Visual feedback during initial test pulse. During initial test pulses, beam intensity was set to be just below the point where the generation of a so-called hyperechoic mark (HEM) indicates temperatures above 80°C–90°C. This mark is visible in B-mode US due to the hyperechogenic character of microbubbles. These consist of steam. Shown is an exemplary nodule before (A) and directly after (B) such a test pulse. Clearly visible is the HEM, which vanishes within seconds afterwards.