K. Chinzei, K. Miller, "Measurement of Compressive Behavior of Swine Brain Tissue," in Proc. World Congress on Medical Physics and Biomedical Engineering

Measurement of Compressive Behavior of Swine Brain Tissue
Kiyoyuki CHINZEI,   Karol MILLER
Biomechanics Div., Mechanical Eng. Lab., MITI/Japan,  chin@mel.go.jp
Dept. Mechanical and Materials Eng., The Univ. of Western Australia,  kmiller@mech.uwa.edu.au

Introduction: Virtual Reality in surgical simulation requires the mechanical property of human organs, e.g., the liver, brain. However, previous works were not adequate for this purpose. We obtained strain-stress curves of swine brain tissue under compression in vitro.
Method: Cylindrical (F»30, h»10 mm) specimens were extracted from non-frozen swine brains*. It was a composite of the Arachnoid membrane, gray and white matters. Each specimen was axially compressed by a constant compression rate until the strain reached to about -0.5. The axial load, the axial and radial displacement were recorded. Three compression rates were examined: 5x102, 5x101, 5x10-3 mm/min (V1,2,3).
Results: For each rate, 11, 13, 5 cases were acquired respectively. Averaged stress-strain curves are shown in Fig. 1. The curves are concave upward containing no linear portion. The stress shows strong dependence on strain-rate (compression rate).
Discussion: The standard bi-phasic model faces a serious problem: strong stress Ð strain-rate dependence can not be easily explained. Therefore, the single-phase, nonÐlinear, viscoelastic model approach is suggested.
Conclusions: 1) Stress-strain curves of swine brain tissue are obtained.  2) Stress is non-linear, highly stress-rate dependent.  3) Single-phase, nonÐlinear, viscoelastic model is suggested.
Reference: K. Chinzei, K. Miller, ÒCompression of Swine Brain Tissue; Experiment In VitroÓ, J Mech Eng Lab, 50-4, pp. 19-28, 1996