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- 2015
- Calibration process of OSL detectors
- Iodine-131
- OSL-BeO
- Dosimetry of staff and patients
- Optically Stimulated Luminescence (OSL)
- Akdeniz University
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The Calibration Process of OSL Detectors used for Staff and Patient Dosimetry in Hospital Environment
摘要： The optically stimulated luminescence (OSL-BeO) dosemeter is increasingly being used as a dosimetric technique in various fields such as medical dosimetry. According to our fixed dose protocol, the activities of 3.7-7.4 GBq I-131 source is used for thyroid carcinoma therapy. The in house calibration process for usage of OSL’s at hospital was arranged according to the encapsulated I-131. The measurement point was planned in three different radial distances from source free in air. The dose-rate measurement was done by Geiger-Muller (GM), and then three pieces of OSL was placed in the same positions for one hour. The inverse square law consistency was found (R2=0.99). The calibration coefficient was calculated. For determining the performance of OSL at different dose rates, it used for personnel and patient dosimetry. The average annual dose/2mon to the whole body for all staff by OSL were 0.80 mSv. After administration of 3.7 GBq (100 mCi) therapeutic dose to selected patients, the average pectoral dose was 97.5+32.6 mSv. This calibration process is helpful for confidence of OSL detectors used for dosimetry of staff and patients treated with high activity I-131.
关键词： Calibration process of OSL detectors,Iodine-131,OSL-BeO,Dosimetry of staff and patients,Optically Stimulated Luminescence (OSL)
更新于2025-09-04 15:30:14
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Securing Color Fidelity in 3D Architectural Heritage Scenarios
摘要： Ensuring color ?delity in image-based 3D modeling of heritage scenarios is nowadays still an open research matter. Image colors are important during the data processing as they affect algorithm outcomes, therefore their correct treatment, reduction and enhancement is fundamental. In this contribution, we present an automated solution developed to improve the radiometric quality of an image datasets and the performances of two main steps of the photogrammetric pipeline (camera orientation and dense image matching). The suggested solution aims to achieve a robust automatic color balance and exposure equalization, stability of the RGB-to-gray image conversion and faithful color appearance of a digitized artifact. The innovative aspects of the article are: complete automation, better color target detection, a MATLAB implementation of the ACR scripts created by Fraser and the use of a speci?c weighted polynomial regression. A series of tests are presented to demonstrate the ef?ciency of the developed methodology and to evaluate color accuracy (‘color characterization’).
关键词： structure for motion,photometric calibration,color management,color acquisition,photogrammetry,automation,color balance
更新于2025-09-04 15:30:14
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Calibration strategies for use of the nanoDot OSLD in CT applications
摘要： Aluminum oxide based optically stimulated luminescent dosimeters (OSLD) have been recognized as a useful dosimeter for measuring CT dose, particularly for patient dose measurements. Despite the increasing use of this dosimeter, appropriate dosimeter calibration techniques have not been established in the literature; while the manufacturer offers a calibration procedure, it is known to have relatively large uncertainties. The purpose of this work was to evaluate two clinical approaches for calibrating these dosimeters for CT applications, and to determine the uncertainty associated with measurements using these techniques. Three unique calibration procedures were used to calculate dose for a range of CT conditions using a commercially available OSLD and reader. The three calibration procedures included calibration (a) using the vendor‐provided method, (b) relative to a 120 kVp CT spectrum in air, and (c) relative to a megavoltage beam (implemented with 60Co). The dose measured using each of these approaches was compared to dose measured using a calibrated farmer‐type ion chamber. Finally, the uncertainty in the dose measured using each approach was determined. For the CT and megavoltage calibration methods, the dose measured using the OSLD nanoDot was within 5% of the dose measured using an ion chamber for a wide range of different CT scan parameters (80–140 kVp, and with measurements at a range of positions). When calibrated using the vendor‐recommended protocol, the OSLD measured doses were on average 15.5% lower than ion chamber doses. Two clinical calibration techniques have been evaluated and are presented in this work as alternatives to the vendor‐provided calibration approach. These techniques provide high precision for OSLD‐based measurements in a CT environment.
关键词： calibration,OSLD,dosimetry,CT
更新于2025-09-04 15:30:14
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Methods for Calibrating High-Resolution Optical Reflectometers Operating in the Frequency Domain
摘要： The operating principle of an optical high-resolution re?ectometer running in the frequency domain (OFDR re?ectometer) is examined. A mathematical model for measuring the parameters of ?ber-optic systems using an OFDR re?ectometer is presented. The accuracy characteristics of OFDR re?ectometers are analyzed and the instrument accuracy is estimated quantitatively. Methods for calibrating OFDR re?ectometers based on a distance scale are proposed and equipment for these methods is discussed.
关键词： calibration,OFDR re?ectometry,optical ?ber,re?ectometry,?ber optic systems
更新于2025-09-04 15:30:14
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Scalable heliostat calibration system (SHORT) - Calibrate a whole heliostat field in a single night
摘要： Efficient operation of a solar plant requires precise control of the solar field, in order to achieve the desired flux on the receiver. In order to do so, accurate knowledge about the relation between heliostat axis encoder values and the actual orientation of the reflective surface is essential. Such information is gained from heliostat calibration, making it an essential part of plant operation. Being able to perform such a calibration frequently allows maintaining high efficiency of the solar field, by compensating for drift or other deviations which can occur over time.Such a solution is imperative for using small sized heliostats, where the solar field potentially containstens or even hundreds of thousands of them.Even for whatever heliostat such a calibration allowsa more precise control on their aiming point leading to a better plant performance. The presented solution addresses this withan automatic procedure, which is able to calibrate a full solar field during one night by using cameras and artificial targets within the solar field. The method has been successfully tested at the Plataforma Solar de Almeria (PSA), showing that a beam accuracy of about 0.6 mrad can be achieved.
关键词： heliostat calibration,artificial targets,solar field,kinematic model,camera
更新于2025-09-04 15:30:14
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Comparison of on-wafer TRL calibration to ISS SOLT calibration with open-short de-embedding up to 500 GHz
摘要： Sub-mm circuit design requires accurate on-wafer characterization of passive and active devices. In industry, characterization of these devices is often performed with off-wafer SOLT calibration. In this work, validity of this characterization procedure above 110 GHz is investigated by an exhaustive study of on-wafer and alumina off-wafer calibration using measurement and electromagnetic (EM) simulation up to 500 GHz. The EM simulation is performed at two different levels, first at the intrinsic level of the devices under test for reference and afterward up to the probe level to simulate different standards used in the off-wafer calibration or in the on-wafer calibration in presence of the probe. Further, EM simulation data is calibrated with the same procedures and tools that is used in the measurement; therefore, it includes the probe-to-substrate coupling. In addition, precise EM model of a commercial impedance standard substrate (ISS) is developed and used to perform the SOLT calibration. A good agreement is observed between measurement and EM modelling for the off-wafer calibration as well as for the on-wafer calibration. Results clearly highlights a limitation of alumina off-wafer methodology above 200 GHz for characterization of Silicon based technologies. Finally a discussion is given on the pros and cons of the off-wafer and on-wafer methodologies.
关键词： probe station,calibration,S-parameter measurement,TRL,THz,SiGe HBT,on-wafer,500 GHz,SOLT
更新于2025-09-04 15:30:14
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A discontinuous Galerkin model for fluorescence loss in photobleaching of intracellular polyglutamine protein aggregates
摘要： Background: Intracellular phase separation and aggregation of proteins with extended poly-glutamine (polyQ) stretches are hallmarks of various age-associated neurodegenerative diseases. Progress in our understanding of such processes heavily relies on quantitative fluorescence imaging of suitably tagged proteins. Fluorescence loss in photobleaching (FLIP) is particularly well-suited to study the dynamics of protein aggregation in cellular models of Chorea Huntington and other polyQ diseases, as FLIP gives access to the full spatio-temporal profile of intensity changes in the cell geometry. In contrast to other methods, also dim aggregates become visible during time evolution of fluorescence loss in cellular compartments. However, methods for computational analysis of FLIP data are sparse, and transport models for estimation of transport and diffusion parameters from experimental FLIP sequences are missing. Results: In this paper, we present a computational method for analysis of FLIP imaging experiments of intracellular polyglutamine protein aggregates also called inclusion bodies (IBs). By this method, we can determine the diffusion constant and nuclear membrane transport coefficients of polyQ proteins as well as the exchange rates between aggregates and the cytoplasm. Our method is based on a reaction-diffusion multi-compartment model defined on a mesh obtained by segmentation of the cell images from the FLIP sequence. The discontinuous Galerkin (DG) method is used for numerical implementation of our model in FEniCS, which greatly reduces the computing time. The method is applied to representative experimental FLIP sequences, and consistent estimates of all transport parameters are obtained. Conclusions: By directly estimating the transport parameters from live-cell image sequences using our new computational FLIP approach surprisingly fast exchange dynamics of mutant Huntingtin between cytoplasm and dim IBs could be revealed. This is likely relevant also for other polyQ diseases. Thus, our method allows for quantifying protein dynamics at different stages of the protein aggregation process in cellular models of neurodegeneration.
关键词： FLIP,Computational method,Multi-compartment,Rate coefficient,Discontinuous Galerkin,Calibration,Protein aggregation
更新于2025-09-04 15:30:14
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Assignment of the Number of Equivalent Reference Fluorophores to Dyed Microspheres
摘要： A procedure will be described to assign to each dyed microsphere a number called the Equivalent number of Reference Fluorophores (ERF). The ERF unit gives the number of reference fluorophores in solution which produce the same fluorescence signal as a single dyed microsphere. In the first step, fluorescence measurements were carried out on serial dilutions of a solution of reference fluorophores. The resulting fluorescence intensities and the corresponding concentrations were used to calibrate the response of the fluorometer. The calibration consisted of establishing a linear relation between the intensities and concentrations. In the second step, the fluorescence intensity from a suspension of microspheres was measured in order to determine the equivalent concentration of reference fluorophores which gave the same fluorescence intensity as the suspension of microspheres. This was performed by utilizing the calibration line obtained in the first step. In the third step, a flow cytometer and a light obscuration apparatus were used to measure the total concentration of microspheres in the suspensions used for the fluorescence measurements. In addition to the total microsphere concentration, the flow cytometer also enabled the measurement of the concentration of a sub population of microspheres which are used to calibrate the fluorescence scale of a flow cytometer. The fourth step utilized the data collected in steps one, two, and three to assign a value of ERF to individual microspheres. The set of microspheres with assigned ERF values will be used to establish a linear fluorescence scale in each channel of a flow cytometer. The discussion will emphasize the estimate of uncertainties in each step of the assignment process.
关键词： fluorescence,concentration,calibration,ERF,microspheres,flow cytometer
更新于2025-09-04 15:30:14
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Rapid tracking of extrinsic projector parameters in fringe projection using machine learning
摘要： In this work, we propose to enable the angular re-orientation of a projector within a fringe projection system in real-time without the need for re-calibrating the system. The estimation of the extrinsic orientation parameters of the projector is performed using a convolutional neural network and images acquired from the camera in the setup. The convolutional neural network was trained to classify the azimuth and elevation angles of the projector approximated by a point source through shadow images of the measured object. The images used to train the neural network were generated through the use of CAD rendering, by simulating the illumination of the object model from di?erent directions and then rendering an image of its shadow. The accuracy to which the azimuth and elevation angles are estimated is within 1 classi?cation bin, where 1 bin is designated as a ± 10° patch of the illumination dome. To evaluate use of the proposed system in fringe projection, a pyramidal additively manufactured object was measured. The point clouds generated using the proposed method were compared to those obtained by an established fringe projection calibration method. The maximum dimensional error in the point cloud generated when using the convolutional network as compared to the established calibration method for the object measured was found to be 1.05 mm on average.
关键词： real-time tracking,convolutional neural network,fringe projection,machine learning,projector calibration
更新于2025-09-04 15:30:14
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A two-step calibration method of lenslet-based light field cameras
摘要： The calibration of lenslet-based light field camera is the key issue to many applications, especially the three-dimensional shape measurement. In this paper, a two-step physically based calibration method is proposed, where every parameter is described with its own physical meaning. The parameters about the main lens of the light field camera are calibrated with the central sub-aperture image, and the parameters about the micro-lens array are calibrated with the epipolar images, subsequently. To improve the calibration result, the distortion correction of the main lens and a nonlinear optimization method are applied also. The calibration method is validated with a commercially available light field camera and compared to Dansereau’s calibration method. Typical RMS reprojection errors are 0.0017, 0.0032 mm for 30.0, 35.1 mm calibration grids.
关键词： Micro-lens array,Light field camera,Light field,Calibration,Main lens
更新于2025-09-04 15:30:14