Electrosurgical snare

A surgical snare 400 comprising: a coaxial cable 411 having inner and outer conductors 406,412; a head assembly 419 at a distal end of the coaxial-cable 411; and a snare wire 403. The head-assembly 419 comprises: an end cap 408 having an energy transfer structure connected to inner-conductor 406; and channels 413,414 in which the snare-wire 403 is disposed forming a retractable loop beyond the energy-transfer-structure. Coaxial-cable 411 may convey microwave energy where the energy-transfer-structure is configured as a microwave radiating antenna. Coaxial-cable 411 may convey radio frequency energy. The snare-wire 403 may be slidably mounted in the head-assembly 419, where the retractable loop is retractable toward the energy-transfer-structure and where the energy-transfer-structure may provide a reaction surface having a sharpened edge for contacting the fully retracted loop, so facilitating the cutting of biological tissue captured by snare-wire 403. The head-assembly 419 may include a fixed boss 404 electrically mounted on outer conductor 412, with a first end of the snare-wire 403 connected to a push rod 401 thats axially slidable relative to coaxial-cable 411 and where a second end of snare-wire 403 connects to the fixed boss 404. The head-assembly 419 may include an impedance transformer portion 409.