Test object intended for use in orthopedic surgery and associated evaluation and control methods

Abstract

The present invention relates to a test object (100) for use in orthopedic surgery, in particular for imaging a lumbar spine of a subject, the test object comprising a receiving volume (5) housing: - 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 orthopedic implant (20a, 20b, 21a, 21b, 25a, 25b) connecting the first vertebra element and the second vertebra element, and - a scattering medium (30) surrounding the first vertebra element, the second vertebra element and the orthopedic implant, the scattering medium having scattering properties similar to those of a portion of a body of the subject located in proximity to the first vertebra element. vertebra and the second vertebra.Figure to be published with the abstract: Figure 1.

Description

Title of the invention: Test object intended to be used in orthopedic surgery and associated evaluation and control methods 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 the 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 simulating specific clinical situations. They are commonly used in the field of medical imaging to control 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] In order 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 the acquisition of 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 postoperative images in orthopedic surgery.

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

[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 of patients. This then ensures better post-operative monitoring of patients who have undergone orthopedic surgery. In particular, this will enable 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 complementary 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 of smaller diameter 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 parallelepiped shape 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 vertebrae elements having properties similar to those of a plurality of vertebrae of the subject are provided, each vertebrae element of the plurality of vertebrae 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 complementary 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 complementary 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 upon 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] [Fig. 1] schematically represents a first example of a test object in accordance with the invention,

[0022] [Fig.2a] represents a schematic view from above of a second example of a test object in accordance with the invention;

[0023] [Fig.2b] represents a schematic side view of the second example of an object- test in accordance with the invention;

[0024] [Fig.2c] represents another schematic side view of the second example of a test object in accordance with the invention;

[0025] [Fig.3] schematically represents a set of vertebrae included in the test object of [Fig.l];

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

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

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

[0029] [Fig.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 post-operative images acquired after an intervention, in particular 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 called 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, in particular suitable for imaging of 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.l]). 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 making it possible 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 lumbar spine of the subject.

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

[0041] As can be seen in [Fig.l], 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 it is used for acquiring images (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 receiving volume 5 of parallelepiped shape, 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.l], only three positioning markers M1, M2, M3 are also visible in [Fig.l]).

[0044] In practice, each positioning marker M1, M2, M3 is formed in a radio-transparent material so as not to hinder 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 the present 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 Thl2. It can also be the vertebrae of the sacrum such as the vertebra SL

[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 spinal column. 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 here, for example, to the five lumbar vertebrae L1, L2, L3, L4, L5, to a dorsal vertebra Th 12 and to a sacral vertebra SI.

[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 portion concerned 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 subject's spine. 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 Th 12.

[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 here less than or equal to 35 degrees. This then indicates a slight scoliosis. More preferably, 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 polymeric material. Preferably, the polymeric material comprises a polyepoxide. It For example, an epoxy resin is used to represent the bony portions of each vertebra. For example, a polyurethane is used to represent the flexible portions (such as the spinal cord) of the subject's spine.

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

[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 the present description, an “orthopedic implant” corresponds to a material used in orthopedic surgery to maintain bone portions in order to avoid the risks of rotation or displacement of these bone portions. This then makes it possible to ensure 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 vertebra elements 10a, 10b. More particularly, the orthopedic implant 20a, 20b, 21a, 21b, 25a, 25b here makes it possible to secure the first vertebra element 10a and the second vertebra element 10b. The orthopedic implant 20a, 20b, 21a, 21b, 25a, 25b therefore makes it possible to reproduce the positioning of orthopedic equipment 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 “Ti6A14V” (defined according to the ISO 5832-3 standard). 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 of 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 elements of adjacent vertebrae. 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 10b. This makes it possible to fix the first vertebra element 10a and the second vertebra element 10b so 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 ([Fig.2a]). More particularly, by defining a first implantation direction ZI 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 ZI 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 α (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 PI ([Fig.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 ([Fig.2c]). In a preferred embodiment, the first plane PI 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 element of vertebra 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 additionally 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 implemented 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 extemal skeletal fixation,” Clin. Orthop. 189, 125-130 (1984).

[0073] Alternatively, other spinal fixation techniques may 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) can form a non-zero angle between them.

[0075] As a further variant, the first implantation direction and the second implantation direction may be substantially parallel.

[0076] Alternatively, the test object may comprise orthopedic implants for which implantation has not been performed properly. Implantation problems are, for example, an orthopedic implant that is not strictly within the vertebral element (corresponding to a situation where the orthopedic implant is not strictly intraosseous) or poor positioning or alignment of the orthopedic implants within 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 vertebra assembly 2; 200 is positioned in the receiving housing 7 defined in the receiving volume 5. In practice, the vertebra assembly 2; 200 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 [Fig.l], 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 diffusing medium 30 is adapted to reproduce the surrounding environment surrounding the subject's spine. The diffusing 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, 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 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 the present 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 may comprise artifacts simulating the presence of pathologies on the intervertebral discs such as the presence of osteoarthritis or pronounced wear for example.

[0088] In [Fig.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, equipped with a processor and a memory. A data medium 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 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 postoperative images in orthopedic surgery. In other words, the test object according to the invention presents 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 (and in particular for imaging the lumbar spine of a subject) to be evaluated.

[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). [Fig.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 method 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 Iml of the test object 1; 100. This image Iml 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 Iml is shown in [Fig.5]. In this figure, an orthopedic implant 20 is visible as well as a vertebra element 10.

[0100] As shown in [Fig.4], the evaluation method continues with a step E6 of processing the Iml image 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 Iml image 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 Iml image and provides, as output, the segmentation of the pixels of this acquired Iml image to identify the pixels corresponding to the orthopedic implant, on the one hand, and to the vertebral element, on the other hand.

[0102] In step E8, the processor determines a first area of ​​interest ROI 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 ROI 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] [Fig.6] shows an example of an acquired image on which a first area of ​​interest ROI and a second area of ​​interest RO2 corresponding to this first example have been identified.

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

[0107] In this second example, the second part of the 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, the two areas of interest are therefore associated with the vertebra elements.

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

[0109] As shown in [Fig.4], the evaluation method continues with a step E10 of determining a parameter for evaluating the quality of the image Iml acquired by comparing the first area of ​​interest ROI 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 ROI 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 ROI or of the second area of ​​interest RO2 according to the following formula: [YES] SNR = Average (ROI pixel values) Standard deviation (ROI pixel values) and / or SNR Average! Pixel values ​​(ROi) Standard deviation! Pixel values ​​RO2)

[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 ROI and on the determination of the standard deviation of the pixel values ​​associated with the first area of ​​interest ROI. It may 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 English term) determined between the first area of ​​interest ROI and the second area of ​​interest RO2. More particularly, the contrast-to-noise ratio CNR is determined, from the values ​​of the pixels of the first area of ​​interest ROI and the second area of ​​interest RO2 according to the following formula:

[0114] CNR = Average^ ROI Pixel Values)-Average(ROI Pixel Values) 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 ROI, 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 ROI.

[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 image quality. Here, the signal-to-noise ratio SNR and the contrast-to-noise ratio CNR are for example both 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 Iml image.

[0119] If the evaluation parameter is based on the signal-to-noise ratio SNR, a high value of the latter allows us to conclude that the image quality is good. The higher the value of 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 allows us to conclude that the image quality is good. The higher the value of 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 quality of images before acquiring images on patients (following a surgical intervention). This then guarantees better post-operative monitoring of patients who have undergone a surgical intervention 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 to control 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, an adjustment of the product of the tube current by the X-ray exposure time or an adjustment of the kilovolts for imaging systems using X-rays. The adjustment may also concern a modification of the parameters of the reconstruction algorithm in CT or MRI. The adjustment may also concern a modification of 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 orthopedic surgery (this method is also referred to as "control method" in the remainder of this description). [Fig.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 Iml of the test object 1; 100. This image Iml 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 by magnetic resonance or ultrasound. An example of an acquired image Iml is shown in [Fig.5].

[0127] As shown in [Fig.7], the control method continues with a step E24 of processing the Iml image 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 Iml image 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 Iml image and provides, as output, the segmentation of the pixels of this acquired Iml image 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 method. However, it makes it possible to accelerate the implementation of this control method and to improve its efficiency.

[0130] As shown in [Fig.7], the control method then comprises a step E26 of determining, on the acquired image, a data item characterizing the test object 1; 100. A data item characterizing the test object 1; 100 is for example a dimension of this test object 1; 100, the Cobb angle [3, the implantation angle a of 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 Iml. This analysis of the acquired image Iml 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 Iml 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 vertebra 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 less (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 commands an adjustment of the setting parameters of the medical imaging system.

[0136] As indicated previously, this involves, for example, an adjustment of the product of the tube current by the X-ray exposure time or an adjustment of the kilovolts for imaging systems using X-rays. It can also involve a change in the parameters of the reconstruction algorithm in CT or MRI. The adjustment can also involve a change in 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. A test object (1; 100) for use 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 polymeric material comprises a polyepoxide.

3. 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, wherein the diffusing medium (30) comprises a polymeric material.

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

8. Test object (1; 100) according to any one of claims 1 to 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.

11. 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, 21a, 21b, 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. A test object (1; 100) according to any one of claims 1 to 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. A test object (1; 100) according to any one of claims 1 to 12, further comprising a plurality of vertebral elements (10a, 10b, 10c, 10d, 10e, 10f, 10g) having properties similar to those of a plurality of vertebrae of the subject, each vertebral element (10a, 10b, 10c, 10d, 10e, 10f, 10g) of the plurality of vertebral elements comprising a polymer material, two adjacent vertebral elements (10a, 10b) of the plurality of vertebral elements 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 (|3) 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 for 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, - acquiring, by the medical imaging system, an image (Iml) of the test object (1; 100), - determining, in the acquired image (Iml), a first area of ​​interest (ROI) 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), and - determining a parameter for evaluating the quality of the acquired image (Iml) by comparing the first area of ​​interest (ROI) 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. Method for 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, - acquiring, by the medical imaging system, an image (Iml) of the test object (1; 100), - determination, on the acquired image (Iml), 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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