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.
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.
Early studies suggest that some PDT photosensitizers can be used as sonosensitizer for sonodynamic therapy (SDT). In this study, sonodynamic effects of a novel water soluble chlorin YLG-1 were evaluated. SDT of YLG-1 solution was carried out using an ultrasound transducer of 450 KHz at 2.0 W/cm2 for 0 – 600 s. Comparison of spectroscopic profiles of YLG-1 before and after SDT demonstrated that sonification could cause the reduction of YLG-1 absorbance and fluorescence emission but did not cause obvious change of the Raman spectrum. No significant by-products were identified from spectroscopic study. Nevertheless, this study demonstrated that the sonification mediated sensitizer fluorescence bleaching effect could be partially blocked by the addition of NaN3, which suggests a possible involvement of singlet oxygen in the process of sonification of YLG-1 compound.
KEYWORDS: Photodynamic therapy, Digital photography, Skin, Photography, RGB color model, Quantitative analysis, Software development, Color difference, Light sources and illumination
Portwine stain (PWS) birthmarks are congenital vascular malformations of the skin. Pulse dye laser (PDL) is current treatment option for PWS. As a possible alternative, vascular targeting photodynamic therapy (PDT) is currently under formal clinical trials for the treatment of PWS in China. Color blanching is an important indicator of treatment effectiveness. There is a need to develop an objective and quantitative color analysis system for the evaluation of PWS color before and after PDT treatment.In this study, the CIE L*a*b* color space coordinate was used to quantify skin and PWS coloron digital color photos.A custom-made multi-color template (PWS Color Card) for the accurate color correction of digital photos. Hardware and software were developed and tested for quantitative PWS color and size analyses before and after PDT treatment. Results suggest that PWS color, its color blanching and treatment efficacy in PDT treatment can be quantitatively analyzed using digital photos in conjunction with suitable color analysis and color correction algorithm.
Optical coherence tomography (OCT) technology can be used to obtain high resolution cross sectional image of living biological tissues. Early study suggested that some tissue optical properties could also be measured using OCT. In this study, OCT was used to measure the total attenuation coefficient of living kidney of rat and dog models. Results suggested that the total attenuation coefficient of the superficial cortex layer could by derived from a single scattering model. The total attenuation coefficient could be affected by ischemia.
Optical coherence tomography (OCT) is an imaging technology which can be used to obtain the high resolution cross sectional image of living biological tissues. It has been used to evaluate the structure and function of animal and human kidneys. Preliminary animal and human data suggest that OCT imaging might be a useful non-invasive tool for characterizing renal tubular lumens, such as the opening status of tubular lumens. In this pilot study, living animal kidneys (dog, rat and mouse) were imaged using a swept source OCT (SS OCT) or spectral domain OCT(SD OCT). In vivo imaging scans were carried out using an OCT microscope setup (5×) and by placing the imaging probe above the surface of the living kidney. Semi-quantitative analysis of the OCT images was performed to evaluate the density of the kidney tubules on the surface layer of the cortex. In addition, histological images of the kidneys were restructured to form nephron three-dimensional structure for comparison with the 3D OCT imaging. This study suggests that quantitative OCT imaging might be useful for visualizing the fine structure of the living kidney and determining the density of renal tubules.
Optical coherence tomography (OCT) is a useful optical biopsy tool. Its potential in the evaluation of living kidney has been demonstrated. One of such applications is to predict the acute tubular necrosis (ATN) associated with kidney transplantation. The light dense and lucent regions seen in 2D OCT scanning are considered as a useful marker of the renal tubules. In this study, the OCT examination of living human kidney was carried out using a swept source (SS) OCT (SS-OCT) system. The light lucent regions in the cortex obtained on the OCT scan were defined as low signal cavities. The structure features of characteristic cavities in 2D and simulated 3D OCT images were quantitatively analyzed using Amira and Matlab programs. Although the imaging acquisition and real-time analysis were feasible for the examination of donor kidney before and after the transplantation, as the imaging acquisition was obtained under the hand-hold fashion, OCT images might become blurred and the tubules became hardly distinguishable from cortex background, especially for 3D images. In order to optimize the scanning parameters of the OCT imaging process, the influence of the jittering of the living kidney on the quality of OCT imaging and the distortion of the renal tubule structure were studied.
Some of the key optical properties of a new water soluble chlorine (YLG-1) were evaluated. The sensitizer has a strong absorption at 398 nm and 655 nm in DMSO. A strong red fluorescence is detected under the excitation of 398 nm. The fluorescence life time is approximately 5 ns and fluorescence quantum yield 20%. The sensitizer does not accumulate in normal skin after topical use or IV injection. Preliminary in vivo results suggest that this novel chlorine causes little cutaneous phototoxicity. Its potentials in photodynamic therapy (PDT) deserve further study.
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