What are thermal and mechanical indices, and why do we need them?

Recent advances in novel ultrasonic imaging techniques such as color power Doppler imaging, contrast agent enhanced imaging and harmonics ultrasonic imaging further add to the amount of the exposure. To address the concern on this public health issue, a join effort between AIUM, FDA and NEMA resulted in the formation of Ultrasonic Devices Output Display Standard Committee. The committee's mission is to develop a better regulatory guideline to address the technical shortcomings of FDA regulation. Two indicators have been established: Thermal Index (TI) for addressing the problem of ultrasound induced temperature elevation in human tissue, and Mechanical Index (MI) for addressing the concern of non-thermal ultrasonic bioeffects. In this presentation, we will define and illustrate the interpretation of these indices.