Siemens Healthcare GmbH Research Articles

Comparison of screening performance metrics and patient dose of two mammographic image acquisition modes in the Danish National Breast Cancer Screening Programme

IntroductionIn this study, screening performance metrics and radiation dose were compared for two image acquisition modes for breast cancer screening with MAMMOMAT Inspiration (Siemens Healthcare GmbH, Forchheim, Germany). This mammography system can operate without an anti-scatter grid in place but using software scatter correction instead. This grid-less acquisition mode (PRIME) requires less patient dose due to the increase in primary radiation reaching the detector. This study retrospectively analyses data from the Region of Southern Denmark where the grid-less mode has been installed in November 2013 and replaced grid-based screening. Methods and materialsA total of 72,188 screening cases from the same geographical region in Denmark were included in the study. They were subdivided into two study populations: cases acquired before and after installation of the grid-less acquisition mode. Sensitivity and specificity of breast cancer screening were calculated for the two populations; thus representing the performance of grid-less and grid-based screening. To measure the entrance surface air kerma (ESAK) additional phantom tests were carried out. Polymethylmethacrylate (PMMA) attenuation plates with different thicknesses (20–70 mm in steps of 10 mm) simulated the compressed breast (21 mm–90 mm) and a solid-state dosimeter was used. ResultsStatistical testing of the results showed that screening with grid-less acquisition provides equivalent performance with respect to sensitivity and specificity compared to grid-based screening. The specificity was 98.11% (95% confidence interval (CI) from 97.93% to 98.29%) and 97.96% (95% CI from 97.84% to 98.09%) for screening with grid-less acquisition and grid-based acquisition, respectively. The cancer detection rate as a measure for sensitivity was equal (0.55%) for grid-less screening and grid-based screening. An average glandular dose saving between 13.5% and 36.4% depending on breast thickness in grid-less acquisition was obtained compared to grid-based acquisition. ConclusionStatistically significant equivalence was shown with an equivalence margin of 0.12% points for cancer detection rate and with an equivalence margin of 0.40% points for specificity. A marked patient dose savings in grid-less acquisition of up to 36% compared to grid-based acquisition was achieved. It can be concluded that grid-less acquisition with software scatter correction is an alternative to grid-based acquisition in mammography.

Unique percutaneous direct puncture technique for occlusion of a hypoglossal canal dural arteriovenous fistula

PurposeTo report percutaneous transcranial puncture, embolization and occlusion of a very symptomatic hypoglossal canal/anterior condylar vein dural arteriovenous fistula (DAVF) using syngo iGuide navigational software in a patient in whom...

Comparación de dos métodos para la cuantificación en suero de subclases de inmunoglobulinas

Background and aimThe quantification of serum immunoglobulins, and particularly of IgG and IgG subclasses, is of interest for the diagnosis of numerous diseases. The usual detection methods provide different results according to the analyser used. The aim of this study was to compare the results obtained with two different analysers in the measurement of the concentration of IgG and IgG subclasses. Material and methodsA total of 116 serum samples, regardless of the clinical diagnosis of the patients to whom the samples belonged, were analysed. The analyses were performed on a BNII® System (Siemens Healthcare GmbH, Germany) and Optilite® system (The Binding Site Group Ltd., Birmingham). ResultsThe correlation between total IgG concentration (mg/dl) and the sum of the individual IgG subclasses detected was higher using the Optilite® analyser (0.976 vs. 0.866). The percentage of agreement between assays ranged from 43% to 71%, with the lower limit being for the IgG3 agreement. An absence of the usual IgG subclass physiological proportion (IgG1>IgG2>IgG3>IgG4) was detected using BNII®. These findings were a due to the significantly lower proportion of IgG3 obtained by BNII® compared to Optilite® (P<.001), whereas the IgG4 concentration was not significantly different between analysers (P=.117). ConclusionsDifferences between the results obtained with the two different methods suggest that they should not be interchangeable, and that each clinical laboratory should only use one type of analyser. The reference ranges should be standardised according to the results obtained.

IP269. Intraoperative Cone Beam Computed Tomography Pulmonary Angiography: An Effective Adjunct Imaging Tool for Rapid Diagnosis and Safe Catheter-Directed Thrombolysis

Submassive and massive pulmonary embolism (PE) is associated with high mortality, and effective treatment lies within a short window of time. In these instances, rapid diagnosis and treatment are vital for providing fast and efficacious care. We report a novel technique of intraoperative cone beam computed tomography pulmonary angiography (CBCT-PA) for diagnosis and treatment of PE in selected highly morbid cases. Between April 2015 and February 2016, patients who underwent intraoperative CBCT-PA were retrospectively reviewed. In our hybrid operating room equipped with a robotic angiography system (Artis zeego; Siemens Healthcare GmbH, Erlangen, Germany), CBCT-PA images were acquired using a 5-second CBCT protocol (syngo DynaCT; Siemens) after injection of 40 mL of 50% iodinated contrast material at 8 mL/s through a pigtail catheter in the main pulmonary artery. Four patients underwent intraoperative CBCT-PA during the study period. Two of four patients (50%) were hemodynamically unstable in the intensive care unit and deemed unstable for transfer to computed tomography imaging in the radiology suite. These patients were taken directly to the operating room under high suspicion of massive PE and for possible intervention. In one patient, CBCT-PA revealed a large embolus in the left pulmonary artery (Fig 1), prompting an attempt at mechanical thrombectomy. In the other patient, CBCT demonstrated only a small subsegmental embolus in the right lower lobe pulmonary artery (Fig 2), which made PE the unlikely cause for acute decompensation. In the remaining two patients, CBCT imaging was performed for follow-up after placement of thrombolytic catheters the day before. CBCT demonstrated residual clot in subsegmental branches, and thrombolytic catheters were repositioned. Both patients did well after removal of thrombolytic catheters and prescription of systemic anticoagulation. CBCT-PA is an effective adjunct imaging tool for diagnosis of PE in the operating room, especially in hemodynamically unstable patients, for whom transfer to the radiology imaging suite is often unsafe, and during catheter-directed thrombolysis. Until conventional computed tomography imaging becomes routinely available in the operating room, such novel intraoperative imaging options can be a valuable addition to the PE response team algorithm to optimize care in patients with PE.Fig 2Oblique coronal reconstruction of computed tomography image showing small embolus in the left lower lobe pulmonary artery (arrow).View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Effect of varying computed tomography acquisition and reconstruction parameters on semi-automated clot volume quantification.

AIMTo examine effects of computed tomography (CT) image acquisition/reconstruction parameters on clot volume quantification in vitro for research method validation purposes.METHODSThis study was performed in conformance with HIPAA and IRB Regulations (March 2015-November 2016). A ten blood clot phantom was designed and scanned on a dual-energy CT scanner (SOMATOM Force, Siemens Healthcare GmBH, Erlangen, Germany) with varying pitch, iterative reconstruction, energy level and slice thickness. A range of clot and tube sizes were used in an attempt to replicate in vivo emboli found within central and segmental branches of the pulmonary arteries in patients with pulmonary emboli. Clot volume was the measured parameter and was analyzed by a single image analyst using a semi-automated region growing algorithm implemented in the FDA-approved Siemens syngo.via image analysis platform. Mixed model analysis was performed on the data.RESULTSOn the acquisition side, the continuous factor of energy showed no statistically significant effect on absolute clot volume quantification (P = 0.9898). On the other hand, when considering the fixed factor of pitch, there were statistically significant differences in clot volume quantification (P < 0.0001). On the reconstruction side, with the continuous factor of reconstruction slice thickness no statistically significant effect on absolute clot volume quantification was demonstrated (P = 0.4500). Also on the reconstruction side, with the fixed factor of using iterative reconstructions there was also no statistically significant effect on absolute clot volume quantification (P = 0.3011). In addition, there was excellent R2 correlation between the scale-measured mass of the clots both with respect to the CT measured volumes and with respect to volumes measure by the water displacement method.CONCLUSIONAside from varying pitch, changing CT acquisition parameters and using iterative reconstructions had no significant impact on clot volume quantification with a semi-automated region growing algorithm.

Initial clinical results with a fusion prototype for mammography and three-dimensional ultrasound with a standard mammography system and a standard ultrasound probe.

Combinations *Equal contributors. of different imaging techniques in fusion devices appear to be associated with improvements in diagnostic assessment. The aim of this study was to test the feasibility of using an automated standard three-dimensional (3D) ultrasound (US) device fused with standard mammography for the first time in breast cancer patients. Digital mammograms and 3D automated US images were obtained in 23 patients with highly suspicious breast lesions. A recently developed fusion machine consisting of an ABVS 3D US transducer from an Acuson S2000 machine and a conventional Mammomat Inspiration device (both Siemens Healthcare GmbH, Erlangen, Germany) were used for the purpose. The feasibility of the examinations, imaging coverage, and patients' experience of the procedure were examined. In 15 out of 19 patients, the region of interest (ROI) with the tumor marked in the mammogram was visible on US. The examination was experienced positively by the patients, with no unexpected pain or injury. The examination was time-saving and well tolerated. In conclusion, we have shown initial clinical feasibility of an US/radiography fusion prototype with good localization and evaluation of the ROIs. The combined examination was well tolerated. The simultaneous evaluation with mammography and US imaging may be able to improve detection and reduce examiner-related variability.

PET attenuation correction for rigid MR Tx/Rx coils from 176Lu background activity

One challenge for PET-MR hybrid imaging is the correction for attenuation of the 511 keV annihilation radiation by the required RF transmit and/or RF receive coils. Although there are strategies for building PET transparent Tx/Rx coils, such optimised coils still cause significant attenuation of the annihilation radiation leading to artefacts and biases in the reconstructed activity concentrations. We present a straightforward method to measure the attenuation of Tx/Rx coils in simultaneous MR-PET imaging based on the natural 176Lu background contained in the scintillator of the PET detector without the requirement of an external CT scanner or PET scanner with transmission source. The method was evaluated on a prototype 3T MR-BrainPET produced by Siemens Healthcare GmbH, both with phantom studies and with true emission images from patient/volunteer examinations. Furthermore, the count rate stability of the PET scanner and the x-ray properties of the Tx/Rx head coil were investigated. Even without energy extrapolation from the two dominant γ energies of 176Lu to 511 keV, the presented method for attenuation correction, based on the measurement of 176Lu background attenuation, shows slightly better performance than the coil attenuation correction currently used. The coil attenuation correction currently used is based on an external transmission scan with rotating 68Ge sources acquired on a Siemens ECAT HR + PET scanner. However, the main advantage of the presented approach is its straightforwardness and ready availability without the need for additional accessories.

Chinese Pediatric Reference Intervals for Serum Cortisol on IMMULITE 2000.

Clinical interpretation of the test results for cortisol based on continuous reference intervals with appropriate partitions improves pediatric diagnosis; however, these values are available only for Caucasians. To develop the pediatric reference intervals for Chinese population, we examined the serum cortisol levels in 1,143 healthy Chinese children aged 4–18 years (566 boys and 577 girls), using an IMMULITE 2000 Immunoassay System (Siemens Healthcare GmbH). Phlebotomy was performed at 7–9 a.m. for 284 boys and 287 girls and at 1–3 p.m. for the others. They were divided into four age groups according to the Clinical and Laboratory Standards Institute guideline EP28-A3c, with the last group further stratified according to sampling time. Separate reference intervals of 49.6–323.7, 70.9–395.3, and 90.1–448.7 nmol/L were established for children aged 4–8, 9–12, and 13–15 years, respectively. Further, reference intervals of 118.2–464.7 and 71.4–446.7 nmol/L were established for morning and afternoon cortisol levels, respectively, in children aged 16–18 years. Further studies are necessary to transfer and validate these reference intervals in other analytical systems and pediatric populations, and to allow for broader applications.

A comparison of relative proton stopping power measurements across patient size using dual- and single-energy CT

Purpose: To evaluate the accuracy and precision across phantom size of a dual-energy computed tomography (DECT) technique used to calculate relative proton stopping power (SPR) in tissue-simulating materials and a silicone implant relative to conventional single-energy CT (SECT).Material and methods: A 32 cm lateral diameter (CIRS model 062M, Norfolk, Virginia) electron density phantom containing inserts which simulated the chemical composition of eight tissues in a solid-water background was scanned using SECT and DECT. A liquid water insert was included to confirm CT number accuracy. All materials were also placed in four water tanks, ranging from 15 to 45 cm in lateral width and scanned using DECT and SECT. A silicone breast implant was scanned in the same water phantoms. SPR values were calculated based on commercial software (syngo CT Dual Energy, Siemens Healthcare GmbH) and compared to reference values derived from proton beam measurements. Accuracy and precision were quantified across phantom size using percent error and standard deviation. Graphical and regression analysis were used to determine whether SECT or DECT was superior in estimating SPR across phantom size.Results: Both DECT and SECT SPR data resulted in good agreement with the reference values. Percent error was ±3% for both DECT and SECT in all materials except lung and dense bone. The coefficient of variation (CV) across materials and phantom sizes was 1.12% for SECT and 0.96% for DECT. Material-specific regression and graphical analysis did not reveal size dependence for either technique but did show reduced systematic bias with DECT for dense bone and liver. Mean percent error in SPR for the implant was reduced from 11.46% for SECT to 0.49% for DECT.Conclusions: We demonstrate the superior ability of DECT to mitigate systematic bias in bones and liver and estimate SPR in a silicone breast implant.

Abstract 222: Utility of Non-Contrast, Non-EKG Gated Multi-Detector Computed Tomography to Rule Out Obstructive Coronary Artery Disease in Heart Transplant Recipients

Background: Annual or biannual coronary angiography is recommended after heart transplantation. This is associated with radiation and contrast exposure in addition to being invasive. Absence of coronary calcium on CT in non-transplanted patients has a high negative predictive value (NPV) to rule out obstructive CAD. Objective: To determine whether the absence of coronary calcium on non-contrast, non-gated MDCT has a high NPV to rule out obstructive CAD in heart transplant recipients. Methods: We included patients with a non-contrast, non-gated chest CT within 1 year of undergoing a coronary angiogram from 2006 to 2016. Obstructive CAD was defined as stenosis &gt;50%. Coronary artery calcium scores (CACS) were calculated by the Agatston method using the syngo.via platform (Siemens Healthcare GmbH, Germany). For analysis, CACS were categorized based on a) presence or absence of coronary calcium (i.e., CACS=0 or CACS&gt;0) or b) severity of calcification (i.e., CACS=0, CACS 0-100 and CACS&gt;100). Results: We reviewed 76 consecutive angiograms and corresponding CTs. Prevalence of obstructive CAD was 9.2% (n=7). Prevalence of CACS=0 was 89.5% (n=68) of which 5 had obstructive CAD presenting a NPV of 93%. 8 patients had CACS&gt;0 of which 2 had obstructive CAD on angiogram (positive predictive value=25%). CACS was found to correlate with severity of CAD by angiography(p&lt;0.05). Of 7 angiograms with obstructive CAD, stenosis &gt;50% was found in 10 vessels - 5 LAD, 1 D1, 1 LCx, 2 OM branches and 1 RCA. Calculating CACS enabled detection of 1/5 LAD lesions; lesion in D1 was detected as an LAD lesion; lesions in the OM branches and RCA were not detected. Conclusion: Absence of coronary calcium on MDCT has a high NPV in ruling out obstructive CAD in heart transplant recipients. However, only 2/10 obstructive lesions on angiogram had calcification plaques detected on corresponding vessels on CT. The clinical significance of this is yet to be determined.

Dynamic MRI Assessment of Normal Knee Kinematics

Background: Knee motion is complex and has been studied intensively. The concept of an instant center of rotation postulates that the axis around which the tibia flexes and extends moves with knee flexion and extension. This concept has been contradicted by the concept of fixed axes around which the tibia and patella flex and extend during knee motion. Advanced imaging technologies help to further characterize knee motion and facilitate localization of the axis around which the tibia flexes and extends. Using dynamic magnetic resonance imaging (MRI), the purpose of this study was 1) to establish a setup for dynamic MRI knee measurements, 2) to construct a cadaver knee model and 3) to generate a mathematical algorithm to facilitate a 3-dimensional characterization of knee kinematics and calculate a defined and fixed axis around which the tibia flexes and extends. Methods: MR images were obtained using a 1.5T Magnetom Avanto MRI Scanner (Siemens Healthcare GmbH, Erlangen). A u-shaped 16 channel RF (radiofrequency) coil array with 160 mm inner diameter and a length of 180 mm was used and covered the cadaver knee on three sides. The fourth side of the knee is open to allow knee motion. A pneumatic movement device was specifically designed to generate reproducible and repetitive knee flexion and extension. The MRI sequence was synchronized with the frequency of the motion cycle. Ten cadaver knees were thawed, dissected and prepped with contrast media filled spheres. They were then fixed in the movement device and were scanned with dynamic MRI. The center of rotation was calculated using circular interpolation and the error (F) was calculated comparing the measured value at any time point with an ideal position based on the calculated flexion-extension axis (=nonlinear curve optimization). Results: Knee movement was analyzed within a motion arch of 90°. All knee specimens had intact ligamentous structures, no meniscal pathology, and no osteoarthritic changes of the cartilage surface. A fixed axis around which the tibia flexes and extends was localized in all ten specimens and the accuracy of the axis was calculated. Conclusions: This study presents a novel technique of using dynamic MRI to visualize knee kinematics ex vivo and confirms the presence of a fixed axis around the tibia flexes and extends. The passive movement device and the mathematical algorithm generates an accurate system to evaluate knee motion that will be of further assistance in characterization of physiologic biomechanics and in detection of pathological kinematics of the knee joint in vivo.

P3.04-008 CATS: Computed Tomography-Assisted Thoracoscopic Surgery - A Novel Approach in Patients with Deep Intrapulmonary Lesions of Unknown Dignity: Topic: Miscellaneous I

National Lung Screening Trial using low-dose CT may result in a relative reduction in mortality from lung cancer. Screening programs to be implemented will result in more patients being diagnosed with unclear pulmonary lesions and indicate excisional biopsy. Minimal invasive resection of small, deep intrapulmonary lesions can be challenging as the lesions are difficult to localize during VATS surgery. We introduced an intraoperative cone-beam computed tomography (CBCT) system in a hybrid operating theatre to place a marking wire immediately prior to VATS removal of the suspected lesions. Fifteen patients (5 m, 10 f, median age 63yrs) with solitary, deep intrapulmonary nodules of unknown histological status were identified for intraoperative wire marking. While being under general anesthesia for VATS, patients were placed on the operating table. and a marking wire was placed within the lesion under 3D laser and fluoroscopic guidance using the CBCT system (Artis zeego, Siemens Healthcare GmbH, Germany). Then wedge resection by VATS was performed in the same setting without any repositioning the patient. Complete resection with adequate safety margins was confirmed for all lesions. Marking wire placement facilitated resection in 15 out of 16 lesions. Histologically, mean lesion size was 7.5mm. The mean distance of the lesion to the pleural surface was 15.9mm (mean lesion depth/lesion diameter ratio = 2.3). Eleven lesions proved to be malignant, either primary lung cancer or metastases from prior malignancies. Five lesions turned out to be benign. Mean procedural time for marking wire placement was 35min; mean VATS duration was 36min. There is a learning curve for the whole team involving anesthesiology, radiology, and thoracic surgery. CATS is a new, safe, and effective procedure for minimally invasive resection of small, deeply localized intrapulmonary lesions. The benefits of CATS are: (1) 'one-stop shopping' procedure to locate and remove small lung lesions (2) lower risk for the patient (no patient relocation intraoperatively, no marking wire loss), and (3) no necessity to coordinate scheduling between CT and operating theatre.

Impact of iterative metal artifact reduction on dose calculation accuracy – Phantom study

Introduction Dose calculation in radiation therapy is based on computed tomography (CT) data. Dental materials cause streaking artifacts that lower image quality and affect dose calculation accuracy. Purpose The study investigates the impact of the iterative metal artifact reduction algorithm (iMAR, Siemens Healthcare GmbH) on image quality and dose calculation accuracy depending on different dental materials such as metal alloys and oxide ceramics. Materials and Methods A phantom simulating the mouth region composed of different tissue equivalent materials was used. The phantom was equipped with different numbers of cylinders made of non-precious-alloys (CoCr and titanium) and zirconia. CT data were acquired and corrected using two sets of correction parameters. Image quality was determined by comparison to synthetically generated CT data. IMRT and VMAT plans were calculated on each CT dataset using the dose calculation algorithms XVMC (Monaco), Collapsed Cone and Pencil Beam (Oncentra) and compared to 2D dose measurements using Gafchromic films. Dose calculation accuracy was determined using the gamma method. Results Image quality could be improved significantly. Absolute deviation of Hounsfield units compared to synthetic CT data decreased from 190 to 84 for standard correction parameters and to 66 for optimized parameters with a dependency on the used dental materials and number of inserts. Dose calculation accuracy improved significantly from a passing rate of 95% for plans calculated on uncorrected to 97% for plans calculated on corrected or synthetic CT data. Accuracy depends on the dental material used. For the phantoms with the largest average Hounsfield units deviations (CoCr, zirconia) the passing rates increase from 91% to 97% on corrected and 96% on synthetic CT data. Conclusion Image quality and dose calculation accuracy could be significantly improved when iMAR was used for correction of CT data. Disclosure The Authors state that there is no conflict of interest. The work was supported by the Wilhelm Sander Foundation.

Verification of a research prototype for hemodynamic analysis of cerebral aneurysms.

Owing to its clinical importance, there has been a growing body of research on understanding the hemodynamics of cerebral aneurysms. Traditionally, this work has been performed using general-purpose, state-of-the-art commercial solvers. This has meant requiring engineering expertise for making appropriate choices on the geometric discretization, time-step selection, choice of boundary conditions etc. Recently, a CFD research prototype has been developed (Siemens Healthcare GmbH, Prototype - not for diagnostic use) for end-to-end analysis of aneurysm hemodynamics. This prototype enables anatomical model preparation, hemodynamic computations, advanced visualizations and quantitative analysis capabilities. In this study, we investigate the accuracy of the hemodynamic solver in the prototype against a commercially available CFD solver ANSYS CFX 16.0 (ANSYS Inc., Canonsburg, PA, www.ansys.com) retrospectively on a sample of twenty patient-derived aneurysm models, and show good agreement of hemodynamic parameters of interest.

TH-CD-202-02: A Preliminary Study Evaluating Beam-Hardening Artifact Reduction On CT Direct Electron-Density Images

Purpose: A prototype reconstruction algorithm that can provide direct electron density (ED) images from single energy CT scans is being currently developed by Siemens Healthcare GmbH. This feature can eliminate the need for kV specific calibration curve for radiation treatemnt planning. An added benefit is that beam-hardening artifacts are also reduced on direct-ED images due to the underlying material decomposition. This study is to quantitatively analyze the reduction of beam-hardening artifacts on direct-ED images and suggest additional clinical usages. Methods: HU and direct-ED images were reconstructed on a head phantom scanned on a Siemens Definition AS CT scanner at five tube potentials of 70kV, 80kV, 100kV, 120kV and 140kV respectively. From these images, mean, standard deviation (SD), and local NPS were calculated for regions of interest (ROI) of same locations and sizes. A complete analysis of beam-hardening artifact reduction and image quality improvement was conducted. Results: Along with the increase of tube potentials, ROI means and SDs decrease on both HU and direct-ED images. The mean value differences between HU and direct-ED images are up to 8% with absolute value of 2.9. Compared to that on HU images, the SDs are lower on direct-ED images, and the differences are up to 26%. Interestingly, the local NPS calculated from direct-ED images shows consistent values in the low spatial frequency domain for images acquired from all tube potential settings, while varied dramatically on HU images. This also confirms the beam -hardening artifact reduction on ED images. Conclusions: The low SDs on direct-ED images and relative consistent NPS values in the low spatial frequency domain indicate a reduction of beam-hardening artifacts. The direct-ED image has the potential to assist in more accurate organ contouring, and is a better fit for the desired purpose of CT simulations for radiotherapy.

MO-DE-207A-01: Impact of Statistical Weights On Detection of Low-Contrast Details in Model-Based Iterative CT Reconstruction

Purpose: Penalized-weighted least-square reconstruction has become an important research topic in CT, to reduce dose without affecting image quality. Two components impact image quality in this reconstruction: the statistical weights and the use of an edge-preserving penalty term. We are interested in assessing the influence of statistical weights on their own, without the edge-preserving feature. Methods: The influence of statistical weights on image quality was assessed in terms of low-contrast detail detection using LROC analysis. The task amounted to detect and localize a 6-mm lesion with random contrast inside the FORBILD head phantom. A two-alternative forced-choice experiment was used with two human observers performing the task. Reconstructions without and with statistical weights were compared, both using the same quadratic penalty term. The beam energy was set to 30keV to amplify spatial differences in attenuation and thereby the role of statistical weights. A fan-beam data acquisition geometry was used. Results: Visual inspection of images clearly showed a difference in noise between the two reconstructions methods. As expected, the reconstruction without statistical weights exhibited noise streaks. The other reconstruction appeared better in this aspect, but presented other disturbing noise patterns and artifacts induced by the weights. The LROC analysis yield the following 95-percent confidence interval for the difference in reader-averaged AUC (reconstruction without weights minus reconstruction with weights): [0.0026,0.0599]. The mean AUC value was 0.9094. Conclusion: We have investigated the impact of statistical weights without the use of edge-preserving penalty in penalized weighted least-square reconstruction. A decrease rather than increase in image quality was observed when using statistical weights. Thus, the observers were better able to cope with the noise streaks than the noise patterns and artifacts induced by the statistical weights. It may be that different results would be obtained if the penalty term was used with a pixel-dependent weight. F Noo receives research support from Siemens Healthcare GmbH

TU‐H‐BRC‐06: Temperature Simulation of Tungsten and W25Re Targets to Deliver High Dose Rate 10 MV Photons

Purpose:To study the impact of electron beam size, target thickness, and target temperature on the ability of the flattening filter‐free mode (FFF) treatment head to deliver high‐dose‐rate irradiations.Methods:The dose distribution and transient temperature of the X‐ray target under 10 MeV electron beam with pulse length of 5 microseconds, and repetition rate of 1000 Hz was studied. A MCNP model was built to calculate the percentage depth dose (PPD) distribution in a water phantom at a distance of 100 cm. ANSYS software was used to run heat transfer simulations. The PPD and temperature for both tungsten and W25Re targets for different electron beam sizes (FHWM 0.2, 0.5, 1 and 2 mm) and target thickness (0.2 to 2 mm) were studied.Results:Decreasing the target thickness from 1 mm to 0.5 mm, caused a surface dose increase about 10 percent. For both target materials, the peak temperature was about 1.6 times higher for 0.5 mm electron beam compared to the 1 mm beam after reaching their equilibrium. For increasing target thicknesses, the temperature rise caused by the first pulse is similar for all thicknesses, however the temperature difference for subsequent pulses becomes larger until a constant ratio is reached. The target peak temperature after reaching equilibrium can be calculated by adding the steady state temperature and the amplitude of the temperature oscillation.Conclusion:This work indicates the potential to obtain high dose rate irradiation by selecting target material, geometry and electron beam parameters. W25Re may not outperformed tungsten when the target is thick due to its relatively low thermal conductivity. The electron beam size only affects the target temperature but not the PPD. Thin target is preferred to obtain high dose rate and low target temperature, however, the resulting high surface dose is a major concern.NIH funding:R21 EB015957‐01; DOD funding:W81XWH‐13‐1‐0165BL, PM, PB, and RF are founders of TibaRay, Inc. BL is also a borad member. BL and PM have received research grants from Varian Medical System, Inc. and RaySearch Laboratory. RF is an employee of Siemens Healthcare GmbH

Virtual stenting of intracranial aneurysms: application of hemodynamic modification analysis.

Practical application of hemodynamic modification analysis based on computational fluid dynamics (CFD) in intracranial aneurysms is still under study. To determine the clinical applicability of virtual stenting of aneurysms by comparing the simulated results with clinical outcome of real stenting. Three-dimensional (3D) digital subtraction angiography (DSA) images were imported to a dedicated integrated prototypic CFD platform (Siemens Healthcare GmbH) which allows all necessary steps of 3D models for CFD analysis. The results of CFD simulation with virtual implantation of a stent can be visualized in the same platform for qualitative comparisons on a color-coded volume visualization window. Five small intracranial aneurysms with and without virtual stenting were analyzed and assessed on a qualitative level. Expert rating were performed for evaluating the simulated results, and comparing those to the long-term follow-up outcomes of real stenting. CFD simulation after virtual stenting was feasible in five differently located aneurysms and corresponded to the long-term changes of stented aneurysms by showing alteration in flow pattern. There was no significant difference (P = 0.5) between the simulated hemodynamic changes after virtual stenting and the angiographic changes after stenting in four aneurysms except one. There was good agreement regarding the assessment of the changes by two raters (kappa = 0.657). CFD analysis using patient-specific virtual stenting of the CFD platform may be used as a simple and less time-consuming test tool predicting the involution of aneurysms after stent placement by analyzing the vector visualization of the flow changes.

Value assignment of the WHO 6th International Standard for blood coagulation factor VIII and von Willebrand factor in plasma (07/316).

Value assignment of the WHO 6th International Standard for blood coagulation factor VIII and von Willebrand factor in plasma (07/316).