WO2023089100A1

WO2023089100A1 - Method of positioning a cutting device involved in a surgical cutting process performed in an operation space

Info

Publication number: WO2023089100A1
Application number: PCT/EP2022/082424
Authority: WO
Inventors: Michael PEYER; Jonas Walti
Original assignee: Advanced Osteotomy Tools - Aot Ag
Priority date: 2021-11-18
Filing date: 2022-11-18
Publication date: 2023-05-25

Abstract

A method of positioning components involved in a surgical cutting process performed in an operation space, wherein the components comprise at least a cutting device having an intervention member configured to cut an object and a robot configured to move the intervention member relative to the object, comprises the steps of: defining a cut with a specific geometry to be applied to the object; defining a proviso for operating the cutting device; and simulating an activity of the cutting device in which the robot moves the intervention member relative to the object to apply the predefined cut to the object. Simulating the activity of the cutting device comprises computing a target position of the cutting device appropriate for the robot of the cutting device to perform the target activity in accordance with the proviso.

Description

DESCRI PTION

Title

METHOD OF POSITIONING A CUTTING DEVICE INVOLVED IN A SURGICAL CUTTING PROCESS PERFORMED IN AN OPERATION SPACE

Technical Field

[0001 ] The present invention relates to a computer-implemented method of positioning a cutting device including a robot involved in a surgical cutting process performed in an operation space.

Background Art

[0002] In many medical or surgical applications it is desired to cut tissue and, particularly, hard tissue such as bones. For such cutting various cutting devices are used, wherein in recent years automatic cutting by means of robots has becoming increasingly popular. Such semi or fully automatic cutting devices typically utilise the robot to move an intervention member or cutting tool relative to the tissue and to an appropriate target position for perform the surgical cutting process. For example, sophisticated cutting devices may comprise a laser device as intervention member.

[0003] However, a problem of known such cutting devices is that the typically have limited working volumes due to the limited volume of action of the robot. There are also issues with certain robot joint configurations such as singularities, robot to robot, or robot to cutting device collisions which have to be taken into account. Further, the line of sight to the navigation system for the cutting device, e.g. tracking marker to tracking camera, is limited in some operating room. For instance, the blocking objects such as the other medical devices around the place can cause robot collisions, e.g. tracking marker on patient, surgical instruments, or personal, other equipment. Furthermore, the surgical covers and the robot cable management can make the robot motions difficult. [0004] The above issues typically make it necessary to reposition the cutting device during operation. This usually is undesired as operation has to stop and reassume after repositioning. It also prolongs the surgery and may also negatively impact the outcome of the cutting, e.g., accuracy issues. In the worst case, a working arrangement cannot be found at all and the whole surgery needs to be aborted. Also, many limitations make it difficult to find a placement for the cutting device to efficiently perform the planned intervention without or only little moving the cutting device or the patient during the procedure. As mentioned, usually, many different discrete positions of the intervention member are needed to perform a full cutting, e.g., an osteotomy. The complexity of evaluating the best position of the cutting device further depends on the complexity of the cut, the shape of the operation space, and the type and number of other components involved in operation.

[0005] Therefore, there is a need for a system allowing to provide an efficient cutting procedure by means of a (semi-)automatic and particularly computer-aided cutting device considering the given situation in the operation space.

Disclosure of the Invention

[0006] According to the invention this need is settled by the subject-matter defined in the independent claims. Preferred embodiments are subject of the dependent claims.

[0007] In one aspect, the invention relates to a, preferably computer-implemented, method of positioning components involved in a surgical cutting process performed in an operation space, wherein the components comprise at least a cutting device having an intervention member configured to cut an object and a robot configured to move the intervention member relative to the object.

[0008] The method comprises the steps of: defining a cut with a specific geometry to be applied to the object; defining a proviso for operating the cutting device; and simulating an activity of the cutting device in which the robot moves the intervention member relative to the object to apply the predefined cut to the object. Such activity may include a movement of any component. Thereby, simulating the activity of the cutting device comprises computing a target position of the cutting device appropriate for the robot of the cutting device to perform the target activity in accordance with the proviso. [0009] The term “activity” in connection with the cutting device particularly relates to a movement of the cutting device to perform or provide the predefined cut to the object. Such activity may include a motion sequence of the robot and the intervention member from the initial position to a final position in the operation space. The initial position typically is the location and orientation of the cutting device and its intervention member before start of the operation, i.e. the cutting process, and the final position typically is the location and orientation of the cutting device and its intervention member after the cutting process. The position in between the initial and final position may be referred to as target positions.

[0010] The surgical cutting process can be computer-aided, i.e. using a cutting device controlled by a computer program.

[0011 ] The robot of the cutting device can be any type of robot suitable for providing a cut as desired. Advantageously, the surgical robot is a robotic arm including a system base and an articulated arm allowing kinematic movement of the intervention member mounted to the arm. The arm of the robot can comprise rigid segments, wherein each two adjacent rigid segments are connected by an adjustable or controllable joint.

[0012] The invention member can particularly be a laser head, e.g. a laser osteotome, or any other tool such as a drill, a probe holder or a position guidance, mounted to the robot. In cases of a robotic arm being involved, the intervention member may be mounted to the end the robotic arm and, more specifically, to the outermost or most distal rigid segment of the arm. The laser head can be used for cutting the object.

[0013] The term “operation space” can be the place or location, typically an operating room, in which a patient undergoes a surgery involving cutting the object.

[0014] The object can be or comprise of a human or animal soft or hard tissue. Specifically, it can be a human or animal hard tissue like cartilage, nail and, in particular, bone.

[0015] The predefined cut advantageously includes a specific geometry, e.g. a three- dimensional geometry having varying shapes in all three dimensions.

[0016] The term “position” as used in connection with various components involved in the invention may relate to a location and orientation of the respective component. Thereby, the position may be an absolute position associated to a world coordinate system. Or it can be a relative position related to other components involved.

[0017] The term “proviso” as used herein refers to a parameter, fact, condition or constraint involved in operation of the cutting device which may have an effect on the performance, accuracy or efficiency of the operation. It may provide a definition of operating guidance for the cutting device or its operation. It can include a certain policy such as the motion sequence of the robot may not have a collision with any other medical device or patient, the kinematics of the cutting device should have minimised number of displacements of the cutting device, or the angle change of the robot arm, for example of rigid segments relative to each other, during the movement should be as small as possible. In case the proviso comprises plural constraints, parameters or conditions such as minimizing the number of displacements as well as minimizing the time of operation, the single constraints, parameters or conditions can be weighted. Like this, the constraints, parameters or conditions considered to be more important can have a higher relevance or score than others.

[0018] The term “simulating” in connection with the invention may refer to a digital replication or preproduction of the cutting process over time, using a computer. In other words, the simulation may use a digital representation as described in more detail below or a model of the cutting device and the predefined cut in the computer to reproduce the activity of the cutting device that will be performed in a later real live cutting process. Using the simulation of the activity, the motion sequence of the robot and the intervention members can be observed. In particular, the simulation allows to mimic the operation or at least a portion of it prior the real live execution of the operation. Like this, problems arising from an inappropriate positioning of the cutting device can be identified prior start of the operation. In particular, the appropriate or even optimal target position of the cutting device can be virtually computed or determined. Later, in a step after the performing the method according to the invention, the real cutting device can then be positioned as computed or determined. Hence, the method is performed pre-operatively preferably in a computer-aided simulation, and is not a treatment of the human or animal body by surgery or therapy, and is not a diagnostic method performed on the human or animal body.

[0019] For example, the method according to the invention allows for efficiently finding collisions of the cutting device with other medical devices, with the patient or any other components. Or disadvantageous displacement of the robot can be prevented and repositioning of the cutting device can be prevented in the real operation.

[0020] According to the present invention, the position of the cutting device can be effectively determined before the real life of physical operating takes place. This avoids that the cutting device has to be moved during the operation, e.g., due to collisions with the other equipment in the operating room, or constraints of the movement of the robot. Such pre-operatively determination of the cutting device enables the operation being performed without interruption caused rearrangement of the cutting device. Therefore, a more efficient and secure operation can be achieved. Furthermore, the method may be repeated intra-operatively, e.g., when a change of the setting in operation space occurs or the like.

[0021 ] Preferably, the proviso comprises preventing displacements of the cutting device relative to the object. In other words, the proviso may comprise reducing or even minimizing a number of displacements of the cutting device relative to the object. Since displacing the cutting device typically involves an interruption of the cutting or surgical process, it usually is beneficial to keep the displacements as few as possible or to prevent displacements as far as possible and appropriate. Furthermore, displacements may be a source of mistakes or may depend on accurate handling by involved persons such that, again, keeping the number of displacements may be beneficial.

[0022] Preferably, the proviso comprises achieving a short time of operating of the cutting device to apply the cut to the object. In other words, the proviso may comprise reducing or minimizing a time of operating the cutting device to apply the cut to the object. Like this, the operation can be performed in an efficient manner.

[0023] Preferably, the method comprising a step of determining a position of the object. By means of the determined position, the object such as a body or a body part of a patient can be determined at its intended or actual position. The cut can then be defined precisely as it is executed later in the surgical process. Like this, the movement of the intervention member by the robot can accurately be simulated.

[0024] Preferably, the step of determining the position of the object comprises obtaining position data from a medical imaging technique. Such medical imaging technique may involve radiology, which may use imaging technologies of X-ray radiography, magnetic resonance imaging, ultrasound, endoscopy, elastography, tactile imaging, thermography, medical photography, nuclear medicine functional imaging techniques as positron emission tomography or single-photon emission computed tomography. It may further involve electroencephalography, magnetoencephalography, electrocardiography, and others.

[0025] By using such medical imaging techniques, a pre- or intra-operative scan can be obtained allowing accurate and efficient determination of the position of the object. Thereby, standard medical imaging techniques can be used which provide a dataset representing the three dimensional (3D) position of the object or even a 3D representation of the object itself at the position. Such dataset can efficiently be used in the method of the invention.

[0026] Preferably, the step of determining the position of the object comprises optically monitoring the object. Such optical monitoring allows for accurately determining and observing the object which may be beneficial for the simulation and the later operation.

[0027] Thereby, optically monitoring the object preferably comprises fixing a three-dimension marker to the object and acquiring the position of the object by an optical detector detecting the position of the marker. Such three-dimensional markers and optical detectors allow for an efficient and accurate monitoring.

[0028] The optical detector preferably has a field of view in which the object is arranged and the proviso preferably comprises preventing disruption of the object being in the field of view of the optical detector. By preventing disruption of the object, the later surgical process can efficiently be monitored and controlled.

[0029] Even though in some embodiments the components may comprise the cutting device only, preferably they comprise at least one further component particularly selected from an optical detector, a trolley, a spray apparatus and an aspiration device. Having a plurality of such components in the operation space increases complexity of optimizing positioning of the cutting device. Therefore, simulating the situation and providing positions for all involved components may particularly be beneficial. In particular, not only the suitable position of the robot but also the appropriate positions of the further components can be determined or evaluated using the present invention. This is particularly advantageous if one of the components is arranged in a position that would make the motion sequence of the robot complex or even cause collisions of with the robot movement. Such situations can be prevented by involving the further components.

[0030] Accordingly, the present invention can guide the user by software to find an appropriate placement of all or at least plural components for allowing optimized operation of the cutting device. Also the other components such as the tracking camera and the patient as well as the further medical devices can be optimally positioned.

[0031 ] Thereby, simulating the activity of the cutting device preferably comprises computing further positions of each of the surgical components appropriate for the cutting device to perform the activity. Such simulation allows for efficiently optimizing the operation space.

[0032] When involving further components, the method preferably comprises fixing a further three-dimensional marker to each of the at least one further component and acquiring the position by the optical detector, wherein the at least one further component is arranged in the field of view of the optical detector. This allows to optically monitor all components involved in the operation.

[0033] Thereby, the proviso preferably comprises preventing disruption of the at least one further component being in the field of view of the optical detector.

[0034] In advantageous embodiments, the robot of the cutting device has a robot arm. Such robot arms typically have rigid segments interconnected by adjustable joints. In connection with robot arms, the term “rigid segment” relates to a solid, inflexible typically longitudinal element. A rigid segment can be bar- or rod-like shaped.

[0035] Alternatively to robots with robot arms, also other types of robots may involve joints for movement.

[0036] In embodiments of robots including joints, simulating the activity of the cutting device preferably comprises determining a sequence of torsions of the joints of the robot. Like this, movement of the cutting device by the robot can efficiently be simulated.

[0037] Preferably, the activity of the cutting device is simulated based on inverse kinematics. Particularly when robots with joints such as joints involved in robot arms are concerned, inverse kinematics may allow efficient simulation. By using inverse kinematics, it is possible to pre-compute and optimize the robot configuration, e.g. joint positions, for every single Cartesian goal position of the robot flange. Every resulting position can then be checked against possible constraints, parameters or conditions or that is defined in the proviso, for instance, does the robot collide with something, is the line of sight still acceptable etc., in order to see if the current tool installation efficiently works out for the complete intervention or not.

[0038] Preferably, simulating the target activity of the robot of the cutting device comprises simulating a plurality of alternative activities of the cutting device, in which the robot moves the intervention member relative to the object to apply the predefined cut to the object, and associating a compliance grade representing a level of compliance with the defined proviso to each alternative activity.

[0039] Thereby, simulating the activity of the cutting device preferably comprises, for each alternative activity, computing an alternative position of the cutting device appropriate for the robot to move the cutting device to perform the respective activity.

[0040] The compliance grade or all compliance grades of all alternative activities can be provided in a graphical representation allowing the operator or other personnel to efficiently organize the operation space. For example, the various compliance grades relating to the alternative activities may be depicted in a map of the operation space, e.g. in a heat map allowing identification of the most appropriate positions.

[0041 ] Preferably, the robot has a kinematics with a plurality of rigid segments, wherein each two adjacent rigid segments are connected by a joint and form an articulated angle. Such robot including a robot arm may provide appropriate flexibility or degrees of freedom and accuracy for applying the cut.

[0042] Thereby, the method preferably comprises a step of determining the articulated angle for each two adjacent rigid segments using a Luebeck C-Function. Such determination allows for an efficient simulation. [0043] Thereby, the method preferably further comprises a step of increasing the compliance grade of the activity when one of the articulated angles during the activity of the robot is smaller than a predefined value of angle.

[0044] Simulating the target activity of the robot of the cutting device preferably comprises associating the compliance grade of each of the alternative activities to its alternative position. Thereby, simulating the target activity of the robot of the cutting device comprises comparing the compliance grades associated to the alternative positions and providing the alternative position with the most appropriate compliance grade as the target position.

[0045] Like this, the compliance grade may efficiently indicate the ranking or rating of the configuration of the cutting device. The compliance grade being an indicator of appropriateness of the position of the cutting device and, eventually, the further components can also be referred to as score.

[0046] Preferably, the method further comprises a step of increasing the compliance grade of the activity by a predefined value in accordance with the proviso when one of the articulated angles during the activity of the robot is smaller than a predefined value of angle in the proviso, e.g. less than 15° away from the boundary. For example, the configuration of the robot arm or the rigid segments thereof would be rated as advantageous, if the robot arm does not come too close to a boundary, where the room for further movement of the robot arm is limited. The boundary for the articulated angle can be a specific angle such as for instance 180 degrees, i.e. the articulated angle cannot be larger due to limitation of the mechanical construction of the robot arm. The increase of the compliance grade can be seen as a penalty score. When considering the proviso, the presention application would therefore prefer a configuration having a lower score.

[0047] Preferably, the method further comprises a step of increasing the compliance grade of the activity when the at least one angle change exceeds a predefined value of angle change in the proviso. In other words, a greater angle change is not desired since that may be indicative of a larger movement of the robot arm or the rigid segments thereof relative to each other.

[0048] The compliance grade indicates a value that is proportional or in reverse proportion to the recommendation of the configuration. In other words, the method may provide a map with several recommended configurations having low or high compliance grades. Such configuration may include the position where the robot can be placed and the initial orientation of the robot arm or, more specifically, its rigid segments and joints.

[0049] Preferably, the method further comprises setting the compliance grade of the activity to a value larger than the predefined compliance value, which would mark the activity as invalid or unfeasible, when a motion sequence of robot during the activity of the cutting device includes a collision with the further surgical components or the object.

[0050] Preferably, the method further comprises the step of simulating the activity of the cutting device including association of the compliance grade of each of the alternative activities to its alternative position.

[0051 ] Preferably, simulating the activity of the cutting device comprises comparing the compliance grades associated to the alternative positions and providing the alternative position with the most appropriate compliance grade as the target position.

[0052] Accordingly, the present invention can recommend one or more positions for the cutting device to be most appropriate. In an embodiment, all positions where the robot can be placed are defined in a discrete grid and the one or more recommended positions can be visualized with colors, which can in form of a heat-map indicating the ranking of the positions or using any other visualization techniques. The visualization can interactively guide the user to place the robot at one of the valid and recommended positions.

[0053] Preferably, the method comprises a step of setting the compliance grade of the activity to a value larger or lower than the predefined compliance value when a motion sequence of robot during the activity of the cutting device includes a collision with the further surgical components or the object. Like this, the compliance grade may efficiently represent a rating of the position of the cutting device.

[0054] Preferably, the method comprises a step of pre-positioning the further components, monitoring the position of each of the components relative to the object by means of an optical detector, and calculating positions of each of the components allowing the robot of the cutting device to move the intervention member to apply the cut to the object in consideration of the defined proviso. [0055] Preferably, defining the cut to be applied to the object comprises generating a digital representation of the cutting device and the cut. Such digital representation may allow for an efficient simulation by a computer. Thereby, simulating the activity of the cutting device preferably involves using the digital representation of the cutting device and the predefined cut.

[0056] As mentioned, the method according to the invention is different from a method for treatment of the human or animal body by surgery or therapy, or a diagnostic method practised on the human or animal body.

[0057] In general, the present invention can guide the user, preferably by software, to find an optimal placement for the cutting device, the tracking camera and the patient. By means of so called "inverse kinematics" computations, it can be possible to pre-compute and optimize the robot configuration such as joint positions for every single Cartesian goal position of the robot flange. Every resulting position can then be checked against possible constraints, e.g., does the robot collide with something, is the line of sight still ok etc., thereby verify if the current tool installation works out for the complete intervention or not.

[0058] One aspect of the present invention would be an intra operating room brute-force method approach, wherein the software checks and rates the validity of a given installation in the operating room and certain variations of it with a scoring system.

[0059] All tools such as system trolley and tracking camera are placed around the patient, which is already equipped with the target marker, based on a "rough guess" or some static, default installation guidance. Basic constraints like procedure-based patient orientation, placement of other equipment etc. is already respected.

[0060] As soon as the navigation system detects the position of the patient and the robot, the software can compute the validity of the current setup based on all known constraints. An internal error-function is used to compute a score for the current setup.

[0061 ] Additionally, the method may compute scores for slightly different placements. The additional positions may be defined by a discrete grid for a certain area or volume with specific gaps, e.g., a 100 cm by 100 cm grid with 10cm gaps in all directions would lead to 100 possibilities for one plane. [0062] The different grid positions can be ranked based on the resulting score. This ranking is visualized with colors, in manner of a heat-map, or other techniques in a 3D rendering of the installation-situation.

[0063] A graphic user interface (GUI) may guide the user interactively to move the cutting device, the patient, and/or the other surgical components, to a valid position.

[0064] Another aspect of the present invention would be the full simulation approach. The principle from above can be used to simulate the validity of a planned intervention pre-operatively by software only, where no surgical equipment or patient is physically involved. This is useful for planning the intervention on a simple desktop computer without the physical cutting device or other physical components, and verifying if the pre- operatively planned cuts can be performed smoothly by the cutting device.

[0065] The current operating room setup may be interactively defined with a GUI or directly proposed by a software implementing the method, based on kind of procedure, and visualized. A similar technique as described above may then be used to optimize the placement of the tools and/or the patient and to check the validity of the installation. To find a good and realistic arrangement, as many constraints, parameters or conditions as possible can be concerned, e.g., line of sight of the navigation system, obstructing objects, limited robot working volume, limited robot motions, limited patient placement possibilities etc.

[0066] Because there are multiple degrees of freedom but also many restrictions applying to solve the problem, some kind of semi-automated guidance supported by a good visualization is crucial. Machine learning techniques may also support the task significantly.

[0067] As discussed above an error-function can be used for computing the score for the current setup, where the following properties should be respected by a good error function:

• robot joint movements (less is better)

• avoid robot joint singularities

• avoid collisions

• keep line of sight between tracking system and all tracked object, e.g. between camera and patient markers and/or between tracking camera and laser osteotome • intervention related restrictions

The error function can be defined as compliance grade in the proviso which is considered when simulating the movement of the cutting device.

[0068] As an example, the following procedure may be considered when coding the method of present invention:

Foreach gridcell g ( for example 24x24 gridcells on a xy-Plane are tested, each with 88mm distance ) {

Place Path in Relation to Robot , as if the robot was standing at g

Score ( gridCell g ) = IKComputation Robot -> Path ( see below )

Set Visualizationcolor g based on computed score }

IKComputation score Robot -> Path : (Used for sweetspot colors and the actual cutting precomputation ) {

Independently compute the score of the configurations below, then select the one with the best score

( for example there are 5x2x3=30 configurations tested : 5 zAngles of the laserhead ( -20 , -10 , 0 , +10 , +20 deg ) and 2 f lipConf iguations ( on/off ) ; delta angle -5 / 0 / +5 )

Foreach configuration

{

Calculate FlangeMatrix foreach path vertex ( using relative robot-path placement , zAngle , flip irrelevant )

Determine the 7 robot- JointAngles foreach FlangeMatrix (using the "Luebeck C-Funktion" and the flip param; delta Angle )

Accumulate a PENALTYscore of the path, starting with the first vertex going to the last , initial score=zero ( see RobotPathOptimization : : compute JointsScore ( ) )

• PENALTYscore += angular change of the j oint with the highest change ( to previous vertex in path => angular change equals movement time )

• PENALTYscore += Joint angles close to our robot angle boundaries ( increasing penalty if a j oint is less then 15 degree away from boundary => if the patient moves , the robot might not be able to react )

• PENALTYscore += extraPENALTY if in unfavorable configuration ( near axis 57 reconfiguration, high angular change gets extra penalty)

• Configuration invalid if : angle boundaries violated, slow j oint 5 and j oint 7 angle reconfiguration detected, head not safely positioned, ...

} Return : lowest valid PENALTYscore or ERROR }

Brief Description of the Drawings [0069] The present invention is described in more detail hereinbelow by way of an exemplary embodiment and with reference to the attached drawings, in which:

Fig. 1 shows an exemplary cutting device placed at a position, at which the predefined cut to the object can be performed;

Fig. 2 shows an exemplary constraint of the movement in which the robot with the intervention member can be moved;

Fig. 3 shows an exemplary configuration or placement of the cutting device at a certain place, where the laser head or any other surgical equipment is blocking the line of sight or the other surgical equipment blocking the line of sight when performing the predefined cut;

Fig. 4 shows a further exemplary configuration or placement of the cutting device at a certain place, where the laser head would have a collision with the target or the other surgical equipment when performing the predefined cut;

Fig. 5 shows an exemplary rating procedural according to the proviso; and

Fig. 6 shows a plurality of positions in a grid with rating where the robot is recommended to be placed.

Description of Embodiments

[0070] In the following description certain terms are used for reasons of convenience and are not intended to limit the invention. The terms “right”, “left”, “up”, “down”, “under" and “above" refer to directions in the figures. The terminology comprises the explicitly mentioned terms as well as their derivations and terms with a similar meaning. Also, spatially relative terms, such as "beneath", "below", "lower", "above", "upper", "proximal", "distal", and the like, may be used to describe one element's or feature's relationship to another element or feature as illustrated in the figures. These spatially relative terms are intended to encompass different positions and orientations of the devices in use or operation in addition to the position and orientation shown in the figures. For example, if a device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be "above" or "over" the other elements or features. Thus, the exemplary term "below" can encompass both positions and orientations of above and below. The devices may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein interpreted accordingly. Likewise, descriptions of movement along and around various axes include various special device positions and orientations. [0071 ] To avoid repetition in the figures and the descriptions of the various aspects and illustrative embodiments, it should be understood that many features are common to many aspects and embodiments. Omission of an aspect from a description or figure does not imply that the aspect is missing from embodiments that incorporate that aspect. Instead, the aspect may have been omitted for clarity and to avoid prolix description. In this context, the following applies to the rest of this description: If, in order to clarify the drawings, a figure contains reference signs which are not explained in the directly associated part of the description, then it is referred to previous or following description sections. Further, for reason of lucidity, if in a drawing not all features of a part are provided with reference signs it is referred to other drawings showing the same part. Like numbers in two or more figures represent the same or similar elements.

[0072] Fig. 1 shows a cutting device 1 configured to be positioned in accordance with an embodiment of a computer implemented pre-operative method of positioning components involved in a surgical cutting process performed in an operation space to perform the predefined cut to the object according to the invention. The cutting device 1 comprises a robot 10 and an intervention member 20 embodied as laser head to cut an object 30 such as a bone of a patient. The robot 10 is provided with a system base 11 and a robot arm having a plurality of rod-shaped rigid segments 12 connected to each other by joints J1 , J2, J3, J4, J5. The intervention member 20 is mounted to the outermost or most distal of the rigid segments 12. The rigid segments 12 and joints J1 , J2, J3, J4, J5 are configured to move the intervention member 20 to be positioned relative to the object 30 along three axis 20x, 20y, 20z and rotation about each axis 20x, 20y, 20z.

[0073] In the pre-operative method a cut 34 with a specific geometry to be applied to the object 30 is defined. More specifically, the predefined cut 34 includes a definition of the position of the object 30 and the specific geometry 34. The object 30 is supported to be moved along three axis 30x, 30y, 30z and rotated about any axis as exemplified by rotation 30rot(z) about the axis 30z relative to the cutting device 1 .

[0074] In the pre-operative method a proviso for operating the cutting device 1 is defined. Further an activity of the cutting device 1 is simulated in which the robot 10 moves the intervention member 20 relative to the object 30 to apply the predefined cut 34 to the object 30. Thereby, simulating the activity of the cutting device 10 comprises computing a target position of the cutting device 1 by moving its system base 11 in a two dimensional coordinate system having two axis 11x, 11y. The target position is particularly appropriate for the robot 10 to perform the target activity in accordance with the proviso.

[0075] As a result of the pre-operative method, the cutting device 1 is placed at a position at which the predefined cut 34 can efficiently be applied to the object 30. Within the pre-operative method, in order to determine the position, a motion sequence of the robot 10 and the intervention member 20, i.e., the movement of the cutting device 1 for performing the predefined cut 34, is digitally simulated. Based on the motion sequence, as inverse kinematics techniques are used to calculate the most appropriate position(s). As shown, there are a plurality of positions along the x- and y-axes 11x, 11y at which the cutting tool 1 can perform the predefined cut 34. Each of these positions is rated. The highest ranking indicates the most suitable position at which the cutting device 1 is best placed for efficiently applying the predefined cut to the object 30.

[0076] As mentioned, the robot 10 is arranged at the most appropriate position by moving the system base 11 as indicated by the arrows 11x and 11 y, typically within the horizontal plane that is the floor of the operating room. Depending on the position, the robot arm moves or guides the intervention member 20 towards the object 30. The robot arm undergoes a motion sequence, from the initial position towards the target position at which the intervention member 20 performs and finishes the predefined cut 34.

[0077] Fig. 2 shows the cutting device 1 , wherein highlighted by the dotted line, a so-called elbow constraint of the movement of the robot 10 together with the intervention member 20 is exemplified. In the shown elbow constraint of the robot 10 the rigid segments 12 interconnected by joints J2, J3, J4 and J5 are near to a straight orientation towards each other. Thus, the joints J2, J3, J4, J5 are close to a final limit of changing the angle into one direction such that a further movement of the respective rigid segments 12 in relation to this direction is limited. In this arrangement of the robot arm, a correction of movement of the intervention member 20, e.g., due to an unexpected movement of the object 30 or the cutting device 1 , is likely not to be possible without repositioning the cutting device 1 or the object 3. Therefore, positions requiring such arrangement for performing the movement of the cutting device 1 in order to apply the predefined cut 34 get a low rating or a penalty. [0078] As can be seen in Fig. 2, the intervention member 20 is configured to be able to rotate 20rot(z) about the z- axis 20z. The degree of movement of the cutting device 1 depends on the elbow configuration and the leaser head orientation.

[0079] Fig. 4 shows another constraint resulting from a configuration or positing of the cutting device 1 , where the intervention member 20 has a collision with a portion 60 of the object 30 when the cutting device 1 performs the cut 34. This indicates that the robot is initially placed at an in appropriate position and needs to be moved during the operation or the intervention must be replanned.

[0080] Another constraint is shown in Fig. 3, where the line of sight between a tracking system 50 and an object tracking element 31 is at least partially blocked by the intervention member 20. Thereby, execution of cutting is prevented as only a cutting device tracking element 21 but not the object tracking element 31 is properly visible to the tracking system 50. Again, such arrangement would require repositioning of the cutting device 1 which is to be prevented as much as possible.

[0081 ] The provisio of the pre-operative method considers the constraints and down rates those positions at which the cutting device 1 would require repositioning or decrease flexibility of correcting movements of the intervention member 20. In particular, the proviso defines the optimum of the motion sequence of the cutting device 1 using parameters such as angle change of the joints J1 , J2, J3, JH4, J5.

[0082] Fig. 5 shows an exemplary rating procedure according to the proviso of the pre-operative method. In general, the rating can be divided in three steps, i.e. (i) virtually positioning the cutting device with a plurality of configurations, (ii) computing the score of each of the configurations using inverse kinematics and different rating functions, and (iii) visualizing the configurations by the score. The plurality of configurations refers to the different positions of the cutting device and consequently the different motion sequence of the cutting device.

[0083] The computation of the scores of the configuration can be performed independently, followed by selecting the one with the best score. For instance, the test is performed with following parameters, where the configurations tested are 5x2x3=30

• 5 zAngles of the laser head (-20, -10, 0, +10, +20 degree) around laser beam

• 2 flipconfigurations (on/off) • Delta angle (-5, 0, +5 degree) joint 5 and 7

[0084] In particular, the TooltoPath Matrix for each pat vertex can be calculated, using relative robot patch placement, where zAngle and flip are irrelevant.

[0085] Then, the joint angles for each TooltoPath Matrix are determined, using the “Luebeck C-Funktion” and the flip param; delta Angle.

[0086] As the next step, a “penalty” score of the path is accumulated, starting with the first vertex going to the last, initial Sj = 0, in particular:

• PenaltyScore += angular change of the joint with the highest change to previous vertex in path => angular change equals movement time. In other words, the smaller the angular change is, the better the configuration is. This is because the smaller angular change indicates a shorter motion sequence.

• PenaltyScore += joint angles close to the robot angle boundaries (increasing penalty if a joint is less than 15 degree away from boundary => if the patient moves, the robot might not be able to react)

• PenaltyScore += extraPenalty if in unfavorable configuration (near axis 57 reconfiguration, high angular change gets extra penalty)

• Configuration invalid if: angle boundaries violated, slow 57 reconfiguration detected, laser head not safely positioned.

[0087] Under the consideration of the above the penalties, the score for all configurations can be evaluated. The configuration with lowest score can be suggested.

[0088] Fig. 6 shows the result of the pre-operative method, i.e. a plurality of positions in a grid with ratings associated to each of the positions. Thereby, the positions having the lowest ratings are considered as recommendation of the placement of the robot 10. Each grid point indicates a possible position of the robot 10. The grid point with recommendable position, i.e. position having the lowest or, depending on the type of rating, highest score, can be highlighted. The better the position is, the more recommendable the grid will be highlighted. The recommendation of the grid points can be visualised using any graphic technique, for instance, in manner of a heat map.

[0089] This description and the accompanying drawings that illustrate aspects and embodiments of the present invention should not be taken as limiting-the claims defining the protected invention. In other words, while the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Various mechanical, compositional, structural, electrical, and operational changes may be made without departing from the spirit and scope of this description and the claims. In some instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the invention. Thus, it will be understood that changes and modifications may be made by those of ordinary skill within the scope and spirit of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below.

[0090] The disclosure also covers all further features shown in the Figs, individually although they may not have been described in the afore or following description. Also, single alternatives of the embodiments described in the figures and the description and single alternatives of features thereof can be disclaimed from the subject matter of the invention or from disclosed subject matter. The disclosure comprises subject matter consisting of the features defined in the claims or the exemplary embodiments as well as subject matter comprising said features.

[0091 ] Furthermore, in the claims the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single unit or step may fulfil the functions of several features recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The terms “essentially”, “about”, “approximately” and the like in connection with an attribute or a value particularly also define exactly the attribute or exactly the value, respectively. The term “about” in the context of a given numerate value or range refers to a value or range that is, e.g., within 20%, within 10%, within 5%, or within 2% of the given value or range. Components described as coupled or connected may be electrically or mechanically directly coupled, or they may be indirectly coupled via one or more intermediate components. Any reference signs in the claims should not be construed as limiting the scope.

[0092] A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. In particular, e.g., a computer program can be a computer program product stored on a computer readable medium which computer program product can have computer executable program code adapted to be executed to implement a specific method such as the method according to the invention. Furthermore, a computer program can also be a data structure product or a signal for embodying a specific method such as the method according to the invention.

Claims

1 . A method of positioning at least one component involved in a surgical cutting process performed in an operation space, wherein the at least one component comprises at least a cutting device having an intervention member configured to cut an object and a robot configured to move the intervention member relative to the object, the method comprising: defining a cut with a specific geometry to be applied to the object, defining a proviso for operating the cutting device, and simulating an activity of the cutting device in which the robot moves the intervention member relative to the object to apply the predefined cut to the object, wherein simulating the activity of the cutting device comprises computing a target position of the cutting device appropriate for the robot of the cutting device to perform the target activity in accordance with the proviso.

2. The method of claim 1 , wherein the proviso comprises preventing displacements of the cutting device relative to the object.

3. The method of claim 1 or 2, wherein the proviso comprises achieving a short time of operating of the cutting device to apply the cut to the object.

4. The method of any one of the preceding claims, comprising a step of determining a position of the object.

5. The method of claim 4, wherein determining the position of the object comprises obtaining position data from a medical imaging technique.

6. The method of claim 4 or 5, wherein determining the position of the object comprises optically monitoring the object. The method of claim 6, wherein optically monitoring the object comprises fixing a three-dimension marker to the object and acquiring the position of the object by an optical detector detecting the position of the marker. The method of claim 7, wherein the optical detector has a field of view in which the object is arranged and the proviso comprises preventing disruption of the object being in the field of view of the optical detector. The method of any one of the preceding claims, wherein the at least one component comprises at least one further component in addition to the cutting device preferably selected from an optical detector, a trolley, a spray apparatus and an aspiration device. The method of claim 9, wherein simulating the activity of the cutting device comprises computing further positions of each of the at least one further component appropriate for the cutting device to perform the activity. The method of claim 9 or 10, comprising fixing a further three-dimensional marker to each of the at least one further component and acquiring the position by an optical detector detecting the position of the further three-dimensional marker. The method of claim 11 , wherein the optical detector has a field of view in which the at least one further component is arranged and the proviso comprises preventing disruption of the at least one further component being in the field of view of the optical detector. The method of claim 8 and/or 12, wherein the cutting device is arranged in the field of view of the optical detector and the proviso comprises preventing disruption of the cutting device being in the field of view of the optical detector. The method of any one of the preceding, wherein simulating the activity of the cutting device comprises determining a sequence of torsions of joints of the robot. The method of any one of the preceding claims, wherein the activity of the cutting device is simulated based on inverse kinematics. The method of any one of the preceding claims, wherein simulating the target activity of the robot of the cutting device comprises simulating a plurality of alternative activities of the cutting device, in which the robot moves the intervention member relative to the object to apply the predefined cut to the object, and associating a compliance grade representing a level of compliance with the defined proviso to each alternative activity. The method of claim 16, wherein simulating the activity of the cutting device comprises, for each alternative activity, computing an alternative position of the cutting device appropriate for the robot of the cutting device to perform the respective alternative activity. The method of claim 17, wherein simulating the target activity of the robot of the cutting device comprises associating the compliance grade of each of the alternative activities to its alternative position. The method of claim 18, wherein simulating the target activity of the robot of the cutting device comprises comparing the compliance grades associated to the alternative positions and providing the alternative position with the most appropriate compliance grade as the target position. The method of claim 18 or 19, wherein simulating the target activity of the robot of the cutting device comprises providing a representation of the compliance grade of each alternative position. The method of claim 20, wherein the representation comprises a map of the operation space on which each alternative position with its compliance grade is depicted. The method of claim of any one of preceding claims, wherein the robot has a kinematics with a plurality of rigid segments, and wherein each two adjacent rigid segments are connected by a joint and form an articulated angle. The method of claim 22, comprising a step of determining the articulated angle for each two adjacent rigid segments using a Luebeck C-Function. The method of claim 23, comprising a step of increasing the compliance grade of the activity when one of the articulated angles during the activity of the robot is smaller than a predefined value of angle. The method of claim 23 or 24, comprising a step of increasing the compliance grade of the activity when the at least one angle change exceeds a predefined value of angle change. The method of any one of claims 16 to 25, comprising a step of setting the compliance grade of the activity to a value larger than the predefined compliance value when a motion sequence of robot during the activity of the cutting device includes a collision with at least one further component or the object. The method of any one of claims 9 to 26, comprising a step of pre-positioning the at least one further component, monitoring the position of each of the at least one further component relative to the object by means of an optical detector, and calculating positions of each of the at least one further component allowing the robot of the cutting device to move the intervention member to apply the cut to the object in consideration of the defined proviso. The method of any one of the preceding claims being a computer- implemented method. The method of any one of the preceding claims, wherein defining the cut to be applied to the object comprises generating a digital representation of the cutting device and the cut. The method of claim 29, wherein simulating the activity of the cutting device involves using the digital representation of the cutting device and the predefined cut. The method of any one of the preceding claims, not being a method for treatment of the human or animal body by surgery or therapy, and not being a diagnostic method practised on the human or animal body. A computer program comprising computer code means causing a computer to perform the method according to any one of the preceding claims when being loaded to and executed by the computer. The computer program of claim 32, wherein the step of defining a cut with a specific geometry to be applied to an object can be implemented by receiving an input on such a cut, and wherein the step of defining a proviso for operating the cutting device, can be implemented by receiving an input on such a proviso.