Diagnostics
Watching the flow
The role of lymphangiography By Elliott Weiss and Moira Stilwell raditionally, the diagnosis of lymphedema has been purely clinical, based on the clinical history and the findings on physical examination. Sometimes one is born with lymphedema (e.g., Milroy’s Disease), or it develops during the teenage years (e.g., Meige Disease), or later in life, (e.g., Lymphedema Tarda). It can also be seen in combination with other congenital conditions. In other cases, lymphedema occurs secondary to conditions such as malignancies (cancer) or infections (most commonly filariasis), among many others. Originally this condition was considered to be due to a ‘blockage’ or other forms of lymphatic flow malfunction, limiting the transport of lymphatic fluid. With each new medical imaging technology, our understanding of lymphedema evolves. With the advent of X-ray technology, the use of medical imaging allowed for investigations of the lymphatic system, primarily using a technique called lymphangiography with the procedure called a lymphangiogram. Started in 1952, the original version of this test involved injecting a dye under the skin to map out the lymphatic vessels. It was a very painful technique, using standard X-ray technology, but it was considered the gold standard of imaging and viewing lymphatic flow over the next 40 years. During that time, nuclear medicine technology developed in parallel with traditional X-rays. Improvements in technology, safety and comfort, led to it replacing the traditional lymphangiogram. In the past, both methods
were seen as binary tests; either you had normal lymphatic flow or not. Nuclear medicine technology has become more sophisticated and is used to diagnose, measure and stage this condition. It is now used to follow the course of disease before and after treatment.
visualization of lymphatic flow over time. The images may be obtained at various time intervals. This allows for an understanding of the lymphatic flow through the lymphatic vessels. Sentinel node biopsies such as in breast cancer management, use this technology
What is a nuclear medicine lymphangiogram, also known as a lymphangio-scintographic scan (LSG)? A LSG involves an injection of a sterile medical grade tracer under the skin, typically sub-dermally or subcutaneously. The tracer, which is tagged with a radioisotope such as technetium-99m (99mTc), is picked up by the lymphatic system and normally travels up the lymphatic vessels to the lymph nodes. A scanning device called a gamma-ray detector measures the radioactive tracer, as it is moves up the limb. The intensity and distribution of 99mTc is tracked and produces an outline of the lymphatic vessels, although typically it is measured in the superficial lymphatic system. This technology is considered to be a functional imaging modality as it allows for
to stage patients with a known malignancy before surgery. What was initially used as a static (yes-no) technology is now able to follow lymphatic flow in real time. This allows physicians and surgeons to have a much better understanding of lymphatic function and assist in decision-making.
Photo: centraloregonradiology.com
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Dr. Elliott Weiss, MD FRCPC is a specialist in Physical Medicine & Rehabilitation who is primarily based out of Providence Healthcare in Vancouver. Dr. Weiss has been involved in the care of patients with lymphedema for over thirty years. Dr. Moira Stilwell, MD FRCPC is a Radiologist and Nuclear Medicine physician. She practises Nuclear Medicine in Vancouver, British Columbia. Drs. Erin Brown, Kathryn Issac and Weiss have established a provincial lymphedema clinic at Vancouver General Hospital.
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What are the risks of LSG? There are three main concerns regarding a nuclear medicine lymphoscintigraphy: • t he effects of radiation • the possibility of infection •w hether the procedure might make lymphedema worse Radiation exposure is very low. Normally, the tracer passes from the lymphatics into the blood supply, then very quickly to the kidneys and the bladder. That is why the bladder is often visible in these scans. As well, 99mTc has a short half-life (six hours) and it is nearly completely decayed within a day, without any known long-term effects. A sterile technique is used to minimize the risk of infection. Allergic reactions are rare. People with a medical/contrast dye allergy are generally not allergic to this particular agent. Summer 2021