High-throughput light sheet imaging of adult and larval C. elegans Parkinson's disease model using a low-cost optofluidic device and a fluorescent microscope.

Recent advancements at the interface of microfluidics technology and light sheet fluorescence microscopy have opened the door for high-throughput and high-content investigation of C. elegans disease models. In this paper, we report on the development of a simple, miniaturized, and low-cost optofluidic platform that can be added to a conventional inverted fluorescent microscope for continuous light sheet imaging of transgenic worm populations with high lateral and axial resolutions of 1.1 µm and 2.4 µm, respectively. The optofluidic device is made entirely of PDMS with integrated optics for light sheet generation. Laser excitation is delivered to the device via a low-cost free space laser, and cross-sections of worm populations are imaged as they pass continuously through a channel. Results show the platform can image NW1229 whole worms with pan-neural fluorescent expression at a throughput of >20 worms per minute at L3 and young adult (YA) stages. As a benchmark test, we show that the low-cost device can quantify the reduced neuronal expressions of L3 and YA NW1229 worms when exposed to 500 µM 6-OHDA neurodegenerative agent. Following the benchmark validation, we utilized the platform in a novel application for imaging human alpha-synuclein reporter in populations of Parkinson's transgenic model (ERS100). Results show the ability of the low-cost platform to reliably detect and quantify the anomalous neural phenotypic changes in ERS100 populations at L3 and YA stages with high spatial resolution. The findings of this study show the potential of our low-cost optofluidic add-on platform to equip conventional fluorescent microscopes with light sheet capability for quantitative phenotypic studies of transgenic C. elegans at high resolution and throughput.

Gap junction Delta-2b (gjd2b/Cx35.1) depletion causes hyperopia and visual-motor deficiencies in the zebrafish.

The zebrafish is a powerful model to investigate the developmental roles of electrical synapses because many signaling pathways that regulate the development of the nervous system are highly conserved from fish to humans. Here, we provide evidence linking the mammalian connexin-36 (Cx36) ortholog gjd2b/Cx35.1, a major component of electrical synapses in the zebrafish, with a refractive error in the context of morphological, molecular, and behavioral changes of zebrafish larvae. Two abnormalities were identified. The optical coherence tomography analysis of the adult retina confirmed changes to the refractive properties caused by eye axial length reduction, leading to hyperopic shifts. The gjd2b/Cx35.1 depletion was also correlated with morphological changes to the head and body ratios in larvae. The differential expression of Wnt/ß-catenin signaling genes, connexins, and dopamine receptors suggested a contribution to the observed phenotypic differences. The alteration of visual-motor behavioral responses to abrupt light transitions was aggravated in larvae, providing evidence that cone photoreceptor cell activity was enhanced when gjd2b/Cx35.1 was depleted. The visual disturbances were reversed under low light conditions in gjd2b -/- /Cx35.1-/- larvae. Since qRT-PCR data demonstrated that two rhodopsin genes were downregulated, we speculated that rod photoreceptor cells in gjd2b/Cx35.1-/- larvae were less sensitive to bright light transitions, thus providing additional evidence that a cone-mediated process caused the VMR light-ON hyperactivity after losing Cx35.1 expression. Together, this study provides evidence for the role of gjd2b/Cx35.1 in the development of the visual system and visually guided behaviors.

Machine Learning-Assisted Short-Wave InfraRed (SWIR) Techniques for Biomedical Applications: Towards Personalized Medicine.

Personalized medicine transforms healthcare by adapting interventions to individuals' unique genetic, molecular, and clinical profiles. To maximize diagnostic and/or therapeutic efficacy, personalized medicine requires advanced imaging devices and sensors for accurate assessment and monitoring of individual patient conditions or responses to therapeutics. In the field of biomedical optics, short-wave infrared (SWIR) techniques offer an array of capabilities that hold promise to significantly enhance diagnostics, imaging, and therapeutic interventions. SWIR techniques provide in vivo information, which was previously inaccessible, by making use of its capacity to penetrate biological tissues with reduced attenuation and enable researchers and clinicians to delve deeper into anatomical structures, physiological processes, and molecular interactions. Combining SWIR techniques with machine learning (ML), which is a powerful tool for analyzing information, holds the potential to provide unprecedented accuracy for disease detection, precision in treatment guidance, and correlations of complex biological features, opening the way for the data-driven personalized medicine field. Despite numerous biomedical demonstrations that utilize cutting-edge SWIR techniques, the clinical potential of this approach has remained significantly underexplored. This paper demonstrates how the synergy between SWIR imaging and ML is reshaping biomedical research and clinical applications. As the paper showcases the growing significance of SWIR imaging techniques that are empowered by ML, it calls for continued collaboration between researchers, engineers, and clinicians to boost the translation of this technology into clinics, ultimately bridging the gap between cutting-edge technology and its potential for personalized medicine.

Three-dimensional opto-thermo-mechanical model for predicting photo-thermal optical coherence tomography responses in multilayer geometries.

Photothermal optical coherence tomography (PT-OCT) is a functional extension of OCT with the ability to generate qualitative maps of molecular absorptions co-registered with the micron-resolution structural tomograms of OCT. Obtaining refined insight into chemical information from PT-OCT images, however, requires solid understanding of the multifactorial physics behind generation of PT-OCT signals and their dependence on system and sample parameters. Such understanding is needed to decouple the various physical effects involved in the PT-OCT signal to obtain more accurate insight into sample composition. In this work, we propose an analytical model that considers the opto-thermo-mechanical properties of multi-layered samples in 3-D space, eliminating several assumptions that have been limiting previous PT-OCT models. In parametric studies, the model results are compared with experimental signals to investigate the effect of sample and system parameters on the acquired signals. The proposed model and the presented findings open the door for: 1) better understanding of the effects of system parameters and tissue opto-thermo-mechanical properties on experimental signals; 2) informed optimization of experimentation strategies based on sample and system parameters; 3) guidance of downstream signal processing for predicting tissue molecular composition.

Rapid and Low-Cost Detection and Quantification of SARS-CoV-2 Antibody Titers of ICU Patients with Respiratory Deterioration Using a Handheld Thermo-Photonic Device.

While research suggests that COVID-19 vaccines are effective in producing anti-SARS-CoV-2 antibodies that reduce the risk of COVID-19 and its potentially severe complications, how long these antibodies persist after the infection/vaccination is unknown. Longitudinal studies and rapid and scalable platforms are needed for large-scale sero-diagnosis and vaccine evaluation. In this study, we examine the efficacy of our recently-developed handheld thermo-photonic device for rapid and low-cost assessment of the adaptive immune response of COVID+ and COVID- patients admitted to the intensive care unit (ICU) at a local hospital due to respiratory deterioration. Antibody testing included detection and quantification of IgG and IgM via thermo-photonic sensing of a commercially available COVID-19 IgG/IgM rapid test as well as standard measurements with quantitative enzyme-linked immunosorbent assays (qELISA). The results demonstrate that the thermo-photonic reader in conjunction with COVID-19 IgG/IgM test cassettes can detect and quantify IgG levels in COVID-19 antibody assays within the clinically relevant range and with a high correlation to those obtained from qELISA. We also found that the IgG antibody is more reliable for detecting individuals with an adaptive immune response to SARS-CoV-2 compared to the IgM antibody. The developed reader offers a low-cost, portable, and scalable solution for accessing the antibody titer of individuals against SARS-CoV-2 and can be used in local hospital settings.

Low-Cost Resistive Microfluidic Salinity Sensor for High-Precision Detection of Drinking Water Salt Levels.

Rapid, inexpensive, and precise water salinity testing remains indispensable in water quality monitoring applications. Despite many sensors and commercialized devices to monitor seawater salinity, salt detection and quantification at very low levels of drinking water (below 120 ppm) have been overlooked. In this paper, we report on optimization of a low-cost microfluidic sensor to measure water salinity in the range of 1-120 ppm. The proposed design employs two copper microbridge wires suspended orthogonally in a PDMS microchannel to measure salinity based on the electrical resistance between the wires. The preliminary design of the sensor microchannel with a rectangular cross-section width (w) of 900 µm and height (h) of 500 µm could measure the water salinity in the range of 1-20 ppm in less than 1 min with detection sensitivity, limit of detection (LOD), and limit of quantification (LOQ) of 17.1 ohm/ohm·cm, 0.31 ppm, and 0.37 ppm, respectively. Data from the preliminary design was used for developing and validating a numerical model which was subsequently used for parametric studies and optimization to improve the sensor's performance. The optimized design demonstrated an order of magnitude increase in sensitivity (385 ohm/ohm·cm), a 6-fold wider detection range (1-120 ppm), and a 15-fold enhancement in miniaturization of the microfluidic channel (w = 200 µm and h = 150 µm) with LOD and LOQ of 0.39 and 0.44 ppm, respectively. In the future, the sensor can be integrated into a hand-held device to remove present impediments for low-cost and ubiquitous salinity surveillance of drinking water.

Comparison of Long-Wave and Mid-Wave Infrared Imaging Modalities for Photothermal Coherence Tomography of Human Teeth.

The ability to detect dental caries at early stages lies at the heart of minimal intervention dentistry, enabling the curing or arresting of carious lesions before they advance to the cavity stage. Enhanced truncated-correlation photothermal coherence tomography (eTC-PCT) using mid-wave infrared (MWIR) cameras has recently been shown to offer tomographic visualization of early caries. The tomographic slicing ability of such systems, however, is believed to be limited by direct radiative thermal emission through the translucent dental enamel in the 3-5 µm MWIR spectral range. Such radiative emissions can dominate the delayed conductive thermal contributions needed for tomographic reconstruction of internal dental defects. It has been hypothesized that long-wave infrared (LWIR) eTC-PCT systems may offer better tomographic performance by taking advantage of the intrinsic attenuation of direct radiative emission by dental enamel in the LWIR spectral range, enabling more effective delayed conductive thermal contributions from subsurface caries. More than an order of magnitude lower cost of the system is another key attribute of LWIR eTC-PCT which can open the door for downstream translation of the technology to clinics. In this report, we offer a systematic comparison of the performance/effectiveness of caries detection with LWIR and MWIR eTC-PCT systems for detecting natural caries, bacterial caries, and artificially demineralized enamel surfaces. Our results suggest that the low-cost LWIR based eTC-PCT system provides 3D visualization and 2D slice-by-slice images of early caries and internal micro-cracks similar to those obtained from the more expensive MWIR-based eTC-PCT system, albeit with ∼1.3dB lower signal-to-noise ratio.

Low-cost optofluidic add-on enables rapid selective plane illumination microscopy of C. elegans with a conventional wide-field microscope.

SIGNIFICANCE: Selective plane illumination microscopy (SPIM) is an emerging fluorescent imaging technique suitable for noninvasive volumetric imaging of C. elegans. These promising microscopy systems, however, are scarce in academic and research institutions due to their high cost and technical complexities. Simple and low-cost solutions that enable conversion of commonplace wide-field microscopes to rapid SPIM platforms promote widespread adoption of SPIM by biologist for studying neuronal expressions of C. elegans. AIM: We sought to develop a simple and low-cost optofluidic add-on device that enables rapid and immobilization-free volumetric SPIM imaging of C. elegans with conventional fluorescent microscopes. APPROACH: A polydimethylsiloxane (PDMS)-based device with integrated optical and fluidic elements was developed as a low-cost and miniaturized SPIM add-on for the conventional wide-field microscope. The developed optofluidic chip contained an integrated PDMS cylindrical lens for on-chip generation of the light-sheet across a microchannel. Cross-sectional SPIM images of C. elegans were continuously acquired by the native objective of microscope as worms flowed in an L-shape microchannel and through the light sheet. RESULTS: On-chip SPIM imaging of C. elegans strains demonstrated possibility of visualizing the entire neuronal system in few seconds at single-neuron resolution, with high contrast and without worm immobilization. Volumetric visualization of neuronal system from the acquired cross-sectional two-dimensional images is also demonstrated, enabling the standard microscope to acquire three-dimensional fluorescent images of C. elegans. The full-width at half-maximum width of the point spread function was measured as 1.1 and 2.4 µm in the lateral and axial directions, respectively. CONCLUSION: The developed low-cost optofluidic device is capable of continuous SPIM imaging of C. elegans model organism with a conventional fluorescent microscope, at high speed, and with single neuron resolution.

Transient-mode photothermal optical coherence tomography.

Photothermal optical coherence tomography (PT-OCT) is an emerging extension of OCT, which forms images based on both scattering and absorption of light. The speed of PT-OCT, however, has been limited by the necessity for lock-in detection with extensive temporal sampling of the sample's PT response. Here, we demonstrate transient-mode PT-OCT (TM-PT-OCT), which increases the effective A-line rate by orders of magnitude from 10-100 Hz to 1.5-7.5 kHz, by interrogating the sample's transient thermal response to a single diode laser pulse. Functional imaging of moving samples with TM-PT-OCT at video rate is also presented. This significant improvement in imaging speed is expected to open the door for downstream integration of PT-OCT in clinical systems for in vivo imaging.

High-speed label-free confocal microscopy of Caenorhabditis elegans with near infrared spectrally encoded confocal microscopy.

Caenorhabditis elegans (C. elegans) is an optically transparent nematode that shares many gene orthologs and homologs with humans. C. elegans are widely used in large populations for genetic studies relevant to human biology and disease. Success of such studies frequently relies on the ability to image C. elegans structure at high-resolution and high-speed. In this manuscript, we report on the feasibility and suitability of a high-speed variant of reflectance confocal microscopy, known as spectrally encoded confocal microscopy (SECM), for label-free imaging of C. elegans. The developed system utilizes near-infrared illumination in conjunction with refractive and diffractive optics to instantaneously image a confocal image line at a speed of up to 147 kHz with lateral and axial resolutions of 2µm and 10µm, respectively. Our imaging results from wild-type C. elegans and four mutant strains (MT2124, MT1082, CB61, and CB648) demonstrate the ability of SECM in revealing the overall geometry, key internal organs, and mutation-induced structural variations, opening the door for downstream integration of SECM in microfluidic platforms for high throughput structural imaging of C. elegans.

Handheld Thermo-Photonic Device for Rapid, Low-Cost, and On-Site Detection and Quantification of Anti-SARS-CoV-2 Antibody.

With the emergence of vaccines and antibody therapeutics, rapid and scalable platforms are needed to quantify the antibody response of individuals. Lateral flow immunoassay (LFA) based test strips provide a rapid, low-cost, and point-of-care approach to antibody testing against the SARS-CoV-2 virus. These convenient and scalable tests, however, are qualitative in nature and cannot quantify the immune response of the infected and/or vaccinated individuals. This study reports on the development of a rapid, low cost and portable thermo-photonic device that enables sensitive detection and quantification of antibody levels using commercially available COVID-19 Antibody LFAs. Unlike conventional LFA readers, the developed technology is based on sensing the infrared thermal radiation of tag gold nanoparticles following laser excitation (aka photothermal response). Our proof-of-concept results with humanized monoclonal anti-SARS-CoV-2 Spike receptor-binding domain (RBD) IgG demonstrate that the thermo-photonic technology can detect and quantify antibody concentrations within the clinically relevant range and with a limit of detection of [Formula: see text]/ml. The reader in conjunction with antibody LFAs offers a low-cost, portable, and scalable solution for assessment of the degree of immunity in populations, quality control of convalescent plasma donations for antibody therapeutics, and monitoring the immune response of infected individuals and vaccine recipients.

Effects of lipid composition on photothermal optical coherence tomography signals.

SIGNIFICANCE: Photothermal optical coherence tomography (PT-OCT) has the promise to offer structural images coregistered with chemical composition information, which can offer a significant impact in early detection of diseases such as atherosclerosis. AIM: We take the first step in understanding the relation between PT-OCT signals and the endogenous tissue composition by considering the interplay between the opto-thermo-physical properties of tissue as a function of its lipid composition and the ensuing effects on the PT-OCT signals. APPROACH: Multiparameter theoretical estimates for PT-OCT signal as a function of composition in a two-component lipid-water model are derived and discussed. Experimental data from various concentrations of lipid in the form of droplets and injections under bovine cardiac muscle align with theoretical predictions. RESULTS: Theoretical and experimental results suggest that the variations of heat capacity and mass density with tissue composition significantly contribute to the amount of optical path length difference measured by OCT phase. CONCLUSION: PT-OCT has the potential to offer key insights into the chemical composition of the subsurface lipid pools in tissue; however, the interpretation of results needs to be carried out by keeping the nonlinear interplay between the tissue of opto-thermo-physical properties and PT-OCT signals in mind.

Aproximación a la respuesta comunitaria a la pandemia por COVID-19 de los equipos de Atención Primaria de Salud aragoneses / Approach to the community response to the COVID-19 pandemic of Aragonese Primary Healthcare Teams

INTRODUCCIÓN: ¿cómo seguir trabajando la orientación y participación comunitaria en Atención Primaria durante la pandemia por COVID-19?. OBJETIVOS Y MÉTODOS: observar, describir, reflexionar y documentar aspectos relativos a la atención comunitaria en el momento actual de pandemia por COVID-19 en los equipos de Atención Primaria (EAP) de Aragón. Estudio exploratorio-descriptivo observacional transversal con enfoque cualitativo, con dos fases. 1ª: recopilación de experiencias comunitarias y localización de informantes clave. 2ª: descripción de acciones comunitarias. Análisis descriptivo y tipo DAFO. RESULTADOS: se detectaron 47 iniciativas. Participaron 11 expertas y 54 informantes clave. El 66,6% consideró el rol de los EAP como consultores/colaboradores. El 64,9% de las iniciativas contempló la diversidad. El 49,1% no sabía si valoraron diferencias por género. Destacaron la importancia de lo comunitario para superar la crisis y la cooperación y coordinación con la comunidad e instituciones locales. DISCUSIÓN: protocolos con orientación biomédica, miedo e incertidumbre por la COVID-19 dificultaron el desarrollo de iniciativas comunitarias; frente a esto, fue clave la trayectoria comunitaria previa de los EAP, el trabajo en equipo, con especial relevancia el de las trabajadoras sociales, y su motivación. La participación del EAP como colaborador refuerza la importancia del liderazgo compartido. Son necesarios espacios colaborativos, apoyo institucional y coordinación intersectorial. CONCLUSIÓN: durante la pandemia, las comunidades deben ser parte de la respuesta; la orientación comunitaria de los EAP es clave. Es preciso visibilizar, acompañar y reforzar el trabajo comunitario y estimular la coordinación con Salud Pública

INTRODUCTION: How to continue working on community guidance and participation in Primary Care during the COVID-19 pandemic?. OJECTIVES AND METHODS: To observe, report, reflect and document autonomous community experiences of Aragonese Primary Care Teams (PCT) during the COVID-19 pandemic. A two-phase exploratory-descriptive observational, cross-sectional study with a qualitative approach. Phase 1: compilation of experiences in community health and location of key informants. Phase 2: description of community actions. Descriptive and SWOT analysis. RESULTS: A total of 47 initiatives were detected; 11 experts and 54 key informants took part. A total of 66.6% considered the role of the PCT as consultants or collaborators; 64.9% of initiatives considered diversity. A total of 49.1% did not know whether they evaluated differences by sex. They highlighted the importance of the community to overcome the crisis, and cooperation and coordination with community and local institutions. DISCUSSION: Protocols with biomedical guidance, fear and uncertainty due to COVID-19 hindered development of community initiatives. In light of this, the previous community trajectory of PCTs, teamwork with special relevance of social workers and their motivation were fundamental. PCT involvement as a partner strengthens the importance of shared leadership. Collaborative spaces, institutional support and intersectoral coordination are all necessary. CONCLUSION: During the pandemic, communities must be part of the response; PCT community guidance is essential. Visibility, working alongside and strengthening community work and stimulating public health coordination are all necessary requirements

Adolescentes en conflicto: respuesta intersectorial y abordaje comunitario / Adolescents in conflict: intersectoral response and community approach

Presentamos un proyecto intersectorial de minimización de riesgos en dos grupos de adolescentes en riesgo social en el barrio de San Pablo (Zaragoza). Para ello realizamos diversos talleres formativos e intervenciones con agentes del barrio sobre conductas saludables, mediación del conflicto, comunicación, salud afectivo-sexual, etc., con adolescentes con graves dificultades de convivencia en su centro escolar, donde ya habían agotado los posibles apoyos socioeducativos. Con estas actividades formativas realizadas con ellos y sus familias se ha propiciado una relación más saludable con su entorno educativo y social, mejorando su relación con el mismo, la comunicación y el autocuidado. En algún caso se ha conseguido dar continuidad al proceso educativo, a pesar de las limitaciones existentes. El trabajo intersectorial es una herramienta básica para abordar el cuidado del bienestar de poblaciones en riesgo de exclusión social

We report an intersectoral collaboration intended to minimize risks in two groups of adolescents at social risk in the San Pablo neighbourhood (Zaragoza). We conducted a series of workshops and interventions, in coordination with agents in the neighbourhood, on healthy behaviours, conflict mediation, communication and sexual and emotional health. These were targeted at adolescents with serious coexistence challenges in the classroom, where they had already exhausted all socio-educational support opportunities. With these educational activities aimed at the adolescents and their families we achieved a healthier relationship with their social and educational environment, which improved communication and self-care. In some instances, we were able to provide continuity to their educational process, despite existing limitations. Intersectoral collaboration is a basic tool to tackle the welfare of populations at risk of social exclusion

Low-Cost Active Thermography using Cellphone Infrared Cameras: from Early Detection of Dental Caries to Quantification of THC in Oral Fluid.

Active thermography (AT) is a widely studied non-destructive testing method for the characterization and evaluation of biological and industrial materials. Despite its broad range of potential applications, commercialization and wide-spread adaption of AT has long been impeded by the cost and size of infrared (IR) cameras. In this paper, we demonstrate that this cost and size limitation can be overcome using cell-phone attachment IR cameras. A software development kit (SDK) is developed that controls camera attributes through a simple USB interface and acquires camera frames at a constant frame rate up to 33 fps. To demonstrate the performance of our low-cost AT system, we report and discuss our experimental results on two high impact potential applications. The first set of experiments is conducted on a dental sample to investigate the clinical potential of the developed low-cost technology for detecting early dental caries, while the second set of experiments is conducted on the oral-fluid based lateral flow immunoassay to determine the viability of our technology for detecting and quantifying cannabis consumption at the point-of-care. Our results suggest achievement of reliable performance in the low-cost platform, comparable to those of costly and bulky research-grade systems, paving the way for translation of AT techniques to market.

Thermographic detection and quantification of THC in oral fluid at unprecedented low concentrations.

With recent changes in the legalization of cannabis around the world, there is an urgent need for rapid, yet sensitive, screening devices for testing drivers and employees under the influence of cannabis at the roadside and at the workplace, respectively. Oral fluid lateral flow immunoassays (LFAs) have recently been explored for such applications. While LFAs offer on-site, low-cost and rapid detection of tetrahydrocannabinol (THC), their nominal detection threshold is about 25 ng/ml, which is well above the 1-5 ng/ml per se limits set by regulations. In this paper, we report on the development of a thermo-photonic imaging system that utilizes the commercially available low-cost LFAs but offers detection of THC at unprecedented low concentrations. Our reader technology examines photothermal responses of gold nanoparticles (GNPs) in LFA through lock-in thermography (LIT). Our results (n = 300) suggest that the demodulation of localized surface plasmon resonance responses of GNPs captured by infrared cameras allows for detection of THC concentrations as low as 2 ng/ml with 96% accuracy. Quantification of THC concentration is also achievable with our technology through calibration.

Clinical Translation of Tethered Confocal Microscopy Capsule for Unsedated Diagnosis of Eosinophilic Esophagitis.

Esophagogastroduodenoscopy (EGD) is a widely used procedure, posing significant financial burden on both healthcare systems and patients. Moreover, EGD is time consuming, sometimes difficult to tolerate, and suffers from an imperfect diagnostic yield as the limited number of collected biopsies does not represent the whole organ. In this paper, we report on technological and clinical feasibility of a swallowable tethered endomicroscopy capsule, which is administered without sedation, to image large regions of esophageal and gastric mucosa at the cellular level. To demonstrate imaging capabilities, we conducted a human pilot study (n = 17) on Eosinophilic Esophagitis (EoE) patients and healthy volunteers from which representative cases are presented and discussed. Results indicate that, compared to endoscopic biopsy, unsedated tethered capsule endomicroscopy obtains orders of magnitude more cellular information while successfully resolving characteristic tissue microscopic features such as stratified squamous epithelium, lamina propria papillae, intraepithelial eosinophils, and gastric cardia and body/fundic mucosa epithelia. Based on the major import of whole organ, cellular-level microscopy to obviate sampling error and the clear cost and convenience advantages of unsedated procedure, we believe that this tool has the potential to become a simpler and more effective device for diagnosing and monitoring the therapeutic response of EoE and other esophageal diseases.

Comparative study on the detection of early dental caries using thermo-photonic lock-in imaging and optical coherence tomography.

Early detection of dental caries is known to be the key to the effectiveness of therapeutic and preventive approaches in dentistry. However, existing clinical detection techniques, such as radiographs, are not sufficiently sensitive to detect and monitor the progression of caries at early stages. As such, in recent years, several optics-based imaging modalities have been proposed for the early detection of caries. The majority of these techniques rely on the enhancement of light scattering in early carious lesions, while a few of them are based on the enhancement of light absorption at early caries sites. In this paper, we report on a systemic comparative study on the detection performances of optical coherence tomography (OCT) and thermophotonic lock-in imaging (TPLI) as representative early caries detection modalities based on light scattering and absorption, respectively. Through controlled demineralization studies on extracted human teeth and µCT validation experiments, several detection performance parameters of the two modalities such as detection threshold, sensitivity and specificity have been qualitatively analyzed and discussed. Our experiment results suggests that both modalities have sufficient sensitivity for the detection of well-developed early caries on occlusal and smooth surfaces; however, TPLI provides better sensitivity and detection threshold for detecting very early stages of caries formation, which is deemed to be critical for the effectiveness of therapeutic and preventive approaches in dentistry. Moreover, due to the more specific nature of the light absorption contrast mechanism over light scattering, TPLI exhibits better detection specificity, which results in less false positive readings and thus allows for the proper differentiation of early caries regions from the surrounding intact areas. The major shortcoming of TPLI is its inherent depth-integrated nature, prohibiting the production of depth-resolved/B-mode like images. The outcomes of this research justify the need for a light-absorption based imaging modality with the ability to produce tomographic and depth-resolved images, combining the key advantages of OCT and TPLI.