# ASSESSMENT OF CAVITATION FROM DIAGNOSTIC ULTRASOUND

> **NIH NIH R01** · YALE UNIVERSITY · 1991 · $195,862

## Abstract

Cavitation at the cellular scale - or microcavitation - has been
implicated as a potential biological risk to the patient, analogous
to low level ionizing radiation.  Cavitation can be caused by
acoustic waves of relatively low energy density which can create
a small, but very high concentration of energy in the form of a
collapsing bubble.  The energy of a single bubble collapse has been
estimated to be, in the units of ionizing radiation, on the order
of 300 million electron volts, deposited in a region the size of
the cell nucleus.  Theoretical estimates of the acoustic conditions
to produce such bubbles fall in the range of some diagnostic
ultrasound equipment, yet clinical confirmation of this possibility
has been absent, either because experimental methods have been too
insensitive to cellular activity on a spatial scale of one micron
and on a temporal scale of a microsecond, or because the
theoretical estimates include assumptions that do not obtain in
vivo.

The work outlined in this proposal continues our earlier
experimental and theoretical work, extending it to a) more
sensitive systems of cavitation detection, b) more clinically
relevant fluids (e.g. blood, amniotic fluid, aqueous and vitreous
humor - which have a range of viscosities), c) more comprehensive
theoretical models for bubble inception and action, d) a closer
look at the interaction of ultrasound with biological membranes -
in the presence and absence of free radical scavengers, and e) to
high pulse amplitude systems (such as in Extracorporal Shock Wave
Lithotripters) that can induce cavitation in vivo.

Our quantitative results with active and passive cavitation
detection reveal a new and valuable perspective with regard to the
likelihood of deleterious effects from cavitation induced by
diagnostic ultrasound:  In particular, the preoccupation with the
question of whether cavitation occurs is replaced with the more
realistic questions of how often it occurs and with what
consequences.  Moreover, the size of cavitation nuclei appears to
be of relatively small importance compared to the number and
concentration of nuclei, which appears to be an extremely small
fraction of the "particles" that are exposed to the diagnostic
ultrasound beam.  Whereas gas saturation effects also appear of
relatively small importance, the visco-elastic characteristics of
the biological environment play a much greater role in determining
the potential location, inception, and violence of cavitation.  The
extension of this work to biological fluids and clinical
instrumentation should provide definitive evidence on these
questions and thus provide a basis on which to assess
quantitatively the risk from diagnostic ultrasound.

## Key facts

- **NIH application ID:** 3178262
- **Project number:** 5R01CA039374-06
- **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:** 1991
- **Award amount:** $195,862
- **Award type:** 5
- **Project period:** 1985-09-01 → 1992-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3178262

## Citation

> US National Institutes of Health, RePORTER application 3178262, ASSESSMENT OF CAVITATION FROM DIAGNOSTIC ULTRASOUND (5R01CA039374-06). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3178262. Licensed CC0.

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