Purpose: Photoacoustic imaging (PAI) technology can clearly show three-dimensional images of superficial lymphatic vessels and the venous system. This study analyzed the morphological findings of lymphatic vessels in the affected extremities of patients with lymphedema.
Materials and Methods: We used the PAI-05 system with a semi-spherical detector array, which was made by Canon Inc. (Japan), Hitachi, Ltd. (Japan), and Japan Probe Co, Ltd.(Japan). Four patients (1 male, 3 females) with lower extremity lymphedema, including one primary case and three secondary cases, underwent a PAI study. Indocyanine green (ICG), was administered subcutaneously at three sites in the dorsal aspect of the affected foot, and ICG fluorescent lymphography was performed using a near-infrared camera system, before PAI examination. In those patients in whom dermal backflow(DBF) was observed with fluorescent lymphography, lesions were also examined with PAI, if possible. 1), 2)
Results: More lymphatic collecting vessels were observed with PAI than with fluorescent lymphography. In PAI images, each lymphatic vessel in a lymphatic bundle was observed (fig. 1), which was detected as a diffuse line in fluorescent lymphography. PAI also revealed the depth of each vessel. DBF was visualized as dense interconnecting three-dimensional structures of lymphatic vessels comprising dilated precollectors or lymphatic capillaries above and collecting vessels below(fig.2).
Conclusions: PAI showed collecting lymphatic vessels that were not observed with fluorescent lymphography, as well as the three-dimensional structure of DBF. PAI is a promising imaging modality, especially for detection of morphological changes in lymphatic vessels during progression of lymphedema.
Acknowledgement: This work was funded by the ImPACT Program of the Council for Science, Technology, and Innovation (Cabinet Office, Government of Japan).
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