Photoelastic stress analysis in blood vessel phantoms: three-dimensional visualization and saccular aneurysm with bleb

Fabrication of 3D Capillary Vessel Models with Circulatory Connection Ports

Bionic microscopic vessel models can contribute to the development of vascular treatment skills and techniques for clinical training. Most microscopic vessel models are limited to two dimensions, but three-dimensional (3D) models are important for surgery, such as on retina microscopic vessels, for the observation of colon microvessels, for measuring the deformability of red blood cell (RBC), and so on. Therefore, bionic 3D blood vessel models are increasingly in demand. For this reason, it is necessary to establish 3D fabrication techniques for microchannels. In this study, we established two fabrication methods for 3D microfluidic devices for the development of microscopic vessel models. First, we employed an exposure method using photolithographic technology. Second, we employed a 3D method using femtosecond laser and mask hybrid exposure (FMEx). Both methods made it possible to fabricate a millimeter-scale 3D structure with a submicrometer resolution and achieve an easy injection of solution. This is because it was possible to fabricate typical microfluidic channels used for model inlet and outlet ports. Furthermore, in the FMEx method, we employed an acid-diffusion effect using a chemically amplified resist to form a circular channel cross-section. The acid-diffusion effect made it realizable to fabricate a smooth surface independent of the laser scanning line width. Thus, we succeeded in establishing two methods for the fabrication of bionic 3D microfluidic devices with microfluidic channels having diameters of 15⁻16 µm for mimicking capillary vessels.

In vitro measurement of tissue integrity during saccular aneurysm embolizations for simulator-based training

In the domain of endovascular neurosurgery, the measurement of tissue integrity is needed for simulator-based training and for the development of new intravascular instruments and treatment techniques. In vitro evaluation of tissue manipulation can be achieved using photoelastic stress analysis and vasculature modeling with photoelastic materials. In this research we constructed two types of vasculature models of saccular aneurysms for differentiation of embolization techniques according to the respect for tissue integrity measurements based on the stress within the blood vessel model wall. In an aneurysm model with 5 mm dome diameter, embolization using MicroPlex 10 (Complex 1D, with 4 mm diameter loops), a maximum area of 3.97 mm² with stress above 1 kPa was measured. This area increased to 5.50 mm² when the dome was touched deliberately with the release mechanism of the coil, and to 4.87 mm² for an embolization using Micrusphere, (Spherical 18 Platinum Coil). In a similar way trans-cell stent-assisted coil embolization was also compared to human blood pressure simulation using a model of a wide-necked saccular aneurysm with 7 mm diameter. The area with stress above 1kPa was below 1 mm² for the pressure simulation and maximized at 3.79 mm² during the trans-cell insertion of the micro-catheter and at 8.92 mm² during the embolization. The presented results show that this measurement system is useful for identifying techniques compromising tissue integrity, comparing and studying coils and embolization techniques for a specific vasculature morphology and comparing their natural stress variations such as that produced by blood pressure.