J Surg Oncol. 2020;121:48-50. wileyonlinelibrary.com/journal/jso 48 | © 2019 Wiley Periodicals, Inc. Received: 26 April 2019 | Accepted: 12 May 2019 DOI: 10.1002/jso.25575 RESEARCH ARTICLE Photoacoustic lymphangiography Hiroki Kajita MD 1 | Anna Oh MD 1 | Moemi Urano MS 2 | Masashi Takemaru MD 1 | Nobuaki Imanishi MD, PhD 2 | Marika Otaki MD 1 | Takayuki Yagi MS 2,3 | Sadakazu Aiso MD, PhD 2,4,5 | Kazuo Kishi MD, PhD 1 1 Department of Plastic and Reconstructive Surgery, Keio University School of Medicine, Tokyo, Japan 2 Department of Anatomy, Keio University School of Medicine, Tokyo, Japan 3 Department of Technology Development, Luxonus Inc., Kawasaki, Kanagawa, Japan 4 SIT Research Laboratories, Shibaura Institute of Technology, Tokyo, Japan 5 Management Division, Luxonus Inc., Kawasaki, Kanagawa, Japan Correspondence Hiroki Kajita, Department of Plastic and Reconstructive Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku‐ku, Tokyo 160‐8582 Japan. Email: jmrbx767@keio.jp Funding information ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan); ImPACT No.185‐4/ 2016‐PM10‐03‐01 Abstract Background and objectives: Photoacoustic lymphangiography, which is based on photoacoustic technology, is an optical imaging that visualizes the distribution of light absorbing tissue components like hemoglobin or melanin, as well as optical absorption contrast imaging agents like indocyanine green (ICG) in the lymphatic channels, with high spatial resolution. In this report, we introduce the three‐dimensional (3D) images of human lymphatic vessels obtained with photoacoustic lymphangiography. Methods: We used the 3D photoacoustic visualization system (PAI‐05). Some healthy subjects and lymphedema patients were recruited. To image the lymphatic structures of the limbs ICG was administered subcutaneously as in fluorescence lymphangiography. Photoacoustic images were acquired by irradiating the tissue using a laser at wavelengths of near‐infrared region. On the same occasion, fluorescence images were also recorded. Results: The lymphatic vessels up to the diameter of 0.2 mm could be observed three‐ dimensionally with the venules around them. In the patient‐group, dermal backflow patterns were often observed as dense interconnecting 3D structures of lymphatic vessels. Collecting vessels passing below the dermis were also observed, which were not observed by fluorescence lymphography. Conclusions: Photoacoustic lymphangiography provided the detailed observation of each lymphatic vessel, leading to deeper understanding of 3D structures and physiological state of the vessel. KEYWORDS indocyanine green, lymphography, lymphedema, lymphatic vessels, photoacoustic techniques 1 | INTRODUCTION Photoacoustic lymphangiography, 1 which is based on photoacoustic technology, 2 is an optical imaging that visualizes the distribution of light absorbing tissue components like hemoglobin or melanin, as well as optical absorption contrast imaging agents like indocyanine green (ICG) in the lymphatic channels, with high spatial resolution. In this report, we introduce the three‐dimensional (3D) images of human lymphatic vessels obtained with photoacoustic lymphangiography. 2 | MATERIALS AND METHODS We used the 3D photoacoustic visualization system (PAI‐05). 3 Twenty healthy subjects and 30 lymphedema patients were recruited. Written informed consent has been obtained and Abbreviation: ICG, indocyanine green.