A Role for Near Infrared Fluorescent Imaging in the Evaluation of Lymphatic Function

The use of near infrared fluorescence (NIRF) for the imaging of lymph flow is now a decade old.^1,2 The technique was initially introduced to overcome some of the limitations of existing lymphatic imaging techniques. The technique provides a high level of spatial resolution, limited only by the ability of the light source to penetrate into deeper layers of the tissue. The pulsatile activity of the lymphatics is readily visualized and can be quantitated.

In the current issue of Lymphatic Research and Biology, two articles address the role of this imaging technique. In the article by Groenlund and colleagues, the inter-individual and intra-individual variability of NIRF was investigated in healthy individuals. They further investigated the influence of temperature changes and exercise on the measured variables, determining that the results were stable over extended time periods and that they were furthermore sensitive to the changes induced by exercise and local hyperthermia. Lymphatic pumping pressure is the quantifiable variable that demonstrates reproducibility in their hands.

A second article by Lopera and colleagues has also utilized normal volunteers to assess the utility of NIRF. In this case, the investigators explored the potential for the imaging procedure to document the impact of compression therapy upon the lymphatic function of the limb. Lymphatic pumping activity was assessed before and after an intervention that included both a 15-minute period of manual lymph drainage and short-term application of a compression garment. They quantitated lymphatic function through the number, size, displacement, and speed of the observed lymph packets. Both displacement and velocity improved in a statistically significant fashion following the interventions.

Clearly, these articles underscore a significant advance in lymphatic imaging. NIRF represents an emerging tool for the precise investigation of lymphatic function in health and disease.