Background The lightscan is a novel imaging technology to assess inflammatory activity in proximal interphalangeal (PIP) joints.
Objectives To compare the lightscan method with musculoskeletal ultrasound (US) and the clinical disease activity score DAS28 in patients with rheumatoid arthritis (RA), osteoarthritis (OA) and healthy controls.
Methods A total of 78 subjects (62 female, mean age 47.6±19.6 years, range 22-85) were examined. The total cohort included 36 patients with active RA (DAS28>2.6), 14 patients with OA, and 28 individuals served as a healthy control group. All patients received clinical joint examination (tender/swollen joints). The DAS28 was evaluated for RA patients. US in grey-scale (GSUS) and power Doppler mode (PDUS) of the PIPs (palmar/dorsal view) were performed. A semi-quantitative US score was designed for GSUS and PDUS. All patients were examined by lightscan. Therefore the PIPs were transilluminated by laser diodes with three different wavelengths (670, 820, and 904 nm), one joint after the other. A CCD camera was recording the scattered-light in a 2-dimensional light pattern. Those black/white bitmaps with a depth of 8 bits were transformed into a false colour image  and analysed with a non-local image segmentation method . This method minimizes the free energy functional of the picture. A direct descent method for the free energy was used to separate the components on the image. A lightscan score of the eight PIP joints results was created. Correlation coefficients were calculated using US and DAS28 as reference.
Results RA patients showed a significant correlation of the lightscan score and the GSUS dorsal score (r=0.377; p=0.037) and the PDUS dorsal/palmar score (r=0.429; p=0.016). The total cohort also presented a significant correlation with the GSUS score (r=0.439; p<0.01) and PDUS score (r=0.462; p<0.01). There was no correlation of DAS28 and the lightscan score. The lightscan score showed significantly lower scores for the healthy control compared to patients with RA or OA (p<0.01). In the ROC-analysis, the lightscan showed better sensitivity and specificity (AUC=0.893) than GSUS (AUC=0.751) and PDUS (AUC=0.684).
Conclusions In the present pilot project, lightscan appears to be a valuable and sensitive tool for assessing inflammation in patients with RA and OA. The best correlations of the lightscan were found compared to PDUS. However, further evaluation is needed.
Minet O, Scheibe P, Zabarylo UJ. Diagnosis of rheumatoid arthritis using light: correction of motion artefacts and color visualization of multispectral images. J Biophotonics. 2010 Mar;3(3):130-7.
Minet O, Gajewski H, Griepentrog JA, Beuthan J. The analysis of laser light scattering during rheumatoid arthritis by image segmentation. Las. Phys. Lett. 4(8) (2007) 604-10.
Disclosure of Interest None Declared