Radiation applicator

Abstract

This invention provides an elongate microwave radiator for insertion into a living body to treat tissue at a predetermined operating frequency. The radiator defines a monopole antenna at its tip. The monopole antenna includes a dielectric material surrounding the monopole. The dielectric material is configured to act as a resonator at the predetermined operating frequency, and encompasses generally the whole of a near-field radiation emitted by the monopole. In an illustrative embodiment, the dielectric material extends from the antenna a distance determined in accordance with the wavelength of the radiation in the dielectric.

1 . An elongate microwave radiator for insertion into a living body to treat tissue at a predetermined operating frequency, the radiator comprising a monopole antenna at its tip, the monopole antenna comprising:
 a monopole; and   a dielectric material surrounding the monopole, the dielectric material being configured to act as a resonator at the predetermined operating frequency, and encompassing generally the whole of a near-field radiation emitted by the monopole.   
     
     
         2 . The radiator as claimed in  claim 1  in which the dielectric material extends from the antenna a distance determined in accordance with the wavelength of the radiation in the dielectric. 
     
     
         3 . The radiator as claimed in  claim 1  in which the dielectric material extends from the antenna a distance determined in accordance with the major dimension (L) of the antenna in the dielectric. 
     
     
         4 . The radiator as claimed in  claim 1  in which the dielectric material extends from the antenna a distance at least substantially equal to 2L 2 /λ, where L is the major dimension of the antenna and λ is the wavelength of the radiation in the dielectric. 
     
     
         5 . The radiator as claimed in  claim 1  in which the dielectric material comprises a substantially cylindrical portion with the antenna extending axially at its centre a distance L. 
     
     
         6 . The radiator as claimed in  claim 2  in which the dielectric material extends from the antenna a distance substantially equal to half the wavelength of the radiation in the dielectric. 
     
     
         7 . The radiator as claimed in  claim 1  in which the monopole comprises a coaxial conductor with a central conductor that projects beyond outer screening of the coaxial conductor at the distal end to form the antenna. 
     
     
         8 . The radiator as claimed in  claim 7  in which the antenna has a length substantially equal to half the wavelength of the radiation in the dielectric. 
     
     
         9 . The radiator as claimed in  claim 7  including a transformer operatively connected between the coaxial conductor and the dielectric material to reduce reflection of radiation back into the coaxial conductor at the boundary with the dielectric material. 
     
     
         10 . The radiator as claimed in  claim 9  in which the transformer includes a space within the coaxial conductor into which packing of the coaxial conductor can expand. 
     
     
         11 . An elongate radiator for insertion into a living body to treat biological tissue at a predetermined operating frequency, the radiator comprising a monopole antenna at a tip thereof, the monopole antenna comprising:
 a monopole; and   dielectric material surrounding and extending beyond the monopole, the dielectric material terminating in a rounded tip portion and being condo to act as a resonator at the predetermined operating frequency to thereby enhance transmission of radiation in a forward direction therefrom.   
     
     
         12 . The radiator as claimed in  claim 11  in which the tip portion is substantially hemispherical. 
     
     
         13 . A method of coupling radiation into biological material, the radiation being generated by an applicator comprising a monopole antenna including a monopole surrounded by a dielectric body of the monopole antenna, the method comprising the steps of:
 configuring the dielectric body of the monopole antenna to act as a resonator; and   selecting the dielectric constant of the dielectric body in accordance with the wavelength of the radiation in the dielectric so that generally the whole of the near-field of the radiation is encompassed by the dielectric body.   
     
     
         14 . The method as claimed in  claim 13  in which the dielectric body extends from the monopole antenna a distance at least substantially equal to 2L 2 /λ, where L is the major dimension of the antenna and λ is the wavelength of the radiation in the dielectric. 
     
     
         15 . The method as claimed in  claim 13  in which the major dimension of the monopole antenna is its length, which is substantially equal to half a wavelength of the radiation in the dielectric. 
     
     
         16 . The method as claimed in  claim 13  in which the dielectric body is located in relation to the biological material so that the far-field radiation lies within the biological material. 
     
     
         17 . The method as claimed in  claim 13  in which the dielectric constant of the dielectric body is high, but is lower than that of the biological material. 
     
     
         18 . The method as claimed in  claim 13  in which the dielectric constant of the dielectric body varies, and is higher at its core than its outer periphery, and the dielectric constant at its outer periphery is lower than that of the surrounding biological matter.