Abstract:
An apparatus and process whereby radio frequency (RF) energy is transmitted to a conductor, creating a standing wave on this conductor. This standing wave travels along the surface of the conductor through the skin effect, and this standing wave kills microorganisms, including prokaryotic cells (bacteria), that are lying along the surface of the conductor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part of application Ser. No. 09/489,871, filed Jan. 20, 2000, now abandoned. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the field of electrotherapeutic methods, and more particularly to methods of treating infections through the use of electromagnetic waves. 
     2. Description of Related Art 
     When a person injures a bone so that an orthopedic surgeon is required to incise the person and place a mechanical device to stabilize the bone, most often the device that is placed is a metal alloy. This “implant” is used to strengthen the bone and hold it mechanically stable while the cells of the bone grow over the defect (“knit”). In some instances, the bone and “implant” will become infected. 
     Currently, the standard procedures for an infected implant are either re-incision of the patient and removal of the implant, or infusion of an antibiotic for a protracted period of time, with subsequent re-incision and removal of the implant if the infection persists. The first solution requires that the patient be taken to an operating suite, anesthesized with a general anesthetic, and then connected to monitors and support devices, such as an endotracheal tube placed to control his breathing, IV lines to administer fluids and blood, urinary catheters, etc. The new, sterile implant is placed immediately, exposing the affected area as filly as during the first operation and then physically removing the infected implant, irrigating the infected area, and then placing a new sterile implant. 
     In other situations, the surgeon may allow the patient to heal six weeks without the implant, and then re-incise the patient and re-introduce another implant During this six week period, the patient is usually treated with intravenous (V) antibiotics to try to kill the bacteria causing the infection. 
     In another method, a surgeon will elect to begin with a six week regimen of IV antibiotics, and if the medication does not work satisfactorily, or if the patient&#39;s condition deteriorates, then the surgeon will elect to remove the infected implant and replace it, as discussed above. Specific problems encountered during the above procedures include an increased risk of mortality (death) and morbidity (inability to function normally) for every instance that an individual has to undergo a major surgery in which he is placed under general anesthetic. 
     Furthermore, there is a significant cost borne by the patient in having a second major surgery. The cost includes the operating suite, surgeons time, the stand-by surgeon&#39;s time, the cost of a second implant, and the cost of the hospital stay after the operation to recuperate sufficiently to be discharged home. 
     Improvements to removal of the implant have been suggested. For example, U.S. Pat. No. 5,330,481, issued on Jul. 19, 1994 to Hood et al., teaches a method of using ultrasonic energy in the range of 20,000 to 40,000 Hertz (20 KHz-40 KHz) at from between 50 and 800 watts power for implantation or removal of an osteal prosthesis. However, that reference does not teach the sterilization of an implant without removing the implant from a human subject. 
     Methods of killing eukariotic cells, such as benign or malignant cancer cells, through sufficient heating with radio frequency (RF) energy have been proposed. For example, U.S. Pat. No. 5,928,217, issued on Jul. 27, 1999 to Mikus et al. discloses the use of a stent system for treatment of prostate tumors in which RF energy in an undisclosed frequency at from between 20 to 40 watts to raise the temperature of the stent to at least 40° C. (104° F.), and preferably 60° C. (140° F.) for between 10 and 40 minutes to destroy the eukariotic tumor cells. However, that reference does not disclose a method of killing prokaryotic cells through a standing wave of RF energy without decernable heating. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention involves a novel process whereby radio frequency energy (RF) is transmitted to a conductor, creating a standing wave on this conductor. This standing wave travels along the surface of the conductor through the skin effect, and this standing wave kills microorganisms, including prokaryotic cells (bacteria), that are lying along the surface of the conductor. It is believed that the prokaryotic cells are killed by either lysing their external membrane or disrupting their DNA to an extent that they can no longer survive. This invention uses Gigahertz frequency RF in the range of eight to twelve point four GigaHertz (8-12.4 GHz), with a minimum power level of 100 milliwatts required to get microorganism destruction. There has been no recorded conductor surface temperature rise, even when the RF has been applied to the conductor for 160 seconds. Using a thermometer that is accurate to 0.1 degree C., no detectable temperature variance was found between the conductor before and immediately after the RF energy in the foregoing range was imparted to the conductor. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The objects of the invention are achieved as set forth in the illustrative embodiments shown in the drawings which form a part of the specification. 
     FIG. 1 is a view in side elevation of the components of a delivery needle assembly of the present invention; 
     FIG. 2 is a view in side elevation, partly in section, of an assembled guide and trochar needle of the present invention; 
     FIG. 3 is a view in side elevation, partly in section, of an assembled guide and transmission needle of the present invention; 
     FIG. 4 is a cross sectional detail view of an exemplary placement at a treatment area of the present invention; and 
     FIG. 5 is a perspective view of a transmission and dispersion assembly of the present invention. 
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     The following detailed description illustrates the invention by way of example and not by way of limitation. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what I presently believe is the best mode of carrying out the invention. As various changes could be made in the constructions described herein without departing from the scope of the invention, it is intended that all matter contained in the description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     Referring now to FIG. 1, a delivery needle of the present invention has three primary components: a needle  3 , a transmission needle  20  and a guide assembly  40 . 
     Needle  3  is preferably a trochar needle or stylet having three longitudinally disposed faces, a triangular point  5  and a head  7 . Each face of the trochar needle is preferably about one-eighth of an inch in width (about 1.9 mm), and the length will vary depending upon the depth of the implanted conductor to be treated, with a three inch (about 75 mm) length being generally appropriate. 
     A transmission needle  20  of the present invention is preferably an insulated twelve gauge copper wire, and the needle  20  has an insulated portion  21 , an exposed portion  25  at one proximal end  23 , and an RG-223 μRF cable  30  with an SMA male connector  33  at its other, distal end  31 . The proximal end  23  and distal end  31  are joined in any convenient way, with a soldered connection being preferred. An adhesive depth control  27  may be attached to assist in placement of the transmission needle  20 . 
     The guide  40  has a handle  43  having a top surface  44  and a bottom surface  45 . A shaft portion  46  has a beveled end  47  and a longitudinal bore  48  therethrough. A cross-piece  50  is spaced from the handle  43  on shaft  46 . The cross-piece  50  has a left side  51  and a right side  52 , an upper surface  53  and a lower surface  55 . The right side  52  of cross-piece  50  has an internally threaded bore therethough, which is generally transverse to the shaft bore  48  and intersects said shaft  46 . A set screw  59  has a head  61  and a threaded shank  63 . The treads  64  cooperate with those of the internally threaded bore  48 . 
     Referring now to FIG. 2, the trochar needle  3  is inserted into the guide  40  through the centrally disposed bore  48  of the shaft  46  until the point  5  of the trochar needle  3  is exposed through beveled end  47 . When the desired depth of trochar needle  3  is achieved, i.e. the conductor  70  is reached, the trochar needle  3  is withdrawn from the guide  40 . The set screw  59  is engaged to the guide  40  to prevent closure of the wound when the trochar needle  3  is withdrawn. In this preferred embodiment, the conductor  70  is a metalic prosthesis. 
     Referring now to FIG. 3, after the trochar needle  3  is removed from guide  40 , the transmission needle  20  is inserted through bore  48  of shaft  46  until it comes into contact with the conductor  70 . 
     FIG. 4 shows a detail view of an exemplary placement of the transmission needle assembly. Referring to FIG. 4, an anatomically safe region  68  on a patient is selected by the user, and a sterile drape  69  is placed over the surrounding m&amp;e The anatomically safe region  68  is determined based upon the type and location of the prosthesis used, and the preference of the treating physician. An implanted conductor  70  is within the anatomically safe region  68 . The anatomically safe region  68  in this example is a region lateral to the pubic bone and lateral to the femoral vessels  75  on the femur between the lesser trochanter  72  and the greater trochanter  73 , well away from the femoral vessels  75  which branch from the aorta  74 . 
     A toggle switch  76  is provided for selection of a first electrode ground  77  through a first conductor wire  78 , or a second electrode ground  79  through a second conductor wire  80 . 
     Referring now to FIG. 5, an oscillator  85  is provided for generation of radio frequency energy. In the preferred embodiment of the present invention, the oscillator  85  is a Hewlett Packard Sweep Oscillator model 8690B. An associated plug-in module  87  provides radio frequency waves in the desired wave length. In the preferred embodiment of the present invention, a wave length of between seven and twelve and one half gigahertz (7-12.5 GHz) has been found to be effective. Therefore, a preferred plug-in module  87  is a Hewlitt Packard 8694B plug-in module that generates frequencies in the range of 8.0 to 12.4 GHz. Ths particular module has an N type female connector for output of radio waves, so for the present invention, an SMA male to N male adapter  89  is fitted to module  87 . A KU band isolator  91  removes spurious radio wave frequencies. Finally, the transmission needle  20  is attached to isolator  91  through SMA male connector  33 . 
     The electrode ground  77  is attached to the first wire  78 . In the preferred embodiment of the present invention, a dual dispersive electrode, available from CONMED Corporation under the trademark THERMOGARD, reference number 51-7310 is used. The grounding wire  78  is parted about twelve inches distant from the electrode  77 , and a resistor  82  is soldered between the parted ends of grounding wire  78 . In this preferred embodiment, a 47Ω, ½ watt, 5% tolerance resistor, available from RADIO SHACK® as part number 271-1105 is used. 
     The RF is then delivered to a conducting orthopedic prosthesis  70  that has a microorganism culture in intimate contact with it. The RF is “drawn” along the conductor  70  to the ground  81  by impedance-matching the input impedance to the ground impedance. In the preferred embodiment, the electrode  77  is folded in half around the conductor  70 , and then secured with two pairs of forceps to ensure appropriate ground contact. (not shown) The remainder of the grounding wire  78  from the electrode  77  is soldered to the distal end of the resistor  82 , and then soldered to the ground  81 . The ground wire  78  is then connected to an appropriate grounding point. The ground wire  78  is then secured to a Faraday cage  95 , to which the electrode grounding wire is finally attached. 
     The present invention is preferably calibrated prior to use. Calibration of the power output of the present invention is accomplished through a detector designed to use a digital multi meter, such as a digital multimeter available from WAL-MART as model DM-301 (not shown). Removing the RF cable from the KU band isolator, the detector has an SMA-male connector attached to RG 223 cable proximally. Distally there is an F-type female connector, attached to the F-type male connector on the proximal end of a 1 GHz video detector (not shown). The distal end of the video detector has another F-type male connector, which is attached to an F-type female connector that is on the proximal end of RG-58 C/U cable, which is 18″ long (not shown). The distal end of this cable is stripped for 2″, and the shielding is soldered into one “banana plug” (ground), while the center pin is soldered into another banana plug (hot). These banana plugs are attached to the multimeter in the hot and ground connections. Operation of this detector, with the multimeter in the 2000 m (2,000 millivolts) setting, allows the power level to be detected and displayed on the multimeter (since there is a direct correlation between the power level and the voltage, P=IE where P=power, I=current, and E=voltage, reading the output voltage provides the ability to find the output power peaks of the sweep oscillator. 
     EXAMPLE 1 
     An exemplary method of using the present invention was tested, with excellent bactericidal results. A Hewlett Packard model 8690B sweep oscillator was selected as the source of RF energy, with a Hewlett Packard model 8694B plug in module to produce the required frequency. An N-male to SMA-male connector was attached to the RF output. A KU-band isolator was attached to the SMA-side of the connector, making sure that the “I” designation of the isolator was the transmitted (proximal) and not the reflected (distal) side. 
     The front panel controls of the sweep oscillator were adjusted as follows: Initially, the “Power” knob was turned to “ 0 ”. The “ΔF” (delta-f) button on the left bank of buttons was depressed. The “Sweep Selector” knob was turned to “CW”. The far left knob, designated as “start/CW” was turned to the desired frequency of 12.125 GHz. 
     The sweep oscillator was activated by switching the “Line” toggle switch in the bottom left comer of the front panel to the “ON” position. The toggle switch is a 3-position toggle switch; in the far left position the equipment is off, in the middle position, the ‘on’position, the equipment is on but it is not transmitting; in the far right position, the sweep oscillator is on and transmitting. This sweep oscillator required at least 5 minutes to warm up before transmitting. 
     Next, a detector was attached, as described above, to the isolator to check the output power level. The multimeter was switched on, with the selector in the “2000 m” position. With the transmission needle properly shielded, the “Line” toggle switch was turned to the far right (transmit) position. The power level was increased to “10”. The “Start/CW” knob was turned until the multimeter display showed a numeric peak (above 1200). Next the power was turned down to “0”, the detector was disconnected from the isolator and then connection from to the cable/Delivery needle to the isolator was established, as described above. 
     The conductor was cultured with a strain of Staphylococcus (S. epidermidis ) until a slime layer developed, simulating an acute infection. Sterilization of the conductor was achieved by attaching a grounding electrode distally to the conductor. Application of the transmission needle on the conductor a distance from the ground electrode was next established. When assured of proper contact between the transmission needle and the conductor, the power control knob was turned to “10” for a maximum of five seconds. Temperatures were found to remain constant throughout the treatment, and using a thermometer accurate to within 0.1° C., operatively attached to the conductor, no heat increase was found. A logarithmic death of the culture used was observed, with the slime layer being disrupted and the bacteria therein apparently killed. 
     EXAMPLE 2 
     In vivo operation of the present invention may be accomplished as follows. The N-male to SMA-male is operatively connected to the connector to the RF output Next the KU-band isolator is attached to the SMA-side of the connector, making sure that the “I” designation of the isolator is the transmitted (proximal) and not the reflected (distal) side. 
     The front panel controls of the sweep oscillator are adjusted by first turning the “Power” knob to ″0. The “ΔF” (delta-f) button on the left bank of buttons is then depressed. The “Sweep Selector” knob is set to “CW”. Then using the “start/CW” knob, set the frequency to about 12.125 GHz. 
     The sweep oscillator is turned on by switching the “Line” toggle switch on the sweep oscillator to the “ON” position. The sweep oscillator requires at least 5 minutes to warm up before transmitting. 
     The output power level is checked by first attaching the detector, described above, to the isolator. The multimeter is then turned on, with the selector in the “2000 m” position. With the transmission needle properly shielded, the “Line” toggle switch on the sweep oscillator is turned to the transmit position. The power level is next turned up to “10”. The “Start/CW” knob of the sweep oscillator is adjusted until the multimeter display shows a numeric peak, above 1200. The power control of the sweep oscillator is then turned down to “0”. The detector is then disconnected from the isolator. The cable/Delivery needle is then connected to the isolator. 
     To sterilize the conductor: The “anatomically safe” region where the physician has determined to insert the delivery needle is anesthetized. Using sterile technique, the area is prepared and draped. Anesthetization is accomplished by using a three inch 18 to 21 gauge needle to deliver local anesthetic to the anatomically safe region in increments of approximately 1 centimeter per dosage. This requires inserting the needle, applying a wheal of anesthetic, then advancing the needle, applying another dosage, and continuing until the conductor has been contacted, delivering a final dosage at the level of the conductor. The anesthetic needle is then removed. 
     With the delivery needle attached to the isolator, the guide and trochar needle is advanced to the proper depth, within the anatonically safe regions through the same puncture site made by the anesthetic needle, until the trochar needle contacts the conductor. The depth control is then slid down to the skin level and the knurled knob is tightened so the depth control will not move. The trochar needle is removed and the transmission needle is inserted to the same depth. When proper contact between the transmission needle and the conductor is assured, the power control knob of the sweep oscillator is turned to a level of “10” for a maximum of five seconds. When the approach to the conductor does not allow pure proximal contact with the conductor, a second grounding electrode may be placed proximally, with the two grounding electrodes attached to a two-position toggle switch, to allow either one to be selected. (See FIG.  4 ). When two grounding electrodes are used, the toggle switch is positioned from the first position to the second position The power control knob of the sweep oscillator is turned to level “10” for five more seconds. The power control knob of the sweep oscillator is then turned to “0”. The transmission needle is removed, pressure is applied to the puncture site until bleeding stops, and a sterile dressing is applied. 
     Numerous variations will occur to those skilled in the art in light of the foregoing disclosure. For example, the trocar needle could be replaced by any implement effective to reach the implanted conductor. Although a frequency of from between 7.0 GHz to 12.4 GHz is utilized, it is believed that higher frequencies could be employed in the production of a standing wave on the conductor, up to 15 TeraHertz (15 THz). Although the exemplary method is described as being suitable for implanted conductors, other conductors could be sterilized, such as the hull of a ship, and using strip line copper foil, for example. The examples are merely illustrative. 
     In view of the above, it will be seen that the several objects and advantages of the present invention have been achieved and other advantageous results have been obtained.