Rationale and derivation of Mi and Ti - A review

This review article provides a summary rationale and derivation for the mec hanical index (MI) and thermal index (TI) formulas presented in the body of the "Standard for real-time display of thermal and mechanical acoustic out put indices on diagnostic ultrasound equipment" (AIUM/NEMA 1998).(1) For pu rposes of simplicity, this standard is referred to in this article by its c olloquial "nickname," the "output display standard" or ODS. This review exp ands on the summary information provided in Appendix A of the ODS, Numerous references are made to the root publications from which the formulas were derived. As will be discussed in the derivation notes that follow, key part s of the MI and TI models rely heavily on experimental data. This document does not attempt to do any more than describe the relevant results of the e xperiments. A general overview is provided in the Introduction and Rational e for the nontechnical reader and the more rigorous Models and Derivation N otes provides a detailed mathematical review of the MI and TI models. A com plete set of defined terms is provided in Appendix 1. (C) 1999 World Federa tion for Ultrasound in Medicine & Biology.