Aspects of the present disclosure are directed to, for example, a method for determining a temperature distribution across an ablation catheter tip. The method including contacting tissue with a distal tip of an ablation catheter, receiving temperature data from a plurality of thermocouples distributed about the distal tip of the ablation catheter, and based on the received temperature data, determine a temperature distribution across the distal tip of the ablation catheter. Also disclosed is a method of controlling the temperature of an ablation catheter tip while creating a desired lesion using various energy sources and energy delivery methodologies.

An ultrasonic surgical instrument (10) includes a housing (112) having an elongated shaft (150) extending therefrom with an ultrasonic transducer (140) disposed therein. The ultrasonic transducer (140) is operably coupled to a waveguide (154). An ultrasonic blade (162) made from a first metal is operably coupled to the waveguide (154) and extends therefrom. The ultrasonic blade (162) is configured to vibrate upon activation of the ultrasonic transducer (140) to treat tissue. A second, dissimilar metal (500) is disposed on the ultrasonic blade. A thermocouple (600) is formed by a first electrical lead (520) extending from a reference junction (153) and a second electrical lead (510) coupled to the second, dissimilar metal (500). The thermocouple (600) is configured to detect a temperature difference between reference junction (153) and the portion of the blade (162) supporting the second, dissimilar metal (500). The thermocouple (600) derives a temperature at the second, dissimilar metal (500) from a voltage generated at a junction between the first metal and the second, dissimilar metal and a temperature at the reference junction (153).