We have proposed a noninvasive technique to observe an arteriovenous fistula using an optical transillumination image of a blood vessel. To improve the accuracy of inner-diameter measurement of the vessel, we examined the effectiveness of the imagesubtraction technique using multi-wavelength light sources. In the experiment, we fabricated a model-phantom to simulate a human forearm. It contained the tube filled with replaceable absorber liquid which simulated the blood in different wavelengths of illuminating light. The transillumination images of the blood column were recorded with the liquid of different absorption coefficients. The imagesubtraction technique was applied and the images were analyzed. With the subtraction, the sharpness of the column image was improved by 55%, and the error in the diameter measurement was reduced from 28% to 4%. This result verified the effectiveness of the image-subtraction to promote the clinical application of the proposed technique for the controlled care of the arteriovenous fistula.
