Introduction:
Encouraged by the promising results from several pioneering studies on RA patients, we are further advancing the translation of the emerging PA imaging technology to the clinical management of inflammatory arthritis. Aiming at a point-of-care device for rheumatology clinics, we developed an automatic 3D imaging system combining the emerging photoacoustic imaging with conventional Doppler ultrasound for detecting human inflammatory arthritis. It can enable early detection and early treatment modification, changing the current procedures in rheumatology clinics. The performance of our automatic 3D imaging system combining the emerging PA imaging with the conventional Doppler US was examined via a longitudinal study in a clinically relevant AIA rat model. The performance of this system was then examined via an initial study on RA patients with clinically confirmed inflammation in their finger joints. It was validated that the PA imaging function of this system could detect and display the hyperemia deep in the joints with good sensitivity and high image quality. The 3D Doppler US imaging function enabled by this system could also detect the enhanced flow due to the active inflammation in the joints.
Automatic Imaging System:
Figure 1. Photo of (a) the automatic PA/US imaging system, (b) the imaging probe holder, robot arm, water tank and patient hand rest, and (c) the probe holder with US probe inside and fiber bundle on both sides.
Example results:
Figure 2. Series of a RA patient’s right PIP2 joint images. (a) Long-axis US B-mode images (gray scale) with superimposed PA signals (color scale). (b) Long-axis US B-mode images (gray scale) with superimposed power Doppler US signals (color scale). (c) Short-axis US B-mode images (gray scale) with superimposed PA signals (color scale). (d) Short-axis US B-mode images (gray scale) with superimposed power Doppler US signals (color scale). White arrows mark the hyperemia area in PA and the large vessels in Doppler.
Figure 3. 3D volumetric rendering of (a) the B-mode and PA image and (b) the B-mode and Doppler US image of the patient’s right PIP2 joint. The 2D images along different views are shown in (c) and (d), where the plane for each view is marked in (a) and (b).