ABSTRACT
The lymphatic system is distributed throughout the whole body and has the capacity to return excess interstitial fluid and proteins from the tissues to the cardiovascular system. It is part of the body’s immune system as it transports foreign materials such as bacteria or cancer cells, together with lymph, to the lymph nodes for assessment by immunocompetent cells. The lymphatic system will be affected when lymph vessels, ducts, nodes, or lymph tissues become blocked, infected, inflamed, or invaded by cancer cells. Scintigraphic investigations of the lymphatic system are applied in patients with suspected lymphedema and for the detection of sentinel lymph node in cancer patients. The principle of lymphoscintigraphy is to image radiotracers injected into the interstitial space and follow their transport through the initial lymphatics, the lymphatic vessels, and lymph nodes to the main lymphatic ducts, and finally to the liver. The most important findings to look out for are focal tracer accumulation outside vessels and dermal backflow, as these signs are pathognomonic for lymphedema. In sentinel lymph node imaging, the optimal injection technique of the radiotracer varies depending on tumour type. The rule of thumb is that the first visualized lymph node with the highest uptake of the radiotracer, located closest to the injection site, is defined as a sentinel lymph node. The sentinel lymph node is the first lymph node that drains lymph, and possible metastatic cancer cells, from the primary tumour.
