Frequency Domain Optical Imaging and Lupus Disease Progression
Systemic lupus erythematosus (SLE) is an autoimmune disease, where the body’s immune system attacks organs throughout the body. However, SLE’s most frequent target is the joints, leading to inflammatory arthritis and pain in 95% of patients.
Lupus joint pain typically afflicts the fingers, wrists, and knees, often on both sides of the body. Lupus-related arthritis does not generally have the “joint nodules” of rheumatoid arthritis, making it more difficult to diagnose and treat. In addition, different patients with lupus can have very different levels of joint pain, which can make it difficult to judge how far along the joint damage is has gone. The only way to see this is to look at the joints themselves through indirect means.
Ultrasound, which uses sound waves, and MRI, which uses electromagnetism to get a sense of fluid flow in the body, can be used to assess the damage in joints affected by inflammatory arthritis. These create pictures similar to an X-ray that can help with diagnosis. However, both ultrasounds and MRI are expensive to use for joint pain and require someone with experience to interpret. This means that, unfortunately, MRIs and ultrasounds are prone to human error. They also require scheduling and appointments, so are not often used to diagnose and track ‘minor’ pains.
The ideal method for looking at joint health would be cheaper, easier to use, and more accurate. A new technology called frequency domain optical imaging fits the bill. It is both minimally invasive and low-cost, can be targeted at the joints in question, and appears to accurately assess arthritis in patients with lupus.
What is Frequency Domain Optical Imaging
Frequency Domain Optical Imaging (FDOI) is a form of optical imaging or Optical Coherence Tomography. Injured or damaged tissues accumulate blood and absorb light, which can be detected with light. Damaged, inflamed joints absorb more light because of the fluid gathered there and appear darker on the image. The light source is shone through the skin and can be tuned as needed to better detect specific tissues.
In a study involving 26 people (16 patients with SLE arthritis and 10 healthy controls) they used a laser at a wavelength of 670mm, at 300-600 MHz, that was directed at the joint in question. The reflected laser light was then captured by a camera, producing a photograph of the joint. Through this method, FDOI was able to detect SLE-caused arthritis with a high (80%) rate of accuracy, and 500mHz seemed to be the best wavelength for detecting inflammation-related arthritis (in this study.)
Lupus Warriors Takeaway
While the fact that optical imaging detected the difference between healthy and arthritic patients is a helpful diagnostic tool and method for actually seeing the progress of lupus in the joints, it is unclear whether it can detect whether SLE-related arthritis involves active inflammation or just pain. It’s possible that it could, with more study, and hopefully it will be explored further in the future.
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