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Wave3000 Example #2:
Ultrasound Propagation Through Bone
Shown below is a 3D-rendered image of a human finger bone using micro-computed
tomography (micro-CT).
The figure below shows the 3D propagation of ultrasound through a short length
of cortical bone taken from the midshaft of the finger bone above. The signal
is a 1 MHz Gaussian shaped pulse, which propagates from right to left. The
materials are bone and blood. As may be seen there is a great deal of scattering
of the wavefront, but the initially arriving wavefront emerges at the other
side in a somewhat coherent way. Note that receivers can be defined anywhere
within or on the object, and the data stored to disk for subsequent processing
and analysis.
Another example demonstrates propagation through trabecular bone taken from
the human heel bone, shown below. This image data was also acquired using micro-CT.
The core is approximately 1 cm in diameter and 1.2 cm in length. The propagation
is carried out again with a 1 MHz broadband pulse, and the source is placed
on the face at one end of the cylinder. Blood is assumed to fill all of the
pore spaces and to surround the core as well.
An animated graphic of the propagating wave is shown in the figure below.
(Note that the core has been rotated so that the left face is now on the left
side.) As may be seen the wave appears to be scattered greatly by the trabeculae.
The images of the propagating wave seem to be an "inverse" image of the bone
(i.e., the pore spaces); this is likely due to the fact that the displacements
are much larger in the pores (fluid) relative to the displacements in the bone
material per se.
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