Conductivity sensor system and device with real-time feedback - Patents.com

Abstract

A real-time impedance measurement needle system having a hollow needle for administering a medical fluid having a distal end and a proximal end, the hollow needle including an opening configured to receive the medical fluid through a fluid channel. The system may also have at least two conductors located at the distal end of the needle near the opening configured to deliver the medical fluid, and at least one detector configured to sense a current flowing between the at least two conductors through biological tissue.

Description

[Technical field]

[0001] <CROSS REFERENCE TO RELATED APPLICATIONS> This application claims the benefit of U.S. Provisional Application No. 63 / 191,723, filed May 21, 2021, and entitled “REAL-TIME FEEDBACK OF RESISTANCE / IMPEDENCE.”

[0002] The aforementioned patent applications are incorporated herein by reference, and such incorporation is limited such that no subject matter contrary to the express disclosure herein is incorporated. Any incorporation by reference of the above documents is further limited such that the claims contained therein are not incorporated herein by reference. Any incorporation by reference of the above documents is further limited such that any definitions provided herein are not incorporated herein by reference, unless expressly included herein.

[0003] <Technical field> The present disclosure relates to needles having sensors that are useful for real-time feedback in medical procedures on various tissues. [Background technology]

[0004] Efforts to improve surgical outcomes and cost structures, especially in spinal surgery or dental procedures, have led to the increased use of minimally invasive procedures. These procedures often use image-guided modalities such as fluoroscopy, CT, neurostimulators, and more recently Doppler ultrasound. While often involving fewer risks than surgery, minimally invasive spinal procedures, pain management procedures, nerve blocks, ultrasound-guided interventions, biopsies, and percutaneous or intraoperative open placements, they continue to involve the risk of ineffective outcomes and iatrogenic injury, such as infection, stroke, paralysis, and death due to penetration of various structures, including but not limited to organs such as the spinal cord, soft tissues, vascular structures, and neural tissues. Because surgical instruments must progress through several layers of body tissues and fluids to reach the desired space within the spinal canal, injury can occur regardless of the surgeon's experience.

[0005] To illustrate, the intrathecal (or subarachnoid) space of the spinal cord region, where many drugs are administered, contains the nerve roots and cerebrospinal fluid (CSF) and is located between two of the three membranes that encase the central nervous system. The outermost membrane of the central nervous system is the dura mater, the second outermost membrane is the arachnoid mater, and the third outermost and innermost membrane is the pia mater. The intraarachnoid space is between the arachnoid mater and the pia mater. To reach this area, surgical instruments may first need to pass through a skin layer, a fat layer, an interspinous ligament, a yellow ligament, the epidural space, the dura mater, the subarachnoid space, and the intraarachnoid space. Furthermore, for needles used to administer drugs, the entire needle opening must be within the subarachnoid space.

[0006] Due to the complications involved in inserting surgical instruments into the intrathecal space, penetration of the spinal cord and nerve tissue is a known complication of minimally invasive spinal procedures and spinal surgery. In addition, some procedures require the use of larger surgical instruments. For example, spinal cord stimulation is a form of minimally invasive spinal procedure in which small wire leads can be inserted into the spinal epidural space, and may require the introduction of a 14-gauge needle into the epidural space to thread the stimulator lead. Needles of this gauge are technically more difficult to control and carry a higher risk of morbidity. Complications may include dural disruption, spinal fluid leak, epidural vein rupture with subsequent hematoma, and direct penetration of the spinal cord or nerve with resultant paralysis. These and other high-risk situations, such as spinal interventions and radiofrequency ablations, may occur when the physician is unable to detect the placement of the needle or surgical device tip in critical anatomical structures.

[0007] Currently, detection of such structures is operator-dependent, with operators utilizing tactile sensation, contrast agents, anatomical landmark palpation, and visualization under image-guided modalities. Patient safety may depend on the physician's training and experience in tactile sensation and image interpretation. Although additional training and experience may aid the physician, iatrogenic damage may occur regardless of the physician's experience and skill due to anatomical variations that may arise naturally or from repeated procedures in the form of scar tissue. Fellowship training in some procedures, such as radiofrequency ablation, may not be rigorous enough to ensure competency. Even with training, the outcome of the procedure may vary considerably. In the case of epidural injections and spinal surgery, variability in the thickness of the yellow ligament, width of the epidural space, dural expansion, epidural lipomatosis, dural septum, and scar tissue may all add challenges to traditional verification methods, even for experienced operators. In addition, repeating radiofrequency procedures, often performed a year or more later when the nerves regenerate, is often less effective and more difficult because the distribution of the nerves after regeneration creates additional anatomical variations. Summary of the Invention

[0008] An electrically conductive sensor system is disclosed that provides a physician with real-time feedback regarding the type of tissue that a hollow needle tip is in contact with prior to injection of a medical fluid, which may be useful in medical procedures where precise location of placement of medical fluid is desired.

[0009] An electrical resistivity sensor useful for real-time tissue identification is disclosed. The sensor includes a hollow hypodermic needle capable of injecting a medical fluid into biological tissue. An electrical resistivity probe is at least partially encased within the hollow hypodermic needle. The disclosed sensor also includes a conductive tip at one end of the electrical resistivity probe. The disclosed sensor is useful for real-time tissue identification during a medical procedure. The disclosed sensor may further include a syringe for delivering the medical fluid to the hollow hypodermic needle. In some embodiments, the sensor may include two or four electrical resistivity probes all partially encased in the needle.

[0010] The present disclosure may be useful for measuring over 21 different types of tissue or biological material with different impedances. Using the unique natural structure of biological materials, sensors and conductors may be arranged in an advantageous manner to enable impedance measurements across biological tissue to help identify potential needle injection sites. The system may further include electrical components to measure resistance and determine voltage, and transmit an output to a clinician to read the impedance level or measurement and determine if the needle is in the correct location before delivering fluid or medicine to the patient.

[0011] In another aspect, a method of retracting a fiber optic sensor includes the steps of: A method is disclosed that includes providing a fiber optic sensor retraction system according to the disclosure above. The method further includes inserting a needle including a fiber optic wavelength sensor into a patient and properly positioning the needle using the fiber optic wavelength sensor. The method includes retracting the fiber optic wavelength sensor and then administering a medical fluid through the hollow needle. [Brief description of the drawings]

[0012] [Figure 1] 1 is an illustrative example of an embodiment of a real-time sensor system according to the present disclosure. [Diagram 2] 1 is an illustrative example of an embodiment of a real-time sensor system according to the present disclosure. [Diagram 3] 1 is an illustrative example of a cross-sectional view of an embodiment of a real-time sensor system according to the present disclosure. [Figure 4] 1 is an illustrative example of an embodiment of a leading edge of a real-time sensor system according to the present disclosure. [Diagram 5] 1 is an illustrative example of an embodiment of a leading edge of a real-time sensor system according to the present disclosure. [Figure 6] 1 is an illustrative example of an embodiment of a real-time sensor system according to the present disclosure. [Figure 7]1 is an illustrative example of an embodiment of a real-time sensor system according to the present disclosure. [Figure 8] 1 is an illustrative example of an embodiment of a real-time sensor system according to the present disclosure. [Figure 9] 1 is an illustrative example of an embodiment of a real-time sensor system according to the present disclosure. [Figure 10] 1 is an illustrative example of an embodiment of a real-time sensor system according to the present disclosure. [Figure 11] 1 is an illustrative example of an embodiment of a real-time sensor system according to the present disclosure. [Figure 12] 1 is an illustrative example of an embodiment of a real-time sensor system according to the present disclosure. [Figure 13] 1 is an illustrative example of an embodiment of a real-time sensor system according to the present disclosure. [Figure 14] 1 is an illustrative example of a connection between a fiber and a processing component according to the present disclosure. [Figure 15] 1 is an illustrative example of a circuit for measuring resistance according to the present disclosure. [Figure 16] 1 is an illustrative example of a circuit for measuring resistance using multiple resistors according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present disclosure relates to a real-time impedance measuring needle system used to detect biological materials such as body fluids including blood and tissue. Various embodiments of the real-time impedance measuring needle system are described in detail with reference to the drawings, in which like reference numbers may represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the real-time impedance measuring needle system disclosed herein. Furthermore, any examples described herein are not intended to be limiting, but merely to describe some of the many possible embodiments of the real-time impedance measuring needle system. Various omissions and substitutions of equivalents are contemplated as the situation may suggest or may provide convenience, but it should be understood that these are intended to cover the application or embodiment without departing from the spirit or scope of the present disclosure. It should also be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting.

[0014] Fiber optic waveguides can be placed inside hollow needles that are useful in medical procedures. Proper placement of the needle can be important in the success of medical procedures such as neurological surgical procedures (i.e., spinal surgery) or dental procedures. Fiber optic waveguides can be used as part of a sensor system that can detect important biological structures. For example, when attempting to inject an anesthetic agent into a patient in a dental environment, it may be desirable to avoid injecting the drug into a blood vessel, which can cause an undesirable systemic reaction in the patient. A fiber optic sensor in the injection needle can be part of a detection system that detects iron ions (e.g., in the blood), which may indicate improper placement of the needle. In this case, the needle can be repositioned to properly inject the anesthetic agent. In some embodiments, the sensor can be located level with the needle tip or bevel. This location can allow the sensor to detect blood or other biomarkers at or near the tip of the needle where the drug or fluid will be delivered.

[0015] In another example, a spinal surgeon may want to locate various biological structures when placing a needle for administration of a drug. In these cases, the surgeon may want to locate spinal fluid or avoid other physiological structures. A fiber optic detector can be placed in the needle that can be part of a detection system that can identify biological tissue in contact with the needle opening.

[0016] In normal operation, the surface of the fiber optic waveguide sensor within the hollow needle may be roughly flush with the tip of the needle (such as a Quincke needle). The fiber optic waveguide may be much smaller than the needle bore, allowing injection of a fluid, such as a medication, to pass through the fiber optic waveguide. In some modalities, the entire needle bore may be filled with the fiber optic waveguide. In these cases, the needle may retract or remove the fiber optic waveguide prior to injection of the fluid.

[0017] Removal of the fiber optic waveguide can be done manually by retracting the fiber optic waveguide into the Y-junction of the inductor temporary placement and delivery system until it leaves the needle bore. Manual removal of the fiber optic waveguide can be a critical operation by the surgeon or surgical staff at the exact injection point if needle tip movement is undesirable. Such manual procedures may also require extra time to the overall procedure. In addition, leakage may occur if the delivery system does not include a hard stop for fiber retraction. However, this is unlikely based on an approach that uses a flexible polymer membrane similar to those used on sealed drug bottles or vials.

[0018] FIG. 1 is a diagram of one embodiment of a real-time impedance measurement needle system 100 (referred to herein as the "system"). At the distal end of a hollow needle 104 (e.g., the end opposite the syringe), the tip of the hollow needle 104 can include or be attached to at least two conductors 102. These conductors 102 can be connected through a connection point, such as a flange (not shown), that can maintain an electrical connection with the at least two conductors 102. When the needle tip is placed at a target location on a patient, the at least two conductors 102 can contact the patient's biological tissue. An electric current can then flow between the at least two conductors 102. The sensed signal can then be transmitted further within the system. The hollow needle 104 can be connected to a Y-coupler 106 that can branch into two different directions away from the hollow needle 104. A first branch or arm 136 can communicate an electrical signal via an electrical cable 110. The first branch or arm 136 can also optically communicate an optical signal via a fiber optic cable 112. A hollow needle 136 may be connected to a third branch or arm 138 of the Y coupler for delivering fluid to living tissue.

[0019] In the first arm 136, the electrical cable 110 may connect to a computing device (not shown), such as an electro-optical module or device 118. The connection may be wired or wireless between the Y coupler 106 and the electro-optical device 118 through an electrical connector 116. The electrical connector 116 may connect to the electro-optical device 118, which may include a signal converter 120 (such as analog to digital or digital to analog) and, in some embodiments, a current source 122. After the signal converter 120, the signal may be sent to a resistive output 130. The output at the resistive output 130 may be displayed or communicated as a numerical value to an output display, a light, a sound, a notification, a liver, and combinations thereof, each of which may be indicative of or based on the measured resistance of the biological tissue. There are many different embodiments in which the output may be communicated to be useful to the clinician.

[0020] In one embodiment, the first arm 136 of the Y coupler 106 may also connect to a fiber optic cable 112, which may carry information based on the iron ion content collected from a sensor on the tip of the optical fiber at the tip of the hollow needle 104. The fiber optic cable 112 may transmit the information to an electro-optic device 118. The fiber optic cable 112 may connect to the electro-optic device 118 through a fiber connector 114. The electro-optic device 118 may have a splitter 124 that receives the information via the fiber connector 114. The biomarker information, such as the iron ion content, may then be split by the splitter 124, with a first signal that may be sent to a photodetector 126 and another second signal that may be sent to an LED 128. The photodetector 126 may then transmit the biomarker information to an output display 132. The biomarker content output may be displayed or communicated in a number of ways, such as a number displayed on the output display 132, a light, a sound, a notification, a heart, and combinations thereof, each of which may be indicative of or based on the measured resistance of the biological tissue. There are many different embodiments in which the output may be communicated in a manner that is useful to the clinician.

[0021] If the output indicates the user is in the wrong tissue or detects a particular biological material or tissue that is not desirable for medical fluid delivery, the user may reposition the needle to a different location to further determine a location for medical fluid delivery. If the user determines that the needle location is suitable for delivery, the user may deliver medical fluid to the tissue into which the needle entered. In some embodiments, when the delivery site is suitable for medical fluid injection, the delivery may be automated or a computing device may be controlled. As described herein, the electro-optical device may have more than one embodiment, and the two connections to the first arm are only one of many embodiments capable of transferring at least two types of information.

[0022] The Y coupler 106 can have a second branch where the first arm 136 begins and splits where the second branch or arm 134 connects to the syringe 108. The connection of the second arm 134 can create a continuous fluid channel (not shown) between the syringe 108 and the hollow needle 104 for delivery of the medical fluid within the syringe 108. There are several embodiments of the hollow needle that can be used in coordination with the Y coupler 106, the syringe 108, and the communication system (i.e., the electrical cable 110, the fiber optic cable 112, and other components connected thereto).

[0023] The simplest embodiment disclosed herein can use a spring with a trigger release to quickly withdraw the fiber. This embodiment is shown in FIG. 1 and may incorporate a spring for stored motive force. As shown, a trigger for the release of the spring is provided, as well as a polymer sealing system to maintain sterile integrity and pressure within the system. When the trigger is engaged, the fiber optic waveguide (which may host the electrical cable 110, the fiber optic cable 112, or both) can be instantly withdrawn from the needle with minimal movement of the needle tip.

[0024] More specifically, a first embodiment of a hollow needle, such as hollow needle 200, is shown in FIG. 2. The walls of hollow needle 200 may have a layer. Inside hollow needle 200, conductor 202 can be attached or integrally connected to the inner wall. Conductor 202 may run along hollow needle 200. A layer of outer insulation 206 may be between conductor 202 and the inner wall of hollow needle 200 to help insulate electrical signals. In some embodiments, and as shown in FIG. 2, outer insulation 206 may be a coating or layer on conductor 202 that extends the length of conductor 202. In other embodiments, outer insulation 206 may be a layer or lining of the needle to prevent electrical signals from being transferred to hollow needle 200 and maintaining electrical signals along conductor 202, and thus, outer insulation 206 may be at least where the conductor is and between other metal or conductive materials such as hollow needle 200. An outer insulator 206 may be external to the conductors (i.e., wrapped around the conductors), but is internal to the hollow needle 200 and lines the inner wall of the hollow needle 200, at least where the conductors 202 are located. Such an insulating material may be made of polyimide or a similar material, although other materials are possible for electrical signal isolation. In the illustration of FIG. 2, there are two conductors, but more conductors can be added to the system. In the illustrated embodiment, at least two conductors are located at the needle tip 208 of the hollow needle 200, located at the distal end of the needle.

[0025] The optical fiber (not shown) may be a waveguide that may movably or slidably fit within the lumen of the fluid channel and may further have an optical coupler. In some embodiments, the optical fiber may have an insulating layer, such as an inner insulating layer 204, that runs along the conduction path so that the electrical signal is not affected by any optical fibers that may be disposed inside the hollow needle 200. In some embodiments, the inner insulating layer may be inside the conductor 202, and in other embodiments, the inner insulating layer 204 may be part of an optical fiber outer coating or layer (not shown). In other embodiments, at least two conductors may have an inner insulating layer 204 on the conductor.

[0026] FIG. 3 is a similar view to FIG. 2, but with further details of a hollow needle 300 with an insulating layer. The layer may be from the inner wall of the hollow needle 300 or may be layered on the outer layer, so that the inner means is closer to the inner wall and the outer means is closer to the outer wall. In one embodiment, there may be an inner conductor 310 that senses or collects electrical signals as described herein. A middle insulator 304 may be between the inner conductor 310 and the outer conductor 306. In some embodiments, there may be an inner insulator 302 on the outside of the inside of the inner conductor 310 (not shown) or on the outer edge of the optical fiber (not shown). In some embodiments, there may be an outer insulating layer 308, which is the outermost layer relative to other components in the needle 300, as shown in FIG. 3.

[0027] FIG. 4 is a cross-sectional view of a hollow needle 400 as described herein. FIG. 4 shows the conductor 404 on the outside of the insulator 402. The insulator 402 may coat the optical fiber 406 at the core 408. In some embodiments, the optical fiber 406 (core 408) may not be present within the hollow needle 400. In other embodiments, the optical fiber 406 may have a coating on its outer edge, such as the insulator 402. Thus, the insulator 402 may be a layer or coating on the optical fiber 406, or the insulator 402 may coat the inner wall of the hollow needle 400. In some embodiments, FIG. 4 may be a cross-sectional view of FIGS. 10 and 11 with two conductors on opposite sides of the hollow needle 400.

[0028] FIG. 5 shows a second embodiment of a hollow needle, where the tip of the hollow needle 500 has three or more conductors. In FIG. 5, there are four conductors 502a-d (collectively). Each of the conductors 502a-d may extend or connect to a respective conductive path 504a-d running along the hollow needle 500. There may be a respective conductive path 504 to connect to each of the respective conductors 502, such as conductor 502a connecting to conductive path 504a, conductor 502b connecting to conductive path 504b, conductor 502c connecting to conductive path 504c, and conductor 502d connecting to conductive path 504d. In the embodiment of FIG. 8, metal coatings, electrodes, or conductive pads (802 in FIG. 8) are disposed on the inner wall. The embodiment of FIG. 5 shows conductive paths extending from the respective conductive pads along the hollow needle 500. The paths carry electrical signals to a computing device for signal analysis and resistance determination (see, for example, FIG. 1). FIG. 5 is a cutaway view of a hollow needle 500 (for the system see FIG. 1 showing hollow needle 104).

[0029] FIG. 6 illustrates a third example embodiment of hollow needle 600, in which four conductors 602a-d are configured in an alternative pattern different from FIG. 5. More specifically, in the embodiment of FIG. 6, conductors 602a-d are staggered. The numeral notation "a-d" represents all the numerals in the sequence a, b, c, and d. In this case, each of the respective conductors may extend parallel to hollow needle 600 along hollow needle 600. At least one conductor path 604a-d may connect from conductors 602a-d to a computing device (not shown) for electrical and optical signal communication. In this case, conductor 602a may connect to the computing device via conductor path 604a. Conductor 602b may connect to the computing device via conductor path 604b, conductor 602c may connect via conductor path 604c, and conductor 602d may connect via conductor path 604d, respectively. In some embodiments, hollow needle 600 may have an angled bevel or opening. In this case, the conductors 602a-d may appear misaligned when lining up the angled needle or needle bevel with the aperture.

[0030] FIG. 7 shows a fourth embodiment of a hollow needle 700, which includes an inner layer that includes a conductor 702. In some embodiments, there may be an inner insulating layer 704 between the conductor and the optical fiber to keep the electrical signal on the correct path. The hollow needle 700 may be made of a metal such as stainless steel or other material used in the field of needles. An outer insulating layer 706 between the conductor 702 and the needle wall may be present between the needle and the conductive path to ensure that the electrical signal does not follow a path other than the ground or conductive path.

[0031] FIG. 8 is a cross-sectional view of the inside of a hollow needle (not shown) as discussed herein. The figure shows an embodiment of a needle with four conductor resistance sensors 802a-d, although in some cases less than four sensors are required, such as at least two. In the embodiment of FIG. 8, four conductor resistance sensors 802a-d are shown showing a cross-sectional view with at least four conductors 802a-d. The conductors 802a-d may be metal pads or metal coatings located on or along the exterior of the inner wall of the hollow needle. A layer of insulation 806 may coat the outer wall of the hollow needle. In some embodiments, the fiber 804 may be an optical fiber with an outer insulated coating or layer 806. In some embodiments, the metal coatings 802a-d may be within a layer of insulation 806, while in other embodiments, the metal coatings 802a-d may be at least partially exposed (not shown, but described herein) to contact biological tissue when the hollow needle engages said biological tissue. 8, the metal coatings 802a-d are flush with the exterior of the inner wall. Thus, objects inside the lumen of the hollow needle do not obstruct the metal coatings 802a-d. One such object may include the optical fiber 804.

[0032] FIG. 9 illustrates one embodiment of the optical signal portion of the system described herein (see FIG. 1). The optical fiber 904 may have a core 908 for transmitting light. The outside of the core 908 may include an outer cladding 910 that reflects light back to the core 908. The hollow needle 900 may include an insulating layer 912 that may insulate electrical signals and prevent grounding through the hollow needle 900. Attached to the inner surface of the insulating layer 904 may include at least one conductor 906. FIG. 9 includes four conductors that sense electrical signals from an electrical source (not shown) and transmit to a computing device (not shown). In some examples, the outer wall of the optical fiber 904 may be coated with an insulator or may have a layer of insulator, such as the insulator layer 912, to protect the electrical signal from grounding when the electrical signal is transmitted to a computing device, as described herein (see, e.g., FIG. 1). In some embodiments, the optical fiber 904 may include a fiber cladding 910 and a core 908 that may reflect light back down to the core 908. More specifically, at least a portion of the end of the optical fiber 904 may be coated. The coating on the tip of the optical fiber 904 may be an iron-detecting coating to trigger a response when contacted with ferrous iron.

[0033] FIG. 10 shows another embodiment of the inside of a hollow needle (not shown). In an embodiment, two metal coatings 1002 are shown on either side of an optical fiber 1004. The metal coatings may be conductors or electrodes through which electricity may enter a circuit. Other arrangements of each of the metal coatings 1002 may be possible. An insulating layer 1006 may coat the outside of the optical fiber 1004, leaving each metal coating 1002 at least partially exposed at the tip of the hollow needle (see, e.g., FIGS. 2 and 11) and at the hollow interior portion of the hollow needle. The hollow interior may contain the optical fiber 1004.

[0034] FIG. 11 is another angle of the hollow needle of FIG. 10 and a view of the tip of a hollow needle 1100 that is similar to FIG. 9 except for the two conductor arrangement. In the embodiment of FIG. 11, an optical fiber 1104 is found within the hollow needle 1100. Two conductors 1102 are found on each side of the fiber 1104 and on a layer of insulation 1106. The layer of insulation 1106 may encompass at least a portion of the conductor 1102. In some embodiments, the conductor 1102 may be at least partially exposed such that the conductor 1102 contacts biological tissue to obtain an optical signal. The conductor (or pad) may be a metal coating or conductive portion that transmits an electrical signal or current through that conductive material.

[0035] FIG. 12 shows an example of a four-conductor resistive sensor from FIG. 8. Similar to 802a-d in FIG. 8, conductors 1200 may be located on or next to the outer wall of optical fiber 1202. In some embodiments, conductors 1200 may run along the fiber. Similar to FIGS. 5-6 and 8, four conductors are shown, collectively referred to as "conductors 1200." In FIG. 13, conductive traces 1300 may extend along optical fiber 1302 (see, e.g., 1202). To create a circuit or data continuous data path, arm 1306 may contact one of the conductors or conductive traces 1300 to create a signal path to an electronic or computing device (see electro-optical device 118 in FIG. 1) that receives signals and data from conductor 1200 in FIG. 12. Arm 1306 may be attached to the inner wall or other interior surface of needle 1304.

[0036] FIG. 14 is a diagram of one embodiment of a connection between electrical and optical data to an electro-optical device 1410. An optical fiber 1408 may have at least one conductor 1402, such as the four fiber optic conductors shown. The conductors 1402 are each connected to an electrical connection 1404. In some embodiments, the signals may be transferred wirelessly, and in other embodiments, the signals may be transferred via a wired or optical connection, such as with an electrical interconnect 1406. The optical data from the optical fiber 1408 may be received by the electro-optical device 1410 via a fiber optic connector 1414 and displayed as an output for a user to see or hear. There may be a fixed electronic or optical interconnect to the fiber conductor 1404. The electrical data may be sent and received via an electrical connector 1412 to the electro-optical device 1410, which may use a couple and a processor to measure resistance and communicate a signal or resistance value. The output may be to an LCD display, or may be a tone, light, or other indicator that a user may read or interpret.

[0037] FIG. 15 shows an embodiment of an electrical component circuit that can calculate the resistance across biological tissue. The resistivity of the tissue can be measured between two electrodes on the probe tip that are located a significant distance from an ohmmeter in the electro-optical module. The ohmmeter measures R wire+traces +R tissue +R wire+traces Show [Table 1] Different types of metals have different temperature coefficients. The resistance of an electrical wire may change with temperature. This effect can be noticeable as the room temperature changes. The general formula for the temperature effect on resistance is (at 20 degrees Celsius): Copper=0.00393 Aluminum = 0.004308 Iron=0.005866 Nickel=0.005866 Gold=0.003715 Tungsten = 0.004403 Silver=0.003819

[0038] In one embodiment, two wires may be used with a constant current. Ohm's law defines resistance, "R," as the ratio of the voltage "V" across a component to the current "I" passing through it, or R=V / I. To measure the resistance, a test current may be applied to the wires and the resulting voltage drop detected. From this, the resistance can be calculated.

[0039] 4-wire test method using a constant current source As shown in FIG. 15, a constant current source 1518 is connected to a resistor loop (R1 wire+traces 1504, R2 wire+traces 1508, R tissue 15 shows a constant current source 1518 applied to and through the constant current loop 1501 from a first electrode 1510 and a second electrode 1512. The first electrode 1510 and the second electrode 1512 are disposed on a biological material or tissue 1514. The tissue 1514 has a resistance R that affects the current flowing between the first electrode 1510 and the second electrode 1512. tissue 1516. Resistance R across the biomaterial or tissue 1514 tissue The measurement of 1516 is R1 wire+traces 1504 to one input of the voltmeter 1502, and R2 wire+traces This is accomplished by the electrical signal looping across trace 1508 back to the second electrode 1512. The voltmeter is within the ohmmeter 1500 and the reading across the voltmeter is the reading between the first electrode 1510 and the second electrode 1512, which is the resistance R of the tissue 1514. tissue 1516. Ohmmeter 1500 may be included in the electro-optical device of Figure 1. The terms "trace" or "trace impedance" may be generated from circuit board components and impedance due to materials used.

[0040] Generally, 4-wire measurement can eliminate the effect of fixed resistors (lead wires) to obtain accurate resistance value of tissue resistance. Different tissues have different resistivities, below are some examples of biological tissues and their resistivities: [Table 2]

[0041] In the present invention, R tissue The accuracy of the readings can be improved by moving the voltage measurement point to the end point of the mating pin, thus bypassing any voltage drop that may occur in the lead wires. Because some embodiments use four lead wires instead of two, this approach is referred to as "4-wire measurement," or alternatively, "4-wire Kelvin."

[0042] In some embodiments, the voltmeter 1502 has such a high impedance that the current flowing through the voltage measurement circuitry in a four-wire system is very small, typically on the order of a fraction of a microamp, so there is virtually no voltage drop across these lead wires and negligible effect on the resistance measurement. In summary, if there is no current flowing through the wires, there can be no voltage drop across them. In one embodiment, the voltmeter may be an analog-to-digital converter chip.

[0043] Two-wire test method using a constant voltage source In another embodiment, a constant voltage may be applied to the sensing electrodes and the current drawn is measured. In this embodiment, the circuit is similar to FIG. 15, but the constant current loop 1518 may not be present. Ohm's law defines resistance, "R," as the ratio of the voltage "V" across a component to the current "I" passing through it. R=V ref / I. Therefore, the current draw is: I=V ref / R. Therefore, the resistance is equal to: R=Vref / I.

[0044] 4-terminal bulk resistivity measurement In yet another embodiment, a four-probe method may be used which involves making electrical contact with the material using four equally spaced co-linear probes (known as a four-point probe). Other configurations are suitable depending on geometric space constraints. This electrical impedance measurement technique uses separate pairs of current carrying and voltage sensing electrodes to provide more accurate measurements than the simpler and more common two-terminal sensing. Current may flow between the two outer probes while voltage sensing is performed on the inner probe.

[0045] Separating the current and voltage electrodes eliminates lead and contact resistance from the measurement, which is an advantage for accurate measurement of low resistance values. The alternating current can also be used to measure the impedance of the tissue within the sensor. Additionally, testing at different frequencies can provide more information about the tissue being tested.

[0046] Resistance R0 is the desired tissue resistivity measurement, R1 and R2 are the current loop contact resistances, R3 and R4 are the voltage loop contact resistances, and R5 and R6 are the resistances between the current and voltage loop contacts. Different configurations of resistances are possible.

[0047] FIG. 16 shows a typical technique used to measure bulk resistance with a four-probe technique. In such a technique, there may be four equally spaced, co-linear probes (known as a four-point probe) to make electrical contact with the material. Other embodiments may include additional configurations depending on geometric space constraints. FIG. 16 shows a constant current source 1618 applied to and flowing through a loop from a first electrode 1620, a second electrode 1622, a third electrode 1624, and a fourth electrode 1626. A voltmeter 1602 is within the ohmmeter 1600. Such electrical impedance measurement techniques can make more accurate measurements than simpler two-terminal sensing techniques, using separate pairs of current carrying and voltage sensing electrodes. In a preferred embodiment, current may flow between the two outer probes while voltage sensing is performed on the two inner probes. Separation of the current and voltage electrodes can eliminate lead and contact resistance from the resistance measurement. This can be advantageous for accurate measurement of low resistance values. Resistance R0 1610 is the desired tissue resistivity measurement, R1 and R2 are the current loop contact resistances 1612a and 1612b, respectively. R3 and R4 are the voltage loop contact resistances 1614a and 1614b, respectively. R5 and R6 are the resistance between current loop contact 1616a and voltage loop contact 1616b, respectively.

[0048] Those skilled in the art to which the subject matter of this disclosure and the present specification relates will recognize that an embodiment may include fewer features than those illustrated by way of example or otherwise contemplated herein in any individual embodiment. The embodiments described herein are not intended to be an exhaustive presentation of the ways in which various features may be combined and / or arranged. Thus, the embodiments are not mutually exclusive combinations of features; rather, the embodiments may include combinations of different individual features selected from different individual embodiments, as would be understood by one skilled in the relevant art. Furthermore, unless otherwise stated, elements described with respect to one embodiment may be implemented in other embodiments, even if not described in such embodiment. Although a dependent claim may refer to a specific combination with one or more other claims in the claim, other embodiments may also include a combination of the dependent claim with the subject matter of each other dependent claim, or a combination of one or more features with other dependent or independent claims. Such combinations are suggested herein, unless it is expressly stated that a particular combination is not intended. Moreover, it is intended that any other independent claim include features of that claim, even if that claim is not directly dependent on that independent claim.

Claims

1. A real-time impedance measurement needle system, comprising: a needle having a distal end, a proximal end, and a fluid channel disposed therethrough, wherein the proximal end and the distal end each include an opening; at least two conductors disposed near the opening of the distal end of the needle; at least one detector configured to sense a current flowing through a biological tissue disposed between the at least two conductors.

2. The real-time impedance measurement needle system according to claim 1, wherein the impedance measurement value is derived from the current of the biological tissue disposed between the at least two conductors.

3. The real-time impedance measurement needle system according to claim 1, wherein the current between the at least two conductors is one of a constant current and an alternating current.

4. The real-time impedance measurement needle system according to claim 1, wherein an indicator of the location of the needle is an output of the detector.

5. The real-time impedance measurement needle system according to claim 4, wherein the output varies according to the resistivity of the biological tissue.

6. The real-time impedance measurement needle system according to claim 5, wherein the output further includes a numerical representation based on the resistance of the biological tissue.

7. The real-time impedance measurement needle system according to claim 5, wherein the diameter of the fluid channel is configured to receive an optical fiber.

8. The real-time impedance measurement needle system according to claim 7, wherein the at least two conductors are on both sides of the needle, and the optical fiber is disposed in the fluid channel.

9. The real-time impedance measurement needle system according to claim 8, wherein the optical fiber further includes an iron detection coating.

10. The real-time impedance measurement needle system according to claim 1, further comprising the needle having an inner wall, wherein the at least two conductors are insulated from the inner wall and are attached to or integrated into the inner wall.

11. The real-time impedance measurement needle system according to claim 10, wherein the at least two conductors extend along the inner wall of the needle, form a conduction path from the distal end to the proximal end, and further the conduction path is connected to a computing device.

12. The real-time impedance measurement needle system according to claim 1, wherein the needle has an inner conductor and an outer conductor.

13. The real-time impedance measurement needle system according to claim 7, wherein a second output is based on an optical signal received by the detector via the optical fiber.

14. The real-time impedance measurement needle system according to claim 1, wherein the at least one detector comprises a circuit board including one or more wireless interfaces.

15. A real-time impedance measurement needle system, a needle having a bore, a proximal end, and a lumen disposed therethrough, at least two conductors disposed in the bore, and at least one detector, each detector including at least one processor, and further the at least one detector is configured to sense an electric current in a biological tissue disposed between the at least two conductors. The real-time impedance measurement needle system.

16. The real-time impedance measurement needle system according to claim 15, further comprising a detector having a coupler.

17. A method for measuring tissue impedance in real time, a needle having a distal end, a proximal end, and a fluid channel disposed therethrough, wherein the proximal end and the distal end each include an opening, at least two conductors disposed near the opening at the distal end of the needle, providing at least one detector configured to sense an electric current flowing through a biological tissue disposed between the at least two conductors; inserting the needle into the biological tissue; sensing, using the at least one detector, an electric current flowing through the biological tissue disposed between the at least two conductors; generating an output based on the current. A method for measuring tissue impedance in real time.

18. until a desired output is generated The method of measuring tissue impedance in real time according to claim 17, further comprising the step of repositioning the needle in response to the output. **Claim 19** The real-time impedance measurement needle system according to claim 1, wherein the number of the at least two conductors is four, and each of the four conductors is provided with a different conduction path. **Claim 20** The real-time impedance measurement needle system according to claim 19, wherein the four conductors are arranged with shifted positions.

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