Invasive Temperature Sensor Systems

Abstract

Disclosed are a device (1), a related kit, and a related method for measuring the temperature at one or more locations in an organ or tissue in a human or animal body. The device includes a catheter (2) having a distal end for insertion into the body and a proximal end for remaining outside the body when the device is in use. The device includes at least one resistive temperature sensor (3) in the tube, and a plurality of wires (4) in the tube connected to the at least one resistive temperature sensor (3). The plurality of wires includes at least some wires passing through the tube (2) from the proximal end of the tube. The device includes a connector (21) located at the proximal end of the tube (2) for electrically connecting the plurality of wires (4) to an external device. The resistive temperature sensor (3) includes a thermal resistor (11) and a first terminal (12) and a second terminal (13), between which a temperature-dependent resistance of the thermal resistor can be measured, wherein each of the two terminals (12, 13) of the resistive temperature sensor (3) is directly connected to at least one of the plurality of wires (4).

Description

[0001] Technical field of the invention

[0002] The present invention relates to the field of interventional medical devices, and in particular sensor catheter devices. The present invention particularly relates to devices, related kits and / or systems for measuring the temperature of one or more locations within the human or animal body, and methods of manufacturing such devices.

[0003] Background of the Invention

[0004] In various medical procedures, there is a need for means and methods to accurately monitor the internal temperature of animals or humans. Catheters are often used to measure body properties at specific locations. For example, US Pat. No. 5,916,153 discloses a catheter for urethral insertion that includes a temperature sensor and a guide wire embedded in the catheter wall. Many catheters known in the art are suitable for percutaneous use, such as intravascular use. However, insertion of such catheters carries the risk of infection, particularly at the catheter tip and at the insertion site where the epidermis is penetrated. Furthermore, to minimize damage to the body and its internal organs, a compact configuration and / or high miniaturization are highly preferred, for example, allowing the sensor arrangement to fit within a catheter having the smallest diameter possible, as far as reasonably achievable. For example, organs may be highly sensitive to damage caused by puncture. Furthermore, when a catheter is inserted into an organ at an angle, for example, where the entry vector has a substantial tangential component relative to the organ's outer surface, there is a further risk of tearing or cutting vessels within the organ. It should be understood that such punctures, cuts, and / or tears should generally be avoided or at least minimized, particularly because such injuries can lead to life-threatening internal bleeding. These considerations are particularly important for the liver, an organ that is particularly sensitive to damage due to its dense vascularization. In hyperthermia therapy, the body temperature of a human or animal is artificially raised and maintained at an elevated level. While this approach can be used to target heat-sensitive cancer cells, the elevated temperature needs to be precisely controlled to avoid damage to healthy cells. Therefore, in such procedures, it is necessary, or at least desirable, to directly monitor the temperature of the body, especially organs that are highly sensitive to overheating. The liver is metabolically very active, so monitoring liver temperature to prevent overheating is a top priority. It will also be apparent that measuring the temperature at multiple locations in the liver may be advantageous. However, as mentioned above, invasively measuring temperature in the liver also carries high risks that should be minimized.

[0005] It is known in the art to use optical sensing to determine body temperature using catheter devices. For example, GB2308652 discloses a temperature-sensitive catheter that includes an optical fiber with a grating, in which the temperature dependence of the Bragg wavelength is used to measure the temperature. This approach has the additional advantage that, for example, multiple Bragg gratings can be coupled to a single optical fiber at multiple locations in the catheter by using different grating frequencies. However, even if a compact device can be achieved, this approach may be limited in the achievable measurement accuracy, and other dependencies (such as the effect of strain on the Bragg wavelength) may confound the measurement.

[0006] As another example, US Pat. No. 9,289,606 discloses a catheter system for electroporation-mediated therapy and similar treatment modalities, in which a tip electrode comprises a cavity whose inner surface is impregnated or coated with a thermochromic / thermochromic material that changes color with temperature. Thus, the electrode temperature can be monitored via optical fiber analysis spectroscopy.

[0007] US 6519485 discloses a system for assessing organ function. The tip of the fiber optic delivery assembly extends to or into the internal organ and illuminates the tissue. In addition, temperature is sensed at the tip, and the collection fiber collects scattered, reflected or emitted light from the surrounding tissue. The intended use of the system is to quickly detect metabolic changes in an organ (such as the liver), such as the onset of shock, before metabolic changes occur in blood chemistry, cardiovascular indicators or other health indicators (as typically monitored in a hospital environment). According to this exemplary prior art disclosure, the temperature sensor can be implemented as an electrically connected sensing element, such as a thermistor, or by light-based technology, such as infrared thermal imaging. However, there is still a need in the art to provide means and methods for monitoring the temperature in the body (e.g., an organ). Preferably, the temperature is monitored at multiple locations, for example, spaced along the longitudinal segment of the catheter, for example, so that local temperature differences can be detected and / or so that an averaging operation can be performed. As mentioned above, a compact arrangement is highly preferred, for example to avoid damage to the organ or to minimize it. Summary of the Invention

[0008] The object of the present invention is to provide a compact, simple, efficient, inexpensive and / or safe device for accurately measuring the temperature at one or more locations along an insertion path in the human or animal body, and to provide a method for easily, efficiently and / or reliably manufacturing such a device.

[0009] Embodiments of the present invention have the advantage that the temperature inside the body of an animal or human (eg, inside an organ) can be accurately monitored.

[0010] Embodiments of the present invention have the advantage that temperature within an animal or human body (eg in an organ) may be monitored, eg at different locations in the organ or tissue of interest, eg at multiple different depths in the tissue or organ of interest.

[0011] Advantageously, embodiments of the present invention provide a temperature sensor integrated into a catheter structure to provide adequate isolation between a foreign object inserted into the body and the body, while easily and quickly achieving thermal equilibrium between the sensor and surrounding body tissue. Advantageously, embodiments of the present invention provide a compact structure, such as a catheter structure having a small diameter, which advantageously reduces the risk of infection and / or tissue damage due to punctures, cuts, tears, and / or lacerations.

[0012] Various embodiments of the present invention have the advantage of providing a soft and / or mechanically compliant (ie, non-rigid) structure, for example, to avoid or reduce tissue damage.For example, the catheter can be formed into a soft and / or highly compliant package.

[0013] Embodiments of the present invention have the advantage that the temperature can be measured accurately and safely in multiple measurement points of the liver.

[0014] Embodiments of the present invention have the advantage that accurate monitoring of body temperature can be achieved so that, based on these measurements, thermal parameters of hyperthermia therapy can be controlled to achieve a good therapeutic effect while avoiding potentially fatal overheating of the body or specific heat-sensitive organs in the body. Embodiments of the present invention have the advantage of using simple and reliable temperature sensors, such as standard resistance temperature detectors (RTDs), such as PT100 or PT1000 sensors. For example, prior art techniques may rely on more complex temperature conversion methods, such as optical detection of optical properties that depend on temperature, which may be more prone to error, less reliable, more expensive, more inaccurate and / or more difficult to read and / or calibrate.

[0015] Embodiments of the present invention have the advantage that multiple temperature measurement points can be provided along the sensing region of a catheter, wherein a three-wire or four-wire readout method can be used at each measurement point, rather than requiring as many as three or four wires per measurement point running along the length of the catheter. Because the number of wires required can advantageously be kept low, the diameter of the catheter can also be kept low.

[0016] Embodiments of the present invention have the advantage that a reliable temperature measurement in an organ or tissue can be obtained by averaging the temperatures measured at a plurality of measurement points.

[0017] Embodiments of the present invention have the advantage that the temperature in an organ or tissue can be described in detail by determining the temperature at a plurality of measurement points within the organ or tissue.

[0018] The above objectives are achieved by the devices and methods according to various embodiments of the present invention.

[0019] In a first aspect, the present invention relates to a device for measuring the temperature at one or more locations in an organ or tissue within a human or animal body. The device comprises a catheter having a distal end and a proximal end, wherein the distal end is adapted for insertion into (or onto) an organ or tissue within the body, while the proximal end remains external to the body during use of the device. The device comprises at least one resistive temperature sensor within the catheter, and a plurality of wires within the catheter connected to the at least one resistive temperature sensor. The plurality of wires may include at least some wires extending from the proximal end of the catheter through the catheter and may include wire segments running between pairs of the resistive temperature sensors. The device comprises a connector at the proximal end of the catheter for electrically connecting at least some of the plurality of wires to an external device. The resistive temperature sensor comprises a thermistor and a first terminal and a second terminal, between which a temperature-dependent resistance of the thermistor can be measured. Each of the two terminals of each resistive temperature sensor is directly connected (e.g., soldered) to at least one of the plurality of wires.

[0020] In the device according to an embodiment of the present invention, the electric wires may be spirally wound around each other.

[0021] In the device according to an embodiment of the present invention, the thermal resistor may be a platinum resistor, such as a PT100 resistor or a PT1000 resistor.

[0022] In an apparatus according to an embodiment of the present invention, the resistive temperature sensor may include a thin film substrate.

[0023] In a device according to an embodiment of the invention, the thermal resistor may comprise elongated electrically conductive metal traces arranged in a meandering pattern on a substrate.

[0024] In a device according to an embodiment of the invention, the resistive temperature sensor may have a thickness in the range of 50 μm to 150 μm, a width in the range of 100 μm to 700 μm, for example in the range of 100 μm to 350 μm, and a length in the range of 1 mm to 10 mm.

[0025] In a device according to an embodiment of the invention, the diameter of the electrical wires (eg each of them) may be in the range of 10 μm to 100 μm, for example in the range of 30 μm to 80 μm.

[0026] In an apparatus according to an embodiment of the present invention, the outer diameter of the conduit may be in the range of 463 μm to 820 μm, and the inner diameter may be in the range of 260 μm to 514 μm.

[0027] In a device according to an embodiment of the present invention, the at least one resistive temperature sensor may be a plurality of resistive temperature sensors.

[0028] In a device according to an embodiment of the present invention, a first plurality of wires (e.g., wires in the plurality of wires) may connect a plurality of resistive temperature sensors in series so that current flows through the plurality of resistive temperature sensors when the device is operating. The first plurality of wires may include or comprise:

[0029] - a first wire from the proximal end of the tube to a first terminal of the first resistance temperature sensor in the series, a second wire from the proximal end of the tube to a second terminal of the last resistance temperature sensor in the series, and

[0030] - a plurality of wire segments, each of which connects the second terminal of a previous resistance temperature sensor in the series to the first terminal of a next resistance temperature sensor in the series. ("Previous" and "Next" refer to a pair of adjacent sensors in the series connection)

[0031] In an apparatus according to an embodiment of the present invention, at least one of the two terminals of each resistive temperature sensor can be directly connected (e.g., welded) to at least two of the plurality of wires extending from the proximal end of the tube to allow the resistive temperature sensor to be read using a three-wire or four-wire readout configuration.

[0032] In an apparatus according to an embodiment of the present invention, a second plurality of wires (e.g., the plurality of wires) for measuring the voltage difference may extend from the proximal end of the tube and may be connected to the plurality of resistive temperature sensors. The second plurality of wires may include or comprise:

[0033] - a first wire extending from the proximal end of the tube to connect to a first terminal of a first resistive temperature sensor in the series,

[0034] - a second wire extending from the proximal end of the tube to connect to the second terminal of the last resistive temperature sensor in the series, and

[0035] - A plurality of wires extending from the proximal end of the tube to be respectively connected to each of the wire segments (43).

[0036] The first plurality of conductors and the second plurality of conductors may be referred to as disconnected groups of conductors.

[0037] Devices according to embodiments of the present invention may include a structural wire within the tube to reduce the flexibility of the tube and / or increase the axial stiffness of the tube, for example, without significantly increasing its bending stiffness. Advantageously, the structural wire may provide additional strength to the tube and / or may increase safety when the insertion device is retracted from the body, for example, by preventing the tube from breaking during retraction.

[0038] In devices according to embodiments of the present invention, the structural wires may be composed of tungsten or a tungsten alloy. In devices according to embodiments of the present invention, the structural wires may include or be composed of stainless steel (e.g., SS 316), carbon fiber, titanium, gold, another metal or metal alloy, and / or polymer fibers. Embodiments are not necessarily limited to these illustrative materials.

[0039] In a device according to an embodiment of the present invention, the thickness of the structured wire may be in the range of 40 μm to 150 μm.

[0040] Devices according to embodiments of the present invention may include one or more filler materials that fill the tube, i.e., fill the voids in the tube that are not occupied by other device features, such as, for example, to fill other voids in the tube. For example, the one or more filler materials may include a deformable filler material. For example, different cross-sections (e.g., separated longitudinally) may be filled with different filler materials, e.g., filler materials having different properties. For example, at least one cross-section may be more flexible than at least one other cross-section, e.g., such that the tube includes both flexible and non-flexible (i.e., less flexible or substantially rigid) cross-sections.

[0041] A device according to an embodiment of the present invention may include an integrated circuit for storing data, which is operably connected to a connector to provide data to an external device when connected. The data includes identification information and / or calibration information and / or sterilization information and / or sensor log information.

[0042] A device according to an embodiment of the present invention may include at least one optical fiber to transmit an optical signal to an organ or tissue when the device is used, and to collect a return optical signal from the organ or tissue, so that in addition to temperature, one or more other physiological parameters of the organ or tissue can be monitored via the optical fiber.

[0043] In a second aspect, the present invention relates to a kit comprising the device according to embodiments of the first aspect of the invention and one or more selected from the following:

[0044] - a needle that pierces the skin,

[0045] - a guide sleeve, used to insert the tube into the body through a puncture in the skin,

[0046] - a readout device for providing a temperature value based on current and / or voltage measured via the plurality of electrical wires when the readout device is operatively connected to the connector.

[0047] In a third aspect, the present invention relates to a method for manufacturing an apparatus according to an embodiment of the first aspect of the invention. The method comprises:

[0048] - manufacturing or obtaining one or more resistive temperature sensors, each resistive temperature sensor comprising an elongated conductive metal trace on a thin film substrate, the metal trace being arranged in a meandering pattern between a first terminal and a second terminal,

[0049] - connect multiple wires to one or more resistive temperature sensors,

[0050] - inserting one or more resistive temperature sensors and a plurality of electrical wires into the catheter so that at least some of the electrical wires remain accessible at or via the proximal end of the tube, and

[0051] - Mechanically connecting a connector to the proximal end of the tube and electrically connecting the connector to the plurality of wires such that an external device can be operatively connected to the one or more resistive temperature sensors via the connector.

[0052] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

[0053] The independent and dependent claims describe particular and preferred features of the invention. Features of the dependent claims may be combined with features of the independent claim or with features of other dependent claims (as deemed appropriate) and not necessarily only as explicitly set out in the claims.

[0054] Brief Description of the Drawings

[0055] Figure 1 An apparatus according to an embodiment of the invention is illustrated.

[0056] Figure 2 An apparatus according to an embodiment of the invention is illustrated.

[0057] Figure 3 A wiring scheme of sensors in a device according to an embodiment of the present invention is explained, as well as an exemplary readout approach according to an embodiment of the present invention.

[0058] Figure 4 An apparatus according to an embodiment of the invention is illustrated.

[0059] Figure 5 A method for configuring conductors in a device according to an embodiment of the present invention is explained.

[0060] The drawings are schematic and non-restrictive. Elements in the drawings are not necessarily shown to scale; for example, for illustrative purposes, elements may be exaggerated or reduced in scale to make the drawings clear and understandable. The present invention is not necessarily limited to the specific embodiments of the invention shown in the drawings. Reference numerals in the claims should not be construed as limiting the scope. The same reference numerals may refer to the same or similar elements in different drawings.

[0061] Detailed description of the embodiments

[0062] Although exemplary embodiments are described below, the present invention is limited only by the appended claims, which are hereby expressly incorporated into this detailed description, with each claim and each combination of claims permitted by a claim-defined dependent structure constituting a separate embodiment of the invention.

[0063] The word "comprising" used in the claims is not limited to the features, elements or steps described below and does not exclude additional features, elements or steps. Thus, it specifies the presence of the features described but does not exclude the further presence or addition of one or more features.

[0064] Sequential references (such as first, second, etc.) in the specification and / or claims may be used to identify similar elements and do not necessarily define a sequence in time, space, ranking, or any other manner. These terms are interchangeable where appropriate, and embodiments of the present invention may involve other sequences than those explicitly described or illustrated herein.

[0065] Spatial references in the specification and / or claims, such as top, bottom, upper, lower, etc., are used for descriptive purposes and not necessarily for describing relative positions. It should be understood that various embodiments may involve other positional arrangements of elements described using such spatial references, unless the relative positioning is necessary to achieve the desired technical effect, i.e., necessary to solve the underlying objective technical problem, which is obvious to a skilled person. Therefore, it is understood that such terms are interchangeable under appropriate circumstances, and that embodiments of the present invention may operate in other orientations than those described or illustrated herein.

[0066] In the detailed description, various specific details are presented. Embodiments of the present invention can be implemented without these specific details. In addition, for the clarity and simplicity of the present invention, well-known features, elements and / or steps need not be described in detail.

[0067] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment, but may. Furthermore, in one or more embodiments, as will be apparent to one of ordinary skill in the art from this disclosure, the particular features, structures, or characteristics can be combined in any suitable manner. References to "an embodiment" or "in an embodiment" should be interpreted in the same manner.

[0068] For the purpose of simplifying the disclosure of the invention and aiding understanding of various aspects of the invention, various features of the invention may be grouped together in a single embodiment, figure, or description thereof. This should not be interpreted as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. On the contrary, as reflected in the appended claims, inventive aspects may lie in fewer features than all the features of a single, previously disclosed embodiment as expressly described in the specification. Accordingly, the claims appended following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the invention.

[0069] Furthermore, although some embodiments described herein include some features included in other embodiments but do not include other features included in other embodiments, as will be understood by those skilled in the art, combinations of features from different embodiments are intended to fall within the scope of the present invention and to form different embodiments. For example, in the appended claims, any of the claimed embodiments can be used in any combination.

[0070] In the description provided herein, numerous specific details are set forth. However, it should be understood that embodiments of the present invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques are not shown in detail to avoid obscuring understanding of this description.

[0071] In a first aspect, the present invention relates to an apparatus for measuring the temperature at one or more locations in the human or animal body.For example, the apparatus may be suitable for monitoring the temperature of an organ or tissue within the body.

[0072] Figure 1 and Figure 2 An exemplary device 1 according to an embodiment of the invention is shown.

[0073] The device may be, or may comprise, or may be considered as a catheter.The device comprises a catheter 2, in particular a thin tube, such as a long, thin, hollow tube, suitable for insertion into a human or animal body, such as into an organ of interest.

[0074] The catheter 2, e.g., an elongated catheter body, typically includes a central channel (or, more accurately, a central channel formed by a surrounding tube). The catheter 2 may include multiple channels, e.g., so that the device can be used for multiple functions simultaneously (or concurrently), wherein the different functions are provided by adapting different channels. For example, another channel may be adapted to inject or extract fluid into the body, to guide an optical fiber for in vivo measurements mediated by optical phenomena (e.g., transduction), etc. However, in a preferred embodiment, the catheter 2 includes a single channel, e.g., a cylindrical body (but not limited to other elongated shapes, such as an elongated prism or having a non-uniform cross-sectional shape; e.g., a flexible catheter can be deformed into many non-standard shapes) without cross-sectional partitions (e.g., radial compartments, angular compartments). The diameter of the catheter is preferably as small as possible, so that implementing multiple channels in the device may not be optimal. However, depending on the application, the possibility of implementing additional functions may offset the disadvantages of the increased diameter, e.g., especially when the alternative is to insert another catheter into the body.

[0075] The diameter of the tube 2 may correspond to the Birmingham wire gauge (stub steel wire gauge), in the range of 21G to 26G, preferably in the range of 22G to 24G, for example 23G ("G" refers only to the conventional "gauge" in the art, not to the conventional unit of measurement). In other words, the nominal outer diameter of the tube may be in the range of 463 μm to 820 μm, preferably in the range of 717 μm to 566 μm, for example in the range of 0.63 to 0.65 mm (for example 641 μm, for example 641.4 μm).

[0076] The tube 2 has a distal end that is closed and intended to be inserted into the body; and a proximal end (different from the first end) that is intended to remain outside the body during normal use of the device, for example at which the tube can be docked with a connector. The terms "distal end" and "proximal end" are used only to distinguish these ends and do not imply any other characteristics described otherwise.

[0077] The tube 2 may be composed of or include a medical-grade material (e.g., a medical-grade polymeric material). In particular, such medical-grade materials may be inert or substantially inert and non-reactive or substantially non-reactive to body fluids and, preferably, other fluids to which they may be exposed during normal use. Such materials may include silicone rubber materials, nylon materials, polyurethane materials, polyvinyl chloride materials, polyethylene terephthalate (PET) materials, latex materials, and / or thermoplastic elastomer materials. For example, the tube may be composed of or include silicone, which is advantageously inert and non-reactive.

[0078] The silicone rubber material may be or include polydimethylsiloxane (PDMS; also known as dimethylpolysiloxane). A suitable biomedical-grade elastomeric material is commercially available under the name Dow Corning Silicone Rubber Q7-4750. Another preferred material may be polyimide and / or polyurethane. The tubing may be specially treated, such as platinum curing, to improve (enhance) biomedical compatibility.

[0079] The tube may be a composite (or combination) of multiple materials, such as a bulk material (e.g., the materials mentioned above), such as silicone and / or natural latex, and a coating applied to at least the outer surface (external surface; radially outward) of the tube. Such a coating may, for example, consist of or include polytetrafluoroethylene and / or a hydrogel and / or a silicone elastomer. The coating may be or include a hydrophilic surface coating to form a slippery film layer when wetted, thereby making the tube easier and safer to insert into the body.

[0080] In general, the tube material, materials and / or coating(s) may include a wide range of materials, such as polymeric materials, which to date have good biocompatibility when exposed to blood and / or interstitial fluids.

[0081] The tube may be a flexible tube, such as a soft catheter as is known in the art. Even though the tube may be considered flexible, the specific stiffness of the tube may vary across embodiments, for example, depending on the specific requirements for the intended application. Furthermore, because the tube preferably has a small diameter, for example to avoid or reduce potential damage to the body, the stiffness of the tube may be less than optimal, which may be increased by the wire and / or material filling the tube, as described below. Note that the length of the tube 2 may be greater than Figure 1 The length illustrated in FIG is much longer (as shown by the dashed line), and the flexibility of the tube is likely exaggerated in the bend shown.

[0082] Device 1 includes at least one resistive temperature sensor 3, i.e., a temperature sensor comprising an electrical conductor 11 (further referred to as a thermal resistor 11) having a temperature-dependent resistance such that the temperature of the conductor (e.g., assuming it is in thermal equilibrium with its environment) can be determined by measuring the resistance of the electrical conductor. For example, the resistive temperature sensor (or at least one of the resistive temperature sensors, e.g., each of the resistive temperature sensors) can be (or can include) a thermal resistor or a resistance temperature detector (RTD). The (or each) resistive temperature sensor 3 includes a first terminal 12 and a second terminal 13 (i.e., an electrical connection point) between which the temperature-dependent resistance is measured. For example, terminals 12, 13 can be pads to which wires can be soldered.

[0083] Specifically, the resistive temperature sensor may be (or may include) a thermal resistor 11. The thermal resistor 11 may be a platinum resistor, for example, composed of platinum or a platinum alloy. The platinum material may be substantially pure or may be doped to adjust its properties. The advantage of platinum is that it has a sufficiently strong and stable (e.g., repeatable) resistance-temperature relationship, which has good linear behavior near body temperature. In addition, platinum is inert in the human body, for example, it is biocompatible and hypoallergenic.

[0084] The thermal resistor may have a resistance of approximately 1000Ω (e.g., 1 kΩ) (e.g., at a specific reference temperature and ignoring normal tolerances in manufacturing). For example, the resistive temperature sensor 3 may be a PT1000 sensor. However, the thermal resistor according to embodiments of the present invention may also have a different value, such as approximately 100Ω (e.g., 0.1 kΩ), or any value, such as in the range of 10Ω to 10,000Ω, preferably in the range of 50Ω to 5 kΩ (at temperatures in the range of interest, such as reference body temperature).

[0085] The thermal resistor 11 may include a conductive (e.g., metal) trace on a substrate. Specifically, in a preferred embodiment, the substrate may be a thin film substrate. For example, the thickness of the thin film substrate may be in the range of 25 μm to 250 μm, preferably in the range of 75 μm to 125 μm, for example, about 100 μm.

[0086] For example, thin film lithography can be used to manufacture the thermal resistor. Thus, the thermal resistor can be formed by depositing a conductive material, such as a metal (e.g. platinum), on a thinned semiconductor substrate (e.g., a thinned silicon wafer) and patterning it into traces using high-resolution lithography techniques. For example, the layer of conductive material in which and from which the resistive element is formed may have a thickness of only 1 nm to 100 nm, for example, even in the range of 1 nm to 10 nm. The thermal resistor can be manufactured using deep reactive ion etching, for example, to precisely define the shape of the thermal resistor element. The dimensions of the thermal resistor (i.e., referring to the thickness, width and length of the substrate providing the resistive element) can be dimensioned to suit the tube 2, for example, the thickness being substantially determined by the thickness of the thin film substrate, for example 100 μm, and the width being in the range of 100 μm to 700 μm, for example, in the range of 100 μm to 350 μm, for example, in the range of 150 μm to 250 μm, for example 190 μm. The length of the thermal resistor 11 can be determined essentially by the length of the conductive trace required to achieve the desired resistance. In order to measure the temperature at a specific location in the body, i.e., to achieve a high spatial resolution of the temperature measurement, the length of the thermal resistor 11 is preferably as short as possible, while still providing sufficient resistance and temperature dependence. For example, the length (of the substrate) can be in the range of 1 mm to 10 mm, for example in the range of 2 mm to 5 mm, for example 3 mm. The thermal resistor 11 can be an elongated (thin; long) conductor arranged in a meandering pattern, for example as Figure 1 "Snag" means following a winding and / or complex path, for example, whereby the length of the thermal resistor is large compared to the area of ​​the convex outer shell of the thermal resistor.

[0087] For example, the thermal resistor 11 may comprise a thin, curved platinum track having a thickness and width of approximately 10 μm. Such a thin, curved platinum track can be manufactured using a lift-off process and physical vapor deposition, as described, for example, by Ceyssens et al., "Extracellular matrix proteins as temporary coatings for thin-film neural implants," Journal of Neural Engineering, 14.1 (2017): 014001. Furthermore, in the case where polyimide is used as a substrate in this prior art document, the same approach, if not similar, can also be applied to a thinned silicon substrate. For example, a thinned silicon substrate may not be as flexible as a polyimide, which can advantageously improve the stability of the thermal resistor under different mechanical loading conditions.

[0088] The thermal resistor may include an additional biocompatible insulating layer, such as an oxide, nitrite, and / or polymer (e.g., a polyparaxylene polymer, such as parylene-C), deposited on the resistor and / or substrate for passivation and / or electrical isolation, for example, to prevent current from flowing to the human or animal body. In addition, such layer(s) may reduce the amount of water vapor and / or body fluids that diffuse through the package to the electroactive device. The layer(s) may also act as a solder mask to prevent solder reflow on the resistor. Such layer(s) may be deposited by physical vapor deposition, such as radio frequency plasma driven sputtering, atomic layer deposition, chemical vapor deposition, or other suitable techniques known in the art.

[0089] The device includes a plurality of wires 4 (a plurality of leads) extending from the proximal end of the tube through the tube 2 (which is intended to remain outside the body during normal use of the device) to and connected to at least one resistive temperature sensor 3. The wires 4 (e.g., each of them) can be composed of (and can include) a suitable conductive metal, such as a highly conductive metal. The wires can be insulated wires, for example, and can include a conductive core material within an electrically insulating sheath material. The electrically insulating sheath (or additional sheath material) can also be adapted to prevent the conductive core material from diffusing out of the wire. The electrically insulating sheath can include (or consist of) polyimide. Each wire can be coated with another material to form an insulation (dielectric) and / or biocompatibility-enhancing layer, for example, to form a moisture and / or diffusion barrier, such as a polyparaxylene polymer, for example, polyparaxylene-C.

[0090] refer to Figure 5 , the wires can be arranged on the back side of the substrate of the temperature sensor(s) 3, i.e., on the side opposite to the side of the substrate where the thermal resistor is located. In other words, the thermal resistor 11 can be covered by the wires, for example, such as to not interfere with heat exchange with the surrounding tissue (e.g., via heat conduction through the tube and optionally the filling material in the tube) and / or to avoid inductive interference with the resistor and / or to protect the thermal resistor (e.g., formed by a thin metal layer) from mechanical damage. It should be clear that "arranged on the back side" should be interpreted as "substantially arranged on the back side", and likewise, "not covered" should be interpreted as "substantially not covered", i.e., a small area can be allowed on the front side where the wires are connected to the terminals 12, 13.

[0091] For example, the wire may comprise copper, gold, platinum, aluminum, and / or other suitable metals. The advantage of gold and / or platinum (or their alloys) wires is that good biocompatibility and medical-grade safety can be achieved. The advantage of copper (or its alloys) wires is that good electrical conductivity can be obtained at a lower cost. The tube material, the coating or sheath of the wire, and / or the layer covering the contact points (i.e., where the connection is made between one or more wires and the terminals of the resistive temperature sensor 3) may be adapted to prevent the wire material (e.g., copper) from diffusing into the human or animal body when the device is inserted into the human body, i.e., to ensure biocompatibility and safety.

[0092] The diameter of the conductors of the plurality of electrical wires may be in the range of 10 μm to 100 μm, for example in the range of 30 μm to 80 μm, preferably in the range of 40 μm to 60 μm, such as 49 μm, 50 μm or 51 μm. For example, (for example, each) electrical wire may comprise a copper core having a diameter of 45 μm, insulated by a sheath layer (for example a polyimide layer) having a thickness of 2 μm.

[0093] The conductors of the plurality of electrical wires are preferably twisted around one another, e.g., loosely wound, e.g., configured as a spiral about a common axis, to reduce the effects of inductively induced electromagnetic noise, e.g., by substantially nulling the area between the conductors. Additionally, twisting the conductors may also advantageously avoid strain on the conductors when the tube is bent.

[0094] Each of the two terminals of the at least one (or each) resistance temperature sensor 3 is directly connected to at least one wire, for example, by welding. Preferably, at least one of the two terminals of the at least one (or each) resistance temperature sensor 3 can be directly connected (e.g., welded) to at least two wires, so as to allow the (each) resistance temperature sensor to be read using a three-wire readout configuration known in the art. More preferably, each of the two terminals of the at least one (or each) resistance temperature sensor 3 can be directly connected (e.g., welded) to at least two wires, so as to allow the (each) resistance temperature sensor to be read using a four-wire readout configuration known in the art. In this four-wire readout technique, a first pair of wires, respectively connected to the first and second terminals of the resistance temperature sensor, conducts a current through a resistor, and a corresponding voltage difference across the resistor is measured between a second pair of wires, respectively connected to the two terminals. This advantageously allows for highly accurate measurement of resistance, and therefore temperature, that is independent of variations in wire resistance.

[0095] As is generally known in the art, in a three-wire readout configuration for an RTD, two wires are connected to one terminal of a resistive temperature sensor, and a third wire is connected to the other terminal of the resistive temperature sensor. In this configuration, it is known that the resistances of the three wires are substantially equal to one another (e.g., having the same length and the same properties, such as diameter, conductivity, material, etc.). Therefore, the total resistance of the sensor, the third wire, and the first wire can be measured, or additionally or alternatively, the total resistance of the sensor, the third wire, and the second wire can be measured. Furthermore, the total resistance of the first wire and the second wire can also be measured, thereby knowing the (equal) resistance of (each) wire. Therefore, the resistance of the sensor can be determined. This approach allows compensation for the resistance of the leads, but only under the assumption that the resistances of the three wires are equal.

[0096] In a four-wire readout configuration for an RTD, as is generally known in the art, two wires are connected to one terminal of the resistive temperature sensor, and two wires are connected to the other terminal of the resistive temperature sensor. One pair of wires (connected to the first and second terminals, respectively) can be used to transmit a current for measurement (e.g., a constant and known current), and the other pair of wires can be used to measure a corresponding voltage drop across the resistive sensor.

[0097] refer to Figure 3 , the plurality of electrical wires 4 may include a first plurality of conductors 41, 43 for connecting the plurality of resistance temperature sensors 3 in series so that a current I flows through the plurality of resistance temperature sensors 3 when the device is in operation. Therefore, the first plurality of conductors 41, 43 include a first conductor extending from the proximal end of the tube (e.g., from a connector) to a first terminal of a first resistance temperature sensor in the series, a second conductor extending from the proximal end of the tube (e.g., from a connector) to a second terminal of a last resistance temperature sensor in the series, and a plurality of conductor segments 43, each of which connects the second terminal of a preceding resistance temperature sensor in the series to the first terminal of a next resistance temperature sensor in the series.

[0098] Furthermore, the plurality of electrical wires 4 may include a second plurality of conductors 42 (different from the first plurality of conductors) for measuring the voltage difference between a pair of terminals of each sensor 3. However, to reduce the number of conductors required to pass through the tube (particularly simultaneously through any cross-section of the tube), the voltage difference between the second terminal of a sensor and the first terminal of the next sensor connected in series can be neglected. Because the aforementioned conductor segments for the series sensor pairs may be relatively short, the resistance of these segments can advantageously be neglected. Thus, the second plurality of conductors 42 may include (e.g., consist of) a first conductor extending from the proximal end of the tube (e.g., from a connector) to the first terminal of the first resistance temperature sensor in the series, a second conductor extending from the proximal end of the tube (e.g., from a connector) to the second terminal of the last resistance temperature sensor in the series, and a plurality of conductors extending from the proximal end of the tube (e.g., from a connector) to each conductor segment 43 (or any terminal to which a conductor segment is connected). Because the distance between adjacent sensors is negligible compared to the longer lead wires between the proximal end of the tube and the first sensor in the series, this approach can provide an advantageous way to compensate for the resistance of the longer lead wire sections (which may vary with environmental factors such as temperature) while ignoring the potential effects of shorter wire segments, thereby reducing the total number of wires passing through the longer lead wire sections of the tube. In other words, good accuracy can be achieved for n sensors in the tube without requiring 3.n or 4.n wires. For example, in this approach, n+3 wires are sufficient to obtain accurate and robust measurements.

[0099] Furthermore, the device may include a structural wire 5 within the tube 2 (e.g., within the tube and extending along a substantial portion of the tube, such as its entire length) to increase the axial stiffness of the device (tube), for example, while substantially maintaining its low bending stiffness. The structural wire 5 may provide some stiffness to the tube (i.e., a "structural" wire may refer to a wire that provides some axial stiffness to the device) while still allowing the tube to bend to some extent. The structural wire may be composed of a metal or metal alloy, such as tungsten or a tungsten alloy. For example, the outer diameter of the tube 2 may be in the range of 463 μm to 820 μm, such as 641 μm, while the inner diameter may be in the range of 260 μm to 514 μm, such as approximately 310 μm, approximately 320 μm, or approximately 337 μm. The tube wall thickness may be in the range of 102 μm to 283 μm, such as 152 μm. For tubes made of (or containing) medical-grade silicon, the stiffness of the tube may be negligible. Thus, the structural wire 5 may help provide some stiffness. For example, the thickness (diameter) of the structural wire 5 can be in the range of 40 μm to 150 μm, such as in the range of 60 μm to 100 μm, such as in the range of 70 μm to 90 μm, such as 80 μm. For example, the tube 2 can include a medical-grade silicon material (e.g., PDMS) and can have an outer diameter of approximately 640 μm and an inner diameter of approximately 310 μm, while the structural wire 5 can be a tungsten wire with a diameter of approximately 80 μm. This combination has been found to provide good rigidity, i.e., a good balance of flexibility and rigidity, while having a small outer diameter and providing sufficient internal space to accommodate the sensor(s) and wires.

[0100] The wires 4 may be wound (eg, loosely coaxially wound) and provided along the structure conductor, or the wires 4 may be wound around the structure conductor, eg, the wires forming a helix around the structure conductor as an axis.

[0101] The structural guide wire 5 is preferably composed of a radiopaque (radio-dense) material, e.g., such that ionizing radiation, such as X-rays, is blocked or at least strongly attenuated. Tungsten (or its alloys) may have the following advantages: good elastic properties (Young's modulus, shear modulus, bulk modulus) to provide a certain rigidity to the device; good radiopacity to allow accurate positioning of the tube and its associated sensor(s) within the body using X-ray fluoroscopy (e.g., real-time motion images obtained by radiography); and good biocompatibility.

[0102] The device 2 may include at least one filling material 6 that fills the tube 2 (filling the space within the tube not occupied by the other features described above). For example, the filling material may include a deformable filling material, which may be a silicone rubber material, a nylon material, a polyurethane material, a polyvinyl chloride material, a polyethylene terephthalate (PET) material, a latex material, and / or a thermoplastic elastomer material. For example, the deformable filter material may be composed of silicone, or may include silicone, which is advantageously inert and non-reactive. The filling material may be or may include PDMS and / or polyimide and / or polyurethane. The filling material may be composed of or include a material similar to or identical to the material constituting the tube 2 (but embodiments are not limited thereto). For example, the filling material may include an optically transparent low-consistency silicone elastomer, such as the MED 6015 product commercially available from NuSil Technology LLC (USA).

[0103] The filler can advantageously ensure that the distance between the one or more temperature sensors in the tube remains fixed and can provide good thermal conductivity between the temperature sensor(s) and surrounding tissue when the device is inserted into the body. Furthermore, the filler can reduce the flexibility of the tube, making it easier to insert into the body, can improve the electrical insulation of components in the device, and / or can improve the biosafety of the device.

[0104] Different cross sections of the tube (in the longitudinal direction) may be filled with different filling materials, for example to provide different bending stiffnesses to the different cross sections.

[0105] refer to Figure 4 , the device 1 may comprise another tube 20 in which and / or through which the tube 2 is inserted. Thus, the other tube 20 may have a larger diameter than the tube 2 and may be more rigid than the tube 2, for example to help guide the tube through the needle hole.

[0106] The device may include a connector 21 located at the proximal end of the tube for electrically connecting the plurality of wires 4 to an external readout device 30 for reading the sensor(s), such as a cable-mounted plug connector. The connector may be a push-pull type connector, i.e., a push-pull cable-mounted plug. The connector may include solder pins for connecting (soldering) the wires. The connector may be composed of (or may include) plastic material(s). Preferably, the connector is temperature resistant, for example, to withstand autoclave sterilization (e.g., in accordance with IEC 60601-1). Preferably, the connector is waterproof, for example, to withstand fluid ingress in both mated and unmated conditions (e.g., in accordance with IP68). Preferably, the connector has a high insulation resistance, for example, at least 10 MΩ, for example, at least 100 MΩ. For example, the connector may include a circular connector, such as the JMX series connector commercially available from Souriau SAS (France), for example, the 6-pin JMXFH1G06MSUDSU connector. The connector may include a push-pull plastic plug with a sealed cable gland backshell.

[0107] The device 1, such as the connector, may also include an integrated circuit for storing data and for providing this data to the readout device 30 via the connector when connected. For example, the integrated circuit may be adapted to store identification information, such as a unique identification number or tag, and / or calibration information, such as information for the sensor or each sensor, and / or sterilization information, such as to store the sterilization time and / or parameters used during the sterilization process, such as identification of the operator or device used for sterilization, a sterilization protocol identifier, sterilization temperature, sterilization duration, etc. The integrated circuit may also be adapted to store this information in a writable memory, such as received from the calibration unit. The integrated circuit (writable memory) may be a programmable read-only memory (i.e., write-once only), for example, to protect the integrity of the stored information, although other types of memory, such as flash memory, may also be used in other embodiments. For example, the integrated circuit may be adapted to record temperature readings, such as to maintain a record of temperature measurements taken during a procedure and / or other relevant information, such as manufacturing data, packaging data, sterilization data, etc.

[0108] The connector may include a readout circuit 30, for example connected to the second plurality of conductors 42 in a differential readout arrangement, and a plurality of operational amplifiers 31 that may provide processed readout data to an external device. However, such a readout circuit 30 may also be integrated in an external readout device instead of the connector, or the functionality of the readout circuit may be split between components integrated in the device 1 and components integrated in the external device.

[0109] The device 1 may include an overmolded strain relief 22 to relieve stress and / or tension between the (eg rigid) connector and the flexible pipe 2 and / or the further pipe 20 .

[0110] The device 1 may also include (optical fibers) to deliver optical signals (e.g., provided via the proximal end of the device) to the organ or tissue, for example, via a transparent tube segment at its distal end (but not limited thereto), and to collect return optical signals from the organ or tissue. The return optical signal may be transmitted and / or reflected by the organ or tissue, for example, by refraction, diffraction, attenuation, scattering, and / or changed by interaction with the organ tissue. Thus, in addition to temperature, one or more other physiological parameters of the organ or tissue may be monitored via (optical fibers). For example, the spectral characteristics of the organ or tissue may be monitored. For example, one or more other physiological parameters may include oxygenation, such as the level of oxygenated and / or deoxygenated hemoglobin. The device may include one or more other optical components, such as gratings, couplers, microlenses, reflectors, beam splitters, etc., as known in the art.

[0111] Various embodiments of the present invention may relate to a kit comprising the device 1 as described above and a needle for piercing the skin and / or an introducer sleeve for inserting the tube 2 into the body through skin puncture.

[0112] Various embodiments of the present invention may be directed to a system (e.g., a kit) comprising a device 1 as described above and a readout device 30 configured to provide a temperature value based on current and / or voltage measured via a plurality of wires 4. The readout device may be adapted to receive calibration data from an integrated circuit within the device and to take this calibration data into account when determining the temperature value. The readout device may be adapted to periodically determine the temperature value, for example, to monitor changes in body temperature over time. The readout device 30 may include a plurality of operational amplifiers 31, which, when the device is in operation, are connected to a second plurality of wires 42 in a differential readout arrangement, for example, via connector 21, and may provide processed readout data, for example, as a digital signal or via a display. The readout device 30 may also include a current source 32, for example, a regulated current source, adapted to maintain a substantially constant current through the first plurality of wires 41. As is known in the art, other features of such a readout device that would be apparent to a skilled artisan may be included, such as a readout bridge arrangement, an analog-to-digital converter, a digital communication device, a power supply, and / or a user interface.

[0113] The system may typically be a system for monitoring the function of an organ (e.g., a liver) in a human or animal body, wherein the device 1 is adapted to be inserted into the organ and collect data related to one or more physiological parameters of the organ, including one or more temperatures in the organ. Other physiological parameters may also be monitored, for example, via optical fiber(s). For example, the readout device may include an optical fiber, a light source (e.g., one or more laser diodes), and / or a photodetector.

[0114] In another aspect, the present invention relates to a method for manufacturing an apparatus according to an embodiment of the first aspect of the present invention. The method comprises manufacturing or obtaining one or more resistive temperature sensors 3, wherein each resistive temperature sensor comprises an elongated conductive metal trace on a thin film substrate. The metal trace is arranged in a meandering pattern between two electrical connection terminals. The method comprises connecting a plurality of wires 4 to the one or more resistive temperature sensors (3), for example via the electrical connection terminals. The method comprises inserting the one or more resistive temperature sensors and the plurality of wires into a catheter 2 such that at least some of the wires remain accessible at the proximal end of the tube. The method comprises mechanically connecting a connector 21 to the proximal end of the tube and electrically connecting the connector to the plurality of wires such that an external device for reading the sensor(s) can be operably connected to the one or more resistive temperature sensors via the connector 21. The method may further comprise inserting a structural wire into the tube to reduce its flexibility. The method may further comprise winding the plurality of wires in a spiral structure, possibly around the structural wire (but not limited thereto). The method may further comprise filling the tube with a filler material after the assembly is inserted into the tube.

[0115] Further features of the method according to embodiments of the present invention or details of the features described above should be clear in view of the description provided above in relation to the apparatus according to embodiments of the present invention, and vice versa.

Claims

1. A device (1) for measuring the temperature in or at one or more locations on an organ or tissue in a human or animal body, the device comprising: a catheter (2) having a distal end and a proximal end, wherein the distal end is adapted to be inserted into or onto an organ or tissue in the body, and the proximal end is adapted to remain outside the body when the device is in use, - at least one resistive temperature sensor (3) in said tube, - a plurality of electrical wires (4) in the tube, connected to the at least one resistive temperature sensor (3), and - a connector (21) at the proximal end of the tube (2) for electrically connecting at least some of the plurality of wires (4) to an external device, wherein the resistive temperature sensor (3) comprises a thermal resistor (11) and a first terminal (12) and a second terminal (13), between which a temperature-dependent resistance of the thermal resistor can be measured, wherein each of the two terminals (12, 13) of the resistive temperature sensor (3) is directly connected to at least one of the plurality of wires (4), wherein the plurality of wires (4) in the tube is n+3 wires (4) for n sensors (3) in the tube, wherein the at least one resistive temperature sensor (3) is a plurality of resistive temperature sensors, and A first plurality of electrical wires (41, 43) connects the plurality of resistance temperature sensors (3) in series to allow current to flow through the plurality of resistance temperature sensors when the device is in operation.

2. The device according to claim 1, wherein The electric wires (4) are wound around each other in a spiral shape.

3. The device according to any one of the preceding claims, characterized in that The thermal resistor (11) is a platinum resistor, and wherein the platinum resistor is a PT100 resistor or a PT1000 resistor.

4. The device according to any one of claims 1 to 3, characterized in that The resistive temperature sensor (3) comprises a thin film substrate, and wherein the thermal resistor (11) is an elongated conductive metal trace arranged in a meandering pattern on the substrate.

5. The device according to any one of claims 1 to 3, characterized in that The thickness of the resistive temperature sensor (3) is in the range of 50 μm to 150 μm, the width is in the range of 100 μm to 700 μm, and the length is in the range of 1 mm to 10 mm, wherein the diameter of the wire (4) is in the range of 10 μm to 100 μm, wherein the outer diameter of the conduit (2) is in the range of 463 μm to 820 μm, and the inner diameter is in the range of 260 μm to 514 μm.

6. The device according to claim 5, characterized in that The diameter of the electric wire (4) is in the range of 30 μm to 80 μm.

7. The device according to any one of claims 1 to 3, characterized in that The first plurality of wires includes the following: - a first wire from said proximal end of said tube to a first terminal of a first resistive temperature sensor in the series, - a second wire from the proximal end of the tube to the second terminal of the last resistive temperature sensor in the series, and - a plurality of wire segments (43), each wire segment connecting the second terminal of a preceding resistive temperature sensor in the series to the first terminal of a next resistive temperature sensor in the series.

8. The device according to claim 7, characterized in that At least one of the two terminals (12, 13) of each resistive temperature sensor (3) is directly connected to at least two of the plurality of wires extending from the proximal end of the tube (2) to allow the resistive temperature sensors to be read using a three-wire or four-wire readout configuration.

9. The device according to claim 7, characterized in that A second plurality of wires (42) for measuring voltage differences extends from the proximal end of the tube (2) and is connected to the plurality of resistive temperature sensors (3), the second plurality of wires comprising the following: - a first wire extending from the proximal end of the tube to connect to the first terminal of the first resistive temperature sensor in the series, - a second wire extending from the proximal end of the tube to connect to the second terminal of the last resistive temperature sensor in the series, and - a plurality of wires extending from the proximal end of the tube to be respectively connected to each of the wire segments (43) or terminals to which the wire segments are connected.

10. The device according to any one of claims 1 to 3, characterized in that A structural wire (5) is included in the tube (2) to increase the axial stiffness of the tube (2), and / or a filler material (6) is filled in the tube (2).

11. The device according to claim 10, characterized in that The structural wire (5) consists of tungsten or a tungsten alloy and / or has a thickness in the range of 40 μm to 150 μm.

12. The device according to any one of claims 1 to 3, characterized in that An integrated circuit for storing data is operatively connected to the connector (21) to provide the data to the external device when connected, wherein the data includes identification information and / or calibration information and / or sterilization information and / or sensor recording information.

13. The device according to any one of claims 1 to 3, characterized in that It also includes at least one optical fiber to transmit optical signals to the organ or tissue when the device is in use and to collect return optical signals from the organ or tissue, so that in addition to temperature, one or more other physiological parameters of the organ or tissue can be monitored via the optical fiber.

14. A kit comprising the device (1) according to any one of the preceding claims, and one or more of the following: - a needle for piercing the skin, - a guide sleeve for inserting the tube (2) into the body through skin puncture, - a readout device (30) for providing a temperature value based on the current and / or voltage measured by means of the plurality of electrical wires (4) when the readout device is operatively connected to the connector (21).

15. A method for manufacturing the apparatus of any one of claims 1 to 13, the method comprising: - manufacturing or obtaining one or more resistive temperature sensors (3), each resistive temperature sensor comprising an elongated conductive metal trace on a thin film substrate, the metal trace being arranged in a meandering pattern between a first terminal (12) and a second terminal (13), - connecting a plurality of electrical wires (4) to the one or more resistive temperature sensors (3), - inserting the one or more resistive temperature sensors and the plurality of electrical wires into a catheter (2) such that at least some of the electrical wires remain accessible at the proximal end of the tube, and - mechanically connecting a connector (21) to the proximal end of the tube and electrically connecting the connector to the plurality of wires such that an external device can be operatively connected to the one or more resistive temperature sensors via the connector (21).

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