Method for manufacturing a radio frequency applicator

A method for manufacturing a radio frequency (RF) applicator that is configured to emit RF energy for a thermoacoustic imaging system, the method comprising:

• covering a ceramic insert with a coating, wherein the ceramic insert has dimensions that substantially match an internal volume of an open-ended, hollow waveguide, and wherein the ceramic insert has a recess therein configured to accept a radio frequency emitter;
• heating the waveguide to a temperature that is above a melting point of the coating;
• placing the coated ceramic insert into the internal volume of the heated waveguide, wherein the internal volume is completely filled except for the recess;
• and
• cooling the waveguide, ceramic insert, and coating to a temperature below the melting point of the coating so that the coating solidifies and fills gaps between facing surfaces of the insert and the waveguide.