Many patients dread providing blood samples for medical tests. Taking the sample can cause pain and, sometimes, spread disease. Researchers have therefore started to develop non-invasive techniques for blood tests: many of these use lasers and other light sources to inspect the blood through the skin. Scientists at Sysmex Corporation in Japan have taken this method one stage further by developing a machine that can automatically identify the number of blood cells in a sample ( Patent 5741213).
Recognising blood cells presents a big challenge for automated counting systems. As blood flows through veins, the cells are deformed in the direction of blood flow. Blood also contains a lot of other ‘junk’ material such as proteins. Computers find it difficult to recognise the cells once they have been deformed against this background ‘junk’ and therefore require a large number of ‘templates’ of each different cell shape.
The Sysmex system shines a laser onto a part of the body that has blood vessels close to the skin, for example an earlobe, lip or finger. A set of fibre optic cables collects the light reflected from the blood vessel and pipes it to an image intensifier. This signal is then sent to a CCD camera and analysed on an Apple Mac computer in real-time. The computer converts the captured image into a two dimensional grid and a mathematical algorithm is used to determine if a particular object is a blood cell or not. Rapid analysis of the blood passing through the system then allows the computer to calculate the number of cells in the blood.