Low Complexity Compression and Speed Enhancement for Optical Scanning Holography

PubMed Central

Tsang, P. W. M.; Poon, T.-C.; Liu, J.-P.; Kim, T.; Kim, Y. S.

2016-01-01

In this paper we report a low complexity compression method that is suitable for compact optical scanning holography (OSH) systems with different optical settings. Our proposed method can be divided into 2 major parts. First, an automatic decision maker is applied to select the rows of holographic pixels to be scanned. This process enhances the speed of acquiring a hologram, and also lowers the data rate. Second, each row of down-sampled pixels is converted into a one-bit representation with delta modulation (DM). Existing DM-based hologram compression techniques suffers from the disadvantage that a core parameter, commonly known as the step size, has to be determined in advance. However, the correct value of the step size for compressing each row of hologram is dependent on the dynamic range of the pixels, which could deviate significantly with the object scene, as well as OSH systems with different opical settings. We have overcome this problem by incorporating a dynamic step-size adjustment scheme. The proposed method is applied in the compression of holograms that are acquired with 2 different OSH systems, demonstrating a compression ratio of over two orders of magnitude, while preserving favorable fidelity on the reconstructed images. PMID:27708410

Ultrafast time-resolved photoemission of a metallic tip/substrate junction

NASA Astrophysics Data System (ADS)

Meng, Xiang; Jin, Wencan; Yang, Hao; Dadap, Jerry; Osgood, Richard; Camillone, Nicholas, III

The strong near-field enhancement of metallic-tip nanostructures has attracted great interest in scanning microscopy techniques, such as surface-enhanced Raman scattering, near-field scanning optical microscopy and tip-enhanced nonlinear imaging. In this talk, we use a full vectorial 3D-FDTD method to investigate the spatial characteristics of the optical field confinement and localization between a tungsten nanoprobe and an infinite planar silver substrate, with two-color ultrafast laser excitation scheme. The degree of two-color excited field enhancement, geometry dependence, the exact mechanism of optical tip-substrate coupling and tip-substrate plasmon resonances are significant in understanding the electrodynamical responses at tip-substrate junction. The demonstrated measurements with subpicosecond time and subnanometer spatial resolution suggest a new approach to ultrafast time-resolved measurements of surface electron dynamics. DE-FG 02-90-ER-14104; DE-FG 02-04-ER-46157.

Optimal acquisition and modeling parameters for accurate assessment of low Ktrans blood-brain barrier permeability using dynamic contrast-enhanced MRI.

PubMed

Barnes, Samuel R; Ng, Thomas S C; Montagne, Axel; Law, Meng; Zlokovic, Berislav V; Jacobs, Russell E

2016-05-01

To determine optimal parameters for acquisition and processing of dynamic contrast-enhanced MRI (DCE-MRI) to detect small changes in near normal low blood-brain barrier (BBB) permeability. Using a contrast-to-noise ratio metric (K-CNR) for Ktrans precision and accuracy, the effects of kinetic model selection, scan duration, temporal resolution, signal drift, and length of baseline on the estimation of low permeability values was evaluated with simulations. The Patlak model was shown to give the highest K-CNR at low Ktrans . The Ktrans transition point, above which other models yielded superior results, was highly dependent on scan duration and tissue extravascular extracellular volume fraction (ve ). The highest K-CNR for low Ktrans was obtained when Patlak model analysis was combined with long scan times (10-30 min), modest temporal resolution (<60 s/image), and long baseline scans (1-4 min). Signal drift as low as 3% was shown to affect the accuracy of Ktrans estimation with Patlak analysis. DCE acquisition and modeling parameters are interdependent and should be optimized together for the tissue being imaged. Appropriately optimized protocols can detect even the subtlest changes in BBB integrity and may be used to probe the earliest changes in neurodegenerative diseases such as Alzheimer's disease and multiple sclerosis. © 2015 Wiley Periodicals, Inc.

FDG-Avid Portal Vein Tumor Thrombosis from Hepatocellular Carcinoma in Contrast-Enhanced FDG PET/CT

PubMed Central

Nguyen, Xuan Canh; Nguyen, Dinh Song Huy; Ngo, Van Tan; Maurea, Simone

2015-01-01

Objective(s): In this study, we aimed to describe the characteristics of portal vein tumor thrombosis (PVTT), complicating hepatocellular carcinoma (HCC) in contrast-enhanced FDG PET/CT scan. Methods: In this retrospective study, 9 HCC patients with FDG-avid PVTT were diagnosed by contrast-enhanced fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT), which is a combination of dynamic liver CT scan, multiphase imaging, and whole-body PET scan. PET and CT DICOM images of patients were imported into the PET/CT imaging system for the re-analysis of contrast enhancement and FDG uptake in thrombus, the diameter of the involved portal vein, and characteristics of liver tumors and metastasis. Results: Two patients with previously untreated HCC and 7 cases with previously treated HCC had FDG-avid PVTT in contrast-enhanced FDG PET/CT scan. During the arterial phase of CT scan, portal vein thrombus showed contrast enhancement in 8 out of 9 patients (88.9%). PET scan showed an increased linear FDG uptake along the thrombosed portal vein in all patients. The mean greatest diameter of thrombosed portal veins was 1.8 ± 0.2 cm, which was significantly greater than that observed in normal portal veins (P<0.001). FDG uptake level in portal vein thrombus was significantly higher than that of blood pool in the reference normal portal vein (P=0.001). PVTT was caused by the direct extension of liver tumors. All patients had visible FDG-avid liver tumors in contrast-enhanced images. Five out of 9 patients (55.6%) had no extrahepatic metastasis, 3 cases (33.3%) had metastasis of regional lymph nodes, and 1 case (11.1%) presented with distant metastasis. The median estimated survival time of patients was 5 months. Conclusion: The intraluminal filling defect consistent with thrombous within the portal vein, expansion of the involved portal vein, contrast enhancement, and linear increased FDG uptake of the thrombus extended from liver tumor are findings of FDG-avid PVTT from HCC in contrast-enhanced FDG PET/CT. PMID:27408876

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muir, Ryan D.; Sullivan, Shane Z.; Oglesbee, Robert A.

Digital lock-in amplification (LIA) with synchronous digitization (SD) is shown to provide significant signal to noise (S/N) and linear dynamic range advantages in beam-scanning microscopy measurements using pulsed laser sources. Direct comparisons between SD-LIA and conventional LIA in homodyne second harmonic generation measurements resulted in S/N enhancements consistent with theoretical models. SD-LIA provided notably larger S/N enhancements in the limit of low light intensities, through the smooth transition between photon counting and signal averaging developed in previous work. Rapid beam scanning instrumentation with up to video rate acquisition speeds minimized photo-induced sample damage. The corresponding increased allowance for higher lasermore » power without sample damage is advantageous for increasing the observed signal content.« less

Low-dose dynamic myocardial perfusion CT image reconstruction using pre-contrast normal-dose CT scan induced structure tensor total variation regularization

NASA Astrophysics Data System (ADS)

Gong, Changfei; Han, Ce; Gan, Guanghui; Deng, Zhenxiang; Zhou, Yongqiang; Yi, Jinling; Zheng, Xiaomin; Xie, Congying; Jin, Xiance

2017-04-01

Dynamic myocardial perfusion CT (DMP-CT) imaging provides quantitative functional information for diagnosis and risk stratification of coronary artery disease by calculating myocardial perfusion hemodynamic parameter (MPHP) maps. However, the level of radiation delivered by dynamic sequential scan protocol can be potentially high. The purpose of this work is to develop a pre-contrast normal-dose scan induced structure tensor total variation regularization based on the penalized weighted least-squares (PWLS) criteria to improve the image quality of DMP-CT with a low-mAs CT acquisition. For simplicity, the present approach was termed as ‘PWLS-ndiSTV’. Specifically, the ndiSTV regularization takes into account the spatial-temporal structure information of DMP-CT data and further exploits the higher order derivatives of the objective images to enhance denoising performance. Subsequently, an effective optimization algorithm based on the split-Bregman approach was adopted to minimize the associative objective function. Evaluations with modified dynamic XCAT phantom and preclinical porcine datasets have demonstrated that the proposed PWLS-ndiSTV approach can achieve promising gains over other existing approaches in terms of noise-induced artifacts mitigation, edge details preservation, and accurate MPHP maps calculation.

DCE-MRI using small-molecular and albumin-binding contrast agents in experimental carcinomas with different stromal content.

PubMed

Farace, Paolo; Merigo, Flavia; Fiorini, Silvia; Nicolato, Elena; Tambalo, Stefano; Daducci, Alessandro; Degrassi, Anna; Sbarbati, Andrea; Rubello, Domenico; Marzola, Pasquina

2011-04-01

To compare DCE-MRI experiments performed using a standard small-molecular (Gd-DTPA) and an albumin-binding (MS-325) contrast agent in two carcinoma models with different stromal content. DU-145 or BXPC-3 cancer cells were subcutaneously injected into nude mice. DCE-MRI was performed by a bolus injection of Gd-DTPA or MS-325 about 2 weeks after inoculation. For quantitative analysis a volume of interest was manually drawn over each tumor. To address the heterogeneous enhancement, each tumor volume was then divided into the 20% most-enhancing and the remaining 80% least-enhancing fractions. Mean tumor enhancement was calculated over these selected tumor volumes and compared between tumor groups and contrast agents. Maps of differential enhancement, peak enhancement and time-to-peak were used for visual evaluation. CD31 and VEGF immunohistochemistry were performed in excised tumors. In the 80% least-enhancing volume, at late time points of the dynamic scan, the mean enhancement elicited by MS-325 was higher in BXPC-3 than in DU-145 tumors. In the 20% most-enhancing volume, using either contrast agents, significant difference between the two tumors types were observed only early, while at later time points of the dynamic scan the difference were obscured by the faster washout observed in the BXPC-3 tumors. Enhancement maps confirmed that BXPC-3 tumors were characterized by marked washout rate using either contrast agent, particularly in the higher enhancing peripheral rim. With MS-325 this washout pattern appeared to be specific to the BXPC-3 carcinomas, since it was not observed in the DU-145 tumors. Finally, in both tumor types, MS-325 produced significantly higher enhancement than Gd-DTPA in the late phase of the dynamic scan. Ex vivo analysis confirmed the marked presence of aberrant infiltrative stroma in BXPC-3 tumors, in which tumor vessels were embedded. In all tumors the central portion was less viable and less infiltrated by stromal tissue then the peripheral areas. Contrast distribution proved to be related to stromal content, which presumably produced the higher enhancement and faster washout observed in the BXPC-3 tumors. In particular, 'early' contrast-enhanced MRI, appeared as the most sensitive technique to detect the tumor portions characterized by a high stromal content, i.e. the peripheral rim of the BXPC-3 tumors. Since the same tumor models were recently investigated using FDG-PET imaging, showing inverse relationship between FDG uptake and stromal content, contrast-enhanced MRI and FDG-PET could provide complementary and comprehensive sensitivity in the assessment of carcinomas. Copyright © 2009 Elsevier Ireland Ltd. All rights reserved.

Magnetic resonance imaging in local staging of endometrial carcinoma: diagnostic performance, pitfalls, and literature review.

PubMed

Zandrino, Franco; La Paglia, Ernesto; Musante, Francesco

2010-01-01

To assess the diagnostic accuracy of magnetic resonance imaging in local staging of endometrial carcinoma, and to review the results and pitfalls described in the literature. Thirty women with a histological diagnosis of endometrial carcinoma underwent magnetic resonance imaging. Unenhanced T2-weighted and dynamic contrast-enhanced Ti-weighted sequences were obtained. Hysterectomy and salpingo-oophorectomy was performed in all patients. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated for the detection of deep myometrial and cervical infiltration. For deep myometrial infiltration T2-weighted sequences reached a sensitivity of 85%, specificity of 76%, PPV of 73%, NVP of 87%, and accuracy of 80%, while contrast-enhanced scans reached a sensitivity of 90%, specificity of 80%, PPV of 82%, NPV of 89%, and accuracy of 85%. For cervical infiltration T2-weighted sequences reached a sensitivity of 75%, specificity of 88%, PPV of 50%, NPV of 96%, and accuracy of 87%, while contrast-enhanced scans reached a sensitivity of 100%, specificity of 94%, PPV of 75%, NPV of 100%, and accuracy of 95%. Unenhanced and dynamic gadolinium-enhanced magnetic resonance allows accurate assessment of myometrial and cervical infiltration. Information provided by magnetic resonance imaging can define prognosis and management.

Time-optimized laser micro machining by using a new high dynamic and high precision galvo scanner

NASA Astrophysics Data System (ADS)

Jaeggi, Beat; Neuenschwander, Beat; Zimmermann, Markus; Zecherle, Markus; Boeckler, Ernst W.

2016-03-01

High accuracy, quality and throughput are key factors in laser micro machining. To obtain these goals the ablation process, the machining strategy and the scanning device have to be optimized. The precision is influenced by the accuracy of the galvo scanner and can further be enhanced by synchronizing the movement of the mirrors with the laser pulse train. To maintain a high machining quality i.e. minimum surface roughness, the pulse-to-pulse distance has also to be optimized. Highest ablation efficiency is obtained by choosing the proper laser peak fluence together with highest specific removal rate. The throughput can now be enhanced by simultaneously increasing the average power, the repetition rate as well as the scanning speed to preserve the fluence and the pulse-to-pulse distance. Therefore a high scanning speed is of essential importance. To guarantee the required excellent accuracy even at high scanning speeds a new interferometry based encoder technology was used, that provides a high quality signal for closed-loop control of the galvo scanner position. Low inertia encoder design enables a very dynamic scanner system, which can be driven to very high line speeds by a specially adapted control solution. We will present results with marking speeds up to 25 m/s using a f = 100 mm objective obtained with a new scanning system and scanner tuning maintaining a precision of about 5 μm. Further it will be shown that, especially for short line lengths, the machining time can be minimized by choosing the proper speed which has not to be the maximum one.

Enhanced Axial Resolution of Wide-Field Two-Photon Excitation Microscopy by Line Scanning Using a Digital Micromirror Device.

PubMed

Park, Jong Kang; Rowlands, Christopher J; So, Peter T C

2017-01-01

Temporal focusing multiphoton microscopy is a technique for performing highly parallelized multiphoton microscopy while still maintaining depth discrimination. While the conventional wide-field configuration for temporal focusing suffers from sub-optimal axial resolution, line scanning temporal focusing, implemented here using a digital micromirror device (DMD), can provide substantial improvement. The DMD-based line scanning temporal focusing technique dynamically trades off the degree of parallelization, and hence imaging speed, for axial resolution, allowing performance parameters to be adapted to the experimental requirements. We demonstrate this new instrument in calibration specimens and in biological specimens, including a mouse kidney slice.

Enhanced Axial Resolution of Wide-Field Two-Photon Excitation Microscopy by Line Scanning Using a Digital Micromirror Device

PubMed Central

Park, Jong Kang; Rowlands, Christopher J.; So, Peter T. C.

2017-01-01

Temporal focusing multiphoton microscopy is a technique for performing highly parallelized multiphoton microscopy while still maintaining depth discrimination. While the conventional wide-field configuration for temporal focusing suffers from sub-optimal axial resolution, line scanning temporal focusing, implemented here using a digital micromirror device (DMD), can provide substantial improvement. The DMD-based line scanning temporal focusing technique dynamically trades off the degree of parallelization, and hence imaging speed, for axial resolution, allowing performance parameters to be adapted to the experimental requirements. We demonstrate this new instrument in calibration specimens and in biological specimens, including a mouse kidney slice. PMID:29387484

Enhanced weak-signal sensitivity in two-photon microscopy by adaptive illumination.

PubMed

Chu, Kengyeh K; Lim, Daryl; Mertz, Jerome

2007-10-01

We describe a technique to enhance both the weak-signal relative sensitivity and the dynamic range of a laser scanning optical microscope. The technique is based on maintaining a fixed detection power by fast feedback control of the illumination power, thereby transferring high measurement resolution to weak signals while virtually eliminating the possibility of image saturation. We analyze and demonstrate the benefits of adaptive illumination in two-photon fluorescence microscopy.

Assessing Tumor Response to Treatment in Patients with Lung Cancer Using Dynamic Contrast-Enhanced CT.

PubMed

Strauch, Louise S; Eriksen, Rie Ø; Sandgaard, Michael; Kristensen, Thomas S; Nielsen, Michael B; Lauridsen, Carsten A

2016-07-21

The aim of this study was to provide an overview of the literature available on dynamic contrast-enhanced computed tomography (DCE-CT) as a tool to evaluate treatment response in patients with lung cancer. This systematic review was compiled according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Only original research articles concerning treatment response in patients with lung cancer assessed with DCE-CT were included. To assess the validity of each study we implemented Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2). The initial search yielded 651 publications, and 16 articles were included in this study. The articles were divided into groups of treatment. In studies where patients were treated with systemic chemotherapy with or without anti-angiogenic drugs, four out of the seven studies found a significant decrease in permeability after treatment. Four out of five studies that measured blood flow post anti-angiogenic treatments found that blood flow was significantly decreased. DCE-CT may be a useful tool in assessing treatment response in patients with lung cancer. It seems that particularly permeability and blood flow are important perfusion values for predicting treatment outcome. However, the heterogeneity in scan protocols, scan parameters, and time between scans makes it difficult to compare the included studies.

Contrast Gradient-Based Blood Velocimetry With Computed Tomography: Theory, Simulations, and Proof of Principle in a Dynamic Flow Phantom.

PubMed

Korporaal, Johannes G; Benz, Matthias R; Schindera, Sebastian T; Flohr, Thomas G; Schmidt, Bernhard

2016-01-01

The aim of this study was to introduce a new theoretical framework describing the relationship between the blood velocity, computed tomography (CT) acquisition velocity, and iodine contrast enhancement in CT images, and give a proof of principle of contrast gradient-based blood velocimetry with CT. The time-averaged blood velocity (v(blood)) inside an artery along the axis of rotation (z axis) is described as the mathematical division of a temporal (Hounsfield unit/second) and spatial (Hounsfield unit/centimeter) iodine contrast gradient. From this new theoretical framework, multiple strategies for calculating the time-averaged blood velocity from existing clinical CT scan protocols are derived, and contrast gradient-based blood velocimetry was introduced as a new method that can calculate v(blood) directly from contrast agent gradients and the changes therein. Exemplarily, the behavior of this new method was simulated for image acquisition with an adaptive 4-dimensional spiral mode consisting of repeated spiral acquisitions with alternating scan direction. In a dynamic flow phantom with flow velocities between 5.1 and 21.2 cm/s, the same acquisition mode was used to validate the simulations and give a proof of principle of contrast gradient-based blood velocimetry in a straight cylinder of 2.5 cm diameter, representing the aorta. In general, scanning with the direction of blood flow results in decreased and scanning against the flow in increased temporal contrast agent gradients. Velocity quantification becomes better for low blood and high acquisition speeds because the deviation of the measured contrast agent gradient from the temporal gradient will increase. In the dynamic flow phantom, a modulation of the enhancement curve, and thus alternation of the contrast agent gradients, can be observed for the adaptive 4-dimensional spiral mode and is in agreement with the simulations. The measured flow velocities in the downslopes of the enhancement curves were in good agreement with the expected values, although the accuracy and precision worsened with increasing flow velocities. The new theoretical framework increases the understanding of the relationship between the blood velocity, CT acquisition velocity, and iodine contrast enhancement in CT images, and it interconnects existing blood velocimetry methods with research on transluminary attenuation gradients. With these new insights, novel strategies for CT blood velocimetry, such as the contrast gradient-based method presented in this article, may be developed.

In Vivo Visualization of Active Polysynaptic Circuits With Longitudinal Manganese-Enhanced MRI (MEMRI).

PubMed

Almeida-Corrêa, Suellen; Czisch, Michael; Wotjak, Carsten T

2018-01-01

Manganese-enhanced magnetic resonance imaging (MEMRI) is a powerful tool for in vivo non-invasive whole-brain mapping of neuronal activity. Mn 2+ enters active neurons via voltage-gated calcium channels and increases local contrast in T 1 -weighted images. Given the property of Mn 2+ of axonal transport, this technique can also be used for tract tracing after local administration of the contrast agent. However, MEMRI is still not widely employed in basic research due to the lack of a complete description of the Mn 2+ dynamics in the brain. Here, we sought to investigate how the activity state of neurons modulates interneuronal Mn 2+ transport. To this end, we injected mice with low dose MnCl 2 2. (i.p., 20 mg/kg; repeatedly for 8 days) followed by two MEMRI scans at an interval of 1 week without further MnCl 2 injections. We assessed changes in T 1 contrast intensity before (scan 1) and after (scan 2) partial sensory deprivation (unilateral whisker trimming), while keeping the animals in a sensory enriched environment. After correcting for the general decay in Mn 2+ content, whole brain analysis revealed a single cluster with higher signal in scan 1 compared to scan 2: the left barrel cortex corresponding to the right untrimmed whiskers. In the inverse contrast (scan 2 > scan 1), a number of brain structures, including many efferents of the left barrel cortex were observed. These results suggest that continuous neuronal activity elicited by ongoing sensory stimulation accelerates Mn 2+ transport from the uptake site to its projection terminals, while the blockage of sensory-input and the resulting decrease in neuronal activity attenuates Mn 2+ transport. The description of this critical property of Mn 2+ dynamics in the brain allows a better understanding of MEMRI functional mechanisms, which will lead to more carefully designed experiments and clearer interpretation of the results.

Impact of Contrast Media Concentration on Low-Kilovolt Computed Tomography Angiography: A Systematic Preclinical Approach.

PubMed

Fleischmann, Ulrike; Pietsch, Hubertus; Korporaal, Johannes G; Flohr, Thomas G; Uder, Michael; Jost, Gregor; Lell, Michael M

2018-05-01

Low peak kilovoltage (kVp) protocols in computed tomography angiography (CTA) demand a review of contrast media (CM) administration practices. The aim of this study was to systematically evaluate different iodine concentrations of CM in a porcine model. Dynamic 70 kVp CTA was performed on 7 pigs using a third-generation dual-source CT system. Three CM injection protocols (A-C) with an identical total iodine dose and iodine delivery rate (150 mg I/kg, 12 s, 0.75 g I/s) differed in iodine concentration and flow rate (protocol A: 400 mg I/mL, 1.9 mL/s; B: 300 mg I/mL, 2.5 mL/s; C: 150 mg I/mL, 5 mL/s). All protocols were applied in a randomized order and compared intraindividually. Arterial enhancement at different locations in the pulmonary artery, the aorta, and aortic branches was measured over time. Time attenuation curves, peak enhancement, time to peak, and bolus tracking delay times needed for static CTA were calculated. The reproducibility of optimal parameters was tested in single-phase CTA. The heart rates of the pigs were comparable for all protocols (P > 0.7). The injection pressure was significantly higher for protocol A (64 ± 5 psi) and protocol C (55 ± 3 psi) compared with protocol B (39 ± 2 psi) (P < 0.001). Average arterial peak enhancement in the dynamic scans was 359 ± 51 HU (protocol A), 382 ± 36 HU (B), and 382 ± 60 HU (C) (A compared with B and C: P < 0.01; B compared with C: P = 0.995). Time to peak enhancement decreased with increasing injection rate. The delay time for bolus tracking depended on the injection rate as well and was highest for protocol A (4.7 seconds) and lowest for protocol C (3.9 seconds) (P = 0.038). The peak enhancement values of the dynamic scans highly correlated with those of the single-phase CTA scans. In 70 kVp CTA, 300 mg I/mL iodine concentrations showed to be superior to high-concentration CM when keeping the iodine delivery rate constant. Besides, iodine concentrations as low as 150 mg I/mL can be administered without compromising vascular enhancement. This opens up new possibilities in CM administration.

Dynamic whole-body PET parametric imaging: I. Concept, acquisition protocol optimization and clinical application.

PubMed

Karakatsanis, Nicolas A; Lodge, Martin A; Tahari, Abdel K; Zhou, Y; Wahl, Richard L; Rahmim, Arman

2013-10-21

Static whole-body PET/CT, employing the standardized uptake value (SUV), is considered the standard clinical approach to diagnosis and treatment response monitoring for a wide range of oncologic malignancies. Alternative PET protocols involving dynamic acquisition of temporal images have been implemented in the research setting, allowing quantification of tracer dynamics, an important capability for tumor characterization and treatment response monitoring. Nonetheless, dynamic protocols have been confined to single-bed-coverage limiting the axial field-of-view to ~15-20 cm, and have not been translated to the routine clinical context of whole-body PET imaging for the inspection of disseminated disease. Here, we pursue a transition to dynamic whole-body PET parametric imaging, by presenting, within a unified framework, clinically feasible multi-bed dynamic PET acquisition protocols and parametric imaging methods. We investigate solutions to address the challenges of: (i) long acquisitions, (ii) small number of dynamic frames per bed, and (iii) non-invasive quantification of kinetics in the plasma. In the present study, a novel dynamic (4D) whole-body PET acquisition protocol of ~45 min total length is presented, composed of (i) an initial 6 min dynamic PET scan (24 frames) over the heart, followed by (ii) a sequence of multi-pass multi-bed PET scans (six passes × seven bed positions, each scanned for 45 s). Standard Patlak linear graphical analysis modeling was employed, coupled with image-derived plasma input function measurements. Ordinary least squares Patlak estimation was used as the baseline regression method to quantify the physiological parameters of tracer uptake rate Ki and total blood distribution volume V on an individual voxel basis. Extensive Monte Carlo simulation studies, using a wide set of published kinetic FDG parameters and GATE and XCAT platforms, were conducted to optimize the acquisition protocol from a range of ten different clinically acceptable sampling schedules examined. The framework was also applied to six FDG PET patient studies, demonstrating clinical feasibility. Both simulated and clinical results indicated enhanced contrast-to-noise ratios (CNRs) for Ki images in tumor regions with notable background FDG concentration, such as the liver, where SUV performed relatively poorly. Overall, the proposed framework enables enhanced quantification of physiological parameters across the whole body. In addition, the total acquisition length can be reduced from 45 to ~35 min and still achieve improved or equivalent CNR compared to SUV, provided the true Ki contrast is sufficiently high. In the follow-up companion paper, a set of advanced linear regression schemes is presented to particularly address the presence of noise, and attempt to achieve a better trade-off between the mean-squared error and the CNR metrics, resulting in enhanced task-based imaging.

Dynamic whole body PET parametric imaging: I. Concept, acquisition protocol optimization and clinical application

PubMed Central

Karakatsanis, Nicolas A.; Lodge, Martin A.; Tahari, Abdel K.; Zhou, Y.; Wahl, Richard L.; Rahmim, Arman

2013-01-01

Static whole body PET/CT, employing the standardized uptake value (SUV), is considered the standard clinical approach to diagnosis and treatment response monitoring for a wide range of oncologic malignancies. Alternative PET protocols involving dynamic acquisition of temporal images have been implemented in the research setting, allowing quantification of tracer dynamics, an important capability for tumor characterization and treatment response monitoring. Nonetheless, dynamic protocols have been confined to single bed-coverage limiting the axial field-of-view to ~15–20 cm, and have not been translated to the routine clinical context of whole-body PET imaging for the inspection of disseminated disease. Here, we pursue a transition to dynamic whole body PET parametric imaging, by presenting, within a unified framework, clinically feasible multi-bed dynamic PET acquisition protocols and parametric imaging methods. We investigate solutions to address the challenges of: (i) long acquisitions, (ii) small number of dynamic frames per bed, and (iii) non-invasive quantification of kinetics in the plasma. In the present study, a novel dynamic (4D) whole body PET acquisition protocol of ~45min total length is presented, composed of (i) an initial 6-min dynamic PET scan (24 frames) over the heart, followed by (ii) a sequence of multi-pass multi-bed PET scans (6 passes x 7 bed positions, each scanned for 45sec). Standard Patlak linear graphical analysis modeling was employed, coupled with image-derived plasma input function measurements. Ordinary least squares (OLS) Patlak estimation was used as the baseline regression method to quantify the physiological parameters of tracer uptake rate Ki and total blood distribution volume V on an individual voxel basis. Extensive Monte Carlo simulation studies, using a wide set of published kinetic FDG parameters and GATE and XCAT platforms, were conducted to optimize the acquisition protocol from a range of 10 different clinically acceptable sampling schedules examined. The framework was also applied to six FDG PET patient studies, demonstrating clinical feasibility. Both simulated and clinical results indicated enhanced contrast-to-noise ratios (CNRs) for Ki images in tumor regions with notable background FDG concentration, such as the liver, where SUV performed relatively poorly. Overall, the proposed framework enables enhanced quantification of physiological parameters across the whole-body. In addition, the total acquisition length can be reduced from 45min to ~35min and still achieve improved or equivalent CNR compared to SUV, provided the true Ki contrast is sufficiently high. In the follow-up companion paper, a set of advanced linear regression schemes is presented to particularly address the presence of noise, and attempt to achieve a better trade-off between the mean-squared error (MSE) and the CNR metrics, resulting in enhanced task-based imaging. PMID:24080962

Dynamic whole-body PET parametric imaging: I. Concept, acquisition protocol optimization and clinical application

NASA Astrophysics Data System (ADS)

Karakatsanis, Nicolas A.; Lodge, Martin A.; Tahari, Abdel K.; Zhou, Y.; Wahl, Richard L.; Rahmim, Arman

2013-10-01

Static whole-body PET/CT, employing the standardized uptake value (SUV), is considered the standard clinical approach to diagnosis and treatment response monitoring for a wide range of oncologic malignancies. Alternative PET protocols involving dynamic acquisition of temporal images have been implemented in the research setting, allowing quantification of tracer dynamics, an important capability for tumor characterization and treatment response monitoring. Nonetheless, dynamic protocols have been confined to single-bed-coverage limiting the axial field-of-view to ˜15-20 cm, and have not been translated to the routine clinical context of whole-body PET imaging for the inspection of disseminated disease. Here, we pursue a transition to dynamic whole-body PET parametric imaging, by presenting, within a unified framework, clinically feasible multi-bed dynamic PET acquisition protocols and parametric imaging methods. We investigate solutions to address the challenges of: (i) long acquisitions, (ii) small number of dynamic frames per bed, and (iii) non-invasive quantification of kinetics in the plasma. In the present study, a novel dynamic (4D) whole-body PET acquisition protocol of ˜45 min total length is presented, composed of (i) an initial 6 min dynamic PET scan (24 frames) over the heart, followed by (ii) a sequence of multi-pass multi-bed PET scans (six passes × seven bed positions, each scanned for 45 s). Standard Patlak linear graphical analysis modeling was employed, coupled with image-derived plasma input function measurements. Ordinary least squares Patlak estimation was used as the baseline regression method to quantify the physiological parameters of tracer uptake rate Ki and total blood distribution volume V on an individual voxel basis. Extensive Monte Carlo simulation studies, using a wide set of published kinetic FDG parameters and GATE and XCAT platforms, were conducted to optimize the acquisition protocol from a range of ten different clinically acceptable sampling schedules examined. The framework was also applied to six FDG PET patient studies, demonstrating clinical feasibility. Both simulated and clinical results indicated enhanced contrast-to-noise ratios (CNRs) for Ki images in tumor regions with notable background FDG concentration, such as the liver, where SUV performed relatively poorly. Overall, the proposed framework enables enhanced quantification of physiological parameters across the whole body. In addition, the total acquisition length can be reduced from 45 to ˜35 min and still achieve improved or equivalent CNR compared to SUV, provided the true Ki contrast is sufficiently high. In the follow-up companion paper, a set of advanced linear regression schemes is presented to particularly address the presence of noise, and attempt to achieve a better trade-off between the mean-squared error and the CNR metrics, resulting in enhanced task-based imaging.

Diagnostic value of the fluoroscopic triggering 3D LAVA technique for primary liver cancer.

PubMed

Shen, Xiao-Yong; Chai, Chun-Hua; Xiao, Wen-Bo; Wang, Qi-Dong

2010-04-01

Primary liver cancer (PLC) is one of the common malignant tumors. Liver acquisition with acceleration volume acquisition (LAVA), which allows simultaneous dynamic enhancement of the hepatic parenchyma and vasculature imaging, is of great help in the diagnosis of PLC. This study aimed to evaluate application of the fluoroscopic triggering 3D LAVA technique in the imaging of PLC and liver vasculature. The clinical data and imaging findings of 38 adults with PLC (22 men and 16 women; average age 52 years), pathologically confirmed by surgical resection or biopsy, were collected and analyzed. All magnetic resonance images were obtained with a 1.5-T system (General Electrics Medical Systems) with an eight-element body array coil and application of the fluoroscopic triggering 3D LAVA technique. Overall image quality was assessed on a 5-point scale by two experienced radiologists. All the nodules and blood vessel were recorded and compared. The diagnostic accuracy and feasibility of LAVA were evaluated. Thirty-eight patients gave high quality images of 72 nodules in the liver for diagnosis. The accuracy of LAVA was 97.2% (70/72), and the coincidence rate between the extent of tumor judged by dynamic enhancement and pathological examination was 87.5% (63/72). Displayed by the maximum intensity projection reconstruction, nearly all cases gave satisfactory images of branches III and IV of the hepatic artery. Furthermore, small early-stage enhancing hepatic lesions and the parallel portal vein were also well displayed. Sequence of LAVA provides good multi-phase dynamic enhancement scanning of hepatic lesions. Combined with conventional scanning technology, LAVA effectively and safely displays focal hepatic lesions and the relationship between tumor and normal tissues, especially blood vessels.

Extended dynamic range of Doppler OCT by application of a new method to high density B-scans using a MHz FDML swept laser source (Conference Presentation)

NASA Astrophysics Data System (ADS)

Elahi, Sahar; Thrane, Lars; Rollins, Andrew M.; Jenkins, Michael W.

2017-02-01

The limited dynamic range of optical coherence tomography (OCT) Doppler velocity measurements makes it difficult to conduct experiments on samples requiring a large dynamic range without phase wrapping at high velocities or loss of sensitivity at slow velocities. Hemodynamics and wall motion undergo significant increases in velocity as the embryonic heart develops. Experimental studies indicate that altered hemodynamics in early-stage embryonic hearts can lead to congenital heart diseases (CHDs), motivating close monitoring of blood flow over several stages of development. We have built a high-speed OCT system using an FDML laser (Optores GmbH, Germany) at a sweep rate of 1.68 MHz (axial resolution - 12 μm, sensitivity - 105 dB, phase stability - 17 mrad). The speed of this OCT system allows us to acquire high-density B-scans to obtain an extended velocity dynamic range without sacrificing the frame rate (100 Hz). The extended dynamic range within a frame is achieved by varying the A-scan interval at which the phase difference is found, enabling detection of velocities ranging from tens of microns per second to hundreds of millimeters per second. The extra lines in a frame can also be utilized to improve the structural and Doppler images via complex averaging. In structural images where the presence of blood causes additional scattering, complex averaging helps retrieve features located deeper in the tissue. Moreover, high-density frames can be registered to 4D volumes to determine the orthogonal direction of flow for calculating shear stress as well as estimating the cardiac output. In conclusion, high density B-scans acquired by our high-speed OCT system enable image enhancement and direct measurement of biological parameters in cohort studies.

Optimal gadolinium dose level for magnetic resonance imaging (MRI) contrast enhancement of U87-derived tumors in athymic nude rats for the assessment of photodynamic therapy

NASA Astrophysics Data System (ADS)

Cross, Nathan; Varghai, Davood; Flask, Chris A.; Feyes, Denise K.; Oleinick, Nancy L.; Dean, David

2009-02-01

This study aims to determine the effect of varying gadopentetate dimeglumine (Gd-DTPA) dose on Dynamic Contrast Enhanced-Magnetic Resonance Imaging (DCE-MRI) tracking of brain tumor photodynamic therapy (PDT) outcome. Methods: We injected 2.5 x 105 U87 cells (derived from human malignant glioma) into the brains of six athymic nude rats. After 9, 12, and 13 days DCE-MRI images were acquired on a 9.4 T micro-MRI scanner before and after administration of 100, 150, or 200 μL of Gd-DTPA. Results: Tumor region normalized DCE-MRI scan enhancement at peak was: 1.217 over baseline (0.018 Standard Error [SE]) at the 100 μL dose, 1.339 (0.013 SE) at the 150 μL dose, and 1.287 (0.014 SE) at the 200 μL dose. DCE-MRI peak tumor enhancement at the 150 μL dose was significantly greater than both the 100 μL dose (p < 3.323E-08) and 200 μL dose (p < 0.0007396). Discussion: In this preliminary study, the 150 μL Gd-DTPA dose provided the greatest T1 weighted contrast enhancement, while minimizing negative T2* effects, in DCE-MRI scans of U87-derived tumors. Maximizing Gd-DTPA enhancement in DCE-MRI scans may assist development of a clinically robust (i.e., unambiguous) technique for PDT outcome assessment.

Stroboscobic near-field scanning optical microscopy for 3D mapping of mode profiles of plasmonic nanostructures (Conference Presentation)

NASA Astrophysics Data System (ADS)

Dana, Aykutlu; Ozgur, Erol; Torunoglu, Gamze

2016-09-01

We present a dynamic approach to scanning near field optical microscopy that extends the measurement technique to the third dimension, by strobing the illumination in sync with the cantilever oscillation. Nitrogen vacancy (NV) centers in nanodiamonds placed on cantilever tips are used as stable emitters for emission enhancement. Local field enhancement and modulation of optical density states are mapped in three dimensions based on fluorescence intensity and spectrum changes as the tip is scanned over plasmonic nanostructures. The excitation of NV centers is done using a total internal reflection setup. Using a digital phase locked loop to pulse the excitation in various tip sample separations, 2D slices of fluorescence enhancement can be recorded. Alternatively, a conventional SNOM tip can be used to selectively couple wideband excitation to the collection path, with subdiffraction resolution of 60 nm in x and y and 10 nm in z directions. The approach solves the problem of tip-sample separation stabilization over extended periods of measurement time, required to collect data resolved in emission wavelength and three spatial dimensions. The method can provide a unique way of accessing the three dimensional field and mode profiles of nanophotonics structures.

Personalized assessment of radiation risks from the one-stop-shop myocardial 256-slice CT examination.

PubMed

Perisinakis, Kostas; Seimenis, Ioannis; Tzedakis, Antonis; Pagonidis, Kostas; Papadakis, Antonios E; Damilakis, John

2013-10-15

This study provides data on the cumulative life attributable risk (LAR) of radiation-induced cancer from the combination of coronary CT angiography (CCTA), dynamic CT perfusion (CTP) and delayed enhancement (DE) CT scans, required for reliable risk-benefit analysis of the one-stop-shop CCTA + CTP + DECT cardiac examination. Monte Carlo simulation of the dynamic CTP and DECT exposures on 62 adult individuals was employed to determine radiation absorbed dose to exposed radiosensitive organs. Corresponding data for CCTA were derived using patient chest circumference and previously published data. Individual-specific LARs of cancer were estimated using organ/tissue-specific radiogenic cancer risk factors. Total LAR from CCTA + CTP + DECT scans' sequence were estimated and compared to nominal intrinsic risk of cancer. The main contribution, up to 80%, to cumulative radiation burden from CCTA + CTP + DECT scan-sequence was found to originate from the CTP scan. The total LAR from CCTA + CTP + DECT for females was found 4-6 times higher, compared to males. The mean cumulative risk of radiogenic cancer associated with the complete CCTA + CTP + DECT scan sequence was found to marginally increase the intrinsic risk for cancer induction by less than 0.6% and 0.1% for females and males, respectively. The radiation risk from the 256-slice CCTA + CTP + DECT scan sequence may be considered low and should not constitute an obstacle for the clinical endorsement of the one-stop-shop cardiac CT examination, given that its clinical value has been well verified. Nevertheless, every effort should be made towards optimization of the dynamic CTP component which is the main contributor to patient radiation burden. © 2013.

Simultaneous acquisition sequence for improved hepatic pharmacokinetics quantification accuracy (SAHA) for dynamic contrast-enhanced MRI of liver.

PubMed

Ning, Jia; Sun, Yongliang; Xie, Sheng; Zhang, Bida; Huang, Feng; Koken, Peter; Smink, Jouke; Yuan, Chun; Chen, Huijun

2018-05-01

To propose a simultaneous acquisition sequence for improved hepatic pharmacokinetics quantification accuracy (SAHA) method for liver dynamic contrast-enhanced MRI. The proposed SAHA simultaneously acquired high temporal-resolution 2D images for vascular input function extraction using Cartesian sampling and 3D large-coverage high spatial-resolution liver dynamic contrast-enhanced images using golden angle stack-of-stars acquisition in an interleaved way. Simulations were conducted to investigate the accuracy of SAHA in pharmacokinetic analysis. A healthy volunteer and three patients with cirrhosis or hepatocellular carcinoma were included in the study to investigate the feasibility of SAHA in vivo. Simulation studies showed that SAHA can provide closer results to the true values and lower root mean square error of estimated pharmacokinetic parameters in all of the tested scenarios. The in vivo scans of subjects provided fair image quality of both 2D images for arterial input function and portal venous input function and 3D whole liver images. The in vivo fitting results showed that the perfusion parameters of healthy liver were significantly different from those of cirrhotic liver and HCC. The proposed SAHA can provide improved accuracy in pharmacokinetic modeling and is feasible in human liver dynamic contrast-enhanced MRI, suggesting that SAHA is a potential tool for liver dynamic contrast-enhanced MRI. Magn Reson Med 79:2629-2641, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Accelerated pharmacokinetic map determination for dynamic contrast enhanced MRI using frequency-domain based Tofts model.

PubMed

Vajuvalli, Nithin N; Nayak, Krupa N; Geethanath, Sairam

2014-01-01

Dynamic Contrast Enhanced Magnetic Resonance Imaging (DCE-MRI) is widely used in the diagnosis of cancer and is also a promising tool for monitoring tumor response to treatment. The Tofts model has become a standard for the analysis of DCE-MRI. The process of curve fitting employed in the Tofts equation to obtain the pharmacokinetic (PK) parameters is time-consuming for high resolution scans. Current work demonstrates a frequency-domain approach applied to the standard Tofts equation to speed-up the process of curve-fitting in order to obtain the pharmacokinetic parameters. The results obtained show that using the frequency domain approach, the process of curve fitting is computationally more efficient compared to the time-domain approach.

Dynamic contrast enhanced CT in nodule characterization: How we review and report.

PubMed

Qureshi, Nagmi R; Shah, Andrew; Eaton, Rosemary J; Miles, Ken; Gilbert, Fiona J

2016-07-18

Incidental indeterminate solitary pulmonary nodules (SPN) that measure less than 3 cm in size are an increasingly common finding on computed tomography (CT) worldwide. Once identified there are a number of imaging strategies that can be performed to help with nodule characterization. These include interval CT, dynamic contrast enhanced computed tomography (DCE-CT), (18)F-fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG-PET-CT). To date the most cost effective and efficient non-invasive test or combination of tests for optimal nodule characterization has yet to be determined.DCE-CT is a functional test that involves the acquisition of a dynamic series of images of a nodule before and following the administration of intravenous iodinated contrast medium. This article provides an overview of the current indications and limitations of DCE- CT in nodule characterization and a systematic approach to how to perform, analyse and interpret a DCE-CT scan.

Vascular bursts enhance permeability of tumour blood vessels and improve nanoparticle delivery

NASA Astrophysics Data System (ADS)

Matsumoto, Yu; Nichols, Joseph W.; Toh, Kazuko; Nomoto, Takahiro; Cabral, Horacio; Miura, Yutaka; Christie, R. James; Yamada, Naoki; Ogura, Tadayoshi; Kano, Mitsunobu R.; Matsumura, Yasuhiro; Nishiyama, Nobuhiro; Yamasoba, Tatsuya; Bae, You Han; Kataoka, Kazunori

2016-06-01

Enhanced permeability in tumours is thought to result from malformed vascular walls with leaky cell-to-cell junctions. This assertion is backed by studies using electron microscopy and polymer casts that show incomplete pericyte coverage of tumour vessels and the presence of intercellular gaps. However, this gives the impression that tumour permeability is static amid a chaotic tumour environment. Using intravital confocal laser scanning microscopy we show that the permeability of tumour blood vessels includes a dynamic phenomenon characterized by vascular bursts followed by brief vigorous outward flow of fluid (named ‘eruptions’) into the tumour interstitial space. We propose that ‘dynamic vents’ form transient openings and closings at these leaky blood vessels. These stochastic eruptions may explain the enhanced extravasation of nanoparticles from the tumour blood vessels, and offer insights into the underlying distribution patterns of an administered drug.

Investigating the Temporal Patterns within and between Intrinsic Connectivity Networks under Eyes-Open and Eyes-Closed Resting States: A Dynamical Functional Connectivity Study Based on Phase Synchronization

PubMed Central

Wang, Xun-Heng; Li, Lihua; Xu, Tao; Ding, Zhongxiang

2015-01-01

The brain active patterns were organized differently under resting states of eyes open (EO) and eyes closed (EC). The altered voxel-wise and regional-wise resting state active patterns under EO/EC were found by static analysis. More importantly, dynamical spontaneous functional connectivity has been observed in the resting brain. To the best of our knowledge, the dynamical mechanisms of intrinsic connectivity networks (ICNs) under EO/EC remain largely unexplored. The goals of this paper were twofold: 1) investigating the dynamical intra-ICN and inter-ICN temporal patterns during resting state; 2) analyzing the altered dynamical temporal patterns of ICNs under EO/EC. To this end, a cohort of healthy subjects with scan conditions of EO/EC were recruited from 1000 Functional Connectomes Project. Through Hilbert transform, time-varying phase synchronization (PS) was applied to evaluate the inter-ICN synchrony. Meanwhile, time-varying amplitude was analyzed as dynamical intra-ICN temporal patterns. The results found six micro-states of inter-ICN synchrony. The medial visual network (MVN) showed decreased intra-ICN amplitude during EC relative to EO. The sensory-motor network (SMN) and auditory network (AN) exhibited enhanced intra-ICN amplitude during EC relative to EO. Altered inter-ICN PS was found between certain ICNs. Particularly, the SMN and AN exhibited enhanced PS to other ICNs during EC relative to EO. In addition, the intra-ICN amplitude might influence the inter-ICN synchrony. Moreover, default mode network (DMN) might play an important role in information processing during EO/EC. Together, the dynamical temporal patterns within and between ICNs were altered during different scan conditions of EO/EC. Overall, the dynamical intra-ICN and inter-ICN temporal patterns could benefit resting state fMRI-related research, and could be potential biomarkers for human functional connectome. PMID:26469182

Elucidating the correlation between morphology and ion dynamics in polymerized ionic liquids.

NASA Astrophysics Data System (ADS)

Heres, Maximilian; Cosby, Tyler; Iacob, Ciprian; Runt, James; Benson, Roberto; Liu, Hongjun; Paddison, Stephen; Sangoro, Joshua

Charge transport and dynamics are investigated for a series of poly-ammonium and poly-imidazolium-based polymerized ionic liquids (polyIL) with a common bis(trifluoromethylsulfonyl)imide anion using broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry. A significant enhancement of the Tg independent ionic conductivity is observed for ammonium based polyIL with shorter pendant groups, in comparison to imidazolium based systems. These results emphasize the importance of polymer backbone spacing as well as counter-ion size on ionic conductivity in polymerized ionic liquids. NSF DMR 1508394.

Tuning of successively scanned two monolithic Vernier-tuned lasers and selective data sampling in optical comb swept source optical coherence tomography

PubMed Central

Choi, Dong-hak; Yoshimura, Reiko; Ohbayashi, Kohji

2013-01-01

Monolithic Vernier tuned super-structure grating distributed Bragg reflector (SSG-DBR) lasers are expected to become one of the most promising sources for swept source optical coherence tomography (SS-OCT) with a long coherence length, reduced sensitivity roll-off, and potential capability for a very fast A-scan rate. However, previous implementations of the lasers suffer from four main problems: 1) frequencies deviate from the targeted values when scanned, 2) large amounts of noise appear associated with abrupt changes in injection currents, 3) optically aliased noise appears due to a long coherence length, and 4) the narrow wavelength coverage of a single chip limits resolution. We have developed a method of dynamical frequency tuning, a method of selective data sampling to eliminate current switching noise, an interferometer to reduce aliased noise, and an excess-noise-free connection of two serially scanned lasers to enhance resolution to solve these problems. An optical frequency comb SS-OCT system was achieved with a sensitivity of 124 dB and a dynamic range of 55-72 dB that depended on the depth at an A-scan rate of 3.1 kHz with a resolution of 15 μm by discretely scanning two SSG-DBR lasers, i.e., L-band (1.560-1.599 μm) and UL-band (1.598-1.640 μm). A few OCT images with excellent image penetration depth were obtained. PMID:24409394

Quantitative myocardial perfusion from static cardiac and dynamic arterial CT

NASA Astrophysics Data System (ADS)

Bindschadler, Michael; Branch, Kelley R.; Alessio, Adam M.

2018-05-01

Quantitative myocardial blood flow (MBF) estimation by dynamic contrast enhanced cardiac computed tomography (CT) requires multi-frame acquisition of contrast transit through the blood pool and myocardium to inform the arterial input and tissue response functions. Both the input and the tissue response functions for the entire myocardium are sampled with each acquisition. However, the long breath holds and frequent sampling can result in significant motion artifacts and relatively high radiation dose. To address these limitations, we propose and evaluate a new static cardiac and dynamic arterial (SCDA) quantitative MBF approach where (1) the input function is well sampled using either prediction from pre-scan timing bolus data or measured from dynamic thin slice ‘bolus tracking’ acquisitions, and (2) the whole-heart tissue response data is limited to one contrast enhanced CT acquisition. A perfusion model uses the dynamic arterial input function to generate a family of possible myocardial contrast enhancement curves corresponding to a range of MBF values. Combined with the timing of the single whole-heart acquisition, these curves generate a lookup table relating myocardial contrast enhancement to quantitative MBF. We tested the SCDA approach in 28 patients that underwent a full dynamic CT protocol both at rest and vasodilator stress conditions. Using measured input function plus single (enhanced CT only) or plus double (enhanced and contrast free baseline CT’s) myocardial acquisitions yielded MBF estimates with root mean square (RMS) error of 1.2 ml/min/g and 0.35 ml/min/g, and radiation dose reductions of 90% and 83%, respectively. The prediction of the input function based on timing bolus data and the static acquisition had an RMS error compared to the measured input function of 26.0% which led to MBF estimation errors greater than threefold higher than using the measured input function. SCDA presents a new, simplified approach for quantitative perfusion imaging with an acquisition strategy offering substantial radiation dose and computational complexity savings over dynamic CT.

The promise of dynamic contrast-enhanced imaging in radiation therapy.

PubMed

Cao, Yue

2011-04-01

Dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) and computed tomography (CT) scanning are emerging as valuable tools to quantitatively map the spatial distribution of vascular parameters, such as perfusion, vascular permeability, blood volume, and mean transit time in tumors and normal organs. DCE MRI/CT have shown prognostic and predictive value for response of certain cancers to chemotherapy and radiation therapy. DCE MRI/CT offer the promise of early assessment of tumor response to radiation therapy, opening a window for adaptively optimizing radiation therapy based upon functional alterations that occur earlier than morphologic changes. DCE MRI/CT has also shown the potential of mapping dose responses in normal organs and tissue for evaluation of individual sensitivity to radiation, providing additional opportunities to minimize risks of radiation injury. The evidence for potentially applying DCE MRI and CT for selection and delineation of radiation boost targets is growing. The clinical use of DCE MRI and CT scanning as a biomarker or even a surrogate endpoint for radiation therapy assessment of tumor and normal organs must consider technical validation issues, including standardization, reproducibility, accuracy and robustness, and clinical validation of the sensitivity and specificity for each specific problem of interest. Although holding great promise, to date, DCE MRI and CT scanning have not been qualified as a surrogate endpoint for radiation therapy assessment or for treatment modification in any prospective phase III clinical trial for any tumor site. Copyright © 2011 Elsevier Inc. All rights reserved.

Visualization of carrier dynamics in p(n)-type GaAs by scanning ultrafast electron microscopy

PubMed Central

Cho, Jongweon; Hwang, Taek Yong; Zewail, Ahmed H.

2014-01-01

Four-dimensional scanning ultrafast electron microscopy is used to investigate doping- and carrier-concentration-dependent ultrafast carrier dynamics of the in situ cleaved single-crystalline GaAs(110) substrates. We observed marked changes in the measured time-resolved secondary electrons depending on the induced alterations in the electronic structure. The enhancement of secondary electrons at positive times, when the electron pulse follows the optical pulse, is primarily due to an energy gain involving the photoexcited charge carriers that are transiently populated in the conduction band and further promoted by the electron pulse, consistent with a band structure that is dependent on chemical doping and carrier concentration. When electrons undergo sufficient energy loss on their journey to the surface, dark contrast becomes dominant in the image. At negative times, however, when the electron pulse precedes the optical pulse (electron impact), the dynamical behavior of carriers manifests itself in a dark contrast which indicates the suppression of secondary electrons upon the arrival of the optical pulse. In this case, the loss of energy of material’s electrons is by collisions with the excited carriers. These results for carrier dynamics in GaAs(110) suggest strong carrier–carrier scatterings which are mirrored in the energy of material’s secondary electrons during their migration to the surface. The approach presented here provides a fundamental understanding of materials probed by four-dimensional scanning ultrafast electron microscopy, and offers possibilities for use of this imaging technique in the study of ultrafast charge carrier dynamics in heterogeneously patterned micro- and nanostructured material surfaces and interfaces. PMID:24469803

Visualization of carrier dynamics in p(n)-type GaAs by scanning ultrafast electron microscopy.

PubMed

Cho, Jongweon; Hwang, Taek Yong; Zewail, Ahmed H

2014-02-11

Four-dimensional scanning ultrafast electron microscopy is used to investigate doping- and carrier-concentration-dependent ultrafast carrier dynamics of the in situ cleaved single-crystalline GaAs(110) substrates. We observed marked changes in the measured time-resolved secondary electrons depending on the induced alterations in the electronic structure. The enhancement of secondary electrons at positive times, when the electron pulse follows the optical pulse, is primarily due to an energy gain involving the photoexcited charge carriers that are transiently populated in the conduction band and further promoted by the electron pulse, consistent with a band structure that is dependent on chemical doping and carrier concentration. When electrons undergo sufficient energy loss on their journey to the surface, dark contrast becomes dominant in the image. At negative times, however, when the electron pulse precedes the optical pulse (electron impact), the dynamical behavior of carriers manifests itself in a dark contrast which indicates the suppression of secondary electrons upon the arrival of the optical pulse. In this case, the loss of energy of material's electrons is by collisions with the excited carriers. These results for carrier dynamics in GaAs(110) suggest strong carrier-carrier scatterings which are mirrored in the energy of material's secondary electrons during their migration to the surface. The approach presented here provides a fundamental understanding of materials probed by four-dimensional scanning ultrafast electron microscopy, and offers possibilities for use of this imaging technique in the study of ultrafast charge carrier dynamics in heterogeneously patterned micro- and nanostructured material surfaces and interfaces.

Potential for differentiation of pseudoprogression from true tumor progression with dynamic susceptibility-weighted contrast-enhanced magnetic resonance imaging using ferumoxytol versus gadoteridol: A pilot study

PubMed Central

Gahramanov, Seymur; Raslan, Ahmed; Muldoon, Leslie L.; Hamilton, Bronwyn E.; Rooney, William D.; Varallyay, Csanad G.; Njus, Jeffrey M.; Haluska, Marianne; Neuwelt, Edward A.

2010-01-01

Purpose We evaluated dynamic susceptibility-weighted contrast-enhanced magnetic resonance imaging (DSC-MRI) using gadoteridol in comparison to the iron oxide nanoparticle blood pool agent, ferumoxytol in patients with glioblastoma multiforme (GBM) who received standard radiochemotherapy (RCT). Methods and Materials Fourteen patients with GBM received standard RCT and underwent 19 MRI sessions that included DSC-MRI acquisitions with gadoteridol on day 1 and ferumoxytol on day 2. Relative cerebral blood volume (rCBV) values were calculated from DSC data obtained from each contrast agent. T1-weighted acquisition post-gadoteridol administration was used to identify enhancing regions. Results In 7 MRI sessions of clinically presumptive active tumor, gadoteridol-DSC showed low rCBV in 3 and high rCBV in 4, while ferumoxytol-DSC showed high rCBV in all 7 sessions (p=0.002). After RCT, 7 MRI sessions showed increased gadoteridol contrast enhancement on T1-weighted scans coupled with low rCBV without significant differences between contrast agents (p=0.9). Based on post-gadoteridol T1-weighted scans, DSC-MRI, and clinical presentation four patterns of response to RCT were observed: 1) regression, 2) pseudoprogression, 3) true progression, and 4) mixed response. Conclusion We conclude that DSC-MRI with a blood-pool agent such as ferumoxytol may provide a better monitor of tumor rCBV than DSC-MRI with gadoteridol. Lesions demonstrating increased enhancement on T1-weighted MRI coupled with low ferumoxytol rCBV, are likely exhibiting pseudoprogression, while high rCBV with ferumoxytol is a better marker than gadoteridol for determining active tumor. These interesting pilot observations suggest that ferumoxytol may differentiate tumor progression from pseudoprogression, and warrant further investigation. PMID:20395065

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hubbard, L; Ziemer, B; Lipinski, J

Purpose: To evaluate the accuracy of a low-dose, first-pass-analysis (FPA) dynamic computed tomography angiography and perfusion (CTAP) technique, for whole-organ anatomical and functional assessment of coronary artery disease (CAD). Methods: An angioplasty balloon was advanced into the left anterior descending (LAD) coronary artery of five swine (35–45 kg) to induce several levels of stenosis at maximal hyperemia (intracoronary adenosine, 240 µg/min). Reference fluorescence microspheres and intravenous contrast (370 mg/mL iodine, 25 mL, 7 mL/s) were injected centrally and dynamic imaging was performed using a 320-slice CT scanner at 100 kVp and 200 mA. Twenty volume scans were acquired per stenosismore » level to capture complete aortic and myocardial enhancement curves, but only two volume scans were used for whole-organ dynamic FPA CTAP measurement. All CTAP measurements in the LAD were compared to the reference microsphere perfusion measurements using linear regression, concordance correlation, and Bland-Altman analysis. Results: The result of dynamic FPA CTAP measurement in the LAD was in good agreement with the reference microsphere perfusion measurement (P-CTAP = 1.01 P-MICRO + 0.16, R{sup 2} = 0.95). The root mean square error (RMSE) and difference (RMSD) of measurement were 0.51 mL/min/g and 0.47 mL/min/g, respectively. Bland-Altman analysis demonstrated negligible systematic measurement bias. Additionally, the concordance correlation coefficient (CCC) was found to be ρ = 0.97, indicating excellent agreement between dynamic FPA CTAP measurement and the reference microsphere perfusion measurement. Lastly, the effective dose of the proposed technique using the “simulated” two-volume scan CTAP acquisition protocol was 2.6 mSv; much lower than the ∼10 mSv effective dose of current dynamic CTP techniques alone. Conclusion: The results indicate the potential for significant improvements in CAD assessment through low-dose, quantitative dynamic FPA CTAP. Such improvements are afforded through whole-organ CT scanning technology, and have the potential to improve patient outcomes and lead to healthier patient lives. Conflict of Interest (only if applicable): Grant funding from Toshiba America Medical Systems.« less

A hybrid scanning force and light microscope for surface imaging and three-dimensional optical sectioning in differential interference contrast.

PubMed

Stemmer, A

1995-04-01

The design of a scanned-cantilever-type force microscope is presented which is fully integrated into an inverted high-resolution video-enhanced light microscope. This set-up allows us to acquire thin optical sections in differential interference contrast (DIC) or polarization while the force microscope is in place. Such a hybrid microscope provides a unique platform to study how cell surface properties determine, or are affected by, the three-dimensional dynamic organization inside the living cell. The hybrid microscope presented in this paper has proven reliable and versatile for biological applications. It is the only instrument that can image a specimen by force microscopy and high-power DIC without having either to translate the specimen or to remove the force microscope. Adaptation of the design features could greatly enhance the suitability of other force microscopes for biological work.

L-Phenylalanine functionalized silver nanoparticles: Photocatalytic and nonlinear optical applications

NASA Astrophysics Data System (ADS)

Nidya, M.; Umadevi, M.; Sankar, Pranitha; Philip, Reji; Rajkumar, Beulah J. M.

2015-04-01

An extensive study on the behavior of L-Phenylalanine capped silver nanoparticles (Phe-Ag NPs) in the aqueous phase and in a sol-gel thin film showed different UV/Vis, Transmission Electron Microscope (TEM), Dynamic Light Scattering and Zeta potential profiles. Scanning Electron Microscope (SEM) images of the samples in the sol gel film showed Ag embedded in the SiO2 matrix. Surface Enhanced Raman Spectra (SERS) confirmed that both in the aqueous media and in the sol gel film, the attachment of Phe to the Ag NP surface was through the benzene ring, with the sol-gel film showing a better enhancement. Photocatalytic degradation of crystal violet was measured spectrophotometrically using Phe-Ag NPs as a nanocatalyst under visible light illumination. Intensity-dependent nonlinear optical absorption of Phe-Ag measured using the open aperture Z-scan technique revealed that the material is an efficient optical limiter with potential applications.

Magnetic Resonance Imaging Findings of Intrahepatic Bile Duct Adenoma: A Report of 4 Cases.

PubMed

Liang, Wenjie; Xu, Shunliang

2015-01-01

Intrahepatic bile duct adenoma (BDA) is a rare type of benign hepatic lesions. In this study, 4 cases of BDA diagnosed from surgical resection pathology were examined. Their clinical and magnetic resonance imaging (MRI) data were retrospectively analyzed. The 4 cases (1 men and 3 women) were aged 21 to 55 years without obvious clinical symptoms. Three were identified through routine examination. Three had a history of chronic hepatitis B virus infection. Two cases were accompanied by hepatocellular carcinoma, and one had a higher level of α-fetoprotein. The MRI images of BDA all manifested as peripheral hepatic nodules with abnormal signals. The diameters of the lesions in the 4 cases were 7.7 to 17.0 mm. The MRI images showed slight hypointensity on T1WI and slight hyperintensity on T2WI in all cases, and they showed slight hyperintensity in 2 cases and hyperintensity in 2 cases on diffusion-weighted imaging. Dynamic contrast-enhanced MRI scans show hyperintensity in the arterial phase and slight hyperintensity in the late stage in 3 cases. The other case shows hyperintensity in the arterial and portal phases and isointensity at the delayed phase. During follow-up, 3 cases were recurrence-free. The other case was complicated by the reoccurrence of HCC. In general, BDA shows specific MRI characteristics, and peripheral hepatic nodules show slight hypointensity on T1WI and slight hyperintensity on T2WI. Dynamic contrast-enhanced MRI scans showed obvious enhancement in the arterial phase and continuous enhancement at the late stage.

Effect of parallel radiofrequency transmission on arterial input function selection in dynamic contrast-enhanced 3 Tesla pelvic MRI.

PubMed

Chafi, Hatim; Elias, Saba N; Nguyen, Huyen T; Friel, Harry T; Knopp, Michael V; Guo, BeiBei; Heymsfield, Steven B; Jia, Guang

2016-01-01

To evaluate whether parallel radiofrequency transmission (mTX) can improve the symmetry of the left and right femoral arteries in dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) of prostate and bladder cancer. Eighteen prostate and 24 bladder cancer patients underwent 3.0 Tesla DCE-MRI scan with a single transmission channel coil. Subsequently, 21 prostate and 21 bladder cancer patients were scanned using the dual channel mTX upgrade. The precontrast signal ( S0) and the maximum enhancement ratio (MER) were measured in both the left and the right femoral arteries. Within the patient cohort, the ratio of S0 and MER in the left artery to that in the right artery ( S0_LR, MER_LR) was calculated with and without the use of mTX. Left to right asymmetry indices for S0 ( S0_LRasym) and MER ( MER_LRasym) were defined as the absolute values of the difference between S0_LR and 1, and the difference between MER_LR and 1, respectively. S0_LRasym, and MER_LRasym were 0.21 and 0.19 for prostate cancer patients with mTX, and 0.43 and 0.45 for the ones imaged without it (P < 0.001). Also, for the bladder cancer patients, S0_LRasym, and MER_LRasym were 0.11 and 0.9 with mTX, while imaging without it yielded 0.52 and 0.39 (P < 0.001). mTX can significantly improve left-to-right symmetry of femoral artery precontrast signal and contrast enhancement. © 2015 Wiley Periodicals, Inc.

Hepatic perivascular epithelioid cell tumor (PEComa): dynamic CT, MRI, ultrasonography, and pathologic features--analysis of 7 cases and review of the literature.

PubMed

Tan, Yan; Xiao, En-hua

2012-10-01

To evaluate the dynamic CT, MRI, ultrasonography, and pathologic features of hepatic perivascular epithelioid cell tumor (PEComa), improving the understanding and diagnosis of the tumor. A retrospective analysis of CT, MRI, ultrasonography, and pathologic features of 7 hepatic PEComas diagnosed by pathology during 1st January 2005 to 1st September 2011 in our hospital. The performance of dynamic CT, MRI, and ultrasonography revealed that lesions were regular masses with well-defined borders, the maximum diameters were 2.5-8.5 cm (mean = 4 cm), density was homogeneous, contrast-enhanced CT and MRI showed the lesions were significantly and heterogeneously enhanced on arterial phase, less enhanced on portal venous phase, and slightly hypodense on delayed phase. One patient had multiple hepatic lesions and had delayed enhancement. There were no backgrounds of hepatitis and cirrhosis, enlarged lymph nodes, or distant metastases. Pathology showed the gross appearance of the tumor was smooth. Tumor cells were round or polygonal, with clear boundaries and clear membranes, and had abundant translucent cytoplasm. Nuclei were round, with medium size. Tumor cells were epithelial-like cells and arranged in dense sheets. Immunohistochemistry showed that most of them were positive in HMB45 and MelanA, S-100, SMA, while negative in CgA, Syn, CK, CD117, CD10, and CD34. Dynamic CT, MRI, ultrasonography, and pathology of PEComa had some characteristics of benign tumor's performance. Enhanced scan showed PEComa quickly enhanced on arterial phase and enhanced less on portal venous phase. Knowing these characteristics could help to improve the understanding and diagnosis of hepatic PEComa.

Software-based stacking techniques to enhance depth of field and dynamic range in digital photomicrography.

PubMed

Piper, Jörg

2010-01-01

Several software solutions are powerful tools to enhance the depth of field and improve focus in digital photomicrography. By these means, the focal depth can be fundamentally optimized so that three-dimensional structures within specimens can be documented with superior quality. Thus, images can be created in light microscopy which will be comparable with scanning electron micrographs. The remaining sharpness will no longer be dependent on the specimen's vertical dimension or its range in regional thickness. Moreover, any potential lack of definition associated with loss of planarity and unsteadiness in the visual accommodation can be mitigated or eliminated so that the contour sharpness and resolution can be strongly enhanced.Through the use of complementary software, ultrahigh ranges in brightness and contrast (the so-called high-dynamic range) can be corrected so that the final images will also be free from locally over- or underexposed zones. Furthermore, fine detail in low natural contrast can be visualized in much higher clarity. Fundamental enhancements of the global visual information will result from both techniques.

Medulloblastoma with Atypical Dynamic Imaging Changes: Case Report with Literature Review.

PubMed

Song, Shuang-Shuang; Wang, Jian-Hong; Fu, Wei-Wei; Li, Ying; Sui, Qing-Lan; Liu, Xue-Jun

2017-09-01

We analyzed a case of medulloblastoma with atypical dynamic imaging changes retrospectively to summarize the atypical magnetic resonance imaging (MRI) features of medulloblastoma by reviewing the literature. An atypical case of medulloblastoma in the cerebellar hemisphere confirmed by pathology was analyzed retrospectively, and the literature about it was reviewed. The radiologic findings of the patient were based on 3 examinations. The first examination showed that the cortex of the bilateral cerebellar hemisphere had diffuse nodular thickening, with a high signal on diffusion-weighted imaging and significant enhancement. Contrast enhancement MRI 1 year later showed the signal of cerebellar hemisphere returned to normal but revealed an enhanced nodule. A reexamination 6 months later showed an irregular mass with a high-density shadow in the cerebellar vermis on CT scan. The T2-weighted image revealed multiple degenerative cysts, and the mass had significant enhancement. The radiologic characteristics of atypical medulloblastomas vary in adults and children. Understanding the radiologic characteristics of medulloblastomas, such as MRI features, age of onset, and location of atypical medulloblastomas, can help improve the diagnosis of medulloblastomas. Copyright © 2017. Published by Elsevier Inc.

Quantification of traumatic meningeal injury using dynamic contrast enhanced (DCE) fluid-attenuated inversion recovery (FLAIR) imaging

NASA Astrophysics Data System (ADS)

Castro, Marcelo A.; Williford, Joshua P.; Cota, Martin R.; MacLaren, Judy M.; Dardzinski, Bernard J.; Latour, Lawrence L.; Pham, Dzung L.; Butman, John A.

2016-03-01

Traumatic meningeal injury is a novel imaging marker of traumatic brain injury, which appears as enhancement of the dura on post-contrast T2-weighted FLAIR images, and is likely associated with inflammation of the meninges. Dynamic Contrast Enhanced MRI provides a better discrimination of abnormally perfused regions. A method to properly identify those regions is presented. Images of seventeen patients scanned within 96 hours of head injury with positive traumatic meningeal injury were normalized and aligned. The difference between the pre- and last post-contrast acquisitions was segmented and voxels in the higher class were spatially clustered. Spatial and morphological descriptors were used to identify the regions of enhancement: a) centroid; b) distance to the brain mask from external voxels; c) distance from internal voxels; d) size; e) shape. The method properly identified thirteen regions among all patients. The method failed in one case due to the presence of a large brain lesion that altered the mask boundaries. Most false detections were correctly rejected resulting in a sensitivity and specificity of 92.9% and 93.6%, respectively.

Final Technical Report for SISGR: Ultrafast Molecular Scale Chemical Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hersam, Mark C.; Guest, Jeffrey R.; Guisinger, Nathan P.

2017-04-10

The Northwestern-Argonne SISGR program utilized newly developed instrumentation and techniques including integrated ultra-high vacuum tip-enhanced Raman spectroscopy/scanning tunneling microscopy (UHV-TERS/STM) and surface-enhanced femtosecond stimulated Raman scattering (SE-FSRS) to advance the spatial and temporal resolution of chemical imaging for the study of photoinduced dynamics of molecules on plasmonically active surfaces. An accompanying theory program addressed modeling of charge transfer processes using constrained density functional theory (DFT) in addition to modeling of SE-FSRS, thereby providing a detailed description of the excited state dynamics. This interdisciplinary and highly collaborative research resulted in 62 publications with ~ 48% of them being co-authored by multiplemore » SISGR team members. A summary of the scientific accomplishments from this SISGR program is provided in this final technical report.« less

[Optimization of diagnosis indicator selection and inspection plan by 3.0T MRI in breast cancer].

PubMed

Jiang, Zhongbiao; Wang, Yunhua; He, Zhong; Zhang, Lejun; Zheng, Kai

2013-08-01

To optimize 3.0T MRI diagnosis indicator in breast cancer and to select the best MRI scan program. Totally 45 patients with breast cancers were collected, and another 35 patients with benign breast tumor served as the control group. All patients underwent 3.0T MRI, including T1- weighted imaging (T1WI), fat suppression of the T2-weighted imaging (T2WI), diffusion weighted imaging (DWI), 1H magnetic resonance spectroscopy (1H-MRS) and dynamic contrast enhanced (DCE) sequence. With operation pathology results as the gold standard in the diagnosis of breast diseases, the pathological results of benign and malignant served as dependent variables, and the diagnostic indicators of MRI were taken as independent variables. We put all the indicators of MRI examination under Logistic regression analysis, established the Logistic model, and optimized the diagnosis indicators of MRI examination to further improve MRI scan of breast cancer. By Logistic regression analysis, some indicators were selected in the equation, including the edge feature of the tumor, the time-signal intensity curve (TIC) type and the apparent diffusion coefficient (ADC) value when b=500 s/mm2. The regression equation was Logit (P)=-21.936+20.478X6+3.267X7+ 21.488X3. Valuable indicators in the diagnosis of breast cancer are the edge feature of the tumor, the TIC type and the ADC value when b=500 s/mm2. Combining conventional MRI scan, DWI and dynamic enhanced MRI is a better examination program, while MRS is the complementary program when diagnosis is difficult.

Inter-reader reproducibility of dynamic contrast-enhanced magnetic resonance imaging in patients with non-small cell lung cancer treated with bevacizumab and erlotinib.

PubMed

van den Boogaart, Vivian E M; de Lussanet, Quido G; Houben, Ruud M A; de Ruysscher, Dirk; Groen, Harry J M; Marcus, J Tim; Smit, Egbert F; Dingemans, Anne-Marie C; Backes, Walter H

2016-03-01

Objectives When evaluating anti-tumor treatment response by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) it is necessary to assure its validity and reproducibility. This has not been well addressed in lung tumors. Therefore we have evaluated the inter-reader reproducibility of response classification by DCE-MRI in patients with non-small cell lung cancer (NSCLC) treated with bevacizumab and erlotinib enrolled in a multicenter trial. Twenty-one patients were scanned before and 3 weeks after start of treatment with DCE-MRI in a multicenter trial. The scans were evaluated by two independent readers. The primary lung tumor was used for response assessment. Responses were assessed in terms of relative changes in tumor mean trans endothelial transfer rate (K(trans)) and its heterogeneity in terms of the spatial standard deviation. Reproducibility was expressed by the inter-reader variability, intra-class correlation coefficient (ICC) and dichotomous response classification. The inter-reader variability and ICC for the relative K(trans) were 5.8% and 0.930, respectively. For tumor heterogeneity the inter-reader variability and ICC were 0.017 and 0.656, respectively. For the two readers the response classification for relative K(trans) was concordant in 20 of 21 patients (k=0.90, p<0.0001) and for tumor heterogeneity in 19 of 21 patients (k=0.80, p<0.0001). Strong agreement was seen with regard to the inter-reader variability and reproducibility of response classification by the two readers of lung cancer DCE-MRI scans. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Multi-MHz laser-scanning single-cell fluorescence microscopy by spatiotemporally encoded virtual source array

PubMed Central

Wu, Jianglai; Tang, Anson H. L.; Mok, Aaron T. Y.; Yan, Wenwei; Chan, Godfrey C. F.; Wong, Kenneth K. Y.; Tsia, Kevin K.

2017-01-01

Apart from the spatial resolution enhancement, scaling of temporal resolution, equivalently the imaging throughput, of fluorescence microscopy is of equal importance in advancing cell biology and clinical diagnostics. Yet, this attribute has mostly been overlooked because of the inherent speed limitation of existing imaging strategies. To address the challenge, we employ an all-optical laser-scanning mechanism, enabled by an array of reconfigurable spatiotemporally-encoded virtual sources, to demonstrate ultrafast fluorescence microscopy at line-scan rate as high as 8 MHz. We show that this technique enables high-throughput single-cell microfluidic fluorescence imaging at 75,000 cells/second and high-speed cellular 2D dynamical imaging at 3,000 frames per second, outperforming the state-of-the-art high-speed cameras and the gold-standard laser scanning strategies. Together with its wide compatibility to the existing imaging modalities, this technology could empower new forms of high-throughput and high-speed biological fluorescence microscopy that was once challenged. PMID:28966855

Image reconstruction of dynamic infrared single-pixel imaging system

NASA Astrophysics Data System (ADS)

Tong, Qi; Jiang, Yilin; Wang, Haiyan; Guo, Limin

2018-03-01

Single-pixel imaging technique has recently received much attention. Most of the current single-pixel imaging is aimed at relatively static targets or the imaging system is fixed, which is limited by the number of measurements received through the single detector. In this paper, we proposed a novel dynamic compressive imaging method to solve the imaging problem, where exists imaging system motion behavior, for the infrared (IR) rosette scanning system. The relationship between adjacent target images and scene is analyzed under different system movement scenarios. These relationships are used to build dynamic compressive imaging models. Simulation results demonstrate that the proposed method can improve the reconstruction quality of IR image and enhance the contrast between the target and the background in the presence of system movement.

Some Processing and Dynamic-Range Issues in Side-Scan Sonar Work

NASA Astrophysics Data System (ADS)

Asper, V. L.; Caruthers, J. W.

2007-05-01

Often side-scan sonar data are collected in such a way that they afford little opportunity to do more than simply display them as images. These images are often limited in dynamic range and stored only in an 8-bit tiff format of numbers representing less than true intensity values. Furthermore, there is little prior knowledge during a survey of the best range in which to set those eight bits. This can result in clipped strong targets and/or the depth of shadows so that the bits that can be recovered from the image are not fully representative of target or bottom backscatter strengths. Several top-of-the-line sonars do have a means of logging high-bit-rate digital data (sometimes only as an option), but only dedicated specialists pay much attention to such data, if they record them at all. Most users of side-scan sonars are interested only in the images. Discussed in this paper are issues related to storing and processing of high-bit-rate digital data to preserve their integrity for future enhanced, after- the-fact use and ability to recover actual backscatter strengths. This papers discusses issues in the use high-bit- rate, digital side-scan sonar data. This work was supported by the Office of Naval Research, Code 321OA, and the Naval Oceanographic Office, Mine Warfare Program.

Seeing with the nano-eye: accessing structure, function, and dynamics of matter on its natural length and time scales

NASA Astrophysics Data System (ADS)

Raschke, Markus

2015-03-01

To understand and ultimately control the properties of most functional materials, from molecular soft-matter to quantum materials, requires access to the structure, coupling, and dynamics on the elementary time and length scales that define the microscopic interactions in these materials. To gain the desired nanometer spatial resolution with simultaneous spectroscopic specificity we combine scanning probe microscopy with different optical, including coherent, nonlinear, and ultrafast spectroscopies. The underlying near-field interaction mediated by the atomic-force or scanning tunneling microscope tip provides the desired deep-sub wavelength nano-focusing enabling few-nm spatial resolution. I will introduce our generalization of the approach in terms of the near-field impedance matching to a quantum system based on special optical antenna-tip designs. The resulting enhanced and qualitatively new forms of light-matter interaction enable measurements of quantum dynamics in an interacting environment or to image the electromagnetic local density of states of thermal radiation. Other applications include the inter-molecular coupling and dynamics in soft-matter hetero-structures, surface plasmon interferometry as a probe of electronic structure and dynamics in graphene, and quantum phase transitions in correlated electron materials. These examples highlight the general applicability of the new near-field microscopy approach, complementing emergent X-ray and electron imaging tools, aiming towards the ultimate goal of probing matter on its most elementary spatio-temporal level.

Selectable light-sheet uniformity using tuned axial scanning

PubMed Central

Duocastella, Martí; Arnold, Craig B.; Puchalla, Jason

2016-01-01

Light-sheet fluorescence microscopy (LSFM) is an optical sectioning technique capable of rapid three-dimensional (3D) imaging of a wide range of specimens with reduced phototoxicity and superior background rejection. However, traditional light-sheet generation approaches based on elliptical or circular Gaussian beams suffer an inherent trade-off between light-sheet thickness and area over which this thickness is preserved. Recently, an increase in light-sheet uniformity was demonstrated using rapid biaxial Gaussian beam scanning along the lateral and beam propagation directions. Here we apply a similar scanning concept to an elliptical beam generated by a cylindrical lens. In this case, only z-scanning of the elliptical beam is required and hence experimental implementation of the setup can be simplified. We introduce a simple dimensionless uniformity statistic to better characterize scanned light-sheets and experimentally demonstrate custom tailored uniformities up to a factor of 5 higher than those of un-scanned elliptical beams. This technique offers a straightforward way to generate and characterize a custom illumination profile that provides enhanced utilization of the detector dynamic range and field of view, opening the door to faster and more efficient 2D and 3D imaging. PMID:28132409

Final report: Mapping Interactions in Hybrid Systems with Active Scanning Probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berezovsky, Jesse

2017-09-29

This project aimed to study and map interactions between components of hybrid nanodevices using a novel scanning probe approach. To enable this work, we initially constructed a flexible experimental apparatus allowing for simultaneous scanning probe and confocal optical microscopy measurements. This setup was first used for all-optical measurements of nanostructures, with the focus then shifting to hybrid devices in which single coherent electron spins are coupled to micron-scale ferromagnetic elements, which may prove useful for addressing single spins, enhanced sensing, or spin-wave-mediated coupling of spins for quantum information applications. A significant breakthrough was the realization that it is not necessarymore » to fabricate a magnetic structure on a scanning probe – instead a ferromagnetic vortex core can act as an integrated, solid state, scanning probe. The core of the vortex produces a very strong, localized fringe field which can be used analogously to an MFM tip. Unlike a traditional MFM tip, however, the vortex core is scanned within an integrated device (eliminating drift), and can be moved on vastly faster timescales. This approach allows the detailed investigation of interactions between single spins and complex driven ferromagnetic dynamics.« less

An insight into the molecular mechanism of the temporary enhancement effect of isopulegol decanoate on the skin.

PubMed

Liu, Xiaochang; Liu, Meiying; Liu, Chao; Quan, Peng; Zhao, Yongshan; Fang, Liang

2017-08-30

Chemical enhancers are widely used to facilitate drug permeation in transdermal drug delivery system (TDDS) and the effect of chemical enhancers is desired to be temporary. Though temporary enhancement effect of chemical enhancers has been widely discussed, there is still a lack of knowledge about the molecular mechanism of temporary enhancement effect. Using the skin permeation of flurbiprofen as a probe, the temporary enhancement effect of isopulegol decanoate (ISO-10) was evaluated with in vitro permeation experiment and confocal laser scanning microscopy (CLSM). In addition, molecular mechanism of skin recovery was explored with skin retention of ISO-10, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), molecular dynamic (MD) simulation and transepidermal water loss (TEWL). Temporary enhancement effect of ISO-10 was observed by the permeation of flurbiprofen after the treatment of 180min. Furthermore, temporary enhancement effect of ISO-10 on the diffusion of intercellular lipid in the stratum cornuem (SC) was observed by ATR-FTIR, molecular dynamic (MD) simulation. The SC barrier function recovered with the existence of ISO-10 in the lipid bilayer as indicated by the retention study and TEWL. In conclusion, the lipid bilayer accepted the enhancer as a new component to form a new stable arrangement, resulted the recovery of the skin barrier function. This work processed a novel mechanism of the recovery of skin barrier function after the addition of chemical enhancers. Copyright © 2017 Elsevier B.V. All rights reserved.

Dynamic enhanced computed tomography imaging findings of an inflammatory fibroid polyp with massive fibrosis in the stomach

PubMed Central

Shim, Eun Jung; Ahn, Sung Eun; Lee, Dong Ho; Park, Seong Jin; Kim, Youn Wha

2017-01-01

Inflammatory fibroid polyp (IFP) is a rare benign lesion of the gastrointestinal tract. We report a case of computed tomography (CT) imaging finding of a gastric IFP with massive fibrosis. CT scans showed thickening of submucosal layer with overlying mucosal hyperenhancement in the gastric antrum. The submucosal layer showed increased enhancement on delayed phase imaging. An antrectomy with gastroduodenostomy was performed because gastric cancer was suspected, particularly signet ring cell carcinoma. The histopathological diagnosis was an IFP with massive fibrosis. The authors suggest that when the submucosal layer of the gastric wall is markedly thickened with delayed enhancement and preservation of the mucosal layer, an IFP with massive fibrosis should be considered in the differential diagnosis. PMID:28373777

SPECT Myocardial Blood Flow Quantitation Concludes Equivocal Myocardial Perfusion SPECT Studies to Increase Diagnostic Benefits.

PubMed

Chen, Lung-Ching; Lin, Chih-Yuan; Chen, Ing-Jou; Ku, Chi-Tai; Chen, Yen-Kung; Hsu, Bailing

2016-01-01

Recently, myocardial blood flow quantitation with dynamic SPECT/CT has been reported to enhance the detection of coronary artery disease in human. This advance has created important clinical applications to coronary artery disease diagnosis and management for areas where myocardial perfusion PET tracers are not available. We present 2 clinical cases that undergone a combined test of 1-day rest/dipyridamole-stress dynamic SPECT and ECG-gated myocardial perfusion SPECT scans using an integrated imaging protocol and demonstrate that flow parameters are capable to conclude equivocal myocardial perfusion SPECT studies, therefore increasing diagnostic benefits to add value in making clinical decisions.

Bariatric CT Imaging: Challenges and Solutions.

PubMed

Fursevich, Dzmitry M; LiMarzi, Gary M; O'Dell, Matthew C; Hernandez, Manuel A; Sensakovic, William F

2016-01-01

The obesity epidemic in the adult and pediatric populations affects all aspects of health care, including diagnostic imaging. With the increasing prevalence of obese and morbidly obese patients, bariatric computed tomographic (CT) imaging is becoming common in day-to-day radiology practice, and a basic understanding of the unique problems that bariatric patients pose to the imaging community is crucial in any setting. Because larger patients may not fit into conventional scanners, having a CT scanner with an adequate table load limit, a large gantry aperture, a large scan field of view, and a high-power generator is a prerequisite for bariatric imaging. Iterative reconstruction methods, high tube current, and high tube voltage can reduce the image noise that is frequently seen in bariatric CT images. Truncation artifacts, cropping artifacts, and ring artifacts frequently complicate the interpretation of CT images of larger patients. If recognized, these artifacts can be easily reduced by using the proper CT equipment, scan acquisition parameters, and postprocessing options. Lastly, because of complex contrast material dynamics, contrast material-enhanced studies of bariatric patients require special attention. Understanding how the rate of injection, the scan timing, and the total mass of iodine affect vascular and parenchymal enhancement will help to optimize contrast-enhanced studies in the bariatric population. This article familiarizes the reader with the challenges that are frequently encountered at CT imaging of bariatric patients, beginning with equipment selection and ending with a review of the most commonly encountered obesity-related artifacts and the technical considerations in the acquisition of contrast-enhanced images. (©)RSNA, 2016.

Sensitive and reliable multianalyte quantitation of herbal medicine in rat plasma using dynamic triggered multiple reaction monitoring.

PubMed

Yan, Zhixiang; Li, Tianxue; Lv, Pin; Li, Xiang; Zhou, Chen; Yang, Xinghao

2013-06-01

There is a growing need both clinically and experimentally to improve the determination of the blood levels of multiple chemical constituents in herbal medicines. The conventional multiple reaction monitoring (cMRM), however, is not well suited for multi-component determination and could not provide qualitative information for identity confirmation. Here we apply a dynamic triggered MRM (DtMRM) algorithm for the quantification of 20 constituents in an herbal prescription Bu-Zhong-Yi-Qi-Tang (BZYQT) in rat plasma. Dynamic MRM (DMRM) dramatically reduced the number of concurrent MRM transitions that are monitored during each MS scan. This advantage has been enhanced with the addition of triggered MRM (tMRM) for simultaneous confirmation, which maximizes the dwell time in the primary MRM quantitation phase, and also acquires sufficient MRM data to create a composite product ion spectrum. By allowing optimized collision energy for each product ion and maximizing dwell times, tMRM is significantly more sensitive and reliable than conventional product ion scanning. The DtMRM approach provides much higher sensitivity and reproducibility than cMRM. Copyright © 2013 Elsevier B.V. All rights reserved.

Digital Microarrays: Single-Molecule Readout with Interferometric Detection of Plasmonic Nanorod Labels.

PubMed

Sevenler, Derin; Daaboul, George G; Ekiz Kanik, Fulya; Ünlü, Neşe Lortlar; Ünlü, M Selim

2018-05-21

DNA and protein microarrays are a high-throughput technology that allow the simultaneous quantification of tens of thousands of different biomolecular species. The mediocre sensitivity and limited dynamic range of traditional fluorescence microarrays compared to other detection techniques have been the technology's Achilles' heel and prevented their adoption for many biomedical and clinical diagnostic applications. Previous work to enhance the sensitivity of microarray readout to the single-molecule ("digital") regime have either required signal amplifying chemistry or sacrificed throughput, nixing the platform's primary advantages. Here, we report the development of a digital microarray which extends both the sensitivity and dynamic range of microarrays by about 3 orders of magnitude. This technique uses functionalized gold nanorods as single-molecule labels and an interferometric scanner which can rapidly enumerate individual nanorods by imaging them with a 10× objective lens. This approach does not require any chemical signal enhancement such as silver deposition and scans arrays with a throughput similar to commercial fluorescence scanners. By combining single-nanoparticle enumeration and ensemble measurements of spots when the particles are very dense, this system achieves a dynamic range of about 6 orders of magnitude directly from a single scan. As a proof-of-concept digital protein microarray assay, we demonstrated detection of hepatitis B virus surface antigen in buffer with a limit of detection of 3.2 pg/mL. More broadly, the technique's simplicity and high-throughput nature make digital microarrays a flexible platform technology with a wide range of potential applications in biomedical research and clinical diagnostics.

Enhanced Atom Mobility on the Surface of a Metastable Film

NASA Astrophysics Data System (ADS)

Picone, A.; Riva, M.; Fratesi, G.; Brambilla, A.; Bussetti, G.; Finazzi, M.; Duò, L.; Ciccacci, F.

2014-07-01

A remarkable enhancement of atomic diffusion is highlighted by scanning tunneling microscopy performed on ultrathin metastable body-centered tetragonal Co films grown on Fe(001). The films follow a nearly perfect layer-by-layer growth mode with a saturation island density strongly dependent on the layer on which the nucleation occurs, indicating a lowering of the diffusion barrier. Density functional theory calculations reveal that this phenomenon is driven by the increasing capability of the film to accommodate large deformations as the thickness approaches the limit at which a structural transition occurs. These results disclose the possibility of tuning surface diffusion dynamics and controlling cluster nucleation and self-organization.

Enhanced atom mobility on the surface of a metastable film.

PubMed

Picone, A; Riva, M; Fratesi, G; Brambilla, A; Bussetti, G; Finazzi, M; Duò, L; Ciccacci, F

2014-07-25

A remarkable enhancement of atomic diffusion is highlighted by scanning tunneling microscopy performed on ultrathin metastable body-centered tetragonal Co films grown on Fe(001). The films follow a nearly perfect layer-by-layer growth mode with a saturation island density strongly dependent on the layer on which the nucleation occurs, indicating a lowering of the diffusion barrier. Density functional theory calculations reveal that this phenomenon is driven by the increasing capability of the film to accommodate large deformations as the thickness approaches the limit at which a structural transition occurs. These results disclose the possibility of tuning surface diffusion dynamics and controlling cluster nucleation and self-organization.

SU-F-I-16: Short Breast MRI with High-Resolution T2-Weighted and Dynamic Contrast Enhanced T1-Weighted Images

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, J; Son, J; Arun, B

Purpose: To develop and demonstrate a short breast (sb) MRI protocol that acquires both T2-weighted and dynamic contrast-enhanced T1-weighted images in approximately ten minutes. Methods: The sb-MRI protocol consists of two novel pulse sequences. The first is a flexible fast spin-echo triple-echo Dixon (FTED) sequence for high-resolution fat-suppressed T2-weighted imaging, and the second is a 3D fast dual-echo spoiled gradient sequence (FLEX) for volumetric fat-suppressed T1-weighted imaging before and post contrast agent injection. The flexible FTED sequence replaces each single readout during every echo-spacing period of FSE with three fast-switching bipolar readouts to produce three raw images in a singlemore » acquisition. These three raw images are then post-processed using a Dixon algorithm to generate separate water-only and fat-only images. The FLEX sequence acquires two echoes using dual-echo readout after each RF excitation and the corresponding images are post-processed using a similar Dixon algorithm to yield water-only and fat-only images. The sb-MRI protocol was implemented on a 3T MRI scanner and used for patients who had undergone concurrent clinical MRI for breast cancer screening. Results: With the same scan parameters (eg, spatial coverage, field of view, spatial and temporal resolution) as the clinical protocol, the total scan-time of the sb-MRI protocol (including the localizer, bilateral T2-weighted, and dynamic contrast-enhanced T1-weighted images) was 11 minutes. In comparison, the clinical breast MRI protocol took 43 minutes. Uniform fat suppression and high image quality were consistently achieved by sb-MRI. Conclusion: We demonstrated a sb-MRI protocol comprising both T2-weighted and dynamic contrast-enhanced T1-weighted images can be performed in approximately ten minutes. The spatial and temporal resolution of the images easily satisfies the current breast MRI accreditation guidelines by the American College of Radiology. The protocol has the potential of making breast MRI more widely accessible to and more tolerable by the patients. JMA is the inventor of United States patents that are owned by the University of Texas Board of Regents and currently licensed to GE Healthcare and Siemens Gmbh.« less

Dynamic Contrast-Enhanced Magnetic Resonance Imaging as a Pharmacodynamic Biomarker for Pazopanib in Metastatic Renal Carcinoma.

PubMed

Sweis, Randy F; Medved, Milica; Towey, Shannon; Karczmar, Gregory S; Oto, Aytekin; Szmulewitz, Russell Z; O'Donnell, Peter H; Fishkin, Paul; Karrison, Theodore; Stadler, Walter M

2017-04-01

Traditional imaging assessment criteria might not correlate well with clinical benefit from vascular endothelial growth factor pathway-directed therapy in metastatic renal cancer. Preclinical data suggest tumor growth is preceded by a rise in K trans level, a parameter derived from dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) that reflects vascular permeability. We thus hypothesized that K trans might be a predictive biomarker for pazopanib. Patients with metastatic renal cancer were treated with pazopanib at 800 mg oral daily until disease progression. MRI of the abdomen and pelvis with a DCE-MRI sequence was obtained at baseline and every 8 weeks. Seventy-three DCE-MRI scans were completed and 66 were technically assessable. Of the 17 patients with at least 1 DCE-MRI scan after the baseline scan, 16 (94%) had a decline in K trans level. Changes in K trans compared with baseline after 1, 8, 16, and 24 weeks were -49%, -65%, -63%, and -53%, respectively (P = .0052, repeated measures analysis of variance). The median K trans nadir occurred at 8 weeks. The median progression-free survival (PFS) was 32.1 weeks. PFS was longer in patients with higher baseline K trans values (P = .036, log rank). Baseline K trans did not reach significance in a Cox proportional hazard model including clinical prognostic index and previous treatments (P = .083). We show that K trans is a pharmacodynamic biomarker for pazopanib therapy in metastatic renal cancer. Because of the small sample size, the predictive capacity of K trans recovery could not be assessed, but baseline K trans correlated with PFS. Copyright © 2016 Elsevier Inc. All rights reserved.

Phenazopyridine-phthalimide nano-cocrystal: Release rate and oral bioavailability enhancement.

PubMed

Huang, Yu; Li, Jin-Mei; Lai, Zhi-Hui; Wu, Jun; Lu, Tong-Bu; Chen, Jia-Mei

2017-11-15

Both cocrystal and nanocrystal technologies have been widely used in the pharmaceutical development for poorly soluble drugs. However, the synergistic effects due to the integration of these two technologies have not been well investigated. The aim of this study is to develop a nano-sized cocrystal of phenazopyridine (PAP) with phthalimide (PI) to enhance the release rate and oral bioavailability of PAP. A PAP-PI nano-cocrystal with particle diameter of 21.4±0.1nm was successfully prepared via a sonochemical approach and characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and dynamic light scattering (DLS) analysis. An in vitro release study revealed a significant release rate enhancement for PAP-PI nano-cocrystal as compared to PAP-PI cocrystal and PAP hydrochloride salt. Further, a comparative oral bioavailability study in rats indicated significant improvement in C max and oral bioavailability (AUC 0-∞ ) by 1.39- and 2.44-fold, respectively. This study demonstrated that this novel nano-cocrystal technology can be a new promising option to improve release rate and absorption of poorly soluble compounds in the pharmaceutical industry. Copyright © 2017 Elsevier B.V. All rights reserved.

Enhancing Ion Migration in Grain Boundaries of Hybrid Organic-Inorganic Perovskites by Chlorine

DOE PAGES

Yang, Bin; Brown, Chance C.; Huang, Jingsong; ...

2017-05-26

Ionicity plays an important role in determining material properties, as well as optoelectronic performance of organometallic trihalide perovskites (OTPs). Ion migration in OTP films has recently been under intensive investigation by various scanning probe microscopy (SPM) techniques. Controversial findings regarding the role of grain boundaries (GBs) associated with ion migration are often encountered, likely as a result of feedback errors and topographic effects common in to SPM. In this work, electron microscopy and spectroscopy (scanning transmission electron microscopy/electron energy loss spectroscopy) are combined with a novel, open-loop, band-excitation, (contact) Kelvin probe force microscopy (BE-KPFM and BE-cKPFM), in conjunction with abmore » initio molecular dynamics simulations to examine the ion behavior in the GBs of CH 3NH 3PbI 3 perovskite films. Furthermore, this combination of diverse techniques provides a deeper understanding of the differences between ion migration within GBs and interior grains in OTP films. Our work demonstrates that ion migration can be significantly enhanced by introducing additional mobile Cl - ions into GBs. The enhancement of ion migration may serve as the first step toward the development of high-performance electrically and optically tunable memristors and synaptic devices.« less

SU-E-T-82: A Study On Enhanced Dynamic Wedge (EDW) Dosimetry Using 2D Seven29 Ion Chamber Array Detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Syam; Aparna

2015-06-15

Purpose: To study the dosimetric properties of Enhanced Dynamic Wedge (EDW) using PTW Seven29 ion chamber array Methods: PTW Seven29 ion chamber array and Solid Water phantoms for different depths were used for the study. The study was carried out in Varian Clinac ix with photon energies, 6MV & 15MV. Primarily the solid water phantoms with the 2D array were scanned using a CT scanner (GE Optima 580) at different depths. These scanned images were used for EDW planning in an Eclipse treatment planning system (version 10). Planning was done for different wedge angles and for different depths for 6MVmore » & 15MV. A dose of 100 CGy was delivered in each cases. For each delivery, calculated the Monitoring Unit (MU) required. Same set-up was created before delivering the plans in Varian Clinac-ix. For each clinically relevant depth and for different wedge angles, the same MU was delivered as calculated. Different wedged dose distributions where reconstructed from the measured 2D array data using the in-house developed excel program. Results: It is observed that the shoulder like region in the profile which reduces as depth increases. For the same depth and energy, the percentage difference between planned and measured dose is lesser than 3%. For smaller wedge angles, the percentage difference is found to be greater than 3% for the largest wedge angle. Standard deviation between measured doses at shoulder region for planned and measured profiles is 0.08 and 0.02 respectively. Standard deviations between planned and measured wedge factors for different depths (2.5cm, 5cm, 10cm, and 15cm) are (0.0021, 0.0007, 0.0050, 0.0001) for 6MV and (0.0024, 0.0191, 0.0013, 0.0005) for 15MV respectively. Conclusion: The 2D Seven29 ion chamber array is a good tool for the Enhanced Dynamic Wedge (EDW) dosimetry.« less

Investigation of temporal vascular effects induced by focused ultrasound treatment with speckle-variance optical coherence tomography

PubMed Central

Tsai, Meng-Tsan; Chang, Feng-Yu; Lee, Cheng-Kuang; Gong, Cihun-Siyong Alex; Lin, Yu-Xiang; Lee, Jiann-Der; Yang, Chih-Hsun; Liu, Hao-Li

2014-01-01

Focused ultrasound (FUS) can be used to locally and temporally enhance vascular permeability, improving the efficiency of drug delivery from the blood vessels into the surrounding tissue. However, it is difficult to evaluate in real time the effect induced by FUS and to noninvasively observe the permeability enhancement. In this study, speckle-variance optical coherence tomography (SVOCT) was implemented for the investigation of temporal effects on vessels induced by FUS treatment. With OCT scanning, the dynamic change in vessels during FUS exposure can be observed and studied. Moreover, the vascular effects induced by FUS treatment with and without the presence of microbubbles were investigated and quantitatively compared. Additionally, 2D and 3D speckle-variance images were used for quantitative observation of blood leakage from vessels due to the permeability enhancement caused by FUS, which could be an indicator that can be used to determine the influence of FUS power exposure. In conclusion, SVOCT can be a useful tool for monitoring FUS treatment in real time, facilitating the dynamic observation of temporal effects and helping to determine the optimal FUS power. PMID:25071945

Capillary red blood cell velocimetry by phase-resolved optical coherence tomography

NASA Astrophysics Data System (ADS)

Tang, Jianbo; Erdener, Sefik Evren; Fu, Buyin; Boas, David A.

2018-02-01

Quantitative measurement of blood flow velocity in capillaries is challenging due to their small size (around 5-10 μm), and the discontinuity and single-file feature of RBCs flowing in a capillary. In this work, we present a phase-resolved Optical Coherence Tomography (OCT) method for accurate measurement of the red blood cell (RBC) speed in cerebral capillaries. To account for the discontinuity of RBCs flowing in capillaries, we applied an M-mode scanning strategy that repeated A-scans at each scanning position for an extended time. As the capillary size is comparable to the OCT resolution size (3.5×3.5×3.5μm), we applied a high pass filter to remove the stationary signal component so that the phase information of the dynamic component (i.e. from the moving RBC) could be enhanced to provide an accurate estimate of the RBC axial speed. The phase-resolved OCT method accurately quantifies the axial velocity of RBC's from the phase shift of the dynamic component of the signal. We validated our measurements by RBC passage velocimetry using the signal magnitude of the same OCT time series data. These proposed method of capillary velocimetry proved to be a robust method of mapping capillary RBC speeds across the micro-vascular network.

Expansion of Shockley stacking fault observed by scanning electron microscope and partial dislocation motion in 4H-SiC

NASA Astrophysics Data System (ADS)

Yamashita, Yoshifumi; Nakata, Ryu; Nishikawa, Takeshi; Hada, Masaki; Hayashi, Yasuhiko

2018-04-01

We studied the dynamics of the expansion of a Shockley-type stacking fault (SSF) with 30° Si(g) partial dislocations (PDs) using a scanning electron microscope. We observed SSFs as dark lines (DLs), which formed the contrast at the intersection between the surface and the SSF on the (0001) face inclined by 8° from the surface. We performed experiments at different electron-beam scanning speeds, observing magnifications, and irradiation areas. The results indicated that the elongation of a DL during one-frame scanning depended on the time for which the electron beam irradiated the PD segment in the frame of view. From these results, we derived a formula to express the velocity of the PD using the elongation rate of the corresponding DL during one-frame scanning. We also obtained the result that the elongation velocity of the DL was not influenced by changing the direction in which the electron beam irradiates the PD. From this result, we deduced that the geometrical kink motion of the PD was enhanced by diffusing carriers that were generated by the electron-beam irradiation.

Development of a Hybrid Atomic Force Microscopic Measurement System Combined with White Light Scanning Interferometry

PubMed Central

Guo, Tong; Wang, Siming; Dorantes-Gonzalez, Dante J.; Chen, Jinping; Fu, Xing; Hu, Xiaotang

2012-01-01

A hybrid atomic force microscopic (AFM) measurement system combined with white light scanning interferometry for micro/nanometer dimensional measurement is developed. The system is based on a high precision large-range positioning platform with nanometer accuracy on which a white light scanning interferometric module and an AFM head are built. A compact AFM head is developed using a self-sensing tuning fork probe. The head need no external optical sensors to detect the deflection of the cantilever, which saves room on the head, and it can be directly fixed under an optical microscopic interferometric system. To enhance the system’s dynamic response, the frequency modulation (FM) mode is adopted for the AFM head. The measuring data can be traceable through three laser interferometers in the system. The lateral scanning range can reach 25 mm × 25 mm by using a large-range positioning platform. A hybrid method combining AFM and white light scanning interferometry is proposed to improve the AFM measurement efficiency. In this method, the sample is measured firstly by white light scanning interferometry to get an overall coarse morphology, and then, further measured with higher resolution by AFM. Several measuring experiments on standard samples demonstrate the system’s good measurement performance and feasibility of the hybrid measurement method. PMID:22368463

Development of a hybrid atomic force microscopic measurement system combined with white light scanning interferometry.

PubMed

Guo, Tong; Wang, Siming; Dorantes-Gonzalez, Dante J; Chen, Jinping; Fu, Xing; Hu, Xiaotang

2012-01-01

A hybrid atomic force microscopic (AFM) measurement system combined with white light scanning interferometry for micro/nanometer dimensional measurement is developed. The system is based on a high precision large-range positioning platform with nanometer accuracy on which a white light scanning interferometric module and an AFM head are built. A compact AFM head is developed using a self-sensing tuning fork probe. The head need no external optical sensors to detect the deflection of the cantilever, which saves room on the head, and it can be directly fixed under an optical microscopic interferometric system. To enhance the system's dynamic response, the frequency modulation (FM) mode is adopted for the AFM head. The measuring data can be traceable through three laser interferometers in the system. The lateral scanning range can reach 25 mm × 25 mm by using a large-range positioning platform. A hybrid method combining AFM and white light scanning interferometry is proposed to improve the AFM measurement efficiency. In this method, the sample is measured firstly by white light scanning interferometry to get an overall coarse morphology, and then, further measured with higher resolution by AFM. Several measuring experiments on standard samples demonstrate the system's good measurement performance and feasibility of the hybrid measurement method.

Adaptable Diffraction Gratings With Wavefront Transformation

NASA Technical Reports Server (NTRS)

Iazikov, Dmitri; Mossberg, Thomas W.; Greiner, Christoph M.

2010-01-01

Diffraction gratings are optical components with regular patterns of grooves, which angularly disperse incoming light by wavelength. Traditional diffraction gratings have static planar, concave, or convex surfaces. However, if they could be made so that they can change the surface curvature at will, then they would be able to focus on particular segments, self-calibrate, or perform fine adjustments. This innovation creates a diffraction grating on a deformable surface. This surface could be bent at will, resulting in a dynamic wavefront transformation. This allows for self-calibration, compensation for aberrations, enhancing image resolution in a particular area, or performing multiple scans using different wavelengths. A dynamic grating gives scientists a new ability to explore wavefronts from a variety of viewpoints.

Enhancement of dynamic myocardial perfusion PET images based on low-rank plus sparse decomposition.

PubMed

Lu, Lijun; Ma, Xiaomian; Mohy-Ud-Din, Hassan; Ma, Jianhua; Feng, Qianjin; Rahmim, Arman; Chen, Wufan

2018-02-01

The absolute quantification of dynamic myocardial perfusion (MP) PET imaging is challenged by the limited spatial resolution of individual frame images due to division of the data into shorter frames. This study aims to develop a method for restoration and enhancement of dynamic PET images. We propose that the image restoration model should be based on multiple constraints rather than a single constraint, given the fact that the image characteristic is hardly described by a single constraint alone. At the same time, it may be possible, but not optimal, to regularize the image with multiple constraints simultaneously. Fortunately, MP PET images can be decomposed into a superposition of background vs. dynamic components via low-rank plus sparse (L + S) decomposition. Thus, we propose an L + S decomposition based MP PET image restoration model and express it as a convex optimization problem. An iterative soft thresholding algorithm was developed to solve the problem. Using realistic dynamic 82 Rb MP PET scan data, we optimized and compared its performance with other restoration methods. The proposed method resulted in substantial visual as well as quantitative accuracy improvements in terms of noise versus bias performance, as demonstrated in extensive 82 Rb MP PET simulations. In particular, the myocardium defect in the MP PET images had improved visual as well as contrast versus noise tradeoff. The proposed algorithm was also applied on an 8-min clinical cardiac 82 Rb MP PET study performed on the GE Discovery PET/CT, and demonstrated improved quantitative accuracy (CNR and SNR) compared to other algorithms. The proposed method is effective for restoration and enhancement of dynamic PET images. Copyright © 2017 Elsevier B.V. All rights reserved.

Reduction of the unnecessary dose from the over-range area with a spiral dynamic z-collimator: comparison of beam pitch and detector coverage with 128-detector row CT.

PubMed

Shirasaka, Takashi; Funama, Yoshinori; Hayashi, Mutsukazu; Awamoto, Shinichi; Kondo, Masatoshi; Nakamura, Yasuhiko; Hatakenaka, Masamitsu; Honda, Hiroshi

2012-01-01

Our purpose in this study was to assess the radiation dose reduction and the actual exposed scan length of over-range areas using a spiral dynamic z-collimator at different beam pitches and detector coverage. Using glass rod dosimeters, we measured the unilateral over-range scan dose between the beginning of the planned scan range and the beginning of the actual exposed scan range. Scanning was performed at detector coverage of 80.0 and 40.0 mm, with and without the spiral dynamic z-collimator. The dose-saving ratio was calculated as the ratio of the unnecessary over-range dose, with and without the spiral dynamic z-collimator. In 80.0 mm detector coverage without the spiral dynamic z-collimator, the actual exposed scan length for the over-range area was 108, 120, and 126 mm, corresponding to a beam pitch of 0.60, 0.80, and 0.99, respectively. With the spiral dynamic z-collimator, the actual exposed scan length for the over-range area was 48, 66, and 84 mm with a beam pitch of 0.60, 0.80, and 0.99, respectively. The dose-saving ratios with and without the spiral dynamic z-collimator for a beam pitch of 0.60, 0.80, and 0.99 were 35.07, 24.76, and 13.51%, respectively. With 40.0 mm detector coverage, the dose-saving ratios with and without the spiral dynamic z-collimator had the highest value of 27.23% with a low beam pitch of 0.60. The spiral dynamic z-collimator is important for a reduction in the unnecessary over-range dose and makes it possible to reduce the unnecessary dose by means of a lower beam pitch.

Translational viscous drags of an ellipsoid straddling an interface between two fluids.

PubMed

Boniello, Giuseppe; Stocco, Antonio; Gross, Michel; In, Martin; Blanc, Christophe; Nobili, Maurizio

2016-07-01

We study the dynamics of individual polystyrene ellipsoids of different aspect ratios trapped at the air-water interface. Using particle tracking and in situ vertical scanning interferometry techniques we are able to measure translational drags and the protrusion in air of the ellipsoids. We report that translational drags on the ellipsoid are unexpectedly enhanced: despite the fact that a noticeable part of the ellipsoid is in air, drags are found larger than the bulk one in water.

Analysis of time dependent phenomena observed with the LPSP OSO-8 instrument. [solar chromosphere and photosphere

NASA Technical Reports Server (NTRS)

Leibacher, J. W.

1979-01-01

Data obtained by the Laboratoire de Physique Stellaire et Planetaire's ultraviolet spectrometer onboard the OSO-8 spacecraft were analyzed in an effort to dynamically model the solar chromosphere as an aid in enhancing knowledge of the dynamical processes themselves and of spectral line formation in the dynamic chromosphere. Repeated spectral scans of strong, optically thick resonance lines formed in the solar chromosphere were examined for indications of oscillatory velocities and intensities among other indications of velocity which were studied, the blue peak is reasonably well defined, and the position of a parabolic filter fitted by the least squares method was used to define it. Observed chromospheric oscillation periods are discussed as well as the variations in altitude of the emitting region which result primarily from the motion up and down during the oscillation.

A preliminary study into the sensitivity of disease activity detection by serial weekly magnetic resonance imaging in multiple sclerosis.

PubMed Central

Lai, M; Hodgson, T; Gawne-Cain, M; Webb, S; MacManus, D; McDonald, W I; Thompson, A J; Miller, D H

1996-01-01

Long TR and gadolinium enhanced spin echo brain MRI was performed weekly for three months in three patients with relapsing-remitting or secondary progressive multiple sclerosis. During the study, 38 new enhancing lesions were seen; 11 showed enhancement for less than four weeks, and two enhanced on only one scan. All 16 new lesions seen on long TR scans showed initial enhancement. When only every fourth (monthly) scan was analysed, a total of 33 new enhancing lesions were seen. Subject to confirmation in a larger cohort, the results suggest: (a) that blood brain barrier leakage is an invariable event in new lesion development in relapsing-remitting and secondary progressive multiple sclerosis; (b) the small increase in sensitivity of weekly scanning does not justify its use in preference to monthly scanning when monitoring treatments. Images PMID:8609517

Evaluation of glass transition temperature and dynamic mechanical properties of autopolymerized hard direct denture reline resins.

PubMed

Takase, Kazuma; Watanabe, Ikuya; Kurogi, Tadafumi; Murata, Hiroshi

2015-01-01

This study assessed methods for evaluation of glass transition temperature (Tg) of autopolymerized hard direct denture reline resins using dynamic mechanical analysis and differential scanning calorimetry in addition to the dynamic mechanical properties. The Tg values of 3 different reline resins were determined using a dynamic viscoelastometer and differential scanning calorimeter, and rheological parameters were also determined. Although all materials exhibited higher storage modulus and loss modulus values, and a lower loss tangent at 37˚C with a higher frequency, the frequency dependence was not large. Tg values obtained by dynamic mechanical analysis were higher than those by differential scanning calorimetry and higher frequency led to higher Tg, while more stable Tg values were also obtained by that method. These results suggest that dynamic mechanical analysis is more advantageous for characterization of autopolymerized hard direct denture reline resins than differential scanning calorimetry.

Robust low-dose dynamic cerebral perfusion CT image restoration via coupled dictionary learning scheme.

PubMed

Tian, Xiumei; Zeng, Dong; Zhang, Shanli; Huang, Jing; Zhang, Hua; He, Ji; Lu, Lijun; Xi, Weiwen; Ma, Jianhua; Bian, Zhaoying

2016-11-22

Dynamic cerebral perfusion x-ray computed tomography (PCT) imaging has been advocated to quantitatively and qualitatively assess hemodynamic parameters in the diagnosis of acute stroke or chronic cerebrovascular diseases. However, the associated radiation dose is a significant concern to patients due to its dynamic scan protocol. To address this issue, in this paper we propose an image restoration method by utilizing coupled dictionary learning (CDL) scheme to yield clinically acceptable PCT images with low-dose data acquisition. Specifically, in the present CDL scheme, the 2D background information from the average of the baseline time frames of low-dose unenhanced CT images and the 3D enhancement information from normal-dose sequential cerebral PCT images are exploited to train the dictionary atoms respectively. After getting the two trained dictionaries, we couple them to represent the desired PCT images as spatio-temporal prior in objective function construction. Finally, the low-dose dynamic cerebral PCT images are restored by using a general DL image processing. To get a robust solution, the objective function is solved by using a modified dictionary learning based image restoration algorithm. The experimental results on clinical data show that the present method can yield more accurate kinetic enhanced details and diagnostic hemodynamic parameter maps than the state-of-the-art methods.

Characterization of skin tissue soldering using diode laser and indocyanine green: in vitro studies.

PubMed

Khosroshahi, M E; Nourbakhsh, M S; Saremi, S; Tabatabaee, F

2010-03-01

Laser tissue soldering based on protein as biological glues and other compounds can provide greater bond strength and less collateral damage. Endogenous and exogenous materials such as indocyanine green (ICG) are often added to solders to enhance light absorption. The purpose of this in vitro study was to examine the impact of different parameters of laser soldering on the thermo-physical properties of the skin. A mixture of albumin solder and ICG was prepared, and then the coated samples were irradiated by an 810 nm diode laser under different conditions. The temperature rise, number of scans (N(s)), and scan velocity (V(s)) were investigated in this study. The results showed that, at each laser irradiance (I), the tensile strength (sigma) of incisions repaired in static mode was higher than in dynamic mode and that the sigma increased with both increasing N(s) and increasing I. It is therefore important to consider the trade off between scan velocity and surface temperature for achieving an optimum operating condition.

Quantitative colorectal cancer perfusion measurement using dynamic contrast-enhanced multidetector-row computed tomography: effect of acquisition time and implications for protocols.

PubMed

Goh, Vicky; Halligan, Steve; Hugill, Jo-Ann; Gartner, Louise; Bartram, Clive I

2005-01-01

To determine the effect of acquisition time on quantitative colorectal cancer perfusion measurement. Dynamic contrast-enhanced computed tomography (CT) was performed prospectively in 10 patients with histologically proven colorectal cancer using 4-detector row CT (Lightspeed Plus; GE Healthcare Technologies, Waukesha, WI). Tumor blood flow, blood volume, mean transit time, and permeability were assessed for 3 acquisition times (45, 65, and 130 seconds). Mean values for all 4 perfusion parameters for each acquisition time were compared using the paired t test. Significant differences in permeability values were noted between acquisitions of 45 seconds and 65 and 130 seconds, respectively (P=0.02, P=0.007). There was no significant difference for values of blood volume, blood flow, and mean transit time between any of the acquisition times. Scan acquisitions of 45 seconds are too short for reliable permeability measurement in the abdomen. Longer acquisition times are required.

Tube-like natural halloysite/poly(tetrafluoroethylene) nanocomposites: simultaneous enhancement in thermal and mechanical properties

NASA Astrophysics Data System (ADS)

Gamini, Suresh; Vasu, V.; Bose, Suryasarathi

2017-04-01

In the current study, PTFE (polytetrafluroethylene) matrix is reinforced with different wt% (2%-10%) of Halloysite nanotubes (HNTs). PTFE samples are fabricated with 2 wt% increment and are designated from ‘B’to ‘F’ and designation ‘A’ refers to neat PTFE. Thermal and mechanical characterization of the fabricated composites is studied. The calorimetric measurements showed enhanced degree of crystallinity of the nanocomposites, which is from 57.83% to 74.7%. The dynamic mechanical analysis results have shown enhanced storage modulus and loss modulus and reduced damping behaviour, without affecting glass transition temperature. Moreover, significant improvements in mechanical properties are observed from the experimental results. The results are discussed and validated with the existing literature. The phase and the fracture morphology of the nanocomposites is studied using scanning electron microscope and discussed herein.

Fast-scan EM with digital image processing for dynamic experiments

Treesearch

C.W. McMillin; F.C. Billingsley; R.E. Frazer

1974-01-01

The recent introduction of accessory instrumentation capable of display at television scan rates suggests a broadened application for the scanning electron microscope- the direct observation of motion (dynamic events) at magnifications otherwise unattainable. In one illustrative experiment, the transverse surface of southern pine was observed when subjected to large...

Fast-scan em with digital image processing for dynamic experiments

Treesearch

Charles W. McMillin; Fred C. Billingsley; Robert E. Frazer

1973-01-01

The recent introduction of accessory instrumentation capable of display at television scan rates suggests a broadened application for the scanning electron microscope - the direct observation of motion (dynamic events) at magnifactions otherwise unattainable. In one illustrative experiment, the transverse surface of southern pine was observed when subjected to large...

Nanowires: Enhanced Optoelectronic Performance of a Passivated Nanowire-Based Device: Key Information from Real-Space Imaging Using 4D Electron Microscopy (Small 17/2016).

PubMed

Khan, Jafar I; Adhikari, Aniruddha; Sun, Jingya; Priante, Davide; Bose, Riya; Shaheen, Basamat S; Ng, Tien Khee; Zhao, Chao; Bakr, Osman M; Ooi, Boon S; Mohammed, Omar F

2016-05-01

Selective mapping of surface charge carrier dynamics of InGaN nanowires before and after surface passivation with octadecylthiol (ODT) is reported by O. F. Mohammed and co-workers on page 2313, using scanning ultrafast electron microscopy. In a typical experiment, the 343 nm output of the laser beam is used to excite the microscope tip to generate pulsed electrons for probing, and the 515 nm output is used as a clocking excitation pulse to initiate dynamics. Time-resolved images demonstrate clearly that carrier recombination is significantly slowed after ODT treatment, which supports the efficient removal of surface trap states. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Feasibility of free-breathing dynamic contrast-enhanced MRI of gastric cancer using a golden-angle radial stack-of-stars VIBE sequence: comparison with the conventional contrast-enhanced breath-hold 3D VIBE sequence.

PubMed

Li, Huan-Huan; Zhu, Hui; Yue, Lei; Fu, Yi; Grimm, Robert; Stemmer, Alto; Fu, Cai-Xia; Peng, Wei-Jun

2018-05-01

To investigate the feasibility and diagnostic value of free-breathing, radial, stack-of-stars three-dimensional (3D) gradient echo (GRE) sequence ("golden angle") on dynamic contrast-enhanced (DCE) MRI of gastric cancer. Forty-three gastric cancer patients were divided into cooperative and uncooperative groups. Respiratory fluctuation was observed using an abdominal respiratory gating sensor. Those who breath-held for more than 15 s were placed in the cooperative group and the remainder in the uncooperative group. The 3-T MRI scanning protocol included 3D GRE and conventional breath-hold VIBE (volume-interpolated breath-hold examination) sequences, comparing images quantitatively and qualitatively. DCE-MRI parameters from VIBE images of normal gastric wall and malignant lesions were compared. For uncooperative patients, 3D GRE scored higher qualitatively, and had higher SNRs (signal-to-noise ratios) and CNRs (contrast-to-noise ratios) than conventional VIBE quantitatively. Though 3D GRE images scored lower in qualitative parameters compared with conventional VIBE for cooperative patients, it provided images with fewer artefacts. DCE parameters differed significantly between normal gastric wall and lesions, with higher Ve (extracellular volume) and lower Kep (reflux constant) in gastric cancer. The free-breathing, golden-angle, radial stack-of-stars 3D GRE technique is feasible for DCE-MRI of gastric cancer. Dynamic enhanced images can be used for quantitative analysis of this malignancy. • Golden-angle radial stack-of-stars VIBE aids gastric cancer MRI diagnosis. • The 3D GRE technique is suitable for patients unable to suspend respiration. • Method scored higher in the qualitative evaluation for uncooperative patients. • The technique produced images with fewer artefacts than conventional VIBE sequence. • Dynamic enhanced images can be used for quantitative analysis of gastric cancer.

Triple dose of gadolinium-DTPA and delayed MRI in patients with benign multiple sclerosis.

PubMed Central

Filippi, M; Capra, R; Campi, A; Colombo, B; Prandini, F; Marcianò, N; Gasparotti, R; Comi, G

1996-01-01

OBJECTIVES--To evaluate whether a triple dose of gadolinium-DTPA (Gd-DTPA) or delayed MRI increase the number, size, and conspicuousness of enhancing lesions in patients with benign multiple sclerosis. METHODS--T1 weighted brain MRI was carried out on 20 patients with benign multiple sclerosis (expanded disability status scale < 3 with a disease duration > 10 years) in two sessions. In the first session, one scan was obtained before and two scans five to seven minutes and 20-30 minutes after the injection of 0.1 mmol/kg Gd-DTPA (standard dose). In the second session, six to 24 hours later, the same procedure was repeated with 0.3 mmol/kg Gd-DTPA (triple dose). RESULTS--Nine enhancing lesions were found in seven patients (35%) using the standard dose of Gd-DTPA. The numbers of enhancing lesions increased to 13 (P = 0.03) and the number of patients with such lesions to eight (40%) on the delayed standard dose scans. On the early triple dose scans, we found 19 enhancing lesions in 10 patients (50%). The number of enhancing lesions was significantly higher (P = 0.01) than that obtained with the early standard dose. The number of enhancing lesions was 18 and the number of "active" patients 11 (55%) on the delayed triple dose scans. The enhancing areas increased progressively from the early standard dose scans to the delayed triple dose scans. The contrast ratios of the lesions detected in early standard dose scans was lower than those of lesions present in the early (P = 0.01) and delayed (P = 0.04) triple dose scans. CONCLUSIONS--More enhancing lesions were detected in patients with benign multiple sclerosis with both delay of MRI and the use of triple dose of Gd-DTPA suggesting that the amount of inflammation in the lesions of such patients is mild and heterogeneous. Images PMID:8778257

Collateral Ventilation Quantification Using Xenon-Enhanced Dynamic Dual-Energy CT: Differences between Canine and Swine Models of Bronchial Occlusion.

PubMed

Park, Eun-Ah; Goo, Jin Mo; Park, Sang Joon; Lee, Chang Hyun; Park, Chang Min

2015-01-01

The aim of this study was to evaluate whether the difference in the degree of collateral ventilation between canine and swine models of bronchial obstruction could be detected by using xenon-enhanced dynamic dual-energy CT. Eight mongrel dogs and six pigs underwent dynamic dual-energy scanning of 64-slice dual-source CT at 12-second interval for 2-minute wash-in period (60% xenon) and at 24-second interval for 3-minute wash-out period with segmental bronchus occluded. Ventilation parameters of magnitude (A value), maximal slope, velocity (K value), and time-to-peak (TTP) enhancement were calculated from dynamic xenon maps using exponential function of Kety model. A larger difference in A value between parenchyma was observed in pigs than in dogs (absolute difference, -33.0 ± 5.0 Hounsfield units [HU] vs. -2.8 ± 7.1 HU, p = 0.001; normalized percentage difference, -79.8 ± 1.8% vs. -5.4 ± 16.4%, p = 0.0007). Mean maximal slopes in both periods in the occluded parenchyma only decreased in pigs (all p < 0.05). K values of both periods were not different (p = 0.892) in dogs. However, a significant (p = 0.027) difference was found in pigs in the wash-in period. TTP was delayed in the occluded parenchyma in pigs (p = 0.013) but not in dogs (p = 0.892). Xenon-ventilation CT allows the quantification of collateral ventilation and detection of differences between canine and swine models of bronchial obstruction.

Collateral Ventilation Quantification Using Xenon-Enhanced Dynamic Dual-Energy CT: Differences between Canine and Swine Models of Bronchial Occlusion

PubMed Central

Park, Eun-Ah; Park, Sang Joon; Lee, Chang Hyun; Park, Chang Min

2015-01-01

Objective The aim of this study was to evaluate whether the difference in the degree of collateral ventilation between canine and swine models of bronchial obstruction could be detected by using xenon-enhanced dynamic dual-energy CT. Materials and Methods Eight mongrel dogs and six pigs underwent dynamic dual-energy scanning of 64-slice dual-source CT at 12-second interval for 2-minute wash-in period (60% xenon) and at 24-second interval for 3-minute wash-out period with segmental bronchus occluded. Ventilation parameters of magnitude (A value), maximal slope, velocity (K value), and time-to-peak (TTP) enhancement were calculated from dynamic xenon maps using exponential function of Kety model. Results A larger difference in A value between parenchyma was observed in pigs than in dogs (absolute difference, -33.0 ± 5.0 Hounsfield units [HU] vs. -2.8 ± 7.1 HU, p = 0.001; normalized percentage difference, -79.8 ± 1.8% vs. -5.4 ± 16.4%, p = 0.0007). Mean maximal slopes in both periods in the occluded parenchyma only decreased in pigs (all p < 0.05). K values of both periods were not different (p = 0.892) in dogs. However, a significant (p = 0.027) difference was found in pigs in the wash-in period. TTP was delayed in the occluded parenchyma in pigs (p = 0.013) but not in dogs (p = 0.892). Conclusion Xenon-ventilation CT allows the quantification of collateral ventilation and detection of differences between canine and swine models of bronchial obstruction. PMID:25995696

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herfst, Rodolf; Dekker, Bert; Witvoet, Gert

One of the major limitations in the speed of the atomic force microscope (AFM) is the bandwidth of the mechanical scanning stage, especially in the vertical (z) direction. According to the design principles of “light and stiff” and “static determinacy,” the bandwidth of the mechanical scanner is limited by the first eigenfrequency of the AFM head in case of tip scanning and by the sample stage in terms of sample scanning. Due to stringent requirements of the system, simply pushing the first eigenfrequency to an ever higher value has reached its limitation. We have developed a miniaturized, high speed AFMmore » scanner in which the dynamics of the z-scanning stage are made insensitive to its surrounding dynamics via suspension of it on specific dynamically determined points. This resulted in a mechanical bandwidth as high as that of the z-actuator (50 kHz) while remaining insensitive to the dynamics of its base and surroundings. The scanner allows a practical z scan range of 2.1 μm. We have demonstrated the applicability of the scanner to the high speed scanning of nanostructures.« less

The influence of C s/C c correction in analytical imaging and spectroscopy in scanning and transmission electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaluzec, Nestor J.

Aberration correction in scanning/transmission electron microscopy (S/TEM) owes much to the efforts of a small dedicated group of innovators. Leading that frontier has been Prof. Harald Rose. To date his leadership and dynamic personality has spearheaded our ability to leave behind many of the limitations imposed by spherical aberration (C s) in high resolution phase contrast imaging. Following shortly behind, has been the development of chromatic aberration correction (C c) which augments those accomplishments. In this study we will review and summarize how the combination of C s/C c technology enhances our ability to conduct hyperspectral imaging and spectroscopy inmore » today's and future computationally mediated experiments in both thin as well as realistic specimens in vacuo and during in-situ/environmental experiments.« less

The influence of C s/C c correction in analytical imaging and spectroscopy in scanning and transmission electron microscopy

DOE PAGES

Zaluzec, Nestor J.

2014-11-11

Aberration correction in scanning/transmission electron microscopy (S/TEM) owes much to the efforts of a small dedicated group of innovators. Leading that frontier has been Prof. Harald Rose. To date his leadership and dynamic personality has spearheaded our ability to leave behind many of the limitations imposed by spherical aberration (C s) in high resolution phase contrast imaging. Following shortly behind, has been the development of chromatic aberration correction (C c) which augments those accomplishments. In this study we will review and summarize how the combination of C s/C c technology enhances our ability to conduct hyperspectral imaging and spectroscopy inmore » today's and future computationally mediated experiments in both thin as well as realistic specimens in vacuo and during in-situ/environmental experiments.« less

Enhancing the blue shift of SHG signal in GaSe:B/Ce crystal

NASA Astrophysics Data System (ADS)

Karatay, Ahmet; Yuksek, Mustafa; Ertap, Hüseyin; Elmali, Ayhan; Karabulut, Mevlut

2018-02-01

The influence of Ce3+ on the wavelength of second harmonic generation (SHG) signal in boron doped GaSe crystals have been investigated. We found that by substitution of Ce3+ with B3+, SHG signal shifted to lower wavelength. In addition, the nonlinear absorption (NA) properties and ultrafast dynamics of pure, 1 at.% B3+ and 0.5 at.% B3++ 0.5 at.% Ce3+ doped GaSe crystals have been studied by open aperture Z-scan and ultrafast pump probe spectroscopy techniques. From the open aperture Z-scan experiments we observed that all of the crystals showed nonlinear absorption (NA). However, pump-probe experiments revealed that when GaSe crystal is doped, the NA signal turns into a bleaching signal with different lifetimes depending on the type and concentration of the dopant atoms.

Computerized detection of breast lesions in multi-centre and multi-instrument DCE-MR data using 3D principal component maps and template matching

NASA Astrophysics Data System (ADS)

Ertas, Gokhan; Doran, Simon; Leach, Martin O.

2011-12-01

In this study, we introduce a novel, robust and accurate computerized algorithm based on volumetric principal component maps and template matching that facilitates lesion detection on dynamic contrast-enhanced MR. The study dataset comprises 24 204 contrast-enhanced breast MR images corresponding to 4034 axial slices from 47 women in the UK multi-centre study of MRI screening for breast cancer and categorized as high risk. The scans analysed here were performed on six different models of scanner from three commercial vendors, sited in 13 clinics around the UK. 1952 slices from this dataset, containing 15 benign and 13 malignant lesions, were used for training. The remaining 2082 slices, with 14 benign and 12 malignant lesions, were used for test purposes. To prevent false positives being detected from other tissues and regions of the body, breast volumes are segmented from pre-contrast images using a fast semi-automated algorithm. Principal component analysis is applied to the centred intensity vectors formed from the dynamic contrast-enhanced T1-weighted images of the segmented breasts, followed by automatic thresholding to eliminate fatty tissues and slowly enhancing normal parenchyma and a convolution and filtering process to minimize artefacts from moderately enhanced normal parenchyma and blood vessels. Finally, suspicious lesions are identified through a volumetric sixfold neighbourhood connectivity search and calculation of two morphological features: volume and volumetric eccentricity, to exclude highly enhanced blood vessels, nipples and normal parenchyma and to localize lesions. This provides satisfactory lesion localization. For a detection sensitivity of 100%, the overall false-positive detection rate of the system is 1.02/lesion, 1.17/case and 0.08/slice, comparing favourably with previous studies. This approach may facilitate detection of lesions in multi-centre and multi-instrument dynamic contrast-enhanced breast MR data.

Correcting (18)F-fluoride PET static scan measurements of skeletal plasma clearance for tracer efflux from bone.

PubMed

Siddique, Musib; Frost, Michelle L; Moore, Amelia E B; Fogelman, Ignac; Blake, Glen M

2014-03-01

The aim of the study was to examine whether (18)F-fluoride PET ((18)F-PET) static scan measurements of bone plasma clearance (Ki) can be corrected for tracer efflux from bone from the time of injection. The efflux of tracer from bone mineral to plasma was described by a first-order rate constant kloss. A modified Patlak analysis was applied to 60-min dynamic (18)F-PET scans of the spine and hip acquired during trials on the bone anabolic agent teriparatide to find the best-fit values of kloss at the lumbar spine, total hip and femoral shaft. The resulting values of kloss were used to extrapolate the modified Patlak plots to 120 min after injection and derive a sequence of static scan estimates of Ki at 4-min intervals that were compared with the Patlak Ki values from the 60-min dynamic scans. A comparison was made with the results of the standard static scan analysis, which assumes kloss=0. The best-fit values of kloss for the spine and hip regions of interest averaged 0.006/min and did not change when patients were treated with teriparatide. Static scan values of Ki calculated using the modified analysis with kloss=0.006/min were independent of time between 10 and 120 min after injection and were in close agreement with findings from the dynamic scans. In contrast, by 2 h after injection the static scan Ki values calculated using the standard analysis underestimated the dynamic scan results by 20%. Using a modified analysis that corrects for F efflux from bone, estimates of Ki from static PET scans can be corrected for time up to 2 h after injection. This simplified approach may obviate the need to perform dynamic scans and hence shorten the scanning procedure for the patient and reduce the cost of studies. It also enables reliable estimates of Ki to be obtained from multiple skeletal sites with a single injection of tracer.

Optimal scan timing and intravenous route for contrast-enhanced computed tomography in patients after Fontan operation.

PubMed

Park, Eun-Ah; Lee, Whal; Chung, Se-Young; Yin, Yong Hu; Chung, Jin Wook; Park, Jae Hyung

2010-01-01

To determine the optimal scan timing and adequate intravenous route for patients having undergone the Fontan operation. A total of 88 computed tomographic images in 49 consecutive patients who underwent the Fontan operation were retrospectively evaluated and divided into 7 groups: group 1, bolus-tracking method with either intravenous route (n = 20); group 2, 1-minute-delay scan with single antecubital route (n = 36); group 3, 1-minute-delay scan with both antecubital routes (n = 2); group 4, 1-minute-delay scan with foot vein route (n = 3); group 5, 1-minute-delay scan with simultaneous infusion via both antecubital and foot vein routes (n = 2); group 6, 3-minute-delay scan with single antecubital route (n = 22); and group 7, 3-minute-delay scan with foot vein route (n = 3). The presence of beam-hardening artifact, uniform enhancement, and optimal enhancement was evaluated at the right pulmonary artery (RPA), left pulmonary artery (LPA), and Fontan tract. Optimal enhancement was determined when evaluation of thrombus was possible. Standard deviation was measured at the RPA, LPA, and Fontan tract. Beam-hardening artifacts of the RPA, LPA, and Fontan tract were frequently present in groups 1, 4, and 5. The success rate of uniform and optimal enhancement was highest (100%) in groups 6 and 7, followed by group 2 (75%). An SD of less than 30 Hounsfield unit for the pulmonary artery and Fontan tract was found in groups 3, 6, and 7. The optimal enhancement of the pulmonary arteries and Fontan tract can be achieved by a 3-minute-delay scan irrespective of the intravenous route location.

Practical application of contrast-enhanced magnetic resonance mammography [CE-MRM] by an algorithm combining morphological and enhancement patterns.

PubMed

Potente, Giuseppe; Messineo, Daniela; Maggi, Claudia; Savelli, Sara

2009-03-01

The purpose of this article is to report our practical utilization of dynamic contrast-enhanced magnetic resonance mammography [DCE-MRM] in the diagnosis of breast lesions. In many European centers, was preferred a high-temporal acquisition of both breasts simultaneously in a large FOV. We preferred to scan single breasts, with the aim to combine the analysis of the contrast intake and washout with the morphological evaluation of breast lesions. We followed an interpretation model, based upon a diagnostic algorithm, which combined contrast enhancement with morphological evaluation, in order to increase our confidence in diagnosis. DCE-MRM with our diagnostic algorithm has identified 179 malignant and 41 benign lesions; final outcome has identified 178 malignant and 42 benign lesions, 3 false positives and 2 false negatives. Sensitivity of CE-MRM was 98.3%; specificity, 95.1%; positive predictive value, 98.9%; negative predictive value, 92.8% and accuracy, 97.7%.

SPM local oxidation nanolithography with active control of cantilever dynamics

NASA Astrophysics Data System (ADS)

Nishimura, S.; Takemura, Y.; Shirakashi, J.

2007-04-01

Local oxidation nanolithography using scanning probe microscope (SPM) has enabled us to fabricate nanometer-scale oxide wires on material surfaces. Here, we study tapping mode SPM local oxidation experiments for silicon by controlling the dynamic properties of the cantilever. Dependence of feature size of fabricated oxide wires on the amplitude of the cantilever was precisely investigated. The quality factor (Q) was fixed at a natural value of ~500. By enhancing the amplitude of the cantilever, both width and height of fabricated Si oxide wires were decreased. With the variation of the amplitude of the cantilever from 0.5 V to 3.0 V (DC voltage = 22.5 V, scanning speed = 20 nm/s), the feature size of Si oxide wires was well controlled, ranging from 40 nm to 18 nm in width and 2.3 nm to 0.6 nm in height. Standard deviation of width on Si oxide wires formed by tapping mode SPM is around 2.0 nm, which is smaller than that of contact mode Si oxide wires. Furthermore, the variation of the oscillation amplitude of the cantilever does not affect the size uniformity of the wires. These results imply that the SPM local oxidation nanolithography with active control of cantilever dynamics is a useful technique for producing higher controllability on the nanometer-scale fabrication of Si oxide wires.

Simple green approach to reinforce natural rubber with bacterial cellulose nanofibers.

PubMed

Trovatti, Eliane; Carvalho, Antonio J F; Ribeiro, Sidney J L; Gandini, Alessandro

2013-08-12

Natural rubber (NR) is a renewable polymer with a wide range of applications, which is constantly tailored, further increasing its utilizations. The tensile strength is one of its most important properties susceptible of being enhanced by the simple incorporation of nanofibers. The preparation and characterization of natural-rubber based nanocomposites reinforced with bacterial cellulose (BC) and bacterial cellulose coated with polystyrene (BCPS), yielded high performance materials. The nanocomposites were prepared by a simple and green process, and characterized by tensile tests, dynamical mechanical analysis (DMA), scanning electron microscopy (SEM), and swelling experiments. The effect of the nanofiber content on morphology, static, and dynamic mechanical properties was also investigated. The results showed an increase in the mechanical properties, such as Young's modulus and tensile strength, even with modest nanofiber loadings.

Liver perfusion imaging in patients with primary and metastatic liver malignancy: prospective comparison between 99mTc-MAA spect and dynamic CT perfusion.

PubMed

Reiner, Caecilia S; Goetti, Robert; Burger, Irene A; Fischer, Michael A; Frauenfelder, Thomas; Knuth, Alexander; Pfammatter, Thomas; Schaefer, Niklaus; Alkadhi, Hatem

2012-05-01

To prospectively analyze the correlation between parameters of liver perfusion from technetium99m-macroaggregates of albumin (99mTc-MAA) single photon emission computed tomography (SPECT) with those obtained from dynamic CT perfusion in patients with primary or metastatic liver malignancy. Twenty-five consecutive patients (11 women, 14 men; mean age 60.9 ± 10.8; range: 32-78 years) with primary (n = 5) or metastatic (n = 20) liver malignancy planned to undergo selective internal radiotherapy underwent dynamic contrast-enhanced CT liver perfusion imaging (four-dimensional spiral mode, scan range 14.8 cm, 15 scans, cycle time 3 seconds) and 99m)Tc-MAA SPECT after intraarterial injection of 180 MBq 99mTc-MAA on the same day. Data were evaluated by two blinded and independent readers for the parameters arterial liver perfusion (ALP), portal venous perfusion (PVP), and total liver perfusion (TLP) from CT, and the 99mTc-MAA uptake-ratio of tumors in relation to normal liver parenchyma from SPECT. Interreader agreements for quantitative perfusion parameters were high for dynamic CT (r = 0.90-0.98, each P < .01) and 99mTc -MAA SPECT (r = 0.91, P < .01). Significant correlation was found between 99mTc-MAA uptake ratio and ALP (r = 0.7, P < .01) in liver tumors. No significant correlation was found between 99mTc-MAA uptake ratio, PVP (r = -0.381, P = .081), and TLP (r = 0.039, P = .862). This study indicates that in patients with primary and metastatic liver malignancy, ALP obtained by dynamic CT liver perfusion significantly correlates with the 99mTc-MAA uptake ratio obtained by SPECT. Copyright © 2012 AUR. Published by Elsevier Inc. All rights reserved.

Radiation injury vs. recurrent brain metastasis: combining textural feature radiomics analysis and standard parameters may increase 18F-FET PET accuracy without dynamic scans.

PubMed

Lohmann, Philipp; Stoffels, Gabriele; Ceccon, Garry; Rapp, Marion; Sabel, Michael; Filss, Christian P; Kamp, Marcel A; Stegmayr, Carina; Neumaier, Bernd; Shah, Nadim J; Langen, Karl-Josef; Galldiks, Norbert

2017-07-01

We investigated the potential of textural feature analysis of O-(2-[ 18 F]fluoroethyl)-L-tyrosine ( 18 F-FET) PET to differentiate radiation injury from brain metastasis recurrence. Forty-seven patients with contrast-enhancing brain lesions (n = 54) on MRI after radiotherapy of brain metastases underwent dynamic 18 F-FET PET. Tumour-to-brain ratios (TBRs) of 18 F-FET uptake and 62 textural parameters were determined on summed images 20-40 min post-injection. Tracer uptake kinetics, i.e., time-to-peak (TTP) and patterns of time-activity curves (TAC) were evaluated on dynamic PET data from 0-50 min post-injection. Diagnostic accuracy of investigated parameters and combinations thereof to discriminate between brain metastasis recurrence and radiation injury was compared. Diagnostic accuracy increased from 81 % for TBR mean alone to 85 % when combined with the textural parameter Coarseness or Short-zone emphasis. The accuracy of TBR max alone was 83 % and increased to 85 % after combination with the textural parameters Coarseness, Short-zone emphasis, or Correlation. Analysis of TACs resulted in an accuracy of 70 % for kinetic pattern alone and increased to 83 % when combined with TBR max . Textural feature analysis in combination with TBRs may have the potential to increase diagnostic accuracy for discrimination between brain metastasis recurrence and radiation injury, without the need for dynamic 18 F-FET PET scans. • Textural feature analysis provides quantitative information about tumour heterogeneity • Textural features help improve discrimination between brain metastasis recurrence and radiation injury • Textural features might be helpful to further understand tumour heterogeneity • Analysis does not require a more time consuming dynamic PET acquisition.

Si-strip photon counting detectors for contrast-enhanced spectral mammography

NASA Astrophysics Data System (ADS)

Chen, Buxin; Reiser, Ingrid; Wessel, Jan C.; Malakhov, Nail; Wawrzyniak, Gregor; Hartsough, Neal E.; Gandhi, Thulasi; Chen, Chin-Tu; Iwanczyk, Jan S.; Barber, William C.

2015-08-01

We report on the development of silicon strip detectors for energy-resolved clinical mammography. Typically, X-ray integrating detectors based on scintillating cesium iodide CsI(Tl) or amorphous selenium (a-Se) are used in most commercial systems. Recently, mammography instrumentation has been introduced based on photon counting Si strip detectors. The required performance for mammography in terms of the output count rate, spatial resolution, and dynamic range must be obtained with sufficient field of view for the application, thus requiring the tiling of pixel arrays and particular scanning techniques. Room temperature Si strip detector, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel, provided that the sensors are designed for rapid signal formation across the X-ray energy ranges of the application. We present our methods and results from the optimization of Si-strip detectors for contrast enhanced spectral mammography. We describe the method being developed for quantifying iodine contrast using the energy-resolved detector with fixed thresholds. We demonstrate the feasibility of the method by scanning an iodine phantom with clinically relevant contrast levels.

The value of Doppler LiDAR systems to monitor turbulence intensity during storm events in order to enhance aviation safety in Iceland

NASA Astrophysics Data System (ADS)

Yang, Shu; Nína Petersen, Guðrún; Finger, David C.

2017-04-01

Turbulence and wind shear are a major natural hazards for aviation safety in Iceland. The temporal and spatial scale of atmospheric turbulence is very dynamic, requiring an adequate method to detect and monitor turbulence with high resolution. The Doppler Light Detection and Ranging (LiDAR) system can provide continuous information about the wind field using the Doppler effect form emitted light signals. In this study, we use a Leosphere Windcube 200s LiDAR systems stationed near Reykjavik city Airport and at Keflavik International Airport, Iceland, to evaluate turbulence intensity by estimating eddy dissipation rate (EDR). For this purpose, we retrieved radial wind velocity observations from Velocity Azimuth Display (VAD) scans (360°scans at 15° and 75° elevation angle) to compute EDR. The method was used to monitor and characterize storm events in fall 2016 and the following winter. The preliminary result reveal that the LiDAR observations can detect and quantify atmospheric turbulence with high spatial and temporal resolution. This finding is an important step towards enhanced aviation safety in subpolar climate characterized by sever wind turbulence.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Bin; Brown, Chance C.; Huang, Jingsong

Ionicity plays an important role in determining material properties, as well as optoelectronic performance of organometallic trihalide perovskites (OTPs). Ion migration in OTP films has recently been under intensive investigation by various scanning probe microscopy (SPM) techniques. Controversial findings regarding the role of grain boundaries (GBs) associated with ion migration are often encountered, likely as a result of feedback errors and topographic effects common in to SPM. In this work, electron microscopy and spectroscopy (scanning transmission electron microscopy/electron energy loss spectroscopy) are combined with a novel, open-loop, band-excitation, (contact) Kelvin probe force microscopy (BE-KPFM and BE-cKPFM), in conjunction with abmore » initio molecular dynamics simulations to examine the ion behavior in the GBs of CH 3NH 3PbI 3 perovskite films. Furthermore, this combination of diverse techniques provides a deeper understanding of the differences between ion migration within GBs and interior grains in OTP films. Our work demonstrates that ion migration can be significantly enhanced by introducing additional mobile Cl - ions into GBs. The enhancement of ion migration may serve as the first step toward the development of high-performance electrically and optically tunable memristors and synaptic devices.« less

Two-dimensional signal processing with application to image restoration

NASA Technical Reports Server (NTRS)

Assefi, T.

1974-01-01

A recursive technique for modeling and estimating a two-dimensional signal contaminated by noise is presented. A two-dimensional signal is assumed to be an undistorted picture, where the noise introduces the distortion. Both the signal and the noise are assumed to be wide-sense stationary processes with known statistics. Thus, to estimate the two-dimensional signal is to enhance the picture. The picture representing the two-dimensional signal is converted to one dimension by scanning the image horizontally one line at a time. The scanner output becomes a nonstationary random process due to the periodic nature of the scanner operation. Procedures to obtain a dynamical model corresponding to the autocorrelation function of the scanner output are derived. Utilizing the model, a discrete Kalman estimator is designed to enhance the image.

Diagnostic performance of different measurement methods for lung nodule enhancement at quantitative contrast-enhanced computed tomography

NASA Astrophysics Data System (ADS)

Wormanns, Dag; Klotz, Ernst; Dregger, Uwe; Beyer, Florian; Heindel, Walter

2004-05-01

Lack of angiogenesis virtually excludes malignancy of a pulmonary nodule; assessment with quantitative contrast-enhanced CT (QECT) requires a reliable enhancement measurement technique. Diagnostic performance of different measurement methods in the distinction between malignant and benign nodules was evaluated. QECT (unenhanced scan and 4 post-contrast scans) was performed in 48 pulmonary nodules (12 malignant, 12 benign, 24 indeterminate). Nodule enhancement was the difference between the highest nodule density at any post-contrast scan and the unenhanced scan. Enhancement was determined with: A) the standard 2D method; B) a 3D method consisting of segmentation, removal of peripheral structures and density averaging. Enhancement curves were evaluated for their plausibility using a predefined set of criteria. Sensitivity and specificity were 100% and 33% for the 2D method resp. 92% and 55% for the 3D method using a threshold of 20 HU. One malignant nodule did not show significant enhancement with method B due to adjacent atelectasis which disappeared within the few minutes of the QECT examination. Better discrimination between benign and malignant lesions was achieved with a slightly higher threshold than proposed in the literature. Application of plausibility criteria to the enhancement curves rendered less plausibility faults with the 3D method. A new 3D method for analysis of QECT scans yielded less artefacts and better specificity in the discrimination between benign and malignant pulmonary nodules when using an appropriate enhancement threshold. Nevertheless, QECT results must be interpreted with care.

Analysis on the dynamic error for optoelectronic scanning coordinate measurement network

NASA Astrophysics Data System (ADS)

Shi, Shendong; Yang, Linghui; Lin, Jiarui; Guo, Siyang; Ren, Yongjie

2018-01-01

Large-scale dynamic three-dimension coordinate measurement technique is eagerly demanded in equipment manufacturing. Noted for advantages of high accuracy, scale expandability and multitask parallel measurement, optoelectronic scanning measurement network has got close attention. It is widely used in large components jointing, spacecraft rendezvous and docking simulation, digital shipbuilding and automated guided vehicle navigation. At present, most research about optoelectronic scanning measurement network is focused on static measurement capacity and research about dynamic accuracy is insufficient. Limited by the measurement principle, the dynamic error is non-negligible and restricts the application. The workshop measurement and positioning system is a representative which can realize dynamic measurement function in theory. In this paper we conduct deep research on dynamic error resources and divide them two parts: phase error and synchronization error. Dynamic error model is constructed. Based on the theory above, simulation about dynamic error is carried out. Dynamic error is quantized and the rule of volatility and periodicity has been found. Dynamic error characteristics are shown in detail. The research result lays foundation for further accuracy improvement.

Using fluorescence spectroscopy coupled with chemometric analysis to investigate the origin, composition, and dynamics of dissolved organic matter in leachate-polluted groundwater.

PubMed

He, Xiao-Song; Xi, Bei-Dou; Gao, Ru-Tai; Wang, Lei; Ma, Yan; Cui, Dong-Yu; Tan, Wen-Bing

2015-06-01

Groundwater was collected in 2011 and 2012, and fluorescence spectroscopy coupled with chemometric analysis was employed to investigate the composition, origin, and dynamics of dissolved organic matter (DOM) in the groundwater. The results showed that the groundwater DOM comprised protein-, fulvic-, and humic-like substances, and the protein-like component originated predominantly from microbial production. The groundwater pollution by landfill leachate enhanced microbial activity and thereby increased microbial by-product-like material such as protein-like component in the groundwater. Excitation-emission matrix fluorescence spectra combined with parallel factor analysis showed that the protein-like matter content increased from 2011 to 2012 in the groundwater, whereas the fulvic- and humic-like matter concentration exhibited no significant changes. In addition, synchronous-scan fluorescence spectra coupled with two-dimensional correlation analysis showed that the change of the fulvic- and humic-like matter was faster than that of the protein-like substances, as the groundwater flowed from upstream to downstream in 2011, but slower than that of the protein-like substance in 2012 due to the enhancement of microbial activity. Fluorescence spectroscopy combined with chemometric analysis can investigate groundwater pollution characteristics and monitor DOM dynamics in groundwater.

Preparation and characterization of citral-loaded solid lipid nanoparticles.

PubMed

Tian, Huaixiang; Lu, Zhuoyan; Li, Danfeng; Hu, Jing

2018-05-15

Citral-loaded solid lipid nanoparticles (citral-SLNs) were prepared via a high-pressure homogenization method, using glyceryl monostearate (GMS) as the solid lipid and a mixture of Tween 80 (T-80) and Span 80 (S-80) at a weight ratio of 1:1 as the surfactant. The microstructure and properties of the citral-SLNs were characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). The chemical stability of citral in the citral-SLNs was analyzed by solid-phase microextraction gas chromatography (SPME-GC). The GC results showed that 67.0% of the citral remained in the citral-SLN suspensions after 12 days, while only 8.22% remained in the control. Therefore, the encapsulation of citral in the solid lipid can enhance its stability in acidic surroundings. Copyright © 2017 Elsevier Ltd. All rights reserved.

Robust Adaptive Thresholder For Document Scanning Applications

NASA Astrophysics Data System (ADS)

Hsing, To R.

1982-12-01

In document scanning applications, thresholding is used to obtain binary data from a scanner. However, due to: (1) a wide range of different color backgrounds; (2) density variations of printed text information; and (3) the shading effect caused by the optical systems, the use of adaptive thresholding to enhance the useful information is highly desired. This paper describes a new robust adaptive thresholder for obtaining valid binary images. It is basically a memory type algorithm which can dynamically update the black and white reference level to optimize a local adaptive threshold function. The results of high image quality from different types of simulate test patterns can be obtained by this algorithm. The software algorithm is described and experiment results are present to describe the procedures. Results also show that the techniques described here can be used for real-time signal processing in the varied applications.

Low back pain: an assessment using positional MRI and MDT.

PubMed

Hedberg, Karen; Alexander, Lyndsay A; Cooper, Kay; Hancock, Elizabeth; Ross, Jenny; Smith, Francis W

2013-04-01

Current guidelines advise against the use of routine imaging for low back pain. Positional MRI can provide enhanced assessment of the lumbar spine in functionally loaded positions which are often relevant to the presenting clinical symptoms. The purpose of this case report is to highlight the use of positional MRI in the assessment and classification of a subject with low back pain. A low back pain subject underwent a Mechanical Diagnosis and Therapy (MDT) assessment and positional MRI scan of the lumbar spine. The MDT assessment classified the subject as "other" since the subjective history indicated a possible posterior derangement whilst the objective assessment indicated a possible anterior derangement. Positional MRI scanning in flexed, upright and extended sitting postures confirmed the MDT assessment findings to reveal a dynamic spinal stenosis which reduced in flexion and increased in extension. Copyright © 2012 Elsevier Ltd. All rights reserved.

Structural, electronic, and dynamical properties of liquid water by ab initio molecular dynamics based on SCAN functional within the canonical ensemble

NASA Astrophysics Data System (ADS)

Zheng, Lixin; Chen, Mohan; Sun, Zhaoru; Ko, Hsin-Yu; Santra, Biswajit; Dhuvad, Pratikkumar; Wu, Xifan

2018-04-01

We perform ab initio molecular dynamics (AIMD) simulation of liquid water in the canonical ensemble at ambient conditions using the strongly constrained and appropriately normed (SCAN) meta-generalized-gradient approximation (GGA) functional approximation and carry out systematic comparisons with the results obtained from the GGA-level Perdew-Burke-Ernzerhof (PBE) functional and Tkatchenko-Scheffler van der Waals (vdW) dispersion correction inclusive PBE functional. We analyze various properties of liquid water including radial distribution functions, oxygen-oxygen-oxygen triplet angular distribution, tetrahedrality, hydrogen bonds, diffusion coefficients, ring statistics, density of states, band gaps, and dipole moments. We find that the SCAN functional is generally more accurate than the other two functionals for liquid water by not only capturing the intermediate-range vdW interactions but also mitigating the overly strong hydrogen bonds prescribed in PBE simulations. We also compare the results of SCAN-based AIMD simulations in the canonical and isothermal-isobaric ensembles. Our results suggest that SCAN provides a reliable description for most structural, electronic, and dynamical properties in liquid water.

High Precision Sunphotometer using Wide Dynamic Range (WDR) Camera Tracking

NASA Astrophysics Data System (ADS)

Liss, J.; Dunagan, S. E.; Johnson, R. R.; Chang, C. S.; LeBlanc, S. E.; Shinozuka, Y.; Redemann, J.; Flynn, C. J.; Segal-Rosenhaimer, M.; Pistone, K.; Kacenelenbogen, M. S.; Fahey, L.

2016-12-01

High Precision Sunphotometer using Wide Dynamic Range (WDR) Camera TrackingThe NASA Ames Sun-photometer-Satellite Group, DOE, PNNL Atmospheric Sciences and Global Change Division, and NASA Goddard's AERONET (AErosol RObotic NETwork) team recently collaborated on the development of a new airborne sunphotometry instrument that provides information on gases and aerosols extending far beyond what can be derived from discrete-channel direct-beam measurements, while preserving or enhancing many of the desirable AATS features (e.g., compactness, versatility, automation, reliability). The enhanced instrument combines the sun-tracking ability of the current 14-Channel NASA Ames AATS-14 with the sky-scanning ability of the ground-based AERONET Sun/sky photometers, while extending both AATS-14 and AERONET capabilities by providing full spectral information from the UV (350 nm) to the SWIR (1,700 nm). Strengths of this measurement approach include many more wavelengths (isolated from gas absorption features) that may be used to characterize aerosols and detailed (oversampled) measurements of the absorption features of specific gas constituents. The Sky Scanning Sun Tracking Airborne Radiometer (3STAR) replicates the radiometer functionality of the AATS-14 instrument but incorporates modern COTS technologies for all instruments subsystems. A 19-channel radiometer bundle design is borrowed from a commercial water column radiance instrument manufactured by Biospherical Instruments of San Diego California (ref, Morrow and Hooker)) and developed using NASA funds under the Small Business Innovative Research (SBIR) program. The 3STAR design also incorporates the latest in robotic motor technology embodied in Rotary actuators from Oriental motor Corp. having better than 15 arc seconds of positioning accuracy. Control system was designed, tested and simulated using a Hybrid-Dynamical modeling methodology. The design also replaces the classic quadrant detector tracking sensor with a wide dynamic range camera that provides a high precision solar position tracking signal as well as an image of the sky in the 45° field of view around the solar axis, which can be of great assistance in flagging data for cloud effects or other factors that might impact data quality.

Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) Instrument Improvements

NASA Technical Reports Server (NTRS)

Dunagan, Stephen E.; Redemann, Jens; Chang, Cecilia; Dahlgren, Robert; Fahey, Lauren; Flynn, Connor; Johnson, Roy; Kacenelenbogen, Meloe; Leblanc, Samuel; Liss, Jordan;

A fully automated system for quantification of background parenchymal enhancement in breast DCE-MRI

NASA Astrophysics Data System (ADS)

Ufuk Dalmiş, Mehmet; Gubern-Mérida, Albert; Borelli, Cristina; Vreemann, Suzan; Mann, Ritse M.; Karssemeijer, Nico

2016-03-01

Background parenchymal enhancement (BPE) observed in breast dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) has been identified as an important biomarker associated with risk for developing breast cancer. In this study, we present a fully automated framework for quantification of BPE. We initially segmented fibroglandular tissue (FGT) of the breasts using an improved version of an existing method. Subsequently, we computed BPEabs (volume of the enhancing tissue), BPErf (BPEabs divided by FGT volume) and BPErb (BPEabs divided by breast volume), using different relative enhancement threshold values between 1% and 100%. To evaluate and compare the previous and improved FGT segmentation methods, we used 20 breast DCE-MRI scans and we computed Dice similarity coefficient (DSC) values with respect to manual segmentations. For evaluation of the BPE quantification, we used a dataset of 95 breast DCE-MRI scans. Two radiologists, in individual reading sessions, visually analyzed the dataset and categorized each breast into minimal, mild, moderate and marked BPE. To measure the correlation between automated BPE values to the radiologists' assessments, we converted these values into ordinal categories and we used Spearman's rho as a measure of correlation. According to our results, the new segmentation method obtained an average DSC of 0.81 0.09, which was significantly higher (p<0.001) compared to the previous method (0.76 0.10). The highest correlation values between automated BPE categories and radiologists' assessments were obtained with the BPErf measurement (r=0.55, r=0.49, p<0.001 for both), while the correlation between the scores given by the two radiologists was 0.82 (p<0.001). The presented framework can be used to systematically investigate the correlation between BPE and risk in large screening cohorts.

Static and (quasi)dynamic calibration of stroboscopic scanning white light interferometer

NASA Astrophysics Data System (ADS)

Seppä, Jeremias; Kassamakov, Ivan; Nolvi, Anton; Heikkinen, Ville; Paulin, Tor; Lassila, Antti; Hao, Ling; Hæggsröm, Edward

2013-04-01

A scanning white light interferometer can characterize out of plane features and motion in M(N)EMS devices. Like any other form and displacement measuring instrument, the scanning interferometer results should be linked to the metre definition to be comparable and unambiguous. Traceability is built up by careful error characterization and calibration of the interferometer. The main challenge in this calibration is to have a reference device producing accurate and reproducible dynamic out-of-plane displacement when submitted to standard loads. We use a flat mirror attached to a piezoelectric transducer for static and (quasi)dynamic calibration of a stroboscopic scanning light interferometer. First we calibrated the piezo-scanned flexure guided transducer stage using a symmetric differential heterodyne laser interferometer developed at the Centre for Metrology and Accreditation (MIKES). The standard uncertainty of the piezo stage motion calibration was 3.0 nm. Then we used the piezo-stage as a transfer standard to calibrate our stroboscopic interferometer whose light source was pulsed at 200 Hz and 400 Hz with 0.5% duty cycle. We measured the static position and (quasi)dynamic motion of the attached mirror relative to a reference surface. This methodology permits calibrating the vertical scale of the stroboscopic scanning white light interferometer.

A hinge migration mechanism unlocks the evolution of green-to-red photoconversion in GFP-like proteins

DOE PAGES

Kim, Hanseong; Zou, Taisong; Modi, Chintan; ...

2014-12-31

In proteins, functional divergence involves mutations that modify structure and dynamics. In this paper, we provide experimental evidence for an evolutionary mechanism driven solely by long-range dynamic motions without significant backbone adjustments, catalytic group rearrangements, or changes in subunit assembly. Crystallographic structures were determined for several reconstructed ancestral proteins belonging to a GFP class frequently employed in superresolution microscopy. Their chain flexibility was analyzed using molecular dynamics and perturbation response scanning. The green-to-red photoconvertible phenotype appears to have arisen from a common green ancestor by migration of a knob-like anchoring region away from the active site diagonally across the βmore » barrel fold. The allosterically coupled mutational sites provide active site conformational mobility via epistasis. We propose that light-induced chromophore twisting is enhanced in a reverse-protonated subpopulation, activating internal acid-base chemistry and backbone cleavage to enlarge the chromophore. Finally, dynamics-driven hinge migration may represent a more general platform for the evolution of novel enzyme activities.« less

Dynamic 68Ga-DOTATOC PET/CT and static image in NET patients. Correlation of parameters during PRRT.

PubMed

Van Binnebeek, Sofie; Koole, Michel; Terwinghe, Christelle; Baete, Kristof; Vanbilloen, Bert; Haustermans, Karine; Clement, Paul M; Bogaerts, Kris; Verbruggen, Alfons; Nackaerts, Kris; Van Cutsem, Eric; Verslype, Chris; Mottaghy, Felix M; Deroose, Christophe M

2016-06-28

To investigate the relationship between the dynamic parameters (Ki) and static image-derived parameters of 68Ga-DOTATOC-PET, to determine which static parameter best reflects underlying somatostatin-receptor-expression (SSR) levels on neuroendocrine tumours (NETs). 20 patients with metastasized NETs underwent a dynamic and static 68Ga-DOTATOC-PET before PRRT and at 7 and 40 weeks after the first administration of 90Y-DOTATOC (in total 4 cycles were planned); 175 lesions were defined and analyzed on the dynamic as well as static scans. Quantitative analysis was performed using the software PMOD. One to five target lesions per patient were chosen and delineated manually on the baseline dynamic scan and further, on the corresponding static 68Ga-DOTATOC-PET and the dynamic and static 68Ga-DOTATOC-PET at the other time-points; SUVmax and SUVmean of the lesions was assessed on the other six scans. The input function was retrieved from the abdominal aorta on the images. Further on, Ki was calculated using the Patlak-Plot. At last, 5 reference regions for normalization of SUVtumour were delineated on the static scans resulting in 5 ratios (SUVratio). SUVmax and SUVmean of the tumoural lesions on the dynamic 68Ga-DOTATOC-PET had a very strong correlation with the corresponding parameters in the static scan (R²: 0.94 and 0.95 respectively). SUVmax, SUVmean and Ki of the lesions showed a good linear correlation; the SUVratios correlated poorly with Ki. A significantly better correlation was noticed between Ki and SUVtumour(max and mean) (p < 0.0001). As the dynamic parameter Ki correlates best with the absolute SUVtumour, SUVtumour best reflects underlying SSR-levels in NETs.

Dynamic observation on the growth behaviors in manganese silicide/silicon nanowire heterostructures.

PubMed

Hsieh, Yu-Hsun; Chiu, Chung-Hua; Huang, Chun-Wei; Chen, Jui-Yuan; Lin, Wan-Jhen; Wu, Wen-Wei

2015-02-07

Metal silicide nanowires (NWs) are very interesting materials with diverse physical properties. Among the silicides, manganese silicide nanostructures have attracted wide attention due to their several potential applications, including in microelectronics, optoelectronics, spintronics and thermoelectric devices. In this work, we exhibited the formation of pure manganese silicide and manganese silicide/silicon nanowire heterostructures through solid state reaction with line contacts between manganese pads and silicon NWs. Dynamical process and phase characterization were investigated by in situ transmission electron microscopy (in situ TEM) and spherical aberration corrected scanning transmission electron microscopy (Cs-corrected STEM), respectively. The growth dynamics of the manganese silicide phase under thermal effects were systematically studied. Additionally, Al2O3, serving as the surface oxide, altered the growth behavior of the MnSi nanowire, enhancing the silicide/Si epitaxial growth and effecting the diffusion process in the silicon nanowire as well. In addition to fundamental science, this significant study has great potential in advancing future processing techniques in nanotechnology and related applications.

Influence of wing tip morphology on vortex dynamics of flapping flight

NASA Astrophysics Data System (ADS)

Krishna, Swathi; Mulleners, Karen

2013-11-01

The mechanism of flapping wing flight provides insects with extraordinary flight capabilities. The uniquely shaped wing tips give insects an edge in flight performance and the interaction between the leading edge vortices and wing tip vortices enhance their propelling efficiencies and manoeuvrability. These are qualities that are sought after in current-day Micro Air Vehicles. A detailed understanding of the vortex dynamics of flapping flight and the influence of the wing tip planform is imperative for technical application. An experimental study is conducted to investigate the effects of different wing tip planforms on the formation, evolution and interaction of vortical structures. We thereby focus on the interaction between the coherent structures evolving from the leading edge and the wing tip during pitching and flapping motions.The spatial and temporal evolution of the three-dimensional flow structures are determined using Scanning (Stereo) Particle Image Velocimetry and an in-depth coherent structure analysis. By comparing the vortex dynamics, the aerodynamic performance of various wing tip planforms are evaluated.

Laser-Based Slam with Efficient Occupancy Likelihood Map Learning for Dynamic Indoor Scenes

NASA Astrophysics Data System (ADS)

Li, Li; Yao, Jian; Xie, Renping; Tu, Jinge; Feng, Chen

2016-06-01

Location-Based Services (LBS) have attracted growing attention in recent years, especially in indoor environments. The fundamental technique of LBS is the map building for unknown environments, this technique also named as simultaneous localization and mapping (SLAM) in robotic society. In this paper, we propose a novel approach for SLAMin dynamic indoor scenes based on a 2D laser scanner mounted on a mobile Unmanned Ground Vehicle (UGV) with the help of the grid-based occupancy likelihood map. Instead of applying scan matching in two adjacent scans, we propose to match current scan with the occupancy likelihood map learned from all previous scans in multiple scales to avoid the accumulation of matching errors. Due to that the acquisition of the points in a scan is sequential but not simultaneous, there unavoidably exists the scan distortion at different extents. To compensate the scan distortion caused by the motion of the UGV, we propose to integrate a velocity of a laser range finder (LRF) into the scan matching optimization framework. Besides, to reduce the effect of dynamic objects such as walking pedestrians often existed in indoor scenes as much as possible, we propose a new occupancy likelihood map learning strategy by increasing or decreasing the probability of each occupancy grid after each scan matching. Experimental results in several challenged indoor scenes demonstrate that our proposed approach is capable of providing high-precision SLAM results.

Accelerated dynamic EPR imaging using fast acquisition and compressive recovery

NASA Astrophysics Data System (ADS)

Ahmad, Rizwan; Samouilov, Alexandre; Zweier, Jay L.

2016-12-01

Electron paramagnetic resonance (EPR) allows quantitative imaging of tissue redox status, which provides important information about ischemic syndromes, cancer and other pathologies. For continuous wave EPR imaging, however, poor signal-to-noise ratio and low acquisition efficiency limit its ability to image dynamic processes in vivo including tissue redox, where conditions can change rapidly. Here, we present a data acquisition and processing framework that couples fast acquisition with compressive sensing-inspired image recovery to enable EPR-based redox imaging with high spatial and temporal resolutions. The fast acquisition (FA) allows collecting more, albeit noisier, projections in a given scan time. The composite regularization based processing method, called spatio-temporal adaptive recovery (STAR), not only exploits sparsity in multiple representations of the spatio-temporal image but also adaptively adjusts the regularization strength for each representation based on its inherent level of the sparsity. As a result, STAR adjusts to the disparity in the level of sparsity across multiple representations, without introducing any tuning parameter. Our simulation and phantom imaging studies indicate that a combination of fast acquisition and STAR (FASTAR) enables high-fidelity recovery of volumetric image series, with each volumetric image employing less than 10 s of scan. In addition to image fidelity, the time constants derived from FASTAR also match closely to the ground truth even when a small number of projections are used for recovery. This development will enhance the capability of EPR to study fast dynamic processes that cannot be investigated using existing EPR imaging techniques.

Public Data Set: Radially Scanning Magnetic Probes to Study Local Helicity Injection Dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richner, Nathan J; Bongard, Michael W; Fonck, Raymond J

This data set contains openly-documented, machine readable digital research data corresponding to figures published in N.J. Richner et al., 'Radially Scanning Magnetic Probes to Study Local Helicity Injection Dynamics,' accepted for publication in Rev. Sci. Instrum (2018).

R1 changes in the human placenta at 3 T in response to a maternal oxygen challenge protocol.

PubMed

Ingram, Emma; Hawkins, Lauren; Morris, David M; Myers, Jenny; Sibley, Colin P; Johnstone, Edward D; Naish, Josephine H

2016-03-01

Oxygen-enhanced MRI non-invasively monitors placental oxygenation in-vivo. This technique has been demonstrated at 1.5 Tesla (T) in healthy pregnancies. The aim of this study was to investigate whether findings are comparable at 3T. Nine pregnant volunteers underwent MRI at 3T. Scans obtained R1 (1/T1) measures from T1 maps under air, followed by a dynamic series breathing 100% oxygen. A statistically significant negative correlation was found between dR1 and gestation (P = 0.0008, r = -0.90, Pearson correlation test). The effect of the field strength was not significant within regression analysis. Placental Oxygen-Enhanced MRI at 3T gives comparable results to those previously obtained at 1.5T. Copyright © 2016 Elsevier Ltd. All rights reserved.

Partial scan artifact reduction (PSAR) for the assessment of cardiac perfusion in dynamic phase-correlated CT.

PubMed

Stenner, Philip; Schmidt, Bernhard; Bruder, Herbert; Allmendinger, Thomas; Haberland, Ulrike; Flohr, Thomas; Kachelriess, Marc

2009-12-01

Cardiac CT achieves its high temporal resolution by lowering the scan range from 2pi to pi plus fan angle (partial scan). This, however, introduces CT-value variations, depending on the angular position of the pi range. These partial scan artifacts are of the order of a few HU and prevent the quantitative evaluation of perfusion measurements. The authors present the new algorithm partial scan artifact reduction (PSAR) that corrects a dynamic phase-correlated scan without a priori information. In general, a full scan does not suffer from partial scan artifacts since all projections in [0, 2pi] contribute to the data. To maintain the optimum temporal resolution and the phase correlation, PSAR creates an artificial full scan pn(AF) by projectionwise averaging a set of neighboring partial scans pn(P) from the same perfusion examination (typically N approximately 30 phase-correlated partial scans distributed over 20 s and n = 1, ..., N). Corresponding to the angular range of each partial scan, the authors extract virtual partial scans pn(V) from the artificial full scan pn(AF). A standard reconstruction yields the corresponding images fn(P), fn(AF), and fn(V). Subtracting the virtual partial scan image fn(V) from the artificial full scan image fn(AF) yields an artifact image that can be used to correct the original partial scan image: fn(C) = fn(P) - fn(V) + fn(AF), where fn(C) is the corrected image. The authors evaluated the effects of scattered radiation on the partial scan artifacts using simulated and measured water phantoms and found a strong correlation. The PSAR algorithm has been validated with a simulated semianthropomorphic heart phantom and with measurements of a dynamic biological perfusion phantom. For the stationary phantoms, real full scans have been performed to provide theoretical reference values. The improvement in the root mean square errors between the full and the partial scans with respect to the errors between the full and the corrected scans is up to 54% for the simulations and 90% for the measurements. The phase-correlated data now appear accurate enough for a quantitative analysis of cardiac perfusion.

Comparison of dynamic contrast-enhanced MRI parameters of breast lesions at 1.5 and 3.0 T: a pilot study

PubMed Central

Pineda, F D; Medved, M; Fan, X; Ivancevic, M K; Abe, H; Shimauchi, A; Newstead, G M

2015-01-01

Objective: To compare dynamic contrast-enhanced (DCE) MRI parameters from scans of breast lesions at 1.5 and 3.0 T. Methods: 11 patients underwent paired MRI examinations in both Philips 1.5 and 3.0 T systems (Best, Netherlands) using a standard clinical fat-suppressed, T1 weighted DCE-MRI protocol, with 70–76 s temporal resolution. Signal intensity vs time curves were fit with an empirical mathematical model to obtain semi-quantitative measures of uptake and washout rates as well as time-to-peak enhancement (TTP). Maximum percent enhancement and signal enhancement ratio (SER) were also measured for each lesion. Percent differences between parameters measured at the two field strengths were compared. Results: TTP and SER parameters measured at 1.5 and 3.0 T were similar; with mean absolute differences of 19% and 22%, respectively. Maximum percent signal enhancement was significantly higher at 3 T than at 1.5 T (p = 0.006). Qualitative assessment showed that image quality was significantly higher at 3 T (p = 0.005). Conclusion: Our results suggest that TTP and SER are more robust to field strength change than other measured kinetic parameters, and therefore measurements of these parameters can be more easily standardized than measurements of other parameters derived from DCE-MRI. Semi-quantitative measures of overall kinetic curve shape showed higher reproducibility than do discrete classification of kinetic curve early and delayed phases in a majority of the cases studied. Advances in knowledge: Qualitative measures of curve shape are not consistent across field strength even when acquisition parameters are standardized. Quantitative measures of overall kinetic curve shape, by contrast, have higher reproducibility. PMID:25785918

Dynamic Charge Storage in Ionic Liquids-Filled Nanopores: Insight from a Computational Cyclic Voltammetry Study.

PubMed

He, Yadong; Huang, Jingsong; Sumpter, Bobby G; Kornyshev, Alexei A; Qiao, Rui

2015-01-02

Understanding the dynamic charge storage in nanoporous electrodes with room-temperature ionic liquid electrolytes is essential for optimizing them to achieve supercapacitors with high energy and power densities. Herein, we report coarse-grained molecular dynamics simulations of the cyclic voltammetry of supercapacitors featuring subnanometer pores and model ionic liquids. We show that the cyclic charging and discharging of nanopores are governed by the interplay between the external field-driven ion transport and the sloshing dynamics of ions inside of the pore. The ion occupancy along the pore length depends strongly on the scan rate and varies cyclically during charging/discharging. Unlike that at equilibrium conditions or low scan rates, charge storage at high scan rates is dominated by counterions while the contribution by co-ions is marginal or negative. These observations help explain the perm-selective charge storage observed experimentally. We clarify the mechanisms underlying these dynamic phenomena and quantify their effects on the efficiency of the dynamic charge storage in nanopores.

Comparison of image enhancement methods for the effective diagnosis in successive whole-body bone scans.

PubMed

Jeong, Chang Bu; Kim, Kwang Gi; Kim, Tae Sung; Kim, Seok Ki

2011-06-01

Whole-body bone scan is one of the most frequent diagnostic procedures in nuclear medicine. Especially, it plays a significant role in important procedures such as the diagnosis of osseous metastasis and evaluation of osseous tumor response to chemotherapy and radiation therapy. It can also be used to monitor the possibility of any recurrence of the tumor. However, it is a very time-consuming effort for radiologists to quantify subtle interval changes between successive whole-body bone scans because of many variations such as intensity, geometry, and morphology. In this paper, we present the most effective method of image enhancement based on histograms, which may assist radiologists in interpreting successive whole-body bone scans effectively. Forty-eight successive whole-body bone scans from 10 patients were obtained and evaluated using six methods of image enhancement based on histograms: histogram equalization, brightness-preserving bi-histogram equalization, contrast-limited adaptive histogram equalization, end-in search, histogram matching, and exact histogram matching (EHM). Comparison of the results of the different methods was made using three similarity measures peak signal-to-noise ratio, histogram intersection, and structural similarity. Image enhancement of successive bone scans using EHM showed the best results out of the six methods measured for all similarity measures. EHM is the best method of image enhancement based on histograms for diagnosing successive whole-body bone scans. The method for successive whole-body bone scans has the potential to greatly assist radiologists quantify interval changes more accurately and quickly by compensating for the variable nature of intensity information. Consequently, it can improve radiologists' diagnostic accuracy as well as reduce reading time for detecting interval changes.

Imaging the cardiac blood flow during CPR with EBCT in an animal model

NASA Astrophysics Data System (ADS)

Recheis, Wolfgang A.; Schuster, Antonius H.; Pallwein-Prettner, Leo; Kleinsasser, Axel; Loeckinger, Alexander; Hoermann, Christoph; zur Nedden, Dieter

2002-04-01

There are open questions concerning the hemodynamics during cardiopulmonary resuscitation (CPR). The purpose was to evaluate a model of the blood flow during CPR in specified anatomic regions. After cardiac arrest, one intubated swine under full intensive care supervision was scanned during CPR using an automated resuscitation device. CT scans were performed with an EBCT in the 50ms modus at eight levels, therefore covering most of the heart and pulmonary vessels. 50ml contrast agent was administered with 10ml/sec and a delay of five seconds to visualize the contrast agent passage through the heart and pulmonary circulation. The gray-value changes in previously specified ROIs were directly correlated with the resuscitation device position in respect to the thorax. The effects of CPR on the blood flow could be visualized dynamically by quantifying the contrast enhancement. The increase of gray values could be estimated with different delays, depending on the anatomical situation. The inflow and outflow dependent on thumper dynamics could be estimated. At the onset of contrast medium inflow, turbulence could be visualized in the right ventricle, which are caused by the inhomogeneous contrast medium distribution. Triggered EBCT during CPR offers the opportunity to study regional blood flow depending on chest compression.

Intermittent impact dynamics of a cantilever scanning a surface at high speed

NASA Astrophysics Data System (ADS)

Dey, S.; Kartik, V.

2018-03-01

In contact-mode scanning probe microscopy (SPM), the cantilever's dynamics are conventionally investigated by assuming the tip to be always in contact with the sample's surface. At high scanning speeds, however, the cantilever's inertia becomes dominant and the tip can therefore completely detach from the surface and start impacting upon it. Experiments at the macro-scale cannot emulate the complex micro-scale dynamics, as the system exhibits negligible effects due to meniscus forces and the surrounding medium's squeeze film damping; however, they can provide qualitative insight into the cantilever's dynamics at high frequencies, corresponding to those likely to be excited during video-rate SPM imaging. This paper investigates such intermittent impact dynamics for an upscaled cantilever, analytically, numerically, and experimentally. In contact-mode scanning, a critical scan speed exists beyond which the cantilever's tip loses contact with the sample's surface; a closed-form expression for this contact loss frequency is derived. At high scan speeds, impacts cause the cantilever to switch between different contact regimes: in-, off-, and grazing-contact; within each regime, the system's modal configuration is different. Experimentally-obtained Poincare maps indicate quasi-periodic behaviour at frequencies for which the response is repetitive, as is also predicted by the model. Intermittent impacts excite the sub- and super-harmonics of the excitation frequency, which are related to the natural frequencies of different system configurations based on the "effective" tip-end boundary conditions. The cantilever's response exhibits several phenomena, such as modal transition, beating, grazing, and possible chaotic behaviour, depending upon the relation between the excitation harmonics and the natural frequencies.

ART 3.5D: an algorithm to label arteries and veins from three-dimensional angiography.

PubMed

Barra, Beatrice; De Momi, Elena; Ferrigno, Giancarlo; Pero, Guglielmo; Cardinale, Francesco; Baselli, Giuseppe

2016-10-01

Preoperative three-dimensional (3-D) visualization of brain vasculature by digital subtraction angiography from computerized tomography (CT) in neurosurgery is gaining more and more importance, since vessels are the primary landmarks both for organs at risk and for navigation. Surgical embolization of cerebral aneurysms and arteriovenous malformations, epilepsy surgery, and stereoelectroencephalography are a few examples. Contrast-enhanced cone-beam computed tomography (CE-CBCT) represents a powerful facility, since it is capable of acquiring images in the operation room, shortly before surgery. However, standard 3-D reconstructions do not provide a direct distinction between arteries and veins, which is of utmost importance and is left to the surgeon's inference so far. Pioneering attempts by true four-dimensional (4-D) CT perfusion scans were already described, though at the expense of longer acquisition protocols, higher dosages, and sensible resolution losses. Hence, space is open to approaches attempting to recover the contrast dynamics from standard CE-CBCT, on the basis of anomalies overlooked in the standard 3-D approach. This paper aims at presenting algebraic reconstruction technique (ART) 3.5D, a method that overcomes the clinical limitations of 4-D CT, from standard 3-D CE-CBCT scans. The strategy works on the 3-D angiography, previously segmented in the standard way, and reprocesses the dynamics hidden in the raw data to recover an approximate dynamics in each segmented voxel. Next, a classification algorithm labels the angiographic voxels and artery or vein. Numerical simulations were performed on a digital phantom of a simplified 3-D vasculature with contrast transit. CE-CBCT projections were simulated and used for ART 3.5D testing. We achieved up to 90% classification accuracy in simulations, proving the feasibility of the presented approach for dynamic information recovery for arteries and veins segmentation.

Particle formation in SiOx film deposition by low frequency plasma enhanced chemical vapor deposition

NASA Astrophysics Data System (ADS)

Yamaguchi, Tomoyo; Sakamoto, Naoshi; Shimozuma, Mitsuo; Yoshino, Masaki; Tagashira, Hiroaki

1998-01-01

Dust particle formation dynamics in the process of SiOx film deposition from a SiH4 and N2O gas mixture by a low frequency plasma enhanced chemical vapor deposition have been investigated using scanning electron microscopy and laser light scattering. The deposited films are confirmed to be SiOx from the measurements of Auger electron spectroscopy, x-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. It is observed by scanning electron microscopy that particles are deposited on Si substrate at the plasma power frequency f=5 kHz and above both with and without substrate heating (400 °C), while no particle is deposited below f=1 kHz. Moreover, the laser light scattering indicates that particles are generated at the plasma power frequency of f=3 kHz and above in the gas phase, and that they are not generated in the gas phase at below f=3 kHz. Properties (the refractive index, resistivity, and Vickers hardness) of the films with particles are inferior to those of the films without particles. This article has revealed experimentally the effect of plasma power frequency on SiOx particle formation and makes a contribution to the explication of the particle formation mechanism. We suggest that high-quality film deposition with the low frequency plasma enhanced chemical vapor deposition method is attained at f=1 kHz or less without substrate heating.

New frontiers in H-Beta auroral photometry

NASA Astrophysics Data System (ADS)

Unick, C.; Donovan, E.; Connors, M. G.; Spanswick, E.; Jackel, B. J.; Greffen, M. J.; Wilson, C.; Little, J.; Chaddock, D.; Schofield, I.; MacRae, A.; Chen, S.; Crowther, A.; James, S.; Read, A.; Willis, T.

2013-12-01

The proton aurora provides valuable information about magnetotail structure and dynamics. For example, the location of the equatorward boundary of the proton aurora is a robust indicator of magnetotail stretching. Also, proton auroral luminosities combined with in situ ion measurements provide important information about magnetic mapping between the inner CPS and the auroral ionosphere. In this paper, we present a new and innovative proton-auroral (H-Beta) meridian-scanning photometer (MSP) capable of higher spatial and temporal resolution than has been achieved in the past. This H-Beta MSP is the first of a new dual-wavelength (signal/background) MSP design with a single scanning mirror and no other moving parts. The novel filtering architecture allows for a near 100% duty cycle with a 30-second meridian scan and configurable operating modes. The new design is significantly more sensitive than the legacy CANOPUS MSPs. The increased SNR can be employed in a variety of ways, such as to achieve significantly higher time resolution. Here, we present the new instrument design, test data from a commissioning campaign in Athabasca, and some thoughts on how the enhance proton auroral capability can increase the science value of these measurements.

Miscible blends of biobased poly(lactide) with poly(methyl methacrylate): Effects of chopped glass fiber incorporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cousins, Dylan S.; Lowe, Corinne; Swan, Dana

Poly(lactide) (PLA) and poly(methyl methacrylate) (PMMA) are melt compounded with chopped glass fiber using laboratory scale twin-screw extrusion. Physical properties are examined using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), tensile testing, impact testing, X-ray computed tomography (CT) scanning, and field emission scanning electron microscopy (FE-SEM). Molecular weight is determined using gel permeation chromatography (GPC). Miscibility of the blends is implied by the presence of a single glass transition temperature and homogeneous morphology. PLA/PMMA blends tend to show positive deviations from a simple linear mixing rule in their mechanical properties (e.g., tensile toughness, modulus, andmore » stress at break). The addition of 40 wt % glass fiber to the system dramatically increases physical properties. Across all blend compositions, the tensile modulus increases from roughly 3 GPa to roughly 10 GPa. Estimated heat distortion temperatures (HDTs) are also greatly enhanced; the pure PLA sample HDT increases from 75 degrees C to 135 degrees C. Fiber filled polymer blends represent a sustainable class of earth abundant materials which should prove useful across a range of applications.« less

An integrated approach to piezoactuator positioning in high-speed atomic force microscope imaging

NASA Astrophysics Data System (ADS)

Yan, Yan; Wu, Ying; Zou, Qingze; Su, Chanmin

2008-07-01

In this paper, an integrated approach to achieve high-speed atomic force microscope (AFM) imaging of large-size samples is proposed, which combines the enhanced inversion-based iterative control technique to drive the piezotube actuator control for lateral x-y axis positioning with the use of a dual-stage piezoactuator for vertical z-axis positioning. High-speed, large-size AFM imaging is challenging because in high-speed lateral scanning of the AFM imaging at large size, large positioning error of the AFM probe relative to the sample can be generated due to the adverse effects—the nonlinear hysteresis and the vibrational dynamics of the piezotube actuator. In addition, vertical precision positioning of the AFM probe is even more challenging (than the lateral scanning) because the desired trajectory (i.e., the sample topography profile) is unknown in general, and the probe positioning is also effected by and sensitive to the probe-sample interaction. The main contribution of this article is the development of an integrated approach that combines advanced control algorithm with an advanced hardware platform. The proposed approach is demonstrated in experiments by imaging a large-size (50μm ) calibration sample at high-speed (50Hz scan rate).

Direct-injection screening for acidic drugs in plasma and neutral drugs in equine urine by differential-gradient LC-LC coupled MS/MS.

PubMed

Stanley, Shawn M R; Wee, Wei Khee; Lim, Boon Huat; Foo, Hsiao Ching

2007-04-01

Direct-injection LC-LC hybrid tandem MS methods have been developed for undertaking broad-based screening for acidic drugs in protein-precipitated plasma and neutral doping agents in equine urine. In both analyses, analytes present in the matrix were trapped using a HLB extraction column before being refocused and separated on a Chromolith RP-18e monolithic analytical column using a controlled differential gradient generated by proportional dilution of the first column's eluent with water. Each method has been optimised by the adoption of a mobile phase and gradient that was tailored to enhance ionisation in the MS source while maintaining good chromatographic behaviour for the majority of the target drugs. The analytical column eluent was fed into the heated nebulizer (HN) part of the Duospray interface attached to a 4000 QTRAP mass spectrometer. Information dependent acquisition (IDA) with dynamic background subtraction (DBS) was configured to trigger a sensitive enhanced product ion (EPI) scan when a multiple reaction monitoring (MRM) survey scan signal exceeded the defined criteria. Ninety-one percent of acidic drugs in protein-precipitated plasma and 80% of the neutral compounds in equine urine were detected when spiked at 10 ng/ml.

Experimental investigation and oral bioavailability enhancement of nano-sized curcumin by using supercritical anti-solvent process.

PubMed

Anwar, Mohammed; Ahmad, Iqbal; Warsi, Musarrat H; Mohapatra, Sharmistha; Ahmad, Niyaz; Akhter, Sohail; Ali, Asgar; Ahmad, Farhan J

2015-10-01

The biomedical applications of curcumin (CUR) are limited due to its poor oral bioavailability. In this work, CUR nanoparticles were successfully prepared by combining the supercritical anti-solvent (SAS) process with Tween 80 as a solubilizing agent and permeation enhancer. Different processing parameters that can govern the mean particle size and size distribution of nanoparticles were well investigated by manipulating the types of solvents, mixing vessel pressure, mixing vessel temperature, CO2 flow rate, solution flow rate and solution concentration. Solid state characterization was done by Fourier Transform infrared spectroscopy, differential scanning calorimetry, dynamic light scattering, scanning electron microscopy, and powder X-ray diffraction study. Solubility and dissolution profile of SAS-processed CUR were found to be significantly increased in comparison with native CUR. Further, a validated ultra-performance liquid chromatographic method with quadrupole-time of flight-mass spectrometry was developed to investigate the pharmacokinetic parameters after a single oral dose (100mg/kg) administration of CUR (before/after SAS-processed) in male Wistar rats. From the plasma concentration vs. time profile graph, oral bioavailability of SAS-processed CUR was found to be increased approximately 11.6-fold (p<0.001) as compared to native CUR. Copyright © 2015 Elsevier B.V. All rights reserved.

Quantitative three-dimensional dynamic imaging of structure and function of the cardiopulmonary and circulatory systems in all regions of the body

NASA Technical Reports Server (NTRS)

Sturm, R. E.; Ritman, E. L.; Wood, E. H.

1975-01-01

The background for, and design of a third generation, general purpose, all electronic spatial scanning system, the DSR is described. Its specified performance capabilities provide dynamic and stop action three dimensional spatial reconstructions of any portion of the body based on a minimum exposure time of 0.01 second for each 28 multiplanar 180 deg scanning set, a maximum scan repetition rate of sixty 28 multiplane scan sets per second, each scan set consisting of a maximum of 240 parallel cross sections of a minimum thickness of 0.9 mm, and encompassing a maximum cylindrical volume about 23 cm in length and up to 38 cm in diameter.

TU-F-CAMPUS-J-02: Evaluation of Textural Feature Extraction for Radiotherapy Response Assessment of Early Stage Breast Cancer Patients Using Diffusion Weighted MRI and Dynamic Contrast Enhanced MRI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Y; Wang, C; Horton, J

Purpose: To investigate the feasibility of using classic textural feature extraction in radiotherapy response assessment, we studied a unique cohort of early stage breast cancer patients with paired pre - and post-radiation Diffusion Weighted MRI (DWI-MRI) and Dynamic Contrast Enhanced MRI (DCE-MRI). Methods: 15 female patients from our prospective phase I trial evaluating preoperative radiotherapy were included in this retrospective study. Each patient received a single-fraction radiation treatment, and DWI and DCE scans were conducted before and after the radiotherapy. DWI scans were acquired using a spin-echo EPI sequence with diffusion weighting factors of b = 0 and b =more » 500 mm{sup 2} /s, and the apparent diffusion coefficient (ADC) maps were calculated. DCE-MRI scans were acquired using a T{sub 1}-weighted 3D SPGR sequence with a temporal resolution of about 1 minute. The contrast agent (CA) was intravenously injected with a 0.1 mmol/kg bodyweight dose at 2 ml/s. Two parameters, volume transfer constant (K{sup trans} ) and k{sub ep} were analyzed using the two-compartment Tofts kinetic model. For DCE parametric maps and ADC maps, 33 textural features were generated from the clinical target volume (CTV) in a 3D fashion using the classic gray level co-occurrence matrix (GLCOM) and gray level run length matrix (GLRLM). Wilcoxon signed-rank test was used to determine the significance of each texture feature’s change after the radiotherapy. The significance was set to 0.05 with Bonferroni correction. Results: For ADC maps calculated from DWI-MRI, 24 out of 33 CTV features changed significantly after the radiotherapy. For DCE-MRI pharmacokinetic parameters, all 33 CTV features of K{sup trans} and 33 features of k{sub ep} changed significantly. Conclusion: Initial results indicate that those significantly changed classic texture features are sensitive to radiation-induced changes and can be used for assessment of radiotherapy response in breast cancer.« less

Individual differences in functional connectivity during naturalistic viewing conditions.

PubMed

Vanderwal, Tamara; Eilbott, Jeffrey; Finn, Emily S; Craddock, R Cameron; Turnbull, Adam; Castellanos, F Xavier

2017-08-15

Naturalistic viewing paradigms such as movies have been shown to reduce participant head motion and improve arousal during fMRI scanning relative to task-free rest, and have been used to study both functional connectivity and stimulus-evoked BOLD-signal changes. These task-based hemodynamic changes are synchronized across subjects and involve large areas of the cortex, and it is unclear whether individual differences in functional connectivity are enhanced or diminished under such naturalistic conditions. This work first aims to characterize variability in BOLD-signal based functional connectivity (FC) across 2 distinct movie conditions and eyes-open rest (n=31 healthy adults, 2 scan sessions each). We found that movies have higher within- and between-subject correlations in cluster-wise FC relative to rest. The anatomical distribution of inter-individual variability was similar across conditions, with higher variability occurring at the lateral prefrontal lobes and temporoparietal junctions. Second, we used an unsupervised test-retest matching algorithm that identifies individual subjects from within a group based on FC patterns, quantifying the accuracy of the algorithm across the three conditions. The movies and resting state all enabled identification of individual subjects based on FC matrices, with accuracies between 61% and 100%. Overall, pairings involving movies outperformed rest, and the social, faster-paced movie attained 100% accuracy. When the parcellation resolution, scan duration, and number of edges used were increased, accuracies improved across conditions, and the pattern of movies>rest was preserved. These results suggest that using dynamic stimuli such as movies enhances the detection of FC patterns that are unique at the individual level. Copyright © 2017 Elsevier Inc. All rights reserved.

Performance assessment of dynamic spiral scan modes with variable pitch for quantitative perfusion computed tomography.

PubMed

Haberland, Ulrike; Klotz, Ernst; Abolmaali, Nasreddin

2010-07-01

Perfusion computed tomography is increasingly being used in diagnostic radiology. Axial coverage of the traditional approach is limited to the width of the detector. Using continuous periodic table movement coverage can be increased beyond this limit. In this study, we compared tissue flow values determined from scans with a periodic spiral implementation with variable pitch with ones determined from standard dynamic scan modes. A flow phantom (preserved porcine kidney) was scanned with 2 settings of a periodic spiral (Adaptive 4D Spiral) with a range of 100 and 148 mm and a temporal sampling of 1.5 seconds. Additionally, the whole phantom was scanned with the standard dynamic mode (detector width 38.4 mm, temporal sampling 1.0 seconds) at various overlapping positions as a reference. Scan parameters (80 kV, 140 mAs, 40s scan time) were selected similar to a typical brain perfusion study. All scans were repeated 5 times. Tissue flow was calculated with a dedicated deconvolution algorithm. In a center slice and 3 additional slices at various off center positions flow values were recorded in a total of 126 regions of interest (ROI). Reproducibility was determined from the variation of the repeat scans. Agreement between periodic spirals and standard mode was determined by Bland Altman plots and correlation analysis. The reproducibility of the tissue flow determination ranged from 2.7 to 4.4 mL/100 mL/min and was similar for all scan modes. The coefficient of variation ranged from 3.9% to 6.1%. Mean tissue flow in the 126 ROIs ranged from 35 to 121 mL/100 mL/min. There was excellent correlation between both periodic spiral ranges and the standard dynamic mode with a Pearson correlation coefficient of r = 0.97. The regression slope (intercept 0) for the 100 mm range was 1.01, for the 148 mm range it was 0.97. The absolute differences per ROI varied between 1.5 and 4.1 mL/100 mL/min, the relative differences between 1.9% and 6.5%. Differences did not depend on the slice location. Periodic spiral scan modes with variable pitch and a sampling rate of 1.5 seconds can be used for the quantitative determination of tissue flow. Their performance is equivalent to equidistant sampling with standard dynamic scan modes. The ranges of 100 and 148 mm investigated allow coverage of the whole brain or an entire organ for perfusion imaging.

New Aspects of Photocurrent Generation at Graphene pn Junctions Revealed by Ultrafast Optical Measurements

NASA Astrophysics Data System (ADS)

Aivazian, Grant; Sun, Dong; Jones, Aaron; Ross, Jason; Yao, Wang; Cobden, David; Xu, Xiaodong

2012-02-01

The remarkable electrical and optical properties of graphene make it a promising material for new optoelectronic applications. However, one important, but so far unexplored, property is the role of hot carriers in charge and energy transport at graphene interfaces. Here we investigate the photocurrent (PC) dynamics at a tunable graphene pn junction using ultrafast scanning PC microscopy. Pump-probe measurements show a temperature dependent relaxation time of photogenerated carriers that increases from 1.5ps at 290K to 4ps at 20K; while the amplitude of the PC is independent of the lattice temperature. These observations imply that it is hot carriers, not phonons, which dominate ultrafast energy transport. Gate dependent measurements show many interesting features such as pump induced saturation, enhancement, and sign reversal of probe generated PC. These observations reveal that the underlying PC mechanism is a combination of the thermoelectric and built-in electric field effects. Our results enhance the understanding of non-equilibrium electron dynamics, electron-electron interactions, and electron-phonon interactions in graphene. They also determine fundamental limits on ultrafast device operation speeds (˜500 GHz) for graphene-based photodetectors.

A codon-optimized green fluorescent protein for live cell imaging in Zymoseptoria tritici☆

PubMed Central

Kilaru, S.; Schuster, M.; Studholme, D.; Soanes, D.; Lin, C.; Talbot, N.J.; Steinberg, G.

2015-01-01

Fluorescent proteins (FPs) are powerful tools to investigate intracellular dynamics and protein localization. Cytoplasmic expression of FPs in fungal pathogens allows greater insight into invasion strategies and the host-pathogen interaction. Detection of their fluorescent signal depends on the right combination of microscopic setup and signal brightness. Slow rates of photo-bleaching are pivotal for in vivo observation of FPs over longer periods of time. Here, we test green-fluorescent proteins, including Aequorea coerulescens GFP (AcGFP), enhanced GFP (eGFP) from Aequorea victoria and a novel Zymoseptoria tritici codon-optimized eGFP (ZtGFP), for their usage in conventional and laser-enhanced epi-fluorescence, and confocal laser-scanning microscopy. We show that eGFP, expressed cytoplasmically in Z. tritici, is significantly brighter and more photo-stable than AcGFP. The codon-optimized ZtGFP performed even better than eGFP, showing significantly slower bleaching and a 20–30% further increase in signal intensity. Heterologous expression of all GFP variants did not affect pathogenicity of Z. tritici. Our data establish ZtGFP as the GFP of choice to investigate intracellular protein dynamics in Z. tritici, but also infection stages of this wheat pathogen inside host tissue. PMID:26092799

Immersion and dry scanner extensions for sub-10nm production nodes

NASA Astrophysics Data System (ADS)

Weichselbaum, Stefan; Bornebroek, Frank; de Kort, Toine; Droste, Richard; de Graaf, Roelof F.; van Ballegoij, Rob; Botter, Herman; McLaren, Matthew G.; de Boeij, Wim P.

2015-03-01

Progressing towards the 10nm and 7nm imaging node, pattern-placement and layer-to-layer overlay requirements keep on scaling down and drives system improvements in immersion (ArFi) and dry (ArF/KrF) scanners. A series of module enhancements in the NXT platform have been introduced; among others, the scanner is equipped with exposure stages with better dynamics and thermal control. Grid accuracy improvements with respect to calibration, setup, stability, and layout dependency tighten MMO performance and enable mix and match scanner operation. The same platform improvements also benefit focus control. Improvements in detectability and reproducibility of low contrast alignment marks enhance the alignment solution window for 10nm logic processes and beyond. The system's architecture allows dynamic use of high-order scanner optimization based on advanced actuators of projection lens and scanning stages. This enables a holistic optimization approach for the scanner, the mask, and the patterning process. Productivity scanner design modifications esp. stage speeds and optimization in metrology schemes provide lower layer costs for customers using immersion lithography as well as conventional dry technology. Imaging, overlay, focus, and productivity data is presented, that demonstrates 10nm and 7nm node litho-capability for both (immersion & dry) platforms.

Application of 3D Laser Scanning Technology in Inspection and Dynamic Reserves Detection of Open-Pit Mine

NASA Astrophysics Data System (ADS)

Hu, Zhumin; Wei, Shiyu; Jiang, Jun

2017-10-01

The traditional open-pit mine mining rights verification and dynamic reserve detection means rely on the total station and RTK to collect the results of the turning point coordinates of mining surface contours. It resulted in obtaining the results of low precision and large error in the means that is limited by the traditional measurement equipment accuracy and measurement methods. The three-dimensional scanning technology can obtain the three-dimensional coordinate data of the surface of the measured object in a large area at high resolution. This paper expounds the commonly used application of 3D scanning technology in the inspection and dynamic reserve detection of open mine mining rights.

A New High Channel-Count, High Scan-Rate, Data Acquisition System for the NASA Langley Transonic Dynamics Tunnel

NASA Technical Reports Server (NTRS)

Ivanco, Thomas G.; Sekula, Martin K.; Piatak, David J.; Simmons, Scott A.; Babel, Walter C.; Collins, Jesse G.; Ramey, James M.; Heald, Dean M.

2016-01-01

A data acquisition system upgrade project, known as AB-DAS, is underway at the NASA Langley Transonic Dynamics Tunnel. AB-DAS will soon serve as the primary data system and will substantially increase the scan-rate capabilities and analog channel count while maintaining other unique aeroelastic and dynamic test capabilities required of the facility. AB-DAS is configurable, adaptable, and enables buffet and aeroacoustic tests by synchronously scanning all analog channels and recording the high scan-rate time history values for each data quantity. AB-DAS is currently available for use as a stand-alone data system with limited capabilities while development continues. This paper describes AB-DAS, the design methodology, and the current features and capabilities. It also outlines the future work and projected capabilities following completion of the data system upgrade project.

Molecular expressions: exploring the world of optics and microscopy. http://microscopy.fsu.edu.

PubMed

Eliceiri, Kevin W

2004-08-01

Our knowledge of the structure, dynamics and physiology of a cell has increased significantly in the last ten years through the emergence of new optical imaging modalities such as optical sectioning microscopy, computer- enhanced video microscopy and laser-scanning microscopy. These techniques together with the use of genetically engineered fluorophores have helped scientists visualize the 3-dimensional dynamic processes of living cells. However as powerful as these imaging tools are, they can often be difficult to understand and fully utilize. Below I will discuss my favorite website: The Molecular Expressions Web Site that endeavors to present the power of microscopy to its visitors. The Molecular Expressions group does a remarkable job of not only clearly presenting the principles behind these techniques in a manner approachable by lay and scientific audiences alike but also provides representative data from each as well.

High-resolution whole-brain DCE-MRI using constrained reconstruction: Prospective clinical evaluation in brain tumor patients.

PubMed

Guo, Yi; Lebel, R Marc; Zhu, Yinghua; Lingala, Sajan Goud; Shiroishi, Mark S; Law, Meng; Nayak, Krishna

2016-05-01

To clinically evaluate a highly accelerated T1-weighted dynamic contrast-enhanced (DCE) MRI technique that provides high spatial resolution and whole-brain coverage via undersampling and constrained reconstruction with multiple sparsity constraints. Conventional (rate-2 SENSE) and experimental DCE-MRI (rate-30) scans were performed 20 minutes apart in 15 brain tumor patients. The conventional clinical DCE-MRI had voxel dimensions 0.9 × 1.3 × 7.0 mm(3), FOV 22 × 22 × 4.2 cm(3), and the experimental DCE-MRI had voxel dimensions 0.9 × 0.9 × 1.9 mm(3), and broader coverage 22 × 22 × 19 cm(3). Temporal resolution was 5 s for both protocols. Time-resolved images and blood-brain barrier permeability maps were qualitatively evaluated by two radiologists. The experimental DCE-MRI scans showed no loss of qualitative information in any of the cases, while achieving substantially higher spatial resolution and whole-brain spatial coverage. Average qualitative scores (from 0 to 3) were 2.1 for the experimental scans and 1.1 for the conventional clinical scans. The proposed DCE-MRI approach provides clinically superior image quality with higher spatial resolution and coverage than currently available approaches. These advantages may allow comprehensive permeability mapping in the brain, which is especially valuable in the setting of large lesions or multiple lesions spread throughout the brain.

[Contrast-enhanced Ultrasound in Diagnostic Imaging of Muscle Injuries: Perfusion Imaging in the Early Arterial Phase].

PubMed

Hotfiel, T; Carl, H D; Swoboda, B; Engelhardt, M; Heinrich, M; Strobel, D; Wildner, D

2016-03-01

Ultrasound is a standard procedure widely used in the diagnostic investigation of muscle injuries and widely described in the literature. Its advantages include rapid availability, cost effectiveness and the possibility to perform a real-time dynamic examination with the highest possible spatial resolution. In the diagnostic work-up of minor lesions (muscle stiffness, muscle strain), plain ultrasound has so far been inferior to MRI. The case presented by us is an example of the possibilities offered by contrast-enhanced ultrasound (CEUS) in the imaging of muscle injuries compared with plain B-mode image ultrasound and MRI imaging of the affected region. This case report is about a high-performance football player who sustained a muscle injury. He underwent an ultrasound examination (S 2000, 9L4 Probe, Siemens, Germany), which was performed simultaneously in the conventional and contrast-enhanced mode at the level of the lesion. An intravenous bolus injection of 4.8 ml of intravascular contrast agent (SonoVue(®), Bracco, Italy) was given via a cubital intravenous line. After that, the distribution of contrast agent was visualised in the early arterial phase. In addition, a plain magnetic resonance imaging scan of both thighs was performed for reference. On conventional ultrasound, the lesion was not clearly distinguishable from neighbouring tissue, whereas contrast-enhanced ultrasound demonstrated a well delineated, circumscribed area of impaired perfusion with hypoenhancement compared with the surrounding muscles at the clinical level of the lesion in the arterial wash-in phase (0-30 sec, after intravenous administration). The MRI scan revealed an edema signal with perifascial fluid accumulation in the corresponding site. The use of intravascular contrast agent enabled the sensitive detection of a minor injury by ultrasound for the first time. An intramuscular edema seen in the MRI scan showed a functional arterial perfusion impairment on ultrasound, which was sensitively detected in the early phase. Further examinations must be performed on muscle injuries of various degrees of severity in order to validate the application of this procedure and to standardise the examination process. © Georg Thieme Verlag KG Stuttgart · New York.

Dynamic scan control in STEM: Spiral scans

DOE PAGES

Lupini, Andrew R.; Borisevich, Albina Y.; Kalinin, Sergei V.; ...

2016-06-13

Here, scanning transmission electron microscopy (STEM) has emerged as one of the foremost techniques to analyze materials at atomic resolution. However, two practical difficulties inherent to STEM imaging are: radiation damage imparted by the electron beam, which can potentially damage or otherwise modify the specimen and slow-scan image acquisition, which limits the ability to capture dynamic changes at high temporal resolution. Furthermore, due in part to scan flyback corrections, typical raster scan methods result in an uneven distribution of dose across the scanned area. A method to allow extremely fast scanning with a uniform residence time would enable imaging atmore » low electron doses, ameliorating radiation damage and at the same time permitting image acquisition at higher frame-rates while maintaining atomic resolution. The practical complication is that rastering the STEM probe at higher speeds causes significant image distortions. Non-square scan patterns provide a solution to this dilemma and can be tailored for low dose imaging conditions. Here, we develop a method for imaging with alternative scan patterns and investigate their performance at very high scan speeds. A general analysis for spiral scanning is presented here for the following spiral scan functions: Archimedean, Fermat, and constant linear velocity spirals, which were tested for STEM imaging. The quality of spiral scan STEM images is generally comparable with STEM images from conventional raster scans, and the dose uniformity can be improved.« less

Dynamic scan control in STEM: Spiral scans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lupini, Andrew R.; Borisevich, Albina Y.; Kalinin, Sergei V.

Here, scanning transmission electron microscopy (STEM) has emerged as one of the foremost techniques to analyze materials at atomic resolution. However, two practical difficulties inherent to STEM imaging are: radiation damage imparted by the electron beam, which can potentially damage or otherwise modify the specimen and slow-scan image acquisition, which limits the ability to capture dynamic changes at high temporal resolution. Furthermore, due in part to scan flyback corrections, typical raster scan methods result in an uneven distribution of dose across the scanned area. A method to allow extremely fast scanning with a uniform residence time would enable imaging atmore » low electron doses, ameliorating radiation damage and at the same time permitting image acquisition at higher frame-rates while maintaining atomic resolution. The practical complication is that rastering the STEM probe at higher speeds causes significant image distortions. Non-square scan patterns provide a solution to this dilemma and can be tailored for low dose imaging conditions. Here, we develop a method for imaging with alternative scan patterns and investigate their performance at very high scan speeds. A general analysis for spiral scanning is presented here for the following spiral scan functions: Archimedean, Fermat, and constant linear velocity spirals, which were tested for STEM imaging. The quality of spiral scan STEM images is generally comparable with STEM images from conventional raster scans, and the dose uniformity can be improved.« less

Automatic segmentation and quantification of the cardiac structures from non-contrast-enhanced cardiac CT scans

NASA Astrophysics Data System (ADS)

Shahzad, Rahil; Bos, Daniel; Budde, Ricardo P. J.; Pellikaan, Karlijn; Niessen, Wiro J.; van der Lugt, Aad; van Walsum, Theo

2017-05-01

Early structural changes to the heart, including the chambers and the coronary arteries, provide important information on pre-clinical heart disease like cardiac failure. Currently, contrast-enhanced cardiac computed tomography angiography (CCTA) is the preferred modality for the visualization of the cardiac chambers and the coronaries. In clinical practice not every patient undergoes a CCTA scan; many patients receive only a non-contrast-enhanced calcium scoring CT scan (CTCS), which has less radiation dose and does not require the administration of contrast agent. Quantifying cardiac structures in such images is challenging, as they lack the contrast present in CCTA scans. Such quantification would however be relevant, as it enables population based studies with only a CTCS scan. The purpose of this work is therefore to investigate the feasibility of automatic segmentation and quantification of cardiac structures viz whole heart, left atrium, left ventricle, right atrium, right ventricle and aortic root from CTCS scans. A fully automatic multi-atlas-based segmentation approach is used to segment the cardiac structures. Results show that the segmentation overlap between the automatic method and that of the reference standard have a Dice similarity coefficient of 0.91 on average for the cardiac chambers. The mean surface-to-surface distance error over all the cardiac structures is 1.4+/- 1.7 mm. The automatically obtained cardiac chamber volumes using the CTCS scans have an excellent correlation when compared to the volumes in corresponding CCTA scans, a Pearson correlation coefficient (R) of 0.95 is obtained. Our fully automatic method enables large-scale assessment of cardiac structures on non-contrast-enhanced CT scans.

A Carboxyl-Terminated Polybutadiene Liquid Rubber Modified Epoxy Resin with Enhanced Toughness and Excellent Electrical Properties

NASA Astrophysics Data System (ADS)

Dong, Lina; Zhou, Wenying; Sui, Xuezhen; Wang, Zijun; Cai, Huiwu; Wu, Peng; Zuo, Jing; Liu, Xiangrong

2016-07-01

The modification of epoxy (EP) resin with carboxyl-terminated polybutadiene (CTPB) liquid rubber was carried out in this work. The chemical reaction between the oxirane ring of EP and the carboxyl group of CTPB and kinetic parameters were investigated by Fourier transform infrared and differential scanning calorimetry. The resulting pre-polymers were cured with methyl hexahydrophthalic anhydride. Scanning electron microscopic observations indicate that the micro-sized CTPB particles dispersed uniformly in the EP matrix formed a two-phase morphology, mainly contributing to the improved toughness of the modified network. The best overall mechanical performance was achieved with 20 phr CTPB; above it, a fall in the strength and modulus was observed. The storage modulus and loss declined with the CTPB concentration due to its lower modulus and plasticizing effect from dynamic mechanical analysis measurements. Moreover, due to the weak polarity and excellent electrical insulation of CTPB, the CTPB-modified EP presented higher electrical resistivities and breakdown strength, and low dielectric permittivity and loss compared with neat EP.

Preparation of the CNC/Ag/beeswax composites for enhancing antibacterial and water resistance properties of paper.

PubMed

Liu, Kai; Liang, Hunan; Nasrallah, Joseph; Chen, Lihui; Huang, Liulian; Ni, Yonghao

2016-05-20

An effective method of preparing composites containing inorganic (Ag) and organic (beeswax) particles was established in this study. Ag nanoparticles were first immobilized on the cellulose nanocrystals (CNC) during the reduction of AgNO3 in the presence of CNC, then mixed with beeswax by high speed stirring. Scanning transmission electron microscopy (STEM) images indicated that Ag and beeswax particles were uniformly dispersed and stable in the network structure formed by CNC. Upon coating on a paper surface, a layer of beeswax film was evident based on scanning electron microscopy (SEM) images. The dynamic contact angle and antibacterial activity tests indicated that the contact angle of coated paper reached 113.06° and the growth inhibition of Escherichia coli increased to 99.96%, respectively, at a coating amount of 21.53 g/m(2). When applied onto paper surface by coating, the CNC/Ag/beeswax composites can impact paper with antibacterial property and improved water resistance. Copyright © 2016 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, W; Miften, M; Jones, B

Purpose: Pancreatic SBRT relies on extremely accurate delivery of ablative radiation doses to the target, and intra-fractional tracking of fiducial markers can facilitate improvements in dose delivery. However, this requires algorithms that are able to find fiducial markers with high speed and accuracy. The purpose of this study was to develop a novel marker tracking algorithm that is robust against many of the common errors seen with traditional template matching techniques. Methods: Using CBCT projection images, a method was developed to create detailed template images of fiducial marker clusters without prior knowledge of the number of markers, their positions, ormore » their orientations. Briefly, the method (i) enhances markers in projection images, (ii) stabilizes the cluster’s position, (iii) reconstructs the cluster in 3D, and (iv) precomputes a set of static template images dependent on gantry angle. Furthermore, breathing data were used to produce 4D reconstructions of clusters, yielding dynamic template images dependent on gantry angle and breathing amplitude. To test these two approaches, static and dynamic templates were used to track the motion of marker clusters in more than 66,000 projection images from 75 CBCT scans of 15 pancreatic SBRT patients. Results: For both static and dynamic templates, the new technique was able to locate marker clusters present in projection images 100% of the time. The algorithm was also able to correctly locate markers in several instances where only some of the markers were visible due to insufficient field-of-view. In cases where clusters exhibited deformation and/or rotation during breathing, dynamic templates resulted in cross-correlation scores up to 70% higher than static templates. Conclusion: Patient-specific templates provided complete tracking of fiducial marker clusters in CBCT scans, and dynamic templates helped to provide higher cross-correlation scores for deforming/rotating clusters. This novel algorithm provides an extremely accurate method to detect fiducial markers during treatment. Research funding provided by Varian Medical Systems to Miften and Jones.« less

Use of C-Arm Cone Beam CT During Hepatic Radioembolization: Protocol Optimization for Extrahepatic Shunting and Parenchymal Enhancement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoven, Andor F. van den, E-mail: a.f.vandenhoven@umcutrecht.nl; Prince, Jip F.; Keizer, Bart de

PurposeTo optimize a C-arm computed tomography (CT) protocol for radioembolization (RE), specifically for extrahepatic shunting and parenchymal enhancement.Materials and MethodsA prospective development study was performed per IDEAL recommendations. A literature-based protocol was applied in patients with unresectable and chemorefractory liver malignancies undergoing an angiography before radioembolization. Contrast and scan settings were adjusted stepwise and repeatedly reviewed in a consensus meeting. Afterwards, two independent raters analyzed all scans. A third rater evaluated the SPECT/CT scans as a reference standard for extrahepatic shunting and lack of target segment perfusion.ResultsFifty scans were obtained in 29 procedures. The first protocol, using a 6 s delaymore » and 10 s scan, showed insufficient parenchymal enhancement. In the second protocol, the delay was determined by timing parenchymal enhancement on DSA power injection (median 8 s, range 4–10 s): enhancement improved, but breathing artifacts increased (from 0 to 27 %). Since the third protocol with a 5 s scan decremented subjective image quality, the second protocol was deemed optimal. Median CNR (range) was 1.7 (0.6–3.2), 2.2 (−1.4–4.0), and 2.1 (−0.3–3.0) for protocol 1, 2, and 3 (p = 0.80). Delineation of perfused segments was possible in 57, 73, and 44 % of scans (p = 0.13). In all C-arm CTs combined, the negative predictive value was 95 % for extrahepatic shunting and 83 % for lack of target segment perfusion.ConclusionAn optimized C-arm CT protocol was developed that can be used to detect extrahepatic shunts and non-perfusion of target segments during RE.« less

Magnetic field controlled graphene oxide-based origami with enhanced surface area and mechanical properties.

PubMed

Park, Ok-Kyung; Tiwary, Chandra Sekhar; Yang, Yang; Bhowmick, Sanjit; Vinod, Soumya; Zhang, Qingbo; Colvin, Vicki L; Asif, S A Syed; Vajtai, Robert; Penev, Evgeni S; Yakobson, Boris I; Ajayan, Pulickel M

2017-06-01

One can utilize the folding of paper to build fascinating 3D origami architectures with extraordinary mechanical properties and surface area. Inspired by the same, the morphology of 2D graphene can be tuned by addition of magnetite (Fe 3 O 4 ) nanoparticles in the presence of a magnetic field. The innovative 3D architecture with enhanced mechanical properties also shows a high surface area (∼2500 m 2 g -1 ) which is utilized for oil absorption. Detailed microscopy and spectroscopy reveal rolling of graphene oxide (GO) sheets due to the magnetic field driven action of magnetite particles, which is further supported by molecular dynamics (MD) simulations. The macroscopic and local deformation resulting from in situ mechanical loading inside a scanning electron microscope reveals a change in the mechanical response due to a change internal morphology, which is further supported by MD simulation.

Accelerated dynamic EPR imaging using fast acquisition and compressive recovery.

PubMed

Ahmad, Rizwan; Samouilov, Alexandre; Zweier, Jay L

2016-12-01

Electron paramagnetic resonance (EPR) allows quantitative imaging of tissue redox status, which provides important information about ischemic syndromes, cancer and other pathologies. For continuous wave EPR imaging, however, poor signal-to-noise ratio and low acquisition efficiency limit its ability to image dynamic processes in vivo including tissue redox, where conditions can change rapidly. Here, we present a data acquisition and processing framework that couples fast acquisition with compressive sensing-inspired image recovery to enable EPR-based redox imaging with high spatial and temporal resolutions. The fast acquisition (FA) allows collecting more, albeit noisier, projections in a given scan time. The composite regularization based processing method, called spatio-temporal adaptive recovery (STAR), not only exploits sparsity in multiple representations of the spatio-temporal image but also adaptively adjusts the regularization strength for each representation based on its inherent level of the sparsity. As a result, STAR adjusts to the disparity in the level of sparsity across multiple representations, without introducing any tuning parameter. Our simulation and phantom imaging studies indicate that a combination of fast acquisition and STAR (FASTAR) enables high-fidelity recovery of volumetric image series, with each volumetric image employing less than 10 s of scan. In addition to image fidelity, the time constants derived from FASTAR also match closely to the ground truth even when a small number of projections are used for recovery. This development will enhance the capability of EPR to study fast dynamic processes that cannot be investigated using existing EPR imaging techniques. Copyright © 2016 Elsevier Inc. All rights reserved.

Preparation, characterization and dynamical mechanical properties of dextran-coated iron oxide nanoparticles (DIONPs).

PubMed

Can, Hatice Kaplan; Kavlak, Serap; ParviziKhosroshahi, Shahed; Güner, Ali

2018-03-01

Dextran-coated iron oxide nanoparticles (DIONPs) with appropriate surface chemistry exhibit many interesting properties that can be exploited in a variety of biomedical applications such as magnetic resonance imaging (MRI) contrast enhancement, tissue repair, hyperthermia, drug delivery and in cell separation. This paper reports the experimental detail for preparation, characterization and investigation of thermal and dynamical mechanical characteristics of the dextran-coated Fe 3 O 4 magnetic nanoparticles. In our work, DIONPs were prepared in a 1:2 ratio of Fe(II) and Fe(III) salt in the HCl solution with NaOH at given temperature. The obtained dextran-coated iron-oxide nanoparticles structure-property correlation was characterized by spectroscopic methods; attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and XRD. Coating dextran on the iron-oxide proof of important peaks can be seen from the ATR-FTIR. Dramatic crystallinity increment can be observed from the XRD pattern of the iron-oxide dextran nanoparticles. The thermal analysis was examined by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and differential thermal analysis (DTA). Dynamical mechanical properties of dextran nanoparticles were analysed by dynamic mechanical analysis (DMA). Thermal stability of the iron oxide dextran nanoparticles is higher than that of the dextran.

Improved accuracy of quantitative parameter estimates in dynamic contrast-enhanced CT study with low temporal resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Sun Mo, E-mail: Sunmo.Kim@rmp.uhn.on.ca; Haider, Masoom A.; Jaffray, David A.

Purpose: A previously proposed method to reduce radiation dose to patient in dynamic contrast-enhanced (DCE) CT is enhanced by principal component analysis (PCA) filtering which improves the signal-to-noise ratio (SNR) of time-concentration curves in the DCE-CT study. The efficacy of the combined method to maintain the accuracy of kinetic parameter estimates at low temporal resolution is investigated with pixel-by-pixel kinetic analysis of DCE-CT data. Methods: The method is based on DCE-CT scanning performed with low temporal resolution to reduce the radiation dose to the patient. The arterial input function (AIF) with high temporal resolution can be generated with a coarselymore » sampled AIF through a previously published method of AIF estimation. To increase the SNR of time-concentration curves (tissue curves), first, a region-of-interest is segmented into squares composed of 3 × 3 pixels in size. Subsequently, the PCA filtering combined with a fraction of residual information criterion is applied to all the segmented squares for further improvement of their SNRs. The proposed method was applied to each DCE-CT data set of a cohort of 14 patients at varying levels of down-sampling. The kinetic analyses using the modified Tofts’ model and singular value decomposition method, then, were carried out for each of the down-sampling schemes between the intervals from 2 to 15 s. The results were compared with analyses done with the measured data in high temporal resolution (i.e., original scanning frequency) as the reference. Results: The patients’ AIFs were estimated to high accuracy based on the 11 orthonormal bases of arterial impulse responses established in the previous paper. In addition, noise in the images was effectively reduced by using five principal components of the tissue curves for filtering. Kinetic analyses using the proposed method showed superior results compared to those with down-sampling alone; they were able to maintain the accuracy in the quantitative histogram parameters of volume transfer constant [standard deviation (SD), 98th percentile, and range], rate constant (SD), blood volume fraction (mean, SD, 98th percentile, and range), and blood flow (mean, SD, median, 98th percentile, and range) for sampling intervals between 10 and 15 s. Conclusions: The proposed method of PCA filtering combined with the AIF estimation technique allows low frequency scanning for DCE-CT study to reduce patient radiation dose. The results indicate that the method is useful in pixel-by-pixel kinetic analysis of DCE-CT data for patients with cervical cancer.« less

First trimester alcohol exposure alters placental perfusion and fetal oxygen availability affecting fetal growth and development in a non-human primate model.

PubMed

Lo, Jamie O; Schabel, Matthias C; Roberts, Victoria H J; Wang, Xiaojie; Lewandowski, Katherine S; Grant, Kathleen A; Frias, Antonio E; Kroenke, Christopher D

2017-03-01

Prenatal alcohol exposure leads to impaired fetal growth, brain development, and stillbirth. Placental impairment likely contributes to these adverse outcomes, but the mechanisms and specific vasoactive effects of alcohol that links altered placental function to impaired fetal development remain areas of active research. Recently, we developed magnetic resonance imaging techniques in nonhuman primates to characterize placental blood oxygenation through measurements of T 2 * and perfusion using dynamic contrast-enhanced magnetic resonance imaging. The objective of this study was to evaluate the effects of first-trimester alcohol exposure on macaque placental function and to characterize fetal brain development in vivo. Timed-pregnant Rhesus macaques (n=12) were divided into 2 groups: control (n=6) and ethanol exposed (n=6). Animals were trained to self-administer orally either 1.5 g/kg/d of a 4% ethanol solution (equivalent to 6 drinks/d) or an isocaloric control fluid from preconception until gestational day 60 (term is G168). All animals underwent Doppler ultrasound scanning followed by magnetic resonance imaging that consisted of T 2 * and dynamic contrast-enhanced measurements. Doppler ultrasound scanning was used to measure uterine artery and umbilical vein velocimetry and diameter to calculate uterine artery volume blood flow and placental volume blood flow. After noninvasive imaging, animals underwent cesarean delivery for placenta collection and fetal necropsy at gestational day 110 (n=6) or 135 (n=6). Fetal weight and biparietal diameter were significantly smaller in ethanol-exposed animals compared with control animals at gestational day 110. By Doppler ultrasound scanning, placental volume blood flow was significantly lower (P=.04) at gestational day 110 in ethanol-exposed vs control animals. A significant reduction in placental blood flow was evident by dynamic contrast-enhanced magnetic resonance imaging. As we demonstrated recently, T 2 * values vary throughout the placenta and reveal gradients in blood deoxyhemoglobin concentration that range from highly oxygenated blood (long T 2 *) proximal to spiral arteries to highly deoxygenated blood (short T 2 *). Distributions of T 2 *throughout the placenta show significant global reduction in T 2 * (and hence high blood deoxyhemoglobin concentration) in ethanol-exposed vs control animals at gestational day 110 (P=.02). Fetal brain measurements indicated impaired growth and development at gestational day 110, but less so at gestational day 135 in ethanol-exposed vs control animals. Chronic first-trimester ethanol exposure significantly reduces placental perfusion and oxygen supply to the fetal vasculature later in pregnancy. These perturbations of placental function are associated with fetal growth impairments. However, differences between ethanol-exposed and control animals in placental function and fetal developmental outcomes were smaller at gestational day 135 than at gestational day 110. These findings are consistent with placental adaptation to early perturbations that allow for compensated placental function and maintenance of fetal growth. Copyright © 2017 Elsevier Inc. All rights reserved.

Comparison of arterial input functions measured from ultra-fast dynamic contrast enhanced MRI and dynamic contrast enhanced computed tomography in prostate cancer patients

NASA Astrophysics Data System (ADS)

Wang, Shiyang; Lu, Zhengfeng; Fan, Xiaobing; Medved, Milica; Jiang, Xia; Sammet, Steffen; Yousuf, Ambereen; Pineda, Federico; Oto, Aytekin; Karczmar, Gregory S.

2018-02-01

The purpose of this study was to evaluate the accuracy of arterial input functions (AIFs) measured from dynamic contrast enhanced (DCE) MRI following a low dose of contrast media injection. The AIFs measured from DCE computed tomography (CT) were used as ‘gold standard’. A total of twenty patients received CT and MRI scans on the same day. Patients received 120 ml Iohexol in DCE-CT and a low dose of (0.015 mM kg-1) of gadobenate dimeglumine in DCE-MRI. The AIFs were measured in the iliac artery and normalized to the CT and MRI contrast agent doses. To correct for different temporal resolution and sampling periods of CT and MRI, an empirical mathematical model (EMM) was used to fit the AIFs first. Then numerical AIFs (AIFCT and AIFMRI) were calculated based on fitting parameters. The AIFMRI was convolved with a ‘contrast agent injection’ function (AIFMRICON ) to correct for the difference between MRI and CT contrast agent injection times (~1.5 s versus 30 s). The results show that the EMMs accurately fitted AIFs measured from CT and MRI. There was no significant difference (p  >  0.05) between the maximum peak amplitude of AIFs from CT (22.1  ±  4.1 mM/dose) and MRI after convolution (22.3  ±  5.2 mM/dose). The shapes of the AIFCT and AIFMRICON were very similar. Our results demonstrated that AIFs can be accurately measured by MRI following low dose contrast agent injection.

Load-sharing through elastic micro-motion accelerates bone formation and interbody fusion.

PubMed

Ledet, Eric H; Sanders, Glenn P; DiRisio, Darryl J; Glennon, Joseph C

2018-02-13

Achieving a successful spinal fusion requires the proper biological and biomechanical environment. Optimizing load-sharing in the interbody space can enhance bone formation. For anterior cervical discectomy and fusion (ACDF), loading and motion are largely dictated by the stiffness of the plate, which can facilitate a balance between stability and load-sharing. The advantages of load-sharing may be substantial for patients with comorbidities and in multilevel procedures where pseudarthrosis rates are significant. We aimed to evaluate the efficacy of a novel elastically deformable, continuously load-sharing anterior cervical spinal plate for promotion of bone formation and interbody fusion relative to a translationally dynamic plate. An in vivo animal model was used to evaluate the effects of an elastically deformable spinal plate on bone formation and spine fusion. Fourteen goats underwent an ACDF and received either a translationally dynamic or elastically deformable plate. Animals were followed up until 18 weeks and were evaluated by plain x-ray, computed tomography scan, and undecalcified histology to evaluate the rate and quality of bone formation and interbody fusion. Animals treated with the elastically deformable plate demonstrated statistically significantly superior early bone formation relative to the translationally dynamic plate. Trends in the data from 8 to 18 weeks postoperatively suggest that the elastically deformable implant enhanced bony bridging and fusion, but these enhancements were not statistically significant. Load-sharing through elastic micro-motion accelerates bone formation in the challenging goat ACDF model. The elastically deformable implant used in this study may promote early bony bridging and increased rates of fusion, but future studies will be necessary to comprehensively characterize the advantages of load-sharing through micro-motion. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Characterisation of a resolution enhancing image inversion interferometer.

PubMed

Wicker, Kai; Sindbert, Simon; Heintzmann, Rainer

2009-08-31

Image inversion interferometers have the potential to significantly enhance the lateral resolution and light efficiency of scanning fluorescence microscopes. Self-interference of a point source's coherent point spread function with its inverted copy leads to a reduction in the integrated signal for off-axis sources compared to sources on the inversion axis. This can be used to enhance the resolution in a confocal laser scanning microscope. We present a simple image inversion interferometer relying solely on reflections off planar surfaces. Measurements of the detection point spread function for several types of light sources confirm the predicted performance and suggest its usability for scanning confocal fluorescence microscopy.

Comprehensive Assessment of Coronary Artery Disease by Using First-Pass Analysis Dynamic CT Perfusion: Validation in a Swine Model.

PubMed

Hubbard, Logan; Lipinski, Jerry; Ziemer, Benjamin; Malkasian, Shant; Sadeghi, Bahman; Javan, Hanna; Groves, Elliott M; Dertli, Brian; Molloi, Sabee

2018-01-01

Purpose To retrospectively validate a first-pass analysis (FPA) technique that combines computed tomographic (CT) angiography and dynamic CT perfusion measurement into one low-dose examination. Materials and Methods The study was approved by the animal care committee. The FPA technique was retrospectively validated in six swine (mean weight, 37.3 kg ± 7.5 [standard deviation]) between April 2015 and October 2016. Four to five intermediate-severity stenoses were generated in the left anterior descending artery (LAD), and 20 contrast material-enhanced volume scans were acquired per stenosis. All volume scans were used for maximum slope model (MSM) perfusion measurement, but only two volume scans were used for FPA perfusion measurement. Perfusion measurements in the LAD, left circumflex artery (LCx), right coronary artery, and all three coronary arteries combined were compared with microsphere perfusion measurements by using regression, root-mean-square error, root-mean-square deviation, Lin concordance correlation, and diagnostic outcomes analysis. The CT dose index and size-specific dose estimate per two-volume FPA perfusion measurement were also determined. Results FPA and MSM perfusion measurements (P FPA and P MSM ) in all three coronary arteries combined were related to reference standard microsphere perfusion measurements (P MICRO ), as follows: P FPA_COMBINED = 1.02 P MICRO_COMBINED + 0.11 (r = 0.96) and P MSM_COMBINED = 0.28 P MICRO_COMBINED + 0.23 (r = 0.89). The CT dose index and size-specific dose estimate per two-volume FPA perfusion measurement were 10.8 and 17.8 mGy, respectively. Conclusion The FPA technique was retrospectively validated in a swine model and has the potential to be used for accurate, low-dose vessel-specific morphologic and physiologic assessment of coronary artery disease. © RSNA, 2017.

Ultra-Stable Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (5STAR)

NASA Technical Reports Server (NTRS)

Dunagan, Stephen E.; Johnson, Roy R.; Redemann, Jens; Holben, Brent N.; Schmidt, Beat; Flynn, Connor Joseph; Fahey, Lauren; LeBlanc, Samuel; Liss, Jordan; Kacenelenbogen, Meloe S.;

Dynamics of nanoparticle morphology under low energy ion irradiation.

PubMed

Holland-Moritz, Henry; Graupner, Julia; Möller, Wolfhard; Pacholski, Claudia; Ronning, Carsten

2018-08-03

If nanostructures are irradiated with energetic ions, the mechanism of sputtering becomes important when the ion range matches about the size of the nanoparticle. Gold nanoparticles with diameters of ∼50 nm on top of silicon substrates with a native oxide layer were irradiated by gallium ions with energies ranging from 1 to 30 keV in a focused ion beam system. High resolution in situ scanning electron microscopy imaging permits detailed insights in the dynamics of the morphology change and sputter yield. Compared to bulk-like structures or thin films, a pronounced shaping and enhanced sputtering in the nanostructures occurs, which enables a specific shaping of these structures using ion beams. This effect depends on the ratio of nanoparticle size and ion energy. In the investigated energy regime, the sputter yield increases at increasing ion energy and shows a distinct dependence on the nanoparticle size. The experimental findings are directly compared to Monte Carlo simulations obtained from iradina and TRI3DYN, where the latter takes into account dynamic morphological and compositional changes of the target.

Ultrahigh speed Spectral / Fourier domain OCT ophthalmic imaging at 70,000 to 312,500 axial scans per second

PubMed Central

Potsaid, Benjamin; Gorczynska, Iwona; Srinivasan, Vivek J.; Chen, Yueli; Jiang, James; Cable, Alex; Fujimoto, James G.

2009-01-01

We demonstrate ultrahigh speed spectral / Fourier domain optical coherence tomography (OCT) using an ultrahigh speed CMOS line scan camera at rates of 70,000 - 312,500 axial scans per second. Several design configurations are characterized to illustrate trade-offs between acquisition speed, resolution, imaging range, sensitivity and sensitivity roll-off performance. Ultrahigh resolution OCT with 2.5 - 3.0 micron axial image resolution is demonstrated at ∼ 100,000 axial scans per second. A high resolution spectrometer design improves sensitivity roll-off and imaging range performance, trading off imaging speed to 70,000 axial scans per second. Ultrahigh speed imaging at >300,000 axial scans per second with standard image resolution is also demonstrated. Ophthalmic OCT imaging of the normal human retina is investigated. The high acquisition speeds enable dense raster scanning to acquire densely sampled volumetric three dimensional OCT (3D-OCT) data sets of the macula and optic disc with minimal motion artifacts. Imaging with ∼ 8 - 9 micron axial resolution at 250,000 axial scans per second, a 512 × 512 × 400 voxel volumetric 3D-OCT data set can be acquired in only ∼ 1.3 seconds. Orthogonal registration scans are used to register OCT raster scans and remove residual axial eye motion, resulting in 3D-OCT data sets which preserve retinal topography. Rapid repetitive imaging over small volumes can visualize small retinal features without motion induced distortions and enables volume registration to remove eye motion. Cone photoreceptors in some regions of the retina can be visualized without adaptive optics or active eye tracking. Rapid repetitive imaging of 3D volumes also provides dynamic volumetric information (4D-OCT) which is shown to enhance visualization of retinal capillaries and should enable functional imaging. Improvements in the speed and performance of 3D-OCT volumetric imaging promise to enable earlier diagnosis and improved monitoring of disease progression and response to therapy in ophthalmology, as well as have a wide range of research and clinical applications in other areas. PMID:18795054

Dynamic CT for Parathyroid Adenoma Detection: How Does Radiation Dose Compare With Nuclear Medicine?

PubMed

Czarnecki, Caroline A; Einsiedel, Paul F; Phal, Pramit M; Miller, Julie A; Lichtenstein, Meir; Stella, Damien L

2018-05-01

Dynamic CT is increasingly used for preoperative localization of parathyroid adenomas, but concerns remain about the radiation effective dose of CT compared with that of 99m Tc-sestamibi scintigraphy. The purpose of this study was to compare the radiation dose delivered by three-phase dynamic CT with that delivered by 99m Tc-sestamibi SPECT/CT performed in accordance with our current protocols and to assess the possible reduction in effective dose achieved by decreasing the scan length (i.e., z-axis) of two phases of the dynamic CT protocol. The effective dose of a 99m Tc-sestamibi nuclear medicine parathyroid study performed with and without coregistration CT was calculated and compared with the effective dose of our current three-phase dynamic CT protocol as well as a proposed protocol involving CT with reduced scan length. The median effective dose for a 99m Tc-sestamibi nuclear medicine study was 5.6 mSv. This increased to 12.4 mSv with the addition of coregistration CT, which is higher than the median effective dose of 9.3 mSv associated with the dynamic CT protocol. Reducing the scan length of two phases in the dynamic CT protocol could reduce the median effective dose to 6.1 mSv, which would be similar to that of the dose from the 99m Tc-sestamibi study alone. Dynamic CT used for the detection of parathyroid adenoma can deliver a lower radiation dose than 99m Tc-sestamibi SPECT/CT. It may be possible to reduce the dose further by decreasing the scan length of two of the phases, although whether this has an impact on accuracy of the localization needs further investigation.

Curcumin-loaded self-nanomicellizing solid dispersion system: part I: development, optimization, characterization, and oral bioavailability.

PubMed

Parikh, Ankit; Kathawala, Krishna; Song, Yunmei; Zhou, Xin-Fu; Garg, Sanjay

2018-05-29

Curcumin (CUR) is considered as one of the most bioactive molecules ever discovered from nature due to its proven anti-inflammatory and antioxidant in both preclinical and clinical studies. Despite its proven safety and efficacy, the clinical translation of CUR into a useful therapeutic agent is still limited due to its poor oral bioavailability. To overcome its limitation and enhance oral bioavailability by improving its aqueous solubility, stability, and intestinal permeability, a novel CUR formulation (NCF) was developed using the self-nanomicellizing solid dispersion strategy. From the initial screening of polymers for their potential to improve the solubility and stability, Soluplus (SOL) was selected. The optimized NCF demonstrated over 20,000-fold improvement in aqueous solubility as a result of amorphization, hydrogen bonding interaction, and micellization determined using differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance, dynamic light scattering, and transmission electron microscopy. Moreover, the greater stabilizing effect in alkaline pH and light was observed. Furthermore, significant enhancement of dissolution and permeability of CUR across everted sacs of rat small intestine were noticed. Pharmacokinetic studies demonstrated that the oral bioavailability of CUR was increased 117 and 17-fold in case of NCF and physical mixture of CUR and SOL compared to CUR suspension. These results suggest NCF identified as a promising new approach for repositioning of CUR for pharmaceutical application by enhancing the oral bioavailability of CUR. The findings herein stimulate further in vivo evaluations and clinical tests of NCF.

Developmental Changes in Visual Scanning of Dynamic Faces and Abstract Stimuli in Infants: A Longitudinal Study

ERIC Educational Resources Information Center

Hunnius, Sabine; Geuze, Reint H.

2004-01-01

The characteristics of scanning patterns between the ages of 6 and 26 weeks were investigated through repeated assessments of 10 infants. Eye movements were recorded using a corneal-reflection system while the infants looked at 2 dynamic stimuli: the naturally moving face of their mother and an abstract stimulus. Results indicated that the way…

An efficient scan diagnosis methodology according to scan failure mode for yield enhancement

NASA Astrophysics Data System (ADS)

Kim, Jung-Tae; Seo, Nam-Sik; Oh, Ghil-Geun; Kim, Dae-Gue; Lee, Kyu-Taek; Choi, Chi-Young; Kim, InSoo; Min, Hyoung Bok

2008-12-01

Yield has always been a driving consideration during fabrication of modern semiconductor industry. Statistically, the largest portion of wafer yield loss is defective scan failure. This paper presents efficient failure analysis methods for initial yield ramp up and ongoing product with scan diagnosis. Result of our analysis shows that more than 60% of the scan failure dies fall into the category of shift mode in the very deep submicron (VDSM) devices. However, localization of scan shift mode failure is very difficult in comparison to capture mode failure because it is caused by the malfunction of scan chain. Addressing the biggest challenge, we propose the most suitable analysis method according to scan failure mode (capture / shift) for yield enhancement. In the event of capture failure mode, this paper describes the method that integrates scan diagnosis flow and backside probing technology to obtain more accurate candidates. We also describe several unique techniques, such as bulk back-grinding solution, efficient backside probing and signal analysis method. Lastly, we introduce blocked chain analysis algorithm for efficient analysis of shift failure mode. In this paper, we contribute to enhancement of the yield as a result of the combination of two methods. We confirm the failure candidates with physical failure analysis (PFA) method. The direct feedback of the defective visualization is useful to mass-produce devices in a shorter time. The experimental data on mass products show that our method produces average reduction by 13.7% in defective SCAN & SRAM-BIST failure rates and by 18.2% in wafer yield rates.

Reaction monitoring using hyperpolarized NMR with scaling of heteronuclear couplings by optimal tracking

NASA Astrophysics Data System (ADS)

Zhang, Guannan; Schilling, Franz; Glaser, Steffen J.; Hilty, Christian

2016-11-01

Off-resonance decoupling using the method of Scaling of Heteronuclear Couplings by Optimal Tracking (SHOT) enables determination of heteronuclear correlations of chemical shifts in single scan NMR spectra. Through modulation of J-coupling evolution by shaped radio frequency pulses, off resonance decoupling using SHOT pulses causes a user-defined dependence of the observed J-splitting, such as the splitting of 13C peaks, on the chemical shift offset of coupled nuclei, such as 1H. Because a decoupling experiment requires only a single scan, this method is suitable for characterizing on-going chemical reactions using hyperpolarization by dissolution dynamic nuclear polarization (D-DNP). We demonstrate the calculation of [13C, 1H] chemical shift correlations of the carbanionic active sites from hyperpolarized styrene polymerized using sodium naphthalene as an initiator. While off resonance decoupling by SHOT pulses does not enhance the resolution in the same way as a 2D NMR spectrum would, the ability to obtain the correlations in single scans makes this method ideal for determination of chemical shifts in on-going reactions on the second time scale. In addition, we present a novel SHOT pulse that allows to scale J-splittings 50% larger than the respective J-coupling constant. This feature can be used to enhance the resolution of the indirectly detected chemical shift and reduce peak overlap, as demonstrated in a model reaction between p-anisaldehyde and isobutylamine. For both pulses, the accuracy is evaluated under changing signal-to-noise ratios (SNR) of the peaks from reactants and reaction products, with an overall standard deviation of chemical shift differences compared to reference spectra of 0.02 ppm when measured on a 400 MHz NMR spectrometer. Notably, the appearance of decoupling side-bands, which scale with peak intensity, appears to be of secondary importance.

Comparison of triple dose versus standard dose gadolinium-DTPA for detection of MRI enhancing lesions in patients with primary progressive multiple sclerosis.

PubMed Central

Filippi, M; Campi, A; Martinelli, V; Colombo, B; Yousry, T; Canal, N; Scotti, G; Comi, G

1995-01-01

This study was performed to evaluate whether a triple dose of gadolinium-DTPA (Gd-DTPA) increases the sensitivity of brain MRI for detecting enhancing lesions in patients with primary progressive multiple sclerosis (PPMS). T1 weighted brain MRI was obtained for 10 patients with PPMS in two sessions. In the first session, one scan was obtained five to seven minutes after the injection of 0.1 mmol/kg Gd-DTPA (standard dose). In the second session, six to 24 hours later, one scan before and two scans five to seven minutes and one hour after the injection of 0.3 mmol/kg Gd-DTPA (triple dose) were obtained. Four enhancing lesions were detected in two patients when the standard dose of Gd-DTPA was used. The numbers of enhancing lesions increased to 13 and the numbers of patients with such lesions to five when the triple dose of Gd-DTPA was used and to 14 and six in the one hour delayed scans. The mean contrast ratio for enhancing lesions detected with the triple dose of Gd-DTPA was higher than those for lesions present in both the standard dose (P < 0.0009) and the one hour delayed scans (P = 0.04). These data indicate that with a triple dose of Gd-DTPA many more enhancing lesions can be detected in patients with PPMS. This is important both for planning clinical trials and for detecting the presence of inflammation in vivo in the lesions of such patients. Images PMID:8530944

Evaluation of MR scanning, image registration, and image processing methods to visualize cortical veins for neurosurgery

NASA Astrophysics Data System (ADS)

Noordmans, Herke J.; Rutten, G. J. M.; Willems, Peter W. A.; Viergever, Max A.

2000-04-01

The visualization of brain vessels on the cortex helps the neurosurgeon in two ways: to avoid blood vessels when specifying the trepanation entry, and to overcome errors in the surgical navigation system due to brain shift. We compared 3D T1, MR, 3D T1 MR with gadolinium contrast, MR venography as scanning techniques, mutual information as registration technique, and thresholding and multi-vessel enhancement as image processing techniques. We evaluated the volume rendered results based on their quality and correspondence with photos took during surgery. It appears that with 3D T1 MR scans, gadolinium is required to show cortical veins. The visibility of small cortical veins is strongly enhanced by subtracting a 3D T1 MR baseline scan, which should be registered to the scan with gadolinium contrast, even when the scans are made during the same session. Multi-vessel enhancement helps to clarify the view on small vessels by reducing noise level, but strikingly does not reveal more. MR venography does show intracerebral veins with high detail, but is, as is, unsuited to show cortical veins due to the low contrast with CSF.

Resolution-enhanced Mapping Spectrometer

NASA Technical Reports Server (NTRS)

Kumer, J. B.; Aubrun, J. N.; Rosenberg, W. J.; Roche, A. E.

1993-01-01

A familiar mapping spectrometer implementation utilizes two dimensional detector arrays with spectral dispersion along one direction and spatial along the other. Spectral images are formed by spatially scanning across the scene (i.e., push-broom scanning). For imaging grating and prism spectrometers, the slit is perpendicular to the spatial scan direction. For spectrometers utilizing linearly variable focal-plane-mounted filters the spatial scan direction is perpendicular to the direction of spectral variation. These spectrometers share the common limitation that the number of spectral resolution elements is given by the number of pixels along the spectral (or dispersive) direction. Resolution enhancement by first passing the light input to the spectrometer through a scanned etalon or Michelson is discussed. Thus, while a detector element is scanned through a spatial resolution element of the scene, it is also temporally sampled. The analysis for all the pixels in the dispersive direction is addressed. Several specific examples are discussed. The alternate use of a Michelson for the same enhancement purpose is also discussed. Suitable for weight constrained deep space missions, hardware systems were developed including actuators, sensor, and electronics such that low-resolution etalons with performance required for implementation would weigh less than one pound.

Processing of SeaMARC swath sonar imagery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pratson, L.; Malinverno, A.; Edwards, M.

1990-05-01

Side-scan swath sonar systems have become an increasingly important means of mapping the sea floor. Two such systems are the deep-towed, high-resolution SeaMARC I sonar, which has a variable swath width of up to 5 km, and the shallow-towed, lower-resolution SeaMARC II sonar, which has a swath width of 10 km. The sea-floor imagery of acoustic backscatter output by the SeaMARC sonars is analogous to aerial photographs and airborne side-looking radar images of continental topography. Geologic interpretation of the sea-floor imagery is greatly facilitated by image processing. Image processing of the digital backscatter data involves removal of noise by medianmore » filtering, spatial filtering to remove sonar scans of anomalous intensity, across-track corrections to remove beam patterns caused by nonuniform response of the sonar transducers to changes in incident angle, and contrast enhancement by histogram equalization to maximize the available dynamic range. Correct geologic interpretation requires submarine structural fabrics to be displayed in their proper locations and orientations. Geographic projection of sea-floor imagery is achieved by merging the enhanced imagery with the sonar vehicle navigation and correcting for vehicle attitude. Co-registration of bathymetry with sonar imagery introduces sea-floor relief and permits the imagery to be displayed in three-dimensional perspectives, furthering the ability of the marine geologist to infer the processes shaping formerly hidden subsea terrains.« less

Surface active gold nanoparticles biosynthesis by new approach for bionanocatalytic activity.

PubMed

Vasantharaj, S; Sripriya, N; Shanmugavel, M; Manikandan, E; Gnanamani, A; Senthilkumar, P

2018-02-01

In the present day, nanotechnology is one of the most promising leading scientific and potentials areas in modern key technology development toward to the humankind. The synthesis of noble metal nanoparticles (NPs) is an expanding research area due to the possible applications for the development of bio-medical applications. Eco-friendly approach for the biosynthesis of gold nanoparticles (AuNPs) using the aqueous extract from Ruellia tuberosa and Phyllanthus acidus (leaf and twig) for the first time. Surface active AuNPs were characterized by UV-Vis spectroscopy, FTIR (Fourier transform infrared) spectroscopy, DSC (differential scanning colorimetry), DLS (dynamic light scattering) and environmental SEM (scanning electron microscope) analysis at room temperature (RT). Enhanced surface plasmon resonance (SPR) absorbance UV visible optical spectra were detected in the range of 552, 548, 558 and 536 nm. SEM and DLS (transmission mode) analysis confirmed the morphology of the nanoparticles to be spherical with the average size in the range of 88.37, 94.31, 82.23 and 81.36 nm. Further they have enhanced the enzyme activity on α-amylase, cellulase, and xylanase. The results suggest that the phyto-fabricated AuNPs from R. tuberosa and P. acidus is simple, less expensive, eco-friendly, green synthesis and also can be exploited for the potential future industrial and bio-medical applications. Copyright © 2018 Elsevier B.V. All rights reserved.

Performance Enhancement of the RatCAP Awake Rate Brain PET System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaska, P.; Vaska, P.; Woody, C.

The first full prototype of the RatCAP PET system, designed to image the brain of a rat while conscious, has been completed. Initial results demonstrated excellent spatial resolution, 1.8 mm FWHM with filtered backprojection and <1.5 mm FWHM with a Monte Carlo based MLEM method. However, noise equivalent countrate studies indicated the need for better timing to mitigate the effect of randoms. Thus, the front-end ASIC has been redesigned to minimize time walk, an accurate coincidence time alignment method has been implemented, and a variance reduction technique for the randoms is being developed. To maximize the quantitative capabilities required formore » neuroscience, corrections are being implemented and validated for positron range and photon noncollinearity, scatter (including outside the field of view), attenuation, randoms, and detector efficiency (deadtime is negligible). In addition, a more robust and compact PCI-based optical data acquisition system has been built to replace the original VME-based system while retaining the linux-based data processing and image reconstruction codes. Finally, a number of new animal imaging experiments have been carried out to demonstrate the performance of the RatCAP in real imaging situations, including an F-18 fluoride bone scan, a C-11 raclopride scan, and a dynamic C-11 methamphetamine scan.« less

Water-Immersible MEMS scanning mirror designed for wide-field fast-scanning photoacoustic microscopy

NASA Astrophysics Data System (ADS)

Yao, Junjie; Huang, Chih-Hsien; Martel, Catherine; Maslov, Konstantin I.; Wang, Lidai; Yang, Joon-Mo; Gao, Liang; Randolph, Gwendalyn; Zou, Jun; Wang, Lihong V.

2013-03-01

By offering images with high spatial resolution and unique optical absorption contrast, optical-resolution photoacoustic microscopy (OR-PAM) has gained increasing attention in biomedical research. Recent developments in OR-PAM have improved its imaging speed, but have sacrificed either the detection sensitivity or field of view or both. We have developed a wide-field fast-scanning OR-PAM by using a water-immersible MEMS scanning mirror (MEMS-ORPAM). Made of silicon with a gold coating, the MEMS mirror plate can reflect both optical and acoustic beams. Because it uses an electromagnetic driving force, the whole MEMS scanning system can be submerged in water. In MEMS-ORPAM, the optical and acoustic beams are confocally configured and simultaneously steered, which ensures uniform detection sensitivity. A B-scan imaging speed as high as 400 Hz can be achieved over a 3 mm scanning range. A diffraction-limited lateral resolution of 2.4 μm in water and a maximum imaging depth of 1.1 mm in soft tissue have been experimentally determined. Using the system, we imaged the flow dynamics of both red blood cells and carbon particles in a mouse ear in vivo. By using Evans blue dye as the contrast agent, we also imaged the flow dynamics of lymphatic vessels in a mouse tail in vivo. The results show that MEMS-OR-PAM could be a powerful tool for studying highly dynamic and time-sensitive biological phenomena.

Reinforcement of SBR/waste rubber powder vulcanizate with in situ generated zinc dimethacrylate

NASA Astrophysics Data System (ADS)

Wang, X. P.; Cheng, B. K.; Zhang, X.; Jia, D. M.

2016-07-01

Methyl acrylic acid/zinc oxide (MAA/ZnO) was introduced to modify styrene- butadiene rubber/waste rubber powder (SBR/WRP) composites by blending. The enhanced mechanical properties and processing ability were presumably originated from improved compatibility and interfacial interaction between WRP and the SBR matrix by the in situ polymerization of zinc dimethacrylate (ZDMA). A refined interface of the modified SBR/WRP composite was observed by scanning electron microscopy. The formation of ZDMA significantly increased the ionic bond content in the vulcanizate, resulting in exceptional mechanical performance. The comprehensive mechanical properties including tensile strength, tear strength and dynamic heat-building performance reached optimum values with 16 phr MAA.

A predictive software tool for optimal timing in contrast enhanced carotid MR angiography

NASA Astrophysics Data System (ADS)

Moghaddam, Abbas N.; Balawi, Tariq; Habibi, Reza; Panknin, Christoph; Laub, Gerhard; Ruehm, Stefan; Finn, J. Paul

2008-03-01

A clear understanding of the first pass dynamics of contrast agents in the vascular system is crucial in synchronizing data acquisition of 3D MR angiography (MRA) with arrival of the contrast bolus in the vessels of interest. We implemented a computational model to simulate contrast dynamics in the vessels using the theory of linear time-invariant systems. The algorithm calculates a patient-specific impulse response for the contrast concentration from time-resolved images following a small test bolus injection. This is performed for a specific region of interest and through deconvolution of the intensity curve using the long division method. Since high spatial resolution 3D MRA is not time-resolved, the method was validated on time-resolved arterial contrast enhancement in Multi Slice CT angiography. For 20 patients, the timing of the contrast enhancement of the main bolus was predicted by our algorithm from the response to the test bolus, and then for each case the predicted time of maximum intensity was compared to the corresponding time in the actual scan which resulted in an acceptable agreement. Furthermore, as a qualitative validation, the algorithm's predictions of the timing of the carotid MRA in 20 patients with high quality MRA were correlated with the actual timing of those studies. We conclude that the above algorithm can be used as a practical clinical tool to eliminate guesswork and to replace empiric formulae by a priori computation of patient-specific timing of data acquisition for MR angiography.

Virtual substitution scan via single-step free energy perturbation.

PubMed

Chiang, Ying-Chih; Wang, Yi

2016-02-05

With the rapid expansion of our computing power, molecular dynamics (MD) simulations ranging from hundreds of nanoseconds to microseconds or even milliseconds have become increasingly common. The majority of these long trajectories are obtained from plain (vanilla) MD simulations, where no enhanced sampling or free energy calculation method is employed. To promote the 'recycling' of these trajectories, we developed the Virtual Substitution Scan (VSS) toolkit as a plugin of the open-source visualization and analysis software VMD. Based on the single-step free energy perturbation (sFEP) method, VSS enables the user to post-process a vanilla MD trajectory for a fast free energy scan of substituting aryl hydrogens by small functional groups. Dihedrals of the functional groups are sampled explicitly in VSS, which improves the performance of the calculation and is found particularly important for certain groups. As a proof-of-concept demonstration, we employ VSS to compute the solvation free energy change upon substituting the hydrogen of a benzene molecule by 12 small functional groups frequently considered in lead optimization. Additionally, VSS is used to compute the relative binding free energy of four selected ligands of the T4 lysozyme. Overall, the computational cost of VSS is only a fraction of the corresponding multi-step FEP (mFEP) calculation, while its results agree reasonably well with those of mFEP, indicating that VSS offers a promising tool for rapid free energy scan of small functional group substitutions. This article is protected by copyright. All rights reserved. © 2016 Wiley Periodicals, Inc.

Visual scanning behavior is related to recognition performance for own- and other-age faces

PubMed Central

Proietti, Valentina; Macchi Cassia, Viola; dell’Amore, Francesca; Conte, Stefania; Bricolo, Emanuela

2015-01-01

It is well-established that our recognition ability is enhanced for faces belonging to familiar categories, such as own-race faces and own-age faces. Recent evidence suggests that, for race, the recognition bias is also accompanied by different visual scanning strategies for own- compared to other-race faces. Here, we tested the hypothesis that these differences in visual scanning patterns extend also to the comparison between own and other-age faces and contribute to the own-age recognition advantage. Participants (young adults with limited experience with infants) were tested in an old/new recognition memory task where they encoded and subsequently recognized a series of adult and infant faces while their eye movements were recorded. Consistent with findings on the other-race bias, we found evidence of an own-age bias in recognition which was accompanied by differential scanning patterns, and consequently differential encoding strategies, for own-compared to other-age faces. Gaze patterns for own-age faces involved a more dynamic sampling of the internal features and longer viewing time on the eye region compared to the other regions of the face. This latter strategy was extensively employed during learning (vs. recognition) and was positively correlated to discriminability. These results suggest that deeply encoding the eye region is functional for recognition and that the own-age bias is evident not only in differential recognition performance, but also in the employment of different sampling strategies found to be effective for accurate recognition. PMID:26579056

High-resolution whole-brain DCE-MRI using constrained reconstruction: Prospective clinical evaluation in brain tumor patients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Yi, E-mail: yiguo@usc.edu; Zhu, Yinghua; Lingala, Sajan Goud

Purpose: To clinically evaluate a highly accelerated T1-weighted dynamic contrast-enhanced (DCE) MRI technique that provides high spatial resolution and whole-brain coverage via undersampling and constrained reconstruction with multiple sparsity constraints. Methods: Conventional (rate-2 SENSE) and experimental DCE-MRI (rate-30) scans were performed 20 minutes apart in 15 brain tumor patients. The conventional clinical DCE-MRI had voxel dimensions 0.9 × 1.3 × 7.0 mm{sup 3}, FOV 22 × 22 × 4.2 cm{sup 3}, and the experimental DCE-MRI had voxel dimensions 0.9 × 0.9 × 1.9 mm{sup 3}, and broader coverage 22 × 22 × 19 cm{sup 3}. Temporal resolution was 5 smore » for both protocols. Time-resolved images and blood–brain barrier permeability maps were qualitatively evaluated by two radiologists. Results: The experimental DCE-MRI scans showed no loss of qualitative information in any of the cases, while achieving substantially higher spatial resolution and whole-brain spatial coverage. Average qualitative scores (from 0 to 3) were 2.1 for the experimental scans and 1.1 for the conventional clinical scans. Conclusions: The proposed DCE-MRI approach provides clinically superior image quality with higher spatial resolution and coverage than currently available approaches. These advantages may allow comprehensive permeability mapping in the brain, which is especially valuable in the setting of large lesions or multiple lesions spread throughout the brain.« less

Ensemble LUT classification for degraded document enhancement

NASA Astrophysics Data System (ADS)

Obafemi-Ajayi, Tayo; Agam, Gady; Frieder, Ophir

2008-01-01

The fast evolution of scanning and computing technologies have led to the creation of large collections of scanned paper documents. Examples of such collections include historical collections, legal depositories, medical archives, and business archives. Moreover, in many situations such as legal litigation and security investigations scanned collections are being used to facilitate systematic exploration of the data. It is almost always the case that scanned documents suffer from some form of degradation. Large degradations make documents hard to read and substantially deteriorate the performance of automated document processing systems. Enhancement of degraded document images is normally performed assuming global degradation models. When the degradation is large, global degradation models do not perform well. In contrast, we propose to estimate local degradation models and use them in enhancing degraded document images. Using a semi-automated enhancement system we have labeled a subset of the Frieder diaries collection.1 This labeled subset was then used to train an ensemble classifier. The component classifiers are based on lookup tables (LUT) in conjunction with the approximated nearest neighbor algorithm. The resulting algorithm is highly effcient. Experimental evaluation results are provided using the Frieder diaries collection.1

Detectability of early brain meningitis with magnetic resonance imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Runge, V.M.; Wells, J.W.; Williams, N.M.

1995-08-01

The ability of high-field (1.5 T) magnetic resonance imaging (MRI) to detect early brain meningitis was evaluated in a canine model. Contrast dose, timing postinjection, and imaging technique (specifically the use of magnetization transfer) were assessed. Imaging of five canines was performed at 1.5 T 24 hours after injection of Cowans staphylococcus into the cisterna magna. Two control animals also were imaged using the same protocol. Contrast doses of 0.1, 0.3, and 0.8 mmol/kg gadoteridol were compared. Scans were performed at 2, 13, and 22 minutes after an initial injection of 0.1 mmol/kg. Thirty minutes after the initial injection ofmore » contrast, a supplemental dose of 0.2 mmol/kg was given. Scans were then repeated at 2, 12, and 22 minutes after this dose was administered. A second supplemental contrast injection of 0.5 mmol/kg was given at 70 minutes, and immediate postinjection scans with and without MT were acquired. Results. In the animals receiving a cisternal injection of bacteria, the degree of meningeal enhancement was greatest at 0.8 mmol/kg, intermediate at 0.3 mmol/kg, and least at 0.1 mmol/kg. Scans in control studies did not demonstrate abnormal meningeal enhancement. High-contrast dose, MT, and acquisition of immediate postcontrast scans all resulted in statistically significant improvement. On masked film review, abnormal meningeal enhancement was noted in only 2 of 5 experimental dogs at a dose of 0.1 mmol/kg (regardless of the use of MT) compared with all animals at a dose of 0.3 mmol/kg. In 18 of 37 dogs (paired scans with and without MT), when abnormal enhancement was noted, the use of MT improved the visualization of abnormal meningeal enhancement. In early brain meningitis, high-contrast dose (0.3 mmol/kg), MT, and scanning immediately after injection improve detection of abnormal meningeal enhancement, thus facilitating the diagnosis of meningitis. Of these factors, contrast dose is the most important. 14 refs., 9 figs., 2 tabs.« less

Dynamic iterative beam hardening correction (DIBHC) in myocardial perfusion imaging using contrast-enhanced computed tomography.

PubMed

Stenner, Philip; Schmidt, Bernhard; Allmendinger, Thomas; Flohr, Thomas; Kachelrie, Marc

2010-06-01

In cardiac perfusion examinations with computed tomography (CT) large concentrations of iodine in the ventricle and in the descending aorta cause beam hardening artifacts that can lead to incorrect perfusion parameters. The aim of this study is to reduce these artifacts by performing an iterative correction and by accounting for the 3 materials soft tissue, bone, and iodine. Beam hardening corrections are either implemented as simple precorrections which cannot account for higher order beam hardening effects, or as iterative approaches that are based on segmenting the original image into material distribution images. Conventional segmentation algorithms fail to clearly distinguish between iodine and bone. Our new algorithm, DIBHC, calculates the time-dependent iodine distribution by analyzing the voxel changes of a cardiac perfusion examination (typically N approximately 15 electrocardiogram-correlated scans distributed over a total scan time up to T approximately 30 s). These voxel dynamics are due to changes in contrast agent. This prior information allows to precisely distinguish between bone and iodine and is key to DIBHC where each iteration consists of a multimaterial (soft tissue, bone, iodine) polychromatic forward projection, a raw data comparison and a filtered backprojection. Simulations with a semi-anthropomorphic dynamic phantom and clinical scans using a dual source CT scanner with 2 x 128 slices, a tube voltage of 100 kV, a tube current of 180 mAs, and a rotation time of 0.28 seconds have been carried out. The uncorrected images suffer from beam hardening artifacts that appear as dark bands connecting large concentrations of iodine in the ventricle, aorta, and bony structures. The CT-values of the affected tissue are usually underestimated by roughly 20 HU although deviations of up to 61 HU have been observed. For a quantitative evaluation circular regions of interest have been analyzed. After application of DIBHC the mean values obtained deviate by only 1 HU for the simulations and the corrected values show an increase of up to 61 HU for the measurements. One iteration of DIBHC greatly reduces the beam hardening artifacts induced by the contrast agent dynamics (and those due to bone) now allowing for an improved assessment of contrast agent uptake in the myocardium which is essential for determining myocardial perfusion.

Dynamic Contrast-enhanced MR Imaging in Renal Cell Carcinoma: Reproducibility of Histogram Analysis on Pharmacokinetic Parameters

PubMed Central

Wang, Hai-yi; Su, Zi-hua; Xu, Xiao; Sun, Zhi-peng; Duan, Fei-xue; Song, Yuan-yuan; Li, Lu; Wang, Ying-wei; Ma, Xin; Guo, Ai-tao; Ma, Lin; Ye, Hui-yi

2016-01-01

Pharmacokinetic parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) have been increasingly used to evaluate the permeability of tumor vessel. Histogram metrics are a recognized promising method of quantitative MR imaging that has been recently introduced in analysis of DCE-MRI pharmacokinetic parameters in oncology due to tumor heterogeneity. In this study, 21 patients with renal cell carcinoma (RCC) underwent paired DCE-MRI studies on a 3.0 T MR system. Extended Tofts model and population-based arterial input function were used to calculate kinetic parameters of RCC tumors. Mean value and histogram metrics (Mode, Skewness and Kurtosis) of each pharmacokinetic parameter were generated automatically using ImageJ software. Intra- and inter-observer reproducibility and scan–rescan reproducibility were evaluated using intra-class correlation coefficients (ICCs) and coefficient of variation (CoV). Our results demonstrated that the histogram method (Mode, Skewness and Kurtosis) was not superior to the conventional Mean value method in reproducibility evaluation on DCE-MRI pharmacokinetic parameters (K trans & Ve) in renal cell carcinoma, especially for Skewness and Kurtosis which showed lower intra-, inter-observer and scan-rescan reproducibility than Mean value. Our findings suggest that additional studies are necessary before wide incorporation of histogram metrics in quantitative analysis of DCE-MRI pharmacokinetic parameters. PMID:27380733

Microscopic studies of nonlocal spin dynamics and spin transport (invited)

NASA Astrophysics Data System (ADS)

Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris

2015-05-01

Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

Optical cross-talk and surface characterization of SERS nanoimaging bundle substrates

NASA Astrophysics Data System (ADS)

Kiser, John B.; Cullum, Brian M.

2010-04-01

Due to the narrow vibrational bandwidths and unique molecular fingerprints, Raman spectroscopy can be an information rich transduction technique for chemical imaging. Dynamic systems are often difficult to measure using spontaneous Raman due to the relatively weak scattering cross-sections. Using a Raman enhancement mechanism such as surface enhanced Raman scattering (SERS), exposure times can be reduced to a reasonable level for dynamic imaging, due to the increased Raman signal intensity. This paper will discuss the development of a novel SERS substrate, fabricated on the tips of fiber-optic imaging bundles, which can be integrated into a multispectral imaging system for non-scanning chemical imaging. These substrates are fabricated by mechanically tapering a polished fiber optic imaging bundle consisting of 30,000 individual elements; producing 100-nm or smaller diameter core elements on the distal tip. Chemical etching with hydrofluoric acid creates uniform cladding spikes onto which a SERS active metal is vacuum deposited, forming the SERS active surface. By varying the size of the silver islands deposited on the cladding peaks active, surface plasmons can be tuned to various excitation frequencies. The surface of these tapered fiber optic probes will be evaluated by analysis of the SERS signal, location and shape of the active surface plasmons. The cross talk between the fiber elements will also be evaluated.

O-GlcNAcylation enhances anaplastic thyroid carcinoma malignancy.

PubMed

Cheng, Y U; Li, Honglun; Li, Jianlin; Li, Jisheng; Gao, Yan; Liu, Baodong

2016-07-01

O-linked N -acetylglucosamine (O-GlcNAc) glycosylation (O-GlcNAcylation), a dynamic post-translational modification of nuclear and cytoplasmic proteins, may have a critical role in the regulation of biological cell processes and human cancer. O-GlcNAcylation is dynamically regulated by O-GlcNAc transferase (OGT) and O-GlcNAc hydrolase (OGA). Accumulating evidence suggests that O-GlcNAcylation is involved in a variety of types of human cancer. However, the exact role of O-GlcNAcylation in tumor pathogenesis or progression remains to be established. Computed tomography scans of patients with anaplastic thyroid carcinoma (ATC) reveal a rapid growth rate and invasion. The present study demonstrated that O-GlcNAcylation accelerates the progression of ATC. The global O-GlcNAc level of intracellular proteins was increased by overexpression of OGT or downregulation of OGA activity with the specific inhibitor Thiamet-G. By contrast, the global O-GlcNAc level was decreased by silencing of OGT. MTT assay indicated that O-GlcNAcylation significantly promotes cell proliferation. Furthermore, O-GlcNAcylation enhanced cellular biological functions, such as colony formation ability, migration and invasion, of ATC cells in vitro . The findings of the present study suggest that O-GlcNAcylation is associated with malignant properties of thyroid cancer, and may be a potential target for the diagnosis and treatment of thyroid cancer.

Microscopic studies of nonlocal spin dynamics and spin transport (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adur, Rohan; Du, Chunhui; Cardellino, Jeremy

2015-05-07

Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this usingmore » inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.« less

Noninvasive evaluation of active lower gastrointestinal bleeding: comparison between contrast-enhanced MDCT and 99mTc-labeled RBC scintigraphy.

PubMed

Zink, Stephen I; Ohki, Stephen K; Stein, Barry; Zambuto, Domenic A; Rosenberg, Ronald J; Choi, Jenny J; Tubbs, Daniel S

2008-10-01

The purpose of our study was to compare contrast-enhanced MDCT and (99m)Tc-labeled RBC scanning for the evaluation of active lower gastrointestinal bleeding. Over 17 months, 55 patients (32 men, 23 women; age range, 21-92 years) were evaluated prospectively with contrast-enhanced MDCT using 100 mL of iopromide 300 mg I/mL. Technetium-99m-labeled RBC scans were obtained on 41 of 55 patients and select patients underwent angiography for attempted embolization. Each imaging technique was reviewed in a blinded fashion for sensitivity for detection of active bleeding as well as the active lower gastrointestinal bleeding location. Findings were positive on both examinations in eight patients and negative on both examinations in 20 patients. Findings were positive on contrast-enhanced MDCT and negative on (99m)Tc-labeled RBC in two patients; findings were negative on contrast-enhanced MDCT and positive on (99m)Tc-labeled RBC in 11 patients. Statistics showed significant disagreement, with simple agreement = 68.3%, kappa = 0.341, and p = 0.014. Sixteen of 60 (26.7%) contrast-enhanced MDCT scans were positive prospectively, with all accurately localizing the site of bleeding and identification of the underlying lesion in eight of 16 (50%). Nineteen of 41 (46.3%) (99m)Tc-labeled RBC scans were positive. Eighteen of 41 matched patients went on to angiography. In four of these 18 (22.2%) patients, the site of bleeding was confirmed by angiography, but in 14 of 18 (77.8%), the findings were negative. Contrast-enhanced MDCT and (99m)Tc-labeled RBC scanning show significant disagreement for evaluation of active lower gastrointestinal bleeding. Contrast-enhanced MDCT appears effective for detection and localization in cases of active lower gastrointestinal bleeding in which hemorrhage is active at the time of CT.

Spatiotemporal analysis of tumor uptake patterns in dynamic (18)FDG-PET and dynamic contrast enhanced CT.

PubMed

Malinen, Eirik; Rødal, Jan; Knudtsen, Ingerid Skjei; Søvik, Åste; Skogmo, Hege Kippenes

2011-08-01

Molecular and functional imaging techniques such as dynamic positron emission tomography (DPET) and dynamic contrast enhanced computed tomography (DCECT) may provide improved characterization of tumors compared to conventional anatomic imaging. The purpose of the current work was to compare spatiotemporal uptake patterns in DPET and DCECT images. A PET/CT protocol comprising DCECT with an iodine based contrast agent and DPET with (18)F-fluorodeoxyglucose was set up. The imaging protocol was used for examination of three dogs with spontaneous tumors of the head and neck at sessions prior to and after fractionated radiotherapy. Software tools were developed for downsampling the DCECT image series to the PET image dimensions, for segmentation of tracer uptake pattern in the tumors and for spatiotemporal correlation analysis of DCECT and DPET images. DCECT images evaluated one minute post injection qualitatively resembled the DPET images at most imaging sessions. Segmentation by region growing gave similar tumor extensions in DCECT and DPET images, with a median Dice similarity coefficient of 0.81. A relatively high correlation (median 0.85) was found between temporal tumor uptake patterns from DPET and DCECT. The heterogeneity in tumor uptake was not significantly different in the DPET and DCECT images. The median of the spatial correlation was 0.72. DCECT and DPET gave similar temporal wash-in characteristics, and the images also showed a relatively high spatial correlation. Hence, if the limited spatial resolution of DPET is considered adequate, a single DPET scan only for assessing both tumor perfusion and metabolic activity may be considered. However, further work on a larger number of cases is needed to verify the correlations observed in the present study.

Measurement of Murine Single-Kidney Glomerular Filtration Rate Using Dynamic Contrast-Enhanced MRI.

PubMed

Jiang, Kai; Tang, Hui; Mishra, Prasanna K; Macura, Slobodan I; Lerman, Lilach O

2018-06-01

To develop and validate a method for measuring murine single-kidney glomerular filtration rate (GFR) using dynamic contrast-enhanced MRI (DCE-MRI). This prospective study was approved by the Institutional Animal Care and Use Committee. A fast longitudinal relaxation time (T 1 ) measurement method was implemented to capture gadolinium dynamics (1 s/scan), and a modified two-compartment model was developed to quantify GFR as well as renal perfusion using 16.4T MRI in mice 2 weeks after unilateral renal artery stenosis (RAS, n = 6) or sham (n = 8) surgeries. This approach was validated by comparing model-derived GFR and perfusion to those obtained by fluorescein isothiocyanante (FITC)-inulin clearance and arterial spin labeling (ASL), respectively, using the Pearson's and Spearman's rank correlations and Bland-Altman analysis. The compartmental model provided a good fitting to measured gadolinium dynamics in both normal and RAS kidneys. The proposed DCE-MRI method offered assessment of single-kidney GFR and perfusion, comparable to the FITC-inulin clearance (Pearson's correlation coefficient r = 0.95 and Spearman's correlation coefficient ρ = 0.94, P < 0.0001, and mean difference -7.0 ± 11.0 μL/min) and ASL (r = 0.92 and ρ = 0.84, P < 0.0001, and mean difference 4.4 ± 66.1 mL/100 g/min) methods. The proposed DCE-MRI method may be useful for reliable noninvasive measurements of single-kidney GFR and perfusion in mice. Magn Reson Med 79:2935-2943, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

The effect of medium structure complexity on the growth of Saccharomyces cerevisiae in gelatin-dextran systems.

PubMed

Boons, Kathleen; Noriega, Estefanía; Verherstraeten, Niels; David, Charlotte C; Hofkens, Johan; Van Impe, Jan F

2015-04-16

As most food systems are (semi-)solid, the effect of food structure on bacterial growth has been widely acknowledged. However, studies on the growth dynamics of yeasts have neglected the effect of food structure. In this paper, the growth dynamics of the spoilage yeast Saccharomyces cerevisiae was investigated at 23.5 °C in broth, singular, homogeneous biopolymer systems and binary biopolymer systems with a heterogeneous microstructure. The biopolymers gelatin and dextran were used to introduce the different levels of structure. The metabolizing ability of gelatin and dextran by S. cerevisiae was examined. To study microbial behavior in the binary systems at the micro level, mixtures were imaged with confocal laser scanning microscopy (CLSM). Growth dynamics and microscopic images of S. cerevisiae were compared with those obtained for Escherichia coli in the same model system (Boons et al., 2014). Different phase-separated, heterogeneous microstructures were obtained by changing the amount of added gelatin and dextran. Regardless of the microstructure, S. cerevisiae was preferentially located in the dextran phase. Metabolizing ability-tests indicated that gelatin could be consumed by S. cerevisiae but in the presence of glucose, no change in gelatin concentration was observed. No indication of dextran metabolizing ability was observed. When supplementing broth with gelatin or dextran alone, an enhanced growth rate and maximum cell density were observed. This enhancement was further increased by adding a second biopolymer, introducing a heterogeneous microstructure and hence increasing the medium structure complexity. The results obtained indicate that food structure complexity plays a significant role in the growth dynamics of S. cerevisiae, an important food spoiler. Copyright © 2014. Published by Elsevier B.V.

Novel medical image enhancement algorithms

NASA Astrophysics Data System (ADS)

Agaian, Sos; McClendon, Stephen A.

2010-01-01

In this paper, we present two novel medical image enhancement algorithms. The first, a global image enhancement algorithm, utilizes an alpha-trimmed mean filter as its backbone to sharpen images. The second algorithm uses a cascaded unsharp masking technique to separate the high frequency components of an image in order for them to be enhanced using a modified adaptive contrast enhancement algorithm. Experimental results from enhancing electron microscopy, radiological, CT scan and MRI scan images, using the MATLAB environment, are then compared to the original images as well as other enhancement methods, such as histogram equalization and two forms of adaptive contrast enhancement. An image processing scheme for electron microscopy images of Purkinje cells will also be implemented and utilized as a comparison tool to evaluate the performance of our algorithm.

Assessment of cerebral perfusion in childhood strokes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gates, G.F.; Fishman, L.S.; Segall, H.D.

1982-11-01

Thirty-three children who had strokes were studied by dynamic and static scintigraphy, 29 by CT scanning, and 10 by cerebral angiography. The accuracy of dynamic scintigraphy in stroke detection during the first week of clinical symptoms was 94% while CT scanning was 60% accurate and static scintigraphy 11% accurate. During the second week the accuracy of CT scanning increased to 100%, but static scintigraphy improved to only 50%. Fifty percent of scintiangiograms performed during the first week showed either luxuriant perfusion or flip-flop patterns. In some patients these two flow patterns changed to that of cerebral hemispheric ischemia after goingmore » through a phase during which perfusion appeared to be equal in the two hemispheres. Dynamic scintigraphy is believed to be the test of choice for stroke detection in children during the first week.« less

Image-enhanced endoscopy with I-scan technology for the evaluation of duodenal villous patterns.

PubMed

Cammarota, Giovanni; Ianiro, Gianluca; Sparano, Lucia; La Mura, Rossella; Ricci, Riccardo; Larocca, Luigi M; Landolfi, Raffaele; Gasbarrini, Antonio

2013-05-01

I-scan technology is the newly developed endoscopic tool that works in real time and utilizes a digital contrast method to enhance endoscopic image. We performed a feasibility study aimed to determine the diagnostic accuracy of i-scan technology for the evaluation of duodenal villous patterns, having histology as the reference standard. In this prospective, single center, open study, patients undergoing upper endoscopy for an histological evaluation of duodenal mucosa were enrolled. All patients underwent upper endoscopy using high resolution view in association with i-scan technology. During endoscopy, duodenal villous patterns were evaluated and classified as normal, partial villous atrophy, or marked villous atrophy. Results were then compared with histology. One hundred fifteen subjects were recruited in this study. The endoscopist was able to find marked villous atrophy of the duodenum in 12 subjects, partial villous atrophy in 25, and normal villi in the remaining 78 individuals. The i-scan system was demonstrated to have great accuracy (100 %) in the detection of marked villous atrophy patterns. I-scan technology showed quite lower accuracy in determining partial villous atrophy or normal villous patterns (respectively, 90 % for both items). Image-enhancing endoscopic technology allows a clear visualization of villous patterns in the duodenum. By switching from the standard to the i-scan view, it is possible to optimize the accuracy of endoscopy in recognizing villous alteration in subjects undergoing endoscopic evaluation.

Theory of a Quantum Scanning Microscope for Cold Atoms

NASA Astrophysics Data System (ADS)

Yang, D.; Laflamme, C.; Vasilyev, D. V.; Baranov, M. A.; Zoller, P.

2018-03-01

We propose and analyze a scanning microscope to monitor "live" the quantum dynamics of cold atoms in a cavity QED setup. The microscope measures the atomic density with subwavelength resolution via dispersive couplings to a cavity and homodyne detection within the framework of continuous measurement theory. We analyze two modes of operation. First, for a fixed focal point the microscope records the wave packet dynamics of atoms with time resolution set by the cavity lifetime. Second, a spatial scan of the microscope acts to map out the spatial density of stationary quantum states. Remarkably, in the latter case, for a good cavity limit, the microscope becomes an effective quantum nondemolition device, such that the spatial distribution of motional eigenstates can be measured backaction free in single scans, as an emergent quantum nondemolition measurement.

Theory of a Quantum Scanning Microscope for Cold Atoms.

PubMed

Yang, D; Laflamme, C; Vasilyev, D V; Baranov, M A; Zoller, P

2018-03-30

We propose and analyze a scanning microscope to monitor "live" the quantum dynamics of cold atoms in a cavity QED setup. The microscope measures the atomic density with subwavelength resolution via dispersive couplings to a cavity and homodyne detection within the framework of continuous measurement theory. We analyze two modes of operation. First, for a fixed focal point the microscope records the wave packet dynamics of atoms with time resolution set by the cavity lifetime. Second, a spatial scan of the microscope acts to map out the spatial density of stationary quantum states. Remarkably, in the latter case, for a good cavity limit, the microscope becomes an effective quantum nondemolition device, such that the spatial distribution of motional eigenstates can be measured backaction free in single scans, as an emergent quantum nondemolition measurement.

Ab initio theory and modeling of water.

PubMed

Chen, Mohan; Ko, Hsin-Yu; Remsing, Richard C; Calegari Andrade, Marcos F; Santra, Biswajit; Sun, Zhaoru; Selloni, Annabella; Car, Roberto; Klein, Michael L; Perdew, John P; Wu, Xifan

2017-10-10

Water is of the utmost importance for life and technology. However, a genuinely predictive ab initio model of water has eluded scientists. We demonstrate that a fully ab initio approach, relying on the strongly constrained and appropriately normed (SCAN) density functional, provides such a description of water. SCAN accurately describes the balance among covalent bonds, hydrogen bonds, and van der Waals interactions that dictates the structure and dynamics of liquid water. Notably, SCAN captures the density difference between water and ice I h at ambient conditions, as well as many important structural, electronic, and dynamic properties of liquid water. These successful predictions of the versatile SCAN functional open the gates to study complex processes in aqueous phase chemistry and the interactions of water with other materials in an efficient, accurate, and predictive, ab initio manner.

Ab initio theory and modeling of water

PubMed Central

Chen, Mohan; Ko, Hsin-Yu; Remsing, Richard C.; Calegari Andrade, Marcos F.; Santra, Biswajit; Sun, Zhaoru; Selloni, Annabella; Car, Roberto; Klein, Michael L.; Perdew, John P.; Wu, Xifan

2017-01-01

Water is of the utmost importance for life and technology. However, a genuinely predictive ab initio model of water has eluded scientists. We demonstrate that a fully ab initio approach, relying on the strongly constrained and appropriately normed (SCAN) density functional, provides such a description of water. SCAN accurately describes the balance among covalent bonds, hydrogen bonds, and van der Waals interactions that dictates the structure and dynamics of liquid water. Notably, SCAN captures the density difference between water and ice Ih at ambient conditions, as well as many important structural, electronic, and dynamic properties of liquid water. These successful predictions of the versatile SCAN functional open the gates to study complex processes in aqueous phase chemistry and the interactions of water with other materials in an efficient, accurate, and predictive, ab initio manner. PMID:28973868

Re-designing scanning to reduce learning demands: the performance of typically developing 2-year-olds.

PubMed

McCarthy, John; Light, Janice; Drager, Kathryn; McNaughton, David; Grodzicki, Laura; Jones, Jonathan; Panek, Elizabeth; Parkin, Elizabeth

2006-12-01

Children with severe motor impairments who cannot use direct selection are typically introduced to scanning as a means of accessing assistive technology. Unfortunately, it is difficult for young children to learn to scan because the design of current scanning techniques does not always make explicit the offer of items from the selection array; furthermore, it does not provide explicit feedback after activation of the switch to select the target item. In the current study, scanning was redesigned to reduce learning demands by making both the offer of items and the feedback upon selection more explicit through the use of animation realized through HTML and speech output with appropriate intonation. Twenty typically developing 2-year-olds without disabilities were randomly assigned to use either traditional scanning or enhanced scanning to select target items from an array of three items. The 2-year-olds did not learn to use traditional scanning across three sessions. Their performance in Session 3 did not differ from that in Session 1; they did not exceed chance levels of accuracy in either session (mean accuracy of 20% for Sessions 1 and 3). In contrast, the children in the enhanced scanning condition demonstrated improvements in accuracy across the three 10-20-min sessions (mean accuracies of 22 and 48% for Sessions 1 and 3, respectively). There were no reliable differences between the children's performances with the two scanning techniques for Session 1; however, by Session 3, the children were more than twice as accurate using the enhanced scanning technique compared to the traditional design. Results suggest that by redesigning scanning, we may be able to reduce some of the learning demands and thereby reduce some of the instructional time required for children to attain mastery. Clinical implications, limitations, and directions for future research and development are discussed.

Computed tomography of infantile hepatic hemangioendothelioma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lucaya, J.; Enriquez, G.; Amat, L.

1985-04-01

Computed tomography (CT) was performed on five infants with hepatic hemangioendothelioma. Precontrast scans showed solitary or multiple, homogeneous, circumscribed areas with reduced attenuation values. Tiny tumoral calcifications were identified in two patients. Serial scans, after injection of a bolus of contrast material, showed early massive enhancement, which was either diffuse or peripheral. On delayed scans, multinocular tumors became isodense with surrounding liver, while all solitary ones showed varied degrees of centripetal enhancement and persistent central cleftlike unenhanced areas. The authors believe that these CT features are characteristic and obviate arteriographic confirmation.

Toward Prostate Cancer Contouring Guidelines on Magnetic Resonance Imaging: Dominant Lesion Gross and Clinical Target Volume Coverage Via Accurate Histology Fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gibson, Eli; Biomedical Engineering, University of Western Ontario, London, Ontario; Centre for Medical Image Computing, University College London, London

Purpose: Defining prostate cancer (PCa) lesion clinical target volumes (CTVs) for multiparametric magnetic resonance imaging (mpMRI) could support focal boosting or treatment to improve outcomes or lower morbidity, necessitating appropriate CTV margins for mpMRI-defined gross tumor volumes (GTVs). This study aimed to identify CTV margins yielding 95% coverage of PCa tumors for prospective cases with high likelihood. Methods and Materials: Twenty-five men with biopsy-confirmed clinical stage T1 or T2 PCa underwent pre-prostatectomy mpMRI, yielding T2-weighted, dynamic contrast-enhanced, and apparent diffusion coefficient images. Digitized whole-mount histology was contoured and registered to mpMRI scans (error ≤2 mm). Four observers contoured lesion GTVs onmore » each mpMRI scan. CTVs were defined by isotropic and anisotropic expansion from these GTVs and from multiparametric (unioned) GTVs from 2 to 3 scans. Histologic coverage (proportions of tumor area on co-registered histology inside the CTV, measured for Gleason scores [GSs] ≥6 and ≥7) and prostate sparing (proportions of prostate volume outside the CTV) were measured. Nonparametric histologic-coverage prediction intervals defined minimal margins yielding 95% coverage for prospective cases with 78% to 92% likelihood. Results: On analysis of 72 true-positive tumor detections, 95% coverage margins were 9 to 11 mm (GS ≥ 6) and 8 to 10 mm (GS ≥ 7) for single-sequence GTVs and were 8 mm (GS ≥ 6) and 6 mm (GS ≥ 7) for 3-sequence GTVs, yielding CTVs that spared 47% to 81% of prostate tissue for the majority of tumors. Inclusion of T2-weighted contours increased sparing for multiparametric CTVs with 95% coverage margins for GS ≥6, and inclusion of dynamic contrast-enhanced contours increased sparing for GS ≥7. Anisotropic 95% coverage margins increased the sparing proportions to 71% to 86%. Conclusions: Multiparametric magnetic resonance imaging–defined GTVs expanded by appropriate margins may support focal boosting or treatment of PCa; however, these margins, accounting for interobserver and intertumoral variability, may preclude highly conformal CTVs. Multiparametric GTVs and anisotropic margins may reduce the required margins and improve prostate sparing.« less

Normal saline as a natural intravascular contrast agent for dynamic perfusion-weighted MRI of the brain: Proof of concept at 1.5T.

PubMed

Jara, Hernán; Mian, Asim; Sakai, Osamu; Anderson, Stephan W; Horn, Mitchel J; Norbash, Alexander M; Soto, Jorge A

2016-12-01

Gadolinium-based contrast agents have associated risks. Normal saline (NS) is a nontoxic sodium chloride water solution that can significantly increase the magnetic resonance imaging (MRI) relaxation times of blood via transient hemodilution (THD). The purpose of this pilot study was to test in vivo in the head the potential of normal saline as a safer, exogenous perfusion contrast agent. This Health Insurance Portability and Accountability Act (HIPAA)-compliant prospective study was approved by the local Institutional Review Board (IRB): 12 patients were scanned with T 1 -weighted inversion recovery turbo spin echo pulse sequence at 1.5T. The dynamic inversion recovery pulse sequence was run before, during, and after the NS injection for up to 5 minutes: 100 ml of NS was power-injected via antecubital veins at 3-4 ml/s. Images were processed to map maximum enhancement area-under-the-curve, time-to-peak, and mean-transit-time. These maps were used to identify the areas showing significant NS injection-related signal and to generate enhancement time curves. Hardware and pulse sequence stability were studied via phantom experimentation. Main features of the time curves were tested against theoretical modeling of THD signal effects using inversion recovery pulse sequences. Pearson correlation coefficient (R) mapping was used to differentiate genuine THD effects from motion confounders and noise. The scans of 8 out of 12 patients showed NS injection-related effects that correlate in magnitude with tissue type (gray matter ∼15% and white matter ∼3%). Motion artifacts prevented ascertaining NS signal effects in the remaining four patients. Positive and negative time curves were observed in vivo and this dual THD signal polarity was also observed in the theoretical simulations. R-histograms that were approximately constant in the range 0.1 < |R| < 0.8 and leading to correlation fractions of F corr (|R| > 0.5) = 0.45 and 0.59 were found to represent scans with genuine THD signal effects. A measurable perfusion effect in brain tissue was demonstrated in vivo using NS as an injectable intravascular contrast agent. J. Magn. Reson. Imaging 2016;44:1580-1591. © 2016 International Society for Magnetic Resonance in Medicine.

SU-D-303-03: Impact of Uncertainty in T1 Measurements On Quantification of Dynamic Contrast Enhanced MRI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aryal, M; Cao, Y

2015-06-15

Purpose: Quantification of dynamic contrast enhanced (DCE) MRI requires native longitudinal relaxation time (T1) measurement. This study aimed to assess uncertainty in T1 measurements using two different methods. Methods and Materials: Brain MRI scans were performed on a 3T scanner in 9 patients who had low grade/benign tumors and partial brain radiotherapy without chemotherapy at pre-RT, week-3 during RT (wk-3), end-RT, and 1, 6 and 18 months after RT. T1-weighted images were acquired using gradient echo sequences with 1) 2 different flip angles (50 and 150), and 2) 5 variable TRs (100–2000ms). After creating quantitative T1 maps, average T1 wasmore » calculated in regions of interest (ROI), which were distant from tumors and received a total of accumulated radiation doses < 5 Gy at wk-3. ROIs included left and right normal Putamen and Thalamus (gray matter: GM), and frontal and parietal white matter (WM). Since there were no significant or even a trend of T1 changes from pre-RT to wk-3 in these ROIs, a relative repeatability coefficient (RC) of T1 as a measure of uncertainty was estimated in each ROI using the data pre-RT and at wk-3. The individual T1 changes at later time points were evaluated compared to the estimated RCs. Results: The 2-flip angle method produced small RCs in GM (9.7–11.7%) but large RCs in WM (12.2–13.6%) compared to the saturation-recovery (SR) method (11.0–17.7% for GM and 7.5–11.2% for WM). More than 81% of individual T1 changes were within T1 uncertainty ranges defined by RCs. Conclusion: Our study suggests that the impact of T1 uncertainty on physiological parameters derived from DCE MRI is not negligible. A short scan with 2 flip angles is able to achieve repeatability of T1 estimates similar to a long scan with 5 different TRs, and is desirable to be integrated in the DCE protocol. Present study was supported by National Institute of Health (NIH) under grant numbers; UO1 CA183848 and RO1 NS064973.« less

An elastography method based on the scanning contact resonance of a piezoelectric cantilever

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Ji; Li, Faxin, E-mail: lifaxin@pku.edu.cn

2013-12-15

Purpose: Most tissues may become significantly stiffer than their normal states when there are lesions inside. The tissue's modulus can then act as an identification parameter for clinic diagnosis of tumors or fibrosis, which leads to elastography. This study introduces a novel elastography method that can be used for modulus imaging of superficial organs. Methods: This method is based on the scanning contact-resonance of a unimorph piezoelectric cantilever. The cantilever vibrates in its bending mode with the tip pressed tightly on the sample. The contact resonance frequency of the cantilever-sample system is tracked at each scanning point, from which themore » sample's modulus can be derived based on a beam dynamic model and a contact mechanics model. Scanning is performed by a three-dimensional motorized stage and the whole system is controlled by a homemade software program based on LabVIEW. Results: Testing onin vitro beef tissues indicates that the fat and the muscle can be easily distinguished using this system, and the accuracy of the modulus measurement can be comparable with that of nanoindentation. Imaging on homemade gelatin phantoms shows that the depth information of the abnormalities can be qualitatively obtained by varying the pressing force. The detection limit of this elastography method is specially examined both experimentally and numerically. Results show that it can detect the typical lesions in superficial organs with the depth of several centimeters. The lateral resolution of this elastography method/system is better than 0.5 mm, and could be further enhanced by using more scanning points. Conclusions: The proposed elastography system can be regarded as a sensitive palpation robot, which may be very promising in early diagnosis of tumors in superficial organs such as breast and thyroid.« less

ultra-Stable Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (5STAR)

NASA Astrophysics Data System (ADS)

Dunagan, S. E.; Johnson, R. R.; Redemann, J.; Holben, B. N.; Schmid, B.; Flynn, C. J.; Fahey, L.; LeBlanc, S. E.; Liss, J.; Kacenelenbogen, M. S.; Segal-Rosenhaimer, M.; Shinozuka, Y.; Dahlgren, R. P.; Pistone, K.; Karol, Y.

2017-12-01

The Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) combines airborne sun tracking and sky scanning with diffraction spectroscopy to improve knowledge of atmospheric constituents and their links to air pollution and climate. Direct beam hyperspectral measurement of optical depth improves retrievals of gas constituents and determination of aerosol properties. Sky scanning enhances retrievals of aerosol type and size distribution. Hyperspectral cloud-transmitted radiance measurements enable the retrieval of cloud properties from below clouds. These measurements tighten the closure between satellite and ground-based measurements. 4STAR incorporates a modular sun-tracking/ sky-scanning optical head with optical fiber signal transmission to rack mounted spectrometers, permitting miniaturization of the external optical tracking head, and future detector evolution. 4STAR has supported a broad range of flight experiments since it was first flown in 2010. This experience provides the basis for a series of improvements directed toward reducing measurement uncertainty and calibration complexity, and expanding future measurement capabilities, to be incorporated into a new 5STAR instrument. A 9-channel photodiode radiometer with AERONET-matched bandpass filters will be incorporated to improve calibration stability. A wide dynamic range tracking camera will provide a high precision solar position tracking signal as well as an image of sky conditions around the solar axis. An ultrasonic window cleaning system design will be tested. A UV spectrometer tailored for formaldehyde and SO2 gas retrievals will be added to the spectrometer enclosure. Finally, expansion capability for a 4 channel polarized radiometer to measure the Stokes polarization vector of sky light will be incorporated. This paper presents initial progress on this next-generation 5STAR instrument. Keywords: atmosphere; climate; pollution; radiometry; technology; hyperspectral; fiber optic, polarimetry

Random domain name and address mutation (RDAM) for thwarting reconnaissance attacks

PubMed Central

Chen, Xi; Zhu, Yuefei

2017-01-01

Network address shuffling is a novel moving target defense (MTD) that invalidates the address information collected by the attacker by dynamically changing or remapping the host’s network addresses. However, most network address shuffling methods are limited by the limited address space and rely on the host’s static domain name to map to its dynamic address; therefore these methods cannot effectively defend against random scanning attacks, and cannot defend against an attacker who knows the target’s domain name. In this paper, we propose a network defense method based on random domain name and address mutation (RDAM), which increases the scanning space of the attacker through a dynamic domain name method and reduces the probability that a host will be hit by an attacker scanning IP addresses using the domain name system (DNS) query list and the time window methods. Theoretical analysis and experimental results show that RDAM can defend against scanning attacks and worm propagation more effectively than general network address shuffling methods, while introducing an acceptable operational overhead. PMID:28489910

Enhanced capture rate for haze defects in production wafer inspection

NASA Astrophysics Data System (ADS)

Auerbach, Ditza; Shulman, Adi; Rozentsvige, Moshe

2010-03-01

Photomask degradation via haze defect formation is an increasing troublesome yield problem in the semiconductor fab. Wafer inspection is often utilized to detect haze defects due to the fact that it can be a bi-product of process control wafer inspection; furthermore, the detection of the haze on the wafer is effectively enhanced due to the multitude of distinct fields being scanned. In this paper, we demonstrate a novel application for enhancing the wafer inspection tool's sensitivity to haze defects even further. In particular, we present results of bright field wafer inspection using the on several photo layers suffering from haze defects. One way in which the enhanced sensitivity can be achieved in inspection tools is by using a double scan of the wafer: one regular scan with the normal recipe and another high sensitivity scan from which only the repeater defects are extracted (the non-repeater defects consist largely of noise which is difficult to filter). Our solution essentially combines the double scan into a single high sensitivity scan whose processing is carried out along two parallel routes (see Fig. 1). Along one route, potential defects follow the standard recipe thresholds to produce a defect map at the nominal sensitivity. Along the alternate route, potential defects are used to extract only field repeater defects which are identified using an optimal repeater algorithm that eliminates "false repeaters". At the end of the scan, the two defect maps are merged into one with optical scan images available for all the merged defects. It is important to note, that there is no throughput hit; in addition, the repeater sensitivity is increased relative to a double scan, due to a novel runtime algorithm implementation whose memory requirements are minimized, thus enabling to search a much larger number of potential defects for repeaters. We evaluated the new application on photo wafers which consisted of both random and haze defects. The evaluation procedure involved scanning with three different recipe types: Standard Inspection: Nominal recipe with a low false alarm rate was used to scan the wafer and repeaters were extracted from the final defect map. Haze Monitoring Application: Recipe sensitivity was enhanced and run on a single field column from which on repeating defects were extracted. Enhanced Repeater Extractor: Defect processing included the two parallel routes: a nominal recipe for the random defects and the new high sensitive repeater extractor algorithm. The results showed that the new application (recipe #3) had the highest capture rate on haze defects and detected new repeater defects not found in the first two recipes. In addition, the recipe was much simpler to setup since repeaters are filtered separately from random defects. We expect that in the future, with the advent of mask-less lithography and EUV lithography, the monitoring of field and die repeating defects on the wafer will become a necessity for process control in the semiconductor fab.

Use of digital micromirror devices as dynamic pinhole arrays for adaptive confocal fluorescence microscopy

NASA Astrophysics Data System (ADS)

Pozzi, Paolo; Wilding, Dean; Soloviev, Oleg; Vdovin, Gleb; Verhaegen, Michel

2018-02-01

In this work, we present a new confocal laser scanning microscope capable to perform sensorless wavefront optimization in real time. The device is a parallelized laser scanning microscope in which the excitation light is structured in a lattice of spots by a spatial light modulator, while a deformable mirror provides aberration correction and scanning. A binary DMD is positioned in an image plane of the detection optical path, acting as a dynamic array of reflective confocal pinholes, images by a high performance cmos camera. A second camera detects images of the light rejected by the pinholes for sensorless aberration correction.

Microstructure and Mechanical Properties of Laser Solid Formed Ti-6Al-4V Alloy Under Dynamic Shear Loading

NASA Astrophysics Data System (ADS)

Zhou, Ping; Guo, Wei-Guo; Su, Yu; Wang, Jianjun; Lin, Xin; Huang, Weidong

2017-07-01

To investigate the mechanical properties of the Ti-6Al-4V alloy fabricated by laser solid forming technology, both static and dynamic shear tests were conducted on hat-shaped specimens by a servohydraulic testing machine and an enhanced split Hopkinson pressure bar system, over a temperature range of 173-573 K. The microstructure of both the original and deformed specimens was characterized by optical microscopy and scanning electron microscopy. The results show that: (1) the anisotropy of shear properties is not significant regardless of the visible stratification and the prior- β grains that grow epitaxially along the depositing direction; (2) the ultimate shear strength of this material is lower than that of those Ti-6Al-4V alloys fabricated by forging and extrusion; (3) the adiabatic shear bands of approximately 25.6-36.4 μm in width can develop at all selected temperatures during the dynamic shear deformation; and (4) the observed microstructure and measured microhardness indicate that the grains become refined in adiabatic shear band. Estimation of the temperature rise shows that the temperature in shear band exceeds the recrystallization temperature. The process of rotational dynamic recrystallization is considered to be the cause of the grain refinement in shear band.

CO and CO2 dual-gas detection based on mid-infrared wideband absorption spectroscopy

NASA Astrophysics Data System (ADS)

Dong, Ming; Zhong, Guo-qiang; Miao, Shu-zhuo; Zheng, Chuan-tao; Wang, Yi-ding

2018-03-01

A dual-gas sensor system is developed for CO and CO2 detection using a single broadband light source, pyroelectric detectors and time-division multiplexing (TDM) technique. A stepper motor based rotating system and a single-reflection spherical optical mirror are designed and adopted for realizing and enhancing dual-gas detection. Detailed measurements under static detection mode (without rotation) and dynamic mode (with rotation) are performed to study the performance of the sensor system for the two gas samples. The detection period is 7.9 s in one round of detection by scanning the two detectors. Based on an Allan deviation analysis, the 1σ detection limits under static operation are 3.0 parts per million (ppm) in volume and 2.6 ppm for CO and CO2, respectively, and those under dynamic operation are 9.4 ppm and 10.8 ppm for CO and CO2, respectively. The reported sensor has potential applications in various fields requiring CO and CO2 detection such as in the coal mine.

Computer-assisted identification and volumetric quantification of dynamic contrast enhancement in brain MRI: an interactive system

NASA Astrophysics Data System (ADS)

Wu, Shandong; Avgeropoulos, Nicholas G.; Rippe, David J.

2013-03-01

We present a dedicated segmentation system for tumor identification and volumetric quantification in dynamic contrast brain magnetic resonance (MR) scans. Our goal is to offer a practically useful tool at the end of clinicians in order to boost volumetric tumor assessment. The system is designed to work in an interactive mode such that maximizes the integration of computing capacity and clinical intelligence. We demonstrate the main functions of the system in terms of its functional flow and conduct preliminary validation using a representative pilot dataset. The system is inexpensive, user-friendly, easy to deploy and integrate with picture archiving and communication systems (PACS), and possible to be open-source, which enable it to potentially serve as a useful assistant for radiologists and oncologists. It is anticipated that in the future the system can be integrated into clinical workflow so that become routine available to help clinicians make more objective interpretations of treatment interventions and natural history of disease to best advocate patient needs.

Fabrication of Glass Fiber Reinforced Composites Based on Bio-Oil Phenol Formaldehyde Resin

PubMed Central

Cui, Yong; Chang, Jianmin; Wang, Wenliang

2016-01-01

In this study, bio-oil from fast pyrolysis of renewable biomass was added by the mass of phenol to synthesize bio-oil phenol formaldehyde (BPF) resins, which were used to fabricate glass fiber (GF) reinforced BPF resin (GF/BPF) composites. The properties of the BPF resin and the GF/BPF composites prepared were tested. The functional groups and thermal property of BPF resin were thoroughly investigated by Fourier transform infrared (FTIR) spectra and dynamic thermomechanical analysis (DMA). Results indicated that the addition of 20% bio-oil exhibited favorable adaptability for enhancing the stiffness and heat resistance of phenol formaldehyde (PF) resin. Besides, high-performance GF/BPF composites could be successfully prepared with the BPF resin based on hand lay-up process. The interface characteristics of GF/BPF composites were determined by the analysis of dynamic wettability (DW) and scanning electron microscopy (SEM). It exhibited that GF could be well wetted and embedded in the BPF resin with the bio-oil addition of 20%. PMID:28774009

Random catalytic reaction networks

NASA Astrophysics Data System (ADS)

Stadler, Peter F.; Fontana, Walter; Miller, John H.

1993-03-01

We study networks that are a generalization of replicator (or Lotka-Volterra) equations. They model the dynamics of a population of object types whose binary interactions determine the specific type of interaction product. Such a system always reduces its dimension to a subset that contains production pathways for all of its members. The network equation can be rewritten at a level of collectives in terms of two basic interaction patterns: replicator sets and cyclic transformation pathways among sets. Although the system contains well-known cases that exhibit very complicated dynamics, the generic behavior of randomly generated systems is found (numerically) to be extremely robust: convergence to a globally stable rest point. It is easy to tailor networks that display replicator interactions where the replicators are entire self-sustaining subsystems, rather than structureless units. A numerical scan of random systems highlights the special properties of elementary replicators: they reduce the effective interconnectedness of the system, resulting in enhanced competition, and strong correlations between the concentrations.

The effect of chain rigidity on the interfacial layer thickness and dynamics of polymer nanocomposites

NASA Astrophysics Data System (ADS)

Cheng, Shiwang; Carrillo, Jan-Michael Y.; Carroll, Bobby; Sumpter, Bobby G.; Sokolov, Alexei P.

There are growing experimental evidences showing the existence of an interfacial layer that has a finite thickness with slowing down dynamics in polymer nanocomposites (PNCs). Moreover, it is believed that the interfacial layer plays a significant role on various macroscopic properties of PNCs. A thicker interfacial layer is found to have more pronounced effect on the macroscopic properties such as the mechanical enhancement. However, it is not clear what molecular parameter controls the interfacial layer thickness. Inspired by our recent computer simulations that showed the chain rigidity correlated well with the interfacial layer thickness, we performed systematic experimental studies on different polymer nanocomposites by varying the chain stiffness. Combining small-angle X-ray scattering, broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry, we find a good correlation between the polymer Kuhn length and the thickness of the interfacial layer, confirming the earlier computer simulations results. Our findings provide a direct guidance for the design of new PNCs with desired properties.

Ultra-precise micro-motion stage for optical scanning test

NASA Astrophysics Data System (ADS)

Chen, Wen; Zhang, Jianhuan; Jiang, Nan

2009-05-01

This study aims at the application of optical sensing technology in a 2D flexible hinge test stage. Optical fiber sensor which is manufactured taking advantage of the various unique properties of optical fiber, such as good electric insulation properties, resistance of electromagnetic disturbance, sparkless property and availability in flammable and explosive environment, has lots of good properties, such as high accuracy and wide dynamic range, repeatable, etc. and is applied in 2D flexible hinge stage driven by PZT. Several micro-bending structures are designed utilizing the characteristics of the flexible hinge stage. And through experiments, the optimal micro-bending tooth structure and the scope of displacement sensor trip under this optimal micro-bending tooth structure are derived. These experiments demonstrate that the application of optical fiber displacement sensor in 2D flexible hinge stage driven by PZT substantially broadens the dynamic testing range and improves the sensitivity of this apparatus. Driving accuracy and positioning stability are enhanced as well. [1,2

Development of a realistic, dynamic digital brain phantom for CT perfusion validation

NASA Astrophysics Data System (ADS)

Divel, Sarah E.; Segars, W. Paul; Christensen, Soren; Wintermark, Max; Lansberg, Maarten G.; Pelc, Norbert J.

2016-03-01

Physicians rely on CT Perfusion (CTP) images and quantitative image data, including cerebral blood flow, cerebral blood volume, and bolus arrival delay, to diagnose and treat stroke patients. However, the quantification of these metrics may vary depending on the computational method used. Therefore, we have developed a dynamic and realistic digital brain phantom upon which CTP scans can be simulated based on a set of ground truth scenarios. Building upon the previously developed 4D extended cardiac-torso (XCAT) phantom containing a highly detailed brain model, this work consisted of expanding the intricate vasculature by semi-automatically segmenting existing MRA data and fitting nonuniform rational B-spline surfaces to the new vessels. Using time attenuation curves input by the user as reference, the contrast enhancement in the vessels changes dynamically. At each time point, the iodine concentration in the arteries and veins is calculated from the curves and the material composition of the blood changes to reflect the expected values. CatSim, a CT system simulator, generates simulated data sets of this dynamic digital phantom which can be further analyzed to validate CTP studies and post-processing methods. The development of this dynamic and realistic digital phantom provides a valuable resource with which current uncertainties and controversies surrounding the quantitative computations generated from CTP data can be examined and resolved.

Evaluation and mitigation of the interplay effects for intensity modulated proton therapy for lung cancer in a clinical setting

PubMed Central

Kardar, Laleh; Li, Yupeng; Li, Xiaoqiang; Li, Heng; Cao, Wenhua; Chang, Joe Y.; Liao, Li; Zhu, Ronald X.; Sahoo, Narayan; Gillin, Michael; Liao, Zhongxing; Komaki, Ritsuko; Cox, James D.; Lim, Gino; Zhang, Xiaodong

2015-01-01

Purpose The primary aim of this study was to evaluate the impact of interplay effects for intensity-modulated proton therapy (IMPT) plans for lung cancer in the clinical setting. The secondary aim was to explore the technique of iso-layered re-scanning for mitigating these interplay effects. Methods and Materials Single-fraction 4D dynamic dose without considering re-scanning (1FX dynamic dose) was used as a metric to determine the magnitude of dosimetric degradation caused by 4D interplay effects. The 1FX dynamic dose was calculated by simulating the machine delivery processes of proton spot scanning on moving patient described by 4D computed tomography (4DCT) during the IMPT delivery. The dose contributed from an individual spot was fully calculated on the respiratory phase corresponding to the life span of that spot, and the final dose was accumulated to a reference CT phase by using deformable image registration. The 1FX dynamic dose was compared with the 4D composite dose. Seven patients with various tumor volumes and motions were selected. Results The CTV prescription coverage for the 7 patients were 95.04%, 95.38%, 95.39%, 95.24%, 95.65%, 95.90%, and 95.53%, calculated with use of the 4D composite dose, and were 89.30%, 94.70%, 85.47%, 94.09%, 79.69%, 91.20%, and 94.19% with use of the 1FX dynamic dose. For the 7 patients, the CTV coverage, calculated by using single-fraction dynamic dose, were 95.52%, 95.32%, 96.36%, 95.28%, 94.32%, 95.53%, and 95.78%, using maximum MU limit value of 0.005. In other words, by increasing the number of delivered spots in each fraction, the degradation of CTV coverage improved up to 14.6%. Conclusions Single-fraction 4D dynamic dose without re-scanning was validated as a surrogate to evaluate the interplay effects for IMPT for lung cancer in the clinical setting. The interplay effects can be potentially mitigated by increasing the number of iso-layered re-scanning in each fraction delivery. PMID:25407877

Integral force feedback control with input shaping: Application to piezo-based scanning systems in ECDLs.

PubMed

Zhang, Meng; Liu, Zhigang; Zhu, Yu; Bu, Mingfan; Hong, Jun

2017-07-01

In this paper, a hybrid control system is developed by integrating the closed-loop force feedback and input shaping method to overcome the problem of the hysteresis and dynamic behavior in piezo-based scanning systems and increase the scanning speed of tunable external cavity diode lasers. The flexible hinge and piezoelectric actuators are analyzed, and a dynamic model of the scanning systems is established. A force sensor and an integral controller are utilized in integral force feedback (IFF) to directly augment the damping of the piezoelectric scanning systems. Hysteresis has been effectively eliminated, but the mechanical resonance is still evident. Noticeable residual vibration occurred after the inflection points and then gradually disappeared. For the further control of mechanical resonance, based on the theory of minimum-acceleration trajectory planning, the time-domain input shaping method was developed. The turning sections of a scanning trajectory are replaced by smooth curves, while the linear sections are retained. The IFF method is combined with the input shaping method to control the non-linearity and mechanical resonance in high-speed piezo-based scanning systems. Experiments are conducted, and the results demonstrate the effectiveness of the proposed control approach.

Integral force feedback control with input shaping: Application to piezo-based scanning systems in ECDLs

NASA Astrophysics Data System (ADS)

Zhang, Meng; Liu, Zhigang; Zhu, Yu; Bu, Mingfan; Hong, Jun

2017-07-01

In this paper, a hybrid control system is developed by integrating the closed-loop force feedback and input shaping method to overcome the problem of the hysteresis and dynamic behavior in piezo-based scanning systems and increase the scanning speed of tunable external cavity diode lasers. The flexible hinge and piezoelectric actuators are analyzed, and a dynamic model of the scanning systems is established. A force sensor and an integral controller are utilized in integral force feedback (IFF) to directly augment the damping of the piezoelectric scanning systems. Hysteresis has been effectively eliminated, but the mechanical resonance is still evident. Noticeable residual vibration occurred after the inflection points and then gradually disappeared. For the further control of mechanical resonance, based on the theory of minimum-acceleration trajectory planning, the time-domain input shaping method was developed. The turning sections of a scanning trajectory are replaced by smooth curves, while the linear sections are retained. The IFF method is combined with the input shaping method to control the non-linearity and mechanical resonance in high-speed piezo-based scanning systems. Experiments are conducted, and the results demonstrate the effectiveness of the proposed control approach.

High Performance Nuclear Magnetic Resonance Imaging Using Magnetic Resonance Force Microscopy

DTIC Science & Technology

2013-12-12

Micron- Size Ferromagnet . Physical Review Letters, 92(3) 037205 (2004) [22] A. Z. Genack and A. G. Redeld. Theory of nuclear spin diusion in a...perform spatially resolved scanned probe studies of spin dynamics in nanoscale ensembles of few electron spins of varying size . Our research culminated...perform spatially resolved scanned probe studies of spin dynamics in nanoscale ensembles of few electron spins of varying size . Our research culminated

Two-photon imaging of spatially extended neuronal network dynamics with high temporal resolution.

PubMed

Lillis, Kyle P; Eng, Alfred; White, John A; Mertz, Jerome

2008-07-30

We describe a simple two-photon fluorescence imaging strategy, called targeted path scanning (TPS), to monitor the dynamics of spatially extended neuronal networks with high spatiotemporal resolution. Our strategy combines the advantages of mirror-based scanning, minimized dead time, ease of implementation, and compatibility with high-resolution low-magnification objectives. To demonstrate the performance of TPS, we monitor the calcium dynamics distributed across an entire juvenile rat hippocampus (>1.5mm), at scan rates of 100 Hz, with single cell resolution and single action potential sensitivity. Our strategy for fast, efficient two-photon microscopy over spatially extended regions provides a particularly attractive solution for monitoring neuronal population activity in thick tissue, without sacrificing the signal-to-noise ratio or high spatial resolution associated with standard two-photon microscopy. Finally, we provide the code to make our technique generally available.

Impact of airway morphological changes on pulmonary flows in scoliosis

NASA Astrophysics Data System (ADS)

Farrell, James; Garrido, Enrique; Valluri, Prashant

2016-11-01

The relationship between thoracic deformity in scoliosis and lung function is poorly understood. In a pilot study, we reviewed computed tomography (CT) routine scans of patients undergoing scoliosis surgery. The CT scans were processed to segment the anatomy of the airways, lung and spine. A three-dimensional model was created to study the anatomical relationship. Preliminary analysis showed significant airway morphological differences depending on the anterior position of the spine. A computational fluid dynamics (CFD) study was also conducted on the airway geometry using the inspiratory scans. The CFD model assuming non-compliant airway walls was capable of showing pressure drops in areas of high airway resistance, but was unable to predict regional ventilation differences. Our results indicate a dependence between the dynamic deformation of the airway during breathing and lung function. Dynamic structural deformation must therefore be incorporated within any modelling approaches to guide clinicians on the decision to perform surgical correction of the scoliosis.

The shelf-life of airborne laser scanning data for enhancing forest inventory inferences

Treesearch

Ronald E. McRoberts; Qi Chen; Dale D. Gormanson; Brian F. Walters

2018-01-01

The term shelf-life is used to characterize the elapsed time beyond which a commodity loses its usefulness. The term is most often used with reference to foods and medicines, but herein it is used to characterize the elapsed time beyond which airborne laser scanning (ALS) data are no longer useful for enhancing inferences for forest inventory...

[Spiral CT of the head-neck area: the advantages of the early arterial phase in the detection of squamous-cell carcinomas].

PubMed

Conrad, R; Pauleit, D; Layer, G; Kandyba, J; Kohlbecher, R; Hortling, N; Baselides, P; Schild, H

1999-07-01

To determine if scanning in the arterial phase improves detection of squamous cell carcinomas in the pharynx and larynx. In a prospective clinical study 20 patients with a pharyngeal or laryngeal carcinoma were examined with by spiral CT. 80 ml lopromid were intravenously injected as a bolus with a rate of 3 ml/sec. Two consecutive spiral CT scans were performed with start-delay times of 20 and 70 seconds respectively. Delineation and contrast enhancement of tumours, cervical lymph nodes and vessels were evaluated. The radiodensities (HU) of tumors, lymph nodes vessels, pharyngeal wall and muscle were measured. Comparing early and late start delay time scans tumor assessment in the early phase was better in 58%, less in 16% and equal in both scans in 26%. 82% of the pathologic lymph nodes had more peripheral enhancement than surrounding muscle tissue. During the arterial phase the measured radiodensities of the common carotid artery and jugular vein were significantly higher than in the second phase. Contrast-enhanced special CT permits accurate morphologic assessment (size, infiltration) of pharyngeal and supraglottic laryngeal squamous cell carcinoma, while pathologic lymph nodes already have a sufficient contrast enhancement for the detection.

Atomically Thin Al2O3 Films for Tunnel Junctions

NASA Astrophysics Data System (ADS)

Wilt, Jamie; Gong, Youpin; Gong, Ming; Su, Feifan; Xu, Huikai; Sakidja, Ridwan; Elliot, Alan; Lu, Rongtao; Zhao, Shiping; Han, Siyuan; Wu, Judy Z.

2017-06-01

Metal-insulator-metal tunnel junctions are common throughout the microelectronics industry. The industry standard AlOx tunnel barrier, formed through oxygen diffusion into an Al wetting layer, is plagued by internal defects and pinholes which prevent the realization of atomically thin barriers demanded for enhanced quantum coherence. In this work, we employ in situ scanning tunneling spectroscopy along with molecular-dynamics simulations to understand and control the growth of atomically thin Al2O3 tunnel barriers using atomic-layer deposition. We find that a carefully tuned initial H2O pulse hydroxylated the Al surface and enabled the creation of an atomically thin Al2O3 tunnel barrier with a high-quality M -I interface and a significantly enhanced barrier height compared to thermal AlOx . These properties, corroborated by fabricated Josephson junctions, show that atomic-layer deposition Al2O3 is a dense, leak-free tunnel barrier with a low defect density which can be a key component for the next generation of metal-insulator-metal tunnel junctions.

Machine Detection of Enhanced Electromechanical Energy Conversion in PbZr 0.2Ti 0.8O 3 Thin Films

DOE PAGES

Agar, Joshua C.; Cao, Ye; Naul, Brett; ...

2018-05-28

Many energy conversion, sensing, and microelectronic applications based on ferroic materials are determined by the domain structure evolution under applied stimuli. New hyperspectral, multidimensional spectroscopic techniques now probe dynamic responses at relevant length and time scales to provide an understanding of how these nanoscale domain structures impact macroscopic properties. Such approaches, however, remain limited in use because of the difficulties that exist in extracting and visualizing scientific insights from these complex datasets. Using multidimensional band-excitation scanning probe spectroscopy and adapting tools from both computer vision and machine learning, an automated workflow is developed to featurize, detect, and classify signatures ofmore » ferroelectric/ferroelastic switching processes in complex ferroelectric domain structures. This approach enables the identification and nanoscale visualization of varied modes of response and a pathway to statistically meaningful quantification of the differences between those modes. Lastly, among other things, the importance of domain geometry is spatially visualized for enhancing nanoscale electromechanical energy conversion.« less

Enhanced Carbon Diffusion in Austenitic Stainless Steel Carburized at Low Temperature

NASA Astrophysics Data System (ADS)

Ernst, F.; Avishai, A.; Kahn, H.; Gu, X.; Michal, G. M.; Heuer, A. H.

2009-08-01

Austenitic stainless steel AISI 316L was carburized by a novel, low-temperature gas-phase process. Using a calibrated scanning Auger microprobe (SAM) analysis of cross-sectional specimens under dynamic sputtering, we determined the fraction-depth profile of carbon. The profile is concave—very different from the shape expected for concentration-independent diffusion—and indicates a carbide-free solid solution with carbon levels up to 15 at. pct and a case depth of ≈30 μm. A Boltzmann-Matano analysis with a careful evaluation of the stochastic and potential systematic errors indicates that increasing levels of carbon significantly enhance carbon diffusion. For the highest carbon level observed (15 at. pct), the carbon diffusion coefficient is more than two orders of magnitude larger than in dilute solution. The most likely explanation for this strong increase is that carbon-induced local expansion of metal-metal atom distances, observed as an expansion of the lattice parameter, reduces the activation energy for carbon diffusion.

Characterization of tumor microvascular structure and permeability: comparison between magnetic resonance imaging and intravital confocal imaging

NASA Astrophysics Data System (ADS)

Reitan, Nina Kristine; Thuen, Marte; Goa, Pa˚L. Erik; de Lange Davies, Catharina

2010-05-01

Solid tumors are characterized by abnormal blood vessel organization, structure, and function. These abnormalities give rise to enhanced vascular permeability and may predict therapeutic responses. The permeability and architecture of the microvasculature in human osteosarcoma tumors growing in dorsal window chambers in athymic mice were measured by confocal laser scanning microscopy (CLSM) and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). Dextran (40 kDa) and Gadomer were used as molecular tracers for CLSM and DCE-MRI, respectively. A significant correlation was found between permeability indicators. The extravasation rate Ki as measured by CLSM correlated positively with DCE-MRI parameters, such as the volume transfer constant Ktrans and the initial slope of the contrast agent concentration-time curve. This demonstrates that these two techniques give complementary information. Extravasation was further related to microvascular structure and was found to correlate with the fractal dimension and vascular density. The structural parameter values that were obtained from CLSM images were higher for abnormal tumor vasculature than for normal vessels.

Stability and Antimicrobial Activity of Nisin-Loaded Mesoporous Silica Nanoparticles: A Game-Changer in the War against Maleficent Microbes.

PubMed

Behzadi, Faezeh; Darouie, Sheyda; Alavi, S Mehdi; Shariati, Parvin; Singh, Gurvinder; Dolatshahi-Pirouz, Alireza; Arpanaei, Ayyoob

2018-04-25

Antimicrobial agents, such as nisin, are used extensively in the food industry. Here, we investigated various approaches to load nisin onto mesoporous silica nanoparticles (MSNs, 92 ± 10 nm in diameter), to enhance its stability and sustained release. The morphology, size, and surface charge of the as-prepared nanoparticles were analyzed using scanning transmission electron microscopy, dynamic light scattering, and ζ potential measurement. Nisin was either physically adsorbed or covalently attached to the variously functionalized MSNs, with high loading capacities (>600 mg of nisin g -1 of nanoparticles). The results of antibacterial activity analysis of nisin against Staphylococcus aureus showed that, despite the very low antibacterial activity of nisin covalently conjugated onto MSNs, the physical adsorption of nisin onto the unfunctionalized nanoparticles enhances its antimicrobial activities under various conditions, with no significant cytotoxicity effects on mouse fibroblast L929 cells. In conclusion, MSNs can be recommended as suitable carriers for nisin under various conditions.

Machine Detection of Enhanced Electromechanical Energy Conversion in PbZr 0.2Ti 0.8O 3 Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agar, Joshua C.; Cao, Ye; Naul, Brett

Many energy conversion, sensing, and microelectronic applications based on ferroic materials are determined by the domain structure evolution under applied stimuli. New hyperspectral, multidimensional spectroscopic techniques now probe dynamic responses at relevant length and time scales to provide an understanding of how these nanoscale domain structures impact macroscopic properties. Such approaches, however, remain limited in use because of the difficulties that exist in extracting and visualizing scientific insights from these complex datasets. Using multidimensional band-excitation scanning probe spectroscopy and adapting tools from both computer vision and machine learning, an automated workflow is developed to featurize, detect, and classify signatures ofmore » ferroelectric/ferroelastic switching processes in complex ferroelectric domain structures. This approach enables the identification and nanoscale visualization of varied modes of response and a pathway to statistically meaningful quantification of the differences between those modes. Lastly, among other things, the importance of domain geometry is spatially visualized for enhancing nanoscale electromechanical energy conversion.« less

Identifying the charge generation dynamics in Cs+-based triple cation mixed perovskite solar cells.

PubMed

Salado, Manuel; Kokal, Ramesh K; Calio, Laura; Kazim, Samrana; Deepa, Melepurath; Ahmad, Shahzada

2017-08-30

Triple cation based perovskite solar cells offer enhanced moisture tolerance and stability compared to mixed perovskites. Slight substitution of methyl ammonium or formamidinium cation by cesium (Cs + ), was also reported to eliminate halide segregation due to its smaller size. To elucidate the device kinetics and understand the role of the Cs, we undertook different modes of scanning probe microscopy and electrochemical impedance spectroscopy (EIS) experiments. Kelvin probe force microscopy revealed that the incorporation of the Cs cation increases the contact potential difference (CPD), this CPD further increases when Spiro-OMeTAD is used as a hole transport material. The current at the nanoscale level shows improvement with Cs inclusion and further enhancement by the Spiro-OMeTAD deposition, studied under light illumination, which supports the high photocurrent density obtained from the cells. EIS demonstrates that in a triple cation environment, reduced carrier recombination at the TiO 2 /perovskite interface was also obtained which in turn allow us to achieve a higher V oc value.

Working memory load modulation of parieto-frontal connections: evidence from dynamic causal modeling

PubMed Central

Ma, Liangsuo; Steinberg, Joel L.; Hasan, Khader M.; Narayana, Ponnada A.; Kramer, Larry A.; Moeller, F. Gerard

2011-01-01

Previous neuroimaging studies have shown that working memory load has marked effects on regional neural activation. However, the mechanism through which working memory load modulates brain connectivity is still unclear. In this study, this issue was addressed using dynamic causal modeling (DCM) based on functional magnetic resonance imaging (fMRI) data. Eighteen normal healthy subjects were scanned while they performed a working memory task with variable memory load, as parameterized by two levels of memory delay and three levels of digit load (number of digits presented in each visual stimulus). Eight regions of interest, i.e., bilateral middle frontal gyrus (MFG), anterior cingulate cortex (ACC), inferior frontal cortex (IFC), and posterior parietal cortex (PPC), were chosen for DCM analyses. Analysis of the behavioral data during the fMRI scan revealed that accuracy decreased as digit load increased. Bayesian inference on model structure indicated that a bilinear DCM in which memory delay was the driving input to bilateral PPC and in which digit load modulated several parieto-frontal connections was the optimal model. Analysis of model parameters showed that higher digit load enhanced connection from L PPC to L IFC, and lower digit load inhibited connection from R PPC to L ACC. These findings suggest that working memory load modulates brain connectivity in a parieto-frontal network, and may reflect altered neuronal processes, e.g., information processing or error monitoring, with the change in working memory load. PMID:21692148

Physicochemical properties of surimi gels fortified with dietary fiber.

PubMed

Debusca, Alicia; Tahergorabi, Reza; Beamer, Sarah K; Matak, Kristen E; Jaczynski, Jacek

2014-04-01

Although dietary fiber provides health benefits, most Western populations have insufficient intake. Surimi seafood is not currently fortified with dietary fiber, nor have the effects of fiber fortification on physicochemical properties of surimi been thoroughly studied. In the present study, Alaska pollock surimi was fortified with 0-8 g/100 g of long-chain powdered cellulose as a source of dietary fiber. The protein/water concentrations in surimi were kept constant by adding an inert filler, silicon dioxide in inverse concentrations to the fiber fortification. Fiber-fortified surimi gels were set at 90 °C. The objectives were to determine (1) textural and colour properties; (2) heat-induced gelation (dynamic rheology); and (3) protein endothermic transitions (differential scanning calorimetry) of surimi formulated with constant protein/water, but variable fiber content. Fiber fortification up to 6 g/100 g improved (P<0.05) texture and colour although some decline occurred with 8 g/100g of fiber. Dynamic rheology correlated with texture and showed large increase in gel elasticity, indicating enhanced thermal gelation of surimi. Differential scanning calorimetry showed that fiber fortification did not interfere with thermal transitions of surimi myosin and actin. Long-chain fiber probably traps water physically, which is stabilized by chemical bonding with protein within surimi gel matrix. Based on the present study, it is suggested that the fiber-protein interaction is mediated by water and is physicochemical in nature. Copyright © 2013 Elsevier Ltd. All rights reserved.

Bidirectional Contrast agent leakage correction of dynamic susceptibility contrast (DSC)-MRI improves cerebral blood volume estimation and survival prediction in recurrent glioblastoma treated with bevacizumab.

PubMed

Leu, Kevin; Boxerman, Jerrold L; Lai, Albert; Nghiemphu, Phioanh L; Pope, Whitney B; Cloughesy, Timothy F; Ellingson, Benjamin M

2016-11-01

To evaluate a leakage correction algorithm for T 1 and T2* artifacts arising from contrast agent extravasation in dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) that accounts for bidirectional contrast agent flux and compare relative cerebral blood volume (CBV) estimates and overall survival (OS) stratification from this model to those made with the unidirectional and uncorrected models in patients with recurrent glioblastoma (GBM). We determined median rCBV within contrast-enhancing tumor before and after bevacizumab treatment in patients (75 scans on 1.5T, 19 scans on 3.0T) with recurrent GBM without leakage correction and with application of the unidirectional and bidirectional leakage correction algorithms to determine whether rCBV stratifies OS. Decreased post-bevacizumab rCBV from baseline using the bidirectional leakage correction algorithm significantly correlated with longer OS (Cox, P = 0.01), whereas rCBV change using the unidirectional model (P = 0.43) or the uncorrected rCBV values (P = 0.28) did not. Estimates of rCBV computed with the two leakage correction algorithms differed on average by 14.9%. Accounting for T 1 and T2* leakage contamination in DSC-MRI using a two-compartment, bidirectional rather than unidirectional exchange model might improve post-bevacizumab survival stratification in patients with recurrent GBM. J. Magn. Reson. Imaging 2016;44:1229-1237. © 2016 International Society for Magnetic Resonance in Medicine.

High-speed swept source optical coherence Doppler tomography for deep brain microvascular imaging

NASA Astrophysics Data System (ADS)

Chen, Wei; You, Jiang; Gu, Xiaochun; Du, Congwu; Pan, Yingtian

2016-12-01

Noninvasive microvascular imaging using optical coherence Doppler tomography (ODT) has shown great promise in brain studies; however, high-speed microcirculatory imaging in deep brain remains an open quest. A high-speed 1.3 μm swept-source ODT (SS-ODT) system is reported which was based on a 200 kHz vertical-cavity-surface-emitting laser. Phase errors induced by sweep-trigger desynchronization were effectively reduced by spectral phase encoding and instantaneous correlation among the A-scans. Phantom studies have revealed a significant reduction in phase noise, thus an enhancement of minimally detectable flow down to 268.2 μm/s. Further in vivo validation was performed, in which 3D cerebral-blood-flow (CBF) networks in mouse brain over a large field-of-view (FOV: 8.5 × 5 × 3.2 mm3) was scanned through thinned skull. Results showed that fast flows up to 3 cm/s in pial vessels and minute flows down to 0.3 mm/s in arterioles or venules were readily detectable at depths down to 3.2 mm. Moreover, the dynamic changes of the CBF networks elicited by acute cocaine such as heterogeneous responses in various vessel compartments and at different cortical layers as well as transient ischemic events were tracked, suggesting the potential of SS-ODT for brain functional imaging that requires high flow sensitivity and dynamic range, fast frame rate and a large FOV to cover different brain regions.

Cyclic and Linear Monoterpenes in Phospholipid Membranes: Phase Behavior, Bilayer Structure, and Molecular Dynamics.

PubMed

Pham, Quoc Dat; Topgaard, Daniel; Sparr, Emma

2015-10-13

Monoterpenes are abundant in essential oils extracted from plants. These relatively small and hydrophobic molecules have shown important biological functions, including antimicrobial activity and membrane penetration enhancement. The interaction between the monoterpenes and lipid bilayers is considered important to the understanding of the biological functions of monoterpenes. In this study, we investigated the effect of cyclic and linear monoterpenes on the structure and dynamics of lipids in model membranes. We have studied the ternary system 1,2-dimyristoyl-sn-glycero-3-phosphocholine-monoterpene-water as a model with a focus on dehydrated conditions. By combining complementary techniques, including differential scanning calorimetry, solid-state nuclear magnetic resonance, and small- and wide-angle X-ray scattering, bilayer structure, phase transitions, and lipid molecular dynamics were investigated at different water contents. Monoterpenes cause pronounced melting point depression and phase segregation in lipid bilayers, and the extent of these effects depends on the hydration conditions. The addition of a small amount of thymol to the fluid bilayer (volume fraction of 0.03 in the bilayer) leads to an increased order in the acyl chain close to the bilayer interface. The findings are discussed in relation to biological systems and lipid formulations.

Nanoposition sensors with superior linear response to position and unlimited travel ranges

NASA Astrophysics Data System (ADS)

Lee, Sheng-Chiang; Peters, Randall D.

2009-04-01

With the advancement in nanotechnology, the ability of positioning/measuring at subnanometer scale has been one of the most critical issues for the nanofabrication industry and researchers using scanning probe microscopy. Commercial nanopositioners have achieved direct measurements at the scale of 0.01 nm with capacitive sensing metrology. However, the commercial sensors have small dynamic ranges (up to only a few hundred micrometers) and are relatively large in size (centimeters in the transverse directions to the motion), which is necessary for healthy signal detections but making it difficult to use on smaller devices. This limits applications in which large materials (on the scale of centimeters or greater) are handled with needs of subnanometer resolutions. What has been done in the past is to combine the fine and coarse translation stages with different dynamic ranges to simultaneously achieve long travel range and high spatial resolution. In this paper, we present a novel capacitive position sensing metrology with ultrawide dynamic range from subnanometer to literally any practically desired length for a translation stage. This sensor will greatly simplify the task and enhance the performance of direct metrology in a hybrid translational stage covering translation tasks from subnanometer to centimeters.

Determination of Small Animal Long Bone Properties Using Densitometry

NASA Technical Reports Server (NTRS)

Breit, Gregory A.; Goldberg, BethAnn K.; Whalen, Robert T.; Hargens, Alan R. (Technical Monitor)

1996-01-01

Assessment of bone structural property changes due to loading regimens or pharmacological treatment typically requires destructive mechanical testing and sectioning. Our group has accurately and non-destructively estimated three dimensional cross-sectional areal properties (principal moments of inertia, Imax and Imin, and principal angle, Theta) of human cadaver long bones from pixel-by-pixel analysis of three non-coplanar densitometry scans. Because the scanner beam width is on the order of typical small animal diapbyseal diameters, applying this technique to high-resolution scans of rat long bones necessitates additional processing to minimize errors induced by beam smearing, such as dependence on sample orientation and overestimation of Imax and Imin. We hypothesized that these errors are correctable by digital image processing of the raw scan data. In all cases, four scans, using only the low energy data (Hologic QDR-1000W, small animal mode), are averaged to increase image signal-to-noise ratio. Raw scans are additionally processed by interpolation, deconvolution by a filter derived from scanner beam characteristics, and masking using a variable threshold based on image dynamic range. To assess accuracy, we scanned an aluminum step phantom at 12 orientations over a range of 180 deg about the longitudinal axis, in 15 deg increments. The phantom dimensions (2.5, 3.1, 3.8 mm x 4.4 mm; Imin/Imax: 0.33-0.74) were comparable to the dimensions of a rat femur which was also scanned. Cross-sectional properties were determined at 0.25 mm increments along the length of the phantom and femur. The table shows average error (+/- SD) from theory of Imax, Imin, and Theta) over the 12 orientations, calculated from raw and fully processed phantom images, as well as standard deviations about the mean for the femur scans. Processing of phantom scans increased agreement with theory, indicating improved accuracy. Smaller standard deviations with processing indicate increased precision and repeatability. Standard deviations for the femur are consistent with those of the phantom. We conclude that in conjunction with digital image enhancement, densitometry scans are suitable for non-destructive determination of areal properties of small animal bones of comparable size to our phantom, allowing prediction of Imax and Imin within 2.5% and Theta within a fraction of a degree. This method represents a considerable extension of current methods of analyzing bone tissue distribution in small animal bones.

Characterization of C/Enhanced SiC Composite During Creep-Rupture Tests Using an Ultrasonic Guided Wave Scan System

NASA Technical Reports Server (NTRS)

Roth, Don J.; Verrilli, Michael J.; Martin, Richard E.; Cosgriff, Laura M.

2004-01-01

An ultrasonic guided wave scan system was used to nondestructively monitor damage over time and position in a C/enhanced SiC sample that was creep tested to failure at 1200 C in air at a stress of 69 MPa (10 ksi). The use of the guided wave scan system for mapping evolving oxidation profiles (via porosity gradients resulting from oxidation) along the sample length and predicting failure location was explored. The creep-rupture tests were interrupted for ultrasonic evaluation every two hours until failure at approx. 17.5 cumulative hours.

Conformational changes in proteins recovered from jumbo squid (Dosidicus gigas) muscle through pH shift washing treatments.

PubMed

Cortés-Ruiz, Juan A; Pacheco-Aguilar, Ramón; Ramírez-Suárez, Juan C; Lugo-Sánchez, Maria E; García-Orozco, Karina D; Sotelo-Mundo, Rogerio R; Peña-Ramos, Aida

2016-04-01

Conformational and thermal-rheological properties of acidic (APC) and neutral (NPC) protein concentrates were evaluated and compared to those of squid (Dosidicus gigas) muscle proteins (SM). Surface hydrophobicity, sulfhydryl status, secondary structure profile, differential scanning calorimetry and oscillatory dynamic rheology were used to evaluate the effect of treatments on protein properties. Acidic condition during the washing process (APC) promoted structural and conformational changes in the protein present in the concentrate produced. These changes were enhanced during the heat setting of the corresponding sol. Results demonstrate that washing squid muscle under the proposed acidic conditions is a feasible technological alternative for squid-based surimi production improving its yield and gel-forming ability. Copyright © 2015. Published by Elsevier Ltd.

Fluorimetric detection of Sn(2+) ion in aqueous medium using Salicylaldehyde based nanoparticles and application to natural samples analysis.

PubMed

Patil, Kishor S; Mahajan, Prasad G; Patil, Shivajirao R

2017-01-05

The fluorescent 2-[(E)-(2-phenylhydrazinylidene)methyl]phenol nanoparticles (PHPNPs) were prepared by a simple reprecipitation method. The prepared PHPNPs examined by Dynamic Light Scattering show narrower particle size distribution having an average particle size of 93.3nm. The Scanning Electron Microphotograph shows distinct spherical shaped morphology of nanoparticles. The blue shift in UV-absorption and fluorescence spectra of PHPNPs with respect to corresponding spectra of PHP in acetone solution indicates H- aggregates and Aggregation Induced Enhanced Emission (AIEE) for nanoparticles. The nanoparticles show selective tendency towards the recognition of Sn(2+) ions by enhancing the fluorescence intensity preference to Cu(2+), Fe(3+), Fe(2+), Ni(2+), NH4(+), Ca(2+), Pb(2+), Hg(2+) and Zn(2+) ions, which actually seem to quench the fluorescence of nanoparticles. The studies on Langmuir adsorption plot, fluorescence lifetime of PHPNPs, DLS-Zeta sizer, UV-visible and fluorescence titration with and without Sn(2+) helped to propose a suitable mechanism of fluorescence enhancement of nanoparticles by Sn(2+) and their binding ability during complexation. The fluorescence enhancement effect of PHPNPs induced by Sn(2+) is further used to develop an analytical method for detection of Sn(2+) from aqueous medium in environmental samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Fluorimetric detection of Sn2 + ion in aqueous medium using Salicylaldehyde based nanoparticles and application to natural samples analysis

NASA Astrophysics Data System (ADS)

Patil, Kishor S.; Mahajan, Prasad G.; Patil, Shivajirao R.

2017-01-01

The fluorescent 2-[(E)-(2-phenylhydrazinylidene)methyl]phenol nanoparticles (PHPNPs) were prepared by a simple reprecipitation method. The prepared PHPNPs examined by Dynamic Light Scattering show narrower particle size distribution having an average particle size of 93.3 nm. The Scanning Electron Microphotograph shows distinct spherical shaped morphology of nanoparticles. The blue shift in UV-absorption and fluorescence spectra of PHPNPs with respect to corresponding spectra of PHP in acetone solution indicates H- aggregates and Aggregation Induced Enhanced Emission (AIEE) for nanoparticles. The nanoparticles show selective tendency towards the recognition of Sn2 + ions by enhancing the fluorescence intensity preference to Cu2 +, Fe3 +, Fe2 +, Ni2 +, NH4+, Ca2 +, Pb2 +, Hg2 + and Zn2 + ions, which actually seem to quench the fluorescence of nanoparticles. The studies on Langmuir adsorption plot, fluorescence lifetime of PHPNPs, DLS-Zeta sizer, UV-visible and fluorescence titration with and without Sn2 + helped to propose a suitable mechanism of fluorescence enhancement of nanoparticles by Sn2 + and their binding ability during complexation. The fluorescence enhancement effect of PHPNPs induced by Sn2 + is further used to develop an analytical method for detection of Sn2 + from aqueous medium in environmental samples.

Shear-induced enhancements of crystallization kinetics and morphological transformation for long chain branched polylactides with different branching degrees

PubMed Central

Wang, Junyang; Bai, Jing; Zhang, Yaqiong; Fang, Huagao; Wang, Zhigang

2016-01-01

The effects of long chain branching (LCB) degree on the shear-induced isothermal crystallization kinetics of a series of LCB polylactides (LCB PLAs) have been investigated by using rotational rheometer, polarized optical microscopy (POM) and scanning electron microscopy (SEM). Dynamic viscoelastic properties obtained by small-amplitude oscillatory shear (SAOS) tests indicate that LCB PLAs show more broadened relaxation time spectra with increasing LCB degree. Upon a pre-shear at the shear rate of 1 s−1 LCB PLAs show much faster crystallization kinetics than linear PLA and the crystallization kinetics is enhanced with increasing LCB degree. By modeling the system as a suspension the quantitative evaluation of nucleation density can be derived from rheological experiments. The nucleation density is greatly enhanced with increasing LCB degree and a saturation in shear time is observed. Crystalline morphologies for LCB PLAs observed by POM and SEM demonstrate the enhancement of nucleation density with increasing LCB degree and a transformation from spherulitic to orientated crystalline morphologies. The observation can be ascribed to longer relaxation time of the longest macromolecular chains and broadened, complex relaxation behaviors due to the introduction of LCB into PLA, which is essential in stabilizing the orientated crystal nuclei after pre-shear. PMID:27246803

Postoperative enhancement on breast MRI: Time course and pattern of changes.

PubMed

Mahoney, Mary C; Sharda, Radhika G

2018-04-23

Expected postoperative enhancement on breast MRI can appear similar to enhancement seen in recurrent or residual malignancy. Our aim was to assess the time course and patterns of enhancement at the surgical site, thereby helping to distinguish between benign and malignant postoperative enhancement. In 200 MRI scans performed in 153 patients after breast conservation treatment, 43 after surgical excision of atypia, and 4 patients after benign excisional biopsy were categorized by postoperative time interval. We defined 4 patterns of morphologic enhancement on MRI: cavity wall/seroma (Pattern I); thin linear (Pattern II); mass (Pattern III); and fat necrosis (Pattern IV). Of 200 MRI scans, 66 (33%) demonstrated enhancement at the surgical site. Enhancement typically decreased through the postoperative follow-up period. Enhancement was observed in 41% (28/68) of cases beyond the 18-month interval but was uncommon after 5 years. Pattern III enhancement was the morphologic pattern seen most commonly with malignancy (5/19 cases, 26%). When associated with delayed washout kinetics, it was even more strongly predictive of malignancy (4/5 cases, 80%). In patients with a history of excisional biopsy and no prior radiation treatment, the percentage of MRI scans showing enhancement was significantly lower than (21% vs 49% with P-value .0027) in patients who had undergone radiation. Enhancement at the surgical site occurred in one-third of cases up to 5 years after surgery, particularly in patients who underwent both radiation and surgery. Mass enhancement, particularly in conjunction with delayed washout kinetics, is most predictive of malignancy and should prompt biopsy or re-excision. © 2018 Wiley Periodicals, Inc.

Stress Analyzer

NASA Technical Reports Server (NTRS)

1990-01-01

SPATE 900 Dynamic Stress Analyzer is an acronym for Stress Pattern Analysis by Thermal Emission. It detects stress-induced temperature changes in a structure and indicates the degree of stress. Ometron, Inc.'s SPATE 9000 consists of a scan unit and a data display. The scan unit contains an infrared channel focused on the test structure to collect thermal radiation, and a visual channel used to set up the scan area and interrogate the stress display. Stress data is produced by detecting minute temperature changes, down to one-thousandth of a degree Centigrade, resulting from the application to the structure of dynamic loading. The electronic data processing system correlates the temperature changes with a reference signal to determine stress level.

SPM investigation of local aging effects in glassy polymers

NASA Astrophysics Data System (ADS)

Crider, Philip

2005-03-01

We investigate the cooperative and heterogeneous nature of glassy dynamics by nanometer-scale probing in a glassy polymer, Polyvinyl-Actetate (PVAc), with a Scanning Force Microscope (SFM). Using ultra-high-vacuum (UHV) Scanning Capacitive Force Microscopy techniques, nanometer-scale capacitive responses are probed. Dielectric relaxation near the glass transition is investigated, and scanning capabilities are utilized to analyze spatial response on a nanometer scale. The results of these studies may yield insight into the understanding of temperature-dependent cooperative length scales, local aging properties, and energy landscape properties of evolving dipole clusters on a mesoscopic scale. Results are used to test the validity and relevance of current models of glassy dynamics.

Enhanced optical limiting effects in a double-decker bis(phthalocyaninato) rare earth complex using radially polarized beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Jia-Lu; Gu, Bing, E-mail: gubing@seu.edu.cn; Liu, Dahui

2014-10-27

Optical limiting (OL) effects can be enhanced by exploiting various limiting mechanisms and by designing nonlinear optical materials. In this work, we present the large enhancement of OL effects by manipulating the polarization distribution of the light field. Theoretically, we develop the Z-scan and nonlinear transmission theories on a two-photon absorber under the excitation of cylindrical vector beams. It is shown that both the sensitivity of Z-scan technique and the OL effect using radially polarized beams have the large enhancement compared with that using linearly polarized beams (LPBs). Experimentally, we investigate the nonlinear absorption properties of a double-decker Pr[Pc(OC{sub 8}H{submore » 17}){sub 8}]{sub 2} rare earth complex by performing Z-scan measurements with femtosecond-pulsed radially polarized beams at 800 nm wavelength. The observed two-photon absorption process, which originates from strong intramolecular π–π interaction, is exploited for OL application. The results demonstrate the large enhancement of OL effects using radially polarized beams instead of LPBs.« less

ARN Integrated Retail Module (IRM) & 3D Whole Body Scanner System at Fort Carson, Colorado

DTIC Science & Technology

2006-12-01

the Central Issue Facility (CIF), Ft. Carson, CO; and, 4) Develop and validate dynamic local tariffs. Additional information on Apparel...Scanner; 3) Integrate 3D Whole Body scanning technology with the ARN Integrated Retail Module (IRM) for clothing issue at the Central Issue Facility ...CIF), Ft. Carson, CO; and, 4) Develop and validate dynamic local tariffs. The main goals of the ARN 3D scanning research initiative at the Ft

Direct-detected rapid-scan EPR at 250 MHz

NASA Astrophysics Data System (ADS)

Stoner, James W.; Szymanski, Dennis; Eaton, Sandra S.; Quine, Richard W.; Rinard, George A.; Eaton, Gareth R.

2004-09-01

EPR spectra at 250 MHz for a single crystal of lithium phthalocyanine (LiPc) in the absence of oxygen and for a deoxygenated aqueous solution of a Nycomed triarylmethyl (trityl-CD 3) radical were obtained at scan rates between 1.3 × 10 3 and 3.4 × 10 5 G/s. These scan rates are rapid relative to the reciprocals of the electron spin relaxation times (LiPc: T1=3.5 μs and T2=2.5 μs; trityl: T1=12 μs and T2=11.5 μs) and cause characteristic oscillations in the direct-detected absorption spectra. For a given scan rate, shorter values of T2 and increased inhomogeneous broadening cause less deep oscillations that damp out more quickly than for longer T2. There is excellent agreement between experimental and calculated lineshapes and signal amplitudes as a function of radiofrequency magnetic field ( B1) and scan rate. When B1 is adjusted for maximum signal amplitude as a function of scan rate, signal intensity for constant number of scans is enhanced by up to a factor of three relative to slow scans. The number of scans that can be averaged in a defined period of time is proportional to the scan rate, which further enhances signal amplitude per unit time. Longer relaxation times cause the maximum signal intensity to occur at slower scan rates. These experiments provide the first systematic characterization of direct-detected rapid-scan EPR signals.

Application of carbon nanotubes to topographical resolution enhancement of tapered fiber scanning near field optical microscopy probes

NASA Astrophysics Data System (ADS)

Huntington, S. T.; Jarvis, S. P.

2003-05-01

Scanning near field optical microscopy (SNOM) probes are typically tapered optical fibers with metallic coatings. The tip diameters are generally in excess of 300 nm and thus provide poor topographical resolution. Here we report on the attachment multiwalled carbon nanotubes to the probes in order to substantially enhance the topographical resolution, without adversely affecting the optical resolution.

The comparison of different daidzein-PLGA nanoparticles in increasing its oral bioavailability.

PubMed

Ma, Yiran; Zhao, Xinyi; Li, Jian; Shen, Qi

2012-01-01

The aim of this research was to increase the oral bioavailability of daidzein by the formulations of poly(lactic-co-glycolic) acid (PLGA) nanoparticles loaded with daidzein. Amongst the various traditional and novel techniques of preparing daidzein-loaded PLGA nanoparticles, daidzein-loaded phospholipid complexes PLGA nanoparticles and daidzein-loaded cyclodextrin inclusion complexes PLGA nanoparticles were selected. The average drug entrapment efficiency, particle size, and zeta potential of daidzein-loaded phospholipid complexes PLGA nanoparticles and daidzein-loaded cyclodextrin inclusion complexes PLGA nanoparticles were 81.9% ± 5%, 309.2 ± 14.0 nm, -32.14 ± 2.53 mV and 83.2% ± 7.2%, 323.2 ± 4.8 nm, -18.73 ± 1.68 mV, respectively. The morphological characterization of nanoparticles was observed with scanning electron microscopy by stereological method and the physicochemical state of nanoparticles was valued by differential scanning calorimetry. The in vitro drug-release profile of both nanoparticle formulations fitted the Weibull dynamic equation. Pharmacokinetic studies demonstrated that after oral administration of daidzein-loaded phospholipid complexes PLGA nanoparticles and daidzein-loaded cyclodextrin inclusion complexes PLGA nanoparticles to rats at a dose of 10 mg/kg, relative bioavailability was enhanced about 5.57- and 8.85-fold, respectively, compared to daidzein suspension as control. These results describe an effective strategy for oral delivery of daidzein-loaded PLGA nanoparticles and might provide a fresh approach to enhancing the bioavailability of drugs with poor lipophilic and poor hydrophilic properties.

The comparison of different daidzein-PLGA nanoparticles in increasing its oral bioavailability

PubMed Central

Ma, Yiran; Zhao, Xinyi; Li, Jian; Shen, Qi

2012-01-01

The aim of this research was to increase the oral bioavailability of daidzein by the formulations of poly(lactic-co-glycolic) acid (PLGA) nanoparticles loaded with daidzein. Amongst the various traditional and novel techniques of preparing daidzein-loaded PLGA nanoparticles, daidzein-loaded phospholipid complexes PLGA nanoparticles and daidzein-loaded cyclodextrin inclusion complexes PLGA nanoparticles were selected. The average drug entrapment efficiency, particle size, and zeta potential of daidzein-loaded phospholipid complexes PLGA nanoparticles and daidzein-loaded cyclodextrin inclusion complexes PLGA nanoparticles were 81.9% ± 5%, 309.2 ± 14.0 nm, −32.14 ± 2.53 mV and 83.2% ± 7.2%, 323.2 ± 4.8 nm, −18.73 ± 1.68 mV, respectively. The morphological characterization of nanoparticles was observed with scanning electron microscopy by stereological method and the physicochemical state of nanoparticles was valued by differential scanning calorimetry. The in vitro drug-release profile of both nanoparticle formulations fitted the Weibull dynamic equation. Pharmacokinetic studies demonstrated that after oral administration of daidzein-loaded phospholipid complexes PLGA nanoparticles and daidzein-loaded cyclodextrin inclusion complexes PLGA nanoparticles to rats at a dose of 10 mg/kg, relative bioavailability was enhanced about 5.57- and 8.85-fold, respectively, compared to daidzein suspension as control. These results describe an effective strategy for oral delivery of daidzein-loaded PLGA nanoparticles and might provide a fresh approach to enhancing the bioavailability of drugs with poor lipophilic and poor hydrophilic properties. PMID:22346351

Development of optimized techniques and requirements for computer enhancement of structural weld radiographs. Volume 1: Technical report

NASA Technical Reports Server (NTRS)

Adams, J. R.; Hawley, S. W.; Peterson, G. R.; Salinger, S. S.; Workman, R. A.

1971-01-01

A hardware and software specification covering requirements for the computer enhancement of structural weld radiographs was considered. Three scanning systems were used to digitize more than 15 weld radiographs. The performance of these systems was evaluated by determining modulation transfer functions and noise characteristics. Enhancement techniques were developed and applied to the digitized radiographs. The scanning parameters of spot size and spacing and film density were studied to optimize the information content of the digital representation of the image.

[When and how is medical teleconsultation to doctors practising in remote areas of developing countries convenient and reliable? About eight clinical cases].

PubMed

Campanella, Nando; Francioni, Orestina; Taus, Marina; Giovagnoli, Moreno; Morosini, Pierpaolo

2004-01-01

A poorly equipped internal medicine doctor (IMD), practising in remote areas of developing countries, can be assisted with expertise teleconsultations by using the common analogical telephone lines. By that way, the clinical cases he challenges became multidisciplinary and the success of the treatment enhanced. Eight cases are reported as examples. The expertise is made up by eight remote-access experts on different medical fields. The effectiveness of the support of the consultants is compared one to the other. In laboratory, dermatology and, partly, cyto-pathology fields the teleconsultations are reliable and not time-consuming, for the key tool is the digital picture sent by e-mailing. In cardiology (heart ultrasound scan) and radiology fields both effectiveness and benefit-cost ratio are disputable. Heart ultrasound scan is a dynamic test and filming is needed to provide the consultant with good records. In radiology field, the upper digestive tract X-ray scan is usually carried out with few shots, due to the unsustainable charges on the patient. That matter impairs the consultant's effectiveness to support. Although the black-outs of the transmission were common throughout IMD-consultant videoconferences, the physical examination of the patient, performed by the IMC under consultant's direct supervision, is highly supportive both in neurology and paediatric fields. The physiotherapist's show of physical rehabilitation exercises by videoconference is highly supportive as well.

Investigation of MR scanning, image registration, and image processing techniques to visualize cortical veins for neurosurgery

NASA Astrophysics Data System (ADS)

Noordmans, Herke J.; Rutten, G. J. M.; Willems, Peter W. A.; Hoogduin, J.; Viergever, Max A.

2001-01-01

The visualization of brain vessels on the cortex helps the neurosurgeon in two ways: To avoid blood vessels when specifying the trepanation entry, and to overcome errors in the surgical navigation system due to brain shift. We compared 3D T1 MR, 3D T1 MR with gadolinium contrast, MR venography and MR phase contrast angiography as scanning techniques, mutual information as registration technique, and thresholding and multi-vessel enhancement as image processing techniques. We evaluated the volume rendered results based on their quality and correspondence with photos took during surgery. It appears that with 3D T1 MR scans, gadolinium is required to show cortical veins. The visibility of small cortical veins is strongly enhanced by subtracting a 3D T1 MR baseline scan, which should be registered to the scan with gadolinium contrast, even when the scans are made during the same session. Multi-vessel enhancement helps to clarify the view on small vessels by reducing the noise level, but strikingly does not reveal more. MR venography does show intracerebral veins with high detail, but is, as is, unsuited to show cortical veins due to the low contrast with CSF. MR phase contrast angiography can perform equally well as the subtraction technique, but its quality seems to show more inter-patient variability.

Role of A-site Ca and B-site Zr substitution in BaTiO3 lead-free compounds: Combined experimental and first principles density functional theoretical studies

NASA Astrophysics Data System (ADS)

Keswani, Bhavna C.; Saraf, Deepashri; Patil, S. I.; Kshirsagar, Anjali; James, A. R.; Kolekar, Y. D.; Ramana, C. V.

2018-05-01

We report on the combined experimental and theoretical simulation results of lead-free ferroelectrics, Ba(1-x)CaxTiO3 (x = 0.0-0.3) and BaTi(1-y)ZryO3 (y = 0.0-0.2), synthesized by standard solid state reaction method. First principles density functional calculations are used to investigate the electronic structure, dynamical charges, and spontaneous polarization of these compounds. In addition, the structural, ferroelectric, piezoelectric, and dielectric properties are studied using extensive experiments. The X-ray diffraction and temperature dependent Raman spectroscopy studies indicate that the calcium (Ca) substituted compositions exhibit a single phase crystal structure, while zirconium (Zr) substituted compositions are biphasic. The scanning electron micrographs reveal the uniform and highly dense microstructure. The presence of polarization-electric field and strain-electric field hysteresis loops confirms the ferroelectric and piezoelectric nature of all the compositions. Our results demonstrate higher values for polarization, percentage strain, piezoelectric coefficients, and electrostrictive coefficient compared to those existing in the literature. For smaller substitutions of Ca and Zr in BaTiO3, a direct piezoelectric coefficient (d33) is enhanced, while the highest d33 value (˜300 pC/N) is observed for BaTi0.96Zr0.04O3 due to the biphasic ferroelectric behavior. Calculation of Born effective charges indicates that doping with Ca or Zr increases the dynamical charges on Ti as well as on O and decreases the dynamical charge on Ba. An increase in the dynamical charges on Ti and O is ascribed to the increase in covalency of Ti-O bond that reduces the polarizability of the crystal. A broader range of temperatures is demonstrated to realize the stable phase in the Ca substituted compounds. The results indicate enhancement in the temperature range of applicability of these compounds for device applications. The combined theoretical and experimental study is expected to enhance the current scientific understanding of the lead-free ferroelectric materials.

Dynamic transfer applied to secondary ion imaging over large scanned fields with the nanoSIMS 50 at high mass resolution

NASA Astrophysics Data System (ADS)

Slodzian, Georges; Wu, Ting-Di; Duprat, Jean; Engrand, Cécile; Guerquin-Kern, Jean-Luc

2017-12-01

Dynamic transfer is an adaptive optical approach used for coupling a scanning ion probe with the mass spectrometer designed for analyzing sputtered ions emanating from the probe impact. Its tuning is of crucial importance for getting uniform signal collection over large scanning fields and therefore scanning images free of vignetting in a context of high mass resolution. Revisiting the optical design of the NanoSIMS 50 instrument, where the same set of lenses focuses the primary ion probe on the sample and collects secondary ions from the sample, led us to develop novel experimental procedures to achieve dynamic transfer tuning and overcome instrumental imperfections. It is the case for scanning distortion that may be induced by the octopole used for correcting probe astigmatism and may cause irreducible vignetting on scanning images. We show that it is possible to develop complete tuning procedures by compromising temporarily on the sharpness of the probe focus. Most importantly, we show that, in a context of high mass resolution, the transfer does not significantly disturb isotopic ratios over large scanned fields provided external coils are properly adjusted to compensate ambient magnetic fields. Deepening the procedures led us to demonstrate that the scanning center of the probe may not coincide with the imaging center of COOL, Coaxial Objective Lenses forming the probe and extracting secondary ions. We have checked that bringing those two centers into coincidence resulted in a better image quality over large fields. In the present work, we show how to handle the secondary beam in order to position it before it enters the spectrometer. That capability is essential for optimizing transmission at high mass resolution by aligning the secondary beam axis on a given entrance axis of the spectrometer. These results led us to propose several instrumental improvements including the crucial interest of an additional octopole upstream in the primary ion probe column to prevent scanning distortion when performing astigmatism correction and the possibility of offsetting primary beam deviating plates to bring scanning and imaging centers in coincidence.

Enhanced light trapping by focused ion beam (FIB) induced self-organized nanoripples on germanium (100) surface

NASA Astrophysics Data System (ADS)

Kamaliya, Bhaveshkumar; Mote, Rakesh G.; Aslam, Mohammed; Fu, Jing

2018-03-01

In this paper, we demonstrate enhanced light trapping by self-organized nanoripples on the germanium surface. The enhanced light trapping leading to high absorption of light is confirmed by the experimental studies as well as the numerical simulations using the finite-difference time-domain method. We used gallium ion (Ga+) focused ion beam to enable the formation of the self-organized nanoripples on the germanium (100) surface. During the fabrication, the overlap of the scanning beam is varied from zero to negative value and found to influence the orientation of the nanoripples. Evolution of nanostructures with the variation of beam overlap is investigated. Parallel, perpendicular, and randomly aligned nanoripples with respect to the scanning direction are obtained via manipulation of the scanning beam overlap. 95% broadband absorptance is measured in the visible electromagnetic region for the nanorippled germanium surface. The reported light absorption enhancement can significantly improve the efficiency of germanium-silicon based photovoltaic systems.

Development of Bifunctional Gadolinium-Labeled Superparamagnetic Nanoparticles (Gd-MnMEIO) for In Vivo MR Imaging of the Liver in an Animal Model.

PubMed

Kuo, Yu-Ting; Chen, Chiao-Yun; Liu, Gin-Chung; Wang, Yun-Ming

2016-01-01

Liver tumors are common and imaging methods, particularly magnetic resonance imaging (MRI), play an important role in their non-invasive diagnosis. Previous studies have shown that detection of liver tumors can be improved by injection of two different MR contrast agents. Here, we developed a new contrast agent, Gd-manganese-doped magnetism-engineered iron oxide (Gd-MnMEIO), with enhancement effects on both T1- and T2-weighted MR images of the liver. A 3.0T clinical MR scanner equipped with transmit/receiver coil for mouse was used to obtain both T1-weighted spoiled gradient-echo and T2-weighted fast spin-echo axial images of the liver before and after intravenous contrast agent injection into Balb/c mice with and without tumors. After pre-contrast scanning, six mice per group were intravenously injected with 0.1 mmol/kg Gd-MnMEIO, or the control agents, i.e., Gd-DTPA or SPIO. The scanning time points for T1-weighted images were 0.5, 5, 10, 15, 20, 25, and 30 min after contrast administration. The post-enhanced T2-weighted images were then acquired immediately after T1-weighted acquisition. We found that T1-weighted images were positively enhanced by both Gd-DTPA and Gd-MnMEIO and negatively enhanced by SPIO. The enhancement by both Gd-DTPA and Gd-MnMEIO peaked at 0.5 min and gradually declined thereafter. Gd-MnMEIO (like Gd-DTPA) enhanced T1-weighted images and (like SPIO) T2-weighted images. Marked vascular enhancement was clearly visible on dynamic T1-weighted images with Gd-MnMEIO. In addition, the T2 signal was significantly decreased at 30 min after administration of Gd-MnMEIO. Whereas the effects of Gd-MnMEIO and SPIO on T2-weighted images were similar (p = 0.5824), those of Gd-MnMEIO and Gd-DTPA differed, with Gd-MnMEIO having a significant T2 contrast effect (p = 0.0086). Our study confirms the feasibility of synthesizing an MR contrast agent with both T1 and T2 shortening effects and using such an agent in vivo. This agent enables tumor detection and characterization in single liver MRI sections.

Dynamic deformation inspection of a human arm by using a line-scan imaging system

NASA Astrophysics Data System (ADS)

Hu, Eryi

2009-11-01

A line-scan imaging system is used in the dynamic deformation measurement of a human arm when the muscle is contracting and relaxing. The measurement principle is based on the projection grating profilometry, and the measuring system is consisted of a line-scan CCD camera, a projector, optical lens and a personal computer. The detected human arm is put upon a reference plane, and a sinusoidal grating is projected onto the object surface and reference plane at an incidence angle, respectively. The deformed fringe pattern in the same line of the dynamic detected arm is captured by the line-scan CCD camera with free trigger model, and the deformed fringe pattern is recorded in the personal computer for processing. A fast Fourier transform combining with a filtering and spectrum shifting method is used to extract the phase information caused by the profile of the detected object. Thus, the object surface profile can be obtained following the geometric relationship between the fringe deformation and the object surface height. Furthermore, the deformation procedure can be obtained line by line. Some experimental results are presented to prove the feasibility of the inspection system.

Scan patterns when viewing natural scenes: Emotion, complexity, and repetition

PubMed Central

Bradley, Margaret M.; Houbova, Petra; Miccoli, Laura; Costa, Vincent D.; Lang, Peter J.

2011-01-01

Eye movements were monitored during picture viewing and effects of hedonic content, perceptual composition, and repetition on scanning assessed. In Experiment 1, emotional and neutral pictures that were figure-ground compositions or more complex scenes were presented for a 6 s free viewing period. Viewing emotional pictures or complex scenes prompted more fixations and broader scanning of the visual array, compared to neutral pictures or simple figure-ground compositions. Effects of emotion and composition were independent, supporting the hypothesis that these oculomotor indices reflect enhanced information seeking. Experiment 2 tested an orienting hypothesis by repeatedly presenting the same pictures. Although repetition altered specific scan patterns, emotional, compared to neutral, picture viewing continued to prompt oculomotor differences, suggesting that motivationally relevant cues enhance information seeking in appetitive and defensive contexts. PMID:21649664

CT attenuation measurements are valuable to discriminate pledgets used in prosthetic heart valve implantation from paravalvular leakage

PubMed Central

Habets, J; Meijer, T S; Meijer, R C A; Mali, W P Th M; Vonken, E-J P A; Budde, R P J

2012-01-01

Objectives Sutures with polytetrafluorethylene (PTFE) felt pledgets are commonly used in prosthetic heart valve (PHV) implantation. Paravalvular leakage can be difficult to distinguish from PTFE felt pledgets on multislice CT because both present as hyperdense structures. We assessed whether pledgets can be discriminated from contrast-enhanced solutions (blood/saline) on CT images based on attenuation difference in an ex vivo experiment and under in vivo conditions. Methods PTFE felt pledgets were sutured to the suture ring of a mechanical PHV and porcine aortic annulus, and immersed and scanned in four different contrast-enhanced (Ultravist®; 300 mg jopromide ml−1) saline concentrations (10.0, 12.0, 13.6 and 15.0 mg ml−1). Scanning was performed on a 256-slice scanner with eight different scan protocols with various tube voltage (100 kV, 120 kV) and tube current (400 mAs, 600 mAs, 800 mAs, 1000 mAs) settings. Attenuation of the pledgets and surrounding contrast-enhanced saline were measured. Additionally, the attenuation of pledgets and contrast-enhanced blood was measured on electrocardiography (ECG)-gated CTA scans of 19 patients with 22 PHVs. Results Ex vivo CT attenuation differences between the pledgets and contrast-enhanced solutions were larger by using higher tube voltages. CT attenuation values of the pledgets were higher than contrast-enhanced blood in patients: 420±26 Hounsfield units (mean±SD, range 383–494) and 288±41 Hounsfield units (range 202–367), respectively. Conclusions PTFE felt pledgets have consistently higher attenuation than surrounding contrast-enhanced blood. CT attenuation measurements therefore may help to differentiate pledgets from paravalvular leakage, and detect paravalvular leakage in patients with suspected PHV dysfunction. PMID:22919014

Assessing the kidney function parameters glomerular filtration rate and effective renal plasma flow with dynamic FDG-PET/MRI in healthy subjects.

PubMed

Geist, Barbara K; Baltzer, Pascal; Fueger, Barbara; Hamboeck, Martina; Nakuz, Thomas; Papp, Laszlo; Rasul, Sazan; Sundar, Lalith Kumar Shiyam; Hacker, Marcus; Staudenherz, Anton

2018-05-09

A method was developed to assess the kidney parameters glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) from 2-deoxy-2-[ 18 F]fluoro-D-glucose (FDG) concentration behavior in kidneys, measured with positron emission tomography (PET) scans. Twenty-four healthy adult subjects prospectively underwent dynamic simultaneous PET/magnetic resonance imaging (MRI) examination. Time activity curves (TACs) were obtained from the dynamic PET series, with the guidance of MR information. Patlak analysis was performed to determine the GFR, and based on integrals, ERPF was calculated. Results were compared to intra-individually obtained reference values determined from venous blood samples. Total kidney GFR and ERPF as estimated by dynamic PET/MRI were highly correlated to their reference values (r = 0.88/p < 0.0001 and r = 0.82/p < 0.0001, respectively) with no significant difference between their means. The study is a proof of concept that GFR and ERPF can be assessed with dynamic FDG PET/MRI scans in healthy kidneys. This has advantages for patients getting a routine scan, where additional examinations for kidney function estimation could be avoided. Further studies are required for transferring this PET/MRI method to PET/CT applications.

System and method for chromatography and electrophoresis using circular optical scanning

DOEpatents

Balch, Joseph W.; Brewer, Laurence R.; Davidson, James C.; Kimbrough, Joseph R.

2001-01-01

A system and method is disclosed for chromatography and electrophoresis using circular optical scanning. One or more rectangular microchannel plates or radial microchannel plates has a set of analysis channels for insertion of molecular samples. One or more scanning devices repeatedly pass over the analysis channels in one direction at a predetermined rotational velocity and with a predetermined rotational radius. The rotational radius may be dynamically varied so as to monitor the molecular sample at various positions along a analysis channel. Sample loading robots may also be used to input molecular samples into the analysis channels. Radial microchannel plates are built from a substrate whose analysis channels are disposed at a non-parallel angle with respect to each other. A first step in the method accesses either a rectangular or radial microchannel plate, having a set of analysis channels, and second step passes a scanning device repeatedly in one direction over the analysis channels. As a third step, the scanning device is passed over the analysis channels at dynamically varying distances from a centerpoint of the scanning device. As a fourth step, molecular samples are loaded into the analysis channels with a robot.

Six-minute magnetic resonance imaging protocol for evaluation of acute ischemic stroke: pushing the boundaries.

PubMed

Nael, Kambiz; Khan, Rihan; Choudhary, Gagandeep; Meshksar, Arash; Villablanca, Pablo; Tay, Jennifer; Drake, Kendra; Coull, Bruce M; Kidwell, Chelsea S

2014-07-01

If magnetic resonance imaging (MRI) is to compete with computed tomography for evaluation of patients with acute ischemic stroke, there is a need for further improvements in acquisition speed. Inclusion criteria for this prospective, single institutional study were symptoms of acute ischemic stroke within 24 hours onset, National Institutes of Health Stroke Scale ≥3, and absence of MRI contraindications. A combination of echo-planar imaging (EPI) and a parallel acquisition technique were used on a 3T magnetic resonance (MR) scanner to accelerate the acquisition time. Image analysis was performed independently by 2 neuroradiologists. A total of 62 patients met inclusion criteria. A repeat MRI scan was performed in 22 patients resulting in a total of 84 MRIs available for analysis. Diagnostic image quality was achieved in 100% of diffusion-weighted imaging, 100% EPI-fluid attenuation inversion recovery imaging, 98% EPI-gradient recalled echo, 90% neck MR angiography and 96% of brain MR angiography, and 94% of dynamic susceptibility contrast perfusion scans with interobserver agreements (k) ranging from 0.64 to 0.84. Fifty-nine patients (95%) had acute infarction. There was good interobserver agreement for EPI-fluid attenuation inversion recovery imaging findings (k=0.78; 95% confidence interval, 0.66-0.87) and for detection of mismatch classification using dynamic susceptibility contrast-Tmax (k=0.92; 95% confidence interval, 0.87-0.94). Thirteen acute intracranial hemorrhages were detected on EPI-gradient recalled echo by both observers. A total of 68 and 72 segmental arterial stenoses were detected on contrast-enhanced MR angiography of the neck and brain with k=0.93, 95% confidence interval, 0.84 to 0.96 and 0.87, 95% confidence interval, 0.80 to 0.90, respectively. A 6-minute multimodal MR protocol with good diagnostic quality is feasible for the evaluation of patients with acute ischemic stroke and can result in significant reduction in scan time rivaling that of the multimodal computed tomographic protocol. © 2014 American Heart Association, Inc.

Evaluation of a short dynamic 18F-fluoride PET/CT scanning method to assess bone metabolic activity in spinal orthopedics.

PubMed

Peters, Marloes J M; Wierts, Roel; Jutten, Elisabeth M C; Halders, Servé G E A; Willems, Paul C P H; Brans, Boudewijn

2015-11-01

A complication after spinal fusion surgery is pseudarthrosis, but its radiological diagnosis is of limited value. (18)F-fluoride PET with its ability to assess bone metabolism activity could be of value. The goal of this study was to assess the clinical feasibility of calculating the static standardized uptake value (SUV) from a short dynamic scan without the use of blood sampling, thereby obtaining all dynamic and static parameters in a scan of only 30 min. This approach was tested on a retrospective patient population with persisting pain after spinal fusion surgery. In 16 patients, SUVs (SUV max, SUV mean) and kinetic parameters (K 1, k 2, k 3, v b, K i,NLR, K 1/k 2, k 3/(k 2 + k 3), K i,patlak) were derived from static and dynamic PET/CT scans of operated and control regions of the spine, after intravenous administration of 156-214 MBq (18)F-fluoride. Parameter differences between control and operated regions, as well as between pseudarthrosis and fused segments were evaluated. SUVmean at 30 and 60 min was calculated from kinetic parameters obtained from the dynamic data set (SUV mean,2TCM). Agreement between measured and calculated SUVs was evaluated through Bland-Altman plots. Overall, statistically significant differences between control and operated regions were observed for SUV max, SUV mean, K i,NLR, K i,patlak, K 1/k 2 and k 3/(k 2 + k 3). Diagnostic CT showed pseudarthrosis in 6/16 patients, while in 10/16 patients, segments were fused. Of all parameters, only those regarding the incorporation of bone [K i,NLR, K i,patlak, k 3/(k 2 + k 3)] differed statistically significant in the intervertebral disc space between the pseudarthrosis and fused patients group. The mean values of the patient-specific blood clearance rate [Formula: see text] differed statistically significant between the pseudarthrosis and the fusion group, with a p value of 0.011. This may correspond with the lack of statistical significance of the SUV values between pseudarthrosis and fused patients. Bland-Altman plots show that calculated SUV mean,2TCM values corresponded well with the measured SUV mean values. This study shows the feasibility of a 30-min dynamic (18)F-fluoride PET/CT scanning and this may provide dynamic parameters clinically relevant to the diagnosis of pseudarthrosis.

Evaluation of optimized magnetic resonance perfusion imaging scanning time window after contrast agent injection for differentiating benign and malignant breast lesions

PubMed Central

Dong, Jie; Wang, Dawei; Ma, Zhenshen; Deng, Guodong; Wang, Lanhua; Zhang, Jiandong

2017-01-01

The aim of the study was evaluate the 3.0 T magnetic resonance (MR) perfusion imaging scanning time window following contrast injection for differentiating benign and malignant breast lesions and to determine the optimum scanning time window for increased scanner usage efficiency and reduced diagnostic adverse risk factors. A total of 52 women with breast abnormalities were selected for conventional MR imaging and T1 dynamic-enhanced imaging. Quantitative parameters [volume transfer constant (Ktrans), rate constant (Kep) and extravascular extracellular volume fraction (Ve)] were calculated at phases 10, 20, 30, 40 and 50, which represented time windows at 5, 10, 15, 20 and 25 min, respectively, following injection of contrast agent. The association of the parameters at different phases with benign and malignant tumor diagnosis was analyzed. MR perfusion imaging was verified as an effective modality in the diagnosis of breast malignancies and the best scanning time window was identified: i) Values of Ktrans and Kep at all phases were statistically significant in differentiating benign and malignant tumors (P<0.05), while the value of Ve had statistical significance only at stage 10, but not at any other stages (P>0.05); ii) values of Ve in benign tumors increased with phase number, but achieved no obvious changes at different phases in malignant tumors; iii) the optimum scanning time window of breast perfusion imaging with 3.0 T MR was between phases 10 and 30 (i.e., between 5 and 15 min after contrast agent injection). The variation trend of Ve values at different phases may serve as a diagnostic reference for differentiating benign and malignant breast abnormalities. The most efficient scanning time window was indicated to be 5 min after contrast injection, based on the observation that the Ve value only had statistical significance in diagnosis at stage 10. However, the optimal scanning time window is from 5 to 15 min following the injection of contrast agent, since that the variation trend of Ve is able to serve as a diagnostic reference. PMID:28450944

Evaluation of optimized magnetic resonance perfusion imaging scanning time window after contrast agent injection for differentiating benign and malignant breast lesions.

PubMed

Dong, Jie; Wang, Dawei; Ma, Zhenshen; Deng, Guodong; Wang, Lanhua; Zhang, Jiandong

2017-03-01

The aim of the study was evaluate the 3.0 T magnetic resonance (MR) perfusion imaging scanning time window following contrast injection for differentiating benign and malignant breast lesions and to determine the optimum scanning time window for increased scanner usage efficiency and reduced diagnostic adverse risk factors. A total of 52 women with breast abnormalities were selected for conventional MR imaging and T1 dynamic-enhanced imaging. Quantitative parameters [volume transfer constant (K trans ), rate constant (K ep ) and extravascular extracellular volume fraction (V e )] were calculated at phases 10, 20, 30, 40 and 50, which represented time windows at 5, 10, 15, 20 and 25 min, respectively, following injection of contrast agent. The association of the parameters at different phases with benign and malignant tumor diagnosis was analyzed. MR perfusion imaging was verified as an effective modality in the diagnosis of breast malignancies and the best scanning time window was identified: i) Values of K trans and K ep at all phases were statistically significant in differentiating benign and malignant tumors (P<0.05), while the value of V e had statistical significance only at stage 10, but not at any other stages (P>0.05); ii) values of V e in benign tumors increased with phase number, but achieved no obvious changes at different phases in malignant tumors; iii) the optimum scanning time window of breast perfusion imaging with 3.0 T MR was between phases 10 and 30 (i.e., between 5 and 15 min after contrast agent injection). The variation trend of V e values at different phases may serve as a diagnostic reference for differentiating benign and malignant breast abnormalities. The most efficient scanning time window was indicated to be 5 min after contrast injection, based on the observation that the V e value only had statistical significance in diagnosis at stage 10. However, the optimal scanning time window is from 5 to 15 min following the injection of contrast agent, since that the variation trend of V e is able to serve as a diagnostic reference.

Resonant Scanning with Large Field of View Reduces Photobleaching and Enhances Fluorescence Yield in STED Microscopy.

PubMed

Wu, Yong; Wu, Xundong; Lu, Rong; Zhang, Jin; Toro, Ligia; Stefani, Enrico

2015-10-01

Photobleaching is a major limitation of superresolution Stimulated Depletion Emission (STED) microscopy. Fast scanning has long been considered an effective means to reduce photobleaching in fluorescence microscopy, but a careful quantitative study of this issue is missing. In this paper, we show that the photobleaching rate in STED microscopy can be slowed down and the fluorescence yield be enhanced by scanning with high speed, enabled by using large field of view in a custom-built resonant-scanning STED microscope. The effect of scanning speed on photobleaching and fluorescence yield is more remarkable at higher levels of depletion laser irradiance, and virtually disappears in conventional confocal microscopy. With ≥6 GW∙cm(-2) depletion irradiance, we were able to extend the fluorophore survival time of Atto 647N and Abberior STAR 635P by ~80% with 8-fold wider field of view. We confirm that STED Photobleaching is primarily caused by the depletion light acting upon the excited fluorophores. Experimental data agree with a theoretical model. Our results encourage further increasing the linear scanning speed for photobleaching reduction in STED microscopy.

A quantitative damage imaging technique based on enhanced CCRTM for composite plates using 2D scan

NASA Astrophysics Data System (ADS)

He, Jiaze; Yuan, Fuh-Gwo

2016-10-01

A two-dimensional (2D) non-contact areal scan system was developed to image and quantify impact damage in a composite plate using an enhanced zero-lag cross-correlation reverse-time migration (E-CCRTM) technique. The system comprises a single piezoelectric wafer mounted on the composite plate and a laser Doppler vibrometer (LDV) for scanning a region in the vicinity of the PZT to capture the scattered wavefield. The proposed damage imaging technique takes into account the amplitude, phase, geometric spreading, and all of the frequency content of the Lamb waves propagating in the plate; thus, a reflectivity coefficients of the delamination is calculated and potentially related to damage severity. Comparisons are made in terms of damage imaging quality between 2D areal scans and 1D line scans as well as between the proposed and existing imaging conditions. The experimental results show that the 2D E-CCRTM performs robustly when imaging and quantifying impact damage in large-scale composites using a single PZT actuator with a nearby areal scan using LDV.

An enhanced CCRTM (E-CCRTM) damage imaging technique using a 2D areal scan for composite plates

NASA Astrophysics Data System (ADS)

He, Jiaze; Yuan, Fuh-Gwo

2016-04-01

A two-dimensional (2-D) non-contact areal scan system was developed to image and quantify impact damage in a composite plate using an enhanced zero-lag cross-correlation reverse-time migration (E-CCRTM) technique. The system comprises a single piezoelectric actuator mounted on the composite plate and a laser Doppler vibrometer (LDV) for scanning a region to capture the scattered wavefield in the vicinity of the PZT. The proposed damage imaging technique takes into account the amplitude, phase, geometric spreading, and all of the frequency content of the Lamb waves propagating in the plate; thus, the reflectivity coefficients of the delamination can be calculated and potentially related to damage severity. Comparisons are made in terms of damage imaging quality between 2-D areal scans and linear scans as well as between the proposed and existing imaging conditions. The experimental results show that the 2-D E-CCRTM performs robustly when imaging and quantifying impact damage in large-scale composites using a single PZT actuator with a nearby areal scan using LDV.

Analytical and numerical analysis of imaging mechanism of dynamic scanning electron microscopy.

PubMed

Schröter, M-A; Holschneider, M; Sturm, H

2012-11-02

The direct observation of small oscillating structures with the help of a scanning electron beam is a new approach to study the vibrational dynamics of cantilevers and microelectromechanical systems. In the scanning electron microscope, the conventional signal of secondary electrons (SE, dc part) is separated from the signal response of the SE detector, which is correlated to the respective excitation frequency for vibration by means of a lock-in amplifier. The dynamic response is separated either into images of amplitude and phase shift or into real and imaginary parts. Spatial resolution is limited to the diameter of the electron beam. The sensitivity limit to vibrational motion is estimated to be sub-nanometer for high integration times. Due to complex imaging mechanisms, a theoretical model was developed for the interpretation of the obtained measurements, relating cantilever shapes to interaction processes consisting of incident electron beam, electron-lever interaction, emitted electrons and detector response. Conclusions drawn from this new model are compared with numerical results based on the Euler-Bernoulli equation.

Comprehensive Population-Averaged Arterial Input Function for Dynamic Contrast–Enhanced vMagnetic Resonance Imaging of Head and Neck Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onxley, Jennifer D.; Yoo, David S.; Muradyan, Naira

2014-07-01

Purpose: To generate a population-averaged arterial input function (PA-AIF) for quantitative analysis of dynamic contrast-enhanced MRI data in head and neck cancer patients. Methods and Materials: Twenty patients underwent dynamic contrast-enhanced MRI during concurrent chemoradiation therapy. Imaging consisted of 2 baseline scans 1 week apart (B1/B2) and 1 scan after 1 week of chemoradiation therapy (Wk1). Regions of interest (ROIs) in the right and left carotid arteries were drawn on coronal images. Plasma concentration curves of all ROIs were averaged and fit to a biexponential decay function to obtain the final PA-AIF (AvgAll). Right-sided and left-sided ROI plasma concentration curves were averagedmore » separately to obtain side-specific AIFs (AvgRight/AvgLeft). Regions of interest were divided by time point to obtain time-point-specific AIFs (AvgB1/AvgB2/AvgWk1). The vascular transfer constant (K{sub trans}) and the fractional extravascular, extracellular space volume (V{sub e}) for primaries and nodes were calculated using the AvgAll AIF, the appropriate side-specific AIF, and the appropriate time-point-specific AIF. Median K{sub trans} and V{sub e} values derived from AvgAll were compared with those obtained from the side-specific and time-point-specific AIFs. The effect of using individual AIFs was also investigated. Results: The plasma parameters for AvgAll were a{sub 1,2} = 27.11/17.65 kg/L, m{sub 1,2} = 11.75/0.21 min{sup −1}. The coefficients of repeatability (CRs) for AvgAll versus AvgLeft were 0.04 min{sup −1} for K{sub trans} and 0.02 for V{sub e}. For AvgAll versus AvgRight, the CRs were 0.08 min{sup −1} for K{sub trans} and 0.02 for V{sub e}. When AvgAll was compared with AvgB1/AvgB2/AvgWk1, the CRs were slightly higher: 0.32/0.19/0.78 min{sup −1}, respectively, for K{sub trans}; and 0.07/0.08/0.09 for V{sub e}. Use of a PA-AIF was not significantly different from use of individual AIFs. Conclusion: A PA-AIF for head and neck cancer was generated that accounts for differences in right carotid artery versus left carotid artery, day-to-day fluctuations, and early treatment-induced changes. The small CRs obtained for K{sub trans} and V{sub e} indicate that side-specific AIFs are not necessary. However, a time-point-specific AIF may improve pharmacokinetic accuracy.« less

Reaction monitoring using hyperpolarized NMR with scaling of heteronuclear couplings by optimal tracking.

PubMed

Zhang, Guannan; Schilling, Franz; Glaser, Steffen J; Hilty, Christian

2016-11-01

Off-resonance decoupling using the method of Scaling of Heteronuclear Couplings by Optimal Tracking (SHOT) enables determination of heteronuclear correlations of chemical shifts in single scan NMR spectra. Through modulation of J-coupling evolution by shaped radio frequency pulses, off resonance decoupling using SHOT pulses causes a user-defined dependence of the observed J-splitting, such as the splitting of 13 C peaks, on the chemical shift offset of coupled nuclei, such as 1 H. Because a decoupling experiment requires only a single scan, this method is suitable for characterizing on-going chemical reactions using hyperpolarization by dissolution dynamic nuclear polarization (D-DNP). We demonstrate the calculation of [ 13 C, 1 H] chemical shift correlations of the carbanionic active sites from hyperpolarized styrene polymerized using sodium naphthalene as an initiator. While off resonance decoupling by SHOT pulses does not enhance the resolution in the same way as a 2D NMR spectrum would, the ability to obtain the correlations in single scans makes this method ideal for determination of chemical shifts in on-going reactions on the second time scale. In addition, we present a novel SHOT pulse that allows to scale J-splittings 50% larger than the respective J-coupling constant. This feature can be used to enhance the resolution of the indirectly detected chemical shift and reduce peak overlap, as demonstrated in a model reaction between p-anisaldehyde and isobutylamine. For both pulses, the accuracy is evaluated under changing signal-to-noise ratios (SNR) of the peaks from reactants and reaction products, with an overall standard deviation of chemical shift differences compared to reference spectra of 0.02ppm when measured on a 400MHz NMR spectrometer. Notably, the appearance of decoupling side-bands, which scale with peak intensity, appears to be of secondary importance. Copyright © 2016 Elsevier Inc. All rights reserved.

Harmonic demodulation and minimum enhancement factors in field-enhanced near-field optical microscopy.

PubMed

Scarpettini, A F; Bragas, A V

2015-01-01

Field-enhanced scanning optical microscopy relies on the design and fabrication of plasmonic probes which had to provide optical and chemical contrast at the nanoscale. In order to do so, the scattering containing the near-field information recorded in a field-enhanced scanning optical microscopy experiment, has to surpass the background light, always present due to multiple interferences between the macroscopic probe and sample. In this work, we show that when the probe-sample distance is modulated with very low amplitude, the higher the harmonic demodulation is, the better the ratio between the near-field signal and the interferometric background results. The choice of working at a given n harmonic is dictated by the experiment when the signal at the n + 1 harmonic goes below the experimental noise. We demonstrate that the optical contrast comes from the nth derivative of the near-field scattering, amplified by the interferometric background. By modelling the far and near field we calculate the probe-sample approach curves, which fit very well the experimental ones. After taking a great amount of experimental data for different probes and samples, we conclude with a table of the minimum enhancement factors needed to have optical contrast with field-enhanced scanning optical microscopy. © 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society.

Nanopatterning dynamics on Si(100) during oblique 40-keV Ar+ erosion with metal codeposition: Morphological and compositional correlation

NASA Astrophysics Data System (ADS)

Redondo-Cubero, A.; Gago, R.; Palomares, F. J.; Mücklich, A.; Vinnichenko, M.; Vázquez, L.

2012-08-01

The formation and dynamics of nanopatterns produced on Si(100) surfaces by 40-keV Ar+ oblique (α = 60°) bombardment with concurrent Fe codeposition have been studied. Morphological and chemical analysis has been performed by ex situ atomic force microscopy, Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, and scanning and transmission electron microscopies. During irradiation, Fe atoms incorporated into the target surface react with Si to form silicides, a process enhanced at this medium-ion energy range. The silicides segregate at the nanoscale from the early irradiation stages. As the irradiation proceeds, a ripple pattern is formed without any correlation with silicide segregation. From the comparison with the pattern dynamics reported previously for metal-free conditions, it is demonstrated that the metal incorporation alters both the pattern dynamics and the morphology. Although the pattern formation and dynamics are delayed for decreasing metal content, once ripples emerge, the same qualitative pattern of morphological evolution is observed for different metal content, resulting in an asymptotic saw-tooth-like facetted surface pattern. Despite the medium ion energy employed, the nanopatterning process with concurrent Fe deposition can be explained by those mechanisms proposed for low-ion energy irradiations such as shadowing, height fluctuations, silicide formation and segregation, ensuing composition dependent sputter rate, and ion sculpting effects. In particular, the interplay between the ion irradiation and metal flux geometries, differences in sputtering rates, and the surface pattern morphology produces a dynamic compositional patterning correlated with the evolving morphological one.

Scan patterns when viewing natural scenes: emotion, complexity, and repetition.

PubMed

Bradley, Margaret M; Houbova, Petra; Miccoli, Laura; Costa, Vincent D; Lang, Peter J

2011-11-01

Eye movements were monitored during picture viewing, and effects of hedonic content, perceptual composition, and repetition on scanning assessed. In Experiment 1, emotional and neutral pictures that were figure-ground compositions or more complex scenes were presented for a 6-s free viewing period. Viewing emotional pictures or complex scenes prompted more fixations and broader scanning of the visual array, compared to neutral pictures or simple figure-ground compositions. Effects of emotion and composition were independent, supporting the hypothesis that these oculomotor indices reflect enhanced information seeking. Experiment 2 tested an orienting hypothesis by repeatedly presenting the same pictures. Although repetition altered specific scan patterns, emotional, compared to neutral, picture viewing continued to prompt oculomotor differences, suggesting that motivationally relevant cues enhance information seeking in appetitive and defensive contexts. Copyright © 2011 Society for Psychophysiological Research.

Resolution enhancement in a double-helix phase engineered scanning microscope (RESCH microscope) (Presentation Recording)

NASA Astrophysics Data System (ADS)

Jesacher, Alexander; Ritsch-Marte, Monika; Piestun, Rafael

2015-08-01

Recently we introduced RESCH microscopy [1] - a scanning microscope that allows slightly refocusing the sample after the acquisition has been performed, solely by performing appropriate data post-processing. The microscope features a double-helix phase-engineered emission point spread function in combination with camera-based detection. Based on the principle of transverse resolution enhancement in Image Scanning Microscopy [2,3], we demonstrate similar resolution improvement in RESCH. Furthermore, we outline a pathway for how the collected 3D sample information can be used to construct sharper optical sections. [1] A. Jesacher, M. Ritsch-Marte and R. Piestun, accepted for Optica. [2] C.J.R. Sheppard, "Super-resolution in Confocal imaging," Optik, 80, 53-54 (1988). [3] C.B. Müller and J. Enderlein "Image Scanning Microscopy," Phys. Rev. Lett. 104, 198101 (2010).

Imaging via complete cantilever dynamic detection: General dynamic mode imaging and spectroscopy in scanning probe microscopy

DOE PAGES

Somnath, Suhas; Collins, Liam; Matheson, Michael A.; ...

2016-09-08

We develop and implement a multifrequency spectroscopy and spectroscopic imaging mode, referred to as general dynamic mode (GDM), that captures the complete spatially- and stimulus dependent information on nonlinear cantilever dynamics in scanning probe microscopy (SPM). GDM acquires the cantilever response including harmonics and mode mixing products across the entire broadband cantilever spectrum as a function of excitation frequency. GDM spectra substitute the classical measurements in SPM, e.g. amplitude and phase in lock-in detection. Here, GDM is used to investigate the response of a purely capacitively driven cantilever. We use information theory techniques to mine the data and verify themore » findings with governing equations and classical lock-in based approaches. We explore the dependence of the cantilever dynamics on the tip–sample distance, AC and DC driving bias. This approach can be applied to investigate the dynamic behavior of other systems within and beyond dynamic SPM. In conclusion, GDM is expected to be useful for separating the contribution of different physical phenomena in the cantilever response and understanding the role of cantilever dynamics in dynamic AFM techniques.« less

Lecithin-coated gold nanoflowers (GNFs) for CT scan imaging applications and biochemical parameters; in vitro and in vivo studies.

PubMed

Aziz, Farooq; Bano, Khizra; Siddique, Ahmad Hassan; Bajwa, Sadia Zafar; Nazir, Aalia; Munawar, Anam; Shaheen, Ayesha; Saeed, Madiha; Afzal, Muhammad; Iqbal, M Zubair; Wu, Aiguo; Khan, Waheed S

2018-01-09

We report a novel strategy for the fabrication of lecithin-coated gold nanoflowers (GNFs) via single-step design for CT imaging application. Field-emission electron microscope confirmed flowers like morphology of the as-synthesized nanostructures. Furthermore, these show absorption peak in near-infrared (NIR) region at λ max 690 nm Different concentrations of GNFs are tested as a contrast agent in CT scans at tube voltage 135 kV and tube current 350 mA. These results are compared with same amount of iodine at same CT scan parameters. The results of in vitro CT scan study show that GNFs have good contrast enhancement properties, whereas in vivo study of rabbits CT scan shows that GNFs enhance the CT image clearly at 135 kV as compared to that of iodine. Cytotoxicity was studied and blood profile show minor increase of white blood cells and haemoglobin, whereas decrease of red blood cells and platelets.

Measurement needs guided by synthetic radar scans in high-resolution model output

NASA Astrophysics Data System (ADS)

Varble, A.; Nesbitt, S. W.; Borque, P.

2017-12-01

Microphysical and dynamical process interactions within deep convective clouds are not well understood, partly because measurement strategies often focus on statistics of cloud state rather than cloud processes. While processes cannot be directly measured, they can be inferred with sufficiently frequent and detailed scanning radar measurements focused on the life cycleof individual cloud regions. This is a primary goal of the 2018-19 DOE ARM Cloud, Aerosol, and Complex Terrain Interactions (CACTI) and NSF Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaigns in central Argentina, where orographic deep convective initiation is frequent with some high-impact systems growing into the tallest and largest in the world. An array of fixed and mobile scanning multi-wavelength dual-polarization radars will be coupled with surface observations, sounding systems, multi-wavelength vertical profilers, and aircraft in situ measurements to characterize convective cloud life cycles and their relationship with environmental conditions. While detailed cloud processes are an observational target, the radar scan patterns that are most ideal for observing them are unclear. They depend on the locations and scales of key microphysical and dynamical processes operating within the cloud. High-resolution simulations of clouds, while imperfect, can provide information on these locations and scales that guide radar measurement needs. Radar locations are set in the model domain based on planned experiment locations, and simulatedorographic deep convective initiation and upscale growth are sampled using a number of different scans involving RHIs or PPIs with predefined elevation and azimuthal angles that approximately conform with radar range and beam width specifications. Each full scan pattern is applied to output atsingle model time steps with time step intervals that depend on the length of time required to complete each scan in the real world. The ability of different scans to detect key processes within the convective cloud life cycle are examined in connection with previous and subsequent dynamical and microphysical transitions. This work will guide strategic scan patterns that will be used during CACTI and RELAMPAGO.

[Reconstruction of Vehicle-human Crash Accident and Injury Analysis Based on 3D Laser Scanning, Multi-rigid-body Reconstruction and Optimized Genetic Algorithm].

PubMed

Sun, J; Wang, T; Li, Z D; Shao, Y; Zhang, Z Y; Feng, H; Zou, D H; Chen, Y J

2017-12-01

To reconstruct a vehicle-bicycle-cyclist crash accident and analyse the injuries using 3D laser scanning technology, multi-rigid-body dynamics and optimized genetic algorithm, and to provide biomechanical basis for the forensic identification of death cause. The vehicle was measured by 3D laser scanning technology. The multi-rigid-body models of cyclist, bicycle and vehicle were developed based on the measurements. The value range of optimal variables was set. A multi-objective genetic algorithm and the nondominated sorting genetic algorithm were used to find the optimal solutions, which were compared to the record of the surveillance video around the accident scene. The reconstruction result of laser scanning on vehicle was satisfactory. In the optimal solutions found by optimization method of genetic algorithm, the dynamical behaviours of dummy, bicycle and vehicle corresponded to that recorded by the surveillance video. The injury parameters of dummy were consistent with the situation and position of the real injuries on the cyclist in accident. The motion status before accident, damage process by crash and mechanical analysis on the injury of the victim can be reconstructed using 3D laser scanning technology, multi-rigid-body dynamics and optimized genetic algorithm, which have application value in the identification of injury manner and analysis of death cause in traffic accidents. Copyright© by the Editorial Department of Journal of Forensic Medicine

Three-dimensional dynamic deformation monitoring using a laser-scanning system

NASA Astrophysics Data System (ADS)

Al-Hanbali, Nedal N.; Teskey, William F.

1994-10-01

Non-contact dynamic deformation monitoring (e.g. with a laser scanning system) is very useful in monitoring changes in alignment and changes in size and shape of coupled operating machines. If relative movements between coupled operating machines are large, excessive wear in the machines or unplanned shutdowns due to machinery failure will occur. The purpose of non-contact dynamic deformation monitoring is to identify the causes of large movements and point to remedial action that can be taken to prevent them. The laser scanning system is a laser-based 3D vision system. The system-technique is based on an auto- synchronized triangulation scanning scheme. The system provides accurate, fast, and reliable 3D measurements and can measure objects between 0.5 m to 100 m with a field of view of 40 degree(s) X 50 degree(s). The system is flexible in terms of providing control over the scanned area and depth. The system also provides the user with the intensity image in addition to the depth coded image. This paper reports on the preliminary testing of this system to monitor surface movements and target (point) movements. The monitoring resolution achieved for an operating motorized alignment test rig in the lab was 1 mm for surface movements and 0.50 m for target movements. Raw data manipulation, local calibration, and the method of relating measurements to control points will be discussed. Possibilities for improving the resolution and recommendations for future development will also be presented.

Scanning-electron-microscope used in real-time study of friction and wear

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Buckley, D. H.

1975-01-01

Small friction and wear apparatus built directly into scanning-electron-microscope provides both dynamic observation and microscopic view of wear process. Friction and wear tests conducted using this system have indicated that considerable information can readily be gained.

Direct estimation of tracer-kinetic parameter maps from highly undersampled brain dynamic contrast enhanced MRI.

PubMed

Guo, Yi; Lingala, Sajan Goud; Zhu, Yinghua; Lebel, R Marc; Nayak, Krishna S

2017-10-01

The purpose of this work was to develop and evaluate a T 1 -weighted dynamic contrast enhanced (DCE) MRI methodology where tracer-kinetic (TK) parameter maps are directly estimated from undersampled (k,t)-space data. The proposed reconstruction involves solving a nonlinear least squares optimization problem that includes explicit use of a full forward model to convert parameter maps to (k,t)-space, utilizing the Patlak TK model. The proposed scheme is compared against an indirect method that creates intermediate images by parallel imaging and compressed sensing before to TK modeling. Thirteen fully sampled brain tumor DCE-MRI scans with 5-second temporal resolution are retrospectively undersampled at rates R = 20, 40, 60, 80, and 100 for each dynamic frame. TK maps are quantitatively compared based on root mean-squared-error (rMSE) and Bland-Altman analysis. The approach is also applied to four prospectively R = 30 undersampled whole-brain DCE-MRI data sets. In the retrospective study, the proposed method performed statistically better than indirect method at R ≥ 80 for all 13 cases. This approach provided restoration of TK parameter values with less errors in tumor regions of interest, an improvement compared to a state-of-the-art indirect method. Applied prospectively, the proposed method provided whole-brain, high-resolution TK maps with good image quality. Model-based direct estimation of TK maps from k,t-space DCE-MRI data is feasible and is compatible up to 100-fold undersampling. Magn Reson Med 78:1566-1578, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Signal enhancement in optical projection tomography via virtual high dynamic range imaging of single exposure

NASA Astrophysics Data System (ADS)

Yang, Yujie; Dong, Di; Shi, Liangliang; Wang, Jun; Yang, Xin; Tian, Jie

2015-03-01

Optical projection tomography (OPT) is a mesoscopic scale optical imaging technique for specimens between 1mm and 10mm. OPT has been proven to be immensely useful in a wide variety of biological applications, such as developmental biology and pathology, but its shortcomings in imaging specimens containing widely differing contrast elements are obvious. The longer exposure for high intensity tissues may lead to over saturation of other areas, whereas a relatively short exposure may cause similarity with surrounding background. In this paper, we propose an approach to make a trade-off between capturing weak signals and revealing more details for OPT imaging. This approach consists of three steps. Firstly, the specimens are merely scanned in 360 degrees above a normal exposure but non-overexposure to acquire the projection data. This reduces the photo bleaching and pre-registration computation compared with multiple different exposures in conventional high dynamic range (HDR) imaging method. Secondly, three virtual channels are produced for each projection image based on the histogram distribution to simulate the low, normal and high exposure images used in the traditional HDR technology in photography. Finally, each virtual channel is normalized to the full gray scale range and three channels are recombined into one image using weighting coefficients optimized by a standard eigen-decomposition method. After applying our approach on the projection data, filtered back projection (FBP) algorithm is carried out for 3-dimentional reconstruction. The neonatal wild-type mouse paw has been scanned to verify this approach. Results demonstrated the effectiveness of the proposed approach.

Brain perfusion imaging using a Reconstruction-of-Difference (RoD) approach for cone-beam computed tomography

NASA Astrophysics Data System (ADS)

Mow, M.; Zbijewski, W.; Sisniega, A.; Xu, J.; Dang, H.; Stayman, J. W.; Wang, X.; Foos, D. H.; Koliatsos, V.; Aygun, N.; Siewerdsen, J. H.

2017-03-01

Purpose: To improve the timely detection and treatment of intracranial hemorrhage or ischemic stroke, recent efforts include the development of cone-beam CT (CBCT) systems for perfusion imaging and new approaches to estimate perfusion parameters despite slow rotation speeds compared to multi-detector CT (MDCT) systems. This work describes development of a brain perfusion CBCT method using a reconstruction of difference (RoD) approach to enable perfusion imaging on a newly developed CBCT head scanner prototype. Methods: A new reconstruction approach using RoD with a penalized-likelihood framework was developed to image the temporal dynamics of vascular enhancement. A digital perfusion simulation was developed to give a realistic representation of brain anatomy, artifacts, noise, scanner characteristics, and hemo-dynamic properties. This simulation includes a digital brain phantom, time-attenuation curves and noise parameters, a novel forward projection method for improved computational efficiency, and perfusion parameter calculation. Results: Our results show the feasibility of estimating perfusion parameters from a set of images reconstructed from slow scans, sparse data sets, and arc length scans as short as 60 degrees. The RoD framework significantly reduces noise and time-varying artifacts from inconsistent projections. Proper regularization and the use of overlapping reconstructed arcs can potentially further decrease bias and increase temporal resolution, respectively. Conclusions: A digital brain perfusion simulation with RoD imaging approach has been developed and supports the feasibility of using a CBCT head scanner for perfusion imaging. Future work will include testing with data acquired using a 3D-printed perfusion phantom currently and translation to preclinical and clinical studies.

Quantification of cancellous bone-compaction due to DHS Blade insertion and influence upon cut-out resistance.

PubMed

Windolf, Markus; Muths, Raphael; Braunstein, Volker; Gueorguiev, Boyko; Hänni, Markus; Schwieger, Karsten

2009-01-01

Compaction of cancellous bone is believed to prevent cut-out. This in vitro study quantified the compaction in the femoral head due to insertion of a dynamic hip screw-blade with and without predrilling and investigated the resulting implant anchorage under cyclic loading. Eight pairs of human cadaveric femoral heads were instrumented with a dynamic hip screw-blade made of Polyetheretherketon. Pairwise instrumentation was performed either with or without predrilling the specimens. CT scanning was performed before and after implantation, to measure bone-compaction. Subsequently the implant was removed and a third scan was performed to analyze the relaxation of the bone structure. Commercial implants were reinserted and the specimens were cyclically loaded until onset of cut-out occurred. The bone-implant interface was monitored by means of fluoroscopic imaging throughout the experiment. Paired t-tests were performed to identify differences regarding compaction, relaxation and cycles to failure. Bone density in the surrounding of the implant increased about 30% for the non-predrilled and 20% for the predrilled group when inserting the implant. After implant removal the predrilled specimens fully relaxed; the non-predrilled group showed about 10% plastic deformation. No differences were found regarding cycles to failure (P=0.32). Significant bone-compaction due to blade insertion was verified. Even though compaction was lower when predrilling the specimens, mainly elastic deformation was present, which is believed to primarily enhance the implant anchorage. Cyclic loading tests confirmed this thesis. The importance of the implantation technique with regard to predrilling is therefore decreased.

Three-dimensional online surface reconstruction of augmented fluorescence lifetime maps using photometric stereo (Conference Presentation)

NASA Astrophysics Data System (ADS)

Unger, Jakob; Lagarto, Joao; Phipps, Jennifer; Ma, Dinglong; Bec, Julien; Sorger, Jonathan; Farwell, Gregory; Bold, Richard; Marcu, Laura

2017-02-01

Multi-Spectral Time-Resolved Fluorescence Spectroscopy (ms-TRFS) can provide label-free real-time feedback on tissue composition and pathology during surgical procedures by resolving the fluorescence decay dynamics of the tissue. Recently, an ms-TRFS system has been developed in our group, allowing for either point-spectroscopy fluorescence lifetime measurements or dynamic raster tissue scanning by merging a 450 nm aiming beam with the pulsed fluorescence excitation light in a single fiber collection. In order to facilitate an augmented real-time display of fluorescence decay parameters, the lifetime values are back projected to the white light video. The goal of this study is to develop a 3D real-time surface reconstruction aiming for a comprehensive visualization of the decay parameters and providing an enhanced navigation for the surgeon. Using a stereo camera setup, we use a combination of image feature matching and aiming beam stereo segmentation to establish a 3D surface model of the decay parameters. After camera calibration, texture-related features are extracted for both camera images and matched providing a rough estimation of the surface. During the raster scanning, the rough estimation is successively refined in real-time by tracking the aiming beam positions using an advanced segmentation algorithm. The method is evaluated for excised breast tissue specimens showing a high precision and running in real-time with approximately 20 frames per second. The proposed method shows promising potential for intraoperative navigation, i.e. tumor margin assessment. Furthermore, it provides the basis for registering the fluorescence lifetime maps to the tissue surface adapting it to possible tissue deformations.

Application of DIRI dynamic infrared imaging in reconstructive surgery

NASA Astrophysics Data System (ADS)

Pawlowski, Marek; Wang, Chengpu; Jin, Feng; Salvitti, Matthew; Tenorio, Xavier

2006-04-01

We have developed the BioScanIR System based on QWIP (Quantum Well Infrared Photodetector). Data collected by this sensor are processed using the DIRI (Dynamic Infrared Imaging) algorithms. The combination of DIRI data processing methods with the unique characteristics of the QWIP sensor permit the creation of a new imaging modality capable of detecting minute changes in temperature at the surface of the tissue and organs associated with blood perfusion due to certain diseases such as cancer, vascular disease and diabetes. The BioScanIR System has been successfully applied in reconstructive surgery to localize donor flap feeding vessels (perforators) during the pre-surgical planning stage. The device is also used in post-surgical monitoring of skin flap perfusion. Since the BioScanIR is mobile; it can be moved to the bedside for such monitoring. In comparison to other modalities, the BioScanIR can localize perforators in a single, 20 seconds scan with definitive results available in minutes. The algorithms used include (FFT) Fast Fourier Transformation, motion artifact correction, spectral analysis and thermal image scaling. The BioScanIR is completely non-invasive and non-toxic, requires no exogenous contrast agents and is free of ionizing radiation. In addition to reconstructive surgery applications, the BioScanIR has shown promise as a useful functional imaging modality in neurosurgery, drug discovery in pre-clinical animal models, wound healing and peripheral vascular disease management.

Effect of modification with 1,4-α-glucan branching enzyme on the rheological properties of cassava starch.

PubMed

Li, Yadi; Li, Caiming; Gu, Zhengbiao; Hong, Yan; Cheng, Li; Li, Zhaofeng

2017-10-01

Steady and dynamic shear measurements were used to investigate the rheological properties of cassava starches modified using the 1,4-α-glucan branching enzyme (GBE) from Geobacillus thermoglucosidans STB02. GBE treatment lowered the hysteresis loop areas, the activation energy (E a ) values and the parameters in rheological models of cassava starch pastes. Moreover, GBE treatment increased its storage (G') and loss (G″) moduli, and decreased their tan δ (ratio of G″/G') values and frequency-dependencies. Scanning electron microscopic studies showed the selective and particular attack of GBE on starch granules, and X-ray diffraction analyses showed that GBE treatment produces significant structural changes in amylose and amylopectin. These changes demonstrate that GBE modification produces cassava starch with a more structured network and improved stability towards mechanical processing. Differential scanning calorimetric analysis and temperature sweeps indicated greater resistance to granule rupture, higher gel rigidity, and a large decrease in the rate of initial conformational ordering with increasing GBE treatment time. Pronounced changes in rheological parameters revealed that GBE modification enhances the stability of cassava starch and its applicability in the food processing industry. Copyright © 2017 Elsevier B.V. All rights reserved.

Value of a step-up diagnosis plan: CRP and CT-scan to diagnose and manage postoperative complications after major abdominal surgery.

PubMed

Straatman, Jennifer; Cuesta, Miguel A; Gisbertz, Suzanne S; Van der Peet, Donald L

2014-12-01

Postoperative complications frequently follow major abdominal surgery and are associated with increased morbidity and mortality. Early diagnosis and treatment of complications is associated with improved patient outcome. In this study we assessed the value of a step-up diagnosis plan by C-reactive protein and CT-scan (computed tomography-scan) imaging for detection of postoperative complications following major abdominal surgery.An observational cohort study was conducted of 399 consecutivepatients undergoing major abdominal surgery between January 2009 and January 2011. Indication for operation, type of surgery, postoperative morbidity, complications according to the Clavien-Dindo classification and mortality were recorded. Clinical parameters were recorded until 14 days postoperatively or until discharge. Regular C-reactive protein (CPR) measurements in peripheral blood and on indication -enhanced CT-scans were performed.Eighty-three out of 399 (20.6 %) patients developed a major complication in the postoperative course after a median of seven days (IQR 4-9 days). One hundred and thirty two patients received additional examination consisting of enhanced CT-scan imaging, and treatment by surgical reintervention or intensive care observation. CRP levels were significantly higher in patients with postoperative complications. On the second postoperative dayCRP levels were on average 197.4 mg/L in the uncomplicated group, 220.9 mg/L in patients with a minor complication and 280.1 mg/L in patients with major complications (p < 0,001).CT-scan imaging showed a sensitivity of 91.7 % and specificity of 100 % in diagnosis of major complications. Based on clinical deterioration and the increase of CRP, an additional enhanced CT-scan offered clear discrimination between patients with major abdominal complications and uncomplicated patients. Adequate treatment could then be accomplished.

Quantification of surface displacements and electromechanical phenomena via dynamic atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balke, Nina; Jesse, Stephen; Yu, Pu

Detection of dynamic surface displacements associated with local changes in material strain provides access to a number of phenomena and material properties. Contact resonance-enhanced methods of atomic force microscopy (AFM) have been shown capable of detecting ~1–3 pm-level surface displacements, an approach used in techniques such as piezoresponse force microscopy, atomic force acoustic microscopy, and ultrasonic force microscopy. Here, based on an analytical model of AFM cantilever vibrations, we demonstrate a guideline to quantify surface displacements with high accuracy by taking into account the cantilever shape at the first resonant contact mode, depending on the tip–sample contact stiffness. The approachmore » has been experimentally verified and further developed for piezoresponse force microscopy (PFM) using well-defined ferroelectric materials. These results open up a way to accurate and precise measurements of surface displacement as well as piezoelectric constants at the pm-scale with nanometer spatial resolution and will allow avoiding erroneous data interpretations and measurement artifacts. Furthermore, this analysis is directly applicable to all cantilever-resonance-based scanning probe microscopy (SPM) techniques.« less

Quantification of surface displacements and electromechanical phenomena via dynamic atomic force microscopy

DOE PAGES

Balke, Nina; Jesse, Stephen; Yu, Pu; ...

2016-09-15

Detection of dynamic surface displacements associated with local changes in material strain provides access to a number of phenomena and material properties. Contact resonance-enhanced methods of atomic force microscopy (AFM) have been shown capable of detecting ~1–3 pm-level surface displacements, an approach used in techniques such as piezoresponse force microscopy, atomic force acoustic microscopy, and ultrasonic force microscopy. Here, based on an analytical model of AFM cantilever vibrations, we demonstrate a guideline to quantify surface displacements with high accuracy by taking into account the cantilever shape at the first resonant contact mode, depending on the tip–sample contact stiffness. The approachmore » has been experimentally verified and further developed for piezoresponse force microscopy (PFM) using well-defined ferroelectric materials. These results open up a way to accurate and precise measurements of surface displacement as well as piezoelectric constants at the pm-scale with nanometer spatial resolution and will allow avoiding erroneous data interpretations and measurement artifacts. Furthermore, this analysis is directly applicable to all cantilever-resonance-based scanning probe microscopy (SPM) techniques.« less

Radionuclide-anesthetic flow study: a new technique for the study of regional anesthesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauman, J.M.; Middaugh, R.E.; Cawthon, M.A.

1986-09-01

A new technique to study the dynamics of in vivo distribution of regional anesthetics is described. Five hundred microcuries of technetium-99m diethylenetriaminepentaacetic acid (DTPA) added to the anesthetic in a syringe prior to injection allows both dynamic and static imaging to assess the initial distribution of the injected anesthetic. Superimposed bone scans or transmission scans help delineate anatomy. The radionuclide-anesthetic flow study is a simple, safe technique to investigate both the spread of regional anesthetics and the factors that affect it.

Identification of nanoparticles and nanosystems in biological matrices with scanning probe microscopy.

PubMed

Angeloni, Livia; Reggente, Melania; Passeri, Daniele; Natali, Marco; Rossi, Marco

2018-04-17

Identification of nanoparticles and nanosystems into cells and biological matrices is a hot research topic in nanobiotechnologies. Because of their capability to map physical properties (mechanical, electric, magnetic, chemical, or optical), several scanning probe microscopy based techniques have been proposed for the subsurface detection of nanomaterials in biological systems. In particular, atomic force microscopy (AFM) can be used to reveal stiff nanoparticles in cells and other soft biomaterials by probing the sample mechanical properties through the acquisition of local indentation curves or through the combination of ultrasound-based methods, like contact resonance AFM (CR-AFM) or scanning near field ultrasound holography. Magnetic force microscopy can detect magnetic nanoparticles and other magnetic (bio)materials in nonmagnetic biological samples, while electric force microscopy, conductive AFM, and Kelvin probe force microscopy can reveal buried nanomaterials on the basis of the differences between their electric properties and those of the surrounding matrices. Finally, scanning near field optical microscopy and tip-enhanced Raman spectroscopy can visualize buried nanostructures on the basis of their optical and chemical properties. Despite at a still early stage, these methods are promising for detection of nanomaterials in biological systems as they could be truly noninvasive, would not require destructive and time-consuming specific sample preparation, could be performed in vitro, on alive samples and in water or physiological environment, and by continuously imaging the same sample could be used to dynamically monitor the diffusion paths and interaction mechanisms of nanomaterials into cells and biological systems. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Nanotechnology Approaches to Biology > Nanoscale Systems in Biology. © 2018 Wiley Periodicals, Inc.

Simulations For Investigating the Contrast Mechanism of Biological Cells with High Frequency Scanning Acoustic Microscopy

NASA Astrophysics Data System (ADS)

Juntarapaso, Yada

Scanning Acoustic Microscopy (SAM) is one of the most powerful techniques for nondestructive evaluation and it is a promising tool for characterizing the elastic properties of biological tissues/cells. Exploring a single cell is important since there is a connection between single cell biomechanics and human cancer. Scanning acoustic microscopy (SAM) has been accepted and extensively utilized for acoustical cellular and tissue imaging including measurements of the mechanical and elastic properties of biological specimens. SAM provides superb advantages in that it is non-invasive, can measure mechanical properties of biological cells or tissues, and fixation/chemical staining is not necessary. The first objective of this research is to develop a program for simulating the images and contrast mechanism obtained by high-frequency SAM. Computer simulation algorithms based on MatlabRTM were built for simulating the images and contrast mechanisms. The mechanical properties of HeLa and MCF-7 cells were computed from the measurement data of the output signal amplitude as a function of distance from the focal planes of the acoustics lens which is known as V(z) . Algorithms for simulating V(z) responses involved the calculation of the reflectance function and were created based on ray theory and wave theory. The second objective is to design transducer arrays for SAM. Theoretical simulations based on Field II(c) programs of the high frequency ultrasound array designs were performed to enhance image resolution and volumetric imaging capabilities. Phased array beam forming and dynamic apodization and focusing were employed in the simulations. The new transducer array design will be state-of-the-art in improving the performance of SAM by electronic scanning and potentially providing a 4-D image of the specimen.

Enhancements for a Dynamic Data Warehousing and Mining System for Large-Scale HSCB Data

DTIC Science & Technology

2016-04-21

Intelligent Automation Incorporated Enhancements for a Dynamic Data Warehousing and Mining ...Page | 2 Intelligent Automation Incorporated Progress Report No. 1 Enhancements for a Dynamic Data Warehousing and Mining System Large-Scale

Scanning angle Raman spectroscopy: Investigation of Raman scatter enhancement techniques for chemical analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meyer, Matthew W.

2013-01-01

This thesis outlines advancements in Raman scatter enhancement techniques by applying evanescent fields, standing-waves (waveguides) and surface enhancements to increase the generated mean square electric field, which is directly related to the intensity of Raman scattering. These techniques are accomplished by employing scanning angle Raman spectroscopy and surface enhanced Raman spectroscopy. A 1064 nm multichannel Raman spectrometer is discussed for chemical analysis of lignin. Extending dispersive multichannel Raman spectroscopy to 1064 nm reduces the fluorescence interference that can mask the weaker Raman scattering. Overall, these techniques help address the major obstacles in Raman spectroscopy for chemical analysis, which include themore » inherently weak Raman cross section and susceptibility to fluorescence interference.« less

Exploiting Continuous Scanning Laser Doppler Vibrometry in timing belt dynamic characterisation

NASA Astrophysics Data System (ADS)

Chiariotti, P.; Martarelli, M.; Castellini, P.

2017-03-01

Dynamic behaviour of timing belts has always interested the engineering community over the years. Nowadays, there are several numerical methods to predict the dynamics of these systems. However, the tuning of such models by experimental approaches still represents an issue: an accurate characterisation does require a measurement in operating conditions since the belt mounting condition might severely affect its dynamic behaviour. Moreover, since the belt is constantly moving during running conditions, non-contact measurement methods are needed. Laser Doppler Vibrometry (LDV) and imaging techniques do represent valid candidates for this purpose. This paper aims at describing the use of Continuous Scanning LDV (CSLDV) as a tool for the dynamic characterisation of timing belts in IC (Internal Combustion) engines (cylinder head). The high-spatial resolution data that can be collected in short testing time makes CSLDV highly suitable for such application. The measurement on a moving surface, however, represents a challenge for CSLDV. The paper discusses how the belt in-plane speed influences CSLDV signal and how an order-based multi-harmonic excitation might affect the recovery of Operational Deflection Shapes in a CSLDV test. A comparison with a standard Discrete Scanning LDV measurement is also given in order to show that a CSLDV test, if well designed, can indeed provide the same amount of information in a drastically reduced amount of time.

Dynamic contrast-enhanced MRI: Study of inter-software accuracy and reproducibility using simulated and clinical data.

PubMed

Beuzit, Luc; Eliat, Pierre-Antoine; Brun, Vanessa; Ferré, Jean-Christophe; Gandon, Yves; Bannier, Elise; Saint-Jalmes, Hervé

2016-06-01

To test the reproducibility and accuracy of pharmacokinetic parameter measurements on five analysis software packages (SPs) for dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), using simulated and clinical data. This retrospective study was Institutional Review Board-approved. Simulated tissues consisted of pixel clusters of calculated dynamic signal changes for combinations of Tofts model pharmacokinetic parameters (volume transfer constant [K(trans) ], extravascular extracellular volume fraction [ve ]), longitudinal relaxation time (T1 ). The clinical group comprised 27 patients treated for rectal cancer, with 36 3T DCE-MR scans performed between November 2012 and February 2014, including dual-flip-angle T1 mapping and a dynamic postcontrast T1 -weighted, 3D spoiled gradient-echo sequence. The clinical and simulated images were postprocessed with five SPs to measure K(trans) , ve , and the initial area under the gadolinium curve (iAUGC). Modified Bland-Altman analysis was conducted, intraclass correlation coefficients (ICCs) and within-subject coefficients of variation were calculated. Thirty-one examinations from 23 patients were of sufficient technical quality and postprocessed. Measurement errors were observed on the simulated data for all the pharmacokinetic parameters and SPs, with a bias ranging from -0.19 min(-1) to 0.09 min(-1) for K(trans) , -0.15 to 0.01 for ve , and -0.65 to 1.66 mmol.L(-1) .min for iAUGC. The ICC between SPs revealed moderate agreement for the simulated data (K(trans) : 0.50; ve : 0.67; iAUGC: 0.77) and very poor agreement for the clinical data (K(trans) : 0.10; ve : 0.16; iAUGC: 0.21). Significant errors were found in the calculated DCE-MRI pharmacokinetic parameters for the perfusion analysis SPs, resulting in poor inter-software reproducibility. J. Magn. Reson. Imaging 2016;43:1288-1300. © 2015 Wiley Periodicals, Inc.

Investigation of Optical Cavity Modes and Ultrafast Carrier Dynamics in Zinc Oxide Rods Using Second-Harmonic Generation and Transient Absorption Pump-Probe Microscopy

NASA Astrophysics Data System (ADS)

Mehl, Brian Peter

The polydispersity intrinsic to nanoscale and microscale semiconductor materials poses a major challenge to using individual objects as building blocks for device applications. The ability to manipulate the shape of ZnO structures is enormous, making it an ideal material for studying shape-dependent phenomena. We have built a nonlinear microscope used to directly image optical cavity modes in ZnO rods using second-harmonic generation. Images of second-harmonic generation in needle-shaped ZnO rods obtained from individual structures show areas of enhanced second-harmonic intensity along the longitudinal axis of the rod that are periodically distributed and symmetrically situated relative to the rod midpoint. The spatial modulation is a direct consequence of the fundamental optical field coupling into standing wave resonator modes of the ZnO structure, leading to an enhanced backscattered second-harmonic condition that cannot be achieved in bulk ZnO. A more complicated second-harmonic image is observed when excitation is below the band gap, which is attributed to whispering gallery modes. Additionally, the nonlinear microscope was combined with transient absorption pump-probe to follow the electron-hole recombination dynamics at different points within individual needle-shaped ZnO rods to characterize spatial differences in dynamical behavior. The results from pump-probe experiments are correlated with spatially resolved ultrafast emission measurements, and scanning electron microscopy provides structural details. Dramatically different electron-hole recombination dynamics are observed in the narrow tips compared to the interior, with the ends exhibiting a greater propensity for electron-hole plasma formation and faster recombination of carriers across the band gap that stem from a physical confinement of the charge carriers. In the interior of the rod, a greater fraction of the electron-hole recombination is trap-mediated and occurs on a significantly longer time scale.

[Value of MR imaging in the diagnosis of intraductal papillary neoplasm of the bile duct].

PubMed

Song, Fengxiang; Zhou, Jun; Shi, Yuxin; Zeng, Mengsu; Zhou, Kangrong; Ding, Yuqin; Cao, Yingli; Zhou, Jianjun

2015-01-01

To analyze the value of MR imaging in diagnosis of intraductal papillary neoplasm of the bile duct (IPN-B). Fourteen patients with intraductal papillary neoplasms of the bile duct confirmed by surgical pathology were included in this study. The patients underwent MR routine plain scanning and enhancement scanning (including T1WI, T2WI with fat suppression, FALSH T1WI, and three-phase enhancement scanning), diffusion weighted imaging(DWI) and magnetic resonance cholangiopancreatography (MRCP) before operation. The imaging data were reviewed and analyzed retrospectively in comparison with the surgical and pathological results. In these patients, 7 cases had tumors located in the left lobe, 2 cases had tumors in both the left and right lobes, 2 cases in the hepatic hilum, 2 cases in the common bile duct, and 1 case in both the right lobe and the common bile duct. Solitary or multiple intraductal masses could be found in 12 cases, with 11 cases appeared as papillary masses and one case as flat mass. In the other two cases the tumor was not visible (one case had too many stones, and in another case the tumor was too small). The tumors in the 12 cases showed hypointensity on T1WI and hyperintensity on T2WI. On the dynamic contrast-enhanced MRI, 11 cases showed mild and one showed moderate enhancement in arterial phase, and all the cases showed mildly and gradually delayed enhancement. On DWI, the lesion areas showed high signal intensity in all the cases, and the ADC value of the tumor area (1.697×10(-3)mm(2)/s) was significantly lower than that of the normal bile (3.973×10(-3)mm(2)/s) (t = -10.94, P < 0.05). Twelve cases demonstrated filling defects on primary MRCP coronary thin section images. On 3D-reconstruction MRCP images, 7 cases exhibited diffuse bile duct dilatation with the tumor areas more prominent, 3 cases exhibited aneurysmal bile dilatation, while the rest 4 cases exhibited segmental or lobar bile duct dilatation ( including 2 with invisible tumors ). In the 3 cases with aneurysmal bile dilatation, the multiple directions of MRCP images helped to find the communication between the aneurysmal dilatation and the bile duct. All the cases showed significant proximal bile duct dilatation (the extent of dilatation >100%), and 9 cases also showed distal bile duct dilatation. Bile duct stones were noted in 6 cases, 4 at the tumor area, and the other 2 away from the tumor area. No adjacent tissue invasion and no distal tissue or lymph node metastasis were observed. Intraductal papillary neoplasms of the bile ducts have characteristic imaging appearances on MRI, and MRI is an important method helpful to making correct diagnosis.

Advanced approach for intraoperative MRI guidance and potential benefit for neurosurgical applications.

PubMed

Busse, Harald; Schmitgen, Arno; Trantakis, Christos; Schober, Ralf; Kahn, Thomas; Moche, Michael

2006-07-01

To present an advanced approach for intraoperative image guidance in an open 0.5 T MRI and to evaluate its effectiveness for neurosurgical interventions by comparison with a dynamic scan-guided localization technique. The built-in scan guidance mode relied on successive interactive MRI scans. The additional advanced mode provided real-time navigation based on reformatted high-quality, intraoperatively acquired MR reference data, allowed multimodal image fusion, and used the successive scans of the built-in mode for quick verification of the position only. Analysis involved tumor resections and biopsies in either scan guidance (N = 36) or advanced mode (N = 59) by the same three neurosurgeons. Technical, surgical, and workflow aspects were compared. The image quality and hand-eye coordination of the advanced approach were improved. While the average extent of resection, neurologic outcome after functional MRI (fMRI) integration, and diagnostic yield appeared to be slightly better under advanced guidance, particularly for the main surgeon, statistical analysis revealed no significant differences. Resection times were comparable, while biopsies took around 30 minutes longer. The presented approach is safe and provides more detailed images and higher navigation speed at the expense of actuality. The surgical outcome achieved with advanced guidance is (at least) as good as that obtained with dynamic scan guidance. (c) 2006 Wiley-Liss, Inc.

Theranostic gold-magnetite hybrid nanoparticles for MRI-guided radiosensitization.

PubMed

Maniglio, D; Benetti, F; Minati, L; Jovicich, J; Valentini, A; Speranza, G; Migliaresi, C

2018-08-03

The main limitation of drug-enhanced radiotherapy concerns the difficulty to evaluate the effectiveness of cancer targeting after drug administration hindering the standardization of therapies based on current radiosensitizing compounds. The challenge regards the development of systems able to combine imaging and radiotherapy enhancement in order to perform highly reliable cancer theragnosis. For these reasons, gold-magnetite hybrid nanoparticles (H-NPs) are proposed as innovative theranostic nanotools for imaging-guided radiosensitization in cancer treatment. In this work we propose a novel method for the synthesis of hydrophilic and superparamagnetic Tween20-stabilized gold-magnetite H-NPs. Morphology and chemical composition of nanoparticles were assessed by transmission electron microscopy, x-ray diffraction analysis and ion-coupled plasma optical emission spectroscopy. Colloidal stability and magnetic properties of nanoparticles were determined by dynamic light scattering and magnetometry. The potentialities of H-NPs for magnetic resonance imaging were studied using a human 4T-MRI scanner. Nanoparticles were proven to induce concentration-dependent contrast enhancement in T2*-weighted MR-images. The cytotoxicity, the cellular uptake and the radiosensitization activity of H-NPs were investigated in human osteosarcoma MG63 cell cultures and murine 3T3 fibroblasts, using specific bioassays and laser scanning confocal microscopy. H-NPs did not exhibit significant toxicity and were demonstrated to be internalized by cells. A significant x-ray enhancement at specific H-NPs exposure concentrations was evidenced on MG63 cell line.

Probing the low-frequency vortex dynamics in a nanostructured superconducting strip

NASA Astrophysics Data System (ADS)

Silva, C. C. de Souza; Raes, B.; Brisbois, J.; Cabral, L. R. E.; Silhanek, A. V.; Van de Vondel, J.; Moshchalkov, V. V.

2016-07-01

We investigate by scanning susceptibility microscopy the response of a thin Pb strip, with a square array of submicron antidots, to a low-frequency ac magnetic field applied perpendicularly to the film plane. By mapping the local permeability of the sample within the field range where vortices trapped by the antidots and interstitial vortices coexist, we observed two distinct dynamical regimes occurring at different temperatures. At a temperature just below the superconducting transition, T /Tc=0.96 , the sample response is essentially dominated by the motion of highly mobile interstitial vortices. However, at a slightly lower temperature, T /Tc=0.93 , the interstitial vortices freeze up leading to a strong reduction of the ac screening length. We propose a simple model for the vortex response in this system which fits well to the experimental data. Our analysis suggests that the observed switching to the high mobility regime stems from a resonant effect, where the period of the ac excitation is just large enough to allow interstitial vortices to thermally hop through the weak pinning landscape produced by random material defects. This argument is further supported by the observation of a pronounced enhancement of the out-of-phase response at the crossover between both dynamical regimes.

Real-time dynamic range and signal to noise enhancement in beam-scanning microscopy by integration of sensor characteristics, data acquisition hardware, and statistical methods

NASA Astrophysics Data System (ADS)

Kissick, David J.; Muir, Ryan D.; Sullivan, Shane Z.; Oglesbee, Robert A.; Simpson, Garth J.

2013-02-01

Despite the ubiquitous use of multi-photon and confocal microscopy measurements in biology, the core techniques typically suffer from fundamental compromises between signal to noise (S/N) and linear dynamic range (LDR). In this study, direct synchronous digitization of voltage transients coupled with statistical analysis is shown to allow S/N approaching the theoretical maximum throughout an LDR spanning more than 8 decades, limited only by the dark counts of the detector on the low end and by the intrinsic nonlinearities of the photomultiplier tube (PMT) detector on the high end. Synchronous digitization of each voltage transient represents a fundamental departure from established methods in confocal/multi-photon imaging, which are currently based on either photon counting or signal averaging. High information-density data acquisition (up to 3.2 GB/s of raw data) enables the smooth transition between the two modalities on a pixel-by-pixel basis and the ultimate writing of much smaller files (few kB/s). Modeling of the PMT response allows extraction of key sensor parameters from the histogram of voltage peak-heights. Applications in second harmonic generation (SHG) microscopy are described demonstrating S/N approaching the shot-noise limit of the detector over large dynamic ranges.

An enhanced fast scanning algorithm for image segmentation

NASA Astrophysics Data System (ADS)

Ismael, Ahmed Naser; Yusof, Yuhanis binti

2015-12-01

Segmentation is an essential and important process that separates an image into regions that have similar characteristics or features. This will transform the image for a better image analysis and evaluation. An important benefit of segmentation is the identification of region of interest in a particular image. Various algorithms have been proposed for image segmentation and this includes the Fast Scanning algorithm which has been employed on food, sport and medical images. It scans all pixels in the image and cluster each pixel according to the upper and left neighbor pixels. The clustering process in Fast Scanning algorithm is performed by merging pixels with similar neighbor based on an identified threshold. Such an approach will lead to a weak reliability and shape matching of the produced segments. This paper proposes an adaptive threshold function to be used in the clustering process of the Fast Scanning algorithm. This function used the gray'value in the image's pixels and variance Also, the level of the image that is more the threshold are converted into intensity values between 0 and 1, and other values are converted into intensity values zero. The proposed enhanced Fast Scanning algorithm is realized on images of the public and private transportation in Iraq. Evaluation is later made by comparing the produced images of proposed algorithm and the standard Fast Scanning algorithm. The results showed that proposed algorithm is faster in terms the time from standard fast scanning.

Effect of antimicrobial peptide on dynamics of phosphocholine membrane: role of cholesterol and physical state of bilayer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Veerendra K.; Mamontov, Eugene; Anunciado, Divina B.

Antimicrobial peptides are universal in all forms of life and are well known for their strong interaction with the cell membrane. This makes them a popular target for investigation of peptide-lipid interactions. Here we report the effect of melittin, an important antimicrobial peptide, on the dynamics of membranes based on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid in both the solid gel and fluid phases. To probe the phase transition, elastic neutron intensity temperature scans have been carried out on DMPC-based unilamellar vesicles (ULV) with and without melittin. We have found that addition of a small amount (0.2 mol%) melittin eliminates the steep fallmore » in the elastic intensity at 296 K associated with the solid gel to fluid phase transition, which is observed for pure DMPC vesicles. Quasielastic neutron scattering (QENS) experiments have been carried out on DMPC ULV in the solid gel and fluid phases with and without 0.2 mol % melittin. The data analysis invariably shows the presence of lateral and internal motions of the DMPC molecule. We found that melittin does have a profound effect on the dynamics of lipid molecules, especially on the lateral motion, and affects it in a different way, depending on the phase of the bilayers. In the solid gel phase, it acts as a plasticizer, enhancing the lateral motion of DMPC. However, in the fluid phase it acts as a stiffening agent, restricting the lateral motion of the lipid molecules. These observations are consistent with the mean squared displacements extracted from the elastic intensity temperature scans. Cholesterol is a vital component of eukaryotic membrane, which is a natural target for melittin. To investigate the effect of melittin on vesicles supplemented with cholesterol, QENS experiments have also been carried out on DMPC ULV with 20 mol% cholesterol in the presence and absence of 0.2 mol% melittin. Remarkably, the effects of melittin on the membrane dynamics disappear in the presence of 20 mol % cholesterol. Thus, our measurements indicate that the destabilizing effect of the peptide melittin on membranes can be mitigated by the presence of cholesterol.« less

Effect of antimicrobial peptide on dynamics of phosphocholine membrane: role of cholesterol and physical state of bilayer

DOE PAGES

Sharma, Veerendra K.; Mamontov, Eugene; Anunciado, Divina B.; ...

2015-06-24

Antimicrobial peptides are universal in all forms of life and are well known for their strong interaction with the cell membrane. This makes them a popular target for investigation of peptide-lipid interactions. Here we report the effect of melittin, an important antimicrobial peptide, on the dynamics of membranes based on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid in both the solid gel and fluid phases. To probe the phase transition, elastic neutron intensity temperature scans have been carried out on DMPC-based unilamellar vesicles (ULV) with and without melittin. We have found that addition of a small amount (0.2 mol%) melittin eliminates the steep fallmore » in the elastic intensity at 296 K associated with the solid gel to fluid phase transition, which is observed for pure DMPC vesicles. Quasielastic neutron scattering (QENS) experiments have been carried out on DMPC ULV in the solid gel and fluid phases with and without 0.2 mol % melittin. The data analysis invariably shows the presence of lateral and internal motions of the DMPC molecule. We found that melittin does have a profound effect on the dynamics of lipid molecules, especially on the lateral motion, and affects it in a different way, depending on the phase of the bilayers. In the solid gel phase, it acts as a plasticizer, enhancing the lateral motion of DMPC. However, in the fluid phase it acts as a stiffening agent, restricting the lateral motion of the lipid molecules. These observations are consistent with the mean squared displacements extracted from the elastic intensity temperature scans. Cholesterol is a vital component of eukaryotic membrane, which is a natural target for melittin. To investigate the effect of melittin on vesicles supplemented with cholesterol, QENS experiments have also been carried out on DMPC ULV with 20 mol% cholesterol in the presence and absence of 0.2 mol% melittin. Remarkably, the effects of melittin on the membrane dynamics disappear in the presence of 20 mol % cholesterol. Thus, our measurements indicate that the destabilizing effect of the peptide melittin on membranes can be mitigated by the presence of cholesterol.« less

Whole brain inhomogeneous magnetization transfer (ihMT) imaging: Sensitivity enhancement within a steady-state gradient echo sequence.

PubMed

Mchinda, Samira; Varma, Gopal; Prevost, Valentin H; Le Troter, Arnaud; Rapacchi, Stanislas; Guye, Maxime; Pelletier, Jean; Ranjeva, Jean-Philippe; Alsop, David C; Duhamel, Guillaume; Girard, Olivier M

2018-05-01

To implement, characterize, and optimize an interleaved inhomogeneous magnetization transfer (ihMT) gradient echo sequence allowing for whole-brain imaging within a clinically compatible scan time. A general framework for ihMT modelling was developed based on the Provotorov theory of radiofrequency saturation, which accounts for the dipolar order underpinning the ihMT effect. Experimental studies and numerical simulations were performed to characterize and optimize the ihMT-gradient echo dependency with sequence timings, saturation power, and offset frequency. The protocol was optimized in terms of maximum signal intensity and the reproducibility assessed for a nominal resolution of 1.5 mm isotropic. All experiments were performed on healthy volunteers at 1.5T. An important mechanism driving signal optimization and leading to strong ihMT signal enhancement that relies on the dynamics of radiofrequency energy deposition has been identified. By taking advantage of the delay allowed for readout between ihMT pulse bursts, it was possible to boost the ihMT signal by almost 2-fold compared to previous implementation. Reproducibility of the optimal protocol was very good, with an intra-individual error < 2%. The proposed sensitivity-boosted and time-efficient steady-state ihMT-gradient echo sequence, implemented and optimized at 1.5T, allowed robust high-resolution 3D ihMT imaging of the whole brain within a clinically compatible scan time. Magn Reson Med 79:2607-2619, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Dynamic in vivo imaging of small animal brain using pulsed laser diode-based photoacoustic tomography system

NASA Astrophysics Data System (ADS)

Upputuri, Paul Kumar; Pramanik, Manojit

2017-09-01

We demonstrate dynamic in vivo imaging using a low-cost portable pulsed laser diode (PLD)-based photoacoustic tomography system. The system takes advantage of an 803-nm PLD having high-repetition rate ˜7000 Hz combined with a fast-scanning single-element ultrasound transducer leading to a 5 s cross-sectional imaging. Cortical vasculature is imaged in scan time of 5 s with high signal-to-noise ratio ˜48. To examine the ability for dynamic imaging, we monitored the fast uptake and clearance process of indocyanine green in the rat brain. The system will find applications to study neurofunctional activities, characterization of pharmacokinetic, and biodistribution profiles in the development process of drugs or imaging agents.

Airborne polarimetric Doppler weather radar: trade-offs between various engineering specifications

NASA Astrophysics Data System (ADS)

Vivekanandan, Jothiram; Loew, Eric

2018-01-01

NCAR EOL is investigating potential configurations for the next-generation airborne phased array radar (APAR) that is capable of retrieving dynamic and microphysical characteristics of clouds and precipitation. The APAR will operate at C band. The APAR will use the electronic scanning (e-scan) feature to acquire the optimal number of independent samples for recording research-quality measurements. Since the airborne radar has only a limited time for collecting measurements over a specified region (moving aircraft platform ˜ 100 m s-1), beam multiplexing will significantly enhance its ability to collect high-resolution, research-quality measurements. Beam multiplexing reduces errors in radar measurements while providing rapid updates of scan volumes. Beamwidth depends on the size of the antenna aperture. Beamwidth and directivity of elliptical, circular, and rectangular antenna apertures are compared and radar sensitivity is evaluated for various polarimetric configurations and transmit-receive (T/R) elements. In the case of polarimetric measurements, alternate transmit with alternate receive (single-channel receiver) and simultaneous reception (dual-channel receiver) is compared. From an overall architecture perspective, element-level digitization of T/R module versus digital sub-array is considered with regard to flexibility in adaptive beamforming, polarimetric performance, calibration, and data quality. Methodologies for calibration of the radar and removing bias in polarimetric measurements are outlined. The above-mentioned engineering options are evaluated for realizing an optimal APAR system suitable for measuring the high temporal and spatial resolutions of Doppler and polarimetric measurements of precipitation and clouds.

Biofibres from biofuel industrial byproduct-Pongamia pinnata seed hull.

PubMed

Manjula, Puttaswamy; Srinikethan, Govindan; Shetty, K Vidya

2017-01-01

Biodiesel production using Pongamia pinnata (P. pinnata) seeds results in large amount of unused seed hull. These seed hulls serve as a potential source for cellulose fibres which can be exploited as reinforcement in composites. These seed hulls were processed using chlorination and alkaline extraction process in order to isolate cellulose fibres. Scanning electron microscopy (SEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR) analysis demonstrated the morphological changes in the fibre structure. Cellulose microfibres of diameter 6-8 µm, hydrodynamic diameter of 58.4 nm and length of 535 nm were isolated. Thermal stability was enhanced by 70 °C and crystallinity index (CI) by 19.8% ensuring isolation of crystalline cellulose fibres. The sequential chlorination and alkaline treatment stemmed to the isolation of cellulose fibres from P. pinnata seed hull. The isolated cellulose fibres possessed enhanced morphological, thermal, and crystalline properties in comparison with P. pinnata seed hull. These cellulose microfibres may potentially find application as biofillers in biodegradable composites by augmenting their properties.

Surface modification of polyester fabrics by atmospheric-pressure air/He plasma for color strength and adhesion enhancement

NASA Astrophysics Data System (ADS)

Zhang, Chunming; Zhao, Meihua; Wang, Libing; Qu, Lijun; Men, Yajing

2017-04-01

Surface properties of water-based pigmented inks for ink-jet printed polyester fabrics were modified with atmospheric-pressure air/He plasma to improve the color strength and pigment adhesion of the treated surfaces. The influence of various parameters, including the surface morphology, chemical compositions, surface energy and dynamic contact angles of the control and plasma treated samples was studied. Color strength and edge definition were used to evaluate the ink-jet printing performance of fabrics. The change in pigment adhesion to polyester fibers was analyzed by SEM (scanning electron microscopy). AFM (Atomic force microscope) and XPS (X-ray photoelectron spectroscopy) analyses indicated the increase in surface roughness and the oxygen-containing polar groups(Cdbnd O, Csbnd OH and COOH) reinforced the fixation of pigments on the fiber surface. The result from this study suggested that the improved pigment color yield was clearly affected by alteration of pigment adhesion enhanced by plasma surface modification. Polyester fabrics exhibited better surface property and ink-jet printing performance after the air/He mixture plasma treatment comparing with those after air plasma treatment.

Origin of optical non-linear response in TiN owing to excitation dynamics of surface plasmon resonance electronic oscillations

NASA Astrophysics Data System (ADS)

Divya, S.; Nampoori, V. P. N.; Radhakrishnan, P.; Mujeeb, A.

2014-08-01

TiN nanoparticles of average size 55 nm were investigated for their optical non-linear properties. During the experiment the irradiated laser wavelength coincided with the surface plasmon resonance (SPR) peak of the nanoparticle. The large non-linearity of the nanoparticle was attributed to the plasmon resonance, which largely enhanced the local field within the nanoparticle. Both open and closed aperture Z-scan experiments were performed and the corresponding optical constants were explored. The post-excitation absorption spectra revealed the interesting phenomenon of photo fragmentation leading to the blue shift in band gap and red shift in the SPR. The results are discussed in terms of enhanced interparticle interaction simultaneous with size reduction. Here, the optical constants being intrinsic constants for a particular sample change unusually with laser power intensity. The dependence of χ(3) is discussed in terms of the size variation caused by photo fragmentation. The studies proved that the TiN nanoparticles are potential candidates in photonics technology offering huge scope to study unexplored research for various expedient applications.

Arrangement at the nanoscale: Effect on magnetic particle hyperthermia

NASA Astrophysics Data System (ADS)

Myrovali, E.; Maniotis, N.; Makridis, A.; Terzopoulou, A.; Ntomprougkidis, V.; Simeonidis, K.; Sakellari, D.; Kalogirou, O.; Samaras, T.; Salikhov, R.; Spasova, M.; Farle, M.; Wiedwald, U.; Angelakeris, M.

2016-11-01

In this work, we present the arrangement of Fe3O4 magnetic nanoparticles into 3D linear chains and its effect on magnetic particle hyperthermia efficiency. The alignment has been performed under a 40 mT magnetic field in an agarose gel matrix. Two different sizes of magnetite nanoparticles, 10 and 40 nm, have been examined, exhibiting room temperature superparamagnetic and ferromagnetic behavior, in terms of DC magnetic field, respectively. The chain formation is experimentally visualized by scanning electron microscopy images. A molecular Dynamics anisotropic diffusion model that outlines the role of intrinsic particle properties and inter-particle distances on dipolar interactions has been used to simulate the chain formation process. The anisotropic character of the aligned samples is also reflected to ferromagnetic resonance and static magnetometry measurements. Compared to the non-aligned samples, magnetically aligned ones present enhanced heating efficiency increasing specific loss power value by a factor of two. Dipolar interactions are responsible for the chain formation of controllable density and thickness inducing shape anisotropy, which in turn enhances magnetic particle hyperthermia efficiency.

On-shot characterization of single plasma mirror temporal contrast improvement

NASA Astrophysics Data System (ADS)

Obst, L.; Metzkes-Ng, J.; Bock, S.; Cochran, G. E.; Cowan, T. E.; Oksenhendler, T.; Poole, P. L.; Prencipe, I.; Rehwald, M.; Rödel, C.; Schlenvoigt, H.-P.; Schramm, U.; Schumacher, D. W.; Ziegler, T.; Zeil, K.

2018-05-01

We report on the setup and commissioning of a compact recollimating single plasma mirror (PM) for temporal contrast enhancement at the Draco 150 TW laser during laser-proton acceleration experiments. The temporal contrast with and without PM is characterized single-shot by means of self-referenced spectral interferometry with extended time excursion at unprecedented dynamic and temporal range. This allows for the first single-shot measurement of the PM trigger point, which is interesting for the quantitative investigation of the complex pre-plasma formation process at the surface of the target used for proton acceleration. As a demonstration of high contrast laser plasma interaction we present proton acceleration results with ultra-thin liquid crystal targets of ∼ 1 μm down to 10 nm thickness. Focus scans of different target thicknesses show that highest proton energies are reached for the thinnest targets at best focus. This indicates that the contrast enhancement is effective such that the acceleration process is not limited by target pre-expansion induced by laser light preceding the main laser pulse.

Effects of Irradiation on Albite's Chemical Durability.

PubMed

Hsiao, Yi-Hsuan; La Plante, Erika Callagon; Krishnan, N M Anoop; Le Pape, Yann; Neithalath, Narayanan; Bauchy, Mathieu; Sant, Gaurav

2017-10-19

Albite (NaAlSi 3 O 8 ), a framework silicate of the plagioclase feldspar family and a common constituent of felsic rocks, is often present in the siliceous mineral aggregates that compose concrete. When exposed to radiation (e.g., in the form of neutrons) in nuclear power plants, the crystal structure of albite can undergo significant alterations. These alterations may degrade its chemical durability. Indeed, careful examinations of Ar + -implanted albite carried out using Fourier transform infrared spectroscopy (FTIR) and molecular dynamics simulations show that albite's crystal structure, upon irradiation, undergoes progressive disordering, resulting in an expansion in its molar volume (i.e., a reduction of density) and a reduction in the connectivity of its atomic network. This loss of network connectivity (i.e., rigidity) results in an enhancement of the aqueous dissolution rate of albite-measured using vertical scanning interferometry (VSI) in alkaline environments-by a factor of 20. This enhancement in the dissolution rate (i.e., reduction in chemical durability) of albite following irradiation has significant impacts on the durability of felsic rocks and of concrete containing them upon their exposure to radiation in nuclear power plant (NPP) environments.

Iterative reconstruction for CT perfusion with a prior-image induced hybrid nonlocal means regularization: Phantom studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Bin; Lyu, Qingwen; Ma, Jianhua

2016-04-15

Purpose: In computed tomography perfusion (CTP) imaging, an initial phase CT acquired with a high-dose protocol can be used to improve the image quality of later phase CT acquired with a low-dose protocol. For dynamic regions, signals in the later low-dose CT may not be completely recovered if the initial CT heavily regularizes the iterative reconstruction process. The authors propose a hybrid nonlocal means (hNLM) regularization model for iterative reconstruction of low-dose CTP to overcome the limitation of the conventional prior-image induced penalty. Methods: The hybrid penalty was constructed by combining the NLM of the initial phase high-dose CT inmore » the stationary region and later phase low-dose CT in the dynamic region. The stationary and dynamic regions were determined by the similarity between the initial high-dose scan and later low-dose scan. The similarity was defined as a Gaussian kernel-based distance between the patch-window of the same pixel in the two scans, and its measurement was then used to weigh the influence of the initial high-dose CT. For regions with high similarity (e.g., stationary region), initial high-dose CT played a dominant role for regularizing the solution. For regions with low similarity (e.g., dynamic region), the regularization relied on a low-dose scan itself. This new hNLM penalty was incorporated into the penalized weighted least-squares (PWLS) for CTP reconstruction. Digital and physical phantom studies were performed to evaluate the PWLS-hNLM algorithm. Results: Both phantom studies showed that the PWLS-hNLM algorithm is superior to the conventional prior-image induced penalty term without considering the signal changes within the dynamic region. In the dynamic region of the Catphan phantom, the reconstruction error measured by root mean square error was reduced by 42.9% in PWLS-hNLM reconstructed image. Conclusions: The PWLS-hNLM algorithm can effectively use the initial high-dose CT to reconstruct low-dose CTP in the stationary region while reducing its influence in the dynamic region.« less

Exciton dynamics of C60-based single-photon emitters explored by Hanbury Brown-Twiss scanning tunnelling microscopy.

PubMed

Merino, P; Große, C; Rosławska, A; Kuhnke, K; Kern, K

2015-09-29

Exciton creation and annihilation by charges are crucial processes for technologies relying on charge-exciton-photon conversion. Improvement of organic light sources or dye-sensitized solar cells requires methods to address exciton dynamics at the molecular scale. Near-field techniques have been instrumental for this purpose; however, characterizing exciton recombination with molecular resolution remained a challenge. Here, we study exciton dynamics by using scanning tunnelling microscopy to inject current with sub-molecular precision and Hanbury Brown-Twiss interferometry to measure photon correlations in the far-field electroluminescence. Controlled injection allows us to generate excitons in solid C60 and let them interact with charges during their lifetime. We demonstrate electrically driven single-photon emission from localized structural defects and determine exciton lifetimes in the picosecond range. Monitoring lifetime shortening and luminescence saturation for increasing carrier injection rates provides access to charge-exciton annihilation dynamics. Our approach introduces a unique way to study single quasi-particle dynamics on the ultimate molecular scale.

Movement Correction Method for Human Brain PET Images: Application to Quantitative Analysis of Dynamic [18F]-FDDNP Scans

PubMed Central

Wardak, Mirwais; Wong, Koon-Pong; Shao, Weber; Dahlbom, Magnus; Kepe, Vladimir; Satyamurthy, Nagichettiar; Small, Gary W.; Barrio, Jorge R.; Huang, Sung-Cheng

2010-01-01

Head movement during a PET scan (especially, dynamic scan) can affect both the qualitative and quantitative aspects of an image, making it difficult to accurately interpret the results. The primary objective of this study was to develop a retrospective image-based movement correction (MC) method and evaluate its implementation on dynamic [18F]-FDDNP PET images of cognitively intact controls and patients with Alzheimer’s disease (AD). Methods Dynamic [18F]-FDDNP PET images, used for in vivo imaging of beta-amyloid plaques and neurofibrillary tangles, were obtained from 12 AD and 9 age-matched controls. For each study, a transmission scan was first acquired for attenuation correction. An accurate retrospective MC method that corrected for transmission-emission misalignment as well as emission-emission misalignment was applied to all studies. No restriction was assumed for zero movement between the transmission scan and first emission scan. Logan analysis with cerebellum as the reference region was used to estimate various regional distribution volume ratio (DVR) values in the brain before and after MC. Discriminant analysis was used to build a predictive model for group membership, using data with and without MC. Results MC improved the image quality and quantitative values in [18F]-FDDNP PET images. In this subject population, medial temporal (MTL) did not show a significant difference between controls and AD before MC. However, after MC, significant differences in DVR values were seen in frontal, parietal, posterior cingulate (PCG), MTL, lateral temporal (LTL), and global between the two groups (P < 0.05). In controls and AD, the variability of regional DVR values (as measured by the coefficient of variation) decreased on average by >18% after MC. Mean DVR separation between controls and ADs was higher in frontal, MTL, LTL and global after MC. Group classification by discriminant analysis based on [18F]-FDDNP DVR values was markedly improved after MC. Conclusion The streamlined and easy to use MC method presented in this work significantly improves the image quality and the measured tracer kinetics of [18F]-FDDNP PET images. The proposed MC method has the potential to be applied to PET studies on patients having other disorders (e.g., Down syndrome and Parkinson’s disease) and to brain PET scans with other molecular imaging probes. PMID:20080894

Application of low dose radiation and low concentration contrast media in enhanced CT scans in children with congenital heart disease.

PubMed

Liu, Zhimin; Song, Lei; Yu, Tong; Gao, Jun; Zhang, Qifeng; Jiang, Ling; Liu, Yong; Peng, Yun

2016-09-01

The aim of this study was to explore the feasibility of using low dose radiation and low concentration contrast media in enhanced CT examinations in children with congenital heart disease. Ninety patients with congenital heart disease were randomly divided into three groups of 30 patients each who underwent contrast-enhanced cardiac scans on a Discovery CT750 HD scanner. Group A received 270 mg I/mL iodixanol, and group B received 320 mg I/mL iodixanol contrast media and was scanned with prospective ECG triggering mode. Group C received 320 mg I/mL iodixanol and was scanned with conventional retrospective ECG gating mode. The same weight-based contrast injection protocol was used for all three groups. Images were reconstructed using a 30% adaptive statistical iterative reconstruction (ASIR) algorithm and a 50% ASIR in groups A and B and a 30% ASIR in group C. The subjective and objective image quality evaluations, diagnostic accuracies, radiation doses and amounts of contrast media in the three groups were measured and compared. All images in the three groups met the diagnostic requirements, with the same diagnostic accuracy and image quality scores greater than 3 in a 4-point scoring system. However, ventricular enhancement and the objective noise, signal-to-noise ratio, contrast-to-noise ratio and subjective image quality scores in group C were better than those in groups A and B (all P<.001). The effective radiation dose in groups A and B was 84% lower than that in group C (P<.001); group A received the lowest contrast dose (14% lower than that of groups B and C). Enhanced CT scan images with low dose radiation and low concentration contrast media can meet the diagnostic requirements for examining children with congenital heart disease while reducing the potential risk of radiation damage and contrast-induced nephropathy. © 2016 John Wiley & Sons Ltd.

Towards endometriosis diagnosis by gadofosveset-trisodium enhanced magnetic resonance imaging.

PubMed

Schreinemacher, Marc H; Backes, Walter H; Slenter, Jos M; Xanthoulea, Sofia; Delvoux, Bert; van Winden, Larissa; Beets-Tan, Regina G; Evers, Johannes L H; Dunselman, Gerard A J; Romano, Andrea

2012-01-01

Endometriosis is defined as the presence of endometrial tissue outside the uterus. It affects 10-15% of women during reproductive age and has a big personal and social impact due to chronic pelvic pain, subfertility, loss of work-hours and medical costs. Such conditions are exacerbated by the fact that the correct diagnosis is made as late as 8-11 years after symptom presentation. This is due to the lack of a reliable non-invasive diagnostic test and the fact that the reference diagnostic standard is laparoscopy (invasive, expensive and not without risks). High-molecular weight gadofosveset-trisodium is used as contrast agent in Magnetic Resonance Imaging (MRI). Since it extravasates from hyperpermeable vessels more easily than from mature blood vessels, this contrast agent detects angiogenesis efficiently. Endometriosis has high angiogenic activity. Therefore, we have tested the possibility to detect endometriosis non-invasively using Dynamic Contrast-Enhanced MRI (DCE-MRI) and gadofosveset-trisodium as a contrast agent in a mouse model. Endometriotic lesions were surgically induced in nine mice by autologous transplantation. Three weeks after lesion induction, mice were scanned by DCE-MRI. Dynamic image analysis showed that the rates of uptake (inwash), persistence and outwash of the contrast agent were different between endometriosis and control tissues (large blood vessels and back muscle). Due to the extensive angiogenesis in induced lesions, the contrast agent persisted longer in endometriotic than control tissues, thus enhancing the MRI signal intensity. DCE-MRI was repeated five weeks after lesion induction, and contrast enhancement was similar to that observed three weeks after endometriosis induction. The endothelial-cell marker CD31 and the pericyte marker α-smooth-muscle-actin (mature vessels) were detected with immunohistochemistry and confirmed that endometriotic lesions had significantly higher prevalence of new vessels (CD31 only positive) than the uterus and control tissues. The diagnostic value of gadofosveset-trisodium to detect endometriosis should be tested in human settings.

Evaluating dynamic contrast-enhanced and photoacoustic CT to assess intra-tumor heterogeneity in xenograft mouse models

NASA Astrophysics Data System (ADS)

Stantz, Keith M.; Liu, Bo; Cao, Minsong; Reinecke, Dan; Dzemidzic, Mario; Liang, Yun; Kruger, Robert

2006-03-01

Purpose: To evaluate photoacoustic CT spectroscopy (PCT-S) and dynamic contrast-enhanced CT (DCE-CT) ability to measure parameters - oxygen saturation and vascular physiology - associated with the intra-tumor oxygenation status. Material and Methods: Breast (VEGF165 enhance MCF-7) and ovarian (SKOV3x) cancer cells were implanted into the fat pads and flanks of immune deficient mice and allowed to grow to a diameter of 8-15 mm. CT was used to determine physiological parameters by acquiring a sequence of scans over a 10 minute period after an i.v. injection of a radio-opaque contrast agent (Isovue). These time-dependent contrast-enhanced curves were fit to a two-compartmental model determining tumor perfusion, fractional plasma volume, permeability-surface area produce, and fractional interstitial volume on a voxel-by-voxel basis. After which, the tumors were imaged using photoacoustic CT (Optosonics, Inc., Indianapolis, IN 46202). The near infrared spectra (700-910 nm) within the vasculature was fit to linear combination of measured oxy- and deoxy-hemoglobin blood samples to obtain oxygen saturation levels (SaO II). Results: The PCT-S scanner was first calibrated using different samples of oxygenated blood, from which a statistical error ranging from 2.5-6.5% was measured and a plot of the hemoglobin dissociation curve was consistent with empirical formula. In vivo determination of tumor vasculature SaO II levels were measurably tracked, and spatially correlated to the periphery of the tumor. Tumor depend variations in SaO II - 0.32 (ovarian) and 0.60 (breast) - and in vascular physiology - perfusion, 1.03 and 0.063 mL/min/mL, and fractional plasma volume, 0.20 and 0.07 - were observed. Conclusion: Combined, PCT-S and CED-CT has the potential to measure intra-tumor levels of tumor oxygen saturation and vascular physiology, key parameters associated with hypoxia.

Technical Note: Evaluation of a 160-mm/256-row CT scanner for whole-heart quantitative myocardial perfusion imaging.

PubMed

So, Aaron; Imai, Yasuhiro; Nett, Brian; Jackson, John; Nett, Liz; Hsieh, Jiang; Wisenberg, Gerald; Teefy, Patrick; Yadegari, Andrew; Islam, Ali; Lee, Ting-Yim

2016-08-01

The authors investigated the performance of a recently introduced 160-mm/256-row CT system for low dose quantitative myocardial perfusion (MP) imaging of the whole heart. This platform is equipped with a gantry capable of rotating at 280 ms per full cycle, a second generation of adaptive statistical iterative reconstruction (ASiR-V) to correct for image noise arising from low tube voltage potential/tube current dynamic scanning, and image reconstruction algorithms to tackle beam-hardening, cone-beam, and partial-scan effects. Phantom studies were performed to investigate the effectiveness of image noise and artifact reduction with a GE Healthcare Revolution CT system for three acquisition protocols used in quantitative CT MP imaging: 100, 120, and 140 kVp/25 mAs. The heart chambers of an anthropomorphic chest phantom were filled with iodinated contrast solution at different concentrations (contrast levels) to simulate the circulation of contrast through the heart in quantitative CT MP imaging. To evaluate beam-hardening correction, the phantom was scanned at each contrast level to measure the changes in CT number (in Hounsfield unit or HU) in the water-filled region surrounding the heart chambers with respect to baseline. To evaluate cone-beam artifact correction, differences in mean water HU between the central and peripheral slices were compared. Partial-scan artifact correction was evaluated from the fluctuation of mean water HU in successive partial scans. To evaluate image noise reduction, a small hollow region adjacent to the heart chambers was filled with diluted contrast, and contrast-to-noise ratio in the region before and after noise correction with ASiR-V was compared. The quality of MP maps acquired with the CT system was also evaluated in porcine CT MP studies. Myocardial infarct was induced in a farm pig from a transient occlusion of the distal left anterior descending (LAD) artery with a catheter-based interventional procedure. MP maps were generated from the dynamic contrast-enhanced (DCE) heart images taken at baseline and three weeks after the ischemic insult. Their results showed that the phantom and animal images acquired with the CT platform were minimally affected by image noise and artifacts. For the beam-hardening phantom study, changes in water HU in the wall surrounding the heart chambers greatly reduced from >±30 to ≤ ± 5 HU at all kVp settings except one region at 100 kVp (7 HU). For the cone-beam phantom study, differences in mean water HU from the central slice were less than 5 HU at two peripheral slices with each 4 cm away from the central slice. These findings were reproducible in the pig DCE images at two peripheral slices that were 6 cm away from the central slice. For the partial-scan phantom study, standard deviations of the mean water HU in 10 successive partial scans were less than 5 HU at the central slice. Similar observations were made in the pig DCE images at two peripheral slices with each 6 cm away from the central slice. For the image noise phantom study, CNRs in the ASiR-V images were statistically higher (p < 0.05) than the non-ASiR-V images at all kVp settings. MP maps generated from the porcine DCE images were in excellent quality, with the ischemia in the LAD territory clearly seen in the three orthogonal views. The study demonstrates that this CT system can provide accurate and reproducible CT numbers during cardiac gated acquisitions across a wide axial field of view. This CT number fidelity will enable this imaging tool to assess contrast enhancement, potentially providing valuable added information beyond anatomic evaluation of coronary stenoses. Furthermore, their results collectively suggested that the 100 kVp/25 mAs protocol run on this CT system provides sufficient image accuracy at a low radiation dose (<3 mSv) for whole-heart quantitative CT MP imaging.

CO2-switchable fluorescence of a dendritic polymer and its applications

NASA Astrophysics Data System (ADS)

Gao, Chunmei; Lü, Shaoyu; Liu, Mingzhu; Wu, Can; Xiong, Yun

2015-12-01

The synthesis and properties of CO2 responsive and fluorescent dendritic polymers, poly(amido amine)/Pluronic F127 (PAMAM/F127), are reported in this paper. The morphologies and sizes of PAMAM/F127 dendritic polymers were investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). PAMAM/F127 dendritic polymers showed unimolecular micelle morphologies at low concentrations, and changed to multimolecular micelles at higher concentrations. Additionally, fluorescence spectra and confocal laser scanning microscopy images showed that PAMAM/F127 dendritic polymers exhibited a fluorescent enhancement response to the presence of CO2. Apart from that, the release behavior of PAMAM/F127 gels under simulated body fluids was investigated by choosing curcumin as the hydrophobic drug. The results indicated that PAMAM/F127 dendritic polymers can be used to improve the solubility of curcumin, and the drug released faster in the presence of CO2. Such CO2 responsive fluorescent dendritic polymers are potentially applicable in cellular imaging or drug controlled release.The synthesis and properties of CO2 responsive and fluorescent dendritic polymers, poly(amido amine)/Pluronic F127 (PAMAM/F127), are reported in this paper. The morphologies and sizes of PAMAM/F127 dendritic polymers were investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). PAMAM/F127 dendritic polymers showed unimolecular micelle morphologies at low concentrations, and changed to multimolecular micelles at higher concentrations. Additionally, fluorescence spectra and confocal laser scanning microscopy images showed that PAMAM/F127 dendritic polymers exhibited a fluorescent enhancement response to the presence of CO2. Apart from that, the release behavior of PAMAM/F127 gels under simulated body fluids was investigated by choosing curcumin as the hydrophobic drug. The results indicated that PAMAM/F127 dendritic polymers can be used to improve the solubility of curcumin, and the drug released faster in the presence of CO2. Such CO2 responsive fluorescent dendritic polymers are potentially applicable in cellular imaging or drug controlled release. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06729d

Predicting tumor hypoxia in non-small cell lung cancer by combining CT, FDG PET and dynamic contrast-enhanced CT.

PubMed

Even, Aniek J G; Reymen, Bart; La Fontaine, Matthew D; Das, Marco; Jochems, Arthur; Mottaghy, Felix M; Belderbos, José S A; De Ruysscher, Dirk; Lambin, Philippe; van Elmpt, Wouter

2017-11-01

Most solid tumors contain inadequately oxygenated (i.e., hypoxic) regions, which tend to be more aggressive and treatment resistant. Hypoxia PET allows visualization of hypoxia and may enable treatment adaptation. However, hypoxia PET imaging is expensive, time-consuming and not widely available. We aimed to predict hypoxia levels in non-small cell lung cancer (NSCLC) using more easily available imaging modalities: FDG-PET/CT and dynamic contrast-enhanced CT (DCE-CT). For 34 NSCLC patients, included in two clinical trials, hypoxia HX4-PET/CT, planning FDG-PET/CT and DCE-CT scans were acquired before radiotherapy. Scans were non-rigidly registered to the planning CT. Tumor blood flow (BF) and blood volume (BV) were calculated by kinetic analysis of DCE-CT images. Within the gross tumor volume, independent clusters, i.e., supervoxels, were created based on FDG-PET/CT. For each supervoxel, tumor-to-background ratios (TBR) were calculated (median SUV/aorta SUV mean ) for HX4-PET/CT and supervoxel features (median, SD, entropy) for the other modalities. Two random forest models (cross-validated: 10 folds, five repeats) were trained to predict the hypoxia TBR; one based on CT, FDG, BF and BV, and one with only CT and FDG features. Patients were split in a training (trial NCT01024829) and independent test set (trial NCT01210378). For each patient, predicted, and observed hypoxic volumes (HV) (TBR > 1.2) were compared. Fifteen patients (3291 supervoxels) were used for training and 19 patients (1502 supervoxels) for testing. The model with all features (RMSE training: 0.19 ± 0.01, test: 0.27) outperformed the model with only CT and FDG-PET features (RMSE training: 0.20 ± 0.01, test: 0.29). All tumors of the test set were correctly classified as normoxic or hypoxic (HV > 1 cm 3 ) by the best performing model. We created a data-driven methodology to predict hypoxia levels and hypoxia spatial patterns using CT, FDG-PET and DCE-CT features in NSCLC. The model correctly classifies all tumors, and could therefore, aid tumor hypoxia classification and patient stratification.

Charge dynamics in aluminum oxide thin film studied by ultrafast scanning electron microscopy.

PubMed

Zani, Maurizio; Sala, Vittorio; Irde, Gabriele; Pietralunga, Silvia Maria; Manzoni, Cristian; Cerullo, Giulio; Lanzani, Guglielmo; Tagliaferri, Alberto

2018-04-01

The excitation dynamics of defects in insulators plays a central role in a variety of fields from Electronics and Photonics to Quantum computing. We report here a time-resolved measurement of electron dynamics in 100 nm film of aluminum oxide on silicon by Ultrafast Scanning Electron Microscopy (USEM). In our pump-probe setup, an UV femtosecond laser excitation pulse and a delayed picosecond electron probe pulse are spatially overlapped on the sample, triggering Secondary Electrons (SE) emission to the detector. The zero of the pump-probe delay and the time resolution were determined by measuring the dynamics of laser-induced SE contrast on silicon. We observed fast dynamics with components ranging from tens of picoseconds to few nanoseconds, that fits within the timescales typical of the UV color center evolution. The surface sensitivity of SE detection gives to the USEM the potential of applying pump-probe investigations to charge dynamics at surfaces and interfaces of current nano-devices. The present work demonstrates this approach on large gap insulator surfaces. Copyright © 2018 Elsevier B.V. All rights reserved.

Domestic scan tour report : land use and transportation coordination : lessons learned from domestic scan tour

DOT National Transportation Integrated Search

2003-03-01

Designing transportation systems that enhance mobility, economic opportunity, and community livability is a major challenge for many communities across the country. In the United States, political leaders, planning professionals, and private citizens...

Does intravenous contrast-enhanced computed tomography cause acute kidney injury? Protocol of a systematic review of the evidence

PubMed Central

2014-01-01

Background Contrast-induced acute kidney injury is a common cause of iatrogenic acute kidney injury (AKI). Most of the published estimates of AKI after contrast use originate from the cardiac catheterization literature despite contrast-enhanced computed tomography (CT) scans being the more common setting for contrast use. This systematic review aims to summarize the current evidence about (1)the risk of AKI following intravenous (IV) contrast-enhanced CT scans and(2) the risk of clinical outcomes (i.e. death, hospitalization and need for renal replacement therapy) due to IV contrast-enhanced CT scans. Methods/Design A systematic literature search for published studies will be performed using MEDLINE, EMBASE and The COCHRANE Library databases. Unpublished studies will be identified by searching through grey literature. No language restriction will be applied. The review will consider all studies that have examined the association between IV contrast media and AKI. To be selected, the study should include two arms: one group of exposed patients who received IV contrast material before CT scans and one group of unexposed group who did not receive contrast material before CT scans. Two authors will independently screen titles and abstracts obtained from electronic databases, extract data and will assess the quality of the studies selected using the Cochrane's ‘Risk of Bias’ assessment tool for randomized trials and the Newcastle-Ottawa Scale for observational studies. A random-effects meta-analysis will be performed if there is no remarkable heterogeneity between studies. Discussion This systematic review will provide synthesis of current evidence around the effect of IV contrast material on AKI and other clinical outcomes. Results will be helpful for making evidence-based recommendations and guidelines for clinical and radiologic settings. Systematic review registration PROSPERO CRD42013003799. PMID:25148933

Morphobiochemical diagnosis of acute trabecular microfractures using gamma correction Tc-99m HDP pinhole bone scan with histopathological verification.

PubMed

Bahk, Yong-Whee; Hwang, Seok-Ha; Lee, U-Young; Chung, Yong-An; Jung, Joo-Young; Jeong, Hyeonseok S

2017-11-01

We prospectively performed gamma correction pinhole bone scan (GCPBS) and histopathologic verification study to make simultaneous morphobiochemical diagnosis of trabecular microfractures (TMF) occurred in the femoral head as a part of femoral neck fracture.Materials consisted of surgical specimens of the femoral head in 6 consecutive patients. The specimens were imaged using Tc-99m hydroxymethylene diphosphonate (HDP) pinhole scan and processed by the gamma correction. After cleansing with 10% formalin solution, injured specimen surface was observed using a surgical microscope to record TMF. Morphological findings shown in the photograph, naive pinhole bone scan, GCPBS, and hematoxylin-eosin (H&E) stain of the specimen were reciprocally correlated for histological verification and the usefulness of suppression and enhancement of Tc-99m HDP uptake was biochemically investigated in TMF and edema and hemorrhage using gamma correction.On the one hand, GCPBS was able to depict the calcifying calluses in TMF with enhanced Tc-99m HDP uptake. They were pinpointed, speckled, round, ovoid, rod-like, geographic, and crushed in shape. The smallest callus measured was 0.23 mm in this series. On the other hand, GCPBS biochemically was able to discern the calluses with enhanced high Tc-99m HDP uptake from the normal and edema dipped and hemorrhage irritated trabeculae with washed out uptake.Morphobiochemically, GCPBS can clearly depict microfractures in the femoral head produced by femoral neck fracture. It discerns the microcalluses with enhanced Tc-99m HDP uptake from the intact and edema dipped and hemorrhage irritated trabeculae with suppressed washed out Tc-99m HDP uptake. Both conventional pinhole bone scan and gamma correction are useful imaging means to specifically diagnose the microcalluses naturally formed in TMF.

Administration of Oral Itraconazole Capsule with Whole Milk Shows Enhanced Efficacy As Supported by Scanning Electron Microscopy in a Child with Tinea Capitis Due to Microsporum canis.

PubMed

Chen, Shuang; Ran, Yuping; Dai, Yalin; Lama, Jebina; Hu, Wenying; Zhang, Chaoliang

2015-01-01

Although diagnosis and treatment of tinea capitis in children are not difficult, treatment failures are still somewhat common. We report a case of pediatric tinea capitis cured using oral itraconazole administered with whole milk, after prior treatment failure when oral itraconazole was administered with water. This apparent enhanced efficacy in one individual was demonstrated using scanning electron microscopy. © 2015 Wiley Periodicals, Inc.

Cyclic Voltammetric Wave-Shapes for Microdisk Electrodes: Coupled Effects of Solution Resistance, Double-Layer Capacitance, and Finite Electrochemical Kinetics

DTIC Science & Technology

1991-05-01

vaveshapea. While the use of high scan rates enhances the effect of electrode kinetics upon the voltametry , the deleterious coupled influence of pa 20...waveshapes. While the use of high scan rates enhances the effect of electrode kinetics upon the voltametry , the deleterious coupled influence of P...2 1 󈧚 Aoki et al have in- 23 vestigated linear sweep voltammetry at microdisks in the reversible case, and Zoski and co-workers have developed

Automatic anatomical structures location based on dynamic shape measurement

NASA Astrophysics Data System (ADS)

Witkowski, Marcin; Rapp, Walter; Sitnik, Robert; Kujawinska, Malgorzata; Vander Sloten, Jos; Haex, Bart; Bogaert, Nico; Heitmann, Kjell

2005-09-01

New image processing methods and active photonics apparatus have made possible the development of relatively inexpensive optical systems for complex shape and object measurements. We present dynamic 360° scanning method for analysis of human lower body biomechanics, with an emphasis on the analysis of the knee joint. The anatomical structure (of high medical interest) that is possible to scan and analyze, is patella. Tracking of patella position and orientation under dynamic conditions may lead to detect pathological patella movements and help in knee joint disease diagnosis. The processed data is obtained from a dynamic laser triangulation surface measurement system, able to capture slow to normal movements with a scan frequency between 15 and 30 Hz. These frequency rates are enough to capture controlled movements used e.g. for medical examination purposes. The purpose of the work presented is to develop surface analysis methods that may be used as support of diagnosis of motoric abilities of lower limbs. The paper presents algorithms used to process acquired lower limbs surface data in order to find the position and orientation of patella. The algorithms implemented include input data preparation, curvature description methods, knee region discrimination and patella assumed position/orientation calculation. Additionally, a method of 4D (3D + time) medical data visualization is proposed. Also some exemplary results are presented.

General point dipole theory for periodic metasurfaces: magnetoelectric scattering lattices coupled to planar photonic structures.

PubMed

Chen, Yuntian; Zhang, Yan; Femius Koenderink, A

2017-09-04

We study semi-analytically the light emission and absorption properties of arbitrary stratified photonic structures with embedded two-dimensional magnetoelectric point scattering lattices, as used in recent plasmon-enhanced LEDs and solar cells. By employing dyadic Green's function for the layered structure in combination with the Ewald lattice summation to deal with the particle lattice, we develop an efficient method to study the coupling between planar 2D scattering lattices of plasmonic, or metamaterial point particles, coupled to layered structures. Using the 'array scanning method' we deal with localized sources. Firstly, we apply our method to light emission enhancement of dipole emitters in slab waveguides, mediated by plasmonic lattices. We benchmark the array scanning method against a reciprocity-based approach to find that the calculated radiative rate enhancement in k-space below the light cone shows excellent agreement. Secondly, we apply our method to study absorption-enhancement in thin-film solar cells mediated by periodic Ag nanoparticle arrays. Lastly, we study the emission distribution in k-space of a coupled waveguide-lattice system. In particular, we explore the dark mode excitation on the plasmonic lattice using the so-called array scanning method. Our method could be useful for simulating a broad range of complex nanophotonic structures, i.e., metasurfaces, plasmon-enhanced light emitting systems and photovoltaics.

Enhanced resolution imaging of ultrathin ZnO layers on Ag(111) by multiple hydrogen molecules in a scanning tunneling microscope junction

NASA Astrophysics Data System (ADS)

Liu, Shuyi; Shiotari, Akitoshi; Baugh, Delroy; Wolf, Martin; Kumagai, Takashi

2018-05-01

Molecular hydrogen in a scanning tunneling microscope (STM) junction has been found to enhance the lateral spatial resolution of the STM imaging, referred to as scanning tunneling hydrogen microscopy (STHM). Here we report atomic resolution imaging of 2- and 3-monolayer (ML) thick ZnO layers epitaxially grown on Ag(111) using STHM. The enhanced resolution can be obtained at a relatively large tip to surface distance and resolves a more defective structure exhibiting dislocation defects for 3-ML-thick ZnO than for 2 ML. In order to elucidate the enhanced imaging mechanism, the electric and mechanical properties of the hydrogen molecular junction (HMJ) are investigated by a combination of STM and atomic force microscopy. It is found that the HMJ shows multiple kinklike features in the tip to surface distance dependence of the conductance and frequency shift curves, which are absent in a hydrogen-free junction. Based on a simple modeling, we propose that the junction contains several hydrogen molecules and sequential squeezing of the molecules out of the junction results in the kinklike features in the conductance and frequency shift curves. The model also qualitatively reproduces the enhanced resolution image of the ZnO films.

MR imaging with i.v. superparamagnetic iron oxide: efficacy in the detection of focal hepatic lesions.

PubMed

Winter, T C; Freeny, P C; Nghiem, H V; Mack, L A; Patten, R M; Thomas, C R; Elliott, S

1993-12-01

The purpose of this study was to evaluate the efficacy of superparmagnetic iron oxide (SPIO) in the detection of focal hepatic lesions on MR images. The study included 21 patients with 115 focal hepatic lesions and eight patients without focal hepatic lesions. T1- and T2-weighted MR images were obtained at 1.5 T before and 60 min after the end of injection of an SPIO agent. Contrast-enhanced CT scans were obtained in all patients within 10 days after MR imaging. The effect of SPIO on the signal intensity of the liver and spleen was assessed by using quantitative analysis of the region of interest. Efficacy was evaluated by using multiple criteria and unenhanced and SPIO-enhanced images. Evaluations included subjective assessment of image quality, counting the number of lesions detected, and statistical analysis of quantitative changes in the signal intensity of lesions and of normal liver. By all criteria, SPIO-enhanced T2-weighted MR images were superior to unenhanced T2-weighted images and to contrast-enhanced CT scans. Conversely, by all criteria, SPIO-enhanced T1-weighted MR images were worse than unenhanced T1-weighted images and contrast-enhanced CT scans. The mean lesion-to-liver contrast on T2-weighted images was 317% on unenhanced images and 1745% on SPIO-enhanced images. For T1-weighted, the mean contrast was 26% on unenhanced images and 18% on SPIO-enhanced images. SPIO is an efficacious contrast agent for the detection of focal hepatic lesions when T2-weighted MR images are used.

High temporal resolution dynamic contrast-enhanced MRI using compressed sensing-combined sequence in quantitative renal perfusion measurement.

PubMed

Chen, Bin; Zhao, Kai; Li, Bo; Cai, Wenchao; Wang, Xiaoying; Zhang, Jue; Fang, Jing

2015-10-01

To demonstrate the feasibility of the improved temporal resolution by using compressed sensing (CS) combined imaging sequence in dynamic contrast-enhanced MRI (DCE-MRI) of kidney, and investigate its quantitative effects on renal perfusion measurements. Ten rabbits were included in the accelerated scans with a CS-combined 3D pulse sequence. To evaluate the image quality, the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were compared between the proposed CS strategy and the conventional full sampling method. Moreover, renal perfusion was estimated by using the separable compartmental model in both CS simulation and realistic CS acquisitions. The CS method showed DCE-MRI images with improved temporal resolution and acceptable image contrast, while presenting significantly higher SNR than the fully sampled images (p<.01) at 2-, 3- and 4-X acceleration. In quantitative measurements, renal perfusion results were in good agreement with the fully sampled one (concordance correlation coefficient=0.95, 0.91, 0.88) at 2-, 3- and 4-X acceleration in CS simulation. Moreover, in realistic acquisitions, the estimated perfusion by the separable compartmental model exhibited no significant differences (p>.05) between each CS-accelerated acquisition and the full sampling method. The CS-combined 3D sequence could improve the temporal resolution for DCE-MRI in kidney while yielding diagnostically acceptable image quality, and it could provide effective measurements of renal perfusion. Copyright © 2015 Elsevier Inc. All rights reserved.

Preparation of zein nanoparticles by using solution-enhanced dispersion with supercritical CO2 and elucidation with computational fluid dynamics.

PubMed

Li, Sining; Zhao, Yaping

2017-01-01

Nanoparticles have attracted more and more attention in the medicinal field. Zein is a biomacromolecule and can be used as a carrier for delivering active ingredients to prepare controlled release drugs. In this article, we presented the preparation of zein nanoparticles by solution-enhanced dispersion by supercritical CO 2 (SEDS) approach. Scanning electron microscopy and transmission electron microscopy were applied to characterize the size and morphology of the obtained particles. The nozzle structure and the CO 2 flow rate greatly affected the morphology and the size of the particles. The size of zein was able to be reduced to 50-350 nm according to the different conditions. The morphologies of the resultant zein were either sphere or the filament network consisted of nanoparticles. The influence of the nozzle structure and the CO 2 flow rate on the velocity field was elucidated by using computational fluid dynamics. The nozzle structure and the CO 2 flow rate greatly affected the distribution of the velocity field. However, a similar velocity field could also be obtained when the nozzle structure or the CO 2 flow rate, or both were different. Therefore, the influence of the nozzle structure and the CO 2 flow rate on the size and morphology of the particles, can boil down to the velocity field. The results demonstrated that the velocity field can be a potential criterion for producing nanoparticles with controllable morphology and size, which is useful to scale-up the SEDS process.

Improved Carrier Transport in Perovskite Solar Cells Probed by Femtosecond Transient Absorption Spectroscopy.

PubMed

Serpetzoglou, Efthymis; Konidakis, Ioannis; Kakavelakis, George; Maksudov, Temur; Kymakis, Emmanuel; Stratakis, Emmanuel

2017-12-20

CH 3 NH 3 PbI 3 perovskite thin films have been deposited on glass/indium tin oxide/hole transport layer (HTL) substrates, utilizing two different materials as the HTLs. In the first configuration, the super hydrophilic polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), known as PEDOT:PSS, was employed as the HTL material, whereas in the second case, the nonwetting poly(triarylamine) semiconductor polymer, known as PTAA, was used. It was found that when PTAA is used as the HTL material, the averaged power conversion efficiency (PCE) of the perovskite solar cells (PSCs) remarkably increases from 12.60 to 15.67%. To explore the mechanism behind this enhancement, the aforementioned perovskite/HTL arrangements were investigated by time-resolved transient absorption spectroscopy (TAS) performed under inert conditions. By means of TAS, the charge transfer, carrier trapping, and hole injection dynamics from the photoexcited perovskite layers to the HTL can be directly monitored via the characteristic bleaching profile of the perovskite at ∼750 nm. TAS studies revealed faster relaxation times and decay dynamics when the PTAA polymer is employed, which potentially account for the enhanced PCE observed. The TAS results are correlated with the structure and crystalline quality of the corresponding perovskite films, investigated by scanning electron microscopy, X-ray diffraction, atomic force microscopy, micro-photoluminescence, and transmittance spectroscopy. It is concluded that TAS is a benchmark technique for the understanding of the carrier transport mechanisms in PSCs and constitutes a figure-of-merit tool toward their efficiency improvement.

Magnetic drug targeting through a realistic model of human tracheobronchial airways using computational fluid and particle dynamics.

PubMed

Pourmehran, Oveis; Gorji, Tahereh B; Gorji-Bandpy, Mofid

2016-10-01

Magnetic drug targeting (MDT) is a local drug delivery system which aims to concentrate a pharmacological agent at its site of action in order to minimize undesired side effects due to systemic distribution in the organism. Using magnetic drug particles under the influence of an external magnetic field, the drug particles are navigated toward the target region. Herein, computational fluid dynamics was used to simulate the air flow and magnetic particle deposition in a realistic human airway geometry obtained by CT scan images. Using discrete phase modeling and one-way coupling of particle-fluid phases, a Lagrangian approach for particle tracking in the presence of an external non-uniform magnetic field was applied. Polystyrene (PMS40) particles were utilized as the magnetic drug carrier. A parametric study was conducted, and the influence of particle diameter, magnetic source position, magnetic field strength and inhalation condition on the particle transport pattern and deposition efficiency (DE) was reported. Overall, the results show considerable promise of MDT in deposition enhancement at the target region (i.e., left lung). However, the positive effect of increasing particle size on DE enhancement was evident at smaller magnetic field strengths (Mn [Formula: see text] 1.5 T), whereas, at higher applied magnetic field strengths, increasing particle size has a inverse effect on DE. This implies that for efficient MTD in the human respiratory system, an optimal combination of magnetic drug career characteristics and magnetic field strength has to be achieved.

Two-phase computed tomography study of warthin tumor of parotid gland: differentiation from other parotid gland tumors and its pathologic explanation.

PubMed

Woo, Seung Hoon; Choi, Dae-Seob; Kim, Jin-pyeong; Park, Jung Je; Joo, Yeon Hee; Chung, Phil-Sang; Kim, Bo-Young; Ko, Young-Hyeh; Jeong, Han-Sin; Kim, Hyung-Jin

2013-01-01

The objective of this study was to define the radiological characteristics of 2-phase computed tomography (CT) of parotid gland Warthin tumors (WTs) with a pathologic basis for these findings. We prospectively enrolled 116 patients with parotid gland tumor who underwent preoperative 2-phase CT scans(scanning delays of 30 and 120 seconds). The attenuation changes and enhancement patterns were analyzed according to pathology. We also evaluated size-matched samples of WTs and pleomorphic adenoma by staining CD31, vascular endothelial growth factor-receptor 2, collagen IV, and smooth muscle actin. Computed tomography numbers in WTs were significantly higher than those in other tumors in early-phase scans and lower in delayed scans. Pathologically, CD31(+) blood vessel area was significantly higher in WTs than in pleomorphic adenomas. In addition, WTs had an extensive capillary network and many leaky blood vessels. The enhancement pattern of early fill-in and early washout is the typical finding of WTs on 2-phase CT scans, which may be attributed pathologically to abundant blood vessel and extensive capillary network.

Strong surface enhanced Raman scattering from gold nanoarrays obtained by direct laser writing

NASA Astrophysics Data System (ADS)

Ivanov, V. G.; Todorov, N. D.; Petrov, L. S.; Ritacco, T.; Giocondo, M.; Vlakhov, E. S.

2016-10-01

We report for surface enhanced Raman scattering (SERS) from arrays of gold nanoparticles produced by 2-photons photo-reduction of the metallic precursor (HAuCl4) hosted in a Poly-Vinyl Alcohol (PVA) matrix, on glass substrates. Samples with the same pattern but featuring different nanoparticles size and density were obtained by varying the writing laser power and scanning speed. The Raman spectra were recorded from samples immersed in a solution of rhodamine-6G (R6G), as well as, after exposure of the samples in xylene. SERS enhancement factors of up to ∼104 were obtained for both analytes. The measurements show that the SERS enhancement is maximized on golden strips produced at higher writing laser power and lower scanning speed, where closer nanoparticles packing is obtained..

Essentials of multiangle data-processing methodology for smoke polluted atmospheres

Treesearch

Vladimir Kovalev; A. Petkov; Cyle Wold; Shawn Urbanski; WeiMin Hao

2011-01-01

Essentials for investigating smoke plume characteristics with scanning lidar are discussed. Particularly, we outline basic principles for determining dynamics, heights, and optical properties of smoke plumes and layers in wildfire-polluted atmospheres. Both simulated and experimental data obtained in vicinities of wildfires with a two-wavelength scanning lidar are...

A High Rigidity and Precision Scanning Tunneling Microscope with Decoupled XY and Z Scans.

PubMed

Chen, Xu; Guo, Tengfei; Hou, Yubin; Zhang, Jing; Meng, Wenjie; Lu, Qingyou

2017-01-01

A new scan-head structure for the scanning tunneling microscope (STM) is proposed, featuring high scan precision and rigidity. The core structure consists of a piezoelectric tube scanner of quadrant type (for XY scans) coaxially housed in a piezoelectric tube with single inner and outer electrodes (for Z scan). They are fixed at one end (called common end). A hollow tantalum shaft is coaxially housed in the XY -scan tube and they are mutually fixed at both ends. When the XY scanner scans, its free end will bring the shaft to scan and the tip which is coaxially inserted in the shaft at the common end will scan a smaller area if the tip protrudes short enough from the common end. The decoupled XY and Z scans are desired for less image distortion and the mechanically reduced scan range has the superiority of reducing the impact of the background electronic noise on the scanner and enhancing the tip positioning precision. High quality atomic resolution images are also shown.

Hyaluronan degrading silica nanoparticles for skin cancer therapy

NASA Astrophysics Data System (ADS)

Scodeller, P.; Catalano, P. N.; Salguero, N.; Duran, H.; Wolosiuk, A.; Soler-Illia, G. J. A. A.

2013-09-01

We report the first nanoformulation of Hyaluronidase (Hyal) and its enhanced adjuvant effect over the free enzyme. Hyaluronic acid (HA) degrading enzyme Hyal was immobilized on 250 nm silica nanoparticles (SiNP) maintaining specific activity of the enzyme via the layer-by-layer self-assembly technique. This process was characterized by dynamic light scattering (DLS), zeta potential, infrared and UV-Vis spectroscopy, transmission electron microscopy (TEM) and enzymatic activity measurements. The nanoparticles were tested in vivo as adjuvants of carboplatin (CP), peritumorally injected in A375 human melanoma bearing mice and compared with the non-immobilized enzyme, on the basis of equal enzymatic activity. Alcian Blue staining of A375 tumors indicated large overexpression of hyaluronan. At the end of the experiment, tumor volume reduction with SiNP-immobilized Hyal was significantly enhanced compared to non-immobilized Hyal. Field emission scanning electron microscopy (FE-SEM) images together with energy dispersive X-ray spectroscopy (EDS) spectra confirmed the presence of SiNP on the tumor. We mean a proof of concept: this extracellular matrix (ECM) degrading enzyme, immobilized on SiNP, is a more effective local adjuvant of cancer drugs than the non-immobilized enzyme. This could prove useful in future therapies using other or a combination of ECM degrading enzymes.We report the first nanoformulation of Hyaluronidase (Hyal) and its enhanced adjuvant effect over the free enzyme. Hyaluronic acid (HA) degrading enzyme Hyal was immobilized on 250 nm silica nanoparticles (SiNP) maintaining specific activity of the enzyme via the layer-by-layer self-assembly technique. This process was characterized by dynamic light scattering (DLS), zeta potential, infrared and UV-Vis spectroscopy, transmission electron microscopy (TEM) and enzymatic activity measurements. The nanoparticles were tested in vivo as adjuvants of carboplatin (CP), peritumorally injected in A375 human melanoma bearing mice and compared with the non-immobilized enzyme, on the basis of equal enzymatic activity. Alcian Blue staining of A375 tumors indicated large overexpression of hyaluronan. At the end of the experiment, tumor volume reduction with SiNP-immobilized Hyal was significantly enhanced compared to non-immobilized Hyal. Field emission scanning electron microscopy (FE-SEM) images together with energy dispersive X-ray spectroscopy (EDS) spectra confirmed the presence of SiNP on the tumor. We mean a proof of concept: this extracellular matrix (ECM) degrading enzyme, immobilized on SiNP, is a more effective local adjuvant of cancer drugs than the non-immobilized enzyme. This could prove useful in future therapies using other or a combination of ECM degrading enzymes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02787b

Tip-enhanced near-field Raman spectroscopy with a scanning tunneling microscope and side-illumination optics.

PubMed

Yi, K J; He, X N; Zhou, Y S; Xiong, W; Lu, Y F

2008-07-01

Conventional Raman spectroscopy (RS) suffers from low spatial resolution and low detection sensitivity due to the optical diffraction limit and small interaction cross sections. It has been reported that a highly localized and significantly enhanced electromagnetic field could be generated in the proximity of a metallic tip illuminated by a laser beam. In this study, a tip-enhanced RS system was developed to both improve the resolution and enhance the detection sensitivity using the tip-enhanced near-field effects. This instrument, by combining RS with a scanning tunneling microscope and side-illumination optics, demonstrated significant enhancement on both optical sensitivity and spatial resolution using either silver (Ag)-coated tungsten (W) tips or gold (Au) tips. The sensitivity improvement was verified by observing the enhancement effects on silicon (Si) substrates. Lateral resolution was verified to be below 100 nm by mapping Ag nanostructures. By deploying the depolarization technique, an apparent enhancement of 175% on Si substrates was achieved. Furthermore, the developed instrument features fast and reliable optical alignment, versatile sample adaptability, and effective suppression of far-field signals.

Managing vulvovaginal hematoma by arterial embolization as first-line hemostatic therapy.

PubMed

Takagi, Kenjiro; Akashi, Keiko; Horiuchi, Isao; Nakamura, Eishin; Samejima, Koki; Ushijima, Junko; Okochi, Tomohisa; Hamamoto, Kohei; Tanno, Keisuke

2017-04-01

A puerperal vulvovaginal hematoma may continue to grow after a surgical procedure and may require blood transfusion. Thus, we selected arterial embolization for hemostasis as the first-line management in two cases of large vulvovaginal hematoma. Case 1 was a 32-year-old pregnant woman. After delivery, a 10-cm vulvar hematoma developed. An enhanced computed tomography (CT) scan revealed active bleeding. Arterial embolization was performed and complete hemostasis was obtained. Case 2 was a 34-year-old woman with a recurring hematoma after delivery. An enhanced CT scan revealed extravasation in the hematoma. Gelatin sponges were applied and complete hemostasis was obtained. In both cases, arterial embolization was successful without requiring blood transfusions. We successfully managed two cases of puerperal vulvovaginal hematoma by arterial embolization based on the evaluation of an enhanced CT scan. In conclusion, we suggest arterial embolization to be a viable option for first-line treatment in the management of vulvovaginal hematomas. Copyright © 2017. Published by Elsevier B.V.

Computer enhancement of radiographs

NASA Technical Reports Server (NTRS)

Dekaney, A.; Keane, J.; Desautels, J.

1973-01-01

Examination of three relevant noise processes and the image degradation associated with Marshall Space Flight Center's (MSFC) X-ray/scanning system was conducted for application to computer enhancement of radiographs using MSFC's digital filtering techniques. Graininess of type M, R single coat and R double coat X-ray films was quantified as a function of density level using root-mean-square (RMS) granularity. Quantum mottle (including film grain) was quantified as a function of the above film types, exposure level, specimen material and thickness, and film density using RMS granularity and power spectral density (PSD). For various neutral-density levels the scanning device used in digital conversion of radiographs was examined for noise characteristics which were quantified by RMS granularity and PSD. Image degradation of the entire pre-enhancement system (MG-150 X-ray device; film; and optronics scanner) was measured using edge targets to generate modulation transfer functions (MTF). The four parameters were examined as a function of scanning aperture sizes of approximately 12.5 25 and 50 microns.

Sensitivity enhancement for detection of hyperpolarized 13 C MRI probes with 1 H spin coupling introduced by enzymatic transformation in vivo.

PubMed

von Morze, Cornelius; Tropp, James; Chen, Albert P; Marco-Rius, Irene; Van Criekinge, Mark; Skloss, Timothy W; Mammoli, Daniele; Kurhanewicz, John; Vigneron, Daniel B; Ohliger, Michael A; Merritt, Matthew E

2018-07-01

Although 1 H spin coupling is generally avoided in probes for hyperpolarized (HP) 13 C MRI, enzymatic transformations of biological interest can introduce large 13 C- 1 H couplings in vivo. The purpose of this study was to develop and investigate the application of 1 H decoupling for enhancing the sensitivity for detection of affected HP 13 C metabolic products. A standalone 1 H decoupler system and custom concentric 13 C/ 1 H paddle coil setup were integrated with a clinical 3T MRI scanner for in vivo 13 C MR studies using HP [2- 13 C]dihydroxyacetone, a novel sensor of hepatic energy status. Major 13 C- 1 H coupling J CH  = ∼150 Hz) is introduced after adenosine triphosphate-dependent enzymatic transformation of HP [2- 13 C]dihydroxyacetone to [2- 13 C]glycerol-3-phosphate in vivo. Application of WALTZ-16 1 H decoupling for elimination of large 13 C- 1 H couplings was first tested in thermally polarized glycerol phantoms and then for in vivo HP MR studies in three rats, scanned both with and without decoupling. As configured, 1 H-decoupled 13 C MR of thermally polarized glycerol and the HP metabolic product [2- 13 C]glycerol-3-phosphate was achieved at forward power of approximately 15 W. High-quality 3-s dynamic in vivo HP 13 C MR scans were acquired with decoupling duty cycle of 5%. Application of 1 H decoupling resulted in sensitivity enhancement of 1.7-fold for detection of metabolic conversion of [2- 13 C]dihydroxyacetone to HP [2- 13 C]glycerol-3-phosphate in vivo. Application of 1 H decoupling provides significant sensitivity enhancement for detection of HP 13 C metabolic products with large 1 H spin couplings, and is therefore expected to be useful for preclinical and potentially clinical HP 13 C MR studies. Magn Reson Med 80:36-41, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Dynamic-scanning-electron-microscope study of friction and wear

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Buckley, D. H.

1974-01-01

A friction and wear apparatus was built into a real time scanning electron microscope (SEM). The apparatus and SEM comprise a system which provides the capability of performing dynamic friction and wear experiments in situ. When the system is used in conjunction with dispersive X-ray analysis, a wide range of information on the wearing process can be obtained. The type of wear and variation with speed, load, and time can be investigated. The source, size, and distribution of wear particles can be determined and metallic transferal observed. Some typical results obtained with aluminum, copper, and iron specimens are given.

DYNAMISM OF DOT SUBRETINAL DRUSENOID DEPOSITS IN AGE-RELATED MACULAR DEGENERATION DEMONSTRATED WITH ADAPTIVE OPTICS IMAGING.

PubMed

Zhang, Yuhua; Wang, Xiaolin; Godara, Pooja; Zhang, Tianjiao; Clark, Mark E; Witherspoon, C Douglas; Spaide, Richard F; Owsley, Cynthia; Curcio, Christine A

2018-01-01

To investigate the natural history of dot subretinal drusenoid deposits (SDD) in age-related macular degeneration, using high-resolution adaptive optics scanning laser ophthalmoscopy. Six eyes of four patients with intermediate age-related macular degeneration were studied at baseline and 1 year later. Individual dot SDD within the central 30° retina were examined with adaptive optics scanning laser ophthalmoscopy and optical coherence tomography. A total of 269 solitary SDD were identified at baseline. Over 12.25 ± 1.18 months, all 35 Stage 1 SDD progressed to advanced stages. Eighteen (60%) Stage 2 lesions progressed to Stage 3 and 12 (40%) remained at Stage 2. Of 204 Stage 3 SDD, 12 (6.4%) disappeared and the rest remained. Twelve new SDD were identified, including 6 (50%) at Stage 1, 2 (16.7%) at Stage 2, and 4 (33.3%) at Stage 3. The mean percentage of the retina affected by dot SDD, measured by the adaptive optics scanning laser ophthalmoscopy, increased in 5/6 eyes (from 2.31% to 5.08% in the most changed eye) and decreased slightly in 1/6 eye (from 10.67% to 10.54%). Dynamism, the absolute value of the areas affected by new and regressed lesions, ranged from 0.7% to 9.3%. Adaptive optics scanning laser ophthalmoscopy reveals that dot SDD, like drusen, are dynamic.

Quantitative evaluation of contrast agent uptake in standard fat-suppressed dynamic contrast-enhanced MRI examinations of the breast.

PubMed

Kousi, Evanthia; Smith, Joely; Ledger, Araminta E; Scurr, Erica; Allen, Steven; Wilson, Robin M; O'Flynn, Elizabeth; Pope, Romney J E; Leach, Martin O; Schmidt, Maria A

2018-01-01

To propose a method to quantify T 1 and contrast agent uptake in breast dynamic contrast-enhanced (DCE) examinations undertaken with standard clinical fat-suppressed MRI sequences and to demonstrate the proposed approach by comparing the enhancement characteristics of lobular and ductal carcinomas. A standard fat-suppressed DCE of the breast was performed at 1.5 T (Siemens Aera), followed by the acquisition of a proton density (PD)-weighted sequence, also fat suppressed. Both sequences were characterized with test objects (T 1 ranging from 30 ms to 2,400 ms) and calibration curves were obtained to enable T 1 calculation. The reproducibility and accuracy of the calibration curves were also investigated. Healthy volunteers and patients were scanned with Ethics Committee approval. The effect of B 0 field inhomogeneity was assessed in test objects and healthy volunteers. The T 1 of breast tumors was calculated at different time points (pre-, peak-, and post-contrast agent administration) for 20 patients, pre-treatment (10 lobular and 10 ductal carcinomas) and the two cancer types were compared (Wilcoxon rank-sum test). The calibration curves proved to be highly reproducible (coefficient of variation under 10%). T 1 measurements were affected by B 0 field inhomogeneity, but frequency shifts below 50 Hz introduced only 3% change to fat-suppressed T 1 measurements of breast parenchyma in volunteers. The values of T 1 measured pre-, peak-, and post-contrast agent administration demonstrated that the dynamic range of the DCE sequence was correct, that is, image intensity is approximately directly proportional to 1/T 1 for that range. Significant differences were identified in the width of the distributions of the post-contrast T 1 values between lobular and ductal carcinomas (P < 0.05); lobular carcinomas demonstrated a wider range of post-contrast T 1 values, potentially related to their infiltrative growth pattern. This work has demonstrated the feasibility of fat-suppressed T 1 measurements as a tool for clinical studies. The proposed quantitative approach is practical, enabled the detection of differences between lobular and invasive ductal carcinomas, and further enables the optimization of DCE protocols by tailoring the dynamic range of the sequence to the values of T 1 measured. © 2017 The Authors. Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

NMR-based investigations into target DNA search processes of proteins.

PubMed

Iwahara, Junji; Zandarashvili, Levani; Kemme, Catherine A; Esadze, Alexandre

2018-05-10

To perform their function, transcription factors and DNA-repair/modifying enzymes must first locate their targets in the vast presence of nonspecific, but structurally similar sites on genomic DNA. Before reaching their targets, these proteins stochastically scan DNA and dynamically move from one site to another on DNA. Solution NMR spectroscopy provides unique atomic-level insights into the dynamic DNA-scanning processes, which are difficult to gain by any other experimental means. In this review, we provide an introductory overview on the NMR methods for the structural, dynamic, and kinetic investigations of target DNA search by proteins. We also discuss advantages and disadvantages of these NMR methods over other methods such as single-molecule techniques and biochemical approaches. Copyright © 2018 Elsevier Inc. All rights reserved.

Registration of parametric dynamic F-18-FDG PET/CT breast images with parametric dynamic Gd-DTPA breast images

NASA Astrophysics Data System (ADS)

Magri, Alphonso; Krol, Andrzej; Lipson, Edward; Mandel, James; McGraw, Wendy; Lee, Wei; Tillapaugh-Fay, Gwen; Feiglin, David

2009-02-01

This study was undertaken to register 3D parametric breast images derived from Gd-DTPA MR and F-18-FDG PET/CT dynamic image series. Nonlinear curve fitting (Levenburg-Marquardt algorithm) based on realistic two-compartment models was performed voxel-by-voxel separately for MR (Brix) and PET (Patlak). PET dynamic series consists of 50 frames of 1-minute duration. Each consecutive PET image was nonrigidly registered to the first frame using a finite element method and fiducial skin markers. The 12 post-contrast MR images were nonrigidly registered to the precontrast frame using a free-form deformation (FFD) method. Parametric MR images were registered to parametric PET images via CT using FFD because the first PET time frame was acquired immediately after the CT image on a PET/CT scanner and is considered registered to the CT image. We conclude that nonrigid registration of PET and MR parametric images using CT data acquired during PET/CT scan and the FFD method resulted in their improved spatial coregistration. The success of this procedure was limited due to relatively large target registration error, TRE = 15.1+/-7.7 mm, as compared to spatial resolution of PET (6-7 mm), and swirling image artifacts created in MR parametric images by the FFD. Further refinement of nonrigid registration of PET and MR parametric images is necessary to enhance visualization and integration of complex diagnostic information provided by both modalities that will lead to improved diagnostic performance.

Hologic QDR 2000 whole-body scans: a comparison of three combinations of scan modes and analysis software

NASA Technical Reports Server (NTRS)

Spector, E.; LeBlanc, A.; Shackelford, L.

1995-01-01

This study reports on the short-term in vivo precision and absolute measurements of three combinations of whole-body scan modes and analysis software using a Hologic QDR 2000 dual-energy X-ray densitometer. A group of 21 normal, healthy volunteers (11 male and 10 female) were scanned six times, receiving one pencil-beam and one array whole-body scan on three occasions approximately 1 week apart. The following combinations of scan modes and analysis software were used: pencil-beam scans analyzed with Hologic's standard whole-body software (PB scans); the same pencil-beam analyzed with Hologic's newer "enhanced" software (EPB scans); and array scans analyzed with the enhanced software (EA scans). Precision values (% coefficient of variation, %CV) were calculated for whole-body and regional bone mineral content (BMC), bone mineral density (BMD), fat mass, lean mass, %fat and total mass. In general, there was no significant difference among the three scan types with respect to short-term precision of BMD and only slight differences in the precision of BMC. Precision of BMC and BMD for all three scan types was excellent: < 1% CV for whole-body values, with most regional values in the 1%-2% range. Pencil-beam scans demonstrated significantly better soft tissue precision than did array scans. Precision errors for whole-body lean mass were: 0.9% (PB), 1.1% (EPB) and 1.9% (EA). Precision errors for whole-body fat mass were: 1.7% (PB), 2.4% (EPB) and 5.6% (EA). EPB precision errors were slightly higher than PB precision errors for lean, fat and %fat measurements of all regions except the head, although these differences were significant only for the fat and % fat of the arms and legs. In addition EPB precision values exhibited greater individual variability than PB precision values. Finally, absolute values of bone and soft tissue were compared among the three combinations of scan and analysis modes. BMC, BMD, fat mass, %fat and lean mass were significantly different between PB scans and either of the EPB or EA scans. Differences were as large as 20%-25% for certain regional fat and BMD measurements. Additional work may be needed to examine the relative accuracy of the scan mode/software combinations and to identify reasons for the differences in soft tissue precision with the array whole-body scan mode.

Performance of the strongly constrained and appropriately normed density functional for solid-state materials

DOE PAGES

Isaacs, Eric B.; Wolverton, Chris

2018-06-22

Constructed to satisfy 17 known exact constraints for a semilocal density functional, the strongly constrained and appropriately normed (SCAN) meta-generalized-gradient-approximation functional has shown early promise for accurately describing the electronic structure of molecules and solids. One open question is how well SCAN predicts the formation energy, a key quantity for describing the thermodynamic stability of solid-state compounds. To answer this question, we perform an extensive benchmark of SCAN by computing the formation energies for a diverse group of nearly 1000 crystalline compounds for which experimental values are known. Due to an enhanced exchange interaction in the covalent bonding regime, SCANmore » substantially decreases the formation energy errors for strongly bound compounds, by approximately 50% to 110 meV/atom, as compared to the generalized gradient approximation of Perdew, Burke, and Ernzerhof (PBE). However, for intermetallic compounds, SCAN performs moderately worse than PBE with an increase in formation energy error of approximately 20%, stemming from SCAN's distinct behavior in the weak bonding regime. The formation energy errors can be further reduced via elemental chemical potential fitting. We find that SCAN leads to significantly more accurate predicted crystal volumes, moderately enhanced magnetism, and mildly improved band gaps as compared to PBE. Altogether, SCAN represents a significant improvement in accurately describing the thermodynamics of strongly bound compounds.« less

Performance of the strongly constrained and appropriately normed density functional for solid-state materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isaacs, Eric B.; Wolverton, Chris

Constructed to satisfy 17 known exact constraints for a semilocal density functional, the strongly constrained and appropriately normed (SCAN) meta-generalized-gradient-approximation functional has shown early promise for accurately describing the electronic structure of molecules and solids. One open question is how well SCAN predicts the formation energy, a key quantity for describing the thermodynamic stability of solid-state compounds. To answer this question, we perform an extensive benchmark of SCAN by computing the formation energies for a diverse group of nearly 1000 crystalline compounds for which experimental values are known. Due to an enhanced exchange interaction in the covalent bonding regime, SCANmore » substantially decreases the formation energy errors for strongly bound compounds, by approximately 50% to 110 meV/atom, as compared to the generalized gradient approximation of Perdew, Burke, and Ernzerhof (PBE). However, for intermetallic compounds, SCAN performs moderately worse than PBE with an increase in formation energy error of approximately 20%, stemming from SCAN's distinct behavior in the weak bonding regime. The formation energy errors can be further reduced via elemental chemical potential fitting. We find that SCAN leads to significantly more accurate predicted crystal volumes, moderately enhanced magnetism, and mildly improved band gaps as compared to PBE. Altogether, SCAN represents a significant improvement in accurately describing the thermodynamics of strongly bound compounds.« less

Three-dimensional imaging of micro-specimen by optical scanning holography

NASA Astrophysics Data System (ADS)

Liu, Jung-Ping; Tsou, Cheng-Hao

2017-04-01

Optical scanning holography (OSH) is a scanning-type digital holographic technique. In OSH, a heterodyne interference pattern is generated to raster scan the object. OSH can be operated in the incoherent mode and thus is able to record a fluorescence hologram. In addition, resolution of the OSH is proportional to the density of the interference pattern. Here we use a high-NA microscope objective to generate a dynamic Fresnel zone plate to record a hologram of micro-specimen. The achieved transverse resolution and longitudinal resolution are 0.78μm and 3.1μm, respectively.

SU-E-T-133: Dosimetric Impact of Scan Orientation Relative to Target Motion During Spot Scanning Proton Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoker, J; Summers, P; Li, X

2014-06-01

Purpose: This study seeks to evaluate the dosimetric effects of intra-fraction motion during spot scanning proton beam therapy as a function of beam-scan orientation and target motion amplitude. Method: Multiple 4DCT scans were collected of a dynamic anthropomorphic phantom mimicking respiration amplitudes of 0 (static), 0.5, 1.0, and 1.5 cm. A spot-scanning treatment plan was developed on the maximum intensity projection image set, using an inverse-planning approach. Dynamic phantom motion was continuous throughout treatment plan delivery.The target nodule was designed to accommodate film and thermoluminescent dosimeters (TLD). Film and TLDs were uniquely labeled by location within the target. The phantommore » was localized on the treatment table using the clinically available orthogonal kV on-board imaging device. Film inserts provided data for dose uniformity; TLDs provided a 3% precision estimate of absolute dose. An inhouse script was developed to modify the delivery order of the beam spots, to orient the scanning direction parallel or perpendicular to target motion.TLD detector characterization and analysis was performed by the Imaging and Radiation Oncology Core group (IROC)-Houston. Film inserts, exhibiting a spatial resolution of 1mm, were analyzed to determine dose homogeneity within the radiation target. Results: Parallel scanning and target motions exhibited reduced target dose heterogeneity, relative to perpendicular scanning orientation. The average percent deviation in absolute dose for the motion deliveries relative to the static delivery was 4.9±1.1% for parallel scanning, and 11.7±3.5% (p<<0.05) for perpendicularly oriented scanning. Individual delivery dose deviations were not necessarily correlated to amplitude of motion for either scan orientation. Conclusions: Results demonstrate a quantifiable difference in dose heterogeneity as a function of scan orientation, more so than target amplitude. Comparison to the analyzed planar dose of a single field hint that multiple-field delivery alters intra-fraction beam-target motion synchronization and may mitigate heterogeneity, though further study is warranted.« less

Dynamic focus-tracking MEMS scanning micromirror with low actuation voltages for endoscopic imaging.

PubMed

Strathman, Matthew; Liu, Yunbo; Li, Xingde; Lin, Lih Y

2013-10-07

We demonstrate a 3-D scanning micromirror device that combines 2-D beam scanning with focus control in the same device using micro-electro-mechanical-systems (MEMS) technology. 2-D beam scanning is achieved with a biaxial gimbal structure and focus control is obtained with a deformable mirror membrane surface. The micromirror with 800 micrometer diameter is designed to be sufficiently compact and efficient so that it can be incorporated into an endoscopic imaging probe in the future. The design, fabrication and characterization of the device are described in this paper. Using the focus-tracking MEMS scanning mirror, we achieved an optical scanning range of >16 degrees with <40 V actuation voltage at resonance and a tunable focal length between infinity and 25 mm with <100V applied bias.

High Dynamic Range Pixel Array Detector for Scanning Transmission Electron Microscopy.

PubMed

Tate, Mark W; Purohit, Prafull; Chamberlain, Darol; Nguyen, Kayla X; Hovden, Robert; Chang, Celesta S; Deb, Pratiti; Turgut, Emrah; Heron, John T; Schlom, Darrell G; Ralph, Daniel C; Fuchs, Gregory D; Shanks, Katherine S; Philipp, Hugh T; Muller, David A; Gruner, Sol M

2016-02-01

We describe a hybrid pixel array detector (electron microscope pixel array detector, or EMPAD) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128×128 pixel detector consists of a 500 µm thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit. The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity. A 1.1 kHz framing rate enables rapid data collection and minimizes sample drift distortions while scanning. By capturing the entire unsaturated diffraction pattern in scanning mode, one can simultaneously capture bright field, dark field, and phase contrast information, as well as being able to analyze the full scattering distribution, allowing true center of mass imaging. The scattering is recorded on an absolute scale, so that information such as local sample thickness can be directly determined. This paper describes the detector architecture, data acquisition system, and preliminary results from experiments with 80-200 keV electron beams.

Insights into radiation damage from atomic resolution scanning transmission electron microscopy imaging of mono-layer CuPcCl16 films on graphene.

PubMed

Mittelberger, Andreas; Kramberger, Christian; Meyer, Jannik C

2018-03-19

Atomically resolved images of monolayer organic crystals have only been obtained with scanning probe methods so far. On the one hand, they are usually prepared on surfaces of bulk materials, which are not accessible by (scanning) transmission electron microscopy. On the other hand, the critical electron dose of a monolayer organic crystal is orders of magnitudes lower than the one for bulk crystals, making (scanning) transmission electron microscopy characterization very challenging. In this work we present an atomically resolved study on the dynamics of a monolayer CuPcCl 16 crystal under the electron beam as well as an image of the undamaged molecules obtained by low-dose electron microscopy. The results show the dynamics and the radiation damage mechanisms in the 2D layer of this material, complementing what has been found for bulk crystals in earlier studies. Furthermore, being able to image the undamaged molecular crystal allows the characterization of new composites consisting of 2D materials and organic molecules.

Accelerated Brain DCE-MRI Using Iterative Reconstruction With Total Generalized Variation Penalty for Quantitative Pharmacokinetic Analysis: A Feasibility Study.

PubMed

Wang, Chunhao; Yin, Fang-Fang; Kirkpatrick, John P; Chang, Zheng

2017-08-01

To investigate the feasibility of using undersampled k-space data and an iterative image reconstruction method with total generalized variation penalty in the quantitative pharmacokinetic analysis for clinical brain dynamic contrast-enhanced magnetic resonance imaging. Eight brain dynamic contrast-enhanced magnetic resonance imaging scans were retrospectively studied. Two k-space sparse sampling strategies were designed to achieve a simulated image acquisition acceleration factor of 4. They are (1) a golden ratio-optimized 32-ray radial sampling profile and (2) a Cartesian-based random sampling profile with spatiotemporal-regularized sampling density constraints. The undersampled data were reconstructed to yield images using the investigated reconstruction technique. In quantitative pharmacokinetic analysis on a voxel-by-voxel basis, the rate constant K trans in the extended Tofts model and blood flow F B and blood volume V B from the 2-compartment exchange model were analyzed. Finally, the quantitative pharmacokinetic parameters calculated from the undersampled data were compared with the corresponding calculated values from the fully sampled data. To quantify each parameter's accuracy calculated using the undersampled data, error in volume mean, total relative error, and cross-correlation were calculated. The pharmacokinetic parameter maps generated from the undersampled data appeared comparable to the ones generated from the original full sampling data. Within the region of interest, most derived error in volume mean values in the region of interest was about 5% or lower, and the average error in volume mean of all parameter maps generated through either sampling strategy was about 3.54%. The average total relative error value of all parameter maps in region of interest was about 0.115, and the average cross-correlation of all parameter maps in region of interest was about 0.962. All investigated pharmacokinetic parameters had no significant differences between the result from original data and the reduced sampling data. With sparsely sampled k-space data in simulation of accelerated acquisition by a factor of 4, the investigated dynamic contrast-enhanced magnetic resonance imaging pharmacokinetic parameters can accurately estimate the total generalized variation-based iterative image reconstruction method for reliable clinical application.

MR-monitored LITT as a palliative concept in patients with high grade gliomas: preliminary clinical experience.

PubMed

Reimer, P; Bremer, C; Horch, C; Morgenroth, C; Allkemper, T; Schuierer, G

1998-01-01

The purpose of this study was to evaluate the clinical utility of laser-induced thermotherapy (LITT) as a palliative treatment for patients with high-grade gliomas. Four consenting patients with recurrent high grade III/IV gliomas near the primary language or motor areas were palliatively treated with LITT (2-5 W, 3-13 minutes; Neodym YAG Laser, Dornier, Friedrichshafen, Germany). Temperature monitoring was performed by T1-weighted turbo-fast low-angle shot (FLASH) imaging at 1.5 T (Siemens Magnetom SP 4000, Siemens, Erlangen, Germany). MRI studies before LITT included contrast-enhanced conventional scans and functional activation studies to localize the primary motor cortex or language areas using an echo-planar imaging (EPI) spin-echo (SE) sequence. Follow-up studies consisted of contrast-enhanced conventional scans as well as diffusion studies (contrast-enhanced Fourier-acquired steady-state technique and EPI-SE) and perfusion studies (EPI-SE with .2 mmol of gadolinium (Gd)/kg body weight) to differentiate post-therapeutic effects from residual or recurrent tumor growth. Local tumor control was achieved in areas with laser energy deposition with clinically stable conditions > or = 6 months. Conventional contrast-enhanced scans demonstrated strong enhancement surrounding ablated tumor components, which showed a reduction in CBV/CBF. Perfusion studies were useful to discriminate granulomatous tissue enhancement from residual or recurrent tumor growth. Careful application of LITT may evolve as an alternative palliative concept for patients with end-stage high-grade cerebral gliomas reducing clinical symptoms from circumscribed areas of pathology.

Quantifying hypoxia in human cancers using static PET imaging.

PubMed

Taylor, Edward; Yeung, Ivan; Keller, Harald; Wouters, Bradley G; Milosevic, Michael; Hedley, David W; Jaffray, David A

2016-11-21

Compared to FDG, the signal of 18 F-labelled hypoxia-sensitive tracers in tumours is low. This means that in addition to the presence of hypoxic cells, transport properties contribute significantly to the uptake signal in static PET images. This sensitivity to transport must be minimized in order for static PET to provide a reliable standard for hypoxia quantification. A dynamic compartmental model based on a reaction-diffusion formalism was developed to interpret tracer pharmacokinetics and applied to static images of FAZA in twenty patients with pancreatic cancer. We use our model to identify tumour properties-well-perfused without substantial necrosis or partitioning-for which static PET images can reliably quantify hypoxia. Normalizing the measured activity in a tumour voxel by the value in blood leads to a reduction in the sensitivity to variations in 'inter-corporal' transport properties-blood volume and clearance rate-as well as imaging study protocols. Normalization thus enhances the correlation between static PET images and the FAZA binding rate K 3 , a quantity which quantifies hypoxia in a biologically significant way. The ratio of FAZA uptake in spinal muscle and blood can vary substantially across patients due to long muscle equilibration times. Normalized static PET images of hypoxia-sensitive tracers can reliably quantify hypoxia for homogeneously well-perfused tumours with minimal tissue partitioning. The ideal normalizing reference tissue is blood, either drawn from the patient before PET scanning or imaged using PET. If blood is not available, uniform, homogeneously well-perfused muscle can be used. For tumours that are not homogeneously well-perfused or for which partitioning is significant, only an analysis of dynamic PET scans can reliably quantify hypoxia.

Quantifying hypoxia in human cancers using static PET imaging

NASA Astrophysics Data System (ADS)

Taylor, Edward; Yeung, Ivan; Keller, Harald; Wouters, Bradley G.; Milosevic, Michael; Hedley, David W.; Jaffray, David A.

2016-11-01

Compared to FDG, the signal of 18F-labelled hypoxia-sensitive tracers in tumours is low. This means that in addition to the presence of hypoxic cells, transport properties contribute significantly to the uptake signal in static PET images. This sensitivity to transport must be minimized in order for static PET to provide a reliable standard for hypoxia quantification. A dynamic compartmental model based on a reaction-diffusion formalism was developed to interpret tracer pharmacokinetics and applied to static images of FAZA in twenty patients with pancreatic cancer. We use our model to identify tumour properties—well-perfused without substantial necrosis or partitioning—for which static PET images can reliably quantify hypoxia. Normalizing the measured activity in a tumour voxel by the value in blood leads to a reduction in the sensitivity to variations in ‘inter-corporal’ transport properties—blood volume and clearance rate—as well as imaging study protocols. Normalization thus enhances the correlation between static PET images and the FAZA binding rate K 3, a quantity which quantifies hypoxia in a biologically significant way. The ratio of FAZA uptake in spinal muscle and blood can vary substantially across patients due to long muscle equilibration times. Normalized static PET images of hypoxia-sensitive tracers can reliably quantify hypoxia for homogeneously well-perfused tumours with minimal tissue partitioning. The ideal normalizing reference tissue is blood, either drawn from the patient before PET scanning or imaged using PET. If blood is not available, uniform, homogeneously well-perfused muscle can be used. For tumours that are not homogeneously well-perfused or for which partitioning is significant, only an analysis of dynamic PET scans can reliably quantify hypoxia.

Application of albumin protein and indocyanine green chromophore for tissue soldering by using an IR diode laser: ex vivo and in vivo studies.

PubMed

Khosroshahi, M E; Nourbakhsh, M S; Saremi, S; Hooshyar, A; Rabbani, Sh; Tabatabai, F; Anvari, M Sotudeh

2010-12-01

We sought to examine the impact of different parameters of laser soldering on the thermophysical properties of the skin and to optimize these parameters for sealing a full-thickness incision in the rat skin under closed feedback control under in vivo conditions. Laser tissue soldering based on protein as biologic glues and other compounds can provide greater bond strength and less collateral damage. Endogenous and exogenous materials such as indocyanine green (ICG) are often added to solders to enhance light absorption. In ex vivo study, the temperature increase, number of scan (Ns), and scan velocity (Vs) were investigated. In ex vivo studies, four skin incisions were made over rat dorsa and were closed by using two different methods: (a) wound closure by suture and (b) closure by using an automated temperature-controlled system. An automated soldering system was developed based on a diode laser, IR detector, photodiode, digital thermocouple, and camera. The true temperature of heated tissue was determined by using a calibration software method. The results showed that at each laser irradiance (I), the tensile strength (σ) of incisions repaired in the static mode is higher than in the dynamic mode. It must also be noted that the tensile strength of the repaired skin wound was increased by increasing the irradiance in both static and dynamic modes. However, in parallel, an increase in the corresponding temperature was observed. The tensile strength was measured for sutured and laser-soldered tissue after 2 to 10 postoperative days. Histopathologic studies showed a better healing and less inflammatory reactions than with those caused by standard sutures after day 7. It is demonstrated that automated laser soldering technique can be practical provided the optothermal properties of tissue is carefully optimized.

Optical techniques: using coarse and detailed scans for the preventive acquisition of fingerprints with chromatic white-light sensors

NASA Astrophysics Data System (ADS)

Hildebrandt, Mario; Dittmann, Jana; Vielhauer, Claus; Leich, Marcus

2011-11-01

The preventive application of automated latent fingerprint acquisition devices can enhance the Homeland Defence, e.g. by improving the border security. Here, contact-less optical acquisition techniques for the capture of traces are subject to research; chromatic white light sensors allow for multi-mode operation using coarse or detailed scans. The presence of potential fingerprints could be detected using fast coarse scans. Those Regions-of- Interest can be acquired afterwards with high-resolution detailed scans to allow for a verification or identification of individuals. An acquisition and analysis of fingerprint traces on different objects that are imported or pass borders might be a great enhancement for security. Additionally, if suspicious objects require a further investigation, an initial securing of potential fingerprints could be very useful. In this paper we show current research results for the coarse detection of fingerprints to prepare the detailed acquisition from various surface materials that are relevant for preventive applications.

Enhanced visualization of acute macular neuroretinopathy by Heidelberg Retina Tomography.

PubMed

Mirshahi, Alireza; Scharioth, Gàbor B; Klais, Christina M C; Baatz, Holger

2006-08-01

We report Heidelberg Retina Tomography (HRT) findings in a case of bilateral acute macular neuroretinopathy in a 22-year-old man. In addition to fundus photography, fluorescein and indocyanine green angiography, and visual field testing, HRT scans of the macula were performed early in the disease and at a follow up of 2 months. We found typical paracentral scotomata in visual field testing corresponding to sharply delineated, hyporeflective areas of the macula as visualized in HRT II scans. Those lesions were almost invisible on regular fundus photographs. Angiography results were unremarkable. The lesion size decreased over time. The visibility of the lesions was markedly enhanced by HRT scans, thus the diagnosis and follow up of acute macular neuroretinopathy could be facilitated by this non-invasive imaging technique.

Improvement to the scanning electron microscope image adaptive Canny optimization colorization by pseudo-mapping.

PubMed

Lo, T Y; Sim, K S; Tso, C P; Nia, M E

2014-01-01

An improvement to the previously proposed adaptive Canny optimization technique for scanning electron microscope image colorization is reported. The additional feature, called pseudo-mapping technique, is that the grayscale markings are temporarily mapped to a set of pre-defined pseudo-color map as a mean to instill color information for grayscale colors in chrominance channels. This allows the presence of grayscale markings to be identified; hence optimization colorization of grayscale colors is made possible. This additional feature enhances the flexibility of scanning electron microscope image colorization by providing wider range of possible color enhancement. Furthermore, the nature of this technique also allows users to adjust the luminance intensities of selected region from the original image within certain extent. © 2014 Wiley Periodicals, Inc.

Multiphase CT scanning and different intravenous contrast media concentrations in combined F-18-FDG PET/CT: Effect on quantitative and clinical assessment.

PubMed

Rebière, Marilou; Verburg, Frederik A; Palmowski, Moritz; Krohn, Thomas; Pietsch, Hubertus; Kuhl, Christiane K; Mottaghy, Felix M; Behrendt, Florian F

2012-08-01

To evaluate the influence of multiphase CT scanning and different intravenous contrast media on contrast enhancement, attenuation correction and image quality in combined PET/CT. 140 patients were prospectively enrolled for F-18-FDG-PET/CT including a low-dose unenhanced, arterial and venous contrast enhanced CT. The first (second) 70 patients, received contrast medium with 370 (300) mg iodine/ml. The iodine delivery rate (1.3mg/s) and total iodine load (44.4g) were identical for both groups. Contrast enhancement and maximum and mean standardized FDG uptake values (SUVmax and SUVmean) were determined for the un-enhanced, arterial and venous PET/CT at multiple anatomic sites and PET reconstructions were visually evaluated. Arterial contrast enhancement was significantly higher for the 300mg/ml contrast medium compared to 370mgI/ml at all anatomic sites. Venous enhancement was not different between the two contrast media. SUVmean and SUVmax were significantly higher for the contrast enhanced compared to the non-enhanced PET/CT at all anatomic sites (all P<0.001). Tracer uptake was significantly higher in the arterial than in the venous PET/CT in the arteries using both contrast media (all P<0.001). No differences in tracer uptake were found between the contrast media (all P>0.05). Visual assessment revealed no relevant differences between the different PET reconstructions. There is no relevant qualitative influence on the PET scan from the use of different intravenous contrast media in its various phases in combined multiphase PET/CT. For quantitative analysis of tracer uptake it is required to use an identical PET/CT protocol. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Artifact mitigation of ptychography integrated with on-the-fly scanning probe microscopy

DOE PAGES

Huang, Xiaojing; Yan, Hanfei; Ge, Mingyuan; ...

2017-07-11

In this paper, we report our experiences with conducting ptychography simultaneously with the X-ray fluorescence measurement using the on-the-fly mode for efficient multi-modality imaging. We demonstrate that the periodic artifact inherent to the raster scan pattern can be mitigated using a sufficiently fine scan step size to provide an overlap ratio of >70%. This allows us to obtain transmitted phase contrast images with enhanced spatial resolution from ptychography while maintaining the fluorescence imaging with continuous-motion scans on pixelated grids. Lastly, this capability will greatly improve the competence and throughput of scanning probe X-ray microscopy.

A spacecraft attitude and articulation control system design for the Comet Halley intercept mission

NASA Technical Reports Server (NTRS)

Key, R. W.

1981-01-01

An attitude and articulation control system design for the Comet Halley 1986 intercept mission is presented. A spacecraft dynamics model consisting of five hinge-connected rigid bodies is used to analyze the spacecraft attitude and articulation control system performance. Inertial and optical information are combined to generate scan platform pointing commands. The comprehensive spacecraft model has been developed into a digital computer simulation program, which provides performance characteristics and insight pertaining to the control and dynamics of a Halley Intercept spacecraft. It is shown that scan platform pointing error has a maximum value of 1.8 milliradians during the four minute closest approach interval. It is also shown that the jitter or scan platform pointing rate error would have a maximum value of 2.5 milliradians/second for the nominal 1000 km closest approach distance trajectory and associated environment model.

A new strategy for fast radiofrequency CW EPR imaging: Direct detection with rapid scan and rotating gradients

PubMed Central

Subramanian, Sankaran; Koscielniak, Janusz W.; Devasahayam, Nallathamby; Pursley, Randall H.; Pohida, Thomas J.; Krishna, Murali C.

2007-01-01

Rapid field scan on the order of T/s using high frequency sinusoidal or triangular sweep fields superimposed on the main Zeeman field, was used for direct detection of signals without low-frequency field modulation. Simultaneous application of space-encoding rotating field gradients have been employed to perform fast CW EPR imaging using direct detection that could, in principle, approach the speed of pulsed FT EPR imaging. The method takes advantage of the well-known rapid-scan strategy in CW NMR and EPR that allows arbitrarily fast field sweep and the simultaneous application of spinning gradients that allows fast spatial encoding. This leads to fast functional EPR imaging and, depending on the spin concentration, spectrometer sensitivity and detection band width, can provide improved temporal resolution that is important to interrogate dynamics of spin perfusion, pharmacokinetics, spectral spatial imaging, dynamic oxymetry, etc. PMID:17350865

Electrical immunosensor based on a submicron-gap interdigitated electrode and gold enhancement.

PubMed

Ahn, Junhyoung; Lee, Tae Han; Li, Taihua; Heo, Kwang; Hong, Seunghun; Ko, Jeongheon; Kim, Yongsam; Shin, Yong-Beom; Kim, Min-Gon

2011-08-15

We demonstrated that the detection of human interleukin 5 (IL5) with a higher sensitivity than the enzyme-linked immunosorbent assay (ELISA) was possible using mass-producible submicron-gap interdigitated electrodes (IDEs) combined with signal amplification by a gold nanoparticle (AuNP) and gold enhancement. IDEs, facing comb-shape electrodes, can act as simple and miniaturized devices for immunoassay. An IDE with a gap size of 400nm was fabricated by a stepper photolithography process and was applied for the immunoassay of human IL5. A biotinylated anti-human IL5 was immobilized on the streptavidin-modified IDE, and biotin-bovine serum albumin (BSA) and BSA were added sequentially to reduce non-specific binding between the streptavidin-immobilized IDE surface and other proteins. The immunoassay procedure included three main steps: the reaction of human IL5 to form antigen-antibody complexes, the binding of AuNP conjugation with an antibody against human IL5 for the sandwich immunoassay, and gold enhancement for electrical signal amplification. The measurement of electrical current at each step showed that the gold enhancement step was very critical in detection of the concentration of human IL5. Analysis by scanning electron microscope (SEM) showed that close to 1μm particles were formed from 10nm AuNP by the gold enhancement reaction using gold ions and hydroxylamine. Under optimized conditions, human IL5 could be analyzed at 1pgmL(-1) with a wide dynamic range (from 10(-3) to 100ngmL(-1) concentrations). Copyright © 2011 Elsevier B.V. All rights reserved.

Cumulative River Dynamic Assessment using Topo-Hydrographical High Definition Surveying in the Danube River area - Km 347-Km344

NASA Astrophysics Data System (ADS)

Nichersu, Iulian; Mierla, Marian; Trifanov, Cristian

2013-04-01

Cumulative River Dynamic Assessment using Topo-Hydrographical High Definition Surveying in the Danube River area - Km 347-Km344 Iulian NICHERSU, Cristian TRIFANOV, Marian MIERLA The purpose of this paper is to depict and illustrate the benefits of Topo-Hydrographical High Definition Surveying (THHDS), also known as 3D multi-beam scanning, on a topo-hydrological survey application in Danube Valley. This research investigates the evolution of Danube river dynamics. We start with cross-sections made in 2002, 2007 and 2010 in this area and we coupled with 2012 THHDS. 3D multi-beam scanning method of data acquisition improve the spatial hydrological model and offers better dynamics assessment for future studies, considering that this area is carried out dredging works to improve navigation conditions - THHDS technique true modeling capabilities have applications in hydrotechnical works. Dynamics stands out on all 3 axes and cartographic documents have used both the 1930, 1950, and orthophoto images taken during flight to obtain the 3D model of the floodplain through LIDAR method, in 2007.

Performance of an extended dynamic range time delay integration charge coupled device (XDR TDI CCD) for high-intrascene dynamic range scanning

NASA Astrophysics Data System (ADS)

Levine, Peter A.; Dawson, Robin M.; Andrews, James T.; Bhaskaran, Mahalingham; Furst, David; Hsueh, Fu-Lung; Meray, Grazyna M.; Sudol, Thomas M.; Swain, Pradyumna K.; Tower, John R.

2003-05-01

Many applications, such as industrial inspection and overhead reconnaissance benefit from line scanning architectures where time delay integration (TDI) significantly improves sensitivity. CCDs are particularly well suited to the TDI architecture since charge is transferred virtually noiselessly down the column. Sarnoff's TDI CCDs have demonstrated extremely high speeds where a 7200 x 64, 8 um pixel device with 120 output ports demonstrated a vertical line transfer rate greater than 800 kHz. The most recent addition to Sarnoff's TDI technology is the implementation of extended dynamic range (XDR) in high speed, back illuminated TDI CCDs. The optical, intrascene dynamic range can be adjusted in the design of the imager with measured dynamic ranges exceeding 2,000,000:1 with no degradation in low light performance. The device provides a piecewise linear response to light where multiple slopes and break points can be set during the CCD design. A description of the device architecture and measured results from fabricated XDR TDI CCDs are presented.

Effectiveness and usability of Scanning Wizard software: a tool for enhancing switch scanning.

PubMed

Koester, Heidi Horstmann; Simpson, Richard C

2017-11-24

Scanning Wizard software helps scanning users improve the setup of their switch and scanning system. This study evaluated Scanning Wizard's effectiveness and usability. Ten people who use switch scanning and ten practitioners used Scanning Wizard in the initial session. Usability was high, based on survey responses averaging over 4.5 out of 5, and qualitative feedback was very positive. Five switch users were able to complete the multi-week protocol, using settings on their own scanning system that were recommended from the Scanning Wizard session. Using these revised settings, text entry rates improved by an average of 71%, ranging from 29% to 172% improvement. Results suggest that Scanning Wizard is a useful tool for improving the configuration of scanning systems for people who use switch scanning to communicate. Implications for Rehabilitation Some individuals with severe physical impairments use switch scanning for spoken and written communication. Scanning Wizard software helps scanning users improve the setup of their switch and scanning system. This study demonstrated high usability of Scanning Wizard (with 10 switch userpractitioner teams) and increased text entry rate by an average of 71% (for five switch users). Results suggest that Scanning Wizard is a useful tool for improving the configuration of scanning systems for people who use switch scanning to communicate.

Method for dose-reduced 3D catheter tracking on a scanning-beam digital x-ray system using dynamic electronic collimation

NASA Astrophysics Data System (ADS)

Dunkerley, David A. P.; Funk, Tobias; Speidel, Michael A.

2016-03-01

Scanning-beam digital x-ray (SBDX) is an inverse geometry x-ray fluoroscopy system capable of tomosynthesis-based 3D catheter tracking. This work proposes a method of dose-reduced 3D tracking using dynamic electronic collimation (DEC) of the SBDX scanning x-ray tube. Positions in the 2D focal spot array are selectively activated to create a regionof- interest (ROI) x-ray field around the tracked catheter. The ROI position is updated for each frame based on a motion vector calculated from the two most recent 3D tracking results. The technique was evaluated with SBDX data acquired as a catheter tip inside a chest phantom was pulled along a 3D trajectory. DEC scans were retrospectively generated from the detector images stored for each focal spot position. DEC imaging of a catheter tip in a volume measuring 11.4 cm across at isocenter required 340 active focal spots per frame, versus 4473 spots in full-FOV mode. The dose-area-product (DAP) and peak skin dose (PSD) for DEC versus full field-of-view (FOV) scanning were calculated using an SBDX Monte Carlo simulation code. DAP was reduced to 7.4% to 8.4% of the full-FOV value, consistent with the relative number of active focal spots (7.6%). For image sequences with a moving catheter, PSD was 33.6% to 34.8% of the full-FOV value. The root-mean-squared-deviation between DEC-based 3D tracking coordinates and full-FOV 3D tracking coordinates was less than 0.1 mm. The 3D distance between the tracked tip and the sheath centerline averaged 0.75 mm. Dynamic electronic collimation can reduce dose with minimal change in tracking performance.

A Novel Real-Time Reference Key Frame Scan Matching Method.

PubMed

Mohamed, Haytham; Moussa, Adel; Elhabiby, Mohamed; El-Sheimy, Naser; Sesay, Abu

2017-05-07

Unmanned aerial vehicles represent an effective technology for indoor search and rescue operations. Typically, most indoor missions' environments would be unknown, unstructured, and/or dynamic. Navigation of UAVs in such environments is addressed by simultaneous localization and mapping approach using either local or global approaches. Both approaches suffer from accumulated errors and high processing time due to the iterative nature of the scan matching method. Moreover, point-to-point scan matching is prone to outlier association processes. This paper proposes a low-cost novel method for 2D real-time scan matching based on a reference key frame (RKF). RKF is a hybrid scan matching technique comprised of feature-to-feature and point-to-point approaches. This algorithm aims at mitigating errors accumulation using the key frame technique, which is inspired from video streaming broadcast process. The algorithm depends on the iterative closest point algorithm during the lack of linear features which is typically exhibited in unstructured environments. The algorithm switches back to the RKF once linear features are detected. To validate and evaluate the algorithm, the mapping performance and time consumption are compared with various algorithms in static and dynamic environments. The performance of the algorithm exhibits promising navigational, mapping results and very short computational time, that indicates the potential use of the new algorithm with real-time systems.

Characterization of Visual Scanning Patterns in Air Traffic Control

PubMed Central

McClung, Sarah N.; Kang, Ziho

2016-01-01

Characterization of air traffic controllers' (ATCs') visual scanning strategies is a challenging issue due to the dynamic movement of multiple aircraft and increasing complexity of scanpaths (order of eye fixations and saccades) over time. Additionally, terminologies and methods are lacking to accurately characterize the eye tracking data into simplified visual scanning strategies linguistically expressed by ATCs. As an intermediate step to automate the characterization classification process, we (1) defined and developed new concepts to systematically filter complex visual scanpaths into simpler and more manageable forms and (2) developed procedures to map visual scanpaths with linguistic inputs to reduce the human judgement bias during interrater agreement. The developed concepts and procedures were applied to investigating the visual scanpaths of expert ATCs using scenarios with different aircraft congestion levels. Furthermore, oculomotor trends were analyzed to identify the influence of aircraft congestion on scan time and number of comparisons among aircraft. The findings show that (1) the scanpaths filtered at the highest intensity led to more consistent mapping with the ATCs' linguistic inputs, (2) the pattern classification occurrences differed between scenarios, and (3) increasing aircraft congestion caused increased scan times and aircraft pairwise comparisons. The results provide a foundation for better characterizing complex scanpaths in a dynamic task and automating the analysis process. PMID:27239190

Nanoscale Spatiotemporal Diffusion Modes Measured by Simultaneous Confocal and Stimulated Emission Depletion Nanoscopy Imaging.

PubMed

Schneider, Falk; Waithe, Dominic; Galiani, Silvia; Bernardino de la Serna, Jorge; Sezgin, Erdinc; Eggeling, Christian

2018-06-19

The diffusion dynamics in the cellular plasma membrane provide crucial insights into molecular interactions, organization, and bioactivity. Beam-scanning fluorescence correlation spectroscopy combined with super-resolution stimulated emission depletion nanoscopy (scanning STED-FCS) measures such dynamics with high spatial and temporal resolution. It reveals nanoscale diffusion characteristics by measuring the molecular diffusion in conventional confocal mode and super-resolved STED mode sequentially for each pixel along the scanned line. However, to directly link the spatial and the temporal information, a method that simultaneously measures the diffusion in confocal and STED modes is needed. Here, to overcome this problem, we establish an advanced STED-FCS measurement method, line interleaved excitation scanning STED-FCS (LIESS-FCS), that discloses the molecular diffusion modes at different spatial positions with a single measurement. It relies on fast beam-scanning along a line with alternating laser illumination that yields, for each pixel, the apparent diffusion coefficients for two different observation spot sizes (conventional confocal and super-resolved STED). We demonstrate the potential of the LIESS-FCS approach with simulations and experiments on lipid diffusion in model and live cell plasma membranes. We also apply LIESS-FCS to investigate the spatiotemporal organization of glycosylphosphatidylinositol-anchored proteins in the plasma membrane of live cells, which, interestingly, show multiple diffusion modes at different spatial positions.

Characterization of Visual Scanning Patterns in Air Traffic Control.

PubMed

McClung, Sarah N; Kang, Ziho

2016-01-01

Characterization of air traffic controllers' (ATCs') visual scanning strategies is a challenging issue due to the dynamic movement of multiple aircraft and increasing complexity of scanpaths (order of eye fixations and saccades) over time. Additionally, terminologies and methods are lacking to accurately characterize the eye tracking data into simplified visual scanning strategies linguistically expressed by ATCs. As an intermediate step to automate the characterization classification process, we (1) defined and developed new concepts to systematically filter complex visual scanpaths into simpler and more manageable forms and (2) developed procedures to map visual scanpaths with linguistic inputs to reduce the human judgement bias during interrater agreement. The developed concepts and procedures were applied to investigating the visual scanpaths of expert ATCs using scenarios with different aircraft congestion levels. Furthermore, oculomotor trends were analyzed to identify the influence of aircraft congestion on scan time and number of comparisons among aircraft. The findings show that (1) the scanpaths filtered at the highest intensity led to more consistent mapping with the ATCs' linguistic inputs, (2) the pattern classification occurrences differed between scenarios, and (3) increasing aircraft congestion caused increased scan times and aircraft pairwise comparisons. The results provide a foundation for better characterizing complex scanpaths in a dynamic task and automating the analysis process.

Control and dynamics study for the satellite power system. Volume 1: MPTS/SPS collector dynamic analysis and surface deformation

NASA Technical Reports Server (NTRS)

Wang, S. J.

1980-01-01

The basic dynamic properties and performance characteristics of the microwave power transmission satellite antenna were analyzed in an effort to develop criteria, requirements, and constraints for the control and structure design. The vibrational properties, the surface deformation, and the corresponding scan loss under the influence of disturbances are considered.

A High Rigidity and Precision Scanning Tunneling Microscope with Decoupled XY and Z Scans

PubMed Central

Chen, Xu; Guo, Tengfei; Hou, Yubin; Zhang, Jing

2017-01-01

A new scan-head structure for the scanning tunneling microscope (STM) is proposed, featuring high scan precision and rigidity. The core structure consists of a piezoelectric tube scanner of quadrant type (for XY scans) coaxially housed in a piezoelectric tube with single inner and outer electrodes (for Z scan). They are fixed at one end (called common end). A hollow tantalum shaft is coaxially housed in the XY-scan tube and they are mutually fixed at both ends. When the XY scanner scans, its free end will bring the shaft to scan and the tip which is coaxially inserted in the shaft at the common end will scan a smaller area if the tip protrudes short enough from the common end. The decoupled XY and Z scans are desired for less image distortion and the mechanically reduced scan range has the superiority of reducing the impact of the background electronic noise on the scanner and enhancing the tip positioning precision. High quality atomic resolution images are also shown. PMID:29270242

Kinetic analysis of IMP split dose method for two consecutive measurement of cerebral blood flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nishizawa, S.; Yonekura, Y.; Tanaka, F.

1994-05-01

The split dose method for two consecutive measurements of cerebral blood flow (CBF) with I-123 IMP seems to offer a great merit to the SPECT study of the brain. However, because of complexity of the dynamics of IMP, it is not clear if microsphere (MS) model permits a estimation of CBF for the 2nd dose. We applied kinetic (KN) analysis based on 2 compartment model to the dynamic SPECT scan data, and compared the results with those obtained by MS model. Dynamic SPECT (1-min scans for 50 min) was performed using 3-head SPECT camera in 5 patients to test themore » reproducibility of measured CBF and in 9 patients to test the vascular response to acetazolamide (ACZ). Two doses of IMP (111 MBq each) were injected at the time of, and 25 min after, the scan initiation. ACZ (1g) was administered at 13 min. Arterial blood samples were drawn manually during the scan and an octanol extracted input function was obtained. Dynamic scan data for 22 min was used for CBF by KN analysis (K1), and 4-min scan data at 5 min for CBF by MS model (Km), for each dose. For 2nd CBF by MS model, simple subtraction of brain activity due to the I st dose was done using 4-min scan data just prior to the 2nd dose. Reproducibility of measured CBF by KN analysis was excellent (r=0.949, 1st K1=39.2{plus_minus}5.6 and 2nd K1=38.5{plus_minus}6.6 ml/l00g/min: mean{plus_minus}SD). Vascular response to ACZ was good (1st K1=42.4{plus_minus}7.8 to 2nd K1=67.9{plus_minus}10.0) in areas without ischemia, but poor (1st K1=41.1{plus_minus}8.5 to 2nd K1=46.1{plus_minus}11.1) in ischemic areas. Compared to KN analysis, MS model underestimated 3.5% for the 1st CBF measurement and 12.8% for the 2nd. However, excellent correlation was observed not only between 1st K1 and Km (r=0.993, slope=0.920) but between 2nd K1 and Km (r=0.994, slope=0.814), and the results permitted a reasonable correction for Km.« less

Synthesis, characterization and multifunctional properties of plasmonic Ag-TiO2 nanocomposites

NASA Astrophysics Data System (ADS)

Prakash, Jai; Kumar, Promod; Harris, R. A.; Swart, Chantel; Neethling, J. H.; Janse van Vuuren, A.; Swart, H. C.

2016-09-01

We report on the synthesis of multifunctional Ag-TiO2 nanocomposites and their optical, physio-chemical, surface enhanced Raman scattering (SERS) and antibacterial properties. A series of Ag-TiO2 nanocomposites were synthesized by sol-gel technique and characterized by x-ray diffraction, scanning and transmission electron microscopy, energy-dispersed x-ray analysis, photoluminescence, UV-vis, x-ray photoelectron and Raman spectroscopy and Brunauer-Emmett-Teller method. The Ag nanoparticles (NPs) (7-20 nm) were found to be uniformly distributed around and strongly attached to TiO2 NPs. The novel optical responses of the nanocomposites are due to the strong electric field from the localized surface plasmon (LSP) excitation of the Ag NPs and decreased recombination of photo-induced electrons and holes at Ag-TiO2 interface providing potential materials for photocatalysis. The nanocomposites show enhancement in the SERS signals of methyl orange (MO) molecules with increasing Ag content attributed to the long-range electromagnetic enhancement from the excited LSP of the Ag NPs. To further understand the SERS activity, molecular mechanics and molecular dynamics simulations were used to study the geometries and SERS enhancement of MO adsorbed onto Ag-TiO2 respectively. Simulation results indicate that number of ligands (MO) that adsorb onto the Ag NPs as well as binding energy per ligand increases with increasing NP density and molecule-to-surface orientation is mainly flat resulting in strong bond strength between MO and Ag NP surface and enhanced SERS signals. The antimicrobial activity of the Ag-TiO2 nanocomposites was tested against the bacterium Staphylococcus aureus and enhanced antibacterial effect was observed with increasing Ag content explained by contact killing action mechanism. These results foresee promising applications of the plasmonic metal-semiconductor based nano-biocomposites for both chemical and biological samples.

Dynamic in vivo imaging of small animal brain using pulsed laser diode-based photoacoustic tomography system.

PubMed

Upputuri, Paul Kumar; Pramanik, Manojit

2017-09-01

We demonstrate dynamic in vivo imaging using a low-cost portable pulsed laser diode (PLD)-based photoacoustic tomography system. The system takes advantage of an 803-nm PLD having high-repetition rate ∼7000  Hz combined with a fast-scanning single-element ultrasound transducer leading to a 5 s cross-sectional imaging. Cortical vasculature is imaged in scan time of 5 s with high signal-to-noise ratio ∼48. To examine the ability for dynamic imaging, we monitored the fast uptake and clearance process of indocyanine green in the rat brain. The system will find applications to study neurofunctional activities, characterization of pharmacokinetic, and biodistribution profiles in the development process of drugs or imaging agents. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Structural and dynamic characterization of ultrafine fibers based on the poly-3-hydroxybutyrate-dipyridamole system

NASA Astrophysics Data System (ADS)

Olkhov, A. A.; Karpova, S. G.; Staroverova, O. V.; Krutikova, A. A.; Orlov, N. A.; Kucherenko, E. L.; Iordanskii, A. L.

2016-11-01

The fibrous materials (the mats) based on poly-3-hydroxybutyrate (PHB) containing the drug, dipiridomole (DPD) were produced by electrospinning (ES). Thermophysical and dynamical properties of the single filaments and the mats were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and probe electron paramagnetic resonance spectroscopy (EPR). The effect of annealing temperature on the structure and crystallinity of the fibers was examined. It was shown that the loading of DPD influences on both the melting enthalpy and the morphology of the fibers. Besides the analysis of EPR spectra revealed that there are two populations of spin-probes distributed in the rigid and nonrigid amorphous regions of the PHB fibers respectively. For all fibrous materials with different content of DPD (0-5%) the correlation between thermophysical (DSC) and dynamic data (EPR) was observed.

Vulcanization characteristics and dynamic mechanical behavior of natural rubber reinforced with silane modified silica.

PubMed

Chonkaew, Wunpen; Minghvanish, Withawat; Kungliean, Ulchulee; Rochanawipart, Nutthaya; Brostow, Witold

2011-03-01

Two silane coupling agents were used for hydrolysis-condensation reaction modification of nanosilica surfaces. The surface characteristics were analyzed using Fourier transform infrared spectroscopy (FTIR). The vulcanization kinetics of natural rubber (NR) + silica composites was studied and compared to behavior of the neat NR using differential scanning calorimetry (DSC) in the dynamic scan mode. Dynamic mechanical analysis (DMA) was performed to evaluate the effects of the surface modification. Activation energy E(a) values for the reaction are obtained. The presence of silica, modified or otherwise, inhibits the vulcanization reaction of NR. The neat silica containing system has the lowest cure rate index and the highest activation energy for the vulcanization reaction. The coupling agent with longer chains causes more swelling and moves the glass transition temperature T(g) downwards. Below the glass transition region, silica causes a lowering of the dynamic storage modulus G', a result of hindering the cure reaction. Above the glass transition, silica-again modified or otherwise-provides the expected reinforcement effect.

Column-by-column observation of dislocation motion in CdTe: Dynamic scanning transmission electron microscopy

NASA Astrophysics Data System (ADS)

Li, Chen; Zhang, Yu-Yang; Pennycook, Timothy J.; Wu, Yelong; Lupini, Andrew R.; Paudel, Naba; Pantelides, Sokrates T.; Yan, Yanfa; Pennycook, Stephen J.

2016-10-01

The dynamics of partial dislocations in CdTe have been observed at the atomic scale using aberration-corrected scanning transmission electron microscopy (STEM), allowing the mobility of different dislocations to be directly compared: Cd-core Shockley partial dislocations are more mobile than Te-core partials, and dislocation cores with unpaired columns have higher mobility than those without unpaired columns. The dynamic imaging also provides insight into the process by which the dislocations glide. Dislocations with dangling bonds on unpaired columns are found to be more mobile because the dangling bonds mediate the bond exchanges required for the dislocations to move. Furthermore, a screw dislocation has been resolved to dissociate into a Shockley partial-dislocation pair along two different directions, revealing a way for the screw dislocation to glide in the material. The results show that dynamic STEM imaging has the potential to uncover the details of dislocation motion not easily accessible by other means.

Accurate 3D reconstruction by a new PDS-OSEM algorithm for HRRT

NASA Astrophysics Data System (ADS)

Chen, Tai-Been; Horng-Shing Lu, Henry; Kim, Hang-Keun; Son, Young-Don; Cho, Zang-Hee

2014-03-01

State-of-the-art high resolution research tomography (HRRT) provides high resolution PET images with full 3D human brain scanning. But, a short time frame in dynamic study causes many problems related to the low counts in the acquired data. The PDS-OSEM algorithm was proposed to reconstruct the HRRT image with a high signal-to-noise ratio that provides accurate information for dynamic data. The new algorithm was evaluated by simulated image, empirical phantoms, and real human brain data. Meanwhile, the time activity curve was adopted to validate a reconstructed performance of dynamic data between PDS-OSEM and OP-OSEM algorithms. According to simulated and empirical studies, the PDS-OSEM algorithm reconstructs images with higher quality, higher accuracy, less noise, and less average sum of square error than those of OP-OSEM. The presented algorithm is useful to provide quality images under the condition of low count rates in dynamic studies with a short scan time.

Dynamic covalent chemistry of bisimines at the solid/liquid interface monitored by scanning tunnelling microscopy.

PubMed

Ciesielski, Artur; El Garah, Mohamed; Haar, Sébastien; Kovaříček, Petr; Lehn, Jean-Marie; Samorì, Paolo

2014-11-01

Dynamic covalent chemistry relies on the formation of reversible covalent bonds under thermodynamic control to generate dynamic combinatorial libraries. It provides access to numerous types of complex functional architectures, and thereby targets several technologically relevant applications, such as in drug discovery, (bio)sensing and dynamic materials. In liquid media it was proved that by taking advantage of the reversible nature of the bond formation it is possible to combine the error-correction capacity of supramolecular chemistry with the robustness of covalent bonding to generate adaptive systems. Here we show that double imine formation between 4-(hexadecyloxy)benzaldehyde and different α,ω-diamines as well as reversible bistransimination reactions can be achieved at the solid/liquid interface, as monitored on the submolecular scale by in situ scanning tunnelling microscopy imaging. Our modular approach enables the structurally controlled reversible incorporation of various molecular components to form sophisticated covalent architectures, which opens up perspectives towards responsive multicomponent two-dimensional materials and devices.

Dynamic measurement of fluorescent proteins spectral distribution on virus infected cells

NASA Astrophysics Data System (ADS)

Lee, Ja-Yun; Wu, Ming-Xiu; Kao, Chia-Yun; Wu, Tzong-Yuan; Hsu, I.-Jen

2006-09-01

We constructed a dynamic spectroscopy system that can simultaneously measure the intensity and spectral distributions of samples with multi-fluorophores in a single scan. The system was used to monitor the fluorescence distribution of cells infected by the virus, which is constructed by a recombinant baculoviruses, vAcD-Rhir-E, containing the red and green fluorescent protein gene that can simultaneously produce dual fluorescence in recombinant virus-infected Spodoptera frugiperda 21 cells (Sf21) under the control of a polyhedrin promoter. The system was composed of an excitation light source, a scanning system and a spectrometer. We also developed an algorithm and fitting process to analyze the pattern of fluorescence distribution of the dual fluorescence produced in the recombinant virus-infected cells. All the algorithm and calculation are automatically processed in a visualized scanning program and can monitor the specific region of sample by calculating its intensity distribution. The spectral measurement of each pixel was performed at millisecond range and the two dimensional distribution of full spectrum was recorded within several seconds. We have constructed a dynamic spectroscopy system to monitor the process of virus-infection of cells. The distributions of the dual fluorescence were simultaneously measured at micrometer resolution.

The introduction of capillary structures in 4D simulated vascular tree for ART 3.5D algorithm further validation

NASA Astrophysics Data System (ADS)

Barra, Beatrice; El Hadji, Sara; De Momi, Elena; Ferrigno, Giancarlo; Cardinale, Francesco; Baselli, Giuseppe

2017-03-01

Several neurosurgical procedures, such as Artero Venous Malformations (AVMs), aneurysm embolizations and StereoElectroEncephaloGraphy (SEEG) require accurate reconstruction of the cerebral vascular tree, as well as the classification of arteries and veins, in order to increase the safety of the intervention. Segmentation of arteries and veins from 4D CT perfusion scans has already been proposed in different studies. Nonetheless, such procedures require long acquisition protocols and the radiation dose given to the patient is not negligible. Hence, space is open to approaches attempting to recover the dynamic information from standard Contrast Enhanced Cone Beam Computed Tomography (CE-CBCT) scans. The algorithm proposed by our team is called ART 3.5 D. It is a novel algorithm based on the postprocessing of both the angiogram and the raw data of a standard Digital Subtraction Angiography from a CBCT (DSACBCT) allowing arteries and veins segmentation and labeling without requiring any additional radiation exposure for the patient and neither lowering the resolution. In addition, while in previous versions of the algorithm just the distinction of arteries and veins was considered, here the capillary phase simulation and identification is introduced, in order to increase further information useful for more precise vasculature segmentation.

Hybrid CMOS-Graphene Sensor Array for Subsecond Dopamine Detection.

PubMed

Nasri, Bayan; Wu, Ting; Alharbi, Abdullah; You, Kae-Dyi; Gupta, Mayank; Sebastian, Sunit P; Kiani, Roozbeh; Shahrjerdi, Davood

2017-12-01

We introduce a hybrid CMOS-graphene sensor array for subsecond measurement of dopamine via fast-scan cyclic voltammetry (FSCV). The prototype chip has four independent CMOS readout channels, fabricated in a 65-nm process. Using planar multilayer graphene as biologically compatible sensing material enables integration of miniaturized sensing electrodes directly above the readout channels. Taking advantage of the chemical specificity of FSCV, we introduce a region of interest technique, which subtracts a large portion of the background current using a programmable low-noise constant current at about the redox potentials. We demonstrate the utility of this feature for enhancing the sensitivity by measuring the sensor response to a known dopamine concentration in vitro at three different scan rates. This strategy further allows us to significantly reduce the dynamic range requirements of the analog-to-digital converter (ADC) without compromising the measurement accuracy. We show that an integrating dual-slope ADC is adequate for digitizing the background-subtracted current. The ADC operates at a sampling frequency of 5-10 kHz and has an effective resolution of about 60 pA, which corresponds to a theoretical dopamine detection limit of about 6 nM. Our hybrid sensing platform offers an effective solution for implementing next-generation FSCV devices that can enable precise recording of dopamine signaling in vivo on a large scale.

Atmospheric structure and helium abundance on Saturn from Cassini/UVIS and CIRS observations

NASA Astrophysics Data System (ADS)

Koskinen, T. T.; Guerlet, S.

2018-06-01

We combine measurements from stellar occultations observed by the Cassini Ultraviolet Imaging Spectrograph (UVIS) and limb scans observed by the Composite Infrared Spectrometer (CIRS) to create empirical atmospheric structure models for Saturn corresponding to the locations probed by the occultations. The results cover multiple locations at low to mid-latitudes between the spring of 2005 and the fall of 2015. We connect the temperature-pressure (T-P) profiles retrieved from the CIRS limb scans in the stratosphere to the T-P profiles in the thermosphere retrieved from the UVIS occultations. We calculate the altitudes corresponding to the pressure levels in each case based on our best fit composition model that includes H2, He, CH4 and upper limits on H. We match the altitude structure to the density profile in the thermosphere that is retrieved from the occultations. Our models depend on the abundance of helium and we derive a volume mixing ratio of 11 ± 2% for helium in the lower atmosphere based on a statistical analysis of the values derived for 32 different occultation locations. We also derive the mean temperature and methane profiles in the upper atmosphere and constrain their variability. Our results are consistent with enhanced heating at the polar auroral region and a dynamically active upper atmosphere.

Nano titania aided clustering and adhesion of beneficial bacteria to plant roots to enhance crop growth and stress management.

PubMed

Palmqvist, N G M; Bejai, S; Meijer, J; Seisenbaeva, G A; Kessler, V G

2015-05-13

A novel use of Titania nanoparticles as agents in the nano interface interaction between a beneficial plant growth promoting bacterium (Bacillus amyloliquefaciens UCMB5113) and oilseed rape plants (Brassica napus) for protection against the fungal pathogen Alternaria brassicae is presented. Two different TiO2 nanoparticle material were produced by the Sol-Gel approach, one using the patented Captigel method and the other one applying TiBALDH precursor. The particles were characterized by transmission electron microscopy, thermogravimetric analysis, X-ray diffraction, dynamic light scattering and nano particle tracking analysis. Scanning electron microscopy showed that the bacterium was living in clusters on the roots and the combined energy-dispersive X-ray spectroscopy analysis revealed that titanium was present in these cluster formations. Confocal laser scanning microscopy further demonstrated an increased bacterial colonization of Arabidopsis thaliana roots and a semi-quantitative microscopic assay confirmed an increased bacterial adhesion to the roots. An increased amount of adhered bacteria was further confirmed by quantitative fluorescence measurements. The degree of infection by the fungus was measured and quantified by real-time-qPCR. Results showed that Titania nanoparticles increased adhesion of beneficial bacteria on to the roots of oilseed rape and protected the plants against infection.

Nano titania aided clustering and adhesion of beneficial bacteria to plant roots to enhance crop growth and stress management

NASA Astrophysics Data System (ADS)

Palmqvist, N. G. M.; Bejai, S.; Meijer, J.; Seisenbaeva, G. A.; Kessler, V. G.

2015-05-01

A novel use of Titania nanoparticles as agents in the nano interface interaction between a beneficial plant growth promoting bacterium (Bacillus amyloliquefaciens UCMB5113) and oilseed rape plants (Brassica napus) for protection against the fungal pathogen Alternaria brassicae is presented. Two different TiO2 nanoparticle material were produced by the Sol-Gel approach, one using the patented Captigel method and the other one applying TiBALDH precursor. The particles were characterized by transmission electron microscopy, thermogravimetric analysis, X-ray diffraction, dynamic light scattering and nano particle tracking analysis. Scanning electron microscopy showed that the bacterium was living in clusters on the roots and the combined energy-dispersive X-ray spectroscopy analysis revealed that titanium was present in these cluster formations. Confocal laser scanning microscopy further demonstrated an increased bacterial colonization of Arabidopsis thaliana roots and a semi-quantitative microscopic assay confirmed an increased bacterial adhesion to the roots. An increased amount of adhered bacteria was further confirmed by quantitative fluorescence measurements. The degree of infection by the fungus was measured and quantified by real-time-qPCR. Results showed that Titania nanoparticles increased adhesion of beneficial bacteria on to the roots of oilseed rape and protected the plants against infection.

Moisture-Mediated Interactions Between Amorphous Maltodextrins and Crystalline Fructose.

PubMed

Thorat, Alpana; Marrs, Krystin N; Ghorab, Mohamed K; Meunier, Vincent; Forny, Laurent; Taylor, Lynne S; Mauer, Lisa J

2017-05-01

The effects of coformulating amorphous maltodextrins (MDs) and crystalline fructose, a deliquescent solid, on the moisture sorption, deliquescence point (RH 0 ), and glass transition temperature (T g ) behaviors were determined. Moisture sorption profiles of binary fructose:MD mixtures and individual ingredients were generated using controlled relative humidity (RH) desiccators and by dynamic vapor sorption techniques. Blends exhibited synergistic moisture uptake at RHs below the RH 0 of fructose, attributed to partial dissolution of fructose in plasticized MD matrices without a significant reduction in the RH 0 of the undissolved fructose. Increasing storage temperature decreased the onset RH for moisture sorption synergy. At all storage RHs, the measured T g (2nd scan) was significantly reduced in fructose:MD mixtures compared to individual MDs, and was related to both the synergistic moisture uptake in the blends and heat-induced ternary fructose-MD-water interactions in the differential scanning calorimeter. Differences were found between the behavior of fructose:MD blends and previous reports of sucrose:MD and NaCl:MD blends, caused in part by the lower RH 0 of fructose. The enhanced moisture sorption in blends of deliquescent and amorphous ingredients could lead to problematic moisture-induced changes if storage conditions are not controlled. © 2017 Institute of Food Technologists®.

Optical detection of ultrasound using an apertureless near-field scanning optical microscopy system

NASA Astrophysics Data System (ADS)

Ahn, Phillip; Zhang, Zhen; Sun, Cheng; Balogun, Oluwaseyi

2013-01-01

Laser ultrasonics techniques are power approaches for non-contact generation and detection of high frequency ultrasound on a local scale. In these techniques, optical diffraction limits the spatial information that can be accessed from a measurement. In order to improve the lateral spatial resolution, we incorporate an apertureless near-field scanning optical microscope (aNSOM) into laser ultrasonics setup for local detection of laser generated ultrasound. The aNSOM technique relies on the measurement of a weak backscattered near-field light intensity resulting from the oblique illumination of a nanoscale probe-tip positioned close to a sample surface. We enhance the optical near-field intensity by coupling light to surface plasmon polaritons (SPPs) on the shaft of an atomic force microscopy (AFM) cantilever. The SPPs propagate down the AFM shaft, localize at the tip apex, and are backscattered to the far-field when the separation distance between the probe tip and the sample surface is comparable to the probe-tip radius. The backscattered near-field intensity is dynamically modulated when an ultrasonic wave arrives at the sample surface leading to a transient change in the tip-sample separation distance. We present experimental results detailing measurement of broadband and narrowband laser generated ultrasound in solids with frequencies reaching up to 180 MHz range.

Nano titania aided clustering and adhesion of beneficial bacteria to plant roots to enhance crop growth and stress management

PubMed Central

Palmqvist, N. G. M.; Bejai, S.; Meijer, J.; Seisenbaeva, G. A.; Kessler, V. G.

2015-01-01

A novel use of Titania nanoparticles as agents in the nano interface interaction between a beneficial plant growth promoting bacterium (Bacillus amyloliquefaciens UCMB5113) and oilseed rape plants (Brassica napus) for protection against the fungal pathogen Alternaria brassicae is presented. Two different TiO2 nanoparticle material were produced by the Sol-Gel approach, one using the patented Captigel method and the other one applying TiBALDH precursor. The particles were characterized by transmission electron microscopy, thermogravimetric analysis, X-ray diffraction, dynamic light scattering and nano particle tracking analysis. Scanning electron microscopy showed that the bacterium was living in clusters on the roots and the combined energy-dispersive X-ray spectroscopy analysis revealed that titanium was present in these cluster formations. Confocal laser scanning microscopy further demonstrated an increased bacterial colonization of Arabidopsis thaliana roots and a semi-quantitative microscopic assay confirmed an increased bacterial adhesion to the roots. An increased amount of adhered bacteria was further confirmed by quantitative fluorescence measurements. The degree of infection by the fungus was measured and quantified by real-time-qPCR. Results showed that Titania nanoparticles increased adhesion of beneficial bacteria on to the roots of oilseed rape and protected the plants against infection. PMID:25970693

Direct observation and control of hydrogen-bond dynamics using low-temperature scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Kumagai, Takashi

2015-08-01

Hydrogen(H)-bond dynamics are involved in many elementary processes in chemistry and biology. Because of its fundamental importance, a variety of experimental and theoretical approaches have been employed to study the dynamics in gas, liquid, solid phases, and their interfaces. This review describes the recent progress of direct observation and control of H-bond dynamics in several model systems on a metal surface by using low-temperature scanning tunneling microscopy (STM). General aspects of H-bond dynamics and the experimental methods are briefly described in chapter 1 and 2. In the subsequent four chapters, I present direct observation of an H-bond exchange reaction within a single water dimer (chapter 3), a symmetric H bond (chapter 4) and H-atom relay reactions (chapter 5) within water-hydroxyl complexes, and an intramolecular H-atom transfer reaction (tautomerization) within a single porphycene molecule (chapter 6). These results provide novel microscopic insights into H-bond dynamics at the single-molecule level, and highlight significant impact on the process from quantum effects, namely tunneling and zero-point vibration, resulting from the small mass of H atom. Additionally, local environmental effect on H-bond dynamics is also examined by using atom/molecule manipulation with the STM.

Recovery of Background Structures in Nanoscale Helium Ion Microscope Imaging.

PubMed

Carasso, Alfred S; Vladár, András E

2014-01-01

This paper discusses a two step enhancement technique applicable to noisy Helium Ion Microscope images in which background structures are not easily discernible due to a weak signal. The method is based on a preliminary adaptive histogram equalization, followed by 'slow motion' low-exponent Lévy fractional diffusion smoothing. This combined approach is unexpectedly effective, resulting in a companion enhanced image in which background structures are rendered much more visible, and noise is significantly reduced, all with minimal loss of image sharpness. The method also provides useful enhancements of scanning charged-particle microscopy images obtained by composing multiple drift-corrected 'fast scan' frames. The paper includes software routines, written in Interactive Data Language (IDL),(1) that can perform the above image processing tasks.

Frequency, outcome, and risk factors of contrast media extravasation in 142,651 intravenous contrast-enhanced CT scans.

PubMed

Hwang, Eui Jin; Shin, Cheong-Il; Choi, Young Hun; Park, Chang Min

2018-06-06

To evaluate the frequency, outcome, and risk factors of intravenous contrast media (CM) extravasation during contrast-enhanced CT scans in a large population. After institutional review board approval, 142,651 patients (72,976 males and 69,675 females; mean age, 59.9 ± 13.0 years) who underwent contrast-enhanced CT scans with intravenous CM between January 2015 and April 2017 were retrospectively included. The frequency of CM extravasations and their clinical outcomes were investigated. Risk factors of CM extravasation were evaluated using logistic regression with generalized estimating equation analyses. In addition, the frequency and risk factors of large-volume (≥100 ml) CM extravasation were also investigated. CM extravasation occurred in 0.23% (321/142,651) of patients, all of which were of mild degree and resolved without any sequelae through conservative management. Multivariate analysis revealed that female gender [odds ratio (OR) = 1.61; p < 0.001], 60 < age ≤ 70 years (OR = 1.71; p = 0.004) or age > 70 years (OR = 2.49; p < 0.001), patients in general wards (OR = 2.71; p < 0.001) or ICUs (OR = 4.76; p < 0.001), 9.4 < CM viscosity ≤ 10.0 (OR = 1.65; p = 0.015), 10.0 < CM viscosity ≤ 10.6 (OR = 1.60; p = 0.002), and CM viscosity > 16.0 (OR = 2.55, p < 0.001) were independent risk factors for CM extravasation. CM extravasation during contrast-enhanced CT scans was uncommon with no substantial clinical consequences. Several risk factors that may have the potential to reduce the occurrence of CM extravasation were identified. • The observed frequency of contrast media extravasation during contrast-enhanced CT scans was 0.23% (321/142,651). • Significant risk factors for contrast media extravasation were female gender, age older than 60 years, patients in general wards or ICUs, and the viscosity of contrast media greater than 9.4 mPa∙s. • The main preventive action for contrast media extravasation would be to lower the viscosity of contrast media.

Correlation-induced superconductivity dynamically stabilized and enhanced by laser irradiation.

PubMed

Ido, Kota; Ohgoe, Takahiro; Imada, Masatoshi

2017-08-01

Studies on out-of-equilibrium dynamics have paved a way to realize a new state of matter. Superconductor-like properties above room temperatures recently suggested to be in copper oxides achieved by selectively exciting vibrational phonon modes by laser have inspired studies on an alternative and general strategy to be pursued for high-temperature superconductivity. We show that the superconductivity can be enhanced by irradiating laser to correlated electron systems owing to two mechanisms: First, the effective attractive interaction of carriers is enhanced by the dynamical localization mechanism, which drives the system into strong coupling regions. Second, the irradiation allows reaching uniform and enhanced superconductivity dynamically stabilized without deteriorating into equilibrium inhomogeneities that suppress superconductivity. The dynamical superconductivity is subject to the Higgs oscillations during and after the irradiation. Our finding sheds light on a way to enhance superconductivity that is inaccessible in equilibrium in strongly correlated electron systems.

Nonparametric modeling of longitudinal covariance structure in functional mapping of quantitative trait loci.

PubMed

Yap, John Stephen; Fan, Jianqing; Wu, Rongling

2009-12-01

Estimation of the covariance structure of longitudinal processes is a fundamental prerequisite for the practical deployment of functional mapping designed to study the genetic regulation and network of quantitative variation in dynamic complex traits. We present a nonparametric approach for estimating the covariance structure of a quantitative trait measured repeatedly at a series of time points. Specifically, we adopt Huang et al.'s (2006, Biometrika 93, 85-98) approach of invoking the modified Cholesky decomposition and converting the problem into modeling a sequence of regressions of responses. A regularized covariance estimator is obtained using a normal penalized likelihood with an L(2) penalty. This approach, embedded within a mixture likelihood framework, leads to enhanced accuracy, precision, and flexibility of functional mapping while preserving its biological relevance. Simulation studies are performed to reveal the statistical properties and advantages of the proposed method. A real example from a mouse genome project is analyzed to illustrate the utilization of the methodology. The new method will provide a useful tool for genome-wide scanning for the existence and distribution of quantitative trait loci underlying a dynamic trait important to agriculture, biology, and health sciences.

The Hydrodynamics and Odorant Transport Phenomena of Olfaction in the Hammerhead Shark

NASA Astrophysics Data System (ADS)

Rygg, Alex; Craven, Brent

2013-11-01

The hammerhead shark possesses a unique head morphology that is thought to facilitate enhanced olfactory performance. The olfactory organs, located at the distal ends of the cephalofoil, contain numerous lamellae that increase the surface area for olfaction. Functionally, for the shark to detect chemical stimuli, water-borne odors must reach the olfactory sensory epithelium that lines these lamellae. Thus, odorant transport from the aquatic environment to the sensory epithelium is the first critical step in olfaction. Here we investigate the hydrodynamics and odorant transport phenomena of olfaction in the hammerhead shark based on an anatomically-accurate reconstruction of the head and olfactory chamber from high-resolution micro-CT and MRI scans of a cadaver specimen. Computational fluid dynamics (CFD) simulations of water flow in the reconstructed model reveal the external and internal hydrodynamics of olfaction during swimming. Odorant transport in the olfactory organ is investigated using a multi-scale approach, whereby molecular dynamics (MD) simulations are used to calculate odorant partition coefficients that are subsequently utilized in macro-scale CFD simulations of odorant deposition. The hydrodynamic and odorant transport results are used to elucidate several important features of olfactory function in the hammerhead shark.

Quantification of Dynamic 11C-Phenytoin PET Studies.

PubMed

Mansor, Syahir; Boellaard, Ronald; Froklage, Femke E; Bakker, Esther D M; Yaqub, Maqsood; Voskuyl, Rob A; Schwarte, Lothar A; Verbeek, Joost; Windhorst, Albert D; Lammertsma, Adriaan

2015-09-01

The overexpression of P-glycoprotein (Pgp) is thought to be an important mechanism of pharmacoresistance in epilepsy. Recently, (11)C-phenytoin has been evaluated preclinically as a tracer for Pgp. The aim of the present study was to assess the optimal plasma kinetic model for quantification of (11)C-phenytoin studies in humans. Dynamic (11)C-phenytoin PET scans of 6 healthy volunteers with arterial sampling were acquired twice on the same day and analyzed using single- and 2-tissue-compartment models with and without a blood volume parameter. Global and regional test-retest (TRT) variability was determined for both plasma to tissue rate constant (K1) and volume of distribution (VT). According to the Akaike information criterion, the reversible single-tissue-compartment model with blood volume parameter was the preferred plasma input model. Mean TRT variability ranged from 1.5% to 16.9% for K1 and from 0.5% to 5.8% for VT. Larger volumes of interest showed better repeatabilities than smaller regions. A 45-min scan provided essentially the same K1 and VT values as a 60-min scan. A reversible single-tissue-compartment model with blood volume seems to be a good candidate model for quantification of dynamic (11)C-phenytoin studies. Scan duration may be reduced to 45 min without notable loss of accuracy and precision of both K1 and VT, although this still needs to be confirmed under pathologic conditions. © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

Dynamic focus-tracking MEMS scanning micromirror with low actuation voltages for endoscopic imaging

PubMed Central

Strathman, Matthew; Liu, Yunbo; Li, Xingde; Lin, Lih Y.

2013-01-01

We demonstrate a 3-D scanning micromirror device that combines 2-D beam scanning with focus control in the same device using micro-electro-mechanical-systems (MEMS) technology. 2-D beam scanning is achieved with a biaxial gimbal structure and focus control is obtained with a deformable mirror membrane surface. The micromirror with 800 micrometer diameter is designed to be sufficiently compact and efficient so that it can be incorporated into an endoscopic imaging probe in the future. The design, fabrication and characterization of the device are described in this paper. Using the focus-tracking MEMS scanning mirror, we achieved an optical scanning range of >16 degrees with <40 V actuation voltage at resonance and a tunable focal length between infinity and 25 mm with <100V applied bias. PMID:24104304

Line-scan hyperspectral imaging platform for agro-food safety and quality evaluation: System enhancement and characterization

USDA-ARS?s Scientific Manuscript database

Line-scan-based hyperspectral imaging techniques have often served as a research tool to develop rapid multispectral methods based on only a few spectral bands for rapid online applications. With continuing technological advances and greater accessibility to and availability of optoelectronic imagin...

Using GIS Tools and Environmental Scanning to Forecast Industry Workforce Needs

ERIC Educational Resources Information Center

Gaertner, Elaine; Fleming, Kevin; Marquez, Michelle

2009-01-01

The Centers of Excellence (COE) provide regional workforce data on high growth, high demand industries and occupations for use by community colleges in program planning and resource enhancement. This article discusses the environmental scanning research methodology and its application to data-driven decision making in community college program…

Screening of Carotenoids in Tomato Fruits by Using Liquid Chromatography with Diode Array-Linear Ion Trap Mass Spectrometry Detection.

PubMed

Gentili, Alessandra; Caretti, Fulvia; Ventura, Salvatore; Pérez-Fernández, Virginia; Venditti, Alessandro; Curini, Roberta

2015-08-26

This paper presents an analytical strategy for a large-scale screening of carotenoids in tomato fruits by exploiting the potentialities of the triple quadrupole-linear ion trap hybrid mass spectrometer (QqQLIT). The method involves separation on C30 reversed-phase column and identification by means of diode array detection (DAD) and atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). The authentic standards of six model compounds were used to optimize the separative conditions and to predict the chromatographic behavior of untargeted carotenoids. An information dependent acquisition (IDA) was performed with (i) enhanced-mass scan (EMS) as the survey scan, (ii) enhanced-resolution (ER) scan to obtain the exact mass of the precursor ions (16-35 ppm), and (iii) enhanced product ion (EPI) scan as dependent scan to obtain structural information. LC-DAD-multiple reaction monitoring (MRM) chromatograms were also acquired for the identification of targeted carotenoids occurring at low concentrations; for the first time, the relative abundance between the MRM transitions (ion ratio) was used as an extra tool for the MS distinction of structural isomers and the related families of geometrical isomers. The whole analytical strategy was high-throughput, because a great number of experimental data could be acquired with few analytical steps, and cost-effective, because only few standards were used; when applied to characterize some tomato varieties ('Tangerine', 'Pachino', 'Datterino', and 'Camone') and passata of 'San Marzano' tomatoes, our method succeeded in identifying up to 44 carotenoids in the 'Tangerine'" variety.

Nanoscale imaging of photocurrent enhancement by resonator array photovoltaic coatings.

PubMed

Ha, Dongheon; Yoon, Yohan; Zhitenev, Nikolai B

2018-04-06

Nanoscale surface patterning commonly used to increase absorption of solar cells can adversely impact the open-circuit voltage due to increased surface area and recombination. Here, we demonstrate absorptivity and photocurrent enhancement using silicon dioxide (SiO 2 ) nanosphere arrays on a gallium arsenide (GaAs) solar cell that do not require direct surface patterning. Due to the combined effects of thin-film interference and whispering gallery-like resonances within nanosphere arrays, there is more than 20% enhancement in both absorptivity and photocurrent. To determine the effect of the resonance coupling between nanospheres, we perform a scanning photocurrent microscopy based on a near-field scanning optical microscopy measurement and find a substantial local photocurrent enhancement. The nanosphere-based antireflection coating (ARC), made by the Meyer rod rolling technique, is a scalable and a room-temperature process; and, can replace the conventional thin-film-based ARCs requiring expensive high-temperature vacuum deposition.

Nanoscale imaging of photocurrent enhancement by resonator array photovoltaic coatings

NASA Astrophysics Data System (ADS)

Ha, Dongheon; Yoon, Yohan; Zhitenev, Nikolai B.

2018-04-01

Nanoscale surface patterning commonly used to increase absorption of solar cells can adversely impact the open-circuit voltage due to increased surface area and recombination. Here, we demonstrate absorptivity and photocurrent enhancement using silicon dioxide (SiO2) nanosphere arrays on a gallium arsenide (GaAs) solar cell that do not require direct surface patterning. Due to the combined effects of thin-film interference and whispering gallery-like resonances within nanosphere arrays, there is more than 20% enhancement in both absorptivity and photocurrent. To determine the effect of the resonance coupling between nanospheres, we perform a scanning photocurrent microscopy based on a near-field scanning optical microscopy measurement and find a substantial local photocurrent enhancement. The nanosphere-based antireflection coating (ARC), made by the Meyer rod rolling technique, is a scalable and a room-temperature process; and, can replace the conventional thin-film-based ARCs requiring expensive high-temperature vacuum deposition.

Giant optical field enhancement in multi-dielectric stacks by photon scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Ndiaye, C.; Zerrad, M.; Lereu, A. L.; Roche, R.; Dumas, Ph.; Lemarchand, F.; Amra, C.

2013-09-01

Dielectric optical thin films, as opposed to metallic, have been very sparsely explored as good candidates for absorption-based optical field enhancement. In such materials, the low imaginary part of the refractive index implies that absorption processes are usually not predominant. This leads to dielectric-based optical resonances mainly via waveguiding modes. We show here that when properly designed, a multi-layered dielectric thin films stack can give rise to optical resonances linked to total absorption. We report here, on such dielectric stack designed to possess a theoretical optical field enhancement above 1000. Using photon scanning tunneling microscopy, we experimentally evaluate the resulting field enhancement of the stack as well as the associated penetration depth. We thus demonstrate the capability of multi-dielectric stacks in generating giant optical field with tunable penetration depth (down to few dozens of nm).

STM-induced light emission enhanced by weakly coupled organic ad-layers

NASA Astrophysics Data System (ADS)

Cottin, M. C.; Ekici, E.; Bobisch, C. A.

2018-03-01

We analyze the light emission induced by the tunneling current flowing in a scanning tunneling microscopy experiment. In particular, we study the influence of organic ad-layers on the light emission on the initial monolayer of bismuth (Bi) on Cu(111) in comparison to the well-known case of organic ad-layers on Ag(111). On the Bi/Cu(111)-surface, we find that the scanning tunneling microscopy-induced light emission is considerably enhanced if an organic layer, e.g., the fullerene C60 or the perylene derivate perylene-tetracarboxylic-dianhydride, is introduced into the tip-sample junction. The enhancement can be correlated with a peculiarly weak interaction between the adsorbed molecules and the underlying Bi/Cu(111) substrate as compared to the Ag(111) substrate. This allows us to efficiently enhance and tune the coupling of the tunneling current to localized excitations of the tip-sample junction, which in turn couple to radiative decay channels.

Institutional Dynamics of Education Reforms and Quality of Primary Education in Uganda

ERIC Educational Resources Information Center

Nyenje, Aida; James, Nkata L.

2016-01-01

This article scans Uganda's topical responsibility to transformation of the country's primary school education arrangement with attention to the institutional dynamics that constitute school factors such as the curriculum, assessment methods, course content, subject composition, teaching methods, and instructional materials; among others that…

Gelatinisation kinetics of corn and chickpea starches using DSC, RVA, and dynamic rheometry

USDA-ARS?s Scientific Manuscript database

The gelatinisation kinetics (non-isothermal) of corn and chickpea starches at different heating rates were calculated using differential scanning calorimetry (DSC), rapid visco analyser (RVA), and oscillatory dynamic rheometry. The data obtained from the DSC thermogram and the RVA profiles were fitt...

Real time automated inspection

DOEpatents

Fant, Karl M.; Fundakowski, Richard A.; Levitt, Tod S.; Overland, John E.; Suresh, Bindinganavle R.; Ulrich, Franz W.

1985-01-01

A method and apparatus relating to the real time automatic detection and classification of characteristic type surface imperfections occurring on the surfaces of material of interest such as moving hot metal slabs produced by a continuous steel caster. A data camera transversely scans continuous lines of such a surface to sense light intensities of scanned pixels and generates corresponding voltage values. The voltage values are converted to corresponding digital values to form a digital image of the surface which is subsequently processed to form an edge-enhanced image having scan lines characterized by intervals corresponding to the edges of the image. The edge-enhanced image is thresholded to segment out the edges and objects formed by the edges are segmented out by interval matching and bin tracking. Features of the objects are derived and such features are utilized to classify the objects into characteristic type surface imperfections.

Early Dynamic 68Ga-DOTA-D-Phe1-Tyr3-Octreotide PET/CT in Patients With Hepatic Metastases of Neuroendocrine Tumors.

PubMed

Sänger, Philipp Wilhelm; Freesmeyer, Martin

2016-06-01

Whole-body PET with Ga-DOTA-D-Phe-Tyr-octreotide (Ga-DOTATOC) and contrast-enhanced CT (ceCT) are considered a standard for the staging of neuroendocrine tumors (NETs). This study sought to verify whether early dynamic (ed) Ga-DOTATOC PET/CT can reliably detect liver metastases of NETs (hypervascular, nonhypervascular; positive or negative for somatostatin receptors) and to verify if the receptor positivity has a significant impact on the detection of tumor hypervascularization. Twenty-seven patients with NET were studied by ceCT and standard whole-body PET according to established Ga-DOTATOC protocols. In addition, edPET data were obtained by continuous scanning during the first 300 seconds after bolus injections of the radiotracer. Early dynamic PET required an additional low-dose, native CT image of the liver for the purpose of attenuation correction. Time-activity and time-contrast curves were obtained, the latter being calculated by the difference between tumor and reference regions. Early dynamic PET/CT proved comparable with ceCT in readily identifying hypervascular lesions, irrespective of the receptor status, with activities rising within 16 to 40 seconds. Early dynamic PET/CT also readily identified nonhypervascular, receptor-positive lesions. Positive image contrasts were obtained for hypervascular, receptor-positive lesions, whereas early negative contrasts were obtained for nonhypervascular, receptor-negative lesions. The high image contrast of hypervascular NET metastases in early arterial phases suggests that edPET/CT can become a useful alternative in patients with contraindications to ceCT. The high density of somatostatin receptors did not seem to interfere with the detection of the lesion's hypervascularization.

Synergistic effect of scaffold composition and dynamic culturing environment in multilayered systems for bone tissue engineering.

PubMed

Rodrigues, Márcia T; Martins, Albino; Dias, Isabel R; Viegas, Carlos A; Neves, Nuno M; Gomes, Manuela E; Reis, Rui L

2012-11-01

Bone extracellular matrix (ECM) is composed of mineralized collagen fibrils which support biological apatite nucleation that participates in bone outstanding properties. Understanding and mimicking bone morphological and physiological parameters at a biological scale is a major challenge in tissue engineering scaffolding. Using emergent (nano)technologies scaffold designing may be critically improved, enabling highly functional tissue substitutes for bone applications. This study aims to develop novel biodegradable composite scaffolds of tricalcium phosphate (TCPs) and electrospun nanofibers of poly(ϵ-caprolactone) (PCL), combining TCPs osteoconductivity with PCL biocompatibility and elasticity, mimicking bone structure and composition. We hypothesized that scaffolds with such structure/composition would stimulate the proliferation and differentiation of bone marrow stromal cells (BMSCs) towards the osteogenic phenotype. Composite scaffolds, developed by electrospining using consecutive stacked layers of PCL and TCPs, were characterized by FTIR spectroscopy, X-Ray diffraction and scanning electronic microscopy. Cellular behavior was assessed in goat BMSCs seeded onto composite scaffolds and cultured in static or dynamic conditions, using basal or osteogenic media during 7, 14 or 21 days. Cellular proliferation was quantified and osteogenic differentiation confirmed by alkaline phosphatase activity, alizarin red staining and immunocytochemistry for osteocalcin and collagen I. Results suggest that PCL-TCP scaffolds provide a 3D support for gBMSCs proliferation and osteogenic differentiation with production of ECM. TCPs positively stimulate the osteogenic process, especially under dynamic conditions, where PCL-TCP scaffolds are sufficient to promote osteogenic differentiation even in basal medium conditions. The enhancement of the osteogenic potential in dynamic conditions evidences the synergistic effect of scaffold composition and dynamic stimulation in gBMSCs osteogenic differentiation. Copyright © 2012 John Wiley & Sons, Ltd.

The impact of ultra-low amounts of amino-modified MMT on dynamics and properties of densely cross-linked cyanate ester resins

NASA Astrophysics Data System (ADS)

Bershtein, Vladimir; Fainleib, Alexander; Egorova, Larisa; Gusakova, Kristina; Grigoryeva, Olga; Kirilenko, Demid; Konnikov, Semen; Ryzhov, Valery; Yakushev, Pavel; Lavrenyuk, Natalia

2015-04-01

Thermostable nanocomposites based on densely cross-linked cyanate ester resins (CER), derived from bisphenol E and doped by 0.01 to 5 wt. % amino-functionalized 2D montmorillonite (MMT) nanoparticles, were synthesized and characterized using Fourier transform infrared (FTIR), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDXS), wide-angle X-ray diffraction (WAXD), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), far-infrared (Far-IR), and creep rate spectroscopy (CRS) techniques. It was revealed that ultra-low additives, e.g., 0.025 to 0.1 wt. %, of amino-MMT nanolayers covalently embedded into CER network exerted an anomalously large impact on its dynamics and properties resulting, in particular, in some suppression of dynamics, increasing the onset of glass transition temperature by 30° to 40° and twofold rise of modulus in temperature range from 20°C to 200°C. Contrarily, the effects became negligibly small or even negative at increased amino-MMT contents, especially at 2 and 5 wt. %. That could be explained by TEM/EDXS data displaying predominance of individual amino-MMT nanolayers and their thin (2 to 3 nanolayers) stacks over more thick tactoids (5 to 10 nanolayers) and the large amino-MMT aggregates (100 to 500 nm in thickness) reversing the composite structure produced with increasing of amino-MMT content within CER matrix. The revealed effect of ultra-low amino-MMT content testifies in favor of the idea about the extraordinarily enhanced long-range action of the `constrained dynamics' effect in the case of densely cross-linked polymer networks.

Development of a dynamic quality assurance testing protocol for multisite clinical trial DCE-CT accreditation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Driscoll, B.; Keller, H.; Jaffray, D.

2013-08-15

Purpose: Credentialing can have an impact on whether or not a clinical trial produces useful quality data that is comparable between various institutions and scanners. With the recent increase of dynamic contrast enhanced-computed tomography (DCE-CT) usage as a companion biomarker in clinical trials, effective quality assurance, and control methods are required to ensure there is minimal deviation in the results between different scanners and protocols at various institutions. This paper attempts to address this problem by utilizing a dynamic flow imaging phantom to develop and evaluate a DCE-CT quality assurance (QA) protocol.Methods: A previously designed flow phantom, capable of producingmore » predictable and reproducible time concentration curves from contrast injection was fully validated and then utilized to design a DCE-CT QA protocol. The QA protocol involved a set of quantitative metrics including injected and total mass error, as well as goodness of fit comparison to the known truth concentration curves. An additional region of interest (ROI) sensitivity analysis was also developed to provide additional details on intrascanner variability and determine appropriate ROI sizes for quantitative analysis. Both the QA protocol and ROI sensitivity analysis were utilized to test variations in DCE-CT results using different imaging parameters (tube voltage and current) as well as alternate reconstruction methods and imaging techniques. The developed QA protocol and ROI sensitivity analysis was then applied at three institutions that were part of clinical trial involving DCE-CT and results were compared.Results: The inherent specificity of robustness of the phantom was determined through calculation of the total intraday variability and determined to be less than 2.2 ± 1.1% (total calculated output contrast mass error) with a goodness of fit (R{sup 2}) of greater than 0.99 ± 0.0035 (n= 10). The DCE-CT QA protocol was capable of detecting significant deviations from the expected phantom result when scanning at low mAs and low kVp in terms of quantitative metrics (Injected Mass Error 15.4%), goodness of fit (R{sup 2}) of 0.91, and ROI sensitivity (increase in minimum input function ROI radius by 146 ± 86%). These tests also confirmed that the ASIR reconstruction process was beneficial in reducing noise without substantially increasing partial volume effects and that vendor specific modes (e.g., axial shuttle) did not significantly affect the phantom results. The phantom and QA protocol were finally able to quickly (<90 min) and successfully validate the DCE-CT imaging protocol utilized at the three separate institutions of a multicenter clinical trial; thereby enhancing the confidence in the patient data collected.Conclusions: A DCE QA protocol was developed that, in combination with a dynamic multimodality flow phantom, allows the intrascanner variability to be separated from other sources of variability such as the impact of injection protocol and ROI selection. This provides a valuable resource that can be utilized at various clinical trial institutions to test conformance with imaging protocols and accuracy requirements as well as ensure that the scanners are performing as expected for dynamic scans.« less

Absolute quantification of regional renal blood flow in swine by dynamic contrast-enhanced magnetic resonance imaging using a blood pool contrast agent.

PubMed

Lüdemann, Lutz; Nafz, Benno; Elsner, Franz; Grosse-Siestrup, Christian; Meissler, Michael; Kaufels, Nicola; Rehbein, Hagen; Persson, Pontus B; Michaely, Henrik J; Lengsfeld, Philipp; Voth, Matthias; Gutberlet, Matthias

2009-03-01

To evaluate for the first time in an animal model the possibility of absolute regional quantification of renal medullary and cortical perfusion by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) using a blood pool contrast agent. A total of 18 adult female pigs (age, 16-22 weeks; body weight, 45-65 kg; no dietary restrictions) were investigated by DCE-MRI. Absolute renal blood flow (RBF) measured by an ultrasound transit time flow probe around the renal vein was used as the standard of reference. An inflatable stainless cuff placed around the renal artery near its origin from the abdominal aorta was used to reduce RBF to 60%, 40%, and 20% of the baseline flow. The last measurement was performed with the cuff fully reopened. Absolute RBF values during these 4 perfusion states were compared with the results of DCE-MRI performed on a 1.5-T scanner with an 8-channel phased-array surface coil. All scans were acquired in breath-hold technique in the coronal plane using a field of view of 460 mm.Each dynamic scan commenced with a set of five 3D T1-weighted gradient echo sequences with different flip angles (alpha = 2 degrees, 5 degrees, 10 degrees, 20 degrees, 30 degrees): TE, 0.88 milliseconds; TR, 2.65 milliseconds; slice thickness, 8.8 mm for 4 slices; acquisition matrix, 128 x 128; and acquisitions, 4. These data served to calculate 3D intrinsic longitudinal relaxation rate maps (R10) and magnetization (M0). Immediately after these images, the dynamic 3D T1-weighted gradient echo images were acquired with the same parameters and a constant alpha = 30 degrees, half Fourier, 1 acquisition, 64 frames, a time interval of 1.65 seconds between each frame, and a total duration of 105.6. Three milliliters of an albumin-binding blood pool contrast agent (0.25 mmol/mL gadofosveset trisodium, Vasovist, Bayer Schering Pharma AG, Berlin, Germany) was injected at a rate of 3 mL/s. Perfusion was calculated using the arterial input function from the aorta, which was extracted from the dynamic relaxation rate change maps and perfusion images were calculated on a voxel-by-voxel basis using a singular value decomposition. In 11 pigs, 4 different perfusion states were investigated sequentially. The reduced kidney perfusion measured by ultrasound highly correlated with total renal blood flow determined by DCE-MRI, P < 0.001. The correlation coefficient between both measurements was 0.843. Regional cortical and medullary renal flow was also highly correlated (r = 0.77/0.78, P < 0.001) with the degree of flow reduction. Perfusion values smaller than 50 mL/min/100 cm were overestimated by MRI, high perfusion values slightly underestimated. DCE-MRI using a blood pool contrast agent allows absolute quantification of total kidney perfusion as well as separate determination of cortical and medullary flow. The results show that our technique has sufficient accuracy and reproducibility to be transferred to the clinical setting.

Low dose dynamic myocardial CT perfusion using advanced iterative reconstruction

NASA Astrophysics Data System (ADS)

Eck, Brendan L.; Fahmi, Rachid; Fuqua, Christopher; Vembar, Mani; Dhanantwari, Amar; Bezerra, Hiram G.; Wilson, David L.

2015-03-01

Dynamic myocardial CT perfusion (CTP) can provide quantitative functional information for the assessment of coronary artery disease. However, x-ray dose in dynamic CTP is high, typically from 10mSv to >20mSv. We compared the dose reduction potential of advanced iterative reconstruction, Iterative Model Reconstruction (IMR, Philips Healthcare, Cleveland, Ohio) to hybrid iterative reconstruction (iDose4) and filtered back projection (FBP). Dynamic CTP scans were obtained using a porcine model with balloon-induced ischemia in the left anterior descending coronary artery to prescribed fractional flow reserve values. High dose dynamic CTP scans were acquired at 100kVp/100mAs with effective dose of 23mSv. Low dose scans at 75mAs, 50mAs, and 25mAs were simulated by adding x-ray quantum noise and detector electronic noise to the projection space data. Images were reconstructed with FBP, iDose4, and IMR at each dose level. Image quality in static CTP images was assessed by SNR and CNR. Blood flow was obtained using a dynamic CTP analysis pipeline and blood flow image quality was assessed using flow-SNR and flow-CNR. IMR showed highest static image quality according to SNR and CNR. Blood flow in FBP was increasingly over-estimated at reduced dose. Flow was more consistent for iDose4 from 100mAs to 50mAs, but was over-estimated at 25mAs. IMR was most consistent from 100mAs to 25mAs. Static images and flow maps for 100mAs FBP, 50mAs iDose4, and 25mAs IMR showed comparable, clear ischemia, CNR, and flow-CNR values. These results suggest that IMR can enable dynamic CTP at significantly reduced dose, at 5.8mSv or 25% of the comparable 23mSv FBP protocol.

Lift enhancement by bats' dynamically changing wingspan

PubMed Central

Wang, Shizhao; Zhang, Xing; He, Guowei; Liu, Tianshu

2015-01-01

This paper elucidates the aerodynamic role of the dynamically changing wingspan in bat flight. Based on direct numerical simulations of the flow over a slow-flying bat, it is found that the dynamically changing wingspan can significantly enhance the lift. Further, an analysis of flow structures and lift decomposition reveal that the elevated vortex lift associated with the leading-edge vortices intensified by the dynamically changing wingspan considerably contributed to enhancement of the time-averaged lift. The nonlinear interaction between the dynamically changing wing and the vortical structures plays an important role in the lift enhancement of a flying bat in addition to the geometrical effect of changing the lifting-surface area in a flapping cycle. In addition, the dynamically changing wingspan leads to the higher efficiency in terms of generating lift for a given amount of the mechanical energy consumed in flight. PMID:26701882

Influence of Contrast Media on Bone Mineral Density (BMD) Measurements from Routine Contrast-Enhanced MDCT Datasets using a Phantom-less BMD Measurement Tool.

PubMed

Toelly, Andrea; Bardach, Constanze; Weber, Michael; Gong, Rui; Lai, Yanbo; Wang, Pei; Guo, Yulin; Kirschke, Jan; Baum, Thomas; Gruber, Michael

2017-06-01

Aim  To evaluate the differences in phantom-less bone mineral density (BMD) measurements in contrast-enhanced routine MDCT scans at different contrast phases, and to develop an algorithm for calculating a reliable BMD value. Materials and Methods  112 postmenopausal women from the age of 40 to 77 years (mean age: 57.31 years; SD 9.61) who underwent a clinically indicated MDCT scan, consisting of an unenhanced, an arterial, and a venous phase, were included. A retrospective analysis of the BMD values of the Th12 to L4 vertebrae in each phase was performed using a commercially available phantom-less measurement tool. Results  The mean BMD value in the unenhanced MDCT scans was 79.76 mg/cm³ (SD 31.20), in the arterial phase it was 85.09 mg/cm³ (SD 31.61), and in the venous phase it was 86.18 mg/cm³ (SD 31.30). A significant difference (p < 0.001) was found between BMD values on unenhanced and contrast-enhanced MDCT scans. There was no significant difference between BMD values in the arterial and venous phases (p = 0.228). The following conversion formulas were calculated using linear regression: unenhanced BMD = -2.287 + 0.964 * [arterial BMD value] and -4.517 + 0.978 * [venous BMD value]. The intrarater agreement of BMD measurements was calculated with an intraclass correlation (ICC) of 0.984 and the interobserver reliability was calculated with an ICC of 0.991. Conclusion  Phantom-less BMD measurements in contrast-enhanced MDCT scans result in increased mean BMD values, but, with the formulas applied in our study, a reliable BMD value can be calculated. However, the mean BMD values did not differ significantly between the arterial and venous phases. Key points   · BMD can be assessed on routine CT scans using a phantom-less tool.. · i. v. contrast agent significantly elevates BMD values measured on routine CT scans.. · BMD values measured in the arterial and venous phase did not differ significantly.. · Conversion formulas were defined for the calculation of a reliable BMD.. · The phantom-less tool showed good reliability and is a promising method.. Citation Format · Toelly A, Bardach C, Weber M et al. Influence of Contrast Media on Bone Mineral Density (BMD) Measurements from Routine Contrast-Enhanced MDCT Datasets using a Phantom-less BMD Measurement Tool. Fortschr Röntgenstr 2017; 189: 537 - 543. © Georg Thieme Verlag KG Stuttgart · New York.

Dynamic Denoising of Tracking Sequences

PubMed Central

Michailovich, Oleg; Tannenbaum, Allen

2009-01-01

In this paper, we describe an approach to the problem of simultaneously enhancing image sequences and tracking the objects of interest represented by the latter. The enhancement part of the algorithm is based on Bayesian wavelet denoising, which has been chosen due to its exceptional ability to incorporate diverse a priori information into the process of image recovery. In particular, we demonstrate that, in dynamic settings, useful statistical priors can come both from some reasonable assumptions on the properties of the image to be enhanced as well as from the images that have already been observed before the current scene. Using such priors forms the main contribution of the present paper which is the proposal of the dynamic denoising as a tool for simultaneously enhancing and tracking image sequences. Within the proposed framework, the previous observations of a dynamic scene are employed to enhance its present observation. The mechanism that allows the fusion of the information within successive image frames is Bayesian estimation, while transferring the useful information between the images is governed by a Kalman filter that is used for both prediction and estimation of the dynamics of tracked objects. Therefore, in this methodology, the processes of target tracking and image enhancement “collaborate” in an interlacing manner, rather than being applied separately. The dynamic denoising is demonstrated on several examples of SAR imagery. The results demonstrated in this paper indicate a number of advantages of the proposed dynamic denoising over “static” approaches, in which the tracking images are enhanced independently of each other. PMID:18482881

Arterial tree tracking from anatomical landmarks in magnetic resonance angiography scans

NASA Astrophysics Data System (ADS)

O'Neil, Alison; Beveridge, Erin; Houston, Graeme; McCormick, Lynne; Poole, Ian

2014-03-01

This paper reports on arterial tree tracking in fourteen Contrast Enhanced MRA volumetric scans, given the positions of a predefined set of vascular landmarks, by using the A* algorithm to find the optimal path for each vessel based on voxel intensity and a learnt vascular probability atlas. The algorithm is intended for use in conjunction with an automatic landmark detection step, to enable fully automatic arterial tree tracking. The scan is filtered to give two further images using the top-hat transform with 4mm and 8mm cubic structuring elements. Vessels are then tracked independently on the scan in which the vessel of interest is best enhanced, as determined from knowledge of typical vessel diameter and surrounding structures. A vascular probability atlas modelling expected vessel location and orientation is constructed by non-rigidly registering the training scans to the test scan using a 3D thin plate spline to match landmark correspondences, and employing kernel density estimation with the ground truth center line points to form a probability density distribution. Threshold estimation by histogram analysis is used to segment background from vessel intensities. The A* algorithm is run using a linear cost function constructed from the threshold and the vascular atlas prior. Tracking results are presented for all major arteries excluding those in the upper limbs. An improvement was observed when tracking was informed by contextual information, with particular benefit for peripheral vessels.

Quantification of the uncertainty in coronary CTA plaque measurements using dynamic cardiac phantom and 3D-printed plaque models

NASA Astrophysics Data System (ADS)

Richards, Taylor; Sturgeon, Gregory M.; Ramirez-Giraldo, Juan Carlos; Rubin, Geoffrey; Segars, Paul; Samei, Ehsan

2017-03-01

The purpose of this study was to quantify the accuracy of coronary computed tomography angiography (CTA) stenosis measurements using newly developed physical coronary plaque models attached to a base dynamic cardiac phantom (Shelley Medical DHP-01). Coronary plaque models (5 mm diameter, 50% stenosis, and 32 mm long) were designed and 3D-printed with tissue equivalent materials (calcified plaque with iodine enhanced lumen). Realistic cardiac motion was achieved by fitting known cardiac motion vectors to left ventricle volume-time curves to create synchronized heart motion profiles executed by the base cardiac phantom. Realistic coronary CTA acquisition was accomplished by synthesizing corresponding ECG waveforms for gating and reconstruction purposes. All scans were acquired using a retrospective gating technique on a dual-source CT system (Siemens SOMATOM FLASH) with 75ms temporal resolution. Multi-planar reformatted images were reconstructed along vessel centerlines and the enhanced lumens were manually segmented by 5 independent operators. On average, the stenosis measurement accuracy was 0.9% positive bias for the motion free condition (0 bpm). The measurement accuracy monotonically decreased to 18.5% negative bias at 90 bpm. Contrast-tonoise (CNR), vessel circularity, and segmentation conformity also decreased monotonically with increasing heart rate. These results demonstrate successful implementation of the base cardiac phantom with 3D-printed coronary plaque models, adjustable motion profiles, and coordinated ECG waveforms. They further show the utility of the model to ascertain metrics of coronary CT accuracy and image quality under a variety of plaque, motion, and acquisition conditions.

18F-Fluorodeoxyglucose PET/CT and dynamic contrast-enhanced MRI as imaging biomarkers in malignant pleural mesothelioma.

PubMed

Hall, David O; Hooper, Clare E; Searle, Julie; Darby, Michael; White, Paul; Harvey, John E; Braybrooke, Jeremy P; Maskell, Nick A; Masani, Vidan; Lyburn, Iain D

2018-02-01

The purpose of this study was to compare the use of fluorine-18-fluorodeoxyglucose (F-FDG) PET with computed tomography (CT) and dynamic contrast-enhanced (DCE) MRI to predict prognosis and monitor treatment in malignant pleural mesothelioma. F-FDG PET/CT and DCE-MRI studies carried out as part of the South West Area Mesothelioma Pemetrexed trial were used. F-FDG PET/CT and DCE-MRI studies were carried out before treatment, and after two cycles of chemotherapy, on patients treated with pemetrexed and cisplatin. A total of 73 patients were recruited, of whom 65 had PET/CT and DCE-MRI scans. Baseline measurements from F-FDG PET/CT (maximum standardized uptake value, metabolic tumour volume and total lesion glycolysis) and DCE-MRI (integrated area under the first 90s of the curve and washout slope) were compared with overall survival (OS) using Kaplan-Meier and Cox regression analyses, and changes in imaging measurements were compared with disease progression. PET/CT and DCE-MRI measurements were not correlated with each other. Maximum standardized uptake value, metabolic tumour volume and total lesion glycolysis were significantly related to OS with Cox regression analysis and Kaplan-Meir analysis, and DCE-MRI washout curve shape was significantly related to OS. DCE-MRI curve shape can be combined with F-FDG PET/CT to give additional prognostic information. Changes in measurements were not related to progression-free survival. F-FDG PET/CT and DCE-MRI give prognostic information in malignant pleural mesothelioma. Neither PET/CT nor DCE-MRI is useful for monitoring disease progression.

Preparation of zein nanoparticles by using solution-enhanced dispersion with supercritical CO2 and elucidation with computational fluid dynamics

PubMed Central

Li, Sining; Zhao, Yaping

2017-01-01

Nanoparticles have attracted more and more attention in the medicinal field. Zein is a biomacromolecule and can be used as a carrier for delivering active ingredients to prepare controlled release drugs. In this article, we presented the preparation of zein nanoparticles by solution-enhanced dispersion by supercritical CO2 (SEDS) approach. Scanning electron microscopy and transmission electron microscopy were applied to characterize the size and morphology of the obtained particles. The nozzle structure and the CO2 flow rate greatly affected the morphology and the size of the particles. The size of zein was able to be reduced to 50–350 nm according to the different conditions. The morphologies of the resultant zein were either sphere or the filament network consisted of nanoparticles. The influence of the nozzle structure and the CO2 flow rate on the velocity field was elucidated by using computational fluid dynamics. The nozzle structure and the CO2 flow rate greatly affected the distribution of the velocity field. However, a similar velocity field could also be obtained when the nozzle structure or the CO2 flow rate, or both were different. Therefore, the influence of the nozzle structure and the CO2 flow rate on the size and morphology of the particles, can boil down to the velocity field. The results demonstrated that the velocity field can be a potential criterion for producing nanoparticles with controllable morphology and size, which is useful to scale-up the SEDS process. PMID:28496324

Measurements of Ion-Neutral Coupling in the Auroral F Region in Response to Increases in Particle Precipitation

NASA Astrophysics Data System (ADS)

Kiene, A.; Bristow, W. A.; Conde, M. G.; Hampton, D. L.

2018-05-01

Neutral winds are a key factor in the dynamics of the ionosphere-thermosphere system. Previous observations have shown that neutral and ion flows are strongly coupled during periods of auroral activity when ion drag forcing can become the dominant force driving neutral wind flow. This is primarily due to increases in ion density due to enhanced particle precipitation as well as associated increases the strength of the electric fields that drive ion motions. Due to this strong coupling, numerical simulations of neutral dynamics have difficulty reproducing neutral wind observations when they are driven by modeled precipitation and modeled convection. It is therefore desirable whenever possible to have concurrent coincident measurements of auroral precipitation and ion convection. Recent advancements in high-resolution fitting of Super Dual Auroral Radar Network ion convection data have enabled the generation of steady maps of ion drifts over Alaska, coinciding with several optics sites. The Super Dual Auroral Radar Network measurements are compared with scanning Doppler imager neutral wind measurements at similar altitude, providing direct comparisons of ion and neutral velocities over a wide field and for long periods throughout the night. Also present are a digital all-sky imager and a meridian spectrograph, both of which provide measurements of auroral intensity on several wavelengths. In this study, we combine these data sets to present three case studies that show significant correlation between increases in F region precipitation and enhancements in ion-neutral coupling in the evening sector. We investigate the time scales over which the coupling takes place and compare our findings to previous measurements.

Super-resolution chemical imaging with dynamic placement of plasmonic hotspots

NASA Astrophysics Data System (ADS)

Olson, Aeli P.; Ertsgaard, Christopher T.; McKoskey, Rachel M.; Rich, Isabel S.; Lindquist, Nathan C.

2015-08-01

We demonstrate dynamic placement of plasmonic "hotspots" for super-resolution chemical imaging via Surface Enhanced Raman Spectroscopy (SERS). A silver nanohole array surface was coated with biological samples and illuminated with a laser. Due to the large plasmonic field enhancements, blinking behavior of the SERS hotspots was observed and processed using a Stochastic Optical Reconstruction Microscopy (STORM) algorithm enabling localization to within 10 nm. However, illumination of the sample with a single static laser beam (i.e., a slightly defocused Gaussian beam) only produced SERS hotspots in fixed locations on the surface, leaving noticeable gaps in any final image. But, by using a spatial light modulator (SLM), the illumination profile of the beam could be altered, shifting any hotspots across the nanohole array surface in sub-wavelength steps. Therefore, by properly structuring an illuminating light field with the SLM, we show the possibility of positioning plasmonic hotspots over a metallic nanohole surface on-the-fly. Using this and our SERS-STORM imaging technique, we show potential for high-resolution chemical imaging without the noticeable gaps that were present with static laser illumination. Interestingly, even illuminating the surface with randomly shifting SLM phase profiles was sufficient to completely fill in a wide field of view for super-resolution SERS imaging of a single strand of 100-nm thick collagen protein fibrils. Images were then compared to those obtained with a scanning electron microscope (SEM). Additionally, we explored alternative methods of phase shifting other than holographic illumination through the SLM to create localization of hotspots necessary for SERS-STORM imaging.

[Design and verification of Luo-Ye pump-based stress formation for cultivation of tissue-engineered blood vessel].

PubMed

Liao, Wen-Jun; Chen, Wan-Wen; Wen, Zhang; Wu, Yue-Heng; Li, Dong-Feng; Zhou, Jia-Hui; Zheng, Jian-Yi; Lin, Zhan-Yi

2016-06-20

To improve Luo-Ye pump-based stress-forming system and optimize the stimulating effect on smooth muscle cells during cultivation of tissue-engineered blood vessels (TEBV). A new Luo-Ye pump-based TEBV 3D culture system was developed by adding an air pump to the output of the bioreactor. A pressure guide wire was used to measure the stress at different points of the silicone tube inside the TEBV bio-reactor, and fitting curves of the stress changes over time was created using Origin 8.0 software. The TEBVs were constructed by seeding vascular smooth muscle cells (VSMCs) isolated from human umbilical artery on polyglycolic acid (PGA) and cultured under dynamic conditions with 40 mmHg resistance (improved group), dynamic conditions without resistance (control group) or static condition (static group) for 4 weeks. The harvested TEBVs were then examined with HE staining, masson staining, α-SMA immunohistochemical staining, and scanning and transmission electron microscopy with semi-quantitative analysis of collagen content and α-SMA expression. The measured stress values and the fitting curves showed that the stress stimuli from the Luo-Ye pump were enhanced by adding an air pump to the output of the bioreactor. Histological analysis revealed improved VSMC density, collagen content and α-SMA expression in the TEBVs constructed with the improved method as compared with those in the control and static groups. Adding an air pump to the Luo-Ye pump significantly enhances the stress stimulation in the TEBV 3-D culture system to promote the secretion function of VSMCs.

Development of solid dispersions of artemisinin for transdermal delivery.

PubMed

Shahzad, Yasser; Sohail, Sadia; Arshad, Muhammad Sohail; Hussain, Talib; Shah, Syed Nisar Hussain

2013-11-30

Solid dispersions of the poorly soluble drug artemisinin were developed using polymer blends of polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) with the aim of enhancing solubility and in vitro permeation of artemisinin through skin. Formulations were characterised using a combination of molecular dynamics (MD) simulations, differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Solubility of artemisinin was determined in two solvents: de-ionised water and phosphate buffered saline (PBS; pH 7.4), while in vitro drug permeation studies were carried out using rabbit skin as a model membrane. MD simulations revealed miscibility between the drug and polymers. DSC confirmed the molecular dispersion of the drug in the polymer blend. Decrease in crystallinity of artemisinin with respect to polymer content and the absence of specific drug-polymer interactions were confirmed using XRD and FT-IR, respectively. The solubility of artemisinin was dramatically enhanced for the solid dispersions, as was the permeation of artemisinin from saturated solid-dispersion vehicles relative to that from saturated solutions of the pure drug. The study suggests that high energy solid forms of artemisinin could possibly enable transdermal delivery of artemisinin. Copyright © 2013 Elsevier B.V. All rights reserved.

Nanomelatonin triggers superior anticancer functionality in a human malignant glioblastoma cell line

NASA Astrophysics Data System (ADS)

Yadav, Sanjeev Kumar; Srivastava, Anup Kumar; Dev, Atul; Kaundal, Babita; Choudhury, Subhasree Roy; Karmakar, Surajit

2017-09-01

Melatonin (MEL) has promising medicinal value as an anticancer agent in a variety of malignancies, but there are difficulties in achieving a therapeutic dose due to its short half-life, low bioavailability, poor solubility and extensive first-pass metabolism. In this study chitosan/tripolyphosphate (TPP) nanoparticles were prepared by an ionic gelation method to overcome the therapeutic challenges of melatonin and to improve its anticancer efficacy. Characterization of the melatonin-loaded chitosan (MEL-CS) nanoformulation was performed using transmission and scanning electron microscopies, dynamic light scattering, Fourier transform infrared spectroscopy, Raman spectroscopy and x-ray diffraction. In vitro release, cellular uptake and efficacy studies were tested for their enhanced anticancer potential in human U87MG glioblastoma cells. Confocal studies revealed higher cellular uptake of MEL-CS nanoparticles and enhanced anticancer efficacy in human malignant glioblastoma cancer cells than in healthy non-malignant human HEK293T cells in mono- and co-culture models. Our study has shown for the first time that MEL-CS nanocomposites are therapeutically more effective as compared to free MEL at inducing functional anticancer efficacy in the human brain tumour U87MG cell line.

One-pot synthesis of multifunctional nanoscale metal-organic frameworks as an effective antibacterial agent against multidrug-resistant Staphylococcus aureus

NASA Astrophysics Data System (ADS)

Chowdhuri, Angshuman Ray; Das, Balaram; Kumar, Amit; Tripathy, Satyajit; Roy, Somenath; Sahu, Sumanta Kumar

2017-03-01

Drug-resistant bacteria are an increasingly serious threat to global public health. In particular, infections from multidrug-resistant (MDR) Gram-positive bacteria (i.e. Staphylococcus aureus) are growing global health concerns. In this work, we report the first use of nanoscale metal-organic frameworks (NMOFs) coencapsulating an antibiotic (vancomycin) and targeting ligand (folic acid) in one pot to enhance therapeutic efficacy against MDR S. aureus. Zeolitic imidazolate framework (ZIF-8) NMOFs, which have globular morphologies coencapsulating vancomycin and folic acid, are characterized by transmission electron microscopy, field-emission scanning electron microscopy, powder x-ray diffraction, ulltraviolet-visible spectroscopy, and dynamic light-scattering techniques. We determined that the presence of folic acid on the surface of the NMOFs is significant in the sense of effective uptake by MDR S. aureus through endocytosis. The functionalized NMOFs transport vancomycin across the cell wall of MDR S. aureus and enhance antibacterial activity, which has been confirmed from studies of the minimum inhibitory concentration, minimum bactericidal concentration, cytotoxicity of bacterial cells, and generation of reactive oxygen species. This work shows that functionalized NMOFs hold great promise for effective treatment of MDR S. aureus.

Hybrid boron nitride-natural fiber composites for enhanced thermal conductivity.

PubMed

Xia, Changlei; Garcia, Andres C; Shi, Sheldon Q; Qiu, Ying; Warner, Nathaniel; Wu, Yingji; Cai, Liping; Rizvi, Hussain R; D'Souza, Nandika A; Nie, Xu

2016-10-05

Thermal conductivity was dramatically increased after adding natural fiber into hexagonal boron nitride (hBN)/epoxy composites. Although natural fiber does not show high-thermal conductivity itself, this study found that the synergy of natural fiber with hBN could significantly improve thermal conductivity, compared with that solely using hBN. A design of mixtures approach using constant fibers with increasing volume fractions of hBN was examined and compared. The thermal conductivity of the composite containing 43.6% hBN, 26.3% kenaf fiber and 30.1% epoxy reached 6.418 W m -1 K -1 , which was 72.3% higher than that (3.600 W m -1 K -1 ) of the 69.0% hBN and 31.0% epoxy composite. Using the scanning electron microscope (SEM) and micro computed tomography (micro-CT), it was observed that the hBN powders were well distributed and ordered on the fiber surfaces enhancing the ceramic filler's interconnection, which may be the reason for the increase in thermal conductivity. Additionally, the results from mechanical and dynamic mechanical tests showed that performances dramatically improved after adding kenaf fibers into the hBN/epoxy composite, potentially benefiting the composite's use as an engineered material.

Hybrid boron nitride-natural fiber composites for enhanced thermal conductivity

NASA Astrophysics Data System (ADS)

Xia, Changlei; Garcia, Andres C.; Shi, Sheldon Q.; Qiu, Ying; Warner, Nathaniel; Wu, Yingji; Cai, Liping; Rizvi, Hussain R.; D'Souza, Nandika A.; Nie, Xu

2016-10-01

Thermal conductivity was dramatically increased after adding natural fiber into hexagonal boron nitride (hBN)/epoxy composites. Although natural fiber does not show high-thermal conductivity itself, this study found that the synergy of natural fiber with hBN could significantly improve thermal conductivity, compared with that solely using hBN. A design of mixtures approach using constant fibers with increasing volume fractions of hBN was examined and compared. The thermal conductivity of the composite containing 43.6% hBN, 26.3% kenaf fiber and 30.1% epoxy reached 6.418 W m-1 K-1, which was 72.3% higher than that (3.600 W m-1 K-1) of the 69.0% hBN and 31.0% epoxy composite. Using the scanning electron microscope (SEM) and micro computed tomography (micro-CT), it was observed that the hBN powders were well distributed and ordered on the fiber surfaces enhancing the ceramic filler’s interconnection, which may be the reason for the increase in thermal conductivity. Additionally, the results from mechanical and dynamic mechanical tests showed that performances dramatically improved after adding kenaf fibers into the hBN/epoxy composite, potentially benefiting the composite’s use as an engineered material.

Compact plane illumination plugin device to enable light sheet fluorescence imaging of multi-cellular organisms on an inverted wide-field microscope

PubMed Central

Guan, Zeyi; Lee, Juhyun; Jiang, Hao; Dong, Siyan; Jen, Nelson; Hsiai, Tzung; Ho, Chih-Ming; Fei, Peng

2015-01-01

We developed a compact plane illumination plugin (PIP) device which enabled plane illumination and light sheet fluorescence imaging on a conventional inverted microscope. The PIP device allowed the integration of microscope with tunable laser sheet profile, fast image acquisition, and 3-D scanning. The device is both compact, measuring approximately 15 by 5 by 5 cm, and cost-effective, since we employed consumer electronics and an inexpensive device molding method. We demonstrated that PIP provided significant contrast and resolution enhancement to conventional microscopy through imaging different multi-cellular fluorescent structures, including 3-D branched cells in vitro and live zebrafish embryos. Imaging with the integration of PIP greatly reduced out-of-focus contamination and generated sharper contrast in acquired 2-D plane images when compared with the stand-alone inverted microscope. As a result, the dynamic fluid domain of the beating zebrafish heart was clearly segmented and the functional monitoring of the heart was achieved. Furthermore, the enhanced axial resolution established by thin plane illumination of PIP enabled the 3-D reconstruction of the branched cellular structures, which leads to the improvement on the functionality of the wide field microscopy. PMID:26819828

Compact plane illumination plugin device to enable light sheet fluorescence imaging of multi-cellular organisms on an inverted wide-field microscope.

PubMed

Guan, Zeyi; Lee, Juhyun; Jiang, Hao; Dong, Siyan; Jen, Nelson; Hsiai, Tzung; Ho, Chih-Ming; Fei, Peng

2016-01-01

We developed a compact plane illumination plugin (PIP) device which enabled plane illumination and light sheet fluorescence imaging on a conventional inverted microscope. The PIP device allowed the integration of microscope with tunable laser sheet profile, fast image acquisition, and 3-D scanning. The device is both compact, measuring approximately 15 by 5 by 5 cm, and cost-effective, since we employed consumer electronics and an inexpensive device molding method. We demonstrated that PIP provided significant contrast and resolution enhancement to conventional microscopy through imaging different multi-cellular fluorescent structures, including 3-D branched cells in vitro and live zebrafish embryos. Imaging with the integration of PIP greatly reduced out-of-focus contamination and generated sharper contrast in acquired 2-D plane images when compared with the stand-alone inverted microscope. As a result, the dynamic fluid domain of the beating zebrafish heart was clearly segmented and the functional monitoring of the heart was achieved. Furthermore, the enhanced axial resolution established by thin plane illumination of PIP enabled the 3-D reconstruction of the branched cellular structures, which leads to the improvement on the functionality of the wide field microscopy.

Laser development for optimal helicopter obstacle warning system LADAR performance

NASA Astrophysics Data System (ADS)

Yaniv, A.; Krupkin, V.; Abitbol, A.; Stern, J.; Lurie, E.; German, A.; Solomonovich, S.; Lubashitz, B.; Harel, Y.; Engart, S.; Shimoni, Y.; Hezy, S.; Biltz, S.; Kaminetsky, E.; Goldberg, A.; Chocron, J.; Zuntz, N.; Zajdman, A.

2005-04-01

Low lying obstacles present immediate danger to both military and civilian helicopters performing low-altitude flight missions. A LADAR obstacle detection system is the natural solution for enhancing helicopter safety and improving the pilot situation awareness. Elop is currently developing an advanced Surveillance and Warning Obstacle Ranging and Display (SWORD) system for the Israeli Air Force. Several key factors and new concepts have contributed to system optimization. These include an adaptive FOV, data memorization, autonomous obstacle detection and warning algorithms and the use of an agile laser transmitter. In the present work we describe the laser design and performance and discuss some of the experimental results. Our eye-safe laser is characterized by its pulse energy, repetition rate and pulse length agility. By dynamically controlling these parameters, we are able to locally optimize the system"s obstacle detection range and scan density in accordance with the helicopter instantaneous maneuver.

Plasmonic superfocusing on metallic tips for near-field optical imaging and spectroscopy

NASA Astrophysics Data System (ADS)

Neacsu, Catalin C.; Olmon, Rob; Berweger, Samuel; Kappus, Alexandria; Kirchner, Friedrich; Ropers, Claus; Saraf, Lax; Raschke, Markus B.

2008-03-01

Realization of localized light sources through nonlocal excitation is important in the context of plasmon photonics, molecular sensing, and in particular near-field optical techniques. Here, the efficient conversion of propagating surface plasmons, launched on the shaft of a scanning probe tip, into localized plasmon at the apex provides a true nanoconfined light source. Focused ion beam milling is used to generate periodic surface nanostructures on the tip shaft that allow for tailoring the plasmon excitation. Using ultrashort visible and mid-IR transients the dynamics of the propagation and subsequent scattered emission is characterized. The strong field enhancement and spatial field confinement at the apex is demonstrated studying the coupling of the tip in near-field interaction with a flat sample surface. It is used in scattering near-field spectroscopic imaging (s-SNOM) to probe surface nanostructures with spatial resolution down to 10 nm.

Effect of Loading Rate and Surface Conditions on Flexural Strength of Borosilicate Glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nie, X; Chen, Wayne; Wereszczak, Andrew A

2009-01-01

This study evaluates the loading rate and surface condition dependence of the flexural strength of a borosilicate glass. The glass specimens are subjected to three different surface treatments before four-point bending tests to study the effect of surface flaws. Quasistatic (Material Test System 810) and dynamic (Kolsky bar) experiments are performed at loading rates ranging from 0.7 to 4 x 10{sup 6} MPa/s. The results show that the flexural strength of the borosilicate glass has a strong dependence on the loading rate. A chemically etched surface produces an enhanced flexural strength by about an order of magnitude. Scanning electron microscopymore » images on fracture surfaces indicate that the failure is governed by different types of flaws under different surface treatment conditions. Edge failure is also identified for samples possessing high flexural strength.« less

Enhancing the Dyeability of Polypropylene Fibers by Melt Blending with Polyethylene Terephthalate

PubMed Central

Moradian, Siamak; Ameri, Farhad

2013-01-01

Attempts were made to modify polypropylene fibers by melt blending with polyethylene terephthalate in order to enhance the dyeability of the resultant fiber. Five blends of polypropylene/polyethylene terephthalate/compatibilizer were prepared and subsequently spun into fibers. Three disperse dyes were used to dye such modified fibers at boiling and 130°C. The dyeing performance of the blend fibers, as well as the morphological, chemical, thermal, and mechanical properties, of the corresponding blends was characterized by means of spectrophotometry, polarized optical microscopy, scanning electron microscopy (SEM), FT-IR spectroscopy, differential scanning calorimetry (DSC), and tensile testing. PMID:24288485

NASA Tech Briefs, September 2011

NASA Technical Reports Server (NTRS)

2011-01-01

Topics covered include: Fused Reality for Enhanced Flight Test Capabilities; Thermography to Inspect Insulation of Large Cryogenic Tanks; Crush Test Abuse Stand; Test Generator for MATLAB Simulations; Dynamic Monitoring of Cleanroom Fallout Using an Air Particle Counter; Enhancement to Non-Contacting Stress Measurement of Blade Vibration Frequency; Positively Verifying Mating of Previously Unverifiable Flight Connectors; Radiation-Tolerant Intelligent Memory Stack - RTIMS; Ultra-Low-Dropout Linear Regulator; Excitation of a Parallel Plate Waveguide by an Array of Rectangular Waveguides; FPGA for Power Control of MSL Avionics; UAVSAR Active Electronically Scanned Array; Lockout/Tagout (LOTO) Simulator; Silicon Carbide Mounts for Fabry-Perot Interferometers; Measuring the In-Process Figure, Final Prescription, and System Alignment of Large; Optics and Segmented Mirrors Using Lidar Metrology; Fiber-Reinforced Reactive Nano-Epoxy Composites; Polymerization Initiated at the Sidewalls of Carbon Nanotubes; Metal-Matrix/Hollow-Ceramic-Sphere Composites; Piezoelectrically Enhanced Photocathodes; Iridium-Doped Ruthenium Oxide Catalyst for Oxygen Evolution; Improved Mo-Re VPS Alloys for High-Temperature Uses; Data Service Provider Cost Estimation Tool; Hybrid Power Management-Based Vehicle Architecture; Force Limit System; Levitated Duct Fan (LDF) Aircraft Auxiliary Generator; Compact, Two-Sided Structural Cold Plate Configuration; AN Fitting Reconditioning Tool; Active Response Gravity Offload System; Method and Apparatus for Forming Nanodroplets; Rapid Detection of the Varicella Zoster Virus in Saliva; Improved Devices for Collecting Sweat for Chemical Analysis; Phase-Controlled Magnetic Mirror for Wavefront Correction; and Frame-Transfer Gating Raman Spectroscopy for Time-Resolved Multiscalar Combustion Diagnostics.

Assessment of Gd-EOB-DTPA-enhanced MRI for HCC and dysplastic nodules and comparison of detection sensitivity versus MDCT.

PubMed

Inoue, Tatsuo; Kudo, Masatoshi; Komuta, Mina; Hayaishi, Sosuke; Ueda, Taisuke; Takita, Masahiro; Kitai, Satoshi; Hatanaka, Kinuyo; Yada, Norihisa; Hagiwara, Satoru; Chung, Hobyung; Sakurai, Toshiharu; Ueshima, Kazuomi; Sakamoto, Michiie; Maenishi, Osamu; Hyodo, Tomoko; Okada, Masahiro; Kumano, Seishi; Murakami, Takamichi

2012-09-01

We aimed to evaluate gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) for the detection of hepatocellular carcinomas (HCCs) and dysplastic nodules (DNs) compared with dynamic multi-detector row computed tomography (MDCT), and to discriminate between HCCs and DNs. Eighty-six nodules diagnosed as HCC or DNs were retrospectively investigated. Gd-EOB-DTPA-enhanced MRI and dynamic MDCT were compared with respect to their diagnostic ability for hypervascular HCCs and detection sensitivity for hypovascular tumors. The ability of hepatobiliary images of Gd-EOB-DTPA-enhanced MRI to discriminate between these nodules was assessed. We also calculated the EOB enhancement ratio of the tumors. For hypervascular HCCs, the diagnostic ability of Gd-EOB-DTPA-enhanced MRI was significantly higher than that of MDCT for tumors less than 2 cm (p = 0.048). There was no difference in the detection of hypervascular HCCs between hepatobiliary phase images of Gd-EOB-DTPA-enhanced MRI (43/45: 96%) and dynamic MDCT (40/45: 89%), whereas the detection sensitivity of hypovascular tumors by Gd-EOB-DTPA-enhanced MRI was significantly higher than that by dynamic MDCT (39/41: 95% vs. 25/41: 61%, p = 0.001). EOB enhancement ratios were decreased in parallel with the degree of differentiation in DNs and HCCs, although there was no difference between DNs and hypovascular well-differentiated HCCs. The diagnostic ability of Gd-EOB-DTPA-enhanced MRI for hypervascular HCCs less than 2 cm was significantly higher than that of MDCT. For hypovascular tumors, the detection sensitivity of hepatobiliary phase images of Gd-EOB-DTPA-enhanced MRI was significantly higher than that of dynamic Gd-EOB-DTPA-enhanced MRI and dynamic MDCT. It was difficult to distinguish between DNs and hypovascular well-differentiated HCCs based on the EOB enhancement ratio.

Enhancements for a Dynamic Data Warehousing and Mining System for Large-scale HSCB Data

DTIC Science & Technology

2016-08-29

Intelligent Automation Incorporated Enhancements for a Dynamic Data Warehousing and Mining ...Page | 2 Intelligent Automation Incorporated Monthly Report No. 5 Enhancements for a Dynamic Data Warehousing and Mining System Large-Scale HSCB...System for Large-scale HSCB Data Monthly Report No. 5 Reporting Period: July 20, 2016 – Aug 19, 2016 Contract No. N00014-16-P-3014

Enhancements for a Dynamic Data Warehousing and Mining System for Large-scale HSCB Data

DTIC Science & Technology

2016-07-20

Intelligent Automation Incorporated Enhancements for a Dynamic Data Warehousing and Mining ...Page | 2 Intelligent Automation Incorporated Monthly Report No. 4 Enhancements for a Dynamic Data Warehousing and Mining System Large-Scale HSCB...including Top Videos, Top Users, Top Words, and Top Languages, and also applied NER to the text associated with YouTube posts. We have also developed UI for

Enhancements for a Dynamic Data Warehousing and Mining System for Large-Scale HSCB Data

DTIC Science & Technology

2016-07-20

Intelligent Automation Incorporated Enhancements for a Dynamic Data Warehousing and Mining ...Page | 2 Intelligent Automation Incorporated Monthly Report No. 4 Enhancements for a Dynamic Data Warehousing and Mining System Large-Scale HSCB...including Top Videos, Top Users, Top Words, and Top Languages, and also applied NER to the text associated with YouTube posts. We have also developed UI for

Crosslinked bicontinuous biobased PLA/NR blends via dynamic vulcanization using different curing systems.

PubMed

Yuan, Daosheng; Chen, Kunling; Xu, Chuanhui; Chen, Zhonghua; Chen, Yukun

2014-11-26

In this study, blends of entirely biosourced polymers, namely polylactide (PLA) and natural rubber (NR), were prepared through dynamic vulcanization using dicumyl peroxide (DCP), sulphur (S) and phenolic resin (2402) as curing agents, respectively. The crosslinked NR phase was found to be a continuous structure in all the prepared blends. The molecular weight changes of PLA were studied by gel permeation chromatography. Interfacial compatibilization between PLA and NR was investigated using Fourier transform infrared spectroscopy and scanning electron microscopy. The thermal properties of blends were evaluated by differential scanning calorimetry and thermogravimetric analysis instrument. It was found that the molecular weight of PLA and interfacial compatibilizaion between PLA and NR showed a significant influence on the mechanical and thermal properties of blends. The PLA/NR blend (60/40 w/w) by DCP-induced dynamic vulcanization owned the finest mechanical properties and thermal stability. Copyright © 2014 Elsevier Ltd. All rights reserved.

Frequency-scanning interferometry using a time-varying Kalman filter for dynamic tracking measurements.

PubMed

Jia, Xingyu; Liu, Zhigang; Tao, Long; Deng, Zhongwen

2017-10-16

Frequency scanning interferometry (FSI) with a single external cavity diode laser (ECDL) and time-invariant Kalman filtering is an effective technique for measuring the distance of a dynamic target. However, due to the hysteresis of the piezoelectric ceramic transducer (PZT) actuator in the ECDL, the optical frequency sweeps of the ECDL exhibit different behaviors, depending on whether the frequency is increasing or decreasing. Consequently, the model parameters of Kalman filter appear time varying in each iteration, which produces state estimation errors with time-invariant filtering. To address this, in this paper, a time-varying Kalman filter is proposed to model the instantaneous movement of a target relative to the different optical frequency tuning durations of the ECDL. The combination of the FSI method with the time-varying Kalman filter was theoretically analyzed, and the simulation and experimental results show the proposed method greatly improves the performance of dynamic FSI measurements.

Enhancer regions show high histone H3.3 turnover that changes during differentiation

PubMed Central

Deaton, Aimee M; Gómez-Rodríguez, Mariluz; Mieczkowski, Jakub; Tolstorukov, Michael Y; Kundu, Sharmistha; Sadreyev, Ruslan I; Jansen, Lars ET; Kingston, Robert E

2016-01-01

The organization of DNA into chromatin is dynamic; nucleosomes are frequently displaced to facilitate the ability of regulatory proteins to access specific DNA elements. To gain insight into nucleosome dynamics, and to follow how dynamics change during differentiation, we used a technique called time-ChIP to quantitatively assess histone H3.3 turnover genome-wide during differentiation of mouse ESCs. We found that, without prior assumptions, high turnover could be used to identify regions involved in gene regulation. High turnover was seen at enhancers, as observed previously, with particularly high turnover at super-enhancers. In contrast, regions associated with the repressive Polycomb-Group showed low turnover in ESCs. Turnover correlated with DNA accessibility. Upon differentiation, numerous changes in H3.3 turnover rates were observed, the majority of which occurred at enhancers. Thus, time-ChIP measurement of histone turnover shows that active enhancers are unusually dynamic in ESCs and changes in highly dynamic nucleosomes predominate at enhancers during differentiation. DOI: http://dx.doi.org/10.7554/eLife.15316.001 PMID:27304074

Fly-scan ptychography

DOE PAGES

Huang, Xiaojing; Lauer, Kenneth; Clark, Jesse N.; ...

2015-03-13

We report an experimental ptychography measurement performed in fly-scan mode. With a visible-light laser source, we demonstrate a 5-fold reduction of data acquisition time. By including multiple mutually incoherent modes into the incident illumination, high quality images were successfully reconstructed from blurry diffraction patterns. Thus, this approach significantly increases the throughput of ptychography, especially for three-dimensional applications and the visualization of dynamic systems.

Symposium N: Materials and Devices for Thermal-to-Electric Energy Conversion

DTIC Science & Technology

2010-08-24

X - ray diffraction, transmission electron microscopy, scanning electron microscopy, and dynamic light scattering. Thermal conductivity measurements...SEM), X - ray diffraction (XRD) measurements as well as Raman spectroscopy. The results from these techniques indicate a clear modification...was examined by using scanning electron microscope (SEM; HITACHI S-4500 model) attached with an energy dispersive x - ray spectroscopy. The electrical

Nonlinear analysis and dynamic compensation of stylus scanning measurement with wide range

NASA Astrophysics Data System (ADS)

Hui, Heiyang; Liu, Xiaojun; Lu, Wenlong

2011-12-01

Surface topography is an important geometrical feature of a workpiece that influences its quality and functions such as friction, wearing, lubrication and sealing. Precision measurement of surface topography is fundamental for product quality characterizing and assurance. Stylus scanning technique is a widely used method for surface topography measurement, and it is also regarded as the international standard method for 2-D surface characterizing. Usually surface topography, including primary profile, waviness and roughness, can be measured precisely and efficiently by this method. However, by stylus scanning method to measure curved surface topography, the nonlinear error is unavoidable because of the difference of horizontal position of the actual measured point from given sampling point and the nonlinear transformation process from vertical displacement of the stylus tip to angle displacement of the stylus arm, and the error increases with the increasing of measuring range. In this paper, a wide range stylus scanning measurement system based on cylindrical grating interference principle is constructed, the originations of the nonlinear error are analyzed, the error model is established and a solution to decrease the nonlinear error is proposed, through which the error of the collected data is dynamically compensated.

Methods for the correction of vascular artifacts in PET O-15 water brain-mapping studies

NASA Astrophysics Data System (ADS)

Chen, Kewei; Reiman, E. M.; Lawson, M.; Yun, Lang-sheng; Bandy, D.; Palant, A.

1996-12-01

While positron emission tomographic (PET) measurements of regional cerebral blood flow (rCBF) can be used to map brain regions that are involved in normal and pathological human behaviors, measurements in the anteromedial temporal lobe can be confounded by the combined effects of radiotracer activity in neighboring arteries and partial-volume averaging. The authors now describe two simple methods to address this vascular artifact. One method utilizes the early frames of a dynamic PET study, while the other method utilizes a coregistered magnetic resonance image (MRI) to characterize the vascular region of interest (VROI). Both methods subsequently assign a common value to each pixel in the VROI for the control (baseline) scan and the activation scan. To study the vascular artifact and to demonstrate the ability of the proposed methods correcting the vascular artifact, four dynamic PET scans were performed in a single subject during the same behavioral state. For each of the four scans, a vascular scan containing vascular activity was computed as the summation of the images acquired 0-60 s after radiotracer administration, and a control scan containing minimal vascular activity was computed as the summation of the images acquired 20-80 s after radiotracer administration. t-score maps calculated from the four pairs of vascular and control scans were used to characterize regional blood flow differences related to vascular activity before and after the application of each vascular artifact correction method. Both methods eliminated the observed differences in vascular activity, as well as the vascular artifact observed in the anteromedial temporal lobes. Using PET data from a study of normal human emotion, these methods permitted the authors to identify rCBF increases in the anteromedial temporal lobe free from the potentially confounding, combined effects of vascular activity and partial-volume averaging.

Rapid Multi-Tracer PET Tumor Imaging With F-FDG and Secondary Shorter-Lived Tracers.

PubMed

Black, Noel F; McJames, Scott; Kadrmas, Dan J

2009-10-01

Rapid multi-tracer PET, where two to three PET tracers are rapidly scanned with staggered injections, can recover certain imaging measures for each tracer based on differences in tracer kinetics and decay. We previously showed that single-tracer imaging measures can be recovered to a certain extent from rapid dual-tracer (62)Cu - PTSM (blood flow) + (62)Cu - ATSM (hypoxia) tumor imaging. In this work, the feasibility of rapidly imaging (18)F-FDG plus one or two of these shorter-lived secondary tracers was evaluated in the same tumor model. Dynamic PET imaging was performed in four dogs with pre-existing tumors, and the raw scan data was combined to emulate 60 minute long dual- and triple-tracer scans, using the single-tracer scans as gold standards. The multi-tracer data were processed for static (SUV) and kinetic (K(1), K(net)) endpoints for each tracer, followed by linear regression analysis of multi-tracer versus single-tracer results. Static and quantitative dynamic imaging measures of FDG were both accurately recovered from the multi-tracer scans, closely matching the single-tracer FDG standards (R > 0.99). Quantitative blood flow information, as measured by PTSM K(1) and SUV, was also accurately recovered from the multi-tracer scans (R = 0.97). Recovery of ATSM kinetic parameters proved more difficult, though the ATSM SUV was reasonably well recovered (R = 0.92). We conclude that certain additional information from one to two shorter-lived PET tracers may be measured in a rapid multi-tracer scan alongside FDG without compromising the assessment of glucose metabolism. Such additional and complementary information has the potential to improve tumor characterization in vivo, warranting further investigation of rapid multi-tracer techniques.

Rapid Multi-Tracer PET Tumor Imaging With 18F-FDG and Secondary Shorter-Lived Tracers

PubMed Central

Black, Noel F.; McJames, Scott; Kadrmas, Dan J.

2009-01-01

Rapid multi-tracer PET, where two to three PET tracers are rapidly scanned with staggered injections, can recover certain imaging measures for each tracer based on differences in tracer kinetics and decay. We previously showed that single-tracer imaging measures can be recovered to a certain extent from rapid dual-tracer 62Cu – PTSM (blood flow) + 62Cu — ATSM (hypoxia) tumor imaging. In this work, the feasibility of rapidly imaging 18F-FDG plus one or two of these shorter-lived secondary tracers was evaluated in the same tumor model. Dynamic PET imaging was performed in four dogs with pre-existing tumors, and the raw scan data was combined to emulate 60 minute long dual- and triple-tracer scans, using the single-tracer scans as gold standards. The multi-tracer data were processed for static (SUV) and kinetic (K1, Knet) endpoints for each tracer, followed by linear regression analysis of multi-tracer versus single-tracer results. Static and quantitative dynamic imaging measures of FDG were both accurately recovered from the multi-tracer scans, closely matching the single-tracer FDG standards (R > 0.99). Quantitative blood flow information, as measured by PTSM K1 and SUV, was also accurately recovered from the multi-tracer scans (R = 0.97). Recovery of ATSM kinetic parameters proved more difficult, though the ATSM SUV was reasonably well recovered (R = 0.92). We conclude that certain additional information from one to two shorter-lived PET tracers may be measured in a rapid multi-tracer scan alongside FDG without compromising the assessment of glucose metabolism. Such additional and complementary information has the potential to improve tumor characterization in vivo, warranting further investigation of rapid multi-tracer techniques. PMID:20046800

Versatile optical system for static and dynamic thermomagnetic recording using a scanning laser microscope

NASA Astrophysics Data System (ADS)

Clegg, Warwick W.; Jenkins, David F. L.; Helian, Na; Windmill, James; Windmill, Robert

2001-12-01

Scanning Laser Microscopes (SLM) have been used to characterise the magnetic domain properties of various magnetic and magneto-optical materials. The SLM in our laboratory has been designed to enable both static and dynamic read-write operations to be performed on stationary media. In a conventional (static) SLM, data bits are recorded thermo-magnetically by focusing a pulse of laser light onto the sample surface. If the laser beam has a Gaussian intensity distribution (TEM00) then so will the focused laser spot. The resultant temperature profile will largely mirror the intensity distribution of the focused spot, and in the region where the temperature is sufficiently high for switching to occur, in the presence of bias field, a circular data bit will be recorded. However, in a real magneto-optical drive the bits are written onto non-stationary media, and the resultant bit will be non-circular. A versatile optical system has been developed to facilitate both recording and imaging of data bits. To simulate the action of a Magneto-Optical drive, the laser is pulsed via an Acousto-Optic Modulator, whilst being scanned across the sample using a galvanometer mounted mirror, thus imitating a storage medium rotating above a MO head with high relative velocity between the beam and medium. Static recording is simply achieved by disabling the galvanometer scan mirror. Polar magneto-optic Kerr effect images are acquired using multiple-segment photo-detectors for diffraction-limited scanned spot detection, with either specimen scanning for highest resolution or beam scanning for near real-time image acquisition. Results will be presented to illustrate the systems capabilities.

Integrated remote sensing and visualization (IRSV) system for transportation infrastructure operations and management, phase two, volume 3 : advanced consideration in LiDAR technology for bridge evaluation.

DOT National Transportation Integrated Search

2012-03-01

This report describes Phase Two enhancement of terrestrial LiDAR scanning for bridge damage : evaluation that was initially developed in Phase One. Considering the spatial and reflectivity : information contained in LiDAR scans, two detection algorit...

Hemispherical Scanning Imaging DOAS: Resolving nitrogen dioxide in the urban environment

NASA Astrophysics Data System (ADS)

Leigh, R. J.; Graves, R. R.; Lawrence, J.; Faloon, K.; Monks, P. S.

2012-12-01

Imaging DOAS techniques have been used for nitrogen dioxide and sulfer dioxide for a number of years. This presentation describes a novel system which images concentrations of nitrogen dioxide by scanning an imaging spectrometer 360 degrees azimuthally, covering a region from 5 degrees below the horizon, to the zenith. The instrument has been built at the University of Leicester (UK), on optical designs by Surrey Satellite Technologies Ltd, and incorporates an Offner relay with Schwarzchild fore-optics, in a rotating mount. The spectrometer offers high fidelity spectroscopic retrievals of nitrogen dioxide as a result of a reliable Gaussian line shape, zero smile and low chromatic aberration. The full hemispherical scanning provides complete coverage of nitrogen dioxide concentrations above approximately 5 ppbv in urban environments. Through the use of multiple instruments, the three-dimensional structure of nitrogen dioxide can be sampled and tomographically reconstructed, providing valuable information on nitrogen dioxide emissions and downwind exposure, in addition to new understanding of boundary layer dynamics through the use of nitrogen dioxide as a tracer. Furthermore, certain aerosol information can be retrieved through absolute intensity measurements in each azimuthal direction supplemented by traditional techniques of O4 spectroscopy. Such measurements provide a new tool for boundary layer measurement and monitoring at a time when air quality implications on human health and climate are under significant scrutiny. This presentation will describe the instrument and tomographic potential of this technique. First measurements were taken as part of the international PEGASOS campaign in Bologna, Italy. Results from these measurements will be shown, including imaging of enhanced NO2 in the Bologna urban boundary layer during a severe thunderstorm. A Hemispherical Scanning Imaging DOAS instrument operating in Bologna, Italy in June 2012. Visible in the background over Bologna is an instrumented Zepplin measuring NO2 and ozone among other species. A hemispherical panorama of nitrogen dioxide concentrations, as measured by the HSI-DOAS instrument in Bologna.

Performance Analysis of a NASA Integrated Network Array

NASA Technical Reports Server (NTRS)

Nessel, James A.

2012-01-01

The Space Communications and Navigation (SCaN) Program is planning to integrate its individual networks into a unified network which will function as a single entity to provide services to user missions. This integrated network architecture is expected to provide SCaN customers with the capabilities to seamlessly use any of the available SCaN assets to support their missions to efficiently meet the collective needs of Agency missions. One potential optimal application of these assets, based on this envisioned architecture, is that of arraying across existing networks to significantly enhance data rates and/or link availabilities. As such, this document provides an analysis of the transmit and receive performance of a proposed SCaN inter-network antenna array. From the study, it is determined that a fully integrated internetwork array does not provide any significant advantage over an intra-network array, one in which the assets of an individual network are arrayed for enhanced performance. Therefore, it is the recommendation of this study that NASA proceed with an arraying concept, with a fundamental focus on a network-centric arraying.

A Novel Real-Time Reference Key Frame Scan Matching Method

PubMed Central

Mohamed, Haytham; Moussa, Adel; Elhabiby, Mohamed; El-Sheimy, Naser; Sesay, Abu

2017-01-01

Unmanned aerial vehicles represent an effective technology for indoor search and rescue operations. Typically, most indoor missions’ environments would be unknown, unstructured, and/or dynamic. Navigation of UAVs in such environments is addressed by simultaneous localization and mapping approach using either local or global approaches. Both approaches suffer from accumulated errors and high processing time due to the iterative nature of the scan matching method. Moreover, point-to-point scan matching is prone to outlier association processes. This paper proposes a low-cost novel method for 2D real-time scan matching based on a reference key frame (RKF). RKF is a hybrid scan matching technique comprised of feature-to-feature and point-to-point approaches. This algorithm aims at mitigating errors accumulation using the key frame technique, which is inspired from video streaming broadcast process. The algorithm depends on the iterative closest point algorithm during the lack of linear features which is typically exhibited in unstructured environments. The algorithm switches back to the RKF once linear features are detected. To validate and evaluate the algorithm, the mapping performance and time consumption are compared with various algorithms in static and dynamic environments. The performance of the algorithm exhibits promising navigational, mapping results and very short computational time, that indicates the potential use of the new algorithm with real-time systems. PMID:28481285

Online Multitasking Line-Scan Imaging Techniques for Simultaneous Safety and Quality Evaluation of Apples

NASA Astrophysics Data System (ADS)

Kim, Moon Sung; Lee, Kangjin; Chao, Kaunglin; Lefcourt, Alan; Cho, Byung-Kwan; Jun, Won

We developed a push-broom, line-scan imaging system capable of simultaneous measurements of reflectance and fluorescence. The system allows multitasking inspections for quality and safety attributes of apples due to its dynamic capabilities in simultaneously capturing fluorescence and reflectance, and selectivity in multispectral bands. A multitasking image-based inspection system for online applications has been suggested in that a single imaging device that could perform a multitude of both safety and quality inspection needs. The presented multitask inspection approach in online applications may provide an economically viable means for a number of food processing industries being able to adapt to operate and meet the dynamic and specific inspection and sorting needs.

A dynamical weak scale from inflation

NASA Astrophysics Data System (ADS)

You, Tevong

2017-09-01

Dynamical scanning of the Higgs mass by an axion-like particle during inflation may provide a cosmological component to explaining part of the hierarchy problem. We propose a novel interplay of this cosmological relaxation mechanism with inflation, whereby the backreaction of the Higgs vacuum expectation value near the weak scale causes inflation to end. As Hubble drops, the relaxion's dissipative friction increases relative to Hubble and slows it down enough to be trapped by the barriers of its periodic potential. Such a scenario raises the natural cut-off of the theory up to ~ 1010 GeV, while maintaining a minimal relaxion sector without having to introduce additional scanning scalars or new physics coincidentally close to the weak scale.

Scale Invariance in Lateral Head Scans During Spatial Exploration.

PubMed

Yadav, Chetan K; Doreswamy, Yoganarasimha

2017-04-14

Universality connects various natural phenomena through physical principles governing their dynamics, and has provided broadly accepted answers to many complex questions, including information processing in neuronal systems. However, its significance in behavioral systems is still elusive. Lateral head scanning (LHS) behavior in rodents might contribute to spatial navigation by actively managing (optimizing) the available sensory information. Our findings of scale invariant distributions in LHS lifetimes, interevent intervals and event magnitudes, provide evidence for the first time that the optimization takes place at a critical point in LHS dynamics. We propose that the LHS behavior is responsible for preprocessing of the spatial information content, critical for subsequent foolproof encoding by the respective downstream neural networks.

Scale Invariance in Lateral Head Scans During Spatial Exploration

NASA Astrophysics Data System (ADS)

Yadav, Chetan K.; Doreswamy, Yoganarasimha

2017-04-01

Universality connects various natural phenomena through physical principles governing their dynamics, and has provided broadly accepted answers to many complex questions, including information processing in neuronal systems. However, its significance in behavioral systems is still elusive. Lateral head scanning (LHS) behavior in rodents might contribute to spatial navigation by actively managing (optimizing) the available sensory information. Our findings of scale invariant distributions in LHS lifetimes, interevent intervals and event magnitudes, provide evidence for the first time that the optimization takes place at a critical point in LHS dynamics. We propose that the LHS behavior is responsible for preprocessing of the spatial information content, critical for subsequent foolproof encoding by the respective downstream neural networks.

Design of voice coil motor dynamic focusing unit for a laser scanner

NASA Astrophysics Data System (ADS)

Lee, Moon G.; Kim, Gaeun; Lee, Chan-Woo; Lee, Soo-Hun; Jeon, Yongho

2014-04-01

Laser scanning systems have been used for material processing tasks such as welding, cutting, marking, and drilling. However, applications have been limited by the small range of motion and slow speed of the focusing unit, which carries the focusing optics. To overcome these limitations, a dynamic focusing system with a long travel range and high speed is needed. In this study, a dynamic focusing unit for a laser scanning system with a voice coil motor (VCM) mechanism is proposed to enable fast speed and a wide focusing range. The VCM has finer precision and higher speed than conventional step motors and a longer travel range than earlier lead zirconium titanate actuators. The system has a hollow configuration to provide a laser beam path. This also makes it compact and transmission-free and gives it low inertia. The VCM's magnetics are modeled using a permeance model. Its design parameters are determined by optimization using the Broyden-Fletcher-Goldfarb-Shanno method and a sequential quadratic programming algorithm. After the VCM is designed, the dynamic focusing unit is fabricated and assembled. The permeance model is verified by a magnetic finite element method simulation tool, Maxwell 2D and 3D, and by measurement data from a gauss meter. The performance is verified experimentally. The results show a resolution of 0.2 μm and travel range of 16 mm. These are better than those of conventional focusing systems; therefore, this focusing unit can be applied to laser scanning systems for good machining capability.