A prototype system based on optoacoustic and hyperspectral imaging has been developed as part of an EC-funded project to give early diagnosis of arthritis of the hands. The technology will be shown by the Fraunhofer Institute for Biomedical Engineering IBMT, which led the IACOBUS project, at the Medica trade fair in Düsseldorf, Germany from 16 to 19 November.
The prototype 3D finger scanner searches joints for sites of inflammation as well as other pathological changes. ‘One of the advantages of this method is that it enables us to detect the condition while it is still in its early stages, since many forms of arthritis affect the fingers first,’ said Dr Marc Fournelle, IACOBUS project manager at Fraunhofer IBMT.
Rheumatoid arthritis and osteoarthritis, both of which frequently affect the joints of the hands, are two common forms of rheumatic diseases. These joint diseases are chronic in nature and cannot be cured yet, but early diagnosis and medical treatment improves the long-term outcome.
The scanner operates using an optoacoustic imaging technique, in which the fingers are subjected to extremely short laser light pulses of variable wavelength. As the tissue absorbs these brief light pulses a minimal amount of warming occurs, which in turn causes the tissue to expand a tiny bit. This expansion then causes slight pressure pulses which the scanner registers using an acoustic transducer in the same way that ultrasound imaging procedures do. From the pattern of the pressure pulses the device can pinpoint exactly where inflammation is forming.
To refine the diagnosis, the optoacoustic procedure is enhanced with a hyperspectral imaging system. This method is based on scanning the finger with strong white light, with the result that light of certain wavelengths is absorbed by the inflamed tissue. By analysing which wavelengths are found in the light that is not absorbed by the tissue, scientists can determine whether or not the tissue is affected. Given that both of these procedures primarily produce images of soft tissue – blood vessels in particular – the system also provides ultrasound images that are likewise created using the scanner’s acoustic transducer.
‘As always, the images produced by ultrasound depict soft tissue such as muscles, tendons and joint capsules as well as the surface of the bones, which means that our scanner gives physicians a familiar image to work with,’ says Fournelle.
The ultrasound image is then combined with the data from the hyperspectral imaging and the optoacoustic procedure, enabling doctors to identify any sites of inflammation in the tissue.
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