Background: Mouse model is a unique tool for preclinical evaluation of photosensitizing drugs for their potential applications in photodynamic therapy (PDT). The fluorescent property of photosensitizer provides a useful means for in situ measurement of photosensitizer distribution. However, the autofluorescence of mouse tissues might potentially affect in situ photosensitizer fluorescence measurement. Objectives: The aim of this study was to evaluate the autofluorescence in lab mice and its influence on the in situ measurement of photosensitizer fluorescence. Materials and Materials and methods: ICR mice, commonly used lab animal model, were used. Mice were fed with regular diet and clean water. Domestically produced photosensitizing drug Hemoporfin® was used as a model sensitizer. Costume-built fluorescence imaging and spectroscope systems were used for fluorescence examination under the excitation wavelength of 400 ± 5 nm, generated from a laser or LED panel. In situ fluorescence was examined before and after i.v. injection of Hemoporfin®. Results: Epifluorescence imaging examination showed yellowish and reddish autofluorescence fluorescence in the mouth, nose, paws and tail areas. The absorption and emission spectra of mouse tissue overlaid to some degrees with that of Hemoporfin®. In situ fluorescence examination of ICR mice showed significant influence of autofluorescence on the spectral and intensity measurement of Hemoporfin® fluorescence. Such influence might be eliminated by post-measurement spectral correction algorithms. Conclusions: The autofluorescence in mouse tissues poses a significant influence on the in situ measurement of fluorescence emission of Hemoporfin®. Careful postmeasurement spectral correction is needed for accurately measuring photosensitizer fluorescence.
Background: Singlet oxygen (1O2) is a key therapeutic molecule in photodynamic therapy (PDT). Quantitation of 1O2 luminescence is important for monitoring and optimizing PDT process. Objective: The aim of this study was to evaluate a custom-built superconducting strip single photon detector (SSPD)-based time-resolved photon counting system for 1O2 luminescence detection. Materials and Methods: The wavelength responses of optical collection system were verified by a spectrum analyzer. A dual-channel signal generator simulates pulsed signals of different frequencies were used to verify the circuit system. 1O2 luminescence generated by the photoexcitation of Rose Bengal solution was examined. Results: The 1O2 detection system could transmit photons of 1270 nm and the time-resolved system showed the response down to the nanosecond range and was capable of converting the different time responses into a square wave signal. When 10 μM aqueous and methanolic RB solutions were excited with a 20 mW 532 nm laser the measured 1O2 lifetimes were 2.93±0.37 μs and 9.45±0.83 μs, respectively. At the same concentration, when the excitation power increased the number of singlet oxygen produced per unit of time also increased. Conclusions: The custom-built SSPD-based 1O2 detection system provides a reliable and sensitive means for the quantitation of 1O2 luminescence generated from PDT process.
Background and objectives: Dermatoscope is an important optical tool for dermatologists. Its illumination system is a key component for high quality visual observation and digital photography. The aim of this study was to evaluate the illumination system of a high-end handhold dermatoscope. Materials and Methods: DermLite DL5 was used for this study. The dermatoscope equipped with sophisticated illumination system for visualization under white, yellow and ultraviolet (UV) light with or without the use of polarization. A fiber optic spectrometer was used to measure the spectra of each lighting mode. A handhold spectrometer was used to measure the color temperature, luminance and chromatic aberration of various lighting conditions under non-polarized, cross-polarized and parallel-polarized modes. The uniformity of each lighting condition was analyzed by pixel analysis of projected digital images. Results: The peak wavelength of the UV LEDs was 377 nm and the full width at half maximum (FWHM) was 21.27 nm. The peak wavelength of the yellow LEDs was 591 nm and the FWHM was 15.5 nm. The color temperature of white LEDs was over 9000 k in several modes, whereas the color temperature of the yellow LEDs varied widely and the color temperature of mixed lighting remained stable at 5000 k. The uniformity of white, yellow and mixed lighting was less than ±10%. Conclusions: The designed higher color temperature of the tested handhold dermatoscope can accommodate the physician's view of skin blood vessels. Good uniformity under different lighting and viewing modes not only satisfies the human eye but also ensure the high quality of dermatoscope digital image of the skin.
Background: Quantitative measurement of photosensitizer during photodynamic therapy (PDT) is critical. One of the practical approaches is to measure photosensitizer’s fluorescence, however, the influence of tissue optic properties needs to be considered in in situ measurement. Objective: To design and validate a combined system for dual detection of fluorescence and tissue diffuse reflectance. Materials and Method: For fluorescence detection, a 405 nm laser was used for excitation, a power meter for monitoring laser power and a fiber optic spectrometer for recording fluorescence. For diffuse reflectance measurement, a halogen lamp was used as light source and a fiber optic spectrometer for recording diffuse reflectance. Hemoporfin (HMME) was used as a model photosensitizer. Mice were used to evaluate the dual detection function of fluorescence and tissue diffuse reflectance after i.v. injection of HMME. Results: Solutions of different concentrations of HMME were used to test the intensity responses of the fluorescence detection system. A linear correlation was observed at HMME concentration lower than 10 μg/ml. Dual-band correction using corresponding diffuse reflectance data was used for the correction of original fluorescence spectrum. Diffuse reflectance corrected fluorescence data might truly reflect HMME concentration in the skin tissue. Conclusion: The preliminary evaluation suggests that the combined system can be used for quantitative measurement of photosensitizer fluorescence.
Background: Superconducting strip photon detector (SSPD) have been applied to monitor singlet oxygen ( 1O2) luminescence produced during photodynamic therapy (PDT) due to its high detection efficiency, low dark count and fast detection speed. Objective: This study calibrate of the detection efficiency and dark counts of a new SSPD system for singlet oxygen luminescence detection. Materials and Method: The input photons that passing through the attenuator, polarization controller and optical fiber were carefully controlled so that the average photon arrival-time interval was much larger than the response time of SSPD detector. The electrical signals generated from SSPD detector were collected after passing through a low-noise amplifier and analyzed using data acquisition card. Bias current started at 10 μA and increased by 1 μA step until saturation. The electrical signal pulses were recorded. The detection efficiency was determined by the ratio of the electrical signal pulse count minus the dark count to the number of photons input to the detector. Dark counts were measured by adjusting the bias current with the light input channel completely closed and in a dark environment. The experimental temperature was controlled at 2.2 K. Result: The best detection efficiency was achieved when the bias current was 23 μA with the input photon power of -107.6 dBm. The detection efficiency was 88% and 90% for two tested detectors with the optimized polarization. The dark count rate was less than 100 cps. Conclusions: This study demonstrated that the optimization of attenuator, polarization controller and bias current can improve the detection efficiency of SSPD system for singlet oxygen detection.
Dermoscopy is a useful tool for observing the vascular profile of port-wine stain (PWS) birthmarks. However, due to the complicity of the vascular profile, there is a lack of consensus on the classification of dermoscopic features of PWS vessels. This study investigated the potentials of deep learning-assisted methods in the classification of dermoscopy image-based of PWS vascular profiles. The classified images were used as training samples, and the RegNet network with better classification effect was selected to establish the migration learning method. The results showed that the accuracy of the RegNet network on the validation set was 82.63%. The preliminary study suggests that deep learning assisted PWS vascular contour type classification is feasible.
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