METHOD AND APPARATUS FOR DETERMINING INTERNAL ORGAN SHIFT

Abstract

Provided are a method and apparatus for determining displacement of an internal object disposed in a patient's body. The method includes positioning an arrangement of electrodes of a capacitive sensor adjacent to a patient's body part, such that each electrode is spaced apart from the body part, wherein the body part at least partly encloses the internal object of the patient. Providing, with the capacitive sensor, a plurality of sensor signals, wherein each sensor signal is indicative of a capacitance in a vicinity of at least one electrode of the arrangement of electrodes, determining a set of capacitance values for at least a subset of the electrodes of the arrangement of electrodes based on processing the plurality of sensor signals, and determining a displacement of the internal object with respect to the body part based on comparing the determined set of capacitance values with a set of reference capacitance values.

Claims

1. A method for determining a displacement of an internal object disposed in a body of a patient, the method comprising: positioning an arrangement of electrodes of a capacitive sensor adjacent to a body part of the patient, such that each electrode is spaced apart from the body part, wherein the body part at least partly encloses the internal object of the patient; providing, with the capacitive sensor, a plurality of sensor signals, wherein each sensor signal is indicative of a capacitance in a vicinity of at least one electrode of the arrangement of electrodes; determining a set of capacitance values for at least a subset of the electrodes of the arrangement of electrodes based on processing the plurality of sensor signals; and determining a displacement of the internal object with respect to the body part based on comparing the determined set of capacitance values with a set of reference capacitance values.

2. The method according to claim 1, wherein determining the displacement of the internal object comprises: determining an occurrence of the displacement of the internal object with respect to the body part; and determining at least one of a size and a direction of the displacement of the internal object with respect to the body part.

3. The method according to claim 1, wherein the set of reference capacitance values is indicative of the capacitance values of the at least subset of electrodes when the arrangement of electrodes is at least one of positioned at a reference position or positioned in a reference orientation with respect to the body part.

4. The method according to claim 1, wherein at least one of the set of capacitance values is determined at a measurement time or the set of reference capacitance values is indicative of the capacitance values of the at least subset of electrodes at a reference time preceding the measurement time.

5. The method according to claim 1, further comprising one or more of: at least one of each sensor signal or each capacitance value is indicative of at least one of a capacitance between one of the electrodes and a ground, between one of the electrodes and an outer surface of the patient, between one of the electrodes and a reference electrode of the capacitance sensor, or between two electrodes of the capacitance sensor; and the capacitance in the vicinity of the at least one electrode of the arrangement of electrodes is at least one of a capacitance between said at least one electrode and a ground, between said at least one electrode and an outer surface of the patient, between said at least one electrode and a reference electrode of the capacitance sensor, and between said at least one electrode and a further electrode of the capacitance sensor.

6. The method according to claim 1, further comprising: determining the set of reference capacitance values based on positioning the arrangement of electrodes at a reference position and in a reference orientation with respect to the body part of the patient and based on measuring the reference capacitance values using the capacitive sensor.

7. The method according to claim 1, further comprising: determining the set of reference capacitance values based on a simulation calculation with the arrangement of electrodes being positioned at a reference position and in a reference orientation with respect to the body part of the patient.

8. The method according to claim 1, further comprising one or more of: determining the set of reference capacitance values based on positioning the arrangement of electrodes at a reference position and in a reference orientation with respect to the body part of the patient and based on measuring the reference capacitance values using the capacitive sensor, and storing the determined set of reference capacitance values in a data storage; and determining the set of reference capacitance values based on a simulation calculation with the arrangement of electrodes being positioned at a reference position and in a reference orientation with respect to the body part of the patient, and storing the determined set of reference capacitance values in a data storage.

9. The method according to claim 1, wherein determining the displacement of the internal object comprises: computing a deviation between each capacitance value of the determined set of capacitance values and at least one reference capacitance value of the set of reference capacitance values; and comparing the computed deviation for each capacitance value of the determined set of capacitance values with a threshold value, thereby determining whether the capacitance in the vicinity of one or more electrodes has changed.

10. The method according to claim 9, further comprising; identifying one or more electrodes in the vicinity of which the capacitance has changed; and comprising one or more of: determining an occurrence of the displacement of the internal object with respect to the body part based on determining that the capacitance in the vicinity of one or more individual electrodes has changed; and at least one of checking or determining an occurrence of a patient motion relative to the arrangement of electrodes based on determining that the capacitance in the vicinity of at least one electrode arranged at a first boundary of the arrangement of electrodes and in the vicinity of at least one further electrode arranged at a second boundary opposite to the first boundary of the arrangement of electrodes has changed.

11. The method according to claim 10, wherein the occurrence of the patient motion relative to the arrangement of electrodes is at least one of checked or determined based on: determining a first number of electrodes arranged at the first boundary of the arrangement of electrodes, in the vicinity of which the capacitance has changed; determining a second number of electrodes arranged at the second boundary of the arrangement of electrodes, in the vicinity of which the capacitance has changed; and comparing the first number of electrodes arranged at the first boundary with the second number of electrodes arranged at the second boundary of the arrangement of electrodes.

12. The method according to claim 11, wherein the occurrence of the patient motion relative to the arrangement of electrodes is at least one of checked or determined based on determining that the first number of electrodes arranged at the first boundary substantially equals or matches the second number of electrodes arranged at the second boundary of the arrangement of electrodes.

13. The method according to claim 9, wherein the threshold values for the deviations between the capacitance values and the reference capacitance values are determined based on at least one of a calibration measurement or a simulation calculation.

14. The method according to claim 1, wherein the displacement of the internal object with respect to the body part is determined using at least one of a classificator, an artificial intelligence module or a neural network.

15. The method according to claim 1, further comprising: determining, with at least one surface scanner, a first position of at least a part of a skin of the patient at a first time; determining, with the at least one surface scanner, a second position of the at least part of the skin at a second time different than the first time; and determining an occurrence of the displacement of the internal object with respect to the body part based on comparing the determined first position and the determined second position of the at least part of the skin.

16. The method according to claim 1, further comprising: determining, with at least one distance sensor, a first distance between at least a part of the patient and at least one fixed point in an environment of the patient at a first time; determining, with the at least one distance sensor, a second distance between the at least part of the patient and the at least one fixed point in the environment of the patient at a second time different than the first time; and determining an occurrence of the displacement of the internal object with respect to the body part based on comparing the determined first distance and the determined second distance between the at least part of the patient and the at least one fixed point.

17. The method according to claim 1, further comprising one or more of: (i) determining, with at least one surface scanner, a first position of at least a part of a skin of the patient at a first time: determining, with the at least one surface scanner, a second position of the at least part of the skin at a second time different than the first time; and determining an occurrence of the displacement of the internal object with respect to the body part based on comparing the determined first position and the determined second position of the at least part of the skin; and (ii) determining, with at least one distance sensor (20), a first distance between at least a part of the patient and at least one fixed point in an environment of the patient at a first time; determining, with the at least one distance sensor (20), a second distance between the at least part of the patient and the at least one fixed point in the environment of the patient at a second time different than the first time; and determining an occurrence of the displacement of the internal object with respect to the body part based on comparing the determined first distance and the determined second distance between the at least part of the patient and the at least one fixed point; wherein at least one of the at least one surface scanner or the at least one distance sensor is at least one of a camera, a surface camera, a thermo-camera, a 3D camera, a stereo camera, a range camera, a laser sensor, a LIDAR sensor, a radar sensor, a time-of-flight sensor, or an ultrasound sensor.

18. The method according to claim 1, further comprising: generating an alert signal in response to determining the displacement of the internal object with respect to the body part.

19. The method according to claim 1, further comprising: providing a pre-operative scan of at least a part of the body part, the pre-operative scan including at least a part of the internal object; and adjusting at least one of a shape, a geometry, a position, or an orientation of the at least part of the internal object in the pre-operative scan based on the determined displacement of the internal object with respect to the body part.

20. The method according to claim 1, wherein the internal object is at least one of at least a part of an internal organ of the patient, at least a part of a brain of the patient, at least a part of a lung of the patient, at least a part of a liver of the patient, or at least a part of a spine of the patient.

21. (canceled)

22. An apparatus for determining a displacement of an internal object disposed in a body of a patient, the apparatus comprising: a capacitive sensor including at least one arrangement of electrodes, wherein the at least one arrangement of electrodes is configured to be arranged adjacent to a body part of a patient, which body part at least partly encloses the internal object, and wherein the capacitive sensor is configured to generate a plurality of sensor signals, each sensor signal being indicative of a capacitance in a vicinity of at least one electrode of the arrangement of electrodes; and at least one processor configured to receive and process the plurality of sensor signals to determine a set of capacitance values for at least a subset of the electrodes of the arrangement of electrodes; wherein the at least one processor is configured to determine a displacement of the internal object with respect to the body part based on comparing the determined set of capacitance values with a set of reference capacitance values.

23. The apparatus according to claim 22, wherein the arrangement of electrodes includes at least one of an array of electrodes or a grid of electrodes.

24. The apparatus according to claim 22, wherein the electrodes of the arrangement electrodes are at least one of arranged in a uniform pattern, arranged in a three-dimensional configuration, or arranged in at least one of a semi-spherical configuration, a spherical configuration, or an arc-shaped configuration.

25. (canceled)

26. (canceled)

27. The apparatus according to claim 22, wherein the arrangement of electrodes includes an arc-shaped array of electrodes and at least one further arc-shaped array of electrodes; and wherein the arc-shaped array and the at least one further arc-shaped array are at least one of directed in different directions or extend in different directions.

28. The apparatus according to claim 22, wherein the electrodes of the arrangement of electrodes are arranged on at least one of a head clamp for immobilizing a head of the patient, an immobilization mask for immobilizing at least a part of the patient, and a patient support for supporting at least a part of the patient.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0120] In the following, the invention is described with reference to the appended figures which give background explanations and represent specific embodiments of the invention. The scope of the invention is however not limited to the specific features disclosed in the context of the figures, wherein

[0121] FIG. 1 shows an apparatus for determining a displacement of an internal object according to an exemplary embodiment;

[0122] FIG. 2 shows a capacitive sensor of an apparatus for determining a displacement of an internal object according to an exemplary embodiment;

[0123] FIG. 3 shows a capacitive sensor of an apparatus for determining a displacement of an internal object according to an exemplary embodiment;

[0124] FIGS. 4A to 4C each show a capacitive sensor of an apparatus for determining a displacement of an internal object according to an exemplary embodiment;

[0125] FIG. 5 shows a flowchart illustrating steps of a method for determining a displacement of an internal object according to an exemplary embodiment; and

[0126] FIG. 6 shows a flowchart illustrating steps of a method for determining a displacement of an internal object according to an exemplary embodiment.

[0127] The figures are schematic only and not true to scale. In principle, identical or like parts, elements and/or steps are provided with identical or like reference numerals in the figures.

DESCRIPTION OF EMBODIMENTS

[0128] FIG. 1 shows an apparatus 10 for determining a displacement of an internal object 104 disposed in a body 102 of a patient 100 according to an exemplary embodiment in accordance with the sixth aspect of the present disclosure.

[0129] In the example shown in FIG. 1 the internal object 104 is a part of or constitutes the entire brain of the patient 100. Alternatively, the internal object 104 can be at least a part of an internal organ of the patient 100, at least a part of a lung of the patient 100, at least a part of a liver of the patient 100, at least a part of a spine of the patient 100 or any other internal structure or object of the patient. The internal object 104 is disposed and/or arranged in a body part 103 of the patient, which in the example shown in FIG. 1 refers to a head 103 of the patient 100.

[0130] A part 105 of the patient's brain is to be excised, removed and/or resected, e.g. in a surgical treatment or radiation treatment, wherein resection of part 105 can lead to a displacement and/or shift of the internal object 104 and/or a part of the patient's 100 brain.

[0131] For determining such displacement and/or shift, the apparatus 10 comprises a capacitive sensor 12 including at least one arrangement 14 of electrodes 16 having a plurality of electrodes 16. The arrangement 14 of electrodes 16 is positioned adjacent to, close to and/or near the body part 103 or head 103 of the patient 100, such that each electrode 16 of the arrangement 14 is spaced apart from the body part 103 or head 103 and/or such that each electrode 16 is not in contact with the patient 100.

[0132] In the example shown in FIG. 1, the arrangement 14 of electrodes 16 includes an array 15 and/or grid 15 of electrodes 16. Specifically, the arrangement 14 includes a grid 15 of sixteen electrodes 16 arranged in a two-dimensional configuration on a substrate in four lines and four rows. Any other dimension of the grid 15 or array 15 is conceivable. Also, other configurations, e.g. as described with reference to subsequent figures, or a plurality of arrangements 14 can be used.

[0133] The apparatus 10 further comprises a processor 18, a processing circuitry 18 and/or a control circuitry 18 configured to process sensor signals provided by the capacitive sensor 12.

[0134] Further, the apparatus 10 comprises a data storage 19 or data storage device, on which a set of reference capacitance values can be stored. These reference capacitance values can e.g. be determined before or during performing the actual medical treatment, as described in more detail hereinabove and hereinbelow.

[0135] For determining the displacement of the object 104, the capacitive sensor 12 is driven and generates a plurality of sensor signals, each being indicative of a capacitance in a vicinity of at least one electrode 16. Therein, the capacitance in the vicinity of the at least one electrode 16 of the arrangement of electrodes 12 is at least one of a capacitance between said at least one electrode 16 and a ground or ground potential, between said at least one electrode 16 and an outer surface of the patient 100, between said at least one electrode 16 and a reference electrode of the capacitance sensor 12, and between said at least one electrode 16 and a further electrode 16 of the capacitance sensor 12.

[0136] The processor 18 then receives and processes the plurality of sensor signals of the electrodes 16 to determine a set of capacitance values for at least a subset of the electrodes 16 of the arrangement 14 of electrodes 16. In other words, the processor 18 may acquire the set of capacitance values, e.g. at a measurement time.

[0137] The processor 18 then compares the set of determined capacitance values, e.g. elementwise and/or electrode-wise, with the reference capacitance values of the set of reference capacitance values. The reference capacitance values may have been determined and/or acquired at a reference time preceding the measurement time. For instance, the reference capacitance values may have been determined before resecting and/or irradiation the part 105 of the patient's 100 brain in a measurement, wherein the arrangement 14 is positioned at a reference position and/or in a reference orientation with respect to the body part 103 or head 103 of the patient 100. Further, the set of capacitance values may have been acquired and/or determined after the part 105 of the patient's 100 brain has been resected and/or irradiated. Due to this treatment, the internal object 104 and/or a part of the brain has been displaced with respect to and/or relative to the body part 103 or head 103. Accordingly, based on and/or by comparing the determined set of capacitance values with the set of reference capacitance values, this displacement of the internal object 104 can reliably be determined with high precision and accuracy. Also, markers attached to the patient 100 may not be required.

[0138] Generally, the processor 18 may determine an occurrence of the displacement, an extent or size of the displacement and/or a direction of the displacement. The direction can be determined in two or three spatial directions, e.g. if the arrangement 14 of electrodes 16 has a three-dimensional configuration as will be further discussed in subsequent figures.

[0139] It should be noted that the set of capacitance values can be determined or updated over time, e.g. during the medical treatment, thereby allowing to track a position and/or orientation of the internal object 104. Therein, “tracking” may mean determining over time.

[0140] Further, if the displacement is detected and/or determined, an alert may be provided, e.g. on user interface 21 of the apparatus 10, which may provide guidance to a surgeon or operator of the apparatus 10 as to whether a displacement of the object 104 has occurred and/or to which position and/or orientation the object 104 has moved.

[0141] In the example shown in FIG. 1, the arrangement 14 of electrodes 16 is arranged on and/or mounted to a patient support 101 supporting at least a part of the patient 100. Specifically, the arrangement 14 of FIG. 1 is mounted to an edge or rail of the patient support 101. Any other configuration is conceivable. For instance, the arrangement 14 may span or bridge at least partly over the patient support 101, such that the patient 100 is positionable between the arrangement 14 of electrodes 16 and the patient support 101. Also, the arrangement 14 of electrodes 16 may be arranged on top of the patient support 101, such that patient 100 can be positionable above the arrangement 14 of electrodes 16.

[0142] Further, the arrangement 14 of electrodes 16 could likewise be mounted on at least one of a head clamp, e.g. a Mayfield clamp, for immobilizing a head of the patient 100, an immobilization mask for immobilizing at least a part of the patient 100.

[0143] Moreover, the apparatus 10 comprises a surface scanner 20 and/or distance sensor 20. The surface scanner 20 and/or the distance sensor 20 can, for example, be a camera, a surface camera, a thermo-camera, a 3D camera, a stereo camera, a range camera, a laser sensor, a LIDAR sensor, a radar sensor, a time-of-flight sensor, or an ultrasound sensor.

[0144] Based on the surface scanner 20 and/or distance sensor 20, the a patient motion and/or global displacement of the object 104 can be determined in order to determine whether or not a displacement of the internal object 104 with respect to and/or relative to the body part 103 or head 103 has occurred. For instance, a first position of at least a part of a skin of the patient 100 may be determined at a first time with the surface scanner 20 and/or a first distance between at least a part of the patient 100 and at least one fixed point in an environment of the patient 100 may be determined with the distance sensor 20 at a first time. At a second time different than the first time, e.g. subsequent to the first time, a second position of the at least part of the skin and/or a second distance between the at least part of the patient 100 and the at least one fixed point in the environment of the patient 100 may be determined. By comparing the first and second position and/or the first and second distance, a patient motion and/or global displacement of the object 104 may be detected. This may allow reliably determining whether a displacement of the internal object 104 relative to the body part 103 (local displacement) or a displacement of the body part 103 relative to the arrangement 14 of electrodes 16 (global displacement) has occurred.

[0145] FIG. 2 shows a capacitive sensor 12 of an apparatus 10 for determining a displacement of an internal object 104 disposed in a body 102 of a patient 100 according to an exemplary embodiment in accordance with the sixth aspect of the present disclosure. If not stated otherwise, the capacitive sensor 12 of FIG. 2 comprises the same elements and/or features as the capacitive sensor 12 described with reference to FIG. 1.

[0146] In the example shown in FIG. 2, the arrangement 14 of electrodes 16 has a three-dimensional configuration. This may allow to infer three-dimensional information and/or information in three-dimensional space from the sensor signals and/or the determined set of capacitance values. Accordingly, the displacement of the internal object 104 may be determined in three-dimensional space.

[0147] Further, the electrodes 16 of the arrangement 14 of electrodes 16 are arranged in a semi-spherical and/or arc-like configuration, such that the arrangement 14 encompasses and/or surrounds at least a part of the patient's head 103 or body part 103.

[0148] FIG. 3 shows a capacitive sensor 12 of an apparatus 10 for determining a displacement of an internal object 104 disposed in a body 102 of a patient 100 according to an exemplary embodiment in accordance with the sixth aspect of the present disclosure. If not stated otherwise, the capacitive sensor 12 of FIG. 3 comprises the same elements and/or features as the capacitive sensors 12 described with reference to FIGS. 1 and 2.

[0149] In the example shown in FIG. 3, the capacitive sensor 12 and/or the arrangement 14 of electrodes 16 includes an arc-shaped array 14a of electrodes 16 and a further arc-shaped array 14b of electrodes 16, wherein the arc-shaped array 14a and the further arc-shaped array 14b are directed and/or extend in different directions and/or spatial directions. Therein, each of arrays 14a, 14b encompasses and/or surrounds at least a part of the patient's head 103 or body part 103. Specifically, the array 14a at least partly encompasses a top of the patient's head 103 and the further array 14b at least partly encompasses a forehead of the patient 100. The further array 14b spans bridge-like across at least a part of the patient support 101.

[0150] FIG. 4A to 4C each show a capacitive sensor of an apparatus 10 for determining a displacement of an internal object 104 disposed in a body 102 of a patient 100 according to an exemplary embodiment in accordance with the sixth aspect of the present disclosure. Specifically, FIG. 4A shows the apparatus with capacitive sensor 12 and FIGS. 4B and 4C illustrate the capacitive sensor 12 of the apparatus 10. If not stated otherwise, the apparatus 10 and/or the capacitive sensors 12 of FIGS. 4A to 4C comprise the same elements and/or features as the capacitive sensors 12 described with reference to FIGS. 1 to 3.

[0151] The capacitive sensor 12 and/or the arrangement 14 of electrodes 16 of FIGS. 4A to 4C have a similar configuration as described with reference to FIG. 1. Further, FIG. 4B illustrates changes in the capacitance values or capacitances of the electrodes 16 that can occur when a local displacement of the internal object 104, i.e. a displacement of the object 104 relative to the body part 103 occurs (indicated by the arrow in FIG. 4A). FIG. 4C on the other hand illustrates changes in the capacitance values or capacitances of the electrodes 16 that can occur when a global displacement of the internal object 104, i.e. a displacement of the body part 103 relative to the arrangement 14 of electrodes 16 occurs.

[0152] The arrangement 14 of electrodes 16 in the example of FIGS. 4A to 4C is a grid 15 that is arranged close to the patient's 100 head 103 or body part, but not in contact therewith. The grid 15 comprises four by four electrodes 16 on a square arranged laterally in juxtaposition with and/or near a side of the head 103 of the patient 100.

[0153] By means of the apparatus 10 and/or the capacitive sensor 12, the reference capacitance value for each electrode 16 can be measured, e.g. by applying a voltage and integrating over the current or any other suitable technique to determine the capacitance values, when the arrangement 14 of electrodes 16 is positioned at a reference position and/or reference orientation with respect to the body part 103. The reference capacitance values can then be stored in the data storage 19, e.g. in a matrix and/or e.g. a single value for each electrode 16.

[0154] Optionally, it can be determined and/or monitored whether a patient motion occurs using the surface scanner 20 and/or distance sensor 20, as e.g. described with reference to FIG. 1.

[0155] Further, e.g. during the actual medical treatment, the capacitance values of the electrodes 16 and/or the set of capacitance values may be determined and/or measured, e.g. continuously.

[0156] By comparing the determined set of capacitance values with the stored set of reference capacitance values, it may be decided whether or not a local displacement of the internal object 104 relative to the body part 103 has occurred and/or whether a global displacement of the body part 103 relative to the arrangement 14 of electrodes 16 has occurred.

[0157] If a local displacement is detected, optionally, at least one of a size and a direction of the displacement can be calculated with the processor 18.

[0158] For example, e.g. in a “signature based” evaluation, a deviation and/or difference of each capacitance value of the set of capacitance values and the corresponding reference capacitance value of the set of reference capacitance values can be calculated. In other words, the element-wise and/or electrode-wise difference between the current capacitance values and the reference capacitance values can be calculated for some of or all of the electrodes 16.

[0159] The calculated deviations and/or differences can then be compared to threshold values to identify the electrodes 16 among the arrangement 14 of electrodes 16, in the vicinity of which the capacitance has changed. Accordingly, the “change” in capacitance can be evaluated based on determining if the differences and/or deviations reach, are below or are above the corresponding threshold value.

[0160] If only the capacitance in the vicinity of individual electrodes has changed, a local displacement of the object 104 relative to the body part 103 has occurred. This scenario is illustrated in FIG. 4B, wherein the shaded electrodes 16 illustrate the individual electrodes 16 for which the capacitance value has changed with respect to the corresponding reference capacitance value.

[0161] Optionally, occurrence of the local displacement can be checked and/or cross-checked by excluding that a patient motion and/or a global displacement has occurred, e.g. using an external sensor, such as the surface scanner 20 and/or distance sensor 20 of FIG. 1.

[0162] FIG. 4C illustrates the scenario, in which a global displacement of the object 104 has occurred, wherein the shaded electrodes 16 illustrate the electrodes 16 for which the capacitance value has changed with respect to the corresponding reference capacitance value.

[0163] To detect a global displacement, the processor 18 may, for example, determine the numbers of electrodes 16 whose capacitance has changed and evaluate the position of the identified electrodes on in the arrangement 14 of electrodes 16. If, as illustrated in the example of FIG. 4C, a first number of electrodes 16 arranged at a first boundary 25a or border 25a of the arrangement 14 of electrodes 16 and a second number electrodes 16 arranged at a second boundary 25b or border 25b of the arrangement 14 of electrodes 16 are substantially equal, a global displacement of the body part 103 with respect to the arrangement 14 of electrodes 16 might have occurred.

[0164] It should be noted that the set of reference capacitance values and/or the threshold values for the differences and/or deviations can be determined based on a measurement and/or based on a simulation calculation, e.g. in a “model based” evaluation. For instance, the correspondence between the displacement of the object 104 relative to the body part 103, e.g. a brain shift or tumor movement, may be simulated using e.g. an finite-element-model. The threshold values, typical signatures, typical sensor signals and/or changes in the capacitance values can then be derived from the model.

[0165] Apart from that, an artificial intelligence module, a classifier, a classificatory, and/or an artificial neural network may be used to determine the displacement of the object 104 relative to the body part 103 and/or the global displacement of the body part. For training, medical images, e.g. X-ray, CT, MRT, or the like, could be acquired from a subject or a phantom during surgery and the capacitance values can be measured and/or acquired as a function of time. The changes of capacity, optionally with the extent and/or direction and/or type of an organ movement, can then be labelled, e.g. manually, and used as input data for the training. E.g. a trained neural network can then be used to detect patterns of capacitance values and/or changes in capacitance values to determine a local and/or global displacement of the object 104.

[0166] Moreover, a phantom may be used to determine the set of reference capacitance values and/or the threshold values for the deviations. For instance, the capacitance values may be determined from a plurality of phantoms e.g. selectively filled with water, to determine the correspondence between the amount of water and/or air as well as the position relative to the patient 100 and the measured capacitance values or their changes.

[0167] The apparatus 10 according to the present disclosure may be advantageously used for cranial surgery. Therein, the arrangement 14 of electrodes 16 could be mounted to a head clamp used for cranial surgery. Alternatively or additionally, the arrangement 14 of electrodes 16 may be part of a couch 101, table 101 and/or patient support 101 used for radiotherapy or surgery, e.g. in the thorax or abdomen.

[0168] FIG. 5 shows a flowchart illustrating steps of a method for determining a displacement of an internal object 104 disposed in a body 102 of a patient 100 according to an exemplary embodiment in accordance with the method of the first aspect of the present disclosure. For performing the method, e.g. the apparatus 10 of the previous figures and/or parts thereof may be used.

[0169] In a first step S1, the arrangement 14 of electrodes 16 of the capacitive sensor 12 is arranged adjacent to the body part 103 of the patient 100, such that each electrode 16 is spaced apart from the body part 103.

[0170] In a second step S2, a plurality of sensor signals, is provided with the capacitive sensor 12, wherein each sensor signal is indicative of a capacitance in a vicinity of at least one electrode 16 of the arrangement 14 of electrodes 16.

[0171] In a further step S3, the set of capacitance values for at least a subset of the electrodes 16 of the arrangement 14 of electrodes 16 is determined with the processor 18 based on processing the plurality of sensor signals.

[0172] Further, the method comprises in step S4 determining the displacement of the internal object 104 with respect to the body part 103 based on comparing the determined set of capacitance values with the set of reference capacitance values, which may e.g. be stored in the data storage 19 or retrieved from another source.

[0173] Therein, step S4 may comprise determining the occurrence of the displacement of the internal object 104 with respect to the body part 103. Optionally, at least one of a size and a direction of the displacement of the internal object 104 with respect to the body part 103 may be calculated with the processor 18.

[0174] Moreover, determining the displacement of the internal object 104 relative to the body part 103 in step S4 may optionally comprise computing a deviation between each capacitance value of the determined set of capacitance values and at least one reference capacitance value of the set of reference capacitance values, and comparing the computed deviation for each capacitance value of the determined set of capacitance values with a threshold value, thereby determining whether the capacitance in the vicinity of one or more electrodes 16 has changed.

[0175] Further, it may be determined whether the capacitance in the vicinity of one or more individual electrodes 16 has changed in order to detect a local displacement, as described hereinabove.

[0176] Alternatively or additionally, it may be checked in step S4 whether a patient motion relative to the arrangement 14 of electrodes 16 has occurred, e.g. based on determining the numbers of electrodes 16 and/or their position in the arrangement 14 of electrodes 16 to determine a global displacement of the object 104. For instance, a first number of electrodes 16 arranged at the first boundary 25a of the arrangement 14 of electrodes 16, in the vicinity of which the capacitance has changed, and a second number of electrodes 16 arranged at the second boundary 25b of the arrangement 14 of electrodes 16, in the vicinity of which the capacitance has changed, may be compared to each other, as described hereinabove. If the first and second number substantially match, a global displacement might have occurred.

[0177] FIG. 6 shows a flowchart illustrating steps of a method for determining a displacement of an internal object 104 disposed in a body 102 of a patient 100 according to an exemplary embodiment in accordance with the method of the first aspect of the present disclosure. For performing the method, e.g. the apparatus 10 of the previous figures and/or parts thereof may be used. If not stated otherwise, the method of FIG. 6 comprises the same steps as the method of FIG. 5.

[0178] The method of FIG. 6 further comprises optional step S2′, in which the set of reference capacitance values is determined based on positioning the arrangement 14 of electrodes 16 at a reference position and in a reference orientation with respect to the body part 103 of the patient 100 and based on measuring the reference capacitance values using the capacitive sensor 12, e.g. on the patient 101 or using a phantom. Alternatively or additionally, the set of reference capacitance values can be determined based on a simulation calculation with the arrangement 14 of electrodes 16 being positioned at the reference position and in the reference orientation with respect to the body part 103 of the patient 100. Also, the set of reference capacitance values may be stored in the data storage 19 in step S2′.

[0179] Further, the threshold values for the deviations between the capacitance values and the reference capacitance values may be determined in step S2′ based on a calibration measurement and/or based on a simulation calculation, as described hereinabove.

[0180] Moreover, FIG. 6 illustrates the optional step S4′, in which it is monitored and/or determined whether a global displacement of the object 104 has occurred, e.g. using the surface scanner 20 and/or the distance sensor 20, as described hereinabove.

[0181] For instance, a first position of at least a part of a skin of the patient 100 can be determined with the surface scanner 20 at a first time. Further, a second position of the at least part of the skin can be determined with the surface scanner 20 at a second time different than the first time, and a displacement of the internal object 104 with respect to the body part 103 can be determined based on comparing the determined first position and the determined second position of the at least part of the skin. This may mean that a local displacement can be determined based on detecting with the surface scanner 20 that no global displacement has occurred and/or based on excluding a global displacement using the surface scanner 20.

[0182] Alternatively or additionally, a first distance between at least a part of the patient 100 and at least one fixed point in an environment of the patient 100 can be determined with the distance sensor 20 at a first time. Further, a second distance between the at least part of the patient 100 and the at least one fixed point in the environment of the patient 100 can be determined with the distance sensor 20 at a second time different than the first time, and a displacement of the internal object 104 with respect to the body part 103 can be determined based on comparing the determined first distance and the determined second distance between the at least part of the patient 100 and the at least one fixed point. This may mean that a local displacement can be determined based on detecting with the distance sensor 20 that no global displacement has occurred and/or based on excluding a global displacement using the distance sensor 20.

[0183] It should be noted that in a further optional step, an alert signal can be generated in response to determining the displacement of the internal object 104 with respect to the body part 103.

[0184] Moreover, a pre-operative scan or image of at least a part of the body part 103 and the internal object 104 may be provided, and at least one of a shape, a geometry, a position and an orientation of the at least part of the internal object 104 may be adjusted in the pre-operative scan based on the determined displacement of the internal object 104 with respect to the body part 103.

[0185] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0186] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope