T. Hiro et al., ARE SOFT ECHOES REALLY SOFT - INTRAVASCULAR ULTRASOUND ASSESSMENT OF MECHANICAL-PROPERTIES IN HUMAN ATHEROSCLEROTIC TISSUE, The American heart journal, 133(1), 1997, pp. 1-7
To examine the accuracy of intravascular ultrasound (IVUS) in assessin
g the biophysical properties of atherosclerotic plaque, 33 human iliac
arteries were imaged with a 25 MHz IVUS transducer and classified int
o four groups on the basis of IVUS appearance: minimally diseased arte
rial wall, bright echogenic plaque with acoustic shadowing, bright ech
ogenic plaque without shadowing, and hypoechogenic plaque (so-called '
'soft echoes''). The hardness of each plaque was assessed with an ultr
asensitive compression ergonometer. The radial static stress-strain re
lations fit well (r > 0.98) to exponential curves, providing a compres
sion stiffness constant(K) defined as the coefficient of the exponenti
al power. K for bright echogenic plaque with shadowing was significant
ly greater than that of the other tissues. However, K among minimally
diseased entire arterial wall, hypoechogenic plaque, and bright echoge
nic plaque without shadowing was not significantly different, but thes
e tissues are not physically soft compared with adipose tissue. Theref
ore, tissue characterization by IVUS distinguishes calcified from nonc
alcified plaque and accurately predicts its biomechanical hardness. Ho
wever, soft echoes, although less firm than calcium, do not necessaril
y correspond to soft tissue.