# ASSESSMENT OF CAVITATION FROM DIAGNOSTIC ULTRASOUND

> **NIH NIH R01** · YALE UNIVERSITY · 1992 · $254,947

## Abstract

The use of diagnostic ultrasound in medicine has expanded enormously over
the past few years and has become a vital clinical tool in the diagnosis
and assessment of a large variety of ailments and conditions.  There has
been a steady evolution in the complexity and sophistication of the imaging
and Doppler modalities that provide the principal instrumental tools for
clinicians.  These devices have tended, in general, to evolve to higher
working frequencies to improve resolution, and consequently, because of the
higher attenuation, to larger acoustic intensities and pressure amplitudes.
There are two principal mechanisms whereby diagnostic ultrasound can
interact with tissue with the potential for a bioeffect:  a) a thermal
mechanism resulting from absorption of the ultrasonic pressure wave and
subsequent temperature elevation of the tissue; b) the phenomenon of
acoustic cavitation in which relatively small amounts of energy are
concentrated to microscopic scales, thus producing intense localized
pressure and temperature.  Concern for these potentialities has prompted
concerted action by the FDA, American Institute for Ultrasound in Medicine,
and NEMA to draft Output Display Standards for Real-Time Display of Thermal
and Mechanical Indices.  The current mechanical index (MI) is based on in
vitro tests of the acoustical conditions for bubble nucleation in liquids
containing prescribed bubble nuclei (polystyrene spheres and albumin-coated
bubbles), as well as a theoretical model of the interaction of ultrasound
with materials.  Yet this work, though involving careful experimentation
and theoretical efforts by many independent researchers, still cannot
answer the question:  Does diagnostic ultrasound produce bubbles in human
tissue?  The question has not been answered definitively because acoustical
detection of micron-sized bubbles that last a microsecond is an extremely
difficult task, especially if this transient, weak event is buried in the
backscattered noise from blood cells, tissue inhomogeneities, etc.  The
proposed effort will couple the most sensitive bubble detection system with
advanced signal processing techniques to determine the minimum conditions
for acoustic cavitation inception in vivo.  Of equal importance, yet not
fully addressed thus far, is the question of the role played by the pulse
duration and duty cycle of the acoustical imaging or doppler signal in
determining bubble nucleation and activity, the latter being related, in
all likelihood, to the degree of bioeffect that is possible when the
mechanical index is exceeded.  Thus, a systematic study of these parameter
regimes is envisioned, for liquids, blood, and tissue equivalent phantoms.
The above work on in vivo detection and duty cycle will be complemented by
a continuation of studies of bioeffects induced in epithelia of frogs by
diagnostic and therapeutic ultrasound, in order to understand better the
formation of free radicals and the changes in ionic conductance that can...

## Key facts

- **NIH application ID:** 3178258
- **Project number:** 2R01CA039374-07
- **Recipient organization:** YALE UNIVERSITY
- **SAM.gov UEI:** FL6GV84CKN57
- **Principal Investigator:** ROBERT E APFEL
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1992
- **Award amount:** $254,947
- **Award type:** 2
- **Project period:** 1985-09-01 → 1996-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3178258

## Citation

> US National Institutes of Health, RePORTER application 3178258, ASSESSMENT OF CAVITATION FROM DIAGNOSTIC ULTRASOUND (2R01CA039374-07). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3178258. Licensed CC0.

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