Three important acoustic output quantities are the spatial-peak temporal-peak negative pressure (p_), the spatial-peak temporal- average intensity (ISPTA) and the temporal-average acoustic power (W).
Measurement of worst-case acoustic outputs in clinical environments requires appropriate equipment and techniques.
In general, ISPTA and W are greatest for spectral Doppler mode, and least for M- and B-modes. Values of p_ show little variation between modes. For all three quantities there is considerable variation between different probes and makes of machines.
Surveys since 1971 demonstrate that p_ values have increased steadily. An increase in ISPTA and W values occurred particularly in the early 1980s. B-mode ISPTA values have continued to show noticeable recent increases. All three quantities may still be increasing slowly, in most modes.
Whittingham TA. The acoustic output of diagnostic machines. In: The Safe Use of Ultrasound in Medical Diagnosis. Pubs: The British Medical Ultrasound Society & The British Institute of Radiology (2000).
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