A more compact photoacoustic imaging system to detect periodontitis

Photoacoustic imaging has shown value in periodontal disease, but the large size of conventional photoacoustic transducers prevents imaging of more posterior teeth, i.e., molars. Here, we report a clinical "hockey stick"-style transducer repurposed for photoacoustic (PA) via an integrated fiber bundle. The shape of the hockey stick transducer facilitates imaging of the 1st pre-molars in contrast to conventional photoacoustic transducer designs. This tool was then deployed for photoacoustic imaging of periodontal disease and the periodontal pocket via a food-grade contrast agent (cuttlefish ink). We characterized the resolution and imaging range and then validated the system with a swine model and human subjects. We could image four additional teeth per quadrant with the smaller design versus a commercial photoacoustic transducer. Three raters evaluated the performance of the hockey stick transducer. The measurements between the probing and the PA methods were blinded, but the outcomes were highly correlated. We showed a bias of [~]0.3 mm for the imaging-based technique versus conventional probing. In addition, the inter-reliability was over 0.60 for three different raters of varying experience suggesting that this approach to evaluating dental health is teachable and reproducible. Finally, we demonstrated the utility in a human subject and can image teeth much more posterior in the mouth than with conventional photoacoustic transducers.