Abstract:
Echogenic markers can be applied to probes such as medical needles, including radiofrequency cannulae, injection needles, biopsy needles, microwave antennae, and spinal needles, among others. For example, in certain embodiments, the probes may have a distal end, a proximal end, a shaft, and an echogenic feature in the form of one or more indentations on the shaft. In certain embodiments, the probes may have a first echogenic feature in the form of an indentation in a surface of the probe and a second echogenic feature in the form of a roughening of the surface of the probe.

Description:
PRIORITY CLAIM 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/683,190, filed Aug. 14, 2012, which is incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The invention relates generally to probes used in medical procedures. The invention relates more specifically to means of enhancing the ultrasound image of probes used in medical procedures. The invention relates more specifically to field therapy. 
       BACKGROUND OF THE INVENTION 
       [0003]    The use of radiofrequency (RF) generators and electrodes to be applied to tissue for pain relief or functional modification is well known. For example, the RFG-3B RF lesion generator of Radionics, Inc., Burlington, Mass. and its associated electrodes enable electrode placement of the electrode near target tissue and heating of the target tissue by RF power dissipation of the RF signal output in the target tissue. For example, the G4 generator of Cosman Medical, Inc., Burlington, Mass. and its associated electrodes such as the Cosman CSK, and cannula such as the Cosman CC and RFK cannula, enable electrode placement of the electrode near target tissue and heating of the target tissue by RF power dissipation of the RF signal output in the target tissue. Temperature monitoring of the target tissue by a temperature sensor in the electrode can control the process. Heat lesions with target tissue temperatures of 60 to 95 degrees Celsius are common. Tissue dies by heating above about 45 degrees Celsius, so this process produces the RF heat lesion. RF generator output is also applied using a pulsed RF method, whereby RF output is applied to tissue intermittently such that tissue is exposed to high electrical fields and average tissue temperature are lower, for example 42 degrees Celsius or less. 
         [0004]    RF generators and electrodes are used to treat pain, cancer, and other diseases. Examples are the equipment and applications of Cosman Medical, Inc., Burlington, Mass. such as the G4 radiofrequency generator, the CSK electrode, CC cannula, and DGP-PM ground pad. Related information is given in the paper by Cosman E R and Cosman B J, “Methods of Making Nervous System Lesions”, in Wilkins R H, Rengachary S (eds.); Neurosurgery, New York, McGraw Hill, Vol. 3, 2490-2498; and is hereby incorporated by reference in its entirety. Related information is given in the book chapter by Cosman E R Sr and Cosman E R Jr. entitled “Radiofrequency Lesions.”, in Andres M. Lozano, Philip L. Gildenberg, and Ronald R. Tasker, eds., Textbook of Stereotactic and Functional Neurosurgery (2nd Edition), 2009, and is hereby incorporated by reference in its entirety. 
         [0005]    The Cosman CC cannula and RFK cannula, manufactured by Cosman Medical, Inc. in Burlington, Mass., include each an insulated cannula having a pointed metal shaft that is insulated except for an uninsulated electrode tip. The CC cannula has a straight shaft. The RFK cannula has a curved shaft; one advantage of a curved shaft is that it can facilitate maneuvering of the cannula&#39;s tip within tissue. Each cannula includes a removable stylet rod that occludes the inner lumen of the cannula&#39;s shaft, for instance during insertion of the cannula into solid tissue, and can be removed to allow for injection of fluids or insertion of instruments, like an electrode. The cannula has a hub at its proximal end having a luer fitting to accommodate a separate thermocouple (TC) electrode, for example the Cosman CSK electrode, Cosman TCD electrode, and Cosman TCN electrode, that can deliver electrical signal output such as RF voltage or stimulation to the uninsulated electrode tip. The Cosman CSK and TCD electrodes have a shaft that is stainless steel. The Cosman TCN electrode has a shaft that is Nitinol. Related information is given in Cosman Medical brochure “Four Electrode RF Generator”, brochure number 11682 rev A, copyright 2010, Cosman Medical, Inc., and is hereby incorporated by reference herein in its entirety. One limitation of the CC and RFK RF cannulae is that they do not include echogenic markers. 
         [0006]    A paper by S N Goldberg et al. entitled “Hepatic Metastases: Percutaneous Radiofrequency Ablation with Cool-Tip Electrodes,” Radiology 2007, vol. 205, no. 2, pp. 367-373 describes various techniques and considerations relating to tissue ablation with RF electrodes have cooled electrode tips, and is incorporated herein by reference. The Cool-Tip Electrode of Radionics and Valley Lab, Inc. is a 16-gauge (or 1.6 millimeter diameter) electrode with partially insulated shaft and water-cooling channel inside its rigid, straight cannula shaft. The brochure from Radionics is hereby incorporated by reference in its entirety. The Cool-Tip Electrode is used for making large RF heat ablations of cancerous tumors, primarily in soft-tissue organs and bone. It has a closed trocar point that includes a metal plug that is welded to the metal tubing that is part of the electrode shaft. The distal end of the metal plug is sharpened to form a three sided, axially symmetric trocar. The distal end is a closed and sealed metal structure. The sharpened portion of the distal tip does not include the metal tubing itself, but rather the sharpened end of the metal plug that is welded to the metal tubing. This has the limitation that the shaft is not curved. This has the limitation that the shaft does not contain both echogenic markers and a curved tip. This has the limitation that it is not a hollow shaft covered in part by electrical insulation and having echogenic markers. 
         [0007]    A paper by Rosenthal et al entitled “Percutaneous Radiofrequency Treatment of Osteoid Osteoma,” Seminars in Musculoskeletal Radiology, Vol. 1, No. 2, 1997 reports the treatment of a primary benign bone tumor using a percutaneously placed radiofrequency electrode, and is incorporated herein by reference. 
         [0008]    Medical needles are used for epidural anesthesia, for example, for the introduction of catheters into the epidural space for the purpose of treating pain. Examples of epidural introducer needles include the tuohy needle, and the needle disclosed in U.S. Pat. No. 5,810,788 authored by Racz. Related information on epidural anesthesia and epidural needles is in “Epidural Lysis of Adhesions and Percutaneous Neuroplasty” by Gabor B. Racz, Miles R. Day, James E. Heavner, Jeffrey P. Smith, Jared Scott, Carl E. Noe, Laslo Nagy and Hana Ilner (2012), in the book “Pain Management—Current Issues and Opinions”, Dr. Gabor Racz (Ed.), ISBN: 978-953-307-813-7, InTech, and is hereby incorporated by reference in its entirety. One limitation of epidural needles in the prior art is that they do not have electrical insulation. Another limitation of epidural needles in the prior art is that they cannot functional as radiofrequency cannulae with a defined active tip. 
         [0009]    Touhy needles with echogenic markings are well known. One example is the “Tuohy Ultrasonic” manufactured by Spectra Medical Devices of Wilmington, Mass., USA shown in the company&#39;s 2013 catalog, which is incorporated herein by reference in full. The tuohy needle distal end has a slight curve directly opposite the bevel. One limitation of echogenic tuohy needles in the prior art is that the shaft curvature is not configured for steering of the needle within tissue. Another limitation of echogenic tuohy needles in the prior art is that they do not have a bend in their shafts that is 5 mm or more from their most distal point. Another limitation of echogenic tuohy needles in the prior art is that they do not have electrical insulation along their shafts. Another limitation of echogenic tuohy needles in the prior art is that they are not configured for radiofrequency lesioning. 
         [0010]    US Patent Applications 2012/009504 A1 by Massengale et al describes an echogenic nerve block apparatus. In FIG. 2D, Massengale shows a needle “body or shaft 24 that terminates in a generally flat, planar surface 26. In this particular example, the needle has a slight curve or bends 27 near the tip of the needle that defines that flat planar surface 26 . . . . The needle illustrated in FIG. 2D is sometimes referred to as a TUOHY needle or a needle having a TUOHY-type point.” One limitation of the art in Massengale is that the needle shaft is substantially straight. One limitation of the art in Massengale is that the slight curve in the needle is not 5 mm or more from the distal point of the needle. One limitation of the art in Massengale is that the needles cannot be rotated into a position that reduces the angle of incidence of incoming ultrasound waves over a substantial length of the needle, for example a length of 5 mm or more. One limitation of the art in Massengale is that the needles shown are not RF cannulae. Massengale also shows “soft tissue tunneling devices [that] include an elongate shaft having a rounded distal end. The distal end and/or the elongate shaft may be made echogenic in a manner similar to the echogenic needle and/or catheter as described above. These devices may further include a handle secured to the shaft in which the handle is configured to permit a user of the tunneling device to manually manipulate the tunneling device. The elongate shaft may be malleable so as to permit a shape of the shaft to be altered prior to use of the tunneling device. For example, the shaft may have a non-linear shape including, but not limited to, a curved shape.” One limitation of the soft tissue tunneling devices disclosed in Massengale is that they are not needles with sharp tips. One limitation of the soft tissue tunneling devices disclosed in Massengale is that they are not RF cannulae. One limitation of the soft tissue tunneling devices disclosed in Massengale is that they are not configured to delivery RF energy for therapeutic purposes. 
         [0011]    Needles are used in medicine for a variety of applications, including without limitation injecting of anesthetics, neurolyltic agents, injection of medicine, and injection of radiographic contrast. Needles are used in medicine to inject and insert substances and devices in a variety of targets in the human body including muscles, nerves, organs, blood vessels, bone, connective tissue, body cavities, bodily spaces, bodily potential spaces. 
         [0012]    U.S. Pat. No. 4,582,061 authored by F J Fry, in which a straight needle with ultrasonically reflective displacement scale is presented, is hereby incorporated by reference in its entirety. One limitation of this invention is that the echogenic probe has a straight shaft. 
         [0013]    U.S. Pat. No. 4,869,259 authored by D J Elkins, in which an echogenically enhanced surgical instrument and method for production thereof is presented, is hereby incorporated by reference in its entirety. One limitation of this invention is that the echogenic needle has a straight shaft. 
         [0014]    U.S. Pat. No. 5,081,991 authored by Bosley et al., in which echogenic devices material and method is presented, is hereby incorporated by reference in its entirety. One limitation of this invention is that the echogenic needle has a straight shaft. 
         [0015]    U.S. Pat. No. 5,383,466 authored by L. Partika, in which an instrument having enhanced ultrasound visibility is presented, is hereby incorporated by reference in its entirety. One limitation of this invention is that the echogenic needle has a straight shaft. 
         [0016]    U.S. Pat. No. 5,490,521 authored by R E Davis and G L McLellan, in which an ultrasound biopsy needle is presented, is hereby incorporated by reference in its entirety. One limitation of this invention is that the ultrasound needle has a straight shaft. 
         [0017]    U.S. Pat. No. 5,759,154 authored by D V Hoyns, in which a print mask technique for echogenic enhancement of medical device is presented, is hereby incorporated by reference in its entirety. One limitation of this invention is that the echogenic needle has a straight shaft. 
         [0018]    U.S. Pat. No. 5,921,933 authored by R G Sarkins et al., in which medical devices with echogenic coatings are presented, is hereby incorporated by reference in its entirety. One limitation of this invention is that the echogenic needle has a straight shaft. 
         [0019]    US Patent Application 2009/0137906 A1 authored by Maruyama et al., in which an ultrasound piercing needle is presented, is hereby incorporated by reference in its entirety. One limitation of this invention is that the echogenic needle has a straight shaft. Another limitation is that the needle is not a radiofrequency cannula. Another limitation is that the needle is not a radiofrequency electrode. Another limitation is that the needle is not a microwave antenna. Another limitation is that the means of echogenic enhancement does not utilize both macroscopic depressions in the needle surface and microscopic roughing of the needle surface. 
         [0020]    The present invention seeks to overcome the limitations and disadvantages of the prior art. 
       SUMMARY OF THE INVENTION 
       [0021]    The present invention relates generally to the application of echogenic markers to radiofrequency cannulae and electrodes. An advantage of the present invention is that radiofrequency probes can be more easily visualized and directed in the human body by means of ultrasound guidance. 
         [0022]    The present invention relates generally to the application of echogenic markers and a curved tip to a medical needle, including radiofrequency cannulae, injection needles, biopsy needles, microwave antennae, and spinal needles. An advantage of the present invention is that medical needles can be more easily visualized and directed in the human body by means of ultrasound guidance when the needle is inserted at a steep angle relative to the ultrasound beam. 
         [0023]    The present invention relates generally to the application of echogenic markers to medical probes wherein multiple types of echogenic markers are applied to the same probe and the multiple types of echogenic markers have different spatial scale and angles. An advantage of the present invention is that medical needles can be more easily visualized and directed in the human body by means of ultrasound guidance for a wide range of probe insertion angles relative to the ultrasound transceiver. 
         [0024]    In one aspect, a radiofrequency probe can have an echogenic feature. 
         [0025]    In certain embodiments, the probe can have a curved tip. The probe can be a cannula, an electrode, or a unitized injection electrode. The probe can be tissue-piercing. The probe can have a stiff shaft. The probe can include a shaft is composed of metal. The probe can be a radiofrequency cannula with a bevel configured for placement in the epidural space. The probe can be a needle configured to introduce a catheter. The probe can have a distal and proximal end, and a first and a second indentation in a surface of the probe, wherein the first indentation includes a distal aspect having a first angle relative to the surface of the probe, and the second indentation includes a distal aspect having a second angle relative to the surface of the probe. 
         [0026]    In another aspect, a needle can have a curved tip and an echogenic feature. 
         [0027]    In certain embodiments, the needle includes a shaft is composed of metal. The needle can be a radiofrequency cannula, part of a unitized radiofrequency electrode, an epidural needle, or a spinal needle. The needle can be configured for effecting a nerve block. The needle can have a distal and proximal end, and a first and a second indentation in a surface of the needle, wherein the first indentation includes a distal aspect having a first angle relative to the surface of the needle, and the second indentation includes a distal aspect having a second angle relative to the surface of the needle. 
         [0028]    In another aspect, a medical probe can have a first echogenic feature and a second echogenic feature, wherein the first echogenic feature is an indentation in the surface of the probe, and the second echogenic feature is a roughing of the surface of the probe. The first and second feature can be in the same location on the shaft. 
         [0029]    In certain embodiments, the probe can be a needle, a radiofrequency cannula, a radiofrequency electrode, an internally-cooled radiofrequency electrode, a radiofrequency needle, an epidural needle, a biopsy needle, or a spinal needle. The probed can have a curved tip, a sharp bevel, or a blunt tip. 
         [0030]    In certain embodiments, the roughing of the probe&#39;s surface can be produced by sandblasting or beadblasting. 
         [0031]    In certain embodiments, the indentation can have a three-sided pyramidal shape. 
         [0032]    In certain embodiments, the probe can include a shaft having a multitude of echogenic indentations. 
         [0033]    In another aspect, a radiofrequency cannula can have at least one echogenic feature. 
         [0034]    In another aspect, a curved-tip radiofrequency cannula can have at least one echogenic feature. 
         [0035]    In another aspect, a radiofrequency electrode can have at least one echogenic feature. 
         [0036]    In another aspect, a curved medical needle can have at least one echogenic feature. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0037]      FIG. 1  is an illustration of an exemplary insulated, curved echogenic needle and its associated stylet and electrode. 
           [0038]      FIG. 2  is an illustration of an exemplary insulated, straight echogenic needle and its associated stylet and electrode. 
           [0039]      FIG. 3  is an illustration of an exemplary insulated, curved, echogenic, unitized electrode. 
           [0040]      FIG. 4  is an illustration of an exemplary curved, echogenic needle. 
           [0041]      FIG. 5  is an illustration of an exemplary echogenic marker. 
           [0042]      FIGS. 6A-C  are illustrations of an exemplary echogenic marker. 
           [0043]      FIGS. 7A-F  are illustrations is an illustration of exemplary echogenic markers in a cross-sectional view. 
           [0044]      FIG. 8A  is an illustration of exemplary straight, electrically-insulated needle each placed in tissue and visualized using an ultrasound beam. 
           [0045]      FIG. 8B  is an illustration of exemplary curved, electrically-insulated needle each placed in tissue and visualized using an ultrasound beam. 
           [0046]      FIG. 9A  is an illustration of an exemplary echogenic marker on a straight, electrically-insulated needle each placed in tissue and visualized using an ultrasound beam. 
           [0047]      FIG. 9B  is an illustration of an exemplary echogenic marker on a curved, electrically-insulated needle each placed in tissue and visualized using an ultrasound beam. 
       
    
    
     DETAILED DESCRIPTION 
       [0048]    Referring to  FIG. 1 , a needle with shaft  100  is shown. The shaft  100  be substantially cylindrical. The needle can be hollow with an inner lumen. The inner lumen of the shaft  100  can open to the outside via a hole in the tip of the shaft  100  or holes along the shaft. The needle has a sharpened distal end, and is terminated by hub  120  at its proximal end. The needle can configured to penetrate biological tissue, such as the skin&#39;s surface, soft tissue around the spine, visceral organs, limbs, muscles, blood vessels, the liver, the kidney, the prostate, and other human and animal tissues. The needle&#39;s distal end can have a bevel  101 . The needle can be a biopsy needle. The needle&#39;s distal end  101  can have a tissue-piercing geometry, such as a chiba tip. The needle&#39;s distal end  101  can have a rounded tip and stiff shaft capable of piecing tissue. The needle&#39;s distal end  101  can have an epidural geometry, such as a tuohy tip. The needle can be radiofrequency cannula. The needle can be configured to deliver high frequency electrical energy to tissue. The needle can be configured for radiofrequency lesioning. The needle can be configured for pulsed radiofrequency treatment. The needle can be configured for lesioning of nervous tissue. The needle can be configured for lesioning of cancerous tissue. The needle can be configured for insertion into blood vessels. The needle can be configured by insertion in the epidural space. The needle can be configured for use in and around the spine. The needle can be configured for a nerve block procedure. The shaft can be composed of a metallic substance such as stainless steel. The shaft  100  can be rigid. The shaft  100  can be composed of an electrically conductive substance. The metallic shaft  100  is covered with electrical insulation  115 . The electrical insulation  115  can be configured to transmit sound waves without substantially impeding or scattering them. The electrical insulation  115  can be a plastic coating. The needle&#39;s active tip is the metallic portion of the shaft which is not covered with insulation  115 , ie the region of the shaft that is distal to the insulation. The needle&#39;s hub  120  can be a luer hub. The needle&#39;s hub  120  can a locking luer hub. The needle&#39;s hub  120  can admit a syringe or tubing for injection of fluids, such as saline, steroids, anesthetics, neurolytic agents, coagulants, chemotherapy agents, and other medical fluids. 
         [0049]    The shaft  100  can be bent at its distal end. The angle of the bend can be 5 degrees. The angle of the bend can be 10 degrees. The angle of the bend can be 15 degrees. The angle of the bend can be 20 degrees. The angle of the bend can be 25 degrees. The angle of the bend can be 30 degrees. The angle of the bend can be a value greater than 30 degrees. The angle of the bend can be a value less than 30 degrees. The shaft  100  can be straight. 
         [0050]    The bend  102  in the shaft can be positioned substantially at the same location as the distal end of the electrical insulation  115 . The bend  102  in the shaft can be positioned proximal to the distal end of the electrical insulation  115 . The bend  102  in the shaft can be positioned distal to the distal end of the electrical insulation  115 . The bend  102  in the shaft  100  can be a curve that starts at a proximal point along the shaft, and continues all the way to the most distal point of the shaft  100 . The bend  102  in the shaft  100  can be a curve that starts and stops proximal to the most distal point of the shaft. The bend  102  in the shaft  100  can have lengths of straight shaft both distal and proximal to the shaft, as illustrated in  FIG. 1 . The bend  102  can be 1 mm from the most distal point of the shaft  100 . The bend  102  can be 2 mm from the most distal point of the shaft  100 . The bend  102  can be 3 mm from the most distal point of the shaft  100 . The bend  102  can be 4 mm from the most distal point of the shaft  100 . The bend  102  can be 5 mm from the most distal point of the shaft  100 . The bend  102  can be 6 mm from the most distal point of the shaft  100 . The bend  102  can be 7 mm from the most distal point of the shaft  100 . The bend  102  can be 8 mm from the most distal point of the shaft  100 . The bend  102  can be 9 mm from the most distal point of the shaft  100 . The bend  102  can be 10 mm from the most distal point of the shaft  100 . The bend  102  can be more than 10 mm from the most distal point of the shaft  100 . The bend  102  can be between 5 mm and 10 mm from the most distal point of the shaft. The bend  102  can be configured to improve the steerability of the shaft  100  through tissue. 
         [0051]    The echogenic markers  105  can be positioned on the active tip of the shaft  100 , and the echogenic markers  110  can be positioned under or within the insulation  115 . The echogenic markers  105  can be positioned distal to the bent section of the shaft  100 , and the echogenic markers  110  can be positioned proximal to the bent section of the shaft  100 . The echogenic markers  105  can be positioned along the bent section of the shaft  100 , and the echogenic markers  110  can be positioned proximal to the bent section of the shaft  100 . The cluster of markers  105  can appear different to the cluster of markers  110  when viewed using ultrasound imaging. The cluster of markers  105  can be physically separated from the cluster of markers  110  so that the two clusters can be distinguished when viewed using ultrasound imaging. In one embodiment, the echogenic markers  105  can be omitted. In one embodiment, the echogenic markers  110  can be omitted. 
         [0052]    The echogenic markers  105  and  110  can be configured to enhance the needle&#39;s shaft visibility when viewed with ultrasound imaging. For example, the echogenic markers  105  and  110  can be configured such that when the needle is inserted to a living body and an ultrasound transceiver in contact with the skin of the living body is directed at the needle, the ultrasound image of the needle is enhanced relative to what its image if the needle shaft did not have the echogenic markers  105  and  110 . The echogenic markers  105  and  110  can be indentations in the surface of the shaft  100 . The echogenic markers  105  and  110  can be produced by means of stamping a shape or shapes into the shaft  100 . The echogenic markers  105  can be produced by means of sand blasting the shaft  100 . The echogenic markers  105  and  110  can be produced by means of bead blasting the shaft  100 . The echogenic markers  105  can be produced by means of roughing the surface of the shaft  100 . The echogenic markers  105  and  110  can be produced by means of laser ablation the surface of the shaft  100 . The echogenic markers  105  and  110  can be linear depressions in the surface of the shaft  100 . The echogenic markers  105  and  110  can be circumferential grooves in the surface of the shaft  100 . The echogenic markers  105  and  110  can be material variations in the insulation  115 . The echogenic markers  105  can produce echogenic enhancement by a different means than the echogenic markers  110 . The echogenic markers  105  and  110  can each be a multitude of markers, each of which markers have a size in the range 0.005 and 0.020 inches on the surface of the needle shaft  100 , and depth between 0.002 and 0.005 inches into the surface of the needle shaft  100 . The echogenic markers  105  and  110  can include both macroscopic echogenic dents (examples of one of which include the markers shown in  FIG. 5 ,  FIGS. 6A-C , and  FIGS. 7A-F ) in the surface of shaft  100  and a microscopic roughing of the surface (such as that produced by sandblasting or beadblasting) of the shaft  100 ; one advantage of this embodiment is that the macroscopic dents can reflect ultrasound waves when the shaft  100  is positioned at a steep angle relative to the ultrasound transceiver and the microscopic surface roughing produces an enhanced image of the entire shaft when the shaft  100  is positioned at shallow angles relative to the ultrasound transceiver. In one example, the echogenic marker  105  can be produced by sandblasting the surface of the shaft  100  and then producing at least one macroscopic dent in the surface of the shaft  100  where the sandblasting was applied. In one example, the echogenic marker  105  can be produced by producing at least one macroscopic dent in the surface of the shaft  100  and then sandblasting the surface of the shaft  100  at and around the location or locations of the said at least one macroscopic indentation. In one example, the echogenic marker  105  can be a macroscopic indentation at a first location on the shaft  100  and sandblasting at a second location on the shaft  100 . 
         [0053]    The needle&#39;s inner lumen can admit a stylet  160  with cap  165 . The stylet cap  165  can engage with the needle hub  120 . The stylet can fill some or all of the needle&#39;s hollow shaft to facilitate insertion of the needle into biological tissue. The stylet&#39;s shaft  160  can be composed of stainless steel. The stylet&#39;s shaft  160  can be composed of a plastic. The stylet&#39;s shaft  160  can be substantially rigid. The stylet&#39;s shaft  160  can be substantially flexible. When the stylet&#39;s cap  165  is fully engaged with the needle&#39;s hub  120 , the stylet&#39;s distal end can be substantially flush with the distal end of the needle shaft  100 . When the stylet&#39;s cap  165  is fully engaged with the needle&#39;s hub  120 , the stylet&#39;s  160  distal end can extend beyond the distal end of the needle shaft. The stylet  160  can be a flexible material, and when the stylet&#39;s cap  165  is fully engaged with the needle&#39;s hub  120 , the stylet&#39;s  160  distal end can extend beyond the distal end of the needle shaft to provide tactile feedback that an structure, such as the dura matter, has been encountered as the needle is advanced into bodily tissue without piercing that structure. 
         [0054]    The needle&#39;s inner lumen can admit an electrode with distal tip  130 , shaft  135 , hub  140 , cable  145 , and connector  150 . The electrode  135  can be a radiofrequency electrode, well known to one skilled in the art. The electrode hub  140  can engage with the cannula hub  120 . The electrode tip  130  can house a temperature sensor. The connector  150  can couple the electrode to an electrical power supply, such as a nerve stimulator, radiofrequency generator, or PENS generator. The electrode  135  can be an internally-cooled electrode, such as by fluid circulating within the electrode shaft. 
         [0055]    In one embodiment, the cannula hub  120  can have an additional connection so that fluid can be injected at the same time the electrode  135  is fully inserted into the cannula shaft  100  and the electrode hub  140  is fully engaged into the cannula hub  120 . In another embodiment, the electrode hub  140  has an additional fluid connection so that fluid can be injected into and through the cannula shaft  100  at the same time the electrode  135  is fully inserted into the cannula shaft  100  and the electrode hub  140  is fully engaged into the cannula hub  120 . 
         [0056]    The active tip of the cannula shaft  100  can be less than 1 mm in length. The active tip of the cannula shaft  100  can be 1 mm in length. The active tip of the cannula shaft  100  can be 2 mm in length. The active tip of the cannula shaft  100  can be 4 mm in length. The active tip of the cannula shaft  100  can be 5 mm in length. The active tip of the cannula shaft  100  can be 6 mm in length. The active tip of the cannula shaft  100  can be 10 mm in length. The active tip of the cannula shaft  100  can be 15 mm in length. The active tip of the cannula shaft  100  can be 20 mm in length. The active tip of the cannula shaft  100  can be 30 mm in length. The active tip of the cannula shaft  100  can be 40 mm in length. The active tip of the cannula shaft  100  can be 50 mm in length. The active tip of the cannula shaft  100  can be 60 mm in length. The active tip of the cannula shaft  100  can be greater than 60 mm in length. The active tip of the cannula can be between 1 mm and 60 mm in length. 
         [0057]    The cannula shaft&#39;s diameter can be less than 23 gauge. The cannula shaft&#39;s diameter can be 22 gauge. The cannula shaft&#39;s diameter can be 21 gauge. The cannula shaft&#39;s diameter can be 20 gauge. The cannula shaft&#39;s diameter can be 18 gauge. The cannula shaft&#39;s diameter can be 16 gauge. The cannula shaft&#39;s diameter can be 15 gauge. The cannula shaft&#39;s diameter can be 14 gauge. The cannula shaft&#39;s diameter can be greater than 16 gauge. The cannula shaft&#39;s diameter can be between 23 and 14 gauge. 
         [0058]    The cannula shaft&#39;s length can be less than 5 cm. The cannula shaft&#39;s length can be 5 cm. The cannula shaft&#39;s length can be 10 cm. The cannula shaft&#39;s length can be 15 cm. The cannula shaft&#39;s length can be 20 cm. The cannula shaft&#39;s length can be 25 cm. The cannula shaft&#39;s length can be less than 5 cm. The cannula shaft&#39;s length can be between 5 cm and 25 cm. The cannula shaft&#39;s length can be greater than 25 cm. 
         [0059]    The cannula shaft&#39;s diameter can be less than 23 gauge. The cannula shaft&#39;s diameter can be 22 gauge. The cannula shaft&#39;s diameter can be 21 gauge. The cannula shaft&#39;s diameter can be 20 gauge. The cannula shaft&#39;s diameter can be 18 gauge. The cannula shaft&#39;s diameter can be 16 gauge. The cannula shaft&#39;s diameter can be greater than 16 gauge. The cannula shaft&#39;s diameter can be between 23 and 16 gauge. 
         [0060]    In one embodiment, the needle does not admit a stylet  160 . 
         [0061]    In one embodiment, a radiofrequency cannula has both a bent distal tip and markers that enhance said radiofrequency cannula&#39;s image when said cannula is positioned in the human body and viewed with an ultrasound imaging apparatus. One advantage of this embodiment is that a radiofrequency cannula can be easily positioned using ultrasound guidance. One advantage of this embodiment is that a radiofrequency cannula can be easily positioned near soft tissue anatomy that is visible using ultrasound imaging. One advantage of this embodiment is that a radiofrequency cannula can be easily positioned near soft tissue anatomy that is visible using ultrasound imaging and not visible using radiographic imaging, such as x-ray. One advantage of this embodiment is that a curved radiofrequency cannula can be steered by a physician during its placement in bodily tissue. One advantage of this embodiment is that a curved tip can be used to make the tip more perpendicular to the ultrasound transceiver than is the shaft. One advantage of this embodiment is that a curved tip can be used to make the tip more perpendicular to an ultrasound transceiver than is the shaft, and thus allow both an enhanced ultrasound image of the tip and a steep approach to target anatomy. 
         [0062]    It is understood that in other embodiments electrical insulation can be applied in multiple segments to the cannula shaft  100 , including the placement of insulation distal to the active tip. It is understood that the cannula shaft  100  can have an overall curved shape. It is understood that the cannula shaft  100  can have multiple curves. 
         [0063]    In another embodiment, the device in  FIG. 1  can have a substantially straight shaft. In another embodiment, the angle  102  can be zero. 
         [0064]    Referring to  FIG. 2 , another embodiment of the present invention is shown in which the insulated cannula has a straight shaft  200 . The elements presented in  FIG. 2  and analogous to those presented in  FIG. 1 . In one embodiment of the present invention, a radiofrequency cannula has a straight shaft  200  and markers that enhance said radiofrequency cannula&#39;s image when said cannula is positioned in the human body and viewed with an ultrasound imaging apparatus. One advantage of this embodiment is that a radiofrequency cannula can be easily positioned near soft tissue anatomy that is visible using ultrasound imaging. One advantage of this embodiment is that a radiofrequency cannula can be easily positioned near soft tissue anatomy that is visible using ultrasound imaging and not visible using radiographic imaging, such as x-ray. 
         [0065]    Referring to  FIG. 3 , an electrode is presented wherein the electrode&#39;s shaft  300  has a bent distal end, the electrode has a hub  320  at its proximal end, the electrode&#39;s shaft is covered by electrical insulation  315  along its proximal length which forms an uninsulated active tip near or at the electrode&#39;s distal end, the electrode&#39;s bent distal active tip has one or more echogenic markers  305 , the electrode&#39;s shaft can have additional echogenic markers  310 , the cabling  345  connects to an electrical connector  350  for connection to a radiofrequency generator or nerve stimulator and delivery of radiofrequency energy or stimulation waveforms to the active tip of the electrode, and the cabling  345  connects to a fluid connector  355  for delivery of fluid through the electrode&#39;s hollow shaft  300  and out from holes along the shaft  300  or at the distal tip of the shaft  300 . The echogenic markers  305  and  310  can be configured to be visually distinguished when viewed using ultrasound imaging. In one embodiment, the shaft  300  can be straight over its entire length. In one embodiment, the electrode&#39;s shaft can be configured to pierce tissue. In one embodiment, the electrode&#39;s shaft can be sharpened. In one embodiment, the electrode is a radiofrequency electrode. In one embodiment, the electrode has a temperature sensor at its tip and is configured so that a radiofrequency generator can contain the measured temperature when radiofrequency power is delivered via the electrode into living tissue, such as that of a human body. In one embodiment, the electrode is a injection needle configured for stimulation-guided injections near or in nervous tissue. The dimensions of the active tip, the shaft length, the bend, and the shaft diameter can fall in the same ranges as those of the needle presented in  FIG. 1 . In one embodiment, the electrode omits the markers  310 . In another embodiment, the apparatus  300 ,  302 ,  305 ,  310 ,  315 ,  320 ,  345 ,  350 ,  355  can be a microwave antenna, such as that used for medical tissue ablation. In another embodiment, the apparatus  300 ,  302 ,  305 ,  310 ,  315 ,  320 ,  345 ,  350 ,  355  can be a probe for use in biological tissue, such as the human body. In another embodiment, the device in  FIG. 3  can be a unitized injection electrode, such as the electrodes shown U.S. Pat. No. 7,862,563 by Cosman et al. 
         [0066]    In another embodiment, the electrode presented in  FIG. 3  can have a substantially straight shaft. In another embodiment, the angle of bend  302  can be zero. 
         [0067]    It is understood that the probe presented in  FIG. 3  can have multiple electrical contact (as in a bipolar electrode), multiple segments of insulation, and multiple curves. 
         [0068]    Referring to  FIG. 4 , a needle  400  is presented that has a bent tip and echogenic markers, and that does not have electrical insulation. The needle can be hollow for injection of fluid and the introduction of the stylet  460 . The needle&#39;s shaft  415  is not insulated. The needle  400  has echogenic elements  405  and  410 . The needle&#39;s shaft can be rigid. The shaft of the needle  400  can be metallic, such as a stainless steel hypotube. The needle  400  can be tissue-piecing. The needle  400  can have a sharpened tip. The elements of the needle presented in  FIG. 4  are analogous to those of the needle presented in  FIG. 1 . In one embodiment, the needle  400  is a spinal needle. In one embodiment, the needle  400  is for injection in or near nervous tissue. In one embodiment, the needle  400  is for injection in the epidural space. In one embodiment, the needle  400  is for injection in blood vessels. One advantage of the needle  400  is that the echogenic markers can enhance the image of the needle  400  when placed in the human body and viewed using an ultrasound probe placed at the skin&#39;s surface. One advantage of the needle  400  with a curved tip is that the needle can be rotated so that the tip is more perpendicular to the ultrasound wavefront without changing the trajectory of the needle&#39;s shaft  415 . One advantage of the needle  400  with a curved tip is that the needle can be rotated so that the tip is more perpendicular to the ultrasound wavefront without changing the trajectory of the needle&#39;s shaft  415 , and thereby the ultrasound image of the needle&#39;s tip can be enhanced even when the needle&#39;s shaft  415  is substantially parallel to the ultrasound waves. In one embodiment, the needle  400  does not have a bent tip. In one embodiment, the needle  400  has a shaft that is straight over its entire length. 
         [0069]    The bend  402  in the shaft of needle  400  can be a curve that starts at a proximal point along the shaft, and continues all the way to the most distal point of the shaft  400 . The bend  402  in the shaft  400  can be a curve that starts and stops proximal to the most distal point of the shaft. The bend  402  in the shaft  400  can have lengths of straight shaft both distal and proximal to the shaft, as illustrated in  FIG. 1 . The bend  402  can be 1 mm from the most distal point of the shaft  400 . The bend  402  can be 2 mm from the most distal point of the shaft  400 . The bend  402  can be 3 mm from the most distal point of the shaft  400 . The bend  402  can be 4 mm from the most distal point of the shaft  400 . The bend  402  can be 5 mm from the most distal point of the shaft  400 . The bend  402  can be 6 mm from the most distal point of the shaft  400 . The bend  402  can be 7 mm from the most distal point of the shaft  400 . The bend  402  can be 8 mm from the most distal point of the shaft  400 . The bend  402  can be 9 mm from the most distal point of the shaft  400 . The bend  402  can be 10 mm from the most distal point of the shaft  400 . The bend  402  can be more than 10 mm from the most distal point of the shaft  400 . The bend  402  can be between 5 mm and 10 mm from the most distal point of the shaft. The bend  402  can be configured to improve the steerability of the shaft  400  through tissue. 
         [0070]    Referring to  FIG. 5 , presented in three perpendicular views is one example of an echogenic marker in the shaft of a needle, electrode, or probe, such as those presented in  FIGS. 1, 2, 3, and 4 . The marker is depression in the side of the probe, and can be formed, for example, by cutting, laser ablating, stamping, or pressing into the side of the probe. Elements  510 ,  512 ,  515  present a view of the echogenic marker&#39;s incut planes looking in the radial direction from the outside of the probe, ie as the marker appears looking at the probe&#39;s shaft from the outside. The length and the width of the echogenic marker can each be in the range 0.005 inches to 0.020 inches. The length and the width of the echogenic marker can each be less than 0.005 inches. The length and the width of the echogenic marker can each be greater than 0.020 inches. Elements  500 ,  505 ,  509  present a cross-sectional view of the said echogenic marker though the probe&#39;s wall  509 , of which only a short segment is shown, in the radial-axial direction. Element  500  and  505  represent surfaces that are on the more outer surface of the probe&#39;s wall  509 ; the bottom of wall  509  is inside the inner lumen of the probe&#39;s shaft. Element  500  is a cross section through the intersection of planes  510  and  512 . Element  505  shows a cross-sectional cut of plane  515 . Elements  520 ,  522 ,  529  present a view of the said echogenic marker constructed by cutting through the probe&#39;s wall  529 , of which only a segment is shown, perpendicular the axis of the cylindrical probe, and looking in the direction of planes  520  and  522 , which correspond to planes  510  and  512 , respectively, in the view  510 ,  512 ,  515 . Element  500  is a cross section through the intersection of planes  520  and  522 . 
         [0071]    The marker in  FIG. 5  can be oriented with the long axis of the probe&#39;s shaft; for example, the planes  510  and  512  can be distal to the plane  515 . The probe&#39;s wall  509 ,  529  can the wall of a stainless steel tube. For example, for a shaft that is 21 gauge tubing with outer diameter 0.032 inches and inner diameter 0.020, the thickness of wall  509 ,  529  is 0.006 inches. The depth of the marker in the wall  509 ,  529  can be less than the thickness of the wall. The depth of the marker in the wall  509 ,  529  can be less than 0.002 inches. The depth of the marker in the wall  509 ,  529  can be 0.002 inches. The depth of the marker in the wall  509 ,  529  can be 0.003 inches. The depth of the marker in the wall  509 ,  529  can be 0.004 inches. The depth of the marker in the wall  509 ,  529  can be 0.005 inches. The depth of the marker in the wall  509 ,  529  can be 0.006 inches. The depth of the marker in the wall  509 ,  529  can be greater than 0.006 inches. The depth of the marker in the wall  509 ,  529  can be in the range 0.002 to 0.006 inches. The depth of the marker in the wall  509 ,  529  can be equal or greater to the wall thickness so that the marker provides outlets for fluid outflow from the inner lumen of the shaft. The three planes  510 ,  512 , and  515  can be mutually orthogonal to each other. The three planes  510 ,  512 ,  515  can be non-perpendicular to each other. Planes  510  and  512  can be perpendicular to each other, and plane  515  can be non-perpendicular to plane  510  and non-perpendicular to plane  512 . The marker in  FIG. 5  can be constructed so that plane  515  has a more shallow angle with respect to the outside of the probe than do planes  510  and  512 ; in this embodiment, line  505  is closer to parallel with the outer wall of the probe shaft  509  than is line  500 ; in this embodiment, when the planes  510  and  512  are positioned distal to plane  515  and the probe is placed in a living body within the fan of an ultrasound probe, the shallow angle of  515  occludes less of planes  510  and  512  from ultrasound beam and planes  510  and  512  are more perpendicular to the ultrasound beam (as shown, for example, in  FIG. 9A ). In one embodiment, multiple instances of the marker shown in  FIG. 5  can be placed at multiple position on the shaft of a probe like those shown in  FIGS. 1, 2, 3, and 4 ; one advantage of using multiple markers is to improve the signal to noise ratio of the probe&#39;s signal in an ultrasound image; another advantage of using multiple markers to the enhance the probe&#39;s image when viewed from different angles using ultrasound imaging. In one embodiment, multiple instances of the marker shown in  FIG. 5  are placed at specific locations which can be used to judge scale and/or distinguish parts of the probe (such the tip) in an ultrasound image. 
         [0072]    Referring to  FIGS. 6A-C , presented in three perpendicular views is one example of an echogenic marker in the shaft of a needle, electrode, or probe, such as those presented in  FIGS. 1, 2, 3, and 4 . The marker is depression in the side of the probe, and can be formed, for example, by cutting, laser ablating, stamping, or pressing into the side of the probe. Elements  610  and  615  present a view of the echogenic marker&#39;s incut surfaces looking in the radial direction from the outside of the probe, ie as the marker appears looking at the probe&#39;s shaft from the outside. The surface  610  can be curved. The surface  615  can be curved. The surface  615  can be planar. Elements  600 ,  605 ,  609  present a cross-sectional view of the said echogenic marker though the probe&#39;s wall  609  in the radial-axial direction. Element  600  and  605  represent surfaces that are on the more outer surface of the probe&#39;s wall  609 , of which only a short segment is shown; the bottom of wall  609  is inside the inner lumen of the probe&#39;s shaft. Element  600  is a cross section through surface  610 . Element  605  shows a cross-sectional cut of surface  615 . Elements  620  and  629  present a view of the said echogenic marker constructed by cutting through the probe&#39;s wall  629 , of which only a segment is shown, perpendicular the long axis of the cylindrical probe, and looking in the direction of surface  620 , which corresponds to plane  610  in the view  610 ,  615 . Element  600  is a cross section through the surface  620 . 
         [0073]    The marker can be oriented with the long axis of the probe&#39;s shaft; for example, the surface  610  can be distal to the surface  615 . The probe&#39;s wall  609 ,  629  can the wall of a stainless steel tube. For example, for a shaft that is 21 gauge tubing with outer diameter 0.032 inches and inner diameter 0.020, the thickness of wall  609 ,  629  is 0.006 inches. The depth of the marker in the wall  609 ,  629  can be less than the thickness of the wall. The depth of the marker in the wall  609 ,  629  can be less than 0.002 inches. The depth of the marker in the wall  609 ,  629  can be 0.002 inches. The depth of the marker in the wall  609 ,  629  can be 0.003 inches. The depth of the marker in the wall  609 ,  629  can be 0.004 inches. The depth of the marker in the wall  609 ,  629  can be 0.005 inches. The depth of the marker in the wall  609 ,  629  can be 0.006 inches. The depth of the marker in the wall  609 ,  629  can be greater than 0.006 inches. The depth of the marker in the wall  609 ,  629  can be in the range 0.002 to 0.006 inches. The depth of the marker in the wall  609 ,  629  can be equal or greater to the wall thickness so that the marker provides outlets for fluid outflow from the inner lumen of the shaft. The marker in  FIG. 5  can be constructed so that plane  615  has a more shallow angle with respect to the outside of the probe than does surface  610 ; in this embodiment, line  605  is closer to parallel with the outer wall of the probe shaft  609  than is line  600 ; in this embodiment, when the surface  610  is positioned distal to surface  615  and the probe is placed in a living body within the fan of an ultrasound probe, the shallow angle of  615  occludes less of surface  610  from ultrasound beam and surface  610  is more perpendicular to the ultrasound beam (as shown, for example, in  FIG. 9A ). In one embodiment, multiple instances of the marker shown in  FIGS. 6A-C  can be placed at multiple position on the shaft of a probe like those shown in  FIGS. 1, 2, 3, and 4 ; one advantage of using multiple markers is to improve the signal to noise ratio of the probe&#39;s signal in an ultrasound image; another advantage of using multiple markers to the enhance the probe&#39;s image when viewed from different angles using ultrasound imaging. In one embodiment, multiple instances of the marker shown in  FIGS. 6A-C  are placed at specific locations which can be used to judge scale and/or distinguish parts of the probe (such the tip) in an ultrasound image. In one embodiment, a single probe such as one of those presented in  FIGS. 1, 2, 3, and 4 , contain multiple type of dent-like markers, for example, both markers of the type presented in  FIG. 5  and markers of the type presented in  FIGS. 6A-C ; one advantage of this embodiment is that it can improve visibility of the probe under different conditions. 
         [0074]    Referring to  FIGS. 7A-F , presented in cross-section are six embodiments of individual echogenic markers that can be incorporated into a probe like those presented in  FIGS. 1, 2, 3 , and  4 . Each marker is shown in an axial-radial cross-sectional view similar to that of marker  500 ,  505 , and  509  of  FIGS. 6A-C  and that of marker  600 ,  605 , and  609  of  FIGS. 6A-C . For each example marker, elements further to the left are more distal along the probe&#39;s shaft (ie closer to the tissue-penetrating end of the probe), and element further to the right are more proximal along the probe&#39;s shaft (ie closer to the hub of the probe). For the marker shown by surface  700 , surface  705 , and wall  709 , angle  703  is the angle between surface  700  and the outer surface of the shaft, and angle  704  is the angle between surface  705  and the outer surface of the shaft. The angle  703  can be small than the angle  704 ; one advantage of this embodiment is that when the shaft is viewed at a steep angle relative to the ultrasound probe (as shown, for example, in  FIG. 8A  and  FIG. 8B ), the shallow angle of surface  705  relative to the probes surface allows ultrasound pulses to bounce off surface  700 . For the marker shown by surface  710 , surface  715 , and wall  719 , angle  713  is the angle between surface  710  and the outer surface of the shaft, and angle  714  is the angle between surface  715  and the outer surface of the shaft. The angle  713  is smaller than angle  703 ; as such, when the probe is placed at a steeper angle relative to the ultrasound beam, surface  710  is more perpendicular to the ultrasound beam and reflects more ultrasound waves back to the ultrasound probe, thereby increasing the ultrasound signal induced by the marker  710 ,  715 ,  719  relative to marker  700 ,  705 ,  709  at that angle. The angle  714  is larger than angle  704 ; as such, even at steep angles, surface  715  allows more ultrasound waves to contact surface  710  than it would if angle  714  had the same value as  704 . The marker shown by surface  720 ,  725 , and  729  is characterized by angle  723  that is closer to a right angle than are angles  703  and  713 ; as such, sound reflections back to the ultrasound transceiver are increased at very steep shaft angles. The marker shown by surface  720 ,  725 , and  729  is characterized by angle  724  that is closer to 180 than are angles  704  and  714 ; as such, sound waves from the ultrasound transceiver are allowed an unimpeded path to surface  720  over a wider range of shaft angles than would be allowed were angle  724  equal in value to  704  or  714 . The echogenic marker shown by shaft wall  739  and curved surface with distal part  730  and proximal part  735  is a curved depression in the surface of the shaft. One advantage of a curved, concave marker is that sound waves from the ultrasound transceiver can reflect off the surface and back toward the transceiver for a wide variety of shaft orientations relative to the transceiver. The distal part of the surface  730  can have a sharper curvature than the proximal part of the surface  735 , so the proximal part does not block incoming ultrasound waves incident on the shaft at shallow angles and the distal part has a part roughly perpendicular to incoming sound waves incident on the shaft at shallow angles which can reflect said ultrasound waves back toward the ultrasound transceiver. The echogenic marker shown by shaft wall  749  and curved surface with distal part  740  and proximal part  745  is a curved depression in the surface of the shaft with a longer length in the axial direction (equivalent to the shaft&#39;s distal-proximal direction) than that of marker  730 ,  735 ,  739 , and with a proximal part  745  that has a more gradual slope than the proximal part  735  of the marker. The shallower slope of proximal part  745  relative to proximal part  735  allows incoming sound waves to contact distal part  740  for steeper shaft angles relative to the ultrasound beam. The echogenic marker shown by shaft wall  759  and curved surface with distal part  750  and proximal part  755  is a curved depression in the surface of the shaft with a longer length in the axial direction (equivalent to the shaft&#39;s distal-proximal direction) than that of marker  740 ,  745 ,  749 , and with a proximal part  755  that has a more gradual slope than the proximal part  745  of the marker. The shallower slope of proximal part  755  relative to proximal part  745  allows incoming sound waves to contact distal part  750  for steeper shaft angles relative to the ultrasound beam. The proximal part  750  can has generally steeper curvature than proximal part  740 ; as such, when this marker is used on a probe that is inserted more parallel to the central axis of the ultrasound beam, the proximal part  750  will be more likely to reflect ultrasound signals back toward the ultrasound transceiver. 
         [0075]    In one embodiment, a single probe such as one of those presented in  FIGS. 1, 2, 3, and 4 , contain multiple types of dent-like markers, for example, drawn from the six markers presented in  FIGS. 7A-F . One advantage of this embodiment is that it can improve visibility of the probe under different conditions. One advantage of this embodiment is that the probe is more likely to reflect ultrasound waves back toward the ultrasound transceiver. 
         [0076]    Referring to  FIG. 8A , in accordance with the present invention, a probe  800  with echogenic markers  801  and  802  is presented. The probe  800  has a straight shaft and can be of the types presented in  FIGS. 1, 2, 3, and 4 . The markers  801  are on the tip of the probe  800 . The markers  802  are on the shaft of the probe  800 . The markers  802  can be positioned under electrical insulation on the shaft of the probe  800 . The probe  800  can be a radiofrequency cannula. The probe  800  can be a radiofrequency electrode. The probe  800  can be a microwave antenna. The probe is placed in a biological tissue  815 . The biological tissue  815  can be a living body. The biological tissue  815  can be the human body. The biological tissue  815  can be the spine of a human. The biological tissue  815  can be a limb of a human. The biological tissue  815  can incorporate a human organ, such as the liver, kidney, prostate, lung, spleen, and pancreas. The biological tissue  815  can be an internal part of the human body. The probe  800  can be placed in a living body as part of a medical procedure. The probe  800  can be directed at a structure within the body, such as a tumor, a painful nerve, or nervous tissue. An ultrasound transceiver  805  is placed on the surface of the biological tissue  815 . The ultrasound probe  805  can be placed on the surface of the skin. The ultrasound probe can be placed on an internal surface within a living body in the course of a surgical procedure. The ultrasound probe  805  is directed at the probe  800  and emits bursts of sound waves into the tissue. The sound waves include beams  810 ,  811 , and  812 . Beam  810  is incident on the probe  800  at its distal end of its straight tip, at the distal end of the cluster of markers  801 . Beam  811  is incident on the probe  800  at the proximal end of its straight tip, between the cluster of markers  801  and the cluster of markers  802 . Beam  812  is incident on the probe  800  at the proximal end of the cluster of markers  802 . An array of ultrasound beams are present between beams  810  and  811 , and between  811  and  812 , as is understood by one skilled in the art. 
         [0077]    Referring to  FIG. 8B , in accordance with the present invention, a probe  850  with echogenic markers  851  and  852  is presented. The elements in  FIG. 8B  are identical to those in  FIG. 8A  except that probe  851  has a bent tip, whereas probe  800  has a straight tip. The tip lengths of probes  800  and  850  are identical, and the extent of markers  801  and  851  are identical. The ultrasound probe  855  transmits ultrasound beams  860 ,  861 , and  862  into bodily tissue  865 , and beams  860 ,  861 , and  862  are incident on the probe  850 . An array of ultrasound beams are present between beams  860  and  861 , and between  861  and  862 , as is understood by one skilled in the art. 
         [0078]    Referring to both  FIGS. 8A and 8B , the angle of the proximal shaft of probe  850  relative to ultrasound probe  855  is the same as the angle of the proximal shaft of probe  800  relative to the ultrasound probe  805 . Due to the curve tip of probe  850 , the image of the tip of probe  850  is larger in the ultrasound image produced by ultrasound probe  855 , than is the image of the tip of probe  800  in the ultrasound image produced by ultrasound probe  805 . Due to the curve tip of probe  850 , the image of the echogenic markers  851  on the tip of probe  850  is larger in the ultrasound image produced by ultrasound probe  855 , than is the image of the echogenic markers  801  on the tip of probe  800  in the ultrasound image produced by ultrasound probe  805 . One advantage of a probe with echogenic markers and a bent tip is that its tip can be rotated to produce a larger ultrasound image signature in an ultrasound image than a probe with echogenic markers a straight tip placed in the living body with the same proximal shaft trajectory relative to the ultrasound transceiver. The echogenic markers  851  on probe  850  are more perpendicular to the ultrasound beams  860 ,  861 ,  862  than are the echogenic markers  801  on probe  800  relative to ultrasound beams  810 ,  811 ,  812 . One advantage of a probe with echogenic markers and a bent tip is that if its echogenic markers produce a stronger ultrasound signal when oriented more perpendicular to the ultrasound beams, said probe with the echogenic markers and a bent tip can be oriented so that its echogenic markers produce a stronger ultrasound signal than the echogenic markers would if the probe had a straight tip. 
         [0079]    Referring to  FIG. 9A , an ultrasound marker with distal surface  900  and proximal surface  905  is presented in a cross-sectional view like that of marker  500 ,  505  in  FIG. 5 . The ultrasound marker  900 ,  905  is incut into the wall  909  of the tip of a straight probe, of which only a short segment is shown, that can be one of the probes presented in  FIGS. 1, 2, 3, and 4 . Surface  906  is the outer surface of the probe. The probe is placed within a living body and the shaft of the probe is oriented at a steep angle relative to the incoming ultrasound beam  910 . The width of the beam that contacts the distal marker surface  900  is small since the surface  906  blocks the ultrasound beam. The reflected beam  911  is not directed toward the ultrasound transceiver since the angle of incidence of beam  910  on the distal surface  900  is steep. 
         [0080]    Referring to  FIG. 9B , an ultrasound marker with distal surface  950  and proximal surface  955  is presented in a cross-sectional view like that of marker  500 ,  505  in  FIG. 5 . The ultrasound marker  950 ,  955  is incut into the wall  959  of the tip of a bent-tip probe, of which only a short segment is shown, that can be one of the probes presented in  FIGS. 1, 2, 3, and 4 . Surface  956  is the outer surface of the probe. The probe is placed within a living body and the shaft of the probe is oriented at the same steep angle relative to the incoming ultrasound beam  960  as is the shaft of the probe in  FIG. 9A  relative to incoming beam  910 ; however, due to the bend in the tip of the probe in  FIG. 9B , the width of the beam that contacts the distal marker surface  950  is large since the surface  956  does not occlude the distal marker surface  950 . The reflected beam  961  is direct toward the ultrasound transceiver because the surface  950  is substantially perpendicular to the incoming beam  960 . One advantage of a probe with ultrasound-enhancing markers and a curved tip is that the ultrasound image of the probe can be improved for steep angles of placement. One advantage of a radiofrequency cannula with ultrasound-enhancing markers and a curved tip is that the ultrasound image of the cannula can be improved for steep angles of placement. 
         [0081]    While various patents have been incorporated herein by reference, to the extent there is any inconsistency between incorporated material and that of the written specification, the written specification shall control. In addition, while the disclosure has been described in detail with respect to specific embodiments thereof, it will be apparent to those skilled in the art that various alterations, modifications and other changes may be made to the disclosure without departing from the spirit and scope of the present disclosure. It is therefore intended that the claims cover all such modifications, alterations and other changes encompassed by the appended claims.