Near Infrared Imaging (NIR) Spectroscopy

A burn imaging device developed at NRC could give doctors life-saving vision

A young man caught in a gas explosion is rushed into an emergency ward. The doctors and nurses know that immediate surgery is necessary if he's to survive the terrible burns to most of his body. But which skin should the surgeon remove and replace with a graft and which skin will heal on its own? It's the crucial question — yet a difficult one for even an experienced burn surgeon, let alone other physicians.

Photos of first degree burn, second degree burn and third degree burn.

But a new, award-winning NRC medical imaging technology presently in development could give all physicians the life-saving view they need to rapidly assess burns.

"The device has the potential to revolutionize the practice of burn surgery," says Dr. Karen Cross, a resident plastic surgeon at the Ross Tilley Burn Centre at the Sunnybrook and Women's College Health Science Centre in Toronto.

The near infrared (NIR) device is a non-invasive medical imaging tool being developed by the Spectroscopy Group at the National Research Council Institute for Biodiagnostics (NRC-IBD) in collaboration with the Ross Tilley Burn Centre. The Centre treats 85 - percent of major burn injuries in Ontario, and is one of Canada's main burn research centres.

NIR spectroscopic imaging system used to assess burns

The NIR imaging device tackles the primary challenge in assessing and treating burns: determining the burn depth. Skin consists of a number of layers (see diagram). First-degree burns, reddish superficial ones, impact only the top layer of the skin. As a result enough tissue survives for the skin to regenerate on its own. Third-degree burns, ones that involve blackened, charred flesh, extend through the skin into the underlying muscle and other tissues. These burns always require skin grafts.

It's second-degree, or partial-thickness, burns that provide the greatest diagnostic and treatment challenge. Second-degree burns effect both the upper epidermis and the underlying dermis layers. However, whether second-degree burns heal on their own depends on the damage done to blood vessels in the skin's dermal layer.

"In order for tissue to be viable, the blood has to provide oxygen and nutrients to the site for it to heal," explains Larry Leonardi, the NRC-IBD team leader on the NIR imaging project. "If blood is not oxygenated because of damage to the blood vessels, it's not going to start the healing process at the burn site."

Enter the NIR imaging device. It's a non-invasive, painless way to literally "see" the depth and extent of skin damage by measuring the light absorbed by haemoglobin and water in the body's tissues. Presently physicians assess burn depth primarily based on factors visible to the naked eye.

NIR Image of normal and oxygen-deprived skin at a 650 nm wavelength

The prototype NIR imaging device now under development consists of an infrared light source and highly sensitive CCD (charge-couple device) camera that records the reflected light.

The near infrared light from a tungsten-halogen bulb penetrates the body up to a depth of several millimetres to centimetres. As the light travels through the skin, some is absorbed by chromophores, or light-absorbing molecules, in the skin's layers. By beaming light onto a patient's skin and measuring reflected light, researchers can quantify the chromophores haemoglobin (both oxygenated and de-oxygenated) and water within the skin and underlying tissues.

"We're looking at tissue oxygenation and tissue blood volume as indicators of whether that tissue is going to survive or not," explains Leonardi, who notes that the technology was initially conceived of for studying tissue health during reconstructive plastic surgery.

To date, in tests at the Ross Tilley Burn Centre the researchers have demonstrated that the NIR imaging device can accurately and rapidly differentiate between first and third-degree burns. And, importantly, the prototype device is patient and hospital friendly.

"All the patient does is just lie there," says Leonardi. "As the nurse starts undressing the wound, the camera system is rolled in. The camera head is designed to tilt and move because we move the camera around to suit the patient. In 30 seconds the assessment is done and the camera is rolled out."

The data is sent to the NRC-IBD for processing. Because the research trials are preliminary, data from the NIR imaging device is not immediately accessible to the burn surgeons and is not used in determining patient treatment.

However, with the prototype system's increasing success this could soon change.

"The quality and quantity of data the team can obtain from just one burn is both impressive and enormous," says Dr. Cross. " This technology has made giant leaps in the area of burn surgery and we're now looking at the technology's potential to identify partial burns," says Dr. Cross.

She notes that this is a complex process. There may be a dead non-viable region in the centre of a burn that will never heal on its own, another area around this that's in flux and a further outer ring that might heal on its own. She says for this reason, the technology could be a literal life-saver for less experience surgeons.

"Fifty percent of all burns in Ontario are cared for in facilities that are not considered burn centres," says Dr. Cross. "This type of device could be really helpful to a doctor who has very little experience in determining burn depth."

For Leonardi, he now envisions the NIR imaging device eventually being used to help make diagnoses and to monitor post-surgery graft survival. It might also be used more widely to monitor wound healing in general, or to monitor a patient's tissue water content.

The NRC-IBD team is presently looking for licensees to develop this patented technology, which has already won several awards including the Wound Healing Society Young Investigator Award and the Johnson and Johnson's Award.

Beyond the incalculable medical benefits, the NRC-IBD device could have a significant impact on the healthcare system's bottom line by hastening recovery and improving treatment outcomes. The approximately 200,000 burns that occur annually in Canada cost approximately $117 million to treat.

Recommended Links

• NRC's Areas of Research: Biotechnology
• NRC Institute for Biodiagnostics (NRC-IBD)

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