A plane layered model to estimate in situ ultrasound exposures |
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Authors: | S W Smith H F Stewart D P Jenkins |
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Institution: | Department of Radiology, Duke University Medical Center, Durham, North Carolina, 27706, USA;Department of Anatomy, Georgetown University School of Medicine and Dentistry, Washington, DC 20007, USA;Department of Anatomy, Georgetown University School of Medicine and Dentistry, Washington, DC 20007, USA |
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Abstract: | Determination of in situ ultrasound exposures in experimental animals and patients is necessary to assess any potential hazard of ultrasound implied by reported biological effects in animals. A layered model was used to calculate total attenuation of ultrasound pulses as they passed through tissue layers to an organ site, thus enabling calculation of in situ intensities from free-field transducer emissions. The model assumes plane homogeneous layers of tissue of known thickness, attenuation and acoustic impedance. Calculations based on the model, compared with in situ measurements in a human cadaver specimen, were accurate to within approximately +/- 3 dB. We then calculated in situ clinical exposures using published obstetric B-scans. Total attenuation to the fetus averaged approximately 11 dB at 3.5 MHz. |
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Keywords: | ultrasonics dosimetry attenuation |
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