Cs. Hall et al., BROAD-BAND MEASUREMENTS OF THE ATTENUATION COEFFICIENT AND BACKSCATTER COEFFICIENT FOR SUSPENSIONS - A POTENTIAL CALIBRATION TOOL, The Journal of the Acoustical Society of America, 101(2), 1997, pp. 1162-1171
Tissue characterization would be facilitated by improved methods of ca
libration with which to make absolute measurements of the backscatter
and attenuation of tissue or contrast agents, In this paper, the use o
f polystyrene microspheres is examined as a potential broadband in vit
ro calibration tool by employing an experimental system designed to ch
aracterize ultrasonic contrast agents. The frequency-dependent attenua
tion coefficient and backscatter coefficient were measured for a serie
s of microsphere size distributions with a broadband ultrasound system
using a custom-built specimen chamber and a novel suspension mixing t
echnique. The measurements were used in a broadband reduction method t
o yield the backscatter coefficient. The range of ka spanned in this s
tudy is from ka = 0.5 to ka = 12. The broadband nature of the pulses p
ermitted simultaneous measurement of different regimes of scattering o
f the microspheres (specifically, the transition region from Rayleigh
to short-wavelength asymptotic scattering). Experimental results were
compared with corresponding theoretical predictions for the attenuatio
n and backscatter of solid elastic spheres in liquid and yielded good
quantitative agreement. Discussion of some possible applications of th
is technique to the fields of tissue characterization and contrast is
presented. (C) 1997 Acoustical Society of America.