Indocyanine green (ICG) lymphography is a scan of the superficial lymphatics, helps define lymphatic dysfunction and delineate individualized lymphedema treatment. This study also helps visualize lymphedema in the asymptomatic limb. Superficial lymphatics accounts for 70% of the lymphatic system.
Indocyanine green (ICG) is a contrast that fluoresces in the near infrared range and therefore needs a special camera to be seen after injection. Low dose ICG injected into the subcutaneous tissue has been used to map lymphatics; this is known as ICG lymphography. The ICG binds to a protein called albumin, which is taken up into the lymphatics, and transported within the lymph fluid. In this way, the function of the lymphatics can be assessed.
We offer an initial consultation and ICG scan and if found with lymphedema an appropriate treatment plan is discussed.
In case ICG scan is normal in the presence of a swollen leg or arm, differential diagnosis for edema cause(s) is made.
In case of primary and secondary lymphedema, ICG scan will help define individual characteristics and pattern of lymph flow that with help customize decongestive therapy.
Higher risks for lymphedema development in cancer includes lymph nodes removal and/or radiation. After completion of cancer treatment, ICG scan can detect early signs of lymphedema and initiate preventive measures and/or treatment.
Procedure: After cleaning the skin with antiseptic, topical anesthetic is applied to numb injection site(s); and local anesthesia can be injected at injection site to numb and reduce pain. A tiny dose of ICG is injected subcutaneously, typically 0.1 ml (0.25 mg – 0.5 mg) per injection site, from 2 to 3 sites in the web space between fingers or toes in the affected arm or leg.
After a period of time from minutes to hour(s) the infrared camera scans the affected area and a black and white image is displayed on a video screen.
In normally functioning lymphatics, ICG is quickly taken up by the lymphatic system. The dye is rapidly transported in normal linear channels to the groin or armpit. Slow transport of dye indicates that the lymphatics have suffered secondary changes.
Benefits: The purpose of this test is to visualize the flow of the superficial lymphatics and areas of abnormalities such as dermal backflow. In addition important information regarding the function of the lymphatics can be gained from assessing the speed of lymphatic transport up the affected limb. The test aids in individualizing lymphedema treatment to improve effectiveness.
Precautions: ICG lymphography is a safe technique. Allergic reactions to ICG are very rare in general. The package insert states it contains ‘no more than 5% of sodium iodide’ ~ mainly used as a preservative.
Contraindication: Patients allergic to iodide, iodine and/or shellfish.
Side Effects: There is a theoretical risk of introducing infection by giving injections into the limb affected by lymphedema but this is unlikely as sterile needles and antiseptic skin preparation are used routinely. Other side effects may include allergic reaction, bruising, hematoma, temporary numbness, burning sensation at the injection site, and temporary local green coloration or discoloration of the skin.
Furthermore, ICG lymphography does not involve exposure to radiation.
Local anesthetic is routinely used in order to minimize the pain of ICG injection.
The dye has a green color and may leave a small green patch on the skin at the foot or hand lasting for a few days usually 3 – 7 days following the test.
After ICG lymphography, you can resume normal activities straight away, for example, it is fine for you to drive yourself home.