The ducal imaging with photoacoustic imaging (PAI) that is an emerging technology and clinical ultrasound
imaging that is an established modality is developed for the imaging of early inflammatory arthritis. PAI is sensitive
to blood volume, not limited by flow like ultrasound, holding great promise for the earliest detection of increase in
blood volume and angiogenesis - a key early finding inflammation PAI has the capability of assessing inflammation
in superficial human soft tissues, offering potential benefits in diagnosis, treatment and monitoring of inflammatory
arthritis. PAI combined with ultrasonography (US), is a real time dual-modality system developed and tested to
identify active synovitis in metacarpophalangeal (MCP) joints of 10 arthritis patients and 10 normal volunteers.
Photoacoustic images of the joints were acquired at 580-nm laser wavelength, which provided the desired balance
between the optical contrast of hemoglobin over bone cortex and the imaging depth. Confirmed by US Doppler
imaging, the results from ten patients and ten normal volunteers demonstrated satisfactory sensitivity of PAI in
assessing enhanced blood flow due to active synovitis. This preliminary study suggests that photoacoustic imaging,
by identifying early increase in blood volume, related to increased vascularity, a hallmark of joint inflammation,
could be a valuable supplement to musculoskeletal US.