Method and system for determining properties within a vessel

Abstract

The invention relates to a method for determining a property in a vessel or heart (V) of a patient. It comprises the steps of placing an element in the vessel or heart (V) and determining an urging force (2) acting to the element. Furthermore, at least one of an acceleration (3) and a velocity (4) of the element is determined. At least one property of a surrounding medium of the element is determined based on the urging force and at least one of the acceleration (3) and the velocity (4) of the element.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method and system for determining properties of tissue or fluid in a vessel according to the preamble of the independent claims. BACKGROUND

[0002] Minimally invasive treatment of vessels is known in the prior art. For example, catheter devices can be employed to deliver implants. Such treatments are used for example to treat diseases such as stenosis of vessels or aneurysms. Similarly, micro-robots have been employed in the prior art to image and / or treat internal sites of a patient's body.

[0003] However, a persistent problem in therapeutic and diagnostic applications of such devices is the inability to obtain accurate information about the surroundings of the device.

[0004] In particular, imaging techniques used in conjunction with minimally invasive treatments typically only provide limited information about the properties of the surrounding tissue. For example, contrast imaging using X-rays provides anatomical information of the vessel system, but can not provide information about mechanical properties or flow obstruction properties in the blood flow. As a result, it is often necessary to employ multiple methods in parallel, making the collection of such information slow, costly and difficult. It is particularly difficult to obtain these information in real-time during treatment using minimally invasive methods. SUMMARY

[0005] It is therefore an object of the present invention to overcome the drawbacks of the prior art, in particular to provide a method and system allowing to determine different properties of tissue or fluid in a vessel surrounding a device used to treat or diagnose a human body in a simple manner.

[0006] This and other objects are achieved by the method and system according to the features of the independent claims of the present invention.

[0007] The present invention relates to a system for determining properties in a vessel or heart (V) of a patient. The system comprises an element to be placed in the vessel or heart. The system further comprises means for determining a propulsion force acting to the element, and means for determining at least one of an acceleration and a velocity of the element. Preferably, the system comprises means for determining both the acceleration and the velocity of the element.

[0008] Such means can in particular comprise a sensor, for example an accelerometer, or a sensor adapted to measure a distance to a reference point located inside or outside the patient's body. Additionally or alternatively, the means for determining the propulsion force can further comprise an imaging device and / or a computer for analyzing images generated by the imaging device.

[0009] Additionally, the system comprises a mechanism for determining at least one property of the surrounding medium of the element based on the propulsion force and at least one of the acceleration and the velocity. Such a mechanism can comprise a computer, preferably a computer running software code. Preferably, the mechanism determines the at least one property based on both the acceleration and the velocity of the element.

[0010] The method according to the present application provides a way of determining a vessel property of a patient. The method comprises the following steps:

[0011] - placing an element in a vessel or heart

[0012] - determining a propulsion force acting on the element

[0013] - determining at least one of an actual acceleration and an actual velocity of the element, in particular both the actual acceleration and the actual velocity of the element,

[0014] - determining at least one property of the surrounding medium of the element based on the propulsion force and at least one of the actual acceleration and the actual velocity of the element, in particular both the actual acceleration and the actual velocity of the element.

[0015] The vessel property that can be determined using the method described herein can be a mechanical property, such as the elasticity, stiffness, ductility and / or hardness of the tissue. By inference, it is also possible to determine anatomical or histological properties of the tissue, in particular the presence of necrotic or cancerous tissue. Of course, it is also possible to determine physical properties of the blood, such as the viscosity and / or the flow rate. Additionally or alternatively, the properties can include vessel properties that affect the flow, such as obstacles that impede, slow down or accelerate the blood flow in the vessel or create turbulence. It is also conceivable to acquire other diagnostic relevant properties, such as the presence of an aneurysm, a blood clot / thrombus, a gas bubble and / or a vessel wall defect.

[0016] The surrounding medium should in particular be understood as all biological material located in the vicinity of the element that can interact with the element. It can be a liquid, a solid, a gas or comprise a soft material.

[0017] The element should be understood as any device suitable for moving at least temporarily, freely within the human body. It can in particular be a micro robot, a sensor, a drug carrier or a floating element. In particular, the element can comprise magnetic elements, such as ferromagnetic particles located inside and / or on the surface of the element. The element can also be composed of a ferromagnetic material.

[0018] In particular, the method can be used only for analyzing the vessel properties. Specifically, the method can be performed only for the purpose of determining certain properties of interest. Thus, the element is introduced only for the purpose of providing data to perform the method and not for other purposes. Additionally or alternatively, the method can be performed with a medical device that is introduced into the body also for performing another action. For example, a micro robot can be introduced into the body for delivering a drug or a target site of treatment. The method can then be performed to determine when the micro robot reaches the target site or even to define an optimal target site. It is also conceivable to employ a separate element to perform the method in parallel to another treatment.

[0019] Unless otherwise stated, the propulsion force shall generally be understood as the total force applied to the element without any interaction with the patient's body. For example, if the element is magnetic and actuated by a magnetic field, the propulsion force is the force applied to the element by the magnetic field, without considering blood flow or other forces due to body functions, such as body friction, blood flow or thrombus occlusion. Similarly, if the element comprises a self-propulsion mechanism such as a propeller or a jet, the propulsion force will be the force applied by this self-propulsion mechanism. If a combination of a self-propulsion mechanism and a magnetic field is employed, the propulsion force will comprise both forces. For a given mass of the element, the theoretical acceleration and velocity can also be calculated from the propulsion force.

[0020] Due to influences such as friction, gravity, drag forces and other factors, the actual and the theoretical acceleration and velocity will never be identical. In more complex models, such influences will be taken into account.

[0021] For example, if some parameters of the tissue or fluid in the vicinity of the device are known, they are taken into account to calculate the theoretical acceleration or final velocity that the element should reach in this tissue based on the propulsion force. For example, if the drag force that is applied to the element by the blood independent of the velocity is known, the theoretical final velocity of the element can be calculated.

[0022] In contrast, the actual acceleration and / or the actual velocity of the element shall be understood as the real acceleration and / or real velocity of the element with respect to the patient's body. Thereby, the difference between the actual acceleration or velocity and the theoretical acceleration or velocity, which can be determined from the propulsion force divided by the mass of the element, yields information about the environment of the element, e.g. the viscosity of the blood, or obstacles.

[0023] Thus, the actual propulsion force shall be understood as the product of the actual acceleration and the mass of the element. For a given element, the actual acceleration is thereby the equivalent parameter of the actual propulsion force.

[0024] The propulsion force can be measured or determined based on known parameters, such as parameters of the actuator, e.g. the magnetic field acting to the element.

[0025] Preferably, the propulsion force is determined on the basis of a sensor comprised in the element. This is particularly advantageous if the exact position of the element is unknown or difficult to determine. For example, if the element is located within a large vessel and is driven by a magnetic field, it can not be possible to know the exact properties of the magnetic field at the location where the element is located. Thereby, this problem is solved if the force with which the magnetic field is exerted to the element can be measured.

[0026] Additionally or alternatively, it is also conceivable to employ another sensor comprised in the element to measure the actual acceleration.

[0027] Preferably, the method further comprises the step of imaging the region of the patient in which the element is located. In particular, the imaging can be performed using one of X-ray imaging, magnetic resonance imaging (MRI), computed tomography, positron emission tomography (PET) and ultrasound imaging. This can provide a number of advantages when performing the method. On the one hand, if a certain mechanical property is determined by means of the method, the imaging data can assist in the correct positioning and interpretation (e.g. assignment to a certain type of tissue). On the other hand, it is also conceivable to employ the imaging data to measure the actual acceleration and / or velocity of the element.

[0028] Alternatively or additionally, it is also conceivable to employ a database of patients to correct and interpret data for navigating the element or data collected by the method according to the application. In such a database, not only information about typical patients or groups of patients and individual information of patients can be stored, but also corrections and interpretations can be made by employing artificial intelligence methods. In particular, certain information for correction or interpretation can be collected by deep learning or machine learning methods. Such methods can be implemented during the method according to the application and / or in the preparation thereof.

[0029] Alternatively or additionally, it is also conceivable to use data generated by employing the first element to modify parameters (e.g. magnetic field) related to navigating a subsequent element.

[0030] Preferably, at least one property of the surrounding medium is additionally based on the imaging data. For example, the imaging data can provide information on whether a certain amount of different types of tissue is present. Additionally or alternatively, the imaging data can indicate the presence of an obstacle in the blood. Thereby, one property of the surrounding medium of the element is based on the imaging data, while other properties such as the mechanical properties of different tissue types or obstacles. The combination of imaging data and mechanical properties can allow to finally determine what type of tissue and / or what kind of obstacle is located in the vessel.

[0031] The person skilled in the art will understand that this is merely a non-limiting example of how imaging data can be advantageously used in the method according to the application. However, it is possible to perform the method without employing imaging data.

[0032] Preferably, the method further comprises the step of determining the position of the element. This provides additional information about the position of certain tissue types in the patient's body. This is particularly advantageous in case of planning a treatment or removal of those tissues, e.g. by a therapeutic technique. Preferably, the position is determined by means of an imaging technique.

[0033] Preferably, the method further comprises the step of saving at least one property of the surrounding medium in relation to the position or the time into a memory. This allows for an analysis of a plurality of positions in the vessel at one work stage. In particular, the data can be analyzed subsequently, e.g. to create a one-, two- or three-dimensional property map. For example, a stenosis or an aneurysm of a vessel can be determined along the longitudinal axis of said vessel by means of the method according to the present application. If the level of a stenosis or an aneurysm is determined and saved at a plurality of points, a graph showing the stenosis or aneurysm along the longitudinal axis can be obtained. Similarly, data can also be collected in two or three dimensions.

[0034] Preferably, the step of calculating at least one property of the surrounding medium is performed by a computer running a software code. This allows in particular for an automatic execution of the method and is thereby fast, reliable and cost-effective.

[0035] Preferably, the at least one property of the surrounding medium is one of a mechanical property, a hemodynamic property, an anatomical property and a histological property. For example, it can be the viscosity of the blood, the Young's modulus of the tissue, the flow velocity of the blood and / or the size or shape of the vessel, in particular its diameter.

[0036] Preferably, the element arranged in the vessel comprises a magnetic element, and the step of determining the propulsion force comprises determining the field strength of a magnetic field. Determining the field strength should in particular comprise calculating the properties of the magnetic field at a point in space, in particular at the position of the element, based on known parameters of the unit generating the magnetic field, but can also comprise measuring the magnetic field at a point in space. The measurement of the magnetic field can be performed by the element and thereby at its position and / or at a reference position.

[0037] Preferably, the method further comprises the step of calculating a theoretical acceleration or velocity of the element based on the propulsion force acting to the element.

[0038] Preferably, the step of calculating a theoretical value of the velocity and acceleration of the element is further based on the position of the element and the imaging data required in the imaging step. For example, the size of the vessel and the blood volume can be taken into account based on the imaging data. Additionally or alternatively, the velocity and fluctuation of the blood flow can be measured and taken into account, in particular by means of a Doppler ultrasound imaging measurement. In particular, the position of the element with respect to the vessel wall can also be taken into account.

[0039] Preferably, the method further comprises the step of measuring the flow velocity of the fluid surrounding the element, in particular of the blood in the vessel or the heart. Additionally, at least one property of the surrounding medium can be determined based on the flow velocity. In particular, the flow velocity can be determined by means of Doppler ultrasound imaging. However, it is also conceivable to measure the flow velocity with sensors comprised in and / or on the element.

[0040] Preferably, the method further comprises the step of localizing the element by means of at least one detector and / or a marker. The marker can be arranged on the element and the detector can be arranged in a pre-set position in or with respect to the patient's body. For example, the detector can be arranged on the outside of the vessel, on a bone such as the skull or on an organ such as the heart. The detector is to be understood as any device suitable for detecting or assisting in detecting the element in its vicinity. The marker is associated with the element and facilitates the detection of the element, in particular by means of the sensor.

[0041] The detector is also suitable for measuring the distance to the element. The detector can in particular preferably be an electronic sensor, a magnetic sensor or an optical sensor. The marker can be an NFC chip, a magnet or a radiopaque material. A fluorescent or isotopic marker can also be employed.

[0042] The present invention also relates to a computer program product for analyzing a surrounding medium of an element in a patient's body. It comprises software code which, when running on a computer, is suitable for determining at least one property of the surrounding medium of the element based on at least one of the actual acceleration and the actual velocity of the element, in particular both the actual acceleration and the actual velocity of the element. The computer program product can in particular be suitable for processing imaging data and preferably determining at least one property of the surrounding medium based on imaging data acquired by an imaging device. For example, the computer program product can be suitable for determining at least one of the velocity and the acceleration of the element based on the imaging data.

[0043] The present invention also relates to a system for determining a property of a vessel. It comprises an element suitable for being carried by and / or actively moved in a body fluid, as well as a measuring unit and a computing unit. The measuring unit is suitable for determining at least one of the velocity and the acceleration of the element. The computing unit is suitable for determining at least one property of the vessel based on at least one of the acceleration and the velocity of the element. Preferably, at least one of the measuring unit and the computing unit is suitable for determining the propulsion force acting on the element. For example, the computation can calculate the propulsion force based on an operating parameter such as a property of a magnetic field. Additionally or alternatively, the measuring unit is also suitable for measuring the force exerted on the element, for example by measuring the magnetic field. In particular, the computing unit can determine at least one property of the vessel by executing a method as described herein, in particular preferably by running software code suitable for executing the steps of a method as described above.

[0044] The skilled person will understand that the system is especially suitable for performing any of the method steps as described hereinbefore.

[0045] Preferably, the system comprises an imaging device suitable for imaging the region in the patient's body where the element is located. This especially allows performing all steps described in the context of the method according to the application, wherein the imaging unit can be used. In particular, the imaging unit can be any of PET, MRI, ultrasound, X-ray and CT. BRIEF DESCRIPTION OF DRAWINGS

[0046] In the following, the application is described in detail with reference to the following figures, which show:

[0047] Figure 1 An element in a vessel is schematically shown.

[0048] Figure 2 An element is schematically shown under the influence of different forces.

[0049] Figure 3 An element in a narrow vessel is schematically shown.

[0050] Figure 4 An element in a vessel and an imaging device are schematically shown.

[0051] Figure 5 A marker on a vessel is schematically shown.

[0052] Figure 6 An element in a vessel with a thrombus is schematically shown.

[0053] Figure 7 A system according to the application is schematically shown.

[0054] Figure 8 A magnetic element is schematically shown. DETAILED DESCRIPTION

[0055] Figure 1 An element 1 in a vessel V is schematically shown. Here, the element 1 is a mobile element comprising a ferromagnetic material. Thereby, the element 1 is attracted by an external magnet (not shown, see Fig. 2) and is moved in the vessel V. The element 1 is schematically shown in a first position P1 in Fig. 1 and in a second position P2 in Fig. 2. Figure 8The applied magnetic field can guide and / or propel element 1 within the blood vessel V. Thus, a force 2 can be applied to element 1. In this case, assuming no influence from bodily functions such as blood flow, friction, or gravity, the force 2 applied by the magnetic field will be the only force acting on element 1. Therefore, in this example, it represents the propulsive force. However, due to flow resistance, the element also experiences a resistive force. Here, the resistive force is unknown and should be determined to ascertain the fluid properties of the blood and the friction of the blood vessel wall. However, flow resistance and friction can also be included in the propulsive force. The actual acceleration 3 or velocity 4 of the element can also be measured. Here, the acceleration 3 is measured, for example, by an accelerometer contained in the element. Alternatively, the acceleration can also be measured, for example, by means of an imaging device. The actual acceleration 3 characterizes the difference between force 2 and the resistive force. Therefore, the resistive force can be calculated, thereby also calculating the fluid properties of the blood and blood vessels. This is, of course, particularly advantageous when the fluid properties of the blood are affected by a disease.

[0056] Figure 2 It schematically represents the relationship with Figure 1 Similar elements are shown in the diagram. The vasculature V is not shown here for clarity. Furthermore, the elements have different shapes and are cubic rather than quasi-spherical. However, they also incorporate ferromagnetic materials and can be propelled by a magnetic field. Figure 2 The schematically illustrated state represents the equilibrium state when the element has reached its final velocity 4. Thus, the propulsive force 2 and the resistive force 5 have equal norm values, but opposite signs. The final velocity 4 can therefore be used to calculate parameters of the blood, such as its viscosity. In a similar embodiment of the method, the magnetic field can change its direction at a certain frequency. Instead of measuring velocity, one can measure the frequency of the element's motion and thereby determine the fluid properties of the blood.

[0057] Figure 3 A different type of element 1 is schematically shown. It is spherical and passively carried by fluid in a blood vessel V. It also includes a sensor suitable for measuring the actual acceleration 3 of element 1. Here, the blood vessel has a constriction that causes a temporary increase in blood flow velocity. Therefore, the accelerometer 6 detects the temporary acceleration (and deceleration in the widened region). Because element 1 is passively carried in this example, the propulsive force is zero. Therefore, the actual acceleration 3 can be directly used to determine the characteristics of the blood vessel V, in this case, the presence of constriction.

[0058] Figure 4An element 1 is shown which is carried by a fluid in a vessel V. For the sake of clarity, the propulsion mechanism is not shown in this schematic view, but the skilled person will understand that any of the described ways of moving, steering or guiding the device can be employed in this embodiment. Here, an imaging unit 7 with an X-ray imaging device is employed. The element 1 is visible in X-ray imaging. In addition, the blood contains a contrast agent so that the vessel system is also visible under X-rays. A Doppler imaging unit 8 is employed to visualize the flow 9 of blood in the vessel system. Of course, the Doppler imaging unit and the X-ray imaging device can each be connected to one computer or to the same computer, e.g. a computer comprising the computer program product according to the application, to use the imaging results in the calculation.

[0059] Figure 5 An element 1 is shown which is moving in a vessel V. Here, a plurality of detectors 10 are arranged around the vessel V. They are formed by closed copper coils around the vessel. The element comprises a permanent magnet which generates a magnetic field around it. Thereby, when the element 1 passes the detectors 10, the moving magnetic field induces a detectable current in the detectors. It is also possible to provide a transmitting chip on the robot and a receiver / detector arranged on the body which can triangulate the robot position.

[0060] Figure 6 Another application of the method is shown. Here, the element is moving in a vessel and is propelled by a magnetic field which exerts a force 2 on the element 1 by a ferromagnetic element contained in the element 1. However, a blood clot C has formed in the vessel V which blocks or restricts the blood flow. Thus, the element 1 also stops moving once it hits the blood clot C. Thereby, the actual velocity of the element becomes zero while the propulsion force 2 is not zero. This allows to determine a property, in this case the presence of a blood clot. Of course, it is also conceivable that the actual acceleration of the element 1 can be measured additionally which would give further information about the position of the blood clot C and / or its mechanical properties (a softer blood clot C would lead to a smaller negative acceleration value).

[0061] Figure 7A system according to the invention is schematically illustrated. It includes an element 1 in which a sensor 6 is arranged. The sensor shown here is adapted to measure the acceleration of the element and optionally to measure fundamental values ​​such as temperature and pressure. The system also includes a measuring unit 11 and an analyzer unit 12. The measuring unit is particularly adapted to receive acceleration values ​​from the sensor. However, the measuring unit can also measure values ​​based on a marker or detector 10. Although this method is not required, it is advantageous to measure the actual propulsive force acting on the element 1 in some embodiments. Thus, in this non-limiting example, the measuring unit 11 is also adapted to measure the magnetic field at the location of the element, particularly through interaction with the sensor 6. The analyzer unit 12 is adapted to process the values ​​received from the measuring unit 11 and the values ​​received by the measuring unit 11. In addition, it includes a memory 15 for storing the values. For example, it can receive the actual acceleration value from the sensor 6 contained in the element 1. In addition, the propulsive force can be obtained from an external magnetic unit (see see...). Figure 8 The parameters are known from the sensor 6 or measured by the sensor. In any case, the analyzer unit is adapted to process and analyze these values ​​to determine at least one characteristic of the blood vessel. The characteristic values ​​may be selectively stored in the memory 15. It is conceivable to combine the system with a display suitable for displaying data based on the values ​​stored in the memory, particularly two-dimensional and / or three-dimensional data illustrations, such as reconstructing the patient's anatomy. It should be understood that any examples and embodiments described herein can be implemented using this system.

[0062] Figure 8 A magnetic element 14 that can be used to drive element 1 is shown. Here, it includes an electromagnet capable of being selectively turned on and off to generate magnetic field 14. Of course, a permanent magnet can also be used. It is also conceivable to use electrical energy to operate the impeller, propeller, or other propulsion mechanism.

Claims

1. A system for determining a property in a vessel or heart (V) of a patient, comprising: - a magnetic element (1) adapted to be actuated by a magnetic field for placement in the vessel or heart (V), - a mechanism for determining a magnetic propulsion force acting to the magnetic element by the magnetic field, - an imaging device adapted to image a region surrounding the magnetic element and to allow determining a position of the magnetic element relative to an anatomical structure, - a mechanism for determining at least one of an actual acceleration (3) and an actual velocity of the magnetic element (1) based on imaging data acquired by the imaging device, - a mechanism for determining at least one property of a surrounding tissue of the magnetic element (1) based on at least one of: a difference between a theoretical acceleration determined based on the magnetic propulsion force calculation and the actual acceleration (3) of the magnetic element (1); and a difference between a theoretical velocity determined based on the magnetic propulsion force calculation and the actual velocity of the magnetic element (1), the property being selected from elasticity, stiffness, ductility and / or hardness.

2. The system according to claim 1, wherein the magnetic element (1) further comprises a sensor (6) for measuring the magnetic propulsion force.

3. The system according to any of the preceding claims, the imaging device being one of X-ray imaging, magnetic resonance imaging, computed tomography, positron emission tomography and ultrasound imaging.

4. The system according to claim 1 or 2, further comprising a mechanism for determining a position of the magnetic element (1).

5. The system according to claim 4, further comprising a memory (15) for saving at least one property of the surrounding tissue in relation to the position and / or time.

6. The system according to claim 1 or 2, comprising a computer running software code for calculating at least one property of the surrounding tissue.

7. The system according to claim 1 or 2, further comprising a mechanism for measuring a flow velocity of a liquid surrounding the magnetic element (1).

8. The system according to claim 1 or 2, further comprising at least one detector (10) or marker arranged to the magnetic element.

9. A computer program product for analyzing a surrounding tissue of a magnetic element (1) in a patient, the computer program product being for use in a system according to any of claims 1 to 8, comprising software code adapted to determine at least one of an actual velocity and an actual acceleration of the magnetic element based on imaging data when run on a computer, and further adapted to determine at least one property of a surrounding tissue of the magnetic element (1) based on at least one of the actual acceleration (3) and the actual velocity of the magnetic element (1) and a theoretical acceleration and / or a theoretical velocity determined by the magnetic propulsion force. ​

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