Calibration Conditions Research Articles

Assessment of long-term radon concentration measurement precision in field conditions (Serbian Schools) for a survey carried out by an international collaboration

In an international collaboration, a long-term radon concentration survey was carried out in schools of Southern Serbia with radon detectors prepared, etched and read-out in Italy. In such surveys it is necessary to evaluate measurement precision in field conditions, and to check whether quality assurance protocols were effective in keeping uncertainties under control, despite the complex organisation of measurements. In the first stage of the survey, which involves only some of the total number of municipalities, paired detectors were exposed in each monitored room in order to experimentally assess measurement precision. Paired passive devices (containing CR-39 detectors) were exposed for two consecutive 6-month periods. Two different measurement systems were used to read out CR-39s of the first and second period, respectively. The median of the coefficient of variation (CV) of the measured exposures was 8 % for 232 paired devices of the first 6-month period and 4 % for 242 paired devices of the second 6-month period, respectively. This difference was mainly due to a different track count repeatability of the two read-out systems, which was 4 and 1 %, respectively, as the median value of CV of repeated countings. The in-field measured precision results are very similar to the precision assessed in calibration conditions and are much lower than the room-to-room variation of radon concentration in the monitored schools. Moreover, a quality assurance protocol was followed to reduce extra-exposures during detector transport from Rome to schools measured and back.

Evaluation of the analyzer Glycomat 3000 (Biocode Hycel) for HbA1c

HbA(1c) represents a key parameter in the monitoring of glycemic balance in diabetic patients. It may be assayed by various methods, among which high-pressure liquid chromatography (HPLC). We have evaluated a new HPLC analyzer, Glycomat 3000 (Biocode Hycel). HbA(1c) values are well correlated (r(2) = 0.994) with those obtained by the HPLC analyzer used routinely in our laboratory (Variant II, Bio-Rad). However, the precision of assays can be at the limit of acceptability (CV of repeatability between 0.7 and 1.4% and CV of reproducibility between 3.3 and 4.1%) if strict conditions of calibration and quality control are not implemented. The assay is sensitive to the interference of modified fractions of hemoglobin (labile HbA(1c) and carbamylated Hb) in the clinical range, and to the presence of HbF. Besides, Glycomat 3000 is a friendly and easy to use analyzer.

Distribution of standing-wave errors in real-ear sound-level measurements

Standing waves can cause measurement errors when sound-pressure level (SPL) measurements are performed in a closed ear canal, e.g., during probe-microphone system calibration for distortion-product otoacoustic emission (DPOAE) testing. Alternative calibration methods, such as forward-pressure level (FPL), minimize the influence of standing waves by calculating the forward-going sound waves separate from the reflections that cause errors. Previous research compared test performance (Burke et al., 2010) and threshold prediction (Rogers et al., 2010) using SPL and multiple FPL calibration conditions, and surprisingly found no significant improvements when using FPL relative to SPL, except at 8 kHz. The present study examined the calibration data collected by Burke et al. and Rogers et al. from 155 human subjects in order to describe the frequency location and magnitude of standing-wave pressure minima to see if these errors might explain trends in test performance. Results indicate that while individual results varied widely, pressure variability was larger around 4 kHz and smaller at 8 kHz, consistent with the dimensions of the adult ear canal. The present data suggest that standing-wave errors are not responsible for the historically poor (8 kHz) or good (4 kHz) performance of DPOAE measures at specific test frequencies.

Fast assessment of diene values in pyrolysis gasoline by UV-visible spectroscopy and multivariate calibration

Conjugated dienes in pyrolysis gasoline samples were assayed by spectrophotometry. The calibrations were carried out by partial least squares regression using spectrophotometric data and the reference method UOP-326. The maximum deviation observed for an independent set of samples was 12% compared with the reference method. Spectral data preprocessing and weighting were investigated for the modeling. Values of root mean square error of calibration and prediction, and normalized root mean squared error were used as criteria to define the best calibration condition. 26 non-hydrogenated and 21 hydrogenated pyrolysis gasoline samples were used to model the spectral data by PLS regression.

Study on Efficiency Character of Axial Internal Combustion Fluid Pump

Integrating traditional engine and plunger pump, a new type power equipment─Internal Combustion Fluid Pump(ICFP) was developed, through which thermal energy can be turned into hydraulic pressure directly. As a main factor affecting ICFP’s performances, efficiency is the basis to design its structure. For three-cylinder axial ICFP, it’s dynamics model was setup, and its efficiency character was studied. The simulating results show that ICFP’s effective thermal efficiency is 37.44% at calibration condition, which is higher than engine-pump system by 23.06%. For the three-cylinder ICFP, the effective thermal efficiency experiments are done. Errors are within 5%, and it proved that the simulation results are correct.

Spectral method for the correction of the Cerenkov light effect in plastic scintillation detectors: A comparison study of calibration procedures and validation in Cerenkov light‐dominated situations

The purposes of this work were: (1) To determine if a spectral method can accurately correct the Cerenkov light effect in plastic scintillation detectors (PSDs) for situations where the Cerenkov light is dominant over the scintillation light and (2) to develop a procedural guideline for accurately determining the calibration factors of PSDs. The authors demonstrate, by using the equations of the spectral method, that the condition for accurately correcting the effect of Cerenkov light is that the ratio of the two calibration factors must be equal to the ratio of the Cerenkov light measured within the two different spectral regions used for analysis. Based on this proof, the authors propose two new procedures to determine the calibration factors of PSDs, which were designed to respect this condition. A PSD that consists of a cylindrical polystyrene scintillating fiber (1.6 mm3) coupled to a plastic optical fiber was calibrated by using these new procedures and the two reference procedures described in the literature. To validate the extracted calibration factors, relative dose profiles and output factors for a 6 MV photon beam from a medical linac were measured with the PSD and an ionization chamber. Emphasis was placed on situations where the Cerenkov light is dominant over the scintillation light and on situations dissimilar to the calibration conditions. The authors found that the accuracy of the spectral method depends on the procedure used to determine the calibration factors of the PSD and on the attenuation properties of the optical fiber used. The results from the relative dose profile measurements showed that the spectral method can correct the Cerenkov light effect with an accuracy level of 1%. The results obtained also indicate that PSDs measure output factors that are lower than those measured with ionization chambers for square field sizes larger than 25 x 25 cm2, in general agreement with previously published Monte Carlo results. The authors conclude that the spectral method can be used to accurately correct the Cerenkov light effect in PSDs. The authors confirmed the importance of maximizing the difference of Cerenkov light production between calibration measurements. The authors also found that the attenuation of the optical fiber, which is assumed to be constant in the original formulation of the spectral method, may cause a variation of the calibration factors in some experimental setups.

Determination of Frying Quality of Vegetable Oils used for Preparing Falafel using Infrared Spectroscopy and Multivariate Calibration

The frying qualities of palm and soybean oils are determined using infrared spectroscopy and multivariate calibration. Compare to soybean oil, palm oil is more resistive to the chemical and physical changes and this is attributed to the high degree of unsaturation of soybean oil (61.9%) compare to palm oil (13.8%). After 48 h in service, the oil samples were effectively clustered into two groups using principal component analysis which indicated that both oils still maintain their chemical identities. Partial least squares regression (PLS1 and PLS2) a long with mid-FTIR data are used for predicting free fatty acid, viscosity, and total polar compounds of the used oils without running expensive standard procedures. PLS1 and PLS2 outperformed PCR and MLR for predicting the quality indicators of the frying oils. For palm oil and at the optimum calibration conditions, the obtained accuracies (SD) are 105.6% (0.05), 99.8% (1.10), and 103.9% (0.16) for free fatty acid, viscosity, and total polar compounds, respectively. The proposed method is simple, less-expensive, and has comparable accuracy/precision with standard procedures that often used for monitoring frying oils.

Formation of the microgeometry of the body surface of cylindrical work rolls during texturing and mat finishing of precision strips

The requirements of the consumers of precision strips imposed on their surface roughness parameters are considered. Various methods of texturing roll bodies are analyzed, and the advantages of electric-discharge texturing are shown. The effect of the roll texturing and stand calibration conditions on the roll roughness parameters is studied, and the formation of a microrelief on a strip surface during mat finishing is investigated. Stand calibration is shown to decrease the roughness height indices and to substantially improve the microrelief uniformity. The optimum conditions of texturing of work rolls and mat finishing of precision strips of various purposes are determined and implemented on a reversing four-high 800 mill.

Ｅｘｐｏｓｕｒｅ Ｉｎｄｅｘ導入時のキャリブレーションにおける誤差要因の検討

Exposure indicators of digital radiography systems have been termed by manufacturers individually. The International Electrotechnical Commission (IEC) provided a concept of exposure index (EI) that unified the exposure indicators in order to recognize the deviations from the intended exposure. Although the IEC determined the calibration conditions between the exposure indicator and the air kerma at the detector surface, the tolerance was described was limited concerning the beam conditions. The purpose of this study is to evaluate the calibration error regarding the geometry and the added filtrations. The relative errors of calibrations based on the IEC condition were derived using the value of exposure indicators at EI value of 200, 500 and 1000 for field size of 10×10 cm, 20×20 cm, 30×30 cm and 43×43 cm, and source-image receptor distance (SID) of 100 cm, 120 cm, 150 cm and 200 cm. The beam qualities using added filtrations of 0.5 mm Cu+2 mm Al, 0.6 mm Cu and 21 mm Al were adjusted to RQA 5. The air kerma at the detector surface over the clinical use ranged from 0.18 to 26.3 µGy. Consequently, the relative errors for the calibrations were less than 6% at a field size of more than 10 × 10 cm and at SID of more than 100 cm with all added filtrations.

Non-goal scene analysis for soccer video

The broadcast soccer video is usually recorded by one main camera, which is constantly gazing somewhere of playfield where a highlight event is happening. So the camera parameters and their variety have close relationship with semantic information of soccer video, and much interest has been caught in camera calibration for soccer video. The previous calibration methods either deal with goal scene, or have strict calibration conditions and high complexity. So, it does not properly handle the non-goal scene such as midfield or center-forward scene. In this paper, based on a new soccer field model, a field symbol extraction algorithm is proposed to extract the calibration information. Then a two-stage calibration approach is developed which can calibrate camera not only for goal scene but also for non-goal scene. The preliminary experimental results demonstrate its robustness and accuracy.

ITER-relevant calibration technique for soft x-ray spectrometer

The ITER-oriented JET research program brings new requirements for the low-Z impurity monitoring, in particular for the Be—the future main wall component of JET and ITER. Monitoring based on Bragg spectroscopy requires an absolute sensitivity calibration, which is challenging for large tokamaks. This paper describes both “component-by-component” and “continua” calibration methods used for the Be IV channel (75.9 Å) of the Bragg rotor spectrometer deployed on JET. The calibration techniques presented here rely on multiorder reflectivity calculations and measurements of continuum radiation emitted from helium plasmas. These offer excellent conditions for the absolute photon flux calibration due to their low level of impurities. It was found that the component-by-component method gives results that are four times higher than those obtained by means of the continua method. A better understanding of this discrepancy requires further investigations.

External calibration of a polarimetric synthetic-aperture radar for a limited number of types of reference reflectors

Capabilities of the external calibration of a polarimetric synthetic-aperture radar (SAR) and the monitoring of the radar parameters under flight conditions for a limited number of types of reference calibration targets are determined. An analytic form of the algorithm for neutralization of SAR hardware distortions in the measurement of the scattering matrix of the observed object is proposed and possibilities for application of this algorithm under the conditions of unrealizable total polarimetric calibration are analyzed. The possibilities of determining the particular calibration parameters and their combinations with the use of one or two reference reflectors are analyzed. It is shown that, in the measurement of the scattering matrix of a reciprocal object, it is sufficient to use two types of reference reflectors.

Modified calibration protocol evaluated in a model-based testing of SBR flexibility

The purpose of this paper is to refine the BIOMATH calibration protocol for SBR systems, in particular to develop a pragmatic calibration protocol that takes advantage of SBR information-rich data, defines a simulation strategy to obtain proper initial conditions for model calibration and provides statistical evaluation of the calibration outcome. The updated calibration protocol is then evaluated on a case study to obtain a thoroughly validated model for testing the flexibility of an N-removing SBR to adapt the operating conditions to the changing influent wastewater load. The performance of reference operation using fixed phase length and dissolved oxygen set points and two real-time control strategies is compared to find optimal operation under dynamic conditions. The results show that a validated model of high quality is obtained using the updated protocol and that the optimization of the system's performance can be achieved in different manners by implementing the proposed control strategies.

Influence of calibration method on distortion-product otoacoustic emission measurements: I. test performance.

Calibration errors in distortion-product otoacoustic emission (DPOAE) measurements because of standing waves cause unpredictable changes in stimulus and DPOAE response level. The purpose of this study was to assess the extent to which these errors affect DPOAE test performance. Standard calibration procedures use sound pressure level (SPL) to determine specified levels. Forward pressure level (FPL) is an alternate calibration method that is less susceptible to standing waves. However, FPL derivation requires prior cavity measurements, which have associated variability. In an attempt to address this variability, four FPL methods were compared with SPL: a reference calibration derived from 25 measurements before all data collection and a daily calibration measurement, both of which were made at body and room temperature. Data were collected from 52 normal-hearing and 103 hearing-impaired subjects. DPOAEs were measured for f2 frequencies ranging from 2 to 8 kHz in half-octave steps, with L2 ranging from -20 to 70 dB SPL (5-dB steps). At each f2, DPOAEs were measured in five calibration conditions: SPL, daily FPL at body temperature (daily body), daily FPL at room temperature (daily room), reference FPL at body temperature (ref body), and reference FPL at room temperature (ref room). Data were used to construct receiver operating characteristic (ROC) curves for each f2, calibration method, and L2. From these curves, areas under the ROC curve (AROC) were estimated. The results of this study are summarized by the following observations: (1) DPOAE test performance was sensitive to stimulus level, regardless of calibration method, with the best test performance observed for moderate stimulus level conditions. (2) An effect of frequency was observed for all calibration methods, with the best test performance at 6 kHz and the worst performance at 8 kHz. (3) At clinically applicable stimulus levels, little difference in test performance among calibration methods was noted across frequencies, except at 8 kHz. At 8 kHz, FPL-based calibration methods provided superior performance compared with the standard SPL calibration. (4) A difference between FPL calibration methods was observed at 8 kHz, with the best test performance occurring for daily calibrations at body temperature. With the exception of 8 kHz, there was little difference in test performance across calibration methods. At 8 kHz, AROCs and specificities for fixed sensitivities indicate that FPL-based calibration methods provide superior performance compared with the standard SPL calibration for clinically relevant levels. Temperature may have an impact on FPL calculations relative to DPOAE test performance. Although the differences in AROC among calibration procedures were not statistically significant, the present results indicate that standing wave errors may impact DPOAE test performance and can be reduced by using FPL, although the largest effects were restricted to 8 kHz.

Identification of a Coiled Coil in Werner Syndrome Protein That Facilitates Multimerization and Promotes Exonuclease Processivity

Werner syndrome (WS) is a rare progeroid disorder characterized by genomic instability, increased cancer incidence, and early onset of a variety of aging pathologies. WS is unique among early aging syndromes in that affected individuals are developmentally normal, and phenotypic onset is in early adulthood. The protein defective in WS (WRN) is a member of the large RecQ family of helicases but is unique among this family in having an exonuclease. RecQ helicases form multimers, but the mechanism and consequence of multimerization remain incompletely defined. Here, we identify a novel heptad repeat coiled coil region between the WRN nuclease and helicase domains that facilitates multimerization of WRN. We mapped a novel and unique DNA-dependent protein kinase phosphorylation site proximal to the WRN multimerization region. However, phosphorylation at this site affected neither exonuclease activity nor multimeric state. We found that WRN nuclease is stimulated by DNA-dependent protein kinase independently of kinase activity or WRN nuclease multimeric status. In addition, WRN nuclease multimerization significantly increased nuclease processivity. We found that the novel WRN coiled coil domain is necessary for multimerization of the nuclease domain and sufficient to multimerize with full-length WRN in human cells. Importantly, correct homomultimerization is required for WRN function in vivo as overexpression of this multimerization domain caused increased sensitivity to camptothecin and 4-nitroquinoline 1-oxide similar to that in cells lacking functional WRN protein.

SU‐GG‐T‐188: A Field Size Specific Backscatter Correction Algorithm for Accurate EPID Dosimetry

Purpose: Portal dose images acquired with an amorphous silicon electronic portal imaging device (EPID) suffer from artifacts related to backscattered radiation. The backscatter signal varies as a function of field size (FS) and location on the EPID. Most current portal dosimetry algorithms fail to account for the FS dependence. The ramifications of this omission are investigated and solutions for correcting the measured dose images for FS specific backscatter are proposed. Method and Materials: A series of open field dose images were obtained for field sizes ranging from 2×2 to 30×40 cm2 and analyzed to determine the amount of backscatter present. Two methods to account for the relationship between FS and backscatter are offered: discrete FS specific correction matrices and a single generalized equation. Each approach was tested on the clinical dosimetric images for 10 patients, 49 treatment fields to see whether there was an improvement in the dosimetric result over the vendor's algorithm. Results: Backscatter manifests itself as an asymmetry in the measured signal primarily in the inplane direction. The maximum error is 3.6% for 10×10 and 12.5×12.5 cm2 field sizes. The asymmetry decreased with increasing FS to 0.6% for fields larger than 30×30 cm2. The dosimetric comparison between the measured and predicted dose images was significantly improved (p ≪ .001) with the FS specific backscatter correction. The average percentage of points passing a 2%, 2mm gamma criteria increased from 90.6% to between 96.7% and 97.2%. Conclusion: The error observed in a measured portal dose image depends on how much its FS differs from the 30×40 cm2 calibration conditions. The proposed methods for correcting for FS specific backscatter effectively improved the ability of the EPID to perform dosimetric measurements. Correcting for FS specific backscatter is important for accurate EPID dosimetry and can be carried out using the described methods.

SU-GG-I-50: When Should We Recalibrate the Grayscale Standard Display Function in Different Ambient Lighting Conditions?

Purpose: Liquid‐crystal display (LCD) monitors for medical use may not be always used under the same ambient lighting condition for calibration of the grayscale standard display function (GSDF). The purpose of this study is to clarify need for recalibration to the GSDF in different ambient lighting conditions. Method and Materials: An LCD monitor (two‐mega pixels, Radiforce GS220, Eizo, Japan) was used in this study. The calculated diffuse reflection coefficient of this LCD monitor was 0.0026 sr−1. This LCD monitor was calibrated to the GSDF including four ambient lighting conditions such as typical diagnostic reading stations (10 lx and 60 lx), hospital clinical viewing stations (250 lx), and operating rooms (400 lx) levels based on guidelines of the American Association of Physicists in Medicine task group (AAPM TG) 18. The maximum deviation from the contrast response was calculated at various tentative changes in ambient lighting conditions. Results: When the ambient lighting condition changed, the maximum deviation of contrast responses increased. The degree of the effect of the change of ambient lighting depended on the ambient lighting conditions used for the calibration to the GSDF. The darker the ambient lighting condition for calibration was, the greater the variation in the contrast response was. If 50 lx and 100 lx were added to typical diagnostic reading stations (10 lx), the maximum deviations of the contrast response were −10.3% and −18.5%, respectively. Those maximum deviations of the contrast response were beyond an acceptable range (±10%) of AAPM TG18. Thus, the contrast in especially dark regions of medical images will be decreased. Conclusion: As the LCD monitor calibrated included typical diagnostic reading stations (10 lx), the need for recalibration to the GSDF with ambient lighting conditions increased over 50 lx to maintain imagecontrast.

A field size specific backscatter correction algorithm for accurate EPID dosimetry

Portal dose images acquired with an amorphous silicon electronic portal imaging device (EPID) suffer from artifacts related to backscattered radiation. The backscatter signal varies as a function of field size (FS) and location on the EPID. Most current portal dosimetry algorithms fail to account for the FS dependence. The ramifications of this omission are investigated and solutions for correcting the measured dose images for FS specific backscatter are proposed. A series of open field dose images were obtained for field sizes ranging from 2 x 2 to 30 x 40 cm2. Each image was analyzed to determine the amount of backscatter present. Two methods to account for the relationship between FS and backscatter are offered. These include the use of discrete FS specific correction matrices and the use of a single generalized equation. The efficacy of each approach was tested on the clinical dosimetric images for ten patients, 49 treatment fields. The fields were evaluated to determine whether there was an improvement in the dosimetric result over the commercial vendor's current algorithm. It was found that backscatter manifests itself as an asymmetry in the measured signal primarily in the inplane direction. The maximum error is approximately 3.6% for 10 x 10 and 12.5 x 12.5 cm2 field sizes. The asymmetry decreased with increasing FS to approximately 0.6% for fields larger than 30 x 30 cm2. The dosimetric comparison between the measured and predicted dose images was significantly improved (p << .001) when a FS specific backscatter correction was applied. The average percentage of points passing a 2%, 2 mm gamma criteria increased from 90.6% to between 96.7% and 97.2% after the proposed methods were employed. The error observed in a measured portal dose image depends on how much its FS differs from the 30 x 40 cm2 calibration conditions. The proposed methods for correcting for FS specific backscatter effectively improved the ability of the EPID to perform dosimetric measurements. Correcting for FS specific backscatter is important for accurate EPID dosimetry and can be carried out using the methods presented within this investigation.

Calibration of the barrel muon drift tubes system in CMS

In this report, results on the calibration process of the Drift Tubes (DT) system of the Compact Muon Solenoid experiment are presented. The full commissioning of the calibration procedure has been deployed in year 2008 with the CMS Computing, Software and Analysis challenge (CSA08), which has tested the full work-flow needed for CMS data-taking during the LHC start-up operations. In autumn 2008, the same Calibration work-flow was applied to a high statistics cosmic ray muon data taking period: the Cosmic Run At Four Tesla (CRAFT) period. The accurate measurement of the main calibration conditions corresponding to the Time Pedestals and the Drift Velocity provide the necessary space-time relationship used in the first stage of the muon local reconstruction.

Toward a Real-Time In Vivo Dosimetry System Using Plastic Scintillation Detectors

In the present study, we have presented and validated a plastic scintillation detector (PSD) system designed for real-time multiprobe in vivo measurements. The PSDs were built with a dose-sensitive volume of 0.4 mm(3). The PSDs were assembled into modular detector patches, each containing five closely packed PSDs. Continuous dose readings were performed every 150 ms, with a gap between consecutive readings of <0.3 ms. We first studied the effect of electron multiplication. We then assessed system performance in acrylic and anthropomorphic pelvic phantoms. The PSDs were compatible with clinical rectal balloons and were easily inserted into the anthropomorphic phantom. With an electron multiplication average gain factor of 40, a twofold increase in the signal/noise ratio was observed, making near real-time dosimetry feasible. Under calibration conditions, the PSDs agreed with the ion chamber measurements to 0.08%. Precision, evaluated as a function of the total dose delivered, ranged from 2.3% at 2 cGy to 0.4% at 200 cGy. Real-time PSD measurements are highly accurate and precise. These PSDs can be mounted onto rectal balloons, transforming these clinical devices into in vivo dose detectors without modifying current clinical practice. Real-time monitoring of the dose delivered near the rectum during prostate radiotherapy should help radiation oncologists protect this sensitive normal structure.