the human fallopian tube is made up of four segments . the intramural segment , with a length of approximately 10 mm , is variably straight , curved , and sometimes tortuous . the second segment , the isthmic , is approximately 2 - 3 cm in length and is the area in which laparoscopic tubal ligation is usually directed . this section contains the narrowest lumen of the tube , with average thickness of about 0 . 4 mm , but with a potential range of 0 . 1 - 2 . 0 mm . it also has the thickest musculature , i . e ., an inner longitudinal layer and an outer circular layer , of the extra - uterine tube . the full thickness of the wall of the isthmic portion has not been adequately determined ; however , unpublished studies of hysterectomy specimens in parous females indicate a full thickness of approximately 3 - 4 mm . the final two fallopian tube segments consist of the ampullary and the fimbrial segments . fig1 shows a schematic illustration of one system 10 of the invention in which microwave energy 12 is delivered locally to the isthmic section 14 of the fallopian tube 16 for tubal occlusion . the isthmic section 14 is chosen because the wall of the fallopian tube in this region is relatively thick and robust . fig1 a shows a cross - sectional view of the fallopian tube wall and system 10 ( and particularly of the applicator 22 of system 10 ) at the isthmic section 14 . fig1 also shows the orientation and general location of the ovary 18 and uterus 20 . more particularly , fig1 shows that the system 10 includes an applicator 22 and a power control section 24 . for ease of illustration , the section 24 and applicator 22 are shown unconnected , while in fact the applicator body 22 a flexibly extends between the fallopian tube 16 and the coupler 34 . the symbol 30 thus illustrates that the applicator 22 connects integrally with the section 24 . a connector 32 mates the applicator 22 with section 24 . since the applicator 22 passes into the female body in a transcervical - transuterine fashion the diameter “ d ” of the applicator 22 is sufficiently small to pass through the cervix . typically , therefore , the applicator 22 is flexible and cylindrical , with a d diameter of between 1 - 3 mm , or smaller . in one embodiment , the power control section 24 contains a controller 25 ( including a dual directional coupler 34 , a forward power meter 36 , and a reflected power meter 38 ) and a microwave generator 40 . the generator 40 provides microwave power to the applicator 22 ; and the forward and reflected power meters 36 , 38 provide measurement of microwave power to and from the female patient through the dual directional coupler 34 . the controller 25 provides overall control of the power delivered to the patient and can include user interfaces and computerized hardware ( not shown ) to facilitate control . the microwave generator 40 can for example be an amt model 1120 which produces 50 watts of microwave power in the channel used to power the applicator 22 . the power is controlled manually by adjusting a dc voltage applied to the back panel of the generator 40 . the dual directional coupler 34 diverts one - hundredth of the power applied to the applicator 22 to permit measurement of the forward power by the power meter 36 . it also diverts one - hundredth of any power reflected from the applicator 22 for the same purpose by the reflected power meter 38 . this serves to confirm normal operation of the applicator 22 during a procedure , since reflected power is negligible when the applicator 22 is functioning normally . the system 10 can also include a microwave - immune thermometry system 42 , though not required . the system 42 is known in the art and is for example manufactured by luxtron in mountain view , calif . it contains a fiber optic probe that is approximately 0 . 5 mm in diameter and that feeds into a second lumen of the applicator 22 ( described in more detail below ). the probe permits measurement of the temperature of tissue adjacent to the applicator 22 during treatment to confirm conformance to treatment protocols such as described herein . as used herein , “ applicator ” operates similar to a catheter . further detail of catheters may be ascertained with reference to pct application wo 92 / 11895 , which is incorporated herein by reference . fig1 a illustrates further detailed features of the fallopian tube 16 of fig1 in a cross - sectional view . the outside of the tube 16 includes a serosal lining 50 which encloses the longitudinal muscle fibers 52 , circular muscle fibers 54 , mucosal folds 56 , lamina propria 57 and lumen 17 . also illustrated is a schematic outline 60 of the applicator 22 in operational position within the tube lumen 17 . fig2 illustrates one applicator 22 ′ constructed according to the invention . the connector 32 ′ provides for connection to the dual directional coupler 34 . the applicator 22 ′ is constructed by removing the outer shield from one end of a piece of flexible coaxial cable 70 . this exposes the insulating layer , inside of which is the inner conductor 72 . the inner conductor 72 forms the monopole which couples microwave energy 12 into surrounding tissue . the length “ l ” of the monopole is inversely proportional to the driving frequency . thus , for example , l is about 4 cm at 915 mhz . this value gives a real input impedance at the driving frequency ( i . e ., a resonance ). it also provides a heating zone that is a few centimeters in length . the other end of the coaxial cable 70 is soldered to a standard coaxial connector 32 ′ ( type sma ) to provide connection to a larger feedline from the directional coupler 34 . the coaxial cable assembly is placed inside a nylon catheter 74 , which has been sealed at the distal end 76 to prevent direct contact with tissue . fig2 also shows the optional thermometry catheter 80 arranged adjacent to the applicator 22 ′. the catheter 80 includes a thermometry probe 82 , known in the art , to measure the temperature of the heating zone created by the monopole 72 . fig2 a shows another embodiment of an applicator 90 constructed according to the invention . the applicator 90 utilizes a monopole 92 of greater diameter “ x ”— as compared to the monopole 72 of fig2 — so that it has a shorter resonant length . the shorter length is convenient for placement in the organ to be heated . this applicator 90 is constructed as above , except that the insulation is removed from around the inner conductor 92 so that it can be soldered to a separate piece of outer shield material 94 . a gap 96 is maintained between the monopole 92 and the shield 94 of the coaxial cable ; and the assembly is configured within a sealed catheter 74 . those skilled in the art should thus appreciate that the applicator 90 , and certain other systems and applicators described herein , can be utilized in the treatment and heating of tissues other than the fallopian tube . a third applicator 100 is shown in fig2 b . the applicator 100 includes a choke 102 to reduce currents flowing from the distal monopole 104 back toward the insertion point into tissue . such currents may heat overlying tissue that is not the target of the treatment . the choke 102 has a cylindrical conductor 102 a surrounding the outer shield of the coaxial cable ; but separated from it by an insulating layer 102 b . the choke 102 is connected electrically to the outer shield at its distal end 106 , but not at its proximal end 108 . fig2 c shows an alternative choke arrangement of the invention , where the choke 102 ′ is inverted as compared to fig2 b . the applicator 100 ′ of fig2 c operates similarly as in fig2 b , where currents from the distal end 105 of the monopole 104 ′ are reduced towards the insertion point into tissue . the conductor 102 a ′ connects to the center conductor at the proximal end 109 of the choke 102 ′. fig2 d shows an alternative configuration wherein a proximal end 200 of an applicator 202 ( for example , utilizing a coaxial cable 204 ) includes a ground plane 206 ( generally formed by wires 206 a , 206 b , 206 c to form an approximate ground plane , wire 206 c indicating out of page direction ) deployed within the uterus 208 to reduce current flow back to the proximal end 200 . the monopole antenna 210 functions as described above , with its distal end 211 within the fallopian tube 212 . the wires 206 a - c ( shown illustratively with three wires , where fewer or greater numbers of wires can be used ) are separated by less than a wavelength of the applied energy to approximate a solid ground plane . a microwave applicator was developed and tested in a rabbit model , with the goal of developing a system to sterilize a human female through a transvaginal - transcervical - transuterine retrograde technique . the clinical procedure would create an occluding lesion in the isthmic portion of the human fallopian tube in an out - patient procedure . the microwave applicator consisted of a flexible coaxial cable from which the inner conductor was extended to form a resonant monopole antenna . see , e . g ., items 22 ′ and 72 of fig2 . the coaxial cable and monopole were placed within a sealed teflon catheter of 3 mm diameter . see , e . g ., item 74 of fig2 . a second parallel catheter of 1 mm diameter was secured to the first to provide guidance for a microwave - immune thermometry probe . see , e . g ., item 80 of fig2 . following laparotomy exposure , the applicator was placed with a transvaginal - transcervical retrograde technique in each uterine horn in succession . the temperature was elevated to 65 degrees c . for five minutes . thirty days following treatment , there was marked constriction and discoloration of the treated site as well as significant architectural effacement of the tissue composing the uterine wall . in some cases , the uterine lumen was completely occluded . by way of background , the microwave applicator of these tests heats tissue through a physical mechanism that does not depend on the flow of current from a metallic conductor in direct contact with tissue . in fact , the energy may pass through an insulating outer layer of the applicator , which is preferably biocompatible , for example , teflon . the applicator system elevates the temperature of living tissue through absorption of microwave energy . the energy is delivered by the applicator when inserted into proximity with the tissue to be heated . the applicator of these experiments contains a coaxial cable for transferring microwave energy from a generator outside the body to the site of heating without significant deposition of energy in overlying tissue . at the site of intended heating , the applicator contains a monopole antenna for coupling microwave energy to the surrounding tissue without direct contact of a metal conductor with tissue . the monopole is embedded in a cylinder of insulating , biocompatible material , such as polytetraflouroethylene ( teflon ). at the site of intended heating , the oscillating current and charge on the monopole conductor produce oscillating electric and magnetic fields in the surrounding tissue . the oscillating electric field causes polar molecules in tissue , such as water , to rotate in place , generating frictional heating . the presence of an overlying layer of insulating material does not prevent the formation of electric and magnetic fields in tissue , because the length of the monopole is chosen to form a resonant or approximately resonant structure . such a structure ensures coordination of the electric and magnetic fields such that they sustain themselves outside the applicator and thus radiate energy away from the applicator . the length of a resonant structure is inversely proportional to the microwave frequency and is inversely proportional to the square root of a weighted average of the permittivity ( dielectric constant ) of the insulating layer and the surrounding tissue . at 915 mhz or 2450 mhz ( mhz = 10 6 cycles / second ), the length of an insulated monopole at or near resonance in tissue is one centimeter to several centimeters . these values of microwave frequency are those permitted by the fcc for use in industrial , scientific , or medical applications ( ism frequencies ). the microwave applicator used in these experiments is adequately shown in fig2 . it consisted of a 1 . 6 mm diameter , flexible , coaxial cable with an extension of the inner conductor to form a monopole at the location of intended energy deposition . the point at which the inner conductor emerges from the feedline is called the driving point , or junction . the coaxial cable was placed within one lumen of a “ custom catheter ”; a second lumen of the custon catheter was available for a thermometry probe with which to measure tissue temperature ( note , those skilled in the art should appreciate that the two catheters 74 , 80 of fig2 can be combined into a single custom catheter with two lumens , one for the applicator 22 ′ and one for the thermometry probe 82 ). the resonance length of the antenna can be computed as an inverse function of frequency . at the resonance length , the antenna deposits energy most efficiently . preliminary calculations show this length to be approximately 3 cm at 915 mhz . in order to fit the anatomy of other subjects , it is desirable to use a shorter monopole , such as the next - highest ism frequency of 2450 mhz . the antenna was constructed from standard flexible coaxial cable ( 1 . 6 mm od , 50 ohms ), from which the outer braid was removed at the tip to form the monopole of resonance length . at the proximal end of the cable , we installed a standard , miniature microwave connector ( sma type ) for connection to the microwave generator . the antenna was placed within a catheter of 2 . 2 mm outer diameter . we measured the impedance of the antenna over the frequency range 700 mhz to 1100 mhz with a hewlett packard network analyzer model 8753c . the length of the distal section of the prototype antenna was trimmed or lengthened , as appropriate , to make the impedance purely real at 915 mhz . the voltage reflection coefficient was less than 0 . 1 . to characterize the heating pattern of the applicator , we immersed it in tissue - equivalent phantom , a semi - transparent , viscous liquid mixture with the same conductivity and dielectric constant as soft tissue at microwave frequencies . the applicator was secured to a sheet of liquid crystal from edmund scientific , barrington , n . j ., which indicates temperature over a 5 degrees c . range with a calibrated color change . the liquid crystal sheet had a rectangular cut - out to accommodate the applicator in a plane parallel to its long axis . we photographed the liquid crystal sheet at 2 minutes after application of 30 watts of microwave power in order to visualize the heating pattern of the applicator . we found the length heated above 40 degrees c . at 2 minutes was a 3 cm zone extending 2 cm proximal to the junction . after the first heating of a rabbit , we constructed a second applicator in the form of a choked dipole in order to prevent significant energy deposition on the feedline . the choke consisted of a new cylindrical conductor insulated from the feedline by a dielectric layer ( see , e . g ., fig2 a ). the new conductor was electrically connected to the feedline only at the antenna junction . the gap between the feedline and new conductor had a length of approximately one quarterwavelength ; consequently , an approximate choke , or open circuit , is formed on the feedline , according to transmission line theory . this approximate choke tends to block the microwave current that otherwise would flow on the feedline and heat tissue proximal to the target zone . we refer to this applicator below as the choked dipole . this antenna was inserted in a catheter of 3 mm od . as noted above , the length of this heating zone may be greater than required ultimately in a clinical system and is a practical consequence of our use of 915 mhz in these experiments . the microwave applicator we designed allowed us to perform experiments of microwave heating in vivo . other components used in the experiments of this section are shown in fig1 . we chose anestrus rabbits as the animal model for the following reasons : the uterine horn of the anestrus rabbit is similar in size and shape to the isthmic segment of the human fallopian tube ; the animal can be maintained easily in anestrus ; experimental manipulation is technically easy and morbidity tends to be extremely low ; and the animals are colony bred , thus allowing selection for age and weight uniformity . pre - estrous female rabbits ( 3 . 5 to 5 kg ) were purchased from milbrook farms ( amherst , mass .). all treatments were performed under general anesthesia , which consisted of ketamine / xylazine ( 2 . 0 / 0 . 2 mg / kg im ) induction followed by intubation and maintenance anesthesia ( 1 . 5 % halothane / 100 % oxygen ). all rabbits were prepared for laparotomy using standard aseptic techniques . a midline incision was made , then the bladder was elevated out of the incision and separated from the lower uterine segment . the uterus was isolated , and connective tissue was dissected away to allow a nearly straight insertion into one uterine horn with a transvaginal - transcervical approach . the microwave catheter was then inserted . the uterine horn was isolated thermally from adjacent bowel and bladder by saline - filled balloons packed around the horn . after the microwave heat treatment , an ovarectomy was performed . all animals survived the experimental treatments without serious morbidity , and were sacrificed with intravenous kci , following deep anesthesia , at 31 (+/− 4 ) days after treatment . immediately following euthanasia , each uterus was removed en bloc . the tissue was placed in neutral 4 % neutral buffered formaldehyde and submitted forhistologic processing . five tissue sections were taken from the lesioned or control segment in each horn . representative histologic sections were taken through the treated region , as well as proximal and distal to the treated area . rabbit i was treated with the unchoked monopole of fig2 a in both uterine horns . in the left horn , a maximum temperature of 65 degrees c . was maintained for 10 minutes by applying 7 watts of forward microwave power at 915 mhz . in the right horn , a maximum temperature of 70 degrees c . was maintained for 5 minutes by applying 10 watts of forward microwave power . the reflected power was approximately 10 %. rabbits ii through iv were treated with the choked dipole of fig2 b in both uterine horns . the target temperature , time at target temperature , and microwave power for each horn in each subject are shown in table 1 . reflected power was approximately 10 %. in five of the six treatments in rabbits ii through iv , the temperature distribution adjacent and parallel to the microwave catheter was measured in the steady - state . the longitudinal temperature distribution measured in the steady - state at the surface of the microwave catheter had a maximum value located approximately at the antenna junction ; temperature values decreased distal and proximal to the junction . to quantify the length of the temperature distribution , the value of body temperature was subtracted from the maximum temperature , and this value was divided by two to yield a quantity defined as dt50 . the length along the applicator surface at which temperatures above dt50 were measured was defined as l50 . for five treatments with the choked dipole , the average value of l50 was 5 . 3 cm +/− 0 . 8 cm . lesions were observed on the serosa of the uterine horn immediately after treatment . the average length of lesion was 3 . 8 cm +/− 1 . 5 cm , and the location of the lesion center was on average 1 . 6 cm +/− 0 . 5 cm proximal to the applicator junction . the lesions did not extend around the entire circumference of the horn , but instead involved a quarter or half arc of a circle . no charring of tissue was observed at any location in any of the treatments . after sacrifice , gross assessment of the treated uteruses showed pale discoloration and a markedly reduced circumference of the treated segment of uterus horn . the normal uterine anatomy contains numerous folds and villi covered by specialized columnar epithelium on the surface and numerous glands in the submucosa . by contrast , the 30 - day post - treatment uterine horns showed very marked edema and vascular dilitation resulting in significant thickening of the submucosa , near complete loss of the submucosal glands and the covering epithelium and the influx of a mixed inflammatory infiltrate . these pathologic changes generally resulted in extensive architectural effacement of the inner portion of the uterine wall anatomy and occlusion of all or part of the lumen space . in some cases , the tissue damage and resultant healing were significant enough to cause complete occlusion of the lumen . in these instances , the lumen and adjacent tissues were completely replaced by fibrosis and inflammation . in the first rabbit , acute blanching of the overlying bowel was observed , indicating significant thermal damage beyond the target tissue . in subsequent experiments , the uterine horn was isolated thermally to allow study of only the target tissue . other experimentation will reduce the thermal dose , while still producing blockage of the horn , or will devise a modified technique to avoid thermal damage to overlying bowel . in contrast to the effects of rf heating , no charring of tissue was observed . the length of the heated zone we observed was suitable for a study of tissue effects , but it may be too long for tubal occlusion in a human patient . in future studies , we plan to use a generator operating at 2450 mhz , since the resonance dipole length and hence value of l50 will decrease in inverse proportion . external lesion formation appears to be sensitive to the degree of contact of the applicator within the horn , since lesions did not form around the entire circumference . however , this did not seem to affect effacement or internal occlusion of the horn . we believe that highly - controlled microwave hypethermia may be used to safely and effectively occlude the human fallopian tube in an out - patient setting . while indicating the need for further refinement and testing , the results presented here suggest not only that the anestrous rabbit uterus is an appropriate and useful animal model for studying human fallopian tube occlusion , but that complete tubal occulsion can be produced accurately and effectively with the appropriate microwave applicator . our initial experimental treatments were not without complications , including acute blanching of the bowel overlying the treated portion of uterus . this effect demonstrated the potential for significant thermal damage beyond the target if an inappropriate thermal dose was used . in subsequent experiments , the uterine horn was isolated from the bowel to allow for a more intense study of the microwave hyperthermia effects in the target tissue ( uterus ), without the risk of damaging a critical organ . in these experiments , a microwave applicator within a 3 mm od catheter has been developed for inducing thermal blockage of the uterine horn of a rabbit . when a maximum temperature of 70 deg . c was maintained for 5 minutes , the architecture of the uterine horn was completely effaced four weeks after treatment . during the treatment , no charring of tissue occurred and no associated self - limiting of heating occurred , as has been observed with radio - frequency applicators . overlying bowel was damaged during one treatment , in which the uterine horn was not thermally isolated . additional background for the invention may be found with reference to the following article , incorporated herein by reference and written by the inventors hereof : manganiello et al ., a bipolar radiofrequency catheter fails to occlude a feline uterine horn : a model for fallopian tube occlusion , journal of the american association of gynecologic laparoscopists , vol . 5 , no . 3 , 25 - 28 ( august 1998 ). the invention thus provides several advantages , including : 1 ) the methods herein can be performed in an outpatient setting with little or no morbidity , 2 ) the methods herein eliminate the need for a general anesthetic 3 ) the invention is cost effective , 4 ) the invention is simple and easy to perform . and 5 ) the invention assures reliable contraception . the invention thus attains the objects set forth above , among those apparent from the preceding description . since certain changes may be made in the above methods and systems without departing from the scope of the invention , it is intended that all matter contained in the above description or shown in the accompanying drawing be interpreted as illustrative and not in a limiting sense . it is also to be understood that the following claims are to cover all generic and specific features of the invention described herein , and all statements of the scope of the invention which , as a matter of language , might be said to fall there between .