Sh. Wang et Kk. Shung, AN APPROACH FOR MEASURING ULTRASONIC BACKSCATTERING FROM BIOLOGICAL TISSUES WITH FOCUSED TRANSDUCERS, IEEE transactions on biomedical engineering, 44(7), 1997, pp. 549-554
When the standard substitution method is used with a focused transduce
r to measure the backscattering coefficient from biological tissues in
cluding blood, it yields erroneous results, Extending the backscatteri
ng measurements to frequencies beyond 15 MHz necessitates the use of f
ocused transducers because of the worsened signal-to-noise ratio - cau
sed by the increased attenuation and the smaller transducer aperture s
ize - in order to make the measurements close to the transducer, An ap
proach which allows the use of focused transducers in backscattering m
easurements has been developed, It has been used to measure the backsc
attering coefficient of red cell suspensions of hematocrit ranging fro
m a few percent to 30% in the frequency range from 5MHz to 30MHz, The
results at hematocrits below 20% agree well with those obtained with t
he standard substitution method, although they differ as the hematocri
t is increased beyond 20%, The experimental results also show that the
fourth-power dependence of backscatter on frequency is in general app
roximately valid for suspended erythrocytes of hematocrit between 6% a
nd 30%.