Yuta Okada

Numerical evaluation method for catheter prototypes using photo-elastic stress analysis on patient-specific vascular model.

To date, no quantitative analysis has been developed to evaluate catheter performance inside the vascular lumen.

Photoelastic Stress Analysis on Patient-Specific Anatomical Model of Cerebral Artery

In this paper, we propose a novel method to develop biomimetic models using polyurethane elastomer, which has high photoelastic coefficient, and a method to analyze stress states on the model by photoelastic effect. By using this method, stress condition on vascular wall is clearly visualized on vascular fringe as rainbow-colored photoelastic pattern, and stress can be quantitatively measured from that pattern. Ideally, retardation and path length of transmitted light through the polyurethane model should be observed for photoelastic analysis. Our method has capability to observe these two parameters simultaneously. Retardation and path length were determined from RGB value of rainbow-colored photoelastic stress pattern and permeability of light, respectively. The accuracy of stress analysis was evaluated by tensile test using cylindrical polyurethane models. 5.73% error was found in the result of photoelastic stress analysis. Lastly using the model produced by new method, we could analyze stress states quantitatively on the model of cerebral artery. Consequently, our method should be valuable for not only surgical simulations but also hemodynamic studies and pathological studies.

Catheter insertion path reconstruction with autonomous system for endovascular surgery

In order to reduce fluoroscope usage in endovascular surgery there is a need to develop autonomous catheter insertion systems. We propose a system for tracking the position of the catheter using a magnetic motion capture sensor to provide feedback to a catheter driving mechanism to perform autonomous catheter insertion in major vasculature. Catheter insertion path reconstruction experiments were performed with the system inside silicone model of major vasculature to simulate surgery. As result the system reproduced a path inside the silicone blood vessel phantom with less than 7 mm of error. We found that error in path reconstruction depends on the models cross-section diameter, the properties of the catheter insertion mechanism, the magnetic sensor and the system guidance technique.

Patient-Specific IVR Surgical Simulator for Endovascular Intervention

In this paper, we propose a method to reproduce fluoroscopic image which is utilized during endovascular surgery process, without using x-raying by introducing augmented reality technique, for constructing an endovascular simulator comprised of an in vitro patient- specific blood vessel model. To reproduce the fluoroscopic image, proposed method firstly matches the refraction index of the blood vessel model to that of circumferential material (glycerin solution) to make the vascular model invisible and generate a condition similar to x-ray image, then add background image and other information by using AR. This method allows reproducing several medical imaging techniques, such as DSA (digital subtraction angiography) technique and vascular road mapping techniques, which are utilized during endovascular surgery for easy image recognition. Consequently it allows reproducing comprehensive surgical process, which is not limited to just operating medical tools inside blood vessel. Here the blood vessel model reproduces patient-specific vascular structure at 13 mm resolution, and it also reproduces physical properties of arterial tissue, and thus it allows reproducing surgical feeling and the behavior of operated surgical tools. Consequently presented method should be helpful for doctors for making surgical training without animal testing.

PHOTOELASTIC Stress Analysis on Patient-Specific Anatomical Model of Cerebral Artery by Reflection Method

Artery models and surgical simulators are required for safety surgery. We have proposed a novel method to produce biological models using polyurethane elastomer, which has high photoelastic coefficient. And a method is to analyze stress on the model by circular polarized light method. the quantitative stress is analyzed from rainbow-colored photoelastic pattern. But the measurement area is restricted for the fringe area of the artery model. In this paper, we propose stress measurement on biological model by reflection method, which is a stress measurement method using photoelastic effect. With this method, stress is measured in area wider than that of circular polarized light method. For the reflection method, the Reflection layer was coated between first layer of polyurethane elastomer and second layer of it. From SEM image of cross section of this artery model image, we confirmed uniform thickness of acrylic resin and adhesion between polyurethane layer and acrylic layer. To use this reflection model, We could quantify the error of photo elastic stress analysis. the measurement accuracy of stress state of model reflection area was found to be 9.1% about stress magnitude and plusmn 7[deg] about stress directions. And an application on artery model is verified experimentally. Finally, Stress on the vascular wall caused by the contact with a catheter was successfully measured. Consequently, it should be valuable for various applications not only surgical simulations but also hemodynamic studies and pathological studies.