Ultrasound Phantoms/Animals Experiments

Abstract

As previously mentioned, two of the advantages of ultrasound are its short wavelength in tissue and the small acoustic impedence differences between various soft tissues. This means that reflections, standing waves, and refraction effects are minimized (especially compared to microwave applications)--facts which make the task of characterizing the SAR pattern in tissues considerably easier. In particular, this means that the shape of the intensity pattern often remains approximately the same in tissue as it is in a homogeneous liquid media (Fig. 1. This allows the primary calibration of a transducer to be performed in either a non-absorbing water media, and the correction for attenuation done later (a procedure similar to that used in radiation treatment planning), or in an absorbing media with an attenuation coeffecient similar to tissue. Of course, if significant bone or air surfaces are present these are more difficult to account for. Phantom work for ultrasound then primarily occurs in homogeneous liquid media for static phantoms, while dynamic phantoms can be useful in testing feedback control systems, and a variety of animal preparations are useful for in vivo testing.