Medical device development, including intravascular treatment devices and equipment for drug delivery, often involves fluid phenomena. Visualization and measurement of fluid behavior are essential for design and development. However, conventional fluid visualization methods are often impractical for daily use because of their high cost, time-consuming nature, and complexity. A fluid visualization method using an event-based camera is proposed. It can be used to capture the brightness change with high temporal resolution using a low-power laser. The approach can be safely used at any experimental site by utilizing a low-power laser as a light source, and it is easier to implement than conventional methods. Experiments were conducted to visualize and analyze the flow in a blood vessel model using water mixed with tracer particles. The results demonstrate that obtaining commonly known flow properties and confirming appropriate flow visualization using a circular tube model are possible. The usefulness of the method for typical lesion models, such as vascular stenosis and cerebral aneurysm, was also demonstrated. The flow could be understood qualitatively by accumulating the changes in illumination caused by particle movement over a specific time period. Furthermore, the velocity vectors and distributions were analyzed quantitatively using particle image velocimetry and particle tracking velocimetry by exporting event-based camera results as video images at arbitrary frame rates.

In the treatment of acute cerebral infarction, it is important to remove the thrombus quickly without causing side effects such as intracranial hemorrhage. A new laser treatment system for acute cerebral infarction has been developed to address certain weaknesses of current treatment methods such as catheter devices and drugs. This laser system uses a 532nm pulsed laser to remove thrombus without damaging the vessel wall, but it is difficult to adjust the position of the catheter tip to a clot within an effective range. We then developed a real-time monitoring function to evaluate the distance between the thrombus and the catheter tip. In the real-time monitoring function, we used 785nm CW laser added to 532nm pulsed laser, evaluated the 785nm laser reflected from the tip of the optical fiber. A power of the reflected 785nm is based on the Fresnel equations, and time change levels of reflected 785nm reflects how bubbles generated by pulsed lasers disappear. As a result of evaluation of in vitro studies, it turned out that how its change is affected by the distance between the thrombus and the tip of the catheter. When the area around the catheter tip is filled with fluid, the signal disappears quickly and easily, and when there is a blood clot, it disappears less easily. These results suggest that it may be possible to adjust the position of the optical fiber by evaluating the change in Fresnel reflection after pulsed laser irradiation.

NM (Nuclear medicine) uses radioisotopes to diagnose and treat biological functions. This paper outlines the history and principles of PET. Measurement of projection data by electron-positron annihilation, 3D scan that contributed to the advancement of PET performance, TOF and other representative technologies will be explained.