|The gadget uses a near-infrared camera to capture a real-time video image of the patient`s veins.
A projector then beams this image back onto the patient`s skin to show the exact location of the veins, making them easier for medics to locate.
Dr Herbert Zeman, the biomedical engineer who invented the vein contrast enhancer (VCE) device, said it could detect veins up to 8mm below the surface of the skin and map them out within 0.06mm of their correct position.
The light beams sent out illuminate the skin at a wavelength of 740 nanometers. This wavelength of light is strongly absorbed by blood, and hence the veins, but is scattered by the surrounding tissue.
Dr Zeman explained: `Fat and tissue look light, veins and blood look dark.`
This image is fed to a PC that maps it onto a bright green background in real time.
After boosting the contrast between the tissues and the veins, the PC sends this image to a projector which beams it onto the skin in green.
This should help the person trying to pinpoint a suitable vein for an injection or drip, Dr Zeman hopes.
It may be particularly useful for children, who have small veins and puppy fat that can make it hard to find a vein.
Three prototypes of the VCE device, which fit into a package the size of a shoebox, will be trialled at a hospital in Tennessee later this year.
Jackie Haugh, president of the National Association of Phlebotomists, said: `If it worked, it would be an asset for every patient.
She said it would be particularly useful for emergency situations when doctors need to find a vein to give drugs and fluid rapidly.
`When ill people are dehydrated or in shock it can be really hard to find a vein. For cannulation it would be an extra asset.`
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