Abstract:
Systems and methods for treating tumors on or within internal organs of mammals that have been imaged with endoscopic ultrasound are described. The system uses an expandable bipolar electrode assembly that can be imaged by ultrasound and can penetrate, e.g., the stomach, intestine or bowel wall, etc. and be positioned in or around the tumor on an internal organ while being guided by an operator who visualizes its position with ultrasound imaging. It utilizes an electrode assembly that extends down an internal cavity in the endoscope to allow the operator to spread the electrodes for pulse delivery of a nanosecond pulsed electric field (nsPEF) to the tumor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority to U.S. Prov. 61/161,043 filed Mar. 17, 2009 and 61/186,798 filed Jun. 12, 2009, and is also a continuation-in-part of U.S. Pat. App. 12/722,441 filed Mar. 11, 2010, each of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This application is directed to systems and methods for treating tumors on internal organs that have been identified using endoscopic ultrasound by precisely positioning a pulsed field delivery device on or in the tumor guided by ultrasound imaging. 
       BACKGROUND OF THE INVENTION 
       [0003]    Endoscopic ultrasound (EUS) combines endoscopy and ultrasound in order to obtain images and information about the digestive tract and the surrounding tissue and organs. Endoscopy refers to the procedure of inserting a long flexible tube via the mouth or the rectum to visualize the digestive tract, whereas ultrasound uses high-frequency sound waves to produce images of the organs and structures inside the body such as ovaries, uterus, liver, gallbladder, pancreas, aorta, etc. 
         [0004]    In EUS a small ultrasound transducer is installed on the tip of the endoscope. By inserting the endoscope through the esophagus into the stomach, the ultrasound transducer can be placed against the inner surface of the stomach or gastrointestinal tract so that sound waves can be beamed through the stomach wall to obtain high quality ultrasound images of the organs on the other side of the stomach wall such as the kidney, pancreas and liver. Because of the proximity of the EUS transducer to the organ(s) of interest, the images obtained are frequently more accurate and more detailed than the ones obtained by traditional ultrasound where the transducer in placed on the skin. Tumors on internal organs have ultrasound reflection properties that are different from the organ so that they can be easily detected with EUS. An example of EUS is shown and described in U.S. Pat. No. 7,318,806, which is incorporated herein by reference in its entirety. 
         [0005]    Some of these ultrasound imaging endoscopes have been designed with an open channel down the center into which a fine needle aspirator or other instruments can be inserted to allow the sampling of tumor tissue by poking through the stomach wall and into the tumor tissue for aspiration. The aspirated tissue sample can then be stained and observed by a pathologist to obtain an immediate diagnosis of malignancy. 
         [0006]    Nanosecond pulsed electric fields (nsPEF) have been found to trigger both necrosis and apoptosis in skin tumors. Treatment with nsPEF independently initiates the process of apoptosis within the tumor cells themselves causing the tumor to slowly self-destruct without requiring toxic drugs or permanent permeabilization. In addition to initiating apoptosis in the tumor cells, nanosecond pulsed electric fields halt blood flow in the capillaries feeding it which in turn reduces blood flow to the tumor and activation of apoptosis pathways causing the tumor to slowly shrink and disappear within an average of 47 days. 
         [0007]    An example of nsPEF is shown and described in U.S. Pat. No. 6,326,177, which is incorporated herein by reference in its entirety. 
         [0008]    Various devices utilizing EUS are known yet they are generally insufficient to treat tumors accessible via endoscopic access utilizing nsPEF. Accordingly, there exists a need for methods and devices which are efficacious and safe in facilitating the treatment of tumors in patients. 
       SUMMARY OF THE INVENTION 
       [0009]    In delivering nanosecond pulsed electric fields (nsPEF) to a region of tissue, such as a tumor, it is possible to precisely control the number of pulses delivered as well as the frequency of those pulses to deliver electrotherapy via an electrode assembly designed to draw tissue into a recessed cavity in order to immobilize the tissue and position the electrodes firmly against or within the tissue. The recessed cavity may be varied in its size to match a size of any particular tumor to be treated such that the treated tumor may be received within the cavity in close proximity or in direct contact against the electrodes. 
         [0010]    The electrode assembly may be configured into a variety of configurations for delivering electrotherapy and may also utilize suction to fix in place the tissue being treated. For example, six (6) spaced apart planar electrodes may be positioned circumferentially about the recessed cavity. In other variations, the electrode assembly may comprise a support member having a pair of “U”-shaped planar electrodes disposed on the periphery of the recessed cavity. Other variations may include a pair of spaced apart parallel plate electrodes while other variations may include a plurality of needle electrodes which are mounted at the base of a back plate to control the penetration depth of the tissue as it is sucked into the recessed cavity. 
         [0011]    The back plate of each recessed cavity may have multiple apertures, such as on the order of 100 μm in diameter. An air pump, e.g., an oscillating diaphragm air pump or other suction source, is then coupled to the support member on the side of the base wall support opposite the recessed cavity and is used to generate a mild suction that pulls the tissue to be treated into the cup-like volume. 
         [0012]    In use, the support member may suction or draw in tissue to be treated from various regions of the body into the recessed cavity into contact or proximity to the electrodes. Drawing in the tissue may further facilitate tissue treatment by clearly defining the treatment area to be treated for the operator. When nsPEF is applied to a tissue region such as a tumor, if a large resistance between the electrode and the tumor restricts current flow (such as the presence of the stratum corneum in skin), the field may not pass into the tumor effectively. Thus it may be desirable to apply, in one example, a minimum current of 20 A (although lower currents may be applied if so desired) that may pass through the tumor during nsPEF application to have a desired effect of triggering tumor apoptosis. In order to prevent damage to tissues surrounding the tumor, the nsPEF therapy may be applied at a pulse frequency that will not heat the tissue above, e.g., 40° C. (the minimum temperature for hyperthermia effects). Therapy with nsPEF treatment is thus able to initiate apoptosis within the tumor cells without raising the temperature more than a few degrees so as to prevent harm to surrounding tissues from heat transfer. In one example, if 100 ns pulses were applied, the frequency of the applied pulses is desirably 7 pulses per second (Hz) or lower to prevent damage to surrounding tissues. 
         [0013]    With the electrode assemblies described herein, treatment of tissue regions such as skin tumors may be effected by applying nsPEF while specifying various parameters. For instance, one or all of the following parameters may be adjusted to provide optimal treatment of tissue to effect tumor apoptosis: (1) pulse amplitude (kV/cm); (2) pulse duration (ns); (3) pulse application frequency (Hz); and/or (4) pulse number applied. 
         [0014]    Because the value of these parameters may vary widely over a number of ranges, it has been determined that particular ranges may be applied for effecting optimal tissue treatment which may effect tumor apoptosis in as few as a single treatment. In varying pulse amplitude, an applied amplitude as low as, e.g., 20 kV/cm, may be sufficient for initiating an apoptotic response in the treated tissue. The pulse amplitude may, of course, be increased from 20 kV/cm, e.g., up to 40 kV/cm or greater. However, an applied amplitude of at least, e.g., 30 kV/cm or greater, may be applied for optimal response in the treated tissue. In varying pulse duration, durations in the range of, e.g., 50-900 ns, may be highly effective although shorter durations may be applied if the number of pulses is increased exponentially. In varying pulse application frequency, frequencies up to 7 Hz may be applied with 100 ns pulses without heating surrounding tissues to hyperthermic levels. Because tissue heating may be dependent on pulse width multiplied by the frequency of application, shorter pulses may be applied at proportionately higher frequencies with similar heat generation. In varying the number of pulses applied, the pulse number determines the total energy applied to the tissue region. Generally, applying a minimum pulse number of 600 pulses may result in complete remission of tumors. In one example, nsPEF therapy having a pulse duration of 100 ns may be applied over a range of, e.g., 1000-2000 pulses, to effectively treat the tissue region. 
         [0015]    Given the range of parameters, a relationship between these parameters has been correlated to determine a minimum number of electrical pulses which may effectively treat a tissue region, e.g., a tumor, with a single treatment of nsPEF therapy to cause complete apoptosis in the tumor tissue. Generally, the number of electrical pulses increases exponentially as the pulse duration is shortened. The correlation for a given pulse duration or width and number of pulses, N, to effectuate complete tumor remission after a single treatment may be described in the following equation: 
         [0000]      N=28,714e −0.026t    
         [0000]    where,
 
N=minimum number of pulses to cause tumor apoptosis with a single treatment
 
t=pulse duration (in nanoseconds)
 
         [0016]    This non-linear dependence of pulse number on pulse width suggests that the effectiveness of the nsPEF therapy described herein is not simply due to energy delivery to the tumor as that is linearly proportional to N times t given a constant voltage and current. 
         [0017]    In one particular variation, an elongate instrument which may be delivered via or through an endoscopic device may utilize any one or more of the nsPEF parameters described herein for tumor treatment. The endoscopic device, particularly an EUS device, may be used to image or locate a tissue region to be treated. Ultrasound imaging may be particularly useful in locating one or more tumors for treatment although conventional endoscopic imaging may also be utilized. With the targeted tissue region located within the body, the nsPEF instrument may be positioned or advanced within one or more working channels in the endoscope until a tapered piercing end of the nsPEF instrument is projected from a distal end of the endoscope. 
         [0018]    The nsPEF instrument may also have an expandable or reconfigurable bipolar electrode assembly that may extend or reposition itself into a deployed profile. With the electrode assembly deployed, the piercing tip may be penetrated into or through the tissue to be treated (such as the tumor) while under the guidance of ultrasound imaging from the endoscope for desirably positioning the instrument. The outer reference electrodes may be actuated by the operator to reconfigure the electrodes for pulse delivery and/or to retract them for insertion and/or withdrawal from the patient. Moreover, the electrodes may be coupled via an electrical cable having at least two conductors which may also extend through the endoscope or electrode assembly to conduct the pulsed electric fields to the distal end effector. 
         [0019]    The electrode assembly may be advanced into the tissue to be treated until the deployed outer electrodes are positioned on or against a surface of the tumor or tissue region. The deployed outer electrodes may be spread or reconfigured into a variety of shapes, e.g., hemi-circular plate configuration. Moreover, to facilitate contact between the electrode assembly and the tissue surface of the targeted tumor, suction may be applied through, e.g., a working channel either through the endoscope, electrode assembly, or both for drawing the tumor into apposition against the electrode assembly. Other mechanisms such as tissue graspers may also be used. 
         [0020]    In other variations, the electrode assembly may be configured to project distally from the shaft of the nsPEF instrument to surround the tissue to be treated, such as a tumor. Various numbers of conductive needles may be utilized such that the tumor to be treated is surrounded by the needle array and the electric field created between the needles may be uniformly applied to the tumor. These instruments may utilize any of the nsPEF parameters as described herein to effectively treat the tissue with e.g., a single treatment of nsPEF therapy. 
         [0021]    Following nanosecond pulse application, the treatment instrument may be withdrawn from the tumor and the outer electrodes may be reconfigured back to their original low profile configuration for retraction back into the endoscope. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  illustrates a schematic diagram of an apparatus for generating a nanosecond pulsed electric field (nsPEF) for treating tumors. 
           [0023]      FIGS. 2A to 2F  illustrate perspective views of variations of electrode assemblies which may be used to apply the nsPEF upon tissue adhered via a retaining mechanism, such as a suction mechanism. 
           [0024]      FIGS. 3A and 3B  show side and perspective views, respectively, of an exemplary suction electrode assembly having a plurality of needle electrodes projecting into a recessed cavity. 
           [0025]      FIGS. 4A and 4B  show side and perspective views, respectively, of another variation of the suction electrode assembly having two apposed electrodes positioned on either side of the recessed cavity. 
           [0026]      FIGS. 5A and 5B  show side and perspective views, respectively, of yet another variation of the suction electrode assembly having at least six circumferentially positioned electrodes around the recessed cavity. 
           [0027]      FIGS. 6A to 6D  illustrate side views of various tissue regions drawn into the recessed cavity for tissue treatment via nsPEF application. 
           [0028]      FIG. 7  shows a perspective view of an example of a portable nsPEF treatment assembly readied for transportation or shipping. 
           [0029]      FIG. 8  shows a graph of the applied pulse voltage with a rise time of, e.g., 15 ns and the current waveform delivered to the treated tissue. 
           [0030]      FIG. 9  shows a graph illustrating the correlation for a given pulse duration or width and number of applied pulses to eliminate tumors in, e.g., a single treatment. 
           [0031]      FIG. 10  illustrates a chart of the Optimum Pulse Number where a majority of tumors were successfully treated with no signs of resurgence after a single treatment when pulsed with at least 1500 to 2000 pulses. 
           [0032]      FIG. 11  illustrates a chart of the Percent Efficacy after one treatment where the efficacy is shown to increase from 1500 pulses and higher. 
           [0033]      FIG. 12  illustrates a chart of the Optimum Amplitude of the pulses where the number of tumors successfully treated after a single treatment increases at higher amplitudes. 
           [0034]      FIG. 13  shows a chart recording tumor detection via GFP detection under fluorescent microscopy for tissue treated via nsPEF therapy with various electrode assemblies. 
           [0035]      FIG. 14  shows a chart recording trans-illumination and reflected light images adjacent to one another of the treated tissues (melanomas) corresponding to the various electrode assemblies. 
           [0036]      FIG. 15  shows a chart with the measured change in GFP signal area normalized on a logarithmic scale over a period of time following nsPEF treatment with various electrode assemblies. 
           [0037]      FIG. 16  shows a chart with the measured change in tumor area normalized on a logarithmic scale over a period of days following nsPEF treatment with various electrode assemblies. 
           [0038]      FIG. 17  shows histological sections of both the treated tumors as well as skin immediately adjacent to the suction electrode location taken at different times after nsPEF treatment&#39;. 
           [0039]      FIG. 18  shows a chart indicative of the number of tumors treated along with the number eliminated (e.g., by 1, 2, or 3 treatments) relative to the number of pulses applied during nsPEF treatment. 
           [0040]      FIG. 19  shows a chart indicative of the number of tumors treated along with the number eliminated (e.g., by 1, 2, or 3 treatments) relative to the pulse amplitude applied during nsPEF treatment. 
           [0041]      FIG. 20  shows a chart indicative of the number of tumors treated along with the number eliminated (e.g., by 1, 2, or 3 treatments) relative to the pulse frequency applied during nsPEF treatment. 
           [0042]      FIG. 21  shows a chart recording tumor detection via GFP detection under fluorescent microscopy for tissue treated via nsPEF at various amplitudes. 
           [0043]      FIG. 22  shows a chart recording trans-illumination images of treated tissue at various amplitudes. 
           [0044]      FIG. 23  shows a chart recording reflected light images of treated tissue at various amplitudes. 
           [0045]      FIG. 24  shows a chart recording the temperature increase within a tumor over a period of several minutes during nsPEF treatment. 
           [0046]      FIG. 25  shows a chart recording the reflected light images of different nsPEF-treated tumors for various electrode assembly configurations. 
           [0047]      FIG. 26  shows a chart of number of tumors treated and the percentage of tumor regrowth recorded over the range of pulses applied during a single treatment for a pulse duration of 25 ns at 30 kV/cm and with 20-25 Hz pulse frequency. 
           [0048]      FIG. 27  shows a chart of number of tumors treated and the percentage of tumor regrowth recorded over the range of pulses applied during a single treatment for a pulse duration of 50 ns at 30 kV/cm and a pulse frequency of 20 Hz. 
           [0049]      FIGS. 28-30  show perspective views of a nsPEF instrument having a plurality of reference electrodes which are reconfigurable between a low-profile delivery shape and an extended deployed shape. 
           [0050]      FIG. 31  shows a perspective view of a nsPEF instrument deployed from an EUS. 
           [0051]      FIG. 32  shows a perspective view of a nsPEF instrument advanced into an organ and/or tumor under guidance of ultrasound imaging from the endoscope. 
           [0052]      FIG. 33  shows a perspective view of a nsPEF instrument having one or more openings for drawing a suction to adhere tissue to be treated to the instrument. 
           [0053]      FIGS. 34A and 34B  show perspective views of another variation of a nsPEF instrument having a four-needle array projecting from a shaft for tissue treatment. 
           [0054]      FIG. 34C  shows an example of the electric field distribution formed by the four-needle array during nsPEF therapy. 
           [0055]      FIGS. 35A and 35B  show perspective views of another variation of a nsPEF instrument having a six-needle array projecting from a shaft for tissue treatment. 
           [0056]      FIG. 35C  shows an example of the electric field distribution formed by the six-needle array during nsPEF therapy. 
           [0057]      FIGS. 36A and 36B  show perspective views of yet another variation of a nsPEF instrument having an eight-needle array projecting from a shaft and piercing length for tissue treatment. 
           [0058]      FIG. 36C  shows an example of the electric field distribution formed by the eight-needle array during nsPEF therapy. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0059]    As illustrated in the schematic of  FIG. 1 , an apparatus  10  (as described below) is illustrated schematically for intracellular electro-manipulation which includes a power supply  12  (a high voltage power supply, e.g., 20 kV or higher) and a delivery system  14  may be adapted to direct the electric pulse, particularly a nanosecond pulsed electric field (nsPEF), output to a load  16  such as target cells positioned in proximity to the delivery system  14 . The pulse generator may include a pulse forming network  18  and a high voltage switch  20 , such as a spark gap. The pulse forming network  18  may be a high voltage cable, a strip-line, or a pulse forming network constructed of individual capacitors and inductors in a transmission line arrangement with a matching network  22 . The high voltage switch  20  can suitably be a gaseous, liquid or solid state switch, e.g., a spark gap. The energy in the pulse forming network  18  may be stored capacitively, which utilizes a closing switch  20  to release a pulse, or inductively, which requires an opening switch to release a pulse. Upon triggering of the switch  20 , an electrical pulse is delivered through the delivery system  14  and launched into the load  16 , e.g., the target cells in suspension or tissue form. The switch  20  can be triggered by a variety of common methods, e.g., optically or electrically. 
         [0060]    The power supply  12  may utilize a high voltage DC power supply (e.g., Matsusada RB30-30P) to charge up, e.g., a coaxial cable (such as through a current limiting resistor), to a high voltage creating a capacitor on the coaxial cable between the inner conductor and its outer conductive shielding. When the inner conductor is rapidly brought to ground by a switch  20 , a corresponding pulse of high voltage with, e.g., 5-15 ns rise and fall times, is generated across the load. The duration of this pulse may be determined by the length of cable used, and the amplitude may be determined by the voltage at which the coaxial cable was charged. Thus, in one variation, a coaxial cable having a length of, e.g., 20 meters, may be used to generate a pulse duration of, e.g., 100 ns. 
         [0061]    By this method, it is possible to precisely control the number of pulses delivered as well as the frequency of those pulses simply by controlling the discharge switch for the coaxial cable&#39;s inner conductor. The generator  10  itself (including all components) may be sufficiently portable to fit into a rolling suitcase. 
         [0062]    To control the system, a microcontroller such as a digital programmable logic device (e.g., Microchip PIC16F887) may be incorporated into the assembly to control the pulse delivery. The user may input information to the microcontroller-based system via, e.g., a keypad, and a liquid crystal display (LCD) may be implemented to display information to the user. The circuit may be battery-powered. 
         [0063]    The “load”  16 , which includes the target cells in tissue or suspended in a medium, is placed between two or more electrodes. These electrodes may be solid material (in any of a number of suitable shapes, e.g., planar, cylindrical, spherical, etc), wires or meshes or combinations thereof. One (set of) electrode(s) is connected to the high voltage connection of the pulse generator, and a second (set of) electrode(s) is connected to the ground connection of the pulse generator in a suitable manner, e.g., via a second stripline or high voltage cable. The electrode material is a conductor, most commonly metal. 
         [0064]    If such a pulse-forming network is charged up to, e.g., 18 kV, and then released, this charge can produce an almost rectangular ultra-short duration pulse which when applied to a load equal to twice the cable impedance can produce a maximum voltage of 18 kV. The corresponding electric field intensity between two electrodes separated by 1.0 mm is 180 kV/cm. The maximum electrical power, V 2 /R, which can be achieved with these conditions is 3.24 MW (assuming R=100Ω), while the energy (power x pulse duration) transferred into the load is only 0.32 Joule if the pulse duration is 100 ns. For a 100 μL volume of cell suspension, this energy transfer results in a calculated maximum temperature increase of only about 1 K for a single pulse. 
         [0065]    As mentioned above, in applying a nanosecond pulsed electric fields (nsPEF) an electrode assembly may be utilized. An example of some electrode assemblies which may be utilized are shown and described in further detail in U.S. Prov. Pat. App. 60/916,898 filed May 9, 2007 (and in corresponding WO 2008/141221 A1), each of which are incorporated herein by reference in its entirety. 
         [0066]    In one variation of an electrode, a medical instrument for delivering electrotherapy illustratively comprises an outer support member having an open distal end and a base wall portion within the support member arranged to form a cup-like open volume in the distal end of the support member. At least one aperture is formed in the cup-like volume for applying a suction mechanism to the cup-like region. At least a first and a second electrode have at least a portion extending into the cup-like region. A system for delivering electrotherapy comprises a medical instrument having a suction mechanism for providing a source of suction within the cup-like volume to hold a tissue portion to be treated, and a power supply coupled to the first and second electrodes for applying electrical signals to provide electrotherapy to the tissue. When the tissue or tumor to be treated is adhered to the instrument by the suction mechanism, the tumor may be positioned in apposition to the electrode assembly for effectively delivering the pulses. A variety of pulse generators can be used. However, the pulse generator is desirably capable of delivering high voltage pulses (e.g., in the 1-900 ns range) which are imposed across a pair of spaced apart electrodes, to generate electrical fields on the order of, e.g., 20 to 100 kV/cm. 
         [0067]    The electrode assembly may be designed to draw tissue into the recessed cup-like volume in order to immobilize the tissue and position the electrodes firmly against or within the tissue. This allows for desirable targeted treatment of the tissue. For positioning electrodes against the tissue, flat (planar) electrodes can be positioned along the inner walls of the cup-like volume. For positioning electrodes within the tissue, needle-like electrodes protruding essentially perpendicular from the backside portion of the cup-like volume can be provided for penetrating a controllable constant distance into the tissue as it is drawn into the recessed cup-like volume. 
         [0068]      FIGS. 2A to 2D  show variations of electrode assemblies for delivering electrotherapy using suction electrodes. The electrode assemblies may utilize stainless steel electrodes which are electropolished to eliminate any sharp edges that can lead to corona formation at high voltages and are then embedded in a dielectric material, such as a plastic. Very small holes  38  may be formed or drilled into the base of the recessed cavity  39  and during use a suction may be applied through the holes to draw the tissue to be treated into the recessed cavity  39 , e.g., cup-like volume having an inner diameter of about 4 mm and a depth of about 2 mm, for electric field application. The dimensions of recessed cavity  39  are intended to be illustrative and not limiting. Accordingly, recessed cavity  39  may be varied in its size to match a size of any particular tumor to be treated such that the treated tumor may be received within the cavity in close proximity or in direct contact against the electrodes.  FIG. 2A  shows an example of an electrode assembly comprising a support member  30  having a cylindrical cross section having, e.g., six (6) spaced apart planar electrodes  32 , positioned circumferentially about the recessed cavity  39 . The electrodes  32  are electrically isolated from one another by a dielectric material  34 , such as plastic upon which the electrodes can be, e.g., partially embedded. In the arrangements shown the electrodes  32  have one exposed side (without plastic) along the wall of the cavity  39  to allow direct contact to the skin. The opposite sides of the electrode  32  may be coated with plastic. In operation, electrodes in apposition from one another form bias pairs. A plurality of apertures  38  in the back plate  36  are shown for applying a suction force to immobilize a region of skin or epithelium therein. 
         [0069]      FIG. 2B  shows another variation of the electrode assembly comprising support member  30  having a cylindrical cross section and having a pair of “U”-shaped planar electrodes  40  and  42  disposed on the periphery of the recessed cavity  39 . The electrodes  40 ,  42  may be electrically isolated from one another by a dielectric material, such as plastic  44  upon which the electrodes can be embedded.  FIG. 2C  shows another variation comprising a support member  30  having a rectangular cross section and having a pair of spaced apart parallel plate electrodes  46  and  48 . The back plate  50  having a plurality of apertures  52  therein may be formed from a dielectric material.  FIG. 2D  shows another variation comprising a support member  30  having a plurality of needle electrodes  54  which are mounted at the base of the back plate  56  to control the penetration depth of the tissue as it is sucked into the cup-shaped volume. The distance between the center needle and each of the four outer needles may vary but is shown in this example as about 2 mm. 
         [0070]      FIGS. 2E and 2F  show perspective and end views, respectively, of yet another variation of an electrode assembly. In this example, support member  30  may also define the recessed cavity  39  and the plurality of apertures  38  defined over the back plate  36 . A plurality of needle electrodes  54 , e.g., six (6) needle electrodes, may project into the cavity  39  from the back plate  36  with the needle electrodes  54  arranged in a parallel array. In this variation, a linear arrangement of three (3) needle electrodes  54  may be aligned in parallel with an adjacent linear arrangement of three (3) needle electrodes  54 , as shown, with the apertures  38  positioned about the electrode array. 
         [0071]    Since each electrode is electrically isolated from one another, electrodes can be connected to separate electrically conductive (e.g. copper) wires, such as wires that end on a connector projecting out of the side of the plastic cylinder. This allows each electrode to be connected to a different pulse generator and biased differently for maximum versatility, if so desired. 
         [0072]    As previously mentioned, the back plate of each recessed cavity may have multiple apertures, such as on the order of 100 μm in diameter. An air pump, e.g., an oscillating diaphragm air pump or other suction source, is then coupled to the support member on the side of the base wall support opposite the recessed cavity and is used to generate a mild suction that pulls the tissue to be treated into the cup-like volume. 
         [0073]    The electrodes may comprise an electrical conductor that is resistant to corrosion such as, for example, stainless steel. The electrodes portioned at the distal end are preferably electropolished or otherwise planarized. Electropolishing removes corners and sharp edges to minimize undesirable corona discharge when large voltages associated with generating nsPEF are applied to the electrodes. 
         [0074]    In utilizing the generated nsPEF through any one of the electrode assemblies to treat tumors, such as melanoma tumors, the parameters in above-described U.S. Pat. No. 6,326,177 are generally insufficient in effectively treating such tumors. The disclosed number of pulses, i.e., 20 pulses, at 100 ns is insufficient; rather, 1500 pulses at 100 ns instead would be optimal for treating such tumors. 
         [0075]    Turning now to  FIGS. 3A ,  4 A, and  5 A, side views of exemplary suction electrodes developed for use and experimentation are shown.  FIGS. 3B ,  4 B, and  5 B show corresponding perspective views of the electrode treatment distal end effectors. Each support member  60  may be seen having a recessed cavity  39  for contacting and receiving the tissue to be treated.  FIG. 3B  illustrates the recessed cavity  39  of support member  60  having a plurality of needle electrodes  62 , as previously described.  FIG. 4B  illustrates the recessed cavity  39  having at least two electrodes  64  positioned in apposition on either end of the cavity  39  for treating the tissue region positioned therebetween and  FIG. 5B  illustrates a variation having at least six electrodes  66  electrically isolated from one another and positioned about a circumference of recessed cavity  39 , as previously described. 
         [0076]    In use,  FIGS. 6A to 6D  show side views of the support member  60  suctioning or drawing in tissue to be treated from various regions of the body to illustrate how the tissue may be drawn into the recessed cavity  39  into contact or proximity to the electrodes. Drawing in the tissue may further facilitate tissue treatment by clearly defining the treatment area to be treated for the operator. As shown in  FIG. 6A , a region of tissue  70  from a subject&#39;s face may be readily drawn into recessed cavity  39 .  FIG. 6B  illustrates a region of tissue  72  from a subject&#39;s arm,  FIG. 6C  illustrates a region of tissue  74  from a subject&#39;s stomach, and  FIG. 6D  likewise illustrates a region of tissue  76  to be treated from the subject&#39;s leg. 
         [0077]    Because the components of the assembly are portable, the assembly may be stored or housed in a housing  80  for ready shipping or transportation, as shown in  FIG. 7 . An example is shown in the graph of  FIG. 8  of the applied pulse voltage  90  having a rise time of, e.g., 15 ns in this particular example, and the resulting current waveform  92  delivered to the tissue region, e.g., tumor, when utilizing an electrode treatment assembly having a six-electrode configuration, as previously described. 
         [0078]    When nsPEF is applied to a tissue region such as a tumor, if a large resistance between the electrode and the tumor restricts current flow (such as the presence of the stratum corneum in skin), the field may not pass into the tumor effectively. Thus it may be desirable to apply, in one example, a minimum current of 20 A (although lower currents may be applied if so desired) that may pass through the tumor during nsPEF application to have a desired effect of triggering tumor apoptosis. In order to prevent damage to tissues surrounding the tumor, the nsPEF therapy may be applied at a pulse frequency that will not heat the tissue above, e.g., 40° C. (the minimum temperature for hyperthermia effects). Therapy with nsPEF treatment is thus able to initiate apoptosis within the tumor cells without raising the temperature more than a few degrees so as to prevent harm to surrounding tissues from heat transfer. In one example, if 100 ns pulses were applied, the frequency of the applied pulses is desirably 7 pulses per second (Hz) or lower to prevent damage to surrounding tissues. 
         [0079]    With the electrode assemblies described herein, treatment of tissue regions such as skin tumors may be effected by applying nsPEF while specifying various parameters. For instance, one or all of the following parameters may be adjusted to provide optimal treatment of tissue to effect tumor apoptosis: (1) pulse amplitude (kV/cm); (2) pulse duration (ns); (3) pulse application frequency (Hz); and/or (4) pulse number applied. 
         [0080]    Because the value of these parameters may vary widely over a number of ranges, it has been determined that particular ranges may be applied for effecting optimal tissue treatment which may effect tumor apoptosis in as few as a single treatment. In varying pulse amplitude, an applied amplitude as low as, e.g., 20 kV/cm, may be sufficient for initiating an apoptosis response in the treated tissue. The pulse amplitude may, of course, be increased from 20 kV/cm, e.g., up to 40 kV/cm or greater. However, an applied amplitude of at least, e.g., 30 kV/cm or greater, may be applied for optimal response in the treated tissue. In varying pulse duration, durations in the range of, e.g., 50-900 ns, may be highly effective although shorter durations may be applied if the number of pulses is increased exponentially. In varying pulse application frequency, frequencies up to 7 Hz may be applied with 100 ns pulses without heating surrounding tissues to hyperthermic levels. Because tissue heating may be dependent on pulse width multiplied by the frequency of application, shorter pulses may be applied at proportionately higher frequencies with similar heat generation. In varying the number of pulses applied, the pulse number determines the total energy applied to the tissue region. Generally, applying a minimum pulse number of 600 pulses may result in complete remission of tumors. In one example, nsPEF therapy having a pulse duration of 100 ns may be applied over a range of, e.g., 1000-2000 pulses, to effectively treat the tissue region. 
         [0081]    Given the range of parameters, a relationship between these parameters has been correlated to determine a minimum number of electrical pulses which may effectively treat a tissue region, e.g., a tumor, with a single treatment of nsPEF therapy to cause complete apoptosis in the tumor tissue. Generally, the number of electrical pulses increases exponentially as the pulse duration is shortened. Data obtained and as shown in the following Table 1 show the minimum number of pulses which may be applied for a given pulse width to completely eliminate, e.g., a melanoma, with a single nsPEF treatment utilizing the devices described herein. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Pulse duration or width (ns) vs. number of pulses 
               
               
                 to eliminate a tumor with a single treatment. 
               
             
          
           
               
                   
                 Pulse duration 
                 Pulses required to 
               
               
                   
                 (ns) 
                 eliminate tumor 
               
               
                   
                   
               
             
          
           
               
                   
                 25 
                 15000 
               
               
                   
                 50 
                 8000 
               
               
                   
                 100 
                 2000 
               
               
                   
                 300 
                 600 
               
               
                   
                   
               
             
          
         
       
     
         [0082]    The values of Table 1 are plotted in the chart of  FIG. 9  and provides a correlation illustrated by curve  100  where for a given pulse duration or width, any number of pulses, N, at or above the curve  100  may result in complete tumor remission after a single treatment as described herein. The curve  100  may be described in the following equation (1): 
         [0000]      N=28,714e −0.026t   (1)
 
         [0000]    where,
 
N=minimum number of pulses to cause tumor apoptosis with a single treatment
 
t=pulse duration (in nanoseconds)
 
         [0083]    This non-linear dependence of pulse number on pulse width suggests that the effectiveness of the nsPEF therapy described herein is not simply due to energy delivery to the tumor as that is linearly proportional to N times t given a constant voltage and current. 
       Example 1 
       [0084]    In optimizing the device, multiple experiments have shown that tumors, such as melanoma tumors, may be eliminated utilizing nsPEF when exposed to 100 ns long pulses having a 15 ns rise time where the minimum number of pulses range from, e.g. 1500 to 2000 pulses, as illustrated in the chart of  FIG. 10  which shows the Optimum Pulse Number where a majority of tumors were successfully treated after a single treatment when pulsed with at least 1500 to 2000 pulses. Accordingly, as shown in the graph of  FIG. 11 , the Percent Efficacy after one treatment is shown to increase from 1500 pulses and higher. 
         [0085]    As also indicated in the chart of  FIG. 12  which illustrates Optimum Amplitude of the pulses, the number of tumors successfully treated after a single treatment begins to rise at higher amplitudes, e.g., from 25 kV/cm. Thus, the minimum pulse amplitude observed is 30 kV/cm in this example while the optimum pulse amplitude is 40 kV/cm or greater in this example for effectively treating tumors such as melanoma tumors. 
         [0086]    Aside from pulse amplitude, another parameter is pulse frequency. It has been determined that the optimum pulse frequency is 7 Hz as higher frequencies may result in excessive heat applied to the tissue, as previously described. Thus, if a maximum frequency of 7 Hz were utilized to deliver at least 2000 pulses, the treatment time to optimally treat a tumor would be at least 4 to 5 minutes at about, e.g., 4.76 minutes. In utilizing the parameters described above for the nsPEF, a treated tumor may be effectively eliminated within a week or two following a single application of the nsPEF. Additional treatments of the tumor or tumors may be effected if necessary or desired. 
       Example 2 
       [0087]    In this particular example, Murine B16-F10 melanoma cells transfected with enhanced green fluorescent protein (eGFP) were obtained and stored in liquid nitrogen until use. These cells were cultured and injected into 4-6 week old female Nu/Nu mice (immunodeficient, hairless, albino) using standard procedures at four injection sites each. Tumors were detected visually by the bulges they produced and by GFP detection under fluorescent microscopy. 
         [0088]    Various suction electrode assemblies, shown in  FIG. 13 , were used where electrode assemblies  110 ,  112 , and  114  each had a recessed cavity with an inner diameter of about 4 mm and a depth of about 2 mm while the electrode assembly  116  utilized an array of needles positioned within the recessed cavity where a distance between the center needle and each of the outer needles was about 2 mm. In each of the assemblies, one or more electrodes  118  were used to discharge the energy into the treated tissue while the remaining electrodes functioned as return electrodes. 
         [0089]    A suction was drawn (e.g., 500 mm Hg) within the recessed cavity to pull the tumor therein and nsPEF therapy was applied with 100 ns pulse widths while either the pulse number, amplitude, or frequency was varied. A typical treatment applied 2700 pulses with a pulse width of 100 ns at 30 kV/cm and a frequency of 5-7 Hz. The suction electrode assembly was rotated 45° every 500 pulses to ensure uniform field distribution across the tumor. 
         [0090]    GFP fluorescence changes following nsPEF application using the electrode pictured at the top of each column were noted at 0 min, 5 min, 1 hr, 2 hr, 3 hr, and 4 hr. GFP fluorescence changes, if any, were also noted for tumors which had only suction applied as well as suction plus heat applied (37° C. for 10 min) but without nsPEF treatment.  FIG. 13  shows the resulting tumor activity for each of the electrode assemblies  110 ,  112 ,  114 , and  116 . Tumors that showed signs of regrowth, generally indicated by renewed GFP production, were retreated using the same parameters as the first treatment. Tumors were considered eliminated when no regrowth was detected within two weeks after the last treatment. 
         [0091]      FIG. 14  also shows trans-illumination and reflected light images adjacent to one another of the treated tissues (melanomas) corresponding to the various electrode assemblies  110 ,  112 ,  114 , and  116 . The images were recorded on the days indicated in the upper left corner of each pair of figures, e.g., 0, 3, 7, etc., where nsPEF treatment (if applied) occurred on day 0. 
         [0092]      FIG. 15  shows the measured change in GFP signal area normalized on a logarithmic scale over a period of time in hours following nsPEF treatment with the indicated suction electrode type, i.e., the 6-pole dual plot correlates to electrode assembly  110 , the 6-pole plot correlates to electrode assembly  112 , the 2-pole plot correlates to electrode assembly  114 , and the needle plot correlates to electrode assembly  116 . The indicated error bars represent the standard error of the mean (SEM) with N=10-12.  FIG. 16  shows the measured change in tumor area normalized on a logarithmic scale over a period of days following nsPEF treatment with the indicated suction electrode type assembly. As above, the indicated error bars represent a standard error (SEM) of N=10-12. 
         [0093]    As shown in  FIG. 17 , histological sections of the treated tumors and skin immediately adjacent to suction electrode location were taken at different times after treatment with 2000 pulses at 30 kV/cm and a frequency of 7 Hz. Images in the three left columns were taken from skin (melanoma, epidermis, and blood cells) with tumors before (i.e., 0 hr) and several times after nsPEF treatment (i.e., at 1 hr, 6 hrs, 24 hrs, and 48 hrs). Images in the two right columns were taken from skin (blood in adjacent skin and epidermis in adjacent skin) immediately adjacent to the nsPEF-treated region and no morphological changes could be detected there indicating that the nsPEF treatment effects on skin and melanomas are highly localized to the region between the electrodes. 
         [0094]    Thus, in varying the range of pulse numbers from 500-2700 while using the same amplitude (e.g., 30 kV/cm), duration (e.g., 100 ns), and frequency (e.g., 5 Hz), a minimum of 2000 pulses has shown desirable complete elimination of tumors, although fewer pulses may be applied if desired, as indicated in the chart of  FIG. 18 . In varying the range of pulse amplitude while using the same pulse duration (e.g., 100 ns), pulse number (e.g., 2000 pulses), and frequency (e.g., 7 Hz), a minimum amplitude of 30 kV/cm has shown desirable elimination of tumors, although the amplitude may be lowered or increased if so desired, as indicated in the chart of  FIG. 19 . In varying the range of pulse frequency, it is generally desirable to use the highest pulse application frequency possible without damaging the surrounding tissue given the temperature rise in the tissue, as indicated in the chart of  FIG. 20 . Applying nsPEF at 1 Hz at 30 kV/cm and 20 A to tissue may increase the tumor temperature by 2° C. whereas 5 Hz increased the tumor temperature by 6-7° C. Applying a frequency of 7 Hz may limit the temperature rise of the treated tissue to 37° C. which is below the hyperthermia threshold of 41° C. For an amplitude of 30 kV/cm, applying pulses at 5 Hz or higher was more effective than using lower frequencies. 
       Example 3 
       [0095]    Typical melanoma responses to nsPEF therapy in the 10-25 kV/cm range were recorded where four melanomas on one mouse were treated with either 10, 15, 20 or 25 kV/cm nsPEF (2000 pulses, 100 ns, 7 Hz). The GFP fluorescence at each respective pulse amplitude over a period of 0, 1, 6, and 8 days were recorded, as shown in  FIG. 21 , as were the trans-illumination, as shown in  FIG. 22 , and reflected light images, as shown in  FIG. 23 . The temperature increase inside a tumor over a period of several minutes during nsPEF application were also recorded, as shown in  FIG. 24 . 
         [0096]    A pulse amplitude of 30 kV/cm with 100 ns long pulses were applied beginning at the indicated frequency  120  with frequency of 1 Hz and 5 Hz. Pulsing was stopped at the indicated frequency  122  for 5 Hz and at 124 for 1 Hz. The 1 Hz pulse application increased tumor temperature by 2° C. while the 5 Hz pulse application increased the temperature by 7° C. 
         [0097]    The appearance of nsPEF-treated skin on the indicated day following nsPEF therapy is shown in  FIG. 25  in reflected light images of 20 different nsPEF-treated tumors. The electrode configuration  110 ,  112 ,  114 , and  116  used is shown with respect to each column. 
       Example 4 
       [0098]    A number of tumors were treated with nsPEF therapy over a range of pulses. With a pulse duration of 25 ns at 30 kV/cm and with 20-25 Hz pulse frequency, the number of tumors treated and the percentage of tumor regrowth were recorded over the range of pulses applied during a single treatment, as shown in the chart of  FIG. 26 . The chart illustrates how tumor elimination may be effected when at least 15,000 pulses were applied. Although the percentage of tumors eliminated was less than 100% at 15,000 pulses, complete tumor regrowth elimination may be potentially effected by treatment at a greater number of pulses when applied at these particular parameters. 
         [0099]      FIG. 27  likewise illustrates the number of tumors treated and the percentage of tumor regrowth over the number of pulses applied. As shown, with a pulse duration of 50 ns at 30 kV/cm and a pulse frequency of 20 Hz, the optimal pulse number applied for a single treatment may completely eliminate tumor regrowth at 8000 pulses. With these particular parameters, a number greater than 8000 pulses may also be potentially applied to effectuate complete tumor elimination. 
       Example 5 
       [0100]    In one particular variation, an elongate instrument which may be delivered via or through an endoscopic device may utilize any one or more of the nsPEF parameters described herein for tumor treatment. The endoscopic device, particularly an EUS device, may be used to image or locate a tissue region to be treated. Ultrasound imaging may be particularly useful in locating one or more tumors for treatment although conventional endoscopic imaging may also be utilized. With the targeted tissue region located within the body, the nsPEF instrument  140  may be positioned or advanced within one or more working channels in the endoscope until a tapered piercing end of the nsPEF instrument is projected from a distal end of the endoscope to deliver a highly localized treatment. The nsPEF instrument  140  may be configured either as a bipolar or monopolar electrode configuration. 
         [0101]    Generally, the nsPEF instrument  140  may be positioned upon the distal end of an elongate shaft  130  (such as an insulated conducting cable disposed within a flexible stainless steel tubing) which is sufficiently flexible for advancement through the endoscopic working lumen, as shown in the perspective view of  FIG. 28 . In its low-profile delivery configuration, the piercing tip  132  which may also function as a conducting electrode may project distally from the shaft  130  for piercing directly into the tissue to be treated or through a tissue region and/or for delivery and/or retraction through the endoscopic working lumen or patient body. Because the nsPEF instrument  140  as well as shaft  130  is designed to be advanced through the working lumen of an endoscopic device, the nsPEF instrument  140  and/or shaft  130  may have a diameter of, e.g., around 3 mm, for advancement through a working lumen having a diameter of e.g., 3.7 mm, with a working length of, e.g., about 125 cm. One or more reference electrodes  134  (shown in this variation as elongate members) may be positioned proximal to the piercing tip  132  in a low-profile configuration where the one or more reference electrodes  134  are placed against the conducting electrode. A proximal end of each reference electrode  134  may be pivotably connected to the elongate shaft  130  such that when the one or more electrodes  134  are actuated to reconfigure, each electrode  134  may rotate about its pivot to extend into a radial pattern. Moreover, the piercing tip  132  and one or more reference electrodes  134  may be in connected in electrical communication with a pulse generator (as described herein) through corresponding conductors passed through elongate shaft  130 . The nsPEF therapy may be applied through nsPEF instrument  140  with the parameters as described herein. 
         [0102]      FIG. 29  shows a perspective view of the one or more reference electrodes  134  being partially extended or reconfigured about its proximal pivot into its deployed configuration. The electrodes  134  may be actuated by the operator using a mechanism for deploying the electrodes  134  into their deployed configuration. In this variation, one or more corresponding cables or wires  136  attached to each electrode  134  may extend through openings  138  into and through the shaft  130  to an actuator positioned at or along a proximal end of shaft  130 . 
         [0103]    With the electrode assembly fully deployed, as shown in the perspective view of  FIG. 30 , the piercing tip  132  may be penetrated into or through the tissue to be treated (such as the tumor) while under the guidance of ultrasound imaging from the endoscope for desirably positioning the instrument. The one or more reference electrodes  134  are shown in their deployed configuration where each electrode  134  may extend radially from shaft  130 . Although six electrodes  134  are illustrated circumferentially positioned and radially extending about shaft  130  in this embodiment, other variations may utilize different numbers of electrodes which are spread or configured into a variety of different shapes, e.g., a hemi-circular plate configuration. A single treatment via nsPEF instrument  140  with the parameters described herein may stop blood flow to the tumor and initiate apoptosis and/or necrosis resulting in tumor shrinkage. 
         [0104]    As mentioned above, once the nsPEF instrument  140  and shaft  130  have been advanced through a working lumen  152  of endoscope  150 , the one or more reference electrodes  134  may be deployed, as shown in  FIG. 31 . The piercing tip  132  may be advanced into a tissue region to be treated, such as a tumor located on or within an organ  162  until the one or more reference electrodes  134  are positioned on or against a surface  164  of the organ or tumor. The endoscope  150  may be manipulated to position its distal end into proximity to the organ  162  and/or tumor while under guidance from an ultrasound transducer  154  positioned within the distal end of the endoscope  150 . The operator may utilize the captured ultrasound images from the transducer  154  to also guide the deployment of the nsPEF instrument  140  from endoscope  150  and insertion of the instrument into and/or against the organ  162  and into proximity to the tumor for nsPEF treatment, as shown in  FIG. 32  and as described above. 
         [0105]    Moreover, to facilitate contact between the nsPEF instrument  140  and the tissue surface  164  of the targeted tumor, suction may be applied through, e.g., an irrigation and/or suction lumen  156  either through the endoscope  150 , through one or more openings  166  defined along the nsPEF instrument  140  (as shown in  FIG. 33 ), or both for drawing the tumor into apposition against the electrode assembly. Other mechanisms such as tissue graspers  160  advanced through an adjacent working lumen  158  through endoscope  150  may also be used (as shown in  FIG. 32 ) to draw the tumor or organ into apposition with the nsPEF instrument  140 . Following nanosecond pulse application, the treatment instrument  140  may be withdrawn from the tumor and the outer reference electrodes  134  may be reconfigured back to their original low-profile configuration for retraction back into the working lumen  152  of endoscope  150 . Alternatively, for particularly large tumors, nsPEF instrument  140  may be withdrawn from a first location within the organ and/or tumor and repositioned under the guidance of EUS to a second location for additional treatment. This procedure may be repeated as many times as desired by relocating the nsPEF instrument  140  until the entire tumor is treated by nsPEF therapy. 
         [0106]    The nsPEF instrument  140  may penetrate through various tissue regions within the subject&#39;s body, such as through a gastrointestinal wall for treating various tissue regions such as the pancreas, liver, lymph nodes, and other surrounding structures. One exemplary treatment which the nsPEF instrument  140  is suitable for treating may involve minimally invasive treatment of pancreatic carcinoma. Because typical carcinoma sizes may range from 1-2 cm and are usually found within the pancreas 1-2 cm from the outer edge of the organ, the instrument  140  having a piercing tip with a length of about 1-2 cm may be particularly suitable for treating the tumor or tumors. 
       Example 6 
       [0107]    In yet another variation,  FIGS. 34A and 34B  show perspective views of a nsPEF instrument which may utilize any one or more of the nsPEF parameters described herein for tumor treatment. As previously described, because the nsPEF instrument as well as shaft  170  is designed to be advanced through the working lumen of an endoscopic device, the nsPEF instrument and/or shaft  170  may have a diameter of, e.g., around 3 mm, for advancement through a working lumen having a diameter of, e.g., 3.7 mm. A piercing tip  172  may project from shaft  170  and further define four openings (in this particular example) proximal to the piercing tip  172  through which a corresponding needle array may be deployed. As shown in  FIG. 34A , the piercing tip  172  may be advanced from the endoscope lumen and/or pierced through a tissue wall (such as a gastrointestinal wall) or in proximity to an organ to be treated (such as a pancreas) into proximity with a tumor  176  to be treated. The ultrasound transducer  154  positioned within the distal end of the endoscope  150  may be utilized to locate and image a position of tumor  176  such that the nsPEF instrument may be guided into proximity to the tumor  176 , as shown. 
         [0108]    Once in proximity to the tumor  176 , four conductive needles  178 ,  180 ,  182 ,  184  circumferentially arranged about piercing tip  172  may be advanced distally, e.g., 1-2 cm, from shaft  170  through their corresponding openings  174  such that the array of needles extend to span a distance of, e.g., about 1 cm or more between the needles, sufficient to surround the tumor, as shown in  FIG. 34B . The conductive needles may be optionally configured into bipolar needle electrode pairs for forming the pulsed electric field therebetween. With the needle array in position about the tumor  176 , a nsPEF having any of the parameters described herein may be applied through the needle array to generate an electric field pattern that may uniformly expose the carcinoma cells. 
         [0109]      FIG. 34C  illustrates an example of the electric field distribution created between the needle array (e.g., a nanosecond pulsed electric field of 40 kV/cm) for exposing and treating the tumor  176  between the needle array. 
         [0110]    Another variation is shown in the perspective views of  FIGS. 35A and 35B  which illustrate a nsPEF instrument similar to the previous variation but having a six-electrode array  190 ,  192 ,  194 ,  196 ,  198 ,  200  positioned uniformly about piercing tip  172  and advanced through a corresponding opening  174 . As shown, each needle array may project distally and extend at an angle to allow the needle array to surround the tumor  176 , as above. With the tumor  176  desirably surrounded, a nsPEF treatment may be effected to treat the tissue enclosed within the array, as shown by the electric field distribution in  FIG. 35C . This example illustrates the six-electrode array with a 40 kV/cm field applied although any of the nsPEF parameters described herein may be applied. 
         [0111]      FIGS. 36A and 36B  show perspective views of yet another variation which illustrates an eight-needle array. In this variation, the shaft  210  may comprise a piercing length  212 , e.g., 1-2 cm or more, having a piercing tip  214  where the piercing length  212  is narrower in diameter relative to the shaft  210 . The piercing length  212  may be advanced from the endoscope lumen and pierced directly through the tumor  176 , as shown in  FIG. 36B , while under guidance from the ultrasound transducer  154  positioned within the distal end of the endoscope  150 . Once the tumor  176  has been impaled, one or more conductive needles may be advanced from the shaft  210  through openings  216  located proximally of tumor  176  as well as from piercing length  212  through openings  218  located distally of tumor  176 . The proximally located needle array  220  and distally located needle array  222  may extend radially from the instrument to completely surround the tumor  176  to be treated. Although four radially extending needles are illustrated in the proximal needle array  220  and four radially extending needles are illustrated in the distal needle array  222 , the number of needles in either or both arrays may be varied. With the needle arrays suitably positioned, the nsPEF therapy may be applied to treat the tumor  176  located between the needle arrays, as shown by the electric field distribution in  FIG. 36C , where 40 kV/cm is applied. 
         [0112]    The applications of the devices and methods discussed above are not limited to treatment of melanoma tumors but may include any number of further treatment applications. Moreover, such devices and methods may be applied to other treatment sites within the body. Modification of the above-described assemblies and methods for carrying out the invention, combinations between different variations as practicable, and variations of aspects of the invention that are obvious to those of skill in the art are intended to be within the scope of the claims.