High kV Research Articles

A comparative study on diagnosis of silicosis by digital and high kV film-screen chest radiography

Objective: To explore the feasibility of soft copy image of chest digital radiography (DR(SC)) in pneumoconiosis diagnosis by observing the reading effect of DR(SC) and comparing it with high kV film-screen chest radiography (FSR(HkV)) . To provide a basis for the establishment of a regional information network platform for pneumoconiosis diagnosis. Methods: A total of 119 miners who were exposed to silica dust and engaged in copper or lead-zinc mining were collected by the Third People's Hospital of Yunnan from October 2017 to August 2019. The pulmonary X-ray findings of DRSC and FSR(HkV) in each case were independently judged and diagnosed by three experienced diagnostic physicians, and the final decision was made according to the consensus of most doctors. The consistency of the two imaging methods was analyzed by observing the main small opacity shape, the overall density, the range of distribution, the aggregation of the small opacity and the big opacity, and the diagnosis stage. Results: there were 118 males and 1 female with an average age of 46.21 years. Average exposure time 7.38 years. The pulmonary X-ray findings of 113 cases with two imaging methods were mainly the round small opacity of p,q and r,but the reticular irregular opacity were not prominent, Only one case of FSR(HkV) judgment p shape and DR(SC) judgment q shape were observed, The coincidence rate was 99.12% (112/113) . huger opacity were observed in the other 6 cases. The coincidence rate was 95.51% (4/89) between pneumoconiosis-free and stageⅠ, and there was no significant difference between stageⅡand stage Ⅲ (30/30, P>0.05) . Conclusion: The x-ray findings of Silicosis with small round shadow in lung can be used by DR(SC) in diagnosis and staging.

Effect of Concentration and Nozzle-Collector Distance on the Morphology of Nanofibers

Electrospinning is a method for making nanofibers by utilizing an electric field produced by high voltage. Electrospinning process is influenced by several factors including the concentration of the solution, conductivity, viscosity, volatility, surface tension, electric field strength between the needle and the collector, feed / flow rate and environmental conditions which include temperature, humidity and air composition. Electrospinning parameters are used to optimize the size of the nanofiber, concentration of the solution and the distance of the nozzle to collector. In the process of electrospinning PVA solutions that are handled by high dc voltage gets an electrostatic force and electric field. The solution will elongate to form a Taylor cone, then a jet of polymer will undergo thinning and evaporation to form fibers in the collector. The results of morphological analysis using scanning electron microscopy (SEM) showed that the smallest nanofiber was obtained at a solution concentration of 5%, dc high voltage10 kV, and the distance of the nozzle to collector was 15 cms.

High Resolution Low kV SEM EDS – Breaking Convention with Low Working Distance EDS

High Resolution Low kV SEM EDS – Breaking Convention with Low Working Distance EDS

The effect of different motor constants to an commercial propeller

This paper discussed the performance of a propeller with different motor constants such as the speed constants and motor resistance. The performance that was compared are the thrust, torque and total efficiency. There are many motors developed by the manufacturer, but the datasheet given are not complete and lack the information such as rotational speed and torque. This information is useful for designers and hobbyists to size their UAV or multicopter. In the market, there are many types of motors that make it difficult to choose the best motor. This research will perform analysis from the datasheet obtained from the manufacturer to see the effects of different motors to the propeller performance. It was gathered that for lower Kv such as KV980, it is better when higher torque than thrust is required. But for motor with speed constant above 1250 to 1400, the choice of motor will not have significant effect on the propeller performance. However, when size increase with higher Kv (more than 1400) the efficiency will drop.

Effect of Zn content on the microstructural stability and grain growth kinetics of fine-grained extruded Mg–Gd–Zn alloys

Abstract The effect of Zn content on grain growth kinetics of the fine-grained extruded Mg–2Gd–xZn (x = 0, 1, 2, 3 wt%) alloys was investigated by annealing of the as-extruded sheets in the temperature range of 623–723 K for various time durations. Microstructural observations revealed that by adding 1 wt% Zn, the grain growth is significantly hindered, while increasing the Zn content beyond 1 wt% accelerates the grain growth. Evaluation of solute atom concentrations at grain boundaries demonstrated that the slower grain growth of the Mg–2Gd–1Zn alloy is due to the co-segregation of Zn and Gd solute atoms, resulting in a high drag pressure and low grain boundary mobility. For higher Zn contents, the α-Mg matrix is depleted of the Gd atoms due to the formation of the Mg3Gd2Zn3 phase, which had a less significant effect in hindering the grain growth compared to the solute drag effect. The grain growth exponents in the range of 3–5 and Q-values in the range of 63.2–109.6 kJ mol−1 suggested that grain growth is controlled by the grain boundary diffusion. The highest KV in the Hall–Patch relationship was observed for the Mg–2Gd–1Zn alloy, indicating higher resistance of the co-segregated grain boundaries against dislocation pile-ups and slip transfer.

Extraction and Characterization of Biofuel from Industrial Waste organic Pupae-Silkworm

The current work carted out of analysis on the production of fuel from pupae fat extracted from silkworm, and exhaustive investigations were conducted to determine the characteristics of obtained fuel and its blends. The oily organic compounds derived from silkworm is effectively adopted to produce biofuel. The soxhlet extractor is utilized here to separate the oil content from pupae and obtained oil processed into biofuel by undertaking the transesterification process using NaOH as a fast reactive agent along with methanol. The rate of biofuel derived from pupae oil has been noticed to be 65- 70 by vol%. The extracted fuels from the transesterification process were mixed with high-speed diesel at a rate of B10, B20, B30 and B40 on volume base. The most important physical and chemical characteristics of generated fuel and their mixture with conventional diesel were examined. The investigation results reveal that the fuel sample B20 satisfies all the requirements of ASTM standards. Pure biofuel shows that the lesser heating value, higher KV, flash point, fire point and density than that of conventional diesel. The blended samples reveal that all the properties are keep moving towards higher value with an increasing percentage of biofuel presence except calorific value. Finally results in evidence that, well suitable biofuel can be generated from organic waste material like silkworm and effectively use it in practical applications.

Prototype system for interventional dual-energy subtraction angiography.

Dual-energy subtraction angiography (DESA) using fast kV switching has received attention for its potential to reduce misregistration artifacts in thoracic and abdominal imaging where patient motion is difficult to control; however, commercial interventional solutions are not currently available. The purpose of this work was to adapt an x-ray angiography system for 2D and 3D DESA. The platform for the dual-energy prototype was a commercially available x-ray angiography system with a flat panel detector and an 80 kW x-ray tube. Fast kV switching was implemented using custom x-ray tube control software that follows a user-defined switching program during a rotational acquisition. Measurements made with a high temporal resolution kV meter were used to calibrate the relationship between the requested and achieved kV and pulse width. To enable practical 2D and 3D imaging experiments, an automatic exposure control algorithm was developed to estimate patient thickness and select a dual-energy switching technique (kV and ms switching) that delivers a user-specified task CNR at the minimum air kerma to the interventional reference point. An XCAT-based simulation study conducted to evaluate low and high energy image registration for the scenario of 30-60 frame/s pulmonary angiography with respiratory motion found normalized RMSE values ranging from 0.16% to 1.06% in tissue-subtracted DESA images, depending on respiratory phase and frame rate. Initial imaging in a porcine model with a 60 kV, 10 ms, 325 mA / 120 kV, 3.2 ms, 325 mA switching technique demonstrated an ability to form tissue-subtracted images from a single contrast-enhanced acquisition.

Image quality optimization using a narrow vertical detector dental cone-beam CT.

To determine the optimized kV setting for a narrow detector cone-beam CT (CBCT) unit. Clinical (CL) and quantitative (QUANT) evaluations of image quality were performed using an anthropomorphic phantom. Technical (TECH) evaluation was performed with a polymethyl methacrylate phantom. Images were obtained using a PaX-i3D Green CBCT (Vatech, Hwaseong, Korea) device, with a large 21 × 19 and a medium 12 × 9 cm field of view (FOV), and high-dose (HD-ranging from 85 to 110 kV) and low-dose (LD-ranging from 75 to 95 kV) protocols, totaling four groups (21 × 19 cm HD, 21 × 19 cm LD, 12 × 9 cm HD, 12 × 9 cm LD). The radiation dose within each group was fixed by adapting the mA according to a predetermined dose-area product. For CL evaluation, three observers assessed images based on overall quality, sharpness, contrast, artefacts, and noise. For QUANT evaluation, mean gray value shift, % increase of standard deviation (SD), % of beam hardening and contrast-to-noise ratio (CNR) were calculated. For TECH evaluation, segmentation accuracy, CNR, metal artefact SD, metal object area, and sharpness were measured. Representative parameters were chosen for CL, QUANT, and TECH evaluations to determine the optimal kV based on biplot graphs. kV values of the same protocol were compared by the bootstrapping approach. The ones that had statistical differences with the best kV were considered as worse quality. Overall, kV values within the same group showed similar quality (p > 0.05), except for 110 kV in 21 × 19 cm HD and 85 kV in 12 × 9 cm HD of CL score; also 85, 90 kV in 21 × 19 cm HD and 75, 80 kV in 21 × 19 cm LD of QUANT score which were worse (p < 0.05). At a constant dose, low and high kV protocols yield acceptable image quality for a narrow-detector CBCT unit.

Optimizing Analysis Of The Radiographic Image And Entrance Surface Dose Using Computed Radiography In Chest Examination

This research has conducted about exposure factor variation analysis examination of the thorax surface dose and image noise in radiography. Do 10 (ten) times the exposure in the thorax phantom with various exposure factor such as 50 kV- 8 mAs, 50 kV-10 mAs, 55 kV- 8 mAs, 55 kV-10 mAs, 55 kV-10 mAs, 60 kV- 8 mAs, 60 kV-10 mAs, 66 kV-8 mAs, 66 kV-10 mAs, and 102 kV- 1 mAs, 102 kV - 2,5 mAs for high kV technique. For each exposure factor the pinned , TLD placed in the middle of the field to measure the radiation dose level. The optimum exposure conditions of the thorax PA examination (expressed with IgM value) occurs when using exposure factor 55 kV and 8 mAs for IgM values ​​obtained are 1.91, 6.605 for standard deviation values ​​and ESD 0.098 mGy.

Pros and Cons of Intraoperative Radiotherapy: Comparison of Two Clinical Trials in Breast Cancer Management

Context: Intraoperative radiotherapy (IORT) is an accepted standard treatment for early stages of breast cancer in the selected cases. This is proven in two large clinical trials including ELIOT and TARGIT-A ones, which are based on high energy electron beam and low kV X-ray energy, respectively. Published results of two trials aimed at evaluating the local recurrence as the final outcome. In ELIOT study, the local recurrence rate is 4.4% versus 0.4% in patients, who received IORT and External Beam Radiotherapy (EBRT), in comparison to 3.2% and 1.3% in TARGIT-A trial. These differences need to be further evaluated regarding the efficacy and beneficence of IORT. Objectives: The aim of this study is to further analyze the data of these two trials to confirm the strategy of IORT in breast cancer as boost or radical modality. Evidence Acquisition: Two main breast IORT trials were considered in this study. To this end, a computerized search was performed through MEDLINE, PubMed, PubMed Central, ISI web of knowledge, and reference list of related articles. All of the published data from these trials were gathered and their subjects were analyzed and compared. Results: Statistical analysis revealed that in patients with matching clinical, pathological, and biological profiles in both trials, radical IORT using either electron or low kV X-ray is effective and acceptable. It seems that in patients with low risk factors, IORT is more effective than EBRT. Patient selection according to America Society of Radiation Oncology or European Society of Radiation Therapy classification guidelines confirmed that the local recurrence rate of ELIOT in low risk patients, similar to TARGIT, was less than 1.9%. Conclusions: We compared the ELIOT and TARGIT-A trial documents and found all of similarities and differences referred to these two trials recommend, using IORT for selected cases of breast cancer with at least non inferiority in Disease free survival (DFS) and overall survival (OS) as well as superiority in cosmetic, non-breast cancer death, and more.

P261] Image quality assessment of filtered dual energy cone beam CT for radiotherapy

Purpose Dual energy (DE) computed tomography (CT), combines two scans obtained with different photon energy spectra. It is known from diagnostic CT to reduce metal artefacts. This study investigates the feasibility of developing a DE protocol for cone-beam CT (CBCT) in radiotherapy. Methods The DE efficacy depends on the ability to separate the energy spectra of the two scans. Therefore, different thickness of copper (Cu) filtration was added to the high energy scan. The DE CBCT scanning protocol consists of two scans at 80 (low) and 140 (high) kV, respectively. Two different DE protocols with 1 and 2 mm added Cu filtration were created. The filtration was done by physically adding Cu plates onto the kV source of the CBCT system. The mAs was adjusted to keep the doses of both DE protocols on the same level as the standard CBCT. The dose was measured using a CTDI phantom. The DE images, I DE , were created in image space from the high, I high , and low, I low , energy images using I DE ( E ) = w ( E ) ∗ I low + ( 1 - w ( E ) ) ∗ I high where w(E) is a weighting factor dependent on the (pseudo) monochromatic energy, E, of the I DE images. Scans of a Catphan phantom were acquired with the DE CBCT protocols as well as a standard CBCT scan at 100 kV. The Cu filtered DE CBCT scans were investigated with respect to soft tissue image quality as the potential benefit of image artefact reduction should not compromise overall image quality or increase radiation dose compared to the standard CBCT. To quantify the image quality, contrast-to-noise (CNR) measurements were done in regions resembling muscle and fat in the phantom. Results The radiation dose was 100.1% and 101.4% of the standard CBCT dose for the 1 and 2 mm Cu protocols, respectively. The CNR was found to be 1.3 (standard), 1.4 (DE, 1 mm Cu) and 1.3 (DE, 2 mm Cu). Conclusions The filtered DE and standard CBCT protocols showed similar performance in radiation dose and soft tissue image quality. Hence it is feasible to explore the potential benefits of increased soft tissue contrast and artefact reduction for DE CBCT protocols.

High resolution low kV EBSD of heavily deformed and nanocrystalline Aluminium by dictionary-based indexing

We demonstrate the capability of a novel Electron Backscatter Diffraction (EBSD) dictionary indexing (DI) approach by means of orientation mapping of a highly deformed graded microstructure in a shot peened Aluminium 7075-T651 alloy. A low microscope accelerating voltage was used to extract, for the first time from a bulk sample, statistically significant orientation information from a region close to a shot crater, showing both recrystallized nano-grains and heavily deformed grains. We show that the robust nature of the DI method allows for faster acquisition of lower quality patterns, limited only by the camera hardware, compared to the acquisition speed and pattern quality required for the conventional Hough indexing (HI) approach. The proposed method paves the way for the quantitative and accurate EBSD characterization of heavily deformed microstructures at a sub-micrometer length scale in cases where the current indexing techniques largely fail.

"X-Map 2.0" for Edema Signal Enhancement for Acute Ischemic Stroke Using Non-Contrast-Enhanced Dual-Energy Computed Tomography.

A novel imaging technique ("X-map") has been developed to identify acute ischemic lesions for stroke patients using non-contrast-enhanced dual-energy computed tomography (NE-DE-CT). Using the 3-material decomposition technique, the original X-map ("X-map 1.0") eliminates fat and bone from the images, suppresses the gray matter (GM)-white matter (WM) tissue contrast, and makes signals of edema induced by severe ischemia easier to detect. The aim of this study was to address the following 2 problems with the X-map 1.0: (1) biases in CT numbers (or artifacts) near the skull of NE-DE-CT images and (2) large intrapatient and interpatient variations in X-map 1.0 values. We improved both an iterative beam-hardening correction (iBHC) method and the X-map algorithm. The new iBHC (iBHC2) modeled x-ray physics more accurately. The new X-map ("X-map 2.0") estimated regional GM values-thus, maximizing the ability to suppress the GM-WM contrast, make edema signals quantitative, and enhance the edema signals that denote an increased water density for each pixel. We performed a retrospective study of 11 patients (3 men, 8 women; mean age, 76.3 years; range, 68-90 years) who presented to the emergency department with symptoms of acute stroke. Images were reconstructed with the old iBHC (iBHC1) and the iBHC2, and biases in CT numbers near the skull were measured. Both X-map 2.0 maps and X-map 1.0 maps were computed from iBHC2 images, both with and without a material decomposition-based edema signal enhancement (ESE) process. X-map values were measured at 5 to 9 locations on GM without infarct per patient; the mean value was calculated for each patient (we call it the patient-mean X-map value) and subtracted from the measured X-map values to generate zero-mean X-map values. The standard deviation of the patient-mean X-map values over multiple patients denotes the interpatient variation; the standard deviation over multiple zero-mean X-map values denotes the intrapatient variation. The Levene F test was performed to assess the difference in the standard deviations with different algorithms. Using 5 patient data who had diffusion weighted imaging (DWI) within 2 hours of NE-DE-CT, mean values at and near ischemic lesions were measured at 7 to 14 locations per patient with X-map images, CT images (low kV and high kV), and DWI images. The Pearson correlation coefficient was calculated between a normalized increase in DWI signals and either X-map or CT. The bias in CT numbers was lower with iBHC2 than with iBHC1 in both high- and low-kV images (2.5 ± 2.0 HU [95% confidence interval (CI), 1.3-3.8 HU] for iBHC2 vs 6.9 ± 2.3 HU [95% CI, 5.4-8.3 HU] for iBHC1 with high-kV images, P < 0.01; 1.5 ± 3.6 HU [95% CI, -0.8 to 3.7 HU] vs 12.8 ± 3.3 HU [95% CI, 10.7-14.8 HU] with low-kV images, P < 0.01). The interpatient variation was smaller with X-map 2.0 than with X-map 1.0, both with and without ESE (4.3 [95% CI, 3.0-7.6] for X-map 2.0 vs 19.0 [95% CI, 13.3-22.4] for X-map 1.0, both with ESE, P < 0.01; 3.0 [95% CI, 2.1-5.3] vs 12.0 [95% CI, 8.4-21.0] without ESE, P < 0.01). The intrapatient variation was also smaller with X-map 2.0 than with X-map 1.0 (6.2 [95% CI, 5.3-7.3] vs 8.5 [95% CI, 7.3-10.1] with ESE, P = 0.0122; 4.1 [95% CI, 3.6-4.9] vs 6.3 [95% CI, 5.5-7.6] without ESE, P < 0.01). The best 3 correlation coefficients (R) with DWI signals were -0.733 (95% CI, -0.845 to -0.560, P < 0.001) for X-map 2.0 with ESE, -0.642 (95% CI, -0.787 to -0.429, P < 0.001) for high-kV CT, and -0.609 (95% CI, -0.766 to -0.384, P < 0.001) for X-map 1.0 with ESE. Both of the 2 problems outlined in the objectives have been addressed by improving both iBHC and X-map algorithm. The iBHC2 improved the bias in CT numbers and the visibility of GM-WM contrast throughout the brain space. The combination of iBHC2 and X-map 2.0 with ESE decreased both intrapatient and interpatient variations of edema signals significantly and had a strong correlation with DWI signals in terms of the strength of edema signals.

Image quality and dose reduction in sinus computed tomography using iterative reconstruction: a cadaver study.

Concerns about radiation dose in computed tomography (CT) imaging have renewed interest in iterative reconstruction (IR), a technique which has the potential to produce images with less noise at lower radiation doses than traditional filtered back projection (FBP). This study aimed to assess whether application of IR could provide comparable quality sinus CT images to FBP at lower kilovolt (kV) and milliamp (mA) settings, and to establish optimal scan settings for sinus imaging. 30 sinus CT scans were performed on 5 cadaver heads at two kV setting and three mA settings. Each scan was reconstructed using FBP and 3 IR settings, yielding a total of 120 images series. Each image set was blinded and randomly reviewed by 3 rhinologists and 2 neuroradiologists. Using a 5-point Likert scale, 16 anatomical landmarks, were graded with respect to image quality. Data were assessed with respect to dose and IR settings using statistical analysis. Higher kV and mAs settings produced significantly higher quality images for structure identification across all 16 landmarks; however, the suitability for surgery did not increase in a linear fashion and plateaued by a total radiation dose of 0.1201 mSv. IR algorithm did not provide a benefit in the overall score of scans at a fixed kV and mAs. Identification of structures in sinus CT imaging significantly correlate with the kV and mA and overall dose of radiation; however, IR did not provide additional benefit in the image quality.

Dual energy computed tomography for the head.

Dual energy CT (DECT) is a promising technology that provides better diagnostic accuracy in several brain diseases. DECT can generate various types of CT images from a single acquisition data set at high kV and low kV based on material decomposition algorithms. The two-material decomposition algorithm can separate bone/calcification from iodine accurately. The three-material decomposition algorithm can generate a virtual non-contrast image, which helps to identify conditions such as brain hemorrhage. A virtual monochromatic image has the potential to eliminate metal artifacts by reducing beam-hardening effects. DECT also enables exploration of advanced imaging to make diagnosis easier. One such novel application of DECT is the X-Map, which helps to visualize ischemic stroke in the brain without using iodine contrast medium.

The PENGARUH TEGANGAN TABUNG (KV) TERHADAP KUALITAS CITRA RADIOGRAFI PESAWAT SINAR-X DIGITAL RADIOGRAPHY (DR) PADA PHANTOM ABDOMEN

The measurement of image quality of Digital Radiography (DR) with using the abdomen phantom. Image take with low kV to high kV for 10 times exposure. Image processing is done using the image application. The resulting radiograph image is analyzed by FFT analysis, Histogram and Gaussian Filter. In the FFT analysis the radiographic image tends to differ according to the tube voltage variation of 40 kV to 85 kV. In the radiographic image histogram analysis, including the imperfect image category because the distribution of pixel distribution is not yet complete in the gray scale area for all exposure variations. In the analysis using Gaussian filters the resulting radiographic image tends to be the same so that although using low kV and high kV the image will be the same. The use of Gaussian filters can help reduce the use of high kV on abdominal examination and reduce exposure to radiation dose.&#x0D; Keywords: Digital Radiography, Image Quality, Fourier Transform Filter, Gaussian Filter, Histogram.

Declining radiation dose of coronary computed tomography angiography: German cardiac CT registry experience 2009-2014.

Coronary computed tomography angiography (CTA) is increasingly used as a test to rule out coronary artery disease (CAD) in patients with a low to intermediate pre-test probability of the disease. We used the database of the German CT registry, collected between 2009 and 2014 in a broad patient population, to analyze contemporary radiation dose associated with coronary CTA in clinical practice. The prospective observational registry included a total of 7061 patients ≥18years, referred to 12 participating centers for a clinically indicated cardiac CT examination. All centers were cardiology units well experienced in CTA and used multi-slice CT scanners with at least 64 rows. Coronary CTA was performed in a subset of 5001 patients, 59.6±11.8years, body mass index (BMI) 26.9±4.5kg/m2, 38% females. Three time periods with approximately equal numbers of patients were created (01/09-03/10, 04/10-03/11, 04/11-07/14). The dose-length product of all examinations and derived effective dose in mSv (conversion factor k=0.014) as well as the influence of patient characteristics on dose were compared for the three time periods. BMI and proportion of female patients remained stable over time, and mean heart rate decreased from 60.3±9.0 to 58.5±9.3bpm from the first to the last time period (p<0.001). Overall, the mean effective dose of coronary CTA was 3.6mSv (Q1 1.8mSv, Q3 7.4mSv). Within the three time periods, it declined from 5.6 (2.7, 8.6) mSv during the first to 4.8 (2.1, 8.2) mSv during the second and 2.5 (1.3, 4.6) mSv during the last time period (p<0.001). Paralleling the decline in radiation dose over time, the proportion of prospectively ECG-triggered examinations increased (68, 79, 83%; p<0.001), and the proportion of examinations with retrospective gating and no tube current modulation decreased (5.3, 4.0, 1.6%; p<0.001). Tube current (mAs) and voltage (kV) both decreased over time. In multivariable analysis, besides earlier time period, further independent predictors of an increased radiation dose were older age, higher heart rate, and higher BMI as well as the technical factors higher mAs, higher kV, and retrospective gating. At three sites, CT scanners with improved technology were installed during the last time period. In current clinical practice among German cardiology units with specific expertise in cross-sectional cardiovascular imaging, overall radiation dose of coronary CTA was comparably low. Over time, a decline in radiation dose was demonstrated, probably due to a combination of improvements in data acquisition protocols and patient preparation as well as installation of new CT scanners with advanced technology.

Current modulated volume-of-interest imaging for kilovoltage intrafaction monitoring of the prostate.

The focus of this work was to improve the available kV image quality for continuous intrafraction monitoring of the prostate during volumetric modulated arc therapy. This is investigated using a novel blade collimation system enabling tube current modulated (TCM) volume-of-interest (VOI) imaging of prostate fiducial markers during radiotherapy, and Monte Carlo simulation of MV scatter. A four-blade dynamic kV collimator was used to track a VOI containing gold fiducial markers embedded in a dynamic pelvis phantom during gantry rotation. For each fiducial, a VOI margin around each marker was set to be 2σ of the population covariance matrix characterizing prostate motion. This was used to conform to a single or several fiducials and compared to a static field. DRRs were used to calculate the kV attenuation for each VOI as a function of angle and used to optimize x-ray tube current during acquisition. Image quality was assessed with regard to contrast-to-noise ratio (CNR), fiducial detectability, and imaging dose. Monte Carlo simulations in EGSnrc were used to calculate the imaging dose to the phantom and MV scatter fluence to the imaging panel. Fiducials can be accurately located using a VOI containing a single or several fiducials using a relatively high constant kV output. However, when using a 6 × 6 cm2 field the dose can be upwards of 1.5 Gy in bone for constant kV output and 3.1 Gy when applying TCM at 1 Hz imaging over the course of 40 fractions. This can be mitigated through tailoring the imaging field to a single or several fiducials, in which the integral dose is reduced by a factor of 15.6 and 3.7, respectively. For a constant MV treatment field size, the scattered fluence reaching the kV panel varies by less than a factor of two for a completely rotation of the gantry. However, the MV scatter spectrum overlaps with the detector response for a deleterious effect, with a peak MV scatter energy of approximately 100 keV. TCM can be used to overcome the variability in image quality throughout the rotation and therefore improve fiducial CNR and detectability during periods of high kV attenuation. The combination of VOI and TCM introduces an advantageous approach in intrafraction monitoring of the prostate during radiotherapy by both reducing and localizing the imaging dose, while improving image quality and fiducial detectability during periods of high kV attenuation. In addition, the influence of MV scatter has been shown to be most important in low attenuation regions, with a variation by a factor of two.

Variability of Darcian Flux in the Hyporheic Zone at a Natural Channel Bend

Channel bends are one of the most important characteristic features of natural streams. These bends often create the conditions for a hyporheic zone, which has been recognized as a critical component of stream ecosystems. The streambed vertical hydraulic conductivity (Kv), vertical hydraulic gradient (VHG) and Darcian flux (DF) in the hyporheic zone were estimated at 61 locations along a channel bend of the Beiluo River during July 2015 and January 2016. All the streambed attributes showed great spatial variability along the channel bend. Both upward fluxes and downward fluxes occurred during the two test periods, most of studied stream sections were controlled by downwelling, indicating stream water discharge into the subsurface. The average downward flux was higher at the downstream side than at the upstream side of the channel bend, especially in July 2015. The distribution of streambed sediment grain size has a significant influence on the variability of Kv; high percentages of silt and clay sediments generally lead to low Kv values. Higher Kv at the depositional left bank at the upstream site shifted toward the erosional right bank at the downstream site, with Kv values positively correlated with the water depth. This study suggested that the variabilities of Kv and VHG were influenced by the stream geomorphology and that the distribution of Kv was inversely related, to a certain extent, to the distribution of VHG across the channel bend. Kv and VHG were found to have opposite effects on the DF, and the close relationship between Kv and DF indicated that the water fluxes were mainly controlled by Kv.

Differential Kv1.3, KCa3.1, and Kir2.1 expression in "classically" and "alternatively" activated microglia.

Microglia are highly plastic cells that can assume different phenotypes in response to microenvironmental signals. Lipopolysaccharide (LPS) and interferon‐γ (IFN‐γ) promote differentiation into classically activated M1‐like microglia, which produce high levels of pro‐inflammatory cytokines and nitric oxide and are thought to contribute to neurological damage in ischemic stroke and Alzheimer's disease. IL‐4 in contrast induces a phenotype associated with anti‐inflammatory effects and tissue repair. We here investigated whether these microglia subsets vary in their K+ channel expression by differentiating neonatal mouse microglia into M(LPS) and M(IL‐4) microglia and studying their K+ channel expression by whole‐cell patch‐clamp, quantitative PCR and immunohistochemistry. We identified three major types of K+ channels based on their biophysical and pharmacological fingerprints: a use‐dependent, outwardly rectifying current sensitive to the KV1.3 blockers PAP‐1 and ShK‐186, an inwardly rectifying Ba2+‐sensitive Kir2.1 current, and a Ca2+‐activated, TRAM‐34‐sensitive KCa3.1 current. Both KV1.3 and KCa3.1 blockers inhibited pro‐inflammatory cytokine production and iNOS and COX2 expression demonstrating that KV1.3 and KCa3.1 play important roles in microglia activation. Following differentiation with LPS or a combination of LPS and IFN‐γ microglia exhibited high KV1.3 current densities (∼50 pA/pF at 40 mV) and virtually no KCa3.1 and Kir currents, while microglia differentiated with IL‐4 exhibited large Kir2.1 currents (∼ 10 pA/pF at −120 mV). KCa3.1 currents were generally low but moderately increased following stimulation with IFN‐γ or ATP (∼10 pS/pF). This differential K+ channel expression pattern suggests that KV1.3 and KCa3.1 inhibitors could be used to inhibit detrimental neuroinflammatory microglia functions. GLIA 2016;65:106–121