Introduction: Imaging technologies have been developed to assist physicians and dentists in detecting various diseases. Photoacoustic imaging (PAI) is a new technique that shows great applicability to soft tissues. This study aimed to investigate the effect of diode laser intensity modulation on photoacoustic (PA) image quality. Methods: The prototype of the PAI system in this study utilized a non-ionizing 532 nm continuouswave (CW) diode laser illumination. Samples in this study were oral soft tissues of Sprague-Dawley rats fixed in 10% formalin solution. PA images were taken ex vivo by using the PAI system. The laser exposure for oral soft tissue imaging was set in various duty cycles (16%, 24%, 31%, 39%, and 47%). The samples were embedded in paraffin, and PA images were taken from the paraffinembedded tissue blocks in a similar method by using duty cycles of 40%, 45%, 50%, 55%, 60% respectively to reveal the influence of the laser duty cycle on PA image quality. Results: The oral soft tissue is clearly shown as a yellow to red area in PA images, whereas the nonbiological material appears as a blue background. The color of the PA image is determined by the PA intensity. Hence, the PA intensity of oral soft tissue was generally higher than that of the nonbiological material around it. The Kruskal-Wallis test followed by Mann-Whitney post-hoc analysis revealed significant differences (P < 0.05) in the quality of PA images produced by using a 16%-47% duty cycle of laser intensity modulation for direct imaging of oral soft tissue fixed in 10% formalin solution. The PA image quality of paraffin-embedded tissue was higher than that of direct oral soft tissue images, but no significant differences in PA image quality were found between the groups. Conclusion:The PAI system built in this study can image oral soft tissue. The sample preparation and the diode laser intensity modulation may influence the PA image quality for oral soft tissue imaging. Nonetheless, the influence of diode laser intensity modulation is not significant for the PA image quality of paraffin-embedded tissue.
Corrosion process might occur over or beneath the surface of a material. Under-the-surface corrosion is more dangerous than other types as it is visually hidden. This research develops an imaging system to detect crevices resulting from subsurface corrosion. The system is built with a laser-generated acoustic (LGA) method, -using photoacoustic phenomena to generate acoustic waves from a laser and material interaction process, to construct a subsurface image of a metal. Though optical actuator is used, deeper penetration is achieved in the acoustic wave sensing, causing a change of intensity of the waves as they pass corrosion crevices. Measurement of the acoustic wave's intensity is used to construct LGA image illustrating the subsurface condition of an object. There are three main components of the device, which are a laser, a microphone and a data processor. The laser beam is modulated and exposed to an object to create thermal contraction. The microphone records acoustic waves generated in the process and the data processor analyses the result. Comprehensive measurement is done over the entire surface of the object to create 2-dimensional images. This research reports an experimental result of the imaging system on an object with subsurface corrosion crevices. LGA's images produced showed reasonably clear evolution process of the corrosion. In the experiment, the crevices emerge at 230µm depth were detected in the first 5 hours of the corrosion process. An advance analysis showed that the LGA images produced were able to show the evolution process of the shape of the crevices during corrosion. A mathematical model, based on acoustic transmission intensity equation, is designed to further examine the LGA image resulting in a curve which fits the measurement result with MAPE 12% difference.
Introduction: After caries, periodontal tissue inflammation (periodontitis) is the most common oral health problem. Photoacoustic imaging (PAI) is a new technique that uses simple components such as a diode laser and a condenser microphone. This study aimed to evaluate the performance of a simple PAI system in periodontal disease imaging by using an animal model. Methods: Normal periodontal and periodontitis tissues were obtained from Sprague–Dawley rats categorized as the control group, treatment group 1 (7 days of periodontitis induction), treatment group 2 (11 days of periodontitis induction), and treatment group 3 (14 days of periodontitis induction). The PAI system was controlled by LabVIEW and Arduino IDE software from a personal computer. Results: Results revealed that the optimal frequency of laser modulation for periodontal tissue imaging was 19 kHz with a duty cycle of 50%. The photoacoustic (PA) intensity of periodontal tissues was −68.71 dB for treatment group 3, −70.34 dB for treatment group 2, −71.69 dB for treatment group 1, and −73.07 dB for the control group. PA image analysis showed that the PA intensity from periodontal disease groups was higher than the control group. Conclusion: This study indicates the feasibility of using a simple PAI system to differentiate normal periodontal tissues from periodontitis tissues.
Background: Hidden caries is a type of tooth decay that is difficult to identify through visual diagnosis because teeth with hidden caries appear normal on the tooth surface but are damaged underneath. Methods: A photoacoustic imaging system based on visible light using a diode laser with a wavelength of 532 nm was developed to detect hidden caries in teeth. Results:The results indicate that the average of acoustic intensity level for healthy teeth is −74.2 ± 0.1 dB, and the average of acoustic intensity range for teeth with hidden caries is −81.2 ± 0.5 dB. The intensity level for the caries area varies depending on the severity of caries. Conclusion:Based on the acoustic intensity level measured by the interaction of teeth with laser light, the photoacoustic imaging system in the study can accurately detect the presence of hidden caries and recognize the difference between caries teeth and healthy teeth. This research can be developed into a prototype of a simple device that makes it easy to operate in dental practice.
Selectivity improvement of gas sensor based on Poly(3,4-<i>ethylenedioxythiophene</i>):<i>poly</i>(<i>styrenesulfonate</i>) (PEDOT:PSS) thin film to ammonia gas has been studied. The PEDOT:PSS thin films were deposited on glass and FR4 substrates by using a spin-coating technique. PEDOT:PSS solution was spread on the substrate followed by spinning at fixed rate. Then, the imprinting process of gas sensor was performed by injecting ammonia gas into the spin-coating chamber. Finally, the gas sensor was dried on a controllable hot plate. Current-voltage characteristics of the films were measured by using calibrated electrometer. The results show that by imprinting of ammonia gas to the film affects the electrical conductivity of the film. It is also shown that the electron transport in the PEDOT:PSS thin film tends to be ohmic-contact. When the imprinted sensor is exposed in ammonia gas, we obtained that the sensor has short response and recovery time, a good repeatability (reversible), and higher sensitivity to ammonia gas. To this end, we found that ammonia imprinting on the surface of PEDOT:PSS thin film can improve the selectivity of the sensor to ammonia gas. It indicates that our method can be used for fabricating the sensor which has a single selectivity
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