Evaluation of application of EPID for rapid QC testing of linear accelerator

Aim

Evaluation of application of EPID for rapid QC testing of linear accelerator.

Monitoring Daily QA 3 constancy for routine quality assurance on linear accelerators

The purpose of this study was to evaluate the suitability of the Daily QA 3 (Sun Nuclear Corporation, Melbourne, USA) device as a safe quality assurance device for control of machine specific parameters, such as linear accelerator output, beam quality and beam flatness and symmetry. Measurements were performed using three Varian 2300iX linear accelerators. The suitability of Daily QA 3 as a device for quality control of linear accelerator parameters was investigated for both 6 and 10 MV photons and 6, 9, 12, 15 and 18 MeV electrons. Measurements of machine specific using the Daily QA 3 device were compared to corresponding measurements using a simpler constancy meter, Farmer chamber and plane parallel ionisation chamber in a water tank. The Daily QA 3 device showed a linear dose response making it a suitable device for detection of output variations during routine measurements. It was noted that over estimations of variations compared with Farmer chamber readings were seen if the Daily QA 3 wasn’t calibrated for output and sensitivity on a regular eight to ten monthly basis. Temperature-pressure correction factors calculated by Daily QA 3 also contributed towards larger short term variations seen in output measurements. Energy, symmetry and flatness variations detected by Daily QA 3 were consistent with measurements performed in water tank using a parallel plate chamber. It was concluded that the Daily QA 3 device is suitable for routine daily and fortnightly quality assurance of linear accelerator beam parameters however a regular eight-ten monthly dose and detector array calibration will improve error detection capabilities of the device.     

Analysis of the long-term stability of the output of electron beams generated by the Novac11™ IORT accelerator

Aim

The aim of the study was to analyze the long-term stability of electron beams generated by the Novac11? IORT accelerator.

Treatment of Diabetes Mellitus in Dogs Using Isophane Insulin Penfills and the Use of Serum Fructosamine Assays to Diagnose and Monitor the Disease

The objectives of the study were to test the use of a prefilled insulin syringe (Insulatard® Novolet®, isophane insulin, 100 IU/mL) in treating diabetic dogs and to test the clinical usefulness of serum fructosamine measurements in diagnosing and monitoring diabetes mellitus in dogs. For this study 15 dogs from throughout Norway with newly diagnosed diabetes mellitus were included and treated over a period of 180 days. All 15 dogs showed pretreatment hyperglycaemia. Of the 13 dogs tested, all showed elevated pretreatment serum fructosamine values. Within 2 weeks, 3 of the 15 included dogs had dropped out of the study In 8 of the 12 remaining dogs, the clinical signs ceased within this period. Within a month, another dog was euthanised and one had died. Seven of the 10 remaining dogs were clinically normal. Three dogs had normal serum fructosamine concentrations, while in 6 dogs moderately or highly elevated serum fructosamine concentrations persisted. In one case serum fructosamine was not measured at this time. Increase in serum fructosamine concentration seemed to reflect hyperglycaemia and deteriorated clinical condition. Decrease in serum fructosamine concentration seemed to reflect improved glycaemic status and clinical condition. During the study period the owners did a total of approximately 3500 injections on their dogs. No reports of injection difficulties were received. This study documents that Insulatard® Novolet® is easy and safe to use in treating diabetic dogs and that serum fructosamine reflects long-term glucose concentrations in dogs. Serum fructosamine measurements provided a simple and easy way to diagnose persistent hyperglycaemia and monitor the treatment in diabetic patients.     

Commissioning and quality assurance of HalcyonTM 2.0 linear accelerator

BackgroundVarian Medical Systems has introduced a new medical linear accelerator called Halcyon^TM 2.0, which is based on the ring delivery system (RDS). It is a true IGRT machine having 6MV FFF photon energy. In addition to the planar and MV-CBCT imaging techniques it also has an option of ultra-fast kV-iCBCT which enhances the image reconstruction and improves the visualization of soft tissue. The field portals are shaped by a unique dual layer MLC with special stacked and staggered design which enables high modulation with low radiation leakage. Recently, we have commissioned our first Halcyon 2.0 machine. The aim of this work was to systematically investigate various parameters of a newly installed Halcyon^TM 2.0 linear accelerator.Materials and methodsDetailed measurements were conducted as per various guidelines. Also, the measurements were performed to fulfil the national regulatory requirements. Commissioning data of Halcyon 6 MV-FFF beam was performed in a water tank. For absolute measurements, a 0.6-cc waterproof Farmer chamber and electrometer were used. All relative measurements (PDDs, in-line, cross-line and angular profiles) were performed with 0.0125 cc point chamber.ResultsAll the tests were within the acceptable limit. Measured data were compared with factory data as well as the existing medical linear accelerator of the same category. The obtained results were quite satisfactory.ConclusionsThis study summarizes the commissioning experience with Halcyon linear accelerator. Evaluation of mechanical, radiation safety and dosimetric parameters were performed. The obtained parameters were well below the specified tolerance limits.     

High resolution three-dimensional strain mapping of bioprosthetic heart valves using digital image correlation

Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment option for patients deemed at high and intermediate risk for surgical aortic valve replacement. Similar to surgical aortic valves (SAVs), transcatheter aortic valves (TAVs) undergo calcification and mechanical wear over time. However, to date, there have been limited publications on the long-term durability of TAV devices. To assess longevity and mechanical strength of TAVs in comparison to surgical bioprosthetic valves, three-dimensional deformation analysis and strain measurement of the leaflets become an inevitable part of the evaluation. The goal of this study was to measure and compare leaflet displacement and strain of two commonly used TAVs in a side-by-side comparison with a commonly used SAV using a high-resolution digital image correlation (DIC) system. 26-mm Edwards SAPIEN 3, 26-mm Medtronic CoreValve, and 25-mm Carpentier-Edwards PERIMOUNT Magna surgical bioprosthesis were examined in a custom-made valve testing apparatus. A time-varying, spatially uniform pressure was applied to the leaflets at different loading rates. GOM ARAMIS® software was used to map leaflet displacement and strain fields during loading and unloading. High displacement regions were found to be at the leaflet belly region of the three bioprosthetic valves. In addition, the frame of the surgical bioprosthesis was found to be remarkably flexible, in contrary to CoreValve and SAPIEN 3 in which the stent was nearly rigid under a similar loading condition. The experimental DIC measurements can be used to characterize the anisotropic materiel behavior of the bioprosthetic heart valve leaflets and validate heart valve computational simulations.     

Characterization of a commercial scintillation detector for 2-D dosimetry in scanned proton and carbon ion beams

IntroductionPencil beam scanning technique used at CNAO requires beam characteristics to be carefully assessed and periodically checked to guarantee patient safety. This study aimed at characterizing the Lynx® detector (IBA Dosimetry) for commissioning and periodic quality assurance (QA) for proton and carbon ion beams, as compared to EBT3 films, currently used for QA checks.Methods and materialsThe Lynx® is a 2-D high-resolution dosimetry system consisting of a scintillating screen coupled with a CCD camera, in a compact light-tight box. The scintillator was preliminarily characterized in terms of short-term stability, linearity with number of particles, image quality and response dependence on iris setting and beam current; Lynx® was then systematically tested against EBT3 films. The detector response dependence on radiation LET was also assessed.ResultsPreliminary results have shown that Lynx is suitable to be used for commissioning and QA checks for proton and carbon ion scanning beams; the cross-check with EBT3 films showed a good agreement between the two detectors, for both single spot and scanned field measurements. The strong LET dependence of the scintillator due to quenching effect makes Lynx® suitable only for relative 2-D dosimetry measurements.ConclusionLynx® appears as a promising tool for commissioning and periodic QA checks for both protons and carbon ion beams. This detector can be used as an alternative of EBT3 films, allowing real-time measurements and analysis, with a significant time sparing.     

Non-invasive in vivo measurement of the shear modulus of human vocal fold tissue

Voice is the essential part of singing and speech communication. Voice disorders significantly affect the quality of life. The viscoelastic mechanical properties of the vocal fold mucosa determine the characteristics of the vocal folds oscillations, and thereby voice quality. In the present study, a non-invasive method was developed to determine the shear modulus of human vocal fold tissue in vivo via measurements of the mucosal wave propagation speed during phonation. Images of four human subjects' vocal folds were captured using high speed digital imaging (HSDI) and magnetic resonance imaging (MRI) for different phonation pitches, specifically fundamental frequencies between 110 and 440 Hz. The MRI images were used to obtain the morphometric dimensions of each subject's vocal folds in order to determine the pixel size in the high-speed images. The mucosal wave propagation speed was determined for each subject and at each pitch value using an automated image processing algorithm. The transverse shear modulus of the vocal fold mucosa was then calculated from a surface (Rayleigh) wave propagation dispersion equation using the measured wave speeds. It was found that the mucosal wave propagation speed and therefore the shear modulus of the vocal fold tissue were generally greater at higher pitches. The results were in good agreement with those from other studies obtained via in vitro measurements, thereby supporting the validity of the proposed measurement method. This method offers the potential for in vivo clinical assessments of vocal folds viscoelasticity from HSDI.     

Comparison of pre-treatment and in-vivo dosimetry for advanced radiotherapy of prostate cancer

BackgroundThe usage of advanced radiotherapy techniques requires validation of a previously calculated dose with the precise delivery with a linear accelerator. This study aimed to review and evaluate new verification methods of dose distribution. Moreover, our purpose was to define an internal protocol of acceptance for in-vivo measurements of dose distribution.Materials and methodsThis study included 43 treatment plans of prostate cancer calculated using the Monte Carlo algorithm. All plans were delivered using the Volumetric Modulated Arc Therapy (VMAT) technique of advanced radiotherapy by the linear accelerator Elekta VersaHD. The dose distribution was verified using: MatriXX, iViewDose, and in-vivo measurements. The verification also included recalculation of fluence maps of quality assurance plans in another independent algorithm.ResultsThe acceptance criterion of 95% points of dose in agreement was found for pre-treatment verification using MatriXX; the average γ value was 99.09 ± 0.93 (SD) and 99.64 ± 0.35 (SD) for recalculation in the Collapse Cone algorithm. Moreover, using the second algorithm in the verification process showed a positive correlation ρ = 0.58, p < 0.001. However, verification using iViewDose in a phantom and in-vivo did not meet this γ-pass rate.ConclusionsEvaluation of gamma values for in-vivo measurements utilizing iViewDose software was helpful to establish an internal dosimetry protocol for prostate cancer treatments. We assumed value at a minimum of 50% points of the dose in agreement with the 3%/3 mm criterion as an acceptable compliance level. The recalculated dose distribution of QA plans in regard to the Collapse Cone algorithm in the other treatment planning system can be used as a pre-treatment verification method used by a medical physicist in their daily work. The effectiveness of use in iViewDose software, as a pre-treatment tool, is still debatable, unlike the MatriXX device.     

An automatic MRI quality control procedure: Multisite reports for slice thickness and geometric accuracy

In this work, we report multi-scanner quality control monitoring using a standard and automated protocol. This magnetic resonance imaging quality control protocol, based on the American College of Radiology procedures, includes weekly scans of a dedicated phantom followed by specific measurements. The processing step commonly involves manually-performed operations which can be tedious and time-consuming hence motivating their automation. QC data were collected in four sites; data from one of them served for the validation of the automatic analysis tool. Designed as a package of MATLAB^® functions, this tool was successfully validated using Student's t-test and the correlation between automatic measurements and the manual ones. Besides, the multisite QC study enabled to compare the performances of these four MR facilities. In order to avoid misinterpretation or errors in multicenter clinical studies, such approach can be recommended as a preliminary step for including a site in the studies.     

Improvements of Liver MR Imaging Clinical Protocols to Simultaneously Quantify Steatosis and Iron Overload

Purpose

Fat accumulation and iron overload are important cofactors in chronic liver disease. Clinical quantifications of fat fraction and iron are currently assessed using MRI protocols. The purpose is to improve these measurements to simultaneously provide iron and fat maps from a single acquisition.

Glycosylation profile and biological activity of Remicade® compared with Flixabi® and Remsima®

As biosimilars enter the market, comparisons of product quality are needed. Manufacturing differences may lead to differences in critical quality attributes, which affect efficacy. Therefore, critical quality attributes (structure and biological activity) of Remicade® and of 2 biosimilar products (Flixabi®/Renflexis® and Remsima®/Inflectra®) were determined. We assessed binding to tumor necrosis factor in a fluorescence competitive binding assay; potency in a luciferase reporter gene assay; percentages of galactosylated glycan, afucose plus high mannosylated glycans, and charged glycan; FcγRIIIa (CD16) binding (assessed by 3 methods); and antibody-dependent cell-mediated cytotoxicity (ADCC) in the NK92-CD16a cell line and in peripheral blood mononuclear cells (PBMC). The results of Fab-related activity were similar for all products. Compared with Remicade®, Flixabi® had a lower percentage of charged glycan, and Remsima® had a higher percentage of galactosylated glycan and a lower percentage of afucose plus high mannosylated glycans. Whereas Remsima® and Remicade® are expressed in a Sp2/0 cell line, Flixabi® is expressed in a CHO cell line. Despite this difference, galactosylated glycans from the 3 products were not correlated with the expression system. The results of all 3 methods used in this study indicated that FcγRIIIa binding was lower with Remsima® than with Remicade®. The percentage of ADCC in NK92-CD16a cells was lower with Remsima® and higher with Flixabi® compared with Remicade®, but was similar for all 3 products in PBMC. Surface expression of CD16 was 5.7-fold greater on NK92-CD16a cells than on PBMC. Combined percentages of afucosylated and high mannosylated glycans were positively correlated with FcγRIIIa binding and ADCC in NK92-CD16 cells, while no correlation was observed in PBMC.     

Assessment of out-of-field doses in radiotherapy treatments of paediatric patients using Monte Carlo methods and measurements

PurposeTo assess out-of-field doses in radiotherapy treatments of paediatric patients, using Monte Carlo methods to implement a new model of the linear accelerator validated against measurements and developing a voxelized anthropomorphic paediatric phantom.MethodsCT images of a physical anthropomorphic paediatric phantom were acquired and a dosimetric planning using a TPS was obtained. The CT images were used to perform the voxelization of the physical phantom using the ImageJ software and later implemented in MCNP. In order to validate the Monte Carlo model, dose measurements of the 6 MV beam and Linac with 120 MLC were made in a clinical setting, using ionization chambers and a water phantom. Afterwards TLD measurements in the physical anthropomorphic phantom were performed in order to assess the out-of-field doses in the eyes, thyroid, c-spine, heart and lungs.ResultsThe Monte Carlo model was validated for in-field and out-of-field doses with average relative differences below 3%. The average relative differences between TLD measurements and Monte Carlo is 14,3% whilst the average relative differences between TLD and TPS is 55,8%. Moreover, organs up to 22.5 cm from PTV center show TLD and MCNP6 relative differences and TLD and TPS relative differences up to 21.2% and 92.0%, respectively.ConclusionsOur study provides a novel model that could be used in clinical research, namely in dose evaluation outside the treatment fields. This is particularly relevant, especially in pediatric patients, for studying new radiotherapy treatment techniques, since it can be used to estimate the development of secondary tumours.     

Validation clinique du module Oncoflash® en scintigraphie planaire thyroïdienne

IntroductionThe Oncoflash® adaptive filtering algorithm is poorly validated in clinical practice. The objective of this study was to evaluate this algorithm efficacity in order to reduce injected activity or acquisition time on thyroid scintigraphy.MethodsOne hundred and five patients who received a thyroid scan have been tested. Three sets of images (conventional acquisition, gross half-time acquisition, post-processed half-time acquisition by Oncoflash®) were interpreted as open ultrasound and biological data without any view on their medical file and the patient's identity by 2 nuclear doctors. The concordance with the diagnosis retained in the medical file, the quality of the images and the inter-observer reproducibility were evaluated.ResultsNo significant differences were found in terms of agreement with the final diagnosis between post-processed Oncoflash® half-time images and conventional images (κ at 0.81 and 0.74 respectively). The quality of Oncoflash® half-time images was rated good or excellent in 90% of cases compared to 88.6% of cases for conventional acquisitions (P = 0.16). No significant difference in inter-observer agreement was found between the 3 sets of images compared two by two.ConclusionThese results suggest the possibility of using the Oncoflash® module in thyroid scintigraphy to reduce acquisition time or injected activity without impacting interpretation.     

Reliability of Phase Velocity Measurements of Flexural Acoustic Waves in the Human Tibia In-Vivo

Purpose

Axial-transmission acoustics have shown to be a promising technique to measure individual bone properties and detect bone pathologies. With the ultimate goal being the in-vivo application of such systems, quantification of the key aspects governing the reliability is crucial to bring this method towards clinical use.

Materials and Methods

This work presents a systematic reliability study quantifying the sources of variability and their magnitudes of in-vivo measurements using axial-transmission acoustics. 42 healthy subjects were measured by an experienced operator twice per week, over a four-month period, resulting in over 150000 wave measurements. In a complementary study to assess the influence of different operators performing the measurements, 10 novice operators were trained, and each measured 5 subjects on a single occasion, using the same measurement protocol as in the first part of the study.

Results

The estimated standard error for the measurement protocol used to collect the study data was ∼ 17 m/s (∼ 4% of the grand mean) and the index of dependability, as a measure of reliability, was Φ = 0.81. It was shown that the method is suitable for multi-operator use and that the reliability can be improved efficiently by additional measurements with device repositioning, while additional measurements without repositioning cannot improve the reliability substantially. Phase velocity values were found to be significantly higher in males than in females (p < 10⁻⁵) and an intra-class correlation coefficient of r = 0.70 was found between the legs of each subject.

Conclusions

The high reliability of this non-invasive approach and its intrinsic sensitivity to mechanical properties opens perspectives for the rapid and inexpensive clinical assessment of bone pathologies, as well as for monitoring programmes without any radiation exposure for the patient.     

Effectiveness and safety of a long-acting,once-daily,two-phase release formulation of methylphenidate (Ritalin<Superscript>®</Superscript> LA) in school children under daily practice conditions

Long-acting (LA) preparations of methylphenidate allow for once-daily dosing; however, pharmacokinetics may vary and depend on food intake. The objective was to evaluate effectiveness of a two-phase release formulation (Ritalin^® LA) under daily practice conditions. This was a prospective, multicenter, observational study in Germany. Eligibility and dosing were determined by the physician based on the drug label. Outcomes included changes over 3 months of treatment in assessments of effect duration, clinical global impression (CGI), and quality of life (ILK). In 101 sites, 262 patients (197 boys, 63 girls, and two unknown) with a mean age of 10.9 years were enrolled; 50 were treated for the first time; 212 switched medication to Ritalin^® LA. After 3 months, CGI improved in 59.4 % of patients, and well-being overall was rated as good by 61.0 % of parents and 63.7 % of children. Based on parents’ assessment, the proportion of children suffering from strong disease burden decreased from 40.7 to 15.1 %. In 123 insufficient responders to previous ADHD medications, benefit from Ritalin^® LA was above average and effect duration was significantly prolonged as compared to pretreatment. Overall, 28 patients (10.7 %) had treatment-related adverse events with one case being serious; 23 patients (8.8 %) discontinued therapy, 7 (2.7 %) due to poor treatment response; and 212 patients (81 %) continued treatment beyond the study. In line with clinical trial data, Ritalin^® LA provides significant benefit also under routine practice conditions.     

Non-destructive dendrochronology with X-ray computed tomography: The influence of different conservation methods for waterlogged archaeological wood

In this study, the influence of different conservation methods for waterlogged archaeological wood (WAW) on non-destructive dendrochronological dating by micro-computed tomography (µCT) was evaluated. For this purpose, samples of different wood species were conserved using the following methods: alcohol-ether-resin, Kauramin 800®, lactitol/trehalose, saccharose, silicone oil and different polyethylene glycol (PEG) treatments with subsequent freeze-drying. The tree ring measurements of all samples in the digital µCT data were compared with the measurements on an analog linear measuring table in terms of the total number of rings per sample and the mean ring width. The year-to-year ring width measurements in the µCT data agreed very well overall with the corresponding microscopic measurements. It was possible to detect the rings in the samples with µCT in all cases. A dendrochronological cross dating with regional absolutely dated ring width chronologies was successful in two cases. However, the different influence of the conservation agents on the quality of the µCT data was clearly visible. In order to assess this influence, the contrast in the µCT data was determined using grey-scale profiles. A decrease in contrast in the µCT data was detectable for all conservation agents. A particular strong influence is observed for the conservation methods using silicone oil, lactitol/trehalose, PEG and saccharose. Overall, the study performed confirms that µCT is a powerful and accurate method for non-destructive dendrochronology of conserved archaeological objects.     

Evaluation of plan quality improvements in PlanIQ-guided Autoplanning

AimPhilips recently integrated PlanIQ with Autoplan® in Pinnacle³ TPS (V16.2). The objective of the present work is to quantitatively demonstrate how this integration improves the plan quality.BackgroundPinnacle³ Autoplan® is the tool that generates the treatment plans with clinically acceptable plan quality with less manual intervention. In the recent past, a new tool called PlanIQ (Sun Nuclear Corp.) was introduced for a priori estimation of the best possible sparing of an organ at risk (OAR) for a given patient anatomy. Philips has recently integrated PlanIQ tool with Autoplan® for a seamless and efficient planning workflow.Materials and methodsWe have performed this evaluation in Pinnacle³ TPS (V.16.2) for the VMAT treatment technique. All plans were created using Varian True beam machine with the dual arc technique. Basically, we created two sets of VMAT plans using 6 MV photons. In the first set of VMAT plans (AP_RTOG), we used OAR goals from either RTOG guidelines to perform optimization using Autoplan®. Subsequently, we exported the same dataset to the PlanIQ system to perform feasibility analysis on the OAR goals. These newly obtained OAR goals from PlanIQ were used to generate the other set of plans (AP_PlanIQ plans). We compared the dosimetric results from these two sets of plans in five cases, such as brain, head & neck, lung, abdomen and prostate.ResultsWe compared the dosimetric results for AP_RTOG and AP_PlanIQ plans. We used RTOG guidelines to evaluate the plans and observed that while both sets of plans were meeting the RTOG guidelines in terms of OAR sparing, the AP_PlanIQ plans were significantly better in terms of OAR sparing as compared to AP_RTOG plans without any compromise in the target coverage.ConclusionThe results indicate that, although Autoplan helps achieve the user-defined goals without much manual intervention, the plan quality (OAR sparing) can be significantly improved without taking many iterative steps when PlanIQ suggested clinical goals are used in the Autoplan-based optimization.Advances in knowledgeAt present, there are no published material available about the efficacy of the integration of PlanIQ with Autoplanning®. In the present work, our objective is to evaluate the improvements in plan quality resulting from this integration.     

Monte Carlo evaluation of the effect of inhomogeneities on dose calculation for low energy photons intra-operative radiation therapy in pelvic area

The aim of this study was to evaluate the effect of inhomogeneities on dose calculation for low energy photons intra-operative radiation therapy (IORT) in pelvic area. A GATE Monte Carlo model of the INTRABEAM® was adapted for the study. Simulations were performed in the CT scan of a cadaver considering a homogeneous segmentation (water) and an inhomogeneous segmentation (5 tissues from ICRU44). Measurements were performed in the cadaver using EBT3 Gafchromic® films. Impact of inhomogeneities on dose calculation in cadaver was 6% for soft tissues and greater than 300% for bone tissues. EBT3 measurements showed a better agreement with calculation for inhomogeneous media. However, dose discrepancy in soft tissues led to a sub-millimeter (0.65 mm) shift in the effective point dose in depth. Except for bone tissues, the effect of inhomogeneities on dose calculation for low energy photons intra-operative radiation therapy in pelvic area was not significant for the studied anatomy.     

Evaluation of DNA extraction methods of rumen microbial populations

The dynamism of microbial populations in the rumen has been studied with molecular methods that analyze single nucleotide polymorphisms of ribosomal RNA gene fragments (rDNA). Therefore DNA of good quality is needed for this kind of analysis. In this work we report the evaluation of four DNA extraction protocols (mechanical lysis or chemical lysis with CTAB, ethylxanthogenate or DNAzol^®) from ruminal fluid. The suitability of two of these protocols (mechanical lysis and DNAzol^®) was tested on single-strand conformation polymorphism (SSCP) of rDNA of rumen microbial populations. DNAzol^® was a simple method that rendered good integrity, yield and purity. With this method, subtle changes in protozoan populations were detected in young bulls fed with slightly different formulations of a supplement of multinutritional blocks of molasses and urea. Sequences related to Eudiplodinium maggi and a non-cultured Entodiniomorphid similar to Entodinium caudatum, were related to major fluctuating populations in an SSCP assay.