Abstract:
Disclosed are in-vivo interstitial antennas (IVIAs) for thermal treatment and deactivation of tumors by means of microwaves. An IVIA comprises a microwave monopole antenna (MMA) and a medical catheter, and the MMA is inserted into the medical catheter to form the IVIA. The MMA comprises coaxial cable and three types of capacitors. The coaxial cable consists of first and second conductors and a first insulator, and only the first conductor extends less than a quarter wavelength. The first capacitor is located around the end of the extended first conductor and includes the second insulator and the third conductor. The second and third capacitors are located between the first capacitor and the apertures of the MMAs and have about same function. Because of arbitrarily changed input impedance of the first capacitor, almost perfect matching can be achieved and desirable temperature distributions can be obtained due to the second and third capacitors.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to in-vivo interstitial antennas (IVIAs). More precisely, the invention relates to IVIAs for thermal treatment and deactivation of deep-seated tumors including cancers in a human body by means of microwave.  
         [0003]     2. Background of the Related Art  
         [0004]     Conventional surgical operations have been performed for tumors including cancers in a human body. However, such operations not only result in considerable cost and recovery time, but also expose the patients to high risk of secondary infection. To overcome the problems mentioned above, the IVIA using the microwave can be used to treat and deactivate tumors including cancers without any surgical operation. Mainly due to less expense, easy operation and short recover time, the use of the IVIAs has recently been on a dramatic increase, and many studies have been published. Details on a conventional typical IVIA will be described.  
         [0005]      FIG. 1 ( a ) illustrates cross sectional view of the coaxial cable which is main material of the IVIAs, and how the conventional typical IVIA operates in a human body is described in  FIG. 1 ( b )  
         [0006]     The coaxial cable  120  comprises a first conductor  110 , a first insulator  111 , and a second conductor  112  as shown in FIGS.  1 ( a ) and ( b ). When the first conductor  110  extends approximately λ g /4 (λ g : wavelength in the medium), a microwave monopole antenna (MMA) is formed and inserted into a medical catheter  114  to avoid direct contact between the MMA and human body tissues. Therefore, the IVIA consists of the MMA and plastic medical catheter and the medical catheter  114  is a harmless plastic tube with a dielectric constant. For easy fabrication of the IVIAs in this invention, air fills the gap  113  between the MMA and plastic catheter, whereas saline has been used for the gap of conventional IVIAs.  FIG. 1 ( b ) describes a situation where a conventional typical IVIA is inserted into an assumed human body organ and epidermal tissues  115  are shown around the IVIA.  
         [0007]     When current is applied to the IVIA through the first conductor  110  of the coaxial cable  120  in  FIG. 1 ( b ), positive charges are produced around the IVIA and electric fields are, therefore, generated between the positive charges and the distant negative charges. Since the human body tissues is conducting and lossy media, heat is generated by the electric fields and temperature rises around the targeting heating area where the IVIA is inserted in the human body. The temperatures of more than 43 degrees centigrade can be used for treatment and deactivation of tumors including cancers in a human body.  
         [0008]      FIG. 2  shows conventional MMAs. The conventional MMA in  FIG. 2 ( a ) is the most common one whose, first conductor  110  is extended. That in  FIG. 2 ( b ) has the third conductor  210  in a quadrilateral form which is wider than diameter of the first conductor. Therefore, more current can be concentrated around the third conductor  210 . For that in  FIG. 2 ( c ), an end is located around the extended first conductor and includes a third conductor  212  in the form of a metal tube concentrically surrounding the first conductor  110  with both ends open, and the second insulator  212  fills the gap between the first  110  and third  212  conductors.  
         [0009]     When IVIA is used for a human body, the IVIA matching is most important factor to be considered. If the IVIA is not matched, the thermal energy can not be concentrated around the targeting heating area, and the microwave source may be destroyed by unavoidable reflected power. In addition, thermal pattern should also be taken into consideration and isothermal line contour with 43 degrees centigrade is desired to be similar to the shape of tumors including cancers to protect healthy surrounding tissues during the microwave treatment.  
         [0010]     However, conventional IVIAs have been poorly matched due to perfect matching methods unavailable. The poor matching results in poor thermal energy concentration and undesired thermal pattern, and damage to healthy surrounding tissues can therefore occur.  
       SUMMARY OF THE INVENTION  
       [0011]     An objective of the present invention is to provide IVIAs in order to have good matching, desired thermal pattern, high thermal efficiency and little damage to healthy surrounding tissues.  
         [0012]     In addition, it is another object of the present invention to provide the IVIAs for optimizing the thermal pattern to treat and deactivate tumors including cancers in a human body.  
         [0013]     To accomplish the above objects, according to one aspect of the invention, an IVIA using microwaves is provided for thermal treatment of tumors including cancers in a human body. The IVIA consists of a MMA and a medical catheter in the form of dielectric tube with a dielectric constant, and the MMA is inserted into the medical catheter to form the IVIA. The MMA consists of the coaxial cable with the first conductor extending and a first capacitor located around the end of the extended first conductor. The coaxial cable and the first capacitor will be explained in more details.  
         [0014]     Coaxial cable, main material of the MMA, includes a first conductor having a cylindrical form and being used for applying current; a second conductor in the form of a metal tube concentrically surrounding the first conductor and used for ground when applying the current; a first insulator having a dielectric constant and filling the gap between the first and second conductors to insulate from each other; and only the first conductor extending less than a quarter wavelength.  
         [0015]     A first capacitor is located around end of the extended first conductor, has very small length compared to a quarter wavelength and includes a third conductor in the form of a metal tube concentrically surrounding the extended first conductor with one end at the end of the first conductor closed and connected with the first conductor while the other end being open; and a second insulator having a dielectric constant and filling the gap between the first and third conductors.  
         [0016]     According to an embodiment of the invention, the IVIA includes the second insulator of the first capacitor, by which opposite charges can be induced on the side-surface of the third conductor when current flows through the first capacitor. Input impedance of the IVIA can be arbitrarily changed in accordance with the length of the first capacitor and perfect IVIA matching can therefore be possible.  
         [0017]     According to another aspect of the invention, an IVIA using microwaves is given to treat and deactivate tumors including cancers in a human body. The IVIA consists of a MMA and a medical catheter in the form of dielectric tube with a dielectric constant, and the MMA is inserted into the medical catheter to form the IVIA. The MMA comprises coaxial cable with only the first conductor extending, a first and second capacitors, which will be explained in more details.  
         [0018]     Coaxial cable, main material of the MMA, includes a first conductor having a cylindrical form and being used for applying current; a second conductor in the form of a metal tube concentrically surrounding the first conductor and used for ground when applying the current; and a first insulator having a dielectric constant and filling the gap between the first and second conductors to insulate from each other; and only the first conductor extending less than a quarter wavelength.  
         [0019]     The first capacitor is located around the extended first conductor, having a certain length and including a third conductor in the form of a metal tube concentrically surrounding the extended first conductor with one end at the end of the first conductor closed and connected with the first conductor while the other end being open; and a second insulator filling the gap between the first and third conductors.  
         [0020]     The second capacitor is located between the first capacitor and the MMA aperture where the first conductor starts to extend, has a certain length and includes a fourth conductor in the form of metal tube concentrically surrounding the extended first conductor with both ends open and a third insulator filling the gap between the first and fourth conductors.  
         [0021]     According to an embodiment of the invention, due to the first capacitor, an IVIA can be perfectly matched. In addition, an IVIA with desirable thermal pattern can also be provided due to the second capacitor. The extended first conductor is common with coaxial cable, the first and second capacitors.  
         [0022]     According to another aspect of the invention, an IVIA using microwaves is supplied for thermal treatment and deactivation of tumors including cancers in a human body. The IVIA consists of a MMA and a medical catheter in the form of dielectric tube with a dielectric constant, and the MMA is inserted into the medical catheter to form the IVIA. The MMA consists of coaxial cable with the first conductor extending, a first, second and third capacitors, which will be described in more detail.  
         [0023]     Coaxial cable, main material of the MMA, includes a first conductor having a cylindrical form and being used for applying current; a second conductor in the form of a metal tube concentrically surrounding the first conductor and used for ground when applying the current; a first insulator having a dielectric constant and filling the gap between the first and second conductors to insulate from each other; and only the first conductor extending less than a quarter wavelength.  
         [0024]     The first capacitor with a certain length is located around end of the extended first conductor and includes a third conductor in the form of a metal tube concentrically surrounding, the extended first conductor with one end at the end of the first conductor closed and connected with the first conductor while the other end being open; and a second insulator filling the gap between the first and third conductors.  
         [0025]     The second capacitor with a certain length is located between the open end of the first capacitor and the MMA aperture and includes a fourth conductor in the form of a metal tube concentrically surrounding the first conductor with both ends being open, and a third insulator filling the gap between the first and fourth conductors.  
         [0026]     The third capacitor with a certain length is located between the second capacitor and the MMA aperture and includes a fifth conductor in the form of a metal tube concentrically surrounding the first conductor with both ends open, and a fourth insulator filling the gap between the first and fifth conductors.  
         [0027]     According to an embodiment of the invention, the second and third capacitors include the third and fourth insulators, each having arbitrary dielectric constants. The first conductor is common with the first, second and third capacitors. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]     The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which:  
         [0029]      FIG. 1   a  shows a cross sectional view of the coaxial cable used for the IVIAs;  
         [0030]      FIG. 1   b  illustrates how a typical IVIA operates inserted in an assumed human organ;  
         [0031]      FIG. 2  shows conventional representative MMAs;  
         [0032]      FIG. 3  describes an IVIA according to the first embodiment of the invention;  
         [0033]      FIG. 4  shows the first capacitor of the IVIAs;  
         [0034]      FIG. 5  compares the first embodiment of the invention with the conventional IVIAs, in terms of electric energy density, which is proportional to temperature;  
         [0035]      FIG. 6  shows compared measured and calculated matching performances of the IVIA, according to the first embodiment of the invention;  
         [0036]      FIG. 7 ( a ) shows a schematic diagram of the second embodiment of the invention;  
         [0037]      FIG. 7 ( b ) shows measured matching performance of the second embodiment of the invention is compared with calculated one;  
         [0038]      FIG. 8 ( a ) shows a schematic diagram of the third embodiment of the invention;  
         [0039]      FIG. 8 ( b ) shows Measured matching performance of the third embodiment of the invention is compared with calculated one;  
         [0040]      FIG. 9 ( a ) shows compared temperature distributions of the IVIAs according to the first and second embodiments of the invention;  
         [0041]      FIG. 9 ( b ) shows compared temperature distributions of the IVIAs according to the first and third embodiments of the invention; and  
         [0042]      FIG. 9 ( c ) shows compared temperature distributions of the IVIAs according to the second and third embodiments of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0043]     The preferred embodiments of the invention will be hereafter described in detail, with reference to the accompanying drawings.  
       First Embodiment  
       [0044]      FIG. 3  shows a schematic view of an IVIA according to a first embodiment of the invention. As illustrated in  FIG. 3 , the IVIA comprises a coaxial cable  320  consisting of a first conductor  310 , a first insulator  321  and a second conductor  322 , a first capacitor  330  and a catheter  340 .  
         [0045]     Only the first conductor  310  extends less than a quarter wavelength, or, slightly longer than L and is used for applying current.  
         [0046]     The first capacitor  330  is located around the end of the extended first conductor  310  and includes a third conductor  332  in the form of a metal tube concentrically surrounding the extended first conductor with one end at the of the first conductor closed and connected with the first conductor while the other end being open; and a second insulator  331  having a dielectric constant and filling the gap between the first and third conductors. Details on the above description will be explained in  FIG. 4 .  
         [0047]     The coaxial cable  320 , main material of the IVIA, comprises the first conductor  310 , the first insulator  321  and a second conductor  322 . In addition, the first capacitor  330  is located around the end of the extended first conductor.  
         [0048]     Here, the first insulator  321  of the coaxial cable and the second insulator  331  of the first capacitor can be arbitrary but the same insulators are used for convenient fabrication.  
         [0049]     The coaxial cable  320  with the first conductor extending slightly longer than L and the first capacitor  330  are composed of a MMA, all of which are inserted into the medical catheter  340  in the form of a dielectric tube with a dielectric constant to form the IVIA. The gap between the MMA and the catheter  340  comprises air.  
         [0050]      FIG. 4  shows a schematic diagram of the first capacitor of the IVIA which is very important for the invention. The first capacitor  330  is located around the end of the extended first conductor  310 , has a certain length and includes a third conductor  332  in the form of a metal tube concentrically surrounding the extended first conductor  310  with one end at the end of the first conductor  310  closed and connected with the first conductor  310  while the other end open; and the second insulator  331  having a certain dielectric constant and filling the gap between the first  310  and third  332  conductors.  
         [0051]     In addition, the shape of the closed end of the third conductor of the first capacitor  330  may be flat or convex. In such a case, the cross sectional area of the third conductor  332  is much larger than that of the first conductor.  
         [0052]     Hereafter, details on operation of the IVIA according to the first embodiment of the invention will be described.  
         [0053]     When current is applied to the first conductor  310  of the coaxial cable  320 , the current is, along the first conductor  310 , transmitted to the first capacitor  330  located around the end of the extended first conductor  310 . During the current flows through the first capacitor, opposite charges are induced by the second insulator  331  and accumulated on the side-surface of the third conductor  332 . That is, according to the first embodiment of the invention, the IVIA has positive charges during the current flow as shown in  FIG. 4 . In addition, negative charges are, due to the second insulator  331 , induced on the side-surface of the third conductor  332  of the first capacitor  330   
         [0054]     Due to larger cross sectional area of the third conductor  332  than that of the first conductor  310 , the current spreads faster on the surface of the closed end of the first capacitor  330  when it arrives at the end of the first conductor  310 . Negative charges induced on the side-surface of the third conductor  332  make the current on the closed end of the third conductor  332  flow down and stay around the open end of the third conductor  332 . Because of the induced negative charges on the side-surface, the positive charges on the closed end of the third conductor  332  do not stay and flow down. Therefore, the electric field intensity on the end of IVIA becomes weak and healthy surrounding tissues can be protected.  
         [0055]     Given that the surface area of the third conductor  332  is substantially larger than that of the conventional antenna, more current can be concentrated, which results in better thermal efficiency and current concentration.  
         [0056]      FIG. 5  shows electric energy densities of the IVIAs where the IVIA according to the first embodiment of the invention is in  FIG. 5 ( a ), while those of the conventional IVIAs are in FIGS.  5 ( b )-( d ). The electric energy density is proportional to temperature and the temperature decreases with the distance from the IVIAs. Dimensions of the IVIAs are given in Table 1. For the simulations, air fills the gaps between the MMAs and medical catheters and is also used as ambient mediums. The electric energy densities are compared based on simulation results by a 3D-electro magnetic field simulator, computer simulation technology (CST) Microwave Studio, version 4.2.  
         [0057]     As illustrated in  FIG. 5 , when the IVIAs are heated by microwaves, thermal efficiency can be determined by the temperatures around IVIAs. The solid lines indicate the same electric energy densities.  
         [0058]     Since the shape of tumors including cancers in a human body is, in general, oval, the desirable temperature isothermal line should be oval like the solid line generated by the IVIA in FIG.  5 ( a ) according to the first embodiment of the invention. The solid line area in  FIG. 5 ( a ) is larger than other ones in FIGS.  5 ( b ), ( c ) and ( d ). So, the thermal efficiency of the IVIA according to the first embodiment of the invention is better than any other one in FIGS.  5 ( b ), ( c ) and ( d ). Nevertheless, the length of the IVIA in  5 ( a ) is the shortest among those of the conventional IVIAs in  FIG. 5 ( b )-( d ). The distinctive structure of the first capacitor gives excellent performances of the shortest length and oval type of thermal distribution of the IVIA according to the first embodiment of the invention.  
                                             TABLE 1                                       Coaxial cable   Radius of first conductor   0.29 mm                Radius of second conductor   1.4 mm               Dielectric constant   2.1           Catheter   Inner diameter   2.3 mm               Outer diameter   4.2 mm               Dielectric constant   5.1                Ambient media   air                      
 
         [0059]     Measured and calculated matching performances of the IVIA according to the first embodiment of the invention are compared in  FIG. 6 . Fabrication data are listed in Table 2. For the measurements, a vector analyzer is used and power is fed into the first conductor of the IVIA immersed in muscle phantom whose dimensions are 10 cm×10 cm×10 cm. The solid line are the measured results, while the dotted one the calculated ones. The measured matching performance at 2.45 GHz is −28.377 dB, which is the best recorded.  
                       TABLE 2                           Coaxial cable   Radius of first conductor   0.145 mm            Radius of second conductor   0.7 mm           Dielectric constant   2.1       Catheter   Inner diameter   1.15 mm            Outer diameter   2.1 mm           Dielectric constant   5.1       Human tissues   Dimension   10 cm × 10 cm × 10 cm       (Muscle)   Dielectric constant   52.7 + j 13.3                  
 
       Second Embodiment  
       [0060]      FIG. 7 ( a ) describes an IVIA according to the second embodiment of the invention. As illustrated in  FIG. 7 ( a ), the IVIA according to the invention includes coaxial cable  620  with the first conductor  610  extending less than a quarter wavelength, or slightly longer than L, a first capacitor  630 , a second capacitor  640  and a catheter  650 .  FIG. 7 ( b ) compares the measured matching performance of the IVIA according to the second embodiment of the invention with the calculated one, indicating the measured matching result at 2.45 GHz is −21.9 dB.  
         [0061]     The first conductor  610  is a conducting material and used as the central axis of the IVIA.  
         [0062]     The coaxial cable  620  comprises a first conductor  610  having a cylindrical form and used for applying current; a second conductor  622  in the form of metal tube concentrically surrounding the first conductor and used for ground when current applied; a first insulator  621  having a dielectric constant and filling the gap between the first and second conductors to insulate from each other; and the only first conductor extending slightly longer than L.  
         [0063]     The first capacitor  630  with a certain length is located around end of the extended first conductor  610  and includes a third conductor  632  in the form of a metal tube concentrically surrounding the extended first conductor with one end at the extended first conductor closed and connected with the first conductor while the other end being open; and a second insulator  631  having a dielectric constant and filling the gap between the first conductor  610  and the third conductor  632 . The first conductor is common with the first capacitor and the coaxial cable.  
         [0064]     The second capacitor  640  is located in the middle between the open end of the first capacitor  630  and the MMA aperture and comprises a fourth conductor  642  in the form of a metal tube concentrically surrounding the first conductor with both ends open; and a third insulator  641  having a dielectric constant and filling the gap between the first conductor  610  and the fourth conductor  642 .  
         [0065]     According to the second embodiment of the invention, assuming the distance between the open end of the first capacitor  630  and the MMA aperture is L, the second capacitor  640  is L/3 long. A distance between the first capacitor  630  and the second capacitor  640 , a distance between the second capacitor  640  and the coaxial cable  620 , and a length of the second capacitor  640  are the same. And, a space surrounding the coaxial cable  620 , the first capacitor  630 , and the second capacitor  640  comprises air.  
         [0066]     In addition, the first  621 , second  631  and third  641  insulators are the same for easy fabrication.  
         [0067]     When power is fed into the first conductor  610 , opposite charges are accumulated on surface of the fourth conductor  642 . Electric fields are generated between the opposite charges on the surface of the fourth conductor  642  and charges staying around the open end of the third conductor  632 . Between the opposite charges on the surface of the fourth conductor  642  and charges accumulated around the MMA aperture, electric field also produced. Therefore, the second capacitor  640  is similar to a kind of electric bridge connecting the coaxial cable  620  with the first capacitor  630  when current is flowing. Therefore, the second capacitor  640  optimizes the temperature distributions more similar to the shape of tumors including cancers in a human body. Details on the second capacitor  640  will be explained in following  FIG. 9 .  
         [0068]     The MMA consists of the coaxial cable  620  with the first conductor  610  extended, the first  630  and second  640  capacitors, all of which are inserted into a medical catheter to form the IVIA. Air fills the gap between the MMA and catheter.  
         [0069]     According to the second embodiment of the invention, same as the first, one end of the first capacitor  630  is closed, more precisely; one end of the third conductor  632  at the end of the first conductor  610  is closed and connected with the first conductor.  
         [0070]     In addition, the closed end of the first capacitor  630  may be flat or convex. In such a case, since the cross sectional area of the closed end is much larger than that of the first conductor  610 , current reaching the end of the extended first conductor  610  spreads faster on the closed surface of the third conductor  632 .  
         [0071]     According to the second embodiment of the invention, the IVIA includes the second  631  and third  641  insulators. Due to the insulators, opposite charges are, during the current flows through the first and, second capacitors, induced and accumulated on the side surface of the third conductor  632  and surface of the fourth conductor  642 .  
       Third Embodiment  
       [0072]      FIG. 8 ( a ) shows a schematic diagram of an IVIA according to the third embodiment of the invention. The IVIA includes a coaxial cable  720  with a first conductor  710  extending less than a quarter wavelength, or, slightly longer than L, a first capacitor  730 , a second capacitor  740 , a third capacitor  750  and a catheter  760 .  FIG. 8 ( b ) compares the measured matching performance of the IVIA according to the third embodiment of the invention with the calculated one, indicating the measured matching result is −24.4 dB at 2.45 GHz.  
         [0073]     The first conductor  710  is common with the coaxial cable, the first, second and third capacitors and used as the central axis of the IVIA.  
         [0074]     The coaxial cable  720  comprises a first conductor  710  having a cylindrical form and used for applying current; a second conductor  742  in the form of a metal tube concentrically surrounding the first conductor and used for ground when current is applied; and a first insulator  721  having a dielectric constant and filling the gap between the first  710  and second  722  conductors to insulate from each other, and only the first conductor extending less than a quarter wavelength, or slightly longer than L.  
         [0075]     The first capacitor  730  with a very small length is located around end of the extended first conductor  710  and includes a third conductor  732  in the form of a metal tube concentrically surrounding the extended first conductor with one end closed and connected with the first conductor while the other end being open; and a second insulator  731  having a certain dielectric constant and filling the gap between the first  710  and third  732  conductors.  
         [0076]     The second  740  and third  750  capacitors are located between the first capacitor  730  and the MMA aperture, and the functions of the two capacitors are about same. The second capacitor  740  comprises a fourth conductor  742  in the form of a metal tube concentrically surrounding the extended first conductor with both ends open; and a third insulator  741  filling the gap between the first  710  and the fourth  742  conductors.  
         [0077]     The third capacitor  750  is located between the second capacitor  740  and the MMA aperture and comprises a fifth conductor  752  in the form of a metal tube concentrically surrounding the first conductor with both ends open; and a fourth insulator  751  having a certain dielectric constant and filling the gap between the first  710  and the fifth  752  conductors.  
         [0078]     In such a case, the second  740  and third  750  capacitors are of the same length of L/5. The second capacitor  740  begins at L/5 from the open end of the first capacitor and the third capacitor  750  begins at L/5 from the one end of the second capacitor  740 . A distance between the first and the second capacitors, a distance between the second capacitor  740  and the third capacitor  750 , a distance between the third capacitor  750  and the coaxial cable  720 , and a length of the second and the third capacitors  740 , 750  are the same.  
         [0079]     In addition, the first  721 , second  731 , third  741  and fourth  751  insulators are same with each other for easy fabrication in this invention.  
         [0080]     The MMA comprises the coaxial cable  720  with the first conductor extending less than a quarter wavelength, or, slightly longer than L, the first capacitor  730 , the second capacitor  740  and the third capacitor  750 , all of which are inserted into a medical catheter  760  in the form of a dielectric tube having a dielectric constant to form the IVIA according to third embodiment of the invention. The gap between the catheter  760  and the MMA comprises air.  
         [0081]     According to the third embodiment of the invention, one end of the first capacitor  730 , more precisely; one end of the third conductor  732  is closed and connected with the extended first conductor  710 , while the other end is open.  
         [0082]     In addition, the closed end of the first capacitor  730  may be flat or convex. In such a case, since the cross sectional area of the third conductor  732  is much larger than that of the first conductor  710 , current reaching the end of the first conductor  710  spreads faster on the surface of the closed end of the third conductor  732  than along the first conductor  710 .  
         [0083]     According to the third embodiment of the invention, opposite charges can be induced on the surface of the third  732 , fourth  742  and fifth  752  conductors due to the second  731 , third  741  and fourth  751  insulators during the current flows through the first  730 , second  740 , and third  750  capacitors. The induced opposite charges contribute to the desirable temperature distribution pattern of the IVIA for the treatment and deactivation of tumors including cancers by means of microwaves.  
         [0084]     When designing the IVIAs of the present invention, matching and temperature distributions should be considered. Using the first capacitor  730 , the IVIA according to the third embodiment of the invention can be perfectly matched like the first and second embodiments of the invention. Using the second  740  and third  750  capacitors, desirable temperature distribution can be obtained like the second embodiment of the invention. Each embodiment of the invention will be compared with each other and the compared results will be plotted in  FIG. 9 .  
         [0085]     Temperature distribution is one of important factors to be considered, because any temperature of more than 43 degrees centigrade can be used for the treatment and deactivation of tumors including cancers in a human body. The temperature distributions of the IVIAs according to the first to third embodiments of the invention are pictured by a IRCON (Inspect IR 500 PS) digital camera and they are compared with each other in  FIG. 9 .  
         [0086]     Temperature measurements are carried out in the following ways. Two IVIAs are inserted into a 10 cm×10 cm×10 cm muscle phantom and then microwave power is fed into each IVIA. The distance between two IVIAs is 5 cm and four thermometer fiber optic sensors are attached at four different points on the IVIAs. If any of four reaches at 100 degrees centigrade, the microwave power supplied by a generator is automatically stopped and half of the phantom should be separated as soon as possible to take pictures.  
         [0087]     If the shape of 43 degrees centigrade isothermal line is more similar to egg, the IVIA is better for the treatment and deactivation of tumors including cancers because of the inherent shape of the tumors including cancers.  
         [0088]      FIG. 9 ( a ) shows temperature distributions patterns of the IVIAs according to the first and second embodiments of the invention. Here, the Z direction is the longitudinal axis of the IVIA and the ρ direction is perpendicular to the Z direction. As illustrated in  FIG. 9 ( a ), the isothermal contour with 43 degrees centigrade of the second embodiment of the invention is shorter in terms of the Z direction and longer in terms of the ρ direction than that of the first embodiment of the invention.  
         [0089]      FIG. 9 ( b ) illustrates the temperature distribution patterns of the IVIAs according to the first and third embodiments of the invention. As illustrated in  FIG. 9 ( b ), the isothermal contour with 43 degrees centigrade of the third embodiment of the invention is shorter in terms of the Z direction and longer in terms of the ρ direction than that of the third embodiment of the invention.  
         [0090]      FIG. 9 ( c ) illustrates the temperature distribution patterns of IVIAs according to the second and third embodiments of the invention. As illustrated in  FIG. 9 ( c ), the isothermal contour with 43 degrees centigrade of the third embodiment of the invention is shorter in terms of the Z direction and longer in terms of the ρ direction than that of the second embodiment of the invention.  
         [0091]     The compared results show that the third embodiment of the invention has the best performance in terms of the thermal distribution pattern, even though the first embodiment of the invention has the best matching performance. Due to the first capacitor together with the second and third capacitors, the IVIAs can be designed with perfect matching and desirable temperature distributions.  
         [0092]     While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.