New camera shows blood flow

A Swiss company has developed a camera which shows how blood is circulating through the skin in real-time.

The camera is designed to help assess the extent and severity of burns.

The device has been trialled by burn specialists and reconstructive surgeons at CHUV University Hospital in Lausanne, Switzerland.

Clinical data from the trial is being presented at the 14th European Burns Association Congress in the Hague on Wednesday.

Colour variations

The machine uses what is called “laser Doppler imaging” and has been developed by Aimago, a start-up company based at the Swiss university, Ecole Polytechnique Federale de Lausanne.

The device is connected to a flexible arm and is placed over the burn area with the camera facing the burn. On the other side of the machine is a video screen on which colour variations show differences in the intensity of blood circulation.

“Red means high blood flow, blue means low blood flow,” Michael Friedrich of Aimago said. “This information (the specialist) can use to see whether the burnt tissue still has blood supply or not.

“If the tissue has no blood supply it cannot recover, it’s going to die so you need to do skin grafting. However, if the skin is perfused (ie blood is still flowing through it), then it’s going to heal spontaneously without scarring.”
A rival laser Doppler machine by Moor Instruments A rival laser Doppler machine by Moor Instruments

Greg Williams, who heads the burns unit at Chelsea and Westminster Hospital told the BBC his hospital was one of several in the UK already using a rival laser Doppler imager built by Moor Instruments and which was recently approved by the National Institute for Health and Clinical Excellence (NICE).

He said that while that machine was bulky and provided only static images, he was yet to be convinced of the need for a real-time alternative.

“There are a range of depths of burns between a superficial and a full-thickness burn where experienced burn clinicians will get the diagnosis wrong about a third of the time,” he said.

“With the laser Doppler and clinical judgement, you get it right about 98% of the time.

“Whether this new device will offer any more advantages or not, I’d have to see the machine and compare it with what we are using.”

Doppler shift

Aimago’s “EasyLDI” machine works by firing laser beams at the skin which are reflected by red blood cells in small vessels in the skin.

The movement of the red blood cells results in a tiny shift in the frequency of the light as it impacts upon the cells, and it is these “Doppler” shifts which the device detects and transforms into colour variations on the screen.

The camera can deliver more than 12 images a second, which means users can detect the effect of the patient’s heart beat in the circulation images, it is claimed.

While the primary use is for burns victims, its makers say it could also be used in reconstructive surgery to determine the viability of skin tissue before it is transferred from one part of the body to another. (Neil Bowdler/BBC News)