Patent ID: 7611508

Claim:
A microwave ablation antenna comprising: a substantially non-helical coaxial antenna having a center conductor and an outer conductor extending along an axis to allow positioning of a proximal end of the coaxial antenna within a patient at a site of a tumor and a distal end of the coaxial antenna outside of a patient to be connected to a microwave source having a microwave frequency; and a sleeve outside and electrically insulated from the outer conductor and the center conductor, the sleeve extending along the axis to provide a relative phase shift between microwave energy traveling axially outside the outer conductor and within the sleeve, and microwave energy traveling axially outside the sleeve, the relative phase shift equal substantially to an odd multiple of one half a wavelength of the microwave frequency; whereby microwave energy distal to the sleeve is suppressed by destructive cancellation of the microwave energy at an exit of the sleeve.