model calibration Dotaz Zobrazit nápovědu
In the previous paper [11], a method for geometrical and transducer-time-delay auto-calibration of an ultrasonic computed tomography (USCT) system has been described, aiming at calibration of individual ultrasonic (US) transducer positions. The present contribution describes a novel modification of the method utilizing the particular USCT system concept: the exactly known spatial relations among transducers grouped in each of the transducer array systems (TASes). The algorithms used for the calibration remain based on the principles similar to the global positioning system (GPS) navigation, however, the positions and orientations of complete TASes are calibrated, rather than individual positions of transducers. This way, the number of unknowns is substantially reduced while the number of available equations remains unchanged. Consequently, a solution substantially more robust with respect to measurement noise can be obtained based on this highly overdetermined equation system. The method is capable of calibrating the individual positions of all ultrasonic transducers via their positions in TASes as well as their individual time delays at once during sc. empty measurement, without a need for any particular arrangements, e.g. calibration phantoms.
The paper deals with the physical skull phantoms Bundesinstitut fuer Strahlenschutz and BPAM-001, which are used in order to calibrate in vivo detection systems for estimation of (241)Am activity in the skeleton. Their voxel models were made and used in the Monte Carlo simulations. The results of the simulation were compared with measurements and reasonable agreement was observed. Several aspects such as materials and source distributions used in the models were discussed.
- MeSH
- aktinoidy analýza MeSH
- fantomy radiodiagnostické normy MeSH
- kalibrace MeSH
- kosti a kostní tkáň metabolismus MeSH
- lebka MeSH
- lidé MeSH
- metoda Monte Carlo MeSH
- počítačová rentgenová tomografie metody MeSH
- počítačová simulace MeSH
- počítačové zpracování obrazu MeSH
- radiometrie přístrojové vybavení metody MeSH
- software MeSH
- teoretické modely MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Two video sequences of hand motion are analyzed using passive markers for medical diagnostic purposes. Th e correct detection of the marker's position is essential for the next motion evaluation step. GretagMacbeth ColorChecker chart is used for color correction of the video sequences, compensation of diff erent contrast, and brightness conditions during the motion recording. Diff erent color calibration methods were compared based on linear, and cubic Hermite functions, and the multiple linear regression model. Th eir effi ciencies were evaluated from the movement analysis point of view. Th e best results were achieved with multiple linear regression model.
- MeSH
- audiovizuální záznam metody normy využití MeSH
- barva MeSH
- diagnostické techniky a postupy využití MeSH
- diagnostické zobrazování metody přístrojové vybavení využití MeSH
- financování organizované MeSH
- lidé MeSH
- lineární modely MeSH
- počítačové zpracování obrazu metody přístrojové vybavení využití MeSH
- pohyb fyziologie MeSH
- regresní analýza MeSH
- ruka fyziologie MeSH
- teoretické modely MeSH
- Check Tag
- lidé MeSH
A comparison of calibration results and procedures in terms of air kerma length product, PKL, and air kerma, K, was conducted between eight dosimetry laboratories. A pencil-type ionization chamber (IC), generally used for computed tomography dose measurements, was calibrated according to three calibration methods, while its residual signal and other characteristics (sensitivity profile, active length) were assessed. The results showed that the "partial irradiation method" is the preferred method for the pencil-type IC calibration in terms of PKL and it could be applied by the calibration laboratories successfully. Most of the participating laboratories achieved high level of agreement (>99%) for both dosimetry quantities (PKL and K). Estimated relative standard uncertainties of comparison results vary among laboratories from 0.34% to 2.32% depending on the quantity, beam quality and calibration method applied. Detailed analysis of the assigned uncertainties have been presented and discussed.
- MeSH
- dávka záření MeSH
- ionty * MeSH
- kalibrace MeSH
- laboratoře normy MeSH
- mezinárodní spolupráce MeSH
- odchylka pozorovatele MeSH
- počítačová rentgenová tomografie metody MeSH
- radiometrie metody MeSH
- reprodukovatelnost výsledků MeSH
- statistické modely MeSH
- vzduch MeSH
- Publikační typ
- časopisecké články MeSH
- srovnávací studie MeSH
- Geografické názvy
- Evropa MeSH
In nuclear facilities stack monitors are used for the measurement of the volumetric activity of noble gases. Spectrometric measurement is needed because the content of stack effluents is always a mixture of radionuclides. In some nuclear power plants new types of monitors were installed based on HPGe detectors. For efficiency calibration a standard with the radionuclide Xe-127 was developed and calibration curve constructed in the energy range 81 keV-1293 keV. Experiental efficiencies were checked using an MC model.
- MeSH
- analýza selhání vybavení MeSH
- dávka záření MeSH
- design vybavení MeSH
- internacionalita MeSH
- jaderné elektrárny přístrojové vybavení normy MeSH
- kalibrace MeSH
- poločas MeSH
- radioaktivní látky znečišťující vzduch analýza MeSH
- radiometrie přístrojové vybavení normy MeSH
- referenční hodnoty MeSH
- referenční standardy MeSH
- vzácné plyny analýza MeSH
- Publikační typ
- časopisecké články MeSH
PURPOSE: The aim of this study was to develop a simple, robust, and easy-to-use calibration procedure for correcting misalignments in rosette MRI k-space sampling, with the objective of producing images with minimal artifacts. METHODS: Quick automatic calibration scans were proposed for the beginning of the measurement to collect information on the time course of the rosette acquisition trajectory. A two-parameter model was devised to match the measured time-varying readout gradient delays and approximate the actual rosette sampling trajectory. The proposed calibration approach was implemented, and performance assessment was conducted on both phantoms and human subjects. RESULTS: The fidelity of phantom and in vivo images exhibited significant improvement compared with uncorrected rosette data. The two-parameter calibration approach also demonstrated enhanced precision and reliability, as evidenced by quantitative T2*$$ {\mathrm{T}}_2^{\ast } $$ relaxometry analyses. CONCLUSION: Adequate correction of data sampling is a crucial step in rosette MRI. The presented experimental results underscore the robustness, ease of implementation, and suitability for routine experimental use of the proposed two-parameter rosette trajectory calibration approach.
- MeSH
- algoritmy * MeSH
- artefakty * MeSH
- fantomy radiodiagnostické * MeSH
- kalibrace MeSH
- lidé MeSH
- magnetická rezonanční tomografie * metody MeSH
- mozek diagnostické zobrazování MeSH
- počítačové zpracování obrazu * metody MeSH
- reprodukovatelnost výsledků MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
The study examined the effect of the choice of reference method on the functionality and reliability of calibrations in near-IR (NIR) spectroscopy intended for measuring the fat content in raw cow's milk. The fat content in the milk samples was evaluated using methods according to either Röse-Gottlieb or Gerber. The same samples were then subjected to analysis on an Antaris FT-NIR spectrometer. Using a partial least-squares algorithm, calibration models were created for both methods from the values measured. The calibration models show very good values of standard error of calibration: 0.133 for the Gerber method and 0.095 for the Röse-Gottlieb method. These calibrations were subsequently used to analyze 30 new samples of cow's milk of undefined fat content, and the differences in the values were evaluated using statistical paired t-test to a median value at a probability level of α = 0.05. No statistically significant differences were found. It was revealed that the reference method used for calibrating the device evaluating the fat content in raw cow's milk has no effect on the functionality and reliability of the calibration model.
The contribution deals with the first step in using proper wave-equation based ultrasound propagation model in image reconstruction from the ultrasonic computed tomography data. Particularly, it compares the transducer calibration results obtained via direct measurement of the empty image field and consequential data processing based on a simple direct-propagation model with the simulation results obtained via solving the single-frequency wave equation under proper border conditions reflecting the realistic measurement geometry. The results show a reasonable qualitative agreement when a certain degree of phase-shifted coupling from the transmitting transducer elements to the neighbouring elements of the transducer field is admitted.
- MeSH
- algoritmy MeSH
- financování organizované MeSH
- interpretace obrazu počítačem metody normy MeSH
- kalibrace MeSH
- měniče MeSH
- radiační rozptyl MeSH
- reprodukovatelnost výsledků MeSH
- senzitivita a specificita MeSH
- ultrasonografie normy přístrojové vybavení MeSH
- vylepšení obrazu metody normy MeSH
- Publikační typ
- hodnotící studie MeSH
- srovnávací studie MeSH
- validační studie MeSH
- Geografické názvy
- Česká republika MeSH
A passive sampler based on stir bars coated with polydimethylsiloxane (PDMS) was calibrated for the measurement of time-weighted average concentrations of hydrophobic micropollutants, including polycyclic aromatic hydrocarbons, polychlorinated biphenyls and organochlorine pesticides, in water. Stir bar/water partition coefficients were measured by equilibrating bars with sheets made of silicone rubber material for which partition coefficients had been reported previously. Kinetic parameters characterising the exchange of analytes between stir bars and water were determined under controlled exposure conditions using a passive dosing system. The dosing system consisted of silicone rubber sheets with a large surface area, spiked with analytes. During stir bar sampler exposure, analytes partitioned from dosing sheets to water in the exposure tank and maintained constant exposure concentrations. Reversible and isotropic exchange kinetics of analytes between sampler and water was confirmed by measuring the release of a range of performance reference compounds (PRCs) from stir bars. Application of a two-resistance model confirmed that, except for hexachlorocyclohexane isomers, uptake of the test compounds under the experimental conditions was controlled by diffusion in the water boundary layer. This permits the application of PRCs for in situ calibration of uptake kinetics of test compounds to stir bars.
- MeSH
- chemická frakcionace metody MeSH
- chemické látky znečišťující vodu analýza chemie izolace a purifikace MeSH
- hydrofobní a hydrofilní interakce * MeSH
- kalibrace MeSH
- kinetika MeSH
- organické látky analýza chemie izolace a purifikace MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
This work is focused on numerical calibrations of the body counter for in vivo measurement of pure beta emitters through the produced bremsstrahlung radiation. Calibrations were performed using the UPh-02T block whole-body phantom and the Lawrence Livermore National Laboratory (LLNL) realistic torso phantom. Neither of these physical phantoms is appropriate for such calibrations; therefore, specific 90Sr sources have been manufactured to be used with the UPh-02T phantom for experimental measurement followed with Monte Carlo (MC) simulations. Calibrations with the LLNL torso phantom were carried out solely using MC technique. Different scenarios of the 90Sr distribution in the human tissues were considered for the spectrometer calibrations. MC simulations with the LLNL confirmed the applicability of the UPh-02T with specific 90Sr/90Y sources for experimental calibrations of the body counters for measurement of pure beta emitters. Differences in count rates in 50-200 keV for UPh-02T and LLNL were not >25% for all considered scenarios.
