A method for tissue-like phantoms preparation for cerebral arteries with aneurysms is presented. Magnetic resonance angiography (MRA) images are used as a source of structural information about the geometry of the simulated cerebral arteries and surrounding brain tissue. Blood vessels were reconstructed as hollow structures with three-layer walls. The inner layer corresponds to the intima of the real vessel, its middle layer - media, and the outer layer - adventitia. The basis for the reconstruction of the first layer of hollow structures and mold for casting surrounding brain tissue were 3D printed. Hollow structures were reconstructed applying layer-by-layer method with use of two-component transparent silicone gel with a variable mass fraction of two components, A and B. Variation the mass fraction of the components and thickness for each layer allows achieving the necessary stress-related properties. Equivalence to the real structure of the cerebral arteries and optical properties were achieved by variation of mass fraction of the additives for each layer matrix. A powder of titanium dioxide was used as scattering particles and a special gel colourant for silicone was applied as an absorbing agent. Hollow structures were added in the mold for casting surrounding brain tissue simulator, so that their geometrical arrangement corresponds to associated blood vessels. The proximal and distal ends of hollow structures are equipped with forked catheters.
A method for evaluation of the shear modulus for the large blood vessel walls is described. Structural images of the investigated part of the blood vessel wall with aneurysm are sequentially obtained using intravascular optical coherence tomography (IOCT) system for at least several cardiocycles. B-scans correspondent to diastole and shear deformation stages between systole and diastole are taken for the evaluation from a sequence of structural images. The pulse wave is considered to be the only deforming stimulus. The surface area of the deforming force is considered to be equal to the scanning area of the IOCT system. B-scans’ profiles are processed and plotted according to the average truncated level of the interference signal intensity. These profiles are divided into overlapping blocks. Shear deformation is estimated for overlapping blocks by the abscissa projection of the average displacement vector. The dimensions of the deformed region are to be equal to corresponding coherence probing depth. Shear modulus in the point of interest of the blood vessel wall is calculated using the classical formula and verified using known values of the Young's modulus and Poisson's ratio.
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