Abstract 5238: Near-infrared fluorescence imaging of human lymphatics in healthy subjects and in cancer survivors
Authors: Rasmussen John C. , Tan I-Chih , Marshall Milton V. , Adams Kristen E. , Kwon Sunkuk , Fife Caroline E. , Maus Erik A. , Smith Latisha A. , Sevick-Muraca Eva M. 
Published: February 2011

Abstract
Near-infrared (NIR) fluorescence imaging was used to non-invasively image the (dys)function of the lymphatics in healthy control subjects and in subjects clinically diagnosed with unilateral lymphedema, a little understood disease characterized by chronic swelling and commonly observed in cancer survivors following therapeutic, complete nodal dissection.
As part of an FDA approved feasibility trial and after informed consent, 24 control and 20 lymphedema (both hereditary and acquired) subjects received multiple intradermal injections of 25 µg of indocyanine green (total dose ≤ 400 µg) in bilateral arms or legs. The limbs were illuminated with NIR excitation light and the resulting fluorescent signal was imaged using custom, intensified CCD cameras. Lymphatic architecture and propulsive lymphatic flow from the injection sites to the nodal basin was observed. The apparent lymph velocities and propulsion periods were determined for the control subjects arms and legs as well as for the asymptomatic and symptomatic limbs of the lymphedema subjects.
While the lymphatics of the control subjects consisted of well-defined vessels which propelled fluid from the injection sites to the regional nodal basin, diseased lymphatics exhibited distinct architectural malformations, such as (i) extravascular fluorescence in which the ICG diffused away from the injection site or leaked out of the lymphatic vessels, (ii) dense networks of lymphatic capillaries, (iii) tortuous lymphatic vessels, and (iv) lymphatic backflow and/or reflux.
Statistical analyses of control subjects found subtle but significant differences in the left and right velocities in both arms (0.84 cm/s and 0.76 cm/s, p=8.1e-5) and legs (0.99 cm/s and 0.87 cm/s, p=0.032) but not in the periods of contralateral limbs. The difference in velocity in control arms (0.79 cm/s) and legs (0.94 cm/s) is small but significant (p=1.22e-7) while the difference in period is not. Significant differences in period exist between control (arms: 48.2 s; legs: 52.2 s) and both asymptomatic (arms: 39.6 s, p=2.68e-6; legs: 65.3 s, p=0.0022) and symptomatic (arms: 33.2 s, p=4.14e-5; legs: 72.1 s, p=0.00014) limbs. Significant differences were also found between the velocities in the control (0.94 cm/s) and both asymptomatic (0.83 cm/s, p=0.0084) and symptomatic (0.78 cm/s, p=0.0036) legs but not in the arms of control and lymphedema subjects.
Results demonstrate that non-invasive NIR fluorescence imaging of microgram amounts of fluorophore can detect architectural and functional lymphatic abnormalities. The lack of significant differences between the velocities and periods of the asymptomatic and symptomatic limbs suggests that lymphedema may be a systemic disease regardless of onset etiology.
Supported in parts by the American Cancer Society and the Longaberger Foundation (RSG-06-213-01-LR) and the National Institutes of Health (R01 HL092923 and U54 CA136404).
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5238.