Fluorescent imaging helps cats and dogs with cancer

A new camera-based technique is helping guide cancer surgery in dogs and cats.

The method, called Near-Infrared Fluorescence (NIRF) imaging, has been introduced at the Hospital for Small Animals to help soft tissue surgeons find and remove tiny lymph nodes that may be affected by cancer spread. 

Imaging device

The technology uses a harmless green dye, most commonly indocyanine green (ICG), which is injected into the tumour while the animal is under general anaesthetic. Using a specialised near-infrared camera, the dye appears bright green and can be clearly seen as it travels along the lymphatic pathways and into the draining lymph nodes, which can be a site for secondary tumours to develop.

To the naked eye, the skin and tissues look normal—so this real-time glow can help the surgeon locate lymph nodes that need to be removed accurately and with confidence. It can also help to confirm whether more than one lymph node needs to be removed.

Targeting lymph nodes

This process focuses on lymph nodes, small organs found throughout the body, sometimes referred to as “glands”, that act like filters for the immune system. In many cancers, these are one of the first places cancer cells may travel to and form secondary tumours.

The NIRF technology is used to focus on sentinel lymph nodes – these are the first nodes that fluid drains to from a tumour, and the most likely site of spread. Removing and checking these nodes can give the clinical team information about how the cancer is behaving and what treatment is likely to help the patient most.

Surgical challenges

Finding lymph nodes during surgery isn’t always straightforward. They can be very small – sometimes only millimetres in size - and hidden within fat tissue, and the body’s drainage pathways can vary from animal to animal. In some patients, tumour cells can drain to more than one lymph node, or tumours on the left-hand side can drain to lymph nodes on the right or vice versa, making the need for accurate mapping more important.

Key benefits

By making lymph drainage pathways visible during surgery, NIRF can help surgeons locate the most relevant lymph node or nodes, including those that are difficult to see. They can then be removed with minimal need for tissue dissection, which is safer for patients. Accurately identifying whether lymph node spread has happened can help vets determine the stage of the cancer more accurately and help tailor the next steps in a pet’s care plan.

Next steps

While the main use at the moment is helping identify the key lymph nodes linked to a tumour, ongoing research suggests the technique could support other procedures in future, such as evaluating blood supply to skin during reconstructive surgery, and to facilitate biliary tract interventions.