Photoacoustic imaging of human inflammatory arthritis

To explore the value of photoacoustic imaging in future rheumatology clinic, in this work a newly developed photoacoustic and ultrasound dual-modality system facilitating real-time B-scan imaging was examined for its performance in mapping the enhanced synovial flow in human peripheral joints affected by inflammatory arthritis. The patients involved in this study were men and women over 18 years old, with clinically diagnosed inflammatory arthritis. Photoacoustic images of metacarpophalangeal joints were acquired at 580-nm wavelength that provides a desired balance between optical absorption of blood and attenuation in background tissue. The increased flow in the affected joints can be displayed successfully in photoacoustic images, and the difference between the arthritis group and the control group can be recognized. The results from arthritis patients and normal volunteers demonstrated the satisfactory sensitivity of photoacoustic imaging in assessing the physiological changes in the joints, specifically enhanced blood flow as a result of active synovitis. This study suggests that photoacoustic imaging, by revealing vascular features suggestive of joint inflammation, could be a valuable supplement to musculoskeletal ultrasound for rheumatology clinic.