The Occlusion Pressure of Superficial Lymphatics in the Upper Extremity of Healthy Volunteers: A Near Infrared Lymphofluoroscopy Approach

Injection of contrast agent Indocyanine Green (ICG) is a tricarbocyanine dye that is commonly used for hepatic, cardiovascular, plastic surgery and ophthalmology applications. It is usually injected intravenously at a dose comprised between 0.1 and 0.5 mg/kg. After administration, ICG binds to plasmatic proteins, lipoproteins and lipids, and is thereafter rapidly and completely cleared from blood by the liver. ICG is excited and emits fluorescence in the near-infrared (around 760 nm).

In this study, we will suspend ICG in 25 ml pure water and subsequently diluted with pure water to reach a final concentration of 1 mg/ml. Each subject will receive a subcutaneous injection of 0.2 ml of diluted ICG (e.i. 200µg), using a hypodermic needle. We will standardize the injection point and inject ICG subcutaneously in the first interdigital space, according to the injection method used for lymphoscintigraphy. In this way, we highlight systematically the same area of the superficial lymphatic network.

We know that in the upper limbs, lateralization or handedness coincides with functional (and/or anatomical) asymmetries. To avoid any bias, the injected arm in healthy patients will be randomized tossing heads or tails.

Fluorescence images acquisition After injection, the injection sites will be covered with tape to avoid camera oversaturation, and to avoid spreading of ICG on the skin and undesirable fluorescent background on the images. To obtain fluorescence imaging of arm lymphatic flow, a near-infrared fluorescence imaging system will be used (Photo Dynamic Eye, or PDE camera from Hammamatsu Photonics - Japan). The camera is maintained in a fix position, 15 cm above the investigation field, by a holding system from Noga Tools. The amplified analogic signal is transformed into a digital signal by a converter from Terratec (Model Grabster AV 450 MX) and transferred to a monitor, which allows to visualize lymphatic network and lymph flow in real-time. Images will be recorded on a dedicated external hard disk drive Iomega, model MDHDU.

The session will take place in a dark room, to allow NIR fluorescence images acquisition.