Abstract. There is currently a need for a safe and effective way to detect and diagnose early stages of childhood caries. A multimodal optical clinical prototype for diagnosing caries demineralization in vivo has been developed. The device can be used to quickly image and screen for any signs of demineralized enamel by obtaining highresolution and high-contrast surface images using a 405-nm laser as the illumination source, as well as obtaining autofluorescence and bacterial fluorescence images. When a suspicious region of demineralization is located, the device also performs dual laser fluorescence spectroscopy using 405-and 532-nm laser excitation. An autofluorescence ratio of the two excitation lasers is computed and used to quantitatively diagnose enamel health. The device was tested on five patients in vivo as well as on 28 extracted teeth with clinically diagnosed carious lesions. The device was able to provide detailed images that highlighted the lesions identified by the clinicians. The autofluorescence spectroscopic ratios obtained from the extracted teeth successfully quantitatively discriminated between sound and demineralized enamel.

Forward-viewing catheters and scopes for diagnosing disease and guiding interventions in small ducts (less than 3 mm diameter) require wide-field high-quality imaging since scope tip bending is difficult and ineffective. A high-fidelity electromechanically coupled finite element (FE) model of a piezoelectric actuated resonant fiber scanner is presented, which enables improvement on the general design of fiber-optic scanner geometry to increase scan frequency and field of view (FOV). Using the proposed model, parametric sweeps on the specific design variables achieved by acid etching of glass fiber are analyzed to identify their effect on scanner performance and to choose improved designs. The resulting complex fiber scanner design requires development of unique microfabrication techniques. Comparison of three model simulations and their experimental testing show that our proposed coupled model has prediction error of ≤12% with respect to experimental data, while other uncoupled models have up to 39% error. The model and microfabrication techniques presented in this paper have significance for fiber scanning-based systems in that they demonstrate reliability for model-driven design and also flexibility for fiber scanner design of complex geometries, allowing for improvement on medical imaging performance.

An ultrathin scanning fiber endoscope, originally developed for cancer diagnosis, was used in a case study to locate plaque and caries. The imaging system incorporated software mitigation of background autofluorescence (AF). In conventional fluorescence imaging, varying AF across a tooth surface can mask low-level porphyrin signals. Laserinduced autofluorescence signals of dental tissue excited using a 405-nm laser typically produce fluorescence over a wavelength range extending from 440-nm to 750-nm. Anaerobic bacterial metabolism produces various porphyrin species (eg. protoporphyrin IX) that are located in carious enamel, dentin, gingivitis sites, and plaque. In our case study, these porphyrin deposits remained as long as one day after prophylaxis. Imaging the tooth surface using 405-nm excitation and subtracting the natural AF enhances the image contrast of low-level porphyrin deposits, which would otherwise be masked by the high background AF. In a case study, healthy tissues as well as sites of early and advanced caries formations were scanned for visual and quantitative signs of red fluorescence associated with porphyrin species using a background mitigation algorithm. Initial findings show increasing amplitudes of red fluorescence as caries severity increases from early to late stages. Sites of plaque accumulation also displayed red fluorescence similar to that found in carious dental tissue. The use of real-time background mitigation of natural dental AF can enhance the detection of low porphyrin concentrations that are indicators of early stage caries formation.

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