Estimation of composition ratio of two contents filled in elastic thin tube through laser-diode-based photoacoustic measurements

Photoacoustic imaging is considered useful for evaluating the effects of treatment because it has a good resolution to capture minute vascular lesions and changes in the progression of atherosclerosis, which is difficult to detect with conventional imaging methods. In this study, the authors prepared a thin silicone tube filled with a mixture of red ink and olive oil as a model that mimics arteriosclerosis. The tube was embedded in a soft phantom. Photoacoustic measurements were performed using 405 nm and 520 nm laser diodes. As a result, the 405 nm laser produced a higher photoacoustic signal as the oil concentration in the mixture increased, whereas the 520 nm laser produced lower photoacoustic signals as the oil concentration increased. By focusing on the difference in the optical absorption at different wavelengths between the red ink and oil, it was shown that there was a possibility of estimating the oil concentration from the ratio of photoacoustic signals between different wavelengths.