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Chapter 1 Safety

1-27

WFUMB. Symposium on Safety of Ultrasound in Medicine: Conclusions and Recommendations on Thermal

and Non-Thermal Mechanisms for Biological Eects of Ultrasound, Ultrasound in Medicine and Biology,

1998: Vol. 24, Supplement1.

Acoustic Output and Measurement

Since the first usage of diagnostic ultrasound, the possible human biological effects (bioeffects) of

ultrasound exposure have been studied by various scientic and medical institutions. In October 1987, the

American Institute of Ultrasound in Medicine(AIUM) ratied a report prepared by its Bioeects Committee

(Bioeects Considerations for the Safety of Diagnostic Ultrasound, J Ultrasound Med., Sept. 1988: Vol.7,

No.9 Supplement), sometimes referred to as the Stowe Report, which reviewed available data on possible

effects of ultrasound exposure. Another report “Bioeffects and Safety of Diagnostic Ultrasound,” dated

January 28, 1993 provides more up to date information.

The acoustic output for this system has been measured and calculated in accordance with the December

1985 “510(K) Guide for Measuring and Reporting Acoustic Output of Diagnostic Ultrasound Medical

Devices,” except that the hydrophone meets the requirements of “Acoustic Output Measurement Standard

for Diagnostic Ultrasound Equipment” (NEMA UD 2-1992)

In Situ, Derated, and Water Value Intensities

All intensity parameters are measured in water. Since water does not absorb acoustic energy, these water

measurements represent a worst case value. Biological tissue does absorb acoustic energy. The true

value of the intensity at any point depends on the amount and type of tissue and the frequency of the

ultrasound that passes through the tissue. The intensity value in the tissue, In Situ, has been estimated

using the following formula:

In Situ = Water [

-(0.23 alf)

]

where: In Situ = In Situ Intensity Value

Water = Water Value Intensity

e = 2.7183

a = Attenuation Factor

Tissue a(dB/cm-MHz)

Brain .53

Heart .66

Kidney .79

Liver .43

Muscle .55

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Samsung SONOACE R3 Instrukcja Użytkownika Strona 45