In medical diagnosis, use of elastography is becoming increasingly more useful. However, treatments usually
assume a planar compression applied to tissue surfaces and measure the deformation. The stress distribution
is relatively uniform close to the surface when using a large, flat compressor but it diverges gradually along
tissue depth. Generally in prostate elastography, the transrectal probes used for scanning and compression are
cylindrical side-fire or rounded end-fire probes, and the force is applied through the rectal wall. These make it
very difficult to detect cancer in prostate, since the rounded contact surfaces exaggerate the non-uniformity of
the applied stress, especially for the distal, anterior prostate.
We have developed a preliminary 2D Finite Element Model (FEM) to simulate prostate deformation in
elastography. The model includes a homogeneous prostate with a stiffer tumor in the proximal, posterior region
of the gland. A force is applied to the rectal wall to deform the prostate, strain and stress distributions can
be computed from the resultant displacements. Then, we assume the displacements as boundary condition and
reconstruct the modulus distribution (inverse problem) using linear perturbation method.
FEM simulation shows that strain and strain contrast (of the lesion) decrease very rapidly with increasing
depth and lateral distance. Therefore, lesions would not be clearly visible if located far away from the probe.
However, the reconstructed modulus image can better depict relatively stiff lesion wherever the lesion is located.