Samsung SONOACE R7 Manual do Utilizador descarregar pdf (Página 45)

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Chapter 1 Safety

X 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 rst usage of diagnostic ultrasound, the possible human biological eects (bioeects) 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 eects

of ultrasound exposure. Another report “Bioeects 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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