Method for Determining the Structure of a Medical Implant for Replacing Removed Tissue

Abstract

A data processing method performed by a computer (2) for determining the structure of a medical implant (12; 18; 20; 22) which is to replace removed tissue in a patient's body, comprising the steps of:—acquiring a 3D dataset which represents remaining tissue (10; 17) which at least partly surrounded the removed tissue before the latter was removed;—determining the required contour of the implant (12; 18; 20; 22) from the 3D dataset;—simulating forces exerted by the remaining tissue (10; 17) on the contour of the implant (12; 18; 20;22); and—determining a structure dataset which represents the structure of the implant (12; 18; 20; 22) such that the implant (12; 18; 20; 22) has the required contour and can absorb the simulated forces.

Claims

1-15. (canceled)

16. A system for determining the structure of a medical implant which is to replace a removed tissue in a patient's body, comprising a computer having a processor which performs the following steps: acquiring a 3D dataset which represents a remaining tissue which at least partly surrounded the removed tissue before removal; determining a required contour of the medical implant from the 3D dataset; identifying a simulated force exerted by the remaining tissue on a contour of the medical implant; and determining a structure dataset which represents a structure of the medical implant such that the medical implant has the required contour to absorb the simulated force; wherein the step of determining the structure dataset involves configuring a wall thickness of the medical implant that is capable of withstanding at least the simulated force.

17. A data processing method, performed by a processor of a computer, for determining a structure of a medical implant which is to replace a removed tissue in a patient's body, comprising the steps of: acquiring, by the processor, a 3D dataset which represents a remaining tissue which at least partly surrounded the removed tissue before the latter was removed; determining, by the processor, a required contour of the medical implant from the 3D dataset; simulating, by the processor, forces exerted by the remaining tissue on a contour of the medical implant; and determining, by the processor, a structure dataset which represents a structure of the medical implant such that the medical implant has the required contour and can absorb the simulated forces; wherein the step of determining the structure dataset involves configuring, by the processor, a wall thickness of the medical implant.

18. The method according to claim 17, wherein the step of determining the structure dataset involves providing, by the processor, the structure with at least one stiffener.

19. The method according to claim 17, wherein the 3D dataset is a medical imaging dataset.

20. The method according to claim 17, wherein the step of determining the required contour of the medical implant from the 3D dataset involves determining, by the processor, a shape of a cavity formed by the remaining tissue in the 3D dataset and using, by the processor, the shape of the cavity as the contour of the medical implant.

21. The method according to claim 17, wherein the step of determining the required contour of the medical implant from the 3D dataset involves matching, by the processor, the 3D dataset to an initial 3D dataset which represents at least parts of the remaining tissue before the removed tissue was removed, in order to determine a shape of a cavity formed by the remaining tissue in the matched 3D dataset, and using, by the processor, the shape of the cavity as the contour of the medical implant.

22. The method according to claim 21, wherein the initial 3D dataset is a medical imaging dataset or a matched atlas.

23. The method according to claim 17, wherein the step of simulating forces exerted by the remaining tissue involves segmenting, by the processor, the remaining tissue on a basis of an atlas and simulating a movement of a segmented remaining tissue.

24. The method according to claim 17, wherein the step of determining the structure dataset involves providing, by the processor, the medical implant with a rigidity which reflects the rigidity of the removed tissue.

25. The method according to claim 17, wherein the step of determining the structure dataset involves arranging, by the processor, the structure of the medical implant so as to form at least one marker which is to be detected by a medical navigation system.

26. The method according to claim 17, wherein the step of determining the structure dataset involves providing, by the processor, the structure of the medical implant with a socket for a marker device which is to be detected by a medical navigation system.

27. The method according to claim 17, wherein the step of determining the structure dataset involves providing, by the processor, the structure of the medical implant with at least one port for a medical liquid or at least one conduit for a medical liquid.

28. A method for producing a medical implant structure, comprising performing the method of claim 17 and further comprising the steps of producing the medical implant structure as represented by the structure dataset and verifying the contour of the produced implant.

29. A non-transitory computer-readable storage medium storing a computer program which, when running on a computer, causes the computer to perform the following steps: acquiring a 3D dataset which represents a remaining tissue which at least partly surrounded a removed tissue before removal; determining a required contour of an implant from the 3D dataset to replace the removed tissue in a patient's body; performing a simulation of forces exerted by the remaining tissue on a contour of the implant; and determining a structure dataset which represents a structure of the implant such that the implant has the required contour; wherein the step of determining the structure dataset involves configuring a wall thickness of the implant.

30. A computer comprising the non-transitory storage medium of claim 29.

31. The system of claim 16, further comprising the processor identifying a shape of a cavity formed by the remaining tissue in the 3D dataset and using the shape identified as the contour of the medical implant.

32. The system of claim 16, wherein the structure of the medical implant includes at least one stiffener.

33. The system of claim 16, further comprising: the processor utilizing an initial 3D dataset representing at least parts of the remaining tissue before removal; and the processor matching the 3D dataset to the initial 3D dataset to identify a shape of a cavity formed by the remaining tissue and using the shape identified as the required contour of the medical implant.

34. The system of claim 16, wherein the structure of the medical implant includes a rigidity which reflects the rigidity of the removed tissue or withstands the simulated force.

35. The system of claim 16, wherein the structure of the medical implant includes at least one marker which is to be detected by a medical navigation system.

Description

[0046] FIG. 1 a system according to the present invention;

[0047] FIG. 2 an illustration of a brain in a pre-operative state;

[0048] FIG. 3 an illustration of the brain from FIG. 2 after a first type of resection;

[0049] FIG. 4 an implant for replacing the removed tissue in the brain as shown in FIG. 3;

[0050] FIG. 5 an illustration of the brain from FIG. 2 after a second type of resection;

[0051] FIG. 6 the illustration of the brain from FIG. 5 after it has been matched to the illustration of the brain from FIG. 2;

[0052] FIG. 7 an implant comprising marker spheres;

[0053] FIG. 8 an implant comprising embossed marker areas;

[0054] FIG. 9 an implant comprising a socket for a marker device;

[0055] FIG. 10 an implant comprising a conduit; and

[0056] FIG. 11 an implant comprising a port.

[0057] FIG. 1 shows a system 1 for determining the structure of a medical implant which is to replace removed tissue in a patient's body. The system 1 comprises a computer 2 which in turn comprises a central processing unit 3, a memory 4 and an interface 5. The computer 2 is connected to an input unit 6, such as a keyboard, a mouse or a touch-sensitive surface, and an output unit 7 such as a monitor. The computer 2 is also connected to a medical imaging device 8 which provides one or more 3D datasets. The medical imaging device 8 can be replaced by any device which is capable of providing a 3D dataset, such as a storage medium, a server or another computer. Via the interface 5, the computer 2 exchanges data with devices connected to the computer 2. The central processing unit 3 performs the method steps as described in this document. The memory 4 stores program code which instructs the central processing unit 3 to perform the method and acts as a working memory for data which have been or are to be processed by the central processing unit 3.

[0058] FIG. 2 shows a brain 9 in a pre-operative state in which the brain 9 comprises tissue to be removed by cranial resection and tissue which is to remain after the resection. An initial 3D dataset which represents the brain 9 in the state shown in FIG. 2 is recorded by the medical imaging device 8 and acquired by the computer 2 from the medical imaging device 8.

[0059] FIG. 3 shows the brain 9 from FIG. 2 after a cranial resection. Parts of the brain tissue have been removed, leaving an area of remaining tissue 10 and a volume 11 which contained the removed tissue before the resection was performed. The medical imaging device 8 creates a first medical imaging dataset which represents the brain 9 in the state shown in FIG. 3. The computer 2 acquires the first medical image dataset from the medical imaging device 8.

[0060] The central processing unit 3 analyses the first medical imaging dataset and identifies the shape and size of the volume 11. In order to prevent damage to the remaining tissue 10, the volume 11 is to be filled with a medical implant. The central processing unit 3 determines the required contour of the implant from the shape and the size of the volume 11.

[0061] The central processing unit 3 then simulates the forces which would be exerted by the remaining tissue 10 on the contour of the implant if the implant were situated in the volume 11. For this purpose, the central processing unit 3 assumes the maximum accelerations which could act on the brain 9 and determines the forces exerted by the remaining tissue 10 which surrounds the volume 11 on the basis of these maximum accelerations and the structure of the remaining tissue 10. This simulation can for example be based on a finite element approach or any other suitable simulation technique, such as a technique based on a mass-spring model.

[0062] One option for simulating the forces exerted by the remaining tissue is to use an atlas of the brain which is matched to the patient's brain 9, in order to segment the remaining tissue 10 into tissue types. The simulation can then be based on the behaviour of the remaining tissue of each respective tissue type, for example by setting the masses and spring properties in the mass-spring model accordingly.

[0063] The central processing unit 3 then determines a structure dataset which represents the structure of the implant such that the implant has the determined required contour and can absorb the simulated forces. A sectional view of an example implant 12 is shown in FIG. 4. The contour of the implant 12 completely fills the volume 11 within the brain 9. In the present example, the medical implant 12 is a hollow implant in which an implant wall 13 encloses a hollow volume 14. The medical implant 12 also comprises an example of a stiffener 15 which connects opposite parts of the implant wall 13 in order to increase the structural stability of the implant.

[0064] The stiffener 15 and the thickness of the walls 13 are configured such that the medical implant 12 has a rigidity which matches the rigidity of the removed tissue. From a mechanical point of view, the implant 12 thus behaves like the removed tissue. The rigidity of the implant depends on a number of parameters, such as the thickness of the implant walls, the structure of any stiffeners within the implant, and the presence or absence of (micro-)cavities in the implant walls and/or stiffener(s).

[0065] It should be noted that the implant 12 need not necessarily comprise a sealed hollow volume 14. The implant 12 can also for example be permeable to a cerebrospinal fluid. The implant 12 can optionally also comprise conduits for a medical liquid, such as for example a system of conduits comprising one inlet port through which the medical liquid is introduced and a plurality of outlet ports through which the introduced medical liquid is provided to the remaining tissue 10.

[0066] The medical implant 12 can optionally also include at least one port through which a medical instrument can pass, such that the medical instrument can reach the remaining tissue 10 through the implant 12.

[0067] In the first example described above, the contour of the implant 12 is derived directly from the first medical image dataset. Depending on the type of resection, this may not result in the correct, i.e. required contour for the implant. FIG. 5 shows the brain 9 in its state after a second type of cranial resection, comprising a volume 16 and remaining tissue 17. However, the shape of the volume 16 does not match the shape of the removed tissue because some of the remaining tissue 17 has moved due to the force of gravity after the resection was performed, as indicated by the reference numeral 17a in FIG. 5. The contour of the implant should however match the shape of the removed tissue rather than the shape of the volume 16 in FIG. 5.

[0068] In this case, the medical imaging device 8 generates a medical imaging dataset which represents the brain 9 after the cranial resection, as in the first example. In this second example, however, the medical imaging dataset is referred to as the second medical imaging dataset and represents the state of the brain 9 as shown in FIG. 5.

[0069] Before the central processing unit 3 determines the required contour of the implant, it matches the second medical imaging dataset, which represents the state of the brain 9 as shown in FIG. 5, to the initial medical imaging dataset which represents the state of the brain 9 as shown in FIG. 2. The result of this matching process is a matched second medical imaging dataset which then represents a matched brain state, as shown in FIG. 6. The result of the matching step is that the position of the remaining tissue 17a in the matched second medical imaging dataset is the same as its position in the initial medical imaging dataset. The volume 16 in the second medical imaging dataset is thus transformed into the volume 16′ in the matched second medical imaging dataset, which has the shape of the removed tissue. The central processing unit 3 then determines the required contour of the implant from the matched second medical imaging dataset.

[0070] The structure of the implant generally consists of the contour of the implant and the internal arrangement of the implant. In one example, the structure dataset is a three-dimensional array of binary information indicating whether or not material is present at a position defined by the position of the binary information within the array. Printing data can also for example be generated from the structure of the implant, such that the implant can be produced using a 3D printer.

[0071] FIG. 7 shows an example implant 18 which comprises three marker spheres 19 within its structure. The marker spheres 19 are preferably formed integral with the implant 18. The marker spheres 19 have a known size and are arranged in a known spatial relationship, such that the position of the implant 18 in space can be determined from the locations of the marker spheres 19 in space. The spatial location of the marker spheres 19 is for example obtained via a medical navigation system. The marker spheres 19 are preferably reflective for infrared light. They can be provided with an IR-reflective coating or be made of an IR-reflective material, for example by using multiple materials in the 3D printing process of the implant 18.

[0072] FIG. 8 shows another example of an implant 20 which comprises embossed areas 21. The sizes and spatial arrangement of the areas 21 is known, such that the spatial position of the implant 20 can be calculated from the spatial locations of the areas 21. The areas 21 are preferably circular. They also preferably reflect infrared light, for example by being provided with an IR-reflective coating or made from an IR-reflective material.

[0073] FIG. 9 shows another example of a medical implant 22 which comprises a socket 23 for receiving a marker device 24. The marker device 24 comprises at least three marker spheres 25 in a known spatial arrangement. If the marker device 24 is plugged into the socket 23, the spatial position of the implant 22 can be calculated from the spatial locations of the marker spheres 25. The marker spheres 25, like the marker spheres 19 of FIG. 7, reflect infrared light.

[0074] FIG. 10 shows the implant 12 with an additional conduit 26 which has an inlet portion and two outlet portions. A medical liquid can be administered through the conduit 26 by introducing it into the inlet portion, from where it is guided to the outlet portions close to the remaining tissue.

[0075] FIG. 11 shows the medical implant 12 with a port 27 which connects opposite sides of the implant 12. The size of the port 27 is selected such that a medical instrument can be guided through the port 27, and therefore through the implant 12, in order to reach the remaining tissue without the implant 12 having to be removed.