A Picture Of Health
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08 October 2010
Researchers have created a system that can use any low–cost video camera to analyse health indicators such as blood pressure, pulse and respiration...
You can check a person’s vital signs – pulse, respiration and blood pressure – manually or by attaching sensors to the body. But a student at the Massachusetts Institute of Technology is working on a system that could measure these health indicators just by putting a person in front of a camera such as a laptop’s Web cam.
So far, student Ming–Zher Poh has demonstrated that the system can indeed extract accurate pulse measurements from ordinary low–res Web cam imagery. Now he’s working on extending the capabilities so it can measure respiration and blood–oxygen levels. He hopes eventually to be able to monitor blood pressure as well. Initial results of his work were published in the journal Optics Express.
Poh suggests that such non–invasive monitoring could prove useful for situations where attaching sensors to the body would be difficult or uncomfortable, such as for monitoring burn victims or newborns. It could also be used for initial telemedicine screening tests over the Internet using a patient’s own Web cam or even cellphone camera.
Such a system could also be built into a bathroom mirror so that patients who need ongoing monitoring could get pulse, respiration, oxygen saturation and blood–pressure readings routinely while they brush their teeth or wash up, displayed on the mirror.
The system measures slight variations in brightness produced by the flow of blood through blood vessels in the face. The pulse data derived from this setup were comparable with the pulse determined by a commercially available blood–volume pulse sensor.
The big challenge was dealing with movements of the subject and variations in the ambient lighting. But Poh was able to adapt signal–processing techniques to extract the pulse signal these variations.
The system produced pulse rates that was within about three beats per minute with the rates obtained from a commercial monitoring device, and was able to obtain valid results even when the subject was moving a bit. In addition, the system was able to get accurate pulse signals from three people in the camera’s view at the same time.
The concept of using a camera to detect such health info is not new, but the innovations that allow the use of such cheap camera is. Poh is now working on the capability to get blood pressure and blood–oxygen measurements from video images. Extracting such data from optical imagery should work, he says, since conventional blood oxygen sensors already work by using optical detection, although they use a dedicated light source rather than ambient lighting.