A medical device includes an insertion tube, which has adistal end for insertion into a body of a subject, and a distaltip, which is fixed to the distal end of the insertion tube andis coupled to apply energy to tissue inside the body. The distaltip has an outer surface with a plurality of circumferentiallydistributed perforations formed therethrough. The perforationshave diameters between 10 µm and 25 µm. A lumen passesthrough the insertion tube and delivers a cooling fluid to thetissue via the perforations.
