Slidable choke microwave antenna

1. A microwave antenna assembly comprising:

a feedline including an inner conductor, an outer conductor and an inner insulator disposed therebetween;

a radiating portion including a dipole antenna coupled to the feedline and a trocar coupled to the dipole antenna at a distal end thereof;

a slidable outer jacket disposed about the radiating portion and the feedline, the slidable outer jacket configured to slide about at least one of the radiating portion and the feedline from a closed configuration, in which the slidable outer jacket is mated with the trocar, and a retracted configuration, in which the slidable outer jacket is retracted proximally to expose at least a portion of the radiating portion; and

a contact assembly disposed around the feedline and in electrical contact with the outer conductor, the contact assembly adapted to provide continuous electrical contact between the outer conductor and the slidable outer jacket, the contact assembly further comprising:

a tubular housing having at least two stop members each of which is disposed at a proximal distal end thereof, respectively; and

a spring member disposed about the tubular housing between the at least two stop members, the spring member adapted to bias the slidable outer jacket.

2. A microwave antenna assembly according to claim 1 , wherein the tubular housing and the spring member are formed from a conductive material.

3. A microwave antenna assembly according to claim 1 , wherein the spring member is coated by a conductive coating having at least one metal compound.

4. A microwave antenna assembly according to claim 1 , wherein the slidable outer jacket is formed from a conductive metal.

5. A microwave antenna assembly according to claim 1 , wherein the slidable outer jacket includes a tapered edge at a distal end thereof and the trocar includes a tapered tip adapted to mate with the tapered edge when the slidable outer jacket is in the closed configuration.

6. A method for performing microwave ablation, the method comprising the steps of:

providing a microwave antenna comprising:

a feedline including an inner conductor, an outer conductor and an inner insulator disposed therebetween;

a radiating portion including a dipole antenna coupled to the feedline and a trocar coupled to the dipole antenna at a distal end thereof;

a slidable outer jacket disposed about the radiating portion and the feedline, the slidable outer jacket configured to slide about at least one of the radiating portion and the feedline from a closed configuration, in which the slidable outer jacket is mated with the trocar, and a retracted configuration, in which the slidable outer jacket is retracted proximally to expose at least a portion of the radiating portion; and

a contact assembly disposed around the feedline and in electrical contact with the outer conductor, the contact assembly adapted to provide continuous electrical contact between the outer conductor and the slidable outer jacket, the contact assembly further comprising:

a tubular housing having at least two stop members each of which is disposed at a proximal end and a distal end thereof, respectively; and

a spring member disposed about the tubular housing between the at least two stop members, the spring member adapted to bias the slidable outer jacket;

moving the slidable outer jacket into a closed configuration, in which the slidable outer jacket is mated with the trocar;

inserting the microwave antenna into tissue; and

moving the slidable outer jacket into a retracted configuration, in which the slidable outer jacket is retracted proximally to expose at least a portion of the radiating portion.

7. The method according to claim 6 , further comprising the step of:

maintaining continuous electrical contact between the outer conductor and the slidable outer jacket during the moving steps.