Verification of AVF Stenosis Using Luminance Conversion by Non-contact Measurement Method

Hemodialysis therapy is an extracorporeal circulatory therapy that substitutes kidney function. At the beginning of therapy, special vessels called arterio-venous fistula (AVF) should be created, which puncture the dilated veins and allow for stable treatment. However, as they are prone to stenosis, a stethoscope is usually used to confirm the procedure before treatment. Although this method is simple and reliable, there are several critical issues to be resolved, such as missed stenosis sounds and difficulties in quantification. In our previous study, we proposed a new non-contact method to quantitatively confirm the AVF state using optical technology. In this study, the same method was used to represent the process from normal state to intense stenosis state in one hemodialysis patient using luminance and grayscale transformation to express the state of blood flow in colour, whose feasibility was verified through multiple comparison tests with ultrasound equipment. The results showed that in the multiple comparison test with Honest Significant Difference, all pairs without significant differences; however, there was a predominant difference between normal and intense stenosis on June 29 (II) and July 25 (V) (p = 0.038). On July 20, when mild stenosis was confirmed by ultrasound equipment findings, stenosis could be determined visually by the luminance and tone conversion. In the quartile evaluation by measurement date, the difference between the first and third quartiles was large on March 7 and June 29, and gradually decreased from June 6. This was considered to reflect the increase in internal pressure with the progression of stenosis and the suppression of venous wall pulsation due to the progression of vessel wall elongation. These results indicated that this method has the potential to visualise the stenosis site.