Marine instruments deployed in seawater inevitably experience biofouling, which severely reduces their service life and hinders ocean monitoring. Marine biofouling greatly affects the service life of marine optical instruments and thus has a detrimental impact on ocean monitoring. The fouling community exhibits an attachment succession phenomenon. Macroscopic fouling organisms have adherent and stubborn attachments, whereas microorganisms during early fouling stages are easy to remove, but excessive cleaning also greatly increases energy consumption. Therefore, monitoring biofouling and selecting appropriate removal timing is critical. Due to the complex and dynamic nature of the marine environment, in-situ detection of microbial fouling on optical window of marine optical instrument is challenging because of many factors such as target characteristics, seawater turbidity, light refraction and scattering. Currently, there are no mature technologies available for in-situ fouling detection so as to remove timely micro fouling. To solve this problem, this study deployed thin poly methyl methacrylate (PMMA) coupons within the coastal seawaters of Qingdao, followed by in-situ mapping of photoacoustic signals using a self-built excitation and detection platform, along with along with of transmittance spectrum analysis on fouled PMMA thin films using PerkinElmer LAMBDA750. By combining results from both techniques with microscopic morphology analysis, we explored the relationship between microbial fouling and photoacoustic signal. The research results will provide a novel approach and technical basis for in-situ detection and timely clearance of microbial fouling on optical windows of marine optical instruments.
Accurate measurement of photosensitizer concentration in real-time in vivo bladder tissue was beneficial for improving the effectiveness of photodynamic therapy and achieving precise treatment of bladder tumor. In this paper, the potential ability of a transurethral photoacoustic imaging technique in visualizing and monitoring the photosensitizer concentration in the photodynamic therapy of bladder was evaluated. A bladder tissue optical model was established, and 3D Monte Carlo light transport method was coupled to calculate the photoacoustic signal. Photoacoustic signals in different photosensitizer concentrations were recorded. Results illustrated that a clear linearity between the photoacoustic signal intensity and photosensitizer concentration can be observed. It revealed that the proposed transurethral photoacoustic imaging technique has the potential to estimate in vivo photosensitizer concentrations and to guide laser-induced photodynamic therapy of bladder tumor.
In recent years, photoacoustic imaging has become a new non-destructive medical imaging technology. In this paper, a photoacoustic imaging technology for human bladder cancer was proposed, which combined transurethral endoscopic photoacoustic excitation in bladder cavity with a transrectal photoacoustic signal detection. By establishing a three-dimensional( 3D) optical model of bladder tissue, the distribution of light energy deposition in the bladder tissue was obtained through the 3D Monte Carlo method. The velocity potential was used to calculate the photoacoustic signal, and the scanning photoacoustic image of bladder tissue was reconstructed. The results showed that the proposed photoacoustic imaging technique with transurethral photoacoustic excitation in bladder cavity was expected to detect early bladder cancer nondestructively.
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