Assistance system and computer-implemented method for displaying a critical limit

Abstract

The invention relates to a surgical assistance system (1) for use in a surgical procedure on a patient (P), said system comprising: an imaging system (18) which is designed to create and, preferably digitally, provide an image in real time in a first data modality; a neuromonitoring probe (20) which is designed to capture, in real time, a signal response of stimulated functional tissue at least at one measurement point (M) on the patient (P) and to provide, in real time, a measurement signal in a second data modality based on the signal response; a tracking system (32, 34, 36, 38) which is designed to determine and provide, in real time, a location of the image and a position of the at least one measurement point (M) with respect to a reference coordinate system (40); a visual display unit (30); and a data-processing unit (42) which is designed to: store the position of the at least one measurement point (M) and the measurement signal in a 3D measurement data set, to generate a boundary surface (G) based on the at least one 3D measurement data set, and to control the visual display unit (30) to visually display a first view which contains the image in the first data modality and at least a portion (g) of the boundary surface (G) such that a critical boundary to the functional tissue is displayed in the image in the first data modality. The invention also relates to a method, to a computer program, and to a computer-readable storage medium according to the dependent claims.

Description

[0001] Assistance system and computer-implemented procedure for displaying a critical limit

[0002] Description

[0003] Technical area

[0004] The present disclosure relates to a medical, in particular surgical, assistance system, in particular a neurosurgical assistance system, for use in a surgical procedure on a patient. The assistance system has a recording system, in particular a visualization system, with one or more cameras for creating and providing, preferably digitally, up-to-date images of the surgical site, as well as a neuromonitoring measuring probe for localizing functional, neuronal tissue. A navigation system of the assistance system provides a reference coordinate system within which the visualization system is navigated. The neuromonitoring measuring probe is provided for measuring (and thus, to a certain extent, visualizing) a distance to functional, in particular neuronal, tissue.Navigation is based on (spatial) tracking of rigid-body reference markers or by image recognition of optical patterns arranged in an optically detectable manner on the component of the visualization system to be navigated. In addition, the present disclosure relates to a computer-implemented method for control, as well as a computer-readable storage medium and a computer program.

[0005] Technical background

[0006] During surgical procedures, particularly neurosurgical interventions on the brain or other tissue with high nerve density, various visualization and measurement systems are typically used for visual, physiological, and functional assessment of the surgical site and as decision-making aids. The typical data collected during the procedure includes images from a recording system placed near the surgical site, such as a surgical microscope and / or endoscope. In addition, intraoperative neuromonitoring (IONM) is used to protect functional, particularly neuronal, tissue during the procedure.

[0007] Neuromonitoring is known to be performed by applying electrical impulses to relevant nerve pathways and recording a signal response using a neuromonitoring probe positioned in the specific surgical area. Depending on the surgical procedure, electrodes are attached to the wrists, ankles, or skull, or to specific muscle groups, through which the functional tissue is exposed to an electrical pulse. A special probe with a measuring head can be used as a (neuromonitoring) measuring probe. However, a standard surgical instrument, which is necessary anyway and also features the measuring head and is in permanent use, is preferred.

[0008] The recorded signal response of the functional tissue must be evaluated primarily as a qualitative signal and cannot be reliably reproduced between different patients, or even between different electrode positions. Therefore, the signal response is assessed individually by the neuromonitoring specialist or the surgeon, who individually defines a threshold beyond which a distance to the functional tissue is interpreted as "too close" and thus too dangerous for guiding a resection instrument there.

[0009] With conventional measurement methods, each signal response is recorded directly in the operating room. If the measuring probe is moved toward the stimulated tissue, for example, a signal is generated at a critical distance; if it is moved away again, the signal is silenced. The real-time measurement signal derived from the signal response can be output to a separate screen or a display of the microscope or endoscope image as a pure numerical value or as a signal bar, with or without coloring. Alternatively, solutions exist with a pure "ampere" function with colored signals that represent excessive or acceptable proximity of the measuring probe to the functional tissue. The disadvantage, however, is that the direction in which the functional tissue is located cannot be determined, and the surgeon must always take a measurement at that location to obtain the measurement signals. This makes it difficult to establish a spatial understanding of the risk areas.

[0010] In addition to this timely, fleeting, and merely qualitative identification of risk areas, state-of-the-art preoperative methods for spatially visualizing functional, particularly neuronal, tissue are available. One such technique is diffusion tensor imaging.

[0011] However, due to repositioning effects of the patient and / or his tissue during the procedure, the disadvantage is that the acquisition of the DT imaging involves inaccuracy or at least uncertainty.

[0012] Summary of the present disclosure

[0013] In contrast, it is the object of the present disclosure to avoid or at least mitigate disadvantages of the prior art and in particular to provide a surgical assistance system, a computer-implemented method for control, a computer-readable storage medium, and a computer program which provides a particularly comprehensible display of a critical boundary to a functional tissue of a patient during a surgical, in particular neurosurgical, procedure.

[0014] The object is achieved according to the invention with regard to a surgical assistance system by the features of claim 1, with regard to a computer-implemented method by the features of claim 10, with regard to a computer program by the features of claim 14 and with regard to a computer-readable storage medium by the features of claim 15.

[0015] A basic idea of ​​the disclosure is therefore to create a surgical assistance system that has a recording system at least for creating and providing up-to-date images of the patient, and that further has a neuromonitoring measuring probe for recording a signal response of stimulated, functional tissue. The recording and the measuring points are both navigated relative to a (uniform or common) reference coordinate system, and a data processing unit of the assistance system is specifically adapted to generate an interface based on the recorded and stored measuring points and the signal responses therein and to control a display unit of the assistance system to display the interface in the context of the recording (at least for a period of time).

[0016] In other words, according to the disclosure, a surgical assistance system is provided for use in a surgical, in particular a neurosurgical, intervention on a patient, comprising: a recording system, in particular a visualization system, which is adapted to create a recording in a first data modality in a timely manner and to provide it, preferably digitally.The recording system preferably has a microscopy camera or an endoscopy camera, or both; a neuromonitoring measuring probe adapted to capture a signal response of a stimulated, functional tissue in real time at at least one measuring point on the patient, preferably at a plurality of measuring points, and to provide a measurement signal in a second data modality in real time based on the respective signal response; a tracking system, in particular a navigation system (for example with a navigation camera), adapted to determine a position of the recording and a position of the at least one measuring point in real time with reference to a reference coordinate system of the assistance system, in particular a coordinate system of the patient, and to provide this information, preferably digitally; a visual display unit, in particular one or more monitors or VR glasses; and a data processing unit.According to the disclosure, the data processing unit is adapted to read in the currently provided position of the at least one measurement point and the currently provided measurement signal, as well as preferably a time of acquisition of the signal response, and to store them as a 3D measurement data set. Furthermore, it is adapted to generate an interface based on this at least one 3D measurement data set, in particular according to a calculation rule stored in the data processing unit for execution. Furthermore, it is adapted to control the visual display unit, generate, and display a first view containing the recording of the first data modality and the interface or at least a section, in particular a sectional contour, of the interface.

[0017] In this way, an assistance system is created by means of which a critical boundary to the functional tissue is displayed to the surgeon in a three-dimensional manner - as an interface - at least within the current image. This allows the surgeon to develop a clear and, thanks to the storage of the measurement data with a correspondingly generated interface - depending on requirements - permanent, spatial representation of the boundary and to incorporate this into their decision-making, particularly during a resection. It is therefore no longer necessary to repeatedly record the measurement signal at a specific point intraoperatively in time to check whether the surgeon has still remembered the measurement correctly. Instead, the position corresponding to the measurement signal is (automatically) recorded for each measurement and "supplemented" in the 3D measurement data set, which can be accessed again even after about five minutes without having to perform the measurement again.This also makes it possible (based on several measurements) to indicate a direction to the functional tissue, such as stimulated nerve pathways.

[0018] According to a further development, the data processing unit is adapted to store multiple 3D measurement data sets. In particular, it is adapted to store the 3D measurement data sets based on their time point, and thus according to their acquisition history.

[0019] In this disclosure, the term "position" refers to a geometric position in three-dimensional space, which is specified in particular using coordinates of a Cartesian coordinate system. In particular, the position can be specified using the three coordinates X, Y, and Z. The term "orientation" in this disclosure, in turn, indicates an alignment (e.g., the position) in space, in particular that of an axis. One can also say that orientation indicates an alignment with a direction or rotational specification in three-dimensional space. In particular, the orientation can be specified using a maximum of three angles.

[0020] In this disclosure, the term "location" defines both a position and an orientation. In particular, the location can be specified using six coordinates: three position coordinates X, Y, and Z, and a maximum of three angular coordinates for the orientation.

[0021] The term “3D” refers to a spatial specification with three coordinates for three spatial directions, such as X, Y, Z.

[0022] Advantageous embodiments are claimed in the subclaims and are explained in particular below.

[0023] According to a further development, the data processing unit is adapted to generate an enveloping surface with an offset, in particular a spherical surface with a radius, around the at least one measuring point and to store it in the 3D measurement data set. A generation rule for the offset is such that the smaller the measurement signal, the larger the offset, and conversely, that the larger the measurement signal, the smaller the offset. This takes into account the fact that the detected signal response - and thus the measurement signal - is stronger the closer the measurement point is to the functional tissue. In particular, a functional relationship of the generation rule is that the offset is inversely proportional to the measurement signal.

[0024] Particularly preferably, the data processing unit is adapted to generate the interface as a common outer surface based on the enveloping surfaces thus generated around the measurement points. This means, in particular, that the data processing unit is adapted to combine, preferably trim, the enveloping surfaces into a single outer surface. This prepares the interface to form an unconvoluted and thus easily interpretable intersection curve with an image plane or focal plane of a 2D image, in particular an image of the third, fourth, or fifth data modality.

[0025] Preferably, the neuromonitoring measuring probe is configured with a proximal handling section and a distal measuring head in the form of a rod-shaped measuring probe or in the form of a suction device. In particular, in a medical suction device, a measuring head is integrated into the distal suction tip, which delivers the measurement signals. The suction tip is spatially tracked to determine the position of the measurement.

[0026] The assistance system proves to be particularly advantageous in a further development with a (further separate) surgical effector, in particular a surgical instrument, wherein the tracking system is additionally adapted to determine and provide at least the position of an operating point of the effector with respect to the reference coordinate system in a timely manner, and the data processing unit is adapted to determine a distance vector from the operating point to the interface and / or the functional tissue and to control the display system to display this distance vector. Preferably, the tracking system is additionally adapted to determine and provide an orientation of the effector in a timely manner.In this way, a spatial relationship can be established between the effector, such as the surgical instrument, and the border as well as the functional tissue, providing the surgeon with a kind of up-to-date navigation map with particularly important information.

[0027] In the present disclosure, the term "effector" refers to a device, an instrument, or similar medical means that can be used to perform the procedure. In particular, the following can be considered an effector: an optical device with a visualization axis, a pointer with a distal tip for surgical navigation, and others. A "working axis" of the effector refers in particular to a longitudinal axis of the effector, in particular a distal section of the effector, such as a longitudinal axis of a region of the cutting section of a scalpel. The working axis can also be defined in the region of the rectilinear section of the instrument's handle, for example in the case of a dental tool with a non-rectilinear distal active section and working point, such as a probe.

[0028] The term "working point" refers to the point or area of ​​the effector that is used for its intended purpose during a procedure. For example, the working point of a scalpel is the scalpel tip; of a pointer, the pointer tip; of a pair of scissors, the cutting tip when closed; of tweezers, the tweezer tip; of a (surgical) drill / bit or cutting machine; of a syringe tip; of a trocar tip; whereas in a dental tool, the working point of a probe is the tip of the instrument. This tip (slightly offset) from the working axis is not the distalmost point, but rather, similar to a hook, slightly "regresses" in a proximal direction.

[0029] According to a preferred development, the assistance system has an input unit, which is formed in particular by a touch display of the display unit. According to the disclosure, the input unit is adapted so that an interface factor can be set and / or changed by the surgeon or user. The data processing unit is subsequently adapted, based on a product of the interface factor and offset, to generate the envelope surfaces, and thus the interface, in particular the outer surface, with respect to the measurement points further outward - in particular closer to the functional tissue - or further inward - in particular further away from the functional tissue - in order to thus define a spatial area of ​​greater or lesser aggressiveness of the intervention. The interface factor is a type of scaling value with which, for example, in the case of a sphere's envelope, it can be "inflated" or "shrunk."

[0030] According to a preferred development, the assistance system comprises a (robot with a) robot arm, in particular a robot arm segment, to which the measuring probe is connected. It is preferred if the tracking system is adapted to determine the position of the at least one measuring point as a function of internal robot kinematics. Alternatively or additionally, the effector is connected to a robot arm, in particular a robot arm segment, of the assistance system, and the tracking system is preferably adapted to determine the position of the effector's operating point as a function of internal robot kinematics.The development with a robot arm offers the possibility of a further, advantageous development in which the data processing unit is adapted to issue an alarm and / or stop and / or reverse the movement of the effector when the operating point crosses the boundary, so that a "no-go area" characterized by a high risk to the functional tissue is reliably blocked from the operating point. The term "robot arm segment" here refers in particular to a robot part of the robot arm mounted between bearings or joints, or in the case of the terminal robot arm segment, in particular to a robot part connected in series between the end effector and the preceding robot arm segment (in the case of only one robot arm segment, the robot base).

[0031] In a preferred development, the data processing unit has an interface for an additional recording system, in particular a visualization system, which is preferably adapted to create at least one additional, preferably preoperative, image of the patient in a, preferably additional, data modality. The interface is preferably adapted for a CT scan, preferably a third data modality, and / or an MRI scan, preferably a fourth data modality, and / or a diffusion tensor scan, preferably a fifth data modality.In order to be able to display these images in the correct position, the data processing unit is adapted to read in the respective additional image via the interface with reference to the reference coordinate system and to control the visual display unit to visually display an additional view containing the respective additional image and the interface or at least the section of the interface, so that the critical boundary to the functional tissue is displayed in the respective additional image. According to a further development, the data processing unit is adapted to display the additional view as a section of the CT image or MRI image and to form the section of the interface as a section contour of the interface with a plane of the section of the CT image or MRI image.

[0032] Preferably, the data processing unit is adapted to store the offset and / or an orientation of the measuring probe and / or an attribute, in particular a numerical or color classification of the measurement signal, in the respective measurement data set. The attribute can be of Boolean type, i.e., it can assume only two possible values, one corresponding to a safe distance range and, for example, has a green color, and the other corresponding to a hazard area and, for example, has a red color. Alternatively, the attribute can assume more than two values, each corresponding to a distance and / or hazard area Z-class. Color or numerical scales are also possible here. In the latter case, the attribute can be a signal classification (signal level), for example, using a scale of discrete numerical values, for example, from 1 to 3 or 1 to 4 or 5.Alternatively, the attribute can be the distance to the functional tissue determined from the measurement signal.

[0033] To generate the interface, the data processing unit is adapted according to a further development with a calculation rule. This rule specifies determining a 3D Gaussian function of the signal response, in particular of the measurement signal, at the positions of the measurement points. Subsequently, a volumetric density field is determined by superposition of the 3D Gaussian functions. The interface is determined as a function of the volumetric density field and a predetermined boundary distance, so that the interface represents the boundary distance to the functional tissue.

[0034] Preferably, the data processing unit is adapted to define tissue aggressiveness using variable gradients. A change in the gradients can preferably be made using the input unit. Preferably, the tracking or navigation system has an image recognition and processing device for recognizing and processing an optical reference mark provided on the measuring probe and / or the effector and / or the recording unit, and / or it has at least one 3D camera or 2D cameras for capturing rigid bodies arranged on the measuring probe and / or the effector and / or the recording unit. Spatial tracking can be performed using optical reference marks.

[0035] With regard to a computer-implemented method for displaying a critical boundary to a functional tissue of a patient during a surgical, in particular neurosurgical, procedure, for a surgical assistance system, in particular for a surgical assistance system according to at least one aspect of the preceding description, the objects are achieved by the following steps:

[0036] Creating a time-based recording of the first data modality by a recording system;

[0037] Providing the timely recording of the first data modality, preferably digital, by the recording system;

[0038] Real-time recording of a signal response of a stimulated, functional tissue at at least one measuring point of the patient, using a neuromonitoring measuring probe;

[0039] Timely provision of a measurement signal of a second data modality, based on the signal response, by the neuromonitoring measuring probe,

[0040] Determining a position of the image and a position of the at least one measuring point in real time, each with reference to a reference coordinate system, in particular of the patient, by means of a tracking system, in particular a navigation system;

[0041] Up-to-date provision of the position of the recording and the position of at least one measuring point, in particular digitally, by the tracking system, in particular the navigation system;

[0042] Reading in the currently provided position of the at least one measuring point and the currently provided measurement signal, and preferably a time of acquisition of the signal response, by a data processing unit; storing the currently provided position of the at least one measuring point and the currently provided measurement signal, and preferably the time of acquisition of the signal response, as a 3D measurement data set, by the data processing unit;

[0043] Generating an interface based on the at least one 3D measurement data set according to a calculation rule by the data processing unit; and

[0044] Controlling a visual display unit by the data processing unit such that the visual display unit displays a first view containing the first data modality recording and at least a portion of the interface, such that a critical boundary to the functional tissue is displayed in the first data modality recording. As a result, analogous to the assistance system of the present disclosure, measurement points with corresponding measurement signals and positions are acquired by means of the neuromonitoring measurement probe and stored in a (uniform) 3D measurement data set. This 3D measurement data set is then used to determine and visually display critical boundaries to functional tissue in order to assist a surgeon during their procedure.

[0045] According to further training, the procedure comprises steps:

[0046] Generating an enveloping surface with an offset, in particular a radius, around the at least one measuring point, wherein the offset is greater the smaller the measuring signal is, and wherein the offset is smaller the larger the measuring signal is, in particular the offset is inversely proportional to the measuring signal;

[0047] Preferably storing the envelope surface in the 3D measurement data set;

[0048] Generation of the interface as a common outer surface based on the enveloping surfaces of several measuring points; each by the data processing unit.

[0049] According to further training, the procedure comprises steps:

[0050] Determining at least one position of an operating point of an effector of the assistance system, preferably additionally an orientation of the effector, with reference to the reference coordinate system, by the tracking system in a timely manner;

[0051] Providing the position of the working point in real time, particularly digitally, by the tracking system; determining a distance vector from the working point to the interface or to the section of the interface and / or to the functional tissue, by the data processing unit; and

[0052] Controlling the display unit so that it displays the distance vector by the data processing unit.

[0053] According to further training, the procedure comprises steps:

[0054] Setting or changing an interface factor by an input unit of the assistance system, which is formed in particular by the display unit of the assistance system designed as a touch display; and

[0055] Generating the enveloping surfaces based on a product of the interface factor and the offsets, so that the interface is generated with respect to the measuring points further outwards, in particular towards the functional tissue, or further inwards, in particular away from the functional tissue, in order to define an aggressiveness of the intervention, by the data processing unit.

[0056] The volume of tissue in the intervention area changes due to the intervention, for example, due to resection. Therefore, the disclosed method also provides the option of deleting 3D measurement data sets.

[0057] According to a further development, the method therefore comprises a step of deleting at least one of the 3D measurement data sets and / or marking at least one of the 3D measurement data sets and / or replacing at least one of the 3D measurement data sets.

[0058] Deletion can be applied to the entire set of 3D measurement data sets, manually or automatically, especially after a relevant event, such as the extraction of a biopsy, a resection, or a lesion. Deletion can also be performed based on a criterion, particularly an age criterion, such as the 3D measurement data set being older than x seconds. Another option is the regional deletion of a 3D measurement data set, provided that a signal response is recorded again at the position of the underlying, already existing measurement point.The above-mentioned steps of deleting / marking / replacing at least one of the 3D measurement data sets can each be carried out by means of an input from the operator or user, preferably by selection on the input unit designed as a touch display, or alternatively or additionally automatically by means of the data processing unit, preferably depending on a predetermined criterion.

[0059] The criterion could, for example, be the age of the acquisition. Deleting data sets ensures that unnecessary, disruptive, or too old measurement data sets—and thus envelope areas, and thus sections of the interface—continue to be displayed. The interface can thus be kept at a meaningful level in terms of its currentness and at a size required by the surgeon, which improves orientation in the surgical area.

[0060] Marking, especially as "expired" or "too old," offers the advantage over simply deleting data in that the development of the interface can be reproducibly recorded / documented over a period of time and subsequently replayed, particularly step by step. It is preferable to display only current measurement data sets, i.e., those not classified as expired or too old.

[0061] Preferably, the steps of generating the interface based on the at least one 3D measurement data set according to the calculation rule by the data processing unit; and controlling the visual display unit by the data processing unit such that the visual display unit displays the first view containing the first data modality recording and at least the portion of the interface, so that the critical boundary to the functional tissue is displayed in the first data modality recording; are performed whenever one or more of the steps of deleting / marking / replacing have occurred. In this way, the interface is, in principle, continuously refreshed or updated.

[0062] With regard to a computer-readable storage medium or a computer program, the objects are achieved in that the storage medium or computer program comprises instructions which, when executed by the computer, cause the computer to carry out the steps of the method according to the present disclosure.

[0063] Although the preferred field of application of the assistance system, computer-implemented method, computer program and computer-readable storage medium according to the disclosure is neurosurgery, in particular brain surgery, the application is not limited thereto, but the invention is generally applicable to medical interventions in which a boundary between a functional, in particular excitable, tissue to be protected on the one hand and a pathological tissue on the other hand must be taken into account intraoperatively.

[0064] Any disclosure related to the surgical assistance system according to the present disclosure applies to the method according to the present disclosure, and vice versa.

[0065] Short description of the characters

[0066] The invention is explained in more detail below using preferred embodiments with the aid of figures. They show:

[0067] Fig. 1 is a schematic side view of a surgical assistance system according to a preferred embodiment;

[0068] Fig. 2 shows a computer-implemented method for a surgical assistance system for displaying a critical boundary to a functional tissue of a patient, according to a preferred embodiment;

[0069] Fig. 3a shows spherical enveloping surfaces generated around measurement points with a constant offset according to the method of Fig. 2; Fig. 3b shows the spherical enveloping surfaces according to Fig. 3a, trimmed to a common outer surface as an interface to the functional tissue;

[0070] Fig. 4 shows a common outer surface produced from enveloping surfaces according to the method according to Fig. 2 as an interface to the functional fabric;

[0071] Fig. 5 Positions of several measuring points within an interface generated according to the method, in a 2D sectional view;

[0072] Fig. 6 Positions of several measuring points, as well as intersection curves of several interfaces generated according to the method, in a 2D sectional view;

[0073] Fig. 7 shows a displayed view with multiple multimodal images of an intervention area together with several generated interfaces and a distance vector of a navigated working point to the functional tissue; and

[0074] Fig. 8 shows a displayed view with multiple images of an intervention area, in the same preoperative data modality, together with a border and a representation of the measuring probe.

[0075] The figures are schematic in nature and are intended to aid understanding of the invention. Identical elements are provided with the same reference numerals. Features of different embodiments may be interchanged.

[0076] Detailed description of preferred embodiments

[0077] Figure 1 shows a surgical assistance system 1 according to a preferred embodiment of the present disclosure in a schematic side view. The assistance system 1 has a surgical robot 2 with a robot base 4, which is locally fixed in the embodiment shown. Alternatively, it can be designed to be mobile (for example, as a medical cart) in order to be able to use the robot 2, for example, as needed, at different locations in an operating room in a hospital. The robot base 4 forms a local reference point to which a multi-segmented robot arm with several robot arm segments 6, 8, 10 is attached, which are connected to one another via joints 12, 14. In this way, the robot arm segments 8 and 10 can be actively moved relative to one another, and the robot arm 6, 8, 10, 12, 14 can be controlled as a whole.

[0078] A recording system 18 of the assistance system 1 is attached to a terminal side 16 of the robot arm. In the embodiment shown, this recording system is designed as a surgical operating microscope and continuously creates and provides a real-time image (microscope image or microscope video stream) of the patient according to a first data modality. The recording system 18 can additionally comprise an endoscope or, for example, an overview camera to create additional, real-time images. The real-time image or images are displayed on a display unit 30 of the assistance system 1, which, in the embodiment shown, is designed as a monitor on which the surgeon can follow his or her procedure on the patient using the image(s) of a procedure area 0 displayed there. Alternatively or additionally, the display unit can be designed, for example, as VR glasses or can additionally comprise these.

[0079] The position of the recording system 18 can be controlled and adjusted by means of the specially adapted central control unit 28 placed in the base 4.

[0080] The assistance system 1 further comprises a neuromonitoring measuring probe 20, manually guided in the embodiment shown, with a measuring head 26, which can be placed by the surgeon at spatial points / measurement points of the patient P in the intervention area O as desired in order to record a signal response of a stimulated, functional tissue, in particular neuronal tissue, and thus determine proximity to the functional tissue. Alternatively, the measuring probe can of course be guided by a robotic arm, which particularly facilitates the precise and reproducible positioning of spatial points / measurement points on the patient P.

[0081] For stimulation, muscle groups or nerve pathways on patient P are equipped with electrodes (not shown) in a conventional manner, which are in neuronal and thus electrical connection with the specific surgical area of ​​patient P in which the procedure - e.g., the resection of tumor tissue - is to be performed. The muscle groups or nerve pathways are repeatedly subjected to a voltage pulse for stimulation, and the signal response of the tissue is recorded by the measuring head 26 placed in the surgical area 0 and converted by the measuring probe 20 into an electrical measurement signal with a second data modality. The closer the measuring head 26 is to the stimulated tissue, the stronger the recorded signal response and thus the measurement signal of the second data modality.

[0082] The measurement signal is provided by a data processing unit 42 of the assistance system 1, which is explained in more detail below.

[0083] A tracking or navigation system 32, 34, 36, 38 of the assistance system 1 spatially tracks both the recording system 18 and the measuring probe 20 and continuously determines their respective positions, in particular the position of the measuring head 26, with reference to a reference coordinate system 40—fixed in the embodiment shown. For this purpose, the tracking or navigation system has a navigation unit 32, a 3D camera 34, a reference mark 38 arranged on the measuring probe 20 and optically detectable by the 3D camera 34, for example in the form of a rigid body or a pattern, as well as angle sensors 36 arranged on the joints 12, 14 of the robot arm 6, 8, 10, 12, 14. The angle sensors 36 and the 3D camera 34 are in signal communication with the navigation unit 32.

[0084] The navigation unit 32 determines, on the one hand, the position of the recording system 18 based on the angles detected at the joints 12, 14 and a robot-internal kinematics stored in the navigation unit 32. On the other hand, it continuously determines at least the position of the measuring head 26 based on the reference mark 38 optically detected by the 3D camera and a relative position of the measuring head 26 to the reference mark 38 stored in the navigation unit 32. To examine the intervention area O with regard to its proximity to neuronal tissue, the surgeon moves the measuring head 26 of the measuring probe 20. This creates a progression of spatially tracked / navigated positions of the measuring head 26 and associated measurement signals along a time axis.According to the disclosure, the data processing unit 42 is adapted to read in the currently provided positions of the measuring head 26 and the currently provided measurement signals at these positions, and preferably the respective time of acquisition of the signal responses / measurement signals, and to store them for each position in a 3D measurement data set consisting of position, measurement signal, and time. Subsequently, according to a calculation rule stored therein, the data processing unit 42 generates an interface based on this at least one 3D measurement data set and controls the visual display unit 30 to visually display a first view containing the currently recorded image of the recording unit 18 and at least a portion of the interface. In this way, the surgeon receives a clear representation of a critical boundary to the patient's functional tissue in the context of the currently recorded image of the intervention area 0.

[0085] Figure 2 shows a computer-implemented method for a surgical assistance system, in particular for the one according to Figure 1, which enables the display of the critical boundary to the functional tissue of the patient P during the surgical, in particular neurosurgical, procedure. According to the disclosure, the method in its preferred embodiment shown in Figure 2 comprises the following steps:

[0086] Creation S1 of the time-current recording of the first data modality by the recording system 18; digital provision S2 of the recording of the first data modality by the recording system 18; time-current detection S3 of the signal response of the stimulated, functional tissue at at least one measuring point on the patient P by the measuring head 26 of the neuromonitoring measuring probe 20; time-current, digital provision S4 of the measurement signal of the second data modality, based on the signal response, by the neuromonitoring measuring probe 20; time-current determination S5 of the position of the recording and the position of the measuring head 26 and thus of the measuring point on the patient P, each with reference to the reference coordinate system 40, by the tracking system 32, 34, 36, 38; time-current, digital provision S6 of the position of the recording and the position of the measuring head 26 and thus of the measuring point on the patient P by the tracking system 32, 34, 36, 38Reading in S7 the currently provided position of the at least one measurement point and the currently provided measurement signal and the time of acquisition of the signal response by the data processing unit 42; storing S8 the currently provided position of the at least one measurement point and the currently provided measurement signal and the time of acquisition of the signal response as a 3D measurement data set by the data processing unit 42; generating S9 an interface based on the 3D measurement data set according to a calculation rule by the data processing unit 42; and controlling S10 the visual display unit 30 by the data processing unit 42 such that the visual display unit 30 displays the first view containing the first data modality recording and at least a portion of the interface, so that the critical boundary to the functional tissue is displayed in the first data modality recording.

[0087] The step S9 of generating the interface on the basis of the 3D measurement data set according to the calculation rule is carried out by the data processing unit 42, preferably by steps:

[0088] Creating S9.1 an enveloping surface with an offset, in particular a radius, around the at least one measurement point, wherein the offset is greater the smaller the measurement signal is, and wherein the offset is smaller the larger the measurement signal is; storing S9.2 the enveloping surface in the 3D measurement data set; and creating S9.3 the boundary surface as a common outer surface based on the enveloping surfaces of several measurement points.

[0089] Preferably, the tracking system, in particular the 3D camera 34 and the navigation unit 32, also tracks an effector (not shown) guided by the surgeon to perform the procedure. As already explained above, the effector is, within the meaning of the disclosure, a surgical instrument that enables the intervention on, in particular, pathological tissue of the patient P. The distance of the effector from the functional tissue of the patient P must therefore be monitored to avoid damaging the latter. To enable this monitoring, the method according to Figure 2 comprises the following additional steps:

[0090] Determining S11, in real time, the position of an operating point of the effector with reference to the reference coordinate system 40 by the tracking system 32, 34; digitally providing S12, in real time, the position of the operating point by the tracking system 32, 34; determining S13 a distance vector from the operating point to the interface or to the section of the interface and / or to the functional tissue by the data processing unit 42; and controlling S14 the display unit 30 so that it displays the distance vector.

[0091] In order to define an aggressiveness of the intervention, which is then reflected in the extent of the interface, the method in its preferred embodiment according to Figure 2 comprises the following step:

[0092] Setting or changing S15 an interface factor by an input unit of the assistance system 1, which is formed by the display unit 30 of the assistance system 1 designed as a touch display, wherein the step of generating S9.1 the envelope surfaces is then carried out based on a product of the interface factor and the offsets, so that the interface with respect to the measuring points is generated further outwards, i.e. towards the functional tissue, with a larger interface factor and higher aggressiveness, and further inwards, i.e. away from the functional tissue, with a smaller interface factor and lower aggressiveness.

[0093] Figure 3a shows, by way of example, a multitude of measuring points M approached by the measuring head 26 with their respective envelope surface H formed by means of the offset. In order not to overload Figure 3, only a few measuring points M with their respective envelope surface H are shown.

[0094] Figure 3b shows the interface G generated from the individual enveloping surfaces H as the common outer surface of the enveloping surfaces H according to Figure 3a. The interface G can be formed as a function of a volumetric density field, which was already mentioned earlier in the description. The calculation rule for this can be designed, in particular, based on known algorithms for calculating molecular surfaces.

[0095] Figure 4 shows a further interface G formed according to the method, wherein again each individual measuring point M is assigned a spherical enveloping surface H depending on the strength of the signal response recorded at the position of the measuring point M, and thus of the measuring signal.

[0096] Figure 5 illustrates in a two-dimensional section the positions of several measuring points M within the interface G.

[0097] Figure 6 shows a 2D image of the intervention area 0 with a multitude of measurement points M and several boundaries g. The boundaries g each represent a sectional contour of an interface G generated according to the disclosed method with the plane of the 2D image. The boundaries g thus represent a section of the interface G in the 2D image.

[0098] Figure 7 shows a view of multiple images, each with a different data modality, displayed by the display system 30. The images are displayed on the monitor 30 according to Figure 1, as shown in Figure 7.

[0099] Figure 7 (left) shows a preoperative diffusion tensor image (DTI) of the surgical site of patient P to illustrate the basic neuronal structure.

[0100] In the center of Figure 7, two sections of a preoperatively acquired MRI image are shown. The MRI tomographic image is shown below, and the MRI tomographic image is shown above together with the effector E and the generated interface G. The interface G clearly and interpretably separates a safe zone, in which the effector E is located and cannot injure functional tissue, from a danger zone in which there is a certain risk of injury to functional tissue.

[0101] Figure 7 (right) shows two time-accurate images of the first data modality of the surgical microscope (MIC) of the recording system 18 according to Figure 1. At the top, the generated interfaces G are shown together with the effectors E. At the bottom, one of the interfaces G is shown together with a distance vector V pointing from the navigated operating point of the effector E to the neural tissue. The distance vector is determined by the data processing unit 42 according to the previous description.

[0102] Figure 8 shows a view of a surgical site displayed by the display unit 30, comprising multiple images. The images are MRI tomographic images with different sectional planes. Each image shows a sectional contour g of the previously determined interface G with the respective sectional plane.

[0103] List of reference symbols

[0104] 1 surgical assistance system

[0105] 2 robots

[0106] 4 Robot base

[0107] 6, 8, 10 robot arm segment

[0108] 12, 14 joint

[0109] 16 End section robot arm

[0110] 18 Recording system

[0111] 20 measuring probe

[0112] 22 optical axis

[0113] 24 measuring axis

[0114] 26 measuring head

[0115] 28 Control unit

[0116] 30 display unit

[0117] 32 Navigation unit

[0118] 34 3D camera

[0119] 36 angle sensor

[0120] 38 optical reference mark

[0121] 40 Reference coordinate system

[0122] 42 Data processing unit

[0123] M measuring point

[0124] H Envelope area

[0125] G interface g section contour interface / section interface v distance vector

[0126] DTI diffusion tensor image

[0127] MRI MRI scan

[0128] CT CT scan

[0129] S1 Step Create current recording

[0130] S2 Step Provide current recording Step Capture signal response Step Provide measurement signal Step Determine position of recording and position of measuring head Step Provide position of recording and position of measuring head Step Read position, measurement signal, time Step Save position, measurement signal, time Step Create boundary surface Step Create envelope surfaces around measurement points Step Save envelope surfaces Step Create boundary surface from envelope surfaces Step Control display unit Step Determine position of effector operating point Step Provide position of effector operating point Step Determine distance vector of effector operating point Step Control display unit Step Set / change boundary surface factor

Claims

Claims 1. A surgical assistance system (1) for use in a surgical, in particular neurosurgical, intervention on a patient (P), comprising: a recording system (18) adapted to create a recording of the patient (P) in a first data modality in real time and to provide it, preferably digitally; a neuromonitoring measuring probe (20) adapted to record a signal response of an excited, functional tissue at at least one measuring point (M) on the patient (P) in real time and, based on the signal response, to provide a measurement signal in a second data modality in real time; a tracking system (32, 34, 36, 38), in particular a navigation system, adapted to determine a position of the recording and a position of the at least one measuring point (M) in real time with reference to a reference coordinate system (40), in particular of the patient (P), and to provide it, in particular digitally; a visual display unit (30);and a data processing unit (42) adapted to: read in the currently provided position of the at least one measuring point (M) and the currently provided measurement signal and preferably a time of detection of the signal response and store them in a 3D measurement data set, generate a boundary surface (G) on the basis of the at least one 3D measurement data set, in particular in accordance with a calculation rule, and control the visual display unit (30) to visually display a first view which contains the recording of the first data modality and at least a section (g) of the boundary surface (G), so that a critical boundary (g, G) to the functional tissue is displayed in the recording of the first data modality.; 2. Surgical assistance system according to claim 1, characterized in that the data processing unit (42) is adapted to generate an enveloping surface (H) with an offset, in particular a radius, for the at least one measuring point (M) and to store it in the 3D measurement data set, the offset being greater the smaller the measurement signal is, and wherein the offset is smaller the larger the measurement signal is, in particular the offset is inversely proportional to the measurement signal, and that the data processing unit (42) is adapted to generate the boundary surface (G) as a common outer surface on the basis of the enveloping surfaces (H) of several measurement points.

3. Surgical assistance system according to one of the preceding claims, characterized in that the neuromonitoring measuring probe (20) is designed with a proximal handling section and a distal measuring head (26) in the form of a rod-shaped measuring probe or in the form of a suction device.

4. Surgical assistance system according to one of the preceding claims, characterized in that the assistance system (1) has a surgical effector (E), in particular a surgical instrument, and the tracking system (32, 34, 36, 38) is adapted to determine and provide, with reference to the reference coordinate system (40), at least one position of an operating point of the effector, preferably additionally an orientation of the effector, in a timely manner, and in that the data processing unit (42) is adapted to determine a distance vector (V) from the operating point to the interface and / or to the functional tissue and to control the display system (30) to display this distance vector (V).

5. Surgical assistance system at least according to claim 2, characterized in that the assistance system has an input unit, which is formed in particular by the display unit (30) designed as a touch display, which is adapted to set and / or change an interface factor on the user side in order to generate the enveloping surfaces (H), and thus in particular the interface (G), further outwards or further inwards with respect to the measuring points (M) based on a product of the interface factor and the offset, in order to define an aggressiveness of the intervention.

6. Surgical assistance system according to one of the preceding claims, characterized in that the measuring probe is connected to a robot arm of the assistance system, and that the tracking system is preferably adapted to determine the position of the at least one measuring point as a function of robot-internal kinematics, and / or the effector is connected to a robot arm of the assistance system, and that the tracking system is adapted to preferably determine the position of the working point as a function of robot-internal kinematics, and that the data processing unit is adapted to issue an alarm and / or to stop and / or reverse a movement of the effector when the boundary surface is exceeded by the working point (no-go area).

7. Surgical assistance system according to one of the preceding claims, characterized in that the data processing unit (42) has an interface for an additional recording system, which is preferably adapted to create at least one additional image (DTI, CT, MRI) of the patient (P) preoperatively in an additional data modality, preferably a preoperative CT image and / or a preoperative MRI image and / or a preoperative diffusion tensor image, and in that the data processing unit (42) is adapted to read the respective additional image (DTI, CT, MRI) via the interface with reference to the reference coordinate system (40) and to control the visual display unit (30) to visually display an additional view containing the respective additional image (DTI, CT, MRI) and at least the section (g) of the interface (G).so that the critical boundary to the functional tissue is shown in the respective additional image.

8. Surgical assistance system according to one of the preceding claims, characterized in that the data processing unit is adapted to store the offset and / or an orientation of the measuring probe and / or an attribute, in particular a numerical or color classification of the measuring signal, in the 3D measurement data set.

9. Surgical assistance system according to one of the preceding claims, characterized in that the data processing unit (42) is adapted to determine a 3D Gaussian function of the measurement signal at the positions of the measurement points (M), to determine a volumetric density field by means of a superposition of the 3D Gaussian functions and to determine the boundary surface (G) as a function of the volumetric density field and a predetermined boundary distance, so that the boundary surface (G) represents the boundary distance to the functional tissue.

10. Computer-implemented method for a surgical assistance system for displaying a critical boundary (g, G) to a functional tissue of a patient (P) during a surgical, in particular neurosurgical, intervention, in particular for a surgical assistance system (1) according to one of the preceding claims, characterized by steps: Creating (S1) a time-current recording of the first data modality by a recording system (18); Providing (S2) the recording of the first data modality, preferably digitally, by the recording system (18); Real-time recording (S3) of a signal response of a stimulated, functional tissue at at least one measuring point (M) of the patient (P) by a neuromonitoring measuring probe (20); Timely provision (S4) of a measurement signal of a second data modality, based on the signal response, by the neuromonitoring measuring probe (20), Determining (S5) a position of the recording and a position of the at least one measuring point (M) in real time, each with reference to a reference coordinate system (40), in particular of the patient (P), by a tracking system (32, 34, 36, 38), in particular a navigation system; Providing (S6) the position of the recording and the position of the at least one measuring point (M) in a timely manner, in particular digitally, via the tracking system (32, 34, 36, 38), in particular the navigation system; Reading (S7) the currently provided position of the at least one measuring point (M) and the currently provided measuring signal and preferably a time of detection of the signal response, by a data processing unit (42); Storing (S8) the currently provided position of the at least one measuring point (M) and the currently provided measuring signal and preferably the time of detection of the signal response as a 3D measurement data set by the data processing unit (42); Generating (S9) a boundary surface (G) on the basis of the at least one 3D measurement data set according to a calculation rule by the data processing unit; and Controlling (S10) a visual display unit (30) by the data processing unit (42) such that the visual display unit (30) displays a first view containing the first data modality recording and at least a portion (g) of the interface (G), such that a critical boundary to the functional tissue is displayed in the first data modality recording.

11. Computer-implemented method according to claim 10, characterized by steps: Generating (S9.1) an enveloping surface (H) with an offset, in particular a radius, around the at least one measuring point (M), wherein the offset is greater the smaller the measuring signal is, and wherein the offset is smaller the larger the measuring signal is, in particular the offset is inversely proportional to the measuring signal; Preferably storing (S9.2) the envelope surface (H) in the 3D measurement data set; Generating (S9.3) the boundary surface (G) as a common outer surface based on the enveloping surfaces (H) of several measuring points; in each case by the data processing unit (42).

12. Computer-implemented method according to claim 10 or 11, characterized by steps: Determining (S11) in real time at least one position of an operating point of an effector (E) of the assistance system (1), preferably additionally an orientation of the effector (E), with reference to the reference coordinate system (40), by the tracking system (32, 34, 36, 38); Providing (S12) the position of the operating point in real time, in particular digitally, by the tracking system (32, 34, 36, 38); Determining (S13) a distance vector (V) from the working point to the interface (G) or to the section (g) of the interface (G) and / or to the functional tissue by the data processing unit (42); and Controlling (S14) the display unit (30) so that it displays the distance vector (V).

13. Computer-implemented method according to at least one of claims 10 to 12, characterized by steps: Setting or changing (S15) an interface factor by an input unit of the assistance system, which is formed in particular by the display unit (30) of the assistance system (1) designed as a touch display; and Generating the enveloping surfaces (H) based on a product of the interface factor and the offsets, so that the interface (G) is generated with respect to the measuring points (M) further outwards, in particular towards the functional tissue, or further inwards, in particular away from the functional tissue, in order to define an aggressiveness of the intervention, by the data processing unit (42).

14. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method steps of the method for indicating a critical limit according to any one of claims 10 to 13.

15. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the method steps of the method for indicating a critical limit according to any one of claims 10 to 13.

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