QA Tests Research Articles

Technological Process of Assembly and QA Testing of Silicone Tracking Modules with Silicon Strip Sensor

Technological Process of Assembly and QA Testing of Silicone Tracking Modules with Silicon Strip Sensor

Recent Approaches of Impurity Profiling in Pharmaceutical Analysis: A Concise Review

Purity profiling is the process of gathering and analyzing information to determine the biological safety of a specific impurity, hence highlighting its importance and range in pharmaceutical research. In the field of pharmaceuticals, impurity has no precise meaning. Identification, structural elucidation, and quantitative determination of impurities and degradation products in bulk medicinal materials and pharmaceutical formulations are all included in impurity profiling. Since unrecognized, possibly poisonous impurities are dangerous to health and should be found and determined by selective procedures in order to increase the safety of drug therapy, impurity profiling has become more significant in contemporary pharmaceutical analysis. Impurities are typically described using words like residual solvents, byproducts, transformation products, degradation products, interaction products, and related products. Impurity identification is carried out using different chromatographic methods in addition to passing the CGMP, QC, QA, and water activity tests, a pharmaceutical ingredient also needs to satisfy the requirements for a new impurity. It is important to separate and characterize impurities in order to collect and evaluate data that determines biological safety, which emphasizes the need for and promise of drug impurity profiling in pharmaceutical research. To separate and measure the pollutants, a range of instrumental analytical techniques have been consistently used. The detection and regulatory evaluation of organic impurities is a very challenging task because to the numerous sources of organic impurities, including microbiological contamination, API breakdown products, and traces of intermediates.

MR compatible detectors assessment for a 0.35 T MR-linac commissioning

PurposeTo assess a large panel of MR compatible detectors on the full range of measurements required for a 0.35 T MR-linac commissioning by using a specific statistical method represented as a continuum of comparison with the Monte Carlo (MC) TPS calculations. This study also describes the commissioning tests and the secondary MC dose calculation validation.Material and methodsPlans were created on the Viewray TPS to generate MC reference data. Absolute dose points, PDD, profiles and output factors were extracted and compared to measurements performed with ten different detectors: PTW 31010, 31021, 31022, Markus 34045 and Exradin A28 MR ionization chambers, SN Edge shielded diode, PTW 60019 microdiamond, PTW 60023 unshielded diode, EBT3 radiochromic films and LiF µcubes. Three commissioning steps consisted in comparison between calculated and measured dose: the beam model validation, the output calibration verification in four different phantoms and the commissioning tests recommended by the IAEA-TECDOC-1583.Main resultsThe symmetry for the high resolution detectors was higher than the TPS data of about 1%. The angular responses of the PTW 60023 and the SN Edge were − 6.6 and − 11.9% compared to the PTW 31010 at 60°. The X/Y-left and the Y-right penumbras measured by the high resolution detectors were in good agreement with the TPS values except for the PTW 60023 for large field sizes. For the 0.84 × 0.83 cm2 field size, the mean deviation to the TPS of the uncorrected OF was − 1.7 ± 1.6% against − 4.0 ± 0.6% for the corrected OF whereas we found − 4.8 ± 0.8% for passive dosimeters. The mean absolute dose deviations to the TPS in different phantoms were 0 ± 0.4%, − 1.2 ± 0.6% and 0.5 ± 1.1% for the PTW 31010, PTW 31021 and Exradin A28 MR respectively.ConclusionsThe magnetic field effects on the measurements are considerably reduced at low magnetic field. The PTW 31010 ionization chamber can be used with confidence in different phantoms for commissioning and QA tests requiring absolute dose verifications. For relative measurements, the PTW 60019 presented the best agreement for the full range of field size. For the profile assessment, shielded diodes had a behaviour similar to the PTW 60019 and 60023 while the ionization chambers were the most suitable detectors for the symmetry. The output correction factors published by the IAEA TRS 483 seem to be applicable at low magnetic field pending the publication of new MR specific values.

Investigation on the accuracy of field widths and the quantitative relationship with energy variations for dynamic jaws helical tomotherapy.

TomoEDGE is an advanced technology for TomoTherapy treatment delivery by introducing a sliding-window dynamic jaw motion. The front and back jaws move independently at the start and end of a target volume along the longitudinal couch direction to reduce the undesired dose to the normal tissues. The accuracy of field width is essential to treatment delivery in this regard. The purpose of this work was to analyze the performance of dynamic jaws on helical tomotherapy and investigate the relationship with energy variation. The Tomotherapy-Quality-Assurance (TQA) Dynamic Field Width procedure was performed monthly across three tomotherapy machines. All field widths were analyzed, especially the FWHM of the 10mm field width. Field width measurements were compared with the ratio of Percentage Depth Dose at 20 and 10cm to render the value of correlation. Changes in beam FWHM and energy were further discussed. Two-year data were collected for this purpose. On average, measured field widths in each unit agreed within 1% tolerance recommendation stated. The average absolute difference between reference and measured FWs in each unit was approximately 0.07mm. An increase of 1.5% in the FW of the 10mm nominal beam width was correlated with a 1% increase in PDD20,10 ratio, implying a positive correlation between the two factors (p<0.002). A positive correlation between nominal 10mm FW and PDD20,10 was observed. In the case that the PDD20,10 marginally passes the QA tests, users are recommended to consider further verification on Dynamic Jaws to ensure the smallest field width to be within tolerance, which is essential to maintain effective treatment in TomoEDGE system. Since the regression of this study was a single-factor model, other confounding factors such as the focal spot size of linear accelerator should also be considered when evaluating the machine status.

Survey on fan-beam computed tomography for radiotherapy: Imaging for dose calculation and delineation

Background and purposeTo obtain an understanding of current practice, professional needs and future directions in the field of fan-beam CT in RT, a survey was conducted. This work presents the collected information regarding the use of CT imaging for dose calculation and structure delineation. Materials and methodsAn online institutional survey was distributed to medical physics experts employed at Belgian and Dutch radiotherapy institutions to assess the status, challenges, and future directions of QA practices for fan-beam CT. A maximum of 143 questions covered topics such as CT scanner availability, CT scanner specifications, QA protocols, treatment simulation workflow, and radiotherapy dose calculation. Answer forms were collected between 1-Sep-2022 and 10-Oct-2022. ResultsA 66 % response rate was achieved, yielding data on a total of 58 CT scanners. For MV photon therapy, all single-energy CT scans are reconstructed in Hounsfield Units for delineation or dose calculation, and a direct- or stoichiometric method was used to convert CT numbers for dose calculation. Limited use of dual-energy CT is reported for photon (N = 3) and proton dose calculations (N = 1). For brachytherapy, most institutions adopt water-based dose calculation, while approximately 26 % of the institutions take tissue heterogeneity into account. Commissioning and regular QA include eleven tasks, which are performed by two or more professions (29/31) with varying frequencies. ConclusionsDual usage of a planning CT limits protocol optimization for both tissue characterization and delineation. DECT has been implemented only gradually. A variation of QA testing frequencies and tests are reported.

184 Automated HDR QA Tests Using an Organic Plastic Scintillator with Opencv

184 Automated HDR QA Tests Using an Organic Plastic Scintillator with Opencv

Features of 2Day.QA® as a 2D radiation dosimeter

PurposeA new commercial 2D ionising radiation dosimeter (2Day.QA®) was developed. This work aims to introduce the basic functions of 2Day.QA®. MethodsThe dosimeter is made mainly of a linear polysaccharide consisting of β(1 → 4) linked d-glucose units and radiation active substances, which make it environmentally friendly. For 2Day.QA® irradiation, radiotherapy ionising radiation sources were used. The analysis of 2Day.QA® was performed using three scanners: Vidar® Red LED Dosimetry Pro Advantage™, Vidar® VXR 12-plus™ and HP Scanjet G3010 flatbed scanner. The stability of 2Day.QA® was tested. Exemplary applications of 2DayQA® for QA studies of accelerator light and radiation field coincidence and brachytherapy source position were carried out. ResultsThe dosimeter responded to the lowest applied dose of 0.95 Gy and saturated at over 94.9 Gy. The quasi-linear dose response is below 20 Gy. Vidar® Red LED Dosimetry Pro Advantage™ has proven to be superior to other scanners at determining dose effects in 2Day.QA®. The stability of the non-irradiated 2Day.QA® is at least 18 months. After 18 months of storage, the dosimeter reacted to irradiation. In the case of the irradiated samples, a slight color drift related to the absorbed dose was observed. Tests of the use of 2Day.QA® to control the quality of the accelerator light and radiation field coincidence and brachytherapy source position have shown that it can be used for such applications. ConclusionsThe study reveals the potential of 2Day.QA® for 2D radiation dosimetry and concludes with recommendations for the use of the dosimeter for radiotherapy QA tests.

The Nuffield Project: Creating Opportunity

Abstract The Nuffield project was set up to offer high achieving year 12 students from disadvantaged socio-economic backgrounds summer research placements. Charlie Fadden, QA Test Management Consultant and Vice Chair of EMBRACE SG, explains the background and the opportunity.

Stereotactic radiosurgery commissioning and QA test cases-A TG-119 approach for Stereotactic radiosurgery.

To develop a standardized set of representative clinical treatment cases that pose a range of optimization problems for evaluating the plan quality and dosimetric accuracy within the commissioning process for linac-based stereotactic radiosurgery (SRS). Five test cases with increasing complexity were created to validate delivery accuracy in SRS commissioning similar to the approach used by AAPM TG-119 in developing a test suite for IMRT commissioning. Standardized structure sets, planning goals, and delivery requirements were specified for each case including a small sphere target, irregular target, irregular target placed off-axis, multi-target, and abutting organs-at-risk (OARs). Various VMAT field arrangements including a single arc, two coplanar arcs, full arc and vertex half arc, and four noncoplanar arcs were tested to generate clinically appropriate treatment plans. The small spherical target was 1.0cm in diameter. The irregular target was a clinical cavity (2.3×2.2×1.4cm³) and was shifted 4.5cm for the irregular target off-axis case. The multi-target case used the irregular target and four spherical targets representing metastases ranging 0.9 to 1.6cm in diameter, placed up to 7.5cm off-axis. The abutting OARs case included an acoustic neuroma and target placed near the optic nerve. All spherical targets received 24Gy and the cavity received 18Gy. The abutting OAR cases included a 3.74cc lesion adjacent to the brainstem receiving 13Gy and a 1.11cc lesion adjacent to the optic nerve receiving 12Gy. All plans used a single-isocenter placed at the target center or geometric center of multiple targets. Planning goals for all cases included constraints for the target and brain minus PTV, along with brainstem and optic nerve where applicable. Deliverability was assessed through ion chamber measurements, in addition to composite and per-field planar measurements on Gafchromic film and small-field diode array. A mean and SD for measured versus planned doses of 101.0%±2.9% was observed over the 14 ion chamber measurements. Mean and SD for gamma pass rates were 98.5%±2.2% and 97.1%±4.9% for film and diode array, respectively, for gamma criteria of 2% and 1mm. These cases could provide the preliminary groundwork for a novel benchmark for institutions to evaluate linac-based SRS commissioning and delivery accuracy prior to clinical implementation. The rapid widespread implementation of linac-based SRS, the complexity associated with dosimetry and delivery, and high-profile treatment deviations that have already resulted from its use, highlight the importance of such a benchmark test suite. Comprehensive dosimetric measurements from this standardized set of SRS optimization problems were used to fine-tune and understand the limitations of our SRS planning and delivery system and establish a set of baseline data for comparison with other delivery platforms.

Technical assessment of the NDI Polaris Vega optical tracking system

The Polaris product line from Northern Digital Inc. is well known for accurate optical tracking measurements in research and medical environments. The Spectra position sensor, to date often found in image guided radiotherapy suites, has however reached its end-of-life, being replaced by the new Vega model. The performance in static and dynamic measurements of this new device has been assessed in controlled laboratory conditions, against the strict requirements for system integration in radiation therapy. The system accuracy has improved with respect to the Spectra in both static (0.045 mm RMSE) and dynamic (0.09 mm IQR, < 20 cm/s) tracking and brings marginal improvement in the measurement latency (14.2 ± 1.8 ms). The system performance was further confirmed under clinical settings with the report of early results from periodic QA tests within specifications. Based on our tests, the Polaris Vega meets the quality standards of radiotherapy applications and can be safely used for monitoring respiratory breathing motion or verifying patient positioning.

Patient-specific IMRT QA verification using machine learning and gamma radiomics.

Gamma function is the standard methodology for comparing dose distributions. It is calculated in dedicated software, and its results verification is not performed. Thus we developed an automatic tool for patient-specific QA results verification through high accuracy machine learning (ML) models based on the radiomics characteristics extraction from gamma images. We used 158 patient-specific QA tests and extracted 105 radiomics features from each gamma image. Three random forest models were developed (ML I, ML II, and ML III). ML I and ML II verified the gamma image approval using criteria of 2%/2mm/15% threshold and 3%/3mm/15% threshold, respectively. ML III verified if the gamma analyzes software recommended protocol was followed to detect if the TPS grid modification step was done. The models were based on the most important features selected using the mean decreased impurity, and their performances were evaluated. ML I included 25 features. Its accuracy was 0.85 using the test set and 0.84 using dataset B. ML II included 10 features, and its accuracy with the test set was 0.98; the same value was achieved using the never seen data (dataset B). The First-order 10th percentile feature was identified as a feature strongly related to the approved classification. ML III selected 23 features with an accuracy of 0.99 for test set and 0.98 for dataset B. An automatic workflow example for gamma analyses QA results verification could be proposed combining the models to detect grid inconsistencies on software evaluation, followed by the test approval classification.

COMPARATIVE ASSESMENT OF DOSE CALIBRATORS USED IN NUCLEAR MEDICINE

Dose calibrators are used to measure the amount of radioactive to be given to the patient. It is necessary to determine the correct dose and measure the amount of radioactive material with the least possible error. To minimize these potential errors, quality control (QA) tests should be carried out periodically according to the United States Nuclear Regulatory Authority (NRC). ATOM LAB 400 (serial number:11070208 ) and 500 (serial number: 15091215) dose calibrators which are actively used in our clinic were used. Our aim is to verify the accuracy of the dose calibrator which needs to be updated by using a recently calibrated dose calibrator. QA tests were performed on both dose calibrators. Test results of the currently certified dose calibrator and ATOM LAB 400 dose calibrator whose certificate will be updated were found to be compatible with each other.The tests performed on both dose calibrators remained with the error limits. Calibration certificate of the ATOM LAB 400 calibrator has been updated in accordance with NRC protocol.

Evaluations of a flat-panel based compact daily quality assurance device for proton pencil beam scanning (PBS) system.

To evaluate the flat-panel detector quenching effect and clinical usability of a flat-panel based compact QA device for PBS daily constancy measurements. The QA device, named Sphinx Compact, is composed of a 20x20 cm2 flat-panel imager mounted on a portable frame with removable plastic modules for constancy checks of proton energy (100MeV, 150MeV, 200MeV), Spread-Out-Bragg-Peak (SOBP) profile, and machine output. The potential quenching effect of the flat-panel detector was evaluated. Daily PBS QA tests of X-ray/proton isocenter coincidence, the constancy of proton spot position and sigma as well as the energy of pristine proton beam, and the flatness of SOBP proton beam through the 'transformed' profile were performed and analyzed. Furthermore, the sensitivity of detecting energy changes of pristine proton beam was also evaluated. The quenching effect was observed at depths near the pristine peak regions. The flat-panel measured range of the distal 80% is within 0.9mm to the defined ranges of the delivered proton beams. X-ray/proton isocenter coincidence tests demonstrated maximum mismatch of 0.3mm between the two isocenters. The device can detect 0.1mm change of spot position and 0.1MeV energy changes of pristine proton beams. The measured transformed SOBP beam profile through the wedge module rendered as flat. Even though the flat-panel detector exhibited quenching effect at the Bragg peak region, the proton range can still be accurately measured. The device can fulfill the requirements of the daily QA tests recommended by the AAPM TG224 Report.

Commissioning and quality assurance of a novel solution for respiratory-gated PBS proton therapy based on optical tracking of surface markers

We present the commissioning and quality assurance of our clinical protocol for respiratory gating in pencil beam scanning proton therapy for cancer patients with moving targets. In a novel approach, optical tracking has been integrated in the therapy workflow and used to monitor respiratory motion from multiple surrogates, applied on the patients’ chest. The gating system was tested under a variety of experimental conditions, specific to proton therapy, to evaluate reaction time and reproducibility of dose delivery control. The system proved to be precise in the application of beam gating and allowed the mitigation of dose distortions even for large (1.4cm) motion amplitudes, provided that adequate treatment windows were selected. The total delivered dose was not affected by the use of gating, with measured integral error within 0.15cGy. Analysing high-resolution images of proton transmission, we observed negligible discrepancies in the geometric location of the dose as a function of the treatment window, with gamma pass rate greater than 95% (2%/2mm) compared to stationary conditions. Similarly, pass rate for the latter metric at the 3%/3mm level was observed above 97% for clinical treatment fields, limiting residual movement to 3mm at end-exhale. These results were confirmed in realistic clinical conditions using an anthropomorphic breathing phantom, reporting a similarly high 3%/3mm pass rate, above 98% and 94%, for regular and irregular breathing, respectively. Finally, early results from periodic QA tests of the optical tracker have shown a reliable system, with small variance observed in static and dynamic measurements.

Data-acquisition system developments for ATLAS pixel QA and QC test toward High-Luminosity LHC

In preparation for the High-luminosity LHC upgrade, the whole ATLAS inner tracker will be replaced by a new silicon detector tracker. The innermost region will be covered by silicon pixel detectors as a high density of produced particles is expected. To operate in such an environment, high-resolution sensors and a high-speed readout system are required. At the moment, the front-end readout chip prototype RD53A and a data acquisition system (the YARR system) based on a commercial FPGA board and dedicated software for quality assurance and quality control test have been developed. Due to the high density of sensor channels, the output speed from RD53A is at maximum 1.28 Gbps per line, sixteen times faster than the readout front-end chip currently used in the ATLAS pixel system. The data acquisition system needs to establish communication with 1.28 Gbps speed during the quality control tests, to validate the data acquisition path, and to optimize the procedure for data taking at high speed. From the quality control perspective this optimization allows to test large numbers of modules simultaneously exploiting the data acquisition speed reducing the time needed for the tests. Another challenging point is the novel concept of readout structure planned for the operation after installation. In High-luminosity LHC, large parts of the ATLAS data acquisition system infrastructure are going to be shared among all sub-detectors, using FELIX systems, while current ATLAS data acquisition systems are dedicated for each sub-detector. This means that all processes done in the present data acquisition system hardware need to be overhauled into software running on the new data acquisition system. To minimize the differences between the data acquisition system for operation and quality control test, we introduced the prototype FELIX system into the data acquisition path of the YARR system. In this proceeding, an established data acquisition structure for quality assurance and quality control test of the new pixel detector is introduced, and results from basic quality control tests of the pixel detector with the new readout chip are presented.

Transversal dose profile reconstruction for clinical proton beams: A detectors inter-comparison

PurposeThe main purpose of this work is the inter-comparison between different devices devoted to the transversal dose profile recostruction for daily QA tests in proton therapy. MethodsThe results obtained with the EBT3 radiochromic films, used as a reference, and other common quality control devices, have been compared with those obtained with a beam profiling system developed at the “Laboratori Nazionali del Sud” of Italian Institute for Nuclear Physics (INFN-LNS, Catania, Italy). It consists of a plastic scintillator screen (thickness 1 mm), mounted perpendicularly to the beam axis and coupled with a highly sensitive CCD detector in a light-tight box. Results and conclusionThe tests, carried out both at the INFN-LNS and Trento Proton Therapy Center facilities, show, in general, a good agreement between the different detectors. The beam profiling system, in particular, appears to be a promising quality control device for 2-D relative dosimetry, because of its linear response in a dose rate range useful for proton therapy treatments, its high spatial resolution and its short acquisition and processing time.

12. MLC QA and Winston-Lutz Test by Electric Portal Imaging Device Using ImageJ

12. MLC QA and Winston-Lutz Test by Electric Portal Imaging Device Using ImageJ

Objective evaluation of imaging performance using a commercially available spherical lesion anechoic phantom

The nature of ultrasound imaging makes it challenging to perform quantitative quality control tests representative of clinical performance. IPEM Report No. 102 outlines several different tests which monitor aspects of the systems performance likely to affect the clinical efficiency following deterioration and change. Such tests include measurement of axial and lateral resolution, slice thickness, contrast resolution and low contrast penetration using ultrasound phantoms. Such phantoms consist of cylindrical objects and wire filaments embedded within homogeneous tissue-mimicking material. The ability of an ultrasound system to resolve the contrast difference between the cylindrical targets and background is regarded as an indicator of imaging performance; however, cylindrical targets are not necessarily representative of the clinical situation where ellipsoidal or spherical lesions may be considered more appropriate. To date, spherical lesion target phantoms have been produced in specialist research laboratories and are, thus, not widely available. Accordingly, this study sought to examine a relatively new commercially available anechoic spherical lesion phantom to determine its efficacy for objective evaluation of performance change. Several modern medical ultrasound systems were tested using the Gammex RMI 408 Spherical Lesion target phantom, containing 2mm and 4mm diameter anechoic spherical targets located within one plane throughout the phantom depth. A Matlab® program was used for automatic objective image quality analysis. Preliminary results will be presented on the automated objective evaluation, metric repeatability and reproducibility. Simulated probe faults will be used to establish test efficacy and the results will be compared to traditional QA testing.

A modern mold room: Meshing 3D surface scanning, digital design, and 3D printing with bolus fabrication.

PurposeThis case series represents an initial experience with implementing 3‐dimensional (3D) surface scanning, digital design, and 3D printing for bolus fabrication for patients with complex surface anatomy where traditional approaches are challenging.Methods and MaterialsFor 10 patients requiring bolus in regions with complex contours, bolus was designed digitally from 3D surface scanning data or computed tomography (CT) images using either a treatment planning system or mesh editing software. Boluses were printed using a fused deposition modeling printer with polylactic acid. Quality assurance tests were performed for each printed bolus to verify density and shape.ResultsFor 9 of 10 patients, digitally designed boluses were used for treatment with no issues. In 1 case, the bolus was not used because dosimetric requirements were met without the bolus. QA tests revealed that the bulk density was within 3% of the reference value for 9 of 12 prints, and with more judicious selection of print settings this could be increased. For these 9 prints, density uniformity was as good as or better than our traditional sheet bolus material. The average shape error of the pieces was less than 0.5 mm, and no issues with fit or comfort were encountered during use.ConclusionsThis study demonstrates that new technologies such as 3D surface scanning, digital design and 3D printing can be safely and effectively used to modernize bolus fabrication.

Determination of the penumbra width of Elekta SRS cone collimator for 6 MV FF and 6 MV FFF energies using gradient-based edge detection

The dosimetric measurements of small fields of radiation are undertaken with detectors such as: GafchromicTM films, diodes, diamond detectors and ionization chambers of small volumes. The penumbra width, e.g. the spatial distance between 80% and 20% dose, is smaller in small fields. This fact increases the curvature and hence the volume effect in the penumbra region. The accuracy in the penumbra calculation is important at the QA test for implementation of the cranial Stereotactic Radiosurgery. The objective of this work was to apply a Gradient-Based Edge Detection plugin to calculate the penumbra of a radiation beam defined with the Elekta SRS Cone Collimators for beams of 6 MV (Flattening Filter – FF) and 6 MV (Flattening Filter Free – FFF) energies using the beam profile obtained with GafchromicTM film. The results corroborate those from the literature, and they allow a quantitative evaluation of the width of dosimetric penumbra by Gradient-Based Edge Detection.