BRAIN SHIFT COMPENSATION FOR CATHETER TRAJECTORY PLANNING

Abstract

The present invention relates to compensating for brain shift in catheter trajectory planning. First brain shift information is determined from an initial brain image dataset, an initial planning dataset, a patient orientation dataset, and first burr hole dataset. The brain image dataset is updated based on the first brain shift information and a trajectory of a first catheter is updated based on the updated brain image dataset. For a subsequent catheter placement, subsequent brain shift information is determined based on the updated brain image dataset, the patient orientation dataset, and a subsequent burr hole dataset. The brain image dataset is updated again based on the subsequent brain shift information. The re-updated brain image dataset is utilized to update trajectories of the subsequent catheter as well as any preceding catheters.

Claims

1-13. (canceled)

14. A system for planning trajectories of at least two catheters, wherein each trajectory ends at a target point which is associated with a corresponding catheter which is one of said catheters and located within a brain which is in turn located in a cranium, comprising a computer having a processor which is configured to: a) acquire an initial brain image dataset which represents a three-dimensional image of at least a part of the brain; b) acquire an initial planning dataset which represents initial trajectories of the catheters; c) acquire a patient orientation dataset which represents the orientation of the cranium; d) acquire a first burr hole dataset which represents the size and location of a first burr hole in the cranium for a first catheter; e) calculate a first brain shift dataset from the initial brain image dataset, the patient orientation dataset and the first burr hole dataset, wherein the first brain shift dataset at least represents a brain shift which would be caused by the first burr hole; f) calculate an updated brain image dataset from the initial brain image dataset and the first brain shift dataset; g) update the trajectory of the first catheter on the basis of the updated brain image dataset; h) acquire a subsequent burr hole dataset which represents the size and location of a subsequent burr hole in the cranium for a subsequent catheter; i) calculate a subsequent brain shift dataset from the updated brain image dataset, the patient orientation dataset and the subsequent burr hole dataset, wherein the subsequent brain shift dataset at least represents a brain shift which would be caused by the subsequent burr hole; j) update the updated brain image dataset on the basis of the subsequent brain shift dataset; and k) update the trajectory of the subsequent catheter and all preceding catheters on the basis of the re-updated brain image dataset, wherein a preceding catheter is a catheter whose trajectory has been previously updated.

15. A data processing method performed by a computer having a processor for planning trajectories of at least two catheters, wherein each trajectory ends at a target point which is associated with a corresponding catheter which is one of said catheters and located within a brain which is in turn located in a cranium, the method comprising the steps of: a) acquiring, at the processor, an initial brain image dataset which represents a three-dimensional image of at least a part of the brain; b) acquiring, at the processor, an initial planning dataset which represents initial trajectories of the catheters; c) acquiring, at the processor, a patient orientation dataset which represents the orientation of the cranium; d) acquiring, at the processor, a first burr hole dataset which represents the size and location of a first burr hole in the cranium for a first catheter; e) calculating, by the processor, a first brain shift dataset from the initial brain image dataset, the patient orientation dataset and the first burr hole dataset, wherein the first brain shift dataset at least represents a brain shift which would be caused by the first burr hole; f) calculating, by the processor, an updated brain image dataset from the initial brain image dataset and the first brain shift dataset; g) updating, by the processor, the trajectory of the first catheter on the basis of the updated brain image dataset; h) acquiring, at the processor, a subsequent burr hole dataset which represents the size and location of a subsequent burr hole in the cranium for a subsequent catheter; i) calculating, by the processor, a subsequent brain shift dataset from the updated brain image dataset, the patient orientation dataset and the subsequent burr hole dataset, wherein the subsequent brain shift dataset at least represents a brain shift which would be caused by the subsequent burr hole; j) updating, by the processor, the updated brain image dataset on the basis of the subsequent brain shift dataset; and k) updating, by the processor, the trajectory of the subsequent catheter and all preceding catheters on the basis of the re-updated brain image dataset, wherein a preceding catheter is a catheter whose trajectory has been updated in a preceding step of the method.

16. The method according to claim 15, wherein the processor is configured to repeat steps h) to k) for at least one other additional catheter.

17. The method according to claim 15, wherein the subsequent brain shift dataset calculated by the processor in step i) also represents a brain shift caused by at least one preceding catheter.

18. The method according to claim 15, wherein the subsequent brain shift dataset calculated by the processor in step i) also represents a brain shift caused by an infusion performed using at least one preceding catheter.

19. The method according to claim 15, wherein calculating the subsequent brain shift dataset by the processor in step i) involves considering the structural properties of at least one preceding catheter.

20. The method according to claim 15, wherein updating a trajectory by the processor in step k) involves considering the structural properties of at least one preceding catheter.

21. The method according to claim 15, wherein h) to k) are repeated for the same subsequent catheter, but with an amended subsequent burr hole dataset.

22. The method according to claim 15, further comprising the steps of acquiring, at the processor, a treatment plan and updating, by the processor, the treatment plan on the basis of the updated trajectories.

23. The method according to claim 15, further comprising the step of checking, by the processor, at least one updated trajectory for compliance with planning guidelines which represent constraints for the trajectory.

24. The method according to claim 15, wherein if more than one catheter is to be inserted through the same burr hole, then updating the trajectory of the first catheter by the processor in step g) or the trajectory of the subsequent catheter by the processor in step k) involves updating, by the processor, the trajectories of two or more catheters which are to be inserted through the same burr hole.

25. The method according to claim 24, wherein updating the trajectories of two or more catheters which are to be inserted through the same burr hole is performed by the processor sequentially for the two or more catheters, and updating the trajectory of a second or subsequent catheter which is one of said two or more catheters involves calculating, by the processor, a brain shift dataset representing a brain shift caused by at least one preceding catheter which is one of said two or more catheters and updating, by the processor, the updated brain image dataset according to the calculated brain shift dataset.

26. A non-transitory, computer-readable storage medium storing instructions for computer program which, when running on a computer, causes the computer to perform the computer implemented medical method having the following steps: a) acquiring, at the processor, an initial brain image dataset which represents a three-dimensional image of at least a part of the brain; b) acquiring, at the processor, an initial planning dataset which represents initial trajectories of the catheters; c) acquiring, at the processor, a patient orientation dataset which represents the orientation of the cranium; d) acquiring, at the processor, a first burr hole dataset which represents the size and location of a first burr hole in the cranium for a first catheter; e) calculating, by the processor, a first brain shift dataset from the initial brain image dataset, the patient orientation dataset and the first burr hole dataset, wherein the first brain shift dataset at least represents a brain shift which would be caused by the first burr hole; f) calculating, by the processor, an updated brain image dataset from the initial brain image dataset and the first brain shift dataset; g) updating, by the processor, the trajectory of the first catheter on the basis of the updated brain image dataset; h) acquiring, at the processor, a subsequent burr hole dataset which represents the size and location of a subsequent burr hole in the cranium for a subsequent catheter; i) calculating, by the processor, a subsequent brain shift dataset from the updated brain image dataset, the patient orientation dataset and the subsequent burr hole dataset, wherein the subsequent brain shift dataset at least represents a brain shift which would be caused by the subsequent burr hole; j) updating, by the processor, the updated brain image dataset on the basis of the subsequent brain shift dataset; and k) updating, by the processor, the trajectory of the subsequent catheter and all preceding catheters on the basis of the re-updated brain image dataset, wherein a preceding catheter is a catheter whose trajectory has been updated in a preceding step of the method.

27. A computer comprising the non-transitory computer-readable storage medium according to claim 26.

Description

[0041] These figures show:

[0042] FIG. 1a an initial brain image dataset of a cranium, a brain and a tumor,

[0043] FIG. 1b the initial brain image dataset of FIG. 1a with an initial planning dataset;

[0044] FIG. 1c a first updated brain image dataset,

[0045] FIG. 1d a second updated brain image dataset,

[0046] FIG. 2 a tissue model for calculating a brain shift

[0047] FIG. 3 a part of the initial brain image dataset with a structure at risk and

[0048] FIG. 4 a system for carrying out the invention.

[0049] FIG. 1a schematically shows an initial brain image dataset which represents a three-dimensional image of a cranium 1 in which a brain 2 is located. Within the brain 2, there is a tumor 3 to be treated. The cranium 1, the brain 2 and the tumor 3 are depicted schematically be simplified outlines, and those items may not be drawn to scale.

[0050] The treatment of the tumor 3 involves placing at least two catheters with their distal ends in the vicinity of the tumor 3. Via the catheters, an infusate for treating the tumor 3 is to be infused. Planning the treatment of the tumor 3 therefore involves two aspects. The first aspect is planning the trajectories of the catheters such that they end at target points in the vicinity of the tumor 3. The second aspect is establishing a treatment plan which represents the amount of infusate to be infused by use of the respective catheters over time. The present invention mainly relates to planning of the catheter trajectories.

[0051] Step a) of the method involves acquiring the initial brain image dataset as shown in FIG. 1a. Step b) involves acquiring an initial planning dataset which represents initial trajectories of the catheters. An exemplary initial planning dataset based on the initial brain image dataset is shown in FIG. 1b. The initial planning dataset comprises initial trajectories of catheters 6 and 7, wherein the trajectories end at target points 8 and 9, respectively. The initial planning dataset was obtained using classical approaches which do not consider a brain shift which is caused by the burr holes 4 and 5 needed for inserting the catheters 6 and 7 or caused by the placement of the catheters 6 and 7.

[0052] Method step c) involves acquiring a patient orientation dataset which represents the orientation of the cranium 1 with respect to the force of gravity, which is indicated in FIG. 1a as the vector g. Step d) involves acquiring a first burr hole dataset which represents the size and location of a first burr hole 4 in the cranium 1 for the first catheter 6.

[0053] Method step e) involves calculating a first brain shift dataset from the initial brain image dataset, the patient orientation dataset, in particular the direction of the force of gravity relative to a cranium 1, and the first burr hole dataset. The first brain shift dataset represents a brain shift which would be caused by the first burr hole 4 due to a loss of cerebrospinal fluid and gravity acting on the brain 2. The brain shift, which represents a movement and/or deformation of the brain 2, is indicated in FIG. 1c. It is represented by the amended shape of the brain 2. The brain shift also causes a movement of the tumor 3 relative to a cranium 1. The position of the tumor 3 without the brain shift is shown by solid circle, while the new position of the tumor 3 due to the first brain shift is indicated by a dashed circle. The target points 8 and 9 move together with the tumor 3. It shall be noted that shifts of the tumor 3 and the target points are exaggerated in order to accentuate them.

[0054] Method step f) involves calculating an updated brain image dataset from the initial brain image dataset and the first brain shift dataset. The updated brain image dataset is shown in FIG. 1c. It can be referred to as the first updated brain image dataset because it represents the brain shift caused by the first burr hole 4.

[0055] Due to the first brain shift, the trajectory of the first catheter 6 no longer ends at the desired target point. Method step g) therefore involves updating the trajectory of the first catheter 6 on the basis of the updated brain image dataset. In particular, a new trajectory is calculated which ends at the desired target point relative to the tumor 3.

[0056] Method step h) involves acquiring a subsequent burr hole dataset which represents the size and location of a second burr hole 5 in the cranium 1 for a second catheter. The second burr hole is a subsequent burr hole and the second catheter 7 is a subsequent catheter.

[0057] Method step i) involves calculating a second brain shift dataset from the updated brain image dataset shown in FIG. 1c, the patient orientation dataset and the second burr hole dataset. The second brain shift dataset represents a second brain shift which would be caused by the second burr hole 5. Step j) involves updating the updated brain image dataset on the basis of the second brain shift dataset. The updated version of the updated brain image dataset can be referred to as second updated brain image dataset. It is shown in FIG. 1d.

[0058] As can be seen from the second updated brain image dataset, the second brain shift caused by the second burr hole 5 results in another displacement of the tumor 3 relative to the cranium 1. The new position of the tumor 3 due to the brain shifts caused by the burr holes 4 and 5 is shown as a dotted circle in FIG. 1d. The displacement of the tumor 3 means that the updated trajectory of the first catheter 6 and the initial trajectory of the second catheter 7 no longer end at the desired target points relative to the tumor 3. Method step k) therefore involves updating the trajectories of the first catheter and the second catheter on the basis of the second updated brain image dataset, such that both trajectories end at desired target points relative to the tumor 3.

[0059] In the present embodiment, the second brain shift is not only caused by the second burr hole 5, but also by the placement of the first catheter 6, which also causes a deformation of the brain 2. In general, a brain shift is calculated from a tissue model, which is in particular a mesh. The brain is considered as an elastic body, such that a mathematical model of deformation can be applied. One exemplary model of deformation is described by the formula

(λ+μ)∇div u+μΔu=−f,

which is a Navier Lamé equation. With appropriate boundary conditions and parameters, such as forces due to gravity, gradient pressure due to loss of cerebrospinal fluid and catheter placement, the equation can be solved, for example using the finite element method.

[0060] An example for a brain shift caused by catheter placement by use of a mesh model is shown in FIG. 2. This Figure shows a mesh 10 which represents a part of the brain tissue. When the catheter 6 is placed, the tissue is deformed by the tip of the catheter 6 pushing the tissue and the side of the catheter shifting the tissue due to frictional forces. The resulting brain shift is shown in FIG. 2.

[0061] FIG. 3 shows the tumor 3 relative to a vessel 11 in its initial position as a solid circle and with an amended position due to the brain shifts as a dotted circle. The vessel 11 is a structure at risk, which means that the catheter 6 must not get closer to the vessel 11 than a predetermined minimum distance, which is a constraint for the trajectory. The minimum distance is shown as a circle around the catheter 6. As can be seen from FIG. 3, the initial trajectory complies with the planning guideline because it is far enough away from the vessel 11. Due to the displacement of the tumor 3, the trajectory of the catheter 6 moves closer to the vessel 11. The minimum distance for the updated trajectory of the catheter 6 is indicated by a dotted circle. As can be seen from FIG. 3, the updated trajectory of the first catheter 6 is closer to the vessel 11 than the minimum distance indicated by the dotted circle 13. This means that the updated trajectory does no longer comply with the planning guidelines. The method for planning the trajectories of the catheters 6 and 7 is therefore repeated with a different initial planning dataset, and in particular with a different first burr hole dataset.

[0062] FIG. 4 schematically shows a system for implementing the method described above. The system comprises a computer 14, an input unit 18, such as a keyboard, a mouse, a touchscreen or the like, and an output unit 19 such as a monitor. The computer 14 comprises a central processing unit 15, a memory unit and an interface 17. The memory unit 16 comprises a computer program which causes the central processing unit 15 to perform the method described herein. The central processing unit 15 acquires data, such as the initial brain image dataset, the initial planning dataset, the patient orientation dataset or a burr hole dataset, from the memory unit 16 or via the interface 17. The computer 14 is adapted to display data on the output unit 19, such as an updated brain image dataset or the initial or updated trajectories of the catheters.