Patent Publication Number: US-2022233091-A1

Title: Medical devices configured with needle electrodes

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of the U.S. patent application titled, “IMPEDANCE-CALIBRATED DIAGNOSTIC MEDICAL DEVICES,” filed on Aug. 9, 2021, and having Ser. No. 17/397,896, which claims the benefit of U.S. Provisional Patent Application No. 63/142,242, filed Jan. 27, 2021; U.S. Provisional Patent Application No. 63/142,247, filed Jan. 27, 2021; U.S. Provisional Patent Application No. 63/142,254, filed Jan. 27, 2021; and U.S. Provisional Patent Application No. 63/142,260, filed Jan. 27, 2021. The present application is also a continuation-in-part of the U.S. patent application titled, “TECHNIQUES FOR CONTROLLING MEDICAL DEVICE TOOLS,” filed on Aug. 26, 2021, and having Ser. No. 17/412,973, which claims the benefit of U.S. Provisional Patent Application No. 63/142,242, filed Jan. 27, 2021; U.S. Provisional Patent Application No. 63/142,247, filed Jan. 27, 2021; U.S. Provisional Patent Application No. 63/142,254, filed Jan. 27, 2021; and U.S. Provisional Patent Application No. 63/142,260, filed Jan. 27, 2021. The subject matter of these related applications is hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     Field of the Various Embodiments 
     Embodiments of the present disclosure relate generally to electronics and medical diagnostic technology and, more specifically, to medical devices configured with needle electrodes. 
     Description of the Related Art 
     In minimally invasive medical procedures, a healthcare professional typically inserts a medical device into the patient&#39;s body and positions an instrument head of the medical device near tissue of a particular tissue type, such as a tumor. Some medical devices include a needle that penetrates the tissue. The needle can be fixed or retractable, where mechanical and/or electrical actuators are implemented to extend and retract the needle, and typically is used to administer various forms of treatment. For example, the needle can be used to extract a sample from a tumor for visual inspection or biopsy, deliver a diagnostic agent, such as a visual and/or radiolabeling dye, and/or deliver a therapeutic agent, such as a therapeutic drug or energy. 
     One drawback of many conventional medical devices, where a needle forms part of the instrument head, is the difficulty in determining, during treatment, whether the tissue type at the location of the needle tip matches an expected tissue type at that location. For example, a healthcare professional can visually inspect an image captured by a camera to determine the tissue type near the tip of a needle and administer treatment after visually confirming that the tissue appears to be a tumor. However, tissue types can vary in appearance, and different tissue types can have similar appearances. Accordingly, visual inspections can be inaccurate. As another example, tissue of one type may be located within tissue of another type, such as a tumor embedded within healthy tissue. A healthcare professional can use a needle to penetrate the healthy tissue and reach the targeted tissue. However, capturing an image of the target tissue at the location of the needle tip prior to, and during, this type of treatment can be difficult, if not impossible. Accordingly, verifying by visual inspection that the tissue type at the location of the needle tip is that of a tumor also can be quite difficult, if not impossible. 
     In view of the above drawbacks, some medical devices, where a needle forms part of the instrument head, include components that enable the tissue contacting the needle to be evaluated and a tissue type to be determined. However, many techniques for determining tissue type are inaccurate and, accordingly, are insufficient for confirming that the tissue type at the location of a needle tip matches an expected tissue type. For example, a medical scan can indicate a targeted tissue type at a given location, and triangulation and ultrasound imaging can confirm that a needle is positioned at the location where the targeted tissue type is expected to exist. However, these techniques typically require calibrating the relevant positioning system with respect to both the instrument head and a mapping of the patient&#39;s body via a medical scan. Errors introduced in the calibration process can produce errors when determining whether the instrument head, including the needle, is positioned correctly at the location of the targeted tissue type. Also, any physiological changes within the patient, such as the size, shape, or location of a tumor, between the time when a medical scan is conducted and a time point when the medical procedure begins can potentially change the tissue type at the target location. Thus, positioning an instrument head based on a medical scan can result in applying a needle to healthy tissue instead of the target tissue. 
     As the foregoing illustrates, what is needed in the art are more effective techniques for determining the tissue type at the location of a needle tip for medical devices, where a needle forms part of the instrument head. 
     SUMMARY 
     Embodiments are disclosed for medical devices. In various embodiments, the medical device includes an instrument head that includes a needle and two or more electrodes disposed on the needle; an impedance bridge coupled to the two or more electrodes; and a processor coupled to the impedance bridge. 
     Embodiments are disclosed for deploying a medical device. In various embodiments, a method includes recording, at one or more frequencies, one or more impedance measurements, wherein each impedance measurement is associated with two or more electrodes disposed on the needle of an instrument head of the medical device; comparing the one or more impedance measurements to one or more characteristic impedances associated with one or more tissue types; and determining, based on the one or more impedance measurements and the one or more characteristic impedances, one or more tissue types at the location associated with the needle. 
     At least one technical advantage of the disclosed design relative to the prior art is that the disclosed medical device is able to automatically determine, during operation, the tissue type of tissue at a location associated with a needle included in an instrument head of the medical device. For example, the disclosed medical device can determine whether the tissue type of tissue at the location associated with the needle matches an expected tissue type at that location prior to or during a procedure that involves the needle, such as extracting a tissue sample and/or delivering a therapeutic drug or energy to the tissue. In this manner, the disclosed medical device can ensure that the needle is applied to a correctly targeted tissue type, such as a tumor, rather than some other tissue type, such as healthy tissue. Also, the disclosed medical device can apply the needle to targeted tissue types more accurately than is possible with conventional medical devices. Consequently, the disclosed medical device can be used to perform various procedures with respect to targeted tissue types, such as and without limitation, delivering therapeutic drugs or energy or extracting tissue samples, more accurately and reliably than what can be achieved using conventional medical devices. These technical advantages provide one or more technological advancements over prior art designs and approaches. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a medical device, according to various embodiments; 
         FIG. 2  is a more detailed illustration of the instrument head of  FIG. 1 , according to various embodiments; 
         FIG. 3  is a more detailed illustration of the instrument head of  FIG. 1 , according to other various embodiments; 
         FIG. 4A  is a more detailed illustration of the instrument head of  FIG. 1 , according to other various embodiments; 
         FIG. 4B  is a close-up illustration of the needle tip of  FIG. 4A , according to various embodiments; 
         FIG. 5  is a more detailed illustration of the external electrical components of  FIG. 1 , according to various embodiments; 
         FIG. 6  is a more detailed illustration of the medical device of  FIG. 1 , according to various embodiments; and 
         FIG. 7  is a flow diagram of method steps for determining one or more tissue types at a location associated with a needle of a medical device, according to various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth to provide a more thorough understanding of the various embodiments. However, in the range of embodiments of the concepts includes some embodiments omitting one or more of these specific details. 
       FIG. 1  illustrates a medical device  100 , according to various embodiments. As shown, the medical device  100  includes, without limitation, an instrument head  108 , wires  104 , and external electrical components  106 . The instrument head  108  is positioned at a location  102  (e.g., a location of a tumor). While not shown, the instrument head  108  includes a needle. While not shown, in some embodiments, the instrument head  108  also includes a medical device tool, such as and without limitation, a camera, a fiber optic light source, a therapeutic drug delivery tool that delivers a therapeutic drug to the location  102 , an energy delivery tool that delivers energy to the location  102 , or a tissue sample extraction tool that extracts a tissue sample from the location  102  for further evaluation. The external electrical components  106  generate current at various frequencies. The wires  104  conduct the current between the external electrical components  106  and the instrument head  108 . The external electrical components  106  include a processor that couples to two or more electrodes disposed on the needle. The processor of the external electrical components  106  measures the impedance of current conducted through tissue between at least two of the two or more electrodes. As described in greater detail below, the medical device  100  determines, based on the impedance measurements, one or more tissue types at the location associated with the needle. For example and without limitation, based on the impedance measurements, the tissue type can indicate whether tissue at the location associated with the needle is a tumor tissue type or a non-tumor tissue type. 
       FIG. 2  is a more detailed illustration of the instrument head  108  of  FIG. 1 , according to various embodiments. As shown, the instrument head  108  includes, without limitation, a needle  202  and a sheath  210 , and wires  104 . As shown, the needle  202  includes a needle tip  204 , electrodes  206 - 1  through  206 - 4 , and electrically insulating material  208 . 
     In various embodiments, the electrically insulating material  208  is located between adjacent pairs of electrodes  206 . As shown, the electrically insulating material  208  includes a set of carve-outs, and each of the two or more electrodes is located within one of the carve-outs of the electrically insulating material  208 . In various embodiments and without limitation, the electrodes  206  are disposed on top of the electrically insulating material  208 . The electrically insulating material  208  can reduce contact and short circuits between adjacent electrodes  206 , which could reduce the accuracy of the impedance measurements. 
     As shown, each of the two or more electrodes  206 - 1  through  206 - 4  is located at a respective location along the length of the needle  202 . For example and without limitation, the first electrode  206 - 1  is located at a first location near the needle tip  204 , and the second electrode  206 - 2  is located at a second location that is further from the needle tip  204 . When the instrument head  108  is positioned at a location  102  in the patient&#39;s body, the needle  202  penetrates tissue at the location  102 . The external electrical components  106  can record, at one or more frequencies, one or more impedance measurements, wherein each impedance measurement is associated with two or more of the electrodes  206 . For example and without limitation, the medical device can record a first impedance measurement of tissue between or contacting the first electrode  206 - 1  and the second electrode  206 - 2  and a second impedance measurement of tissue between or contacting the third electrode  206 - 3  and the fourth electrode  206 - 4 . Based on the first and second impedance measurements, the medical device can determine a first tissue type between the first electrode  206 - 1  and the second electrode  206 - 2  and a second tissue type between the third electrode  206 - 3  and the fourth electrode  206 - 4 . For example and without limitation, the first tissue type based on the first impedance measurement can indicate that the tissue near the needle tip  204  is a tumor, and the second tissue type based on the second impedance measurement can indicate that the tissue further from the needle tip  204  is not a tumor. Based on the tissue types at the location associated with the needle, the external electrical components  106  can determine that the needle tip  204  of the needle  202  has penetrated healthy tissue to the depth of the embedded tumor. However, if the first impedance measurement and the second impedance measurement are the same or similar to one another, or to characteristic impedance measurements of non-tumor tissue, the external electrical components  106  can determine that the needle tip  204  of the needle  202  has not yet penetrated healthy tissue to the depth of the embedded tumor, or that a tumor is not present at the location associated with the needle  202 . 
     While not shown, in some embodiments, one or more of the two or more electrodes  206  is located on a first side of the needle  202 , and at least another one or more of the two or more electrodes is located on a second side of the needle  202 . For example and without limitation, the first electrode  206 - 1  and the second electrode  206 - 2  could be located on a left side of the needle  202 , and the third electrode  206 - 3  and the fourth electrode  206 - 4  could be located on a right side of the needle  202 . The external electrical components  106  can selectably couple to the first electrode  206 - 1  and the second electrode  206 - 2  to record a first impedance measurement. Based on the first impedance measurement, the external electrical components  106  can determine a tissue type on the left side of the needle  202 . The external electrical components  106  can selectably couple to the third electrode  206 - 3  and the fourth electrode  206 - 4  to record a second impedance measurement. Based on the second impedance measurement, the external electrical components  106  can determine a tissue type on the right side of the needle  202 . Based on the first and second impedance measurements, the external electrical components  106  can compare the tissue types on different sides of the needle  202 . For example and without limitation, the external electrical components  106  can determine whether the needle  202  is located within a tumor, within healthy tissue, or between a tumor and healthy tissue. 
     While not shown, in some embodiments, one or more of the two or more electrodes  206  is located on a first side of the needle  202 , and the needle  202  selectably rotates with respect to a length axis of the needle  202 . For example and without limitation, the medical device  100  can include an actuator (e.g. and without limitation, a stepper motor or servo motor), and the actuator is coupled to the instrument head  108  and that, when actuated, rotates the needle  202 . For example, and without limitation, when the instrument head  108  is positioned at a location  102  in the patient&#39;s body, the external electrical components  106  can actuate the actuator to rotate the needle  202  to a first rotational position in which the electrodes  206  are located on a left side of the needle  202 . The external electrical components  106  can record a first impedance measurement to determine a tissue type of tissue associated with the left side of the needle  202 . The external electrical components  106  can actuate the actuator again to rotate the needle  202  to a second rotational position in which the electrodes  206  are located on a right side of the needle  202 . The external electrical components  106  can record a first impedance measurement to determine a tissue type of tissue associated with the right side of the needle  202 . The external electrical components  106  can compare the tissue types on the left side and the right side of the needle  202 . For example and without limitation, the external electrical components  106  can determine whether the needle  202  is located within a tumor, within healthy tissue, or between a tumor and healthy tissue. 
     As shown, the electrodes  206 - 1  through  206 - 4  are disposed on the needle. The wires  104  electrically couple the electrodes  206 - 1  through  206 - 4  to the external electrical components  106 . The sheath  210  physically protects the wires  104 , and, in some embodiments, shields the wires from electromagnetic interference. 
     While not shown, in some embodiments, the needle  202  selectably extends by an adjustable amount relative to the sheath  210 . In various embodiments, the needle  202  can move between a first position that is fully retracted into the sheath  210  (e.g., during deployment or movement of the instrument head  108 ) and a second position that is fully extended from the sheath  210  (e.g., when the instrument head  108  is positioned at the target location  102 ). For example and without limitation, the needle  202  can be coupled to a wire that extends through the sheath  210  to the external electrical components  106 . In some embodiments, an actuator included in the external electrical components  106  exerts pressure on the cable to extend the needle  202  with respect to the sheath  210 . In some embodiments, an actuator included in the external electrical components  106  exerts tension on the cable to retract the needle  202  out of the sheath  210 . In some embodiments, the external electrical components  106  automatically move the needle  202  based on the one or more tissue types at the location associated with the needle. For example and without limitation, when the external electrical components  106  determine that the tissue type at the location associated with the instrument head  108  matches an expected tissue type at the target location  102 , the external electrical components  106  can actuate the actuator to extend the needle  202  with respect to the sheath  210  and penetrate the tissue. In some embodiments, the adjustable amount of the needle  202  extending relative to the sheath  210  includes three or more positions in which the needle  202  is fully exposed, partially exposed, or fully retracted into the sheath  210 . 
     While not shown, in some embodiments, the sheath  210  selectably extends by an adjustable amount relative to the needle  202 . In various embodiments, the sheath  210  can move between a first position that covers the needle  202  (e.g., during deployment or movement of the instrument head  108 ) and a second position that retracts the sheath  210  with respect to the needle  202  (e.g., when the instrument head  108  is positioned at the target location  102 ). For example and without limitation, the sheath  210  can be coupled to a wire that extends to the external electrical components  106 . In some embodiments, an actuator included in the external electrical components  106  can exert pressure on the cable to extend the sheath  210  to cover the needle  202 . In some embodiments, an actuator included in the external electrical components  106  can exert tension on the cable to retract the sheath  210  and expose the needle  202 . In some embodiments, the external electrical components  106  automatically move the sheath  210  based on the one or more tissue types at the location associated with the needle. For example and without limitation, when the external electrical components  106  determine that the tissue type at the location associated with the instrument head  108  matches an expected tissue type at the target location  102 , the external electrical components  106  can actuate the actuator to retract the sheath  210  and expose the needle  202  to penetrate the tissue. In some embodiments, the adjustable amount of the sheath  210  extending relative to the needle  202  includes three or more positions in which the needle  202  is fully exposed, partially exposed, or fully retracted into the sheath  210 . 
     While not shown, in various embodiments, the sheath  210  includes one or more carve-outs, and the sheath  210  selectably rotates to expose or cover the electrodes  206 . For example and without limitation, the external electrical components  106  can include an actuator (e.g. and without limitation, a stepper motor or servo motor), and the actuator is coupled to the instrument head  108  and that, when actuated, rotates the needle  202 . The sheath  210  can selectably rotate between a first rotational position in which the one or more carve-outs exposes a first electrode  206  of the two or more electrodes  206 , and a second rotational position in which the sheath  210  covers the first electrode  206 . For example, and without limitation, when the instrument head  108  is being moved, the external electrical components  106  can actuate the actuator to rotate the sheath  210  to a first rotational position in which the sheath  210  covers the first electrode  206 - 1  and the carve-outs do not expose the first electrode  206 - 1 . Covering the first electrode  206 - 1  can protect the first electrode during movement of the instrument head  108 . When the instrument head is positioned at a location in the patient&#39;s body, the external electrical components  106  can actuate the actuator to rotate the sheath  210  to a second rotational position in which one or more of the carve-outs in the sheath  210  exposes the first electrode  206 - 1 . Exposing the first electrode  206 - 1  can enable the external electrical components  106  to measure impedance measurements of tissue between the first electrode  206 - 1  and another one of the electrodes  206 . In some embodiments, different rotational positions of the sheath  210  expose different respective subsets of the electrodes  206  and cover the remaining electrodes  206  disposed on the needle  202 . In some embodiments, a first rotational position of the sheath  210  covers all of the electrodes  206  disposed on the needle  202 , and a second rotational position of the sheath  210  exposes all of the electrodes  206  through the carve-outs of the sheath  210 . 
       FIG. 3  is a more detailed illustration of the instrument head of  FIG. 1 , according to other various embodiments. As shown, the instrument head  108  includes, without limitation, a needle  202 , wires  104 , and a sheath  210 . As shown, the needle  202  includes a needle tip  204  and a set of electrodes  206 - 1  to  206 - 5 , and electrically insulating material  208 . 
     As shown, each of the electrodes  206  encircles the needle  202  at a respective location along the length of the needle  202 . For example and without limitation, the first electrode  206 - 1  encircles the needle  202  at a first location near the needle tip  204 , and the second electrode  206 - 2  encircles the needle  202  at a second location that is further from the needle tip  204 . When the instrument head  108  is positioned at a location  102  in the patient&#39;s body, the needle  202  penetrates tissue at the location  102 . The external electrical components  106  can record, at one or more frequencies, one or more impedance measurements, wherein each impedance measurement is associated with two or more of the electrodes  206 . For example and without limitation, the medical device can record a first impedance measurement of tissue between or contacting the first electrode  206 - 1  and the second electrode  206 - 2  and a second impedance measurement of tissue between or contacting the third electrode  206 - 3  and the fourth electrode  206 - 4 . Based on the first and second impedance measurements, the medical device can determine a first tissue type between the first electrode  206 - 1  and the second electrode  206 - 2  and a second tissue type between the third electrode  206 - 3  and the fourth electrode  206 - 4 . For example and without limitation, the first tissue type based on the first impedance measurement can indicate that the tissue near the needle tip  204  is a tumor, and the second tissue type based on the second impedance measurement can indicate that the tissue further from the needle tip  204  is not a tumor. Based on the tissue types at the location associated with the needle, the external electrical components  106  can determine that the needle tip  204  of the needle  202  has penetrated healthy tissue to the depth of the embedded tumor. However, if the first impedance measurement and the second impedance measurement are the same or similar to one another, or to characteristic impedance measurements of non-tumor tissue, the external electrical components  106  can determine that the needle tip  204  of the needle  202  has not yet penetrated healthy tissue to the depth of the embedded tumor, or that a tumor is not present at the location associated with the needle  202 . 
     As shown, the electrodes  206  are disposed on top of a layer of electrically insulating material  208 . The electrically insulating material  208  is also located between adjacent pairs of electrodes  206 . As shown, the electrically insulating material  208  encircles the needle  202  between each pair of adjacent electrodes  206 . The electrically insulating material  208  can reduce contact and short circuits between adjacent electrodes  206 , which could reduce the accuracy of the impedance measurements. 
       FIG. 4A  is a more detailed illustration of the instrument head of  FIG. 1 , according to other various embodiments. As shown, the instrument head  108  includes, without limitation, a needle  202  including a cannula terminating in an aperture  402 , wires  104 , and a sheath  210 . As shown, the needle  202  includes a needle tip  204  and a set of electrodes  206 - 1  to  206 - 8 , and electrically insulating material  208 . 
     As shown, each of the electrodes  206  encircles the needle  202  at a respective location along the length of the needle  202 . For example and without limitation, the first electrode  206 - 1  encircles the needle  202  at a first location near the needle tip  204 , and the second electrode  206 - 2  encircles the needle  202  at a second location that is further from the needle tip  204 . In addition, as shown, electrodes  206 - 6  to  206 - 8  are disposed on the needle tip surrounding an aperture  402  of the cannula. When the instrument head  108  is positioned at a location  102  in the patient&#39;s body, the needle  202  penetrates tissue at the location  102 . The external electrical components  106  can record, at one or more frequencies, one or more impedance measurements, wherein each impedance measurement is associated with two or more of the electrodes  206 . For example and without limitation, the medical device can record a first impedance measurement of tissue between or contacting the sixth electrode  206 - 6  and the seventh electrode  206 - 7  and a second impedance measurement of tissue between or contacting the first electrode  206 - 1  and the second electrode  206 - 2 . Based on the first and second impedance measurements, the medical device can determine a first tissue type between the sixth electrode  206 - 6  and the seventh electrode  206 - 7  and a second tissue type between the first electrode  206 - 1  and the second electrode  206 - 2 . For example and without limitation, the first tissue type based on the first impedance measurement can indicate that the tissue contacting the needle tip  204  is a tumor, and the second tissue type based on the second impedance measurement can indicate that the tissue further from the needle tip  204  is not a tumor. Based on the one or more tissue types at the location associated with the needle, the external electrical components  106  can determine that the needle tip  204  of the needle  202  has penetrated healthy tissue to the depth of the embedded tumor. However, if the first impedance measurement and the second impedance measurement are the same or similar to one another, or to characteristic impedance measurements of non-tumor tissue, the external electrical components  106  can determine that the needle tip  204  of the needle  202  has not yet penetrated healthy tissue to the depth of the embedded tumor, or that a tumor is not present at the location associated with the needle  202 . 
       FIG. 4B  is a close-up illustration of the needle tip of  FIG. 4A , according to various embodiments. As shown, the needle tip  204  includes an aperture  402  of a cannula, one or more electrodes  206 , and electrically insulating material  208 . 
     As shown, the electrodes  206  are disposed on the needle tip  204  at locations surrounding the aperture  402  of the cannula. For example and without limitation, in various embodiments in which the needle  202  is included in a therapeutic drug delivery tool, the cannula can convey a therapeutic drug through the aperture  402  and into tissue that is penetrated by the needle tip  204 . For example and without limitation, in various embodiments in which the needle  202  is included in an energy delivery tool, the cannula can convey energy through the aperture  402  and into tissue that is penetrated by the needle tip  204 . For example and without limitation, in various embodiments in which the needle  202  is included in a tissue sample extraction tool, the cannula can receive and store a tissue sample of tissue that is penetrated by the needle tip  204 . 
     When the instrument head  108  is positioned at a location  102  in the patient&#39;s body, the needle  202  penetrates tissue at the location  102 . The external electrical components  106  can record, at one or more frequencies, one or more impedance measurements, wherein each impedance measurement is associated with two or more of the electrodes  206 . For example and without limitation, the medical device can record a first impedance measurement of tissue between or contacting the sixth electrode  206 - 6  and the seventh electrode  206 - 7  and a second impedance measurement of tissue between or contacting the first electrode  206 - 1  and the second electrode  206 - 2 . Based on the first and second impedance measurements, the medical device can determine a first tissue type between the sixth electrode  206 - 6  and the seventh electrode  206 - 7  and a second tissue type between the first electrode  206 - 1  and the second electrode  206 - 2 . For example and without limitation, the first tissue type based on the first impedance measurement can indicate that the tissue contacting the needle tip  204  is a tumor, and the second tissue type based on the second impedance measurement can indicate that the tissue further from the needle tip  204  is not a tumor. Based on the one or more tissue types at the location associated with the needle, the external electrical components  106  can determine that the needle tip  204  of the needle  202  has penetrated healthy tissue to the depth of the embedded tumor. However, if the first impedance measurement and the second impedance measurement are the same or similar to one another, or to characteristic impedance measurements of non-tumor tissue, the external electrical components  106  can determine that the needle tip  204  of the needle  202  has not yet penetrated healthy tissue to the depth of the embedded tumor, or that a tumor is not present at the location associated with the needle  202 . 
     While not shown, in various embodiments, one or more of the two or more electrodes is disposed on an interior surface of a cannula of the needle  202 . For example and without limitation, in various embodiments in which the needle  202  is included in a tissue extraction tool, the cannula of the needle  202  can receive and store a tissue sample of tissue that is penetrated by the needle tip  204 . The external electrical components  106  can record one or more impedance measurements of the tissue sample between the electrodes  206  disposed on the interior surface of the cannula. Based on the one or more impedance measurements, the external electrical components  106  can determine a tissue type of the tissue sample. 
     While not shown, in some embodiments, the needle includes a first cannula and a second cannula that resides within the first cannula. For example and without limitation, the first cannula can include two or more electrodes are disposed on an interior surface of the first cannula, and the second cannula can perform one or more operations, such as delivering a therapeutic drug or energy or extracting a tissue sample. The external electrical components  106  can record one or more impedance measurements of the tissue sample between the electrodes  206  disposed on the interior surface of the first cannula and can determine a tissue type of tissue contacting the interior surface of the first cannula. Based on the one or more impedance measurements and the one or more tissue types at the location associated with the needle, the external electrical components  106  can determine whether or not to perform the one or more operations involving the second cannula. For example and without limitation, if the one or more tissue types at the location associated with the needle is a tumor, the external electrical components  106  can actuate a drug delivery tool to dispense a therapeutic drug from the second cannula. However, if the one or more tissue types at the location associated with the needle include a healthy tissue type, the external electrical components  106  can refrain from actuating the drug delivery tool to avoid dispensing the therapeutic drug to the healthy tissue. As another example and without limitation, the first cannula can perform one or more operations, such as delivering a therapeutic drug or energy or extracting a tissue sample, and the second cannula can include two or more electrodes are disposed on an interior surface of the second cannula. The external electrical components  106  can record one or more impedance measurements of the tissue sample between the electrodes  206  disposed on the interior surface of the second cannula and can determine a tissue type of tissue contacting the interior surface of the second cannula. Based on the one or more impedance measurements and the one or more tissue types at the location associated with the needle, the external electrical components  106  can determine whether or not to perform the one or more operations involving the first cannula. For example and without limitation, if the one or more tissue types at the location associated with the needle include a tumor tissue type, the external electrical components  106  can actuate a drug delivery tool to dispense a therapeutic drug from the first cannula. However, if the one or more tissue types at the location associated with the needle include a healthy tissue type, the external electrical components  106  can refrain from actuating the drug delivery tool to avoid dispensing the therapeutic drug to the healthy tissue. 
       FIG. 5  is a more detailed illustration of the external electrical components of  FIG. 1 , according to various embodiments. As shown, the external electrical components  106  include wires  104 , an amplifier  502 , an impedance bridge  504 , and a processor  506 . The wires  104  conduct current at various frequencies between two or more electrodes  206  and the external electrical components  106 . In various embodiments, the amplifier  502  is an analog interface amplifier that amplifies a supplied voltage and/or a return voltage while the wires  104  conduct current at various frequencies between the impedance bridge  504  and the two or more electrodes  206 . In various embodiments, the impedance bridge  504  is an impedance load that the processor  506  measures to determine an impedance of a circuit including the impedance bridge  504 , the amplifier  502 , and the two or more electrodes  206 . The processor  506  generates frequencies for a current that the wires  104  conduct between the impedance bridge  504  and the selected two or more electrodes  206 . 
     While the wires  104  conduct current at various frequencies, the processor  506  records one or more impedance measurements  508  of the circuit including the at least two electrodes  206 . The processor  506  compares the one or more impedance measurements  508  with characteristic tissue types  512  of respective one or more tissue types. Based on the one or more impedance measurements  508  and the characteristic tissue types  512 , the processor  506  determines one or more tissue types  512  of tissue at the location associated with the needle  202 . For example and without limitation, based on the one or more impedance measurements  508  and the characteristic tissue types  512 , the processor  506  can determine which tissue type is associated with characteristic impedance measurements  510  that are closest to the impedance measurements of the portion of tissue between at least two of the two or more electrodes  206 . In various embodiments, the processor  506  can determine a Cole relaxation frequency of the portion of tissue based on the impedance measurements  508 , and can compare the Cole relaxation frequency to one or more characteristic Cole relaxation frequencies of one or more tissue types. The Cole relaxation frequency corresponds to a frequency associated with a greatest impedance measurement  508  included in the one or more impedance measurements  508 . In various embodiments, the Cole relaxation frequency is a frequency of a maximum normalized impedance measurement of the portion of tissue between at least two of the two or more electrodes  206 . For example and without limitation, based on a Cole relaxation frequency below a threshold frequency (e.g., 10 5  Hz), the processor  506  can determine that the portion of tissue between at least two of the two or more electrodes  206  is a non-tumor tissue type. Similarly, for example and without limitation, based on a Cole relaxation frequency above the threshold frequency, the processor  506  can determine that the portion of tissue between at least two of the two or more electrodes  206  is a tumor tissue type. In various embodiments, the processor  506  determines one or more tissue types at the location associated with the needle  202 . 
     In some embodiments, the processor  506  determines two or more tissue types of tissue at the location associated with the needle based on impedance measurements respectively recorded by different electrode pairs of the two or more electrodes  206 . For example (without limitation), the needle  202  can include a first electrode pair disposed at a first location along the length of the needle  202  and a second electrode pair disposed at a second location along the length of the needle  202 . While the needle  202  is inserted into tissue, the processor  506  can determine tissue types at the first location and the second location based on the respective impedance measurements associated with the first electrode pair and the second electrode pair. The one or more tissue types at the location associated with the needle can indicate whether the needle  202  has been inserted into tissue far enough to reach a location of a targeted tissue type within the tissue. 
     In various embodiments in which the instrument head  108  includes a sheath  210  and a needle  202  that selectably extends by an adjustable amount relative to the sheath  210 , the processor  506  can extend the needle to a first amount relative to the sheath  210 . For example and without limitation, when the instrument head  108  is moving, the processor  506  can actuate an actuator to retract the needle  202  fully into the sheath  210 . When the processor  506  determines that the tissue type  512  at the location associated with the needle  202  matches one or more tissue types at a target location  102 , the processor  506  can actuate the actuator to extend the needle  202  with respect to the sheath. Selectably extending the needle  202  can protect the needle  202  while the instrument head  108  is moving and can prevent the needle  202  from penetrating tissue at a location other than the target location  102 . 
     In various embodiments in which the instrument head  108  includes a needle  202  and a sheath  210  that selectably extends by an adjustable amount relative to the needle  202 , the processor  506  can extend the sheath  210  to a first amount relative to the needle  202 . For example and without limitation, when the instrument head  108  is moving, the processor  506  can actuate an actuator to extend the sheath  210  to cover the needle  202 . When the processor  506  determines that the tissue type  512  at the location associated with the needle  202  matches one or more tissue types at a target location  102 , the processor  506  can actuate the actuator to retract the sheath  210  with respect to the sheath and to expose the needle  202 . Selectably extending the sheath  210  can protect the needle  202  while the instrument head  108  is moving and can prevent the needle  202  from penetrating tissue at a location other than the target location  102 . 
     In various embodiments in which the instrument head  108  includes a medical device tool, the processor  506  performs one or more operations  514  to control the medical device tool based on the one or more tissue types  512  at the location associated with the needle. For example and without limitation, in various embodiments in which the instrument head  108  includes a camera, the processor  506  can perform operations  514  that include activating the camera to capture an image of the tissue at the location  102  associated with the needle  202 . For example and without limitation, in various embodiments in which the instrument head  108  includes a light source, the processor  506  can perform operations  514  that include activating the light source to illuminate the tissue at the location  102  associated with the needle  202 . For example and without limitation, in various embodiments in which the needle  202  is included in a therapeutic drug delivery tool, the processor  506  can perform operations  514  that include activating the therapeutic drug delivery tool to deliver one or more therapeutic drugs to the tissue at the location  102  associated with the needle  202 . For example and without limitation, in various embodiments in which the needle  202  is included in an energy delivery tool, the processor  506  can perform operations  514  that include activating the energy delivery tool to deliver energy to the tissue at the location  102  associated with the needle  202 . For example and without limitation, in various embodiments in which the needle  202  is included in a tissue sample extraction tool, the processor  506  can perform operations  514  that include activating the tissue sample extraction tool to extract a tissue sample from the tissue at the location  102  associated with the needle  202 . 
     In various embodiments in which the needle  202  is included in a medical device tool, the processor  506  determines one or more tissue types at a location associated with the needle  202  at a time point, where the time point is either prior or subsequent to a medical procedure. For example and without limitation, in various embodiments in which the needle  202  is included in a therapeutic drug delivery tool, the processor  506  can record a first one or more impedance measurements  508  to determine the tissue type  512  at the location associated with the needle  202  at a first time point that is before delivery of the therapeutic drug. The processor  506  can also record a second one or more impedance measurements  508  to determine the tissue type  512  at the location associated with the needle  202  at a second time point that is after delivery of the therapeutic drug. Determining the tissue types  512  at time points before and after the delivery of the therapeutic drug can indicate changes to the tissue due to the delivered therapeutic drug. For example and without limitation, in various embodiments in which the needle  202  is included in an energy delivery tool, the processor  506  can record a first one or more impedance measurements  508  to determine the tissue type  512  at the location associated with the needle  202  at a first time point that is before delivery of the energy. The processor  506  can also record a second one or more impedance measurements  508  to determine the tissue type  512  at the location associated with the needle  202  at a second time point that is after delivery of the energy. Determining the tissue types  512  at time points before and after the delivery of the therapeutic drug can indicate changes to the tissue due to the delivered energy. 
     In various embodiments, the processor  506  presents the one or more tissue types at the location  102  associated with the needle  202 . For example and without limitation, the processor  506  can display the one or more tissue types  512  at the location associated with the needle using a visual output (e.g., a light-emitting diode, a liquid crystal display, or the like). For example and without limitation, where the target location  102  is a tumor that is embedded in non-tumor tissue, the displayed tissue type  512  can indicate whether the needle  202  has penetrated the non-tumor tissue to the depth of the tumor. Presenting the indication can inform a user of the medical device  100  that the one or more tissue types at the location  102  associated with the needle the instrument head  108  matches the expected tissue type at a target location. Further, in various embodiments, the processor  506  performs the one or more operations  514  to control a medical device tool based on presenting the tissue type  512  and receiving a signal to activate the medical device tool. 
       FIG. 6  is a more detailed illustration of the medical device  100  of  FIG. 1 , according to various embodiments. As shown, the medical device  100  includes an instrument head  108  and external electrical components  106 . As shown, the instrument head  108  includes a needle  202  and two or more electrodes  206  that are disposed on the needle  202 . The two or more electrodes  206  are coupled to the external electrical components  106  by wires  104 . In various embodiments, without limitation, each of the two or more electrodes  206  is coupled to the external electrical components  106  by one wire  104  or by respective wires of a plurality of wires  104 . In some embodiments, the instrument head  108  includes a medical device tool, such as and without limitation, a therapeutic drug delivery tool, an energy delivery tool, or a tissue sample extraction tool. In various embodiments, the instrument head  108  includes, without limitation, two or more medical device tools, which can be of one kind or of different kinds. 
     As shown, the external electrical components  106  include an amplifier  502 , an impedance bridge  504 , and a processor  506 . The amplifier  502  amplifies a supplied voltage and/or a return voltage while the wires  104  conduct current at various frequencies between the impedance bridge  504  and the two or more electrodes  206 . The impedance bridge  504  is an impedance load that the processor  506  measures to determine an impedance of a circuit including the impedance bridge  504 , the amplifier  502 , the wires  104 , and the two or more electrodes  206 . The processor  506  records, at various frequencies, one or more impedance measurements  508 . The processor  506  compares the two or more impedance measurements  508  with characteristic impedance measurements  510  of respective one or more tissue types. Based on the one or more impedance measurements  508  with characteristic tissue types  512 , the processor  506  determines one or more tissue types  512  at the location  102  associated with the needle  202 . In various embodiments and without limitation, the processor  506  determines the tissue type  512  indicated by the respective impedance measurements  508  based on a Cole relaxation frequency of a portion of tissue contacting the two or more electrodes  206 . In various embodiments and without limitation, the processor  506  determines the tissue type  512  as areas of tumor tissue types and/or non-tumor tissue types. In various embodiments and without limitation, based on the one or more tissue types  512  at the location associated with the needle, the processor  506  determines that the tissue type at the location  102  associated with the needle  202  matches the expected tissue type at a target location, which indicates or confirms that the instrument head  108  is positioned at the target location  102 . For example and without limitation, if the target location  102  is a tumor, the processor  506  can determine whether the needle  202  is positioned at a target location  102  by determining that the one or more tissue types  512  at the location associated with the needle include a tumor tissue type. 
     As shown, the processor  506  is coupled to a conduit  602  that is coupled to the needle  202 . Based on the one or more tissue types  512  at the location associated with the needle, the processor  506  performs one or more operations  514  to control the needle  202 . In various embodiments and without limitation, the needle  202  is included in a therapeutic drug delivery tool, and the processor  1906  performs an operation  514  of causing the needle  202  to deliver one or more therapeutic drugs to tissue at the location  102  associated with the needle  202 . For example and without limitation, the processor  506  can cause one or more therapeutic drugs through one or more drug delivery conduits to and through the needle  202 . In various embodiments and without limitation, the needle  202  is included in an energy delivery tool, and the processor  506  performs an operation  514  of causing the conduit  602  and the needle  202  to deliver energy to tissue at the location  102  associated with the needle  202 . For example and without limitation, the processor  506  can cause current to be conducted through wires in the conduit  602  to and through the needle  202 . In various embodiments and without limitation, the needle  202  is included in a tissue sample extraction tool, and the processor  506  performs an operation  514  of causing the needle  202  to extract a tissue sample from tissue at the location  102  associated with the needle  202 . For example and without limitation, the external electrical components  106  can include an actuator coupled to the needle  202  by wires in the conduit  602 , and the processor  506  can activate the actuator to cause the needle  202  to extract the tissue sample. 
     In various embodiments, the medical device  100  reports the one or more tissue types  512  at the location associated with the needle to a user of the medical device  100 . For example and without limitation, the medical device  100  can display the one or more tissue types  512  at the location associated with the needle using a visual output (e.g., a liquid crystal display (LCD), a light-emitting diode (LED) display to present a visual indication of the one or more tissue types  512  at the location associated with the needle, such as a light, symbol, text, graphic, or the like). In various embodiments and without limitation, the processor  506  can include, in the displayed tissue type  512 , an indication that the one or more tissue types  512  at the location associated with the needle match one or more expected tissue types at a target location (e.g., using a visual output, an audio output, or the like). 
       FIG. 7  is a flow diagram of method steps for controlling the medical device  100  of  FIG. 1 , according to various embodiments. Although the method steps are described in conjunction with the systems of  FIGS. 1-6 , persons skilled in the art will understand that any system configured to perform the method steps, in any order, falls within the scope of the present invention. 
     As shown, a method  700  begins at step  702 , where a processor  506  records, at one or more frequencies, one or more impedance measurements  508 , wherein each impedance measurement  508  is associated with two or more electrodes  206  disposed on a needle  202  included in an instrument head  108  of the medical device  100 . In various embodiments and without limitation, the processor  506  determines a Cole relaxation frequency of tissue between at least two of the two or more electrodes disposed on the needle (e.g., without limitation, as a frequency of a maximum normalized impedance measurement of the tissue between at least two of the two or more electrodes). 
     At step  704 , the processor compares the one or more impedance measurements with characteristic impedance measurements of respective one or more tissue types. For example and without limitation, the processor can compare the impedance measurements with a first set of one or more characteristic impedance measurements of a non-tumor tissue type and a second set of one or more characteristic impedance measurements of a tumor tissue type. 
     At step  706 , the processor determines, based on the two or more impedance measurements, one or more tissue types at the location associated with the needle. In various embodiments and without limitation, the processor determines the tissue type that classifies the tissue as one of a tumor tissue type or a non-tumor tissue type. In various embodiments and without limitation, the processor determines whether the tissue type at the location associated with the location matches an expected tissue type at a target location. The method can return to step  702  to record additional impedance measurements and to determine a second or updated tissue type. 
     In sum, the disclosed medical device measures the impedance of tissue in a location where a needle of an instrument head of a medical device is positioned. The medical device determines the tissue type based on impedance measurements associated with two or more electrodes located on the needle. The disclosed approach advantageously results in the medical device determining the tissue types of tissue associated with the location associated with the needle (e.g., without limitation, on various sides of the instrument head). 
     At least one technical advantage of the disclosed medical device relative to the prior art is that the disclosed medical device is able to determine one or more tissue types of tissue associated with a location associated with the needle of an instrument head of the medical device prior to performing an operation associated with the needle during the operation. For example (without limitation), the disclosed medical device can determine whether the tissue type of the tissue associated with the location associated with the needle matches an expected tissue type at a given target location prior to or during administering a treatment using the needle, such as extracting a tissue sample and/or delivering a therapeutic drug or energy. In this manner, the disclosed medical device can ensure that the needle is applied to a selected tissue type, such as a tumor, rather than some other tissue type, such as healthy tissue. Also, the disclosed medical device can apply the needle at target locations more accurately than is possible with conventional medical devices. Consequently, the disclosed medical device can be used to perform various procedures based on the needle, such as and without limitation, delivering therapeutic drugs or energy or extracting tissue samples, at specific locations more accurately and reliably than what can be achieved using conventional medical devices. These technical advantages provide one or more technological advancements over prior art approaches. 
     1. In some embodiments, a medical device comprises an instrument head that includes a needle and two or more electrodes disposed on the needle; an impedance bridge coupled to the two or more electrodes; and a processor coupled to the impedance bridge. 
     2. The medical device of clause 1, wherein each of the two or more electrodes is located at a respective location along a length of the needle. 
     3. The medical device of clauses 1 or 2, wherein at least one of the two or more electrodes is located on a first side of the needle, and at least another one of the two or more electrodes is located on a second side of the needle. 
     4. The medical device of any of clauses 1-3, wherein at least one of the two or more electrodes encircles the needle. 
     5. The medical device of any of clauses 1-4, wherein at least one of the two or more electrodes is located on a tip of the needle. 
     6. The medical device of any of clauses 1-5, wherein the needle includes an electrically insulating material that is located between at least two of the two or more electrodes. 
     7. The medical device of any of clauses 1-6, wherein the needle includes an electrically insulating material, and each of the two or more electrodes is disposed on top of the electrically insulating material. 
     8. The medical device of any of clauses 1-7, wherein the needle includes an electrically insulating material, and each of the two or more electrodes is disposed within a different carve-out within the electrically insulating material. 
     9. The medical device of any of clauses 1-8, wherein one or more of the two or more electrodes is disposed on an interior surface of a cannula of the needle. 
     10. The medical device of any of clauses 1-9, wherein the needle includes a first cannula and a second cannula that resides within the first cannula, and the two or more electrodes are disposed on either the first cannula or the second cannula. 
     11. The medical device of any of clauses 1-10, wherein the instrument head includes a sheath, and the needle selectably extends by an adjustable amount relative to the sheath. 
     12. The medical device of any of clauses 1-11, wherein the instrument head includes a sheath that selectably extends by an adjustable amount relative to the needle. 
     13. The medical device of any of clauses 1-12, wherein the instrument head includes a sheath that has one or more carve-outs, and the sheath selectably rotates between a first rotational position, in which the one or more carve-outs exposes at least one of the two or more electrodes, and a second rotational position, in which the sheath covers the at least one of the two or more electrodes. 
     14. In some embodiments, a method for determining one or more tissue types at a location associated with a needle of a medical device comprises recording, at one or more frequencies, one or more impedance measurements, wherein each impedance measurement is associated with two or more electrodes disposed on the needle of an instrument head of the medical device; comparing the one or more impedance measurements to one or more characteristic impedances associated with one or more tissue types; and determining, based on the one or more impedance measurements and the one or more characteristic impedances, one or more tissue types at the location associated with the needle. 
     15. The method of clause 14, wherein the one or more impedance measurements include a first impedance measurement associated with an electrode pair included in the two or more electrodes. 
     16. The method of clauses 14 or 15, wherein the needle selectably extends by an adjustable amount relative to a sheath included in the instrument head, and the method further comprises, based on the one or more tissue types at the location associated with the needle, extending the needle to a first amount relative to the sheath. 
     17. The method of any of clauses 14-16, further comprising, based on the one or more tissue types at the location associated with the needle, performing one or more operations to control a medical device tool included in the instrument head. 
     18. The method of any of clauses 14-17, further comprising receiving a tissue sample at the location associated with the needle, wherein the recorded impedance measurements include one or more impedance measurements of the tissue sample. 
     19. The method of any of clauses 14-18, wherein at least one of the one or more impedance measurements is associated with at least two electrodes located on a side of the needle. 
     20. The method of any of clauses 14-19, wherein recording at least one of the one or more impedance measurements occurs prior or subsequent to a medical procedure. 
     Any and all combinations of any of the claim elements recited in any of the claims and/or any elements described in this application, in any fashion, fall within the contemplated scope of the present invention and protection. 
     The descriptions of the various embodiments have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. 
     Aspects of the present embodiments may be embodied as a system, method or computer program product. Accordingly, aspects of the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “module,” a “system,” or a “computer.” In addition, any hardware and/or software technique, process, function, component, engine, module, or system described in the present disclosure may be implemented as a circuit or set of circuits. Furthermore, aspects of the present disclosure may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. 
     Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
     Aspects of the present disclosure are described above with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine. The instructions, when executed via the processor of the computer or other programmable data processing apparatus, enable the implementation of the functions/acts specified in the flowchart and/or block diagram block or blocks. Such processors may be, without limitation, general purpose processors, special-purpose processors, application-specific processors, or field-programmable gate arrays. 
     The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. 
     While the preceding is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.