[The use of determining the sound intensity of diagnostic ultrasonic equipment in obstetrics (author's transl)].
The possible risks when using help energy ultrasound have resulted in worldwide "standard committees" establishing guiding values for the sound intensity which must not be exceeded by diagnostic equipment, 100 mW/cm2 are commonly accepted. The intensity level can be measured with a special very small microphone. The highest values occur at distances of near field length (also "standard working distance") or in the focal point. For measurements of sound intensities of different equipment (Real-time-scanner, Compound-scanner, Encephalographs, Doppler-unit) we used a sonic microphone which was calibrated by the "Physikalische Technische Bundesanstalt" (Physical-Technical Federal Institute). The measurements were carried out in water and correspond approximately to the value in human tissue. Using focusing transducers the sound intensity was much higher than without focusing transducers. Working with such a modern transducer and an old compound-scanner the measurement gave approximately 300 milliwatt per square centimeter. The results show that focusing trasducers cannot be used without a great deal of forethought.
D005260:Female; D006801:Humans; D007743:Labor, Obstetric; D008433:Mathematics; D011247:Pregnancy; D011786:Quality Control; D013016:Sound; D014463:Ultrasonography; D014867:Water
D014867:Water
Zur Bedeutung der Intensitätsmessung diagnostischer Ultraschallgeräte für die Geburtshilfe.