C of the external wall 6 and at another predetermined distance from another lateral wall 6A of the external wall 6.

[0080] The predetermined distance and the other predetermined distance are, for example, of the order of a few centimeters. Preferably, the predetermined distance is of the order of one centimeter.

[0081] As can be seen in Figure 1, the test object 1; 100 also comprises the diffusing medium 30 surrounding the vertebra assembly 2; 200. More particularly, the diffusing medium 30 surrounds the first vertebra element 10a, the second vertebra element 10b and the orthopedic implant 20a, 20b, 21a, 21b, 25a, 25b. In other words here, the diffusing medium 30 fills the receiving housing 7 around the vertebra assembly 2; 200. The receiving volume 5 is therefore full.

[0082] The scattering medium 30 is adapted to reproduce the surrounding environment surrounding the subject's spine. The scattering medium 30 then reproduces the anatomical structures adjacent to the vertebrae. This makes it possible to reproduce a clinical contrast gradient so as to ensure clinical image quality.

[0083] For this purpose, the diffusing medium 30 has diffusion properties similar to those of a portion of the subject's body located near the vertebrae concerned. In other words, the diffusing medium 30 has diffusion properties similar to those of a portion of the subject's body located near the vertebrae concerned. diffusion similar to those of the anatomical structures adjacent to the vertebrae considered.

[0084] In practice, the diffusing medium 30 comprises a polymer material. This material has a density, for example, between 1 and 2. The diffusing medium 30 is, for example, formed from a hydrogel.

[0085] Optionally, the test object may also comprise a disc element 15 positioned between two adjacent vertebra elements.

[0086] In this description, a disc element corresponds to a manufactured element having properties similar to the properties of an intervertebral disc positioned between two adjacent vertebrae. By "similar properties" is meant properties of shapes, dimensions and structures equivalent to those of an intervertebral disc of a subject in order to simulate relevant clinical conditions (in particular for the acquisition of control images after a surgical intervention).

[0087] In other words, the disc element 15 has a shape modeling the anatomy of an intervertebral disc as well as inclusions representing the anatomical details present in the intervertebral discs of a subject. The disc element makes it possible to represent a healthy intervertebral disc of a subject or an intervertebral disc presenting a pathology. In particular, the disc element 15 can comprise artifacts simulating the presence of pathologies on the intervertebral discs such as the presence of osteoarthritis or pronounced wear for example.

[0088] In Figure 3, a disc element 15 is visible between the first vertebra element 10a and another vertebra element 10g. The test object 1; 100 according to the invention may comprise a plurality of disc elements.

[0089] In practice, the disc element 15 here comprises a polymeric material. Preferably, the polymeric material comprises a polyurethane.

[0090] The present invention also relates to a three-dimensional printing system configured to generate the printing of a test object 1; 100 as described previously.

[0091] For this purpose, a control unit (not shown) is provided with a processor and a memory. A data carrier then comprises executable data describing the test object 1; 100 and enabling it to be generated (by three-dimensional printing). The executable data are, for example, stored in the memory.

[0092] The processor is configured to control the three-dimensional printing system (for example based on a stereolithography method) so as to generate the test object 1; 100. More particularly, when the three-dimensional printing system receives the control instruction from the processor, it executes the data allowing the generation of the printing of the test object 1; 100.

[0093] It should be noted that the test object can here be generated digitally (i.e. a virtual three-dimensional representation) from computer-aided design software. The processor then executes instructions corresponding to the data executable by the three-dimensional printing system so as to obtain a digital representation of the test object.

[0094] In other words, according to the present invention, the test object 1; 100 obtained can be a physical object (obtained by a three-dimensional printing system) or a virtual object (obtained using computer-aided design software). This is particularly advantageous, since the evaluation and control methods described below can be implemented solely by computer (all the steps then being implemented by the processor from the digitally generated test object) or by using the usual “physical” medical imaging systems (and the test object manufactured in a factory or obtained by three-dimensional printing).

[0095] Finally, the test object 1; 100 in accordance with the invention has the shape, dimensions, structure, anatomical details (with or without pathologies) of a portion of the subject's spine and the adjacent environment so as to reproduce as much as possible the clinical conditions encountered during the acquisition of postoperative images in orthopedic surgery. In other words, the test object according to the invention has a quality of biomimicry so as to reproduce more particularly the heterogeneities encountered here in and near the subject's spine.

[0096] The test object 1; 100 in accordance with the invention is particularly suitable for enabling the quality of images acquired by a medical imaging system used in orthopedic surgery to be evaluated (and in particular for imaging the lumbar spine of a subject).

[0097] The present invention then relates to a method for evaluating the quality of an image acquired by a medical imaging system used in orthopedic surgery (this method is also referred to as "evaluation method" in the remainder of this description). Figure 4 is a flowchart representing an example of an evaluation method in accordance with the present invention.

[0098] As shown in this figure, the evaluation process begins with a step E2 of providing a test object 1; 100 as described previously. The test object 1; 100 therefore has all the appropriate characteristics to reproduce as much as possible the clinical conditions encountered after orthopedic surgery.

[0099] The evaluation method then comprises a step E4 of acquiring an image Im1 of the test object 1; 100. This image Im1 is here acquired by a medical imaging system used in orthopedic surgery. This is for example an imaging system using X-rays, such as radiography, or scanners for example. It can also be a medical imaging system using magnetic resonance or ultrasound. An example of an acquired image Im1 is shown in Figure 5. In this figure, an orthopedic implant 20 is visible as well as a vertebra element 10.

[0100] As shown in Figure 4, the evaluation method continues with a step E6 of processing the image Im1 acquired in step E4. This step E6 makes it possible, for example, to identify the different parts of the test object 1; 100. In particular, this step E6 is, for example, a segmentation step making it possible to identify the pixels of the acquired image Im1 corresponding to the orthopedic implant, on the one hand, and to the vertebral element, on the other hand.

[0101] This step E6 is for example implemented by computer (more particularly by a control unit, not shown, conventionally equipped with a processor and a memory), by means of a segmentation algorithm. As a variant, it can be implemented by the implementation of an artificial neural network which receives, as input, the acquired image Im1 and provides, in output, the segmentation of the pixels of this acquired Im1 image to identify the pixels corresponding to the orthopedic implant, on the one hand, and to the vertebra element, on the other hand.

[0102] In step E8, the processor determines a first area of ​​interest RO1 associated with a first part of the test object 1; 100 and a second area of ​​interest RO2 associated with a second part of the test object 1; 100.

[0103] In a first example, the first part of the test object 1; 100 is the first vertebra element 10a or the second vertebra element 10b. In other words, the first area of ​​interest RO1 is associated with the first vertebra element 10a or the second vertebra element 10b of the test object 1; 100.

[0104] In this first example, the second part of the test object 1; 100 is the orthopedic implant 20a, 20b, 21a, 21b. In other words, the second area of ​​interest RO2 is associated with the orthopedic implant 20a, 20b, 21a, 21b implanted in the first vertebra element 10a or in the second vertebra element 10b.

[0105] Figure 6 shows an example of an acquired image on which a first area of ​​interest RO1 and a second area of ​​interest RO2 corresponding to this first example have been identified.

[0106] In a second example, the first part of test object 1; 100 is the first vertebra element 10a. The first area of ​​interest RO1 is therefore associated with the first vertebra element 10a.

[0107] In this second example, the second part of test object 1; 100 is the second vertebra element 10b. The second area of ​​interest RO2 is therefore associated with the second vertebra element 10b. In this second example, both areas of interest are therefore associated with the vertebra elements.

[0108] For each of the first area of ​​interest RO1 and the second area of ​​interest RO2, the processor then stores the values ​​of the pixels associated with them respectively.

[0109] As shown in Figure 4, the evaluation method continues with a step E10 of determining a parameter for evaluating the quality of the image Im1 acquired by comparing the first area of ​​interest RO1 and the second area of ​​interest RO2.

[0110] This evaluation parameter is, for example, the signal-to-noise ratio SNR (or "signal-to-noise ratio" according to the commonly used Anglo-Saxon term) determined between the first area of ​​interest RO1 and the second area of ​​interest RO2. More particularly, the signal-to-noise ratio SNR is determined, from the values ​​of the pixels of the first area of ​​interest RO1 or of the second area of ​​interest RO2 according to the following formula:

[0112] The determination of the signal-to-noise ratio SNR is therefore based on the determination of the average of the pixel values ​​associated with the first area of ​​interest RO1 and on the determination of the standard deviation of the pixel values ​​associated with the first area of ​​interest RO1. It can also be based on the determination of the average of the pixel values ​​associated with the second area of ​​interest RO2 and on the determination of the standard deviation of the pixel values ​​associated with the second area of ​​interest RO2.

[0113] Another example of the evaluation parameter is the contrast-to-noise ratio CNR (or "contrast-to-noise ratio" according to the commonly used Anglo-Saxon term) determined between the first area of ​​interest RO1 and the second area of ​​interest RO2. More specifically, the contrast-to-noise ratio CNR is determined, from the pixel values ​​of the first area of ​​interest RO1 and the second area of ​​interest RO2 according to the following formula: rnn d -l / ll cmn > Average (ROI pixel values) - Average (RO2 pixel values) IUU I 141 C / Vn — - - ; - ; — ; - - - Standard deviation (ROI pixel values)

[0115] The determination of the contrast-to-noise ratio CNR is therefore based on the determination of the average of the pixel values ​​associated with the first area of ​​interest RO1, the determination of the average of the pixel values ​​associated with the second area of ​​interest RO2 and on the determination of the standard deviation of the pixel values ​​associated with the first area of ​​interest RO1.

[0116] In practice, the contrast-to-noise ratio CNR evaluates the contrast between the signal (for example associated with the orthopedic implant) and a background signal (associated for example with the vertebral element in which the orthopedic implant is positioned).

[0117] Preferably, several evaluation parameters are determined in step E10 in order to allow a more precise evaluation of the quality. of the image. Here, for example, both the signal-to-noise ratio SNR and the contrast-to-noise ratio CNR are determined.

[0118] The evaluation method ends at step E12 during which the determined evaluation parameter is interpreted to be able to deduce therefrom an evaluation of the quality of the acquired image Im1.

[0119] If the evaluation parameter is based on the signal-to-noise ratio (SNR), a high value of the latter indicates good image quality. The higher the signal-to-noise ratio (SNR), the better the image quality.

[0120] Similarly, if the evaluation parameter is based on the contrast-to-noise ratio (CNR), a high value indicates good image quality. The higher the contrast-to-noise ratio (CNR), the better the image quality.

[0121] Thus, advantageously, the test object 1; 100 according to the invention makes it possible to evaluate the quality of the images obtained by the medical imaging system in question. This then makes it possible to ensure good image quality before acquiring images on patients (following a surgical procedure). This then guarantees better post-operative monitoring of patients who have undergone a surgical procedure in orthopedic surgery. In particular, this will allow effective control of the positioning of orthopedic implants following an operation.

[0122] The test object 1; 100 in accordance with the invention is also particularly suitable for controlling the adjustment parameters of the medical imaging system used in orthopedic surgery (and in particular for imaging the lumbar spine of a subject). This then makes it possible to ensure the good quality of the images acquired by this medical imaging system.

[0123] In practice, this involves, for example, adjusting the product of the tube current times the X-ray exposure time or adjusting the kilovolts for imaging systems using X-rays. The adjustment may also involve changing the parameters of the reconstruction algorithm in CT or MRI. The adjustment may also involve changing the operating parameters of a probe used in ultrasound imaging.

[0124] The present invention then relates to a method for controlling a setting parameter of the medical imaging system used in surgery. orthopedic (this method is also referred to as “control method” in the remainder of this description). Figure 7 is a flowchart representing an example of a control method in accordance with the present invention.

[0125] As shown in this figure, the control method begins with a step E20 of providing a test object 1; 100 as described previously. The test object 1; 100 therefore has all the appropriate characteristics to reproduce as much as possible the clinical conditions encountered after orthopedic surgery.

[0126] The control method then comprises a step E22 of acquiring an image Im1 of the test object 1; 100. This image Im1 is here acquired by a medical imaging system used in orthopedic surgery. This is for example an imaging system using X-rays, such as radiography, or scanners for example. It may also be a medical imaging system using magnetic resonance or ultrasound. An example of an acquired image Im1 is shown in Figure 5.

[0127] As shown in Figure 7, the control method continues with a step E24 of processing the image Im1 acquired in step E22. This step E24 makes it possible, for example, to identify the different parts of the test object 1; 100. In particular, this step E24 is, for example, a segmentation step making it possible to identify the pixels of the acquired image Im1 corresponding to the orthopedic implant, on the one hand, and to the vertebral elements, on the other hand.

[0128] Like step E6 described previously, this step E24 is for example implemented by computer (more particularly by a processor), by means of a segmentation algorithm. Alternatively, it can be implemented by the implementation of an artificial neural network which receives, as input, the acquired image Im1 and provides, as output, the segmentation of the pixels of this acquired image Im1 to identify the pixels corresponding to the orthopedic implant, on the one hand, and to the vertebral element, on the other hand.

[0129] This step E24 is optional in the control process. However, it allows for the acceleration of the implementation of this control process and the improvement of its efficiency.

[0130] As shown in Figure 7, the control method then comprises a step E26 of determining, on the acquired image, data characterizing the object- test 1; 100. A data characterizing the test object 1; 100 is for example a dimension of this test object 1; 100, the Cobb angle [3, the implantation angle has orthopedic implants, the grade of the pathology of a disc element 15 (if the disc element 15 has a pathology), etc.

[0131] In practice, this step E26 is implemented by means of an analysis of the acquired image Im1. This analysis of the acquired image Im1 is for example implemented by the processor from a dedicated image analysis algorithm. Alternatively, step E26 can be implemented by the implementation of an artificial neural network which receives, as input, the acquired image Im1 and provides, as output, the data characterizing the test object 1; 100.

[0132] Then, in step E28, the processor compares the data determined in step E26 with a corresponding reference data item. This reference data item corresponds, for example, to the actual value of the Cobb angle used to manufacture the test object 1; 100 or the actual value of the implantation angle a used when positioning the orthopedic implants in the vertebral elements. All the manufacturing data relating to the test object are, for example, stored in a memory associated with the processor.

[0133] In practice, the comparison between the data determined in step E26 and the corresponding reference data is carried out by determining the difference between this data determined in step E26 and the corresponding reference data.

[0134] If this difference is lower (in absolute value) than a predetermined threshold, the control method continues at step E30 during which a message is sent to indicate that the adjustment parameters of the medical imaging system are suitable. The predetermined threshold is for example 10%, and preferably 5%. The medical imaging system can therefore be used to acquire post-operative images on patients who have undergone orthopedic surgery.

[0135] If in step E28, the processor determines that the difference (in absolute value) between the data determined in step E26 and the corresponding reference data is greater than the predetermined threshold, the control method continues in step E32. During this step E32, the processor orders an adjustment of the setting parameters of the medical imaging system.

[0136] As previously mentioned, this involves, for example, adjusting the product of the tube current times the X-ray exposure time or adjusting the kilovolts for imaging systems using X-rays. It can also involve changing the parameters of the reconstruction algorithm in CT or MRI. The adjustment can also involve changing the operating parameters of a probe used in ultrasound imaging.

[0137] The adjustment of the setting parameters of the medical imaging system is then carried out in step E34. Then the control method resumes in step E22 in order to acquire a new image of the test object 1; 100 with the new setting parameters of the medical imaging system.

[0138] Thus, advantageously, the test object 1; 100 according to the invention makes it possible to check that the medical imaging system is properly adjusted before it is actually used to acquire post-operative images on patients. In other words, the test object 1; 100 makes it possible to check that the medical imaging system is properly calibrated before being used for acquiring post-operative images on patients. This then guarantees better post-operative monitoring of patients who have undergone orthopedic surgery. In particular, this will allow effective monitoring of the positioning of orthopedic implants following surgery.

Claims

CLAIMS

1. Test object (1; 100) intended to be used in orthopedic surgery, the test object (1; 100) comprising a receiving volume (5) housing: - a first vertebra element (10a) having properties similar to those of a first vertebra of a subject, the first vertebra element (10a) comprising a polymer material, - a second vertebra element (10b) having properties similar to those of a second vertebra of the subject adjacent to the first vertebra of the subject, the second vertebra element (10b) comprising the polymer material, - at least one orthopedic implant (20a, 20b, 21a, 21b, 25a, 25b) connecting the first vertebra element (10a) and the second vertebra element (10b), the orthopedic implant (20a, 20b, 21a, 21b, 25a, 25b) comprising a metallic material, and - a diffusing medium (30) surrounding the first vertebra element (10a), the second vertebra element (10b) and the orthopedic implant (20a, 20b, 21a, 21b, 25a, 25b), the diffusing medium (30) having diffusion properties similar to those of a portion of a subject's body located near the first vertebra and the second vertebra.

2. Test object (1; 100) according to claim 1, wherein the polymer material comprises a polyepoxide. [Claim s] Test object (1; 100) according to claim 1 or 2, wherein the orthopedic implant (20a, 20b, 21a, 21b, 25a, 25b) comprises a titanium alloy.

4. A test object (1; 100) according to any one of claims 1 to 3, further comprising a plurality of orthopedic implants (20a, 20b, 21a, 21b, 25a, 25b) connecting the first vertebra element (10a) and the second vertebra element (10b).

5. The test object (1; 100) of claim 4, wherein the plurality of orthopedic implants (20a, 20b, 21a, 21b, 25a, 25b) comprises four screws and two rods connecting the first vertebra element (10a) and the second vertebra element (10b), two screws being positioned in the first vertebra element (10a), two other screws being positioned in the second vertebra element (10b), each rod connecting a screw positioned in the first vertebra element (10a) and another screw positioned in the second vertebra element (10b).

6. Test object (1; 100) according to any one of claims 1 to 5. 5, wherein the diffusing medium (30) comprises a polymeric material.

7. Test object (1; 100) according to any one of claims 1 to 5. 6, wherein the diffusing medium (30) comprises a hydrogel.

8. Test object (1; 100) according to any one of claims 1 to 5. 7, wherein the receiving volume (5) is surrounded by an external wall (6) comprising an elastomeric polymer material.

9. Test object (1; 100) according to claim 8, further comprising at least one positioning marker (M1, M2, M3) located on the external wall (6) of the receiving volume (5).

10. Test object (1; 100) according to any one of claims 1 to 9, in which the receiving volume (5) has a parallelepiped shape. [Claim 1 1 ] Test object (1; 100) according to claim 10, wherein, the first vertebra element (10a), the second vertebra element (10b) and the orthopedic implant (20a, 20b, 21 a, 21 b, 25a, 25b) forming a vertebra assembly (2; 200), said vertebra assembly (2; 200) is positioned at a predetermined distance from a first face of the parallelepiped shape of the receiving volume (5) and at another predetermined distance from a second face of the parallelepiped shape of the receiving volume (5), the second face being orthogonal to the first face.

12. Test object (1; 100) according to any one of claims 1 to 10. 11, further comprising a disc element (15) positioned between the first vertebra element (20a, 20b, 21a, 21b, 25a, 25b) and the second vertebra element (20a, 20b, 21a, 21b, 25a, 25b), the disc element (15) having properties similar to those of an intervertebral disc positioned between the first vertebra and the second vertebra of the subject.

13. Test object (1; 100) according to any one of claims 1 to 10. 12, further comprising a plurality of vertebra elements (10a, 10b, 10c, 10d, 10e, 10f, 10g) having properties similar to those of a plurality of vertebrae of the subject, each vertebra element (10a, 10b, 10c, 10d, 10e, 10f, 10g) of the plurality of vertebra elements comprising a polymeric material, two adjacent vertebra elements (10a, 10b) of the plurality of vertebra elements vertebrae being connected by at least one orthopedic implant (20a, 20b, 21a, 21b, 25a, 25b).

14. Test object (1; 100) according to claim 13, wherein the plurality of vertebral elements (10a, 10b, 10c, 10d, 10e, 10f, 10g) is associated with a Cobb angle (P) less than 35 degrees.

15. Computer data medium comprising data executable by a three-dimensional printing system for generating the printing of a test object (1; 100) according to any one of claims 1 to 14.

16. A method of evaluating a quality of an image acquired by a medical imaging system, the evaluation method comprising steps of: - providing a test object (1; 100) according to any one of claims 1 to 14, - acquisition, by the medical imaging system, of an image (Im1) of the test object (1; 100), - determination, in the acquired image (Im1), of a first area of ​​interest (RO1) associated with a first part of the test object (1; 100) and of a second area of ​​interest (RO2) associated with a second part of the test object (1; 100), and - determination of a parameter for evaluating the quality of the image (Im1) acquired by comparing the first area of ​​interest (RO1) and the second area of ​​interest (RO2).

17. An evaluation method according to claim 16, wherein the first part of the test object (1; 100) is the first vertebra element (10a) and the second part of the test object (1; 100) is the second vertebra element (10b).

18. An evaluation method according to claim 16, wherein the first part of the test object (1; 100) is the first vertebra element (10a) or the second vertebra element (10b) and the second part of the test object (1; 100) is the orthopedic implant (20a, 20b, 21a, 21b, 25a, 25b).

19. An evaluation method according to any one of claims 16 to 18, wherein the evaluation parameter is a signal-to-noise ratio.

20. An evaluation method according to any one of claims 16 to 19, wherein the evaluation parameter is a contrast-to-noise ratio.

21. A method of controlling a setting parameter of a medical imaging system, the control method comprising steps of: - providing a test object (1; 100) according to any one of claims 1 to 14, - acquisition, by the medical imaging system, of an image (Im1) of the test object (1; 100), - determination, on the acquired image (Im1), of data associated with the test object (1; 100), - comparison of the determined data with a corresponding reference data by determining a difference between the determined data and the corresponding reference data, and - control of the adjustment parameter of the medical imaging system by comparing the determined difference to a predetermined threshold.

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