Journal of Ultrasound in Medicine, Vol 3, Issue 9 385-389, Copyright © 1984 by American Institute of Ultrasound in Medicine
Temporal peak intensity as a critical parameter in ultrasound dosimetry
S. B. Barnett and G. Kossoff
The in vitro effect of microsecond pulses of ultrasound is studied in
mammalian cells using two different biologic endpoints. The frequency of
sister chromatid exchanges (SCE) is unchanged in Chinese hamster ovarian
cells insonated with a stationary transducer for 1-30 minutes at an SPTA
intensity of 0.1 W/cm2. Raising the temporal average intensity to 2 W/cm2
by increasing the pulse repetition frequency alone still has no effect,
whereas a change in temporal peak intensity produces an increase in SCE
after insonation for only 1 minute. From experiments involving aggregation
of platelets in suspension around acoustically active hydrophobic pores,
pulse duration is found to be a more effective factor than the pulse
repetition frequency. Results of the two studies show the biologic response
to be strongly dependent on temporal peak intensity and pulse duration, but
weakly dependent on duration of exposure. The temporal average intensity as
a singular dosage specification is considered to be a poor indicator of
potential nonthermal bioeffects associated with microsecond pulses.
