Microwave tissue resection tool
A medical instrument or device is used for resonant delivery of microwave power to tissue for the purpose of resection and coagulation of vessels during surgery and/or other medical procedures. The device enables delivery of large amounts of power to tissue without the need for ground pads by accomplishing an impedance match between tissue and the characteristic impedance of the waveguide that feeds power to it. The device includes a semi-rigid coaxial cable having a center conductor which protrudes from an outer conductor by a length set to be a λ/4 (quarter-wavelength) at the frequency of excitation in the dielectric environment of the tissue of interest. The coaxial cable is shrouded by a dielectric sleeve that provides both thermal and electrical insulation. Fitted against this sleeve is a conductive sleeve whose length is set to be a λ/4 (quarter-wavelength) at the frequency of excitation in the dielectric environment of the dielectric sleeve and the shroud. The device is connected to a feed cable at its proximal end, and can be connected to a source of microwave power. A directional coupler or other wave-sampling mechanism in combination with a power sensor and feedback circuit can be used to monitor reflected power from the device during the procedure, and to control the amount of power supplied to the device.
1 . A device for delivery of microwave power to tissue, comprising:
a coaxial cable;
a resonant sleeve for impedance matching;
a resonant tip; and
a polymer coating for said tip.
2 . The device of claim 1 , further comprising a means for controlling the power delivered to the tissue based on monitoring reflected power from the device.
3 . The device of claim 1 , wherein the device delivers greater than 100 Watts of power to tissue without the need for ground pads.
4 . A medical device comprising:
a coaxial cable having a center conductor and an outer conductor;
a dielectric sleeve shrouding the coaxial cable; and
a conductive sleeve fitted against the dielectric sleeve and contacting the outer conductor;
wherein the center conductor protrudes from the outer conductor by a length, and wherein the device accomplishes an impedance match between tissue of interest and a characteristic impedance of the waveguide that feeds power to the device.
5 . The device of claim 4 , wherein the conductive sleeve is positionable to adjust the impedance matching effect.
6 . The device of claim 4 , wherein the length that the center conductor protrudes from the outer conductor is set to be a quarter-wavelength at the frequency of excitation in the dielectric environment of the tissue.
7 . The device of claim 4 , wherein the conductive sleeve has a length set to be a quarter-wavelength at the frequency of excitation in the dielectric environment of the dielectric sleeve and a shroud which houses the device.
8 . The device of claim 7 , wherein the shroud includes cooling fluid.
9 . The device of claim 7 , wherein the shroud includes microwave absorbing material.
10 . A method of delivering microwave power to tissue, comprising the steps of:
feeding power to a microwave delivery device;
accomplishing an impedance match between the tissue and a characteristic impedance of the waveguide that feeds power to the device; and
delivering microwave power to tissue.