Standardized Calibration Protocol Research Articles

Monitoring the Calibration of In-Office 3D Printers.

Most desktop 3D printers lack features that allow manual calibration of printer parameters. It is crucial to assess the accuracy of printing to minimize the margin of error and variance between each print. Therefore, this study aimed to develop a method for monitoring the calibration of in-office 3D printers. A calibration coupon was designed to have a tolerance and dimensions that define nominal geometry and allow the measurement of variances occurring in X−Y axes and curvature. Ten printing cycles were run on two stereolithography (SLA) 3D printers with two different resins. Additionally, the coupons were positioned in five positions on the build platform to assess errors caused by differences in positioning. Measurements were made on the X and Y axes. No statistical difference was noted between the coupons being printed in different positions on the build platform and between the two resins at both X and Y axes of measurement (p > 0.05). Desktop 3D printers currently lack a standardized calibration protocol, which provides a closed loop for design and manufacturing of printed parts. The coupon in this study will allow monitoring the calibration of desktop 3D printers to ensure high-quality printing.

Electron diffraction characterization of nanocrystalline materials using a Rietveld-based approach. Part II. Application to microstructural analysis

This is the second in a two-paper series concerning the quantitative characterization of nanocrystalline materials using an electron-diffraction-based approach, in which a full-pattern fitting Rietveld-based refinement is applied to electron powder diffraction data in transmission electron microscopy (TEM). Part I [Sinha et al. (2022). J. Appl. Cryst. 55, 953–965] established a standard calibration protocol to determine the instrumental effects, with special emphasis on the camera length and the diameter of the selected area apertures. Possible application cases are now considered to demonstrate the capabilities of the approach, including the evaluation of the phase composition of TEM specimens, an operation that reveals new application fields for this powerful materials characterization technique. In this regard, different types of material specimen are examined: nanocrystalline yttrium oxide, silicon, titanium dioxide and debris from disc brake wear, each one featuring specific aspects to be tackled with the proposed methodology. To demonstrate the limits of the proposed approach as concerns the material characteristics, an analysis of a hematite sample obtained from the heat treatment of natural goethite, displaying a relatively coarse crystallite size, is performed and a critical discussion of the results is given.

Neuronavigation Applied to Piezosurgery: Toward Robotic Image-Aided Craniotomy? A Technical Note

Although simple in its concept, craniotomy can still cause serious consequences to the patient. A recent alternative to standard techniques (i.e., perforator and craniotome) is represented by piezosurgery (PS), which exploits a microvibration-emitting blade that cuts the bone directly from the outer surface of the skull. Although PS has been demonstrated to decrease complications, dural lacerations and neurovascular injuries are still possible from inadvertent penetration of the inner tabula. Modern neuronavigation systems can provide the surgeon with the possibility to track the instrument while carving the skull, thus potentially lowering the complication rates. Two cases of miniretromastoid craniotomy for trigeminal neuralgia were performed using neuronavigated PS. Before surgery, the patients underwent volumetric brain magnetic resonance imaging and computed tomography. The piezosurgical cutter was registered on the S8 StealthStation neuronavigation system (Medtronic, Dublin, Ireland) using the step-by-step cranial standard instrument calibration protocol. The craniotomy was performed with the surgeon using the neuronavigation monitor to visualize both the position and the trajectory of the instrument's blade while penetrating the bone. No dural lacerations or neurovascular injuries were reported. At the end of the procedure, the bone flaps were perfectly repositioned within their craniotomy margins without the use of cranial fixation devices. Neuronavigated PS has the potential to decrease craniotomy-related complication rates. By allowing for real-time visualization of the blade's level of penetration, it provides the surgeon with the ability to halt progression when needed, avoiding dural lacerations and neurovascular injuries. The principles behind this technique could anticipate the advent of robotic-image aided craniotomy.

Survey on utilization of flattening filter-free photon beams in Japan.

To understand the current state of flattening filter-free (FFF) beam implementation in C-arm linear accelerators (LINAC) in Japan, the quality assurance (QA)/quality control (QC) 2018–2019 Committee of the Japan Society of Medical Physics (JSMP) conducted a 37-question survey, designed to investigate facility information and specifications regarding FFF beam adoption and usage. The survey comprised six sections: facility information, devices, clinical usage, standard calibration protocols, modeling for treatment planning (TPS) systems and commissioning and QA/QC. A web-based questionnaire was developed. Responses were collected between 18 June and 18 September 2019. Of the 846 institutions implementing external radiotherapy, 323 replied. Of these institutions, 92 had adopted FFF beams and 66 had treated patients using them. FFF beams were used in stereotactic radiation therapy (SRT) for almost all disease sites, especially for the lungs using 6 MV and liver using 10 MV in 51 and 32 institutions, respectively. The number of institutions using FFF beams for treatment increased yearly, from eight before 2015 to 60 in 2018. Farmer-type ionization chambers were used as the standard calibration protocol in 66 (72%) institutions. In 73 (80%) institutions, the beam-quality conversion factor for FFF beams was calculated from TPR20,10, via the same protocol used for beams with flattening filter (WFF). Commissioning, periodic QA and patient-specific QA for FFF beams also followed the procedures used for WFF beams. FFF beams were primarily used in high-volume centers for SRT. In most institutions, measurement and QA was conducted via the procedures used for WFF beams.

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.

Intra-rater and inter-rater reliability of the rapid entire body assessment (REBA) tool

BackgroundErgonomics researchers and practitioners use many techniques to assess risk. The Rapid Entire Body Assessment (REBA) is a common tool used to facilitate the measurement and evaluation of the risks associated with working postures as a part of ergonomic workload. However, little work has been reported regarding the reliability of REBA reporting. ObjectiveThis study assesses the reliability of this commonly used tool for research and practice. MethodsThe study was conducted as part of the larger Safe Workload Ergonomic Exposure Project (SWEEP), which is a University of Minnesota research initiative for custodians. For this effort, a secondary data analysis was conducted on data collected during a study of custodians’ exposures to risks of musculoskeletal disorders. Eight observers used the REBA tool to sequentially evaluate tasks performed two times in succession by the same individual. ResultsThis study reports high intra-rater reliability (ICC = 0.925) for REBA raw scores and moderate inter-rater reliability (IRR) (Fleiss kappa = 0.54) for a categorical scoring of REBA. ConclusionA moderate amount of IRR was found, and a standardized training and calibration protocol is proposed as a potential means to improve intra- and inter-rater reliability.

Baseline Assessment for the Consistency of Raman Shifts Acquired with 26 Different Raman Systems and Necessity of a Standardized Calibration Protocol.

Although Raman shifts originate from molecular vibrations and in theory must be independent of analytical systems, acquired Raman shifts, in practice, are not so. Since the consistency of Raman shifts acquired with different systems has not been investigated previously, we have compared the Raman spectra of polystyrene, benzonitrile, and cyclohexane obtained with 26 different systems. The medians of 26 measurements for the characteristic peaks were found to be 1001.3, 1001.1, and 802.0 cm-1 for polystyrene, benzonitrile, and cyclohexane, respectively, and were consistent with their corresponding ASTM E1840 values, which have been widely used for the calibration of Raman systems. However, only 16 measurements of the Raman shift of the polystyrene peak (1001.4 cm-1) met the tolerance standard of the European Pharmacopoeia (±1.5 cm-1). Thus, consistency of Raman shifts obtained using different systems is low, and this mainly originates from differences in the Raman systems rather than materials. Although correction of the offset using the Raman shift of the peaks of cyclohexane (802.0 or 2852.4 cm-1) could improve the consistency of the Raman shifts acquired with different systems, the magnitude of improvement was not uniform over the range of shift values. Thus, there is a need for a standardized calibration protocol that can be used for multiple Raman shifts of common materials to improve the consistency of Raman shifts for different systems.

Image-based SPECT calibration based on the evaluation of the Fraction of Activity in the Field of View

BackgroundSPECT quantification is important for dosimetry in targeted radionuclide therapy (TRT) and the calibration of SPECT images is a crucial stage for image quantification. The current standardized calibration protocol (MIRD 23) uses phantom acquisitions to derive a global calibration factor in specific conditions. It thus requires specific acquisitions for every clinical protocols. We proposed an alternative and complementary image-based calibration method that allows to determine a calibration factor adapted to each patient, radionuclide, and acquisition protocol and that may also be used as an additional independent calibration.ResultsThe proposed method relies on a SPECT/CT acquisition of a given region of interest and an initial whole-body (WB) planar image. First, the conjugate view of WB planar images is computed after scatter and attenuation correction. 3D SPECT images are reconstructed with scatter, attenuation, and collimator-detector response (CDR) corrections and corrected from apparent dead-time. The field of view (FOV) of the SPECT image is then projected on the corrected WB planar image. The fraction of activity located in the area corresponding to the SPECT FOV is then calculated based on the counts on the corrected WB planar image. The Fraction of Activity in Field Of View (FAF) is then proposed to compute the calibration factor as the total number of counts in the SPECT image divided by this activity. Quantification accuracy was compared with the standard calibration method both with phantom experiments and on patient data.Both standard and image-based calibrations give good accuracy on large region of interest on phantom experiments (less than 7% of relative difference compared to ground truth). Apparent dead-time correction allows to reduce the uncertainty associated with standard calibration from 2.5 to 1%. The differences found between both methods were lower than the uncertainty range of the standard calibration (<3%). In patient data, although no ground truth was available, both methods give similar calibration factor (average difference 3.64%).ConclusionsA calibration factor may be computed directly from the acquired SPECT image providing that a WB planar image is also available and if both acquisitions are performed before biological elimination. This method does not require to perform phantom acquisition for every different acquisition conditions and may serve to double check the calibration with an independent factor.

38. Image-based SPECT calibration based on the Fraction of Activity in Field of view (FAF)

Introduction SPECT quantification is particularly important for dosimetry in Targeted Radionuclide Therapy (TRT) and the calibration of SPECT images is a crucial stage for image quantification. The current standardized calibration protocol (MIRD 23 [1] ) makes use of phantom acquisitions in specific conditions and require an additional phantom calibration for every clinical acquisition protocol. We proposed an alternative and complementary image-based calibration method that allows obtaining a single calibration factor adapted to each patient, radionuclide and acquisition protocol, without specific phantom acquisition. Methods This method consists in SPECT images quantification from WB planar images. First, the conjugate view of WB planar images is computed after scatter and attenuation corrections. 3D SPECT images are acquired in the same patient position, reconstructed with scatter, attenuation and Collimator Detector Response (CDR) corrections, and finally corrected from apparent dead-time. The Field of View (FOV) of the SPECT images is then projected on the corrected WB planar image. The fraction of activity located in the area corresponding to the SPECT FOV is calculated based on the counts on the corrected WB planar image. The Fraction of Activity in Field of View (FAF) is then proposed to compute the calibration factor as the total number of counts in the SPECT image divided by this activity. Quantification accuracy was compared with the standard calibration method both with phantom experiments and on patient data. Results Both standard and our image-based calibrations give good accuracy (ranges of respectively [−0.97; 2.86]% and [0; 3.16]%) on large region of interest on phantom experiments. Apparent dead-time correction allows reducing the uncertainty associated with standard calibration with a coefficient of variation of the calibration factor of 0.17% instead of 2.39%. The differences on accuracy found between both methods on phantom study were lower (1.01% in average) than the uncertainty range with the standard calibration (2.90% in average). On patient study, although the ground truth is unknown, the standard calibration factor is also close (3.96% in average) to the image based patient specific one. Conclusions Calibration was performed directly on the image acquisition of interest. This method allows overriding the errors caused by imperfect attenuation and scattering corrections due to different conditions. This protocol is as accurate as standardized calibration protocol but only requires an additional WB planar acquisition. The main limitation relies on the need of performing the acquisition before patient biological elimination.

Methane calibration burner and C‐factor determination with cone calorimeter – validation of the standardized calibration protocol

SummaryThe cone calorimeter is one of the major fire tests. In its reference standard ISO 5660‐1, the apparatus (and especially a characteristic of its orifice plate mass flow meter, called C‐Factor) is calibrated using a methane burner set at 5 kW. However, measurements performed in end‐use are in the range 1–10 kW. In addition, standard proposes to check linearity at 1 and 3 kW, which means in the lowest part of the range. This communication establishes the validation of the linearity on the whole range and determines the optimal condition for C‐factor determination. It justifies the technical choices of the standard. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Development and field testing of a rapid and ultra-stable atmospheric carbon dioxide spectrometer

Abstract. We present field test results for a new spectroscopic instrument to measure atmospheric carbon dioxide (CO2) with high precision (0.02 μmol mol−1, or ppm at 1 Hz) and demonstrate high stability (within 0.1 ppm over more than 8 months), without the need for hourly, daily, or even monthly calibration against high-pressure gas cylinders. The technical novelty of this instrument (ABsolute Carbon dioxide, ABC) is the spectral null method using an internal quartz reference cell with known CO2 column density. Compared to a previously described prototype, the field instrument has better stability and benefits from more precise thermal control of the optics and more accurate pressure measurements in the sample cell (at the mTorr level). The instrument has been deployed at a long-term ecological research site (the Harvard Forest, USA), where it has measured for 8 months without on-site calibration and with minimal maintenance, showing drift bounds of less than 0.1 ppm. Field measurements agree well with those of a commercially available cavity ring-down CO2 instrument (Picarro G2301) run with a standard calibration protocol. This field test demonstrates that ABC is capable of performing high-accuracy, unattended, continuous field measurements with minimal use of reference gas cylinders.

WE-G-BRB-08: TG-51 Calibration of First Commercial MRI-Guided IMRT System in the Presence of 0.35 Tesla Magnetic Field.

The first real-time-MRI-guided radiotherapy system has been installed in a clinic and it is being evaluated. Presence of magnetic field (MF) during radiation output calibration may have implications on ionization measurements and there is a possibility that standard calibration protocols may not be suitable for dose measurements for such devices. In this study, we evaluated whether a standard calibration protocol (AAPM- TG-51) is appropriate for absolute dose measurement in presence of MF. Treatment delivery of the ViewRay (VR) system is via three 15,000Ci Cobalt-60 heads positioned 120-degrees apart and all calibration measurements were done in the presence of 0.35T MF. Two ADCL- calibrated ionization-chambers (Exradin A12, A16) were used for TG-51 calibration. Chambers were positioned at 5-cm depth, (SSD=105cm: VR's isocenter), and the MLC leaves were shaped to a 10.5cm × 10.5 cm field size. Percent-depth-dose (PDD) measurements were performed for 5 and 10 cm depths. Individual output of each head was measured using the AAPM- TG51 protocol. Calibration accuracy for each head was subsequently verified by Radiological Physics Center (RPC) TLD measurements. Measured ion-recombination (Pion) and polarity (Ppol) correction factors were less-than 1.002 and 1.006, respectively. Measured PDDs agreed with BJR-25 within ±0.2%. Maximum dose rates for the reference field size at VR's isocenter for heads 1, 2 and 3 were 1.445±0.005, 1.446±0.107, 1.431±0.006 Gy/minute, respectively. Our calibrations agreed with RPC- TLD measurements within ±1.3%, ±2.6% and ±2.0% for treatment-heads 1, 2 and 3, respectively. At the time of calibration, mean activity of the Co-60 sources was 10,800Ci±0.1%. This study shows that the TG- 51 calibration is feasible in the presence of 0.35T MF and the measurement agreement is within the range of results obtainable for conventional treatment machines. Drs. Green, Goddu, and Mutic served as scientific consultants for ViewRay, Inc. Dr. Mutic is on the clinical focus group for ViewRay, Inc., and his spouse holds shares in ViewRay, Inc.

MR intensity measurements of nondenervated muscle in patients following severe forearm trauma

Fluid increases resulting in higher MRI signal intensities in T(2) -weighted and short tau inversion recovery (STIR) sequences can be used to diagnose nerve injury. By comparing the signal intensities over time, MRI may become a new method for monitoring the healing process. Muscle edema is assessed by comparing the signal intensity of affected muscle with that of nonaffected muscle. However, in severe forearm trauma, the signal of nondenervated muscle may also be increased by wound edema, thus masking the effect of denervation. Hence, the purpose of this study was to investigate the influence of wound edema on muscle signal intensity in 29 consecutive patients examined on a 1.5-T MRI scanner at 1, 3, 6, 9 and 12 months after severe forearm trauma. The long-term course of wound edema and the influence of wound distance were thus investigated using a standardized imaging, calibration and post-processing protocol. The signal intensities of nondenervated intrinsic hand muscles were measured in the affected and contralateral sides. Muscle signal intensities were increased on the trauma side at 1 and 3 months (18% and 7.4%, respectively; p < 0.001) and normalized thereafter. In the contralateral hand, no significant signal changes were seen. No relationship was found between wound distance and the severity of wound edema. This study shows that wound edema influences muscle signal intensity comparisons in patients with forearm trauma. When comparing denervated muscle with nondenervated muscle, an additional scan of the contralateral side is indicated during the first 6 months after trauma to assess the extent of wound edema. After 6 months, the ipsilateral side can be used for muscle signal intensity comparisons.

가중유출수질지표를 이용한 활성오니공정모델의 민감도 분석과 매개변수 보정

Many modeling and calibration methods have been developed to analyze and design the biological wastewater treatment process. For the systematic use of activated sludge model (ASM) in a real treatment process, a most important step in this usage is a calibration which can find a key parameter set of ASM, which depends on the microorganism communities and the process conditions of the plants. In this paper, a standardized calibration protocol of the ASM model is developed. First, a weighted effluent quality index(WEQI) is suggested far a calibration protocol. Second, the most sensitive parameter set is determined by a sensitive analysis based on WEQI and then a parameter optimization method are used for a systematic calibration of key parameters. The proposed method is applied to a calibration problems of the single carbon removal process. The results of the sensitivity analysis and parameter estimation based on a WEQI shows a quite reasonable parameter set and precisely estimated parameters, which can improve the quality and the efficiency of the modeling and the prediction of ASM model. Moreover, it can be used for a calibration scheme of other biological processes, such as sequence batch reactor, anaerobic digestion process with a dedicated methodology.

SU-FF-T-26: A Modified TG-51 Formalism for Gamma Knife Dose Rate Calibration

Purpose: The first Lekshell Gamma Knife was developed in 1968. Currently there is no national standard calibration protocol developed specifically for gamma knife dose calibration. Many gamma knife centers perform calibration using TG-21 protocol, while other centers use TG-51 calibration factor ND,W. The purpose of this study is: to exam TG-21 and TG-51 calibration formalism; to compare result of gamma knife dose calibration using these two methods; and to determine if a simplified formula can be applied to gamma knife dose rate calibration. Method and Materials: Exradin A16 ion chamber (wall material C552) was placed in a 16cm spherical polystyrene phantom in our Lekshell Gamma Knife 4C. Dose rate can be calculated using Ngas or ND,W: where M is corrected charge reading; k an unknown correction for polystyrene phantom. Left hand side of the equations is dose rate to water per unit charge. For a given chamber, the factors on the right side of equations are all known except k, which can be determined by comparing above equations. Results: For our A16 chamber: Even if we ignore the unknown correction factor k, the difference between TG-21 and TG-51 calculated dose rate is 1.9%. Thus we estimated k to be in the order of 2% for this A16 ion chamber. Conclusion: A “modified TG-51” formula, , can be used to calibrate gamma knife dose rate. Correction factor k can be determined from the values of ND,W, Ngas, and other known factors found in TG-21. Difference between “modified TG-51” and TG-21 calculated dose rate is expected to be less than 2%.