Sensor system and method for an endoscope for detecting an object

Abstract

The invention relates to a sensor system (100) for an endoscope (110) for electrically detecting an object (160) and / or a fluid at a distal end (101) of the endoscope, the sensor system comprising: at least one first electrically conductive contact surface (131) which is arranged at the distal end (101) of the endoscope (110); and a second electrically conductive contact surface (132); wherein an electrical voltage (124) can be applied between the first contact surface (131) and the second contact surface (132) in such a way that an electrical resistance or an impedance between the first contact surface (131) and the second contact surface (132) changes measurably when an object and / or fluid approaches or contacts the contact surfaces; and wherein, depending on the measured current flow and / or the change in electrical resistance or impedance, a signal (147, 148, 177) is output. The invention also relates to a corresponding method.

Description

[0001]Sensor system and method for an endoscope for detecting an object The invention relates to a sensor system for an endoscope and a method for the preferably electrical detection of an object and / or a fluid at a distal end of the endoscope. The invention further relates to a computer program product for carrying out the method. Technological background Endoscopes are known medical devices for examining cavities in a body or technical cavities. A frequently used type of endoscope has an optical system at the distal endoscope end, i.e. the end facing the body, and is designed to capture images and transmit them to the endoscope operator.In procedures for examining existing human or animal body cavities, such as in the ear, nose, and throat area, or in minimally invasive procedures such as laparoscopy, assistance systems in the form of active or passive holding and positioning systems for endoscopes are used. Passive endoscope holding systems support a surgeon by fixing the endoscope in a predetermined position. Active assistance systems for endoscope guidance, or a guidance system, are, for example, robotic systems that can hold and move an endoscope using motorized kinematics. Particularly in very small body cavities to be examined and with a limited field of view of an endoscope, well-known positioning aids can enable targeted intracorporeal alignment of the endoscopic view and fixation of the position.Holding systems for instrument guidance are particularly advantageous in minimally invasive surgery, as they relieve the surgeon, assistant, or other operating personnel from tiring holding work and ensure a steady and stable endoscopic image from the interior of the body. A well-known motorized positioning system is, for example, ARTip Cruise™ or AESOP (automated endoscope system for optimal positioning; see, for example, US 5841950, Computer Motion Corp., Goleta, CA, USA), originally developed for laparoscopy. Such holding systems range from simple motor-controlled guidance systems with few degrees of freedom to complex holding robots that, in addition to endoscope guidance, also enable remote-controlled instrument manipulation. The well-known control concepts for guidance systems can be divided into programmed holding robots, telemanipulators, and hand-on controls for manual operation.Programmable robots can move along specified or stored points or determined trajectories using a computer program product or the program code contained therein. The trajectories can be calculated in combination with current image analyses. In telemanipulation, an operator's instructions are transmitted to the endoscope or attached instruments via a control console such as a joystick or foot pedal (as in the AESOP system). Manually operated and programmed control systems can also be combined. Minimally invasive medical procedures using manual or motor-assisted holding and positioning systems can result in unintentional collisions with tissue or other objects inside the body.Particularly with motor-controlled guidance systems that move the endoscope automatically, there is an increased risk of collision if these are moved further in the distal direction, i.e. towards the end of the endoscope, and at the same time are not additionally visually controlled by the operator, such as a surgeon, via the endoscope's image capture. In addition, errors in automatic image recognition during automated tracking of the endoscope based on image recognition processes can lead to tissue collisions with the tip of the endoscope and / or a distally attached instrument. Image recognition errors can occur not only with automatic image analysis processes, but also when a surgeon is unable to detect a collision on the image of the site provided, or is unable to detect it in time.If collision detection is too late or missing, minor to serious injuries can occur even with powerful motor drives and a fixed coupling between the endoscope and drive. If a distal instrument is at a higher temperature than the tissue, unintentional prolonged contact with the tissue can cause damage such as burns. Therefore, a key object of the invention is to shorten or prevent collisions with tissue to a minimum. In this way, injuries to the body being examined that could be associated with the collision can be avoided and the safety of the patient being examined can be increased. A well-known safety concept for preventing collision-related injuries was implemented, for example, by a proximal-side slip coupling in the well-known AESOP endoscope holding system.When pressure is applied to the endoscope due to tissue contact at its distal end, a slip clutch on the proximal side is triggered, causing the endoscope to "release" from the guide of the drive system. However, this is a purely mechanical solution that does not actively switch off the drive. Therefore, there is a need for alternative detection systems. Furthermore, object detection in endoscopes can be implemented digitally using image processing. However, this can lead to incorrect detections, which reduce safety. There are also collision detection methods that attempt to improve optical control by providing a laterally arranged image acquisition unit on the endoscope. This additional image acquisition unit is intended to help the surgeon visually detect lateral collisions of the endoscope. However, frontal collisions cannot be reliably detected or avoided here.possible collision injuries can be prevented. There is also the problem that both frontal and lateral image acquisition systems can become contaminated by tissue particles, blood splashes or similar, which can lead to misinterpretations. There is therefore a need to provide a system with as few additional components as possible that actively switches off the drive system in order to reliably detect a collision or contact with objects such as tissue. Since tissue has a certain elasticity, slight deformation is permissible. This allows a certain short contact duration to detect a collision and thus switch off the drive without risk of injury to the object touched. The detection of a potential collision object should be quick and reliable in order to be able to reliably and actively switch off rapid movements in the axial direction of the endoscope.In other words, it should be possible to reliably detect an object, and in particular contact with tissue on the front side of the endoscope. In summary, the object of the invention is to provide a sensor system for an endoscope and corresponding detection methods, each of which reliably and automatically detects approach or collision with objects such as body tissue and can switch off the drive system moving the endoscope. In this way, injuries caused by the endoscope tip or an effector arranged thereon penetrating too deeply into tissue, e.g. of an organ to be examined, are to be prevented. Description of the invention On the basis of the invention, the above-mentioned objects are to be achieved better or in a different way than with conventional sensor systems for endoscopes.These objects are achieved with a sensor system according to the invention and a method for electrically detecting an object and / or a fluid at a distal end of the endoscope, as well as a computer program product according to the features of the independent claims. Preferred embodiments of the invention emerge from the subclaims following the main claim. Positional terms such as "distal" or "proximal" and terms such as "fluid," "object," "standard-compliant," or "guidance system," as used in the following description, are defined below. The terms "proximal" and "distal" are used to describe a position of the endoscope or a holding device of the endoscope.The proximal end of the endoscope refers to the end of the endoscope that can be attached to a base or held by an operator, while the distal end is the endoscope end facing the body, which is located in a body cavity during normal use. An “object” in the context of the present invention is, for example, tissue. The tissue found in a body cavity can in particular be soft tissue, which can deform upon contact or collision with the distal end of the endoscope depending on the degree of elasticity of the tissue. Furthermore, an object can also comprise another instrument. The term “fluid” includes liquids and gases, including vapors. Liquids include, for example, blood, urine, rinsing fluids, water, saline solution, or other liquids. Gases such as smoke gases can, for example, be generated when high-frequency energy is applied.arise during HF surgery when changes in tissue cells are thermally induced by the electrical energy used during cutting or coagulation (e.g. for tissue sealing). In this type of medical procedure, tissue particles can arise during HF activation, which severely impair the image for the endoscope operator. A guidance system for an endoscope is an at least partially active assistance system for endoscope guidance, such as the robotic system described above, which can hold and move an endoscope using a drive motor or motorized kinematics. The term "standard-compliant" means that the requirements of standards for endoscopes are observed. For example, the standard IEC 60601-2-18 "Requirements for Endoscopic Equipment" specifies maximum measuring currents.Safety-relevant aspects are also mentioned in the standard DIN EN 60601-2-18 "Medical electrical equipment - Part 2-18: Particular requirements for the essential safety and essential performance of endoscopic equipment." For intracorporeal endoscopic applications – excluding interventions on the heart or nervous system – alternating currents flowing through a body are permitted up to a maximum of 100 µA, and for direct currents up to a maximum of 10 µA. For interventions on the heart or nervous system, direct currents or alternating currents flowing through a body are limited to a maximum of 10 µA. Resistance is the purely ohmic resistance that occurs when direct voltages / currents are used. Impedance is a complex resistance quantity that occurs when alternating voltages / currents are used, since tissue has a capacitive component in addition to the purely ohmic component.For the electrical collision detection of the endoscope with soft tissue, as described below, determining the resistance is sufficient. For further tissue differentiation, determining the impedance with frequency-dependent amplitude and phase response is useful. According to a first aspect of the invention, a sensor system for an endoscope for electrically detecting an object and / or a fluid at a distal end of the endoscope is disclosed, wherein the sensor system comprises: at least one first electrically conductive contact surface arranged at the distal end of the endoscope; and a second electrically conductive contact surface.An electrical voltage can be applied between the first contact surface and the second contact surface in such a way that an electrical resistance between the first contact surface and the second contact surface changes measurably when an object and / or fluid approaches or comes into contact; and wherein a signal is output as a function of a measured current flow and / or change in the electrical resistance and / or impedance. In this way, an approach to or collision with a fluid or object such as tissue can be reliably detected. The impedance or resistance can change measurably even when an object or fluid approaches. If contact is made between the first and second electrically conductive contact surfaces by frontal contact of the endoscope with tissue, a small current flows, which can also be measured.For this purpose, a voltage is applied from the first contact surface of the endoscope to a second contact surface or a return conductor in the endoscope or a body surface, whereby not only the resistance but also the impedance can be determined. This means that contact between the endoscope and an object or fluid can be used as a switch to activate an alarm signal or to automatically switch off a drive for a guidance system of the endoscope. If the distal end of the endoscope or the endoscope tip comes into contact with soft tissue, the tissue can deform without being damaged depending on the elasticity of the tissue, thereby establishing electrical contact. The sensor system can also detect smoke development due to the application of RF energy (cutting, coagulation) or liquids. To determine the material of the object, the sensor system or its evaluation unit can use known specific resistances.If contact with an object consisting of tissue is to be detected, the specific resistance of muscle tissue, for example, can be 2 (Ω * mm. 2 / m), i.e. based on 1 m length and 1 mm² cross-section at a temperature of 20°C. The specific resistance of various substances or materials is known and example values ​​are summarized in a table in the detailed description. Multifunctional resistance and / or impedance measurements can be carried out via the distal contact surfaces of the endoscope to differentiate between tissue and rinsing fluid. If rinsing fluid is detected as the object, a signal is emitted that does not automatically switch off the guidance system. In addition, the bipolar sensor system can also be used for diagnostic tissue differentiation to distinguish between, for example, fat, blood, muscle or tumor tissue. Depending on the output signal, the evaluation unit of the sensor system can recognize the material of the object or the type of tissue and output the result to an operator.Furthermore, the object to be detected can also comprise another instrument separate from the endoscope. In this case, the first electrical contact surface is arranged at the distal end of the endoscope, while a second electrical contact surface is arranged on the instrument to be detected. For detection, the shaft of the endoscope serves as a first conductive contact surface of the sensor system. In the event of a collision with the instrument to be detected, the latter serves as a second conductive contact surface or return conductor, and a measurement of the current or voltage between them can be performed to reliably detect contact with the other instrument.According to a further preferred embodiment, the sensor system has an evaluation unit which is designed to compare the measured change in at least one parameter from the group of current flow, resistance and / or impedance with a predetermined reference value and, if the predetermined reference value is exceeded or reached, to output the signal as an alarm signal, trigger signal and / or a switch-off signal. By bridging the contact surfaces or poles with an object, which in body cavities is preferably an object made of tissue, a small current flows which indicates contact between the endoscope tip and the object. A constant and standard-compliant voltage U is applied across the at least one first contact surface, wherein the voltage U supplied by a voltage source is independent of the standard-compliant current I drawn from the source. The current I orThe resistance R, which is calculable via the quotient U / I, can be measured or calculated upon contact with an object or fluid and, if a predetermined reference value or a threshold value is exceeded, can trigger a signal that can be used for an alarm and / or to switch off a drive of a guidance system. According to a further preferred embodiment of the sensor system, the endoscope has a guidance system with at least one drive and can be positioned by the at least one drive at least in the longitudinal direction of an endoscope shaft, wherein the output signal is a switch-off signal in order to deactivate the at least one drive of the guidance system of the endoscope by means of a switch. In this way, an endoscope which has an active guidance system such asa robot is moved, can be equipped with a reliable sensor system for detecting tissue contact and the drive or motor of the guidance system can be stopped automatically. In this way, unwanted collisions with tissue inside the body can be quickly detected and further movement of the motor-driven endoscope in the distal or axial direction can be prevented. In this way, tissue injuries can be prevented. According to a further preferred embodiment, the electrical voltage U can be applied to a voltage source via a supply line and a return line, wherein at least one part of the endoscope, preferably a cylindrical conductive shaft, is designed as the first part of the supply line and the voltage at the proximal end of the endoscope can be connected to a voltage source via a second section of the supply line.In this way, an electrical measuring circuit can be implemented exclusively using components of the endoscope. The supply line and the return line are each guided within or via the endoscope to the corresponding contact surfaces at the distal end and output on the proximal side. A cylindrical, conductive metal shaft can serve as an inner tube as part of the supply line and is preferably designed to accommodate an optical transmission system within it. The return line, which is insulated from the supply line, can be, for example, an outer metal shaft or a cable attached to it. Since the endoscope has both contact surfaces and the associated supply and return lines, the endoscope can be used in what is known as bipolar mode. It is advantageous that known endoscopes can be upgraded for use in bipolar mode.For this purpose, existing, mutually insulated, conductive shafts or tube sections of an endoscope can be used for a supply or return line. For example, in the so-called HOPKINS® endoscope, cylindrical tube sections can be used to accommodate glass fibers as light guides or optics such as a rod lens system as a supply line, and a metallic outer shaft can be used as a return line. According to a further preferred embodiment, the electrical voltage is selected from a group of voltages comprising the following voltages: a voltage corresponding to an alternating current of a maximum of 100 µA, preferably a maximum of 50 µA or a maximum of 10 µA, or a direct current of a maximum of 10 µA, preferably a maximum of 5 µA or 2 µA; furthermore, a signal voltage, preferably with a low pulse / pause ratio, preferably less than 50:50; and / or a signal voltage with a modulated data code. In this way, voltages U.Sapplied across the at least one first contact surface and an associated current is impressed, wherein the current intensities supplied by the selected voltage source correspond to the currently applicable standards for endoscopes, such as the IEC 60601-2-18 standard. Furthermore, it is advantageous to provide a modulated signal voltage with a low pulse / pause ratio of less than 50:50, preferably 20:80 or 10:90, since this results in a lower average current load on the object to be detected. In addition, the signal interference immunity is increased. In a preferred embodiment, the signal interference immunity can be increased by modulating a data code for a plausibility check onto the current.According to a further preferred embodiment, the return line is insulated from the supply line and selected from the group of lines comprising: an at least partially conductive shaft of the endoscope; an at least partially conductive cylindrical outer shaft or inner shaft of the endoscope, preferably made of metal; a ground line of an electrical unit, preferably an optoelectronic detector, such as an image sensor (CCD sensor, CMOS sensor); a line in connection with the second contact surface, which can be arranged outside the endoscope on a human or animal body part. Depending on whether the return line is provided in the endoscope or outside the endoscope, the endoscope can be used in bipolar or monopolar mode. For the monopolar mode, neutral electrodes could be used, which for monopolar HF surgery can be arranged, for example, on the back or thigh of the patient.In HF surgery, it is known that the high-frequency electrical current flows into the patient via the monopolar active electrode and is then discharged from the patient via the neutral electrode. Such a neutral electrode made of electrically conductive silicone or metal, with or without conductive gel, could advantageously be used as a "return line" for the sensor system of an endoscope (monopolar approach) during inactive HF operation. With the monopolar approach, it is necessary to always have a neutral electrode or another electrode on the patient's body, and a low measuring current must be applied to certain areas of the patient. However, since the currents are low and conform to standards, the monopolar approach can be performed safely for the patient. One advantage of the monopolar approach is that only one contact surface is in contact with the object, such as the skin.Soft tissue must come into contact in order to detect a collision with an object. The monopolar approach has the disadvantage of making differentiation of the tissue more difficult due to the different paths of the measuring current through the patient, compared to the bipolar approach with two contact surfaces on the front of the endoscope. Detection of fluid or gas as an object is not possible at all with a monopolar approach. If you want to detect different types of tissue or objects such as fluids and / or gas with the sensor system, this can be achieved with the bipolar mode. In order to carry out precise resistance measurements and / or impedance measurements, e.g. of a tissue, special electrode arrangements with at least two or more leads can advantageously be provided. According to a further preferred embodiment, the two contact surfaces form a first electrode arrangement and the sensor system furthermore has a further electrode arrangement.With the help of the additional electrode arrangement, a four-wire measurement can be performed to compensate for the electrode / object contact resistance and to more accurately determine the object resistance. In other words, the influence of the contact resistance from an electrode to the object or tissue is minimized by the four-wire measurement method. With this electrode arrangement, a better material differentiation of the detected object can be achieved and, for example, different types of tissue can be better detected using measured resistance or impedance or current flow as a function of the applied voltage. According to a further preferred embodiment, the sensor system has a Wheatstone measuring bridge for measuring resistance or impedance values. In this way, precision measurements of resistance values ​​and / or impedance values ​​for tissue differentiation can be performed more accurately and can be used for diagnostics or to support the surgeon.The proximal-side evaluation can be carried out precisely using an impedance measuring bridge or an alternating current measuring bridge, e.g., a Wheatstone measuring bridge. According to a further preferred embodiment, the electrically conductive contact surfaces are electrically connectable via a distally arranged conductive switching element, preferably via a spring contact. The switching element is preferably closed and designed to establish contact between the two electrically conductive contact surfaces upon pressure from an object colliding with the switching element. Spring contacts or other elastic elements can be used as the switching element.Preferably, a switching element such as a spring contact is designed to be closed, so that the switching element is surrounded by a protective device, for example made of plastic, at least on the distal side, to prevent injuries in the event of tissue contact and to enable easy cleaning of the endoscope's end surfaces. If the contact is closed via the switching element after sufficient pressure has been applied by the collision object, whereby the pressure usually occurs as a result of the endoscope moving towards the collision object, the sensor system can reliably detect a collision and, for example, deactivate the movement of a robot. In this way, the endoscope, which is moved towards the object via a guidance system, can be automatically stopped with the help of the sensor system and potential injuries can be prevented.According to a further preferred embodiment, a resistor or a resistive conductor is arranged between the first contact surface and the second contact surface. When contact is made with an object, the resistor or resistive conductor is a parallel resistor. At a constant voltage, the total current increases upon contact with the object, which adds further resistance. The change in current can be measured by the sensor system and analyzed by the evaluation unit to determine the resistance or impedance applied by the object.Furthermore, a method for detecting objects and / or fluids is disclosed with a sensor system of an endoscope at a distal end of the endoscope, which comprises: providing at least one first electrically conductive contact surface arranged at the distal end of the endoscope; applying an electrical voltage between the first electrically conductive contact surface and a second electrically conductive contact surface; upon approach or contact of an object and / or fluid, measuring a change in an electrical resistance and / or an impedance and / or a current flow between the first contact surface and the second contact surface; and after evaluation, outputting a signal depending on the measured current flow and / or change in the electrical resistance and / or an impedance.In this way, depending on a measured parameter selected from the group comprising the parameters current flow, electrical resistance or impedance, it can be advantageously used for electrical collision detection. Frequency-dependent impedance values ​​can be used to differentiate between the tissue and, for example, to distinguish between tumor-free tissue and tumor tissue. According to a further preferred embodiment, an evaluation unit with a memory is provided which is designed to carry out the following steps: outputting one or more signals if the measured change in a resistance or impedance is equal to or less than a predetermined reference value; and / or depending on the determined resistance or impedance value and stored reference values, determining a tissue type of the object and / or type of fluid.According to a further preferred embodiment, the method further comprises the following method step: upon output of the signal, deactivation of a drive of the guidance system, which is configured to position the endoscope in the longitudinal direction of an endoscope shaft. In this way, patient safety can be increased because unintentional injuries can be avoided. If the sensor system is also used in combination with HF surgery applications, the following safety aspect of the method is advantageous: prior to an electrosurgical application of the endoscope, the sensor system and / or the drive of the guidance system is / are deactivated with a time lead time, preferably a few ms before HF activation. In this way, possible interference with the measurement technology of the sensor system and thus with the measurement evaluation due to the HF coupling can be avoided.According to a further preferred embodiment, the method further comprises analyzing the image brightness of an image capture device or image sensor of the endoscope; which comprises the following steps: capturing image data using the image capture device of the endoscope; receiving the image data by a control unit; analyzing image data by the control unit to subsequently determine an image brightness and compare the determined image brightness with a predetermined reference value; and outputting a trigger signal for applying the electrical voltage between the contact surfaces when the predetermined reference value of the image brightness is exceeded. In this way, the electrical voltage can only be activated, and thus the sensor system made operational, when changes in image brightness or exceeding predetermined reference values ​​of the image brightness indicate an approaching collision with an object.It should be noted that as the endoscope approaches the object, the image brightness generally increases (in proportion to the square of the distance). If predetermined brightness reference values ​​are exceeded, an imminent tissue collision can be assumed, and only then can the electrical detection be activated. If the electrical detection of collisions is supplemented by image brightness monitoring, it is necessary to take into account the usual parameter adjustments of the image brightness control. This means that the effects of usual image brightness adjustments due to controls in the endoscopic camera (e.g.caused by a camera shutter) and / or due to changes in the light source settings to determine the nominal image brightness in comparison to the current image brightness should be taken into account if object detection is to be activated automatically using image brightness analysis and a comparison with reference values. This means that if an image becomes brighter due to a stronger lighting setting, the sensor system should not be activated. If, on the other hand, the other parameters such as lighting and image brightness parameters remain constant, increased brightness can indicate that the end of the endoscope is approaching an object. In this case, the trigger signal for applying or impressing the electrical voltage is output so that, upon contact with an object, differentiated material detection and / or automatic shutdown of a guidance system can take place.According to a further preferred embodiment, the method further comprises, after the measurement between the contact surfaces, comparing the measured electrical resistance or impedance and / or the current flow with a predetermined reference value; and determining, depending on the predetermined reference value, a tissue or a fluid selected from the group comprising: muscle tissue, fatty tissue, tumor tissue, soft tissue, supporting tissue, saline solution, smoke gas, condensate, rinsing fluid, urine and / or blood. In this way, a differentiation can be made based on the material of the object or the type of fluid. If, for example, condensate or blood is detected, a cleaning device provided in the endoscope can be automatically activated with the output signal of the sensor system in order to carry out cleaning with rinsing fluid and / or gas to dry the distal end surface of the endoscope. In the case of condensate or smoke gas detection, for example,It is not necessary to stop the kinematics of the guidance system, since no collision with an object such as a patient's tissue has occurred. Furthermore, a differentiation of tissue types of the contacted object can advantageously be carried out using frequency-dependent impedance values. Different types of tissue can be differentiated using known specific resistance values ​​or impedance values ​​of the respective materials from textbooks or tables (see Table 1 below for 20 °C or Table 2 in the detailed description) and / or based on experimentally determined resistances or impedances. Table 1 (specific resistance ρ in tissues in the body): The detectable soft tissues essentially include fatty and muscle tissue or connective tissue. In addition, the specific resistances of supporting tissues such as bone and cartilage are known. The specific resistance ρ in Ω* cm of fatty tissue is 10 times higher than the resistance of muscle tissue (see Table 1). If an object has more than one tissue type, an analysis or estimation based on the different specific impedance values ​​as a function of frequency can be used to differentiate, for example, between fatty tissue or muscle tissue or between malignant tumor tissue and benign tissue. According to a further preferred embodiment, the method comprises, after a contact signal and, preferably after positioning the endoscope in the proximal direction of the endoscope, outputting a trigger signal for cleaning the distal optics using a cleaning device.In this way, a distal end surface, such as an image sensor, that has become contaminated through contact with tissue can be cleaned immediately, thus quickly making the endoscope functional again for image acquisition. According to a further aspect, a computer program product is provided that includes program code with instructions that, when executed by a computer, cause the computer to carry out steps of the method for detecting an object and / or fluid using a sensor system. Detailed description of the invention The invention and further advantageous embodiments and developments thereof are described and explained in more detail below with reference to the examples shown in the drawings. The drawings are for illustrative purposes and are not to scale. Terms such as proximal or distal are not to be understood as limiting.The features shown in the following description and the drawings can be used individually or in combination according to the invention. The drawings show: Fig. 1a is a schematic circuit diagram of an embodiment of the sensor system for an endoscope without contact with an object; Fig. 1b is the endoscope part shown in Fig. 1a in contact with the object; Fig. 2a is a schematic circuit diagram of a further embodiment of the sensor system with return and supply lines for bipolar operation; Fig. 2b is a schematic perspective view of the distal region of the endoscope shown in Fig. 2a, wherein the outer shaft with cleaning device and the inner shaft with image capture device and light sources are shown separately; Fig. 3 is a schematic illustration of a further embodiment of a sensor system; Fig.4 shows a flow diagram of a method according to the invention for detecting an object and / or fluid using a sensor system. Fig. 1a and Fig. 1b show schematic block diagrams of an embodiment of the sensor system 100 for the bipolar operation of an endoscope 110. Fig. 1a shows an object 160 without contact with the distal end 101 of the endoscope 110, while Fig. 1b shows the same partial section of Fig. 1a of the endoscope 110, with the distal end 101 of the endoscope 110 in contact with the object 160. Fig. 1a shows, in addition to the endoscope 110, a schematic block diagram of a drive controller 140 and an embodiment of a measuring circuit 120 of a sensor system 100. The distal end 101 of the endoscope 110 has a first electrically conductive contact surface 131 and a second electrically conductive contact surface 132.An electrical voltage Us from a voltage source 124 is applied between the first contact surface 131 and the second contact surface 132 via mutually insulated lines (dotted-dashed supply line and dashed return line) in order to be able to measure an electrical resistance or impedance between the first contact surface 131 and the second contact surface 132 by means of the measuring circuit 120. The supply line (dotted-dashed line) comprises a first section 121 from the voltage source 124 to the proximal end 102 of the endoscope 110 and a further supply line section 151 via the outer shaft 154 of the endoscope 110 to the first contact surface 131.Furthermore, in this embodiment, a return line section 152 (dashed line) is provided, which is a partial section of the inner shaft or optical shaft 155 of the endoscope and electrically connects the second distal-side contact surface 132 to the voltage source 124 via a return line section 122 arranged on the proximal side. The optical shaft 155 has at its distal end an image capture device or image sensor 156 with an optical window and a light guide 111 as a light source, whereby a distal-side first light exit surface is formed. The supply and return sections (151 and 152) in the endoscope 110 are insulated from one another and are preferably cylindrical conductive sections of already existing shafts such as the optical shaft 155 or outer shaft 154, which results in circular or oval-shaped contact surfaces 131, 132 at the distal end 101 of the endoscope or the respective shafts (see also Fig. 2b).The voltage Us is preferably connected to the voltage source 124 via a second section 121 of the supply line at the proximal end 101 of the endoscope, which in operating mode is located far from a body cavity to be examined. The measuring circuit 120 includes a parallel resistor 123, which is connected in parallel to the possible tissue contact, as well as an analysis unit 114 for resistance or impedance measurement. Depending on a measured current flow and / or change in the electrical resistance or impedance, the analysis unit 114 outputs a signal to interrupt or start up the drive control 140. If the evaluation or analysis unit 114 determines contact with an object 160 (as shown in Fig. 1b) based on the measured resistance or impedance, the switch 143 (indicated by the arrow 149) switches from the operating position (a = ON) to the interruption position (b = OFF), so that the drive 145 orMotor M of a guidance system of the endoscope is switched off. Thus, the electrical circuit comprising the voltage source 141 with a voltage Um, the line 142 (electrical line between voltage source 141 and switch 143), the switch 143, the line 144 (line between switch 143 and drive 145), the drive 145, the line 146 (electrical line between drive 145 and voltage source 141) is interrupted with the aid of the switch 143. In this way, a drive 145 for a guidance system for the axial movement of the endoscope 100 in the direction of the object 160 can be stopped and possible injuries to the object 160 can be avoided. In a preferred embodiment of the measuring circuit 120, a signal voltage 125 is modulated, wherein the generated current or resistance or impedance can be measured by the sensor system 100 and evaluated by the analysis unit 114. Modulated signal voltages are suitable for more precise measurements.For example, modulation can occur, generating a time-discrete signal sequence consisting of individual pulses, preferably using a low pulse / pause ratio such as 50:50 or lower. This has the advantage that the touched object 160 is subjected to a lower current load and signal interference immunity is increased. In a further embodiment, a data code for a plausibility check can also be modulated onto the current in order to further increase signal interference immunity. Fig. 2a shows a schematic circuit diagram of a further embodiment of the sensor system 100 with supply line (121, 151) and return line 122 with a schematic perspective partial view of an endoscope. Fig. 2b shows the distal portion of the endoscope 110 shown in Fig. 2a, wherein the outer shaft and inner shafts are shown as separate components.The outer shaft is shown with a cleaning device on the left, and the inner shaft with the image capture device and light sources is shown on the right. The measuring circuit of the embodiment shown in Fig. 2a is shown in a simplified manner and includes the essential components such as a voltage source 124 and an analysis unit 114. The supply line 122 is schematically shown here as being insulated from the first contact surface. The supply line 122 can also be arranged in the proximal region of the endoscope, as long as the supply line is insulated from the return line. It is also not necessary to provide an additional return line in every embodiment, since existing system components of the endoscope can be used.For example, in an endoscope with an image capture device for videos and a distal optoelectronic converter, only one additional measuring voltage-carrying line 121 can be provided, while the return line can be provided via the ground of the already existing video chip supply. Figures 2a and 2b show a cleaning device 170 with two fluid nozzles 171 and 172 with separate fluid channels (not shown here). In this way, two different cleaning fluids, such as a liquid and a gas, can be transported or sprayed separately from one another to the optical window of the image capture device 156 or the image sensor. Water, saline solution, or other physiological solutions can be used as the liquid. Air or carbon dioxide are often used as gases. In this case, heavy contamination such as, for example,of blood is generally better removed with the help of liquids, while slight contamination or condensate on the optical window can be removed using gas. In this embodiment of the cleaning device 170, an upwardly directed two-channel nozzle is preferably used. Alternatively, a single nozzle (not shown) can be used, to which gas and liquid are transported one after the other in the same fluid channel. If rinsing liquid is used for cleaning, the liquid not only wets the optical window of the image sensor 156 and thus the second contact surface 132, but at the same time the distal first and second light exit surfaces 111, 112, which are partially surrounded by the outer shaft, are also cleaned. The rinsing fluid used for cleaning can thus conductively connect both the contact surface 131 of the outer shaft 154 and the contact surface 132 of the inner shaft or optical shaft 155 and thus reduce the resistance orreduce the impedance between the contact surfaces. Using the detected resistivity, the type of fluid can be detected with the sensor system. Example values ​​for resistivities of contamination sources such as blood or cleaning fluids for endoscopes such as saline solution or water are listed in Table 2 below. Table 2: Specific electrical resistivities and electrical conductivities Constantan 0.50 2 * Wood... Copper sulfate- 3.0 * . .. solve ung(10%)Copper 0.017 5,9 * Papier 5.0 * ... ... Seawater 2.0 Silber 6,3 * Polypro- 2.0 * pylene foil Muscle tissue 0.50 5 * Stahl 0,10 ... ... porcelain Salzsäure 1,5 * 0 ,20 10 * (10%) 67 Wolfram 1,9 *Water Sulfuric acid 2.5 * (distilled) (10%) 40 (https: / / www.formel-sammlung.de / formel-Spezifischer-elektrischer-Widerstand-und-elektrischer- Leitfähigkeit-3-25-158.html) Fig. 3 shows a schematic representation of a further embodiment of a sensor system 100 for detecting an object and / or fluid. At a distal end of an endoscope 100, at least one or more measured values ​​115 are recorded by means of an analysis unit 114. Furthermore, a memory unit 116 can be provided. This memory 116 can store a plurality of reference values. For example, different reference values ​​of specific resistances and / or impedance values ​​can be stored in order to be able to differentiate the tissue types of the objects touched by assigning a fluid type or a tissue type by comparison with the stored reference values.YRef 1 is shown as an example for a first reference value for fluid, which can be, for example, a specific resistance for saline solution, which is a suitable liquid 176 for cleaning. Furthermore, a second reference value YRef 2 for the fluid blood is mentioned as an example. For the latter, there can also be multiple blood reference values, since flowing blood in tissue is known to have a different value than blood outside of a tissue, which can appear, for example, as blood splashes on the optical window.For the differentiated detection of a tissue type after contact with an object 160, further reference values ​​161-163 are stored in the memory 116, which include the following types: 161 Reference value 1 (XRef1) for fatty tissue 162 Reference value 2 (XRef2) for muscle tissue 163 Reference value 3 (XRef3) for tumor tissue Other reference values ​​for tissue types such as soft tissue or supporting tissue as well as for fluids such as saline solution, smoke gas, condensate, rinsing fluid, urine and / or blood and other materials to be examined can be stored in the memory for analysis. With the help of the reference values ​​for fluids, blood, for example, can be detected and the cleaning device 170 can then be activated or switched on (see arrow "ON") with the trigger signal 177 for cleaning the optics or image sensor with a cleaning fluid. Depending on which fluid is detected, either gas 175 (e.g. for condensate) or liquid 176 (for blood) should be used as the cleaning fluid.Furthermore, an alarm module 174, such as a loudspeaker, is provided. After comparing a measured change in the current flow and / or the resistance or impedance with a predetermined reference value and determining whether a predetermined reference value has been exceeded or reached, an alarm signal 148 can be output, so that the alarm module 174 emits a visual signal or an acoustic signal (see loudspeaker symbol). Finally, based on the measured value analysis, either a switch-off signal 147 or a switch-on signal (150) can be output to the drive 145. In addition to known values ​​from tables or specialist books, experimentally determined reference values ​​can also be used that apply to the specific body cavity and endoscope application to be examined.Furthermore, the storage unit or memory 116 can, for example, store a plurality of previously acquired image data from an image acquisition device of the endoscope (see reference numeral 156 in Fig. 2) with respect to typical brightness values ​​depending on control parameters in order to compare current image brightness values ​​with image brightness values ​​of the stored images. For the analyses in the analysis unit 114, a processor is provided, which comprises one or more microprocessors and optionally also one or more graphics processors for image analysis. Depending on approaching objects detected by image brightness analysis, the sensor system can be activated in order to subsequently reliably detect contact with the object. Fig. 4 shows a flow diagram of a method 400 according to the invention for detecting an object and / or fluid using a sensor system 100.In the optional method step 404 (indicated by a dashed box), an image brightness analysis can be performed to activate the sensor system 100 upon detection of an object approaching due to the axial movement of the endoscope. Activation or switching on of the sensor system occurs based on the switch-on signal 150 (ON). In method step 401, one or two contact surfaces are provided at a distal end of an endoscope. In step 424, an electrical voltage Us, preferably a modulated signal voltage, is applied between the first contact surface 131 and the second contact surface 132. One contact surface is sufficient if, for example, a neutral electrode is provided.Then, an alternating current of a maximum of 100 µA, preferably a maximum of 50 µA or 10 µA, or a direct current of a maximum of 10 µA, preferably a maximum of 5 µA or 2 µA, can flow into the object or patient via the endoscope's single contact surface, which functions as a monopolar electrode, and be discharged via the patient's neutral electrode, which can be arranged on the back, for example. The aforementioned standard-compliant currents can also flow between two contact surfaces in bipolar operating mode. In method step 414, an electrical resistance or impedance or current flow or a change in the aforementioned parameters is measured between the first contact surface 131 and the second contact surface 132 or a neutral electrode upon approach or contact of an object and / or fluid.A possible evaluation 415 comprises comparing a measured electrical resistance or impedance and / or the current flow with a predetermined reference value (see right arrow YRefn). When a cleaning device is provided and the trigger signal 177 is activated, a typical value for a cleaning fluid 176 is measured as the specific resistance ρ. In this case, it is not necessary to switch off the drive of a guidance system, and the switch 143 of the circuit for the drive 145 can remain in the operating position a). The evaluation unit outputs the switch-on signal 150 = ON to the switch 143. Upon contact with an object, the following sequences can be initiated. Firstly, a switch-off signal 147 (so-called EMERGENCY STOP) can be generated, which sets the interruption position of the switch 143 (to b).Thus, contact of the endoscope with a fluid object can be used as a switch to automatically deactivate a drive for a guidance system of the endoscope. Alternatively or additionally, an alarm signal (acoustic or optical) can be activated. Alternatively or additionally, the measured specific resistances ρ upon contact with an object 160 can be used to compare them with known values ​​XRefn (step 416). The material of the object 160 is then determined with the aid of a reference value (ρ = XRef1 for fatty tissue). List of reference symbols 100 Sensor system 101 Distal end of the endoscope 102 Proximal region of the endoscope Endoscope Distal-side 1st light exit surface (e.g. light guide) Distal-side 2ndLight exit surface Analysis or evaluation unit Measured value Memory Schematic block diagram of an embodiment of a measuring circuit Section of the supply line between voltage source and endoscope Section of the return line between endoscope and voltage source Parallel resistance Electrical voltage Electrical voltage source First electrically conductive contact surface Second electrically conductive contact surface Schematic circuit of the drive control Voltage source Motor or drive Electrical line between voltage source 141 and switch 143 Switch for drive (a: ON or b: dashed emergency OFF position) Electrical return line between switch and drive Drive orMotor of the guidance system Electrical line between drive and voltage source Switch-off signal Alarm signal (acoustic or optical) Arrow between ON position a and OFF position b Switch-on signal (ON) Further section of the electrical supply line via outer shaft Further section of the electrical return line via inner shaft 154 Outer shaft of the endoscope 155 Inner shaft or optics shaft 156 Image capture device or image sensor with imaging optics and distal optics window 160 Object 161 Reference value 1 (XRef1) 162 Reference value 2 (XRef2) 163 Reference value 3 (XRef3) 170 Cleaning device 171 First fluid nozzle 172 Second fluid nozzle 174 Alarm module such as loudspeaker 175 Gas 176 Liquid for cleaning 177 Trigger signal for cleaning the optics window orImage sensor with fluid 400 Method for detecting objects and / or fluids 401 Providing one or two contact surfaces 404 Analysis of image brightness (optional) 414 Measuring 415 Evaluation 416 Comparing the measured values ​​with predetermined reference values ​​(XRefn) 417 Determining the tissue type based on a reference value (XRef1) 424 Applying voltage. U M Supply voltage drive or motor U s Signal voltage XRef 1 first reference value for tissue XRef2 second reference value for another tissue Xref3 third reference value for another tissue (e.g. tumor tissue) YRef 1 first reference value for fluid (saline solution) YRef 2 second reference value for another fluid (blood)

Claims

1. A sensor system (100) for an endoscope (110) for electrically detecting an object (160) and / or a fluid at a distal end (101) of the endoscope, comprising: at least one first electrically conductive contact surface (131) arranged at the distal end (101) of the endoscope (110); and a second electrically conductive contact surface (132); wherein an electrical voltage (124) can be applied between the first contact surface (131) and the second contact surface (132) such that an electrical resistance and / or an impedance between the first contact surface (131) and the second contact surface (132) changes measurably upon approach or contact of an object and / or fluid; and wherein a signal (147, 148, 177) is output as a function of a measured current flow and / or change in the electrical resistance and / or an impedance. 2.Sensor system according to claim 1, wherein the sensor system (100) has an evaluation unit (114) configured to compare the measured change in at least one or more parameters from the group of current flow, resistance, and impedance with a predetermined reference value and, if the predetermined reference value is exceeded or reached, to output the signal as an alarm signal (148), trigger signal (177), and / or a switch-off signal (147).

3. Sensor system according to claim 1 or 2, wherein the endoscope (110) has a guidance system with at least one drive (145) and can be positioned by the at least one drive at least in the longitudinal direction of an endoscope shaft; wherein the output signal is a switch-off signal (147) for deactivating the at least one drive of the guidance system of the endoscope by means of a switch (143).

4. Sensor system according to one of the preceding claims, wherein the electrical voltage (U s) to a voltage source (124) via a supply line (121, 151) and a return line (122, 152), wherein at least a part of the endoscope (110), preferably a cylindrical conductive shaft, is formed as the first part of the supply line (151) and the voltage (124) at the proximal end of the endoscope is connectable to a voltage source (125) via a second section of the supply line (121).

5. Sensor system (100) according to one of the preceding claims, wherein the electrical voltage (124) is selected from a group of voltages comprising: a voltage (124) corresponding to an alternating current of a maximum of 100 µA, preferably a maximum of 50 µA or 10 µA, or a direct current of a maximum of 10 µA, preferably a maximum of 5 µA or 2 µA, a signal voltage (U s ), preferably with a low pulse / pause ratio of less than 50 / 50, preferably 20 / 80 or 10 / 90; and / or a signal voltage (U s) with modulated data code.

6. Sensor system according to claim 4 or 5, wherein the return line is insulated from the supply line and is selected from the group of lines comprising: an at least partially conductive shaft (152) of the endoscope; an at least partially conductive cylindrical outer shaft (152) or inner shaft of the endoscope, preferably made of metal; a ground line of an electrical unit, preferably an optoelectronic detector; a line in connection with the second contact surface (132), which can be arranged outside the endoscope on a human or animal body part.

7. Sensor system according to one of the preceding claims, wherein the two contact surfaces (131, 132) form a first electrode arrangement and furthermore the sensor system (100) has a further electrode arrangement.

8. Sensor system according to one of the preceding claims, wherein the sensor system further comprises a Wheatstone bridge for measuring resistance or impedance values.

9. Sensor system according to one of the preceding claims, wherein the electrically conductive contact surfaces (131, 132) are electrically connectable via a distally arranged conductive switching element, preferably via a spring contact or other elastic element; and wherein the switching element is preferably closed and designed to establish contact between the two electrically conductive contact surfaces (131, 132) with pressure from an object (160) colliding with the switching element.

10. Sensor system according to one of claims 1 to 9, wherein a resistor or a resistor conductor track (123, 126) is arranged between the first contact surface (131) and the second contact surface (132). 11.Method (400) for detecting objects and / or fluids with a sensor system (100) of an endoscope (110) at a distal end (101) of the endoscope, comprising: providing (401) at least one first electrically conductive contact surface (131) arranged at the distal end (101) of the endoscope (110); applying (424) an electrical voltage (124) between the first electrically conductive contact surface (131) and a second electrically conductive contact surface (132); upon approach or contact of an object and / or fluid, measuring (414) a change in at least one or more parameters between the first contact surface (131) and the second contact surface, wherein the at least one parameter is selected from a group of parameters comprising a current flow, an electrical resistance and / or an impedance (132); and after evaluation (415) outputting a signal (147, 148, 177) depending on the measured parameter or parameters.

12. The method according to claim 11, wherein an evaluation unit (114) with a memory (116) is provided, which is designed to carry out the following steps: outputting one or more signals (147, 148, 177) if the measured change in a resistance or impedance is equal to or less than a predetermined reference value (161, 162, 163, 171, 172); and / or depending on the determined resistance and / or impedance value and stored reference values ​​(161, 162, 163, 171, 172), determining a tissue type of the object or type of fluid (176).

13. The method according to claim 11 or 12, further comprising the following method step: upon output of the signal, deactivating a drive (145) of the guidance system, which is configured to position the endoscope (110) in the longitudinal direction of an endoscope shaft. 14.Method according to one of the preceding claims 11 to 13, before an electrosurgical application of the endoscope, deactivating the sensor system (100) and / or the drive (145) of the guidance system with a time lead, preferably a few ms before an RF activation.

15. Method according to one of the preceding claims 11 to 14, wherein the method further comprises an analysis of the image brightness (404) of an image capture device (156) of the endoscope (110); comprising the following steps: acquiring image data by means of the image capture device (156) of the endoscope; receiving the image data by a control unit; analyzing image data by the control unit to subsequently determine an image brightness and comparing the determined image brightness with a predetermined reference value; and. Outputting a trigger signal to open the switch (143) when the predetermined reference value of the image brightness is exceeded.

16. The method according to one of the preceding claims 10 to 14, further comprising: after the measurement (414) between the contact surfaces (131, 132), comparing the measured electrical resistance or impedance and / or the current flow with a predetermined reference value; and determining, as a function of the predetermined reference value, a tissue or a fluid, wherein one or more reference values ​​are selected from the group comprising: muscle tissue, fatty tissue, tumor tissue, soft tissue, supporting tissue, saline solution, flue gas, condensate, rinsing fluid, urine, and / or blood. 17.Method according to one of the preceding claims, after a contact signal and, preferably after positioning (176) of the endoscope in the proximal direction of the endoscope (110), outputting a trigger signal (177) for cleaning the distal optics (156) by a cleaning device (170).

18. A computer program product comprising program code with instructions which, when executed by a computer, cause the computer to perform steps of the method according to one of claims 11 to 17.

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