Measurement and imaging techniques based on laser ultrasound or photoacoustic excitation have been extensively studied for several decades in both industrial and medical fields. This technology is particularly useful as an imaging method for diagnosing vascular conditions, as it enables visualization of the position and shape of blood vessels. However, with conventional imaging approaches, variations in structural parameters such as the inner and outer diameters of the vessel must be assessed visually, making it difficult to instantly recognize the dimensions necessary for diagnosing vascular diseases. To address the issue, this study proposes a novel imaging method that utilizes the frequency response of photoacoustic signals, enabling not only visualization of the vessel's location and shape, but also the structural features such as diameter of sub-millimeter tubes. By analyzing frequency-domain features extracted from the signal spectrum, we image a liquid-filled soft tube embedded in a soft phantom and demonstrate that the structural dimensions, including both the inner and outer diameters, are correlated with the frequency characteristics. These findings suggest that structural information is reflected in the generated images, indicating the potential of this method as a diagnostic support tool that does not rely solely on visual interpretation.
Hosono et al. (Wed,) studied this question.