Patent Publication Number: US-10327804-B2

Title: Percutaneous needle guide and methods of use

Description:
RELATED APPLICATION 
     This patent application is a divisional of U.S. patent application Ser. No. 11/757,516, filed Jun. 4, 2007, now allowed, the entire disclosure of which is expressly incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention pertains to gaining percutaneous access to a subcutaneous target located by a non-invasive medical scanning device and more particularly to guiding insertion of a percutaneous needle through an epidermis of a body to gain the access. 
     BACKGROUND 
     Various designs of percutaneous needle guides for attachment to non-invasive medical scanning devices, for example, hand-held ultrasound transducer probes, are known in the art. These guides may be used to direct a percutaneous needle, for example, a biopsy needle, to a needle entry site, which is located alongside the scanning device on an epidermis of a scanned body, and which corresponds to a subcutaneous target located by the device. In order to direct the needle, these guides include a constraining feature through which the needle must be passed. Many of these guides further include means to adjust an angular orientation of the constraining feature, according to a measured depth of the located target, so that the needle inserted therein is directed to the insertion site at an angle that allows the inserted needle to intersect with the subcutaneous target. 
     Guides which only provide for an angular adjustment of the constraining feature, in order to re-direct the trajectory of the inserted needle, do not take into account situations when a particular angular orientation of the inserted needle is important for the needle to pass through the located target and gain access to a site beyond the target. Furthermore, handling of a guide including the aforementioned constraining feature, in conjunction with a proper handling of the scanning device and the needle, can increase a number of steps that a physician or clinician must take in order to gain percutaneous access to the target or the site beyond the target. Additionally, the constraining feature through which the needle must be passed in order to be guided by these guides can impose unnecessary limitations on a physician or clinician who has developed skills for “free-hand” handling of needles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following drawings are illustrative of particular embodiments of the present invention and therefore do not limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the present invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements. 
         FIGS. 1A-B  are schematics depicting a needle guide attached to a medical scanning device in a first position and second position, respectively, according to some embodiments of the present invention. 
         FIG. 1C  is a plan view of a needle guide kit, according to some embodiments of the present invention. 
         FIGS. 2A-B  are first and second perspective views of a needle guide attached to a medical scanning device, according to some alternate embodiments of the present invention, 
         FIG. 2C  is an exploded perspective view of the needle guide shown in  FIGS. 2A-B , according to some embodiments. 
         FIG. 3A  is a perspective view of a needle guide attached to a medical scanning device, according to additional embodiments of the present invention. 
         FIG. 3B  is a top perspective view of the needle guide shown in  FIG. 3A , according to some embodiments. 
         FIGS. 4A-B  are schematics depicting an exemplary procedure that may employ embodiments of the present invention. 
         FIG. 5A  is a schematic depicting percutaneous needle access obtained according to some methods of the present invention. 
         FIG. 5B  is a reproduction of an exemplary ultrasound scan showing a sacral foramen. 
         FIG. 6A  is a plan view of a percutaneous access needle. 
         FIG. 6B  is a perspective view of an alternate embodiment of the guide shown in  FIGS. 3A-B . 
         FIG. 7  is a flow chart outlining various methods of the present invention. 
         FIG. 8  is a schematic depicting a fixed needle guide, attached to a medical scanning device, according to further alternate embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following description provides practical illustrations for implementing exemplary embodiments of the present invention. Examples of constructions, materials, dimensions, and manufacturing processes are provided for selected elements, and all other elements employ that which is known to those of skill in the field of the invention. Those skilled in the art will recognize that many of the examples provided have suitable alternatives that can be utilized. 
       FIGS. 1A-B  are schematics depicting a needle guide  10  attached to a medical scanning device  100 , for example, a hand-held ultrasound transducer probe, according to some embodiments of the present invention.  FIGS. 1A-B  illustrate device  100  including a transducer surface  101 , to which a plane  2  is approximately tangent at an apex thereof, an external sidewall  103  extending away from transducer surface  101 , a longitudinal axis  4  approximately perpendicular to plane  2 , and a cord  3  extending from device  100 ; cord  3  couples the scanning transducer of device  100  to a console (example shown in  FIG. 5A ), which, for example, controls the transducer function, processes and stores data collected by the transducer, and displays the data. Guide  10  is shown including an indicator element  11 , an adjustment mechanism  15  and a joining structure  13 , which reversibly attaches guide  10  to device  100  such that indicator element  11  is laterally offset from transducer surface  101  and external sidewall  103 . Joining structure  13  may include a pair of spring loaded mounting brackets that may be press fit about external sidewall  103  of device  100 . 
       FIGS. 1A-B  further illustrate indicator element  11  including a pointer  110  being formed as a terminating edge of element  11 , and adjustment mechanism  15  being coupled to joining structure  13  for moving indicator element  11 , with respect to device  100 , in a direction approximately parallel to plane  2  without changing an orientation of pointer  110  as defined by an angle θ. According to the illustrated embodiment, angle θ of pointer  110  is predetermined according to an orientation necessary for a percutaneous needle to pass through a subcutaneous target T in order to gain access to an underlying site; according to an exemplary embodiment, for an application described below, in which the percutaneous needle must pass through a foramen of a boney structure, angle θ is between approximately 55 degrees and 65 degrees. With reference to  FIGS. 1A-B , it should be appreciated that pointer  110  provides guidance for needle insertion without constraining the needle, so that needle handling on the part of a physician or clinician is not unduly restricted or hampered. According to  FIG. 1A , when plane  2  coincides with an epidermis of a body, and scanning device locates subcutaneous target T at a depth D 1 , indicator element  11  is moved, via adjustment mechanism  15 , to locate a terminal end P of pointer  110  at a distance d 1  from axis  4  (axis  4  coinciding with target T); distance d 1  corresponds to an entry site E 1  on the epidermis, to which pointer  110  points by virtue of angle θ, and which entry site E 1  is located a distance x 1  from axis  4 , so that a trajectory of a needle (shown by a dashed line), inserted at E 1  per angle θ, passes through target T at depth D 1 . According to  FIG. 1B , when plane  2  coincides with an epidermis of a body, and scanning device locates subcutaneous target T at a depth D 2 , indicator element  11  is moved, via adjustment mechanism  15 , to locate terminal end P of pointer  110  at another distance d 2  from axis  4 ; distance d 2  corresponds to another entry site E 2  on the epidermis, to which pointer  110  points, and which entry site E 2  is located a distance x 2  from axis  4 , so that a trajectory of a needle (shown by a dashed line), inserted at E 2  per angle θ, passes through target T at depth D 2 . Adjustment mechanism  15  may be any type expanding and collapsing structure (one example being a telescoping structure) for moving indicator element  11 , with respect to device  100 , along a direction approximately parallel to plane  2 , without changing angle θ of pointer  110 ; and, according to some preferred embodiments, adjustment mechanism  15  is calibrated to move indicator element  11 , with respect to device  100 , in predetermined increments, each increment corresponding to a different target depth. 
     With reference to  FIGS. 1A-B , it should be appreciated that each of distances x 1  and x 2  is approximately equal to a tangent of (90°−θ) multiplied by a depth D 1 , D 2 , respectively, and that an offset C) between terminal end P of pointer  110  and plane  2  is accounted for in the positioning of indicator element  11  at distances d 1  and d 2 , such that pointer  110  points to entry sites E 1  and E 2  that are located at distances x 1  and x 2 . As offset C) decreases, for example, by enlarging indicator element  11  so that terminal end P of pointer  110  is moved closer to plane  2 , distances d 1  and d 2  approach distances x 1  and x 2 , respectively. According to alternate embodiments of the present invention, guide  10  is either shifted, with respect to device  100 , toward plane  2 , in its attachment thereto, or indicating element  11  is enlarged (for example, as shown with a dotted line in  FIG. 1B ), so that terminal end P of pointer  110  is approximately tangent with plane  2  (touching, or close to touching entry sites E 1  and E 2 ); for embodiments such as these, offset O is significantly reduced, and distances d 1  and d 2  become approximately equal to distances x 1  and x 2 , respectively. 
     It should be noted that a depth of particular subcutaneous targets may not varying significantly, from body to body (patient to patient), such that needle guides, according to alternate embodiments of the present invention, need not include an adjustment mechanism, such as mechanism  15 .  FIG. 1C  is a plan view of a kit  150  including a plurality of needle guides  151 ,  152 ,  153 ,  FIG. 1C  illustrates each needle guide  151 ,  152 , and  153  having a fixed position, for corresponding terminal ends P 1 , P 2 , and P 3  of pointers  1110 , which are defined by thicknesses t 1 , t 2 , t 3 , respectively. According to the illustrated embodiment, one of guides  151 ,  152  and  153  may be selected and attached to a scanning device, for example device  100 , according to a depth of a target, either foreknown or measured via scanning device  100 , that corresponds to the thickness of the selected guide. According to some preferred embodiments, each guide  151 ,  152 ,  1153  is labeled to indicate a target depth corresponding to thickness t 1 , t 2 , t 3 , and labeled to direct an attachment thereof, via joining structure  13 , in a proper position along sidewall  103  of device  100  so that each pointer  110  points to the needle entry site that corresponds to the depth indicated on the corresponding guide  151 ,  152 ,  153 . Another embodiment of a “fixed” needle guide will be described below, in conjunction with  FIG. 8 . 
     Returning to  FIGS. 1A-B , a flexible and transparent disposable covering  180  is shown surrounding device  100  and attached guide  10 . A fresh covering  180  placed about device  100  and guide  10 , for each successive procedure, protects against contamination between patients when device  100  and guide  10  are reused. Because guide  10  includes pointer  110 , which can be easily viewed through cover  180 , in order to guide a percutaneous needle insertion, and indicator element  11  may be grasped from outside cover  180  for adjustment via adjustment mechanism  15 , there is no need to attach guide  10  outside covering  180 ; however, according to some embodiments, joining structure  113  fits about device sidewall  103  that is enclosed within covering  180 , so that guide  10  may be attached to device  100  outside covering  180 . In either situation, inside or outside covering  180 , a new guide  10  may be used for each successive procedure, or a same guide  10  may be sterilized and reused in each successive procedure. Disposable embodiments of guide  10  may be inexpensively formed, for example, via injection molding, from a plastic such as ABS or nylon, while reusable embodiments of guide  10  may be formed from a metal or a plastic, such as an acetal resin (i.e. Detring) or a polycarbonate, that can withstand autoclave sterilization temperatures. 
       FIGS. 2A-B  are first and second perspective views of another needle guide  20  attached to medical scanning device  100 , according to some alternate embodiments of the present invention.  FIG. 2A  shows device  100  positioned with transducer surface  101  against plane  2  in an orientation very similar to that shown in  FIGS. 1A-B .  FIGS. 2A-B  illustrate needle guide  20  including a Vixo-part joining structure  231 ,  232  coupled to an indicator element  21 , which is in the form of a plate, and joining structure parts  231 ,  232  wrapping around external sidewall  103  of device  100  in order to attach guide  20  to device  100  so that indicator element  21  is laterally offset from device transducer surface  101  and external sidewall  103 ; joining structure parts  231 ,  232  are shown coupled together via interlocking snap-fit features  23 .  FIGS. 2A-B  further illustrate indicator element  21  including a first pointer  209 , a second pointer  210  and a third pointer  211 , each extending over a length, along an exposed face of indicator element  21 , at a different angle, but each having a common terminal end P 20 ; pointers  209 ,  210 ,  211  are shown formed by edges or ledges of increasingly protruding surfaces of the exposed face of element  21 , against which a needle may be rested, however pointers  209 ,  210 ,  211  may alternately be formed by grooves in the exposed face or any other type of marking on the exposed face that may not provide a support for the needle. 
     According to the illustrated embodiment, indicator element  21  is coupled to a lateral extension of each of joining structure parts  231  and  232  such that an adjustment mechanism including a knob  270  may move indicator element  21  with respect to device  100 , when guide  20  is attached thereto, and with respect to the joining structure.  FIG. 2B  illustrates indicator element  21  mounted to joining structure part  231  via pegs  213  that extend, from a surface of indicator element  21 , which is opposite the exposed face thereof, and through slots  201  of the lateral extension of joining structure part  231 ; pegs  213  extending in slots  201  maintain a fixed orientation of each pointer  209 ,  210 ,  211 , while allowing indicator element  21  to be moved toward and away from device  100 , in a direction approximately parallel to plane  2 , by knob  270  of the adjustment mechanism. Thus, the adjustment mechanism may be used to move terminal end P 20  of pointers  209 ,  210 ,  211  into a position corresponding to a measured depth of a subcutaneous target, which has been located by device  100 , in order to guide insertion of a percutaneous needle along a proper trajectory to pass through the located target, as previously described in conjunction with  FIGS. 1A-B . Pointers  209  and  211  on either side of pointer  210  may provide a frame of reference for an acceptable tolerance, for example, approximately ±5 to 10 degrees, on an angle of insertion, as defined by pointer  210 , required to pass the needle through a particular subcutaneous target, or pointers  209 ,  210 ,  211  may provide guides for alternative angles of entry, each angle of entry appropriate for passage of a needle through a different type of subcutaneous target. It should be noted that although  FIG. 2A  shows the three pointers  209 ,  210 ,  211 , alternate embodiments of guide  20  may include just one pointer, or any number of pointers. Referring now to  FIG. 2C , which is an exploded perspective view of needle guide  20 , in conjunction with  FIG. 2B , the adjustment mechanism of guide  20  will be described in greater detail.  FIGS. 2B-C  illustrate the adjustment mechanism including knob  270 , a rack  260  coupled to joining structure part  231 , and a pinion element  276  coupled to knob  270  and including a bore  273  to receive a shaft  215  extending from the surface of indicator element  21  opposite the exposed face thereof. According to the illustrated embodiment, shaft  215  of indicator element  21  extends through a slot  202  of joining structure part  232  and through a slot  203  of joining structure part  231  to mate with bore  273  of pinion element  276 ; when knob  270  is rotated, pinion element  276  rotates about shaft  215  and travels along rack  260  thereby moving indicator element  21  in the direction parallel to plane  2 .  FIG. 2B  illustrates calibration markings  275  located both on knob  270  and above rack  260  so that a position of knob  270  with respect to rack  260  may be correlated by a user to a depth of the target beneath device  100  and located by device  100 , which depth may have been measured by device  100 . According to an alternate embodiment, rather than the illustrated rack-and-pinion interface, slot  202  and/or slot  203  includes a series of detents, or recesses, spaced apart along a length thereof and into which shaft  213  of indicator element  21  may be positioned by sliding shaft  213 , with or without knob  270 , along the length. 
     Joining structure parts  231 ,  232 , indicator element  21 , and the adjustment mechanism components described above may all be formed, for example, via injection molding, from a suitable plastic, for example, ABS, nylon, acetal resin, or polycarbonate, and then snap fitted together to assembly guide  20 . Both device  100  and attached guide  20  may be inserted into a transparent and flexible protective covering, for example, similar to covering  180  shown M  FIGS. 1A-B , for performing a scan and an associated needle insertion, since pointers  209 ,  210 ,  211  of guide  20 , similar to guide  10 , can easily be viewed through the covering, to guide the orientation of a needle to an indicated entry site, and the adjustment mechanism of guide  20  may be manipulated by grasping knob  270  from outside the covering. Alternately, joining structure parts  231 ,  232  of guide  20  may be snapped together around device  100  which has already been inserted into the protective covering so that guide is outside the covering during the scanning and needle insertion. 
       FIG. 3A  is a perspective view of a needle guide  30  attached to medical scanning device  100 , according to additional embodiments of the present invention; and  FIG. 3B  is a top perspective view of needle guide  30 .  FIGS. 3A-B  illustrate a joining structure  33  of guide  30  including a sidewall having portions  331 ,  332 ,  333  and  334  to form a receptacle  335  for holding device  100 ; receptacle  335  includes a first opening  313 , through which device  100  is inserted, and a second opening  315 , through which transducer surface  101  of device  100  is exposed for scanning, and joining structure  33  includes a spring member  360 , which may help to position and to retain device  100  within receptacle  335 . An operator may position device  100  within receptacle  335  such that transducer surface  101  protrudes slightly from second opening  315 , as shown, or such that transducer surface  101  is approximately flush with a flange  340  of joining structure  33 ; flange  340  is shown extending outward from the joining structure sidewall, approximately aligned with opening  315 , and may serve to maintain a constant orientation of device  100  when transducer surface  101  is placed over an epidermis during scanning and needle insertion. 
       FIGS. 3A-B  further illustrate an indicator element  31  of guide  30  including a pointer  310 , formed by a groove in a side surface thereof; indicator element  31  is shown coupled to flange  340  of joining structure  33  via a coupling  312 , into which indicator element  31  is snap-fitted at a fixed angle with respect to joining structure  33 ; according to some embodiments coupling  312  allows indicator element to pivot, per arrow A, into various fixed positions, for example in 10 degree increments. According to the illustrated embodiment, a position of a terminal end P 30  of pointer  310  is fixed in relation to joining structure  33 , and an adjustment mechanism of guide  30  includes a knob  354  to move joining structure  33 , with respect to device  100 , in a direction parallel to a plane (like plane  2  shown in  FIGS. 11A-B  and  FIG. 2A ), which is approximately tangent with an apex of transducer surface  101  and approximately perpendicular to longitudinal axis  4  of device  100 , thereby moving indicator element  31  with respect to device  100  in a direction parallel to the same plane. It should be noted that pointer  310  may alternately be formed by an edge protruding from the side surface of indicator element  31  or just as the side surface itself. 
       FIG. 3B  illustrates the adjusting mechanism of guide  30  including a knob  354 , located adjacent an external surface of sidewall portion  332 , and a shaft  352  extending from knob  354  through sidewall portion  332  to a terminal end  305  thereof, which contacts inserted device  100  (device  100  represented with a dashed line in  FIG. 3B ), and forces device  100  against spring member  360 . Knob  354  may be used to advance or retract terminal end  305  of shaft  352 , per arrow B, causing a relative movement between device  100  and both joining structure  33  and indicator element  31 , so that indicator element  31  remains in a fixed location with respect to joining structure  33  while being moved with respect to device  100 . Although spring member  360  is shown as a leaf spring, it should be appreciated that any type of spring member, which applies a resistive force against device sidewall  103  to hold device  100  in receptacle while allowing movement of device  100  therein, may be incorporated by embodiments of the present invention. 
     Referring back to  FIG. 3A , knob  354  is shown including calibration marks  375  to be used in conjunction with an indicator  385 , which is coupled to sidewall portion  332 , in proximity to knob  354 . With reference to  FIGS. 3A-B  it should be appreciated that a threaded interface between shaft  352  and sidewall portion  332  controls travel, per arrow B, of terminal end  305 ; the controlled travel of terminal end  305 , which is effected by rotating knob  354 , is calibrated to position device  100  with respect to indicator element  31 , such that indicator marks  375 , being aligned with indicator  385 , each correspond to a different depth of a subcutaneous target, located by device  100 , that a needle will pass through being guided by pointer terminal end P 30 , which is located at a distance d from axis  4  of device  100 , and according to the angular orientation of pointer  310 . According to some alternate embodiments, shaft  352  includes detent notches interfacing with sidewall portion  332 , rather than threads, and knob  354  is pushed rather than turned in order to adjust distance d. 
       FIGS. 4A-B  are schematics depicting an exemplary procedure that may employ embodiments of the present invention.  FIG. 4A  illustrates sacral nerves  45  of a patient  40  located adjacent to an anterior surface of the patient&#39;s sacrum  43 , which is the relatively large triangular bone situated at the lower part of the vertebral column.  FIG. 4A  further illustrates access to nerves  45  being gained by a percutaneous needle  400  inserted, from a posterior side of sacrum  43 , through a foramen  51  of sacrum  43  (typically, the third sacral foramen, or S 3 ). Such access is desired in order to provide electrical stimulation, or neuromodulation treatment, to sacral nerves  45 , thereby influencing the behavior of the patient&#39;s organs that sacral nerves  45  innervate, for example, to treat urinary incontinence.  FIG. 4B  illustrates an implanted neuromodulation system including a stimulation device  460  coupled to an elongate medical electrical lead  410  via an extension lead  450 ; prior to coupling with device  460 , lead  410  has been inserted through sacral foramen  51 , for example, via needle  400 , and an electrode of lead  410  has been coupled to underlying sacral nerve  45  in order to deliver controlled electrical stimulation thereto from device  460 . 
     With reference back to  FIG. 4A , it may be appreciated that protuberances of sacrum  43  can provide landmarks for determining an appropriate entry site for needle  400 , and knowledge of a typical curvature of sacrum  43 , in relation to a contour of the exterior body surface, or epidermis of patient  40 , surrounding the needle entry site, has helped to establish an approximately 60 degree angle of insertion for needle  400 , which allows needle  400  to pass through foramen  51  in order to contact nerves  45 , and which angle is known to those skilled in the art. Once properly inserted, as illustrated in  FIG. 4A , needle  400  provides a pathway, through a lumen thereof, by which lead  410  may be implanted as an initial step in the implantation of the system shown in  FIG. 4B . 
     Often times the needle insertion illustrated in  FIG. 4A  is accomplished under local anesthetic by probing with needle  400  and using tactile feedback to find foramen  51 . For a skilled and experience physician, or clinician, such an approach may be acceptable, but, with the advent of non-invasive medical scanning systems, for example, those including handheld ultrasound transducer probes, an approach that employs these systems, to provide more concrete feedback in guiding needle insertion, may be preferred in many instances. 
       FIG. 5A  is a schematic depicting percutaneous needle access obtained according to some methods of the present invention, wherein device  100  and needle guide  30  are employed; and  FIG. 5B  is a reproduction of an exemplary ultrasound scan obtained by device  100  in locating sacral foramen  51 .  FIG. 5A  illustrates transducer surface  101  of device  100  placed over the epidermis of patient  40  and device  100  coupled via cord  3  to a console  6 ; according to exemplary embodiments of the present invention, device  100  and console  6  make up an ultrasound machine wherein device  100  is an ultrasound transducer probe that sends and receives sound waves, and console  6  includes a central processing unit, transducer pulse controls, a display screen  56  and a user interface  65 , for example a key board and/or touch pad. According to the illustrated embodiment, a physician or clinician has placed transducer surface  101  of device  100  over the epidermis of patient  40 , which overlies sacrum  43 , and has located foramen  51  by moving transducer surface  101  along sacrum  43  while scanning. Guide  30  may have been attached to device either before or after scanning to locate foramen  51 . Although not shown, those skilled in the art will appreciate that device  100  and, optionally, guide  30  too, if attached prior to scanning, will typically be placed within a protective covering, for example, like cover  180  previously described, and that a conductive gel will be spread between transducer surface  101  and the covering to facilitate the scanning process.  FIG. 5B  shows an image  560 , which may be generated by device  100 , once foramen  51  has been located by device  100 , and displayed on screen  56 ; image  560  was obtained with a 38 mm broadband linear array ultrasound transducer probe of MicroMaxx® system, available from SonoSite, Inc., using a scanning frequency of 7.5 MHz. 
     With further reference to  FIG. 5B , those skilled in the art will appreciate that a difference in reflection of ultrasound energy from bone and adjacent soft tissue creates the contrast between bone (shown black in image  560 ) and soft tissue (shown gray in image  560 ) that helps to identify the location of foramen  51 . In addition to locating foramen  51 , device  100  in conjunction with image  560  may be used to determine a depth of the posterior opening of foramen  51 ; depths are shown by tick marks along the right hand side of image  560 , and a dashed white line has been superimposed on the image to indicate an approximate depth between 1.5 and 2 cm of the posterior opening of foramen  51 , as measured by the ultrasound probe in this particular instance. The depth of the opening may vary from patient to patient depending upon a thickness of subcutaneous tissue overlying the sacrum for each patient. As previously described, indicator element  31  is moved with respect to device  100 , in the previously described parallel direction, into a position where pointer  310  of indicator element  31  points to an appropriate needle entry site E 51  that corresponds to the fixed angular orientation of indicator element  31  ( FIG. 5A ). With reference back to  FIG. 4A , the fixed angular orientation of indicator element  31  should be approximately 60 degrees to assure passage of needle  400  through foramen  51  to underlying nerves  45 ; however, it should be understood that needle guides of the present invention may be used for other applications wherein other angular orientations are appropriate. It should be noted that any of the previously described embodiments of needle guides, for example, guides  10  and  20 , may be employed for guiding needle  400 . 
     Once foramen  51  has been located, a depth thereof measured, and, if necessary, guide  30  has been adjusted, needle  400  may be inserted at the entry site, and per the orientation indicated by indicator element  31 . According to some methods of the present invention, the insertion of needle  400  may be visualized via ultrasound, for example, on display screen  56  ( FIG. 5A ); a metal shaft of needle  400  will be echogenic for ultrasound visualization, and some embodiments of needle  400  may have a roughened surface known to enhance echogenic properties. Alternately, or additionally, proper insertion of needle  400  may be verified via electrical testing. Turning now to  FIG. 6A , which is a plan view of percutaneous access needle  400 , needle  400  is shown including a conductive shaft  603  attached to a hub  604 , wherein a tip  643  and a proximal portion  641  of shaft  603  are exposed for electrical contact, and a length  642  of shaft  603 , between tip  643  and proximal portion  641  is insulated. According to the illustrated embodiment, once needle  400  is passed through foramen  51 , a test stimulation may be applied at portion  641  in order to determine if tip  643  is contacting nerve  45 ; if contact with nerve  45  is made a motor response in the buttock area will be observed.  FIG. 6B  is a perspective view of an alternate embodiment of guide  30 , denoted as guide  30 ′, which includes electrical contact features to facilitate application of the test stimulation to needle  400 . 
       FIG. 6B  illustrates indicator element  31  of guide  30 ′ including a mounting feature  637  for an electrical contact clip  64 , which is shown coupled via lead wire  670  to a test stimulator device  67 ; contact clip  64 , being mounted to guide  30 ′, as shown, may provide stability to inserted needle  400 , being coupled to clip  64  during the stimulation testing. According to the illustrated embodiment, mounting feature  637  is formed by a post, which protrudes from an end of indicator element  31  and about which clip  64  may be attached for mounting; if a protective covering is disposed about device  100  and guide  30 ′, clip  64  may still be mounted on feature  637  from outside the covering. Although not shown, it should be appreciated that a circuit for test stimulation must be completed by grounding stimulator device  67 ; such grounding is typically accomplished via a ground pad connected to the epidermis of the patient. However,  FIG. 6B  further illustrates a conductive surface  634 , which is coupled to flange  340  of guide  30  and is electrically isolated from mounted contact clip  64 , and which may be used to ground stimulator device  67 . According to the illustrated embodiment, when guide  30 ′ is attached to device  100 , and transducer surface  101  is placed over the epidermis for scanning, a ground wire (not shown) of stimulator device  67  may be coupled to conductive surface  634  of guide  30 ′, which is grounded to the epidermis, for example, via direct contact therewith and/or via an interface of conductive gel. Thus, guide  30 ′ includes useful features facilitating handling of inserted needle  400  in conjunction with device  100  during electrical stimulation testing for verification of proper needle insertion. It should be noted that alternate embodiments of guide  30 ′ need not include both mounting feature  637  and conductive surface  634 , but may include one or the other. 
       FIG. 7  is a flow chart outlining/summarizing various methods of the present invention, which have been discussed in greater detail above.  FIG. 7  illustrates alternative pairs of initial steps: steps  71  and  72  wherein a medical scanning device (i.e. device  100 ) is inserted into a protective covering prior to attaching a needle guide (i.e. guide  10 ,  20 , or  30 ) thereto; and steps  701  and  702  wherein the needle guide is attached to the device and then the device and attached guide inserted into the protective covering.  FIG. 7  shows, following either of these pair of initial steps, a step  73 , wherein scanning is performed to locate a target (i.e. foramen  51 ); however, it should be noted that step  73  may be performed in between steps  71  and  72 , according to an alternate method, such that scanning is performed to locate the target before the needle guide is attached to the device. After step  73 , a depth of the located target is determined, per step  74 , and then the guide is adjusted according to the depth, per step  75 , so that a needle (i.e. needle  400 ) may be oriented and inserted into an entry site E 51 ) indicated by the adjusted needle guide, per step  76 ; of course, if an initial position of an indicator element of the guide happens to coincide with the determined depth of the target, adjustment of the guide, per step  75 , is not necessary. According to some alternate methods, step  76  immediately precedes step  73 , wherein the depth of the located target is foreknown and the needle guide need not be adjusted; an embodiment of a fixed needle guide, that does not include an adjustment mechanism, was described in conjunction with  FIG. 1C , and another embodiment will be described below in conjunction with  FIG. 8 .  FIG. 7  further illustrates optional steps  77  and  78  following insertion of the needle, per step  76 : according to step  77 , the needle is visualized during insertion, and, according to step  78 , electrical testing is performed to verify proper insertion of the needle. It should be noted that either of steps  77  and  78  may be included in a method without the other being included. 
     Various embodiments of adjustable needle guides have been heretofore described, along with one embodiment of a fixed needle guide; now, another embodiment of a fixed needle guide will be described in conjunction with  FIG. 8 .  FIG. 8  is a schematic depicting a fixed needle guide  80 , attached to medical scanning device  100 , wherein plane  2  is approximately tangent to the apex of transducer surface  101  and approximately perpendicular to longitudinal axis  4  of device  100 .  FIG. 8  illustrates guide  80  including a plate  81  and a joining structure  83 , which reversibly attaches guide  80  to device  100  such that plate  81  extends laterally from transducer surface  101  and external sidewall  103  of device  100 .  FIG. 8  further illustrates plate  81  including pointers  811 ,  812 ,  813 , which extend over a length along an exposed surface of plate  81 ; pointers  811 ,  812 ,  813  may be formed as grooves or protruding surfaces, or any other type of marking on the exposed surface of plate  81 . According to the illustrated embodiment, each of pointers  811 ,  812 ,  813  extend at a fixed angle (p with respect to plane  2 , and are space apart from one another in a direction approximately parallel with plane  2 ; each of pointers  811 ,  812 ,  813  points to a needle entry site E 1 , E 2 , E 3 , respectively, each of which corresponds to a depth of a target TD 1 , TD 2 , TD 3 , respectively, and depending on which depth is measured for the target, the corresponding pointer is selected to guide insertion of a percutaneous needle per the corresponding insertion path shown with dashed lines. Each of pointers  811 ,  812 , and  813  may include a visible calibration mark indicating the depth to which each correspond, or some kind of color coding identifying the corresponding depth. Although not shown, it may be appreciated that both device  100  and attached guide  80  may be enclosed in a translucent protective covering, for example, similar to that shown in  FIGS. 1A-B , for scanning and subsequent guiding of a percutaneous needle insertion according to the selected pointer, since pointers  811 ,  812 ,  813 , may be visualized through the covering. 
     In the foregoing detailed description, the invention has been described with reference to specific embodiments. However, it may be appreciated that various modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims.