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. ### Competing Interest Statement J.V.J. is a co-founder of StyloSonics, LLC. ### Funding Statement This study was funded by National Institutes of Health under grants R21 DE029025, R21 DE029917, and R21 AG065776. We also acknowledge infrastructure under grant S10 OD021821. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: All work with human subjects was approved by the IRB of University of California, San Diego and conducted according to the ethical standards set forth by the IRB and the Helsinki Declaration of 1975. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors