Table 7.
AIUM statement on mammalian in vivo biological effects (AIUM, 1988)
| (Approved August, 1976. Revised and approved October, 1987) |
| A review of bioeffects data supports the following statement: |
| In the low megahertz frequency range there have been (as of this date) no independently confirmed significant biological effects in mammalian tissues exposed in vivo to unfocused ultrasound with intensitiesa below 100mW/cm2, or to focusedb ultrasound with intensities below 1W/cm2. Furthermore, for exposure timesc greater than one second and less than 500 s for unfocused ultrasound, or 50 s for focused ultrasound such effects have not been demonstrated even at higher intensities, when the product of intensity and exposure time is less than 50 joules/cm2. |
a
Free-field spatial peak, temporal average (SPTA) for continuous wave exposures, and for pulsed-mode exposures with pulses repeated at frequencies greater than 100 Hz.
b
Quarter-power (−6 dB) beam width smaller than four wavelengths or 4 mm, whichever is less at the exposure frequency.
c
Total time including off-time as well as on-time for repeated pulse exposures.