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- 2019
- Distributed optical fiber sensing
- Optical frequency domain reflection
- Polynomial regression algorithm
- Nonlinear tuning compensation
- Optoelectronic Information Science and Engineering
- Hebei University of Technology
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Assessment of UVA-Riboflavin Corneal Cross-Linking Using Small Amplitude Oscillatory Shear Measurements
摘要： The effect of ultraviolet (UV)–riboflavin cross-linking (CXL) has been measured primarily using the strip extensometry technique. We propose a simple and reliable methodology for the assessment of CXL treatment by using an established rheologic protocol based on small amplitude oscillatory shear (SAOS) measurements. It provides information on the average cross-link density and the elastic modulus of treated cornea samples. METHODS. Three fresh postmortem porcine corneas were used to study the feasibility of the technique, one serving as control and two receiving corneal collagen cross-linking treatment. Subsequently, five pairs of fresh postmortem porcine corneas received corneal collagen cross-linking treatment with riboflavin and UVA-irradiation (370 nm; irradiance of 3 mW/cm2) for 30 minutes (Dresden protocol); the contralateral porcine corneas were used as control samples. After the treatment, the linear viscoelastic moduli of the corneal samples were measured using SAOS measurements and the average cross-linking densities extracted. RESULTS. For all cases investigated, the dynamic moduli of the cross-linked corneas were higher compared to those of the corresponding control samples. The increase of the elastic modulus of the treated samples was between 122% and 1750%. The difference was statistically significant for all tested samples (P ? 0.018, 2-tailed t-test). CONCLUSIONS. We report a simple and accurate methodology for quantifying the effects of cross-linking on porcine corneas treated with the Dresden protocol by means of SAOS measurements in the linear regime. The measured dynamic moduli, elastic and viscous modulus, represent the energy storage and energy dissipation, respectively. Hence, they provide a means to assess the changing physical properties of the cross-linked collagen networks after CXL treatment.
关键词： small amplitude oscillatory shear measurements,linear viscoelasticity,elastic modulus,rheology,cross-link density,corneal collagen cross-linking
更新于2025-09-04 15:30:14
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Normalized power propagation on 1x6 fiber coupler
摘要： The simulation of normalized power propagation on interaction region of 1x6 monolithic fiber coupler is reported. Power distribution on fiber couplers is much affected by arrangement of fibers. The theoretical model has been used to calculate power coupling propagation on linear and pentagonal arrangement of 1x6 fiber coupler. The calculation is based on a matrix transfer which is the solution of coupled-mode theory. The six parallel fiber is in linear array and pentagonal placement. By launching input power to single input of 1x6 monolithic fiber couplers for both configurations, power distribution shows how the initial power is distributed to the others. It is found that linear configuration cannot initiate its power to the initial fiber, and maximum peak is not periodically such as power propagation on 1x2 and 1x3 fiber coupler. By changing the arrangement to be a pentagonal and one fiber as in the center where input power is launched, the input power will be distributed identically from the center to five surrounding fibers. At certain coupling length, about 4.7 mm and 6.3 mm, six fibers with pentagonal configuration will have identical output power for wavelength input 1550 and 1310 nm respectively. Based on this distribution, 1x6 monolithic fiber couplers are applicable as a power divider.
关键词： linear and pentagonal configurations,1x6 monolithic fiber couplers,power propagation
更新于2025-09-04 15:30:14
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Feasibility Study of Patient Specific Quality Assurance Using Transit Dosimetry Based on Measurement with an Electronic Portal Imaging Device
摘要： This study was designed to measure transit dose with an electronic portal imaging device (EPID) in eight patients treated with intensity modulated radiotherapy (IMRT), and to verify the accuracy of dose delivery to patients. The calculated dose map of the treatment planning system (TPS) was compared with the EPID based dose measured on the same plane with a gamma index method. The plan for each patient was verified prior to treatment with a diode array (MapCHECK) and portal dose image prediction (PDIP). To simulate possible patient positioning errors during treatment, outcomes were evaluated after an anthropomorphic phantom was displaced 5 and 10 mm in various directions. Based on 3%/3 mm criteria, the mean±SD passing rates of MapCHECK, PDIP (pre-treatment QA) for 47 IMRT were 99.8±0.1%, 99.0±0.7%, and, respectively. Besides, passing rates using transit dosimetry was 90.0±1.5% for the same condition. Setup errors of 5 and 10 mm reduced the mean passing rates by 1.3% and 3.0% (inferior to superior), 2.2% and 4.3% (superior to inferior), 5.9% and 10.9% (left to right), and 8.9% and 16.3% (right to left), respectively. These findings suggest that the transit dose-based IMRT verification method using EPID, in which the transit dose from patients is compared with the dose map calculated from the TPS, may be useful in verifying various errors including setup and/or patient positioning error, inhomogeneity and target motions.
关键词： Linear accelerator,Transit dose,Gamma index,EPID
更新于2025-09-04 15:30:14