Photosensitizer is a key element of photodynamic therapy (PDT). Currently, only limited numbers of photosensitizers are available for antitumor PDT in China. YLG-1 (Ang-Da-Fen-Qi) is a newly developed second-generation chlorin-type photosensitizer. In this preliminary study, the killing effect of combination of YLG-1 and 652 nm diode laser on human nasopharyngeal carcinoma cells and human ovarian cancer cells were investigated. In vitrostudy suggests that YLG-1 mediated PDT activity has strong cancer cell killing effect and therefore potentials for antitumor PDT applications.
Hemporfin is asecond generation photosensitizerand has been used in combination with laser and LED to treat vascular and cancerousdiseases in China. In this study, four different light sources were evaluated for Hemoporfin PDT. Photobleaching experiments were carried out by exposing Hemoporfin solution to green diode laser, red diode laser, green LED, and red LED, respectively, under the same power density (30 mW/cm2) for different lengths of time. Hemoporfin fluorescence was measured before and after light exposure. Photobleaching kinetics showed the order of greenlaser > green LED > red laser> red LED. This study suggests that all tested light sources could be used for Hemoporfin PDTbut the power density and exposure time of different light sources need to be adjusted in order to achieve the same levels of photodynamic effect.
Optical coherence tomography (OCT) is a useful non-invasive optical tool for imaging various biological tissues. As OCT imaging is based on interferometry, speckle noises are inherent and can degrade the quality of OCT image. The objective of this study was to evaluate the effectiveness of conventional denoising algorithms for OCT image denoising and for improving image quality. OCT images of human skin were obtained from a swept source OCT of 1300 nm. Three image denoising algorithms, including median filtering, mean filtering and Gaussian bilateral filtering, were applied for denoising OCT images of different quality. Five quality evaluation criteria, including signal to noise ratio (SNR), equivalent number of looks (ENL), contrast-to-noise ratio (CNR), cross correlation (XCOR), and peak signal to noise ratio (PSNR) were used for comparing the effectiveness of each denoising process. In terms of improving local contrast, three denoising algorithms showed similar effect. In terms of the equivalent views, Gaussian bilateral filtering algorithm showed the most significant increase and therefore caused certain degrees of blurry. For signal to noise ratio, all three denoising algorithms showed improvement while Gaussian bilateral filtering algorithm had better protection effect of the effective information and edge of the original image. Gaussian bilateral filtering algorithm provides better denoising outcomes for OCT image processing.
In situ quantification of photosensitizer is critical in photodynamic therapy (PDT) and photodiagnosis (PD). Fluorescence detection is a feasible approach for the quantification of fluorescent photosensitizer. However, due to the interference of tissue absorption and scattering on the fluorescence spectrum of photosensitizer, it is still challenging to perform in situ fluorescence quantification. In this preliminary study, a Monte Carlo (MC)-based method was used to simulate the fluorescence spectrum and diffuse reflection spectrum of different biological tissues. A calibration algorithm was developed for the correction of the influence of tissue absorption and scattering on protoporphyrin IX (PpIX) fluorescence. Under the excitation of blue light of 405 nm the dispersion coefficient of the original PpIX fluorescence spectrum of the soft tissue phantoms was 28%, which was reduced to 3% after the correction using the calibration algorithm. Under the excitation of red light of 635 nm, the dispersion coefficient of the original PpIX fluorescence spectrum of the soft tissue phantoms was 25%, which was reduced to 1.5% after the correction using the calibration algorithm. The results show that the MC-based method can effectively improve the accuracy of PpIX fluorescence measurement.
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