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Lasers detect inflamed finger joints

17 Jun 2002

A laser imaging system is set to aid the early diagnosis of rheumatoid arthritis.

A laser-based system has successfully imaged the inflammation in arthritic finger joints for the first time. The German research team says this approach provides an inexpensive and reproducable way to assess inflammation changes. (Arthritis & Rheumatism 46 1177)

"The technique is easy to handle, inexpensive and noninvasive," said lead clinician Alexander Scheel of Georg-August University in Göttingen. "It has many advantages over conventional imaging and provides new information about joint status."

Arthritic joints are typically diagnosed using radiotherapy, but this routinely overlooks early lesions. Other techniques such as ultrasound and magnetic resonance imaging are time consuming and expensive.

The researchers place the finger in a specially designed holder. A continuous-wave diode laser then illuminates the suspicious joint with 2 mW of red light at 675 nm. A CCD camera placed underneath the joint collects the scattered light and transfers the data to a computer for evaluation and processing.

A total of 72 inflamed joints were examined over the six-month trial period and the system correctly classified 60 of them. This corresponds to an accuracy of 83%.

Scheel told Optics.org: "Comparisons between individuals are difficult. To compare pictures of the same patient, the finger had to be placed in the same position as the first examination and this took some time."

"At this stage of the preliminary study, laser imaging is especially useful for sensitive follow-up analysis of joint inflammation and patient response to anti-rheumatic medication," he explained. "It is of limited help for individual early arthritis diagnosis."

The team's goal is to develop a system that can make a diagnosis when the patient is first seen. "To confirm our results we need a large number of patients and want to use other imaging techniques for comparison," said Scheel. "At the moment, the system only images proximal finger joints, imaging of other small joints is of interest."

The device, which is patented, was developed at the Free University of Berlin in cooperation with Siemens.

Jacqueline Hewett is news reporter on Optics.org and Opto & Laser Europe magazine.

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