### ASA 127th Meeting M.I.T. 1994 June 6-10

## 2pBV2. Non-Rayleigh statistics of ultrasonic backscattered echo from
tissues.

**V. M. Narayanan
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*Biomed. Eng. & Sci. Inst., Drexel Univ., Philadelphia, PA 19104
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**R. C. Molthen
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P. M. Shankar
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J. M. Reid
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*Drexel Univ., Philadelphia, PA 19104
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The envelope of the backscattered signal from tissues can exhibit
non-Rayleigh statistics if the number density of scatterers is small or if the
variations in the scattering cross sections are random. The K distribution
which has been used extensively in radar, is introduced to model this
non-Rayleigh behavior. The generalized K distribution is extremely useful since
it encompasses a wide range of distributions such as Rayleigh, Lognormal, and
Rician. Computer simulations were conducted using a simple one-dimensional
discrete scattering model to investigate the properties of the echo envelope.
In addition to cases of low number densities, significant departures from
Rayleigh statistics were seen as the scattering cross sections of the
scatterers become random. The validity of this model was also tested using data
from tissue mimicking phantoms. Results indicate that the density function of
the envelope can be modeled by the K distribution and the parameters of the K
distribution can provide information on the nature of the scattering region in
terms of the number density of the scatterers as well as the scattering cross
sections of the scatterers in the range cell. [Work was supported by NSF Grant
No. BCS-9207385.]