Characterization of the stress-strain relationship of the abdominal aortic wall in vivo.

We hereby propose a new method to determine the regionally passive, elastic, stress-strain relationship of the normal murine abdominal aorta in vivo. The circumferential stress-strain relationship was assessed through Laplace's law, a small deformation framework and a relationship between luminal pressure and diameter variation. The regional diameter variation of the murine abdominal aortas was obtained using a cross-correlation technique on radio-frequency (RF) signals at the extremely high frame rate of 8 kHz. The luminal pressure variation was measured by an ultra-miniature pressure catheter over one cardiac cycle. The change of slope of the stress-strain curve was noticed, which was the contribution of elastin and engaged collagen fibers. The stressstrain relationships before and after this transition was assumed to be linear. Three Young's moduli of the aortic wall were characterized in six mice in vivo: (1) elastin, (2) elastin-collagen and (3) engaged collagen fibers, which were equal to 91.6+/-26.5, 229.0+/-80.4 and 137.5+/-65.6 kPa, respectively. The proposed methodology thus allowed for noninvasive mapping of the mechanical properties of its constituents in vivo.