Fundamental Study for Optical Transillumination Imaging of Arteriovenous Fistula - System Integration into Practical Compact Device for Bedside Application

In dialysis therapy, an arteriovenous (AV) fistula is often required to maintain enough blood flow. The major problem of the AV fistula is its stenosis and occlusion, and the daily management of the AV fistula is one of the most important issues in dialysis. However, the current management techniques in clinical practice are invasive or subjective. To solve this problem, we proposed an optical transillumination imaging technique to visualize the condition of the AV fistula. The measurement of the diameter of AV fistula with this technique makes the early detection of stenosis and occlusion possible. We developed an experimental system and measured the diameter of the AV fistula in transillumination images. Though we could confirm the feasibility of the proposed technique, the developed experimental system was too large and heavy for the bedside use in clinical practice. In this study, we tried to downsize the measurement system and to improve its human interface. The previous system consisted of a heavy CCD camera and light source with each controller. They were connected to a personal computer for control and data processing. All of them were housed in a metal frame to make the whole system large (0.14 m
³
) and heavy (20 kg). We designed a new system using the new devices which were small in size and light in weight. The functions of device control and data processing were integrated into a one-board computer (Raspberry Pi). As a result, the weight of the entire system was reduced to about 1/25 and the volume to about 1/12 of its original values. The system has become usable at bedside and easily movable among the patient's rooms in a hospital. The captured and processed images can be monitored on the 7.0 inch display mounted on a one-board computer. Finally, we examined the feasibility of the new system to measure the diameter of a blood vessel using a model phantom. The diameters measured in the transillumination images were accurate enough for clinical applications. In this study, we confirmed the significant advancement of the proposed technique toward the practical application in clinical use.