Abstract:
The invention is a transvaginal ultrasound probe having an attached echogenic needle that is useful in the treatment of uterine fibroids. The echogenic needle has an echogenic surface near its tip that allows the physician to visualize its location using ultrasound imaging. In one embodiment, the needle has an active electrode at its distal end. The active electrode supplies radio frequency energy to a fibroids causing necrosis of the targeted fibroid or by destroying the fibroid&#39;s vascular supply. The radio frequency needle preferably has a safety device that shuts-off energy if the needle punctures the uterine wall. In a second embodiment, the needle has a cryogen supply tube and cryogen supply. This embodiment destroys fibroid tissue by freezing it or its vascular supply when the tissue comes in contact with the needle&#39;s frozen distal end. The invention further includes the method of using the ultrasound probe with the attached needle.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to surgical needles for tissue ablation, and more particularly, to surgical needles that are for ablation of uterine fibroids. 
   Approximately 20 to 40 percent of women have uterine fibroids (licomyomata). In the United States, fibroids result in approximately 175,000 hysterectomies and 20,000 myomectomies each year. Fibroids are well-defined, non-cancerous tumors that arise from the smooth muscle layer of the uterus. Approximately 25% of women suffer fibroid related symptoms, including menorrhagia (prolonged or heavy menstrual bleeding), pelvic pressure or pain, and reproductive dysfunction. 
   The most common treatments for fibroids include hysterectomy, abdominal myomectomy, laparoscopic myomectomy, hysteroscopic myomectomy, laparoscopy-directed needle mylosis, laparoscopy-directed needle cryomyolysis, high-intensity focused ultrasound ablation of fibroids, and uterine artery embolization. Hysterectomy is a major surgical procedure and carries with it the usual risk of surgery, such as hemorrhaging, lesions, complications, pain, and prolonged recovery. The majority of myomectomies are performed abdominally, wherein a surgeon creates an abdominal incision through which individual fibroids are removed. Abdominal myomectomy and laparoscopic myomectomy, like a hysterectomy, carries the usual risk of surgery. 
   Radio Frequency (RF) myolysis and thermal tissue ablation are two promising methods for treating fibroids. RF myolysis is a technique in which a RF probe is inserted into a fibroid or the surrounding tissue and then RF energy is applied to the tip of the probe. The tissue surrounding the tip is heated by the RF energy causing necrosis within the tissue. Thermal tissue ablation is a technique that is performed with a cryoablation probe. The cryoablation probe destroys the fibroid tissue by freezing it. 
   Current methods incorporating RF or cryoablation techniques require direct visualization of the needle tip or electronic imaging. Normally, under direct visualization techniques an endoscope is inserted into the uterus to position the needle. Direct visualization is often problematic because of the difficulties involved in simultaneously manipulating the endoscope and needle. Typically, when electronic imaging is used, the position of the needle is visualized with a hysteroscope or with an external abdominal ultrasound. Hysteroscopy allows direct visualization of the uterine cavity by inserting a small camera on the end of a long tube directly into the uterus through the vagina and cervix. Similar to an endoscope, a hysteroscope must be simultaneously manipulated with the needle, and thus is problematic. Monitoring the probe&#39;s position with current ultrasound techniques has a number of drawbacks. For example, a clinician using ultrasound imaging from an external source will have difficulty in distinguishing the uterine tissue from the surrounding organs and precisely locating the needle. 
   U.S. Pat. No. 5,979,453 to Savage et al. describes a myolysis needle that requires laparoscopic surgery. In laparoscopic surgery the needle must be placed through the uterine serosa into or near the fibroid. As a result, uterine adhesions often form that may cause chronic pain, infertility, and bowel obstruction. Additionally, during laparoscopic surgery the surgeon cannot visualize the tissue below the surface and must blindly place the needle, as a result placement may be sub-optimal. 
   U.S. Pat. No. 6,146,378 to Mikus et al. discloses a needle placement guide having an endoscope that is inserted into the uterus through the vagina. Using the endoscope, the surgeon positions the endoscopic guide in the correct orientation to the targeted fibroid. After positioning the guide, the endoscope is removed from within the guide and an ablation device is inserted into the guide for subsequent operation on the fibroid. The needle guide suffers from several disadvantages. There is the risk that the needle guide could shift during removal of the endoscope and insertion of the ablation device, resulting in sub-optimal performance. The needle cannot be relocated during the ablation procedure and the endoscope must be reinserted whenever it is necessary to reposition the needle guide. Reinserting and removing the endoscope and ablation device every time the needle must be repositioned increases the time and expense of the surgery. 
   U.S. Pat. No. 6,379,348 to Onik describes a mylolysis needle that is a combination of a cryosurgical and electrosurgical instrument for tissue ablation. The cryo/electro needle is not easily visualized when in use and requires the use of a dilator to create an access channel in the tissue area where the needle is to be inserted. Similar to laparscopic surgery, placement of the cryo/electro needle is done blindly and may not result in optimal performance. 
   Thus, a need exists to provide a medical needle system and method that can provide accurate and reliable targeting of fibroid tumors. It is also desirable to provide a needle that has a safety system that would shut-off electrical current to the needle if the uterine wall is punctured. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention provides a medical needle for transvaginal ultrasound directed reduction of fibroids. The medical needle is adapted for use in conjunction with a transvaginal ultrasound probe. The ultrasound probe has an attached needle guide through which the needle is inserted. The needle has an outer tubular member having an inner surface, a distal end, and a proximal end. The distal end of the outer member is made of an echogenic material so that the tip of the needle has heightened visibility on an ultrasound screen. Located at the distal end is an active electrode that is in communication with a radiofrequency source. An insulating sheath surrounds the entire outer member except for a section that is near the active electrode at the distal end. 
   The needle has a return electrode that is optionally located on the outer member near the active electrode or on an outer tissue surface of a patient. Optionally, the needle may have a temperature sensor that is located near the active electrode. Typically, the distal end will either be a sharpened pointed tip or a beveled tip that defines an opening in the distal end. 
   In a preferred embodiment, the needle has a safety device that will turn off power to the active electrode if the tip of the needle should penetrate a patient&#39;s uterine wall. In the embodiment possessing a beveled tip, an inner cylindrical member having a forward end and blunt rear end is disposed within the outer member. The inner member has a cylindrical outer section that is electrically conductive and a section that is not electrically conductive. Disposed on the inner surface of the outer member is a second electrically conductive surface and a third electrically conductive surface that are not in communication with one another. The second surface is in communication with the RF power source and the third surface is in communication with active electrode. 
   A spring is attached to the forward end of the inner member and the blunt rear end extends outwardly beyond the beveled tip. When pressure is applied to the blunt rear end the spring is compressed and the exposed blunt rear end slides backwardly into the outer member. As the inner tubular member slides into the outer member the electrically conductive surface comes in contact with both the second and third surface so that current passes through the surfaces and RF energy is supplied to the active electrode. 
   In a second embodiment having a safety device, the inner tubular member does not have a conductive surface and there are no second and third conductive surfaces. Rather, a switch is located at the proximal end of the outer member. When pressure is applied to the blunt rear end of the inner member, the inner member slides back into the outer member and thereby closes the switch. When in the closed position, the switch sends a signal to the RF source and RF energy is applied to the active electrode. 
   In a third embodiment, the needle has an outer member, an inner surface, an echogenic distal end, and a proximal end. As in the first embodiment, the echogenic material results in the tip of the needle having a heightened visibility. Within the outer member is a cryogen tube that extends longitudinally from the proximal end to the distal end. Surrounding a section of the outer member from the proximal end to near the distal end is a cryo-insulation sheath. The distal end is in communication with a cryogen supply so that the distal end can be in cryogenic contact with fibroids. 
   The length of the needle in all embodiments is typically from about 25 to 50 centimeters, and somewhat more typically between 30 to 40 centimeters. The diameter of the needle in all embodiments is typically from about 12 to 18 gauge, and somewhat more typically from about 16 to 18 gauge. Normally, the needle has a handle at the proximal end that allows the user to easily grip and manipulate the needle. 
   The invention also includes a method for the electric surgery of fibroids using a transvaginal ultrasound directed echogenic needle. The method comprises the steps of providing a transvaginal ultrasound probe having a transducer and attached needle guide; providing an echogenic needle as described above; inserting the probe into a patient&#39;s uterus; inserting the needle into the uterus through the attached needle guide; sensing the location of the needle and fibroid using ultrasound imaging; guiding and positioning the needle on the surface of a fibroid using ultrasound imaging; and passing a controlled amount of RF energy through the fibroid. The method optionally includes the steps of monitoring tissue temperature, penetrating the surface of the fibroid with the distal end of the needle, and the step of turning off power to the active electrode if the distal end pierces the uterine wall. 
   The invention additionally includes the method for the cryoablation of fibroids in the uterus using a transvaginal ultrasound directed echogenic needle. The method includes the steps of providing a transvaginal ultrasound probe having a transducer and an attached needle guide; providing a cryoablation echogenic needle as described above; inserting the probe into the uterus; inserting the echogenic needle into the uterus through the attached needle guide; sensing the location of the needle and fibroid using ultrasound imaging; guiding and positioning the needle on the surface of a fibroid using ultrasound imaging; delivering a controlled amount of cryogenic supply to the distal end of the needle while it in contact with the surface of the fibroid. The method optionally includes the step of penetrating the fibroid with the distal end of the needle before or after delivering a controlled amount of cryogenic supply. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
     Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
       FIG. 1  is a side view of a transvaginal ultrasound probe having an attached echogenic needle that has been inserted into a uterus; 
       FIG. 2  is a perspective view of an ultrasound monitor displaying an echogenic needle that has been inserted into a uterus; 
       FIG. 3  is a side view of a radio frequency echogenic needle system for use with a transvaginal ultrasound probe; 
       FIG. 4  is a sectional side view of the needle shown in  FIG. 2 ; 
       FIG. 5  is a sectional side view of a radio frequency echogenic needle having a “shut-off” mechanism; 
       FIG. 6  is a sectional side view of a radio frequency echogenic needle having a “shut-off” mechanism and a noninsulated segment that is an active electrode; 
       FIG. 7  is a sectional side view of a radio frequency echogenic needle having a “shut-off” mechanism and an active electrode disposed proximal to the distal end; 
       FIG. 8  is a sectional side view of a radio frequency echogenic needle having a “shut-off” mechanism and an active electrode disposed in the inner member; 
       FIG. 9  is a sectional side view of a radio frequency echogenic needle having a switch “shut-off” mechanism; 
       FIG. 10  is a sectional side view of a cryogenic ablation echogenic needle; and 
       FIG. 11  is a side view of a radio frequency echogenic needle having a return electrode attached to a patient&#39;s thigh. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. 
   Referring more specifically to the drawings, for purposes of illustration, but not of limitation, there is shown in  FIG. 1  an embodiment of the invention referred to generally as  10 .  FIG. 1  illustrates an ultrasound probe  100  having the attached mylosis needle  105  that is inserted into the uterus  15 . The ultrasound probe has a transducer located within its tip  30  so that imaging of the uterus and needle are sent to a display for monitoring. Normally, the ultrasound probe  100  includes clamps  35  that attach the needle to the ultrasound probe. Typically, the clamps are made from a metal or plastic material that fits tightly around the probe and has an attached needle guide. The needle guide is typically a narrow or circular opening through which the needle is inserted. Alternatively, the material comprising the clamps is some other hard material that allows the user to manipulate the needle, although not necessarily with equivalent results. The ultrasound probe useful in the invention is any probe that is designed for insertion through the vagina. 
   As illustrated in  FIGS. 1 and 2 , the ultrasound probe  100  is inserted into the uterus through the vagina. Once the probe is in place, the needle is inserted through the needle guide and into the uterus. The physician uses ultrasound imagery to locate the position of fibroids  50  and the needle  105  in the uterus. The tip of the needle  160  is directed against a targeted fibroid or its vascular supply and RF energy, cryogenic, or thermal treatment is applied to the fibroid to cause necrosis of the tissue. In this regard,  FIG. 2  illustrates an ultrasound monitor  60  that is displaying ultrasound imaging of an echogenic needle  105  that has been inserted into a uterus  15 . Normally, the probe sends data to an ultrasound unit  65  that processes the data and then displays the resulting images on the monitor. 
   In all embodiments, the needle will have an echogenic surface  135  at or near the distal end  120 . For example,  FIG. 3  shows a bumpy or uneven surface  135  on the outer member. Echogenicity refers to a surface&#39;s ability to reflect incident ultrasound waves back to a sensor. The more a surface reflects waves back to the sensor the greater its image will appear on an ultrasound display. Today, there is a variety of different techniques to increase a surface&#39;s echogenicity, including grooves or recesses, bumps, coatings, indentations, and the like. In the invention, the echogenic tip enhances its visualization and helps the physician to more precisely position the tip. Normally, the distal end of the needle or a segment proximal to the distal end will have an echogenic surface. 
   Inserting both the ultrasound probe and echogenic needle into the uterus through the vagina is very advantageous. Traditional laparoscopic myomectomy requires that the ablation needle be inserted into the uterus through the abdomen. During this procedure the needle must be inserted through the uterine serosa, which may result in the formation of uterine adhesions. In contrast, the invention provides an apparatus and method of use for fibroid myomectomy that is a minimally invasive surgical procedure. Adhesions are not expected to form with this method because the echogenic needle is inserted through the vagina rather than penetrating the uterine serosa. A second advantage of the invention is precision and accuracy. The echogenic needle has a heightened ultrasonic visibility that allows the physician to accurately locate and position the needle within the uterus. As a result, the surgical procedure is performed more quickly, the needle is easily repositionable by the surgeon, and most importantly the procedure will have a greater beneficial impact for the patient. 
   With reference to  FIGS. 3 through 10 , needles that are useful in the current invention are illustrated. The needle has an outer tubular member  115 , a proximal end  125 , a distal end  120 , an insulation sheath  200  surrounding a portion of the outer member, and an echogenic surface  135  near the distal end. 
   As shown in  FIG. 3 , a RF needle is broadly designated by reference number  105 . The needle  105  includes an active electrode at the distal end  120 . Typically, the active electrode is a wire, wire loop, metal surface, or the like. The active electrode is in communication with an electrical connector  140  that is attached to the proximal end  125 . The electrical connector  140  is connected to a RF power supply  140   a  so that RF current is supplied to the active electrode. The needle  105  is connected to a RF power source  140   a , and optionally to a temperature display (heat readout)  140   b . Normally, the RF source will also include a means for controlling current to the active electrode. Typically, the RF needles will have a RF insulated sheath  200  that surrounds the outer member  115  and extends from the proximal end  125  to the distal end  120  leaving a segment of the outer member  120   a  ( FIGS. 6 and 7 ) that is RF noninsulated. The RF insulation sheath may be made of any material that is suitable to prevent RF energy passing from the outer member to the tissue being treated, such as a heat shrink polyolefin or Teflon®. 
   The RF needle of the invention delivers either monopolar or bipolar current. With reference to  FIGS. 4 through 9 , a RF needle having a return electrode  210  is illustrated. The return electrode is connected to the power supply so that current passes through the active electrode into the fibroid tissue and back to the return electrode. Normally, the return electrode is located on the outer shaft  115  about 2 to 20 millimeters from the active electrode. Typically, the return electrode  210  is positioned in close proximity to the active electrode so that RF energy that passes from the active electrode through the fibroid is focused and does not dissipate within the uterus. Alternatively, as illustrated in  FIG. 1 , the return electrode  210   a  is located on an outer surface of the patient, such as the thigh or lower back. In this manner, current passes out of the active electrode  175  through the patient&#39;s tissue, and into the return electrode  210   a.    
   In  FIG. 4 , the active electrode  175  is depicted at the distal end  120  within the needle. In this first embodiment, the distal end&#39;s noninsulated outer surface  150  is electrically conductive so that RF energy passes from the active electrode  175  into fibroid tissue. The distal end  120  has a sharpened tip  160  that can penetrate fibroid tissue to deliver RF energy within the fibroid. As shown in  FIG. 4 , the RF needle optionally has a temperature sensor  185  disposed near the distal end  120 . Typically, the temperature sensor will be disposed near the tip of the needle or within the insulation sheath. Normally, the temperature sensor is a thermocouple or thermistor. The sensor provides information that enables the physician to monitor tissue temperature and to adjust the power accordingly. 
   With reference to  FIGS. 5 through 9 , reference number  400  broadly designates a RF needle having a RF energy “shut-off” mechanism. The shut-off mechanism turns off RF energy to the active electrode if the tip of the needle  190  penetrates through the uterine wall. Shutting off power to the active electrode serves several useful purposes. It prevents damage to healthy tissue, which would otherwise be coagulated by RF energy and it alerts the physician that the needle has punctured the uterine wall. 
   In contrast to the first embodiment, RF needle  400  has a sharpened beveled tip  190 , an inner cylindrical member  405 , and a spring  430  disposed within the outer member  115  at the outer member&#39;s proximal end  125 . The inner member  405  is disposed and moveable longitudinally within the outer member  115 . As illustrated in  FIGS. 5 through 9 , the inner member  405  has a forward end  407  and a blunt rear end  425 . The forward end  407  is attached to the spring  430  that is connected to the needle&#39;s proximal end  125 . In the at rest position, the blunt rear end  425  extends outwardly from the beveled tip  190  and is the first part of the distal end  120  to contact uterine tissue. Applying pressure to the blunt rear end  425  compresses the spring  430 , and the inner member  405  slides longitudinally from the distal end  120  towards the proximal end  125 . As a result, the blunt rear end  425  retracts into the outer member  115  and the beveled tip  190  contacts the surface of the targeted tissue. 
   In a first embodiment of RF needle  400 , a segment of the inner cylindrical member has a cylindrical conductive surface, and outer member  115  has a second and third conductive surfaces on its inner surface. The second surface is in communication with the RF power supply  140 , and the third surface is in communication with the active electrode  175 . When in the rest position, the second and third surfaces are not in communication with each other. As pressure is applied to the blunt rear end  425  the inner member  405  retracts into a charged position. When in a charged position, the conductive surfaces  410 ,  415 , and  420  are in communication and RF energy flows from the RF power source to the active electrode. If the distal end  120  punctures the uterine wall pressure against the blunt rear end  425  will be released and the spring  430  will rapidly extend the blunt rear end  425  outwardly. As a result, the conductive surface  410  will move longitudinally away from the second and third surfaces  415 ,  420  and RF energy supplied to the active electrode is shut-off. The exact position of conductive surfaces  410 ,  415 , and  420  is not critical except that it is necessary that all three surfaces simultaneously communicate with each other when the inner member is in a retracted position. 
   In this regard,  FIG. 6  shows a conductive surface  410  on the inner member  405 . The conductive surface  410  is optionally located at the forward end  407  of the inner member  405  or at almost any position along the inner member. The second  420  and third surfaces  415  are located on an inner surface  117  of the outer member  115  so that when the inner member  405  retracts the conductive surfaces  410 ,  415 , and  420  contact each other. When pressure is applied to the blunt rear end  425 , the spring  430  compresses and the inner member retracts into the outer member  115 . As a result, the conductive surfaces  410 ,  415 , and  420  are in communication with one another and RF energy is delivered to the active electrode  175 . 
   The active electrode is at the distal end  120  or alternatively, the noninsulated surface  120   a  of the outer member  115  is the active electrode. In this regard,  FIG. 7  illustrates an RF needle having an insulation sheath  435  disposed between the second conductive surface  420  and the outer member  115 . RF energy is supplied to the second surface through a current line  440  that is in communication with the electrical connector  140 . As shown in  FIG. 7 , conductive surface  410  on the inner member  405  is in electrical communication with the outer member&#39;s  115  inner surface  117 . Typically, the outer member is made from a material, such as stainless steel, that is electrically conductive and suitable for insertion into tissue. When the inner member  405  retracts into the outer member  115  the second surface  420  contacts the conductive surface  410  supplying RF energy to the noninsulated segment  120   a . Optionally, insulation sheath  435  insulates the entire inner surface  117  of the outer member  115  except for segments at the active electrode  120   a  and the third conductive surface  415 . 
   In a second embodiment of a needle having a safety mechanism  400 , the active electrode is located at the blunt rear end. As shown in  FIG. 8 , the active electrode  175  is located at the blunt rear end  425  and an electrical connector  425   a  extends longitudinally from the conductive surface  410  to the active electrode  175 . The outer member  115  has a second conductive surface  420  that is in communication with RF power supply, but rather than having a third surface in communication with the active electrode, the conductive surface  410  on the inner member  405  is in communication with the active electrode  175 . When pressure is applied to the blunt rear end  425 , the spring  430  compresses and the inner member retracts into the outer member. As a result, the conductive surfaces  410 ,  415  contact one another and RF current is applied to the active electrode  175 . Typically, the electrical connector  425   a  is disposed within the inner member  405 . 
   However, the electrical connector  425   a  may be disposed between the surface of the inner member and an optional RF insulation sheath that surrounds the inner member. The optional insulation sheath does not surround the conductive surface  410  or the active electrode  175 . 
   In a third embodiment of a RF needle with a safety mechanism  400 , the inner member is connected to a switch. With reference to  FIG. 9 , a needle is shown having an inner member  405  attached to a switch  450 . The switch  450  is in communication with a RF power source via line  455 . As pressure is applied to the blunt rear end  425  the inner member  405  retracts into the outer member  115  and closes the switch  450 . When in the closed position, the switch  450  sends an electrical signal through line  455  to the RF power supply  140   a  and RF energy is delivered to the active electrode. The active electrode is located at the distal end and is in communication with the switch, or alternatively, the noninsulated distal end  120   a  is the active electrode. 
   In all the embodiments of a needle having a safety mechanism  400  the inner member  405  is typically made from a material that is non-conductive, such as a plastic. Normally, a non-conductive member will have a conductive material, such as stainless steel, inserted into a surface segment so that the inner member has an electrically conductive surface that will contact the second and third surfaces on the outer member. Somewhat more typically, the inner member is made from a metal such as stainless steel that is surrounded by a RF insulation sheath. The insulation sheath surrounds the inner member except for the conductive surface  410 , which is RF non-insulated. 
   With reference to  FIG. 10 , a cryoablation needle is broadly illustrated by reference number  500 . The cryoablation needle has an echogenic distal end having a sharpened tip  160 . The outer member  115  is surrounded by a cryo-insulation sheath  200   a . The insulation sheath  200   a  extends longitudinally from the proximal end  125  to the distal end  120  leaving a segment of the outer member  120   a  that is cryo-noninsulated. Normally, the sheath will be made of any material that prevents the cryogenic effect from passing through the outer member and into the surrounding tissue. A cryogen supply tube  510  is disposed within the outer member and extends from the proximal end  125  to the distal end  120 . A cryogen supply source  520  provides cryogen supply through a cryogen connector  525  to the cryogen supply tube  510 . 
   Typically, cryogenic liquids such as nitrogen, helium and argon are used to produce the cryogenic effect in the targeted tissue. 
   In all embodiments, it is necessary that the needle is longer than the ultrasound probe and has sufficient length to reach fibroids deep in the uterus. Typically, the length of the needle is about 25 to 50 centimeters, and somewhat more typically about 30 to 40 centimeters. The needle&#39;s diameter is dictated by the ultrasound probe&#39;s attached needle guide. Typically, the diameter of the needle is about 12 to 18 gauge, and somewhat more typically about 16 to 18 gauge. However, the needle is not limited to the above recited dimensions and may be varied depending upon the actual length of the probe and the needle guide&#39;s inner diameter. Typically, the outer member is made of any material that is suitable for insertion into tissue, such as stainless steel. 
   Optionally, as shown in  FIG. 3 , the needle will have a handle  130  at its proximal end  125 . The handle  130  allows the user to easily manipulate and move the tip of the needle. Ideally, the handle  130  is large enough to be manipulated with the user&#39;s thumb, index finger and middle finger. Normally, the handle is metal, plastic, rubber, or the like. 
   Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.