WO2021007622A1

WO2021007622A1 - Sensor device for use in internal inspections

Info

Publication number: WO2021007622A1
Application number: PCT/AU2020/050741
Authority: WO
Inventors: Mehmet Rasit Yuce; Fahad Alsunaydih; Jean-Michel Redoute
Original assignee: Monash University
Priority date: 2019-07-17
Filing date: 2020-07-17
Publication date: 2021-01-21

Abstract

A sensor device (1) and method for use in internal inspections. The sensor device may include: at least one sensor portion (5); and a plurality of pressure sensors (16) distributed and located over the at least one sensor portion of the sensor device; wherein each pressure sensor is adapted to measure a pressure level applied to the sensor device at said location of the pressure sensor.

Description

SENSOR DEVICE FOR USE IN INTERNAL INSPECTIONS

TECHNICAL FIELD

[0001] The present disclosure is directed to a sensor device and navigation system and method for use in internal inspections. While embodiments are described with respect to use in medical insertion procedures, including in wireless capsule and insertable endoscopy, it is to be appreciated that the disclosure is not restricted to such an application, and that other applications, including industrial applications, are also envisaged.

BACKGROUND

[0002] Medical insertion procedures, also known as endoscopy, require the insertion of a probe, such as an endoscope within a hollow organ or internal cavity of a patient. These probes can include a camera system to provide a visual image of the interior area being probed. This also allows for visual navigation of the probe though a hollow organ such as the small intestine. An example of such a probe can be found in U.S. Patent Publication no. 2011/0032347 (Lacey, Gerald et a!) which shows an endoscope having a camera at its tip.

[0003] A potential risk associated with such a medical procedure is the possible perforation of the wall of the hollow organ as the probe is inserted through that organ. This can be due to excessive pressure being applied to the organ wall by that probe during its passage. It is therefore necessary to carefully navigate the probe through the circuitous passage provided by the hollow organ to avoid this risk.

[0004] A problem associated with probes that use a camera for navigation is that the camera can be obscured in dark or liquid areas, which can prevent accurate navigation therethrough. U.S. Patent No. 7174202 (British Telecommunications) describes a medical navigation system using a magnetic field system. That system requires one or more field sensors to be associated with an internal probe, with external magnetic field sources being used to respectively radiate magnetic fields to thereby allow the field sensors to be located. However, while the described system allows the position of each field sensor, and therefore the path taken by the probe through a hollow organ, to be mapped, it does not allow for‘real time’ navigation of the probe as it is being inserted through that hollow organ.

[0005] Any discussion in the present disclosure about background or existing technology is included to explain the context of the present disclosure. It is not to be taken as an admission that the background was known or part of the common general knowledge at the priority date of any one of the claims of the specification.

[0006] It would be advantageous to provide a sensor device for an insertable probe that does not rely on an internal or external imaging system to operate, but still allows for real time navigation of the probe.

[0007] Embodiments of this disclosure aim to address or ameliorate one or more

shortcomings or disadvantages of prior techniques for navigating or guiding a probe through an internal tract, or to at least provide a useful alternative thereto.

SUMMARY

[0008] Some embodiments relate to a sensor device for use in internal inspections including:

at least one sensor portion; and

a plurality of pressure sensors distributed and located over the at least one sensor portion of the sensor device;

wherein each pressure sensor is adapted to measure a pressure level applied to the sensor device at a respective location of the pressure sensor.

[0009] Each pressure sensor may preferably be of a capacitive type. The use of alternative sensor types, such as resistive, piezoelectric, optical, electromagnetic or inductive sensors is however also envisaged.

[0010] The sensor portion(s) may include an inner conductive layer, an outer conductive layer, and an insulation layer located therebetween. One or more of said layers may be formed from flexible material. One or more of the layers could alternatively be formed of a rigid material, or a combination of rigid and flexible materials. The inner conductive layer may support a plurality of conductive nodes, each said node forming part of a respective said pressure sensor. The outer conductive layer may be a ground layer. In other embodiments, the outer layer may support the conductive sensor nodes, while the inner layer acts as a ground layer.

[0011] The sensor portion(s) may further include a generally dome shaped rigid support for supporting said inner and outer conductive layers, and said intermediate layer. The said inner and outer conductive layers, and said intermediate layer may be generally dome shaped, for example when disposed about the sensor portion. [0012] In some embodiments, the sensor device comprises a transmitter and a plurality of signal conversion chips, each signal conversion chip receiving signals from a plurality of pressure sensors, wherein the signal conversion chips are in communication with the transmitter and the transmitter is configured to transmit output signals corresponding to signals received from the plurality of pressure sensors to an external system.

[0013] The transmitter may be a wireless transmitter. The signal conversion chips may be capacitive signal conversion chips, for example where the pressure sensors include capacitive pressure sensors.

[0014] The sensor portion may be located on at least one end of a capsule body. In some embodiments, two sensor portions may be respectively located at both ends of the capsule body.

[0015] According to some embodiments, there is provided a navigation system using a sensor device as described above.

[0016] The navigation system may preferably further include at least one digital processor for receiving a pressure level signal from each said pressure sensor, and a data processing system for comparing the received pressure level signals to determine the location(s) of the pressure sensor(s) having the lowest measured pressure level signal. The location of each sensor may be identified by an azimuthal and/or polar angle associated with said location.

[0017] According to some embodiments, there is provided a method of navigating a sensor device using a navigation system as described above. The method may include measuring the pressure level at the location of each said pressure sensor, and identifying the location of the one or more pressure sensors having the lowest measured pressure level, to thereby determine a travel direction for the sensor device associated with the location of said one or more pressure sensor locations.

[0018] The method may include using a spherical coordinate system to identify changes in the travel direction, and may include identifying an azimuthal and/or polar angle defining said travel direction.

[0019] Various embodiments allow for real time navigation of a sensor device within a hollow organ or body cavity without the need for a built-in camera imaging system or external imaging system, while still facilitating real time navigation of the sensor device. [0020] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] It will be convenient to further describe embodiments with reference to the

accompanying drawings, which illustrate embodiments of a sensor device, navigation system and navigation method. Other embodiments are possible, and consequently, the particularity of the accompanying drawings is not to be understood as superseding the generality of the description of the embodiments provided herein.

[0023] In the drawings:

[0024] Figure 1a shows an exploded perspective view of a sensor device according to some embodiments for use in wireless capsule endoscopy;

[0025] Figure 1 b shows a plan view of an inner PCB layer of a sensor portion of the sensor device of Figure 1a;

[0026] Fgiure 1c shows a plan view of an outer conductive ground layer of a sensor portion of the sensor device of Figure 1a;

[0027] Figure 1d is a schematic illustration of the sensor device according to some embodiments attached to an end of an ordinary endoscope for use in insertable endoscopy;

[0028] Figure 2 is a schematic overall view of a navigation system according to some embodiments;

[0029] Figure 3 is a schematic view showing the basic structure of a pressure sensor used in the sensor device of Figure 1a; and

[0030] Figure 4a shows a side view of the sensor device of Figure 1a and polar angle positions;

[0031] Figure 4b shows a top view of the sensor device of Figure 1a and azimuthal angle positions; [0032] Figure 4c is a front view of the sensor device of Figure 1a showing the distribution of the pressure sensor nodes on the sensor portion;

[0033] Figure 5 is a further schematic view of a basic structure of the pressure sensor;

[0034] Figure 6 is a schematic diagram to illustrate signal connection between sensor nodes, a capacitance signal conversion chip and a wireless transceiver;

[0035] Figure 7 is a schematic circuit diagram of an embodiment of an inner conductive layer of the sensor device, illustrating conductors and capacitance signal conversion chips carried on the same substrate layer;

[0036] Figure 8 is a flowchart of a method of navigation of a sensor device;

[0037] Figure 9 is a schematic representation of an endoscope having a sensor device disposed on its distal tip according to some embodiments;

[0038] Figure 10 is a schematic illustration of pressure position determination for a situation where pressure occurs between sensor nodes;

[0039] Figure 11 is a schematic illustration of higher and lower pressure regions on a sensor device as it traverses a small intestine;

[0040] Figure 12 is an example polar position plot to illustrate determination of a point of highest pressure on the sensor device;

[0041] Figure 13 is an example polar position plot to illustrate determination of a point of least pressure on the sensor device;

[0042] Figure 14 is an example user interface display of a navigation system according to some embodiments; and

[0043] Figure 15 is a close up view of part of the user interface display of Figure 14. DETAILED DESCRIPTION

[0044] Embodiments generally relate to a sensor device that is configured to provide pressure feedback signals to assist in determining a future direction of movement of the sensor device in a tract. Some embodiments relate to navigation systems and methods that employ the sensor device for use in internal inspections, such as for gastrointestinal (Gl) tract inspections. While embodiments are described with respect to use in medical insertion procedures, including in wireless capsule and insertable rigid or flexible endoscopy, it is to be appreciated that the disclosure is not restricted to such an application, and that other applications, including industrial applications, are also relevant.

[0045] Referring initially to Figures 1a to 1c, there is shown a sensor device 1 according to some embodiments, when adapted for use in wireless capsule endoscopy (WCE). The sensor device 1 includes a capsule body 3 having a sensor portion 5 located on at least one end thereof.

[0046] Sensor device 1 can be configured for wireless or wired endoscopy. For wireless endoscopy, the sensor device 1 may be formed as a self-contained capsule to traverse the Gl tract while providing real-time data to an external system, such as a workstation 12 (Figure 2). For wired endoscopy, the sensor device 1 may be positioned at a distal end of an endoscopic probe, for example as shown in Figure 1 d, which may be autonomously or manually guided while the sensor device 1 provides real-time data to an external system, such as workstation 12. Wired endoscopy applications may transmit the sensor data from sensor device 1 to the external system via one or more electrical conductors that are electrically coupled to the sensor device 1 and extend through the endoscope. Sensor data collected from the sensor device 1 can be used for various kinds of medical or other investigations or assessments, and can be used to determine a future direction of travel that has a minimal amount of pressure associated with it.

[0047] The embodiment of the sensor device 1 shown in Figure 1a shows two sensor portions 5 located at opposing ends of the capsule body 3. For capsule embodiments, the capsule body 3 may have a generally cylindrical body. The capsule body 3 may have a diameter of around 14 mm and/or a radius of around 7 mm, for example. Each sensor portion may be formed in an approximate hemisphere shape with a 7 mm radius, for example. For capsule embodiments, an end to end length of the sensor device may be around 25 to 35 mm, for example. The following description relates to each of the sensor portions 5.

[0048] Each sensor portion 5 is formed of a series of layers supported over a rigid support dome 9 secured to the main body 3 by a support bracket 7. The main body 3 and the sensor portions 5 preferably form a sealed interior chamber to house internal electronics of the sensor device 1. A printed circuit board (PCB) layer 11 , ground layer 13, and intermediate layer 15 are all formed from flexible material and are mounted in overlying layers over the rigid dome 9. The intermediate insulating layer 15 may have a thickness in the range of around 1.5 mm to about 0.5 mm, optionally around 1 mm, for example. The PCB layer 11 can be made of polyimide and may have a thickness of about 0.1 mm or about 0.075 mm, for example.

[0049] In the embodiments illustrated in Figure 1b, 33 sensor nodes 17 are located on and distributed over the PCB layer 11 at predetermined locations thereon. The sensor nodes 17 are distributed over the PCB layer 11 to substantially cover a generally hemispherical, domed or otherwise rounded end of the sensor portion 5 while leaving small gaps between the sensor nodes 17. The small gaps may be around 1 to 3 mm, for example.

[0050] For capsule embodiments, the main body 3 may house one or more magnets having a sufficient field strength to cooperate with externally applied magnetic fields to allow an external magnetic control system to induce motive force or movement of the sensor device 1 within the tract based on data derived from the pressure sensors on the sensor portion 5.

[0051] As shown in Figure 1b, the PCB layer 11 has a segmented configuration that lends itself to approximating a dome shape when positioned on or adjacent a domed surface. The segmented configuration includes a plurality of segments 11a extending radially outward from a central portion 11b. The segments shown in Figure 1 b include a plurality of non-linear portions, such as petal-shaped or wedge-shaped portions 11c. The segmented configuration shown in Figure 1 b also has a plurality of linear portions 11 d. Each of the segments 11a carries multiple ones of the sensor nodes 17. Optionally, the central portion 11b also carries at least one sensor node 17. In some embodiments, the segments 11a may include only wedge-shaped portions 11c and in other embodiments, the segments may include only linear portions 11 d. In some embodiments, the wedge-shaped portions 11c alternate with the linear portions 11d in a circumferential direction around the central portion 11b. In some embodiments, the central portion 11b does not carry a sensor node 17 and instead defines an aperture for a camera to receive images therethrough. Ground layer 13 and intermediate layer 15 have a same or similar segment shape and configuration to PCB layer 11. Figure 1c shows an example configuration for the ground layer 13 and the intermediate layer 15 that uses a same segmented configuration to PCB layer 11 as described above.

[0052] In other embodiments, a different number of sensor nodes 17 than the 33 show in Figure 1 b may be located on and distributed over the PCB layer 11. For example, one less layer or set of the outer sensor nodes 17 would result in 21 sensor nodes 17 on the PCB layer 11. In another example, one additional outer layer or set of sensor nodes 17 would result in 49 sensor nodes 17, assuming that each of the four wedge-shaped portions of the PCB layer 11 can accommodate three additional sensor nodes 17 and the outer end of each of the linear portions of the PCB layer 11 has one additional sensor node 17. In some embodiments, the outer ring or layer of sensor nodes 17 may have a radial separation of around 20-40 degrees, for example. In some embodiments, the radial separation may be around 30-35 degrees.

[0053] Figure 1 b shows the placement of each sensor node 17 on the initially flat PCB layer 11 prior to forming of that layer into the desired dome shape. Each sensor node 17 may be circular in shape or may be some other shape (e.g. square, triangular or a regular or irregular polygon) that is effective to allow sensing. Each sensor node 17 is formed from or includes conductive material such as, for example, copper. Each sensor node 17 is about 2 mm in diameter in the described embodiment. However, diameters in the range of 2.5 mm to about 1 mm diameter may be used for the sensor nodes 17 in some embodiments.

[0054] The sensor portion 5 furthermore includes an upper conductive ground layer 13 which has the same thickness of the PCB layer 11 , but is covered by a layer of conductive material such as copper and connected to ground. Figure 1c shows the configuration of the initially flat copper layer of the ground layer 13 prior to forming into the dome shape. The same configuration is used for the intermediate insulating layer 15. The ground layer 13 is placed over the top of the sensor portion 5 and will be in direct contact with the internal wall of the passage when being used. The use of other conductive materials such as gold or other biocompatible material on the PCB and ground layers 11 , 13 is also envisaged.

Located between the PCB layer 11 and ground layer 13 is an intermediate insulating layer 15. In the described embodiment, this intermediate layer is formed from

polydimethylsiloxane (PDMS) polymer. The upper (outer) conductive ground layer 13 may also be covered by a thin coating or covering layer of PDMS. The covering layer of PDMS can to assist with biocompatibility and isolate the ground layer 13 from conductive media outside of the sensor device 1 that may affect sensor measurements.

[0055] Figure 1d shows an embodiment of the sensor device 1 according to the present disclosure where the sensor device 1 is mounted at the end of an endoscope 2 for use in insertable endoscopy. In such embodiments, the capsule body 3 only has a single sensor portion 5, disposed at one of the sensor device 1. In some embodiments, for example as shown in Figure 9, the sensor device 1 may have a camera 91 positioned within the sensor portion 5 to receive images through an imaging aperture of the forward path of the sensor device 1 (as the distal tip of the endoscope 2). The imaging aperture may be formed at an apex of the dome shape of the sensor portion 5 and may be covered by a transparent material or lens, for example. The sensor device 1 may also have a light source 92 disposed around or near the sensor portion 5 to emit light in a direction of forward travel of the endoscope 2. As shown in Figure 9, the endoscope 2 may have multiple segments 93 that are controllable using conventional means to steer the direction of progression of the endoscope 2. Other conventional endoscopy tools, sensors or mechanisms can be combined with the sensor device 1. For example, a fluid dispensing mechanism and/or a tissue capture or ablation mechanism may be combined with wired endoscope embodiments described herein.

[0056] Whether wired or wireless, embodiments of the sensor device 1 may include sensors in addition to the pressure sensors described herein. For example, the sensor device 1 may include temperature sensors, pH sensors, accelerometers or other suitably compact sensors.

[0057] The navigation system 20 according to the present disclosure has both an internal system 6, namely the components and body of the sensor device 1 , and an external system 8 as shown in Figure 2. As used herein, the term navigation is intended as a description of a guidance function of the system, rather than necessarily including any steering function. The guidance is intended to allow determination of an optimum path and/or path planning for the sensor device 1. The sensor output from sensor device 1 can be used as feedback to a steering system to help alter the path of the sensor device 1 as it travels its path (e.g. along a gastrointestinal tract). Navigation system 20 can be used in combination with other commercially available systems, for example, whether those systems are based on visualization or are sensor-based systems.

[0058] The internal system 6 includes the components that are embedded into the sensor device 1 as previously described. As shown in Figure 1a, the sensor portion 5 can be attached to or formed on opposing ends of the main body 3 to perform sensing functions in both directions of travel.

[0059] Each pressure sensor is preferably of a capacitive type. The use of alternative sensor types, such as resistive, piezoelectric, optical, electromagnetic or inductive sensors is however also envisaged based on similar principals of structure and operation as described herein. In order to not unnecessarily obscure the present disclosure, embodiments described herein focus on capacitive-type sensors as an example.

[0060] The sensor nodes 17 of the sensor device 1 are connected to a capacitance signal conversion chip 19, such as an AD7147 chip (from Analog Devices, Inc of Norwood, Mass.), which is basically a programmable capacitance-to-digital converter (CDC). Any other device for detecting the capacitance could alternatively be used. The AD7147 chip is about 4mm by 4mm in size and runs from a 2.6 V to 3.6 V supply, with an operating current in low power mode typically around 26 mA. The AD7147 chip has 13 input channels that uses a sigma- delta (å-D) converter to measure the capacitance of each sensor node 17 coupled thereto by respective conductors 18.

[0061] Each sensor node 17 of the sensor device 1 acts as a standalone capacitance pressure sensor (16) which varies its capacitance according to the distance (separation) between the PCB layer 11 and the ground layer 13 as shown in Figure 3 and Figure 5.

Figure 5 shows an example separation distance of about 1.0 mm between the ground payer 13 and the PCB layer 11 that includes the sensor node 17. Figure 3 shows two nodes 17 that are separated by a specific distance and each node 17 represents a capacitor that varies as capacitance = (sk A)/d , where e is the permittivity of free space, k is the relative permittivity of the material between the layers, A is the area and d is the separation distance between the layers. Then, the detected values of the capacitance (measured in e.g.

picofarads, pF, or less than 1 picofarad) are converted to digital values by capacitance signal conversion chip 19.

[0062] According to some embodiments, the converted digital values may have an integer value in the range of 0 to around 30,000, depending on the pressure sensed by the capacitive sensor nodes 17. Values closer to 0 mean the pressure on the sensing node is low and higher values represent high pressure. These converted digital values need to be transferred to the workstation throughout any communication system for processing. A short range wireless radio transceiver 21 , such as a SIMBLEE, can be used through a serial peripheral interface (SPI) to send and receive the data. For capsule embodiments, the short range wireless radio transceiver 21 includes a local power source, such as a battery 23, or has access to power from a battery 23 housed within the sensor body 3. The SIMBLEE is a Bluetooth (e.g. BLE - Bluetooth Low Energy) smart radio transceiver, which has a programmable microcontroller. The microcontroller of the short range wireless radio transceiver 21 gathers and organizes the outputs received via conductors 18 from the capacitance signal conversion chips 19, and then sends them to a receiver 10 that is connected to a workstation 12 via a short range wireless protocol, such as Bluetooth, using point-to-point (P2P) topology. The use of alternative communication components and/or arrangements is also envisaged, including devices having similar functionality to the

SIMBLEE.

[0063] The external system 8 has two main components, the receiver 10 and the workstation 12 (i.e. computer). This is illustrated in Figure 2. The workstation 12 may include a suitable computing device, such as a tablet device, a smartphone, a desktop computer or other computing device capable of executing software applications. The receiver 10 is paired to the short range wireless radio transceiver 21 in the internal system 6 to receive the sensor node data from capacitance signal conversion chips 19 and transfer it to the workstation 12. The receiver 10 may include a computing or electronic device that is in communication with the workstation 12 and has a suitable receiver or transceiver for communicating with the short range wireless radio transceiver 21 or it may be a wireless radio transceiver associated with or forming part of the workstation 12, for example. The receiver 10 may include a SIMBLEE or other radio transceiver, for example.

[0064] Figure 6 illustrates the relationship of the flexible PCB layer 11 with the capacitance signal conversion chips 19 and the short range wireless radio transceiver 21 , with the sensor nodes 17 being coupled to one of the capacitive inputs (CIN) on the capacitance signal conversion chips 19 via conductors 18.

[0065] The workstation 12 has or executes a software algorithm or application 22 to analyse the sensor data received via receiver 10 and display it to the user. A processor 14 (which may include one or multiple computer or other processors) of the workstation 12 accesses the software application 22, which is stored in a memory 15 of the workstation, and executes the software application 22 to process the received signals from sensor device 1 to perform the functions described herein. The software application 22 may include or cooperate with a suitable signal processing and display application, such as Matlab. Sensor data processed by the software application 22 can be readable in real-time by humans (e.g. viewing the output display shown in Figure 14 and 15) or by machines executing suitable control algorithms to direct the sensor device 1 (endoscope 2) in a direction that has minimum resistance to forward movement in the tract.

[0066] The working principle of the algorithm or software application 22 executed by workstation 12 will now be described. It is to be appreciated that the present disclosure is not limited to the described arrangement, and that alternative arrangements could be used to receive and analyse the data. Sensor data received from sensor device 1 is usable in real time but can be saved into the memory 15 of workstation 12 or provided to a different computer system analysis and study. The sensor data can, in combination with location data, allow generation of real-time three-dimensional path data as the sensor device 1 travels through the tract.

[0067] Figure 7 is an illustration of a further embodiment 70 of the flexible inner conductive (PCB) layer 11. Inner conductive layer 70 includes radial mounting portions 71 on the flexible PCB to allow mounting of the capacitance signal conversion chips 19 for easy connection to the conductors 18. Radial mounting portions 71 are disposed at outer radial ends of the wedge-shaped segments 11c, although in other embodiments, they may be disposed at outer radial ends of the linear segments 11 d. Additionally, inner conductive layer 70 has extension portions 73 disposed radially outward of each of the segments 11c, 11 d and radially outward of the sensor nodes 17. The extension portions 73 are free of sensor nodes 17 and can be used to assist in securing the inner conductive layer within the main body 3 when the inner conductive layer 70 is folded around support 9 to adopt a dome-like or approximately hemispherical configuration over sensor portion 5.

[0068] Figure 8 is a flowchart illustrating a method 80 of navigating a sensor device. In the method, forward movement of the sensor device 1 is induced manually, automatically or semiautomatically. If no variation on the path is warranted due to pressure sensed on one or more parts of the sensor portion 5, then the forward movement is continued. If one or more signal outputs from the pressure sensors 16 indicate that a path variation may be required, then the navigation system 20 (executing the application software 22) determines whether the pressure level of the signal outputs meets or exceeds the pre-configured lower pressure threshold. If the pressure level of the signal outputs meets or exceeds the lower pressure threshold, then a new path or direction for the sensor device 1 is determined by the navigation system 20 as described below. If the pressure level of the signal outputs from the pressure sensors 16 meets or exceeds a pre-configured upper pressure threshold, then forward motion of the sensor device 1 is stopped or reversed and adjustment of the sensor device 1 position or the upper pressure threshold is performed before resuming forward motion. Following a change in direction, the navigation system 20 continues to monitor the sensed pressure levels at positions around the sensor portion 5 and if no change in direction is needed, then forward movement continues. If a change in direction is again required, then a then a new path or direction for the sensor device 1 is determined again by the navigation system 20. [0069] The navigation system accoring to the present disclosure relies on determining the location on the sensor portion 5 where the lowest pressure level or highest pressure level is measured during travel of the sensor device 1 along an internal passage. The proposed method of the navigation system presents features relating to navigation, tracking and safety described below.

[0070] Navigation

[0071] In order to describe the mechanism of navigation, a spherical coordinate system (G,q,f) is needed. It is assumed that the path is differential and can be segmented into infinitesimal parts. Now, in order to describe the location of each sensor portion 5 in 3D to navigate the vector r along the direction of the path, it is necessary to identify the azimuthal angle (Q) and the polar angle ( ). The azimuthal angle describes the changes in the path in the right/left directions as shown in Figure 4(b), whereas the polar angle describes the inclination and the declination of the path as shown in Figure 4(a). In this method, the inventors have used the fact that they can precisely and easily identify these angles in a perfect hemisphere or a near approximation of a hemishpere.

[0072] Figure 4(c) shows the distribution of the sensor nodes 17 among the surface of the dome shaped sensor portion 5. The location of each node/pressure sensor 17, 16 can be designated by the azimuthal and/or polar angle associated with the location of the node/pressure sensor. The nodes 17 that represent a pure azimuthal angle (when f=0) are placed along the centre line that passes from the left to the right of the hemisphere from -90° to 90°, where 0 to 90° gives the information of how the path curves to the left and 0 to -90° to the right. The following table shows the angles associated with each of the sensor nodes for the illustrated embodiment of 33 sensor nodes (labelled N1 to N33).

[0073]

[0074] The bending angle for the travelling path of the sensor device 1 can be found if the pressure is directly applied into a node 17 or between two or more nodes 17. If the pressure occurs between two nodes 17, the exact distance of the pressure between the nodes (and hence the angle) can be calculated according to the amount of pressure of one node relative to the amount of pressure of the other node. Similarly, the nodes that represents a pure polar angle (when Q =0) are distributed along the centre line that passes from the top to the bottom of the sensor dome or hemisphere (of sensor portion 5) from -90° to 90°, where 0 to 90° gives the information of the path’s inclination and 0 to -90° shows the path’s declination as shown in Fig. 4a. The same approach of finding the angle in the azimuthal component can be applied into the polar angle. In case the path’s direction is a combination of azimuthal and polar angles, the nodes 17 between the centre lines will give the information of the amount of both angles. In cases where the path is extremely complex and flexible (i.e. small intestine) where the pressure is applied into most of the sensor nodes 17, the location where the least pressure is applied to the sensor section 5 always represents the correct direction of the movement. The above is described as an example coordinate system, however other coordinate systems may be employed in sensor device 1 and navigation system 20.

[0075] Tracking

[0076] As the information of the angles can be detected, it is possible to localize and draw the overall path in 3D by knowing the length of vector r and by building up the data cumulatively. Matlab software has been used to analyse and display the data. It is be appreciated that the use of alternative software is also envisaged to analyse and display the data. [0077] Safety

[0078] A significant concern for navigation of endoscopes through a Gl tract is the possible perforation or other damage of an interior wall of the Gl tract, which can result in bleeding and infection. This can be due to inadequate feedback of position and direction information from the endoscopic probe, possibly combined with inaccurate movement of the probe tip, which can result in an excessive pressure being applied to an interior tract wall by the endoscope tip. The steering force is an important parameter for any insertion procedure, either for medical or general application. In the present disclosure, the range of the pressure readings can be controlled in two ways. One way is by controlling the threshold of the minimum and maximum pressure that the sensor device 1 could experience. This will give the user the information of how strong the insertion force is and warn (e.g. in real time) if the force exceeded the upper threshold. In addition, it can be used to change the thickness of the intermediate layer 15 or its density. As a result, the higher density or thickness will make the capacitance react slower. This feature gives such embodiments the ability to deal with a large range of applications, whether the pressure sensors 16 needs to be very sensitive to low pressure or not.

[0079] The sensor device 1 can be operated in rigid mode or in flexible mode. Rigid mode is designed for partially rigid parts of the digestive system, such as the mouth, pharynx and oesophagus. To localize the applied pressure with respect to the sensor coordinate system, the absolute pressure (ABP) is defined to represent the location of the highest pressure, whether the pressure is located on one sensor node 17 or between multiple sensor nodes 17. It is straightforward to determine a directional variation if the pressure between the capsule and tissues is applied on one sensor node 17 only as each sensor node 17 is assigned to specific polar and azimuth angles. If the pressure occurs between two or more sensor nodes 17, the angular distance of the point of the pressure between the sensor nodes 17 can be found according to the pressure of one sensor node 17 relative to the amount of pressure at one or more other sensor nodes 17. It is then necessary to find the angle of the pressure point using Aa=As/r where As is the angular distance and r is the radius. This is illustrated in Figure 10. An example of determining a highest pressure location is illustrated schematically with reference to polar coordinates in Figure 12. When the sensor device 1 and navigation system 20 are used in flexible mode, the angle between two adjacent sensor nodes 17, y (gamma), is continuously computed in order to determine the location of pressure on the dome or hemisphere of the sensor portion 5. Then by finding y (gamma), the polar and azimuth angles can be calculated and related to the ambient environment coordinates system (t₁, d₁,s₁). Initially, to represent the direction of the motion vector, we need to determine the unit vector in the latitude direction and the longitude direction such that:

[0081] Where <5 has the range of [O, p] and represents the variation in the longitude and s has the range of [0,2p] and represents the variation in the latitude.

[0082] In order to calculate the angle of the pressure between two nodes, we firstly calculate the angle between the nodes:

[0083] g = cos ¹{sin(5₁) sin(S₂ ) + cos^-f) cos(S₂ ) cos a₁— s₂ )} (2)

[0084] where g is the angle between the nodes, ¾ is the polar angle for the first node, d₂ is the polar angle for the second node, o_t and s₂ are the azimuth angles for the first and second nodes respectively. Then, we calculate the orthodromic distance (arc length) between the two nodes as:

[0085] L = (Z ) (3)

[0086] The ABP as illustrated in Fig.10 can be then calculated using the following:

[0088] where P_? is the amount of pressure on the first node and P₂ is the amount of pressure on the second node. Finally, to find the polar angle for the ABP we use:

[0090] where POL_? and POL₂ are the angles of the first and second nodes with respect to the local coordinate system of the capsule, and min polar is the smaller angle between the polar angles. The smaller angle is included in order to use it as a reference to determine the direction of the resultant polar angle. For example, if the pressure between 30° and 60°, the resultant polar angle is 15° and the actual polar angle is 45° (30°+15°). Similarly, for the azimuth angle we use the following:

[0092] where AZh and AZh are the angles of the first and second nodes with respect to the local coordinate system of the capsule, and min Azimuth is the smaller angle between the polar angles.

[0093] Where the sensor device 1 is used in flexible mode, a modified control paradigm is employed. The small intestine has random bends and unpredictable geometry. These deformable and inhomogeneous bends could accommodate more mucosa which require more processing and filtering techniques for image-based navigation methods. In addition, as the small intestine can be considered as a collapsed path, navigation system 20 may be better suited to navigating such paths than image-based navigation, which sometimes requires more processing, such as redefining edges or using colour/texture segmentation.

[0094] In flexible mode, it can be advantageous to find the optimal path based on the least- pressure technique, where sensor nodes 17 that have the lowest pressure indicate the direction of the optimum future path, as schematically illustrated in Figure 11. While the sensor device 1 moves along the collapsed and bent path, the small intestine will be interacting and applying pressure at most of the sensor nodes 17 as shown in Figure 11. However, there will be an area which has minimal or zero pressure, indicating the direction of the optimal path. The control method adopted in such case is opposite to the rigid mode by scanning the sensor nodes 17 with the lowest pressure and then defining the path using equations [1], [2], [3], [4], [5] and [6] defined above. An example of this is illustrated schematically with reference to polar coordinates in Figure 13.

[0095] Referring to Figure 14, an example screenshot or display 1400 is shown. Display 1400 includes a graph that shows the pressure output of each sensor node 17 in real-time. Display 1400 includes a display section 1410 that displays the location of the active nodes (that are experiencing pressure from within the tract) with respect to their local coordinate system. A display section 1420 of display 1400 shows the direction of the optimal path with respect to the capsule coordinate system (t, d,s) whereas display section 1430 shows the direction with respect to the ambient environment coordinate system (t₁, d₁,s₁). Display 1400 also shows the applied pressure in each node and the absolute pressure if it is between two or more nodes in display section 1440. A control section 1425 in display 1400 allows the navigation system 20 to turn on/off the autonomous mode (where available), and to choose the operation mode to be rigid or flexible mode in display section 1470. Selection or configuration of the upper and lower pressure detection thresholds is selectable in display section 1450. The control panel displayed below the graph in display 1400 can be turned on or off in section 1460.

[0096] Referring to Figure 15, an example of how the navigation system 20 analyses the outputs of the sensor device 1 is shown for the first bend depicted at 150 in Figure 14. It is assumed for simplicity that the sensor device 1 is in inertial motion until touching an external environment such as a tract wall and the sensed pressure exceeds the lower pressure threshold. Once the pressure threshold is exceeded, the software application 22 in the navigation system 20 starts reading the pressure signals output from the active sensor nodes 17 (i.e. those sensor nodes 17 that have sensed a pressure above the lower pressure threshold) to determine a future variation in the direction of the sensor device 1. The software application 22 uses the equations described above to make that determination.

[0097] In case of the first bend, nodes 17 with location (0, 30) and (0, 60) are active with different detected amounts of pressure. According to the relative amount of the pressure between the nodes 17, the software application 22 determines the point of ABP and then displays the new direction that the capsule should follow, which is 33° to the left. As the capsule starts aligning with the new direction, the pressure on node (0, 60) reduces until the pressure is completely on node (0, 30). Further alignment with the new direction will render active node (0, 0) and reduce the pressure on node (0, 30) until the capsule becomes totally aligned with the new direction. The sensor nodes 17 will be inactive until another bend occurs.

[0098] The described navigation system 20 integrates a capacitive pressure sensor array to measure spherical coordinate points for both the position and differential path of the capsule, while using a significantly lower amount of data transmission than image-based systems.

[0099] Modifications and variations to embodiments described herein as would be apparent to the person skilled in the art are included in the ambit of the present invention as claimed in the appended claims.

Claims

1. A sensor device for use in internal inspections, including:

at least one sensor portion; and

wherein each pressure sensor is adapted to measure a pressure level applied to the sensor device at said location of the pressure sensor.

2. The sensor device according to claim 1 , wherein each pressure sensor is of a capacitive type.

3. The sensor device according to claim 1 or claim 2, wherein the at least one sensor portion includes an inner conductive layer, an outer conductive layer, and an insulation layer located between the inner conductive layer and the outer conductive layer.

4. The sensor device according to claim 3, wherein said inner conductive layer, insulation layer and outer conductive layer are formed from flexible material.

5. The sensor device according to claim 3 or 4, wherein the inner conductive layer supports a plurality of conductive nodes, each said conductive node forming part of a respective said pressure sensor.

6. The sensor device according to any one of claims 3 to 5, wherein the inner conductive layer includes a plurality of separate segments, each segment supporting at least one of the pressure sensors.

7. The sensor device according to claim 6, wherein each segment extends radially from a central portion of the inner conductive layer.

8. The sensor device according to any one of claims 3 to 7, wherein the insulation layer and the outer conductive layer include a plurality of separate segments and have a same or similar segment configuration as the inner conductive layer.

9. The sensor device according to any one of claims 3 to 8, wherein the outer conductive layer is a ground layer.

10. The sensor device according to any one of claims 3 to 9, wherein the at least one sensor portion further includes a generally dome shaped rigid support for supporting said inner and outer conductive layers, and said intermediate layer.

11. The sensor device according to claim 10, wherein said inner and outer conductive layers, and said intermediate layer are generally dome shaped.

12. The sensor device according to any one of claims 1 to 11 , further comprising a transmitter and a plurality of signal conversion chips, each signal conversion chip receiving signals from a plurality of pressure sensors, wherein the signal conversion chips are in communication with the transmitter and the transmitter is configured to transmit output signals corresponding to signals received from the plurality of pressure sensors to an external system.

13. The sensor device according to claim 12, wherein the transmitter is a wireless transmitter.

14. The sensor device according any one of the preceding claims, wherein the sensor device includes a capsule body having opposing ends, with the at least one sensor portion being located on at least one of the opposing ends of the capsule body.

15. The sensor device according to claim 14, wherein a said sensor portion is respectively located at both ends of the capsule body.

16. A navigation system for a sensor device as claimed in any one of the preceding claims.

17. The navigation system according to claim 16, further including at least one receiver for receiving a pressure level signal from each said pressure sensor, and a data processing system for comparing the received pressure level signals to determine the location(s) of the pressure sensor(s) having the lowest measured pressure level signal.

18. The navigation system according to claim 17, wherein the location of each pressure sensor is identified by an azimuthal and/or polar angle associated with said location.

19. The navigation system according to any one of claims 16 to 18, wherein the navigation system includes the sensor device.

20. A method of navigating a sensor device using a navigation system as claimed in any one of claims 17 to 19, the method including measuring the pressure level at the location of each said pressure sensor, and identifying the location of the one or more pressure sensors having the lowest measured pressure level, to thereby determine a travel direction for the sensor device associated with the location of said one or more pressure sensor locations.

21. The method according to claim 20, including using a spherical coordinate system to identify the changes in the travel direction.

22. The method according to claim 21 , including identifying an azimuthal and/or polar angle associated with the location of said identified pressure sensor(s) defining said travel direction.

23. The method according to any one of claims 20 to 22, including using the determined travel direction to control the sensor device to travel in the travel direction.