Spectral Filtration Research Articles

CT colonography with spectral filtration and advanced modeled iterative reconstruction in the third-generation dual-source CT: image quality, radiation dose and performance in clinical utility

To evaluate image quality, radiation dose and its diagnostic performance in clinical utility of CT colonography (CTC) applying spectral filtration and advanced modeled iterative reconstruction (ADMIRE) techniques in third-generation dual-source CT. A total of 125 patients for screening or diagnostic purposes underwent CTC at 120kVp standard dose (120kVp-STD) with filtered-back projection reconstruction (FBP) in supine position, then at a tin-filtered 150 kVp low dose (Sn150kVp-LD) and a tin-filtered 100 kVp ultra-low dose (Sn100kVp-ULD) with ADMIRE reconstruction in prone position. Radiation metrics were recorded. Objective and subjective image qualities were compared, and the diagnostic performance was assessed for both colonic and extracolonic findings using CTC reporting and data system (C-RADS). The effective dose was significantly lower for Sn150kVp-LD and Sn100kVp-ULD than 120kVp-STD protocol, resulting in 22.5% and 87.5% reductions (1.55±0.30 and 0.25±0.07 mSv vs. 2.00±0.52 mSv; both p<0.01), respectively. Image noise and signal-to-noise ratio were improved significantly for Sn150kVp-LD with ADMIRE compared with 120kVp-STD, both of which had similar excellent 2D and 3D subjective image quality with equivalent diagnostic performance. Sn100kVp-ULD with ADMIRE had decreased subjective image quality and significant different C-RADS extracolonic-score (E-score) compared with 120kVp-STD, however, C-RADS colonic-score (C-score) of that showed no significantly difference. Sn150kVp and Sn100kVp with ADMIRE reconstruction provide an alternative low dose CTC strategy and could be feasible in clinical screening or diagnostic scenarios.

Multi-spectral interference imaging using laser-induced plasma light source

Interference imaging techniques are widely used for studying surface and internal structure of various objects. By varying the operating wavelength of the interference system, one can also obtain the information about the spectral properties of the inspected specimen. For multi-spectral interference imaging applications, wide-band high power light sources are necessary. Most of the existing sources suffer from speckle noise, low brightness or high price. In this paper, we demonstrate the applicability of a laser-induced plasma light source for interference imaging and quantitative phase measurements. Narrow-band spectral filtration of its illumination within a wavelength range 240-2600 nm allows to design cost-effective schemes for a variety of metrological applications including digital holography and spectral-domain optical coherence tomography.

Chest CT in patients after lung transplantation: A retrospective analysis to evaluate impact on image quality and radiation dose using spectral filtration tin-filtered imaging.

ObjectivesThe purpose of this study was to investigate the impact of a 150kV spectral filtration chest imaging protocol (Sn150kVp) combined with advanced modeled iterative reconstruction (ADMIRE) on radiation dose and image quality in patients after lung-transplantation.MethodsThis study included 102 patients who had unenhanced chest-CT examinations available on both, a second-generation dual-source CT (DSCT) using standard protocol (100kVp, filtered-back-projection) and, on a third-generation DSCT using Sn150kVp protocol with ADMIRE. Signal-to-noise-ratio (SNR) was measured in 6 standardized regions. A 5-point Likert scale was used to evaluate subjective image quality. Radiation metrics were compared.ResultsThe mean time interval between the two acquisitions was 1.1±0.7 years. Mean-volume-CT-dose-index, dose-length-product and effective dose were significantly lower for Sn150kVp protocol (2.1±0.5mGy;72.6±16.9mGy*cm;1.3±0.3mSv) compared to 100kVp protocol (6.2±1.8mGy;203.6±55.6mGy*cm;3.7±1.0mSv) (p<0.001), equaling a 65% dose reduction. All studies were considered of diagnostic quality. SNR measured in lung tissue, air inside trachea, vertebral body and air outside the body was significantly higher in 100kVp protocol compared to Sn150kVp protocol (12.5±2.7vs.9.6±1.5;17.4±3.6vs.11.8±1.8;0.7±0.3vs.0.4±0.2;25.2±6.9vs.14.9±3.3;p<0.001). SNR measured in muscle tissue was significantly higher in Sn150kVp protocol (3.2±0.9vs.2.6±1.0;p<0.001). For SNR measured in descending aorta there was a trend towards higher values for Sn150kVp protocol (2.8±0.6 vs. 2.7±0.9;p = 0.3). Overall SNR was significantly higher in 100kVp protocol (5.0±4.0vs.4.0±4.0;p<0.001). On subjective analysis both protocols achieved a median Likert rating of 1 (25th-75th-percentile:1–1;p = 0.122). Interobserver agreement was good (intraclass correlation coefficient = 0.73).ConclusionsCombined use of 150kVp tin-filtered chest CT protocol with ADMIRE allows for significant dose reduction while maintaining highly diagnostic image quality in the follow up after lung transplantation when compared to a standard chest CT protocol using filtered back projection.

Substantial radiation dose reduction with consistent image quality using a novel low-dose stone composition protocol.

To assess a novel low-dose CT-protocol, combining a 150kV spectral filtration unenhanced protocol (Sn150kVp) and a stone-targeted dual-energy CT (DECT) in patients with urolithiasis. 232 (151 male, 49 ± 16.4years) patients with urolithiasis received a low-dose non-contrast enhanced CT (NCCT) for suspected urinary stones either on a third-generation dual-source CT system (DSCT) using Sn150kVp (n = 116, group 1), or on a second-generation DSCT (n = 116 group 2) using single energy (SE) 120kVp. For group 1, a subsequent dual-energy CT (DECT) with a short stone-targeted scan range was performed. Objective and subjective image qualities were assessed. Radiation metrics were compared. 534 stones (group 1: n = 242 stones; group 2: n = 292 stones) were found. In group 1, all 215 stones within the stone-targeted DECT-scan range were identified. DE analysis was able to distinguish between UA and non-UA calculi in all collected stones. 11 calculi (5.12%) were labeled as uric acid (UA) while 204 (94.88%) were labeled as non-UA calculi. There was no significant difference in overall Signal-to-noise-ratio between group 1 and group 2 (p = 0.819). On subjective analysis both protocols achieved a median Likert rating of 2 (p = 0.171). Mean effective dose was significantly lower for combined Sn150kVp and stone-targeted DECT (3.34 ± 1.84mSv) compared to single energy 120kVp NCCT (4.45 ± 2.89mSv) (p < 0.001), equaling a 24.9% dose reduction. The evaluated novel low-dose stone composition protocol allows substantial radiation dose reduction with consistent high diagnostic image quality.

Low level EPR dosimetry of a commercial sugar

This work demonstrated the combined utility of empty tube subtraction, over-modulation, native signal subtraction and spectral filtration in low level dosimetry using commercial sugar samples. The native signal component was found to have an effective peak to peak equivalent of 150 mGy. If the zero dose native signal is accurately modeled and subtracted, the detection limit was estimated to be 0.2 Gy although intercept uncertainties were as low as 25 mGy. This was enabled by resultant slope uncertainties as low as 3% with residual variations of approximately 0.1 Gy.

Single-volume dual-channel acousto-optical tunable filter.

In this paper, we present a novel approach to spectral stereoscopic imaging. It is based on simultaneous spectral filtration of two light beams with a tunable acousto-optical filter (AOTF) of original design. It does not require large crystals and complicated optical relay systems, because two beams diffract in the same volume of the crystal medium but at different angles. We show that this geometry can be composed of a common-type AO cell and two triangular prisms of the same material. We derive equations, which specify the prism angles ensuring the necessary orientation of beams trajectories inside the crystal medium as well as parallel propagation of input and output beams. Some angles were additionally optimized for aberrations minimization by means of ray-tracing simulation. Experimental testing demonstrates rather high quality of spectral images, which is necessary for stereoscopic reconstruction procedure. The proposed approach makes possible development of spectral stereo-imaging components based on different types of previously developed AOTFs.

Technical Note: Radiation dose reduction from computed tomography localizer radiographs using a tin spectral shaping filter.

To evaluate the possibility of lowering radiation dose from a localizer radiograph (LR) using a tin spectral shaping filter and to investigate the effect of this adaptation on the radiation dose and image quality of subsequent computed tomography (CT) examination. The study utilized a set of semianthropomorphic abdomen phantoms, representing small, medium, and large patients. The LR scans were performed with and without a tin spectral shaping filter using various kVp/mA settings. The tube current values of spiral CT examinations following the LR were assessed to evaluate the effect of LR settings on automatic exposure control (AEC). The image quality of CT examinations with various LRs was evaluated by measuring image noise in several regions-of-interest. Organ dose values from LR scans were derived from Monte Carlo simulations performed on a set of virtual anthropomorphic phantoms and the effective dose (ED) values were calculated. The radiation dose from the LR can be strongly reduced by using a tin spectral shaping filter (P<0.001). The optimal settings of the LR scan depend on the size of the scanned subject: for small and medium size subjects, the combination of a tin spectral shaping filter with 100kVp and 20mA resulted in the lowest possible radiation dose (ED=0.007mGy) without compromising the AEC and image quality of subsequent CT. In contrast, the LR settings of 100kVp with a tin spectral shaping filter and the tube current values of 20 and 35mA in large subject (47.4cm in diameter) resulted in significant variation of the TCM values (11.1% and 8.4%, respectively) and the corresponding increase of noise by >5% in subsequent CT examination. For all investigated phantom sizes, the combination of 100Sn kV with a tin spectral shaping filter and tube current values of 75mA results in the lowest possible radiation dose, while still keeping the AEC function unchanged. The study indicated that tin spectral shaping filtration can be applied to LRs for radiation dose reduction, but such adaptation needs to take patient size into account.

Проектування та дослідження оптичної системи пірометра для вимірювання потоку випромінювання твердих частинок у двофазному потоці

There has been improved the measuring instrument of control of oxygen expenditure of a gas torch with the use of a simple tool base which does not demand a high level of qualification of operator. The optical system of pyrometer has been developed and investigated. The pyrometer is designed to measure radiation flux of solid soot particles in a high-temperature two-phase flow. The operating range of spectrum is 0,5·10–6 ... 1,1·10–6 m. At designing of the block scheme of a pyrometer it has been considered that the two-phase torch of a gas burner is a powerful thermal radiator. In the capacity of an emitter the self-radiation of a two-phase torch of a gas burner is used. So a method of thermal control has been defined as the passive one. For the purpose of simplification of the block scheme of a pyrometer the direct reception of optical radiation is used which represents the direct registration of energy falling on the receiver. As a result of it the simple and the reliable design of a pyrometer is gained. Measurement of stream of radiant energy of corpuscles of carbon (of soot) is carried out in a narrow spectral band of electromagnetic waves (0,5·10–6 ...1,1·10–6 м) between emission bands of gases. The problem of an optical spectral filtration at selection of signals against hindrances is carried out by the selective receiver of a stream of radiation. The spectral sensitivity range of the receiver coincides with wave length of range of measurement of stream of radiation of energy of corpuscles of carbon (of soot). It gave the possibility not to use interference filters in optical system of pyrometer. Focusing of energy of radiation on receiver sensing element of radiation is carried out by an optical system. The elements of an objective-lens of the simplified pyrometer are pellucid lens, a diaphragm, the optical filter. As a lens material transparent glass of brand К8 is used. Calculation of a visual field of optical system is executed. Size of a platform of a boresighting accepted equal to d2 = 5·10–3 m. There has been carried out the calculation of focal lengths of an optical system (f1 = 60·10–3 м; f = 50·10–3 м). The transmission coefficient of a quantity of radiant energy in a pyrometer optical system is equal to product of a transmission coefficient of a lens and a light filter transmission coefficient (tо = 0,823)

Prospective evaluation of ultra-low-dose contrast-enhanced 100-kV abdominal computed tomography with tin filter: effect on radiation dose reduction and image quality with a third-generation dual-source CT system.

To investigate the radiation dose exposure, image quality, and diagnostic performance of enhanced 100-kVp abdominopelvic single-energy CT protocol with tin filter (TF). Ninety-three consecutive patients referred for a single-phase enhanced abdominopelvic CT were prospectively included after informed consent. They underwent in addition to a standard protocol (SP) an acquisition with TF. Both examinations were performed on a third-generation dual-source CT system (DSCT), in single energy, using automatic tube current modulation, identical pitch, and identical level of iterative reconstruction. Radiation metrics were compared. Size-specific dose estimates (SSDE), contrast to noise ratio (CNR), and figure of merit (FOM) were calculated. Diagnostic confidence for the assessment of a predetermined list of abdominal lesions was rated by two independent readers. The mean dose of the TF protocol was significantly lower (CDTI 1.56 ± 0.43mGy vs. 8.13 ± 3.32, p < 0.001; SSDE 9.94 ± 3.08 vs. 1.93 ± 0.39, p < 0.001), with an effective dose close to 1mSv (1.14mSv ± 0.34; p < 0.001). TF group exhibited non-significant lower liver CNR (2.76 vs. 3.03, p = 0.56) and was more dose efficient (FOM 10.6 vs. 2.49/mSv, p < 0.001) in comparison to SP. The mean diagnostic confidence for visceral, bone, and peritoneal tumors was equivalent between both groups. Enhanced 100-kVp abdominopelvic CT acquired after spectral shaping with tin filtration can achieve similar diagnostic performance and CNR compared to a standard CT protocol, while reducing the radiation dose by 81%. • 100-kVp spectral filtration enables enhanced abdominal CT with high-dose efficiency. • The radiation dose reaches the 1-mSv range. • Predetermined abdominopelvic lesions can be assessed without impairing on diagnostic confidence.

Long-wavelength spectral filtering in anisotropic tapered fiber

Abstract We report on special tapered large mode area (LMA) polarization-maintaining fibers demonstrating inherit long-wavelength spectral filtering. The attenuation more than 25 dB of long-wavelength spectral range arising after amplified spontaneous emission (ASE) of a preamplifier, and also preservation of polarization state (extinction ratio more than 20 dB) and mode composition is presented in these fibers. Integration of this approach into the amplifier gain medium is promising for solving the problem of effective spectral filtration and polarized light generation.

Оценка согласованности оптимальной динамической спектральной фильтрации в оптико-электронных системах обнаружения объектов

Оценка согласованности оптимальной динамической спектральной фильтрации в оптико-электронных системах обнаружения объектов

Impulsive Raman spectroscopy via precision measurement of frequency shift with low energy excitation.

Stimulated Raman scattering (SRS) has recently become useful for chemically selective bioimaging. It is usually measured via modulation transfer from the pump beam to the Stokes beam. Impulsive stimulated Raman spectroscopy, on the other hand, relies on the spectral shift of ultrashort pulses as they propagate in a Raman active sample. This method was considered impractical with low energy pulses since the observed shifts are very small compared to the excitation pulse bandwidth, spanning many terahertz. Here we present a new apparatus, using tools borrowed from the field of precision measurement, for the detection of low-frequency Raman lines via stimulated-Raman-scattering-induced spectral shifts. This method does not require any spectral filtration and is therefore an excellent candidate to resolve low-lying Raman lines (<200 cm-1), which are commonly masked by the strong Rayleigh scattering peak. Having the advantage of the high repetition rate of the ultrafast oscillator, we reduce the noise level by implementing a lock-in detection scheme with a wavelength shift sensitivity well below 100fm. This is demonstrated by the measurement of low-frequency Raman lines of various liquid samples.

Метод построения дифракционных изображений трещинно-кавернозных зон на основе многомерной спектральной фильтрации и новые возможности изучения свойств геологических сред на основе анализа многомерных сейсмических данных общей точки изображения

Метод построения дифракционных изображений трещинно-кавернозных зон на основе многомерной спектральной фильтрации и новые возможности изучения свойств геологических сред на основе анализа многомерных сейсмических данных общей точки изображения

Динамическая спектральная фильтрация сигналов в оптико-электронных системах обнаружения объектов

Динамическая спектральная фильтрация сигналов в оптико-электронных системах обнаружения объектов

Improvement of LOD in Fluorescence Detection with Spectrally Nonuniform Background by Optimization of Emission Filtering.

The limit-of-detection (LOD) in analytical instruments with fluorescence detection can be improved by reducing noise of optical background. Efficiently reducing optical background noise in systems with spectrally nonuniform background requires complex optimization of an emission filter-the main element of spectral filtration. Here, we introduce a filter-optimization method, which utilizes an expression for the signal-to-noise ratio (SNR) as a function of (i) all noise components (dark, shot, and flicker), (ii) emission spectrum of the analyte, (iii) emission spectrum of the optical background, and (iv) transmittance spectrum of the emission filter. In essence, the noise components and the emission spectra are determined experimentally and substituted into the expression. This leaves a single variable-the transmittance spectrum of the filter-which is optimized numerically by maximizing SNR. Maximizing SNR provides an accurate way of filter optimization, while a previously used approach based on maximizing a signal-to-background ratio (SBR) is the approximation that can lead to much poorer LOD specifically in detection of fluorescently labeled biomolecules. The proposed filter-optimization method will be an indispensable tool for developing new and improving existing fluorescence-detection systems aiming at ultimately low LOD.

Single-energy pediatric chest computed tomography with spectral filtration at 100 kVp: effects on radiation parameters and image quality.

Most of the applied radiation dose at CT is in the lower photon energy range, which is of limited diagnostic importance. To investigate image quality and effects on radiation parameters of 100-kVp spectral filtration single-energy chest CT using a tin-filter at third-generation dual-source CT in comparison to standard 100-kVp chest CT. Thirty-three children referred for a non-contrast chest CT performed on a third-generation dual-source CT scanner were examined at 100kVp with a dedicated tin filter with a tube current-time product resulting in standard protocol dose. We compared resulting images with images from children examined using standard single-source chest CT at 100kVp. We assessed objective and subjective image quality and compared radiation dose parameters. Radiation dose was comparable for children 5years old and younger, and it was moderately decreased for older children when using spectral filtration (P=0.006). Effective tube current increased significantly (P=0.0001) with spectral filtration, up to a factor of 10. Signal-to-noise ratio and image noise were similar for both examination techniques (P≥0.06). Subjective image quality showed no significant differences (P≥0.2). Using 100-kVp spectral filtration chest CT in children by means of a tube-based tin-filter on a third-generation dual-source CT scanner increases effective tube current up to a factor of 10 to provide similar image quality at equivalent dose compared to standard single-source CT without spectral filtration.

Feasibility of Pediatric Chest CT Using Spectral Filtration on Third-generation Dual-source CT.

Objective To prospectively investigate the radiation dose and image quality of pediatric chest CT using Sn100 kV on a third-generation dual-source CT (DSCT)in comparison to standard 100 kV chest CT. Methods From December 12,2015 to June 30,2016,45 consecutive pediatric patients referred for non-contrast chest CT scan in Peking Union Medical College Hospital were prospectively enrolled as study group. They were examined at 100 kV with a dedicated tin filter on a third-generation DSCT. These patients were retrospectively matched with 45 patients who were examined on a second-generation DSCT at 100 kV without tin filter. The radiation dose as well as the lung and mediastinal window image quality(IQ)of the two groups were compared and analyzed statistically. IQ was evaluated using a five-point scale (1=unevaluable,5=excellent). Differences of radiation dose and noise between the two groups were determined with variance analysis and t test,IQ with Mann-Whitney U test,and the consistency of diagnosis with Kappa test. Results The average CT dose index volume of the study group was (0.24±0.11)mGy,which was decreased by 92% compared with the control group [(3.10+1.18)mGy] (t=16.287,P=0.000). Mean dose-length product and mean effective dose for study group were significantly lower than those of control group [(7.13±4.72)mGy·cm vs. (84.78±46.78)mGy·cm,t=11.077,P=0.000;(0.11±0.06)mSv vs.(1.23±0.61)mSv,t=12.334,P=0.000]. There was no significant difference between the two groups in terms of image noise (t=-0.003,P=0.397)and contrast to noise ratio (t=0.545,P=0.488). There was no significant difference between the two groups in lung window IQ (doctor 1:U=796.000,P=0.055;doctor 2:U=889.500,P=0.277),while significant difference was seen concerning of the mediastinal window IQ (doctor 1:U=305.000,P=0.000;doctor 2:U=276.500,P=0.000). Referring to the lung window,the median IQ for the study group and control group was 4 (3-5)and 4 (3-5),respectively. All imaging findings had acceptable IQ. The breath motion artifacts (χ2=13.846,P=0.001)and heart beat artifacts (χ2=53.519,P=0.000)of the study group were significantly lower than those of the control group. Conclusion Compared with standard 100 kV chest CT,the use of tin-filtered Sn100 kV on a third-generation DSCT provided 92% dose reduction in pediatric chest CT examinations while maintaining diagnostically acceptable lung window images.

Calculation of the interference pattern formed by image-carrying light beams diffracted by an acoustic wave in a uniaxial crystal

A scheme of full-field optical coherence microscopy based on a Michelson interferometer with wideband light source and acousto-optic spectral filtration in the output channel is studied. Mathematical formulas for calculating the interference pattern formed by image-carrying light beams diffracted by an acoustic wave in a uniaxial crystal are derived for this scheme. Results of numerical modeling and its comparison with experimental data are given.

Fast Magic-Angle Spinning Three-Dimensional NMR Experiment for Simultaneously Probing H-H and N-H Proximities in Solids.

A fast magic-angle spinning (MAS, 70 kHz) solid-state NMR experiment is presented that combines 1H Double-Quantum (DQ) and 14N-1H HMQC (Heteronuclear Multiple-Quantum Coherence) pulse-sequence elements, so as to simultaneously probe H-H and N-H proximities in molecular solids. The proposed experiment can be employed in both two-dimensional (2D) and three-dimensional (3D) versions: first, a 2D 14N HMQC-filtered 1H-DQ experiment provides specific DQ-SQ correlation peaks for proton pairs that are in close proximities to the nitrogen sites, thereby achieving spectral filtration. Second, a proton-detected three-dimensional (3D) 1H(DQ)-14N(SQ)-1H(SQ) experiment correlates 1H(DQ)-1H(SQ) chemical shifts with 14N shifts such that longer range N···H-H correlations are observed between protons and nitrogen atoms with internuclear NH distances exceeding 3 Å. Both 2D and 3D versions of the proposed experiment are demonstrated for an amino acid hydrochloride salt, l-histidine·HCl·H2O, and a DNA nucleoside, guanosine·2H2O. In the latter case, the achieved spectral filtration ensures that DQ cross peaks are only observed for guanine NH and CH8 1H resonances and not ribose and water 1H resonances, thus providing insight into the changes in the solid-state structure of this hydrate that occur over time; significant changes are observed in the NH and NH21H chemical shifts as compared to the freshly recrystallized sample previously studied by Reddy et al., Cryst. Growth Des. 2015, 15, 5945.

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.