Spectral Filtration Research Articles

Identifying pitching mode of aerial planting projectile by the use of image processing

Aerial planting is a new and affordable method, which is used for purposes of reforestation and restoring pastures. In this study, flight dynamics of an aerial planting projectile has been simulated using data of the wind tunnel test. By creating the projectile graphical model and using the results of dynamic equations for this model, pitching angle has been simulated graphically by recording the pitch attitude of the graphical model and, by applying spectral filtration the rate of pitch angle at any point of the trajectory is calculated. Primary dynamic model parameters including the coefficients of regression equation of motion are estimated by applying the least squares estimator. Comparison of the estimated coefficients from image processing and coefficients given to the simulation program reveals high accuracy of the model resulting from the image processing data used in this method and approves wind tunnel test data by graphical model and calibration of camera measurement. Also, an experimental test setup has been created and the images of projectile falling down in the presence of fan flow have been captured with high-speed digital camera. By decreasing the ambient light intensity, the images and measurement noise of theta angle increases. By applying recursive least square algorithm, sensitivity of coefficients and robustness of this algorithm has been analyzed. The analysis results indicate that the estimation of coefficients using image processing data has great accuracy.

SU‐F‐I‐75: Half‐Value Layer Thicknesses and Homogeneity Coefficients for Fluoroscopic X‐Ray Beam Spectra Incorporating Spectral Filtration

Purpose:The purpose of this investigation is to quantify various first half‐value‐layers (HVLs), second HVLs and homogeneity coefficients (HCs) for a state‐of‐the‐art fluoroscope utilizing spectral (copper) filtration.Methods:A Radcal (Monrovia, Ca) AccuPro dosimeter with a 10×6‐6 calibrated ionization chamber was used to measure air kerma for radiographic x‐ray exposures made on a Siemens (Erlangen, Germany) Artis ZeeGo fluoroscope operated in the service mode. The ionization chamber was centered in the x‐ray beam at 72 cm from the focal spot with a source‐to‐image‐distance of 120 cm. The collimators were introduced to limit the x‐ray field to approximately 5 cm × 5 cm at the ionization chamber plane. Type‐1100 aluminum filters, in 0.5 mm increments, were used to determine the HVL. Two HVL calculation methods were used, log‐linear interpolation and Lambert‐W interpolation as described by Mathieu [Med Phys, 38(8), 4546 (2011)]. Multiple measurements were made at 60, 80, 100, 120 kVp at spectral filtration thicknesses of 0, 0.1, 0.3, 0.6 and 0.9 mm.Results:First HVL, second HVL, and HCs are presented for the fluoroscopic x‐ray beam spectra indicated above, with nearly identical results from the two interpolation methods. Accuracy of the set kVp was also determined and deviated less than 2%. First HVLs for fluoroscopic x‐ray beam spectra without spectral filtration determined in our study were 7%–16% greater than previously published data by Fetterly et al. [Med Phys, 28, 205 (2001)]. However, the FDA minimum HVL requirements changed since that publication, requiring larger HVLs as of 2006. Additionally, x‐ray tube and generator architecture have substantially changed over the last 15 years providing different beam spectra.Conclusion:X‐ray beam quality characteristics for state‐of‐the‐art fluoroscopes with spectral filtration have not been published. This study provides reference data which will be useful for defining beam qualities encountered on fluoroscopes using spectral filtration.

SU‐G‐206‐03: CTDI Per KV at Phantom Center and Periphery: Comparison Between Major CT Manufacturers

Purpose:The purpose of this study was to: 1) compare scanners output by measuring normalized CTDIw (mGy/100mAs) in different CT makes and models and at different kV's, and 2) quantify the relationship between kV and CTDI and compare this relationship between the different manufacturers.Methods:Study included forty scanners of major CT manufacturers and of various models. Exposure was measured at center and 12 o'clock holes of head and body CTDI phantoms, at all available kV's, and with the largest or second largest available collimation in each scanner. Average measured CTDI's from each CT manufacturer were also plotted against kV and the fitting equation: CTDIw (normalized) = a.kVb was calculated. The power (b) value may be considered as an indicator of spectral filtration, which affects the degree of beam hardening. Also, HVLs were measured at several scanners.Results:Results showed GE scanners, on average, had higher normalized CTDIw than those of Siemens and Philips, in both phantom sizes and at all kV's. ANOVA statistic indicated the difference was statistically significant (p < 0.05). Comparison between Philips and Siemens, however, was not statistically significant. Curve fitting showed b values ranged from 2.4 to 2.9 (for Head periphery and center, respectively); and was about 2.8 for Body phantom periphery, and 3.2 at the center of Body phantom. Fitting equations (kV vs. CTDI) will be presented and discussed. GE's CTDIw vs. HVL showed very strong correlation (r > 0.99).Conclusion:Partial characterization of scanners output was performed which may be helpful in dose estimation to internal organs. The relatively higher output from GE scanners may be attributed to lower filtration. Work is still in progress to obtain CTDI values from other scanners as well as to measure their HVLs.

Nanoparticle enhanced spectral filtration of insolation from trough concentrators

A nanoparticle fluid filter consisting of gold nanoparticles and indium tin oxide nanocrystals was fabricated and the optical properties were assessed. Results were integrated against the AM 1.5 solar spectrum to determine solar weighted efficiency of the filter for light energies transmitted above the bandgap to a photovoltaic cell for direct electrical generation while absorbing light below the bandgap that is converted to heat for thermal storage or processing. Temperature dependent bandgaps for both GaAs and cSi were used for optimization of the filter design. GaAs is preferred based upon its higher IR reflectivity, lower temperature coefficient, and greater high-temperature efficiency. However, cSi is significantly cheaper than current and projected GaAs costs. It was found that the experimental filter efficiency was 62% for GaAs and 56% for cSi which was within 6% of previous theoretical predictions.

The impact of spectral filtration on image quality in micro-CT system.

This paper aims to evaluate the impact of spectral filtration on image quality in a microcomputed tomography (micro‐CT) system. A mouse phantom comprising 11 rods for modeling lung, muscle, adipose, and bones was scanned with 17 s and 2 min, respectively. The current (μA) for each scan was adjusted to achieve identical entrance exposure to the phantom, providing a baseline for image quality evaluation. For each region of interest (ROI) within specific composition, CT number variations, noise levels, and contrast‐to‐noise ratios (CNRs) were evaluated from the reconstructed images. CT number variations and CNRs for bone with high density, muscle, and adipose were compared with theoretical predictions. The results show that the impact of spectral filtration on image quality indicators, such as CNR in a micro‐CT system, is significantly associated with tissue characteristics. The findings may provide useful references for optimizing the scanning parameters of general micro‐CT systems in future imaging applications.PACS numbers: 87.57.C‐, 87.57.Q‐, 87.64.kd

SPECTRAL FILTRATION OF IMAGES BY MEANS OF DISPERSIVE SYSTEMS

Instruments for spectral filtration of images are an important element of the systems used in remote sensing, medical diagnostics, in-process measurements. The aim of this study is analysis of the functional features and characteristics of the proposed two image monochromator versions which are based on dispersive spectral filtering. The first is based on the use of a dispersive monochromator, where collimating and camera lenses form a telescopic system, the dispersive element of which is within the intermediate image plane. The second version is based on an imaging double monochromator with dispersion subtraction by back propagation. For the telescopic system version, the spectral and spatial resolutions are estimated, the latter being limited by aberrations and diffraction from the entrance slit. The device has been numerically simulated and prototyped. It is shown that for the spectral bandwidth 10 nm (visible spectral range), the aberration-limited spot size is from 10–20 μm at the image center to about 30 μm at the image periphery for the image size 23–27 mm. The monochromator with dispersion subtraction enables one to vary the spectral resolution (up to 1 nm and higher) by changing the intermediate slit width. But the distinctive feature is a significant change in the selected central wavelength over the image field. The considered designs of dispersive image monochromators look very promising due to the particular advantages over the systems based on tunable filters as regards the spectral resolution, fast tuning, and the spectral contrast. The monochromator based on a telescopic system has a simple design and a rather large image field but it also has a limited light throughput due to small aperture size. The monochromator with dispersion subtraction has higher light throughput, can provide high spectral resolution when recording a full data cube in a series of measuring acts for different dispersive element positions.

Stereoscopic 3-dimensional spectral imaging systems based on a single acousto-optical tunable filter

The novel technique for 3-dimensional (3D) spectral imaging is proposed. It is based on simultaneous spectral acousto-optic filtration of a pair of stereoscopic convergent light beams via single acoustic wave. A few promising configurations of such acousto-optic tunable filters (AOTFs) is proposed, discussed and compared. It is shown that these elements may be ultra-compact and PC controlled modules, ready to be integrated into many existing schemes of stereoscopic 3D imagers.The experiment carried out with the help of single-AOTF-based spectral stereomicroscope demonstrates the efficiency of proposed technique.

DIRECTMEASURING PHASE METHOD OF SMALL DISTANCES MEASUREMENT BY THE OPTOELECTRONIC SENSOR IN DYNAMIC CONDITIONS

Statement of a task The work is devoted to development and researches of a method the small distances precision contactless measurement for creation of the optoelectronic sensor working in dynamic conditions. Technique of researches At realization of calculations the computer facilities and the software of a high level is used, physical and computer methods with a mathematical equipment are used. For precision remote measurements on short routes the advantage is given to optical-location systems with continuous radiation in which time measurements carried out by an indirect method, by use of phase relationship of the direct and reflected beam. For measurement of small distances in dynamic conditions the modified method of location measurements which allows to improve the operative signal processing in a wide dynamic range and to expand the opportunities of known optical methods of ranging is developed. The functioning algorithm and the block diagram directmeasuring phase method of distance measurement is developed, conditions for phase difference measurement on low intermediate frequency which provide high accuracy of measurements are created. Discussions of results Increase of small distances measurements accuracy is connected to reduction of probing pulses duration and increase of radiation capacity. To achieve the given level of accuracy it is possible in megacycle frequency range which forms high requirements to quick-action of the sensor optoelectronic block elements. Use of pin-structures has allowed to reduce photo diodes time constant up to several nanoseconds, that is equivalent to passband width of the order of gigahertz with simultaneous reduction of initial capacity. The choice of a photodetector is determined by its spectral sensitivity and an opportunity simultaneously with the optical system to solve tasks of an optimum spectral filtration at signal extraction on a background of nuisance. Capacity of a laser radiator is regulated by necessity of influence of object surface reflecting properties elimination. Conclusions The carried out calculation for the minimal measured distance of 0,3 m and the appropriate measurement accuracy has shown, that absolute dynamic accuracy of measurement of in-line distance in all range of distances will be not worse than 3 mm.

Recording digital holograms of optically transparent objects in arbitrary spectral intervals based on acousto-optic filtration of radiation

The problem of obtaining digital holographic images of optically transparent objects in arbitrary spectral intervals is considered. A Mach–Zehnder interferometer based optical scheme with acousto-optic spectral filtration of the broadband radiation is presented. The spectral selection allows one to increase the informativeness of digital holograms due to the choice of spectral channels in which elements with different physico-chemical properties have a sufficient contrast. Examples of recorded spectral holographic images of a test object and real objects are presented.

TH-AB-201-09: Effect of X-Ray Beam Quality On Fluoroscope Reported Reference Plane Air Kerma When Measured by DAP Meters: TG190 Protocol Implications for Interventional Fluoroscopes

Purpose: To investigate the accuracy of the correction factor (CF) determined using the AAPM-TG190 protocol and applied to measurements made across a full spectrum of x-ray beam qualities on interventional c-arm fluoroscopes. Methods: The x-ray beam area was measured to allow for the calculation of the air-kerma-area-product (Pk,a). Air kerma was measured using a calibrated ionization chamber centered in the x-ray beam free-in-air. Manual technique factors were set with vendor service support. Data were collected on 10 fluoroscopic systems at 55 kVp to 125 kVp in 10-kVp increments and also at 100 kVp. At each available combination of kVp and spectral filter (copper) thickness, three measurements were taken. A CF for each beam quality was determined by dividing the measured Pk,a by the Pk,a reported by the fluoroscope. Two normalized correction factors (NCFs) were defined to determine the potential error in using a single CF across a spectrum of beam qualities. The first normalized the CF at a given beam quality to the CF at 100 kVp without filtration (NCF[100,0]) and another normalized to the CF at 100 kVp with 0.1 mm copper (NCF[100,0.1]). Results: The accuracy of the CF varied depending on whether it was determined using spectral filtration, which was apparent in comparisons of NCF(100,0) with NCF(100,0.1). In general, the CF was dependent on beam quality, an effect that was most pronounced at low kVps with spectral filtration. Conclusion: For interventional fluoroscopes employing spectral filtration, better accuracy is achieved when copper is used to establish the CF. Additionally, a CF determined at 100 ± 10 kVp may not be optimal for pediatric applications, in which the beam quality typically consists of low kVps and large amounts of copper filtration. The accuracy of the CF can be improved for pediatric applications by using a more clinically relevant beam quality.

SU‐E‐P‐15: Technique Factor Modulation and Reference Plane Air Kerma Rates in Response to Simulated Patient Thickness Variations for a Sample of Current Generation Fluoroscopes

Purpose:To evaluate and compare approaches to technique factor modulation and air kerma rates in response to simulated patient thickness variations for four state‐of‐the‐art and one previous‐generation interventional fluoroscopes.Methods:A polymethyl methacrylate (PMMA) phantom was used as a tissue surrogate for the purposes of determining fluoroscopic reference plane air kerma rates, kVp, mA, and spectral filtration over a wide range of simulated tissue thicknesses. Data were acquired for each fluoroscopic and acquisition dose curve within a default abdomen or body imaging protocol.Results:The data obtained indicated vendor‐ and model‐specific variations in the approach to technique factor modulation and reference plane air kerma rates across a range of tissue thicknesses. Some vendors have made hardware advances increasing the radiation output capabilities of their fluoroscopes; this was evident in the acquisition air kerma rates. However, in the imaging protocol evaluated, all of the state‐of‐the‐art systems had relatively low air kerma rates in the fluoroscopic low‐dose imaging mode as compared to the previous‐generation unit. Each of the newest‐generation systems also employ copper filtration in the selected protocol in the acquisition mode of imaging; this is a substantial benefit, reducing the skin entrance dose to the patient in the highest dose‐rate mode of fluoroscope operation.Conclusion:Understanding how fluoroscopic technique factors are modulated provides insight into the vendor‐specific image acquisition approach and provides opportunities to optimize the imaging protocols for clinical practice. The enhanced radiation output capabilities of some of the fluoroscopes may, under specific conditions, may be beneficial; however, these higher output capabilities also have the potential to lead to unnecessarily high dose rates. Therefore, all parties involved in imaging, including the clinical team, medical physicists, and imaging vendors, must work together to ensure that adequate but not excessive radiation doses are used.

Selective spectral filtration with nanoparticles for concentrating solar collectors

A spectral fluid filter for potential use in hybrid photovoltaic/thermal concentrating solar collectors has been developed, targeting maximum absorption above and transmission below a desired wavelength. In this application, the temperature-dependent bandgap of the potential solar cell is used in the optimization of the filter. Dispersing a mix of colloidal nanoparticles in a heat transfer fluid is shown to absorb 86% of sub-bandgap insolation while absorbing only 18% above bandgap insolation. Transmission above bandgap light would be directly absorbed into the photovoltaic (PV) cell while absorbed photons transfer energy directly into the heat transfer fluid ultimately reducing the number of heat transfer steps. Placement of a filter in front of the PV cell is shown to decrease losses by converting an additional 2% of the total solar energy into thermal energy since it allows recollection of light reflected off the receiver.

New Approaches to Reduce Radiation While Maintaining Image Quality in Multi-Detector-Computed Tomography

This review discusses new technological approaches to reduce radiation dose while maintaining image quality in multi-detector-computed tomography (CT) for both adult and pediatric applications. First, the review focuses on the principles of automatic exposure control (AEC) systems for modulation of the tube current according to patient’s size; as well as special AEC adaptations for cardiac CT and organ-based tube current modulation. The selection of the tube potential (kV) is also discussed, with particular emphasis in a new technology which allows an automatic selection of the tube potential with a corresponding adjustment in the tube current, according to patient’s size and diagnostic task. The principles of iterative reconstruction, which is quickly becoming a standard feature in CT scanners, are also presented with particular emphasis on dose reduction and image quality. A full section is devoted to two latest state-of-the-art applications which can be used for radiation dose reduction: virtual non-contrast imaging with dual-energy CT and ultra-low dose CT with added spectral filtration. In the final section, innovations in CT hardware are presented ranging from the X-ray tube to CT detectors, which enable data acquisition at faster speeds and better efficiency to improve the balance between radiation dose and image quality.

SYMMETRY OF THEIBEXRIBBON OF ENHANCED ENERGETIC NEUTRAL ATOM (ENA) FLUX

The circular ribbon of enhanced energetic neutral atom (ENA) emission observed by the Interstellar Boundary Explorer (IBEX) mission remains a critical signature for understanding the interaction between the heliosphere and the interstellar medium. We study the symmetry of the ribbon flux and find strong, spectrally dependent reflection symmetry throughout the energy range 0.7-4.3?keV. The distribution of ENA flux around the ribbon is predominantly unimodal at 0.7 and 1.1?keV, distinctly bimodal at 2.7 and 4.3?keV, and a mixture of both at 1.7?keV. The bimodal flux distribution consists of partially opposing bilateral flux lobes, located at highest and lowest heliographic latitude extents of the ribbon. The vector between the ribbon center and heliospheric nose (which defines the so-called BV plane) appears to play an organizing role in the spectral dependence of the symmetry axis locations as well as asymmetric contributions to the ribbon flux. The symmetry planes at 2.7 and 4.3?keV, derived by projecting the symmetry axes to a great circle in the sky, are equivalent to tilting the heliographic equatorial plane to the ribbon center, suggesting a global heliospheric ordering. The presence and energy dependence of symmetric unilateral and bilateral flux distributions suggest strong spectral filtration from processes encountered by an ion along its journey from the source plasma to its eventual detection at IBEX.

Chest CT using spectral filtration: radiation dose, image quality, and spectrum of clinical utility.

To determine the radiation dose, image quality, and clinical utility of non-enhanced chest CT with spectral filtration. We retrospectively analysed 25 non-contrast chest CT examinations acquired with spectral filtration (tin-filtered Sn100 kVp spectrum) compared to 25 examinations acquired without spectral filtration (120 kV). Radiation metrics were compared. Image noise was measured. Contrast-to-noise-ratio (CNR) and figure-of-merit (FOM) were calculated. Diagnostic confidence for the assessment of various thoracic pathologies was rated by two independent readers. Effective chest diameters were comparable between groups (P = 0.613). In spectral filtration CT, median CTDIvol, DLP, and size-specific dose estimate (SSDE) were reduced (0.46 vs. 4.3 mGy, 16 vs. 141 mGy*cm, and 0.65 vs. 5.9 mGy, all P < 0.001). Spectral filtration CT had higher image noise (21.3 vs. 13.2 HU, P < 0.001) and lower CNR (47.2 vs. 75.3, P < 0.001), but was more dose-efficient (FOM 10,659 vs. 2,231/mSv, P < 0.001). Diagnostic confidence for parenchymal lung disease and osseous pathologies was lower with spectral filtration CT, but no significant difference was found for pleural pathologies, pulmonary nodules, or pneumonia. Non-contrast chest CT using spectral filtration appears to be sufficient for the assessment of a considerable spectrum of thoracic pathologies, while providing superior dose efficiency, allowing for substantial radiation dose reduction. • Spectral filtration enables non-contrast chest CT with very high dose efficiency. • This approach reduces CTDI vol , DLP, and SSDE (effective chest diameter 28 cm). • Lung nodules, pneumonia, and pleural pathologies can be assessed with uncompromised confidence.

Spatial and spectral mode filtration in phase-locked array of injection lasers with volume Bragg grating

High-power edge-emitting lasers with low divergence of the output beam are highly desired for a number of applications. In order to obtain high optical power one needs to expand the emitting area of the laser which usually leads to multi-mode lasing with broad spectrum and poor beam quality. Here we present the study of using a volume Bragg grating (VBG) as a spatial and spectral mode filter for phase-locked arrays of edge-emitting lasers based on 1D photonic bandgap crystals. Emitters in the arrays are synchronized due to the expanded vertical waveguide, which results in the lasing of high order oscillating modes. One lobe of high order mode was used to create an external cavity with VBG. We studied far-fields, spectra and L-I curves of the external cavity lasers and demonstrated that 500 mW of the output optical power could be concentrated in one lobe with the divergence as low as 1° and spectral width of 0.6 nm.

Spectrum of semiconductor laser with an external birefringent resonator

The semiconductor laser radiation with the external birefringent resonator is investigated. Existence of two main generated spectral lines corresponding to resonances of ordinary and extraordinary waves is established. Effective control of radiation, without loss on a spectral filtration is shown. It is specified possibility of application of two-mode generation in optical communication systems with WDM.

Determination of anxiolytic veterinary drugs from biological fertilizer blood meal using liquid chromatography high-resolution mass spectrometry.

A liquid environment-friendly agricultural material originating from animal blood, blood meal, was employed to detect anxiolytic veterinary drugs using a combination of liquid-liquid extraction (LLE) and positive electrospray ionization Orbitrap mass spectrometry. Every positive ion of the analytes was consistent with [M+H](+) , and the accurate mass analysis and mass spectral filtration with a 2-ppm mass tolerance window were applied to identify and quantitate the analytes and metabolites. The developed LLE method was validated with the lowest calibrated level, linearity (r(2) ), recovery, repeatability and the within-laboratory reproducibility, which were in the ranges of 0.3-1 µg/L, 0.9963-0.9995, 48.3-117.5%, 1.1-12.6% and 2.3-15.7%, respectively. The LLE method was compared with a solid-phase extraction (SPE) method; however, its recoveries were <70% for most of the analytes despite good repeatability of 1.2-7.4%. The analytes and the ascertained acepromazine, azaperone and xylazine metabolites were monitored in four actual liquid blood meal samples, and none of the targeted compounds were observed.

Does the use of additional X-ray beam filtration during cine acquisition reduce clinical image quality and effective dose in cardiac interventional imaging?

The impact of spectral filtration in digital ('cine') acquisition was investigated using a flat panel cardiac interventional X-ray imaging system. A 0.1-mm copper (Cu) and 1.0-mm aluminium (Al) filter added to the standard acquisition mode created the filtered mode for comparison. Image sequences of 35 patients were acquired, a double-blind subjective image quality assessment was completed and dose-area product (DAP) rates were calculated. Entrance surface dose (ESD) and effective dose (E) rates were determined for 20- and 30-cm phantoms. Phantom ESD fell by 28 and 41 % and E by 1 and 0.7 %, for the 20- and 30-cm phantoms, respectively, when using the filtration. Patient DAP rates fell by 43 % with no statistically significant difference in clinical image quality. Adding 0.1-mm Cu and 1.0-mm Al filtration in acquisition substantially reduces patient ESD and DAP, with no significant change in E or clinical image quality.

Peculiarities of approximation of meteorological characteristics having vertical gradient discontinuities close to the tropopause

Carried out is an analysis of errors of different approximation methods for separating the long- and short-wave parts of the spectra of the vertical distribution of meteorological variables and gas components in the areas of dramatic variations of their vertical gradients close to the tropopause. Proposed is an integrated approach using the polynomial, piecewise-linear, and spectral filtration and enabling to minimize the errors of approximation of long- and short-wave components of profiles of meteorological characteristics in the troposphere and stratosphere including the tropopause area. The method is useful for analyzing the mean values and mesoscale variations of meteorological parameters measured by the modern balloon and satellite systems.