|
Functional lymphatics are essential for removal and transport of cellular waste and excess fluid from regional tissues and are dependent upon contractile lymphangion activity for proximal drainage into the venous blood stream. Lymphatic insufficiency in patients with cancer-acquired lymphedema is manifested by progressive dermal backflow, or retrograde flow of lymph into dermal lymphatic capillaries. Prior studies using near-infrared fluorescence (NIRF) lymphatic imaging with ICG as a contrast agent, found that dermal backflow provides early indication of lymphedema onset which, when untreated, persists over months and years, but, with two weeks of physiotherapy, dermal backflow could be resolved or reduced in early head and neck cancer survivorship. Thus, the extent or area of dermal backflow may provide an accurate, longitudinal measure of progressing/improving lymphatic dysfunction. In this work, we develop hardware and software solutions to automate determination of dermal backflow area on 3-dimensional tissue surface profiles for entry into the medical record. Specifically, we incorporate a stereo depth module into our custom NIRF lymphatic imaging system for simultaneous acquisition of depth, color, and NIRF images. Using camera calibration techniques, NIRF images are mapped onto point clouds derived from depth images. Algorithms for image segmentation of dermal backflow and stitching of multiple point clouds for more complete representation of dermal backflow across complex 3-dimensional tissue surfaces are described. Non-clinical testing demonstrates ±3% errors in dermal backflow area determination, with clinical testing on head and neck cancer survivors underway to assess efficacy of physiotherapies provided early after cancer treatment.
|
