Electrosurgical apparatus and method

An electrosurgical instrument configured to ablate duodenal mucosal tissue, the instrument comprising:

• a flexible coaxial cable for conveying microwave energy from a generator located externally to a patient to a treatment site located inside a duodenum of a patient;
• and
• an applicator located at a distal end of the flexible coaxial cable, the applicator having an energy delivery structure connected to receive microwave energy from the coaxial cable and to deliver the received microwave energy into biological tissue at the treatment site,
• wherein the applicator includes a radially extendable portion arranged to move the energy delivery structure into contact with duodenal mucosal tissue at the treatment site,
• wherein the energy delivery structure comprising a flexible dielectric substrate having:
• a conductive layer formed on a first surface thereof, the conductive layer being electrically connected to an inner conductor of the coaxial cable, and
• a plurality of conductive elements formed on a second surface thereof,
• wherein the plurality of conductive elements are electrically grounded and dimensioned to act as radiating elements for the microwave energy received by the energy delivery structure, and
• wherein the flexible dielectric substrate is movable between a storage configuration in which it is suitable for insertion through an instrument channel of a surgical scoping device and a deployed configuration in which it is suitable for delivering microwave energy into the duodenal mucosal tissue at the treatment site,
• wherein the flexible dielectric substrate is in the form of a sheet, and the plurality of conductive elements are arranged in a two-dimensional array on the sheet, and
• wherein the applicator comprises a sleeve mounted around the coaxial cable, the sleeve and the coaxial cable being slidable relative to one another so that the sheet passes through a distal mouth of the sleeve, and
• wherein the sheet has a proximally facing curved surface which engages with the mouth in a manner that causes the sheet to adopt a rolled configuration.