Photoacoustic Technology

Although lymphatic system circulates throughout the body similarly to blood vessels, lymphatic vessels are not easy to observe anatomically or diagnostically because of their small diameter and the transparency of the lymphatic fluid that fills their lumen. Although lymphoscintigraphy and near-infrared fluorescence (NIRF) lymphangiography have been used to observe lymphatic vessels for diagnosing lymphedema, the images obtained using these modalities are insufficient. Due to the inadequate resolution of images obtained with these modalities, it is often difficult to identify each lymphatic vessel clearly. In addition, the conventional data was two-dimensional, displaying only the lymphatic vessels; hence, it was not possible to assess depth from the skin or three-dimensional positional information about the lymphatic and blood vessels. Recently, photoacoustic imaging (PAI), a new imaging technique, has been developed to visualize lymphatic and blood vessels in detail and in three dimensions. This section presents the PAI-based staging classification of lymphedema and preoperative planning for lymphaticovenular anastomosis (LVA).