Thermal Measurements of Resonant Ultrasonic Surgical Horn

Abstract

Temperatures at the distal end of the tip in ultrasonic surgical instruments are of interest because this is the applied part to a patient. It is difficult to directly measure these temperatures using contacting temperature sensors due to high vibration levels. Non-contact infrared (IR) thermography could be an important tool to experimentally determine the tip temperature. However, the low emissivity and polished cylindrical geometry of the tips complicate accurate IR thermography. In this study, we use Cr2O3 high emissivity paint to coat the tip for increased accuracy in IR measurements. Temperature measurements are consistent with heat generation models based on mechanical quality factor of about 5000 for the titanium tip material. It was found that no heat is generated at the tip distal end where strain is low. Air cooling by aspiration is effective at keeping tip distal end temperatures at near ambient levels even with heat transfer by conduction from warmer parts of the tip.