Dual-energy CT in the assessment of mediastinal lymph nodes: Comparative study of virtual non-contrast and true non-contrast images

Energy Technology Data Exchange (ETDEWEB)

Yoo, Seon Young; Kim, Yoo Kyung; Cho, Hyun Hae; Choi, Mi Joo; Shim, Sung Shine; Lee, Jeong Kyong; Baek, Seung Yon [School of Medicine, Ewha Womans University, Seou (Korea, Republic of)

2013-06-15

To evaluate the reliability of virtual non-contrast (VNC) images reconstructed from contrast-enhanced, dual-energy scans compared with true non-contrast (TNC) images in the assessment of high CT attenuation or calcification of mediastinal lymph nodes. A total of 112 mediastinal nodes from 45 patients who underwent non-contrast and dual-energy contrast-enhanced scans were analyzed. Node attenuation in TNC and VNC images was compared both objectively, using computed tomography (CT) attenuation, and subjectively, via visual scoring (0, attenuation ≤ the aorta; 1, > the aorta; 2, calcification). The relationship among attenuation difference between TNC and VNC images, CT attenuation in TNC images, and net contrast enhancement (NCE) was analyzed. CT attenuation in TNC and VNC images showed moderate agreement (intraclass correlation coefficient, 0.612). The mean absolute difference was 7.8 ± 7.6 Hounsfield unit (HU) (range, 0-36 HU), and the absolute difference was equal to or less than 10 HU in 65.2% of cases (73/112). Visual scores in TNC and VNC images showed fair agreement (κ value, 0.335). Five of 16 nodes (31.3%) which showed score 1 (n = 15) or 2 (n = 1) in TNC images demonstrated score 1 in VNC images. The TNC-VNC attenuation difference showed a moderate positive correlation with CT attenuation in TNC images (partial correlation coefficient [PCC] adjusted by NCE: 0.455) and a weak negative correlation with NCE (PCC adjusted by CT attenuation in TNC: -0.245). VNC images may be useful in the evaluation of mediastinal lymph nodes by providing additional information of high CT attenuation of nodes, although it is underestimated compared with TNC images.

Dual-energy CT in the assessment of mediastinal lymph nodes: comparative study of virtual non-contrast and true non-contrast images.

Science.gov (United States)

Yoo, Seon Young; Kim, Yookyung; Cho, Hyun Hae; Choi, Mi Joo; Shim, Sung Shine; Lee, Jeong Kyong; Baek, Seung Yon

2013-01-01

To evaluate the reliability of virtual non-contrast (VNC) images reconstructed from contrast-enhanced, dual-energy scans compared with true non-contrast (TNC) images in the assessment of high CT attenuation or calcification of mediastinal lymph nodes. A total of 112 mediastinal nodes from 45 patients who underwent non-contrast and dual-energy contrast-enhanced scans were analyzed. Node attenuation in TNC and VNC images was compared both objectively, using computed tomography (CT) attenuation, and subjectively, via visual scoring (0, attenuation ≤ the aorta; 1, > the aorta; 2, calcification). The relationship among attenuation difference between TNC and VNC images, CT attenuation in TNC images, and net contrast enhancement (NCE) was analyzed. CT attenuation in TNC and VNC images showed moderate agreement (intraclass correlation coefficient, 0.612). The mean absolute difference was 7.8 ± 7.6 Hounsfield unit (HU) (range, 0-36 HU), and the absolute difference was equal to or less than 10 HU in 65.2% of cases (73/112). Visual scores in TNC and VNC images showed fair agreement (κ value, 0.335). Five of 16 nodes (31.3%) which showed score 1 (n = 15) or 2 (n = 1) in TNC images demonstrated score 1 in VNC images. The TNC-VNC attenuation difference showed a moderate positive correlation with CT attenuation in TNC images (partial correlation coefficient [PCC] adjusted by NCE: 0.455) and a weak negative correlation with NCE (PCC adjusted by CT attenuation in TNC: -0.245). VNC images may be useful in the evaluation of mediastinal lymph nodes by providing additional information of high CT attenuation of nodes, although it is underestimated compared with TNC images.

Non-contrast MRA using an inflow-enhanced, inversion recovery SSFP technique in pediatric abdominal imaging

International Nuclear Information System (INIS)

Serai, Suraj; Towbin, Alexander J.; Podberesky, Daniel J.

2012-01-01

Abdominal contrast-enhanced MR angiography (CE-MRA) is routinely performed in children. CE-MRA is challenging in children because of patient motion, difficulty in obtaining intravenous access, and the inability of young patients to perform a breath-hold during imaging. The combination of pediatric-specific difficulties in imaging and the safety concerns regarding the risk of gadolinium-based contrast agents in patients with impaired renal function has renewed interest in the use of non-contrast (NC) MRA techniques. At our institution, we have optimized 3-D NC-MRA techniques for abdominal imaging. The purpose of this work is to demonstrate the utility of an inflow-enhanced, inversion recovery balanced steady-state free precession-based (b-SSFP) NC-MRA technique. (orig.)

Selection of optimal pulse sequences for conventional and dynamic MR imaging with Gd-DTPA; A fundamental study

Energy Technology Data Exchange (ETDEWEB)

Maeda, Miho; Kita, Keisuke; Maeda, Masayuki (Wakayama Medical Coll. (Japan)) (and others)

1989-11-01

Gadolinium-DTPA (Gd-DTPA) enhances contrast between tissues in magnetic resonance (MR) imaging. The enhancement of tissues depends partly upon the pulse sequences, and the optimal pulse sequence is also influenced by the tissue cncentration of Gd-DTPA. We prepared phantoms of 25% albumin solutions with various concentrations of Gd-DTPA, and imaged them using various pulse sequences with 1.5-T MR system. We also performed MR imaging of 16 patients with tumors (10 brain tumors and 6 hepatic tumors) before and after intravenous administration of Gd-DTPA (0.1 mmol/kg); 6 patients with hepatic tumors underwent dynamic MR imaging during suspended respiration. We made a theoretical equation to calculate the concentration of Gd-DTPA and estimated its tissue concentration in tumors at 0{approx}0.2 mmol/kg. Within these tissue concentrations, the enhancement-to-noise (E/N) ratio was larger in FISP (flip angle of 90deg, TR pf 300 msec, minimal TE) and SE (TR of 400 msec, minimal TE) sequences than in other sequences observed. These sequences may be preferable for conventional enhanced-MRI. Among the pulse sequences with TR of less than 100 msec, FISP (flip angle of 90deg, TR of less than 100 msec, minimal TE) had the largest E/N ratio; which may be useful for dynamic MRI during suspended respiration. The importance of selecting the optimal pulse sequences according to the imaging modality used will be discussed. (author).

Light storage in a doped solid enhanced by feedback-controlled pulse shaping

International Nuclear Information System (INIS)

Beil, F.; Buschbeck, M.; Heinze, G.; Halfmann, T.

2010-01-01

We report on experiments dealing with feedback-controlled pulse shaping to optimize the efficiency of light storage by electromagnetically induced transparency (EIT) in a Pr 3+ :Y 2 SiO 5 crystal. A learning loop in combination with an evolutionary algorithm permits the automatic determination of optimal temporal profiles of intensities and frequencies in the driving laser pulses (i.e., the probe and coupling pulses). As a main advantage, the technique finds optimal solutions even in the complicated multilevel excitation scheme of a doped solid, involving large inhomogeneous broadening. The learning loop experimentally determines optimal temporal intensity profiles of the coupling pulses for a given probe pulse. The optimized intensity pulse shapes enhance the light-storage efficiency in the doped solid by a factor of 2. The learning loop also determines a fast and efficient preparation pulse sequence, which serves to optically prepare the crystal prior to light-storage experiments. The optimized preparation sequence is 5 times faster than standard preparation sequences. Moreover, the optimized preparation sequence enhances the optical depth in the medium by a factor of 5. As a consequence, the efficiency of light storage also increases by another factor of 3. Our experimental data clearly demonstrate the considerable potential of feedback-controlled pulse shaping, applied to EIT-driven light storage in solid media.

Arbitrarily accurate twin composite π -pulse sequences

Science.gov (United States)

Torosov, Boyan T.; Vitanov, Nikolay V.

2018-04-01

We present three classes of symmetric broadband composite pulse sequences. The composite phases are given by analytic formulas (rational fractions of π ) valid for any number of constituent pulses. The transition probability is expressed by simple analytic formulas and the order of pulse area error compensation grows linearly with the number of pulses. Therefore, any desired compensation order can be produced by an appropriate composite sequence; in this sense, they are arbitrarily accurate. These composite pulses perform equally well as or better than previously published ones. Moreover, the current sequences are more flexible as they allow total pulse areas of arbitrary integer multiples of π .

Preliminary study of pseudorandom binary sequence pulsing of ORELA

International Nuclear Information System (INIS)

Larson, N.M.; Olsen, D.K.

1980-03-01

It has been suggested that pseudorandom binary sequence (PRBS) pulsing might enhance the performance of the Oak Ridge Electron Linear Accelerator (ORELA) for neutron-induced, time-of-flight (TOF) cross-section measurements. In this technical memorandum, equations are developed for expected count rates, statistical variances, and backgrounds for a pulsing scheme in which a PRBS is superimposed on the periodic equalintensity ORELA bursts. Introduction of the PRBS modification permits neutrons of different energies originating from different bursts to reach the detector simultaneously, and the signal corresponding to a unique flight time to be extracted mathematically. Relative advantages and disadvantages of measurements from conventional and PRBS pulsing modes are discussed in terms of counting statistics and backgrounds. Computer models of TOF spectra are generated for both pulsing modes, using as examples a 20-meter 233 U fission-chamber measurement and a 155-meter 238 U sample-in transmission measurement. Detailed comparisons of PRBS vs conventional results are presented. This study indicates that although PRBS pulsing could enhance ORELA performance for selected measurements, for general ORELA operation the disadvantages from PRBS pulsing probably outweigh the advantages

Primary lower limb lymphoedema. Classification with non-contrast MR lymphography

Energy Technology Data Exchange (ETDEWEB)

Arrive, Lionel; Derhy, S.; El Mouhadi, S.; Monnier-Cholley, L.; Menu, Y. [Saint-Antoine Hospital, Assistance Publique-Hopitaux de Paris, Department of Radiology, Paris (France); Sorbonne Universites, UPMC Universite Paris 06, Faculte de Medecine Pierre et Marie Curie, Paris (France); Dahan, B. [Cochin Hospital, Department of Emergency Medicine, Paris (France); Becker, C. [HEGP, Department of Thoracic Surgery, Paris (France)

2018-01-15

The purpose of the present study was to analyse the performance of non-contrast MR lymphography for the classification of primary lower limb lymphoedema in 121 consecutive patients with 187 primary lower limb lymphoedemas. 121 consecutive patients with clinically diagnosed primary lower limb lymphoedema underwent non-contrast MR lymphography with a free-breathing 3D fast spin-echo sequence with a very long TR/TE (4000/884 ms). MR examinations were retrospectively reviewed for severity of lymphoedema (absent, mild, moderate, severe) and characteristics of inguinal lymph nodes and iliac and inguinal lymphatic trunks graded as aplasic (no lymph nodes or lymphatic trunks), hypoplasic (less lymph nodes or lymphatic trunks), normal and hyperplasic (more lymph nodes or more and/or dilated trunks). There was an excellent correlation between clinical stage and severity of lymphoedema (Cramer's V of 0,73 (p < 0.001)). Differentiation was feasible between inguinal lymphatic vessel aplasia (21%), hypoplasia (15%), normal pattern (53%) and hyperplasia (11%). Severe lymphoedema was observed in 46% of aplasic patterns and in 37% of hyperplasic patterns, but in only 15% of hypoplasic patterns and never observed in normal patterns (p < 0.001). Non-contrast MR lymphography is able to classify primary lower limb lymphoedemas into hyperplasic, aplasic, hypoplasic and normal patterns. (orig.)

Ultra-high field upper extremity peripheral nerve and non-contrast enhanced vascular imaging.

Directory of Open Access Journals (Sweden)

Shailesh B Raval

Full Text Available The purpose of this study was to explore the efficacy of Ultra-high field [UHF] 7 Tesla [T] MRI as compared to 3T MRI in non-contrast enhanced [nCE] imaging of structural anatomy in the elbow, forearm, and hand [upper extremity].A wide range of sequences including T1 weighted [T1] volumetric interpolate breath-hold exam [VIBE], T2 weighted [T2] double-echo steady state [DESS], susceptibility weighted imaging [SWI], time-of-flight [TOF], diffusion tensor imaging [DTI], and diffusion spectrum imaging [DSI] were optimized and incorporated with a radiofrequency [RF] coil system composed of a transverse electromagnetic [TEM] transmit coil combined with an 8-channel receive-only array for 7T upper extremity [UE] imaging. In addition, Siemens optimized protocol/sequences were used on a 3T scanner and the resulting images from T1 VIBE and T2 DESS were compared to that obtained at 7T qualitatively and quantitatively [SWI was only qualitatively compared]. DSI studio was utilized to identify nerves based on analysis of diffusion weighted derived fractional anisotropy images. Images of forearm vasculature were extracted using a paint grow manual segmentation method based on MIPAV [Medical Image Processing, Analysis, and Visualization].High resolution and high quality signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR]-images of the hand, forearm, and elbow were acquired with nearly homogeneous 7T excitation. Measured [performed on the T1 VIBE and T2 DESS sequences] SNR and CNR values were almost doubled at 7T vs. 3T. Cartilage, synovial fluid and tendon structures could be seen with higher clarity in the 7T T1 and T2 weighted images. SWI allowed high resolution and better quality imaging of large and medium sized arteries and veins, capillary networks and arteriovenous anastomoses at 7T when compared to 3T. 7T diffusion weighted sequence [not performed at 3T] demonstrates that the forearm nerves are clearly delineated by fiber tractography. The

Optimized, unequal pulse spacing in multiple echo sequences improves refocusing in magnetic resonance.

Science.gov (United States)

Jenista, Elizabeth R; Stokes, Ashley M; Branca, Rosa Tamara; Warren, Warren S

2009-11-28

A recent quantum computing paper (G. S. Uhrig, Phys. Rev. Lett. 98, 100504 (2007)) analytically derived optimal pulse spacings for a multiple spin echo sequence designed to remove decoherence in a two-level system coupled to a bath. The spacings in what has been called a "Uhrig dynamic decoupling (UDD) sequence" differ dramatically from the conventional, equal pulse spacing of a Carr-Purcell-Meiboom-Gill (CPMG) multiple spin echo sequence. The UDD sequence was derived for a model that is unrelated to magnetic resonance, but was recently shown theoretically to be more general. Here we show that the UDD sequence has theoretical advantages for magnetic resonance imaging of structured materials such as tissue, where diffusion in compartmentalized and microstructured environments leads to fluctuating fields on a range of different time scales. We also show experimentally, both in excised tissue and in a live mouse tumor model, that optimal UDD sequences produce different T(2)-weighted contrast than do CPMG sequences with the same number of pulses and total delay, with substantial enhancements in most regions. This permits improved characterization of low-frequency spectral density functions in a wide range of applications.

Use of the Frank sequence in pulsed EPR

DEFF Research Database (Denmark)

Tseitlin, Mark; Quine, Richard W.; Eaton, Sandra S.

2011-01-01

The Frank polyphase sequence has been applied to pulsed EPR of triarylmethyl radicals at 256MHz (9.1mT magnetic field), using 256 phase pulses. In EPR, as in NMR, use of a Frank sequence of phase steps permits pulsed FID signal acquisition with very low power microwave/RF pulses (ca. 1.5m......W in the application reported here) relative to standard pulsed EPR. A 0.2mM aqueous solution of a triarylmethyl radical was studied using a 16mm diameter cross-loop resonator to isolate the EPR signal detection system from the incident pulses. Keyword: Correlation spectroscopy,Multi-pulse EPR,Low power pulses,NMR,EPR...

Study of the fast inversion recovery pulse sequence. With reference to fast fluid attenuated inversion recovery and fast short TI inversion recovery pulse sequence

International Nuclear Information System (INIS)

Tsuchihashi, Toshio; Maki, Toshio; Suzuki, Takeshi

1997-01-01

The fast inversion recovery (fast IR) pulse sequence was evaluated. We compared the fast fluid attenuated inversion recovery (fast FLAIR) pulse sequence in which inversion time (TI) was established as equal to the water null point for the purpose of the water-suppressed T 2 -weighted image, with the fast short TI inversion recovery (fast STIR) pulse sequence in which TI was established as equal to the fat null point for purpose of fat suppression. In the fast FLAIR pulse sequence, the water null point was increased by making TR longer. In the FLAIR pulse sequence, the longitudinal magnetization contrast is determined by TI. If TI is increased, T 2 -weighted contrast improves in the same way as increasing TR for the SE pulse sequence. Therefore, images should be taken with long TR and long TI, which are longer than TR and longer than the water null point. On the other hand, the fat null point is not affected by TR in the fast STIR pulse sequence. However, effective TE was affected by variation of the null point. This increased in proportion to the increase in effective TE. Our evaluation indicated that the fast STIR pulse sequence can control the extensive signals from fat in a short time. (author)

Virtual Non-Contrast CT Using Dual-Energy Spectral CT: Feasibility of Coronary Artery Calcium Scoring.

Science.gov (United States)

Song, Inyoung; Yi, Jeong Geun; Park, Jeong Hee; Kim, Sung Mok; Lee, Kyung Soo; Chung, Myung Jin

2016-01-01

To evaluate the feasibility of coronary artery calcium scoring based on three virtual noncontrast-enhanced (VNC) images derived from single-source spectral dual-energy CT (DECT) as compared with true noncontrast-enhanced (TNC) images. This prospective study was conducted with the approval of our Institutional Review Board. Ninety-seven patients underwent noncontrast CT followed by contrast-enhanced chest CT using single-source spectral DECT. Iodine eliminated VNC images were reconstructed using two kinds of 2-material decomposition algorithms (material density iodine-water pair [MDW], material density iodine-calcium pair [MDC]) and a material suppressed algorithm (material suppressed iodine [MSI]). Two readers independently quantified calcium on VNC and TNC images. The Spearman correlation coefficient test and Bland-Altman method were used for statistical analyses. Coronary artery calcium scores from all three VNC images showed excellent correlation with those from the TNC images (Spearman's correlation coefficient [ρ] = 0.94, 0.88, and 0.89 for MDW, MDC, and MSI, respectively; p VNC images also correlated well with those from TNC images (ρ = 0.92, 0.87, and 0.91 for MDW, MDC, and MSI, respectively; p VNC images, coronary calcium from MDW correlated best with that from TNC. The coronary artery calcium scores and volumes were significantly lower from the VNC images than from the TNC images (p VNC images from contrast-enhanced CT using dual-energy material decomposition/suppression is feasible for coronary calcium scoring. The absolute value from VNC tends to be smaller than that from TNC.

Tin-filter enhanced dual-energy-CT: image quality and accuracy of CT numbers in virtual noncontrast imaging.

Science.gov (United States)

Kaufmann, Sascha; Sauter, Alexander; Spira, Daniel; Gatidis, Sergios; Ketelsen, Dominik; Heuschmid, Martin; Claussen, Claus D; Thomas, Christoph

2013-05-01

To measure and compare the objective image quality of true noncontrast (TNC) images with virtual noncontrast (VNC) images acquired by tin-filter-enhanced, dual-source, dual-energy computed tomography (DECT) of upper abdomen. Sixty-three patients received unenhanced abdominal CT and enhanced abdominal DECT (100/140 kV with tin filter) in portal-venous phase. VNC images were calculated from the DECT datasets using commercially available software. The mean attenuation of relevant tissues and image quality were compared between the TNC and VNC images. Image quality was rated objectively by measuring image noise and the sharpness of object edges using custom-designed software. Measurements were compared using Student two-tailed t-test. Correlation coefficients for tissue attenuation measurements between TNC and VNC were calculated and the relative deviations were illustrated using Bland-Altman plots. Mean attenuation differences between TNC and VNC (HUTNC - HUVNC) image sets were as follows: right liver lobe -4.94 Hounsfield units (HU), left liver lobe -3.29 HU, vena cava -2.19 HU, spleen -7.46 HU, pancreas 1.29 HU, fat -11.14 HU, aorta 1.29 HU, bone marrow 36.83 HU (all P VNC and TNC series were observed for liver, vena portae, kidneys, pancreas, muscle and bone marrow (Pearson's correlation coefficient ≥0.75). Mean image noise was significantly higher in TNC images (P VNC and TNC images (P = .19). The Hounsfield units in VNC images closely resemble TNC images in the majority of the organs of the upper abdomen (kidneys, liver, pancreas). In spleen and fat, Hounsfield numbers in VNC images are tend to be higher than in TNC images. VNC images show a low image noise and satisfactory edge sharpness. Other criteria of image quality and the depiction of certain lesions need to be evaluated additionally. Copyright © 2013 AUR. Published by Elsevier Inc. All rights reserved.

MRI of spondylodiscities: contribution of gadolinium-DTPA and fat suppression sequence

International Nuclear Information System (INIS)

Cova, M.A.; Dalla Palma, L.; Pozzi-Mucelli, R.S.; Ricci, C.

1993-01-01

Twenty-six patients with a clinical diagnosis of spondylodiscitis were examined with non-contrast and contrast-enhanced MRI in order to define the contribution of gadolinium-DTPA (Gd-DTPA) and different pulse sequences, including a fat suppression sequence (SPIR). Spin echo (SE) T1-weighted images before and after Gd-DTPA injection and SE T2-weighted images were obtained in all patients. Twelve patients were also examined using the SPIR sequence following Gd-DTPA injection. Signal intensity and morphological features of the disc and vertebral lesions were then evaluated. The SE T1-weighted sequence with Gd-DTPA was very effective in showing the pathological changes at the level of the disc as an area of low signal intensity surrounded by a peripheral rim of enhancement in 24 of 26 cases (92%). This feature was not visible on non-enhanced images. As regards contiguous vertebral lesions this sequence was less informative, since in 8 of 26 cases (31%) the vertebral lesions became isointense and therefore not detectable. In 12 cases there was extension into the surrounding structures (spinal canal and/or paravertebral tissues). An enhanced SE T1-weighted sequence provided good anatomical definition of the extension of the infection in the spinal canal in all cases with this type of involvement (7 of 12). Regarding the 7 cases with paravertebral extension, no extension was visible in 1 case due to the reduced contrast with the surrounding fat following Gd-DTPA injection. The enhanced SPIR sequence was very effective, particularly in detecting the lesions in the vertebral bodies, avoiding the limitation of the enhanced SE T1-weighted sequence. The SPIR sequence was also effective in showing the extension within the spinal canal and the paravertebral fat. On the basis of our results the combination of a SE T1-weighted sequence without contrast and SPIR sequence with Gd-DTPA seems to be the best approach in cases of spondylodiscitis. (orig.)

Fat suppression in MR imaging with binomial pulse sequences

International Nuclear Information System (INIS)

Baudovin, C.J.; Bryant, D.J.; Bydder, G.M.; Young, I.R.

1989-01-01

This paper reports on a study to develop pulse sequences allowing suppression of fat signal on MR images without eliminating signal from other tissues with short T1. They have developed such a technique involving selective excitation of protons in water, based on a binomial pulse sequence. Imaging is performed at 0.15 T. Careful shimming is performed to maximize separation of fat and water peaks. A spin-echo 1,500/80 sequence is used, employing 90 degrees pulse with transit frequency optimized for water with null excitation of 20 H offset, followed by a section-selective 180 degrees pulse. With use of the binomial sequence for imagining, reduction in fat signal is seen on images of the pelvis and legs of volunteers. Patient studies show dramatic improvement in visualization of prostatic carcinoma compared with standard sequences

Virtual non-contrast CT using dual energy spectral CT: Feasibility of coronary artery calcium scoring

International Nuclear Information System (INIS)

Song, In Young; Yi, Jeong Geun; Park, Jeong Hee; Lee, Sung Mok; Lee, Kyung Soo; Chung, Myung Jin

2016-01-01

To evaluate the feasibility of coronary artery calcium scoring based on three virtual noncontrast-enhanced (VNC) images derived from single-source spectral dual-energy CT (DECT) as compared with true noncontrast-enhanced (TNC) images. This prospective study was conducted with the approval of our Institutional Review Board. Ninety-seven patients underwent noncontrast CT followed by contrast-enhanced chest CT using single-source spectral DECT. Iodine eliminated VNC images were reconstructed using two kinds of 2-material decomposition algorithms (material density iodine-water pair [MDW], material density iodine-calcium pair [MDC]) and a material suppressed algorithm (material suppressed iodine [MSI]). Two readers independently quantified calcium on VNC and TNC images. The Spearman correlation coefficient test and Bland-Altman method were used for statistical analyses. Coronary artery calcium scores from all three VNC images showed excellent correlation with those from the TNC images (Spearman's correlation coefficient [ρ] = 0.94, 0.88, and 0.89 for MDW, MDC, and MSI, respectively; p < 0.001 for all pairs). Measured coronary calcium volumes from VNC images also correlated well with those from TNC images (ρ = 0.92, 0.87, and 0.91 for MDW, MDC, and MSI, respectively; p < 0.001 for all pairs). Among the three VNC images, coronary calcium from MDW correlated best with that from TNC. The coronary artery calcium scores and volumes were significantly lower from the VNC images than from the TNC images (p < 0.001 for all pairs). The use of VNC images from contrast-enhanced CT using dual-energy material decomposition/suppression is feasible for coronary calcium scoring. The absolute value from VNC tends to be smaller than that from TNC

Virtual non-contrast CT using dual energy spectral CT: Feasibility of coronary artery calcium scoring

Energy Technology Data Exchange (ETDEWEB)

Song, In Young; Yi, Jeong Geun; Park, Jeong Hee [Dept. of Radiology, Konkuk University School of Medicine, Seoul (Korea, Republic of); Lee, Sung Mok; Lee, Kyung Soo; Chung, Myung Jin [Dept. of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of)

2016-06-15

To evaluate the feasibility of coronary artery calcium scoring based on three virtual noncontrast-enhanced (VNC) images derived from single-source spectral dual-energy CT (DECT) as compared with true noncontrast-enhanced (TNC) images. This prospective study was conducted with the approval of our Institutional Review Board. Ninety-seven patients underwent noncontrast CT followed by contrast-enhanced chest CT using single-source spectral DECT. Iodine eliminated VNC images were reconstructed using two kinds of 2-material decomposition algorithms (material density iodine-water pair [MDW], material density iodine-calcium pair [MDC]) and a material suppressed algorithm (material suppressed iodine [MSI]). Two readers independently quantified calcium on VNC and TNC images. The Spearman correlation coefficient test and Bland-Altman method were used for statistical analyses. Coronary artery calcium scores from all three VNC images showed excellent correlation with those from the TNC images (Spearman's correlation coefficient [ρ] = 0.94, 0.88, and 0.89 for MDW, MDC, and MSI, respectively; p < 0.001 for all pairs). Measured coronary calcium volumes from VNC images also correlated well with those from TNC images (ρ = 0.92, 0.87, and 0.91 for MDW, MDC, and MSI, respectively; p < 0.001 for all pairs). Among the three VNC images, coronary calcium from MDW correlated best with that from TNC. The coronary artery calcium scores and volumes were significantly lower from the VNC images than from the TNC images (p < 0.001 for all pairs). The use of VNC images from contrast-enhanced CT using dual-energy material decomposition/suppression is feasible for coronary calcium scoring. The absolute value from VNC tends to be smaller than that from TNC.

Identification and assessment of Anderson-Fabry disease by cardiovascular magnetic resonance noncontrast myocardial T1 mapping.

Science.gov (United States)

Sado, Daniel M; White, Steven K; Piechnik, Stefan K; Banypersad, Sanjay M; Treibel, Thomas; Captur, Gabriella; Fontana, Marianna; Maestrini, Viviana; Flett, Andrew S; Robson, Matthew D; Lachmann, Robin H; Murphy, Elaine; Mehta, Atul; Hughes, Derralynn; Neubauer, Stefan; Elliott, Perry M; Moon, James C

2013-05-01

Anderson-Fabry disease (AFD) is a rare but underdiagnosed intracellular lipid disorder that can cause left ventricular hypertrophy (LVH). Lipid is known to shorten the magnetic resonance imaging parameter T1. We hypothesized that noncontrast T1 mapping by cardiovascular magnetic resonance would provide a novel and useful measure in this disease with potential to detect early cardiac involvement and distinguish AFD LVH from other causes. Two hundred twenty-seven subjects were studied: patients with AFD (n=44; 55% with LVH), healthy volunteers (n=67; 0% with LVH), patients with hypertension (n=41; 24% with LVH), patients with hypertrophic cardiomyopathy (n=34; 100% with LVH), those with severe aortic stenosis (n=21; 81% with LVH), and patients with definite amyloid light-chain (AL) cardiac amyloidosis (n=20; 100% with LVH). T1 mapping was performed using the shortened modified Look-Locker inversion sequence on a 1.5-T magnet before gadolinium administration with primary results derived from the basal and midseptum. Compared with health volunteers, septal T1 was lower in AFD and higher in other diseases (AFD versus healthy volunteers versus other patients, 882±47, 968±32, 1018±74 milliseconds; Pgadolinium enhancement (1001±82 versus 891±38 milliseconds; P<0.0001). Noncontrast T1 mapping shows potential as a unique and powerful measurement in the imaging assessment of LVH and AFD.

Modular pulse sequencing in a tokamak system

International Nuclear Information System (INIS)

Chew, A.C.; Lee, S.; Saw, S.H.

1992-01-01

Pulse technique applied in the timing and sequencing of the various part of the MUT tokamak system are discussed. The modular architecture of the pulse generating device highlights the versatile application of the simple physical concepts in precise and complicated research experiment. (author)

Double pulse laser ablation and plasma: Laser induced breakdown spectroscopy signal enhancement

International Nuclear Information System (INIS)

Babushok, V.I.; DeLucia, F.C.; Gottfried, J.L.; Munson, C.A.; Miziolek, A.W.

2006-01-01

A review of recent results of the studies of double laser pulse plasma and ablation for laser induced breakdown spectroscopy applications is presented. The double pulse laser induced breakdown spectroscopy configuration was suggested with the aim of overcoming the sensitivity shortcomings of the conventional single pulse laser induced breakdown spectroscopy technique. Several configurations have been suggested for the realization of the double pulse laser induced breakdown spectroscopy technique: collinear, orthogonal pre-spark, orthogonal pre-heating and dual pulse crossed beam modes. In addition, combinations of laser pulses with different wavelengths, different energies and durations were studied, thus providing flexibility in the choice of wavelength, pulse width, energy and pulse sequence. The double pulse laser induced breakdown spectroscopy approach provides a significant enhancement in the intensity of laser induced breakdown spectroscopy emission lines up to two orders of magnitude greater than a conventional single pulse laser induced breakdown spectroscopy. The double pulse technique leads to a better coupling of the laser beam with the plasma plume and target material, thus providing a more temporally effective energy delivery to the plasma and target. The experimental results demonstrate that the maximum effect is obtained at some optimum separation delay time between pulses. The optimum value of the interpulse delay depends on several factors, such as the target material, the energy level of excited states responsible for the emission, and the type of enhancement process considered. Depending on the specified parameter, the enhancement effects were observed on different time scales ranging from the picosecond time level (e.g., ion yield, ablation mass) up to the hundred microsecond level (e.g., increased emission intensity for laser induced breakdown spectroscopy of submerged metal target in water). Several suggestions have been proposed to explain

A New Adaptive Gamma Correction Based Algorithm Using DWT-SVD for Non-Contrast CT Image Enhancement.

Science.gov (United States)

Kallel, Fathi; Ben Hamida, Ahmed

2017-12-01

The performances of medical image processing techniques, in particular CT scans, are usually affected by poor contrast quality introduced by some medical imaging devices. This suggests the use of contrast enhancement methods as a solution to adjust the intensity distribution of the dark image. In this paper, an advanced adaptive and simple algorithm for dark medical image enhancement is proposed. This approach is principally based on adaptive gamma correction using discrete wavelet transform with singular-value decomposition (DWT-SVD). In a first step, the technique decomposes the input medical image into four frequency sub-bands by using DWT and then estimates the singular-value matrix of the low-low (LL) sub-band image. In a second step, an enhanced LL component is generated using an adequate correction factor and inverse singular value decomposition (SVD). In a third step, for an additional improvement of LL component, obtained LL sub-band image from SVD enhancement stage is classified into two main classes (low contrast and moderate contrast classes) based on their statistical information and therefore processed using an adaptive dynamic gamma correction function. In fact, an adaptive gamma correction factor is calculated for each image according to its class. Finally, the obtained LL sub-band image undergoes inverse DWT together with the unprocessed low-high (LH), high-low (HL), and high-high (HH) sub-bands for enhanced image generation. Different types of non-contrast CT medical images are considered for performance evaluation of the proposed contrast enhancement algorithm based on adaptive gamma correction using DWT-SVD (DWT-SVD-AGC). Results show that our proposed algorithm performs better than other state-of-the-art techniques.

Neural-network-designed pulse sequences for robust control of singlet-triplet qubits

Science.gov (United States)

Yang, Xu-Chen; Yung, Man-Hong; Wang, Xin

2018-04-01

Composite pulses are essential for universal manipulation of singlet-triplet spin qubits. In the absence of noise, they are required to perform arbitrary single-qubit operations due to the special control constraint of a singlet-triplet qubit, while in a noisy environment, more complicated sequences have been developed to dynamically correct the error. Tailoring these sequences typically requires numerically solving a set of nonlinear equations. Here we demonstrate that these pulse sequences can be generated by a well-trained, double-layer neural network. For sequences designed for the noise-free case, the trained neural network is capable of producing almost exactly the same pulses known in the literature. For more complicated noise-correcting sequences, the neural network produces pulses with slightly different line shapes, but the robustness against noises remains comparable. These results indicate that the neural network can be a judicious and powerful alternative to existing techniques in developing pulse sequences for universal fault-tolerant quantum computation.

Automated detection of acute haemorrhagic stroke in non-contrasted CT images

International Nuclear Information System (INIS)

Meetz, K.; Buelow, T.

2007-01-01

An efficient treatment of stroke patients implies a profound differential diagnosis that includes the detection of acute haematoma. The proposed approach provides an automated detection of acute haematoma, assisting the non-stroke expert in interpreting non-contrasted CT images. It consists of two steps: First, haematoma candidates are detected applying multilevel region growing approach based on a typical grey value characteristic. Second, true haematomas are differentiated from partial volume artefacts, relying on spatial features derived from distance-based histograms. This approach achieves a specificity of 77% and a sensitivity of 89.7% in detecting acute haematoma in non-contrasted CT images when applied to a set of 25 non-contrasted CT images. (orig.)

Non-contrast MRI perfusion angiosome in diabetic feet

Energy Technology Data Exchange (ETDEWEB)

Zheng, Jie [Cardiovascular Imaging Lab, Mallinckrodt Institute of Radiology, St. Louis, MO (United States); Hastings, Mary K.; Mueller, Michael J. [Washington University School of Medicine, The Program in Physical Therapy, St. Louis, MO (United States); Muccigross, David; Hildebolt, Charles F. [Washington University School of Medicine, Mallinckrodt Institute of Radiology, St. Louis, MO (United States); Fan, Zhaoyang [Cedars-Sinai Medical Center, Biomedical Imaging Research Institute, Los Angeles, CA (United States); Gao, Fabao [West China Hospital, Sichuan University, Department of Radiology, Chengdu (China); Curci, John [Washington University School of Medicine, The Department of Surgery, St. Louis, MO (United States)

2015-01-15

The purpose of this study is to develop a non-contrast magnetic resonance imaging (MRI) approach to evaluate skeletal muscle perfusion in the diabetic foot based on the concept of angiosomes of the foot. Five healthy volunteers and five participants with diabetes (HbA1c = 7.2 ± 1.8 %) without a history of peripheral artery disease were examined. The non-contrast perfusion measurements were performed during a toe flexion challenge. Absolute perfusion maps were created and two regions (medial and lateral) on the maps were segmented based on angiosomes. Regional difference in the perfusion of foot muscle was readily visualized in the MRI perfusion angiosomes during the challenge. In the participants with diabetes, the perfusion during toe flexion challenge was significantly lower than in healthy volunteers (P < 0.01). The average perfusion for the medial plantar region of the right foot was lower in subjects with diabetes (38 ± 9 ml/min/100 g) than in healthy subjects (93 ± 33 ml/min/100 g). Non-contrast MRI perfusion angiosome maps demonstrate the feasibility of determining regional perfusion in foot muscles during toe challenge and may facilitate evaluation of muscle perfusion in diabetic feet. (orig.)

Non-contrast MRI perfusion angiosome in diabetic feet

International Nuclear Information System (INIS)

Zheng, Jie; Hastings, Mary K.; Mueller, Michael J.; Muccigross, David; Hildebolt, Charles F.; Fan, Zhaoyang; Gao, Fabao; Curci, John

2015-01-01

The purpose of this study is to develop a non-contrast magnetic resonance imaging (MRI) approach to evaluate skeletal muscle perfusion in the diabetic foot based on the concept of angiosomes of the foot. Five healthy volunteers and five participants with diabetes (HbA1c = 7.2 ± 1.8 %) without a history of peripheral artery disease were examined. The non-contrast perfusion measurements were performed during a toe flexion challenge. Absolute perfusion maps were created and two regions (medial and lateral) on the maps were segmented based on angiosomes. Regional difference in the perfusion of foot muscle was readily visualized in the MRI perfusion angiosomes during the challenge. In the participants with diabetes, the perfusion during toe flexion challenge was significantly lower than in healthy volunteers (P < 0.01). The average perfusion for the medial plantar region of the right foot was lower in subjects with diabetes (38 ± 9 ml/min/100 g) than in healthy subjects (93 ± 33 ml/min/100 g). Non-contrast MRI perfusion angiosome maps demonstrate the feasibility of determining regional perfusion in foot muscles during toe challenge and may facilitate evaluation of muscle perfusion in diabetic feet. (orig.)

Noncontrast computed tomographic Hounsfield unit evaluation of cerebral venous thrombosis: a quantitative evaluation

Energy Technology Data Exchange (ETDEWEB)

Besachio, David A. [University of Utah, Department of Radiology, Salt Lake City (United States); United States Navy, Bethesda, MD (United States); Quigley, Edward P.; Shah, Lubdha M.; Salzman, Karen L. [University of Utah, Department of Radiology, Salt Lake City (United States)

2013-08-15

Our objective is to determine the utility of noncontrast Hounsfield unit values, Hounsfield unit values corrected for the patient's hematocrit, and venoarterial Hounsfield unit difference measurements in the identification of intracranial venous thrombosis on noncontrast head computed tomography. We retrospectively reviewed noncontrast head computed tomography exams performed in both normal patients and those with cerebral venous thrombosis, acquiring Hounsfield unit values in normal and thrombosed cerebral venous structures. Also, we acquired Hounsfield unit values in the internal carotid artery for comparison to thrombosed and nonthrombosed venous structures and compared the venous Hounsfield unit values to the patient's hematocrit. A significant difference is identified between Hounsfield unit values in thrombosed and nonthrombosed venous structures. Applying Hounsfield unit threshold values of greater than 65, a Hounsfield unit to hematocrit ratio of greater than 1.7, and venoarterial difference values greater than 15 alone and in combination, the majority of cases of venous thrombosis are identifiable on noncontrast head computed tomography. Absolute Hounsfield unit values, Hounsfield unit to hematocrit ratios, and venoarterial Hounsfield unit value differences are a useful adjunct in noncontrast head computed tomographic evaluation of cerebral venous thrombosis. (orig.)

Noncontrast computed tomographic Hounsfield unit evaluation of cerebral venous thrombosis: a quantitative evaluation

International Nuclear Information System (INIS)

Besachio, David A.; Quigley, Edward P.; Shah, Lubdha M.; Salzman, Karen L.

2013-01-01

Our objective is to determine the utility of noncontrast Hounsfield unit values, Hounsfield unit values corrected for the patient's hematocrit, and venoarterial Hounsfield unit difference measurements in the identification of intracranial venous thrombosis on noncontrast head computed tomography. We retrospectively reviewed noncontrast head computed tomography exams performed in both normal patients and those with cerebral venous thrombosis, acquiring Hounsfield unit values in normal and thrombosed cerebral venous structures. Also, we acquired Hounsfield unit values in the internal carotid artery for comparison to thrombosed and nonthrombosed venous structures and compared the venous Hounsfield unit values to the patient's hematocrit. A significant difference is identified between Hounsfield unit values in thrombosed and nonthrombosed venous structures. Applying Hounsfield unit threshold values of greater than 65, a Hounsfield unit to hematocrit ratio of greater than 1.7, and venoarterial difference values greater than 15 alone and in combination, the majority of cases of venous thrombosis are identifiable on noncontrast head computed tomography. Absolute Hounsfield unit values, Hounsfield unit to hematocrit ratios, and venoarterial Hounsfield unit value differences are a useful adjunct in noncontrast head computed tomographic evaluation of cerebral venous thrombosis. (orig.)

Investigation of the Effect of Finite Pulse Errors on BABA Pulse Sequence Using Floquet-Magnus Expansion Approach.

Science.gov (United States)

Mananga, Eugene S; Reid, Alicia E

This paper presents the study of finite pulse widths for the BABA pulse sequence using the Floquet-Magnus expansion (FME) approach. In the FME scheme, the first order F 1 is identical to its counterparts in average Hamiltonian theory (AHT) and Floquet theory (FT). However, the timing part in the FME approach is introduced via the Λ 1 ( t ) function not present in other schemes. This function provides an easy way for evaluating the spin evolution during "the time in between" through the Magnus expansion of the operator connected to the timing part of the evolution. The evaluation of Λ 1 ( t ) is useful especially for the analysis of the non-stroboscopic evolution. Here, the importance of the boundary conditions, which provides a natural choice of Λ 1 (0) is ignored. This work uses the Λ 1 ( t ) function to compare the efficiency of the BABA pulse sequence with δ - pulses and the BABA pulse sequence with finite pulses. Calculations of Λ 1 ( t ) and F 1 are presented.

Programmable pulse sequence generator with multiple output lines

Science.gov (United States)

Drabczyk, Hubert

2006-10-01

This paper presents a novel concept of pulse sequence generator and its prototype as an electronic circuit testing laboratory tool. The generator has multiple output lines and is capable of using control data defining different pulse sequences to be given to the outputs. It is also possible to use different voltage levels in output signal and switch output lines for reading data from driven system. The pulse sequence generator can be used for runtime environment simulation, as hardware tester or auxiliary tool in new designs. Important design factors were to keep cost of the tool low and allow integration with other projects by using flexible architecture. The prototype was based on universal programmer with adjustable power supply, '51 microcontroller and Altera Cyclone chip. The generator communicates witch PC computer via RS232 port. Dedicated software was developed in the course of this project, to control the tool and data transmission. The prototype confirmed the possibility to create an inexpensive multipurpose laboratory tool for programming, testing and simulation of digital devices.

Pulse sequence optimization for superparamagnetic iron oxide-enhaced MR imaging in the detection of hepatic VX2 tumors in rabbits

International Nuclear Information System (INIS)

Jang, Hyun Jung; Han, Joon Koo; Lee, Kyoung Ho; Kim, Se Hyung; Choi, Byung Ihn; Kim, Tae Kyoung

2003-01-01

The purpose of this experimental study was to determine the optimal pulse sequences for SPIO-enhanced MR imaging in the evaluation of multiple hepatic tumors. Twelve rabbits with multiple VX2 liver tumors underwent SPOI-enhanced MRI using the following nine pulse sequences: TSE T2-weighted imaging (T2W1), TSE proton density-weighted imaging(PDWI), and GRE T2*-weighted imaging (T2*W1) with seven different echo times (TE). Liver-lesion contrast-to-noise ratios (CNRs) were calculated, and images were also assessed qualitatively by two radiologists, who reached a consensus as to lesion conspicuity and imaging artifacts using a four-level scale. By means of pathologic correlation, the sensitivity and positive predictive value of each sequence was calculated. TSE T2W1 and long-TE (35 msec) FLASH T2*W1 showed the highest liver-lesion CNR. The best lesion conspicuity was seen at TSE T2W1 and medium-TE (12 msec) GRE T2*W1. Short TE GRE T2*W1 showed the least imaging artifacts. The four sequences which demonstrated the best sensitivity were medium-TE (12 msec), GRE T2*W1 (FLASH, 84%; FISP, 82%), TSE W2T1 (79%), and TSE PDWI (76%). All nine sequences showed overall high positive predictive value (86-97%), with no statistically significant difference (p>0.05). In terms of image quality and the detection of sensitivity, TSE T2W1 and medium TE (12 msec) GRE T2*W1 were the top two pulse sequences among the various sequences used for no SPIO-enhanced MRI. They are thus considered to be optimal sequences for evaluating multiple malignant hepatic tumors

MR pulse sequences for selective relaxation time measurements: a phantom study

DEFF Research Database (Denmark)

Thomsen, C; Jensen, K E; Jensen, M

1990-01-01

a Siemens Magnetom wholebody magnetic resonance scanner operating at 1.5 Tesla was used. For comparison six imaging pulse sequences for relaxation time measurements were tested on the same phantom. The spectroscopic pulse sequences all had an accuracy better than 10% of the reference values....

Rotator cuff tears noncontrast MRI compared to MR arthrography

Energy Technology Data Exchange (ETDEWEB)

Lee, Ji Hyun; Yoon, Young Cheol [Sungkyunkwan University, School of Medicine, Department of Radiology, Samsung Medical Center, Gangnam-gu, Seoul (Korea, Republic of); Jung, Jee Young [Chungang University School of Medicine, Department of Radiology, Chungang University Hospital, Seoul (Korea, Republic of); Yoo, Jae Chul [Sungkyunkwan University, School of Medicine, Department of Orthopedic Surgery, Samsung Medical Center, Seoul (Korea, Republic of)

2015-12-15

To compare the accuracy of indirect magnetic resonance arthrography and noncontrast magnetic resonance imaging for diagnosing rotator cuff tears. In total, 333 patients who underwent noncontrast magnetic resonance imaging or indirect magnetic resonance arthrography were included retrospectively. Two musculoskeletal radiologists evaluated the images for the presence of supraspinatus-infraspinatus and subscapularis tendon tears. The overall diagnostic performance was calculated using the arthroscopic findings as the reference standard. Statistical differences between the diagnostic performances of the two methods were analyzed. Ninety-six and 237 patients who underwent noncontrast magnetic resonance imaging and indirect magnetic resonance arthrography were assigned into groups A and B, respectively. Sensitivity for diagnosing articular-surface partial-thickness supraspinatus-infraspinatus tendon tear was slightly higher in group B than in group A. Statistical significance was confirmed by multivariate analysis using the generalized estimating equation (p = 0.046). The specificity for diagnosing subscapularis tendon tear (85 % vs. 68 %, p = 0.012) and grading accuracy (57 % vs. 40 %, p = 0.005) was higher in group B than in group A; the differences were statistically significant for one out of two readers. Univariate analysis using the generalized estimating equation showed that the accuracy for diagnosing subscapularis tendon tear in group B was higher than in group A (p = 0.042). There were no statistically significant differences between the diagnostic performances of both methods for any other parameters. Indirect magnetic resonance arthrography may facilitate more accurate diagnosis and grading of subscapularis tendon tears compared with noncontrast magnetic resonance imaging. (orig.)

Rotator cuff tears noncontrast MRI compared to MR arthrography

International Nuclear Information System (INIS)

Lee, Ji Hyun; Yoon, Young Cheol; Jung, Jee Young; Yoo, Jae Chul

2015-01-01

To compare the accuracy of indirect magnetic resonance arthrography and noncontrast magnetic resonance imaging for diagnosing rotator cuff tears. In total, 333 patients who underwent noncontrast magnetic resonance imaging or indirect magnetic resonance arthrography were included retrospectively. Two musculoskeletal radiologists evaluated the images for the presence of supraspinatus-infraspinatus and subscapularis tendon tears. The overall diagnostic performance was calculated using the arthroscopic findings as the reference standard. Statistical differences between the diagnostic performances of the two methods were analyzed. Ninety-six and 237 patients who underwent noncontrast magnetic resonance imaging and indirect magnetic resonance arthrography were assigned into groups A and B, respectively. Sensitivity for diagnosing articular-surface partial-thickness supraspinatus-infraspinatus tendon tear was slightly higher in group B than in group A. Statistical significance was confirmed by multivariate analysis using the generalized estimating equation (p = 0.046). The specificity for diagnosing subscapularis tendon tear (85 % vs. 68 %, p = 0.012) and grading accuracy (57 % vs. 40 %, p = 0.005) was higher in group B than in group A; the differences were statistically significant for one out of two readers. Univariate analysis using the generalized estimating equation showed that the accuracy for diagnosing subscapularis tendon tear in group B was higher than in group A (p = 0.042). There were no statistically significant differences between the diagnostic performances of both methods for any other parameters. Indirect magnetic resonance arthrography may facilitate more accurate diagnosis and grading of subscapularis tendon tears compared with noncontrast magnetic resonance imaging. (orig.)

MR of normal pancreas : comparison of five pulse sequences and enhancing patterns on dynamic imaging

International Nuclear Information System (INIS)

Jang, Hyun Jung; Kim, Tae Kyoung; Hong, Sung Hwan; Han, Joon Koo; Choi, Byung Ihn

1997-01-01

To compare T1-weighted FLASH and turbo spin echo (SE) T2-weighted sequences with conventional T1- and T2-weighted sequences in imaging normal pancreas and to describe the enhancing patterns on dynamic MR imging. Forty-four patients with presumed hepatic hemangiomas were studied at 1.0T or 1.5T by using conventional SE sequences (T1-weighted, T2-weighted, and heavily T2-weighted), turbo-SE T2-weighted sequences, and breath-hold T1-weighted FLASH sequences acquired before, immediately on, and at 1, 2, 3, and 5 or 10 minutes after injection of a bolus of gadopentetate dimeglumine. No patients had either a history or its clinical features of pancreatic disease. Images were quantitatively analyzed for signal-difference-to noise ratios (SD/Ns) between the pancreas and peripancreatic fat. Percentage enhancement of the pancreas was measured on each dynamic MR image. Conspicuity of the pancreatic border was qualitatively evaluated according to a consensus, reached by three radiologists. Turbo-SE T2-weighted images had a significantly higher SD/N ratio (p<0.001) and better conspicuity of the pancreatic border (p<0.001) than SE T2- and heavily T2-weighted images;T1-weighted SE images had a significantly higher SD/N ratio than T1-weighted FLASH images (p<0.001), but there was no significant difference between tham in qualitative analysis (p=0.346). Percentage enhancement immediately on and at 1, 2, 3, 5, and 10 minutes after administration of contrast material was 39.9%, 44.5%, 42.9%, 40.8%, 36.3%, 29.9%, respectively, with peak enhancement at 1 minute. In MR imaging of normal pancreas, turbo-SE T2-weighted imaging is superior to SE T2- and heavily T2- weighted imaging, and SE T1-weighted imaging is superior to T1-weighted FLASH imaging. On serial gadolinium-enhanced FLASH imaging, normal pancreas shows peak enhancement at 1 minute

Study of {sup 14}N NQR response to SORC pulse sequence

Energy Technology Data Exchange (ETDEWEB)

Konnai, A., E-mail: konnai@nmri.go.jp; Odano, N. [National Maritime Research Institute, Department of Navigation and System Engineering (Japan); Asaji, T. [Nihon University, Department of Chemistry, College of Humanities and Sciences (Japan)

2008-01-15

The behavior of nuclear quadrupole resonance (NQR) signals between RF pulses of the strong off-resonance comb (SORC) as well as the spin-locking spin-echo (SLSE) pulse sequences was studied as for {sup 14}N NQR line {nu}{sub +} of dimethylnitramine (CH{sub 3}){sub 2}NNO{sub 2} at 77 K. The periodic variation of the signal amplitude observed by using SORC pulse sequence could be reasonably explained by the theoretical expression reported in the literature.

Automatic coronary calcium scoring using noncontrast and contrast CT images

Energy Technology Data Exchange (ETDEWEB)

Yang, Guanyu, E-mail: yang.list@seu.edu.cn; Chen, Yang; Shu, Huazhong [Laboratory of Image Science and Technology, School of Computer Science and Engineering, Southeast University, No. 2, Si Pai Lou, Nanjing 210096 (China); Centre de Recherche en Information Biomédicale Sino-Français (LIA CRIBs), Nanjing 210096 (China); Key Laboratory of Computer Network and Information Integration, Southeast University, Ministry of Education, Nanjing 210096 (China); Ning, Xiufang; Sun, Qiaoyu [Laboratory of Image Science and Technology, School of Computer Science and Engineering, Southeast University, No. 2, Si Pai Lou, Nanjing 210096 (China); Key Laboratory of Computer Network and Information Integration, Southeast University, Ministry of Education, Nanjing 210096 (China); Coatrieux, Jean-Louis [INSERM-U1099, Rennes F-35000 (France); Labotatoire Traitement du Signal et de l’Image (LTSI), Université de Rennes 1, Campus de Beaulieu, Bat. 22, Rennes 35042 Cedex (France); Centre de Recherche en Information Biomédicale Sino-Français (LIA CRIBs), Nanjing 210096 (China)

2016-05-15

Purpose: Calcium scoring is widely used to assess the risk of coronary heart disease (CHD). Accurate coronary artery calcification detection in noncontrast CT image is a prerequisite step for coronary calcium scoring. Currently, calcified lesions in the coronary arteries are manually identified by radiologists in clinical practice. Thus, in this paper, a fully automatic calcium scoring method was developed to alleviate the work load of the radiologists or cardiologists. Methods: The challenge of automatic coronary calcification detection is to discriminate the calcification in the coronary arteries from the calcification in the other tissues. Since the anatomy of coronary arteries is difficult to be observed in the noncontrast CT images, the contrast CT image of the same patient is used to extract the regions of the aorta, heart, and coronary arteries. Then, a patient-specific region-of-interest (ROI) is generated in the noncontrast CT image according to the segmentation results in the contrast CT image. This patient-specific ROI focuses on the regions in the neighborhood of coronary arteries for calcification detection, which can eliminate the calcifications in the surrounding tissues. A support vector machine classifier is applied finally to refine the results by removing possible image noise. Furthermore, the calcified lesions in the noncontrast images belonging to the different main coronary arteries are identified automatically using the labeling results of the extracted coronary arteries. Results: Forty datasets from four different CT machine vendors were used to evaluate their algorithm, which were provided by the MICCAI 2014 Coronary Calcium Scoring (orCaScore) Challenge. The sensitivity and positive predictive value for the volume of detected calcifications are 0.989 and 0.948. Only one patient out of 40 patients had been assigned to the wrong risk category defined according to Agatston scores (0, 1–100, 101–300, >300) by comparing with the ground

Investigation of the effect of finite pulse errors on the BABA pulse sequence using the Floquet-Magnus expansion approach

Science.gov (United States)

Mananga, Eugene S.; Reid, Alicia E.

2013-01-01

This paper presents a study of finite pulse widths for the BABA pulse sequence using the Floquet-Magnus expansion (FME) approach. In the FME scheme, the first order ? is identical to its counterparts in average Hamiltonian theory (AHT) and Floquet theory (FT). However, the timing part in the FME approach is introduced via the ? function not present in other schemes. This function provides an easy way for evaluating the spin evolution during the time in between' through the Magnus expansion of the operator connected to the timing part of the evolution. The evaluation of ? is particularly useful for the analysis of the non-stroboscopic evolution. Here, the importance of the boundary conditions, which provide a natural choice of ? , is ignored. This work uses the ? function to compare the efficiency of the BABA pulse sequence with ? and the BABA pulse sequence with finite pulses. Calculations of ? and ? are presented.

Study and realisation of a programmable generator of pulse sequences, for nuclear magnetic resonance

International Nuclear Information System (INIS)

Lambert, Daniel

1974-01-01

After having recalled the operation of pulse-based nuclear magnetic resonance and the use of pulse sequences in NMR-based measurements, and outlined the need for a pulse sequence generator, the author reports the design and realisation of such a device. He describes its general organisation with its base sequence, base clock, sequence start, duration, displays, data transfers, data processing, and signal distribution. He presents the chosen technology (ECL logics), the sequence base set, time bases, multiplexers, comparison sets, the distribution set, the sequence programming, the sampling and output set. He reports tests and the use of the so-designed generator [fr

A dispersion-balanced Discrete Fourier Transform of repetitive pulse sequences using temporal Talbot effect

Science.gov (United States)

Fernández-Pousa, Carlos R.

2017-11-01

We propose a processor based on the concatenation of two fractional temporal Talbot dispersive lines with balanced dispersion to perform the DFT of a repetitive electrical sequence, for its use as a controlled source of optical pulse sequences. The electrical sequence is used to impart the amplitude and phase of a coherent train of optical pulses by use of a modulator placed between the two Talbot lines. The proposal has been built on a representation of the action of fractional Talbot effect on repetitive pulse sequences and a comparison with related results and proposals. It is shown that the proposed system is reconfigurable within a few repetition periods, has the same processing rate as the input optical pulse train, and requires the same technical complexity in terms of dispersion and pulse width as the standard, passive pulse-repetition rate multipliers based on fractional Talbot effect.

Value of noncontrast spiral CT for suspected acute appendicitis

International Nuclear Information System (INIS)

Choi, Pil Yeob; Lee, Sang Wook; Kwon, Jae Soo; Sung, Young Soon; Rho, Myoung Ho; Chang, Jeong A.

1998-01-01

To assess the diagnostic accuracy and clinical efficacy of noncontrast spiral CT in patients with suspected acute appendicitis. Over a six-month period, 100 patients with suspected acute appendicitis were prospectively evaluated with noncontrast spiral CT. All scans were obtained from the lower body of L3 to the symphysis pubis, with 5mm or 10mm collimation and pitch of 1 or 1.5, and without intravenous or oral contrast material. Diagnosis was established by means of surgical or clinical follow-up. Prospective diagnosis based on CT findings was compared with surgical results and clinical follow-up. Acute appendicitis was confirmed in 47 of 100 patients. On the basis of the Ct findings, SI patients were prospectively interpreted as positive for appendicitis, but in six the diagnosis was false-positive. Two of the 47 with acute appendicitis were prospectively interpreted as normal. The preoperative diagnosis of acute appendicitis was, thus, 45 true-positive, 47 true-negative, six false-positive and two false-negative yielding a sensitivity of 96%, a specificity of 89%, an accuracy of 92%, a positive predictive value of 88%, and a negative predictive value of 96%. Using CT, an alternative diagnosis was established in 14 patients. Noncontrast spiral CT is a useful technique for diagnosing acute appendicitis. =20

Virtual non-contrast computer tomography (CT) with spectral CT as an alternative to conventional unenhanced CT in the assessment of gastric cancer.

Science.gov (United States)

Tian, Shi-Feng; Liu, Ai-Lian; Wang, He-Qing; Liu, Jing-Hong; Sun, Mei-Yu; Liu, Yi-Jun

2015-01-01

The purpose of this study was to evaluate computed tomography (CT) virtual non-contrast (VNC) spectral imaging for gastric carcinoma. Fifty-two patients with histologically proven gastric carcinomas underwent gemstone spectral imaging (GSI) including non-contrast and contrast-enhanced hepatic arterial, portal venous, and equilibrium phase acquisitions prior to surgery. VNC arterial phase (VNCa), VNC venous phase (VNCv), and VNC equilibrium phase (VNCe) images were obtained by subtracting iodine from iodine/water images. Images were analyzed with respect to image quality, gastric carcinoma-intragastric water contrast-to-noise ratio (CNR), gastric carcinoma-perigastric fat CNR, serosal invasion, and enlarged lymph nodes around the lesions. Carcinoma-water CNR values were significantly higher in VNCa, VNCv, and VNCe images than in normal CT images (2.72, 2.60, 2.61, respectively, vs 2.35, p≤0.008). Carcinoma- perigastric fat CNR values were significantly lower in VNCa, VNCv, and VNCe images than in normal CT images (7.63, 7.49, 7.32, respectively, vs 8.48, pVNC arterial phase images may be a surrogate for conventional non-contrast CT images in gastric carcinoma evaluation.

Magnetic resonance imaging of the normal pituitary gland using ultrashort TE (UTE) pulse sequences (REV 1.0)

International Nuclear Information System (INIS)

Portman, Olivia; Flemming, Stephen; Cox, Jeremy P.D.; Johnston, Desmond G.; Bydder, Graeme M.

2008-01-01

The purpose of this study was to examine the normal pituitary gland in male subjects with ultrashort echo time (TE) pulse sequences, describe its appearance and measure its signal intensity before and after contrast enhancement. Eleven male volunteers (mean age 57.1 years; range 36-81 years) were examined with a fat-suppressed ultrashort TE (= 0.08 ms) pulse sequence. The studies were repeated after the administration of intravenous gadodiamide. The MR scans were examined for gland morphology and signal intensity before and after enhancement. Endocrinological evaluation included baseline pituitary function tests and a glucagon stimulatory test to assess pituitary cortisol and growth hormone reserve. High signal intensity was observed in the anterior pituitary relative to the brain in nine of the 11 subjects. These regions involved the whole of the anterior pituitary in three subjects, were localised to one side in two examples and were seen inferiorly in three subjects. Signal intensities relative to the brain increased with age, with a peak around the sixth or seventh decade and decreasing thereafter. Overall, the pituitary function tests were considered to be within normal limits and did not correlate with pituitary gland signal intensity. The anterior pituitary shows increased signal intensity in normal subjects when examined with T 1 -weighted ultrashort TE pulse sequences. The cause of this increased intensity is unknown, but fibrosis and iron deposition are possible candidates. The variation in signal intensity with age followed the temporal pattern of iron content observed at post mortem. No relationship with endocrine status was observed. (orig.)

Magnetic resonance imaging of the normal pituitary gland using ultrashort TE (UTE) pulse sequences (REV 1.0)

Energy Technology Data Exchange (ETDEWEB)

Portman, Olivia; Flemming, Stephen; Cox, Jeremy P.D.; Johnston, Desmond G. [Imperial College Faculty of Medicine, St Mary' s Hospital, Endocrinology and Metabolic Medicine, London (United Kingdom); Bydder, Graeme M. [University of California, San Diego, Department of Radiology, San Diego, CA (United States)

2008-03-15

The purpose of this study was to examine the normal pituitary gland in male subjects with ultrashort echo time (TE) pulse sequences, describe its appearance and measure its signal intensity before and after contrast enhancement. Eleven male volunteers (mean age 57.1 years; range 36-81 years) were examined with a fat-suppressed ultrashort TE (= 0.08 ms) pulse sequence. The studies were repeated after the administration of intravenous gadodiamide. The MR scans were examined for gland morphology and signal intensity before and after enhancement. Endocrinological evaluation included baseline pituitary function tests and a glucagon stimulatory test to assess pituitary cortisol and growth hormone reserve. High signal intensity was observed in the anterior pituitary relative to the brain in nine of the 11 subjects. These regions involved the whole of the anterior pituitary in three subjects, were localised to one side in two examples and were seen inferiorly in three subjects. Signal intensities relative to the brain increased with age, with a peak around the sixth or seventh decade and decreasing thereafter. Overall, the pituitary function tests were considered to be within normal limits and did not correlate with pituitary gland signal intensity. The anterior pituitary shows increased signal intensity in normal subjects when examined with T{sub 1}-weighted ultrashort TE pulse sequences. The cause of this increased intensity is unknown, but fibrosis and iron deposition are possible candidates. The variation in signal intensity with age followed the temporal pattern of iron content observed at post mortem. No relationship with endocrine status was observed. (orig.)

Estimate of pulse-sequence data acquisition system for multi-dimensional measurement

Energy Technology Data Exchange (ETDEWEB)

Kitamura, Yasunori; Sakae, Takeji; Nohtomi, Akihiro; Matoba, Masaru [Kyushu Univ., Fukuoka (Japan). Faculty of Engineering; Matsumoto, Yuzuru

1996-07-01

A pulse-sequence data acquisition system has been newly designed and estimated for the measurement of one- or multi-dimensional pulse train coming from radiation detectors. In this system, in order to realize the pulse-sequence data acquisition, the arrival time of each pulse is recorded to a memory of a personal computer (PC). For the multi-dimensional data acquisition with several input channels, each arrival-time data is tagged with a `flag` which indicates the input channel of arriving pulse. Counting losses due to the existence of processing time of the PC are expected to be reduced by using a First-In-First-Out (FIFO) memory unit. In order to verify this system, a computer simulation was performed, Various sets of random pulse trains with different mean pulse rate (1-600 kcps) were generated by using Monte Carlo simulation technique. Those pulse trains were dealt with another code which simulates the newly-designed data acquisition system including a FIFO memory unit; the memory size was assumed to be 0-100 words. And the recorded pulse trains on the PC with the various FIFO memory sizes have been observed. From the result of the simulation, it appears that the system with 3 words FIFO memory unit works successfully up to the pulse rate of 10 kcps without any severe counting losses. (author)

Estimate of pulse-sequence data acquisition system for multi-dimensional measurement

International Nuclear Information System (INIS)

Kitamura, Yasunori; Sakae, Takeji; Nohtomi, Akihiro; Matoba, Masaru; Matsumoto, Yuzuru.

1996-01-01

A pulse-sequence data acquisition system has been newly designed and estimated for the measurement of one- or multi-dimensional pulse train coming from radiation detectors. In this system, in order to realize the pulse-sequence data acquisition, the arrival time of each pulse is recorded to a memory of a personal computer (PC). For the multi-dimensional data acquisition with several input channels, each arrival-time data is tagged with a 'flag' which indicates the input channel of arriving pulse. Counting losses due to the existence of processing time of the PC are expected to be reduced by using a First-In-First-Out (FIFO) memory unit. In order to verify this system, a computer simulation was performed, Various sets of random pulse trains with different mean pulse rate (1-600 kcps) were generated by using Monte Carlo simulation technique. Those pulse trains were dealt with another code which simulates the newly-designed data acquisition system including a FIFO memory unit; the memory size was assumed to be 0-100 words. And the recorded pulse trains on the PC with the various FIFO memory sizes have been observed. From the result of the simulation, it appears that the system with 3 words FIFO memory unit works successfully up to the pulse rate of 10 kcps without any severe counting losses. (author)

Gadofosveset trisodium-enhanced magnetic resonance angiography of the left atrium-A feasibility study

Energy Technology Data Exchange (ETDEWEB)

Wagner, Moritz, E-mail: moritz.wagner@charite.d [Department of Radiology, Charite - University Hospital, Berlin (Germany); Rief, Matthias; Asbach, Patrick [Department of Radiology, Charite - University Hospital, Berlin (Germany); Vogtmann, Thomas [Department of Cardioloy and Angiology, Charite - University Hospital, Berlin (Germany); Huppertz, Alexander [Imaging Science Institute Charite Berlin, Berlin (Germany); Beling, Mark [Department of Cardioloy and Angiology, Charite - University Hospital, Berlin (Germany); Butler, Craig [Mazankowski Alberta Heart Institute, University of Alberta, Edmonton (Canada); Laule, Michael [Department of Cardioloy and Angiology, Charite - University Hospital, Berlin (Germany); Warmuth, Carsten; Taupitz, Matthias; Hamm, Bernd; Lembcke, Alexander [Department of Radiology, Charite - University Hospital, Berlin (Germany)

2010-08-15

Aim: Imaging of the left atrium is regularly performed prior to pulmonary vein isolation. The aim of the study was to evaluate the feasibility of contrast-enhanced high-resolution magnetic resonance angiography (MRA) of the left atrium using the blood-pool contrast agent gadofosveset trisodium in comparison to noncontrast MRA. Materials and methods: Twenty consecutive patients were examined by free-breathing electrocardiogram-gated whole-heart MRA (reconstructed spatial resolution, 0.7 mm x 0.6 mm x 0.8 mm) with a noncontrast T2-prepared steady state free precession sequence (T2-prep SSFP) and a gadofosveset trisodium-enhanced inversion-recovery SSFP sequence (CE IR-SSFP). Contrast-to-noise ratio (CNR) of blood in the left atrium was determined. Depiction of the left atrium was rated by two radiologists in consensus. A cardiologist segmented the MR data sets and rated depiction of the left atrium. Results: Five of 20 patients had irregular breathing patterns with navigator efficiency less than 35% and were excluded from evaluation. CNR was significantly higher for CE IR-SSFP compared with T2-prep SSFP (18.4 {+-} 5.3 vs. 11.7 {+-} 3.5, p < 0.01). Depiction of the left atrium by T2-prep SSFP was rated as good in four patients, moderate in ten patients, and poor in one patient, whereas depiction of the left atrium by CE IR-SSFP was rated as excellent in nine patients, good in four patients, and moderate in two patients. CE IR-SSFP allowed for semiautomated segmentation of the left atrium in 15 patients, whereas T2-prep SSFP allowed for segmentation only in ten patients. Conclusion: Gadofosveset trisodium-enhanced MRA of the left atrium is feasible with significantly improved image quality compared to noncontrast MRA.

New MR pulse sequence

International Nuclear Information System (INIS)

Harms, S.E.; Flamig, D.P.; Griffey, R.H.

1990-01-01

This paper describes a method for fat suppression for three-dimensional MR imaging. The FATS (fat-suppressed acquisition with echo time shortened) sequence employs a pair of opposing adiabatic half-passage RF pulses tuned on fat resonance. The imaging parameters are as follows: TR, 20 msec; TE, 21.7-3.2 msec; 1,024 x 128 x 128 acquired matrix; imaging time, approximately 11 minutes. A series of 54 examinations were performed. Excellent fat suppression with water excitation is achieved in all cases. The orbital images demonstrate superior resolution of small orbital lesions. The high signal-to-noise ratio (SNR) in cranial studies demonstrates excellent petrous bone and internal auditory canal anatomy

Enhancement of High-Intensity Focused Ultrasound Heating by Short-Pulse Generated Cavitation

Directory of Open Access Journals (Sweden)

Shin Yoshizawa

2017-03-01

Full Text Available A target tissue can be thermally coagulated in high-intensity focused ultrasound (HIFU treatment noninvasively. HIFU thermal treatments have been clinically applied to various solid tumors. One of the problems in HIFU treatments is a long treatment time. Acoustically driven microbubbles can accelerate the ultrasonic heating, resulting in the significant reduction of the treatment time. In this paper, a method named “trigger HIFU exposure” which employs cavitation microbubbles is introduced and its results are reviewed. A trigger HIFU sequence consists of high-intensity short pulses followed by moderate-intensity long bursts. Cavitation bubbles induced in a multiple focal regions by rapidly scanning the focus of high-intensity pulses enhanced the temperature increase significantly and produced a large coagulation region with high efficiency.

The Dante pulse sequence description by product operators formalism

International Nuclear Information System (INIS)

Velloso, Marcia Helena Rodrigues; Villar, Daniel Figueroa

1999-01-01

The objective of this work is to supply a didactic example of the application of the product operators formalism for the description of the DANTE (delays alternating with mutation for tailored excitation) pulse sequence

A new RF tagging pulse based on the Frank poly-phase perfect sequence

DEFF Research Database (Denmark)

Laustsen, Christoffer; Greferath, Marcus; Ringgaard, Steffen

2014-01-01

Radio frequency (RF) spectrally selective multiband pulses or tagging pulses, are applicable in a broad range of magnetic resonance methods. We demonstrate through simulations and experiments a new phase-modulation-only RF pulse for RF tagging based on the Frank poly-phase perfect sequence...

Pancreatic cancer screening employing noncontrast magnetic resonance imaging combined with ultrasonography

International Nuclear Information System (INIS)

Kuroki-Suzuki, Seiko; Nagashima, Chieko; Machida, Minoru; Muramatsu, Yukio; Moriyama, Noriyuki; Kuroki, Yoshifumi; Nasu, Katsuhiro

2011-01-01

We have conducted an initial evaluation on the potential of combining noncontrast magnetic resonance imaging (MRI) and ultrasonography (US) to screen for pancreatic cancer. An independent ethics committee approved this study. A total of 2511 patients who underwent US were enrolled. Among them, noncontrast MRI was performed in patients in whom the entire pancreas was difficult to depict or in those with US-suspected pancreatic lesions. In total, using 1.5-T MRI, T1- and T2-weighted imaging, magnetic resonance cholangiopancreatography, and diffusion-weighted imaging, we acquired a variety of images. The efficacy of US and MRI in screening for pancreatic lesions, including pancreatic cancer, was evaluated. Of 2511 patients, 184 underwent MRI, and the pancreas was demonstrated in all of them. Among the 2511, five pancreatic cancers were detected by MRI combined with US (detection rate 0.20%). Of the five pancreatic cancers, three were detected by US (detection rate 0.12%) and two by MRI. Four of the five pancreatic cancers were resectable. By combining noncontrast MRI with US, pancreatic cancer can be detected with high accuracy. Other pancreatic lesions that require follow-up, including intraductal papillary mucinous neoplasms, can also be detected. Thus, pancreatic cancer screening with a combination of US and MRI is suggested. (author)

Hypercapnic normalization of BOLD fMRI: comparison across field strengths and pulse sequences

DEFF Research Database (Denmark)

Cohen, Eric R.; Rostrup, Egill; Sidaros, Karam

2004-01-01

to be more accurately localized and quantified based on changes in venous blood oxygenation alone. The normalized BOLD signal induced by the motor task was consistent across different magnetic fields and pulse sequences, and corresponded well with cerebral blood flow measurements. Our data suggest...... size, as well as experimental, such as pulse sequence and static magnetic field strength (B(0)). Thus, it is difficult to compare task-induced fMRI signals across subjects, field strengths, and pulse sequences. This problem can be overcome by normalizing the neural activity-induced BOLD fMRI response...... for global stimulation, subjects breathed a 5% CO(2) gas mixture. Under all conditions, voxels containing primarily large veins and those containing primarily active tissue (i.e., capillaries and small veins) showed distinguishable behavior after hypercapnic normalization. This allowed functional activity...

PuLSE: Quality control and quantification of peptide sequences explored by phage display libraries.

Science.gov (United States)

Shave, Steven; Mann, Stefan; Koszela, Joanna; Kerr, Alastair; Auer, Manfred

2018-01-01

The design of highly diverse phage display libraries is based on assumption that DNA bases are incorporated at similar rates within the randomized sequence. As library complexity increases and expected copy numbers of unique sequences decrease, the exploration of library space becomes sparser and the presence of truly random sequences becomes critical. We present the program PuLSE (Phage Library Sequence Evaluation) as a tool for assessing randomness and therefore diversity of phage display libraries. PuLSE runs on a collection of sequence reads in the fastq file format and generates tables profiling the library in terms of unique DNA sequence counts and positions, translated peptide sequences, and normalized 'expected' occurrences from base to residue codon frequencies. The output allows at-a-glance quantitative quality control of a phage library in terms of sequence coverage both at the DNA base and translated protein residue level, which has been missing from toolsets and literature. The open source program PuLSE is available in two formats, a C++ source code package for compilation and integration into existing bioinformatics pipelines and precompiled binaries for ease of use.

Pulse sequences and visualization of instruments

International Nuclear Information System (INIS)

Merkle, E.M.; Ulm Univ.; Wendt, M.; Chung, Y.C.; Duerk, J.L.; University Hospitals of Cleveland and Case Western Reserve University, OH; Lewin, J.S.

1998-01-01

While initially advocated primarily for intrasurgical visualization (e.g., craniotomy), interventional MRI rapidly evolved into roles in image-guided localization for needle-based procedures, minimally invasive neurosurgical procedures, and thermal ablation of cancer. In this contest, MRI pulse sequences and scanning methods serve one of four primary roles: (1) speed improvement, (2) device localization, (3) anatomy/lesion differentiation and (4) temperature sensitivity. The first part of this manuscript deals with passive visualization of MR-compatible needles and the effects of field strength, sequence design, and orientation of the needle relative to the static magnetic field of the scanner. Issues and recommendations are given for low-field as well as high-field scanners. The second part contains methods reported to achieve improved acquisition efficiency over conventional phase encoding (wavelets, locally focused imaging, singular value decomposition and keyhole imaging). Finally, the last part of the manuscrpt reports the current status of thermosensitive sequences and their dependence on spinlattice relaxation time (T1), water diffusion coefficient (D) and proton chemical shift (δ). (orig.) [de

Value of contrast enhanced CT scanning in the non-trauma emergency room patient

International Nuclear Information System (INIS)

Wood, L.P.; Parisi, M.; Finch, I.J.

1990-01-01

To determine the value of performing contrast CT in addition to non-contrast CT in the evaluation of acute non-traumatic central nervous system disorders, we retrospectively reviewed 322 cases originating from the emergency room at our institution. The most common indication for scanning was seizure activity (34% of total), followed by headache (30%), focal neurological deficit (10%), and altered mental status (8%). 75% of the noncontrast scans were normal. The contrast enhanced scan revealed abnormalities not evident on the non-contrast scan in only three of these cases, and the information did not alter patient management. We conclude that in the acute setting, if a non-contrast CT is normal, a contrast study is usually unnecessary. Therefore, given the additional risks of contrast infusion, the contrast study, if needed, is generally best obtained at a later date, after more careful evaluation of the patient's history and medical records. If the non-contrast CT scan is abnormal, a contrast enhanced CT scan may be beneficial, but, again, is often not needed to direct acute patient management. (orig.)

Chirped pulse digital holography for measuring the sequence of ultrafast optical wavefronts

Science.gov (United States)

Karasawa, Naoki

2018-04-01

Optical setups for measuring the sequence of ultrafast optical wavefronts using a chirped pulse as a reference wave in digital holography are proposed and analyzed. In this method, multiple ultrafast object pulses are used to probe the temporal evolution of ultrafast phenomena and they are interfered with a chirped reference wave to record a digital hologram. Wavefronts at different times can be reconstructed separately from the recorded hologram when the reference pulse can be treated as a quasi-monochromatic wave during the pulse width of each object pulse. The feasibility of this method is demonstrated by numerical simulation.

Carotid artery dissection on non-contrast CT: Does color improve the diagnostic confidence?

Energy Technology Data Exchange (ETDEWEB)

Saba, Luca, E-mail: lucasaba@tiscali.it [Department of Radiology, Azienda Ospedaliero Universitaria (A.O.U.), di Cagliari – Polo di Monserrato, s.s. 554 Monserrato, Cagliari 09045 (Italy); Argiolas, Giovanni Maria [Department of Radiology, Azienda Ospedaliero Brotzu (A.O.B.), di Cagliari, Cagliari 09100 (Italy); Raz, Eytan [Department of Radiology, New York University School of Medicine, New York (United States); Department of Neurology and Psychiatry, Sapienza University of Rome (Italy); Sannia, Stefano [Department of Radiology, Azienda Ospedaliero Universitaria (A.O.U.), di Cagliari – Polo di Monserrato, s.s. 554 Monserrato, Cagliari 09045 (Italy); Suri, Jasjit S. [Diagnostic and Monitoring Division, AtheroPointTM LLC, Roseville, CA (United States); Electrical Engineering Department (Aff.), Idaho State University, ID (United States); Siotto, Paolo [Department of Radiology, Azienda Ospedaliero Brotzu (A.O.B.), di Cagliari, Cagliari 09100 (Italy); Sanfilippo, Roberto; Montisci, Roberto [Department of Vascular Surgery, Azienda Ospedaliero Universitaria (A.O.U.), di Cagliari – Polo di Monserrato, s.s. 554 Monserrato, Cagliari 09045 (Italy); Piga, Mario [Department of Radiology, Azienda Ospedaliero Universitaria (A.O.U.), di Cagliari – Polo di Monserrato, s.s. 554 Monserrato, Cagliari 09045 (Italy); Wintermark, Max [Department of Radiology, Neuroradiology Division, University of Virginia, Box 800170, Charlottesville, VA, 22908 (United States)

2014-12-15

Highlights: • The use of a color scale to display the non-contrast CT images in lieu of the classic grayscale improves the diagnostic confidence of the readers. • Radiologists should consider the use of a color scale, rather than the conventional grayscale, to assess non-contrast CT studies for possible carotid artery dissection. - Abstract: Purpose: The purpose of this work was to evaluate if the use of color maps, instead of conventional grayscale images, would improve the observer's diagnostic confidence in the non-contrast CT evaluation of internal carotid artery dissection (ICAD). Materials and methods: One hundred patients (61 men, 39 women; mean age, 51 years; range, 25–78 years), 40 with and 60 without ICAD, underwent non-contrast CT and were included in this the retrospective study. In this study, three groups of patients were considered: patients with MR confirmation of ICAD, n = 40; patients with MR confirmation of ICAD absence, n = 20; patients who underwent CT of the carotid arteries because of atherosclerotic disease, n = 40. Four blinded observers with different levels of expertise (expert, intermediate A, intermediate B and trainee) analyzed the non-contrast CT datasets using a cross model (one case grayscale and the following case using the color scale). The presence of ICAD was scored on a 5-point scale in order to assess the observer's diagnostic confidence. After 3 months the four observers evaluated the same datasets by using the same cross-model for the alternate readings (one case color scale and the following case using the grayscale). Statistical analysis included receiver operating characteristics (ROC) curve analysis, the Cohen weighted test and sensitivity, specificity, PPV, NPV, accuracy, LR+ and LR−. Results: The ROC curve analysis showed that, for all observers, the use of color scale resulted in an improved diagnostic confidence with AUC values increasing from 0.896 to 0.936, 0.823 to 0.849, 0.84 to 0.909 and 0

Aortic endograft surveillance: use of fast-switch kVp dual-energy computed tomography with virtual noncontrast imaging.

Science.gov (United States)

Maturen, Katherine E; Kleaveland, Patricia A; Kaza, Ravi K; Liu, Peter S; Quint, Leslie E; Khalatbari, Shokoufeh H; Platt, Joel F

2011-01-01

To assess endoleak detection and patients' radiation exposure using fast-switch peak kilovoltage (kVp) dual-energy computed tomography (DECT) with virtual noncontrast (VNC) imaging. Institutional review board approved retrospective review of triphasic CTs for endograft follow-up: single-energy true noncontrast (TNC) and dual-energy arterial- and venous-phase postcontrast scans on GE HD-750 64-detector scanners. Iodine-subtracted VNC images generated from dual-energy data. Two radiologists (VNC readers) independently performed 2 reading sessions without TNC images: (1) arterial and VNC and (2) venous and VNC. Interrater agreement, leak detection sensitivity, and dose estimates were calculated. Original dictations described 24 endoleaks in 78 scans. Virtual noncontrast reader agreement was high (κ = 0.78-0.79). Virtual noncontrast reader ranges for sensitivity and negative predictive value for leak detection were 87.5% to 95.8% and 94.0% to 98.0% in venous phase. Dose reduction estimate was 40% by eliminating one phase and 64% by eliminating 2 phases of imaging. Virtual noncontrast images from fast-switch peak kilovoltage DECT data can substitute for TNC imaging in the postendograft aorta, conferring substantial dose reduction. Eliminating 1 of 2 postcontrast phases further reduces dose, with greater negative predictive value for leak detection in the venous versus the arterial phase. Thus, the use of a monophasic venous-phase DECT with VNC images is suggested for long-term endograft surveillance in stable patients.

Controllable pulse parameter transcranial magnetic stimulator with enhanced circuit topology and pulse shaping

Science.gov (United States)

Peterchev, Angel V.; DʼOstilio, Kevin; Rothwell, John C.; Murphy, David L.

2014-10-01

Objective. This work aims at flexible and practical pulse parameter control in transcranial magnetic stimulation (TMS), which is currently very limited in commercial devices. Approach. We present a third generation controllable pulse parameter device (cTMS3) that uses a novel circuit topology with two energy-storage capacitors. It incorporates several implementation and functionality advantages over conventional TMS devices and other devices with advanced pulse shape control. cTMS3 generates lower internal voltage differences and is implemented with transistors with a lower voltage rating than prior cTMS devices. Main results. cTMS3 provides more flexible pulse shaping since the circuit topology allows four coil-voltage levels during a pulse, including approximately zero voltage. The near-zero coil voltage enables snubbing of the ringing at the end of the pulse without the need for a separate active snubber circuit. cTMS3 can generate powerful rapid pulse sequences (\\lt 10 ms inter pulse interval) by increasing the width of each subsequent pulse and utilizing the large capacitor energy storage, allowing the implementation of paradigms such as paired-pulse and quadripulse TMS with a single pulse generation circuit. cTMS3 can also generate theta (50 Hz) burst stimulation with predominantly unidirectional electric field pulses. The cTMS3 device functionality and output strength are illustrated with electrical output measurements as well as a study of the effect of pulse width and polarity on the active motor threshold in ten healthy volunteers. Significance. The cTMS3 features could extend the utility of TMS as a research, diagnostic, and therapeutic tool.

Manipulating femtosecond spin-orbit torques with laser pulse sequences to control magnetic memory states and ringing

Science.gov (United States)

Lingos, P. C.; Wang, J.; Perakis, I. E.

2015-05-01

Femtosecond (fs) coherent control of collective order parameters is important for nonequilibrium phase dynamics in correlated materials. Here, we propose such control of ferromagnetic order based on using nonadiabatic optical manipulation of electron-hole (e -h ) photoexcitations to create fs carrier-spin pulses with controllable direction and time profile. These spin pulses are generated due to the time-reversal symmetry breaking arising from nonperturbative spin-orbit and magnetic exchange couplings of coherent photocarriers. By tuning the nonthermal populations of exchange-split, spin-orbit-coupled semiconductor band states, we can excite fs spin-orbit torques that control complex magnetization pathways between multiple magnetic memory states. We calculate the laser-induced fs magnetic anisotropy in the time domain by using density matrix equations of motion rather than the quasiequilibrium free energy. By comparing to pump-probe experiments, we identify a "sudden" out-of-plane magnetization canting displaying fs magnetic hysteresis, which agrees with switchings measured by the static Hall magnetoresistivity. This fs transverse spin-canting switches direction with magnetic state and laser frequency, which distinguishes it from the longitudinal nonlinear optical and demagnetization effects. We propose that sequences of clockwise or counterclockwise fs spin-orbit torques, photoexcited by shaping two-color laser-pulse sequences analogous to multidimensional nuclear magnetic resonance (NMR) spectroscopy, can be used to timely suppress or enhance magnetic ringing and switching rotation in magnetic memories.

High dimensional and high resolution pulse sequences for backbone resonance assignment of intrinsically disordered proteins

Energy Technology Data Exchange (ETDEWEB)

Zawadzka-Kazimierczuk, Anna; Kozminski, Wiktor, E-mail: kozmin@chem.uw.edu.pl [University of Warsaw, Faculty of Chemistry (Poland); Sanderova, Hana; Krasny, Libor [Institute of Microbiology, Academy of Sciences of the Czech Republic, Laboratory of Molecular Genetics of Bacteria, Department of Bacteriology (Czech Republic)

2012-04-15

Four novel 5D (HACA(N)CONH, HNCOCACB, (HACA)CON(CA)CONH, (H)NCO(NCA)CONH), and one 6D ((H)NCO(N)CACONH) NMR pulse sequences are proposed. The new experiments employ non-uniform sampling that enables achieving high resolution in indirectly detected dimensions. The experiments facilitate resonance assignment of intrinsically disordered proteins. The novel pulse sequences were successfully tested using {delta} subunit (20 kDa) of Bacillus subtilis RNA polymerase that has an 81-amino acid disordered part containing various repetitive sequences.

Virtual non-contrast in second-generation, dual-energy computed tomography: Reliability of attenuation values

International Nuclear Information System (INIS)

Toepker, Michael; Moritz, Thomas; Krauss, Bernhard; Weber, Michael; Euller, Gordon; Mang, Thomas; Wolf, Florian; Herold, Christian J.; Ringl, Helmut

2012-01-01

Purpose: To evaluate the reliability of attenuation values in virtual non-contrast images (VNC) reconstructed from contrast-enhanced, dual-energy scans performed on a second-generation dual-energy CT scanner, compared to single-energy, non-contrast images (TNC). Materials and methods: Sixteen phantoms containing a mixture of contrast agent and water at different attenuations (0–1400 HU) were investigated on a Definition Flash-CT scanner using a single-energy scan at 120 kV and a DE-CT protocol (100 kV/SN140 kV). For clinical assessment, 86 patients who received a dual-phase CT, containing an unenhanced single-energy scan at 120 kV and a contrast enhanced (110 ml Iomeron 400 mg/ml; 4 ml/s) DE-CT (100 kV/SN140 kV) in an arterial (n = 43) or a venous phase, were retrospectively analyzed. Mean attenuation was measured within regions of interest of the phantoms and in different tissue types of the patients within the corresponding VNC and TNC images. Paired t-tests and Pearson correlation were used for statistical analysis. Results: For all phantoms, mean attenuation in VNC was 5.3 ± 18.4 HU, with respect to water. In 86 patients overall, 2637 regions were measured in TNC and VNC images, with a mean difference between TNC and VNC of −3.6 ± 8.3 HU. In 91.5% (n = 2412) of all cases, absolute differences between TNC and VNC were under 15 HU, and, in 75.3% (n = 1986), differences were under 10 HU. Conclusions: Second-generation dual-energy CT based VNC images provide attenuation values close to those of TNC. To avoid possible outliers multiple measurements are recommended especially for measurements in the spleen, the mesenteric fat, and the aorta.

Virtual non-contrast in second-generation, dual-energy computed tomography: reliability of attenuation values.

Science.gov (United States)

Toepker, Michael; Moritz, Thomas; Krauss, Bernhard; Weber, Michael; Euller, Gordon; Mang, Thomas; Wolf, Florian; Herold, Christian J; Ringl, Helmut

2012-03-01

To evaluate the reliability of attenuation values in virtual non-contrast images (VNC) reconstructed from contrast-enhanced, dual-energy scans performed on a second-generation dual-energy CT scanner, compared to single-energy, non-contrast images (TNC). Sixteen phantoms containing a mixture of contrast agent and water at different attenuations (0-1400 HU) were investigated on a Definition Flash-CT scanner using a single-energy scan at 120 kV and a DE-CT protocol (100 kV/SN140 kV). For clinical assessment, 86 patients who received a dual-phase CT, containing an unenhanced single-energy scan at 120 kV and a contrast enhanced (110 ml Iomeron 400 mg/ml; 4 ml/s) DE-CT (100 kV/SN140 kV) in an arterial (n=43) or a venous phase, were retrospectively analyzed. Mean attenuation was measured within regions of interest of the phantoms and in different tissue types of the patients within the corresponding VNC and TNC images. Paired t-tests and Pearson correlation were used for statistical analysis. For all phantoms, mean attenuation in VNC was 5.3±18.4 HU, with respect to water. In 86 patients overall, 2637 regions were measured in TNC and VNC images, with a mean difference between TNC and VNC of -3.6±8.3 HU. In 91.5% (n=2412) of all cases, absolute differences between TNC and VNC were under 15HU, and, in 75.3% (n=1986), differences were under 10 HU. Second-generation dual-energy CT based VNC images provide attenuation values close to those of TNC. To avoid possible outliers multiple measurements are recommended especially for measurements in the spleen, the mesenteric fat, and the aorta. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Virtual non-contrast of liver from dual energy CT: a clinical application

International Nuclear Information System (INIS)

Qian Yu'e; Hu Hongjie; Zhang Qiaowei; Hu Peng; Shen Guohui

2011-01-01

Objective: To assess the virtual non-contrast liver CT from dual-energy CT for the clinical application. Methods: In total, 51 patients were included in the study, and all patients underwent multi-phase liver CT on a dual-source CT. The True non-contrast liver CT (TNCT) was performed in a single-energy acquisition mode, but the arterial and portovenous liver CT (VNCT) were performed in a dual- energy mode of 110 kV and 140 kV respectively. The virtual non-contrast CT images were derived from the arterial data using liver virtual non-contrast software. Between the true non-contrast CT and the virtual non- contrast CT, the image quality, mean CT HU values in the liver and muscle, signal to noise (SNR), the radiation dose of volume CT dose index (CTDIvol) and dose length product (DLP) in a single phase and total examination were compared with t test. Results: There was no significant difference in the detection of' liver lesions between TNCT and VNCT. The CT Hu values of muscle on both TNCT and VNCT images were almost equal. The CT HU values of liver on VNCT images were higher than that on TNCT images and the difference was significant [61.32±6.04 vs. (56.85±4.80) HU, t=-3.927, P<0.01]. There was also significant difference of SNR between TNCT (11.28±2.78) and VNCT (8.65±1.56) images (t=-5.590, P<0.01). The CTDIvol and DLP of single phase were (7.07±0.85) mGy and (155.11± 22.52) mGy · cm respectively in TNCT, and (7.05±0.87) mGy and (154.48±23.12) mGy · cm in VNCT. The total CTDIvol and DLP in VNCT were (14.35±1.66) mGy and (313.91±45.08) mGy · cm respectively, but in TNCT the total CTDIvol and DLP reached (21.43±2.46) mGy and (469.02± 66.22) mGy · cm. The difference of CTDIvol and DLP in single phase between TNCT and VNCT showed no significance, but the total CTDIvol and DLP were significantly different (t=16.168 and 13.132, P< 0.01). Conclusion: With the consequent reduction in radiation dose, the VNCT can replace TNCT as an imaging protocol in multi

Comparison of ompP5 sequence-based typing and pulsed-filed gel ...

African Journals Online (AJOL)

In this study, comparison of the outer membrane protein P5 gene (ompP5) sequence-based typing with pulsed-field gel electrophoresis (PFGE) for the genotyping of Haemophilus parasuis, the 15 serovar reference strains and 43 isolates were investigated. When comparing the two methods, 31 ompP5 sequence types ...

Diagnostic accuracy of virtual non-contrast enhanced dual-energy CT for diagnosis of adrenal adenoma: A systematic review and meta-analysis

Energy Technology Data Exchange (ETDEWEB)

Connolly, Michael J.; McInnes, Matthew D.F.; Schieda, Nicola [University of Ottawa Department of Radiology, Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, ON (United States); El-Khodary, Mohamed [McMaster University Department of Radiology, Hamilton, ON (Canada); McGrath, Trevor A. [University of Ottawa, Faculty of Medicine, Ottawa, Ontario (Canada)

2017-10-15

To compare the diagnostic accuracy of dual-energy (DE) virtual non-contrast computed tomography (vNCT) to non-contrast CT (NCT) for the diagnosis of adrenal adenomas. Search of multiple databases and grey literature was performed. Two reviewers independently applied inclusion criteria and extracted data. Risk of bias was assessed using QUADAS-2. Summary estimates of diagnostic accuracy were generated and sources of heterogeneity were assessed. Five studies (170 patients; 192 adrenal masses) were included for diagnostic accuracy assessment; all used dual-source dual-energy CT. Pooled sensitivity for adrenal adenoma on vNCT was 54% (95% CI: 47-62%). Pooled sensitivity for NCT was 57% (95% CI: 45-69%). Pooling of specificity was not performed since no false positives were reported. There was a trend for overestimation of HU density on vNCT as compared to NCT which appeared related to contrast timing. Potential sources of bias were seen regarding the index test and reference standard for the included studies. Potential sources of heterogeneity between studies were seen in adenoma prevalence and intravenous contrast timing. vNCT images generated from dual-energy CT demonstrated comparable sensitivity to NCT for the diagnosis of adenomas; however the included studies are heterogeneous and at high risk for some types of bias. (orig.)

A non-contrast self-navigated 3-dimensional MR technique for aortic root and vascular access route assessment in the context of transcatheter aortic valve replacement: proof of concept

Energy Technology Data Exchange (ETDEWEB)

Renker, Matthias [Medical University of South Carolina, Heart and Vascular Center, Charleston, SC (United States); University Hospital Giessen and Marburg, Department of Medicine I, Giessen (Germany); Varga-Szemes, Akos; Rier, Jeremy D.; Steinberg, Daniel H. [Medical University of South Carolina, Heart and Vascular Center, Charleston, SC (United States); Schoepf, U.J. [Medical University of South Carolina, Heart and Vascular Center, Charleston, SC (United States); Medical University of South Carolina, Department of Radiology and Radiological Science, Charleston, SC (United States); Baumann, Stefan [Medical University of South Carolina, Heart and Vascular Center, Charleston, SC (United States); University of Heidelberg, 1st Department of Medicine, Faculty of Medicine Mannheim, University Medical Centre Mannheim (UMM), Mannheim (Germany); Piccini, Davide [Siemens Healthcare IM BM PI, Advanced Clinical Imaging Technology, Lausanne (Switzerland); University Hospital (CHUV) and University of Lausanne (UNIL), Department of Radiology, Lausanne (Switzerland); Zenge, Michael O.; Mueller, Edgar [Siemens AG Healthcare Sector, Erlangen (Germany); Rehwald, Wolfgang G. [Duke University Medical Center, Cardiovascular MR Center, Durham, NC (United States); Moellmann, Helge [Kerckhoff Heart and Thorax Center, Bad Nauheim (Germany); Hamm, Christian W. [University Hospital Giessen and Marburg, Department of Medicine I, Giessen (Germany); De Cecco, Carlo N. [Medical University of South Carolina, Heart and Vascular Center, Charleston, SC (United States); University of Rome ' ' Sapienza' ' -Polo Pontino, Department of Radiological Sciences, Oncology and Pathology, Latina (Italy)

2016-04-15

Due to the high prevalence of renal failure in transcatheter aortic valve replacement (TAVR) candidates, a non-contrast MR technique is desirable for pre-procedural planning. We sought to evaluate the feasibility of a novel, non-contrast, free-breathing, self-navigated three-dimensional (SN3D) MR sequence for imaging the aorta from its root to the iliofemoral run-off in comparison to non-contrast two-dimensional-balanced steady-state free-precession (2D-bSSFP) imaging. SN3D [field of view (FOV), 220-370 mm{sup 3}; slice thickness, 1.15 mm; repetition/echo time (TR/TE), 3.1/1.5 ms; and flip angle, 115 ] and 2D-bSSFP acquisitions (FOV, 340 mm; slice thickness, 6 mm; TR/TE, 2.3/1.1 ms; flip angle, 77 ) were performed in 10 healthy subjects (all male; mean age, 30.3 ± 4.3 yrs) using a 1.5-T MRI system. Aortic root measurements and qualitative image ratings (four-point Likert-scale) were compared. The mean effective aortic annulus diameter was similar for 2D-bSSFP and SN3D (26.7 ± 0.7 vs. 26.1 ± 0.9 mm, p = 0.23). The mean image quality of 2D-bSSFP (4; IQR 3-4) was rated slightly higher (p = 0.03) than SN3D (3; IQR 2-4). The mean total acquisition time for SN3D imaging was 12.8 ± 2.4 min. Our results suggest that a novel SN3D sequence allows rapid, free-breathing assessment of the aortic root and the aortoiliofemoral system without administration of contrast medium. (orig.)

A non-contrast self-navigated 3-dimensional MR technique for aortic root and vascular access route assessment in the context of transcatheter aortic valve replacement: proof of concept

International Nuclear Information System (INIS)

Renker, Matthias; Varga-Szemes, Akos; Rier, Jeremy D.; Steinberg, Daniel H.; Schoepf, U.J.; Baumann, Stefan; Piccini, Davide; Zenge, Michael O.; Mueller, Edgar; Rehwald, Wolfgang G.; Moellmann, Helge; Hamm, Christian W.; De Cecco, Carlo N.

2016-01-01

Due to the high prevalence of renal failure in transcatheter aortic valve replacement (TAVR) candidates, a non-contrast MR technique is desirable for pre-procedural planning. We sought to evaluate the feasibility of a novel, non-contrast, free-breathing, self-navigated three-dimensional (SN3D) MR sequence for imaging the aorta from its root to the iliofemoral run-off in comparison to non-contrast two-dimensional-balanced steady-state free-precession (2D-bSSFP) imaging. SN3D [field of view (FOV), 220-370 mm 3 ; slice thickness, 1.15 mm; repetition/echo time (TR/TE), 3.1/1.5 ms; and flip angle, 115 ] and 2D-bSSFP acquisitions (FOV, 340 mm; slice thickness, 6 mm; TR/TE, 2.3/1.1 ms; flip angle, 77 ) were performed in 10 healthy subjects (all male; mean age, 30.3 ± 4.3 yrs) using a 1.5-T MRI system. Aortic root measurements and qualitative image ratings (four-point Likert-scale) were compared. The mean effective aortic annulus diameter was similar for 2D-bSSFP and SN3D (26.7 ± 0.7 vs. 26.1 ± 0.9 mm, p = 0.23). The mean image quality of 2D-bSSFP (4; IQR 3-4) was rated slightly higher (p = 0.03) than SN3D (3; IQR 2-4). The mean total acquisition time for SN3D imaging was 12.8 ± 2.4 min. Our results suggest that a novel SN3D sequence allows rapid, free-breathing assessment of the aortic root and the aortoiliofemoral system without administration of contrast medium. (orig.)

Noncontrast-enhanced magnetic resonance renal angiography using a repetitive artery and venous labelling technique at 3 T: comparison with contrast-enhanced magnetic resonance angiography in subjects with normal renal function

Energy Technology Data Exchange (ETDEWEB)

Park, Sung Yoon [Sungkyunkwan University School of Medicine, Department of Radiology and Center for Imaging Science, Samsung Medical Center, Seoul (Korea, Republic of); Severance Hospital, Yonsei University College of Medicine, Department of Radiology and Research Institute of Radiological Science, Seoul (Korea, Republic of); Kim, Chan Kyo; Park, Byung Kwan [Sungkyunkwan University School of Medicine, Department of Radiology and Center for Imaging Science, Samsung Medical Center, Seoul (Korea, Republic of); Kim, EunJu [Philips Healthcare Korea, Seoul (Korea, Republic of)

2014-09-13

To investigate the feasibility of noncontrast-enhanced MR angiography (NC-MRA) using the repetitive artery and venous labelling (RAVEL) technique to evaluate renal arteries compared to contrast-enhanced MR angiography (CE-MRA). Twenty-five subjects with normal renal function underwent NC-MRA using a RAVEL technique and CE-MRA at 3 T. Two independent readers analysed the MRA images. Image quality, number of renal arteries, presence or absence of an early branching vessel, and diameter of the main renal arteries were evaluated. The overall image quality of NC-MRA was fair or greater in 88 % of right and 92 % of left renal arteries, while it was 96 % in both sides with CE-MRA. On NC-MRA, the number of renal arteries in all subjects was perfectly predicted by both readers. Sensitivity and specificity for predicting early branching vessels were 82 % and 100 % for reader 1 and 82 % and 95 % for reader 2. Inter-modality agreement for comparing the diameters of main renal arteries was good or excellent at all segments for both readers. Inter-reader agreement was moderate or good at all segments except at the right distal segment on NC-MRA. NC-MRA with the RAVEL technique at 3 T may have comparable diagnostic feasibility for evaluating renal arteries compared to CE-MRA. (orig.)

Investigation of timing effects in modified composite quadrupolar echo pulse sequences by mean of average Hamiltonian theory

Science.gov (United States)

Mananga, Eugene Stephane

2018-01-01

The utility of the average Hamiltonian theory and its antecedent the Magnus expansion is presented. We assessed the concept of convergence of the Magnus expansion in quadrupolar spectroscopy of spin-1 via the square of the magnitude of the average Hamiltonian. We investigated this approach for two specific modified composite pulse sequences: COM-Im and COM-IVm. It is demonstrated that the size of the square of the magnitude of zero order average Hamiltonian obtained on the appropriated basis is a viable approach to study the convergence of the Magnus expansion. The approach turns to be efficient in studying pulse sequences in general and can be very useful to investigate coherent averaging in the development of high resolution NMR technique in solids. This approach allows comparing theoretically the two modified composite pulse sequences COM-Im and COM-IVm. We also compare theoretically the current modified composite sequences (COM-Im and COM-IVm) to the recently published modified composite pulse sequences (MCOM-I, MCOM-IV, MCOM-I_d, MCOM-IV_d).

Generalized min-max bound-based MRI pulse sequence design framework for wide-range T1 relaxometry: A case study on the tissue specific imaging sequence.

Directory of Open Access Journals (Sweden)

Yang Liu

Full Text Available This paper proposes a new design strategy for optimizing MRI pulse sequences for T1 relaxometry. The design strategy optimizes the pulse sequence parameters to minimize the maximum variance of unbiased T1 estimates over a range of T1 values using the Cramér-Rao bound. In contrast to prior sequences optimized for a single nominal T1 value, the optimized sequence using our bound-based strategy achieves improved precision and accuracy for a broad range of T1 estimates within a clinically feasible scan time. The optimization combines the downhill simplex method with a simulated annealing process. To show the effectiveness of the proposed strategy, we optimize the tissue specific imaging (TSI sequence. Preliminary Monte Carlo simulations demonstrate that the optimized TSI sequence yields improved precision and accuracy over the popular driven-equilibrium single-pulse observation of T1 (DESPOT1 approach for normal brain tissues (estimated T1 700-2000 ms at 3.0T. The relative mean estimation error (MSE for T1 estimation is less than 1.7% using the optimized TSI sequence, as opposed to less than 7.0% using DESPOT1 for normal brain tissues. The optimized TSI sequence achieves good stability by keeping the MSE under 7.0% over larger T1 values corresponding to different lesion tissues and the cerebrospinal fluid (up to 5000 ms. The T1 estimation accuracy using the new pulse sequence also shows improvement, which is more pronounced in low SNR scenarios.

Quantum Logic with Composite Pulse Sequences on Sr^+

Science.gov (United States)

Shewmon, Ruth; Labaziewicz, Jaroslaw; Ge, Yufei; Wang, Shannon; Chuang, Isaac L.

2008-03-01

The optical 5S1/2->4D1/2 transition in Sr^+ is an attractive qubit because it can be addressed by diode lasers, which are relatively inexpensive and easy to operate. We characterize single-qubit rotations as well as a CNOT gate on a Sr^+ ion in a surface electrode Paul trap. To improve these operations, the frequency of the clock laser is stabilized to a high-finesse optical cavity. The resulting linewidth of the laser is approximately 300Hz. Composite pulse sequences, a technique adapted from NMR, have been shown to reduce the effects of systematic errors in a variety of quantum systems. We demonstrate several composite sequences that improve the fidelity of quantum logic operations on Sr^+.

Attenuation values of renal parenchyma in virtual noncontrast images acquired from multiphase renal dual-energy CT: Comparison with standard noncontrast CT.

Science.gov (United States)

Lin, Yuan-Mao; Chiou, Yi-You; Wu, Mei-Han; Huang, Shan-Su; Shen, Shu-Huei

2018-04-01

To compare the renal parenchyma attenuation of virtual noncontrast (VNC) images derived from multiphase renal dual-energy computed tomography (DECT) with standard noncontrast (SNC) images, and to determine the optimum phase for VNC images. Twenty-nine men and 16 women (mean age, 61 ± 13 years; range, 37-89 years) underwent dynamic renal DECT (100/Sn140 kVp) were included in this institutional review board-approved retrospective study. There were four phases of the scan, which included noncontrast, corticomedullary (CMP), nephrographic (NP), and excretory phases (EP). The VNC images was generated from CMP, NP and EP. CT numbers of SNC images and VNC images of each phases were measured in the renal cortex and medulla. Mean standard deviation of subcutaneous fat was measured as image noise on SNC and VNC images. Radiation dose was recorded and potential radiation dose reduction was estimated. Results were tested for statistical significance using the unpaired t-test and agreement using Bland-Altman plot analysis. The difference in mean attenuation between SNC and each phase of VNC images were ≤4 HU. The mean attenuation of renal cortex and medulla was 33.2 ± 4.4 HU, and 34.2 ± 4.8 HU in SNC, 33.6 ± 7.6 HU and 31.1 ± 8.3 HU in VNC of CMP, 34.8 ± 8.6 HU and 35.6 ± 8.5 HU in VNC of NP, 31.5 ± 7.6 HU and 32.4 ± 7.5 HU in VNC of EP. In VNC of CMP, the attenuation of the cortex was higher than the medulla (p VNC of NP, the attenuation of renal cortex was higher than SNC (p VNC of EP, the attenuation of cortex and medulla were lower than SNC (p VNC images from multiphase renal DECT were similar to SNC images. Using the nephrographic phase can gives more comparable VNC images to SNC images in renal parenchyma than other phases. Copyright © 2018 Elsevier B.V. All rights reserved.

Optimal MR pulse sequences for hepatic hemangiomas : comparison of T2-weighted turbo-spin-echo, T2-weighted breath-hold turbo-spin-echo, and T1-weighted FLASH dynamic imaging

International Nuclear Information System (INIS)

Wang, Wen Chao; Choi, Byung Ihn; Han, Joon Koo; Kim, Tae Kyoung; Cho, Soon Gu

1997-01-01

To optimize MR imaging pulse sequences in the imaging of hepatic hemangioma and to evaluate on dynamic MR imaging the enhancing characteristics of the lesions. Twenty patients with 35 hemangiomas were studied by using Turbo-spin-echo (TSE) sequence (T2-weighted, T2- and heavily T2-weighted breath-hold) and T1-weighted FLASH imaging acquired before, immediately on, and 1, 3 and 5 minutes after injection of a bolus of Gd-DTPA (0.1mmol/kg). Phased-array multicoil was employed. Images were quantitatively analyzed for lesion-to-liver signal difference to noise ratios (SD/Ns), and lesion-to-liver signal ratios (H/Ls), and qualitatively analyzed for lesion conspicuity. The enhancing characteristics of the hemangiomas were described by measuring the change of signal intensity as a curve in T1-weighted FLASH dynamic imaging. For T2-weighted images, breath-hold T2-weighted TSE had a slightly higher SD/N than other pulse sequences, but there was no statistical difference in three fast pulse sequences (p=0.211). For lesion conspicuity, heavily T2-weighted breath-hold TSE images was superior to T2-weighted breath-hold or non-breath-hold TSE (H/L, 5.75, 3.81, 2.87, respectively, p<0.05). T2-weighted breath-hold TSE imaging was more effective than T2-weighted TSE imaging in removing lesion blurring or lack of sharpness, and there was a 12-fold decrease in acquisition time (20sec versus 245 sec). T1-weighted FLASH dynamic images of normal liver showed peak enhancement at less than 1 minute, and of hemangioma at more than 3 minutes;the degree of enhancement for hemangioma decreased after a 3 minute delay. T2-weighed breath-hold TSE imaging and Gd-DTPA enhanced FLASH dynamic imaging with 5 minutes delay are sufficient for imaging hepatic hemangiomas

Effects of laser wavelengths and pulse energy ratio on the emission enhancement in dual pulse LIBS

International Nuclear Information System (INIS)

Ahmed, Rizwan; Iqbal, Javed; Baig, M Aslam

2015-01-01

We present new studies on the effects of laser wavelengths, pulse energy ratio and interpulse delay between two laser pulses in the collinear dual pulse configuration of laser-induced breakdown spectroscopy (LIBS) on an iron sample in air using the fundamental (1064 nm) and the second harmonics (532 nm) of Nd:YAG lasers. In the dual pulse LIBS, an optimum value of interpulse delay with an appropriate combination of laser wavelengths, and laser pulse energy ratio, yields a 30 times signal intensity enhancement in the neutral iron lines as compared with single pulse LIBS. A comparison in the spatial variations of electron temperature along the axis of the plume expansion in single and double pulse LIBS has also been studied. (letter)

Dual-energy CT for detection of contrast enhancement or leakage within high-density haematomas in patients with intracranial haemorrhage

Energy Technology Data Exchange (ETDEWEB)

Watanabe, Yoshiyuki; Tsukabe, Akio; Kunitomi, Yuki; Nishizawa, Mitsuo; Arisawa, Atsuko; Tanaka, Hisashi; Tomiyama, Noriyuki [Osaka University Graduate School of Medicine, Department of Diagnostic and Interventional Radiology, Suita, Osaka (Japan); Yoshiya, Kazuhisa; Shimazu, Takeshi [Osaka University Graduate School of Medicine, Department of Traumatology and Acute Critical Medicine, Osaka (Japan)

2014-04-15

Our study aimed to elucidate the diagnostic performance of dual-energy CT (DECT) in the detection of contrast enhancement in intracranial haematomas (ICrH) with early phase dual-energy computed tomography angiography (CTA) and compare the results with those obtained by delayed CT enhancement. Thirty-six patients with ICrH were retrospectively included in this study. All patients had undergone single-energy non-contrast CT and contrast-enhanced dual-source DECT. DECT images were post-processed with commercial software, followed by obtaining iodine images and virtual non-contrast images and generating combined images that created the impression of 120-kVp images. Two neuroradiologists, blinded to the patients' data, reviewed two reading sessions: session A (non-contrast CT and combined CT) and session B (non-contrast CT, combined CT, and iodine images) for detection of contrast enhancement in the haematomas. Contrast leakage or enhancement was detected in 23 (57.5 %) out of 40 haemorrhagic lesions in 36 patients on delayed CT. Three enhanced lesions were depicted only in the DECT iodine images. The sensitivity, specificity, positive predictive value, and negative predictive value of session A were 82.6, 94.1, 95.0, and 80.0 %, respectively, and those of session B were 95.7, 94.1, 95.7, and 94.1 %, respectively. DECT emphasised the iodine enhancement and facilitated the detection of contrast enhancement or leakage. (orig.)

Dual-energy CT for detection of contrast enhancement or leakage within high-density haematomas in patients with intracranial haemorrhage.

Science.gov (United States)

Watanabe, Yoshiyuki; Tsukabe, Akio; Kunitomi, Yuki; Nishizawa, Mitsuo; Arisawa, Atsuko; Tanaka, Hisashi; Yoshiya, Kazuhisa; Shimazu, Takeshi; Tomiyama, Noriyuki

2014-04-01

Our study aimed to elucidate the diagnostic performance of dual-energy CT (DECT) in the detection of contrast enhancement in intracranial haematomas (ICrH) with early phase dual-energy computed tomography angiography (CTA) and compare the results with those obtained by delayed CT enhancement. Thirty-six patients with ICrH were retrospectively included in this study. All patients had undergone single-energy non-contrast CT and contrast-enhanced dual-source DECT. DECT images were post-processed with commercial software, followed by obtaining iodine images and virtual non-contrast images and generating combined images that created the impression of 120-kVp images. Two neuroradiologists, blinded to the patients' data, reviewed two reading sessions: session A (non-contrast CT and combined CT) and session B (non-contrast CT, combined CT, and iodine images) for detection of contrast enhancement in the haematomas. Contrast leakage or enhancement was detected in 23 (57.5 %) out of 40 haemorrhagic lesions in 36 patients on delayed CT. Three enhanced lesions were depicted only in the DECT iodine images. The sensitivity, specificity, positive predictive value, and negative predictive value of session A were 82.6, 94.1, 95.0, and 80.0 %, respectively, and those of session B were 95.7, 94.1, 95.7, and 94.1 %, respectively. DECT emphasised the iodine enhancement and facilitated the detection of contrast enhancement or leakage.

Dual-energy CT for detection of contrast enhancement or leakage within high-density haematomas in patients with intracranial haemorrhage

International Nuclear Information System (INIS)

Watanabe, Yoshiyuki; Tsukabe, Akio; Kunitomi, Yuki; Nishizawa, Mitsuo; Arisawa, Atsuko; Tanaka, Hisashi; Tomiyama, Noriyuki; Yoshiya, Kazuhisa; Shimazu, Takeshi

2014-01-01

Our study aimed to elucidate the diagnostic performance of dual-energy CT (DECT) in the detection of contrast enhancement in intracranial haematomas (ICrH) with early phase dual-energy computed tomography angiography (CTA) and compare the results with those obtained by delayed CT enhancement. Thirty-six patients with ICrH were retrospectively included in this study. All patients had undergone single-energy non-contrast CT and contrast-enhanced dual-source DECT. DECT images were post-processed with commercial software, followed by obtaining iodine images and virtual non-contrast images and generating combined images that created the impression of 120-kVp images. Two neuroradiologists, blinded to the patients' data, reviewed two reading sessions: session A (non-contrast CT and combined CT) and session B (non-contrast CT, combined CT, and iodine images) for detection of contrast enhancement in the haematomas. Contrast leakage or enhancement was detected in 23 (57.5 %) out of 40 haemorrhagic lesions in 36 patients on delayed CT. Three enhanced lesions were depicted only in the DECT iodine images. The sensitivity, specificity, positive predictive value, and negative predictive value of session A were 82.6, 94.1, 95.0, and 80.0 %, respectively, and those of session B were 95.7, 94.1, 95.7, and 94.1 %, respectively. DECT emphasised the iodine enhancement and facilitated the detection of contrast enhancement or leakage. (orig.)

Correction of echo shift in reconstruction processing for ultra-short TE pulse sequence

International Nuclear Information System (INIS)

Takizawa, Masahiro; Ootsuka, Takehiro; Abe, Takayuki; Takahashi, Tetsuhiko

2010-01-01

An ultra-short echo time (TE) pulse sequence is composed of a radial sampling that acquires echo signals radially in the K-space and a half-echo acquisition that acquires only half of the echo signal. The shift in the position of the echo signal (echo shift) caused by the timing errors in the gradient magnetic field pulses affects the image quality in the radial sampling with the half-echo acquisition. To improve image quality, we have developed a signal correction algorithm that detects and eliminates this echo shift during reconstruction by performing a pre-scan within 10 seconds. The results showed that image quality is improved under oblique and/or off-centering conditions that frequently cause image distortion due to hardware error. In conclusion, we have developed a robust ultra-short TE pulse sequence that allows wide latitude in the scan parameters, including oblique and off-centering conditions. (author)

Assessment of myocardial infarction in mice by Late Gadolinium Enhancement MR imaging using an inversion recovery pulse sequence at 9.4T

Directory of Open Access Journals (Sweden)

Herlihy Amy H

2008-01-01

Full Text Available Abstract Purpose To demonstrate the feasibility of using an inversion recovery pulse sequence and to define the optimal inversion time (TI to assess myocardial infarction in mice by late gadolinium enhancement (LGE MRI at 9.4T, and to obtain the maximal contrast between the infarcted and the viable myocardium. Methods MRI was performed at 9.4T in mice, two days after induction of myocardial infarction (n = 4. For cardiovascular MR imaging, a segmented magnetization-prepared fast low angle shot (MP-FLASH sequence was used with varied TIs ranging from 40 to 420 ms following administration of gadolinium-DTPA at 0.6 mmol/kg. Contrast-to-noise (CNR and signal-to-noise ratio (SNR were measured and compared for each myocardial region of interest (ROI. Results The optimal TI, which corresponded to a minimum SNR in the normal myocardium, was 268 ms ± 27.3. The SNR in the viable myocardium was significantly different from that found in the infarcted myocardium (17.2 ± 2.4 vs 82.1 ± 10.8; p = 0.006 leading to a maximal relative SI (Signal Intensity between those two areas (344.9 ± 60.4. Conclusion Despite the rapid heart rate in mice, our study demonstrates that LGE MRI can be performed at 9.4T using a protocol similar to the one used for clinical MR diagnosis of myocardial infarction.

Observation of enhanced field-free molecular alignment by two laser pulses

DEFF Research Database (Denmark)

Bisgaard, Christer; Poulsen, Mikael Dahlerup; Peronne, Emmanuel

2004-01-01

We show experimentally that field-free alignment of iodobenzene molecules, induced by a single, intense, linearly polarized 1.4-ps-long laser pulse, can be strongly enhanced by dividing the pulse into two optimally synchronized pulses of the same duration. For a given total energy of the two...

Performance scaling via passive pulse shaping in cavity-enhanced optical parametric chirped-pulse amplification.

Science.gov (United States)

Siddiqui, Aleem M; Moses, Jeffrey; Hong, Kyung-Han; Lai, Chien-Jen; Kärtner, Franz X

2010-06-15

We show that an enhancement cavity seeded at the full repetition rate of the pump laser can automatically reshape small-signal gain across the interacting pulses in an optical parametric chirped-pulse amplifier for close-to-optimal operation, significantly increasing both the gain bandwidth and the conversion efficiency, in addition to boosting gain for high-repetition-rate amplification. Applied to a degenerate amplifier, the technique can provide an octave-spanning gain bandwidth.

Enhancement of beam pulse controllability for a single-pulse formation system of a cyclotron

International Nuclear Information System (INIS)

Kurashima, Satoshi; Miyawaki, Nobumasa; Kashiwagi, Hirotsugu; Okumura, Susumu; Taguchi, Mitsumasa; Fukuda, Mitsuhiro

2015-01-01

The single-pulse formation technique using a beam chopping system consisting of two types of high-voltage beam kickers was improved to enhance the quality and intensity of the single-pulse beam with a pulse interval over 1 μs at the Japan Atomic Energy Agency cyclotron facility. A contamination rate of neighboring beam bunches in the single-pulse beam was reduced to less than 0.1%. Long-term purification of the single pulse beam was guaranteed by the well-controlled magnetic field stabilization system for the cyclotron magnet. Reduction of the multi-turn extraction number for suppressing the neighboring beam bunch contamination was achieved by restriction of a beam phase width and precise optimization of a particle acceleration phase. In addition, the single-pulse beam intensity was increased by a factor of two or more by a combination of two types of beam bunchers using sinusoidal and saw-tooth voltage waveforms. Provision of the high quality intense single-pulse beam contributed to improve the accuracy of experiments for investigation of scintillation light time-profile and for neutron energy measurement by a time-of-flight method

EXCESS OPTICAL ENHANCEMENT OBSERVED WITH ARCONS FOR EARLY CRAB GIANT PULSES

Energy Technology Data Exchange (ETDEWEB)

Strader, M. J.; Mazin, B. A.; Spiro Jaeger, G. V.; Gwinn, C. R.; Meeker, S. R.; Szypryt, P.; Van Eyken, J. C.; Marsden, D.; Walter, A. B.; Ulbricht, G. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Johnson, M. D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); O' Brien, K. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Stoughton, C. [Fermilab Center for Particle Astrophysics, Batavia, IL 60510 (United States); Bumble, B. [NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91125 (United States)

2013-12-10

We observe an extraordinary link in the Crab pulsar between the enhancement of an optical pulse and the timing of the corresponding giant radio pulse. At optical through infrared wavelengths, our observations use the high time resolution of ARray Camera for Optical to Near-IR Spectrophotometry, a unique superconducting energy-resolving photon-counting array at the Palomar 200 inch telescope. At radio wavelengths, we observe with the Robert C. Byrd Green Bank Telescope and the Green Bank Ultimate Pulsar Processing Instrument backend. We see an 11.3% ± 2.5% increase in peak optical flux for pulses that have an accompanying giant radio pulse arriving near the peak of the optical main pulse, in contrast to a 3.2% ± 0.5% increase when an accompanying giant radio pulse arrives soon after the optical peak. We also observe that the peak of the optical main pulse is 2.8% ± 0.8% enhanced when there is a giant radio pulse accompanying the optical interpulse. We observe no statistically significant spectral differences between optical pulses accompanied by and not accompanied by giant radio pulses. Our results extend previous observations of optical-radio correlation to the time and spectral domains. Our refined temporal correlation suggests that optical and radio emission are indeed causally linked, and the lack of spectral differences suggests that the same mechanism is responsible for all optical emission.

EXCESS OPTICAL ENHANCEMENT OBSERVED WITH ARCONS FOR EARLY CRAB GIANT PULSES

International Nuclear Information System (INIS)

Strader, M. J.; Mazin, B. A.; Spiro Jaeger, G. V.; Gwinn, C. R.; Meeker, S. R.; Szypryt, P.; Van Eyken, J. C.; Marsden, D.; Walter, A. B.; Ulbricht, G.; Johnson, M. D.; O'Brien, K.; Stoughton, C.; Bumble, B.

2013-01-01

We observe an extraordinary link in the Crab pulsar between the enhancement of an optical pulse and the timing of the corresponding giant radio pulse. At optical through infrared wavelengths, our observations use the high time resolution of ARray Camera for Optical to Near-IR Spectrophotometry, a unique superconducting energy-resolving photon-counting array at the Palomar 200 inch telescope. At radio wavelengths, we observe with the Robert C. Byrd Green Bank Telescope and the Green Bank Ultimate Pulsar Processing Instrument backend. We see an 11.3% ± 2.5% increase in peak optical flux for pulses that have an accompanying giant radio pulse arriving near the peak of the optical main pulse, in contrast to a 3.2% ± 0.5% increase when an accompanying giant radio pulse arrives soon after the optical peak. We also observe that the peak of the optical main pulse is 2.8% ± 0.8% enhanced when there is a giant radio pulse accompanying the optical interpulse. We observe no statistically significant spectral differences between optical pulses accompanied by and not accompanied by giant radio pulses. Our results extend previous observations of optical-radio correlation to the time and spectral domains. Our refined temporal correlation suggests that optical and radio emission are indeed causally linked, and the lack of spectral differences suggests that the same mechanism is responsible for all optical emission

Quantum theory of NMR adiabatic pulses and their applications

International Nuclear Information System (INIS)

Ke, Y.

1993-01-01

Recently explosive developments of in vivo NMR spectroscopy (NMRS) and imaging (NMRI) in biological and medical sciences have resulted in the establishment of NMR as one of the most advanced major technique in life sciences. These developments have created huge demands for a variety of NMR adiabatic pulses with play a very important role in NMR experiments in vivo. In order to develop new NMR adiabatic pulses, a rigorous systematical quantum theory for this kind of pulses is greatly needed. Providing such a theory is one of the important goals of this dissertation. Quantum density matrix theory and product operator method have been used throughout this dissertation. Another goal, which is the major goal of this thesis research, is to use the quantum theory as a guide to develop new NMR adiabatic pulses and their applications. To fill this goal, a technique to construct a new type of adiabatic pulses, narrow band selective adiabatic pulses, has been invented, which is described through the example of constructing an adiabatic DANTE inversion pulse. This new adiabatic pulse is the first narrow band selective adiabatic pulses: Adiabatic homonuclear and heteronuclear spectral editing sequences. Unique to the first pulse sequence is a B 1 -field filter which is built by using two non-refocusing adiabatic full passage pulses to refocus the wanted signal and dephase unwanted signals. This extra filter greatly enhance the editing efficiency. Unlike commonly used heteronuclear spectral editing sequences which depend on the polarization transfer or spectral subtraction by phase cycling techniques, the second pulse sequences accomplishes the editing of heteronuclear J-coupled signals based on the fact that this sequence is transparent to the uncoupled spins and is equivalent a 90 degrees excitation pulse to the heteronuclear J-coupled spins. Experimental results have confirmed the ability of spectral editing with these two new sequences

Rotary wave-ejector enhanced pulse detonation engine

Science.gov (United States)

Nalim, M. R.; Izzy, Z. A.; Akbari, P.

2012-01-01

The use of a non-steady ejector based on wave rotor technology is modeled for pulse detonation engine performance improvement and for compatibility with turbomachinery components in hybrid propulsion systems. The rotary wave ejector device integrates a pulse detonation process with an efficient momentum transfer process in specially shaped channels of a single wave-rotor component. In this paper, a quasi-one-dimensional numerical model is developed to help design the basic geometry and operating parameters of the device. The unsteady combustion and flow processes are simulated and compared with a baseline PDE without ejector enhancement. A preliminary performance assessment is presented for the wave ejector configuration, considering the effect of key geometric parameters, which are selected for high specific impulse. It is shown that the rotary wave ejector concept has significant potential for thrust augmentation relative to a basic pulse detonation engine.

Application of computed tomography virtual noncontrast spectral imaging in evaluation of hepatic metastases: a preliminary study.

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Tian, Shi-Feng; Liu, Ai-Lian; Liu, Jing-Hong; Sun, Mei-Yu; Wang, He-Qing; Liu, Yi-Jun

2015-03-05

The objective was to qualitatively and quantitatively evaluate hepatic metastases using computed tomography (CT) virtual noncontrast (VNC) spectral imaging in a retrospective analysis. Forty hepatic metastases patients underwent CT scans including the conventional true noncontrast (TNC) and the tri-phasic contrast-enhanced dual energy spectral scans in the hepatic arterial, portal venous, and equilibrium phases. The tri-phasic spectral CT images were used to obtain three groups of VNC images including in the arterial (VNCa), venous (VNCv), and equilibrium (VNCe) phase by the material decomposition process using water and iodine as a base material pair. The image quality and the contrast-to-noise ratio (CNR) of metastasis of the four groups were compared with ANOVA analysis. The metastasis detection rates with the four nonenhanced image groups were calculated and compared using the Chi-square test. There were no significant differences in image quality among TNC, VNCa and VNCv images (P > 0.05). The quality of VNCe images was significantly worse than that of other three groups (P 0.05). The metastasis detection rate of the four nonenhanced groups with no statistically significant difference (P > 0.05). The quality of VNCa and VNCv images is identical to that of TNC images, and the metastasis detection rate in VNC images is similar to that in TNC images. VNC images obtained from arterial phase show metastases more clearly. Thus, VNCa imaging may be a surrogate to TNC imaging in hepatic metastasis diagnosis.

Application of Computed Tomography Virtual Noncontrast Spectral Imaging in Evaluation of Hepatic Metastases: A Preliminary Study

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Shi-Feng Tian

2015-01-01

Full Text Available Objective: The objective was to qualitatively and quantitatively evaluate hepatic metastases using computed tomography (CT virtual noncontrast (VNC spectral imaging in a retrospective analysis. Methods: Forty hepatic metastases patients underwent CT scans including the conventional true noncontrast (TNC and the tri-phasic contrast-enhanced dual energy spectral scans in the hepatic arterial, portal venous, and equilibrium phases. The tri-phasic spectral CT images were used to obtain three groups of VNC images including in the arterial (VNCa, venous (VNCv, and equilibrium (VNCe phase by the material decomposition process using water and iodine as a base material pair. The image quality and the contrast-to-noise ratio (CNR of metastasis of the four groups were compared with ANOVA analysis. The metastasis detection rates with the four nonenhanced image groups were calculated and compared using the Chi-square test. Results: There were no significant differences in image quality among TNC, VNCa and VNCv images (P > 0.05. The quality of VNCe images was significantly worse than that of other three groups (P 0.05. The metastasis detection rate of the four nonenhanced groups with no statistically significant difference (P > 0.05. Conclusions: The quality of VNCa and VNCv images is identical to that of TNC images, and the metastasis detection rate in VNC images is similar to that in TNC images. VNC images obtained from arterial phase show metastases more clearly. Thus, VNCa imaging may be a surrogate to TNC imaging in hepatic metastasis diagnosis.

Compact field programmable gate array-based pulse-sequencer and radio-frequency generator for experiments with trapped atoms

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Pruttivarasin, Thaned, E-mail: thaned.pruttivarasin@riken.jp [Quantum Metrology Laboratory, RIKEN, Wako-shi, Saitama 351-0198 (Japan); Katori, Hidetoshi [Quantum Metrology Laboratory, RIKEN, Wako-shi, Saitama 351-0198 (Japan); Innovative Space-Time Project, ERATO, JST, Bunkyo-ku, Tokyo 113-8656 (Japan); Department of Applied Physics, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656 (Japan)

2015-11-15

We present a compact field-programmable gate array (FPGA) based pulse sequencer and radio-frequency (RF) generator suitable for experiments with cold trapped ions and atoms. The unit is capable of outputting a pulse sequence with at least 32 transistor-transistor logic (TTL) channels with a timing resolution of 40 ns and contains a built-in 100 MHz frequency counter for counting electrical pulses from a photo-multiplier tube. There are 16 independent direct-digital-synthesizers RF sources with fast (rise-time of ∼60 ns) amplitude switching and sub-mHz frequency tuning from 0 to 800 MHz.

Optimal pulse-sequence parameters for MR imaging of the immature brain

International Nuclear Information System (INIS)

Nowell, M.A.; Hackney, D.B.; Zimmerman, R.A.; Bilaniuk, L.T.; Grossman, R.I.; Goldberg, H.I.

1986-01-01

Appropriate spin-echo pulse sequence parameters generate MR images with very high gray matter/white matter contrast in neonates and young infants. Low-contrast images appear to result from utilization of ''adult-type'' parameters to investigate tissues that have relaxation characteristics quite different than those of adult brain. In these young patients long spin-echo sequences with repetition times of 3,000-3,500 msec and multiple echoes with the longest echo time set at 120-160 msec are employed to yield high-contrast ''T2-weighted'' images

Optimization of parameter values for complex pulse sequences by simulated annealing: application to 3D MP-RAGE imaging of the brain.

Science.gov (United States)

Epstein, F H; Mugler, J P; Brookeman, J R

1994-02-01

A number of pulse sequence techniques, including magnetization-prepared gradient echo (MP-GRE), segmented GRE, and hybrid RARE, employ a relatively large number of variable pulse sequence parameters and acquire the image data during a transient signal evolution. These sequences have recently been proposed and/or used for clinical applications in the brain, spine, liver, and coronary arteries. Thus, the need for a method of deriving optimal pulse sequence parameter values for this class of sequences now exists. Due to the complexity of these sequences, conventional optimization approaches, such as applying differential calculus to signal difference equations, are inadequate. We have developed a general framework for adapting the simulated annealing algorithm to pulse sequence parameter value optimization, and applied this framework to the specific case of optimizing the white matter-gray matter signal difference for a T1-weighted variable flip angle 3D MP-RAGE sequence. Using our algorithm, the values of 35 sequence parameters, including the magnetization-preparation RF pulse flip angle and delay time, 32 flip angles in the variable flip angle gradient-echo acquisition sequence, and the magnetization recovery time, were derived. Optimized 3D MP-RAGE achieved up to a 130% increase in white matter-gray matter signal difference compared with optimized 3D RF-spoiled FLASH with the same total acquisition time. The simulated annealing approach was effective at deriving optimal parameter values for a specific 3D MP-RAGE imaging objective, and may be useful for other imaging objectives and sequences in this general class.

Multishot versus single-shot pulse sequences in very high field fMRI: a comparison using retinotopic mapping.

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Jascha D Swisher

Full Text Available High-resolution functional MRI is a leading application for very high field (7 Tesla human MR imaging. Though higher field strengths promise improvements in signal-to-noise ratios (SNR and BOLD contrast relative to fMRI at 3 Tesla, these benefits may be partially offset by accompanying increases in geometric distortion and other off-resonance effects. Such effects may be especially pronounced with the single-shot EPI pulse sequences typically used for fMRI at standard field strengths. As an alternative, one might consider multishot pulse sequences, which may lead to somewhat lower temporal SNR than standard EPI, but which are also often substantially less susceptible to off-resonance effects. Here we consider retinotopic mapping of human visual cortex as a practical test case by which to compare examples of these sequence types for high-resolution fMRI at 7 Tesla. We performed polar angle retinotopic mapping at each of 3 isotropic resolutions (2.0, 1.7, and 1.1 mm using both accelerated single-shot 2D EPI and accelerated multishot 3D gradient-echo pulse sequences. We found that single-shot EPI indeed led to greater temporal SNR and contrast-to-noise ratios (CNR than the multishot sequences. However, additional distortion correction in postprocessing was required in order to fully realize these advantages, particularly at higher resolutions. The retinotopic maps produced by both sequence types were qualitatively comparable, and showed equivalent test/retest reliability. Thus, when surface-based analyses are planned, or in other circumstances where geometric distortion is of particular concern, multishot pulse sequences could provide a viable alternative to single-shot EPI.

Fully automatic algorithm for segmenting full human diaphragm in non-contrast CT Images

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Karami, Elham; Gaede, Stewart; Lee, Ting-Yim; Samani, Abbas

2015-03-01

The diaphragm is a sheet of muscle which separates the thorax from the abdomen and it acts as the most important muscle of the respiratory system. As such, an accurate segmentation of the diaphragm, not only provides key information for functional analysis of the respiratory system, but also can be used for locating other abdominal organs such as the liver. However, diaphragm segmentation is extremely challenging in non-contrast CT images due to the diaphragm's similar appearance to other abdominal organs. In this paper, we present a fully automatic algorithm for diaphragm segmentation in non-contrast CT images. The method is mainly based on a priori knowledge about the human diaphragm anatomy. The diaphragm domes are in contact with the lungs and the heart while its circumference runs along the lumbar vertebrae of the spine as well as the inferior border of the ribs and sternum. As such, the diaphragm can be delineated by segmentation of these organs followed by connecting relevant parts of their outline properly. More specifically, the bottom surface of the lungs and heart, the spine borders and the ribs are delineated, leading to a set of scattered points which represent the diaphragm's geometry. Next, a B-spline filter is used to find the smoothest surface which pass through these points. This algorithm was tested on a noncontrast CT image of a lung cancer patient. The results indicate that there is an average Hausdorff distance of 2.96 mm between the automatic and manually segmented diaphragms which implies a favourable accuracy.

Minimization of Dead-Periods in MRI Pulse Sequences for Imaging Oblique Planes

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Atalar, Ergin; McVeigh, Elliot R.

2007-01-01

With the advent of breath-hold MR cardiac imaging techniques, the minimization of TR and TE for oblique planes has become a critical issue. The slew rates and maximum currents of gradient amplifiers limit the minimum possible TR and TE by adding dead-periods to the pulse sequences. We propose a method of designing gradient waveforms that will be applied to the amplifiers instead of the slice, readout, and phase encoding waveforms. Because this method ensures that the gradient amplifiers will always switch at their maximum slew rate, it results in the minimum possible dead-period for given imaging parameters and scan plane position. A GRASS pulse sequence has been designed and ultra-short TR and TE values have been obtained with standard gradient amplifiers and coils. For some oblique slices, we have achieved shorter TR and TE values than those for nonoblique slices. PMID:7869900

Noncontrast-enhanced magnetic resonance renal angiography using a repetitive artery and venous labelling technique at 3 T: comparison with contrast-enhanced magnetic resonance angiography in subjects with normal renal function.

Science.gov (United States)

Park, Sung Yoon; Kim, Chan Kyo; Kim, EunJu; Park, Byung Kwan

2015-02-01

To investigate the feasibility of noncontrast-enhanced MR angiography (NC-MRA) using the repetitive artery and venous labelling (RAVEL) technique to evaluate renal arteries compared to contrast-enhanced MR angiography (CE-MRA). Twenty-five subjects with normal renal function underwent NC-MRA using a RAVEL technique and CE-MRA at 3 T. Two independent readers analysed the MRA images. Image quality, number of renal arteries, presence or absence of an early branching vessel, and diameter of the main renal arteries were evaluated. The overall image quality of NC-MRA was fair or greater in 88% of right and 92% of left renal arteries, while it was 96% in both sides with CE-MRA. On NC-MRA, the number of renal arteries in all subjects was perfectly predicted by both readers. Sensitivity and specificity for predicting early branching vessels were 82% and 100% for reader 1 and 82% and 95% for reader 2. Inter-modality agreement for comparing the diameters of main renal arteries was good or excellent at all segments for both readers. Inter-reader agreement was moderate or good at all segments except at the right distal segment on NC-MRA. NC-MRA with the RAVEL technique at 3 T may have comparable diagnostic feasibility for evaluating renal arteries compared to CE-MRA. • Accurate pre-treatment evaluation of renal artery anatomy helps clinical decision-making. • NC-MRA using RAVEL offers acceptable imaging quality for renal artery evaluation. • The 3 T RAVEL technique provides excellent diagnostic performance for renal artery evaluation. • The 3 T RAVEL technique may be an alternative to contrast-enhanced MRA.

Non-contrast thin-section helical CT of urinary tract calculi in children

International Nuclear Information System (INIS)

Strouse, Peter J.; Bates, Gregory D.; Bloom, David A.; Goodsitt, Mitchell M.

2002-01-01

Background: Non-contrast thin-section helical CT has gained acceptance for the diagnosis of urinary tract calculi in adults, but experience with the technique in children is limited. Purpose: To evaluate the utility of non-contrast thin section helical CT for the diagnosis of urinary tract calculi in children. Materials and methods: Radiology databases at three pediatric institutions were searched to identify all pediatric patients evaluated by ''renal stone'' protocol CT scans (no oral or intravenous contrast, scans covering the entire urinary tract obtained in helical mode with narrow collimation (< 5 mm)). CT scans were reviewed for the primary finding of urinary tract calculi, for secondary signs of acute urinary tract obstruction and for evidence of alternative diagnoses. Medical records were reviewed to determine clinical presentation and to confirm the eventual diagnosis. Results: One hundred thirty-seven scans of 113 children (mean age: 11.2 years) were studied. Thirty-eight of 94 examinations (40%) performed on 82 children for acute pain and/or hematuria showed ureteral calculi. Alternative diagnoses were suggested by CT on 16 scans (17%). Twenty-eight scans were performed on 10 asymptomatic children with known calculus disease confirming renal stone burden on 21 scans (75%) and persistent ureteral calculi on 6 scans (21%). Upper tract calculi were demonstrated on 10 of 15 scans (67%) performed to evaluate for calculi in patients with known non-calculus genitourinary tract abnormalities. Conclusions: Non-contrast thin section helical CT is a useful method to diagnose urinary tract calculi in children. Radiation dose in this retrospective study may exceed the lowest possible radiation dose for diagnostic accuracy. Further research is needed to optimize CT imaging parameters, while maintaining diagnostic accuracy and minimizing radiation dose. (orig.)

Pulse electromagnetic fields enhance extracellular electron transfer in magnetic bioelectrochemical systems.

Science.gov (United States)

Zhou, Huihui; Liu, Bingfeng; Wang, Qisong; Sun, Jianmin; Xie, Guojun; Ren, Nanqi; Ren, Zhiyong Jason; Xing, Defeng

2017-01-01

Microbial extracellular electron transfer (EET) is essential in driving the microbial interspecies interaction and redox reactions in bioelectrochemical systems (BESs). Magnetite (Fe 3 O 4 ) and magnetic fields (MFs) were recently reported to promote microbial EET, but the mechanisms of MFs stimulation of EET and current generation in BESs are not known. This study investigates the behavior of current generation and EET in a state-of-the-art pulse electromagnetic field (PEMF)-assisted magnetic BES (PEMF-MBES), which was equipped with magnetic carbon particle (Fe 3 O 4 @N-mC)-coated electrodes. Illumina Miseq sequencing of 16S rRNA gene amplicons was also conducted to reveal the changes of microbial communities and interactions on the anode in response to magnetic field. PEMF had significant influences on current generation. When reactors were operated in microbial fuel cell (MFC) mode with pulse electromagnetic field (PEMF-MMFCs), power densities increased by 25.3-36.0% compared with no PEMF control MFCs (PEMF-OFF-MMFCs). More interestingly, when PEMF was removed, the power density dropped by 25.7%, while when PEMF was reintroduced, the value was restored to the previous level. Illumina sequencing of 16S rRNA gene amplicon and principal component analysis (PCA) based on operational taxonomic units (OTUs) indicate that PEMFs led to the shifts in microbial community and changes in species evenness that decreased biofilm microbial diversity. Geobacter spp. were found dominant in all anode biofilms, but the relative abundance in PEMF-MMFCs (86.1-90.0%) was higher than in PEMF-OFF-MMFCs (82.5-82.7%), indicating that the magnetic field enriched Geobacter on the anode. The current generation of Geobacter -inoculated microbial electrolysis cells (MECs) presented the same change regularity, the accordingly increase or decrease corresponding with switch of PEMF, which confirmed the reversible stimulation of PEMFs on microbial electron transfer. The pulse electromagnetic

Enhanced throughput for infrared automated DNA sequencing

Science.gov (United States)

Middendorf, Lyle R.; Gartside, Bill O.; Humphrey, Pat G.; Roemer, Stephen C.; Sorensen, David R.; Steffens, David L.; Sutter, Scott L.

1995-04-01

Several enhancements have been developed and applied to infrared automated DNA sequencing resulting in significantly higher throughput. A 41 cm sequencing gel (31 cm well- to-read distance) combines high resolution of DNA sequencing fragments with optimized run times yielding two runs per day of 500 bases per sample. A 66 cm sequencing gel (56 cm well-to-read distance) produces sequence read lengths of up to 1000 bases for ds and ss templates using either T7 polymerase or cycle-sequencing protocols. Using a multichannel syringe to load 64 lanes allows 16 samples (compatible with 96-well format) to be visualized for each run. The 41 cm gel configuration allows 16,000 bases per day (16 samples X 500 bases/sample X 2 ten hour runs/day) to be sequenced with the advantages of infrared technology. Enhancements to internal labeling techniques using an infrared-labeled dATP molecule (Boehringer Mannheim GmbH, Penzberg, Germany; Sequenase (U.S. Biochemical) have also been made. The inclusion of glycerol in the sequencing reactions yields greatly improved results for some primer and template combinations. The inclusion of (alpha) -Thio-dNTP's in the labeling reaction increases signal intensity two- to three-fold.

Signal-enhancement reflective pulse oximeter with Fresnel lens

Science.gov (United States)

Chung, Shuang-Chao; Sun, Ching-Cherng

2016-09-01

In this paper, a new reflective pulse oximeter is proposed and demonstrated with implanting a Fresnel lens, which enhances the reflected signal. An optical simulation model incorporated with human skin characteristics is presented to evaluate the capability of the Fresnel lens. In addition, the distance between the light emitting diode and the photodiode is optimized. Compared with the other reflective oximeters, the reflected signal light detected by the photodiode is enhanced to more than 140%.

MR imaging pulse sequence rationale: SD-, T1-, and T2-weighted images

International Nuclear Information System (INIS)

Sax, S.; Weathers, S.W.; Schneiders, N.J.; Horowitz, B.L.; Mawad, M.E.; Sandlin, M.E.; Blackwell, R.; Bryan, R.N.

1986-01-01

Over 500 patients have been examined with a pulse sequence designed to provide spin-density (SD)-weighted images (TR=3 sec, TE=35 msec), T1-weighted images (TR=0.3 sec, TE=35msec), and T2-weighted images (TR=3 sec, TE=105 msec) from which calculated ''synthesized'' images and SD, T1, and T2 calculated images could be obtained. Each image contributes unique information. SD-weighted images optimally display anatomy and often best highlight pathology. T1-weighted images are critical in assessing cerebral hemorrhages. T2-weighted images best display most lesions, but yield incomplete information in 35% of cases. All three types of ''weighted'' images are necessary to optimally display anatomy and fully characterize a lesion. Computerized calculations and simulations suggest that no other combination of pulse sequences yields equal information for a given examination time

Anomalous diffusion measured by a twice-refocused spin echo pulse sequence: analysis using fractional order calculus.

Science.gov (United States)

Gao, Qing; Srinivasan, Girish; Magin, Richard L; Zhou, Xiaohong Joe

2011-05-01

To theoretically develop and experimentally validate a formulism based on a fractional order calculus (FC) diffusion model to characterize anomalous diffusion in brain tissues measured with a twice-refocused spin-echo (TRSE) pulse sequence. The FC diffusion model is the fractional order generalization of the Bloch-Torrey equation. Using this model, an analytical expression was derived to describe the diffusion-induced signal attenuation in a TRSE pulse sequence. To experimentally validate this expression, a set of diffusion-weighted (DW) images was acquired at 3 Tesla from healthy human brains using a TRSE sequence with twelve b-values ranging from 0 to 2600 s/mm(2). For comparison, DW images were also acquired using a Stejskal-Tanner diffusion gradient in a single-shot spin-echo echo planar sequence. For both datasets, a Levenberg-Marquardt fitting algorithm was used to extract three parameters: diffusion coefficient D, fractional order derivative in space β, and a spatial parameter μ (in units of μm). Using adjusted R-squared values and standard deviations, D, β, and μ values and the goodness-of-fit in three specific regions of interest (ROIs) in white matter, gray matter, and cerebrospinal fluid, respectively, were evaluated for each of the two datasets. In addition, spatially resolved parametric maps were assessed qualitatively. The analytical expression for the TRSE sequence, derived from the FC diffusion model, accurately characterized the diffusion-induced signal loss in brain tissues at high b-values. In the selected ROIs, the goodness-of-fit and standard deviations for the TRSE dataset were comparable with the results obtained from the Stejskal-Tanner dataset, demonstrating the robustness of the FC model across multiple data acquisition strategies. Qualitatively, the D, β, and μ maps from the TRSE dataset exhibited fewer artifacts, reflecting the improved immunity to eddy currents. The diffusion-induced signal attenuation in a TRSE pulse sequence

Detection of Subarachnoid Hemorrhage at Acute and Subacute/Chronic Stages: Comparison of Four Magnetic Resonance Imaging Pulse Sequences and Computed Tomography

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Mei-Kang Yuan

2005-03-01

Conclusion: FLAIR and GE T2* MRI pulse sequences, and CT scans, are all statistically significant indicators of acute SAH. GE T2*-weighted images are statistically significant indicators of subacute-to-chronic SAH, whereas other MRI pulse sequences, and CT scans, are not.

Electrical noise modulates perception of electrical pulses in humans: sensation enhancement via stochastic resonance.

Science.gov (United States)

Iliopoulos, Fivos; Nierhaus, Till; Villringer, Arno

2014-03-01

Although noise is usually considered to be harmful for signal detection and information transmission, stochastic resonance (SR) describes the counterintuitive phenomenon of noise enhancing the detection and transmission of weak input signals. In mammalian sensory systems, SR-related phenomena may arise both in the peripheral and the central nervous system. Here, we investigate behavioral SR effects of subliminal electrical noise stimulation on the perception of somatosensory stimuli in humans. We compare the likelihood to detect near-threshold pulses of different intensities applied on the left index finger during presence vs. absence of subliminal noise on the same or an adjacent finger. We show that (low-pass) noise can enhance signal detection when applied on the same finger. This enhancement is strong for near-threshold pulses below the 50% detection threshold and becomes stronger when near-threshold pulses are applied as brief trains. The effect reverses at pulse intensities above threshold, especially when noise is replaced by subliminal sinusoidal stimulation, arguing for a peripheral direct current addition. Unfiltered noise applied on longer pulses enhances detection of all pulse intensities. Noise applied to an adjacent finger has two opposing effects: an inhibiting effect (presumably due to lateral inhibition) and an enhancing effect (most likely due to SR in the central nervous system). In summary, we demonstrate that subliminal noise can significantly modulate detection performance of near-threshold stimuli. Our results indicate SR effects in the peripheral and central nervous system.

Study of the mechanisms of flux enhancement through hairless mouse skin by pulsed DC iontophoresis

International Nuclear Information System (INIS)

Pikal, M.J.; Shah, S.

1991-01-01

Enhanced iontophoretic transport using pulsed DC is usually explained by citing the observed decrease in skin resistance caused by an increase in AC pulse frequency at very small currents. Alternately, it has been suggested that the on-to-off nature of pulsed DC imparts an impact energy to the fluid, thereby increasing transport. This report provides a test of these mechanisms for enhanced delivery via pulsed iontophoresis. The DC resistance of hairless mouse skin during continuous and pulsed DC iontophoresis is measured as a function of time for selected pulse frequencies and duty cycles using current densities ranging from 0.1 to 1.0 mA/cm2. As a test of the impact energy mechanism, the iontophoretic transport of 14C-glucose measured with pulsed DC is compared with similar data obtained previously using continuous DC. It is suggested that pulsed current can yield lower resistance and enhanced drug delivery provided that (a) the steady-state current during the on phase of the pulse is very small and (b) the frequency is low enough to allow depolarization of the skin during the off phase of the pulse. The glucose transport results suggest that the impact energy concept does not apply to iontophoresis

Noninvasive investigation of exocrine pancreatic function: Feasibility of cine dynamic MRCP with a spatially selective inversion-recovery pulse.

Science.gov (United States)

Yasokawa, Kazuya; Ito, Katsuyoshi; Tamada, Tsutomu; Yamamoto, Akira; Hayashida, Minoru; Tanimoto, Daigo; Higaki, Atsushi; Noda, Yasufumi; Kido, Ayumu

2015-11-01

To investigate the feasibility of noncontrast-enhanced cine dynamic magnetic resonance cholangiopancreatography (MRCP) with a spatially selective inversion-recovery (IR) pulse for evaluating exocrine pancreatic function in comparison with the N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA) test as a pancreatic exocrine function test. Twenty subjects with or without chronic pancreatitis were included. MRCP with a spatially selective IR pulse was repeated every 15 seconds for 5 minutes to acquire a total of 20 images (cine-dynamic MRCP). The median and mean frequency of the observation (the number of times) and the moving distance (mean secretion grading scores) of pancreatic juice inflow on cine-dynamic MRCP were compared with a BT-PABA test. The urinary PABA excretion rate (%) had significant positive correlations with both the mean secretion grade (r = 0.66, P = 0.002) and frequency of secretory inflow (r = 0.62, P = 0.004) in cine dynamic MRCP. Both the mean frequency of observations of pancreatic secretory inflow (1.4 ± 1.6 times vs. 14.3 ± 4.2 times, P Cine dynamic MRCP with a spatially selective IR pulse may have potential for estimating the pancreatic exocrine function noninvasively as a substitute for the BT-PABA test. © 2015 Wiley Periodicals, Inc.

Electron heating enhancement by frequency-chirped laser pulses

Energy Technology Data Exchange (ETDEWEB)

Yazdani, E.; Afarideh, H., E-mail: hafarideh@aut.ac.ir [Department of Energy Engineering and Physics, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of); Sadighi-Bonabi, R., E-mail: Sadighi@sharif.ir [Department of Physics, Sharif University of Technology, P.O. Box 11365-9567, Tehran (Iran, Islamic Republic of); Riazi, Z. [Physics and Accelerator School, Tehran (Iran, Islamic Republic of); Hora, H. [Department of Theoretical Physics, University of New South Wales, Sydney 2052 (Australia)

2014-09-14

Propagation of a chirped laser pulse with a circular polarization through an uprising plasma density profile is studied by using 1D-3V particle-in-cell simulation. The laser penetration depth is increased in an overdense plasma compared to an unchirped pulse. The induced transparency due to the laser frequency chirp results in an enhanced heating of hot electrons as well as increased maximum longitudinal electrostatic field at the back side of the solid target, which is very essential in target normal sheath acceleration regime of proton acceleration. For an applied chirp parameter between 0.008 and 0.01, the maximum amount of the electrostatic field is improved by a factor of 2. Furthermore, it is noticed that for a chirped laser pulse with a₀=5, because of increasing the plasma transparency length, the laser pulse can penetrate up to about n{sub e}≈6n{sub c}, where n{sub c} is plasma critical density. It shows 63% increase in the effective critical density compared to the relativistic induced transparency regime for an unchirped condition.

A peripheral component interconnect express-based scalable and highly integrated pulsed spectrometer for solution state dynamic nuclear polarization

Energy Technology Data Exchange (ETDEWEB)

He, Yugui; Liu, Chaoyang, E-mail: chyliu@wipm.ac.cn [Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); State Key Laboratory of Magnet Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Feng, Jiwen; Wang, Dong; Chen, Fang; Liu, Maili [State Key Laboratory of Magnet Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Zhang, Zhi; Wang, Chao [State Key Laboratory of Magnet Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); University of Chinese Academy of Sciences, Beijing 100048 (China)

2015-08-15

High sensitivity, high data rates, fast pulses, and accurate synchronization all represent challenges for modern nuclear magnetic resonance spectrometers, which make any expansion or adaptation of these devices to new techniques and experiments difficult. Here, we present a Peripheral Component Interconnect Express (PCIe)-based highly integrated distributed digital architecture pulsed spectrometer that is implemented with electron and nucleus double resonances and is scalable specifically for broad dynamic nuclear polarization (DNP) enhancement applications, including DNP-magnetic resonance spectroscopy/imaging (DNP-MRS/MRI). The distributed modularized architecture can implement more transceiver channels flexibly to meet a variety of MRS/MRI instrumentation needs. The proposed PCIe bus with high data rates can significantly improve data transmission efficiency and communication reliability and allow precise control of pulse sequences. An external high speed double data rate memory chip is used to store acquired data and pulse sequence elements, which greatly accelerates the execution of the pulse sequence, reduces the TR (time of repetition) interval, and improves the accuracy of TR in imaging sequences. Using clock phase-shift technology, we can produce digital pulses accurately with high timing resolution of 1 ns and narrow widths of 4 ns to control the microwave pulses required by pulsed DNP and ensure overall system synchronization. The proposed spectrometer is proved to be both feasible and reliable by observation of a maximum signal enhancement factor of approximately −170 for {sup 1}H, and a high quality water image was successfully obtained by DNP-enhanced spin-echo {sup 1}H MRI at 0.35 T.

Statistical approach of measurement of signal to noise ratio in according to change pulse sequence on brain MRI meningioma and cyst images

International Nuclear Information System (INIS)

Lee, Eul Kyu; Choi, Kwan Woo; Jeong, Hoi Woun; Jang, Seo Goo; Kim, Ki Won; Son, Soon Yong; Min, Jung Whan; Son, Jin Hyun

2016-01-01

The purpose of this study was to needed basis of measure MRI CAD development for signal to noise ratio (SNR) by pulse sequence analysis from region of interest (ROI) in brain magnetic resonance imaging (MRI) contrast. We examined images of brain MRI contrast enhancement of 117 patients, from January 2005 to December 2015 in a University-affiliated hospital, Seoul, Korea. Diagnosed as one of two brain diseases such as meningioma and cysts SNR for each patient's image of brain MRI were calculated by using Image J. Differences of SNR among two brain diseases were tested by SPSS Statistics21 ANOVA test for there was statistical significance (p < 0.05). We have analysis socio-demographical variables, SNR according to sequence disease, 95% confidence according to SNR of sequence and difference in a mean of SNR. Meningioma results, with the quality of distributions in the order of T1CE, T2 and T1, FLAIR. Cysts results, with the quality of distributions in the order of T2 and T1, T1CE and FLAIR. SNR of MRI sequences of the brain would be useful to classify disease. Therefore, this study will contribute to evaluate brain diseases, and be a fundamental to enhancing the accuracy of CAD development

Statistical approach of measurement of signal to noise ratio in according to change pulse sequence on brain MRI meningioma and cyst images

Energy Technology Data Exchange (ETDEWEB)

Lee, Eul Kyu [Inje Paik University Hospital Jeo-dong, Seoul (Korea, Republic of); Choi, Kwan Woo [Asan Medical Center, Seoul (Korea, Republic of); Jeong, Hoi Woun [The Baekseok Culture University, Cheonan (Korea, Republic of); Jang, Seo Goo [The Soonchunhyang University, Asan (Korea, Republic of); Kim, Ki Won [Kyung Hee University Hospital at Gang-dong, Seoul (Korea, Republic of); Son, Soon Yong [The Wonkwang Health Science University, Iksan (Korea, Republic of); Min, Jung Whan; Son, Jin Hyun [The Shingu University, Sungnam (Korea, Republic of)

2016-09-15

The purpose of this study was to needed basis of measure MRI CAD development for signal to noise ratio (SNR) by pulse sequence analysis from region of interest (ROI) in brain magnetic resonance imaging (MRI) contrast. We examined images of brain MRI contrast enhancement of 117 patients, from January 2005 to December 2015 in a University-affiliated hospital, Seoul, Korea. Diagnosed as one of two brain diseases such as meningioma and cysts SNR for each patient's image of brain MRI were calculated by using Image J. Differences of SNR among two brain diseases were tested by SPSS Statistics21 ANOVA test for there was statistical significance (p < 0.05). We have analysis socio-demographical variables, SNR according to sequence disease, 95% confidence according to SNR of sequence and difference in a mean of SNR. Meningioma results, with the quality of distributions in the order of T1CE, T2 and T1, FLAIR. Cysts results, with the quality of distributions in the order of T2 and T1, T1CE and FLAIR. SNR of MRI sequences of the brain would be useful to classify disease. Therefore, this study will contribute to evaluate brain diseases, and be a fundamental to enhancing the accuracy of CAD development.

A convolutional neural network for intracranial hemorrhage detection in non-contrast CT

Science.gov (United States)

Patel, Ajay; Manniesing, Rashindra

2018-02-01

The assessment of the presence of intracranial hemorrhage is a crucial step in the work-up of patients requiring emergency care. Fast and accurate detection of intracranial hemorrhage can aid treating physicians by not only expediting and guiding diagnosis, but also supporting choices for secondary imaging, treatment and intervention. However, the automatic detection of intracranial hemorrhage is complicated by the variation in appearance on non-contrast CT images as a result of differences in etiology and location. We propose a method using a convolutional neural network (CNN) for the automatic detection of intracranial hemorrhage. The method is trained on a dataset comprised of cerebral CT studies for which the presence of hemorrhage has been labeled for each axial slice. A separate test dataset of 20 images is used for quantitative evaluation and shows a sensitivity of 0.87, specificity of 0.97 and accuracy of 0.95. The average processing time for a single three-dimensional (3D) CT volume was 2.7 seconds. The proposed method is capable of fast and automated detection of intracranial hemorrhages in non-contrast CT without being limited to a specific subtype of pathology.

Optimal emission enhancement in orthogonal double-pulse laser-induced breakdown spectroscopy

International Nuclear Information System (INIS)

Sanginés, R.; Contreras, V.; Sobral, H.; Robledo-Martinez, A.

2015-01-01

Orthogonal double-pulse (DP) laser-induced breakdown spectroscopy (LIBS) was performed using reheating and pre-ablative configurations. The ablation pulse power density was varied by two orders of magnitude and the DP experiments were carried out for a wide range of interpulse delays. For both DP-LIBS schemes, the signal enhancement was evaluated with respect to the corresponding single-pulse (SP) LIBS as a function of the interpulse delay. The reheating scheme shows a sharp maximum signal enhancement of up to 200-fold for low ablative power densities (0.4 GW cm −2 ); however, for power densities larger than 10 GW cm −2 this configuration did not improve the SP outcome. On the other hand, a more uniform signal enhancement of about 4–6 was obtained for the pre-ablative scheme nearly independently of the used ablative power density. In terms of the signal-to-noise ratio (SNR) the pre-ablative scheme shows a monotonic increment with the ablative power density. Whereas the reheating configuration reaches a maximum at 2.2 GW cm −2 , its enhancement effect collapses markedly for fluencies above 10 GW cm −2 . - Highlights: • Comparison of reheating and pre-ablative double-pulse LIBS was done using a wide range of ablation power densities. • Experimental parameters that could achieve optimal signal-to-noise ratio were investigated. • A reheating scheme is better for low-ablation power densities. • A pre-ablative configuration is better for high-ablation power densities

Comparison of contrast and noncontrast magnetic resonance angiography for quantitative analysis of thoracic arteries in young patients with congenital heart defects

Directory of Open Access Journals (Sweden)

Pasqua Alessia

2011-01-01

Full Text Available Background : Contrast MRA (C-MRA is the standard for quantitative analysis of thoracic vessels. We evaluated a noncontrast MRA (NC-MRA sequence (3-D EKG and navigator-gated SSFP for quantitative evaluation of the thoracic aorta and branch pulmonary arteries in young patients with congenital heart disease. Objective : To compare contrast and noncontrast magnetic resonance angiography for quantitative analysis of thoracic arteries in young patients with congenital heart defects. Methods : Measurements of thoracic aorta and branch pulmonary arteries were obtained from C-MRA and NC-MRA images in 51 patients, ages 2-35 years. Vessel diameters were compared using correlation and Bland-Altman analysis. Interobserver variability was assessed using percent variation. Results : C-MRA and NC-MRA measurements were highly correlated (r = 0.91-0.98 except for the right pulmonary artery (r = 0.74, 0.78. Agreement of measurements was excellent (mean difference -0.07 to -0.53 mm; mean % difference -1.8 to -4.9% except for the right pulmonary artery which was less good (mean difference 0.73, -1.38 mm; -3, -10%. Interobserver variability ranged from 5% to 8% for aortic and from 10% to 16% for pulmonary artery measures. The worse agreement and greater variability of the pulmonary artery measures appears due to difficulty standardizing the measurements in patients with abnormal and irregular vessels. Conclusion : These data indicate that C-MRA and NC-MRA measures are comparable and could be used interchangeably, avoiding administration of contrast in selected patients.

Fat-Suppressed T2* Sequences for Routine 3.0-Tesla Lumbar Spine Magnetic Resonance Imaging: A Preliminary Report

International Nuclear Information System (INIS)

McKinney, A. M.; Gadani, S.; Palmer, C. S.; Vidarsson, L.

2008-01-01

Background: Clear depiction of the ligamentum flavum on routine lumbar magnetic resonance imaging (MRI) is essential in accurately describing the extent of degenerative disease. In routine, noncontrast evaluations, focal fatty deposition or hemangiomas can be difficult to distinguish from malignant foci on fast spin-echo (FSE) T2-weighted images. Purpose: To describe the use of T2* fast field echo (T2FFE) in combination with spectral presaturation inversion recovery (SPIR) fat suppression for noncontrast, routine lumbar spine outpatient MR imaging at 3.0 Tesla (3T). Material and Methods: An axial gradient echo (GE) T2FFE sequence was combined with SPIR fat suppression (T2FFE-SPIR), via a 3T Philips Intera (Philips Medical Systems, Best, The Netherlands) scanner, and added to the routine, noncontrast lumbar MRI examinations, which included sagittal FSE T1-weighted (T1WI), T2-weighted (T2WI), short-tau inversion recovery (STIR), and axial FSE T2WI. The sequence was performed in over 500 patients over a 1-year period, without intravenous contrast, and with slice thickness and planes of section identical to the axial FSE T1WI and T2WI images. The sequence typically lasted about 4.5-6 min. Results: The use of T2FFE-SPIR enabled visualization of the ligamentum flavum in degenerative disease, and the exclusion of focal fatty lesions on FSE T2WI. Other benefits included: the identification of malignant foci, the uncommon detection of hemorrhage, and the elimination of spurious flow voids. Several brief examples are provided to demonstrate the utility of this technique. Conclusion: The addition of T2FFE-SPIR to routine, noncontrast protocols in outpatients could provide further confidence in the visualization of the ligamentum flavum in degenerative disease, and can exclude malignancy in T2-bright areas of focal fatty marrow. Larger studies would be helpful to evaluate the accuracy of this technique versus FSE techniques in depicting degenerative, malignant, or inflammatory

Fat-Suppressed T2 Sequences for Routine 3.0-Tesla Lumbar Spine Magnetic Resonance Imaging: A Preliminary Report

Energy Technology Data Exchange (ETDEWEB)

McKinney, A. M.; Gadani, S.; Palmer, C. S.; Vidarsson, L. (Dept. of Radiology, Hennepin County and Univ. of Minnesota Medical Centers, Minneapolis, MN (United States))

2008-09-15

Background: Clear depiction of the ligamentum flavum on routine lumbar magnetic resonance imaging (MRI) is essential in accurately describing the extent of degenerative disease. In routine, noncontrast evaluations, focal fatty deposition or hemangiomas can be difficult to distinguish from malignant foci on fast spin-echo (FSE) T2-weighted images. Purpose: To describe the use of T2 fast field echo (T2FFE) in combination with spectral presaturation inversion recovery (SPIR) fat suppression for noncontrast, routine lumbar spine outpatient MR imaging at 3.0 Tesla (3T). Material and Methods: An axial gradient echo (GE) T2FFE sequence was combined with SPIR fat suppression (T2FFE-SPIR), via a 3T Philips Intera (Philips Medical Systems, Best, The Netherlands) scanner, and added to the routine, noncontrast lumbar MRI examinations, which included sagittal FSE T1-weighted (T1WI), T2-weighted (T2WI), short-tau inversion recovery (STIR), and axial FSE T2WI. The sequence was performed in over 500 patients over a 1-year period, without intravenous contrast, and with slice thickness and planes of section identical to the axial FSE T1WI and T2WI images. The sequence typically lasted about 4.5-6 min. Results: The use of T2FFE-SPIR enabled visualization of the ligamentum flavum in degenerative disease, and the exclusion of focal fatty lesions on FSE T2WI. Other benefits included: the identification of malignant foci, the uncommon detection of hemorrhage, and the elimination of spurious flow voids. Several brief examples are provided to demonstrate the utility of this technique. Conclusion: The addition of T2FFE-SPIR to routine, noncontrast protocols in outpatients could provide further confidence in the visualization of the ligamentum flavum in degenerative disease, and can exclude malignancy in T2-bright areas of focal fatty marrow. Larger studies would be helpful to evaluate the accuracy of this technique versus FSE techniques in depicting degenerative, malignant, or inflammatory

Sequence conservation and combinatorial complexity of Drosophila neural precursor cell enhancers

Directory of Open Access Journals (Sweden)

Kuzin Alexander

2008-08-01

Full Text Available Abstract Background The presence of highly conserved sequences within cis-regulatory regions can serve as a valuable starting point for elucidating the basis of enhancer function. This study focuses on regulation of gene expression during the early events of Drosophila neural development. We describe the use of EvoPrinter and cis-Decoder, a suite of interrelated phylogenetic footprinting and alignment programs, to characterize highly conserved sequences that are shared among co-regulating enhancers. Results Analysis of in vivo characterized enhancers that drive neural precursor gene expression has revealed that they contain clusters of highly conserved sequence blocks (CSBs made up of shorter shared sequence elements which are present in different combinations and orientations within the different co-regulating enhancers; these elements contain either known consensus transcription factor binding sites or consist of novel sequences that have not been functionally characterized. The CSBs of co-regulated enhancers share a large number of sequence elements, suggesting that a diverse repertoire of transcription factors may interact in a highly combinatorial fashion to coordinately regulate gene expression. We have used information gained from our comparative analysis to discover an enhancer that directs expression of the nervy gene in neural precursor cells of the CNS and PNS. Conclusion The combined use EvoPrinter and cis-Decoder has yielded important insights into the combinatorial appearance of fundamental sequence elements required for neural enhancer function. Each of the 30 enhancers examined conformed to a pattern of highly conserved blocks of sequences containing shared constituent elements. These data establish a basis for further analysis and understanding of neural enhancer function.

Design of high-power, broadband 180o pulses and mixing sequences for fast MAS solid state chemical shift correlation NMR spectroscopy

International Nuclear Information System (INIS)

Herbst, Christian; Herbst, Jirada; Kirschstein, Anika; Leppert, Joerg; Ohlenschlaeger, Oliver; Goerlach, Matthias; Ramachandran, Ramadurai

2009-01-01

An approach for the design of high-power, broadband 180 o pulses and mixing sequences for generating dipolar and scalar coupling mediated 13 C- 13 C chemical shift correlation spectra of isotopically labelled biological systems at fast magic-angle spinning frequencies without 1 H decoupling during mixing is presented. Considering RF field strengths in the range of 100-120 kHz, as typically available in MAS probes employed at high spinning speeds, and limited B 1 field inhomogeneities, the Fourier coefficients defining the phase modulation profile of the RF pulses were optimised numerically to obtain broadband inversion and refocussing pulses and mixing sequences. Experimental measurements were carried out to assess the performance characteristics of the mixing sequences reported here

Multi-pulse enhanced laser ion acceleration using plasma half cavity targets

International Nuclear Information System (INIS)

Scott, G. G.; Brenner, C. M.; Neely, D.; Green, J. S.; Robinson, A. P. L.; Spindloe, C.; Bagnoud, V.; Brabetz, C.; Zielbauer, B.; Carroll, D. C.; MacLellan, D. A.; McKenna, P.; Roth, M.; Wagner, F.

2012-01-01

We report on a plasma half cavity target design for laser driven ion acceleration that enhances the laser to proton energy conversion efficiency and has been found to modify the low energy region of the proton spectrum. The target design utilizes the high fraction of laser energy reflected from an ionized surface and refocuses it such that a double pulse interaction is attained. We report on numerical simulations and experimental results demonstrating that conversion efficiencies can be doubled, compared to planar foil interactions, when the secondary pulse is delivered within picoseconds of the primary pulse.

Multi-pulse enhanced laser ion acceleration using plasma half cavity targets

Energy Technology Data Exchange (ETDEWEB)

Scott, G. G.; Brenner, C. M.; Neely, D. [Central Laser Facility, STFC Rutherford Appleton Laboratory, OX11 0QX Didcot (United Kingdom); Department of Physics SUPA, University of Strathclyde, G4 0NG Glasgow (United Kingdom); Green, J. S.; Robinson, A. P. L.; Spindloe, C. [Central Laser Facility, STFC Rutherford Appleton Laboratory, OX11 0QX Didcot (United Kingdom); Bagnoud, V.; Brabetz, C.; Zielbauer, B. [PHELIX Group, Gesellschaft fuer Schwerionenforschung, D-64291 Darmstadt (Germany); Carroll, D. C.; MacLellan, D. A.; McKenna, P. [Department of Physics SUPA, University of Strathclyde, G4 0NG Glasgow (United Kingdom); Roth, M. [Fachbereich Physik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany); Wagner, F. [PHELIX Group, Gesellschaft fuer Schwerionenforschung, D-64291 Darmstadt (Germany); Fachbereich Physik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany)

2012-07-09

We report on a plasma half cavity target design for laser driven ion acceleration that enhances the laser to proton energy conversion efficiency and has been found to modify the low energy region of the proton spectrum. The target design utilizes the high fraction of laser energy reflected from an ionized surface and refocuses it such that a double pulse interaction is attained. We report on numerical simulations and experimental results demonstrating that conversion efficiencies can be doubled, compared to planar foil interactions, when the secondary pulse is delivered within picoseconds of the primary pulse.

Mode-Locking in Broad-Area Semiconductor Lasers Enhanced by Picosecond-Pulse Injection

OpenAIRE

Kaiser, J; Fischer, I; Elsasser, W; Gehrig, E; Hess, O

2004-01-01

We present combined experimental and theoretical investigations of the picosecond emission dynamics of broad-area semiconductor lasers (BALs). We enhance the weak longitudinal self-mode-locking that is inherent to BALs by injecting a single optical 50-ps pulse, which triggers the output of a distinct regular train of 13-ps pulses. Modeling based on multimode Maxwell-Bloch equations illustrates how the dynamic interaction of the injected pulse with the internal laser field efficiently couples ...

Narrowband pulse-enhanced upconversion of chirped broadband pulses

International Nuclear Information System (INIS)

Zhao, Kun; Yuan, Peng; Zhong, Haizhe; Zhang, Dongfang; Zhu, Heyuan; Qian, Liejia; Chen, Liezun; Wen, Shuangchun

2010-01-01

We propose and demonstrate an efficient sum-frequency mixing scheme based on narrowband and chirped broadband pulses. It combines the advantages of wider spectral acceptance bandwidth and of alleviating the temporal walk-off, which are both beneficial to higher conversion efficiency. Chirped sum-frequency pulses at 455 nm with energy up to 360 µJ, corresponding to a conversion efficiency of ∼ 40%, are obtained and the pulses can be compressed to ∼ 110 fs. The sum-frequency mixing scheme may provide a promising route to the efficient generation of deep-ultraviolet femtosecond pulses

Noncontrast chest computed tomography immediately after transarterial chemoembolization in patients with hepatocellular carcinoma: Clinical benefits and effect of radiation reduction on image quality in low-dose scanning

International Nuclear Information System (INIS)

Choi, Joon-Il; Kim, Hyun Beom; Kim, Min Ju; Lee, Jong Seok; Koh, Young Whan; An, Sang Bu; Ko, Heung-kyu; Park, Joong-Won

2011-01-01

Purpose: To evaluate the clinical benefits of noncontrast chest computed tomography (CT) immediately after transarterial chemoembolization in patients with hepatocellular carcinoma and to assess the effect of radiation reduction on image quality in low-dose scanning. Materials and methods: From June to October 2010, we performed standard-dose, noncontrast chest CTs immediately after transarterial chemoembolization in 160 patients and low-dose CTs in 88 patients. We reviewed the entire noncontrast chest CTs and follow-up CTs to reveal the clinical benefits of CT evaluation immediately after transarterial chemoembolization. Using two independent readers, we also retrospectively evaluated the radiation dose and image quality in terms of the image noise, contrast between the liver parenchyma and iodized oil and diagnostic acceptability for the evaluation of treatment response after transarterial chemoembolization. Results: In 5.2% of the patients, additional treatment was performed immediately after the interpretation of the noncontrast chest CT, and additional pulmonary lesions were found in 8.5% of the patients. The measured mean dose-length product for the low-dose scanning was 18.4% of that of the standard-dose scanning. The image noise was significantly higher with the low-dose scanning (p < 0.001). However, all of the low-dose CT scans were diagnostically acceptable, and the mean scores for the subjective assessments of the contrast and diagnostic acceptability showed no significant differences for either reader. Conclusion: A noncontrast chest CT immediately after transarterial chemoembolization has some clinical benefits for immediate decision making and detecting pulmonary lesions. Low-dose, noncontrast chest CTs immediately after transarterial chemoembolization consistently provide diagnostically acceptable images and information on treatment response in patients who have undergone transarterial chemoembolization.

MRI of the brain stem using fluid attenuated inversion recivery pulse sequences

International Nuclear Information System (INIS)

De Coene, B.; Hajnal, J.V.; Pennock, J.M.; Bydder, G.M.

1993-01-01

Heavily T2-weighted fluid-attenuated inversion recovery (FLAIR) sequences with inversion times of 2000-2500 ms and echo times of 130-200 ms were used to image the brain stem of a normal adult and five patients. These sequences produce high signal from many white matter tracts and display high lesion contrast. The corticospinal and parietopontine tracts, lateral and medial lemnisci, superior and inferior cerebellar peduncles, medial longitudinal fasciculi, thalamo-olivary tracts the cuneate and gracile fasiculi gave high signal and were directly visualised. The oculomotor and trigeminal nerves were demonstrated within the brain stem. Lesions not seen with conventional T2-weighted spin echo sequences were seen with high contrast in patients with infarction, multiple sclerosis, sarcoidosis, chunt obstruction and metastatic tumour. The anatomical detail and high lesion contrast given by the FLAIR pulse sequence appear likely to be of value in diagnosis of disease in the brain stem. (orig.)

Dual-Energy Computed Tomography in Stroke Imaging: Technical and Clinical Considerations of Virtual Noncontrast Images for Detection of the Hyperdense Artery Sign.

Science.gov (United States)

Winklhofer, Sebastian; Vittoria De Martini, Ilaria; Nern, Chrisitian; Blume, Iris; Wegener, Susanne; Pangalu, Athina; Valavanis, Antonios; Alkadhi, Hatem; Guggenberger, Roman

The technical feasibility of virtual noncontrast (VNC) images from dual-energy computed tomography (DECT) for the detection of the hyperdense artery sign (HAS) in ischemic stroke patients was investigated. True noncontrast (TNC) scans of 60 patients either with or without HAS (n = 30 each) were investigated. Clot presence and characteristics were assessed on VNC images from DECT angiography and compared with TNC images. Clot characterization included the level of confidence for diagnosing HAS, a qualitative clot burden score, and quantitative attenuation (Hounsfield unit [HU]) measurements. Sensitivity, specificity, and accuracy of VNC for diagnosing HAS were 97%, 90%, and 93%, respectively. No significant differences were found regarding the diagnostic confidence (P = 0.18) and clot burden score (P = 0.071). No significant HU differences were found among vessels with HAS in VNC (56 ± 7HU) and TNC (57 ± 8HU) (P = 0.691) images. Virtual noncontrast images derived from DECT enable an accurate detection and characterization of HAS.

Zero sequence blocking transformers for multi-pulse rectifier in aerospace applications

DEFF Research Database (Denmark)

Yao, Wenli; Blaabjerg, Frede; Zhang, Xiaobin

2014-01-01

The power electronics technology plays an even more important role in the aerospace applications of More Electric Aircrafts (MEA). AutoTransformer Rectifier Units (ATRU) have been widely adopted in aircrafts due to its simplicity and reliability. In this paper, Zero Sequence Blocking Transformers...... (ZSBT) are employed in the DC link to realize parallel rectifier bridges for ATRU, being the proposed 24-pulse rectifier. A star-connected autotransformer is used in this topology to divide the primary side voltage into four three-phase voltage groups, among which there is a phase shift of 15......°. The autotransformer then feeds the load through rectifier bridges, which are in parallel with ZSBTs. Compared to the traditional method that is using six interphase transformers to parallel the rectifier bridges; the proposed 24-pulse rectifier only requires four ZSBTs. This will contribute to a reduction of weight...

Enhanced learning of natural visual sequences in newborn chicks.

Science.gov (United States)

Wood, Justin N; Prasad, Aditya; Goldman, Jason G; Wood, Samantha M W

2016-07-01

To what extent are newborn brains designed to operate over natural visual input? To address this question, we used a high-throughput controlled-rearing method to examine whether newborn chicks (Gallus gallus) show enhanced learning of natural visual sequences at the onset of vision. We took the same set of images and grouped them into either natural sequences (i.e., sequences showing different viewpoints of the same real-world object) or unnatural sequences (i.e., sequences showing different images of different real-world objects). When raised in virtual worlds containing natural sequences, newborn chicks developed the ability to recognize familiar images of objects. Conversely, when raised in virtual worlds containing unnatural sequences, newborn chicks' object recognition abilities were severely impaired. In fact, the majority of the chicks raised with the unnatural sequences failed to recognize familiar images of objects despite acquiring over 100 h of visual experience with those images. Thus, newborn chicks show enhanced learning of natural visual sequences at the onset of vision. These results indicate that newborn brains are designed to operate over natural visual input.

Simulations of NMR pulse sequences during equilibrium and non-equilibrium chemical exchange

International Nuclear Information System (INIS)

Helgstrand, Magnus; Haerd, Torleif; Allard, Peter

2000-01-01

The McConnell equations combine the differential equations for a simple two-state chemical exchange process with the Bloch differential equations for a classical description of the behavior of nuclear spins in a magnetic field. This equation system provides a useful starting point for the analysis of slow, intermediate and fast chemical exchange studied using a variety of NMR experiments. The McConnell equations are in the mathematical form of an inhomogeneous system of first-order differential equations. Here we rewrite the McConnell equations in a homogeneous form in order to facilitate fast and simple numerical calculation of the solution to the equation system. The McConnell equations can only treat equilibrium chemical exchange. We therefore also present a homogeneous equation system that can handle both equilibrium and non-equilibrium chemical processes correctly, as long as the kinetics is of first-order. Finally, the same method of rewriting the inhomogeneous form of the McConnell equations into a homogeneous form is applied to a quantum mechanical treatment of a spin system in chemical exchange. In order to illustrate the homogeneous McConnell equations, we have simulated pulse sequences useful for measuring exchange rates in slow, intermediate and fast chemical exchange processes. A stopped-flow NMR experiment was simulated using the equations for non-equilibrium chemical exchange. The quantum mechanical treatment was tested by the simulation of a sensitivity enhanced 15 N-HSQC with pulsed field gradients during slow chemical exchange and by the simulation of the transfer efficiency of a two-dimensional heteronuclear cross-polarization based experiment as a function of both chemical shift difference and exchange rate constants

Gadobenate dimeglumine-enhanced MR of VX2 carcinoma in rabbit liver: usefulness of the delayed phase imaging and optimal pulse sequence

Energy Technology Data Exchange (ETDEWEB)

Cho, Seung Il; Lee, Jeong Min; Kim, Young Kon; Kim, Chong Soo [College of Medicine, Chonbuk National Univ., Chonju (Korea, Republic of)

2002-07-01

To assess the diagnostic value of delayed imaging using gadobenate dimeglumine (MultiHance) and to determine the optimal pulse sequence for the detection of VX2 carcinoma lesions in the rabbit. Twelve VX2 carcinomas implanted in the livers of eleven New Zealand rabbits were studied. All patients underwent an MR protocal consisting of precontrast T2-and T1-weighted sequences, followed by repetition of the T1-weighted sequence at 0 to 30 (arterial phase). 31-60 (portal phase), and 40 minutes (delayed phase) after the intravenous administration of 0.1 mmol/kg of gadobenate dimeglumine. The signal-to-noise ratio (SNR) of the liver and VX2 tumor, and the lesion-to-liver contrast-to-noise ratio (CNR) of precontrast and postcontrast MR images were quantitatively analyzed, and two experienced radiologists evaluated image quality in terms of lesion conspicuity, artifact, mass delineation, and vascular anatomy. Liver SNR was significantly higher at delayed imaging than at precontrast, arterial, and portal imaging (p<0.05), while lesion SNR was significantly higher at delayed imaging than at precontrast imaging (p<0.05). Lesion CNR was higher at delayed imaging than at precontrast and portal phase imaging (p<0.05), but there was no difference between arterial and delayed imaging. The latter provided better mass delineation than precontrast, arterial and portal phase imaging (p<0.05). While in terms of lesion conspicuity and vascular anatomy, the delayed phase was better than the arterial phase (p<0.05) but similar to the precontrast and portal phase. During the delayed phase, the gradient-echo sequence showed better results than the spin-echo in terms of liver SNR, and lesion SNR and CNR (p<0.05). Because it provides better lesion conspicuity and mass delineation by improving liver SNR and lesion-to-liver CNR, the addition of the delayed phase to a dynamic MRI sequence after gadobenate dimeglumine adminstration facilitates lesion detection. For delayed-phase imaging, the

Gadobenate dimeglumine-enhanced MR of VX2 carcinoma in rabbit liver: usefulness of the delayed phase imaging and optimal pulse sequence

International Nuclear Information System (INIS)

Cho, Seung Il; Lee, Jeong Min; Kim, Young Kon; Kim, Chong Soo

2002-01-01

To assess the diagnostic value of delayed imaging using gadobenate dimeglumine (MultiHance) and to determine the optimal pulse sequence for the detection of VX2 carcinoma lesions in the rabbit. Twelve VX2 carcinomas implanted in the livers of eleven New Zealand rabbits were studied. All patients underwent an MR protocal consisting of precontrast T2-and T1-weighted sequences, followed by repetition of the T1-weighted sequence at 0 to 30 (arterial phase). 31-60 (portal phase), and 40 minutes (delayed phase) after the intravenous administration of 0.1 mmol/kg of gadobenate dimeglumine. The signal-to-noise ratio (SNR) of the liver and VX2 tumor, and the lesion-to-liver contrast-to-noise ratio (CNR) of precontrast and postcontrast MR images were quantitatively analyzed, and two experienced radiologists evaluated image quality in terms of lesion conspicuity, artifact, mass delineation, and vascular anatomy. Liver SNR was significantly higher at delayed imaging than at precontrast, arterial, and portal imaging (p<0.05), while lesion SNR was significantly higher at delayed imaging than at precontrast imaging (p<0.05). Lesion CNR was higher at delayed imaging than at precontrast and portal phase imaging (p<0.05), but there was no difference between arterial and delayed imaging. The latter provided better mass delineation than precontrast, arterial and portal phase imaging (p<0.05). While in terms of lesion conspicuity and vascular anatomy, the delayed phase was better than the arterial phase (p<0.05) but similar to the precontrast and portal phase. During the delayed phase, the gradient-echo sequence showed better results than the spin-echo in terms of liver SNR, and lesion SNR and CNR (p<0.05). Because it provides better lesion conspicuity and mass delineation by improving liver SNR and lesion-to-liver CNR, the addition of the delayed phase to a dynamic MRI sequence after gadobenate dimeglumine adminstration facilitates lesion detection. For delayed-phase imaging, the

Comparison of Accuracy of Contrast Enhanced Computed Tomography with Accuracy of Non-Contrast Magnetic Resonance Imaging in Evaluation of Local Extension of Base of Tongue Malignancies

Directory of Open Access Journals (Sweden)

Ketan Rathod

2018-01-01

Full Text Available Diagnosis of base of tongue malignancy can be obtained through clinical examination and biopsy. Magnetic Resonance Imaging (MRI and Computed Tomography (CT are used to detect its local extension, nodal spread and distant metastases. The main aim of study was to compare the accuracy of MRI and contrast enhanced CT in determining the local extent of base of tongue malignancy. Twenty five patients, biopsy proven cases of squamous cell carcinoma of base of tongue were taken. 1.5 Tesla Magnetic Resonance Unit with T2 weighted axial, coronal image; T1 weighted axial, coronal image; and STIR (Short tau inversion recovery axial and coronal images were used. 16 slice Computed Tomography unit with non-contrast and contrast enhanced images were used. Accuracy of CT to detect midline crossing: 50%; accuracy of MRI to detect midline crossing: 100%; accuracy of CT to detect anterior extension: 92%; accuracy of MRI to detect anterior extension: 100%; accuracy of CT to detect tonsillar fossa invasion: 83%; accuracy of MRI to detect tonsillar fossa invasion: 100%; accuracy of CT to detect oro pharyngeal spread: 83%; accuracy of MRI to detect oro pharyngeal spread: 100%; accuracy of CT to detect bone involvement: 20%; accuracy of MRI to detect bone involvement: 100%. MRI proved to be a better investigation than CT, in terms of evaluation of depth of invasion, presence of bony involvement, extension to opposite side, anterior half of tongue, tonsillar fossa, floor of mouth or oropharynx.

Enhancement of intermediate-field two-photon absorption by rationally shaped femtosecond pulses

International Nuclear Information System (INIS)

Chuntonov, Lev; Rybak, Leonid; Gandman, Andrey; Amitay, Zohar

2008-01-01

We extend the powerful frequency-domain analysis of femtosecond two-photon absorption to the intermediate-field regime of considerable absorption yields, where additionally to the weak-field nonresonant two-photon transitions also four-photon transitions play a role. Consequently, we rationally find that the absorption is enhanced over the transform-limited pulse by any shaped pulse having a spectral phase that is antisymmetric around one-half of the transition frequency and a spectrum that is asymmetric around it (red or blue detuned according to the system). The enhancement increases as the field strength increases. The theoretical results for Na are verified experimentally

Contributions of an adiabatic initial inversion pulse and K-space Re-ordered by inversion-time at each slice position (KRISP) to control of CSF artifacts and visualization of the brain in FLAIR magnetic resonance imaging

International Nuclear Information System (INIS)

Curati, Walter L.; Oatridge, Angela; Herlihy, Amy H.; Hajnal, Joseph V.; Puri, Basant K.; Bydder, Graeme M.

2001-01-01

AIM: The aim of this study was to compare the performance of three fluid attenuated inversion recovery (FLAIR) pulse sequences for control of cerebrospinal fluid (CSF) and blood flow artifacts in imaging of the brain. The first of these sequences had an initial sinc inversion pulse which was followed by conventional k-space mapping. The second had an initial sinc inversion pulse followed by k-space re-ordered by inversion time at each slice position (KRISP) and the third had an adiabatic initial inversion pulse followed by KRISP. MATERIALS AND METHODS: Ten patients with established disease were studied with all three pulse sequences. Seven were also studied with the adiabatic KRISP sequence after contrast enhancement. Their images were evaluated for patient motion artifact, CSF and blood flow artifact as well as conspicuity of the cortex, meninges, ventricular system, brainstem and cerebellum. The conspicuity of lesions and the degree of enhancement were also evaluated. RESULTS: Both the sinc and adiabatic KRISP FLAIR sequences showed better control of CSF and blood flow artifacts than the conventional FLAIR sequence. In addition the adiabatic KRISP FLAIR sequence showed better control of CSF artifact at the inferior aspect of the posterior fossa. The lesion conspicuity was similar for each of the FLAIR sequences as was the degree of contrast enhancement to that shown with a T 1 weighted spin echo sequence. CONCLUSION: The KRISP FLAIR sequence controls high signal artifacts from CSF flow and blood flow and the adiabatic pulse controls high signal artifacts due to inadequate inversion of the CSF magnetization at the periphery of the head transmitter coil. The KRISP FLAIR sequence also improves cortical and meningeal definition as a result of an edge enhancement effect. The effects are synergistic and can be usefully combined in a single pulse sequence. Curati, W.L. et al. (2001)

Magnetic resonance for T-staging of nasopharyngeal carcinoma. The most informative pair of sequences

International Nuclear Information System (INIS)

Lau, Kam Y.; Kan, Wai K.; Sze, Wai M.

2004-01-01

The objective of this study was to evaluate the most informative pair of sequences in magnetic resonance (MR) for T-staging of nasopharyngeal carcinoma (NPC). The MR images of 134 patients with newly diagnosed NRC, from 1996 to 2002, were retrospectively reviewed. All the patients were scanned using 1.5 Tesla MR systems. The images of the nasopharynx were reviewed by two qualified radiologists to determine the positive findings and the T-stage by Union Internationale Contre le Cancer (UICC) (6th edition) System, using each sequence separately. The T-stage derived from a single MR sequence was then compared with the T-stage based on the five selected sequences to assess the number and percentage of patients who were being understaged. Therefore, the overall percentage accuracy of each single sequence could be determined. A pair of sequences providing information to achieve almost 100% diagnostic accuracy was then derived. The overall percentage accuracy of five individual sequences of the nasopharynx is as follows: contrast-enhanced (CE) fat suppression (FS) axial T1 (94.8%), CE FS coronal T1 (88.1%), FS axial T2 (85.8%), non-contrast enhanced (NE) axial T1 (78.4%) and NE coronal T1 (77.6%). CE FS axial T1 has the best accuracy. All the structures that are missed in CE FS axial T1 which lead to apparent understaging, are appreciated in NE axial T1-weighted images. Individual sequences supplement each other in the NPC staging. CE FS axial T1 is the most informative individual sequence. Combination of CE FS axial T1 and NE axial T1 of the nasopharynx provides sufficient information to achieve almost 100% diagnostic accuracy in T-staging; therefore, both should be included in the MR-staging protocol. (author)

PET Imaging Stability Measurements During Simultaneous Pulsing of Aggressive MR Sequences on the SIGNA PET/MR System.

Science.gov (United States)

Deller, Timothy W; Khalighi, Mohammad Mehdi; Jansen, Floris P; Glover, Gary H

2018-01-01

The recent introduction of simultaneous whole-body PET/MR scanners has enabled new research taking advantage of the complementary information obtainable with PET and MRI. One such application is kinetic modeling, which requires high levels of PET quantitative stability. To accomplish the required PET stability levels, the PET subsystem must be sufficiently isolated from the effects of MR activity. Performance measurements have previously been published, demonstrating sufficient PET stability in the presence of MR pulsing for typical clinical use; however, PET stability during radiofrequency (RF)-intensive and gradient-intensive sequences has not previously been evaluated for a clinical whole-body scanner. In this work, PET stability of the GE SIGNA PET/MR was examined during simultaneous scanning of aggressive MR pulse sequences. Methods: PET performance tests were acquired with MR idle and during simultaneous MR pulsing. Recent system improvements mitigating RF interference and gain variation were used. A fast recovery fast spin echo MR sequence was selected for high RF power, and an echo planar imaging sequence was selected for its high heat-inducing gradients. Measurements were performed to determine PET stability under varying MR conditions using the following metrics: sensitivity, scatter fraction, contrast recovery, uniformity, count rate performance, and image quantitation. A final PET quantitative stability assessment for simultaneous PET scanning during functional MRI studies was performed with a spiral in-and-out gradient echo sequence. Results: Quantitation stability of a 68 Ge flood phantom was demonstrated within 0.34%. Normalized sensitivity was stable during simultaneous scanning within 0.3%. Scatter fraction measured with a 68 Ge line source in the scatter phantom was stable within the range of 40.4%-40.6%. Contrast recovery and uniformity were comparable for PET images acquired simultaneously with multiple MR conditions. Peak noise equivalent count

MR imaging of the knee: Improvement of signal and contrast efficiency of T1-weighted turbo spin echo sequences by applying a driven equilibrium (DRIVE) pulse

Energy Technology Data Exchange (ETDEWEB)

Radlbauer, Rudolf, E-mail: rudolf.radlbauer@stpoelten.lknoe.a [MR Physics Group, Department of Radiology, Landesklinikum St. Poelten, Propst Fuehrer Strasse 4, 3100 St. Poelten (Austria); Lomoschitz, Friedrich, E-mail: friedrich.lomoschitz@stpoelten.lknoe.a [MR Physics Group, Department of Radiology, Landesklinikum St. Poelten, Propst Fuehrer Strasse 4, 3100 St. Poelten (Austria); Salomonowitz, Erich, E-mail: erich.salomonowitz@stpoelten.lknoe.a [MR Physics Group, Department of Radiology, Landesklinikum St. Poelten, Propst Fuehrer Strasse 4, 3100 St. Poelten (Austria); Eberhardt, Knut E., E-mail: info@mrt-kompetenzzentrum.d [MRT Competence Center Schloss Werneck, Balthasar-Neumann-Platz 2, 97440 Werneck (Germany); Stadlbauer, Andreas, E-mail: andi@nmr.a [MR Physics Group, Department of Radiology, Landesklinikum St. Poelten, Propst Fuehrer Strasse 4, 3100 St. Poelten (Austria); Department of Neurosurgery, University of Erlangen-Nuremberg, Schwabachanlage 6, 91054 Erlangen (Germany)

2010-08-15

The purpose of this study was to assess the effect of a driven equilibrium (DRIVE) pulse incorporated in a standard T1-weighted turbo spin echo (TSE) sequence as used in our routine MRI protocol for examination of pathologies of the knee. Sixteen consecutive patients with knee disorders were examined using the routine MRI protocol, including T1-weighted TSE-sequences with and without a DRIVE pulse. Signal-to-noise ratios (SNRs) and contrast-to-noise ratio (CNR) of anatomical structures and pathologies were calculated and compared for both sequences. The differences in diagnostic value of the T1-weighted images with and without DRIVE pulse were assessed. SNR was significantly higher on images acquired with DRIVE pulse for fluid, effusion, cartilage and bone. Differences in the SNR of meniscus and muscle between the two sequences were not statistically significant. CNR was significantly increased between muscle and effusion, fluid and cartilage, fluid and meniscus, cartilage and meniscus, bone and cartilage on images acquired using the DRIVE pulse. Diagnostic value of the T1-weighted images was found to be improved for delineation of anatomic structures and for diagnosing a variety of pathologies when a DRIVE pulse is incorporated in the sequence. Incorporation of a DRIVE pulse into a standard T1-weighted TSE-sequence leads to significant increase of SNR and CNR of both, anatomical structures and pathologies, and consequently to an increase in diagnostic value within the same acquisition time.

MR imaging of the knee: Improvement of signal and contrast efficiency of T1-weighted turbo spin echo sequences by applying a driven equilibrium (DRIVE) pulse

International Nuclear Information System (INIS)

Radlbauer, Rudolf; Lomoschitz, Friedrich; Salomonowitz, Erich; Eberhardt, Knut E.; Stadlbauer, Andreas

2010-01-01

The purpose of this study was to assess the effect of a driven equilibrium (DRIVE) pulse incorporated in a standard T1-weighted turbo spin echo (TSE) sequence as used in our routine MRI protocol for examination of pathologies of the knee. Sixteen consecutive patients with knee disorders were examined using the routine MRI protocol, including T1-weighted TSE-sequences with and without a DRIVE pulse. Signal-to-noise ratios (SNRs) and contrast-to-noise ratio (CNR) of anatomical structures and pathologies were calculated and compared for both sequences. The differences in diagnostic value of the T1-weighted images with and without DRIVE pulse were assessed. SNR was significantly higher on images acquired with DRIVE pulse for fluid, effusion, cartilage and bone. Differences in the SNR of meniscus and muscle between the two sequences were not statistically significant. CNR was significantly increased between muscle and effusion, fluid and cartilage, fluid and meniscus, cartilage and meniscus, bone and cartilage on images acquired using the DRIVE pulse. Diagnostic value of the T1-weighted images was found to be improved for delineation of anatomic structures and for diagnosing a variety of pathologies when a DRIVE pulse is incorporated in the sequence. Incorporation of a DRIVE pulse into a standard T1-weighted TSE-sequence leads to significant increase of SNR and CNR of both, anatomical structures and pathologies, and consequently to an increase in diagnostic value within the same acquisition time.

Frequency-locked pulse sequencer for high-frame-rate monochromatic tissue motion imaging.

Science.gov (United States)

Azar, Reza Zahiri; Baghani, Ali; Salcudean, Septimiu E; Rohling, Robert

2011-04-01

To overcome the inherent low frame rate of conventional ultrasound, we have previously presented a system that can be implemented on conventional ultrasound scanners for high-frame-rate imaging of monochromatic tissue motion. The system employs a sector subdivision technique in the sequencer to increase the acquisition rate. To eliminate the delays introduced during data acquisition, a motion phase correction algorithm has also been introduced to create in-phase displacement images. Previous experimental results from tissue- mimicking phantoms showed that the system can achieve effective frame rates of up to a few kilohertz on conventional ultrasound systems. In this short communication, we present a new pulse sequencing strategy that facilitates high-frame-rate imaging of monochromatic motion such that the acquired echo signals are inherently in-phase. The sequencer uses the knowledge of the excitation frequency to synchronize the acquisition of the entire imaging plane to that of an external exciter. This sequencing approach eliminates any need for synchronization or phase correction and has applications in tissue elastography, which we demonstrate with tissue-mimicking phantoms. © 2011 IEEE

High-efficiency intracavity second-harmonic enhancement for a few-cycle laser pulse train

International Nuclear Information System (INIS)

Cai, Yi; Xu, Shixiang; Zeng, Xuanke; Zou, Da; Li, Jingzhen

2012-01-01

This paper presents an intracavity second-harmonic (SH) enhancement technology without the need of input impedance-matching for optimal coupling between the cavity and its input frequency comb. More than 10% SH energy conversion efficiency is available, thus the power of the SH frequency comb can be enhanced beyond 100 relative to single-pass SH generation. Compared with a conventional passive enhancing cavity, for the purpose of high power enhancement, our scheme can operate at much lower finesse and thus broader bandwidth so that it can support several-optical-cycle pulses more easily. If they have the same finesse, both methods perform with similar operating stability. The results show that our novel design is suitable for some applications which need a short wavelength, high intensity, and ultra-broad bandwidth pulse train. (paper)

Visible continuum pulses based on enhanced dispersive wave generation for endogenous fluorescence imaging.

Science.gov (United States)

Cui, Quan; Chen, Zhongyun; Liu, Qian; Zhang, Zhihong; Luo, Qingming; Fu, Ling

2017-09-01

In this study, we demonstrate endogenous fluorescence imaging using visible continuum pulses based on 100-fs Ti:sapphire oscillator and a nonlinear photonic crystal fiber. Broadband (500-700 nm) and high-power (150 mW) continuum pulses are generated through enhanced dispersive wave generation by pumping femtosecond pulses at the anomalous dispersion region near zero-dispersion wavelength of high-nonlinear photonic crystal fibers. We also minimize the continuum pulse width by determining the proper fiber length. The visible-wavelength two-photon microscopy produces NADH and tryptophan images of mice tissues simultaneously. Our 500-700 nm continuum pulses support extending nonlinear microscopy to visible wavelength range that is inaccessible to 100-fs Ti:sapphire oscillators and other applications requiring visible laser pulses.

Prospective Heart Tracking for Whole-heart Magnetic Resonance Angiography

Science.gov (United States)

Moghari, Mehdi H.; Geva, Tal; Powell, Andrew J.

2015-01-01

Purpose To develop a prospective respiratory-gating technique (Heart-NAV) for use with contrast-enhanced 3D inversion recovery (IR) whole-heart magnetic resonance angiography (MRA) acquisitions that directly tracks heart motion without creating image inflow artifact. Methods With Heart-NAV, 1 of the startup pulses for the whole-heart steady-state free precession MRA sequence is used to collect the centerline of k-space, and its 1-dimensional reconstruction is fed into the standard diaphragm-navigator (NAV) signal analysis process to prospectively gate and track respiratory-induced heart displacement. Ten healthy volunteers underwent non-contrast whole-heart MRA acquisitions using the conventional diaphragm-NAV and Heart-NAV with 5 and 10 mm acceptance windows in a 1.5T scanner. Five patients underwent contrast-enhanced IR whole-heart MRA using a diaphragm-NAV and Heart-NAV with a 5 mm acceptance window. Results For non-contrast whole-heart MRA with both the 5 and 10 mm acceptance windows, Heart-NAV yielded coronary artery vessel sharpness and subjective visual scores that were not significantly different than those using a conventional diaphragm-NAV. Scan time for Heart-NAV was 10% shorter (p<0.05). In patients undergoing contrast-enhanced IR whole-heart MRA, inflow artifact was seen with the diaphragm-NAV but not with Heart-NAV. Conclusion Compared to a conventional diaphragm-NAV, Heart-NAV achieves similar image quality in a slightly shorter scan time and eliminates inflow artifact. PMID:26843458

Comparison of different pulse sequences for in vivo determination of T1 relaxation times in the human brain

DEFF Research Database (Denmark)

Kjaer, L; Henriksen, O

1988-01-01

). T1 measurements were performed on the human brain using a whole body MR scanner operating at 1.5 tesla. Three different pulse sequences were compared including two 6-points inversion recovery (IR) sequences with TR = 2.0 s and 4.0, respectively, and a 12-points partial saturation inversion recovery...

Influence of crosstalk on the fast fluid attenuated inversion recovery pulse sequence

International Nuclear Information System (INIS)

Urata, Tohru; Nonoshita, Koji; Miyazaki, Takayuki; Arima, Akira

2000-01-01

The influence of crosstalk on the fast fluid attenuated inversion recovery (fast FLAIR) pulse sequence was studied. On multislice fast FLAIR images, the water null point was shortened in comparison with that on single slice images owing to the crosstalk received from adjacent slices. That influence became greater with decreases in the slice gap and increases in the number of slices. The timing of crosstalk in each slice varied according to excitation order. The process of recovery of longitudinal magnetization changed according to differences in timing; thus, it was possible that the water null point changed in each slice. In brain images with thinner slice gaps, the signal intensity of CSF is increased by the effect of crosstalk. In order to eliminate changes in the water null point caused by crosstalk on fast FLAIR, the multislice sequence requires a sequence with interleaving based on the premise that slice gaps are set for more than 100% of slice thickness. (author)

Influence of crosstalk on the fast fluid attenuated inversion recovery pulse sequence

Energy Technology Data Exchange (ETDEWEB)

Urata, Tohru; Nonoshita, Koji; Miyazaki, Takayuki; Arima, Akira [Funabashi Municipal Medical Center, Chiba (Japan)

2000-04-01

The influence of crosstalk on the fast fluid attenuated inversion recovery (fast FLAIR) pulse sequence was studied. On multislice fast FLAIR images, the water null point was shortened in comparison with that on single slice images owing to the crosstalk received from adjacent slices. That influence became greater with decreases in the slice gap and increases in the number of slices. The timing of crosstalk in each slice varied according to excitation order. The process of recovery of longitudinal magnetization changed according to differences in timing; thus, it was possible that the water null point changed in each slice. In brain images with thinner slice gaps, the signal intensity of CSF is increased by the effect of crosstalk. In order to eliminate changes in the water null point caused by crosstalk on fast FLAIR, the multislice sequence requires a sequence with interleaving based on the premise that slice gaps are set for more than 100% of slice thickness. (author)

Intensity stabilisation of optical pulse sequences for coherent control of laser-driven qubits

Science.gov (United States)

Thom, Joseph; Yuen, Ben; Wilpers, Guido; Riis, Erling; Sinclair, Alastair G.

2018-05-01

We demonstrate a system for intensity stabilisation of optical pulse sequences used in laser-driven quantum control of trapped ions. Intensity instability is minimised by active stabilisation of the power (over a dynamic range of > 104) and position of the focused beam at the ion. The fractional Allan deviations in power were found to be logic gates to be below 10^{-6} per gate.

WE-DE-206-04: MRI Pulse Sequences - Spin Echo, Gradient Echo, EPI, Non-Cartesia

Energy Technology Data Exchange (ETDEWEB)

Pooley, R. [Mayo Clinic (United States)

2016-06-15

Magnetic resonance imaging (MRI) has become an essential part of clinical imaging due to its ability to render high soft tissue contrast. Instead of ionizing radiation, MRI use strong magnetic field, radio frequency waves and field gradients to create diagnostic useful images. It can be used to image the anatomy and also functional and physiological activities within the human body. Knowledge of the basic physical principles underlying MRI acquisition is vitally important to successful image production and proper image interpretation. This lecture will give an overview of the spin physics, imaging principle of MRI, the hardware of the MRI scanner, and various pulse sequences and their applications. It aims to provide a conceptual foundation to understand the image formation process of a clinical MRI scanner. Learning Objectives: Understand the origin of the MR signal and contrast from the spin physics level. Understand the main hardware components of a MRI scanner and their purposes Understand steps for MR image formation including spatial encoding and image reconstruction Understand the main kinds of MR pulse sequences and their characteristics.

Pulse sequences for suppressing leakage in single-qubit gate operations

Science.gov (United States)

Ghosh, Joydip; Coppersmith, S. N.; Friesen, Mark

2017-06-01

Many realizations of solid-state qubits involve couplings to leakage states lying outside the computational subspace, posing a threat to high-fidelity quantum gate operations. Mitigating leakage errors is especially challenging when the coupling strength is unknown, e.g., when it is caused by noise. Here we show that simple pulse sequences can be used to strongly suppress leakage errors for a qubit embedded in a three-level system. As an example, we apply our scheme to the recently proposed charge quadrupole (CQ) qubit for quantum dots. These results provide a solution to a key challenge for fault-tolerant quantum computing with solid-state elements.

The Use of Acoustic Radiation Force Decorrelation-Weighted Pulse Inversion for Enhanced Ultrasound Contrast Imaging.

Science.gov (United States)

Herbst, Elizabeth B; Unnikrishnan, Sunil; Wang, Shiying; Klibanov, Alexander L; Hossack, John A; Mauldin, Frank William

2017-02-01

The use of ultrasound imaging for cancer diagnosis and screening can be enhanced with the use of molecularly targeted microbubbles. Nonlinear imaging strategies such as pulse inversion (PI) and "contrast pulse sequences" (CPS) can be used to differentiate microbubble signal, but often fail to suppress highly echogenic tissue interfaces. This failure results in false-positive detection and potential misdiagnosis. In this study, a novel acoustic radiation force (ARF)-based approach was developed for superior microbubble signal detection. The feasibility of this technique, termed ARF decorrelation-weighted PI (ADW-PI), was demonstrated in vivo using a subcutaneous mouse tumor model. Tumors were implanted in the hindlimb of C57BL/6 mice by subcutaneous injection of MC38 cells. Lipid-shelled microbubbles were conjugated to anti-VEGFR2 antibody and administered via bolus injection. An image sequence using ARF pulses to generate microbubble motion was combined with PI imaging on a Verasonics Vantage programmable scanner. ADW-PI images were generated by combining PI images with interframe signal decorrelation data. For comparison, CPS images of the same mouse tumor were acquired using a Siemens Sequoia clinical scanner. Microbubble-bound regions in the tumor interior exhibited significantly higher signal decorrelation than static tissue (n = 9, P < 0.001). The application of ARF significantly increased microbubble signal decorrelation (n = 9, P < 0.01). Using these decorrelation measurements, ADW-PI imaging demonstrated significantly improved microbubble contrast-to-tissue ratio when compared with corresponding CPS or PI images (n = 9, P < 0.001). Contrast-to-tissue ratio improved with ADW-PI by approximately 3 dB compared with PI images and 2 dB compared with CPS images. Acoustic radiation force can be used to generate adherent microbubble signal decorrelation without microbubble bursting. When combined with PI, measurements of the resulting microbubble signal

Suppression of Protonated Organic Solvents in NMR Spectroscopy Using a Perfect Echo Low-Pass Filtration Pulse Sequence.

Science.gov (United States)

Howe, Peter W A

2018-04-03

Proton NMR spectra are usually acquired using deuterated solvents, but in many cases it is necessary to obtain spectra on samples in protonated solvents. In these cases, the intense resonances of the protonated solvents need to be suppressed to maximize sensitivity and spectral quality. A wide range of highly effective solvent suppression methods have been developed, but additional measures are needed to suppress the 13 C satellites of the solvent. Because the satellites represent 1.1% of the original solvent signal, they remain problematic if unsuppressed. The recently proposed DISPEL pulse sequences suppress 13 C satellites extremely effectively, and this Technical Note demonstrates that combining DISPEL and presaturation results in exceptionally effective solvent suppression. An important element in the effectiveness is volume selection, which is inherent within the DISPEL sequence. Spectra acquired in protonated dimethlysulfoxide and tetrahydrofuran show that optimum results are obtained by modifying the phase cycle, cycling the pulse-field gradients, and using broadband 13 C inversion pulses to reduce the effects of radiofrequency offset and inhomogeneity.

Diagnostic accuracy of unenhanced, contrast-enhanced perfusion and angiographic MRI sequences for pulmonary embolism diagnosis: results of independent sequence readings

Energy Technology Data Exchange (ETDEWEB)

Revel, Marie Pierre [Hopital Europeen Georges Pompidou, APHP, Departments of Radiology, Paris (France); Universite Paris Descartes Sorbonne Paris Cite, Paris (France); Hotel-Dieu, Service de Radiologie, Paris (France); Sanchez, Olivier; Meyer, Guy [Hopital Europeen Georges Pompidou, APHP, Respiratory and intensive care and, Paris (France); Universite Paris Descartes Sorbonne Paris Cite, Paris (France); INSERM Unite 765, Paris (France); Lefort, Catherine; Couchon, Sophie; Hernigou, Anne; Frija, Guy [Hopital Europeen Georges Pompidou, APHP, Departments of Radiology, Paris (France); Niarra, Ralph [Hopital Europeen Georges Pompidou, APHP, Clinical Epidemiology, Paris (France); Universite Paris Descartes Sorbonne Paris Cite, Paris (France); Chatellier, Gilles [Hopital Europeen Georges Pompidou, APHP, Clinical Epidemiology, Paris (France); Universite Paris Descartes Sorbonne Paris Cite, Paris (France); INSERM CIC-EC E4, Paris (France)

2013-09-15

To independently evaluate unenhanced, contrast-enhanced perfusion and angiographic MR sequences for pulmonary embolism (PE) diagnosis. Prospective investigation, including 274 patients who underwent perfusion, unenhanced 2D steady-state-free-precession (SSFP) and contrast-enhanced 3D angiographic MR sequences on a 1.5-T unit, in addition to CTA (CT angiography). Two independent readers evaluated each sequence independently in random order. Sensitivity, specificity, predictive values and inter-reader agreement were calculated for each sequence, excluding sequences judged inconclusive. Sensitivity was also calculated according to PE location. Contrast-enhanced angiographic sequences showed the highest sensitivity (82.9 and 89.7 %, reader 1 and reader 2, respectively), specificity (98.5 and 100 %) and agreement (kappa value 0.77). Unenhanced angiographic sequences, although less sensitive overall (68.7 and 76.4 %), were sensitive for the detection of proximal PE (92.7 and 100 %) and showed high specificity (96.1 and 99.1 %) and good agreement (kappa value 0.62). Perfusion sequences showed lower sensitivity (75.0 and 79.3 %), specificity (84.8 and 89.7 %) and agreement (kappa value 0.51), and a negative predictive value of 84.8 % at best. Compared with contrast-enhanced angiographic sequences, unenhanced sequences demonstrate lower sensitivity, except for proximal PE, but high specificity and agreement. The negative predictive value of perfusion sequences was insufficient to safely rule out PE. (orig.)

Temporal dependence of the enhancement of material removal in femtosecond-nanosecond dual-pulse laser-induced breakdown spectroscopy

International Nuclear Information System (INIS)

Scaffidi, Jon; Pearman, William; Carter, J. Chance; Colston, Bill W. Jr.; Angel, S. Michael

2004-01-01

Despite the large neutral atomic and ionic emission enhancements that have been noted in collinear and orthogonal dual-pulse laser-induced breakdown spectroscopy, the source or sources of these significant signal and signal-to-noise ratio improvements have yet to be explained. In the research reported herein, the combination of a femtosecond preablative air spark and a nanosecond ablative pulse yields eightfold and tenfold material removal improvement for brass and aluminum, respectively, but neutral atomic emission is enhanced by only a factor of 3-4. Additionally, temporal correlation between enhancement of material removal and of atomic emission is quite poor, suggesting that the atomic-emission enhancements noted in the femtosecond-nanosecond pulse configuration result in large part from some source other than simple improvement in material removal

Pulseq-Graphical Programming Interface: Open source visual environment for prototyping pulse sequences and integrated magnetic resonance imaging algorithm development.

Science.gov (United States)

Ravi, Keerthi Sravan; Potdar, Sneha; Poojar, Pavan; Reddy, Ashok Kumar; Kroboth, Stefan; Nielsen, Jon-Fredrik; Zaitsev, Maxim; Venkatesan, Ramesh; Geethanath, Sairam

2018-03-11

To provide a single open-source platform for comprehensive MR algorithm development inclusive of simulations, pulse sequence design and deployment, reconstruction, and image analysis. We integrated the "Pulseq" platform for vendor-independent pulse programming with Graphical Programming Interface (GPI), a scientific development environment based on Python. Our integrated platform, Pulseq-GPI, permits sequences to be defined visually and exported to the Pulseq file format for execution on an MR scanner. For comparison, Pulseq files using either MATLAB only ("MATLAB-Pulseq") or Python only ("Python-Pulseq") were generated. We demonstrated three fundamental sequences on a 1.5 T scanner. Execution times of the three variants of implementation were compared on two operating systems. In vitro phantom images indicate equivalence with the vendor supplied implementations and MATLAB-Pulseq. The examples demonstrated in this work illustrate the unifying capability of Pulseq-GPI. The execution times of all the three implementations were fast (a few seconds). The software is capable of user-interface based development and/or command line programming. The tool demonstrated here, Pulseq-GPI, integrates the open-source simulation, reconstruction and analysis capabilities of GPI Lab with the pulse sequence design and deployment features of Pulseq. Current and future work includes providing an ISMRMRD interface and incorporating Specific Absorption Ratio and Peripheral Nerve Stimulation computations. Copyright © 2018 Elsevier Inc. All rights reserved.

Intra-pulse Cavity Enhanced Measurements of Carbon Monoxide in a Rapid Compression Machine

KAUST Repository

Nasir, Ehson Fawad

2018-05-07

A laser absorption sensor for carbon monoxide concentration was developed for combustion studies in a rapid compression machine using a pulsed quantum cascade laser near 4.89 μm. Cavity enhancement reduced minimum detection limit down to 2.4 ppm at combustion relevant conditions. Off-axis alignment and rapid intra-pulse down-chirp resulted in effective suppression of cavity noise.

Intestinal lesions in pediatric Crohn disease: comparative detectability among pulse sequences at MR enterography

International Nuclear Information System (INIS)

Sohn, Beomseok; Kim, Myung-Joon; Lee, Mi-Jung; Koh, Hong; Han, Kyung Hwa

2014-01-01

Variable sequences can be used in MR enterography, and no consensus exists for the best protocol in children with Crohn disease. To compare the lesion detectability of various MR enterography sequences and to correlate the findings of these sequences with the Pediatric Crohn's Disease Activity Index (PCDAI) in children with Crohn disease. Children with clinically or pathologically confirmed Crohn disease underwent MR enterography, including a single-shot fast spin-echo (SSFSE) sequence, motility imaging (coronal 2-D balanced fast field echo), diffusion-weighted imaging (DWI), and dynamic contrast enhancement imaging (including arterial, portal and delayed phases). The lesion detectability of each sequence was graded 0-2 for each involved bowel segment. The lesion detectability and PCDAI result on different sequences were compared using the weighted least squares method and Student's t-test, respectively. Fifteen children (11 boys, 4 girls, mean age 13.7 ± 1.4 years) with a total of 41 lesions were included in this study. All lesions detected in more than two sequences were visible on the single-shot fast spin-echo (SSFSE) sequence. The relative lesion detection rate was 78.1% on motility imaging, 90.2% on DWI, and 92.7% on arterial, 95.1% on portal and 95.1% on delayed phase imaging. Compared to the SSFSE sequence, motility imaging (P < 0.001) and DWI (P = 0.039) demonstrated lower detectability. The mean PCDAI result in the detected lesions was statistically higher only on dynamic enhancement imaging (P < 0.001). All MR enterography sequences were found to have relatively high lesion detectability in children with Crohn disease, while motility imaging showed the lowest lesion detectability. Lesions detected on dynamic enhancement imaging showed a higher PCDAI result, which suggests that this sequence is specific for active inflammation. (orig.)

Qualitative and quantitative image analysis of CT and MR imaging in patients with neuroendocrine liver metastases in comparison to 68Ga-DOTATOC PET

International Nuclear Information System (INIS)

Flechsig, Paul; Zechmann, Christian M.; Schreiweis, Julian; Kratochwil, Clemens; Rath, Daniel; Schwartz, Lawrence H.; Schlemmer, Heinz-Peter; Kauczor, Hans-Ulrich; Haberkorn, Uwe; Giesel, Frederik L.

2015-01-01

Highlights: • Qualitative analysis revealed significantly higher results for spatial lesion detectability of liver metastasis in CE-MRI as compared to DW-imaging (p < 0.05). • Primary visibility of liver metastases was scored equally in CE-MRI and DW-imaging. • Contrast-enhancement ratios in liver metastases reached highest values for DW-imaging (p < 0.05). • Staging of liver metastases in patients with GEP-NETs should rather be performed using a combination of PET and MRI than of PET and CT. • The combination of functional and morphologic native MR-sequences seems to be sufficient for follow-up imaging in clinical routine, especially in post-interventional follow-up. - Abstract: Purpose: To compare lesion conspicuity in patients with liver metastases arising from gastroenteropancreatic neuroendocrine tumors (GEP-NETs) using MRI, PET and CT. Materials and methods: 16 patients with GEP-NETs were evaluated using non-contrast MRI, contrast-enhanced (CE) MRI using Gd-EOB-DTPA and CE- 68 Ga-DOTATOC PET. Quantitative analyses were performed by two blinded readers using ROI-analyses quantifying contrast ratios (CR) between normal liver-tissue and GEP-NET-metastases. Qualitative analyses were performed evaluating primary visibility and spatial detectability of all lesions. Results: 103 of the same liver metastases were detected on all modalities. Qualitatively, lesion conspicuity was superior on CE-MRI imaging compared to non-contrast MR-sequences (T2, DWI, fl2D, fl3D), as well as arterial- and portal-venous phase CT. Concerning detectability of lesions, CE-MRI was superior to all other modalities. The quantitative ROI-analysis demonstrated improved CR for DWI compared to all other non-contrast MR-sequences (p < 0.001). CE-MRI presented with higher CR-values compared to CE- 68 Ga-DOTATOC PET/CT (p < 0.001). Conclusions: Anatomic imaging using non contrast MRI with fl2D-and fl3D-sequences in combination with the molecular imaging modality 68 Ga-DOTATOC PET is

The Evolution of Bony Vertebrate Enhancers at Odds with Their Coding Sequence Landscape.

Science.gov (United States)

Yousaf, Aisha; Sohail Raza, Muhammad; Ali Abbasi, Amir

2015-08-06

Enhancers lie at the heart of transcriptional and developmental gene regulation. Therefore, changes in enhancer sequences usually disrupt the target gene expression and result in disease phenotypes. Despite the well-established role of enhancers in development and disease, evolutionary sequence studies are lacking. The current study attempts to unravel the puzzle of bony vertebrates' conserved noncoding elements (CNE) enhancer evolution. Bayesian phylogenetics of enhancer sequences spotlights promising interordinal relationships among placental mammals, proposing a closer relationship between humans and laurasiatherians while placing rodents at the basal position. Clock-based estimates of enhancer evolution provided a dynamic picture of interspecific rate changes across the bony vertebrate lineage. Moreover, coelacanth in the study augmented our appreciation of the vertebrate cis-regulatory evolution during water-land transition. Intriguingly, we observed a pronounced upsurge in enhancer evolution in land-dwelling vertebrates. These novel findings triggered us to further investigate the evolutionary trend of coding as well as CNE nonenhancer repertoires, to highlight the relative evolutionary dynamics of diverse genomic landscapes. Surprisingly, the evolutionary rates of enhancer sequences were clearly at odds with those of the coding and the CNE nonenhancer sequences during vertebrate adaptation to land, with land vertebrates exhibiting significantly reduced rates of coding sequence evolution in comparison to their fast evolving regulatory landscape. The observed variation in tetrapod cis-regulatory elements caused the fine-tuning of associated gene regulatory networks. Therefore, the increased evolutionary rate of tetrapods' enhancer sequences might be responsible for the variation in developmental regulatory circuits during the process of vertebrate adaptation to land. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for

Enhancement and stabilization of plasma using collinear long-short double-pulse laser-induced breakdown spectroscopy

Science.gov (United States)

Cui, Minchao; Deguchi, Yoshihiro; Wang, Zhenzhen; Fujita, Yuki; Liu, Renwei; Shiou, Fang-Jung; Zhao, Shengdun

2018-04-01

A collinear long-short dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) method was employed to enhance and stabilize the laser-induced plasma from steel sample. The long-pulse-width laser beam with the pulse width of 60 μs was generated by a Nd: YAG laser which was operated at FR (free running) mode. The comparative experiments were carried out between single pulse LIBS (SP-LIBS) and long-short DP-LIBS. The recorded results showed that the emission intensities and the temperature of plasma were enhanced by long-short DP-LIBS. The plasma images showed that the plasma was bigger and had a longer lifetime in long-short DP-LIBS situation. Through the calculation of time-resolved plasma temperature and intensity ratio, it can be concluded that the plasma was stabilized by the long-pulse-width laser beam. The long-short DP-LIBS method also generated the stable plasma condition from the samples with different initial temperatures, which overcame the difficulties of LIBS in the online measurement for steel production line.

System for increasing laser pulse rate

International Nuclear Information System (INIS)

1980-01-01

A technique of static elements is disclosed for combining a plurality of laser beams having time sequenced, pulsed radiation to achieve an augmented pulse rate. The technique may also be applied in a system for combining both time sequenced pulses and frequency distinct pulses for use in a system for isotope enrichment. (author)

Prediction of Clinical Outcome After Acute Ischemic Stroke: The Value of Repeated Noncontrast Computed Tomography, Computed Tomographic Angiography, and Computed Tomographic Perfusion.

Science.gov (United States)

Dankbaar, Jan W; Horsch, Alexander D; van den Hoven, Andor F; Kappelle, L Jaap; van der Schaaf, Irene C; van Seeters, Tom; Velthuis, Birgitta K

2017-09-01

Early prediction of outcome in acute ischemic stroke is important for clinical management. This study aimed to compare the relationship between early follow-up multimodality computed tomographic (CT) imaging and clinical outcome at 90 days in a large multicenter stroke study. From the DUST study (Dutch Acute Stroke Study), patients were selected with (1) anterior circulation occlusion on CT angiography (CTA) and ischemic deficit on CT perfusion (CTP) on admission, and (2) day 3 follow-up noncontrast CT, CTP, and CTA. Follow-up infarct volume on noncontrast CT, poor recanalization on CTA, and poor reperfusion on CTP (mean transit time index ≤75%) were related to unfavorable outcome after 90 days defined as modified Rankin Scale 3 to 6. Four multivariable models were constructed: (1) only baseline variables (model 1), (2) model 1 with addition of infarct volume, (3) model 1 with addition of recanalization, and (4) model 1 with addition of reperfusion. Area under the curves of the receiver operating characteristic curves of the models were compared using the DeLong test. A total of 242 patients were included. Poor recanalization was found in 21%, poor reperfusion in 37%, and unfavorable outcome in 44%. The area under the curve of the receiver operating characteristic curve without follow-up imaging was 0.81, with follow-up noncontrast CT 0.85 ( P =0.02), CTA 0.86 ( P =0.01), and CTP 0.86 ( P =0.01). All 3 follow-up imaging modalities improved outcome prediction compared with no imaging. There was no difference between the imaging models. Follow-up imaging after 3 days improves outcome prediction compared with prediction based on baseline variables alone. CTA recanalization and CTP reperfusion do not outperform noncontrast CT at this time point. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00880113. © 2017 American Heart Association, Inc.

Plasma density enhancement in atmospheric-pressure dielectric-barrier discharges by high-voltage nanosecond pulse in the pulse-on period: a PIC simulation

International Nuclear Information System (INIS)

Sang Chaofeng; Sun Jizhong; Wang Dezhen

2010-01-01

A particle-in-cell (PIC) plus Monte Carlo collision simulation is employed to investigate how a sustainable atmospheric pressure single dielectric-barrier discharge responds to a high-voltage nanosecond pulse (HVNP) further applied to the metal electrode. The results show that the HVNP can significantly increase the plasma density in the pulse-on period. The ion-induced secondary electrons can give rise to avalanche ionization in the positive sheath, which widens the discharge region and enhances the plasma density drastically. However, the plasma density stops increasing as the applied pulse lasts over certain time; therefore, lengthening the pulse duration alone cannot improve the discharge efficiency further. Physical reasons for these phenomena are then discussed.

Plasma density enhancement in atmospheric-pressure dielectric-barrier discharges by high-voltage nanosecond pulse in the pulse-on period: a PIC simulation

Science.gov (United States)

Sang, Chaofeng; Sun, Jizhong; Wang, Dezhen

2010-02-01

A particle-in-cell (PIC) plus Monte Carlo collision simulation is employed to investigate how a sustainable atmospheric pressure single dielectric-barrier discharge responds to a high-voltage nanosecond pulse (HVNP) further applied to the metal electrode. The results show that the HVNP can significantly increase the plasma density in the pulse-on period. The ion-induced secondary electrons can give rise to avalanche ionization in the positive sheath, which widens the discharge region and enhances the plasma density drastically. However, the plasma density stops increasing as the applied pulse lasts over certain time; therefore, lengthening the pulse duration alone cannot improve the discharge efficiency further. Physical reasons for these phenomena are then discussed.

A novel method for fat suppression in RARE sequences

International Nuclear Information System (INIS)

Higuchi, Nobuya

1999-01-01

Rapid acquisition relaxation-enhanced (RARE) sequences utilize one or several Carr-Purcell-Meiboom-Gill (CPMG) echo trains to sample a number of k-space lines each repetition time TR. The technique can rapidly generate multislice T2-weighted images which, as a rule, are strikingly similar in contrast to conventional T2-weighted spin-echo (SE) images. An exception to this rule is the appearance of very bright signal from fat in T2-weighted RARE images as compared to conventional T2-weighted SE images. To reduce this fat signal, we introduce a time delay, τc, between the 90 degrees x and first 180 degrees y pulse of each echo train such that a phase angle of pi/2 develops between fat and the reference (water) line at echo maxima. The technique leads to single-acquisition fat suppression without the use of frequency-selective saturation pulses and concomitant loss of slices per TR. A Bloch equation analysis is used to identify two major mechanisms contributing to suppression of off-resonance spins such that w τc =pi/2. Namely, the CPMG sequence becomes a CP sequence with no self-correction properties for imperfect 180 degrees pulses leading to enhanced signal decay, and the raw k-space data matrix become segmented into blocks alternately multiplied by +/- i, leading to signal dispersion following Fourier transformation. (K.H.)

Basic evaluation of the new pulse sequence for simultaneous acquisition of T1- and T2-weighted images

International Nuclear Information System (INIS)

Kurose, Atsunari; Takahashi, Tohru; Ohishi, Tae; Ishikawa, Akihiro

2006-01-01

A novel pulse sequence that enables simultaneous acquisition of T1-weighted (T1W) and T2-weighted (T2W) images is presented. In this new technique, the inversion recovery (IR) pulse of conventional fast inversion recovery (Fast IR) is replaced with a pulse train that consists of a fast spin echo (FSE) and 180(y)+90(x) for driven inversion (DI). By using a shorter T1 and independent k-space ordering, the first part of the sequence provides T2W images and the second part provides T1W images, thereby enabling simultaneous acquisition in a single scan time comparable to that of Fast IR. Signal simulation also was conducted, and this was compared with conventional scanning techniques using normal volunteers. In the human studies, both T1W and T2W images showed the same image quality as conventional images, suggesting the potential for this technique to replace the combination of Fast IR and T2W FSE for scan-time reduction. (author)

Time and Frequency Localized Pulse Shape for Resolution Enhancement in STFT-BOTDR

Directory of Open Access Journals (Sweden)

Linqing Luo

2016-01-01

Full Text Available Short-Time Fourier Transform-Brillouin Optical Time-Domain Reflectometry (STFT-BOTDR implements STFT over the full frequency spectrum to measure the distributed temperature and strain along the optic fiber, providing new research advances in dynamic distributed sensing. The spatial and frequency resolution of the dynamic sensing are limited by the Signal to Noise Ratio (SNR and the Time-Frequency (T-F localization of the input pulse shape. T-F localization is fundamentally important for the communication system, which suppresses interchannel interference (ICI and intersymbol interference (ISI to improve the transmission quality in multicarrier modulation (MCM. This paper demonstrates that the T-F localized input pulse shape can enhance the SNR and the spatial and frequency resolution in STFT-BOTDR. Simulation and experiments of T-F localized different pulses shapes are conducted to compare the limitation of the system resolution. The result indicates that rectangular pulse should be selected to optimize the spatial resolution and Lorentzian pulse could be chosen to optimize the frequency resolution, while Gaussian shape pulse can be used in general applications for its balanced performance in both spatial and frequency resolution. Meanwhile, T-F localization is proved to be useful in the pulse shape selection for system resolution optimization.

Applying short-duration pulses as a mean to enhance volatile organic compounds removal by air sparging.

Science.gov (United States)

Ben Neriah, Asaf; Paster, Amir

2017-10-01

Application of short-duration pulses of high air pressure, to an air sparging system for groundwater remediation, was tested in a two-dimensional laboratory setup. It was hypothesized that this injection mode, termed boxcar, can enhance the remediation efficiency due to the larger ZOI and enhanced mixing which results from the pressure pulses. To test this hypothesis, flow and transport experiments were performed. Results confirm that cyclically applying short-duration pressure pulses may enhance contaminant cleanup. Comparing the boxcar to conventional continuous air-injection shows up to a three-fold increase in the single well radius of influence, dependent on the intensity of the short-duration pressure-pulses. The cleanup efficiency of Toluene from the water was 95% higher than that achieved under continuous injection with the same average conditions. This improvement was attributed to the larger zone of influence and higher average air permeability achieved in the boxcar mode, relative to continuous sparging. Mixing enhancement resultant from recurring pressure pulses was suggested as one of the mechanisms which enhance the contaminant cleanup. The application of a boxcar mode in an existing, multiwell, air sparging setup can be relatively straightforward: it requires the installation of an on-off valve in each of the injection-wells and a central control system. Then, turning off some of the wells, for a short-duration, result in a stepwise increase in injection pressure in the rest of the wells. It is hoped that this work will stimulate the additional required research and ultimately a field scale application of this new injection mode. Copyright © 2017 Elsevier B.V. All rights reserved.

Contrast Enhancement in TOF cerebral angiography at 7 T using Saturation and MT pulses under SAR constraints: impact of VERSE and sparse pulses

Science.gov (United States)

Schmitter, Sebastian; Bock, Michael; Johst, Sören; Auerbach, Edward J.; Uğurbil, Kâmil; Van de Moortele, Pierre-François

2011-01-01

Cerebral 3D time of flight (TOF) angiography significantly benefits from ultra high fields, mainly due to higher SNR and to longer T1 relaxation time of static brain tissues, however, SAR significantly increases with B0. Thus, additional RF pulses commonly used at lower field strengths to improve TOF contrast such as saturation of venous signal and improved background suppression by magnetization transfer typically cannot be used at higher fields. In this work we aimed at reducing SAR for each RF pulse category in a TOF sequence. We use the VERSE principle for the slab selective TOF excitation as well as the venous saturation RF pulses. Additionally, MT pulses are implemented by sparsely applying the pulses only during acquisition of the central k-space lines to limit their SAR contribution. Image quality, angiographic contrast and SAR reduction were investigated as a function of VERSE parameters and of the total number of MT pulses applied. Based on these results, a TOF protocol was generated that increases the angiographic contrast by more than 50% and reduces subcutaneous fat signal while keeping the resulting SAR within regulatory limits. PMID:22139829

An analysis of the uncertainty and bias in DCE-MRI measurements using the spoiled gradient-recalled echo pulse sequence

International Nuclear Information System (INIS)

Subashi, Ergys; Choudhury, Kingshuk R.; Johnson, G. Allan

2014-01-01

Purpose: The pharmacokinetic parameters derived from dynamic contrast-enhanced (DCE) MRI have been used in more than 100 phase I trials and investigator led studies. A comparison of the absolute values of these quantities requires an estimation of their respective probability distribution function (PDF). The statistical variation of the DCE-MRI measurement is analyzed by considering the fundamental sources of error in the MR signal intensity acquired with the spoiled gradient-echo (SPGR) pulse sequence. Methods: The variance in the SPGR signal intensity arises from quadrature detection and excitation flip angle inconsistency. The noise power was measured in 11 phantoms of contrast agent concentration in the range [0–1] mM (in steps of 0.1 mM) and in onein vivo acquisition of a tumor-bearing mouse. The distribution of the flip angle was determined in a uniform 10 mM CuSO 4 phantom using the spin echo double angle method. The PDF of a wide range of T1 values measured with the varying flip angle (VFA) technique was estimated through numerical simulations of the SPGR equation. The resultant uncertainty in contrast agent concentration was incorporated in the most common model of tracer exchange kinetics and the PDF of the derived pharmacokinetic parameters was studied numerically. Results: The VFA method is an unbiased technique for measuringT1 only in the absence of bias in excitation flip angle. The time-dependent concentration of the contrast agent measured in vivo is within the theoretically predicted uncertainty. The uncertainty in measuring K trans with SPGR pulse sequences is of the same order, but always higher than, the uncertainty in measuring the pre-injection longitudinal relaxation time (T1 0 ). The lowest achievable bias/uncertainty in estimating this parameter is approximately 20%–70% higher than the bias/uncertainty in the measurement of the pre-injection T1 map. The fractional volume parameters derived from the extended Tofts model were found to be

Genotypic characterization of Salmonella by multilocus sequence typing, pulsed-field gel electrophoresis and amplified fragment length polymorphism

DEFF Research Database (Denmark)

Torpdahl, Mia; Skov, Marianne N.; Sandvang, Dorthe

2005-01-01

subspecies enterica isolates. A total of 25 serotypes were investigated that had been isolated from humans or veterinary sources in Denmark between 1995 and 2001. All isolates were genotyped by multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE) and amplified fragment length...

Dual-source virtual non-contrast CT of the head: a preliminary study

International Nuclear Information System (INIS)

Huang Wei; Xu Yiming; Shao Jin

2011-01-01

Objective: To investigate image quality and clinical value of dual-source dual energy virtual non-contrast (VNC) CT of the head. Methods: Sixty-two patients suspected of cerebrovascular diseases underwent conventional non-contrast (CNC) CT and dual energy CTA examination of the head with dual-source CT. Virtual non-contrast images were reconstructed using dual energy software. The CT values of gray matter, white matter, cerebrospinal fluid, hyperdense hemorrhagic lesion and hypodense ischemic lesion were compared between CNC and VNC images. A four-score scale was used to assess image quality subjectively. Image noise, radiation dosage and detection rate were compared between CNC and VNC images. Paired t test, Wilcoxon signed ranks test and Chi-square test (McNemar test and Kappa test) were used. Results: The CT value on CNC and VNC images, were (43.3±1.5) and (33.2±1.3) HU for gray matter (t=46.98, P 0.05, Kappa = 1.000) at per-patient level. Twenty-two patients with hypodense ischemic lesions were found on VNC images with one false positive case and two false negative cases. The sensitivity, specificity, positive predictive value and negative predictive value were 91.3% (21/23), 97.4% (38/39), 95.5% (21/22) and 95.0% (38/40) respectively. No statistical difference was found in detecting hypodense lesions between VNC and CNC images (χ 2 = 0.00, P>0.05, Kappa = 0.895). In per-lesion analysis, 53 hemorrhage lesions were found on VNC images with false negative results of four lesions and no false positive result. The sensitivity, specificity, positive predictive value and negative predictive value were 93.0% (53/57). 100.0% (38/38), 100.0% (53/.53) and 90.5% (38/42) respectively. There was no significant difference in detection rate of hyperdense lesion between VNC and CNC images (χ 2 = 2.25, P>0.05, Kappa = 0.914). Thirty-eight hypodense lesions were found on VNC images with 2 false positive lesions and 13 false negative lesions. The sensitivity, specificity

Rotational magnetic pulses enhance the magnetofection efficiency in vitro in adherent and suspension cells

International Nuclear Information System (INIS)

Dahmani, Ch.; Mykhaylyk, O.; Helling, Fl.; Götz, St.; Weyh, Th.; Herzog, H.-G.; Plank, Ch.

2013-01-01

The association of magnetic nanoparticles with gene delivery vectors in combination with the use of gradient magnetic fields (magnetofection) enables improved and synchronised gene delivery to cells. In this paper, we report a system comprising rotating permanent magnets to generate defined magnetic field pulses with frequencies from 2.66 to 133 Hz and a field amplitude of 190 or 310 mT at the location of the cells. Low-frequency pulses of 2.66–10 Hz with a magnetic flux density of 190 mT were applied to the examined cells for 30–120 s after magnetofection. These pulses resulted in a 1.5–1.9-fold enhancement in the transfection efficiency compared with magnetofection with only a static magnetic field in both adherent and suspension cells. The magnetic field amplitudes of 190 and 310 mT had similar effects on the transfection efficacy. No increase in the percentage of transgene-expressing suspension cells and no cytotoxic effects (based on the results of the MTT assay) were observed after applying alternating magnetic fields. - Highlights: ► We developed a magnetic system capable of generating defined magnetic pulses based on permanent magnets. ► The main advantage of the system is the lack of heat-induced fluctuations in the working parameters. ► Our system succeeded in enhancing the transfection of adherent human lung epithelial cells and human suspension cells. ► The enhancement in the transfection efficiency compared with static magnetic field is due to the magnetic field pulses. ► The approach could be used as a complementary method for drug targeting

The Optimization of Magnetic Resonance Imaging Pulse Sequences in Order to Better Detection of Multiple Sclerosis Plaques.

Science.gov (United States)

Farshidfar, Z; Faeghi, F; Haghighatkhah, H R; Abdolmohammadi, J

2017-09-01

Magnetic resonance imaging (MRI) is the most sensitive technique to detect multiple sclerosis (MS) plaques in central nervous system. In some cases, the patients who were suspected to MS, Whereas MRI images are normal, but whether patients don't have MS plaques or MRI images are not enough optimized enough in order to show MS plaques? The aim of the current study is evaluating the efficiency of different MRI sequences in order to better detection of MS plaques. In this cross-sectional study which was performed at Shohada-E Tajrish in Tehran - Iran hospital between October, 2011 to April, 2012, included 20 patients who suspected to MS disease were selected by the method of random sampling and underwent routine brain Pulse sequences (Axial T2w, Axial T1w, Coronal T2w, Sagittal T1w, Axial FLAIR) by Siemens, Avanto, 1.5 Tesla system. If any lesion which is suspected to the MS disease was observed, additional sequences such as: Sagittal FLAIR Fat Sat, Sagittal PDw-fat Sat, Sagittal PDw-water sat was also performed. This study was performed in about 52 lesions and the results in more than 19 lesions showed that, for the Subcortical and Infratentorial areas, PDWw sequence with fat suppression is the best choice, And in nearly 33 plaques located in Periventricular area, FLAIR Fat Sat was the most effective sequence than both PDw fat and water suppression pulse sequences. Although large plaques may visible in all images, but important problem in patients with suspected MS is screening the tiny MS plaques. This study showed that for revealing the MS plaques located in the Subcortical and Infratentorial areas, PDw-fat sat is the most effective sequence, and for MS plaques in the periventricular area, FLAIR fat Sat is the best choice.

Radio-frequency oxygen-plasma-enhanced pulsed laser deposition of IGZO films

Science.gov (United States)

Chou, Chia-Man; Lai, Chih-Chang; Chang, Chih-Wei; Wen, Kai-Shin; Hsiao, Vincent K. S.

2017-07-01

We demonstrate the crystalline structures, optical transmittance, surface and cross-sectional morphologies, chemical compositions, and electrical properties of indium gallium zinc oxide (IGZO)-based thin films deposited on glass and silicon substrates through pulsed laser deposition (PLD) incorporated with radio-frequency (r.f.)-generated oxygen plasma. The plasma-enhanced pulsed laser deposition (PEPLD)-based IGZO thin films exhibited a c-axis-aligned crystalline (CAAC) structure, which was attributed to the increase in Zn-O under high oxygen vapor pressure (150 mTorr). High oxygen vapor pressure (150 mTorr) and low r.f. power (10 W) are the optimal deposition conditions for fabricating IGZO thin films with improved electrical properties.

SPIO-enhanced MR imaging for HCC detection in cirrhotic patient : comparison of various techniques for optimal sequence selection

International Nuclear Information System (INIS)

Kim, In Hwan; Lee, Jeong Min; Kwak, Hyo Sung; Kim, Chong Soo; Yu, Hee Chul; Kim, Tae Kon; Lee Soo Tiek

2000-01-01

To compare the efficacy of breathhold and non-breathhold sequences in the detection of hepatocellular carcinoma (HCC) in cirrhotic patients using superparamagnetic iron oxide (SPIO)-enhanced MR imaging, and to determine the optimal sequence combination. By means of unenhanced and iron-oxide-enhanced MRI, 29 patients with 49 nodular HCCs were evaluated for the presence of HCC nodules. Twenty-one were male and eight were female, and their ages ranged from 38 to 71 (mean, 56) years. Eight different MR sequences were used, including four non-breath-hold sequences and four breath-hold, and images were obtained before and after the administration of SPIO particles. Non-breath-hold sequences included T2-, proton density-weighted SE, and TSE imaging, while breath-hold sequences comprised T1-weighted fast low-angle shot (T1w FLASH), half-Fourier acquisition single shot turbo spine echo (HASTE), T2-weighted fast imaging with steady-state free precession (T2 * wFISP) and T2-weighted breath-hold TSE (T2wBHTSE). Image analysis involved both quantitative and qualitative analysis. The quantitative parameters calculated were signal-to noise (S/N) ratios for livers and tumors, contrast to noise (C/N) ratios for tumors seen on precontrast and postcontrast images, and percentage of signal intensity loss (PSIL) after SPIO injection. Images were analysed qualitatively in terms of image artifacts and lesion conspicuity, and prior to calculating sensitivity, the number of lesions detected using various pulse sequences were counted. SPIO had a marked effect on liver S/N ratio but a minimal effect on tumor S/N ratio. PSIL was best in T2 * wFISP images, while T2wSE images showed the second-best results (p less than 0.05). Tumor-to-liver C/N values were also highest with T2 * wFISP, while T2wTSE and HASTE images were next. Qualitative study showed that non-breath hold images and FISP were better than breath hold images in terms of lesion conspicuity. The latter, however, were much better

Aortoiliac stenooculusive disease and aneurysms. Screening with non-contrast enhanced two-dimensional cardiac gated cine phase contrast MR angiography with multiple velocity encoded values and cardiac gated two-dimensional time-of-flight MR angiography

International Nuclear Information System (INIS)

Naganawa, Shinji; Koshikawa, Tokiko; Kato, Katsuhiko

2001-01-01

To evaluate the performance of two-dimensional cine phase contrast MRA with multi-velocity encoded values (multi-VENC cine PC) and ECG-gated two-dimensional time-of-flight MRA (ECG-2D-TOF) for the detection of stenoocclusive lesions and aneurysms in the aortoiliac area, when each method was used individually and when the two methods were used together. Forty-one patients were included in this study. Multi-VENC cine PC and ECG-2D-TOF were obtained first, then contrast enhanced three-dimensional magnetic resonance angiography (CE-3D-MRA) was performed as the standard of reference. Two observers reviewed the images separately without knowledge of patients' symptoms or histories. Sensitivities and specificities were obtained separately for stenooclusive lesions and aneurysms by two reviewers. When the two methods were applied together, high sensitivities (93.0 by observer 1 and 91.9% by observer 2) and adequate specificities (87.6 and 82.3%) were obtained for stenoocclusive lesions. For aneurysms, moderate to high sensitivities (91.1 and 71.1%) and high specificities (98.8 and 99.4%) were obtained. These results suggest that the performance of two non-contrast enhanced MRA techniques may be valuable as a screening tool when the two methods are applied together. (author)

Noncontrast magnetic resonance angiography of the hand: improved arterial conspicuity by multidirectional flow-sensitive dephasing magnetization preparation in 3D balanced steady-state free precession imaging.

Science.gov (United States)

Fan, Zhaoyang; Hodnett, Philip A; Davarpanah, Amir H; Scanlon, Timothy G; Sheehan, John J; Varga, John; Carr, James C; Li, Debiao

2011-08-01

: To develop a flow-sensitive dephasing (FSD) preparative scheme to facilitate multidirectional flow-signal suppression in 3-dimensional balanced steady-state free precession imaging and to validate the feasibility of the refined sequence for noncontrast magnetic resonance angiography (NC-MRA) of the hand. : A new FSD preparative scheme was developed that combines 2 conventional FSD modules. Studies using a flow phantom (gadolinium-doped water 15 cm/s) and the hands of 11 healthy volunteers (6 males and 5 females) were performed to compare the proposed FSD scheme with its conventional counterpart with respect to the signal suppression of multidirectional flow. In 9 of the 11 healthy subjects and 2 patients with suspected vasculitis and documented Raynaud phenomenon, respectively, 3-dimensional balanced steady-state free precession imaging coupled with the new FSD scheme was compared with spatial-resolution-matched (0.94 × 0.94 × 0.94 mm) contrast-enhanced magnetic resonance angiography (0.15 mmol/kg gadopentetate dimeglumine) in terms of overall image quality, venous contamination, motion degradation, and arterial conspicuity. : The proposed FSD scheme was able to suppress 2-dimensional flow signal in the flow phantom and hands and yielded significantly higher arterial conspicuity scores than the conventional scheme did on NC-MRA at the regions of common digitals and proper digitals. Compared with contrast-enhanced magnetic resonance angiography, the refined NC-MRA technique yielded comparable overall image quality and motion degradation, significantly less venous contamination, and significantly higher arterial conspicuity score at digital arteries. : The FSD-based NC-MRA technique is improved in the depiction of multidirectional flow by applying a 2-module FSD preparation, which enhances its potential to serve as an alternative magnetic resonance angiography technique for the assessment of hand vascular abnormalities.

Enhancement of peak intensity in a filament core with spatiotemporally focused femtosecond laser pulses

Energy Technology Data Exchange (ETDEWEB)

Zeng Bin; Chu Wei; Li Guihua; Zhang Haisu; Ni Jielei [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Graduate School of Chinese Academy of Sciences, Beijing 100080 (China); Gao Hui; Liu Weiwei [Institute of Modern Optics, Nankai University, Tianjin, 300071 (China); Yao Jinping; Cheng Ya; Xu Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Chin, See Leang [Center for Optics, Photonics and Laser (COPL) and Department of Physics, Engineering Physics and Optics, Universite Laval, Quebec City, QC, G1V 0A6 (Canada)

2011-12-15

We demonstrate that the peak intensity in the filament core, which is inherently limited by the intensity clamping effect during femtosecond laser filamentation, can be significantly enhanced using spatiotemporally focused femtosecond laser pulses. In addition, the filament length obtained by spatiotemporally focused femtosecond laser pulses is {approx}25 times shorter than that obtained by a conventional focusing scheme, resulting in improved high spatial resolution.

Neutron production enhancements for the Intense Pulsed Neutron Source.

Energy Technology Data Exchange (ETDEWEB)

Iverson, E. B.

1999-01-04

The Intense Pulsed Neutron Source (IPNS) was the first high energy spallation neutron source in the US dedicated to materials research. It has operated for sixteen years, and in that time has had a very prolific record concerning the development of new target and moderator systems for pulsed spallation sources. IPNS supports a very productive user program on its thirteen instruments, which are oversubscribed by more than two times, meanwhile having an excellent overall reliability of 95%. Although the proton beam power is relatively low at 7 kW, the target and moderator systems are very efficient. The typical beam power which gives an equivalent flux for long-wavelength neutrons is about 60 kW, due to the use of a uranium target and liquid and solid methane moderators, precluded at some sources due to a higher accelerator power. The development of new target and moderator systems is by no means stagnant at IPNS. They are presently considering numerous enhancements to the target and moderators that offer prospects for increasing the useful neutron production by substantial factors. Many of these enhancements could be combined, although their combined benefit has not yet been well established. Meanwhile, IPNS is embarking on a coherent program of study concerning these improvements and their possible combination and implementation. Moreover, any improvements accomplished at IPNS would immediately increase the performance of IPNS instruments.

Neutron production enhancements for the Intense Pulsed Neutron Source

International Nuclear Information System (INIS)

Iverson, E. B.

1999-01-01

The Intense Pulsed Neutron Source (IPNS) was the first high energy spallation neutron source in the US dedicated to materials research. It has operated for sixteen years, and in that time has had a very prolific record concerning the development of new target and moderator systems for pulsed spallation sources. IPNS supports a very productive user program on its thirteen instruments, which are oversubscribed by more than two times, meanwhile having an excellent overall reliability of 95%. Although the proton beam power is relatively low at 7 kW, the target and moderator systems are very efficient. The typical beam power which gives an equivalent flux for long-wavelength neutrons is about 60 kW, due to the use of a uranium target and liquid and solid methane moderators, precluded at some sources due to a higher accelerator power. The development of new target and moderator systems is by no means stagnant at IPNS. They are presently considering numerous enhancements to the target and moderators that offer prospects for increasing the useful neutron production by substantial factors. Many of these enhancements could be combined, although their combined benefit has not yet been well established. Meanwhile, IPNS is embarking on a coherent program of study concerning these improvements and their possible combination and implementation. Moreover, any improvements accomplished at IPNS would immediately increase the performance of IPNS instruments

Dual-Energy CT in Enhancing Subdural Effusions that Masquerade as Subdural Hematomas: Diagnosis with Virtual High-Monochromatic (190-keV) Images.

Science.gov (United States)

Bodanapally, U K; Dreizin, D; Issa, G; Archer-Arroyo, K L; Sudini, K; Fleiter, T R

2017-10-01

Extravasation of iodinated contrast into subdural space following contrast-enhanced radiographic studies results in hyperdense subdural effusions, which can be mistaken as acute subdural hematomas on follow-up noncontrast head CTs. Our aim was to identify the factors associated with contrast-enhancing subdural effusion, characterize diffusion and washout kinetics of iodine in enhancing subdural effusion, and assess the utility of dual-energy CT in differentiating enhancing subdural effusion from subdural hematoma. We retrospectively analyzed follow-up head dual-energy CT studies in 423 patients with polytrauma who had undergone contrast-enhanced whole-body CT. Twenty-four patients with enhancing subdural effusion composed the study group, and 24 randomly selected patients with subdural hematoma were enrolled in the comparison group. Postprocessing with syngo.via was performed to determine the diffusion and washout kinetics of iodine. The sensitivity and specificity of dual-energy CT for the diagnosis of enhancing subdural effusion were determined with 120-kV, virtual monochromatic energy (190-keV) and virtual noncontrast images. Patients with enhancing subdural effusion were significantly older (mean, 69 years; 95% CI, 60-78 years; P subdural effusions was reached within the first 8 hours of contrast administration with a mean of 0.98 mg/mL (95% CI, 0.81-1.13 mg/mL), and complete washout was achieved at 38 hours. For the presence of a hyperdense subdural collection on 120-kV images with a loss of hyperattenuation on 190-keV and virtual noncontrast images, when considered as a true-positive for enhancing subdural effusion, the sensitivity was 100% (95% CI, 85.75%-100%) and the specificity was 91.67% (95% CI, 73%-99%). Dual-energy CT has a high sensitivity and specificity in differentiating enhancing subdural effusion from subdural hematoma. Hence, dual-energy CT has a potential to obviate follow-up studies. © 2017 by American Journal of Neuroradiology.

Differential evolution optimization combined with chaotic sequences for image contrast enhancement

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Santos Coelho, Leandro dos [Industrial and Systems Engineering Graduate Program, LAS/PPGEPS, Pontifical Catholic University of Parana, PUCPR Imaculada Conceicao, 1155, 80215-901 Curitiba, Parana (Brazil)], E-mail: leandro.coelho@pucpr.br; Sauer, Joao Guilherme [Industrial and Systems Engineering Graduate Program, LAS/PPGEPS, Pontifical Catholic University of Parana, PUCPR Imaculada Conceicao, 1155, 80215-901 Curitiba, Parana (Brazil)], E-mail: joao.sauer@gmail.com; Rudek, Marcelo [Industrial and Systems Engineering Graduate Program, LAS/PPGEPS, Pontifical Catholic University of Parana, PUCPR Imaculada Conceicao, 1155, 80215-901 Curitiba, Parana (Brazil)], E-mail: marcelo.rudek@pucpr.br

2009-10-15

Evolutionary Algorithms (EAs) are stochastic and robust meta-heuristics of evolutionary computation field useful to solve optimization problems in image processing applications. Recently, as special mechanism to avoid being trapped in local minimum, the ergodicity property of chaotic sequences has been used in various designs of EAs. Three differential evolution approaches based on chaotic sequences using logistic equation for image enhancement process are proposed in this paper. Differential evolution is a simple yet powerful evolutionary optimization algorithm that has been successfully used in solving continuous problems. The proposed chaotic differential evolution schemes have fast convergence rate but also maintain the diversity of the population so as to escape from local optima. In this paper, the image contrast enhancement is approached as a constrained nonlinear optimization problem. The objective of the proposed chaotic differential evolution schemes is to maximize the fitness criterion in order to enhance the contrast and detail in the image by adapting the parameters using a contrast enhancement technique. The proposed chaotic differential evolution schemes are compared with classical differential evolution to two testing images. Simulation results on three images show that the application of chaotic sequences instead of random sequences is a possible strategy to improve the performance of classical differential evolution optimization algorithm.

Automatic segmentation of meningioma from non-contrasted brain MRI integrating fuzzy clustering and region growing

Directory of Open Access Journals (Sweden)

Liao Chun-Chih

2011-08-01

Full Text Available Abstract Background In recent years, magnetic resonance imaging (MRI has become important in brain tumor diagnosis. Using this modality, physicians can locate specific pathologies by analyzing differences in tissue character presented in different types of MR images. This paper uses an algorithm integrating fuzzy-c-mean (FCM and region growing techniques for automated tumor image segmentation from patients with menigioma. Only non-contrasted T1 and T2 -weighted MR images are included in the analysis. The study's aims are to correctly locate tumors in the images, and to detect those situated in the midline position of the brain. Methods The study used non-contrasted T1- and T2-weighted MR images from 29 patients with menigioma. After FCM clustering, 32 groups of images from each patient group were put through the region-growing procedure for pixels aggregation. Later, using knowledge-based information, the system selected tumor-containing images from these groups and merged them into one tumor image. An alternative semi-supervised method was added at this stage for comparison with the automatic method. Finally, the tumor image was optimized by a morphology operator. Results from automatic segmentation were compared to the "ground truth" (GT on a pixel level. Overall data were then evaluated using a quantified system. Results The quantified parameters, including the "percent match" (PM and "correlation ratio" (CR, suggested a high match between GT and the present study's system, as well as a fair level of correspondence. The results were compatible with those from other related studies. The system successfully detected all of the tumors situated at the midline of brain. Six cases failed in the automatic group. One also failed in the semi-supervised alternative. The remaining five cases presented noticeable edema inside the brain. In the 23 successful cases, the PM and CR values in the two groups were highly related. Conclusions Results indicated

Role of PTHrP(1-34) Pulse Frequency Versus Pulse Duration to Enhance Mesenchymal Stromal Cell Chondrogenesis.

Science.gov (United States)

Fischer, Jennifer; Ortel, Marlen; Hagmann, Sebastien; Hoeflich, Andreas; Richter, Wiltrud

2016-12-01

Generation of phenotypically stable, articular chondrocytes from mesenchymal stromal cells (MSCs) is still an unaccomplished task, with formation of abundant, hyaline extracellular matrix, and avoidance of hypertrophy being prime challenges. We recently demonstrated that parathyroid hormone-related protein (PTHrP) is a promising factor to direct chondrogenesis of MSCs towards an articular phenotype, since intermittent PTHrP application stimulated cartilage matrix production and reduced undesired hypertrophy. We here investigated the role of frequency, pulse duration, total exposure time, and underlying mechanisms in order to unlock the full potential of PTHrP actions. Human MSC subjected to in vitro chondrogenesis for six weeks were exposed to 2.5 nM PTHrP(1-34) pulses from days 7 to 42. Application frequency was increased from three times weekly (3 × 6 h/week) to daily maintaining either the duration of individual pulses (6 h/day) or total exposure time (18 h/week; 2.6 h/day). Daily PTHrP treatment significantly increased extracellular matrix deposition regardless of pulse duration and suppressed alkaline-phosphatase activity by 87%. High total exposure time significantly reduced cell proliferation at day 14. Pulse duration was critically important to significantly reduce IHH expression, but irrelevant for PTHrP-induced suppression of the hypertrophic markers MEF2C and IBSP. COL10A1, RUNX2, and MMP13 expression remained unaltered. Decreased IGFBP-2, -3, and -6 expression suggested modulated IGF-I availability in PTHrP groups, while drop of SOX9 protein levels during the PTHrP-pulse may delay chondroblast formation and hypertrophy. Overall, the significantly optimized timing of PTHrP-pulses demonstrated a vast potential to enhance chondrogenesis of MSC and suppress hypertrophy possibly via superior balancing of IGF- and SOX9-related mechanisms. J. Cell. Physiol. 231: 2673-2681, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Radio-frequency oxygen-plasma-enhanced pulsed laser deposition of IGZO films

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Chia-Man Chou

2017-07-01

Full Text Available We demonstrate the crystalline structures, optical transmittance, surface and cross-sectional morphologies, chemical compositions, and electrical properties of indium gallium zinc oxide (IGZO-based thin films deposited on glass and silicon substrates through pulsed laser deposition (PLD incorporated with radio-frequency (r.f.-generated oxygen plasma. The plasma-enhanced pulsed laser deposition (PEPLD-based IGZO thin films exhibited a c-axis-aligned crystalline (CAAC structure, which was attributed to the increase in Zn-O under high oxygen vapor pressure (150 mTorr. High oxygen vapor pressure (150 mTorr and low r.f. power (10 W are the optimal deposition conditions for fabricating IGZO thin films with improved electrical properties.

Profile correction to electron temperature and enhancement factor in soft-x-ray pulse-height-analysis measurements in tokamaks

International Nuclear Information System (INIS)

Sesnic, S.; Diesso, M.; Hill, K.; Holland, A.; Pohl, F.

1988-01-01

Because soft-x-ray pulse-height-analysis spectra contain chordal information, the electron temperature and the radiation intensity (enhancement factor) measurements do not represent the local values. The correction factors for the electron temperature and the enhancement factor as a function of the temperature and density profile parameters and the energy are obtained. The spectrum distortion due to pulse pileup effects is also evaluated. A set of curves is given from which the distortion of the spectrum can be obtained if the electron temperature, the Be filter thickness, and the electronic parameters of the acquisition system are known. PG 1810,1812 ID 131801CON N X-ray diagnostics TT Profile correction to electron temperature and enhancement factor in soft-x-ray pulse-height-analysis measurements in tokamaks AU S. Sesnic, M. Diesso, K. Hill, and A. Holland LO Princeton University, Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 AU F. Pohl LO Max-Planck Institut fuer Plasmaphysik, 8046-Garching, Federal Republic of Germany SD (Presented on 16 March 1988) AB Because soft-x-ray pulse-height-analysis spectra contain chordal information, the electron temperature and the radiation intensity (enhancement factor) measurements do not represent the local values. The correction factors for the electron temperature and the enhancement factor as a function of the temperature and density profile parameters and the energy are obtained. The spectrum distortion due to pulse pileup effects is also evaluated. A set of curves is given from which the distortion of the spectrum can be obtained if the electron tempe

Lung MRI at 1.5 and 3 Tesla: observer preference study and lesion contrast using five different pulse sequences.

Science.gov (United States)

Fink, Christian; Puderbach, Michael; Biederer, Juergen; Fabel, Michael; Dietrich, Olaf; Kauczor, Hans-Ulrich; Reiser, Maximilian F; Schönberg, Stefan O

2007-06-01

To compare the image quality and lesion contrast of lung MRI using 5 different pulse sequences at 1.5 T and 3 T. Lung MRI was performed at 1.5 T and 3 T using 5 pulse sequences which have been previously proposed for lung MRI: 3D volumetric interpolated breath-hold examination (VIBE), true fast imaging with steady-state precession (TrueFISP), half-Fourier single-shot turbo spin-echo (HASTE), short tau inversion recovery (STIR), T2-weighted turbo spin-echo (TSE). In addition to 4 healthy volunteers, 5 porcine lungs were examined in a dedicated chest phantom. Lung pathology (nodules and infiltrates) was simulated in the phantom by intrapulmonary and intrabronchial injections of agarose. CT was performed in the phantom for correlation. Image quality of the sequences was ranked in a side-by-side comparison by 3 blinded radiologists regarding the delineation of pulmonary and mediastinal anatomy, conspicuity of pulmonary nodules and infiltrates, and presence of artifacts. The contrast of nodules and infiltrates (CNODULES and CINFILTRATES) defined by the ratio of the signal intensities of the lesion and adjacent normal lung parenchyma was determined. There were no relevant differences regarding the preference for the individual sequences between both field strengths. TSE was the preferred sequence for the visualization of the mediastinum at both field strengths. For the visualization of lung parenchyma the observers preferred TrueFISP in volunteers and TSE in the phantom studies. At both field strengths VIBE achieved the best rating for the depiction of nodules, whereas HASTE was rated best for the delineation of infiltrates. TrueFISP had the fewest artifacts in volunteers, whereas STIR showed the fewest artifacts in the phantom. For all but the TrueFISP sequence the lesion contrast increased from 1.5 T to 3 T. At both field strengths VIBE showed the highest CNODULES (6.6 and 7.1) and HASTE the highest CINFILTRATES (6.1 and 6.3). The imaging characteristics of different

B1 mapping for bias-correction in quantitative T1 imaging of the brain at 3T using standard pulse sequences.

Science.gov (United States)

Boudreau, Mathieu; Tardif, Christine L; Stikov, Nikola; Sled, John G; Lee, Wayne; Pike, G Bruce

2017-12-01

B 1 mapping is important for many quantitative imaging protocols, particularly those that include whole-brain T 1 mapping using the variable flip angle (VFA) technique. However, B 1 mapping sequences are not typically available on many magnetic resonance imaging (MRI) scanners. The aim of this work was to demonstrate that B 1 mapping implemented using standard scanner product pulse sequences can produce B 1 (and VFA T 1 ) maps comparable in quality and acquisition time to advanced techniques. Six healthy subjects were scanned at 3.0T. An interleaved multislice spin-echo echo planar imaging double-angle (EPI-DA) B 1 mapping protocol, using a standard product pulse sequence, was compared to two alternative methods (actual flip angle imaging, AFI, and Bloch-Siegert shift, BS). Single-slice spin-echo DA B 1 maps were used as a reference for comparison (Ref. DA). VFA flip angles were scaled using each B 1 map prior to fitting T 1 ; the nominal flip angle case was also compared. The pooled-subject voxelwise correlation (ρ) for B 1 maps (BS/AFI/EPI-DA) relative to the reference B 1 scan (Ref. DA) were ρ = 0.92/0.95/0.98. VFA T 1 correlations using these maps were ρ = 0.86/0.88/0.96, much better than without B 1 correction (ρ = 0.53). The relative error for each B 1 map (BS/AFI/EPI-DA/Nominal) had 95 th percentiles of 5/4/3/13%. Our findings show that B 1 mapping implemented using product pulse sequences can provide excellent quality B 1 (and VFA T 1 ) maps, comparable to other custom techniques. This fast whole-brain measurement (∼2 min) can serve as an excellent alternative for researchers without access to advanced B 1 pulse sequences. 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1673-1682. © 2017 International Society for Magnetic Resonance in Medicine.

Electrical pulse – mediated enhanced delivery of silver nanoparticles into living suspension cells for surface enhanced Raman spectroscopy

International Nuclear Information System (INIS)

Lin, J; Li, B; Feng, S; Chen, G; Li, Y; Huang, Z; Chen, R; Yu, Y; Huang, H; Lin, S; Li, C; Su, Y; Zeng, H

2012-01-01

Electrical pulse-mediated enhanced silver nanoparticles delivery is a much better method for intracellular surface-enhanced Raman spectroscopy (SERS) measurements of suspension cells. Robust and high-quality SERS spectra of living suspension cells were obtained based on an electroporation-SERS method, which can overcomes the shortcoming of non-uniform distribution of silver nanoparticles localized in the cell cytoplasm after electroporation and reduces the amount variance of silver nanoparticles delivered into different cells. The electroporation parameters include three 150 V (375 V/cm) electric pulses of 1, 5, and 5 ms durations respectively. Our results indicate that considerable amount of silver nanoparticles can be rapidly delivered into the human promyelocytic leukemia HL60 cells, and the satisfied SERS spectra were obtained while the viability of the treated cells was highly maintained (91.7%). The electroporation-SERS method offers great potential approach in delivering silver nanoparticles into living suspension cells, which is useful for widely biomedical applications including the real-time intracellular SERS analysis of living cells

In Vivo Enhancer Analysis Chromosome 16 Conserved NoncodingSequences

Energy Technology Data Exchange (ETDEWEB)

Pennacchio, Len A.; Ahituv, Nadav; Moses, Alan M.; Nobrega,Marcelo; Prabhakar, Shyam; Shoukry, Malak; Minovitsky, Simon; Visel,Axel; Dubchak, Inna; Holt, Amy; Lewis, Keith D.; Plajzer-Frick, Ingrid; Akiyama, Jennifer; De Val, Sarah; Afzal, Veena; Black, Brian L.; Couronne, Olivier; Eisen, Michael B.; Rubin, Edward M.

2006-02-01

The identification of enhancers with predicted specificitiesin vertebrate genomes remains a significant challenge that is hampered bya lack of experimentally validated training sets. In this study, weleveraged extreme evolutionary sequence conservation as a filter toidentify putative gene regulatory elements and characterized the in vivoenhancer activity of human-fish conserved and ultraconserved1 noncodingelements on human chromosome 16 as well as such elements from elsewherein the genome. We initially tested 165 of these extremely conservedsequences in a transgenic mouse enhancer assay and observed that 48percent (79/165) functioned reproducibly as tissue-specific enhancers ofgene expression at embryonic day 11.5. While driving expression in abroad range of anatomical structures in the embryo, the majority of the79 enhancers drove expression in various regions of the developingnervous system. Studying a set of DNA elements that specifically droveforebrain expression, we identified DNA signatures specifically enrichedin these elements and used these parameters to rank all ~;3,400human-fugu conserved noncoding elements in the human genome. The testingof the top predictions in transgenic mice resulted in a three-foldenrichment for sequences with forebrain enhancer activity. These datadramatically expand the catalogue of in vivo-characterized human geneenhancers and illustrate the future utility of such training sets for avariety of iological applications including decoding the regulatoryvocabulary of the human genome.

Diagnosis of superior labral lesions: comparison of noncontrast MRI with indirect MR arthrography in unexercised shoulders

International Nuclear Information System (INIS)

Dinauer, Philip A.; Flemming, Donald J.; Murphy, Kevin P.; Doukas, William C.

2007-01-01

To prospectively compare the accuracy of noncontrast magnetic resonance imaging (MRI) with indirect MR arthrography (I-MRa) of unexercised shoulders for diagnosis of superior glenoid labral lesions. Institutional Review Board approval and patient informed consent were obtained for this prospective study. Superior labral findings on shoulder MRI and unexercised I-MRa studies of 104 patients were correlated with findings at arthroscopic shoulder surgery. Two musculoskeletal radiologists independently reviewed the two sets of MR images while blinded to arthroscopic results. For each radiologist, the McNemar test was used to detect statistically significant differences between techniques. The superior labrum was intact in 24 and abnormal in 80 subjects. For detection of superior labral lesions by each radiologist, I-MRa was more sensitive (84-91%) than MRI (66-85%), with statistically significant improvement in sensitivity for one reader (p = 0.003). However, I-MRa was less specific (58-71%) than MRI (75-83%). Overall, accuracy was slightly improved on I-MRa (78-86%) compared with MRI (70-83%), but this difference was not statistically significant for either reader. Compared with noncontrast MRI, I-MRa was more sensitive for diagnosis of superior glenoid labral lesions. However, the diagnostic value of I-MRa in shoulders remaining at rest is potentially limited by decreased specificity of the technique. (orig.)

Basivertebral plexus enhancement at MR imaging after Gd-DTPA administration

International Nuclear Information System (INIS)

Bronstein, A.D.; Cohen, W.A.; Maravilla, K.R.

1989-01-01

This paper presents a study to identify noncontrast versus post-Gd-DTPA MR images of the spine, we analyzed the basivertebral plexus. The authors postulate that there are consistent patterns of enhancement specific with Gd-DTPA. This is a retrospective examination of the normal appearance and enhancement patterns of the basivertebral plexus in 805 vertebrae of 30 patients who underwent pre- and post-Gd-DTPA T1-weighted sagittal MR imaging of the spine. All patients show enhancement of the basivertebral plexus in a significant number of vertebrae when pre-and postcontrast images are compared

Hyaline articular cartilage: relaxation times, pulse-sequence parameters and MR appearance at 1.5 T

Energy Technology Data Exchange (ETDEWEB)

Chalkias, S.M. [Dept. of Radiology, A.H.E.P.A. General Hospital of the Aristotelian Univ., Thessaloniki (Greece); Pozzi-Mucelli, R.S. [Dept. of Radiology, Univ. of Trieste (Italy); Pozzi-Mucelli, M. [Orthopaedic Clinic, Univ. of Trieste (Italy); Frezza, F. [Dept. of Radiology, Univ. of Trieste (Italy); Longo, R. [Dept. of Radiology, Univ. of Trieste (Italy)

1994-08-01

In order to optimize the parameters for the best visualization of the internal architecture of the hyaline articular cartilage a study both ex vivo and in vivo was performed. Accurate T1 and T2 relaxation times of articular cartilage were obtained with a particular mixed sequence and then used for the creation of isocontrast intensity graphs. These graphs subsequently allowed in all pulse sequences (spin echo, SE and gradient echo, GRE) the best combination of repetition time (TR), echo time (TE) and flip angle (FA) for optimization of signal differences between MR cartilage zones. For SE sequences maximum contrast between cartilage zones can be obtained by using a long TR (> 1,500 ms) with a short TE (< 30 ms), whereas for GRE sequences maximum contrast is obtained with the shortest TE (< 15 ms) combined with a relatively long TR (> 400 ms) and an FA greater than 40 . A trilaminar appearance was demonstrated with a superficial and deep hypointense zone in all sequences and an intermediate zone that was moderately hyperintense on SE T1-weighted images, slightly more hyperintense on proton density Rho and SE T2-weighted images and even more hyperintense on GRE images. (orig.)

Discriminatory usefulness of pulsed-field gel electrophoresis and sequence-based typing in Legionella outbreaks.

Science.gov (United States)

Quero, Sara; García-Núñez, Marian; Párraga-Niño, Noemí; Barrabeig, Irene; Pedro-Botet, Maria L; de Simon, Mercè; Sopena, Nieves; Sabrià, Miquel

2016-06-01

To compare the discriminatory power of pulsed-field gel electrophoresis (PFGE) and sequence-based typing (SBT) in Legionella outbreaks for determining the infection source. Twenty-five investigations of Legionnaires' disease were analyzed by PFGE, SBT and Dresden monoclonal antibody. The results suggested that monoclonal antibody could reduce the number of Legionella isolates to be characterized by molecular methods. The epidemiological concordance PFGE-SBT was 100%, while the molecular concordance was 64%. Adjusted Wallace index (AW) showed that PFGE has better discriminatory power than SBT (AWSBT→PFGE = 0.767; AWPFGE→SBT = 1). The discrepancies appeared mostly in sequence type (ST) 1, a worldwide distributed ST for which PFGE discriminated different profiles. SBT discriminatory power was not sufficient verifying the infection source, especially in worldwide distributed STs, which were classified into different PFGE patterns.

Irreversible electroporation ablation area enhanced by synergistic high- and low-voltage pulses.

Directory of Open Access Journals (Sweden)

Chenguo Yao

Full Text Available Irreversible electroporation (IRE produced by a pulsed electric field can ablate tissue. In this study, we achieved an enhancement in ablation area by using a combination of short high-voltage pulses (HVPs to create a large electroporated area and long low-voltage pulses (LVPs to ablate the electroporated area. The experiments were conducted in potato tuber slices. Slices were ablated with an array of four pairs of parallel steel electrodes using one of the following four electric pulse protocols: HVP, LVP, synergistic HVP+LVP (SHLVP or LVP+HVP. Our results showed that the SHLVPs more effectively necrotized tissue than either the HVPs or LVPs, even when the SHLVP dose was the same as or lower than the HVP or LVP doses. The HVP and LVP order mattered and only HVPs+LVPs (SHLVPs treatments increased the size of the ablation zone because the HVPs created a large electroporated area that was more susceptible to the subsequent LVPs. Real-time temperature change monitoring confirmed that the tissue was non-thermally ablated by the electric pulses. Theoretical calculations of the synergistic effects of the SHLVPs on tissue ablation were performed. Our proposed SHLVP protocol provides options for tissue ablation and may be applied to optimize the current clinical IRE protocols.

Irreversible electroporation ablation area enhanced by synergistic high- and low-voltage pulses.

Science.gov (United States)

Yao, Chenguo; Lv, Yanpeng; Dong, Shoulong; Zhao, Yajun; Liu, Hongmei

2017-01-01

Irreversible electroporation (IRE) produced by a pulsed electric field can ablate tissue. In this study, we achieved an enhancement in ablation area by using a combination of short high-voltage pulses (HVPs) to create a large electroporated area and long low-voltage pulses (LVPs) to ablate the electroporated area. The experiments were conducted in potato tuber slices. Slices were ablated with an array of four pairs of parallel steel electrodes using one of the following four electric pulse protocols: HVP, LVP, synergistic HVP+LVP (SHLVP) or LVP+HVP. Our results showed that the SHLVPs more effectively necrotized tissue than either the HVPs or LVPs, even when the SHLVP dose was the same as or lower than the HVP or LVP doses. The HVP and LVP order mattered and only HVPs+LVPs (SHLVPs) treatments increased the size of the ablation zone because the HVPs created a large electroporated area that was more susceptible to the subsequent LVPs. Real-time temperature change monitoring confirmed that the tissue was non-thermally ablated by the electric pulses. Theoretical calculations of the synergistic effects of the SHLVPs on tissue ablation were performed. Our proposed SHLVP protocol provides options for tissue ablation and may be applied to optimize the current clinical IRE protocols.

Intra-pulse Cavity Enhanced Measurements of Carbon Monoxide in a Rapid Compression Machine

KAUST Repository

Nasir, Ehson Fawad; Farooq, Aamir

2018-01-01

A laser absorption sensor for carbon monoxide concentration was developed for combustion studies in a rapid compression machine using a pulsed quantum cascade laser near 4.89 μm. Cavity enhancement reduced minimum detection limit down to 2.4 ppm

Enhanced shock wave generation via pre-breakdown acceleration using water electrolysis in negative streamer pulsed spark discharges

Science.gov (United States)

Lee, Kern; Chung, Kyoung-Jae; Hwang, Y. S.

2018-03-01

This paper presents a method for enhancement of shock waves generated from underwater pulsed spark discharges with negative (anode-directed) subsonic streamers, for which the pre-breakdown process is accelerated by preconditioning a gap with water electrolysis. Hydrogen microbubbles are produced at the cathode by the electrolysis and move towards the anode during the preconditioning phase. The numbers and spatial distributions of the microbubbles vary with the amplitude and duration of each preconditioning pulse. Under our experimental conditions, the optimum pulse duration is determined to be ˜250 ms at a pulse voltage of 400 V, where the buoyancy force overwhelms the electric force and causes the microbubbles to be swept out from the water gap. When a high-voltage pulse is applied to the gap just after the preconditioning pulse, the pre-breakdown process is significantly accelerated in the presence of the microbubbles. At the optimum preconditioning pulse duration, the average breakdown delay is reduced by 87% and, more importantly, the energy consumed during the pre-breakdown period decreases by 83%. This reduced energy consumption during the pre-breakdown period, when combined with the morphological advantages of negative streamers, such as thicker and longer stalks, leads to a significant improvement in the measured peak pressure (˜40%) generated by the underwater pulsed spark discharge. This acceleration of pre-breakdown using electrolysis overcomes the biggest drawback of negative subsonic discharges, which is slow vapor bubble formation due to screening effects, and thus enhances the efficiency of the shock wave generation process using pulsed spark discharges in water.

Plasma-enhanced chemical vapor deposition of aluminum oxide using ultrashort precursor injection pulses

NARCIS (Netherlands)

Dingemans, G.; Sanden, van de M.C.M.; Kessels, W.M.M.

2012-01-01

An alternative plasma-enhanced chemical vapor deposition (PECVD) method is developed and applied for the deposition of high-quality aluminum oxide (AlOx) films. The PECVD method combines a continuous plasma with ultrashort precursor injection pulses. We demonstrate that the modulation of the

MR venography using the 3D-MEDIC (multi echo data imaging combination) sequence for lower extremities

International Nuclear Information System (INIS)

Kitagawa, Hisashi; Kishi, Takayuki; Saito, Ryo; Shohji, Tomokazu; Noguchi, Keiji; Sunohara, Nobuo

2008-01-01

It is possible to diagnose varicose vein from medical history and physical examinations including inspection and palpation. Non-contrast enhanced MRV (magnetic resonance venography) is becoming popular because it can be easily performed without being affected by the radiographer's skill. We thought that the use of MEDIC (multi echo data imaging combination) would enable us to delineate varicose veins within a short acquisition time and without need for synchronization or contrast enhancement. We used the SIEMENS MAGNETOM Avanto 1.5-Tesla unit to acquire images. Our subjects were five healthy volunteers and five patients with varicose vein. The signal strength of deep veins and muscles were measured. The SNR (signal-to-nose ratio) of deep veins and the CNR (contrast-to-noise ratio) between deep veins and muscles were also measured. Flip angle, fat suppression methods, MTC (magnetic transfer contrast) pulse, and combined echo. Using the optimum image acquisition protocol following our preliminary study with varicose vein patients, the ability of the 3D-MEDIC method to delineate varicose veins was compared with that of the electrocardiogram (ECG)-synchronized two-dimensional time of flight (2D-TOF) method. We found that the following settings would enable us to acquire images from a wide range=coronal, within short acquisition time and needless ECG-triggering. Flip angle=20 degrees, fat suppression method=water excitation, MTC pulse=ON, combined echo=2. 3D-MEDIC was better than the 2D-TOF method in delineating the varicose vein itself and the connection between the varicose vein and deep veins. It is expected that 3D-MEDIC may be useful in the clinical diagnosis of varicose veins. (author)

Comparative study and application of MR sialography using different pulse sequences

International Nuclear Information System (INIS)

Shi Ruihua; Qi Jianping; Feng Dingyi; Zou Mingli; Hu Junwu; Zhu Wenzhen; Xia Liming; Wang Chengyuan

2004-01-01

Objective: To evaluate the accuracy of MR sialography in demonstrating the main salivary duct systems by using a series of pulse sequences and stimulation of salivation by vitamin C. Methods: MR sialography was prospectively performed with STIR, heavily T 2 weighted FSE, and SS FSE sequences in 17 patients suspected with salivary duct abnormalities and 13 volunteers, respectively, and MR sialography was further performed in 16 patients after vitamin C stimulation. The results of the above three sequences were compared with each other. Results: The main salivary gland duct was depicted in all cases by any of the mentioned sequence. The STIR images were significantly superior to SS FSE and heavily T 2 weighted FSE images for demonstrating the salivary duct system, followed by heavily T 2 weighted FSE images. On STIR images, first- and second- order intraglandular branches were clearly depicted in all cases, and the thinnest branches were about 0.8 mm. On heavily T 2 weighted FSE images, the first-order and the second-order intraglandular branches were delineated in 25 of 30 and 18 of 30 cases, respectively. But on SS FSE images, only 20 to 30 first-order and 10 of 30 second-order intraglandular branches could be detected. MR sialography with vitamin C stimulation revealed the good visualization of the salivary duct system, and the ducts became wider than before. In 7 cases with acute sialadenitis, the main duct became slightly wider and the distal ducts were dilated; In 7 cases with benign tumor, the ducts were displaced but remained continuous; The duct in one patients with submandibular gland cancer showed destruction and discontinuity. The ducts of one patient with Sjogren syndrome and one with sialidosis displayed normal. Conclusion: MR sialography with evoked salivation is noninvasive and allows delineation of both normal and abnormal parotid and submandibular gland duct systems, and the images are especially better on STIR sequence

Enhancement of EUV emission from a liquid microjet target by use of dual laser pulses

Science.gov (United States)

Higashiguchi, Takeshi; Rajyaguru, Chirag; Koga, Masato; Kawasaki, Keita; Sasaki, Wataru; Kubodera, Shoichi; Kikuchi, Takashi; Yugami, Noboru; Kawata, Shigeo; Andreev, Alexander A.

2005-03-01

Extreme ultraviolet (EUV) radiation at the wavelength of around 13nm waws observed from a laser-produced plasma using continuous water-jet. Strong dependence of the conversion efficiency (CE) on the laser focal spot size and jet diameter was observed. The EUV CE at a given laser spot size and jet diameter was further enhanced using double laser pulses, where a pre-pulse was used for initial heating of the plasma.

Diagnosis value of dual-phase contrast enhancement CT combined with virtual non-enhanced images by dual-energy CT in clear cell renal cell carcinoma

International Nuclear Information System (INIS)

Ma Zhoupeng; Zhou Jianjun; Liu Xueling; Wang Chun; Zhang Shunzhuang

2012-01-01

Objective: To explore the diagnostic value of dual-phase contrast enhancement CT combined with virtual non-enhanced images by dual-energy CT in clear cell renal cell carcinoma. Methods: Sixty patients who were suspected of clear cell renal cell carcinoma underwent non-enhanced CT and contrast enhancement CT of early interface-phase between cortex -medulla and parenchymal phase on a dual-energy CT. The true non-enhanced kidney CT (TNCT) was performed in a single-energy acquisition mode, but the dual-phase contrast enhancement CT were performed in a dual-energy mode of 80 kV and 140 kV respectively. The virtual non-enhanced CT (VNCT) images were derived from the data of early interface phase using liver virtual non-contrast software. The diagnose according to VNCT combined dual-phase contrast enhancement CT and dual-phase contrast enhancement CT only were made respectively and compared with χ 2 test. Between the true non-contrast CT and the virtual non-contrast CT, the image quality was compared with Wilcoxon test; The radiation dose of volume CT dose index (CTDIvol) and dose length product(DLP) in a single-phase and total examination, the mean CT HU values of the tumours were compared with t test. Results: The accuracy of VNCT combined dual-phase contrast enhancement CT was higher than that of dual-phase contrast enhancement CT only [93.3% (56/60) vs.78.3% (47/60); χ 2 =5.6, P<0.05]. The detective ability (score) of VNCT was near to that of TNCT and the difference was not obvious (Z=0.00, P>0.05). The radiation dose of volume CT dose index (CTDIvol) and dose length product (DLP) in a single phase and total examination of VNCT [(8.85 ± 1.28) mGy, (196.45 ±21.12) mGy·cm, (17.69±2.35) mGy, (392.90±42.25) mGy · cm] were lower than that of TNCT [(10.20 ± 1.44) mGy,(218.29 ± 29.60) mGy · cm, (30.61 ± 3.27) mGy and (654.86 ± 88.81) mGy ·cm], t=4.21, 3.58, 23.63, 16.12 respectively, P<0.05. The mean CT HU values of tumours on VNCT images was higher than that

Plasmon-enhanced terahertz emission in self-assembled quantum dots by femtosecond pulses

Energy Technology Data Exchange (ETDEWEB)

Carreño, F., E-mail: ferpo@fis.ucm.es; Antón, M. A., E-mail: antonm@fis.ucm.es; Melle, Sonia, E-mail: smelle@fis.ucm.es; Calderón, Oscar G., E-mail: oscargc@fis.ucm.es; Cabrera-Granado, E., E-mail: ecabrera@fis.ucm.es [Facultad de Óptica y Optometría, Universidad Complutense de Madrid, C/ Arcos de Jalón 118, 28037 Madrid (Spain); Cox, Joel, E-mail: jcox27@uwo.ca; Singh, Mahi R., E-mail: msingh@uwo.ca [Department of Physics and Astronomy, The University of Western Ontario, London N6A 3K7 (Canada); Egatz-Gómez, A., E-mail: Ana.Egatz-Gomez.1@nd.edu [Department of Chemical and Biomolecular Engineering, University of Notre Dame, South Bend, Indiana 46556 (United States)

2014-02-14

A scheme for terahertz (THz) generation from intraband transition in a self-assembled quantum dot (QD) molecule coupled to a metallic nanoparticle (MNP) is analyzed. The QD structure is described as a three-level atom-like system using the density matrix formalism. The MNP with spherical geometry is considered in the quasistatic approximation. A femtosecond laser pulse creates a coherent superposition of two subbands in the quantum dots and produces localized surface plasmons in the nanoparticle which act back upon the QD molecule via dipole-dipole interaction. As a result, coherent THz radiation with a frequency corresponding to the interlevel spacing can be obtained, which is strongly modified by the presence of the MNP. The peak value of the terahertz signal is analyzed as a function of nanoparticle's size, the MNP to QD distance, and the area of the applied laser field. In addition, we theoretically demonstrate that the terahertz pulse generation can be effectively controlled by making use of a train of femtosecond laser pulses. We show that by a proper choice of the parameters characterizing the pulse train a huge enhancement of the terahertz signal is obtained.

Efficient and controllable thermal ablation induced by short-pulsed HIFU sequence assisted with perfluorohexane nanodroplets.

Science.gov (United States)

Chang, Nan; Lu, Shukuan; Qin, Dui; Xu, Tianqi; Han, Meng; Wang, Supin; Wan, Mingxi

2018-07-01

A HIFU sequence with extremely short pulse duration and high pulse repetition frequency can achieve thermal ablation at a low acoustic power using inertial cavitation. Because of its cavitation-dependent property, the therapeutic outcome is unreliable when the treatment zone lacks cavitation nuclei. To overcome this intrinsic limitation, we introduced perfluorocarbon nanodroplets as extra cavitation nuclei into short-pulsed HIFU-mediated thermal ablation. Two types of nanodroplets were used with perfluorohexane (PFH) as the core material coated with bovine serum albumin (BSA) or an anionic fluorosurfactant (FS) to demonstrate the feasibility of this study. The thermal ablation process was recorded by high-speed photography. The inertial cavitation activity during the ablation was revealed by sonoluminescence (SL). The high-speed photography results show that the thermal ablation volume increased by ∼643% and 596% with BSA-PFH and FS-PFH, respectively, than the short-pulsed HIFU alone at an acoustic power of 19.5 W. Using nanodroplets, much larger ablation volumes were created even at a much lower acoustic power. Meanwhile, the treatment time for ablating a desired volume significantly reduced in the presence of nanodroplets. Moreover, by adjusting the treatment time, lesion migration towards the HIFU transducer could also be avoided. The SL results show that the thermal lesion shape was significantly dependent on the inertial cavitation in this short-pulsed HIFU-mediated thermal ablation. The inertial cavitation activity became more predictable by using nanodroplets. Therefore, the introduction of PFH nanodroplets as extra cavitation nuclei made the short-pulsed HIFU thermal ablation more efficient by increasing the ablation volume and speed, and more controllable by reducing the acoustic power and preventing lesion migration. Copyright © 2018. Published by Elsevier B.V.

Population Genetic Structure of Listeria monocytogenes Strains as Determined by Pulsed-Field Gel Electrophoresis and Multilocus Sequence Typing

DEFF Research Database (Denmark)

Henri, Clémentine; Félix, Benjamin; Guillier, Laurent

2016-01-01

on the basis of different pulsed-field gel electrophoresis (PFGE) clusters, serotypes, and strain origins and typed by multilocus sequence typing (MLST), and the MLST results were supplemented with MLST data available from Institut Pasteur, representing human and additional food strains from France....... The distribution of sequence types (STs) was compared between food and clinical strains on a panel of 675 strains. High congruence between PFGE and MLST was found. Out of 73 PFGE clusters, the two most prevalent corresponded to ST9 and ST121. Using original statistical analysis, we demonstrated that (i...

Versatile pulse programmer for pulsed nuclear magnetic resonance spectroscopy

International Nuclear Information System (INIS)

Adduci, D.J.

1979-05-01

A description of the sequence of events and the decisions leading to the design of a versatile pulse programmer for pulsed NMR are presented. Background and application information is discussed in order that the reader might better understand the role of the pulse programmer in a NMR spectrometer. Various other design approaches are presented as a basis for comparison. Specifications for this design are proposed, the hardware implementation of the specifications is discussed, and the software operating system is presented

Versatile pulse programmer for pulsed nuclear magnetic resonance spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Adduci, D.J.

1979-05-01

A description of the sequence of events and the decisions leading to the design of a versatile pulse programmer for pulsed NMR are presented. Background and application information is discussed in order that the reader might better understand the role of the pulse programmer in a NMR spectrometer. Various other design approaches are presented as a basis for comparison. Specifications for this design are proposed, the hardware implementation of the specifications is discussed, and the software operating system is presented.

Surface-enhanced Raman spectroscopy (SERS) using Ag nanoparticle films produced by pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Smyth, C.A., E-mail: smythc2@tcd.ie [School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Mirza, I.; Lunney, J.G.; McCabe, E.M. [School of Physics, Trinity College Dublin, Dublin 2 (Ireland)

2013-01-01

Highlights: Black-Right-Pointing-Pointer Pulsed laser deposition (PLD) produces silver nanoparticle films. Black-Right-Pointing-Pointer These films can be used for surface-enhanced Raman spectroscopy (SERS). Black-Right-Pointing-Pointer Commercial film shows good SERS reproducibility but poor signal intensity. Black-Right-Pointing-Pointer PLD shows a good SERS response coupled with good reproducibility. - Abstract: Thin silver nanoparticle films, of thickness 7 nm, were deposited onto glass microslides using pulsed laser deposition (PLD). The films were then characterised using UV-vis spectroscopy and scanning transmission electron microscopy before Rhodamine 6G was deposited onto them for investigation using surface-enhanced Raman spectroscopy (SERS). The sensitivity obtained using SERS was compared to that obtained using a colloidal silver suspension and also to a commercial SERS substrate. The reproducibility of the films is also examined using statistical analysis.

Focal hepatic lesions: contrast-enhancement patterns at pulse-inversion harmonic US using a microbubble contrast agent

Energy Technology Data Exchange (ETDEWEB)

Kim, Eun-A; Yoon, Kwon-Ha; Lee, Young-Hwan; Kim, Hye-Won; Juhng, Seon-Kwan; Won, Jong-Jin [Wonkwang University, Iksan (Korea, Republic of)

2003-12-15

To analyze the contrast-enhancement patterns obtained at pulse-inversion harmonic imaging (PIHI) of focal hepatic lesions, and to thus determine tumor vascularity and the acoustic emission effect. We reviewed pulse-inversion images in 90 consecutive patients with focal hepatic lesions, namely hepatocellular carcinoma (HHC) (n=43), metastases (n=30), and hemangioma (n=17). Vascular and delayed phase images were obtained immediately and five minutes following the injection of a microbubble contrast agent. Tumoral vascularity at vascular phase imaging and the acoustic emission effect at delayed phase imaging were each classified as one of four patterns. Vascular phase images depicted internal vessels in 93% of HCCs, marginal vessels in 83% of metastases, and peripheral enhancement in 71% of hemangiomas. Delayed phase images showed inhomogeneous enhancement in 86% of HCCs; hypoechoic, decreased enhancement in 93% of metastases; and hypoechoic and reversed echogenicity in 65% of hemangiomas. Vascular and delayed phase enhancement patterns were associated with a specificity of 91% or greater, and 92% or greater, respectively, and with positive predictive values of 71% or greater, and 85% or greater, respectively. Contrast-enhancement patterns depicting tumoral vascularity and the acoustic emission effect at PIHI can help differentiate focal hepatic lesions.

Cavitation enhances coagulated size during pulsed high-intensity focussed ultrasound ablation in an isolated liver perfusion system.

Science.gov (United States)

Zhao, Lu-Yan; Liu, Shan; Chen, Zong-Gui; Zou, Jian-Zhong; Wu, Feng

2016-11-24

To investigate whether cavitation enhances the degree of coagulation during pulsed high-intensity focussed ultrasound (HIFU) in an isolated liver perfusion system. Isolated liver was treated by pulsed HIFU or continuous-wave HIFU with different portal vein flow rates. The cavitation emission during exposure was recorded, and real-time ultrasound images were used to observe changes in the grey scale. The coagulation size was measured and calculated. HIFU treatment led to complete coagulation necrosis and total cell destruction in the target regions. Compared to exposure at a duty cycle (DC) of 100%, the mean volumes of lesions induced by 6 s exposure at DCs of 50% and 10% were significantly larger (P cavitation activity for the pulsed-HIFU (P > .05). For continuous-wave HIFU exposure, there was a significant decrease in the necrosis volume and cavitation activity for exposure times of 1, 2, 3, 4, and 6 s with increasing portal perfusion rates. Perfusion flow rates negatively influence cavitation activity and coagulation volume. Ablation is significantly enhanced during pulsed HIFU exposure compared with continuous-wave HIFU.

Enhancement or Reduction of Sonochemical Activity of Pulsed Ultrasound Compared to Continuous Ultrasound at 20 kHz?

Directory of Open Access Journals (Sweden)

Yujing Sun

2013-04-01

Full Text Available Little is known about the efficacy of pulsed ultrasound compared with continuous ultrasound. Previous studies on the efficacy of pulsed ultrasound were not systematic and gave different results. In this study, the effects of pulse length, pulse interval, pulse length × pulse intervals, and treatment time on sonochemical activity were investigated using a simple oxidation of iodide method and a comparison of the efficacy of pulsed ultrasound and continuous ultrasound is made. The results showed that the main factor in the efficacy of pulsed ultrasound was pulse length when pulse length varied from 0.1 to 1 s. However, the main factors were pulse length, the pulse length × pulse interval, and pulse interval when pulse length varied from 1 to 9 s. Pulsed ultrasound had no effect when the pulse length was 0.1 s; however, the sonochemical activity of pulsed ultrasound decreased compared to continuous ultrasound as the pulse length varied from 0.1 to 1 s. The sonochemical activity of pulsed ultrasound either increased or decreased compared to continuous ultrasound when pulse length varied from 1 to 9 s, but the increase or decrease had no clear trend. The sonochemical activity was constant at Ton/Toff = 2 s/2 s and slightly decreased at Ton/Toff = 3 s/2 s with time, whereas the sonochemical activity of continuous ultrasound significantly decreased with time. Enhancement or reduction of sonochemical activity of pulsed ultrasound compared to continuous ultrasound depended on the pulse length and pulse interval.

Acousto-optic replication of ultrashort laser pulses

Science.gov (United States)

Yushkov, Konstantin B.; Molchanov, Vladimir Ya.; Ovchinnikov, Andrey V.; Chefonov, Oleg V.

2017-10-01

Precisely controlled sequences of ultrashort laser pulses are required in various scientific and engineering applications. We developed a phase-only acousto-optic pulse shaping method for replication of ultrashort laser pulses in a TW laser system. A sequence of several Fourier-transform-limited pulses is generated from a single femtosecond laser pulse by means of applying a piecewise linear phase modulation over the whole emission spectrum. Analysis demonstrates that the main factor which limits maximum delay between the pulse replicas is spectral resolution of the acousto-optic dispersive delay line used for pulse shaping. In experiments with a Cr:forsterite laser system, we obtained delays from 0.3 to 3.5 ps between two replicas of 190 fs transform-limited pulses at the central wavelength of laser emission, 1230 nm.

Pulsed magnetization transfer contrast MRI by a sequence with water selective excitation

Energy Technology Data Exchange (ETDEWEB)

Schick, F. [Univ. of Tuebingen (Germany)

1996-01-01

A water selective SE imaging sequence was developed providing suitable properties for the assessment of magnetization transfer (MT) effects in tissues with considerable amounts of fat. The sequence with water selective excitation and slice selective refocusing combines the following features: The RIF exposure on the macromolecular protons is relatively low for single slice imaging without MT prepulses, since no additional pulses for fat saturation are necessary. Water selection by frequency selective excitation diminishes faults in the subtraction of images recorded with and without MT prepulses (which might arise from movements). High differences in the signal amplitudes from hyaline cartilage and muscle tissue were obtained comparing images recorded with irradiation of the series of prepulses for MT and those lacking MT prepulses. Utilizations of the described water selective approach for the assessment of MT effects in lesions of cartilage and bone are demonstrated. MT saturation was also examined in muscles with fatty degeneration of patients suffering from progressive muscular dystrophy. The described technique allows determination of MT effects with good precision in a single slice, especially in regions with dominating fat signals. 22 refs., 5 figs.

Incidental Findings in Abdominal Dual-Energy Computed Tomography: Correlation Between True Noncontrast and Virtual Noncontrast Images Considering Renal and Liver Cysts and Adrenal Masses.

Science.gov (United States)

Slebocki, Karin; Kraus, Bastian; Chang, De-Hua; Hellmich, Martin; Maintz, David; Bangard, Christopher

To assess correlation between attenuation measurements of incidental findings in abdominal second generation dual-energy computed tomography (CT) on true noncontrast (TNC) and virtual noncontrast (VNC) images. Sixty-three patients underwent arterial dual-energy CT (Somatom Definition Flash, Siemens; pitch factor, 0.75-1.0; gantry rotation time, 0.28 seconds) after endovascular aneurysm repair, consisting of a TNC single energy CT scan (collimation, 128 × 0.6 mm; 120 kVp) and a dual-energy arterial phase scan (collimation, 32 × 0.6 mm, 140 and 100 kVp; blended, 120 kVp data set). Attenuation measurements in Hounsfield units (HU) of liver parenchyma and incidental findings like renal and hepatic cysts and adrenal masses on TNC and VNC images were done by drawing regions of interest. Statistical analysis was performed by paired t test and Pearson correlation. Incidental findings were detected in 56 (89%) patients. There was excellent correlation for both renal (n = 40) and hepatic cysts (n = 12) as well as adrenal masses (n = 6) with a Pearson correlation of 0.896, 0.800, and 0.945, respectively, and mean attenuation values on TNC and VNC images of 10.6 HU ± 12.8 versus 5.1 HU ± 17.5 (attenuation value range from -8.8 to 59.1 HU vs -11.8 to 73.4 HU), 6.4 HU ± 5.8 versus 6.3 HU ± 4.6 (attenuation value range from 2.0 to 16.2 HU vs -3.0 to 15.9 HU), and 12.8 HU ± 11.2 versus 12.4 HU ± 10.2 (attenuation value range from -2.3 to 27.5 HU vs -2.2 to 23.6 HU), respectively. As proof of principle, liver parenchyma measurements also showed excellent correlation between TNC and VNC (n = 40) images with a Pearson correlation of 0.839 and mean attenuation values on TNC and VNC images of 47.2 HU ± 10.5 versus 43.8 HU ± 8.7 (attenuation value range from 21.9 to 60.2 HU vs 4.5 to 65.3 HU). In conclusion, attenuation measurements of incidental findings like renal cysts or adrenal masses on TNC and VNC images derived from second generation dual-energy CT scans show excellent

Investigation of the saturation pulse artifact in non-enhanced MR angiography of the lower extremity arteries at 7 Tesla.

Directory of Open Access Journals (Sweden)

Sören Johst

Full Text Available When performing non-enhanced time-of-flight MR angiography of the lower extremity arteries at 7 T with cardiac triggering, the acquisition time is a crucial consideration. Therefore, in previous studies, saturation RF pulses were applied only every second TR. In the axial source images a slight artifact with an appearance similar to aliasing could be observed. The purpose of this study was to investigate the origin of this artifact. The reason for the artifact is supposed to be related to the two effective TRs during acquisition caused by the sparsely applied saturation RF pulse. Several sequence variants were simulated and implemented within the sequence source code to examine this hypothesis. An adaptation of the excitation flip angles for each TR as well as a correction factor for the k-space data was calculated. Additionally, a different ordering of the k-space data during acquisition was implemented as well as the combination of the latter with the k-space correction factor. The observations from the simulations were verified using both a static and a flow phantom and, finally, in a healthy volunteer using the same measurement setup as in previous volunteer and patient studies. Of all implemented techniques, only the reordering of the k-space was capable of suppressing the artifact almost completely at the cost of creating a ringing artifact. The phantom measurements showed the same results as the simulations and could thus confirm the hypothesis regarding the origin of the artifact. This was additionally verified in the healthy volunteer. The origin of the artifact could be confirmed to be the periodic signal variation caused by two effective TRs during acquisition.

Investigation of the saturation pulse artifact in non-enhanced MR angiography of the lower extremity arteries at 7 Tesla.

Science.gov (United States)

Johst, Sören; Maderwald, Stefan; Fischer, Anja; Quick, Harald H; Ladd, Mark E; Orzada, Stephan

2015-01-01

When performing non-enhanced time-of-flight MR angiography of the lower extremity arteries at 7 T with cardiac triggering, the acquisition time is a crucial consideration. Therefore, in previous studies, saturation RF pulses were applied only every second TR. In the axial source images a slight artifact with an appearance similar to aliasing could be observed. The purpose of this study was to investigate the origin of this artifact. The reason for the artifact is supposed to be related to the two effective TRs during acquisition caused by the sparsely applied saturation RF pulse. Several sequence variants were simulated and implemented within the sequence source code to examine this hypothesis. An adaptation of the excitation flip angles for each TR as well as a correction factor for the k-space data was calculated. Additionally, a different ordering of the k-space data during acquisition was implemented as well as the combination of the latter with the k-space correction factor. The observations from the simulations were verified using both a static and a flow phantom and, finally, in a healthy volunteer using the same measurement setup as in previous volunteer and patient studies. Of all implemented techniques, only the reordering of the k-space was capable of suppressing the artifact almost completely at the cost of creating a ringing artifact. The phantom measurements showed the same results as the simulations and could thus confirm the hypothesis regarding the origin of the artifact. This was additionally verified in the healthy volunteer. The origin of the artifact could be confirmed to be the periodic signal variation caused by two effective TRs during acquisition.

The use of Acoustic Radiation Force decorrelation-weighted pulse inversion (ADW-PI) for enhanced ultrasound contrast imaging

Science.gov (United States)

Herbst, Elizabeth; Unnikrishnan, Sunil; Wang, Shiying; Klibanov, Alexander L.; Hossack, John A.; Mauldin, F. William

2016-01-01

Objectives The use of ultrasound imaging for cancer diagnosis and screening can be enhanced with the use of molecularly targeted microbubbles. Nonlinear imaging strategies such as pulse inversion (PI) and “contrast pulse sequences” (CPS) can be used to differentiate microbubble signal, but often fail to suppress highly echogenic tissue interfaces. This failure results in false positive detection and potential misdiagnosis. In this study, a novel Acoustic Radiation Force (ARF) based approach was developed for superior microbubble signal detection. The feasibility of this technique, termed ARF-decorrelation-weighted PI (ADW-PI), was demonstrated in vivo using a subcutaneous mouse tumor model. Materials and Methods Tumors were implanted in the hindlimb of C57BL/6 mice by subcutaneous injection of MC38 cells. Lipid-shelled microbubbles were conjugated to anti-VEGFR2 antibody and administered via bolus injection. An image sequence using ARF pulses to generate microbubble motion was combined with PI imaging on a Verasonics Vantage programmable scanner. ADW-PI images were generated by combining PI images with inter-frame signal decorrelation data. For comparison, CPS images of the same mouse tumor were acquired using a Siemens Sequoia clinical scanner. Results Microbubble-bound regions in the tumor interior exhibited significantly higher signal decorrelation than static tissue (n = 9, p < 0.001). The application of ARF significantly increased microbubble signal decorrelation (n = 9, p < 0.01). Using these decorrelation measurements, ADW-PI imaging demonstrated significantly improved microbubble contrast-to-tissue ratio (CTR) when compared to corresponding CPS or PI images (n = 9, p < 0.001). CTR improved with ADW-PI by approximately 3 dB compared to PI images and 2 dB compared to CPS images. Conclusions Acoustic radiation force can be used to generate adherent microbubble signal decorrelation without microbubble bursting. When combined with pulse inversion

Enhancement of Lamb Wave Imaging Resolution by Step Pulse Excitation and Prewarping

Directory of Open Access Journals (Sweden)

Shangchen Fu

2015-01-01

Full Text Available For the purpose of improving the damage localization accuracy, a prewarping technology is combined with step pulse excitation and this method is used in Lamb wave imaging of plate structures with adjacent damages. Based on the step pulse excitation, various narrowband or burst response can be derived by signal processing technology and this method provides flexibility for further prewarping approach. A narrowband signal warped with a preselected distance is then designed, and the dispersion in the response of this prewarping signal will be greatly reduced. However, in order to calculate the distance for prewarping, the first arrival needs to be estimated from the burst response. From the step-pulse response, narrowband responses at different central frequencies can be obtained, and by averaging peak-value time of their first arrivals, a more accurate estimation can be calculated. By using the prewarping method to the damage scattering signals before imaging, the imaging resolution of the delay-and-sum method can be highly enhanced. The experiment carried out in an aluminum plate with adjacent damages proves the efficiency of this method.

Enhanced self-magnetic field by atomic polarization in partially stripped plasma produced by a short and intense laser pulse

International Nuclear Information System (INIS)

Hu Qianglin; Liu Shibing; Jiang, Y.J.; Zhang Jie

2005-01-01

The enhancement and redistribution of a self-generated quasistatic magnetic field, due to the presence of the polarization field induced by partially ionized atoms, are analytically revealed when a linearly polarized intense and short pulse laser propagates in a partially stripped plasma with higher density. In particular, the shorter wavelength of the laser pulse can evidently intensify the amplitude of the magnetic field. These enhancement and redistribution of the magnetic field are considered physically as a result of the competition of the electrostatic field (electron-ion separation) associated with the plasma wave, the atomic polarization field, and the pondoromotive potential associated with the laser field. This competition leads to the generation of a positive, large amplitude magnetic field in the zone of the pulse center, which forms a significant difference in partially and fully stripped plasmas. The numerical result shows further that the magnetic field is resonantly modulated by the plasma wave when the pulse length is the integer times the plasma wavelength. This apparently implies that the further enhancement and restructure of the large amplitude self-magnetic field can evidently impede the acceleration and stable transfer of the hot-electron beam

General solution to inhomogeneous dephasing and smooth pulse dynamical decoupling

Science.gov (United States)

Zeng, Junkai; Deng, Xiu-Hao; Russo, Antonio; Barnes, Edwin

2018-03-01

In order to achieve the high-fidelity quantum control needed for a broad range of quantum information technologies, reducing the effects of noise and system inhomogeneities is an essential task. It is well known that a system can be decoupled from noise or made insensitive to inhomogeneous dephasing dynamically by using carefully designed pulse sequences based on square or delta-function waveforms such as Hahn spin echo or CPMG. However, such ideal pulses are often challenging to implement experimentally with high fidelity. Here, we uncover a new geometrical framework for visualizing all possible driving fields, which enables one to generate an unlimited number of smooth, experimentally feasible pulses that perform dynamical decoupling or dynamically corrected gates to arbitrarily high order. We demonstrate that this scheme can significantly enhance the fidelity of single-qubit operations in the presence of noise and when realistic limitations on pulse rise times and amplitudes are taken into account.

Determination of pseudo multi-pulse production rate in GM counters by correlation analysis between signal pulses

International Nuclear Information System (INIS)

Hashimoto, Kengo; Ueda, Taizou

1996-01-01

A technique, based on the correlation analysis of signal pulses in time sequence, is proposed to determine the production rate of the pseudo multi-pulse in Geiger-Mueller (GM) counter. With a multi-channel scaler initiated by a signal pulse, subsequent pulses are recorded in sequence. The production of the multi-pulse increases the counting probability immediately after the initiation. By examining the deviation of the measured probability from the ideal counting probability, the production rate and the average lag time to produce the multi-pulse can be determined. By the use of the present technique, the production rate and the average lag time were obtained for the various GM tubes. These results indicate that the consumption of the quench gas results in a significant increase in the production rate but little variation in the lag time, and that the lag time strongly depends on the tube diameter. (author)

Multi-qubit compensation sequences

International Nuclear Information System (INIS)

Tomita, Y; Merrill, J T; Brown, K R

2010-01-01

The Hamiltonian control of n qubits requires precision control of both the strength and timing of interactions. Compensation pulses relax the precision requirements by reducing unknown but systematic errors. Using composite pulse techniques designed for single qubits, we show that systematic errors for n-qubit systems can be corrected to arbitrary accuracy given either two non-commuting control Hamiltonians with identical systematic errors or one error-free control Hamiltonian. We also examine composite pulses in the context of quantum computers controlled by two-qubit interactions. For quantum computers based on the XY interaction, single-qubit composite pulse sequences naturally correct systematic errors. For quantum computers based on the Heisenberg or exchange interaction, the composite pulse sequences reduce the logical single-qubit gate errors but increase the errors for logical two-qubit gates.

1H HR-MAS NMR and S180 cells: metabolite assignment and evaluation of pulse sequence

International Nuclear Information System (INIS)

Oliveira, Aline L. de; Martinelli, Bruno César B.; Lião, Luciano M.; Pereira, Flávia C.; Silveira-Lacerda, Elisangela P.; Alcantara, Glaucia B.

2014-01-01

High resolution magic angle spinning 1 H nuclear magnetic resonance spectroscopy (HR-MAS NMR) is a useful technique for evaluation of intact cells and tissues. However, optimal NMR parameters are crucial in obtaining reliable results. To identify the key steps for the optimization of HR-MAS NMR parameters, we assessed different pulse sequences and NMR parameters using sarcoma 180 (S180) cells. A complete assignment of the metabolites of S180 is given to assist future studies. (author)

A Novel Imaging Technique (X-Map) to Identify Acute Ischemic Lesions Using Noncontrast Dual-Energy Computed Tomography.

Science.gov (United States)

Noguchi, Kyo; Itoh, Toshihide; Naruto, Norihito; Takashima, Shutaro; Tanaka, Kortaro; Kuroda, Satoshi

2017-01-01

We evaluated whether X-map, a novel imaging technique, can visualize ischemic lesions within 20 hours after the onset in patients with acute ischemic stroke, using noncontrast dual-energy computed tomography (DECT). Six patients with acute ischemic stroke were included in this study. Noncontrast head DECT scans were acquired with 2 X-ray tubes operated at 80 kV and Sn150 kV between 32 minutes and 20 hours after the onset. Using these DECT scans, the X-map was reconstructed based on 3-material decomposition and compared with a simulated standard (120 kV) computed tomography (CT) and diffusion-weighted imaging (DWI). The X-map showed more sensitivity to identify the lesions as an area of lower attenuation value than a simulated standard CT in all 6 patients. The lesions on the X-map correlated well with those on DWI. In 3 of 6 patients, the X-map detected a transient decrease in the attenuation value in the peri-infarct area within 1 day after the onset. The X-map is a powerful tool to supplement a simulated standard CT and characterize acute ischemic lesions. However, the X-map cannot replace a simulated standard CT to diagnose acute cerebral infarction. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

OH Production Enhancement in Bubbling Pulsed Discharges

Science.gov (United States)

Lungu, Cristian P.; Porosnicu, Corneliu; Jepu, Ionut; Chiru, Petrica; Zaroschi, Valentin; Lungu, Ana M.; Saito, Nagahiro; Bratescu, Maria; Takai, Osamu; Velea, Theodor; Predica, Vasile

2010-10-01

The generation of active species, such as H2O2, O*, OH*, HO2*, O3, N2*, etc, produced in aqueous solutions by HV pulsed discharges was studied in order to find the most efficient way in waste water treatment taking into account that these species are almost stronger oxidizers than ozone. Plasma was generated inside gas bubbles formed by the argon, air and oxygen gas flow between the special designed electrodes. The pulse width and pulse frequency influence was studied in order to increase the efficiency of the OH active species formation. The produced active species were investigated by optical emission spectroscopy and correlated with electrical parameters of the discharges (frequency, pulse width, amplitude, and rise and decay time).

OH Production Enhancement in Bubbling Pulsed Discharges

International Nuclear Information System (INIS)

Lungu, Cristian P.; Porosnicu, Corneliu; Jepu, Ionut; Chiru, Petrica; Zaroschi, Valentin; Lungu, Ana M.; Saito, Nagahiro; Bratescu, Maria; Takai, Osamu; Velea, Theodor; Predica, Vasile

2010-01-01

The generation of active species, such as H 2 O 2 , O * , OH*, HO 2 *, O 3 , N 2 * , etc, produced in aqueous solutions by HV pulsed discharges was studied in order to find the most efficient way in waste water treatment taking into account that these species are almost stronger oxidizers than ozone. Plasma was generated inside gas bubbles formed by the argon, air and oxygen gas flow between the special designed electrodes. The pulse width and pulse frequency influence was studied in order to increase the efficiency of the OH active species formation. The produced active species were investigated by optical emission spectroscopy and correlated with electrical parameters of the discharges (frequency, pulse width, amplitude, and rise and decay time).

Transformed composite sequences for improved qubit addressing

Science.gov (United States)

Merrill, J. True; Doret, S. Charles; Vittorini, Grahame; Addison, J. P.; Brown, Kenneth R.

2014-10-01

Selective laser addressing of a single atom or atomic ion qubit can be improved using narrow-band composite pulse sequences. We describe a Lie-algebraic technique to generalize known narrow-band sequences and introduce sequences related by dilation and rotation of sequence generators. Our method improves known narrow-band sequences by decreasing both the pulse time and the residual error. Finally, we experimentally demonstrate these composite sequences using 40Ca+ ions trapped in a surface-electrode ion trap.

Prediction of ultrasonic pulse velocity for enhanced peat bricks using adaptive neuro-fuzzy methodology.

Science.gov (United States)

Motamedi, Shervin; Roy, Chandrabhushan; Shamshirband, Shahaboddin; Hashim, Roslan; Petković, Dalibor; Song, Ki-Il

2015-08-01

Ultrasonic pulse velocity is affected by defects in material structure. This study applied soft computing techniques to predict the ultrasonic pulse velocity for various peats and cement content mixtures for several curing periods. First, this investigation constructed a process to simulate the ultrasonic pulse velocity with adaptive neuro-fuzzy inference system. Then, an ANFIS network with neurons was developed. The input and output layers consisted of four and one neurons, respectively. The four inputs were cement, peat, sand content (%) and curing period (days). The simulation results showed efficient performance of the proposed system. The ANFIS and experimental results were compared through the coefficient of determination and root-mean-square error. In conclusion, use of ANFIS network enhances prediction and generation of strength. The simulation results confirmed the effectiveness of the suggested strategies. Copyright © 2015 Elsevier B.V. All rights reserved.

Enhancement of nonlinear optical response of weakly confined excitons in GaAs thin films by spectrally rectangle-shape-pulse-excitation

International Nuclear Information System (INIS)

Kojima, O; Isu, T; Ishi-Hayase, J; Sasaki, M; Tsuchiya, M

2007-01-01

We report the enhancement of the nonlinear optical response of the weakly confined excitons with use of spectrally rectangular pulse. The nonlinear optical response was investigated as a function of excitation energy by a degenerate four-wave-mixing (DFWM) technique. In the case that the laser pulse with the controlled spectral shape excites the plural exciton states simultaneously, the DFWM signal intensity is enhanced by a factor of two in comparison with the intensity under the excitation of a single exciton state. This enhancement is caused by the superposition of the nonlinear optical responses from the plural exciton states

Enhanced detection of nitrogen dioxide via combined heating and pulsed UV operation of indium oxide nano-octahedra

Directory of Open Access Journals (Sweden)

Oriol Gonzalez

2016-10-01

Full Text Available We report on the use of combined heating and pulsed UV light activation of indium oxide gas sensors for enhancing their performance in the detection of nitrogen dioxide in air. Indium oxide nano-octahedra were synthesized at high temperature (900 °C via vapour-phase transport and screen-printed onto alumina transducers that comprised interdigitated electrodes and a heating resistor. Compared to the standard, constant temperature operation of the sensor, mild heating (e.g., 100 °C together with pulsed UV light irradiation employing a commercially available, 325 nm UV diode (square, 1 min period, 15 mA drive current signal, results in an up to 80-fold enhancement in sensitivity to nitrogen dioxide. Furthermore, this combined operation method allows for making savings in power consumption that range from 35% to over 80%. These results are achieved by exploiting the dynamics of sensor response under pulsed UV light, which convey important information for the quantitative analysis of nitrogen dioxide.

Enhanced detection of nitrogen dioxide via combined heating and pulsed UV operation of indium oxide nano-octahedra.

Science.gov (United States)

Gonzalez, Oriol; Roso, Sergio; Vilanova, Xavier; Llobet, Eduard

2016-01-01

We report on the use of combined heating and pulsed UV light activation of indium oxide gas sensors for enhancing their performance in the detection of nitrogen dioxide in air. Indium oxide nano-octahedra were synthesized at high temperature (900 °C) via vapour-phase transport and screen-printed onto alumina transducers that comprised interdigitated electrodes and a heating resistor. Compared to the standard, constant temperature operation of the sensor, mild heating (e.g., 100 °C) together with pulsed UV light irradiation employing a commercially available, 325 nm UV diode (square, 1 min period, 15 mA drive current signal), results in an up to 80-fold enhancement in sensitivity to nitrogen dioxide. Furthermore, this combined operation method allows for making savings in power consumption that range from 35% to over 80%. These results are achieved by exploiting the dynamics of sensor response under pulsed UV light, which convey important information for the quantitative analysis of nitrogen dioxide.

Random Sequence for Optimal Low-Power Laser Generated Ultrasound

Science.gov (United States)

Vangi, D.; Virga, A.; Gulino, M. S.

2017-08-01

Low-power laser generated ultrasounds are lately gaining importance in the research world, thanks to the possibility of investigating a mechanical component structural integrity through a non-contact and Non-Destructive Testing (NDT) procedure. The ultrasounds are, however, very low in amplitude, making it necessary to use pre-processing and post-processing operations on the signals to detect them. The cross-correlation technique is used in this work, meaning that a random signal must be used as laser input. For this purpose, a highly random and simple-to-create code called T sequence, capable of enhancing the ultrasound detectability, is introduced (not previously available at the state of the art). Several important parameters which characterize the T sequence can influence the process: the number of pulses Npulses , the pulse duration δ and the distance between pulses dpulses . A Finite Element FE model of a 3 mm steel disk has been initially developed to analytically study the longitudinal ultrasound generation mechanism and the obtainable outputs. Later, experimental tests have shown that the T sequence is highly flexible for ultrasound detection purposes, making it optimal to use high Npulses and δ but low dpulses . In the end, apart from describing all phenomena that arise in the low-power laser generation process, the results of this study are also important for setting up an effective NDT procedure using this technology.

Magnetic resonance imaging in pediatric appendicitis: a systematic review

International Nuclear Information System (INIS)

Moore, Michael M.; Methratta, Sosamma T.; Kulaylat, Afif N.; Engbrecht, Brett W.; Hollenbeak, Christopher S.; Dillman, Jonathan R.

2016-01-01

Magnetic resonance imaging for the evaluation of appendicitis in children has rapidly increased recently. This change has been primarily driven by the desire to avoid CT radiation dose. This meta-analysis reviews the diagnostic performance of MRI for pediatric appendicitis and discusses current knowledge of cost-effectiveness. We used a conservative Haldane correction statistical method and found pooled diagnostic parameters including a sensitivity of 96.5% (95% confidence interval [CI]: 94.3-97.8%), specificity of 96.1% (95% CI: 93.5-97.7%), positive predictive value of 92.0% (95% CI: 89.3-94.0%) and negative predictive value of 98.3% (95% CI: 97.3-99.0%), based on 11 studies. Assessment of patient outcomes associated with MRI use at two institutions indicates that time to antibiotics was 4.7 h and 8.2 h, time to appendectomy was 9.1 h and 13.9 h, and negative appendectomy rate was 3.1% and 1.4%, respectively. Alternative diagnoses were present in ∝20% of cases, most commonly adnexal cysts and enteritis/colitis. Regarding technique, half-acquisition single-shot fast spin-echo (SSFSE) pulse sequences are crucial. While gadolinium-enhanced T1-weighted pulse sequences might be helpful, any benefit beyond non-contrast MRI has not been confirmed. Balanced steady-state free precession (SSFP) sequences are generally noncontributory. Protocols do not need to exceed five sequences; four-sequence protocols are commonly utilized. Sedation generally is not indicated; patients younger than 5 years might be attempted based on the child's ability to cooperate. A comprehensive pediatric cost-effectiveness analysis that includes both direct and indirect costs is needed. (orig.)

A multi-slice gradient sequence for contrast enhanced MR diagnosis of intracranial tumours

International Nuclear Information System (INIS)

Schoerner, W.; Sander, B.; Kornmesser, W.; Laniado, M.; Nakamura, T.; Felix, R.

1988-01-01

A multi-slice gradient echo sequence (FLASH) was compared with a conventional spin-echo (SE) technique with regard to its value for contrast enhanced MR diagnosis. In 28 patients with cerebral tumours, SE images (SE 400/30; four images/3.4 minutes) and FLASH images (FLASH 315/14; 15 images/1.4 minutes) were obtained before and after gadolinium DTPA. After gadolinium-DTPA results were comparable for both techniques with respect to contrast enhancement, tumor contrast and delineation. Because of the higher efficiency of the FLASH 315/14 technique, this sequence is the method of choice for contrast enhanced cerebral MR imaging. (orig.) [de

Fat-saturated, contrast-enhanced spin echo sequences in magnetic resonance tomographic diagnosis of peritoneal carcinosis

International Nuclear Information System (INIS)

Ricke, J.; Hosten, N.; Stroszczynski, C.; Amthauer, H.; Felix, R.; Sehouli, J.; Buchmann, E.; Rieger, J.

1999-01-01

Purpose: To evaluate contrast-enhanced, fat-saturated spin echo sequences for the detection of peritoneal carcinosis with MRI. Material and Methods: 61 patients, 35 with and 26 without peritoneal carcinosis, were examined with abdominal MRI. Fat-saturated, T 1 -weighted spin echo sequences were performed before and after administration of Gd-DTPA. In addition, 22 patients with peritoneal carcinosis were examined with contrast-enhanced abdominal CT. Results: 32 of 35 patients with peritoneal carcinosis demonstrated contrast enhancement of the visceral and 30 to 35 enhancement of the parietal peritoneum (91 and 86%, respectively). Wall thickening of the intestine or parietal peritoneum were noted in 21 and 20 of 35 patients (60 and 57%, respectively), ascites in 18 of 35 patients (51%). False positive contrast enhancement of the peritoneum was noted in 4 of 26 patients (15%). In the direct comparison of MRI and CT, 22 of 22 patients versus 7 of 22 patients showed contrast enhancement of the visceral peritoneum (100 and 32%, respectively). For other signs of peritoneal carcinosis (e.g., ascites, peritoneal seedings), no differences in diagnostic reliability were demonstrated. Conclusions: The use of fat-saturated, spin echo sequences facilitates the diagnosis of peritoneal carcinosis by artifact reduction and improved detection of peritoneal contrast enhancement. MRI with fat-saturated sequences was superior to CT. (orig.) [de

Comparison of MRI pulse sequences for investigation of lesions of the cervical spinal cord

International Nuclear Information System (INIS)

Campi, A.; Pontesilli, S.; Gerevini, S.; Scotti, G.

2000-01-01

Small spinal cord lesions, even if clinically significant, can be due to the low sensitivity of some pulse sequences. We compared T2-weighted fast (FSE), and conventional (CSE) spin-echo and short-tau inversion-recovery (STIR)-FSE overlooked on MRI sequences to evaluate their sensitivity to and specificity for lesions of different types. We compared the three sequences in MRI of 57 patients with cervical spinal symptoms. The image sets were assessed by two of us individually for final diagnosis, lesion detectability and image quality. Both readers arrived at the same final diagnoses with all sequences, differentiating four groups of patients. Group 1 (30 patients, 53 %), with a final diagnosis of multiple sclerosis (MS). Demyelinating lesions were better seen on STIR-FSE images, on which the number of lesions was significantly higher than on FSE, while the FSE and CSE images showed approximately equal numbers of lesions; additional lesions were found in 9 patients. The contrast-to-noise ratio (CNR) of 17 demyelinating lesions was significantly higher on STIR-FSE images than with the other sequences. Group 2, 19 patients (33 %) with cervical pain, 15 of whom had disc protrusion or herniation: herniated discs were equally well delineated with all sequences, with better myelographic effect on FSE. In five patients with intrinsic spinal cord abnormalities, the conspicuity and demarcation of the lesions were similar with STIR-FSE and FSE. Group 3, 4 patients (7 %) with acute myelopathy of unknown aetiology. In two patients, STIR-FSE gave better demarcation of lesions and in one a questionable additional lesions. Group 4, 4 patients (7 %) with miscellaneous final diagnoses. STIR-FSE had high sensitivity to demyelinating lesions, can be considered quite specific and should be included in spinal MRI for assessment of suspected demyelinating disease. (orig.)

Resonant-enhanced above-threshold ionization of atoms by XUV short laser pulses

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, V.D. [Departamento de Fisica, FCEyN, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina)], E-mail: vladimir@df.uba.ar; Macri, P.A. [Instituto de Investigaciones Fisicas de Mar del Plata (IFIMAR), Departamento de Fisica, FCEyN, Universidad Nacional de Mar del Plata, CONICET, Funes 3350, 7600 Mar del Plata (Argentina); Arbo, D.G. [Instituto de Astronomia y Fisica del Espacio, UBA-CONICET, CC 67 Suc 28 Buenos Aires (Argentina)

2009-01-15

Above-threshold ionization of atoms by XUV short laser pulses is investigated close to the resonant 1s-2p transitions. Both ab initio TDSE and a theoretical Coulomb-Volkov like theory are used to study the enhancement in the ionization probabilities. Our modified Coulomb-Volkov theory, fully accounting for the important 1s-2p transition is able to explain the spectrum as well as the total ionization cross sections.

High repetition rate tunable femtosecond pulses and broadband amplification from fiber laser pumped parametric amplifier.

Science.gov (United States)

Andersen, T V; Schmidt, O; Bruchmann, C; Limpert, J; Aguergaray, C; Cormier, E; Tünnermann, A

2006-05-29

We report on the generation of high energy femtosecond pulses at 1 MHz repetition rate from a fiber laser pumped optical parametric amplifier (OPA). Nonlinear bandwidth enhancement in fibers provides the intrinsically synchronized signal for the parametric amplifier. We demonstrate large tunability extending from 700 nm to 1500 nm of femtosecond pulses with pulse energies as high as 1.2 muJ when the OPA is seeded by a supercontinuum generated in a photonic crystal fiber. Broadband amplification over more than 85 nm is achieved at a fixed wavelength. Subsequent compression in a prism sequence resulted in 46 fs pulses. With an average power of 0.5 W these pulses have a peak-power above 10 MW. In particular, the average power and pulse energy scalability of both involved concepts, the fiber laser and the parametric amplifier, will enable easy up-scaling to higher powers.

Non-contrast CT at comparable dose to an abdominal radiograph in patients with acute renal colic; impact of iterative reconstruction on image quality and diagnostic performance.

LENUS (Irish Health Repository)

McLaughlin, P D

2014-04-01

The aim was to assess the performance of low-dose non-contrast CT of the urinary tract (LD-CT) acquired at radiation exposures close to that of abdominal radiography using adaptive statistical iterative reconstruction (ASiR).

Non-enhanced MR imaging of cerebral aneurysms: 7 Tesla versus 1.5 Tesla.

Science.gov (United States)

Wrede, Karsten H; Dammann, Philipp; Mönninghoff, Christoph; Johst, Sören; Maderwald, Stefan; Sandalcioglu, I Erol; Müller, Oliver; Özkan, Neriman; Ladd, Mark E; Forsting, Michael; Schlamann, Marc U; Sure, Ulrich; Umutlu, Lale

2014-01-01

To prospectively evaluate 7 Tesla time-of-flight (TOF) magnetic resonance angiography (MRA) in comparison to 1.5 Tesla TOF MRA and 7 Tesla non-contrast enhanced magnetization-prepared rapid acquisition gradient-echo (MPRAGE) for delineation of unruptured intracranial aneurysms (UIA). Sixteen neurosurgical patients (male n = 5, female n = 11) with single or multiple UIA were enrolled in this trial. All patients were accordingly examined at 7 Tesla and 1.5 Tesla MRI utilizing dedicated head coils. The following sequences were obtained: 7 Tesla TOF MRA, 1.5 Tesla TOF MRA and 7 Tesla non-contrast enhanced MPRAGE. Image analysis was performed by two radiologists with regard to delineation of aneurysm features (dome, neck, parent vessel), presence of artifacts, vessel-tissue-contrast and overall image quality. Interobserver accordance and intermethod comparisons were calculated by kappa coefficient and Lin's concordance correlation coefficient. A total of 20 intracranial aneurysms were detected in 16 patients, with two patients showing multiple aneurysms (n = 2, n = 4). Out of 20 intracranial aneurysms, 14 aneurysms were located in the anterior circulation and 6 aneurysms in the posterior circulation. 7 Tesla MPRAGE imaging was superior over 1.5 and 7 Tesla TOF MRA in the assessment of all considered aneurysm and image quality features (e.g. image quality: mean MPRAGE7T: 5.0; mean TOF7T: 4.3; mean TOF1.5T: 4.3). Ratings for 7 Tesla TOF MRA were equal or higher over 1.5 Tesla TOF MRA for all assessed features except for artifact delineation (mean TOF7T: 4.3; mean TOF1.5T 4.4). Interobserver accordance was good to excellent for most ratings. 7 Tesla MPRAGE imaging demonstrated its superiority in the detection and assessment of UIA as well as overall imaging features, offering excellent interobserver accordance and highest scores for all ratings. Hence, it may bear the potential to serve as a high-quality diagnostic tool for pretherapeutic assessment and

{sup 1}H HR-MAS NMR and S180 cells: metabolite assignment and evaluation of pulse sequence

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Aline L. de; Martinelli, Bruno César B.; Lião, Luciano M. [Universidade Federal de Goiás (UFG), Goiânia, GO (Brazil). Instituto de Química. Lab. de RMN; Pereira, Flávia C.; Silveira-Lacerda, Elisangela P. [Universidade Federal de Goiás (UFG), Goiânia, GO (Brazil). Instituto de Ciências Biológicas. Laboratório Genética Molecular e Citogenética; Alcantara, Glaucia B., E-mail: glaucia.alcantara@ufms.br [Universidade Federal de Mato Grosso do Sul (UFMS), Campo Grande, MS (Brazil). Inst. de Química

2014-07-01

High resolution magic angle spinning {sup 1}H nuclear magnetic resonance spectroscopy (HR-MAS NMR) is a useful technique for evaluation of intact cells and tissues. However, optimal NMR parameters are crucial in obtaining reliable results. To identify the key steps for the optimization of HR-MAS NMR parameters, we assessed different pulse sequences and NMR parameters using sarcoma 180 (S180) cells. A complete assignment of the metabolites of S180 is given to assist future studies. (author)

Effect of laser pulse energies in laser induced breakdown spectroscopy in double-pulse configuration

International Nuclear Information System (INIS)

Benedetti, P.A.; Cristoforetti, G.; Legnaioli, S.; Palleschi, V.; Pardini, L.; Salvetti, A.; Tognoni, E.

2005-01-01

In this paper, the effect of laser pulse energy on double-pulse laser induced breakdown spectroscopy signal is studied. In particular, the energy of the first pulse has been changed, while the second pulse energy is held fixed. A systematic study of the laser induced breakdown spectroscopy signal dependence on the interpulse delay is performed, and the results are compared with the ones obtained with a single laser pulse of energy corresponding to the sum of the two pulses. At the same time, the crater formed at the target surface is studied by video-confocal microscopy, and the variation in crater dimensions is correlated to the enhancement of the laser induced breakdown spectroscopy signal. The results obtained are consistent with the interpretation of the double-pulse laser induced breakdown spectroscopy signal enhancement in terms of the changes in ambient gas pressure produced by the shock wave induced by the first laser pulse

Ejector-Enhanced, Pulsed, Pressure-Gain Combustor

Science.gov (United States)

Paxson, Daniel E.; Dougherty, Kevin T.

2009-01-01

An experimental combination of an off-the-shelf valved pulsejet combustor and an aerodynamically optimized ejector has shown promise as a prototype of improved combustors for gas turbine engines. Despite their name, the constant pressure combustors heretofore used in gas turbine engines exhibit typical pressure losses ranging from 4 to 8 percent of the total pressures delivered by upstream compressors. In contrast, the present ejector-enhanced pulsejet combustor exhibits a pressure rise of about 3.5 percent at overall enthalpy and temperature ratios compatible with those of modern turbomachines. The modest pressure rise translates to a comparable increase in overall engine efficiency and, consequently, a comparable decrease in specific fuel consumption. The ejector-enhanced pulsejet combustor may also offer potential for reducing the emission of harmful exhaust compounds by making it practical to employ a low-loss rich-burn/quench/lean-burn sequence. Like all prior concepts for pressure-gain combustion, the present concept involves an approximation of constant-volume combustion, which is inherently unsteady (in this case, more specifically, cyclic). The consequent unsteadiness in combustor exit flow is generally regarded as detrimental to the performance of downstream turbomachinery. Among other adverse effects, this unsteadiness tends to detract from the thermodynamic benefits of pressure gain. Therefore, it is desirable in any intermittent combustion process to minimize unsteadiness in the exhaust path.

Intra-pulse laser absorption sensor with cavity enhancement for oxidation experiments in a rapid compression machine

KAUST Repository

Nasir, Ehson Fawad; Farooq, Aamir

2018-01-01

A sensor based on a mid-IR pulsed quantum cascade laser (QCL) and off-axis cavity enhanced absorption spectroscopy (OA-CEAS) has been developed for highly sensitive concentration measurements of carbon monoxide (CO) in a rapid compression machine

Pulse current enhanced electrodialytic soil remediation

DEFF Research Database (Denmark)

Sun, Tian R.; Ottosen, Lisbeth M.; Jensen, Pernille E.

2012-01-01

Energy consumption is an important factor influencing the cost of electrodialytic soil remediation (EDR). It has been indicated that the pulse current (in low frequency range) could decrease the energy consumption during EDR. This work is focused on the comparison of energy saving effect at diffe......Energy consumption is an important factor influencing the cost of electrodialytic soil remediation (EDR). It has been indicated that the pulse current (in low frequency range) could decrease the energy consumption during EDR. This work is focused on the comparison of energy saving effect...

A Bit Stream Scalable Speech/Audio Coder Combining Enhanced Regular Pulse Excitation and Parametric Coding

Directory of Open Access Journals (Sweden)

Albertus C. den Brinker

2007-01-01

Full Text Available This paper introduces a new audio and speech broadband coding technique based on the combination of a pulse excitation coder and a standardized parametric coder, namely, MPEG-4 high-quality parametric coder. After presenting a series of enhancements to regular pulse excitation (RPE to make it suitable for the modeling of broadband signals, it is shown how pulse and parametric codings complement each other and how they can be merged to yield a layered bit stream scalable coder able to operate at different points in the quality bit rate plane. The performance of the proposed coder is evaluated in a listening test. The major result is that the extra functionality of the bit stream scalability does not come at the price of a reduced performance since the coder is competitive with standardized coders (MP3, AAC, SSC.

A Bit Stream Scalable Speech/Audio Coder Combining Enhanced Regular Pulse Excitation and Parametric Coding

Science.gov (United States)

Riera-Palou, Felip; den Brinker, Albertus C.

2007-12-01

This paper introduces a new audio and speech broadband coding technique based on the combination of a pulse excitation coder and a standardized parametric coder, namely, MPEG-4 high-quality parametric coder. After presenting a series of enhancements to regular pulse excitation (RPE) to make it suitable for the modeling of broadband signals, it is shown how pulse and parametric codings complement each other and how they can be merged to yield a layered bit stream scalable coder able to operate at different points in the quality bit rate plane. The performance of the proposed coder is evaluated in a listening test. The major result is that the extra functionality of the bit stream scalability does not come at the price of a reduced performance since the coder is competitive with standardized coders (MP3, AAC, SSC).

Gadolinium-enhanced MR imaging of the wrist in rheumatoid arthritis: value of fat suppression pulse sequences

International Nuclear Information System (INIS)

Nakahara, N.; Uetani, M.; Hayashi, K.; Kawahara, Y.; Matsumoto, T.; Oda, J.

1996-01-01

Objective. To determine the usefulness of fat-suppressed gadolinium (Gd)-enhanced MR imaging of the wrist in patients with rheumatoid arthritis (RA). Design and patients. Fat-suppressed Gd-enhanced T1-weighted spin-echo (SE) images were obtained and compared with other standard techniques in 38 wrists of 27 patients (22-77 years) with RA. Scoring based on the degree of synovial enhancement of each joint was developed and the total scores (J-score) were correlated with radiographic stage, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and symptomatic change in the follow-up study. Results. Synovial proliferations showed marked enhancement in all the wrists. In addition, contrast enhancement in the bone marrow and tenosynovium was seen in 36 and eight wrists respectively. Fat-suppressed Gd-enhanced T1-weighted images demonstrated these abnormalities better than other techniques. The J-scores correlated well with values of CRP (P=0.0034), but not with radiographic stages and ESR. Conclusion. Fat-suppressed Gd-enhanced T1-weighted SE images can clearly demonstrate most of the essential lesions in RA including the proliferative synovium, bone erosion, bone marrow inflammatory change, and tenosynovitis. Scoring based on the extent of Gd-enhancement of synovium can be useful in the assessment of the inflammatory status. (orig.). With 8 figs

Gadolinium-enhanced MR imaging of the wrist in rheumatoid arthritis: value of fat suppression pulse sequences

Energy Technology Data Exchange (ETDEWEB)

Nakahara, N. [Department of Radiology, Nagasaki University School of Medicine, Sakamoto 1-7-1, Nagasaki 852 (Japan); Uetani, M. [Department of Radiology, Nagasaki University School of Medicine, Sakamoto 1-7-1, Nagasaki 852 (Japan); Hayashi, K. [Department of Radiology, Nagasaki University School of Medicine, Sakamoto 1-7-1, Nagasaki 852 (Japan); Kawahara, Y. [Department of Radiology, Nagasaki University School of Medicine, Sakamoto 1-7-1, Nagasaki 852 (Japan); Matsumoto, T. [Department of Orthopedics, Nagasaki University School of Medicine, Nagasaki (Japan); Oda, J. [Department of Orthopedics, Nagasaki University School of Medicine, Nagasaki (Japan)

1996-10-01

Objective. To determine the usefulness of fat-suppressed gadolinium (Gd)-enhanced MR imaging of the wrist in patients with rheumatoid arthritis (RA). Design and patients. Fat-suppressed Gd-enhanced T1-weighted spin-echo (SE) images were obtained and compared with other standard techniques in 38 wrists of 27 patients (22-77 years) with RA. Scoring based on the degree of synovial enhancement of each joint was developed and the total scores (J-score) were correlated with radiographic stage, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and symptomatic change in the follow-up study. Results. Synovial proliferations showed marked enhancement in all the wrists. In addition, contrast enhancement in the bone marrow and tenosynovium was seen in 36 and eight wrists respectively. Fat-suppressed Gd-enhanced T1-weighted images demonstrated these abnormalities better than other techniques. The J-scores correlated well with values of CRP (P=0.0034), but not with radiographic stages and ESR. Conclusion. Fat-suppressed Gd-enhanced T1-weighted SE images can clearly demonstrate most of the essential lesions in RA including the proliferative synovium, bone erosion, bone marrow inflammatory change, and tenosynovitis. Scoring based on the extent of Gd-enhancement of synovium can be useful in the assessment of the inflammatory status. (orig.). With 8 figs.

Enhancing caries resistance with a short-pulsed CO2 9.3-μm laser: a laboratory study (Conference Presentation)

Science.gov (United States)

Rechmann, Peter; Rechmann, Beate M.; Groves, William H.; Le, Charles; Rapozo-Hilo, Marcia L.; Featherstone, John D. B.

2016-02-01

The objective of this laboratory study was to test whether irradiation with a new 9.3µm microsecond short-pulsed CO2-laser enhances enamel caries resistance with and without additional fluoride applications. 101 human enamel samples were divided into 7 groups. Each group was treated with different laser parameters (Carbon-dioxide laser, wavelength 9.3µm, 43Hz pulse-repetition rate, pulse duration between 3μs to 7μs (1.5mJ/pulse to 2.9mJ/pulse). Using a pH-cycling model and cross-sectional microhardness testing determined the mean relative mineral loss delta Z (∆Z) for each group. The pH-cycling was performed with or without additional fluoride. The CO2 9.3μm short-pulsed laser energy rendered enamel caries resistant with and without additional fluoride use.

MR imaging of spine and spinal canal neoplasms: value of Gd-DTPA contrast enhancement

International Nuclear Information System (INIS)

Paprzycki, W.; Gradzki, J.; Sosnowski, P.; Stajgis, M.

1994-01-01

Value of Gadolinium-DTPA contrast enhancement in diagnosis of neoplastic diseases of spinal canal was estimated on the basis of retrospective analysis of MR examinations performed in 75 patients. The analyzed material consisted of 15 cases of intramedullary tumors (group 1.), 38 of subdural extramedullary (group 2.) and 22 extradural ones (group 3.). Contrast enhanced MR contributed significant information to the final diagnosis in all groups. The utmost significance of Gd-DTPA contrast enhancement was ascertained in group 1. Authors conclude that contrast enhancement with Gd-DTPA is indispensable in all these cases of spinal canal neoplasms, where non-contrast MR did not reveal pathologic changes in optimal manner. (author)

Third Harmonic Imaging using a Pulse Inversion

DEFF Research Database (Denmark)

Rasmussen, Joachim; Du, Yigang; Jensen, Jørgen Arendt

2011-01-01

The pulse inversion (PI) technique can be utilized to separate and enhance harmonic components of a waveform for tissue harmonic imaging. While most ultrasound systems can perform pulse inversion, only few image the 3rd harmonic component. PI pulse subtraction can isolate and enhance the 3rd...

Diagnostic value of magnetic resonance imaging and the pathologic basis of parotid Warthin's tumor in 46 cases

International Nuclear Information System (INIS)

Yuan Jianpeng; Huang Suiqiao; Xie Bangkun; Zhong Jinglian; Li Yong

2004-01-01

Objective: To summarize MR manifestations of parotid Warthin's tumor and to investigate their pathological fundament. MR findings of parotid Warthin's tumor including shape, margin, signal intensity on T 1 WI and T 2 WI, homogeneity of the signal, enhancement were analyzed retrospectively in this study. Methods: In total 46 cases (54 lesions) of parotid Warthin's tumor proved by surgery were enrolled. MRI manifestations were comparatively studied with pathological findings. T 1 WI and T 2 WI sequence were used in non-contrast scan, while both non-contrast and enhanced scan were performed in 50 lesions out of 54. Results: The shapes of Warthin's tumor were regular (51/54); the edges were clear (54/54); more than half of the lesions (33/54) presented with low or equal signal intensity on T 2 WI; 50 Warthin's tumors enhanced slightly. The MR features of Warthin's tumors were different from pleomorphic adenoma and other parotid benign tumors. Conclusion: There are certain characteristics of Warthin's tumors on MR images, and these are helpful in determining the histological nature of the tumor

Control of concerted two bond versus single bond dissociation in CH3Co(CO)4 via an intermediate state using pump-dump laser pulses

Science.gov (United States)

Ambrosek, David; González, Leticia

2007-10-01

Wavepacket propagations on ab initio multiconfigurational two-dimensional potential energy surfaces for CH3Co(CO)4 indicate that after irradiation to the lowest first and second electronic excited states, concerted dissociation of CH3 and the axial CO ligand takes place. We employ a pump-dump sequence of pulses with appropriate frequencies and time delays to achieve the selective breakage of a single bond by controlling the dissociation angle. The pump and dump pulse sequence exploits the unbound surface where dissociation occurs in a counterintuitive fashion; stretching of one bond in an intermediate state enhances the single dissociation of the other bond.

Control of concerted two bond versus single bond dissociation in CH(3)Co(CO)(4) via an intermediate state using pump-dump laser pulses.

Science.gov (United States)

Ambrosek, David; González, Leticia

2007-10-07

Wavepacket propagations on ab initio multiconfigurational two-dimensional potential energy surfaces for CH(3)Co(CO)(4) indicate that after irradiation to the lowest first and second electronic excited states, concerted dissociation of CH(3) and the axial CO ligand takes place. We employ a pump-dump sequence of pulses with appropriate frequencies and time delays to achieve the selective breakage of a single bond by controlling the dissociation angle. The pump and dump pulse sequence exploits the unbound surface where dissociation occurs in a counterintuitive fashion; stretching of one bond in an intermediate state enhances the single dissociation of the other bond.

Enhanced discrimination of highly clonal ST22-methicillin-resistant Staphylococcus aureus IV isolates achieved by combining spa, dru, and pulsed-field gel electrophoresis typing data.

LENUS (Irish Health Repository)

Shore, Anna C

2010-05-01

ST22-methicillin-resistant Staphylococcus aureus type IV (ST22-MRSA-IV) is endemic in Irish hospitals and is designated antibiogram-resistogram type-pulsed-field group (AR-PFG) 06-01. Isolates of this highly clonal strain exhibit limited numbers of pulsed-field gel electrophoresis (PFGE) patterns and spa types. This study investigated whether combining PFGE and spa typing with DNA sequencing of the staphylococcal cassette chromosome mec element (SCCmec)-associated direct repeat unit (dru typing) would improve isolate discrimination. A total of 173 MRSA isolates recovered in one Irish hospital during periods in 2007 and 2008 were investigated using antibiogram-resistogram (AR), PFGE, spa, dru, and SCCmec typing. Isolates representative of each of the 17 pulsed-field group 01 (PFG-01) spa types identified underwent multilocus sequence typing, and all isolates were ST22. Ninety-seven percent of isolates (168 of 173) exhibited AR-PFG 06-01 or closely related AR patterns, and 163 of these isolates harbored SCCmec type IVh. The combination of PFGE, spa, and dru typing methods significantly improved discrimination of the 168 PFG-01 isolates, yielding 65 type combinations with a Simpson\\'s index of diversity (SID) of 96.53, compared to (i) pairwise combinations of spa and dru typing, spa and PFGE typing, and dru and PFGE typing, which yielded 37, 44, and 43 type combinations with SIDs of 90.84, 91.00, and 93.57, respectively, or (ii) individual spa, dru, and PFGE typing methods, which yielded 17, 17, and 21 types with SIDs of 66.9, 77.83, and 81.34, respectively. Analysis of epidemiological information for a subset of PFG-01 isolates validated the relationships inferred using combined PFGE, spa, and dru typing data. This approach significantly enhances discrimination of ST22-MRSA-IV isolates and could be applied to epidemiological investigations of other highly clonal MRSA strains.

Fc Receptor-Targeting of Immunogen as a Strategy for Enhanced Antigen Loading, Vaccination, and Protection Using Intranasally-Administered Antigen-Pulsed Dendritic Cells

Science.gov (United States)

Pham, Giang H.; Iglesias, Bibiana V.; Gosselin, Edmund J.

2014-01-01

Dendritic cells (DCs) play a critical role in the generation of adaptive immunity via the efficient capture, processing, and presentation of antigen (Ag) to naïve T cells. Administration of Ag-pulsed DCs is also an effective strategy for enhancing immunity to tumors and infectious disease organisms. Studies have also demonstrated that targeting Ags to Fcγ receptors (FcγR) on Ag presenting cells can enhance humoral and cellular immunity in vitro and in vivo. Specifically, our studies using an F. tularensis (Ft) infectious disease vaccine model have demonstrated that targeting immunogens to FcγR via intranasal (i.n.) administration of monoclonal antibody (mAb)-inactivated Ft (iFt) immune complexes (ICs) enhances protection against Ft challenge. Ft is the causative agent of tularemia, a debilitating disease of humans and other mammals and a category A biothreat agent for which there is no approved vaccine. Therefore, using iFt Ag as a model immunogen, we sought to determine if ex vivo targeting of iFt to FcγR on DCs would enhance the potency of i.n. administered iFt-pulsed DCs. In this study, bone marrow-derived DCs (BMDCs) were pulsed ex vivo with iFt or mAb-iFt ICs. Intranasal administration of mAb-iFt-pulsed BMDCs enhanced humoral and cellular immune responses, as well as protection against Ft live vaccine strain (LVS) challenge. Increased protection correlated with increased iFt loading on the BMDC surface as a consequence of FcγR targeting. However, the inhibitory FcγRIIB had no impact on this enhancement. In conclusion, targeting Ag ex vivo to FcγR on DCs provides a method for enhanced Ag loading of DCs ex vivo, thereby reducing the amount of Ag required, while also avoiding the inhibitory impact of FcγRIIB. Thus, this represents a simple and less invasive strategy for increasing the potency of ex vivo-pulsed DC vaccines against chronic infectious diseases and cancer. PMID:25068496

Fc receptor-targeting of immunogen as a strategy for enhanced antigen loading, vaccination, and protection using intranasally administered antigen-pulsed dendritic cells.

Science.gov (United States)

Pham, Giang H; Iglesias, Bibiana V; Gosselin, Edmund J

2014-09-08

Dendritic cells (DCs) play a critical role in the generation of adaptive immunity via the efficient capture, processing, and presentation of antigen (Ag) to naïve T cells. Administration of Ag-pulsed DCs is also an effective strategy for enhancing immunity to tumors and infectious disease organisms. Studies have also demonstrated that targeting Ags to Fcγ receptors (FcγR) on Ag presenting cells can enhance humoral and cellular immunity in vitro and in vivo. Specifically, our studies using a Francisella tularensis (Ft) infectious disease vaccine model have demonstrated that targeting immunogens to FcγR via intranasal (i.n.) administration of monoclonal antibody (mAb)-inactivated Ft (iFt) immune complexes (ICs) enhances protection against Ft challenge. Ft is the causative agent of tularemia, a debilitating disease of humans and other mammals and a category A biothreat agent for which there is no approved vaccine. Therefore, using iFt Ag as a model immunogen, we sought to determine if ex vivo targeting of iFt to FcγR on DCs would enhance the potency of i.n. administered iFt-pulsed DCs. In this study, bone marrow-derived DCs (BMDCs) were pulsed ex vivo with iFt or mAb-iFt ICs. Intranasal administration of mAb-iFt-pulsed BMDCs enhanced humoral and cellular immune responses, as well as protection against Ft live vaccine strain (LVS) challenge. Increased protection correlated with increased iFt loading on the BMDC surface as a consequence of FcγR-targeting. However, the inhibitory FcγRIIB had no impact on this enhancement. In conclusion, targeting Ag ex vivo to FcγR on DCs provides a method for enhanced Ag loading of DCs ex vivo, thereby reducing the amount of Ag required, while also avoiding the inhibitory impact of FcγRIIB. Thus, this represents a simple and less invasive strategy for increasing the potency of ex vivo-pulsed DC vaccines against chronic infectious diseases and cancer. Copyright © 2014 Elsevier Ltd. All rights reserved.

In situ detection of a heat-shock regulatory element binding protein using a soluble short synthetic enhancer sequence

Energy Technology Data Exchange (ETDEWEB)

Harel-Bellan, A; Brini, A T; Farrar, W L [National Cancer Institute, Frederick, MD (USA); Ferris, D K [Program Resources, Inc., Frederick, MD (USA); Robin, P [Institut Gustave Roussy, Villejuif (France)

1989-06-12

In various studies, enhancer binding proteins have been successfully absorbed out by competing sequences inserted into plasmids, resulting in the inhibition of the plasmid expression. Theoretically, such a result could be achieved using synthetic enhancer sequences not inserted into plasmids. In this study, a double stranded DNA sequence corresponding to the human heat shock regulatory element was chemically synthesized. By in vitro retardation assays, the synthetic sequence was shown to bind specifically a protein in extracts from the human T cell line Jurkat. When the synthetic enhancer was electroporated into Jurkat cells, not only the enhancer was shown to remain undegraded into the cells for up to 2 days, but also its was shown to bind intracellularly a protein. The binding was specific and was modulated upon heat shock. Furthermore, the binding protein was shown to be of the expected molecular weight by UV crosslinking. However, when the synthetic enhancer element was co-electroporated with an HSP 70-CAT reporter construct, the expression of the reporter plasmid was consistently enhanced in the presence of the exogenous synthetic enhancer.

Modeling seismic stimulation: Enhanced non-aqueous fluid extraction from saturated porous media under pore-pressure pulsing at low frequencies

Science.gov (United States)

Lo, Wei-Cheng; Sposito, Garrison; Huang, Yu-Han

2012-03-01

Seismic stimulation, the application of low-frequency stress-pulsing to the boundary of a porous medium containing water and a non-aqueous fluid to enhance the removal of the latter, shows great promise for both contaminated groundwater remediation and enhanced oil recovery, but theory to elucidate the underlying mechanisms lag significantly behind the progress achieved in experimental research. We address this conceptual lacuna by formulating a boundary-value problem to describe pore-pressure pulsing at seismic frequencies that is based on the continuum theory of poroelasticity for an elastic porous medium permeated by two immiscible fluids. An exact analytical solution is presented that is applied numerically using elasticity parameters and hydraulic data relevant to recent proof-of-principle laboratory experiments investigating the stimulation-induced mobilization of trichloroethene (TCE) in water flowing through a compressed sand core. The numerical results indicated that significant stimulation-induced increases of the TCE concentration in effluent can be expected from pore-pressure pulsing in the frequency range of 25-100 Hz, which is in good agreement with what was observed in the laboratory experiments. Sensitivity analysis of our numerical results revealed that the TCE concentration in the effluent increases with the porous medium framework compressibility and the pulsing pressure. Increasing compressibility also leads to an optimal stimulation response at lower frequencies, whereas changing the pulsing pressure does not affect the optimal stimulation frequency. Within the context of our model, the dominant physical cause for enhancement of non-aqueous fluid mobility by seismic stimulation is the dilatory motion of the porous medium in which the solid and fluid phases undergo opposite displacements, resulting in stress-induced changes of the pore volume.

Thin film beam splitter multiple short pulse generation for enhanced Ni-like Ag x-ray laser emission.

Science.gov (United States)

Cojocaru, Gabriel V; Ungureanu, Razvan G; Banici, Romeo A; Ursescu, Daniel; Delmas, Olivier; Pittman, Moana; Guilbaud, Olivier; Kazamias, Sophie; Cassou, Kevin; Demailly, Julien; Neveu, Olivier; Baynard, Elsa; Ros, David

2014-04-15

An alternative, novel multiple pulse generation scheme was implemented directly after the optical compressor output of an x-ray pump laser. The new method uses a polarization sensitive thin film beam splitter and a half-wavelength wave plate for tuning the energy ratio in the multiple short pulses. Based on this method, an extensive study was made of the running parameters for a grazing incidence pumped silver x-ray laser (XRL) pumped with a long pulse of 145 mJ in 6 ns at 532 nm and up to 1.45 J in few picoseconds at 810 nm. Fivefold enhancement in the emission of the silver XRL was demonstrated using the new pump method.

Spectral detector CT-derived virtual non-contrast images: comparison of attenuation values with unenhanced CT.

Science.gov (United States)

Ananthakrishnan, Lakshmi; Rajiah, Prabhakar; Ahn, Richard; Rassouli, Negin; Xi, Yin; Soesbe, Todd C; Lewis, Matthew A; Lenkinski, Robert E; Leyendecker, John R; Abbara, Suhny

2017-03-01

To assess virtual non-contrast (VNC) images obtained on a detection-based spectral detector CT scanner and determine how attenuation on VNC images derived from various phases of enhanced CT compare to those obtained from true unenhanced images. In this HIPAA compliant, IRB approved prospective multi-institutional study, 46 patients underwent pre- and post-contrast imaging on a prototype dual-layer spectral detector CT between October 2013 and November 2015, yielding 84 unenhanced and VNC pairs (25 arterial, 39 portal venous/nephrographic, 20 urographic). Mean attenuation was measured by one of three readers in the liver, spleen, kidneys, psoas muscle, abdominal aorta, and subcutaneous fat. Equivalence testing was used to determine if the mean difference between unenhanced and VNC attenuation was less than 5, 10, or 15 HU. VNC image quality was assessed on a 5 point scale. Mean difference between unenhanced and VNC attenuation was VNC attenuation were equivalent in all tissues except fat using a threshold of VNC overestimated the HU relative to unenhanced images. VNC image quality was rated as excellent or good in 84% of arterial phase and 85% of nephrographic phase cases, but only 40% of urographic phase. VNC images derived from novel dual layer spectral detector CT demonstrate attenuation values similar to unenhanced images in all tissues evaluated except for subcutaneous fat. Further study is needed to determine if attenuation thresholds currently used clinically for common pathology should be adjusted, particularly for lesions containing fat.

Sensitivity of Non-Contrast Computed Tomography for Small Renal Calculi with Endoscopy as the Gold Standard.

Science.gov (United States)

Bhojani, Naeem; Paonessa, Jessica E; El Tayeb, Marawan M; Williams, James C; Hameed, Tariq A; Lingeman, James E

2018-04-03

To compare the sensitivity of non-contrast CT to endoscopy for detection of renal calculi. Imaging modalities for detection of nephrolithiasis have centered on abdominal x-ray (KUB), ultrasound (US), and non-contrast computed tomography (CT). Sensitivities of 58-62% (KUB), 45% (US), and 95-100% (CT) have been previously reported. However, these results have never been correlated with endoscopic findings. Idiopathic calcium oxalate stone formers with symptomatic calculi requiring ureteroscopy (URS) were studied. At the time of surgery, the number and location of all calculi within the kidney were recorded followed by basket retrieval. Each calculus was measured and sent for micro CT and infrared spectrophotometry. All CT scans were reviewed by the same genitourinary radiologist who was blinded to the endoscopic findings. The radiologist reported on the number, location, and size of each calculus. 18 renal units were studied in 11 patients. Average time from CT scan to URS was 28.6 days. The mean number of calculi identified per kidney was 9.2±6.1 for endoscopy and 5.9±4.1 for CT (p<0.004). The mean size of total renal calculi (sum of longest stone diameters) per kidney was 22.4±17.1 mm and 18.2±13.2 mm for endoscopy and CT, respectively (p=0.06). CT scan underreports the number of renal calculi, probably missing some small stones and unable to distinguish those lying in close proximity to one another. However, the total stone burden seen by CT is, on average, accurate when compared to that found on endoscopic examination. Copyright © 2018. Published by Elsevier Inc.

PULSE REFERENCED CONTROL METHOD FOR ENHANCED POWER AMPLIFICATION OF A PULSE MODULATED SIGNAL

DEFF Research Database (Denmark)

1998-01-01

, by introducing continuous delays on the individual pulse edges on the basis of error information provided by an error processing block. One preferred embodiment of the invention comprises: a Correction Unit with means to control the delays of the individual pulse edges as a function of a control input signal $i...

Microjet formation and hard x-ray production from a liquid metal target irradiated by intense femtosecond laser pulses

Energy Technology Data Exchange (ETDEWEB)

Lar' kin, A., E-mail: alexeylarkin@yandex.ru; Uryupina, D.; Ivanov, K.; Savel' ev, A., E-mail: abst@physics.msu.ru [International Laser Center and Faculty of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Bonnet, T.; Gobet, F.; Hannachi, F.; Tarisien, M.; Versteegen, M. [Centre d' Études Nucléaires de Bordeaux-Gradignan, University of Bordeaux-CNRS-IN2P3, 33170 Gradignan (France); Spohr, K. [School of Engineering, University of the West of Scotland, Paisley, Scotland PA1 2BE (United Kingdom); Breil, J.; Chimier, B.; Dorchies, F.; Fourment, C.; Leguay, P.-M.; Tikhonchuk, V. T. [Centre Lasers Intenses et Applications, University of Bordeaux-CNRS-CEA, Talence 33405 (France)

2014-09-15

By using a liquid metal as a target one may significantly enhance the yield of hard x-rays with a sequence of two intense femtosecond laser pulses. The influence of the time delay between the two pulses is studied experimentally and interpreted with numerical simulations. It was suggested that the first arbitrary weak pulse produces microjets from the target surface, while the second intense pulse provides an efficient electron heating and acceleration along the jet surface. These energetic electrons are the source of x-ray emission while striking the target surface. The microjet formation is explained based on the results given by both optical diagnostics and hydrodynamic modeling by a collision of shocks originated from two distinct zones of laser energy deposition.

Microjet formation and hard x-ray production from a liquid metal target irradiated by intense femtosecond laser pulses

International Nuclear Information System (INIS)

Lar'kin, A.; Uryupina, D.; Ivanov, K.; Savel'ev, A.; Bonnet, T.; Gobet, F.; Hannachi, F.; Tarisien, M.; Versteegen, M.; Spohr, K.; Breil, J.; Chimier, B.; Dorchies, F.; Fourment, C.; Leguay, P.-M.; Tikhonchuk, V. T.

2014-01-01

By using a liquid metal as a target one may significantly enhance the yield of hard x-rays with a sequence of two intense femtosecond laser pulses. The influence of the time delay between the two pulses is studied experimentally and interpreted with numerical simulations. It was suggested that the first arbitrary weak pulse produces microjets from the target surface, while the second intense pulse provides an efficient electron heating and acceleration along the jet surface. These energetic electrons are the source of x-ray emission while striking the target surface. The microjet formation is explained based on the results given by both optical diagnostics and hydrodynamic modeling by a collision of shocks originated from two distinct zones of laser energy deposition

Microjet formation and hard x-ray production from a liquid metal target irradiated by intense femtosecond laser pulses

Science.gov (United States)

Lar'kin, A.; Uryupina, D.; Ivanov, K.; Savel'ev, A.; Bonnet, T.; Gobet, F.; Hannachi, F.; Tarisien, M.; Versteegen, M.; Spohr, K.; Breil, J.; Chimier, B.; Dorchies, F.; Fourment, C.; Leguay, P.-M.; Tikhonchuk, V. T.

2014-09-01

By using a liquid metal as a target one may significantly enhance the yield of hard x-rays with a sequence of two intense femtosecond laser pulses. The influence of the time delay between the two pulses is studied experimentally and interpreted with numerical simulations. It was suggested that the first arbitrary weak pulse produces microjets from the target surface, while the second intense pulse provides an efficient electron heating and acceleration along the jet surface. These energetic electrons are the source of x-ray emission while striking the target surface. The microjet formation is explained based on the results given by both optical diagnostics and hydrodynamic modeling by a collision of shocks originated from two distinct zones of laser energy deposition.

Low-intensity pulsed ultrasound enhances bone formation around miniscrew implants.

Science.gov (United States)

Ganzorig, Khaliunaa; Kuroda, Shingo; Maeda, Yuichi; Mansjur, Karima; Sato, Minami; Nagata, Kumiko; Tanaka, Eiji

2015-06-01

Miniscrew implants (MSIs) are currently used to provide absolute anchorage in orthodontics; however, their initial stability is an issue of concern. Application of low-intensity pulsed ultrasound (LIPUS) can promote bone healing. Therefore, LIPUS application may stimulate bone formation around MSIs and enhance their initial stability. To investigate the effect of LIPUS exposure on bone formation after implantation of titanium (Ti) and stainless steel (SS) MSIs. MSIs made of Ti-6Al-4V and 316L SS were placed on rat tibiae and treated with LIPUS. The bone morphology around MSIs was evaluated by scanning electron microscopy and three-dimensional micro-computed tomography. MC3T3-E1 cells cultured on Ti and SS discs were treated with LIPUS, and the temporary expression of alkaline phosphatase (ALP) was examined. Bone-implant contact increased gradually from day 3 to day 14 after MSI insertion. LIPUS application increased the cortical bone density, cortical bone thickness, and cortical bone rate after implantation of Ti and SS MSIs (P<0.05). LIPUS exposure induced ALP upregulation in MC3T3-E1 cells at day 3 (P<0.05). LIPUS enhanced bone formation around Ti and SS MSIs, enhancing the initial stability of MSIs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Controlling semiconductor nanoparticle size distributions with tailored ultrashort pulses

International Nuclear Information System (INIS)

Hergenroeder, R; Miclea, M; Hommes, V

2006-01-01

The laser generation of size-controlled semiconductor nanoparticle formation under gas phase conditions is investigated. It is shown that the size distribution can be changed if picosecond pulse sequences of tailored ultra short laser pulses (<200 fs) are employed. By delivering the laser energy in small packages, a temporal energy flux control at the target surface is achieved, which results in the control of the thermodynamic pathway the material takes. The concept is tested with silicon and germanium, both materials with a predictable response to double pulse sequences, which allows deduction of the materials' response to complicated pulse sequences. An automatic, adaptive learning algorithm was employed to demonstrate a future strategy that enables the definition of more complex optimization targets such as particle size on materials less predictable than semiconductors

Enhancing Food Processing by Pulsed and High Voltage Electric Fields: Principles and Applications.

Science.gov (United States)

Wang, Qijun; Li, Yifei; Sun, Da-Wen; Zhu, Zhiwei

2018-02-02

Improvements in living standards result in a growing demand for food with high quality attributes including freshness, nutrition and safety. However, current industrial processing methods rely on traditional thermal and chemical methods, such as sterilization and solvent extraction, which could induce negative effects on food quality and safety. The electric fields (EFs) involving pulsed electric fields (PEFs) and high voltage electric fields (HVEFs) have been studied and developed for assisting and enhancing various food processes. In this review, the principles and applications of pulsed and high voltage electric fields are described in details for a range of food processes, including microbial inactivation, component extraction, and winemaking, thawing and drying, freezing and enzymatic inactivation. Moreover, the advantages and limitations of electric field related technologies are discussed to foresee future developments in the food industry. This review demonstrates that electric field technology has a great potential to enhance food processing by supplementing or replacing the conventional methods employed in different food manufacturing processes. Successful industrial applications of electric field treatments have been achieved in some areas such as microbial inactivation and extraction. However, investigations of HVEFs are still in an early stage and translating the technology into industrial applications need further research efforts.

Efficient theory of dipolar recoupling in solid-state nuclear magnetic resonance of rotating solids using Floquet-Magnus expansion: application on BABA and C7 radiofrequency pulse sequences.

Science.gov (United States)

Mananga, Eugene S; Reid, Alicia E; Charpentier, Thibault

2012-02-01

This article describes the use of an alternative expansion scheme called Floquet-Magnus expansion (FME) to study the dynamics of spin system in solid-state NMR. The main tool used to describe the effect of time-dependent interactions in NMR is the average Hamiltonian theory (AHT). However, some NMR experiments, such as sample rotation and pulse crafting, seem to be more conveniently described using the Floquet theory (FT). Here, we present the first report highlighting the basics of the Floquet-Magnus expansion (FME) scheme and hint at its application on recoupling sequences that excite more efficiently double-quantum coherences, namely BABA and C7 radiofrequency pulse sequences. The use of Λ(n)(t) functions available only in the FME scheme, allows the comparison of the efficiency of BABA and C7 sequences. Copyright © 2011 Elsevier Inc. All rights reserved.

Cystic angiomatosis with splenic involvement: unusual MRI findings

Energy Technology Data Exchange (ETDEWEB)

Vanhoenacker, F.M. [Dept. of Radiology, Univ. Hospital Antwerp, Edegem (Belgium); Dept. of Radiology, AZ St-Maarten, Campus Duffel, Duffel (Belgium); Schepper, A.M. [Dept. of Radiology, Univ. Hospital Antwerp, Edegem (Belgium); Raeve, H. [Dept. of Pathology, Univ. Hospital Antwerp, Edegem (Belgium); Berneman, Z. [Dept. of Hematology, Univ. Hospital Antwerp, Edegem (Belgium)

2003-12-01

Cystic angiomatosis is a rare disorder with a poor prognosis. We describe a case of a 33-year-old woman who presented with longstanding bone pain, hemolytic anemia, and an enlarged spleen. Radiologically, multiple osseous lesions with a mixed pattern of lytic and sclerotic areas were seen within the shoulders, spine, and pelvis. On CT and MRI of the abdomen, the spleen was markedly enlarged, with internal hyperdense foci on non-contrast CT scan, corresponding to low signal intensity areas on all MR pulse sequences. After administration of contrast, a mottled enhancement pattern throughout the entire spleen was seen both on CT and MRI. Cystic angiomatosis was proven by histological analysis of a biopsy specimen of an involved vertebra and histopathological examination of the spleen after subsequent splenectomy. This is the first report of a patient with disseminated cystic angiomatosis with splenic involvement in which the MRI features differ from the previous reports. Instead of the usual pattern consisting of multiple well-defined cystic lesions, a diffuse involvement replacing the entire spleen, with heterogeneous signal intensities on T2-weighted images and heterogeneous enhancement pattern, was seen in our patient. (orig.)

Cystic angiomatosis with splenic involvement: unusual MRI findings

International Nuclear Information System (INIS)

Vanhoenacker, F.M.; Schepper, A.M.; Raeve, H.; Berneman, Z.

2003-01-01

Cystic angiomatosis is a rare disorder with a poor prognosis. We describe a case of a 33-year-old woman who presented with longstanding bone pain, hemolytic anemia, and an enlarged spleen. Radiologically, multiple osseous lesions with a mixed pattern of lytic and sclerotic areas were seen within the shoulders, spine, and pelvis. On CT and MRI of the abdomen, the spleen was markedly enlarged, with internal hyperdense foci on non-contrast CT scan, corresponding to low signal intensity areas on all MR pulse sequences. After administration of contrast, a mottled enhancement pattern throughout the entire spleen was seen both on CT and MRI. Cystic angiomatosis was proven by histological analysis of a biopsy specimen of an involved vertebra and histopathological examination of the spleen after subsequent splenectomy. This is the first report of a patient with disseminated cystic angiomatosis with splenic involvement in which the MRI features differ from the previous reports. Instead of the usual pattern consisting of multiple well-defined cystic lesions, a diffuse involvement replacing the entire spleen, with heterogeneous signal intensities on T2-weighted images and heterogeneous enhancement pattern, was seen in our patient. (orig.)

Optimal pulse spacing for dynamical decoupling in the presence of a purely dephasing spin bath

International Nuclear Information System (INIS)

Ajoy, Ashok; Alvarez, Gonzalo A.; Suter, Dieter

2011-01-01

Maintaining quantum coherence is a crucial requirement for quantum computation; hence protecting quantum systems against their irreversible corruption due to environmental noise is an important open problem. Dynamical decoupling (DD) is an effective method for reducing decoherence with a low control overhead. It also plays an important role in quantum metrology, where, for instance, it is employed in multiparameter estimation. While a sequence of equidistant control pulses [the Carr-Purcell-Meiboom-Gill (CPMG) sequence] has been ubiquitously used for decoupling, Uhrig recently proposed that a nonequidistant pulse sequence [the Uhrig dynamic decoupling (UDD) sequence] may enhance DD performance, especially for systems where the spectral density of the environment has a sharp frequency cutoff. On the other hand, equidistant sequences outperform UDD for soft cutoffs. The relative advantage provided by UDD for intermediate regimes is not clear. In this paper, we analyze the relative DD performance in this regime experimentally, using solid-state nuclear magnetic resonance. Our system qubits are 13 C nuclear spins and the environment consists of a 1 H nuclear spin bath whose spectral density is close to a normal (Gaussian) distribution. We find that in the presence of such a bath, the CPMG sequence outperforms the UDD sequence. An analogy between dynamical decoupling and interference effects in optics provides an intuitive explanation as to why the CPMG sequence performs better than any nonequidistant DD sequence in the presence of this kind of environmental noise.

NON-CONTRAST MAGNETIC RESONANCE UROGRAPHY

Directory of Open Access Journals (Sweden)

Arpita C

2016-07-01

Full Text Available BACKGROUND AND PURPOSE Magnetic Resonance (MR urography with its optimal contrast resolution and lack of ionizing radiation provides a comprehensive examination of the entire urinary tract noninvasively. MR urography is clinically useful in the evaluation of suspected urinary tract obstruction, haematuria, congenital anomalies, and surgically altered anatomy. It is particularly useful in cases of where there is contraindication of ionizing radiation and in paediatric and pregnant patients. The common MR urographic techniques are: Static-fluid MR urography and excretory MR urography. Static-fluid MR urography uses of heavily T2-weighted sequences to image the urinary tract as a static collection of fluid, can be repeated sequentially (Cine MR urography to better demonstrate the ureters in their entirety and to confirm the presence of fixed stenoses. Excretory MR urography is performed during the excretory phase of enhancement after the intravenous administration of gadolinium-based contrast material; thus, the patient must have sufficient renal function to allow the excretion. Static-fluid and excretory MR urography can be combined with conventional MR imaging for comprehensive evaluation of the urinary tract. The limitations are limited availability, high cost, relatively long examination time, low spatial resolution compared to IVU (Intravenous Urogram and CT Urography; sensitivity to motion (breathing and ureteral peristalsis inherent contraindications like patients with pacemakers, claustrophobia, and relative insensitivity for calcification and ureteric calculi. In this article, an attempt has been made to demonstrate the potential of static-fluid MRU to demonstrate a spectrum of urologic pathology involving the kidneys, ureters, and bladder while discussing the limitations. METHODS Thirty patients with urinary tract abnormalities were evaluated with MR urography performed between May 2014 to April 2016 using routine MR sequences and

Observation of enhanced infrared absorption in silicon supersaturated with gold by pulsed laser melting of nanometer-thick gold films

Science.gov (United States)

Chow, Philippe K.; Yang, Wenjie; Hudspeth, Quentin; Lim, Shao Qi; Williams, Jim S.; Warrender, Jeffrey M.

2018-04-01

We demonstrate that pulsed laser melting (PLM) of thin 1, 5, and 10 nm-thick vapor-deposited gold layers on silicon enhances its room-temperature sub-band gap infrared absorption, as in the case of ion-implanted and PLM-treated silicon. The former approach offers reduced fabrication complexity and avoids implantation-induced lattice damage compared to ion implantation and pulsed laser melting, while exhibiting comparable optical absorptance. We additionally observed strong broadband absorptance enhancement in PLM samples made using 5- and 10-nm-thick gold layers. Raman spectroscopy and Rutherford backscattering analysis indicate that such an enhancement could be explained by absorption by a metastable, disordered and gold-rich surface layer. The sheet resistance and the diode electrical characteristics further elucidate the role of gold-supersaturation in silicon, revealing the promise for future silicon-based infrared device applications.

Development of a Three-dimensional Surgical Navigation System with Magnetic Resonance Angiography and a Three-dimensional Printer for Robot-assisted Radical Prostatectomy.

Science.gov (United States)

Jomoto, Wataru; Tanooka, Masao; Doi, Hiroshi; Kikuchi, Keisuke; Mitsuie, Chiemi; Yamada, Yusuke; Suzuki, Toru; Yamano, Toshiko; Ishikura, Reiichi; Kotoura, Noriko; Yamamoto, Shingo

2018-01-02

We sought to develop a surgical navigation system using magnetic resonance angiography (MRA) and a three-dimensional (3D) printer for robot-assisted radical prostatectomy (RARP). Six patients with pathologically proven localized prostate cancer were prospectively enrolled in this study. Prostate magnetic resonance imaging (MRI), consisting of T2-weighted sampling perfection with application-optimized contrasts using different flip-angle evolutions (SPACE) and true fast imaging with steady-state precession (true FISP), reconstructed by volume rendering, was followed by dynamic contrast-enhanced MRA performed with a volumetric interpolated breath-hold examination (VIBE) during intravenous bolus injection of gadobutrol. Images of arterial and venous phases were acquired over approximately 210 seconds. Selected images were sent to a workstation for generation of 3D volume-rendered images and standard triangulated language (STL) files for 3D print construction. The neurovascular bundles (NVBs) were found in sequence on non-contrast images. Accessory pudendal arteries (APAs) were found in all cases in the arterial phase of contrast enhancement but were ill-defined on non-contrast enhanced MRA. Dynamic contrast-enhanced MRA helped to detect APAs, suggesting that this 3D system using MRI will be useful in RARP.

Odors pulsed at wing beat frequencies are tracked by primary olfactory networks and enhance odor detection

Directory of Open Access Journals (Sweden)

Shreejoy Tripathy

2010-03-01

Full Text Available Each down stroke of an insect’s wings accelerates axial airflow over the antennae. Modeling studies suggest that this can greatly enhance penetration of air and air-born odorants through the antennal sensilla thereby periodically increasing odorant-receptor interactions. Do these periodic changes result in entrainment of neural responses in the antenna and antennal lobe (AL? Does this entrainment affect olfactory acuity? To address these questions, we monitored antennal and AL responses in the moth Manduca sexta while odorants were pulsed at frequencies from 10-72 Hz, encompassing the natural wingbeat frequency. Power spectral density (PSD analysis was used to identify entrainment of neural activity. Statistical analysis of PSDs indicates that the antennal nerve tracked pulsed odor up to 30 Hz. Furthermore, at least 50% of AL local field potentials (LFPs and between 7-25% of unitary spiking responses also tracked pulsed odor up to 30 Hz in a frequency-locked manner. Application of bicuculline (200µM abolished pulse tracking in both LFP and unitary responses suggesting that GABAA receptor activation is necessary for pulse tracking within the AL. Finally, psychophysical measures of odor detection establish that detection thresholds are lowered when odor is pulsed at 20 Hz. These results suggest that AL networks can respond to the oscillatory dynamics of stimuli such as those imposed by the wing beat in a manner analogous to mammalian sniffing.

Tracing outbreaks of Streptococcus equi infection (strangles) in horses using sequence variation in the seM gene and pulsed-field gel electrophoresis.

Science.gov (United States)

Lindahl, Susanne; Söderlund, Robert; Frosth, Sara; Pringle, John; Båverud, Viveca; Aspán, Anna

2011-11-21

Strangles is a serious respiratory disease in horses caused by Streptococcus equi subspecies equi (S. equi). Transmission of the disease occurs by direct contact with an infected horse or contaminated equipment. Genetically, S. equi strains are highly homogenous and differentiation of strains has proven difficult. However, the S. equi M-protein SeM contains a variable N-terminal region and has been proposed as a target gene to distinguish between different strains of S. equi and determine the source of an outbreak. In this study, strains of S. equi (n=60) from 32 strangles outbreaks in Sweden during 1998-2003 and 2008-2009 were genetically characterized by sequencing the SeM protein gene (seM), and by pulsed-field gel electrophoresis (PFGE). Swedish strains belonged to 10 different seM types, of which five have not previously been described. Most were identical or highly similar to allele types from strangles outbreaks in the UK. Outbreaks in 2008/2009 sharing the same seM type were associated by geographic location and/or type of usage of the horses (racing stables). Sequencing of the seM gene generally agreed with pulsed-field gel electrophoresis profiles. Our data suggest that seM sequencing as a epidemiological tool is supported by the agreement between seM and PFGE and that sequencing of the SeM protein gene is more sensitive than PFGE in discriminating strains of S. equi. Copyright © 2011 Elsevier B.V. All rights reserved.

Usefulness of intraoperative ultra low-field magnetic resonance imaging in glioma surgery.

Science.gov (United States)

Senft, Christian; Seifert, Volker; Hermann, Elvis; Franz, Kea; Gasser, Thomas

2008-10-01

The aim of this study was to demonstrate the usefulness of a mobile, intraoperative 0.15-T magnetic resonance imaging (MRI) scanner in glioma surgery. We analyzed our prospectively collected database of patients with glial tumors who underwent tumor resection with the use of an intraoperative ultra low-field MRI scanner (PoleStar N-20; Odin Medical Technologies, Yokneam, Israel/Medtronic, Louisville, CO). Sixty-three patients with World Health Organization Grade II to IV tumors were included in the study. All patients were subjected to postoperative 1.5-T imaging to confirm the extent of resection. Intraoperative image quality was sufficient for navigation and resection control in both high- and low-grade tumors. Primarily enhancing tumors were best detected on T1-weighted imaging, whereas fluid-attenuated inversion recovery sequences proved best for nonenhancing tumors. Intraoperative resection control led to further tumor resection in 12 (28.6%) of 42 patients with contrast-enhancing tumors and in 10 (47.6%) of 21 patients with noncontrast-enhancing tumors. In contrast-enhancing tumors, further resection led to an increased rate of complete tumor resection (71.2 versus 52.4%), and the surgical goal of gross total removal or subtotal resection was achieved in all cases (100.0%). In patients with noncontrast-enhancing tumors, the surgical goal was achieved in 19 (90.5%) of 21 cases, as intraoperative MRI findings were inconsistent with postoperative high-field imaging in 2 cases. The use of the PoleStar N-20 intraoperative ultra low-field MRI scanner helps to evaluate the extent of resection in glioma surgery. Further tumor resection after intraoperative scanning leads to an increased rate of complete tumor resection, especially in patients with contrast-enhancing tumors. However, in noncontrast- enhancing tumors, the intraoperative visualization of a complete resection seems less specific, when compared with postoperative 1.5-T MRI.

Dynamic pulse difference circuit

International Nuclear Information System (INIS)

Erickson, G.L.

1978-01-01

A digital electronic circuit of especial use for subtracting background activity pulses in gamma spectrometry is disclosed which comprises an up-down counter connected to count up with signal-channel pulses and to count down with background-channel pulses. A detector responsive to the count position of the up-down counter provides a signal when the up-down counter has completed one scaling sequence cycle of counts in the up direction. In an alternate embodiment, a detector responsive to the count position of the up-down counter provides a signal upon overflow of the counter

Matlab enhanced multi-threaded tomography optimization sequence (MEMTOS)

International Nuclear Information System (INIS)

Lum, Edward S.; Pope, Chad L.

2016-01-01

Highlights: • Monte Carlo simulation of spent nuclear fuel assembly neutron computed tomography. • Optimized parallel calculations conducted from within the MATLAB environment. • Projection difference technique used to identify anomalies in spent nuclear fuel assemblies. - Abstract: One challenge associated with spent nuclear fuel assemblies is the lack of non-destructive analysis techniques to determine if fuel pins have been removed or replaced or if there are significant defects associated with fuel pins deep within a fuel assembly. Neutron computed tomography is a promising technique for addressing these qualitative issues. Monte Carlo simulation of spent nuclear fuel neutron computed tomography allows inexpensive process investigation and optimization. The main purpose of this work is to provide a fully automated advanced simulation framework for the analysis of spent nuclear fuel inspection using neutron computed tomography. The simulation framework, called Matlab Enhanced Multi-Threaded Tomography Optimization Sequence (MEMTOS) not only automates the simulation process, but also generates superior tomography image results. MEMTOS is written in the MATLAB scripting language and addresses file management, parallel Monte Carlo execution, results extraction, and tomography image generation. This paper describes the mathematical basis for neutron computed tomography, the Monte Carlo technique used to simulate neutron computed tomography, and the overall tomography simulation optimization algorithm. Sequence results presented include overall simulation speed enhancement, tomography and image results obtained for Experimental Breeder Reactor II spent fuel assemblies and light water reactor fuel assemblies. Optimization using a projection difference technique are also described.

Vasovist-enhanced MR angiography

International Nuclear Information System (INIS)

Goyen, M.; Shamsi, K.; Schoenberg, S.O.

2006-01-01

Vasovist (MS-325) is the first intravascular contrast agent approved for use with magnetic resonance angiography in the European Union. Vasovist reversibly binds to albumin, providing extended intravascular enhancement compared to existing extracellular magnetic resonance contrast agents. Prior to approval, Vasovist underwent extensive testing to evaluate the safety and efficacy of the drug; the clinical trials program included blinded, placebo-controlled dose ranging, efficacy in a variety of vascular beds (AIOD, renal, pedal), examination of potential drug interaction with warfarin and comparison with XRA. The clinical trials show that Vasovist-enhanced MR angiography is safe and well-tolerated in patients with vascular disease, effective for the detection of vascular stenosis and aneurysms, significantly more accurate (both more sensitive and specific) than non-contrast MR angiography for the diagnosis of vascular stenoses, and similar to conventional angiography for the overall characterization of vascular disease, without the need for catheterization. (orig.)

Vasovist-enhanced MR angiography

Energy Technology Data Exchange (ETDEWEB)

Goyen, M. [Univ. Medical Center, Hamburg-Eppendorf, Hamburg (Germany); Shamsi, K. [Berlex Lab., Inc., Montville, NJ (United States); Schoenberg, S.O. [Dept. of Clinical Radiology, Univ. Hospitals Grosshadern, Munich (Germany)

2006-02-15

Vasovist (MS-325) is the first intravascular contrast agent approved for use with magnetic resonance angiography in the European Union. Vasovist reversibly binds to albumin, providing extended intravascular enhancement compared to existing extracellular magnetic resonance contrast agents. Prior to approval, Vasovist underwent extensive testing to evaluate the safety and efficacy of the drug; the clinical trials program included blinded, placebo-controlled dose ranging, efficacy in a variety of vascular beds (AIOD, renal, pedal), examination of potential drug interaction with warfarin and comparison with XRA. The clinical trials show that Vasovist-enhanced MR angiography is safe and well-tolerated in patients with vascular disease, effective for the detection of vascular stenosis and aneurysms, significantly more accurate (both more sensitive and specific) than non-contrast MR angiography for the diagnosis of vascular stenoses, and similar to conventional angiography for the overall characterization of vascular disease, without the need for catheterization. (orig.)

Resonant creep enhancement in austenitic stainless steels due to pulsed irradiation at low doses

International Nuclear Information System (INIS)

Kishimoto, N.; Amekura, H.; Saito, T.

1994-01-01

Steady-state irradiation creep of austenitic stainless steels has been extensively studied as one of the most important design parameters in fusion reactors. The steady-state irradiation creep has been evaluated using in-pile and light-ion experiments. Those creep compliances of various austenitic steels range in the vicinity of ε/Gσ = 10 -6 ∼10 -5 (dpa sm-bullet MPa) -1 , depending on chemical composition etc. The mechanism of steady-state irradiation creep has been elucidated, essentially in terms of stress-induced preferential absorption of point defects into dislocations, and their climb motion. From this standpoint, low doses such as 10 -3 ∼10 -1 dpa would not give rise to any serious creep, and the irradiation creep may not be a critical issue for the low-dose fusion devices including ITER. It is, however, possible that pulsed irradiation causes different creep behaviors from the steady-state one due to dynamic unbalance of interstitials and vacancies. The authors have actually observed anomalous creep enhancement due to pulsed irradiation in austenitic stainless steels. The resonant behavior of creep indicates that pulsed irradiation may cause significant deformation in austenitic steels even at such low doses and slow pulsing rates, especially for the SA-materials. The first-wall materials in plasma operation of ∼10 2 s may suffer from unexpected transient creep, even in the near-term fusion deices, such as ITER. Though this effect might be a transient effect for a relatively short period, it should be taken into account that the pulsed irradiation makes influences on stress relaxation of the fusion components and on the irradiation fatigue. The mechanism and the relevant behaviors of pulse-induced creep will be discussed in terms of a point-defect model based on the resonant interstitial enrichment

T1 Gd-enhanced compared with CISS sequences in retinoblastoma: superiority of T1 sequences in evaluation of tumour extension

Energy Technology Data Exchange (ETDEWEB)

Gizewski, Elke R.; Wanke, Isabel; Guengoer, Ali-Riza; Forsting, Michael [University Hospital, Department of Diagnostic and Interventional Neuroradiology, Essen (Germany); Jurklies, Christine [University Hospital Essen, Department of Ophthalmology (Germany)

2005-01-01

Background As adequate therapy for retinoblastoma in young children depends on infiltration of extra-retinal structures, diagnostic modalities play an essential role. Methods: In this widely extended study, 80 children with retinoblastoma were studied with MRI (standard fat-suppressed Gd-enhanced T1, T2 thin-slice sequences (additionally with small loop surface coil), constructive interference in steady state (CISS) sequence covering the orbita). The images were analysed by two blinded neuroradiologists. Histology was used as the gold standard. MRI assumed infiltration of extra-retinal structures in 13 of 80 patients of which ten were confirmed by histology. Affected extra-retinal structures were: optic nerve (five, of which two were on CISS and three on T1 with higher image resolution using the surface coil), scleral infiltration (five, of which four on CISS and T1) and ciliary body infiltration (one on CISS and T1). Another 61 enucleated patients did not have any extra-retinal infiltration in histology. The CISS sequence with multiplanar reconstruction was mainly helpful in revealing exact three-dimensional tumour extension with excellent clinical acceptance and pre-surgical planning but T1 fat-suppressed Gd-enhanced images were superior in revealing exact tumour extension. CISS sequences allow to produce excellent anatomical images and to perform multiplanar reconstruction to better demonstrate tumour extension. However, T1-weighted sequences after contrast application are more sensitive (60 versus 40%) in detecting infiltration of the optic nerve but equal in detecting scleral infiltration. (orig.)

Evaluation of the MRI with Gd-DTPA enhancement in the diagnosis of brain and spinal tumors

Energy Technology Data Exchange (ETDEWEB)

Fukui, Keiji; Sadamoto, Kazuhiko; Miki, Hitoshi; Sakaki, Saburo; Matsuoka, Kenzo.

1988-02-01

Magnetic resonance (MR) imaging was performed using saturation recovery (SR), inversion recovery (IR) and spin echo (SE) pulse sequences before and after the injection of 0.1 mmol of gadolinium diethylenetriamine pentaacetic acid dimeglumine (Gd-DTPA) per kilogram of body weight. Forty-two patients with gliomas (8), meningiomas (12), neurinomas (5), adenoma (1), craniopharyngioma (1), chordoma (1), malignant lymphomas (2), metastatic brain tumors (2), spinal tumors (4), and other tumors (6) were studied. Contrast enhancement was shown in 35 of the 38 patients with brain tumors and in all those with spinal tumors on T/sub 1/-weighted images. The T/sub 1/ relaxation time was decreased in all of these 39 tumors, while the T/sub 2/ relaxation time showed no definite tendency. No marked side effects were observed following the administration of Gd-DTPA. By using Gd-DTPA enhancement, it was possible to differentiate the tumor from the peritumoral edema on MRI, although it was difficult to do so on precontrast MRI. Among the various pulse sequences, the SR sequence provides the best diagnostic value with Gd-DTPA enhancement in the shortest examination time for screening brain and spinal tumors.

Coherent combining pulse bursts in time domain

Science.gov (United States)

Galvanauskas, Almantas

2018-01-09

A beam combining and pulse stacking technique is provided that enhances laser pulse energy by coherent stacking pulse bursts (i.e. non-periodic pulsed signals) in time domain. This energy enhancement is achieved by using various configurations of Fabry-Perot, Gires-Tournois and other types of resonant cavities, so that a multiple-pulse burst incident at either a single input or multiple inputs of the system produces an output with a solitary pulse, which contains the summed energy of the incident multiple pulses from all beams. This disclosure provides a substantial improvement over conventional coherent-combining methods in that it achieves very high pulse energies using a relatively small number of combined laser systems, thus providing with orders of magnitude reduction in system size, complexity, and cost compared to current combining approaches.

Efficiency Enhancement in DC Pulsed Gas Discharge Memory Panel

Science.gov (United States)

Okamoto, Yukio

1983-01-01

Much improvement in the luminous efficiency of a dc pulsed gas discharge memory panel for color TV display was achieved by shortening the sustaining pulse duration. High energy electrons can thus be produced in the pulsed discharge with fast rise times. Calculated optimum value of E/P in a Xe gas discharge is 7-8 V/cm\\cdotTorr.

Trace level detection of compounds related to the chemical weapons convention by 1H-detected 13C NMR spectroscopy executed with a sensitivity-enhanced, cryogenic probehead.

Science.gov (United States)

Cullinan, David B; Hondrogiannis, George; Henderson, Terry J

2008-04-15

Two-dimensional 1H-13C HSQC (heteronuclear single quantum correlation) and fast-HMQC (heteronuclear multiple quantum correlation) pulse sequences were implemented using a sensitivity-enhanced, cryogenic probehead for detecting compounds relevant to the Chemical Weapons Convention present in complex mixtures. The resulting methods demonstrated exceptional sensitivity for detecting the analytes at trace level concentrations. 1H-13C correlations of target analytes at chemical shift information could be derived quickly and simultaneously from the resulting spectra. The fast-HMQC pulse sequences generated magnitude mode spectra suitable for detailed analysis in approximately 4.5 h and can be used in experiments to efficiently screen a large number of samples. The HSQC pulse sequences, on the other hand, required roughly twice the data acquisition time to produce suitable spectra. These spectra, however, were phase-sensitive, contained considerably more resolution in both dimensions, and proved to be superior for detecting analyte 1H-13C correlations. Furthermore, a HSQC spectrum collected with a multiplicity-edited pulse sequence provided additional structural information valuable for identifying target analytes. The HSQC pulse sequences are ideal for collecting high-quality data sets with overnight acquisitions and logically follow the use of fast-HMQC pulse sequences to rapidly screen samples for potential target analytes. Use of the pulse sequences considerably improves the performance of NMR spectroscopy as a complimentary technique for the screening, identification, and validation of chemical warfare agents and other small-molecule analytes present in complex mixtures and environmental samples.

Contrast-enhanced dynamic MR imaging of parasellar tumor using fast spin-echo sequence

International Nuclear Information System (INIS)

Kusunoki, Katsusuke; Ohue, Shiro; Ichikawa, Haruhisa; Saito, Masahiro; Sadamoto, Kazuhiko; Sakaki, Saburo; Miki, Hitoshi.

1995-01-01

We have applied a new dynamic MRI technique that uses a fast spin-echo sequence to parasellar tumors. This sequence has less susceptible effect and better spatial resolution than a gradient echo sequence, providing faster images than a short spin-echo sequence does. Image was obtained in the coronal or sagittal plane using a 1.5T clinical MRI system, and then, dynamic MR images were acquired every 10 to 20 sec after administration of Gd-DTPA (0.1 mmol/kg). The subjects were 12 patients (5 microadenomas, 5 macroadenomas and 2 Rathke's cleft cysts) and 5 normal volunteers. As for volunteers, the cavernous sinus, pituitary stalk and posterior pituitary gland were contrasted on the first image, followed by visualization of the proximal portion adjacent to the junction of the infundibulum and the anterior pituitary gland, and finally by contrasting the distal portion of the anterior pituitary gland. There was a difference with respect to tumor contrast between microadenomas and macroadenomas. In the case of the macroadenomas, the tumor was contrasted at the same time as, or faster than the anterior pituitary gland, while with the microadenomas the tumor was enhanced later than the anterior pituitary gland. No enhancement with contrast medium was seen in Rathke's cleft cysts. In addition, it was possible to differentiate a recurrent tumor from a piece of muscle placed at surgery since the images obtained by the fast spin-echo sequence were clearer than those obtained by gradient echo sequence. (author)

Quantification of coronary artery calcium on the basis of dual-energy coronary CT angiography.

Science.gov (United States)

Schwarz, Florian; Nance, John W; Ruzsics, Balazs; Bastarrika, Gorka; Sterzik, Alexander; Schoepf, U Joseph

2012-09-01

To evaluate the feasibility of using virtual noncontrast material-enhanced (VNC) computed tomographic (CT) series derived from dual-energy CT imaging studies for coronary artery calcium quantification. This HIPAA-compliant study was institutional review board approved; all patients provided written informed consent. Thirty-six patients prospectively underwent noncontrast-enhanced CT calcium scoring followed by coronary CT angiography performed in dual-energy mode. By using different reconstruction algorithms, three VNC series were generated and evaluated for noise and efficiency of virtual iodine removal. Two readers independently quantified calcium on VNC images and true noncontrast-enhanced conventional calcium scoring series. A leave-one-out cross validation was used to assess the accuracy of calcium score prediction from VNC series by means of linear regression. CT value histograms of the VNC series closely resembled the profile in the true noncontrast-enhanced series. There was excellent correlation between calcium volumes on the VNC series and true noncontrast-enhanced series on a per-patient (r = 0.94, P VNC series was excellent (r = 0.82). Multiethnic Study of Atherosclerosis rankings that were derived from the predicted calcium scores also showed excellent agreement (intraclass correlation coefficient = 0.909). Coronary artery calcium identification and quantification based on dual-energy coronary CT angiographic studies may obviate the need for dedicated CT calcium scoring studies. © RSNA, 2012

Time resolved study of the emission enhancement mechanisms in orthogonal double-pulse laser-induced breakdown spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Sanginés, R., E-mail: roberto.sangines@ccadet.unam.mx; Sobral, H.

2013-10-01

The evolution of laser induced ablation plume on aluminum targets has been investigated in orthogonal pre-ablation double pulse scheme at atmospheric pressure from the earliest stages of plasma evolution. Time-resolved emission spectra from neutrals, singly- and doubly-ionized species obtained with the double pulse experiment have been compared with those from the single pulse configuration. Signal-to-noise enhancement reaches values of up to 15 depending on the analyzed species; and the lower the charge state the later its maximum signal-to-noise ratio is reached. Ablation plume dynamics was monitored from 10 ns after the plasma onset via shadowgraphy and fast-photography with narrow interference filters to follow the evolution of individual species. Results show that ionic species from the target are located at the plasma core while nitrogen from the background air is found at the plume peripheral. Initially both configurations exhibit similar ablation plume sizes and their expansions were successfully fitted with the strong explosion model for the first 500 ns. At later times a good agreement was obtained by using the drag model, which predicts that the plume expansion eventually stops due to interaction with the background gas particles. The emission enhancement measured in the double pulse scheme is discussed in terms of the models describing the plume dynamics. - Highlights: • Production of 2 + ions at the earliest stages of plasma evolution • The higher the charge state the inner the location within the ablation plume. • The expansion rate of the second (ablation) plume was measured. • Shock and drag models successfully fit the ablation shock front expansion.

双源CT双能量虚拟平扫技术在颈部淋巴结病变中的应用价值%Preliminary application of dualenergy virtual noncontrast of dualsource CT for cervical lymph nodes diseases

Institute of Scientific and Technical Information of China (English)

贾晓霞; 江杰; 邓亚敏; 杨亚英

2012-01-01

Objective To investigate the clinical applied value of dual-energy virtual non-contrast( VNC) of dual-source CT for the cervical lymph nodes. Methods 48 cases with pathological diagnosis of cervical lymph nodes underwent conventional non-contrast (CNC)and dual-energy enhanced scanning. VNC images were obtained through dual energy post-processing software. Mean CT values, signal to noise ratio(SNR) , image quality, lesion's detectability and radiation dose were comparatively analysed between routine non-contrast and VNC. Results CT attenuations of the cervical lymph nodes between CNC and VNC images were not significantly different(P>0. 05). The image noise of VNC images was significantly lower than that of CNC, while the SNR of VNC images was significantly higher than that of CNC(P0. 05). The necrosis of the cervical lymph nodes could be detected by both CNC and VNC , and the difference was not statistically significant between them (P>0. 05 ) . The radiation dose of VNC was lower than that of VNC(P0.05);虚拟平扫图像噪声明显低于常规平扫,而信号噪声比明显高于常规平扫(P0.05);虚拟平扫及常规平扫对颈部肿大淋巴结内坏死均可见显示;双能量扫描模式较常规扫描模式的总辐射剂量小(P<0.05).结论 在颈部肿大淋巴结检查中,1次双能量增强扫描可获得增强图像和VNC图像,而VNC图像基本不影响病灶的观察同时显著降低了辐射剂量,具有潜在的临床应用价值.

Digital coherent detection research on Brillouin optical time domain reflectometry with simplex pulse codes

International Nuclear Information System (INIS)

Hao Yun-Qi; Ye Qing; Pan Zheng-Qing; Cai Hai-Wen; Qu Rong-Hui

2014-01-01

The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry (BOTDR), where the simplex pulse codes are applied in the sensing system. The time domain signal of every code sequence is collected by the data acquisition card (DAQ). A shift-averaging technique is applied in the frequency domain for the reason that the local oscillator (LO) in the coherent detection is fix-frequency deviated from the primary source. With the 31-bit simplex code, the signal-to-noise ratio (SNR) has 3.5-dB enhancement with the same single pulse traces, accordant with the theoretical analysis. The frequency fluctuation for simplex codes is 14.01 MHz less than that for a single pulse as to 4-m spatial resolution. The results are believed to be beneficial for the BOTDR performance improvement. (general)

Calculating the number of shock waves, expulsion time, and optimum stone parameters based on noncontrast computerized tomography characteristics.

Science.gov (United States)

Foda, Khaled; Abdeldaeim, Hussein; Youssif, Mohamed; Assem, Akram

2013-11-01

To define the parameters that accompanied a successful extracorporeal shock wave lithotripsy (ESWL), namely the number of shock waves (SWs), expulsion time (ET), mean stone density (MSD), and the skin-to-stone distance (SSD). A total of 368 patients diagnosed with renal calculi using noncontrast computerized tomography had their MSD, diameter, and SSD recorded. All patients were treated using a Siemens lithotripter. ESWL success meant a stone-free status or presence of residual fragments 934 HUs and SSD >99 mm. The required number of SWs and the expected ET can be anticipated. Copyright © 2013 Elsevier Inc. All rights reserved.

Dual energy virtual non-contrast technique of dual-source head CT angiography in diagnosis of meningiomas%双源CT双能量颅脑CTA虚拟平扫诊断脑膜瘤

Institute of Scientific and Technical Information of China (English)

谢晓洁; 邓亚敏; 曾宪春; 康绍磊; 韩丹

2012-01-01

Objective To investigate the clinical value of the dual energy virtual non-contrast technique of dual-source head CT angiography (CTA) in preoperative examination of meningioma. Methods CT images of 49 patients with pathologically confirmed meningiomas were retrospectively analyzed. Conventional non-contrast (CNC) and dual energy CTA scan were performed, and virtual non-contrast (VNC) and iodine-enhanced images were obtained with postprocessed technology. The mean CT value, signal-to-noise ratio (SNR), image quality, lesions detectability and radiation dose were compared between VNC and CNC images. The supply artery of tumor and relationship between tumor and adjacent intracranial vessel were observed on head CTA image from head bone removal using dual energy technique. Results CT value, SNR, and image quality scores of CNC were higher than those of VNC (all P<0. 05). The image quality scores of VNC were all above 3, which could meet the diagnostic requirements. There was no statistical difference in the size, shape, intratumoral calcification, necrosis and peritumoral edema of lesions between CNC and VNC images. The ability of VNC to display calcification inside meningioma was somehow limited compared with CNC. The radiation dose of dual energy CTA was 1. 71 mSv (61. 07%) , lower than that of CNC and conventional enhancement scan. Conclusion Dual-source CT dual energy technique can obtain VNC, iodine-enhanced and CTA images by single enhanced scan, and is excellent in preoperative examination for meningioma.%目的 探讨双源CT(DSCT)双能量颅脑CTA虚拟平扫在脑膜瘤术前检查中的临床价值.方法 回顾性分析经手术病理证实的49例脑膜瘤患者的CT图像,包括常规平扫(CNC)及双能量增强图像,经处理得到虚拟平扫(VNC)图和碘图；对比两组平扫病灶平均CT值、SNR、图像质量评分、病灶形态及辐射剂�

Evidence that pulsed electric field treatment enhances the cell wall porosity of yeast cells.

Science.gov (United States)

Ganeva, Valentina; Galutzov, Bojidar; Teissie, Justin

2014-02-01

The application of rectangular electric pulses, with 0.1-2 ms duration and field intensity of 2.5-4.5 kV/cm, to yeast suspension mediates liberation of cytoplasmic proteins without cell lysis. The aim of this study was to evaluate the effect of pulsed electric field with similar parameters on cell wall porosity of different yeast species. We found that electrically treated cells become more susceptible to lyticase digestion. In dependence on the strain and the electrical conditions, cell lysis was obtained at 2-8 times lower enzyme concentration in comparison with control untreated cells. The increase of the maximal lysis rate was between two and nine times. Furthermore, when applied at low concentration (1 U/ml), the lyticase enhanced the rate of protein liberation from electropermeabilized cells without provoking cell lysis. Significant differences in the cell surface of control and electrically treated cells were revealed by scanning electron microscopy. Data presented in this study allow us to conclude that electric field pulses provoke not only plasma membrane permeabilization, but also changes in the cell wall structure, leading to increased wall porosity.

Simulating Metabolite Basis Sets for in vivo MRS Quantification; Incorporating details of the PRESS Pulse Sequence by means of the GAMMA C++ library

NARCIS (Netherlands)

Van der Veen, J.W.; Van Ormondt, D.; De Beer, R.

2012-01-01

In this work we report on generating/using simulated metabolite basis sets for the quantification of in vivo MRS signals, assuming that they have been acquired by using the PRESS pulse sequence. To that end we have employed the classes and functions of the GAMMA C++ library. By using several

Sequence comparison for non-enhanced MRA of the lower extremity arteries at 7 Tesla.

Directory of Open Access Journals (Sweden)

Sören Johst

Full Text Available In this study three sequences for non-contrast-enhanced MRA of the lower extremity arteries at 7T were compared. Cardiac triggering was used with the aim to reduce signal variations in the arteries. Two fast single-shot 2D sequences, a modified Ultrafast Spoiled Gradient Echo (UGRE sequence and a variant of the Quiescent-Interval Single-Shot (QISS sequence were triggered via phonocardiogram and compared in volunteer examinations to a non-triggered 2D gradient echo (GRE sequence. For image acquisition, a 16-channel transmit/receive coil and a manually positionable AngioSURF table were used. To tackle B1 inhomogeneities at 7T, Time-Interleaved Acquisition of Modes (TIAMO was integrated in GRE and UGRE. To compare the three sequences quantitatively, a vessel-to-background ratio (VBR was measured in all volunteers and stations. In conclusion, cardiac triggering was able to suppress flow artifacts satisfactorily. The modified UGRE showed only moderate image artifacts. Averaged over all volunteers and stations, GRE reached a VBR of 4.18±0.05, UGRE 5.20±0.06, and QISS 2.72±0.03. Using cardiac triggering and TIAMO imaging technique was essential to perform non-enhanced MRA of the lower extremities vessels at 7T. The modified UGRE performed best, as observed artifacts were only moderate and the highest average VBR was reached.

Investigation of plasma potential and pulsed discharge characteristics in enhanced glow discharge plasma immersion ion implantation and deposition

International Nuclear Information System (INIS)

Li Liuhe; Lu Qiuyuan; Fu, Ricky K.Y.; Chu, Paul K.

2009-01-01

Enhanced glow discharge plasma immersion ion implantation and deposition (EGD-PII and D) does not require external plasma sources. In this technique, the plasma is produced by self-glow discharge when a high negative voltage is applied to the sample. The small-area, pointed-shape hollow anode and large area tabular cathode form an electron-focused electric field. Using a special electric field design, the electrons from either the plasma or target (secondary electrons) are focused to a special hollow anode. As a result of the special electron-focusing field, the self-glow discharge process can be enhanced to achieve effective ion implantation into the substrate. In this work, the plasma potential distribution is investigated in details and the possible pulse discharge mechanism is discussed. The unique characteristics of the pulsed plasma and plasma extinction are studied.

Recent Pulse Sequences for Heteronuclear Long-Range Correlation and More

DEFF Research Database (Denmark)

Sørensen, Ole W.

This talk will give an overview of the key elements and principles of experiments listed on http://www.crc.dk/nmr/, from where also pulse programs in Bruker and Varian format can be downloaded.......This talk will give an overview of the key elements and principles of experiments listed on http://www.crc.dk/nmr/, from where also pulse programs in Bruker and Varian format can be downloaded....

Contrast enhancement in an optical time-domain reflectometer via self-phase modulation compensation by chirped probe pulses

International Nuclear Information System (INIS)

Alekseev, A E; Potapov, V T; Vdovenko, V S; Simikin, D E; Gorshkov, B G

2016-01-01

In the present paper we propose a novel method for optical time-domain reflectometer (OTDR)–reflectogram contrast enhancement via compensation of nonlinear distortions of propagating probe pulse, which arise due to the self-phase modulation (SPM) effect in optical fiber. The compensation is performed via preliminary frequency modulation (chirp) of the initial probe pulse according to the specific law. As a result the OTDR contrast at some distant predefined fiber point is fully restored to the value of non-distorted probe pulse at the beginning of the fiber line. As a result, the performance of the phase OTDR increases. The point of full SPM compensation could be shifted to any other point of the fiber line via preliminary frequency modulation index change. The feasibility of the proposed method is theoretically proved and experimentally demonstrated. (paper)

Real-time flow - determination of vena cava inferior on two different levels via 'RACE' pulse sequence in MR

International Nuclear Information System (INIS)

Helzel, M.V.; Mueller, E.

1993-01-01

A new and simple parameter for quantiative evaluation of liver perfusion is outlined: Post-sinusoidal quantitative measurement of the entire liver venous flow: This is a result of the differences in evaluated flow volumes at two different levels in the inferior V.cava. The first level is the height of diaphragm, and the second is situated just cranial of the renal vessels. Normal values obtained from a group of healthy volunteers are presented. A gradient-echo pulse sequence called RACE, enabling flow measurements in real-time, is outlined. (orig.) [de

The effective reflection of a pulse sequence from a four-wave mirror with thermal nonlinearity under parametric feedback

Science.gov (United States)

Barashkov, M. S.; Bel'Diugin, I. M.; Zolotarev, M. V.; Kruzhilin, Iu. I.; Krymskii, M. I.

1989-04-01

A four-wave mirror with thermal nonlinearity has been experimentally realized with the interaction of corunning waves under parametric feedback with a nonreciprocal element. The effective reflection of a sequence of pulses with duration of about 300 ns from a neodymium-glass laser with maximal reflection coefficients greater than 30 has been demonstrated. The quality of the radiation reflected from the mirror is studied. A significant reduction in the steady-state lasing threshold has been shown with thermal nonlinearity at small angles of the interacting beam convergence, compared to the case of counterrunning convergence.

Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

International Nuclear Information System (INIS)

Ma, Guangjin; Dallari, William; Borot, Antonin; Tsakiris, George D.; Veisz, Laszlo; Krausz, Ferenc; Yu, Wei

2015-01-01

We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach

Enhancement of mosquito trapping efficiency by using pulse width modulated light emitting diodes

OpenAIRE

Liu, Yu-Nan; Liu, Yu-Jen; Chen, Yi-Chian; Ma, Hsin-Yi; Lee, Hsiao-Yi

2017-01-01

In this study, a light-driving bug zapper is presented for well controlling the diseases brought by insects, such as mosquitoes. In order to have the device efficient to trap the insect pests in off-grid areas, pulse width modulated light emitting diodes (PWM-LED) combined with a solar power module are proposed and implemented. With specific PWM electric signals to drive the LED, it is found that no matter what the ability of catching insects or the consumed power efficiency can be enhanced t...

Detection of Early Ischemic Changes in Noncontrast CT Head Improved with "Stroke Windows".

Science.gov (United States)

Mainali, Shraddha; Wahba, Mervat; Elijovich, Lucas

2014-01-01

Introduction. Noncontrast head CT (NCCT) is the standard radiologic test for patients presenting with acute stroke. Early ischemic changes (EIC) are often overlooked on initial NCCT. We determine the sensitivity and specificity of improved EIC detection by a standardized method of image evaluation (Stroke Windows). Methods. We performed a retrospective chart review to identify patients with acute ischemic stroke who had NCCT at presentation. EIC was defined by the presence of hyperdense MCA/basilar artery sign; sulcal effacement; basal ganglia/subcortical hypodensity; and loss of cortical gray-white differentiation. NCCT was reviewed with standard window settings and with specialized Stroke Windows. Results. Fifty patients (42% females, 58% males) with a mean NIHSS of 13.4 were identified. EIC was detected in 9 patients with standard windows, while EIC was detected using Stroke Windows in 35 patients (18% versus 70%; P Windows (14% and 36%; P Windows (6% and 46%; P Windows significantly improved detection of EIC.

SPIDYAN, a MATLAB library for simulating pulse EPR experiments with arbitrary waveform excitation.

Science.gov (United States)

Pribitzer, Stephan; Doll, Andrin; Jeschke, Gunnar

2016-02-01

Frequency-swept chirp pulses, created with arbitrary waveform generators (AWGs), can achieve inversion over a range of several hundreds of MHz. Such passage pulses provide defined flip angles and increase sensitivity. The fact that spectra are not excited at once, but single transitions are passed one after another, can cause new effects in established pulse EPR sequences. We developed a MATLAB library for simulation of pulse EPR, which is especially suited for modeling spin dynamics in ultra-wideband (UWB) EPR experiments, but can also be used for other experiments and NMR. At present the command line controlled SPin DYnamics ANalysis (SPIDYAN) package supports one-spin and two-spin systems with arbitrary spin quantum numbers. By providing the program with appropriate spin operators and Hamiltonian matrices any spin system is accessible, with limits set only by available memory and computation time. Any pulse sequence using rectangular and linearly or variable-rate frequency-swept chirp pulses, including phase cycling can be quickly created. To keep track of spin evolution the user can choose from a vast variety of detection operators, including transition selective operators. If relaxation effects can be neglected, the program solves the Liouville-von Neumann equation and propagates spin density matrices. In the other cases SPIDYAN uses the quantum mechanical master equation and Liouvillians for propagation. In order to consider the resonator response function, which on the scale of UWB excitation limits bandwidth, the program includes a simple RLC circuit model. Another subroutine can compute waveforms that, for a given resonator, maintain a constant critical adiabaticity factor over the excitation band. Computational efficiency is enhanced by precomputing propagator lookup tables for the whole set of AWG output levels. The features of the software library are discussed and demonstrated with spin-echo and population transfer simulations. Copyright © 2016

Susceptibility contrast imaging of CO2-induced changes in the blood volume of the human brain

DEFF Research Database (Denmark)

Rostrup, Egill; Larsson, H B; Toft, P B

1996-01-01

PURPOSE: To investigate changes in the regional cerebral blood volume (rCBV) in human subjects during rest and hypercapnia by MR imaging, and to compare the results from contrast-enhanced and noncontrast-enhanced susceptibility-weighted imaging. MATERIAL AND METHODS: Five healthy volunteers (aged...... in cerebral hemodynamics than noncontrast-enhanced imaging. The results of the deconvolution analysis suggested that perfusion calculation by conventional tracer kinetic methods may be impracticable because of nonlinear effects in contrast-enhanced MR imaging....

Signal enhancement in collinear double-pulse laser-induced breakdown spectroscopy applied to different soils

Energy Technology Data Exchange (ETDEWEB)

Nicolodelli, Gustavo, E-mail: gunicolodelli@hotmail.com [Embrapa Instrumentation, Rua XV de Novembro, 1452, CEP 13560-970 São Carlos, SP (Brazil); Senesi, Giorgio Saverio, E-mail: giorgio.senesi@imip.cnr.it [Institute of Inorganic Methodologies and Plasmas, CNR, Bari, 70126 Bari (Italy); Romano, Renan Arnon, E-mail: renan.romano@gmail.com [Embrapa Instrumentation, Rua XV de Novembro, 1452, CEP 13560-970 São Carlos, SP (Brazil); Physics Institute of São Carlos, University of São Paulo, IFSC-USP, Av. Trabalhador são-carlense, 400 Pq. Arnold Schimid, 13566-590 São Carlos, SP (Brazil); Oliveira Perazzoli, Ivan Luiz de, E-mail: ivanperazzoli@hotmail.com [Embrapa Instrumentation, Rua XV de Novembro, 1452, CEP 13560-970 São Carlos, SP (Brazil); Milori, Débora Marcondes Bastos Pereira, E-mail: debora.milori@embrapa.br [Embrapa Instrumentation, Rua XV de Novembro, 1452, CEP 13560-970 São Carlos, SP (Brazil)

2015-09-01

Laser-induced breakdown spectroscopy (LIBS) is a well-known consolidated analytical technique employed successfully for the qualitative and quantitative analysis of solid, liquid, gaseous and aerosol samples of very different nature and origin. Several techniques, such as dual-pulse excitation setup, have been used in order to improve LIBS's sensitivity. The purpose of this paper was to optimize the key parameters as excitation wavelength, delay time and interpulse, that influence the double pulse (DP) LIBS technique in the collinear beam geometry when applied to the analysis at atmospheric air pressure of soil samples of different origin and texture from extreme regions of Brazil. Additionally, a comparative study between conventional single pulse (SP) LIBS and DP LIBS was performed. An optimization of DP LIBS system, choosing the correct delay time between the two pulses, was performed allowing its use for different soil types and the use of different emission lines. In general, the collinear DP LIBS system improved the analytical performances of the technique by enhancing the intensity of emission lines of some elements up to about 5 times, when compared with conventional SP-LIBS, and reduced the continuum emission. Further, the IR laser provided the best performance in re-heating the plasma. - Highlights: • The correct choice of the delay time between the two pulses is crucial for the DP system. • An optimization of DP LIBS system was performed allowing its use for different soil and the use of different emission lines. • The DP LIBS system improved the analytical performances of the technique up to about 5 times, when compared with SP LIBS. • The IR laser provided the best performance in re-heating the plasma.

Low radiation dose non-contrast cardiac CT: is it of value in the evaluation of mechanical aortic valve

International Nuclear Information System (INIS)

Bazeed, Mohamed Fayez; Moselhy, Mohamed Saleh; Rezk, Ahmad Ibrahim; Al-Murayeh, Mushabab Ayedh

2012-01-01

Background: Prosthetic bileaflet mechanical valve function has been traditionally evaluated using echocardiography and fluoroscopy. Multidetector computed tomography (MDCT) is a novel technique for cardiac evaluation. Purpose: To evaluate bileaflet mechanical aortic valves using a low-milliampere (mA), non-contrast MDCT protocol with a limited scan range. Material and Methods: Forty patients with a bileaflet mechanical aortic valve were evaluated using a non-contrast, low-mA, ECG-gated 64 MDCT protocol with a limited scan range. MDCT findings of opening and closing valve angles were correlated to fluoroscopy and echocardiography. Also, the valve visibility was evaluated on MDCT and fluoroscopy according to a 3-point grading scale. Results: The visualization score with the MDCT was significantly superior to the fluoroscopy (3 vs. 2.7). A strong correlation was noted between the opening (r = 0.82) and closing (r = 0.96) valve angles with MDCT and fluoroscopy without a statistically significant difference (P = 0.31 and 0.16, respectively). The mean effective radiation dose of the suggested protocol was 4 ± 0.5 mSv. Five valves were evaluated using transesophageal echocardiography because the valves were difficult to evaluate with transthoracic echocardiography, and all of these valves were evaluated optimally with MDCT. A high-pressure gradient was noted in nine valves, and the MDCT showed that seven of these valves inadequately opened, and two valves opened well, which resulted in patient valve mismatch. Incomplete valve closure was noted in five valves, and the echocardiography showed significant transvalvular regurgitation in all five valves. Conclusion: MDCT can provide a precise measurement of valve function and can potentially evaluate high-pressure gradients and transvalvular regurgitation

Low radiation dose non-contrast cardiac CT: is it of value in the evaluation of mechanical aortic valve

Energy Technology Data Exchange (ETDEWEB)

Bazeed, Mohamed Fayez (Dept. of Diagnostic Radiology, Faculty of Medicine, Mansoura Univ. (Egypt)), email: m_bazeed@yahoo.com; Moselhy, Mohamed Saleh (Cardiology Dept. Faculty of Medicine, Suez Canal Univ. (Egypt)); Rezk, Ahmad Ibrahim (Dept. of Cardiac Surgery, Faculty of Medicine, Aim Shams Univ. (Egypt)); Al-Murayeh, Mushabab Ayedh (Dept. of Cardiac Services, Armed Forces Hospitals Southern Region (Saudi Arabia))

2012-05-15

Background: Prosthetic bileaflet mechanical valve function has been traditionally evaluated using echocardiography and fluoroscopy. Multidetector computed tomography (MDCT) is a novel technique for cardiac evaluation. Purpose: To evaluate bileaflet mechanical aortic valves using a low-milliampere (mA), non-contrast MDCT protocol with a limited scan range. Material and Methods: Forty patients with a bileaflet mechanical aortic valve were evaluated using a non-contrast, low-mA, ECG-gated 64 MDCT protocol with a limited scan range. MDCT findings of opening and closing valve angles were correlated to fluoroscopy and echocardiography. Also, the valve visibility was evaluated on MDCT and fluoroscopy according to a 3-point grading scale. Results: The visualization score with the MDCT was significantly superior to the fluoroscopy (3 vs. 2.7). A strong correlation was noted between the opening (r = 0.82) and closing (r = 0.96) valve angles with MDCT and fluoroscopy without a statistically significant difference (P = 0.31 and 0.16, respectively). The mean effective radiation dose of the suggested protocol was 4 +- 0.5 mSv. Five valves were evaluated using transesophageal echocardiography because the valves were difficult to evaluate with transthoracic echocardiography, and all of these valves were evaluated optimally with MDCT. A high-pressure gradient was noted in nine valves, and the MDCT showed that seven of these valves inadequately opened, and two valves opened well, which resulted in patient valve mismatch. Incomplete valve closure was noted in five valves, and the echocardiography showed significant transvalvular regurgitation in all five valves. Conclusion: MDCT can provide a precise measurement of valve function and can potentially evaluate high-pressure gradients and transvalvular regurgitation

Multilocus Sequence Typing Scheme versus Pulsed-Field Gel Electrophoresis for Typing Mycobacterium abscessus Isolates

Science.gov (United States)

Machado, Gabriel Esquitini; Matsumoto, Cristianne Kayoko; Chimara, Erica; Duarte, Rafael da Silva; de Freitas, Denise; Palaci, Moises; Hadad, David Jamil; Lima, Karla Valéria Batista; Lopes, Maria Luiza; Ramos, Jesus Pais; Campos, Carlos Eduardo; Caldas, Paulo César; Heym, Beate

2014-01-01

Outbreaks of infections by rapidly growing mycobacteria following invasive procedures, such as ophthalmological, laparoscopic, arthroscopic, plastic, and cardiac surgeries, mesotherapy, and vaccination, have been detected in Brazil since 1998. Members of the Mycobacterium chelonae-Mycobacterium abscessus group have caused most of these outbreaks. As part of an epidemiological investigation, the isolates were typed by pulsed-field gel electrophoresis (PFGE). In this project, we performed a large-scale comparison of PFGE profiles with the results of a recently developed multilocus sequence typing (MLST) scheme for M. abscessus. Ninety-three isolates were analyzed, with 40 M. abscessus subsp. abscessus isolates, 47 M. abscessus subsp. bolletii isolates, and six isolates with no assigned subspecies. Forty-five isolates were obtained during five outbreaks, and 48 were sporadic isolates that were not associated with outbreaks. For MLST, seven housekeeping genes (argH, cya, glpK, gnd, murC, pta, and purH) were sequenced, and each isolate was assigned a sequence type (ST) from the combination of obtained alleles. The PFGE patterns of DraI-digested DNA were compared with the MLST results. All isolates were analyzable by both methods. Isolates from monoclonal outbreaks showed unique STs and indistinguishable or very similar PFGE patterns. Thirty-three STs and 49 unique PFGE patterns were identified among the 93 isolates. The Simpson's index of diversity values for MLST and PFGE were 0.69 and 0.93, respectively, for M. abscessus subsp. abscessus and 0.96 and 0.97, respectively, for M. abscessus subsp. bolletii. In conclusion, the MLST scheme showed 100% typeability and grouped monoclonal outbreak isolates in agreement with PFGE, but it was less discriminative than PFGE for M. abscessus. PMID:24899019

Adenosine stress cardiovascular magnetic resonance with variable-density spiral pulse sequences accurately detects coronary artery disease: initial clinical evaluation.

Science.gov (United States)

Salerno, Michael; Taylor, Angela; Yang, Yang; Kuruvilla, Sujith; Ragosta, Michael; Meyer, Craig H; Kramer, Christopher M

2014-07-01

Adenosine stress cardiovascular magnetic resonance perfusion imaging can be limited by motion-induced dark-rim artifacts, which may be mistaken for true perfusion abnormalities. A high-resolution variable-density spiral pulse sequence with a novel density compensation strategy has been shown to reduce dark-rim artifacts in first-pass perfusion imaging. We aimed to assess the clinical performance of adenosine stress cardiovascular magnetic resonance using this new perfusion sequence to detect obstructive coronary artery disease. Cardiovascular magnetic resonance perfusion imaging was performed during adenosine stress (140 μg/kg per minute) and at rest on a Siemens 1.5-T Avanto scanner in 41 subjects with chest pain scheduled for coronary angiography. Perfusion images were acquired during injection of 0.1 mmol/kg Gadolinium-diethylenetriaminepentacetate at 3 short-axis locations using a saturation recovery interleaved variable-density spiral pulse sequence. Significant stenosis was defined as >50% by quantitative coronary angiography. Two blinded reviewers evaluated the perfusion images for the presence of adenosine-induced perfusion abnormalities and assessed image quality using a 5-point scale (1 [poor] to 5 [excellent]). The prevalence of obstructive coronary artery disease by quantitative coronary angiography was 68%. The average sensitivity, specificity, and accuracy were 89%, 85%, and 88%, respectively, with a positive predictive value and negative predictive value of 93% and 79%, respectively. The average image quality score was 4.4±0.7, with only 1 study with more than mild dark-rim artifacts. There was good inter-reader reliability with a κ statistic of 0.67. Spiral adenosine stress cardiovascular magnetic resonance results in high diagnostic accuracy for the detection of obstructive coronary artery disease with excellent image quality and minimal dark-rim artifacts. © 2014 American Heart Association, Inc.

Enhanced spatio-temporal alignment of plantar pressure image sequences using B-splines.

Science.gov (United States)

Oliveira, Francisco P M; Tavares, João Manuel R S

2013-03-01

This article presents an enhanced methodology to align plantar pressure image sequences simultaneously in time and space. The temporal alignment of the sequences is accomplished using B-splines in the time modeling, and the spatial alignment can be attained using several geometric transformation models. The methodology was tested on a dataset of 156 real plantar pressure image sequences (3 sequences for each foot of the 26 subjects) that was acquired using a common commercial plate during barefoot walking. In the alignment of image sequences that were synthetically deformed both in time and space, an outstanding accuracy was achieved with the cubic B-splines. This accuracy was significantly better (p align real image sequences with unknown transformation involved, the alignment based on cubic B-splines also achieved superior results than our previous methodology (p alignment on the dynamic center of pressure (COP) displacement was also assessed by computing the intraclass correlation coefficients (ICC) before and after the temporal alignment of the three image sequence trials of each foot of the associated subject at six time instants. The results showed that, generally, the ICCs related to the medio-lateral COP displacement were greater when the sequences were temporally aligned than the ICCs of the original sequences. Based on the experimental findings, one can conclude that the cubic B-splines are a remarkable solution for the temporal alignment of plantar pressure image sequences. These findings also show that the temporal alignment can increase the consistency of the COP displacement on related acquired plantar pressure image sequences.

Phase-coded multi-pulse technique for ultrasonic high-order harmonic imaging of biological tissues in vitro

International Nuclear Information System (INIS)

Ma Qingyu; Zhang Dong; Gong Xiufen; Ma Yong

2007-01-01

Second or higher order harmonic imaging shows significant improvement in image clarity but is degraded by low signal-noise ratio (SNR) compared with fundamental imaging. This paper presents a phase-coded multi-pulse technique to provide the enhancement of SNR for the desired high-order harmonic ultrasonic imaging. In this technique, with N phase-coded pulses excitation, the received Nth harmonic signal is enhanced by 20 log 10 N dB compared with that in the single-pulse mode, whereas the fundamental and other order harmonic components are efficiently suppressed to reduce image confusion. The principle of this technique is theoretically discussed based on the theory of the finite amplitude sound waves, and examined by measurements of the axial and lateral beam profiles as well as the phase shift of the harmonics. In the experimental imaging for two biological tissue specimens, a plane piston source at 2 MHz is used to transmit a sequence of multiple pulses with equidistant phase shift. The second to fifth harmonic images are obtained using this technique with N = 2 to 5, and compared with the images obtained at the fundamental frequency. Results demonstrate that this technique of relying on higher order harmonics seems to provide a better resolution and contrast of ultrasonic images

Diagnosing upper extremity deep vein thrombosis with non-contrast-enhanced Magnetic Resonance Direct Thrombus Imaging: A pilot study.

Science.gov (United States)

Dronkers, C E A; Klok, F A; van Haren, G R; Gleditsch, J; Westerlund, E; Huisman, M V; Kroft, L J M

2018-03-01

Diagnosing upper extremity deep vein thrombosis (UEDVT) can be challenging. Compression ultrasonography is often inconclusive because of overlying anatomic structures that hamper compressing veins. Contrast venography is invasive and has a risk of contrast allergy. Magnetic Resonance Direct Thrombus Imaging (MRDTI) and Three Dimensional Turbo Spin-echo Spectral Attenuated Inversion Recovery (3D TSE-SPAIR) are both non-contrast-enhanced Magnetic Resonance Imaging (MRI) sequences that can visualize a thrombus directly by the visualization of methemoglobin, which is formed in a fresh blood clot. MRDTI has been proven to be accurate in diagnosing deep venous thrombosis (DVT) of the leg. The primary aim of this pilot study was to test the feasibility of diagnosing UEDVT with these MRI techniques. MRDTI and 3D TSE-SPAIR were performed in 3 pilot patients who were already diagnosed with UEDVT by ultrasonography or contrast venography. In all patients, UEDVT diagnosis could be confirmed by MRDTI and 3D TSE-SPAIR in all vein segments. In conclusion, this study showed that non-contrast MRDTI and 3D TSE-SPAIR sequences may be feasible tests to diagnose UEDVT. However diagnostic accuracy and management studies have to be performed before these techniques can be routinely used in clinical practice. Copyright © 2018 Elsevier Ltd. All rights reserved.

Laser pulses for coherent xuv Raman excitation

Science.gov (United States)

Greenman, Loren; Koch, Christiane P.; Whaley, K. Birgitta

2015-07-01

We combine multichannel electronic structure theory with quantum optimal control to derive femtosecond-time-scale Raman pulse sequences that coherently populate a valence excited state. For a neon atom, Raman target populations of up to 13% are obtained. Superpositions of the ground and valence Raman states with a controllable relative phase are found to be reachable with up to 4.5% population and arbitrary phase control facilitated by the pump pulse carrier-envelope phase. Analysis of the optimized pulse structure reveals a sequential mechanism in which the valence excitation is reached via a fast (femtosecond) population transfer through an intermediate resonance state in the continuum rather than avoiding intermediate-state population with simultaneous or counterintuitive (stimulated Raman adiabatic passage) pulse sequences. Our results open a route to coupling valence excitations and core-hole excitations in molecules and aggregates that locally address specific atoms and represent an initial step towards realization of multidimensional spectroscopy in the xuv and x-ray regimes.

Optical design and studies of a tiled single grating pulse compressor for enhanced parametric space and compensation of tiling errors

Science.gov (United States)

Daiya, D.; Patidar, R. K.; Sharma, J.; Joshi, A. S.; Naik, P. A.; Gupta, P. D.

2017-04-01

A new optical design of tiled single grating pulse compressor has been proposed, set-up and studied. The parametric space, i.e. the laser beam diameters that can be accommodated in the pulse compressor for the given range of compression lengths, has been calculated and shown to have up to two fold enhancement in comparison to our earlier proposed optical designs. The new optical design of the tiled single grating pulse compressor has an additional advantage of self compensation of various tiling errors like longitudinal and lateral piston, tip and groove density mismatch, compared to the earlier designs. Experiments have been carried out for temporal compression of 650 ps positively chirped laser pulses, at central wavelength 1054 nm, down to 235 fs in the tiled grating pulse compressor set up with the proposed design. Further, far field studies have been performed to show the desired compensation of the tiling errors takes place in the new compressor.

Three-level system driven by delayed pulses of finite duration

International Nuclear Information System (INIS)

Ishkhanyan, Artur; Suominen, Kalle-Antti

2002-01-01

We find the exact solution to the three-state problem for a class of intuitive and counterintuitive sequences of delayed pulses of finite duration in terms of the Clausen's generalized hypergeometric function, which reduces to simple analytic expressions, involving elementary functions only, for final occupation probabilities. These analytic results show that the sequence of delayed pulses, independently of the pulse order and applied detunings, can completely remove the population from the initially populated state (thus creating a quantum superposition of two other involved states). This conclusion extends the original result of Vitanov and Stenholm [Phys. Rev. A 55, 648 (1997)], to the case of nonzero two-photon detuning and more general pulse shapes

Application of nonlinear pulse shaping of femtosecond pulse generation in a fiber amplifier at 500 MHz repetition rate

Science.gov (United States)

Liu, Yang; Luo, Daping; Wang, Chao; Zhu, Zhiwei; Li, Wenxue

2018-03-01

We numerically and experimentally demonstrate that a nonlinear pulse shaping technique based on pre-chirping management in a short gain fiber can be exploited to improve the quality of a compressed pulse. With prior tuning of the pulse chirp, the amplified pulse express different nonlinear propagating processes. A spectrum with s flat top and more smooth wings, showing a similariton feature, generates with the optimal initial pulse chirp, and the shortest pulses with minimal pulse pedestals are obtained. Experimental results show the ability of nonlinear pulse shaping to enhance the quality of compressed pulses, as theoretically expected.

Intra-pulse laser absorption sensor with cavity enhancement for oxidation experiments in a rapid compression machine

KAUST Repository

Nasir, Ehson Fawad

2018-05-23

A sensor based on a mid-IR pulsed quantum cascade laser (QCL) and off-axis cavity enhanced absorption spectroscopy (OA-CEAS) has been developed for highly sensitive concentration measurements of carbon monoxide (CO) in a rapid compression machine. The duty cycle and the pulse repetition rate of the laser were optimized for increased tuning range, high chirp rate, and small line width to achieve effective laser-cavity coupling. This enabled spectrally resolved CO line-shape measurements at high pressures (P ~10 bar). A gain factor of 133 and a time resolution of 10 μs were demonstrated. CO concentration-time profiles during the oxidation of highly dilute n-octane/air mixtures were recorded, illustrating new opportunities in RCM experiments for chemical kinetics.

Quasi-Coherent Noise Jamming to LFM Radar Based on Pseudo-random Sequence Phase-modulation

Directory of Open Access Journals (Sweden)

N. Tai

2015-12-01

Full Text Available A novel quasi-coherent noise jamming method is proposed against linear frequency modulation (LFM signal and pulse compression radar. Based on the structure of digital radio frequency memory (DRFM, the jamming signal is acquired by the pseudo-random sequence phase-modulation of sampled radar signal. The characteristic of jamming signal in time domain and frequency domain is analyzed in detail. Results of ambiguity function indicate that the blanket jamming effect along the range direction will be formed when jamming signal passes through the matched filter. By flexible controlling the parameters of interrupted-sampling pulse and pseudo-random sequence, different covering distances and jamming effects will be achieved. When the jamming power is equivalent, this jamming obtains higher process gain compared with non-coherent jamming. The jamming signal enhances the detection threshold and the real target avoids being detected. Simulation results and circuit engineering implementation validate that the jamming signal covers real target effectively.

Pulsed laser deposition of Ag nanoparticles on titanium hydroxide/oxide nanobelt arrays for highly sensitive surface-enhanced Raman spectroscopy

International Nuclear Information System (INIS)

Jing, Yuting; Wang, Huanwen; Zhao, Jie; Yi, Huan; Wang, Xuefeng

2015-01-01

Highlights: • Silver nanoparticles (NPs) were deposited on Ti(OH) 4 nanobelt by pulsed laser deposition (PLD). • The highest enhancement factor of 10 6 and a maximum relative standard deviation (RSD) of 0.18. • Ag 2 O play important role for the high sensitivity Raman phenomenon. • Charge transfer from Ag NPs is also responsible for the enhancement ability. - Abstract: Surface-enhanced Raman scattering (SERS) substrate of Ti(OH) 4 nanobelt arrays (NBAs) was synthesized by a hydrothermal reaction, on which silver nanoparticles (NPs) were deposited by pulsed laser deposition (PLD). Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) revealed the effective high specific surface area with silver NPs decorated on three-dimensional NBAs. Using rhodamine 6G (R6G) as an analyte molecule, the highest enhancement factor of 10 6 and a maximum relative standard deviation (RSD) of 0.18 were obtained. It has been found that the specific morphology of these composite nanobelt arrays and the formation of Ag 2 O play important role for the high sensitivity Raman phenomenon. In addition, the surface plasmon resonance wavelength of Ag decorated Ti(OH) 4 NBAs and the charge transfer from Ag NPs are also responsible for the enhancement ability. For comparison SERS was investigated with silver particles decorated on TiO 2 NBAs, which is much less active

Neural Sequence Generation Using Spatiotemporal Patterns of Inhibition.

Directory of Open Access Journals (Sweden)

Jonathan Cannon

2015-11-01

Full Text Available Stereotyped sequences of neural activity are thought to underlie reproducible behaviors and cognitive processes ranging from memory recall to arm movement. One of the most prominent theoretical models of neural sequence generation is the synfire chain, in which pulses of synchronized spiking activity propagate robustly along a chain of cells connected by highly redundant feedforward excitation. But recent experimental observations in the avian song production pathway during song generation have shown excitatory activity interacting strongly with the firing patterns of inhibitory neurons, suggesting a process of sequence generation more complex than feedforward excitation. Here we propose a model of sequence generation inspired by these observations in which a pulse travels along a spatially recurrent excitatory chain, passing repeatedly through zones of local feedback inhibition. In this model, synchrony and robust timing are maintained not through redundant excitatory connections, but rather through the interaction between the pulse and the spatiotemporal pattern of inhibition that it creates as it circulates the network. These results suggest that spatially and temporally structured inhibition may play a key role in sequence generation.

Neural Sequence Generation Using Spatiotemporal Patterns of Inhibition.

Science.gov (United States)

Cannon, Jonathan; Kopell, Nancy; Gardner, Timothy; Markowitz, Jeffrey

2015-11-01

Stereotyped sequences of neural activity are thought to underlie reproducible behaviors and cognitive processes ranging from memory recall to arm movement. One of the most prominent theoretical models of neural sequence generation is the synfire chain, in which pulses of synchronized spiking activity propagate robustly along a chain of cells connected by highly redundant feedforward excitation. But recent experimental observations in the avian song production pathway during song generation have shown excitatory activity interacting strongly with the firing patterns of inhibitory neurons, suggesting a process of sequence generation more complex than feedforward excitation. Here we propose a model of sequence generation inspired by these observations in which a pulse travels along a spatially recurrent excitatory chain, passing repeatedly through zones of local feedback inhibition. In this model, synchrony and robust timing are maintained not through redundant excitatory connections, but rather through the interaction between the pulse and the spatiotemporal pattern of inhibition that it creates as it circulates the network. These results suggest that spatially and temporally structured inhibition may play a key role in sequence generation.

Producing High Intense Attosecond Pulse Train by Interaction of Three-Color Pulse and Overdense Plasma

Science.gov (United States)

Salehi, M.; Mirzanejad, S.

2017-05-01

Amplifying the attosecond pulse by the chirp pulse amplification method is impossible. Furthermore, the intensity of attosecond pulse is low in the interaction of laser pulse and underdense plasma. This motivates us to propose using a multi-color pulse to produce the high intense attosecond pulse. In the present study, the relativistic interaction of a three-color linearly-polarized laser-pulse with highly overdense plasma is studied. We show that the combination of {{ω }}1, {{ω }}2 and {{ω }}3 frequencies decreases the instance full width at half maximum reflected attosecond pulse train from the overdense plasma surface. Moreover, we show that the three-color pulse increases the intensity of generated harmonics, which is explained by the relativistic oscillating mirror model. The obtained results demonstrate that if the three-color laser pulse interacts with overdense plasma, it will enhance two orders of magnitude of intensity of ultra short attosecond pulses in comparison with monochromatic pulse.

Method for pulse to pulse dose reproducibility applied to electron linear accelerators

International Nuclear Information System (INIS)

Ighigeanu, D.; Martin, D.; Oproiu, C.; Cirstea, E.; Craciun, G.

2002-01-01

An original method for obtaining programmed beam single shots and pulse trains with programmed pulse number, pulse repetition frequency, pulse duration and pulse dose is presented. It is particularly useful for automatic control of absorbed dose rate level, irradiation process control as well as in pulse radiolysis studies, single pulse dose measurement or for research experiments where pulse-to-pulse dose reproducibility is required. This method is applied to the electron linear accelerators, ALIN-10 of 6.23 MeV and 82 W and ALID-7, of 5.5 MeV and 670 W, built in NILPRP. In order to implement this method, the accelerator triggering system (ATS) consists of two branches: the gun branch and the magnetron branch. ATS, which synchronizes all the system units, delivers trigger pulses at a programmed repetition rate (up to 250 pulses/s) to the gun (80 kV, 10 A and 4 ms) and magnetron (45 kV, 100 A, and 4 ms).The accelerated electron beam existence is determined by the electron gun and magnetron pulses overlapping. The method consists in controlling the overlapping of pulses in order to deliver the beam in the desired sequence. This control is implemented by a discrete pulse position modulation of gun and/or magnetron pulses. The instabilities of the gun and magnetron transient regimes are avoided by operating the accelerator with no accelerated beam for a certain time. At the operator 'beam start' command, the ATS controls electron gun and magnetron pulses overlapping and the linac beam is generated. The pulse-to-pulse absorbed dose variation is thus considerably reduced. Programmed absorbed dose, irradiation time, beam pulse number or other external events may interrupt the coincidence between the gun and magnetron pulses. Slow absorbed dose variation is compensated by the control of the pulse duration and repetition frequency. Two methods are reported in the electron linear accelerators' development for obtaining the pulse to pulse dose reproducibility: the method

Multilocus sequence typing scheme versus pulsed-field gel electrophoresis for typing Mycobacterium abscessus isolates.

Science.gov (United States)

Machado, Gabriel Esquitini; Matsumoto, Cristianne Kayoko; Chimara, Erica; Duarte, Rafael da Silva; de Freitas, Denise; Palaci, Moises; Hadad, David Jamil; Lima, Karla Valéria Batista; Lopes, Maria Luiza; Ramos, Jesus Pais; Campos, Carlos Eduardo; Caldas, Paulo César; Heym, Beate; Leão, Sylvia Cardoso

2014-08-01

Outbreaks of infections by rapidly growing mycobacteria following invasive procedures, such as ophthalmological, laparoscopic, arthroscopic, plastic, and cardiac surgeries, mesotherapy, and vaccination, have been detected in Brazil since 1998. Members of the Mycobacterium chelonae-Mycobacterium abscessus group have caused most of these outbreaks. As part of an epidemiological investigation, the isolates were typed by pulsed-field gel electrophoresis (PFGE). In this project, we performed a large-scale comparison of PFGE profiles with the results of a recently developed multilocus sequence typing (MLST) scheme for M. abscessus. Ninety-three isolates were analyzed, with 40 M. abscessus subsp. abscessus isolates, 47 M. abscessus subsp. bolletii isolates, and six isolates with no assigned subspecies. Forty-five isolates were obtained during five outbreaks, and 48 were sporadic isolates that were not associated with outbreaks. For MLST, seven housekeeping genes (argH, cya, glpK, gnd, murC, pta, and purH) were sequenced, and each isolate was assigned a sequence type (ST) from the combination of obtained alleles. The PFGE patterns of DraI-digested DNA were compared with the MLST results. All isolates were analyzable by both methods. Isolates from monoclonal outbreaks showed unique STs and indistinguishable or very similar PFGE patterns. Thirty-three STs and 49 unique PFGE patterns were identified among the 93 isolates. The Simpson's index of diversity values for MLST and PFGE were 0.69 and 0.93, respectively, for M. abscessus subsp. abscessus and 0.96 and 0.97, respectively, for M. abscessus subsp. bolletii. In conclusion, the MLST scheme showed 100% typeability and grouped monoclonal outbreak isolates in agreement with PFGE, but it was less discriminative than PFGE for M. abscessus. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Current Extensions on PULSE

Directory of Open Access Journals (Sweden)

Sanda Dragos

2010-09-01

Full Text Available Using a learning management system (LMS is a common practise nowadays. Such instruments are used in educational institutions to enhance and support the teaching act as well as in industry for training purposes. In a computer science department of an university such instrument tends to be a basic requirement. That is because not only it allows a better management of courses and a better communication between students and professors, but can also serve as a perfect instrument for presenting teaching related materials for computer science subjects. During the years I have created and used several such instruments: a System with Interactive ackNowledgement and Evaluation of students work during laboratory sessions (SINE, a Php Utility used in Laboratories for Student Evaluation (PULSE, and PULSE Extended. The aim of this paper is to present the current enhancements of PULSE.

A pulse generator for xenon lamps

CERN Document Server

Janata, E

2002-01-01

A pulse generator is described, which enhances the analyzing light emitted from a xenon lamp as used in kinetic photospectrometry experiments. The lamp current is increased to 600 A for a duration of 3 ms; the current is constant within +-0.2% during a time interval of 2 ms. Because of instabilities of the lamp arc during pulsing, the use of the enhanced light source is limited to measuring times up to 500 mu s. The enhancement in light intensity depends on the wavelength and amounts to more than 400-fold in the UV-region.

Online Kidney Position Verification Using Non-Contrast Radiographs on a Linear Accelerator with on Board KV X-Ray Imaging Capability

International Nuclear Information System (INIS)

Willis, David J.; Kron, Tomas; Hubbard, Patricia; Haworth, Annette; Wheeler, Greg; Duchesne, Gillian M.

2009-01-01

The kidneys are dose-limiting organs in abdominal radiotherapy. Kilovoltage (kV) radiographs can be acquired using on-board imager (OBI)-equipped linear accelerators with better soft tissue contrast and lower radiation doses than conventional portal imaging. A feasibility study was conducted to test the suitability of anterior-posterior (AP) non-contrast kV radiographs acquired at treatment time for online kidney position verification. Anthropomorphic phantoms were used to evaluate image quality and radiation dose. Institutional Review Board approval was given for a pilot study that enrolled 5 adults and 5 children. Customized digitally reconstructed radiographs (DRRs) were generated to provide a priori information on kidney shape and position. Radiotherapy treatment staff performed online evaluation of kidney visibility on OBI radiographs. Kidney dose measured in a pediatric anthropomorphic phantom was 0.1 cGy for kV imaging and 1.7 cGy for MV imaging. Kidneys were rated as well visualized in 60% of patients (90% confidence interval, 34-81%). The likelihood of visualization appears to be influenced by the relative AP separation of the abdomen and kidneys, the axial profile of the kidneys, and their relative contrast with surrounding structures. Online verification of kidney position using AP non-contrast kV radiographs on an OBI-equipped linear accelerator appears feasible for patients with suitable abdominal anatomy. Kidney position information provided is limited to 2-dimensional 'snapshots,' but this is adequate in some clinical situations and potentially advantageous in respiratory-correlated treatments. Successful clinical implementation requires customized partial DRRs, appropriate imaging parameters, and credentialing of treatment staff.

Research on temperature characteristics of laser energy meter absorber irradiated by ms magnitude long pulse laser

Science.gov (United States)

Li, Nan; Qiao, Chunhong; Fan, Chengyu; Zhang, Jinghui; Yang, Gaochao

2017-10-01

The research on temperature characteristics for large-energy laser energy meter absorber is about continuous wave (CW) laser before. For the measuring requirements of millisecond magnitude long pulse laser energy, the temperature characteristics for absorber are numerically calculated and analyzed. In calculation, the temperature field distributions are described by heat conduction equations, and the metal cylinder cavity is used for absorber model. The results show that, the temperature of absorber inwall appears periodic oscillation with pulse structure, the oscillation period and amplitude respectively relate to the pulse repetition frequency and single pulse energy. With the wall deep increasing, the oscillation amplitude decreases rapidly. The temperature of absorber outerwall is without periodism, and rises gradually with time. The factors to affect the temperature rise of absorber are single pulse energy, pulse width and repetition frequency. When the laser irradiation stops, the temperature between absorber inwall and outerwall will reach agreement rapidly. After special technology processing to enhance the capacity of resisting laser damage for absorber inwall, the ms magnitude long pulse laser energy can be obtained with the method of measuring the temperature of absorber outerwall. Meanwhile, by optimization design of absorber structure, when the repetition frequency of ms magnitude pulse laser is less than 10Hz, the energy of every pulse for low repetition frequency pulse sequence can be measured. The work offers valuable references for the design of ms magnitude large-energy pulse laser energy meter.

双源CT双能量虚拟平扫在结直肠病变的应用%Preliminary Application of Dual-energy Dual-source CT Virtual Non-contrast Imaging in Colorectal Lesions

Institute of Scientific and Technical Information of China (English)

王勇; 雷静; 韩丹; 赵卫; 杨石平; 熊倩

2014-01-01

Purpose To assess the feasibility of applying dual-energy dual-source CT virtual non-contrast (VNC) imaging in the diagnosis of colorectal diseases. Materials and Methods Eighty-ifve patients with clinically suspected colorectal lesions underwent abdominal CT scan as well as arterial and venous phase dual-energy enhanced scan, VCN images of arterial and venous phase were obtained using the dual-energy software, the differences of image quality, radiation dose and diagnostic coincidence rate between the true non-contrast scan and VNC images were compared. Results The radiation dose of two-phase dual-energy scan was 34.8%lower when compared with the conventional three-phase scans. The CT values of the intestinal lesions, metastasis lymph nodes and intestinal fat in VNC were lower than the true unenhanced scan (P0.05), and neither was the diagnostic coincidence rate for intestinal diseases (P>0.05). The noise level of images obtained from VNC was lower than that of the real non-contrast scan (P0.05). Conclusion For colorectal lesions, the virtual non-contrast images from the dual-energy dual-source CT scan can be used to reduce the radiation dose without effecting image quality and diagnosis accuracy.%目的：探讨双源CT双能量虚拟平扫（VNC）技术在结直肠病变诊断中应用的可行性。资料与方法对85例临床疑诊结直肠病变患者行腹部CT平扫及动、静脉期双能量增强扫描，经双能软件处理得到动、静脉期VNC图，比较真实平扫与VNC在图像质量、辐射剂量及诊断符合率方面的差异。结果双能双期扫描辐射剂量较常规三期扫描辐射剂量降低约34.8%。VNC CT值在肠道病变、转移淋巴结、肠周脂肪中低于真实平扫（P0.05）。真实平扫及动、静脉期VNC观察到的肠壁厚度、淋巴结大小、周围侵犯及肝转移差异无统计学意义（P>0.05），对肠道疾病的诊断符合率差异无统计学意义（P>0.05�

Modified Hermite Pulse-Based Wideband Communication for High-Speed Data Transfer in Wireless Sensor Applications

Directory of Open Access Journals (Sweden)

Kushal P. Pradhan

2017-12-01

Full Text Available With technological advances in the field of communication, the need for reliable high-speed data transfer is increasing. The deployment of large number of wireless sensors for remote monitoring and control and streaming of high definition video, voice and image data, etc. are imposing a challenge to the existing network bandwidth allocation for reliable communication. Two novel schemes for ultra-wide band (UWB communication technology have been proposed in this paper with the key objective of intensifying the data rate by taking advantage of the orthogonal properties of the modified Hermite pulse (MHP. In the first scheme, a composite pulse is transmitted and in the second scheme, a sequence of multi-order orthogonal pulses is transmitted in the place of a single UWB pulse. The MHP pulses exhibit a mutually orthogonal property between different ordered pulses and due to this property, simultaneous transmission is achieved without collision in the UWB system, resulting in an increase in transmission capacity or improved bit error rate. The proposed schemes for enhanced data rate will offer high volume data monitoring, assessment, and control of wireless devices without overburdening the network bandwidth and pave the way for new platforms for future high-speed wireless sensor applications.

A new phase modulated binomial-like selective-inversion sequence for solvent signal suppression in NMR.

Science.gov (United States)

Chen, Johnny; Zheng, Gang; Price, William S

2017-02-01

A new 8-pulse Phase Modulated binomial-like selective inversion pulse sequence, dubbed '8PM', was developed by optimizing the nutation and phase angles of the constituent radio-frequency pulses so that the inversion profile resembled a target profile. Suppression profiles were obtained for both the 8PM and W5 based excitation sculpting sequences with equal inter-pulse delays. Significant distortions were observed in both profiles because of the offset effect of the radio frequency pulses. These distortions were successfully reduced by adjusting the inter-pulse delays. With adjusted inter-pulse delays, the 8PM and W5 based excitation sculpting sequences were tested on an aqueous lysozyme solution. The 8 PM based sequence provided higher suppression selectivity than the W5 based sequence. Two-dimensional nuclear Overhauser effect spectroscopy experiments were also performed on the lysozyme sample with 8PM and W5 based water signal suppression. The 8PM based suppression provided a spectrum with significantly increased (~ doubled) cross-peak intensity around the suppressed water resonance compared to the W5 based suppression. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

TU-G-204-06: Correlation Between Texture Analysis-Based Model Observer and Human Observer in Diagnosis of Ischemic Infarct in Non-Contrast Head CT of Adults

International Nuclear Information System (INIS)

Li, B; Fujita, A; Buch, K; Sakai, O

2015-01-01

Purpose: To investigate the correlation between texture analysis-based model observer and human observer in the task of diagnosis of ischemic infarct in non-contrast head CT of adults. Methods: Non-contrast head CTs of five patients (2 M, 3 F; 58–83 y) with ischemic infarcts were retro-reconstructed using FBP and Adaptive Statistical Iterative Reconstruction (ASIR) of various levels (10–100%). Six neuro -radiologists reviewed each image and scored image quality for diagnosing acute infarcts by a 9-point Likert scale in a blinded test. These scores were averaged across the observers to produce the average human observer responses. The chief neuro-radiologist placed multiple ROIs over the infarcts. These ROIs were entered into a texture analysis software package. Forty-two features per image, including 11 GLRL, 5 GLCM, 4 GLGM, 9 Laws, and 13 2-D features, were computed and averaged over the images per dataset. The Fisher-coefficient (ratio of between-class variance to in-class variance) was calculated for each feature to identify the most discriminating features from each matrix that separate the different confidence scores most efficiently. The 15 features with the highest Fisher -coefficient were entered into linear multivariate regression for iterative modeling. Results: Multivariate regression analysis resulted in the best prediction model of the confidence scores after three iterations (df=11, F=11.7, p-value<0.0001). The model predicted scores and human observers were highly correlated (R=0.88, R-sq=0.77). The root-mean-square and maximal residual were 0.21 and 0.44, respectively. The residual scatter plot appeared random, symmetric, and unbiased. Conclusion: For diagnosis of ischemic infarct in non-contrast head CT in adults, the predicted image quality scores from texture analysis-based model observer was highly correlated with that of human observers for various noise levels. Texture-based model observer can characterize image quality of low contrast

TU-G-204-06: Correlation Between Texture Analysis-Based Model Observer and Human Observer in Diagnosis of Ischemic Infarct in Non-Contrast Head CT of Adults

Energy Technology Data Exchange (ETDEWEB)

Li, B; Fujita, A; Buch, K; Sakai, O [Boston University Medical Center, Boston, MA (United States)

2015-06-15

Purpose: To investigate the correlation between texture analysis-based model observer and human observer in the task of diagnosis of ischemic infarct in non-contrast head CT of adults. Methods: Non-contrast head CTs of five patients (2 M, 3 F; 58–83 y) with ischemic infarcts were retro-reconstructed using FBP and Adaptive Statistical Iterative Reconstruction (ASIR) of various levels (10–100%). Six neuro -radiologists reviewed each image and scored image quality for diagnosing acute infarcts by a 9-point Likert scale in a blinded test. These scores were averaged across the observers to produce the average human observer responses. The chief neuro-radiologist placed multiple ROIs over the infarcts. These ROIs were entered into a texture analysis software package. Forty-two features per image, including 11 GLRL, 5 GLCM, 4 GLGM, 9 Laws, and 13 2-D features, were computed and averaged over the images per dataset. The Fisher-coefficient (ratio of between-class variance to in-class variance) was calculated for each feature to identify the most discriminating features from each matrix that separate the different confidence scores most efficiently. The 15 features with the highest Fisher -coefficient were entered into linear multivariate regression for iterative modeling. Results: Multivariate regression analysis resulted in the best prediction model of the confidence scores after three iterations (df=11, F=11.7, p-value<0.0001). The model predicted scores and human observers were highly correlated (R=0.88, R-sq=0.77). The root-mean-square and maximal residual were 0.21 and 0.44, respectively. The residual scatter plot appeared random, symmetric, and unbiased. Conclusion: For diagnosis of ischemic infarct in non-contrast head CT in adults, the predicted image quality scores from texture analysis-based model observer was highly correlated with that of human observers for various noise levels. Texture-based model observer can characterize image quality of low contrast

Effect of pulse sequence parameter selection on signal strength in positive-contrast MRI markers for MRI-based prostate postimplant assessment

Energy Technology Data Exchange (ETDEWEB)

Lim, Tze Yee [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 and The University of Texas at Houston Graduate School of Biomedical Sciences, 6767 Bertner Avenue, Houston, Texas 77030 (United States); Kudchadker, Rajat J., E-mail: rkudchad@mdanderson.org; Wang, Jihong; Ibbott, Geoffrey S. [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States); Stafford, R. Jason [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States); MacLellan, Christopher [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 and The University of Texas at Houston Graduate School of Biomedical Sciences, 6767 Bertner Avenue, Houston, Texas 77030 (United States); Rao, Arvind [Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States); Frank, Steven J. [Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States)

2016-07-15

Purpose: For postimplant dosimetric assessment, computed tomography (CT) is commonly used to identify prostate brachytherapy seeds, at the expense of accurate anatomical contouring. Magnetic resonance imaging (MRI) is superior to CT for anatomical delineation, but identification of the negative-contrast seeds is challenging. Positive-contrast MRI markers were proposed to replace spacers to assist seed localization on MRI images. Visualization of these markers under varying scan parameters was investigated. Methods: To simulate a clinical scenario, a prostate phantom was implanted with 66 markers and 86 seeds, and imaged on a 3.0T MRI scanner using a 3D fast radiofrequency-spoiled gradient recalled echo acquisition with various combinations of scan parameters. Scan parameters, including flip angle, number of excitations, bandwidth, field-of-view, slice thickness, and encoding steps were systematically varied to study their effects on signal, noise, scan time, image resolution, and artifacts. Results: The effects of pulse sequence parameter selection on the marker signal strength and image noise were characterized. The authors also examined the tradeoff between signal-to-noise ratio, scan time, and image artifacts, such as the wraparound artifact, susceptibility artifact, chemical shift artifact, and partial volume averaging artifact. Given reasonable scan time and managable artifacts, the authors recommended scan parameter combinations that can provide robust visualization of the MRI markers. Conclusions: The recommended MRI pulse sequence protocol allows for consistent visualization of the markers to assist seed localization, potentially enabling MRI-only prostate postimplant dosimetry.

Design of auto-control high-voltage control system of pulsed neutron generator

International Nuclear Information System (INIS)

Lv Juntao

2008-01-01

It is difficult to produce multiple anode controlling time sequences under different logging mode for the high-voltage control system of the conventional pulsed neutron generator. It is also difficult realize sequential control among anode high-voltage, filament power supply and target voltage to make neutron yield stable. To these problems, an auto-control high-voltage system of neutron pulsed generator was designed. It not only can achieve anode high-voltage double blast time sequences, which can measure multiple neutron blast time sequences such as Σ, activated spectrum, etc. under inelastic scattering mode, but also can realize neutron generator real-time measurement of multi-state parameters and auto-control such as target voltage pulse width modulation (PWM), filament current, anode current, etc., there by it can produce stable neutron yield and realize stable and accurate measurement of the pulsed neutron full spectral loging tool. (authors)

Random noise effects in pulse-mode digital multilayer neural networks.

Science.gov (United States)

Kim, Y C; Shanblatt, M A

1995-01-01

A pulse-mode digital multilayer neural network (DMNN) based on stochastic computing techniques is implemented with simple logic gates as basic computing elements. The pulse-mode signal representation and the use of simple logic gates for neural operations lead to a massively parallel yet compact and flexible network architecture, well suited for VLSI implementation. Algebraic neural operations are replaced by stochastic processes using pseudorandom pulse sequences. The distributions of the results from the stochastic processes are approximated using the hypergeometric distribution. Synaptic weights and neuron states are represented as probabilities and estimated as average pulse occurrence rates in corresponding pulse sequences. A statistical model of the noise (error) is developed to estimate the relative accuracy associated with stochastic computing in terms of mean and variance. Computational differences are then explained by comparison to deterministic neural computations. DMNN feedforward architectures are modeled in VHDL using character recognition problems as testbeds. Computational accuracy is analyzed, and the results of the statistical model are compared with the actual simulation results. Experiments show that the calculations performed in the DMNN are more accurate than those anticipated when Bernoulli sequences are assumed, as is common in the literature. Furthermore, the statistical model successfully predicts the accuracy of the operations performed in the DMNN.

Automatic gallbladder segmentation using combined 2D and 3D shape features to perform volumetric analysis in native and secretin-enhanced MRCP sequences.

Science.gov (United States)

Gloger, Oliver; Bülow, Robin; Tönnies, Klaus; Völzke, Henry

2017-11-24

We aimed to develop the first fully automated 3D gallbladder segmentation approach to perform volumetric analysis in volume data of magnetic resonance (MR) cholangiopancreatography (MRCP) sequences. Volumetric gallbladder analysis is performed for non-contrast-enhanced and secretin-enhanced MRCP sequences. Native and secretin-enhanced MRCP volume data were produced with a 1.5-T MR system. Images of coronal maximum intensity projections (MIP) are used to automatically compute 2D characteristic shape features of the gallbladder in the MIP images. A gallbladder shape space is generated to derive 3D gallbladder shape features, which are then combined with 2D gallbladder shape features in a support vector machine approach to detect gallbladder regions in MRCP volume data. A region-based level set approach is used for fine segmentation. Volumetric analysis is performed for both sequences to calculate gallbladder volume differences between both sequences. The approach presented achieves segmentation results with mean Dice coefficients of 0.917 in non-contrast-enhanced sequences and 0.904 in secretin-enhanced sequences. This is the first approach developed to detect and segment gallbladders in MR-based volume data automatically in both sequences. It can be used to perform gallbladder volume determination in epidemiological studies and to detect abnormal gallbladder volumes or shapes. The positive volume differences between both sequences may indicate the quantity of the pancreatobiliary reflux.

Enhanced regulatory sequence prediction using gapped k-mer features.

Science.gov (United States)

Ghandi, Mahmoud; Lee, Dongwon; Mohammad-Noori, Morteza; Beer, Michael A

2014-07-01

Oligomers of length k, or k-mers, are convenient and widely used features for modeling the properties and functions of DNA and protein sequences. However, k-mers suffer from the inherent limitation that if the parameter k is increased to resolve longer features, the probability of observing any specific k-mer becomes very small, and k-mer counts approach a binary variable, with most k-mers absent and a few present once. Thus, any statistical learning approach using k-mers as features becomes susceptible to noisy training set k-mer frequencies once k becomes large. To address this problem, we introduce alternative feature sets using gapped k-mers, a new classifier, gkm-SVM, and a general method for robust estimation of k-mer frequencies. To make the method applicable to large-scale genome wide applications, we develop an efficient tree data structure for computing the kernel matrix. We show that compared to our original kmer-SVM and alternative approaches, our gkm-SVM predicts functional genomic regulatory elements and tissue specific enhancers with significantly improved accuracy, increasing the precision by up to a factor of two. We then show that gkm-SVM consistently outperforms kmer-SVM on human ENCODE ChIP-seq datasets, and further demonstrate the general utility of our method using a Naïve-Bayes classifier. Although developed for regulatory sequence analysis, these methods can be applied to any sequence classification problem.

Enhanced regulatory sequence prediction using gapped k-mer features.

Directory of Open Access Journals (Sweden)

Mahmoud Ghandi

2014-07-01

Full Text Available Oligomers of length k, or k-mers, are convenient and widely used features for modeling the properties and functions of DNA and protein sequences. However, k-mers suffer from the inherent limitation that if the parameter k is increased to resolve longer features, the probability of observing any specific k-mer becomes very small, and k-mer counts approach a binary variable, with most k-mers absent and a few present once. Thus, any statistical learning approach using k-mers as features becomes susceptible to noisy training set k-mer frequencies once k becomes large. To address this problem, we introduce alternative feature sets using gapped k-mers, a new classifier, gkm-SVM, and a general method for robust estimation of k-mer frequencies. To make the method applicable to large-scale genome wide applications, we develop an efficient tree data structure for computing the kernel matrix. We show that compared to our original kmer-SVM and alternative approaches, our gkm-SVM predicts functional genomic regulatory elements and tissue specific enhancers with significantly improved accuracy, increasing the precision by up to a factor of two. We then show that gkm-SVM consistently outperforms kmer-SVM on human ENCODE ChIP-seq datasets, and further demonstrate the general utility of our method using a Naïve-Bayes classifier. Although developed for regulatory sequence analysis, these methods can be applied to any sequence classification problem.

Pulse carving using nanocavity-enhanced nonlinear effects in photonic crystal Fano structures

DEFF Research Database (Denmark)

Bekele, Dagmawi Alemayehu; Yu, Yi; Hu, Hao

2018-01-01

We experimentally demonstrate the use of a photonic crystal Fano resonance for carving-out short pulses from long-duration input pulses. This is achieved by exploiting an asymmetric Fano resonance combined with carrier-induced nonlinear effects in a photonic crystal membrane structure. The use...... of a nanocavity concentrates the input field to a very small volume leading to an efficient nonlinear resonance shift that carves a short pulse out of the input pulse. Here, we demonstrate shortening of ∼500  ps and ∼100  ps long pulses to ∼30  ps and ∼20  ps pulses, respectively. Furthermore, we demonstrate...

Repetitive transcranial magnetic stimulator with controllable pulse parameters

Science.gov (United States)

Peterchev, Angel V.; Murphy, David L.; Lisanby, Sarah H.

2011-06-01

The characteristics of transcranial magnetic stimulation (TMS) pulses influence the physiological effect of TMS. However, available TMS devices allow very limited adjustment of the pulse parameters. We describe a novel TMS device that uses a circuit topology incorporating two energy storage capacitors and two insulated-gate bipolar transistor (IGBT) modules to generate near-rectangular electric field pulses with adjustable number, polarity, duration, and amplitude of the pulse phases. This controllable pulse parameter TMS (cTMS) device can induce electric field pulses with phase widths of 10-310 µs and positive/negative phase amplitude ratio of 1-56. Compared to conventional monophasic and biphasic TMS, cTMS reduces energy dissipation up to 82% and 57% and decreases coil heating up to 33% and 41%, respectively. We demonstrate repetitive TMS trains of 3000 pulses at frequencies up to 50 Hz with electric field pulse amplitude and width variability less than the measurement resolution (1.7% and 1%, respectively). Offering flexible pulse parameter adjustment and reduced power consumption and coil heating, cTMS enhances existing TMS paradigms, enables novel research applications and could lead to clinical applications with potentially enhanced potency.

Measurement of left atrial volume by 2D and 3D non-contrast computed tomography compared with cardiac magnetic resonance imaging

DEFF Research Database (Denmark)

Fredgart, Maise Høigaard; Carter-Storch, Rasmus; Møller, Jacob Eifer

2018-01-01

Background: Cardiac magnetic resonance imaging (MRI) is considered the gold standard for assessment of left atrial (LA) volume. We assessed the feasibility of evaluating LA volume using 3D non-contrast computed tomography (NCCT). Furthermore, since manual tracing of LA volume is time consuming, we...... evaluated the accuracy of the LA area using 2D NCCT imaging for LA volume assessment. Methods: MRI and NCCT imaging were performed in 69 patients before and one year after aortic valve replacement. In 3D MRI and 3D NCCT, each slice was manually traced, excluding the pulmonary veins and atrial appendage...

Dynamic oxygen-enhanced MRI of cerebrospinal fluid.

Directory of Open Access Journals (Sweden)

Taha M Mehemed

Full Text Available Oxygen causes an increase in the longitudinal relaxation rate of tissues through its T1-shortening effect owing to its paramagnetic properties. Due to such effects, MRI has been used to study oxygen-related signal intensity changes in various body parts including cerebrospinal fluid (CSF space. Oxygen enhancement of CSF has been mainly studied using MRI sequences with relatively longer time resolution such as FLAIR, and T1 value calculation. In this study, fifteen healthy volunteers were scanned using fast advanced spin echo MRI sequence with and without inversion recovery pulse in order to dynamically track oxygen enhancement of CSF. We also focused on the differences of oxygen enhancement at sulcal and ventricular CSF. Our results revealed that CSF signal after administration of oxygen shows rapid signal increase in both sulcal CSF and ventricular CSF on both sequences, with statistically significant predominant increase in sulcal CSF compared with ventricular CSF. CSF is traditionally thought to mainly form from the choroid plexus in the ventricles and is absorbed at the arachnoid villi, however, it is also believed that cerebral arterioles contribute to the production and absorption of CSF, and controversy remains in terms of the precise mechanism. Our results demonstrated rapid oxygen enhancement in sulcal CSF, which may suggest inhaled oxygen may diffuse into sulcal CSF space rapidly probably due to the abundance of pial arterioles on the brain sulci.

SU-E-J-224: Using UTE and T1 Weighted Spin Echo Pulse Sequences for MR-Only Treatment Planning; Phantom Study

Energy Technology Data Exchange (ETDEWEB)

Yu, H; Fatemi, A [Sunnybrook Health Sciences Centre, Toronto, Ontario (Canada); Sahgal, A [University of Toronto, Toronto, ON (Canada)

2015-06-15

Purpose: Investigating a new approach in MRI based treatment planning using the combination of (Ultrashort Echo Time) UTE and T1 weighted spin echo pulse sequences to delineate air, bone and water (soft tissues) in generating pseudo CT images comparable with CT. Methods: A gel phantom containing chicken bones, ping pang balls filled with distilled water and air bubbles, was made. It scanned with MRI using UTE and 2D T1W SE pulse sequences with (in plane resolution= 0.53mm, slice thickness= 2 mm) and CT with (in plane resolution= 0.5 mm and slice thickness= 0.75mm) as a ground truth for geometrical accuracy. The UTE and T1W SE images were registered with CT using mutual information registration algorithm provided by Philips Pinnacle treatment planning system. The phantom boundaries were detected using Canny edge detection algorithm for CT, and MR images. The bone, air bubbles and water in ping pong balls were segmented from CT images using threshold 300HU, - 950HU and 0HU, respectively. These tissue inserts were automatically segmented from combined UTE and T1W SE images using edge detection and relative intensity histograms of the phantom. The obtained segmentations of air, bone and water inserts were evaluated with those obtained from CT. Results: Bone and air can be clearly differentiated in UTE images comparable to CT. Combining UTE and T1W SE images successfully segmented the air, bone and water. The maximum segmentation differences from combine MRI images (UTE and T1W SE) and CT are within 1.3 mm, 1.1mm for bone, air, respectively. The geometric distortion of UTE sequence is small less than 1 pixel (0.53 mm) of MR image resolution. Conclusion: Our approach indicates that MRI can be used solely for treatment planning and its quality is comparable with CT.

Non-contrast-enhanced MR portography with balanced steady-state free-precession sequence and time-spatial labeling inversion pulses: comparison of imaging with flow-in and flow-out methods.

Science.gov (United States)

Furuta, Akihiro; Isoda, Hiroyoshi; Yamashita, Rikiya; Ohno, Tsuyoshi; Kawahara, Seiya; Shimizu, Hironori; Fujimoto, Koji; Kido, Aki; Kusahara, Hiroshi; Togashi, Kaori

2014-09-01

To compare and evaluate images of non-contrast-enhanced MR portography acquired with two different methods, the flow-in and flow-out methods. Twenty-five healthy volunteers were examined using respiratory-triggered three-dimensional balanced steady-state free-precession (SSFP) with two selective inversion recovery pulses (flow-in method) and one tagging pulse and one nonselective inversion recovery pulse (flow-out method). For quantitative analysis, vessel-to-liver contrast (Cv-l) ratios of the main portal vein (MPV), right portal vein (RPV), and left portal vein (LPV) were measured. The quality of portal vein visualization was scored using a four-point scale. The Cv-ls of the MPV, RPV, and LPV were all significantly higher with the flow-out than flow-in method (MPV = 0.834 ± 0.06 versus 0.711 ± 0.10; RPV = 0.861 ± 0.04 versus 0.729 ± 0.11; LPV = 0.786 ± 0.08 versus 0.545 ± 0.22; P flow-out method showed higher scores than with the flow-in method. With the flow-out method, visual scores of the MPV, RPV, portal vein branches of segments 4 (P4), and 8 (P8) were significantly better than with the flow-in method (MPV = 3.4 ± 0.7 versus 2.6 ± 0.9; RPV = 4.0 ± 0.0 versus 3.5 ± 0.9; P4 = 2.8 ± 1.3 versus 1.6 ± 1.0; P8 = 4.0 ± 0.0 versus 2.9 ± 1.1; P flow-out method improves the visualization of the intrahepatic portal vein in comparison with the flow-in method. J. Magn. Reson. Imaging 2014;40:583-587. © 2013 Wiley Periodicals, Inc. © 2013 Wiley Periodicals, Inc.

Centrically reordered inversion recovery half-Fourier single-shot turbo spin-echo sequence: improvement of the image quality of oxygen-enhanced MRI

International Nuclear Information System (INIS)

Ohno, Yoshiharu; Hatabu, Hiroto; Higashino, Takanori; Kawamitsu, Hideaki; Watanabe, Hirokazu; Takenaka, Daisuke; Cauteren, Marc van; Sugimura, Kazuro

2004-01-01

Purpose: The purpose of the study presented here was to determine the improvement in image quality of oxygen-enhanced magnetic resonance (MR) subtraction imaging obtained with a centrically reordered inversion recovery half-Fourier single-shot turbo spin-echo (c-IR-HASTE) sequence compared with that obtained with a conventional sequentially reordered inversion recovery single-shot HASTE (s-IR-HASTE) sequence for pulmonary imaging. Materials and methods: Oxygen-enhanced MR imaging using a 1.5 T whole body scanner was performed on 12 healthy, non-smoking volunteers. Oxygen-enhanced MR images were obtained with the coronal two-dimensional (2D) c-IR-HASTE sequence and 2D s-IR-HASTE sequence combined with respiratory triggering. For a 256x256 matrix, 132 phase-encoding steps were acquired including four steps for phase correction. Inter-echo spacing for each sequence was 4.0 ms. The effective echo time (TE) for c-IR-HASTE was 4.0 ms, and 16 ms for s-IR-HASTE. The inversion time (TI) was 900 ms. To determine the improvement in oxygen-enhanced MR subtraction imaging by c-IR-HASTE, CNRs of subtraction image, overall image quality, and image degradation of the c-IR-HASTE and s-IR-HASTE techniques were statistically compared. Results: CNR, overall image quality, and image degradation of c-IR-HASTE images showed significant improvement compared to those s-IR-HASTE images (P<0.05). Conclusion: Centrically reordered inversion recovery half-Fourier single-shot turbo spin-echo (c-IR-HASTE) sequence enhanced the signal from the lung and improved the image quality of oxygen-enhanced MR subtraction imaging

Cationic peptide exposure enhances pulsed-electric-field-mediated membrane disruption.

Science.gov (United States)

Kennedy, Stephen M; Aiken, Erik J; Beres, Kaytlyn A; Hahn, Adam R; Kamin, Samantha J; Hagness, Susan C; Booske, John H; Murphy, William L

2014-01-01

The use of pulsed electric fields (PEFs) to irreversibly electroporate cells is a promising approach for destroying undesirable cells. This approach may gain enhanced applicability if the intensity of the PEF required to electrically disrupt cell membranes can be reduced via exposure to a molecular deliverable. This will be particularly impactful if that reduced PEF minimally influences cells that are not exposed to the deliverable. We hypothesized that the introduction of charged molecules to the cell surfaces would create regions of enhanced transmembrane electric potential in the vicinity of each charged molecule, thereby lowering the PEF intensity required to disrupt the plasma membranes. This study will therefore examine if exposure to cationic peptides can enhance a PEF's ability to disrupt plasma membranes. We exposed leukemia cells to 40 μs PEFs in media containing varying concentrations of a cationic peptide, polyarginine. We observed the internalization of a membrane integrity indicator, propidium iodide (PI), in real time. Based on an individual cell's PI fluorescence versus time signature, we were able to determine the relative degree of membrane disruption. When using 1-2 kV/cm, exposure to >50 μg/ml of polyarginine resulted in immediate and high levels of PI uptake, indicating severe membrane disruption, whereas in the absence of peptide, cells predominantly exhibited signatures indicative of no membrane disruption. Additionally, PI entered cells through the anode-facing membrane when exposed to cationic peptide, which was theoretically expected. Exposure to cationic peptides reduced the PEF intensity required to induce rapid and irreversible membrane disruption. Critically, peptide exposure reduced the PEF intensities required to elicit irreversible membrane disruption at normally sub-electroporation intensities. We believe that these cationic peptides, when coupled with current advancements in cell targeting techniques will be useful tools in

Femtosecond pulse shaping using the geometric phase.

Science.gov (United States)

Gökce, Bilal; Li, Yanming; Escuti, Michael J; Gundogdu, Kenan

2014-03-15

We demonstrate a femtosecond pulse shaper that utilizes polarization gratings to manipulate the geometric phase of an optical pulse. This unique approach enables circular polarization-dependent shaping of femtosecond pulses. As a result, it is possible to create coherent pulse pairs with orthogonal polarizations in a 4f pulse shaper setup, something until now that, to our knowledge, was only achieved via much more complex configurations. This approach could be used to greatly simplify and enhance the functionality of multidimensional spectroscopy and coherent control experiments, in which multiple coherent pulses are used to manipulate quantum states in materials of interest.

Enhanced optical confinement of dye-doped dielectric nanoparticles using a picosecond-pulsed near-infrared laser

International Nuclear Information System (INIS)

Kittiravechote, A; Chiang, W-Y; Usman, A; Liau, I; Masuhara, H

2014-01-01

We demonstrate a novel strategy to increase the capability of confining numerous dye-doped polymeric nanobeads (diameter 100 nm) with laser trapping. Unlike most classical works of optical trapping that address mainly the stiffness of the optical trap, our work concerns an increase in the number of particles confined near the laser focus. We developed an imaging system of light scattering in which a condenser lamp was employed to illuminate the focal plane of the objective lens, and the scattering of the incoherent light was specifically measured to determine the number of confined nanobeads. In contrast to preceding work that used mainly continuous-wave or femtosecond-pulsed lasers, we employed a picosecond-pulsed laser with the half-wavelength of the laser particularly falling within the absorption band of the dopant. Our results show that the number of doped nanobeads held by the laser is significantly greater than that of the bare nanobeads of the same dimension. In striking contrast, the confinement of the nanobeads of the two types was comparable when a continuous-wave laser of the same wavelength and power was employed. The number of confined dye-doped nanobeads increased nonlinearly with the power of the pulsed laser; this dependence was fitted satisfactorily with a second-order polynomial. Supported by theoretical analysis, we attribute the enhanced confinement of doped nanobeads in part to an increased effective refractive index resulting from two-photon resonance between the optical field of the laser and the dopant of the nanobead. We envisage that our findings would evoke applications that benefit from controlled confinement or aggregation of nanomaterials with the employment of near-infrared pulsed lasers. (letter)

Contrast-enhanced Magnetic Resonance Imaging of Pelvic Bone Metastases at 3.0 T: Comparison Between 3-dimensional T1-weighted CAIPIRINHA-VIBE Sequence and 2-dimensional T1-weighted Turbo Spin-Echo Sequence.

Science.gov (United States)

Yoon, Min A; Hong, Suk-Joo; Lee, Kyu-Chong; Lee, Chang Hee

2018-06-12

This study aimed to compare 3-dimensional T1-weighted gradient-echo sequence (CAIPIRINHA-volumetric interpolated breath-hold examination [VIBE]) with 2-dimensional T1-weighted turbo spin-echo sequence for contrast-enhanced magnetic resonance imaging (MRI) of pelvic bone metastases at 3.0 T. Thirty-one contrast-enhanced MRIs of pelvic bone metastases were included. Two contrast-enhanced sequences were evaluated for the following parameters: overall image quality, sharpness of pelvic bone, iliac vessel clarity, artifact severity, and conspicuity and edge sharpness of the smallest metastases. Quantitative analysis was performed by calculating signal-to-noise ratio and contrast-to-noise ratio of the smallest metastases. Significant differences between the 2 sequences were assessed. CAIPIRINHA-VIBE had higher scores for overall image quality, pelvic bone sharpness, iliac vessel clarity, and edge sharpness of the metastatic lesions, and had less artifacts (all P 0.05). Our results suggest that CAIPIRINHA-VIBE may be superior to turbo spin-echo for contrast-enhanced MRI of pelvic bone metastases at 3.0 T.

Assessment of left ventricular hemodynamics by Gd-DTPA enhanced high speed cine MRI

International Nuclear Information System (INIS)

Matsumura, Kentaro; Nakase, Emiko; Kawai, Ichiro

1992-01-01

To assess the validity of Gd-DTPA enhanced high speed cine MRI in left ventricular (LV) volumes and ejection fraction (EF), high speed cine MRI was compared with intra-venous digital subtraction left ventriculography (IV-DSA) in 14 patients. All patients underwent conventional cine MRI and Gd-DTPA enhanced high speed MRI, simultaneously. The pulse sequences of high speed MRI were TR 8 ms (TR 6 ms plus rewind pulse 2 ms), TE 3.2 ms, matrix 128, phase encode 8 or 6 and NEX 1. Comparison with LV-volume showed a high correlation (y = 0.854x + 1,699, r = 0.985) between high speed cine MRI and VI-DSA. To make left ventricular volume curve by area-length method in cine MRI, manual tracing of LV-cavity was more difficult in conventional cine MRI-method than enhanced high speed cine MRI-method. In conclusion, first pass-Gd-DTPA enhanced high speed cine MRI, using the horizontal long axis approach and the multiphase study, is a highly, accurate reproducible method of evaluating LV-volumetry. (author)

Ultrafast T2-weighted single shot spin-echo sequences: applications on abdominal and pelvic pathologies

International Nuclear Information System (INIS)

Martin, J.; Martin, C.; Falco, J.; Esteban, L.

1999-01-01

The magnetic resonance imaging (MRI) sequences that obtain all the data using a sole excitation pulse of 90 degree centigrade, filling the K space in a single repetition time (TR) is known as snap shot or single shot (SS). The SS sequence based on the rapid acquisition with relaxation enhancement (SS-RARE) method, designed by Hening (1) and a variation of it with a half-Fourier reconstruction (SS-HF-RARE (HASTEL)) (2, 3) are capable of obtaining high contrast images in T2, in very short times, that oscillate between one to several seconds. The clinical application of these sequences to abdominal and pelvic pathologies is increasing, providing and improvement in the contrast resolution, but also in the spatial resolution, with a high relation signal/noise ratio, high contrast and absence of movement artifacts. (Author)

Criteria to average out the chemical shift anisotropy in solid-state NMR when irradiated with BABA I, BABA II, and C7 radiofrequency pulse sequences.

Science.gov (United States)

Stephane Mananga, Eugene

2013-01-01

Floquet-Magnus expansion is used to study the effect of chemical shift anisotropy in solid-state NMR of rotating solids. The chemical shift interaction is irradiated with two types of radiofrequency pulse sequences: BABA and C7. The criteria for the chemical shift anisotropy to be averaged out in each rotor period are obtained. Copyright © 2013 Elsevier Inc. All rights reserved.

Three-dimensional gradient echo versus spin echo sequence in contrast-enhanced imaging of the pituitary gland at 3 T

Energy Technology Data Exchange (ETDEWEB)

Kakite, Suguru, E-mail: sugkaki@med.tottori-u.ac.jp [Division of Radiology, Department of Pathophysiological and Therapeutic Science, Faculty of Medicine, Tottori University, 36-1, Nishicho, Yonago 683-8503 (Japan); Fujii, Shinya [Division of Radiology, Department of Pathophysiological and Therapeutic Science, Faculty of Medicine, Tottori University, 36-1, Nishicho, Yonago 683-8503 (Japan); Kurosaki, Masamichi [Department of Neurosurgery, Faculty of Medicine, Tottori University, 36-1, Nishicho, Yonago 683-8503 (Japan); Kanasaki, Yoshiko; Matsusue, Eiji; Kaminou, Toshio; Ogawa, Toshihide [Division of Radiology, Department of Pathophysiological and Therapeutic Science, Faculty of Medicine, Tottori University, 36-1, Nishicho, Yonago 683-8503 (Japan)

2011-07-15

Introduction: To clarify whether a three-dimensional-gradient echo (3D-GRE) or spin echo (SE) sequence is more useful for evaluating sellar lesions on contrast-enhanced T1-weighted MR imaging at 3.0 Tesla (T). Methods: We retrospectively assessed contrast-enhanced T1-weighted images using 3D-GRE and SE sequences at 3.0 T obtained from 33 consecutive patients with clinically suspected sellar lesions. Two experienced neuroradiologists evaluated the images qualitatively in terms of the following criteria: boundary edge of the cavernous sinus and pituitary gland, border of sellar lesions, delineation of the optic nerve and cranial nerves within the cavernous sinus, susceptibility and flow artifacts, and overall image quality. Results: At 3.0 T, 3D-GRE provided significantly better images than the SE sequence in terms of the border of sellar lesions, delineation of cranial nerves, and overall image quality; there was no significant difference regarding the boundary edge of the cavernous sinus and pituitary gland. In addition, the 3D-GRE sequence showed fewer pulsation artifacts but more susceptibility artifacts. Conclusion: Our results indicate that 3D-GRE is the more suitable sequence for evaluating sellar lesions on contrast-enhanced T1-weighted imaging at 3.0 T.

Combining multi-pulse excitation and chirp coding in contrast-enhanced ultrasound imaging

International Nuclear Information System (INIS)

Crocco, M; Sciallero, C; Trucco, A; Pellegretti, P

2009-01-01

The development of techniques to separate the response of the contrast agent from that of the biological tissues is of great importance in ultrasound medical imaging. In the literature, one can find various solutions involving the use of multiple transmitted signals and the weighted sum of related echoes. In this paper, the combination of one of these multi-pulse techniques with a coded excitation is proposed and assessed. Coded excitation has been used mainly to increase the signal-to-noise ratio (SNR) and the penetration depth, provided that a matched filtering is applied in the reception chain. However, it has been shown that a signal with a long duration time also increases the backscattered echoes produced by the microbubbles and, consequently, the contrast-to-tissue ratio. Therefore, the implementation of a multi-pulse technique using a long coded pulse can yield a better contrast-to-tissue ratio and SNR. This paper investigates the combination of the linear chirp pulse with a multi-pulse technique based on the transmission of three pulses. The performance was evaluated using both simulated and real signals, assessing the improvement in the contrast-to-tissue ratio and SNR, the visual quality of the images obtained and the axial accuracy. A comparison with the same multi-pulse technique implemented using a traditional amplitude-modulated pulse revealed that the deployment of a chirp pulse produces several noticeable advantages and only a minor drawback

MRI evaluation of myometrial invasion by endometrial carcinoma. Comparison between fast-spin-echo T2W and coronal FMPSPGR Gadolinium-Dota-Enhanced Sequences

International Nuclear Information System (INIS)

Nasi, Francesca; Fiocchi, Federica; Pecchi, Annarita; Torricelli, Pietro; Rivasi, Francesco

2005-01-01

Purpose. The depth of myometrial invasion by endometrial carcinoma strongly affects the incidence of metastasis to regional nodes and influences the surgical strategies. The aim of this paper is to compare the results of FSE T2-w and Gadolinium-enhanced FMPSGR MR sequences in assessing the depth of myometrial invasion by endometrial cancer. Materials and methods. Forty-five women with histopathologically-proven endometrial carcinoma underwent preoperative MRI. Axial SE TI w, axial, sagittal and para-coronal FSE T2w and para-coronal Gadolinium enhanced FMPSGR sequences were performed using a high field strength magnet (1.5T). Within one month of MR all patients underwent hysterectomy, and anatomical evaluation of the surgical specimen was done sectioning the uterus along the short axis. Based upon the results of the histological evaluation the results of the FSE T2w and Gadolinium-enhanced sequences were compared and the statistical difference between the results obtained was statistically evaluated. Results. The histological evaluation showed intra mucosal neoplasm in 11 patients, myometrial infiltration less than 50% in 31 patients, myometrial infiltration more than 50% in 12 patients and transmural cancer 1 patient. Statistical evaluation showed that the FSE T2w sequence had a global sensitivity and specificity of 80.6% and 87.6%, respectively, with a mean Negative Predictive Value of 92.6% and a mean Positive Predictive Value of 86%. Gadolinium-enhanced FMPSPGR sequence had a global sensitivity and specificity of 90.6% and 93.3%, respectively, with a mean Negative Predictive Value of 96,3% and a mean Positive Predictive Value of 88%. The staging accuracy (χ 2 test) on FMPSPGR images (95%) was higher than that on FSE T2w images (78%). Conclusions. In our experience Gadolinium-enhanced dynamic sequences increase the accuracy of MR imaging in diagnosing the depth of myometrial invasion. In particular they improve the visualisation of the inner myometrium, the so

Usefulness of enhanced breathhold 3D spoiled gradient-echo MRA for intrathoracic mass

International Nuclear Information System (INIS)

Kobayashi, Takeshi; Kadoya, Masumi; Kamimura, Ryoichi; Takashima, Tsutomu

1999-01-01

Enhanced Breathhold 3D Spoiled Gradient-echo MRA was very attractive method for not only evaluating relationship between intrathoracic mass and intrathoracic vessels, but also visualizing small pulmonary vessels that could not be detected conventional MRA methods. Moreover, this methods could be applied for evaluating vascularity of the lesions. This method will be accepted as routine pulse sequence for evaluating intrathoracic mass especially malignant tumors. (author)

Use of pulsed-neutron capture logs to identify steam breakthrough

International Nuclear Information System (INIS)

Masse, P.J.; Gosney, T.C.; Long, D.L.

1991-01-01

This paper reports on identification of steam-breakthrough zones in a stacked sand/shale sequence with variable lateral continuity which is difficult. Such identification, however, would allow the modification of field operations to enhance recovery through improved vertical sweep and heat injection. Twenty pulsed-neutron capture (PNC) logs were run to identify the steam-breakthrough zone(s) in a seven-pattern area of Mobil's Middle expansion (MIDX) Steamflood Project in the South Belridge field. These PNC data were combined with data from recent replacement wells and a detailed geologic analysis. Evaluation of this combined information allowed identification of potential steam-breakthrough zone(s), and operations were modified to reduce and eliminate steam breakthrough

Susceptibility contrast imaging of CO2-induced changes in the blood volume of the human brain

DEFF Research Database (Denmark)

Rostrup, Egill; Larsson, H B; Toft, P B

1996-01-01

PURPOSE: To investigate changes in the regional cerebral blood volume (rCBV) in human subjects during rest and hypercapnia by MR imaging, and to compare the results from contrast-enhanced and noncontrast-enhanced susceptibility-weighted imaging. MATERIAL AND METHODS: Five healthy volunteers (aged...... to be in accordance with results obtained by other methods. Noncontrast functional MR (fMR) imaging showed signal increases in gray matter, but also inconsistent changes in some white matter regions. CONCLUSION: In this experiment, contrast-enhanced imaging seemed to show a somewhat higher sensitivity towards changes...

Functional assessment of human enhancer activities using whole-genome STARR-sequencing.

Science.gov (United States)

Liu, Yuwen; Yu, Shan; Dhiman, Vineet K; Brunetti, Tonya; Eckart, Heather; White, Kevin P

2017-11-20

Genome-wide quantification of enhancer activity in the human genome has proven to be a challenging problem. Recent efforts have led to the development of powerful tools for enhancer quantification. However, because of genome size and complexity, these tools have yet to be applied to the whole human genome.  In the current study, we use a human prostate cancer cell line, LNCaP as a model to perform whole human genome STARR-seq (WHG-STARR-seq) to reliably obtain an assessment of enhancer activity. This approach builds upon previously developed STARR-seq in the fly genome and CapSTARR-seq techniques in targeted human genomic regions. With an improved library preparation strategy, our approach greatly increases the library complexity per unit of starting material, which makes it feasible and cost-effective to explore the landscape of regulatory activity in the much larger human genome. In addition to our ability to identify active, accessible enhancers located in open chromatin regions, we can also detect sequences with the potential for enhancer activity that are located in inaccessible, closed chromatin regions. When treated with the histone deacetylase inhibitor, Trichostatin A, genes nearby this latter class of enhancers are up-regulated, demonstrating the potential for endogenous functionality of these regulatory elements. WHG-STARR-seq provides an improved approach to current pipelines for analysis of high complexity genomes to gain a better understanding of the intricacies of transcriptional regulation.

Sensitive detection of chlorine in iron oxide by single pulse and dual pulse laser-induced breakdown spectroscopy

Science.gov (United States)

Pedarnig, J. D.; Haslinger, M. J.; Bodea, M. A.; Huber, N.; Wolfmeir, H.; Heitz, J.

2014-11-01

The halogen chlorine is hard to detect in laser-induced breakdown spectroscopy (LIBS) mainly due to its high excited state energies of 9.2 and 10.4 eV for the most intense emission lines at 134.72 nm and 837.59 nm, respectively. We report on sensitive detection of Cl in industrial iron oxide Fe2O3 powder by single-pulse (SP) and dual-pulse (DP) LIBS measurements in the near infrared range in air. In compacted powder measured by SP excitation (Nd:YAG laser, 532 nm) Cl was detected with limit of detection LOD = 440 ppm and limit of quantitation LOQ = 720 ppm. Orthogonal DP LIBS was studied on pressed Fe2O3 pellets and Fe3O4 ceramics. The transmission of laser-induced plasma for orthogonal Nd:YAG 1064 nm and ArF 193 nm laser pulses showed a significant dependence on interpulse delay time (ipd) and laser wavelength (λL). The UV pulses (λL = 193 nm) were moderately absorbed in the plasma and the Cl I emission line intensity was enhanced while IR pulses (λL = 1064 nm) were not absorbed and Cl signals were not enhanced at ipd = 3 μs. The UV laser enhancement of Cl signals is attributed to the much higher signal/background ratio for orthogonal DP excitation compared to SP excitation and to the increased plasma temperature and electron number density. This enabled measurement at a very short delay time of td ≥ 0.1 μs with respect to the re-excitation pulse and detection of the very rapidly decaying Cl emission with higher efficiency.

Evaluation of Dixon Sequence on Hybrid PET/MR Compared with Contrast-Enhanced PET/CT for PET-Positive Lesions

International Nuclear Information System (INIS)

Jeong, Ju Hye; Cho, Ihn Ho; Kong, Eun Jung; Chun, Kyung Ah

2014-01-01

Hybrid positron emission tomography and magnetic resonance (PET/MR) imaging performs a two-point Dixon MR sequence for attenuation correction. However, MR data in hybrid PET/MR should provide anatomic and morphologic information as well as an attenuation map. We evaluated the Dixon sequence of hybrid PET/MR for anatomic correlation of PET-positive lesions compared with contrast-enhanced PET/computed tomography (CT) in patients with oncologic diseases. Twelve patients underwent a single injection, dual imaging protocol. PET/CT was performed with an intravenous contrast agent (85±13 min after 18 F-FDG injection of 403± 45 MBq) and then (125±19 min after injection) PET/MR was performed. Attenuation correction and anatomic allocation of PET were performed using contrast-enhanced CT for PET/CT and Dixon MR sequence for hybrid PET/MR. The Dixon MR sequence and contrast-enhanced CT were compared for anatomic correlation of PET-positive lesions (scoring scale ranging from 0 to 3 for visual ratings). Additionally, standardized uptake values (SUVs) for the detected lesions were assessed for quantitative comparison. Both hybrid PET/MR and contrast-enhanced PET/CT identified 55 lesions with increased FDG uptake in ten patients. In total, 28 lymph nodes, 11 bone lesions, 3 dermal nodules, 3 pleural thickening lesions, 2 thyroid nodules, 1 pancreas, 1 liver, 1 ovary, 1 uterus, 1 breast, 1 soft tissue and 2 lung lesions were present. The best performance was observed for anatomic correlation of PET findings by the contrast-enhanced CT scans (contrast-enhanced CT, 2.64± 0.70; in-phase, 1.29±1.01; opposed-phase, 1.29±1.15; water-weighted, 1.71±1.07; fat weighted, 0.56±1.03). A significant difference was observed between the scores obtained from the contrast-enhanced CT and all four coregistered Dixon MR images. Quantitative evaluation revealed a high correlation between the SUVs measured with hybrid PET/MR (SUVmean, 2.63±1.62; SUVmax, 4.30±2.88) and contrast-enhanced PET

Evaluation of Dixon Sequence on Hybrid PET/MR Compared with Contrast-Enhanced PET/CT for PET-Positive Lesions

Energy Technology Data Exchange (ETDEWEB)

Jeong, Ju Hye; Cho, Ihn Ho; Kong, Eun Jung; Chun, Kyung Ah [Yeungnam Univ. Hospital, Daegu (Korea, Republic of)

2014-03-15

Hybrid positron emission tomography and magnetic resonance (PET/MR) imaging performs a two-point Dixon MR sequence for attenuation correction. However, MR data in hybrid PET/MR should provide anatomic and morphologic information as well as an attenuation map. We evaluated the Dixon sequence of hybrid PET/MR for anatomic correlation of PET-positive lesions compared with contrast-enhanced PET/computed tomography (CT) in patients with oncologic diseases. Twelve patients underwent a single injection, dual imaging protocol. PET/CT was performed with an intravenous contrast agent (85±13 min after {sup 18}F-FDG injection of 403± 45 MBq) and then (125±19 min after injection) PET/MR was performed. Attenuation correction and anatomic allocation of PET were performed using contrast-enhanced CT for PET/CT and Dixon MR sequence for hybrid PET/MR. The Dixon MR sequence and contrast-enhanced CT were compared for anatomic correlation of PET-positive lesions (scoring scale ranging from 0 to 3 for visual ratings). Additionally, standardized uptake values (SUVs) for the detected lesions were assessed for quantitative comparison. Both hybrid PET/MR and contrast-enhanced PET/CT identified 55 lesions with increased FDG uptake in ten patients. In total, 28 lymph nodes, 11 bone lesions, 3 dermal nodules, 3 pleural thickening lesions, 2 thyroid nodules, 1 pancreas, 1 liver, 1 ovary, 1 uterus, 1 breast, 1 soft tissue and 2 lung lesions were present. The best performance was observed for anatomic correlation of PET findings by the contrast-enhanced CT scans (contrast-enhanced CT, 2.64± 0.70; in-phase, 1.29±1.01; opposed-phase, 1.29±1.15; water-weighted, 1.71±1.07; fat weighted, 0.56±1.03). A significant difference was observed between the scores obtained from the contrast-enhanced CT and all four coregistered Dixon MR images. Quantitative evaluation revealed a high correlation between the SUVs measured with hybrid PET/MR (SUVmean, 2.63±1.62; SUVmax, 4.30±2.88) and contrast-enhanced

Clinical usefulness of fluid-attenuated inversion recovery (FLAIR) sequences in intracranial lesions focusing on emergent cases

Energy Technology Data Exchange (ETDEWEB)

Kuramochi, Masashi; Niitsu, Mamoru; Itai, Yuji [Tsukuba Univ., Ibaraki (Japan). Inst. of Clinical Medicine; Wada, Mitsuyoshi

1997-06-01

Fluid-Attenuated Inversion Recovery (FLAIR) Pulse Sequences with inversion times of 1700 ms and echo times of 110 ms were used to demonstrate the brain of cerebrovascular disease (CVD) and brain trauma. The long inversion times and long echo times nulls the signal from cerebrospinal fluid and produces heavy T{sub 2} weighting images. We compared FLAIR Pulse Sequences with T{sub 2} weighted image Pulse Sequences for signal intensities of CVD and trauma. FLAIR Pulse Sequences is useful to detect at the periphery of the cerebral hemispheres, but infratentorial small infarctions often cannot be detected for its iso-intensity and slight intensity changes. In all patient of traumatic-subarachnoid hemorrhage (t-SAH) can be definitely detected high signal intensity of the cerebral hemispheres. (author)

Left Gastric Vein Visualization with Hepatopetal Flow Information in Healthy Subjects Using Non-Contrast-Enhanced Magnetic Resonance Angiography with Balanced Steady-State Free-Precession Sequence and Time-Spatial Labeling Inversion Pulse.

Science.gov (United States)

Furuta, Akihiro; Isoda, Hiroyoshi; Ohno, Tsuyoshi; Ono, Ayako; Yamashita, Rikiya; Arizono, Shigeki; Kido, Aki; Sakashita, Naotaka; Togashi, Kaori

2018-01-01

To selectively visualize the left gastric vein (LGV) with hepatopetal flow information by non-contrast-enhanced magnetic resonance angiography under a hypothesis that change in the LGV flow direction can predict the development of esophageal varices; and to optimize the acquisition protocol in healthy subjects. Respiratory-gated three-dimensional balanced steady-state free-precession scans were conducted on 31 healthy subjects using two methods (A and B) for visualizing the LGV with hepatopetal flow. In method A, two time-spatial labeling inversion pulses (Time-SLIP) were placed on the whole abdomen and the area from the gastric fornix to the upper body, excluding the LGV area. In method B, nonselective inversion recovery pulse was used and one Time-SLIP was placed on the esophagogastric junction. The detectability and consistency of LGV were evaluated using the two methods and ultrasonography (US). Left gastric veins by method A, B, and US were detected in 30 (97%), 24 (77%), and 23 (74%) subjects, respectively. LGV flow by US was hepatopetal in 22 subjects and stagnant in one subject. All hepatopetal LGVs by US coincided with the visualized vessels in both methods. One subject with non-visualized LGV in method A showed stagnant LGV by US. Hepatopetal LGV could be selectively visualized by method A in healthy subjects.

Diffusion-weighted MR imaging of the abdomen with pulse triggering

International Nuclear Information System (INIS)

Muertz, P.; Pauleit, D.; Traeber, F.; Kreft, B.P.; Schild, H.H.

2000-01-01

Purpose: The aim of this work was to reduce the influence of motion on diffusion-weighted MR images of the abdomen by pulse triggering of single-shot sequences. Methods: Five healthy volunteers were examined both without and with finger pulse-triggering of a diffusion-weighted single-shot echo planar MR imaging sequence at 1.5 T. Series of diffusion-weighted images were acquired at different phases of the cardiac cycle by varying the time delay between finger pulse and sequence acquisition. The measurements were repeated three times. The diffusion weighted images were analysed by measuring the signal intensities and by determining the ADC values within the spleen, kidney and liver. Results: The magnitude of motion artifacts on diffusion weighted images shows a strong dependence on the trigger delay. The optimum trigger delay is found to be between 500 and 600 ms. For these values the abdominal organs appear homogeneous on all diffusion weighted images and the strongest signal intensities are detected. At optimum triggering the accuracy of the apparent diffusion coefficients is up to 10 times better than without triggering. Moreover, the standard deviation of the repeated measurements is smaller than 12% for all volunteers and for all organs. Without triggering the standard deviation is larger by a factor of 4 on average. Conclusion: Pulse triggering of single-shot sequences leads to significant reduction of motion related artifacts on diffusion weighted images of the abdomen and provides more accurate and reproducible ADC values. (orig.) [de

PULSE DRYING EXPERIMENT AND BURNER CONSTRUCTION

Energy Technology Data Exchange (ETDEWEB)

Robert States

2006-07-15

Non steady impingement heat transfer is measured. Impingement heating consumes 130 T-BTU/Yr in paper drying, but is only 25% thermally efficient. Pulse impingement is experimentally shown to enhance heat transfer by 2.8, and may deliver thermal efficiencies near 85%. Experimental results uncovered heat transfer deviations from steady theory and from previous investigators, indicating the need for further study and a better theoretical framework. The pulse burner is described, and its roll in pulse impingement is analyzed.

Enhanced skin permeation of naltrexone by pulsed electromagnetic fields in human skin in vitro.

Science.gov (United States)

Krishnan, Gayathri; Edwards, Jeffrey; Chen, Yan; Benson, Heather A E

2010-06-01

The aim of the present study was to evaluate the skin permeation of naltrexone (NTX) under the influence of a pulsed electromagnetic field (PEMF). The permeation of NTX across human epidermis and a silicone membrane in vitro was monitored during and after application of the PEMF and compared to passive application. Enhancement ratios of NTX human epidermis permeation by PEMF over passive diffusion, calculated based on the AUC of cumulative NTX permeation to the receptor compartment verses time for 0-4 h, 4-8 h, and over the entire experiment (0-8 h) were 6.52, 5.25, and 5.66, respectively. Observation of the curve indicated an initial enhancement of NTX permeation compared to passive delivery whilst the PEMF was active (0-4 h). This was followed by a secondary phase after termination of PEMF energy (4-8 h) in which there was a steady increase in NTX permeation. No significant enhancement of NTX penetration across silicone membrane occurred with PEMF application in comparison to passively applied NTX. In a preliminary experiment PEMF enhanced the penetration of 10 nm gold nanoparticles through the stratum corneum as visualized by multiphoton microscopy. This suggests that the channels through which the nanoparticles move must be larger than the 10 nm diameter of these rigid particles. (c) 2009 Wiley-Liss, Inc. and the American Pharmacists Association

High-order harmonic and attosecond pulse generation for a few-cycle laser pulse in modulated hollow fibres

International Nuclear Information System (INIS)

Zhang Xiangyun; Sun Zhenrong; Wang Yufeng; Chen Guoliang; Wang Zugeng; Li Ruxin; Zeng Zhinan; Xu Zhizhan

2007-01-01

High harmonic generation from Ar and He atoms by a few-cycle laser pulse in periodic and chirped hollow fibres is investigated theoretically by a self-consistent model. Based on enhanced high harmonics in a periodic hollow fibre, a chirped hollow fibre is proposed to improve quasi-phase matching for the generated harmonics near the cutoff. The results show that the extended and enhanced harmonics near the cutoff are well phase-matched, and a single x-ray pulse with a duration of 279 as in Ar gas and 255 as in He gas can be achieved by frequency synthesizing of high harmonics in the well-selected cutoff bandwidth. The results show that this technique is a potential candidate to generate an intense isolated attosecond pulse in the 'water window' spectrum

Effect of sequential isoproturon pulse exposure on Scenedesmus vacuolatus.

Science.gov (United States)

Vallotton, Nathalie; Eggen, Rik Ilda Lambertus; Chèvre, Nathalie

2009-04-01

Aquatic organisms are typically exposed to fluctuating concentrations of herbicides in streams. To assess the effects on algae of repeated peak exposure to the herbicide isoproturon, we subjected the alga Scenedesmus vacuolatus to two sequential pulse exposure scenarios. Effects on growth and on the inhibition of the effective quantum yield of photosystem II (PSII) were measured. In the first scenario, algae were exposed to short, 5-h pulses at high isoproturon concentrations (400 and 1000 microg/l), each followed by a recovery period of 18 h, while the second scenario consisted of 22.5-h pulses at lower concentrations (60 and 120 microg/l), alternating with short recovery periods (1.5 h). In addition, any changes in the sensitivity of the algae to isoproturon following sequential pulses were examined by determining the growth rate-EC(50) prior to and following exposure. In both exposure scenarios, we found that algal growth and its effective quantum yield were systematically inhibited during the exposures and that these effects were reversible. Sequential pulses to isoproturon could be considered a sequence of independent events. Nevertheless, a consequence of inhibited growth during the repeated exposures is the cumulative decrease in biomass production. Furthermore, in the second scenario, when the sequence of long pulses began to approach a scenario of continuous exposure, a slight increase in the tolerance of the algae to isoproturon was observed. These findings indicated that sequential pulses do affect algae during each pulse exposure, even if algae recover between the exposures. These observations could support an improved risk assessment of fluctuating exposures to reversibly acting herbicides.

Time-stretch microscopy based on time-wavelength sequence reconstruction from wideband incoherent source

International Nuclear Information System (INIS)

Zhang, Chi; Xu, Yiqing; Wei, Xiaoming; Tsia, Kevin K.; Wong, Kenneth K. Y.

2014-01-01

Time-stretch microscopy has emerged as an ultrafast optical imaging concept offering the unprecedented combination of the imaging speed and sensitivity. However, dedicated wideband and coherence optical pulse source with high shot-to-shot stability has been mandated for time-wavelength mapping—the enabling process for ultrahigh speed wavelength-encoded image retrieval. From the practical point of view, exploiting methods to relax the stringent requirements (e.g., temporal stability and coherence) for the source of time-stretch microscopy is thus of great value. In this paper, we demonstrated time-stretch microscopy by reconstructing the time-wavelength mapping sequence from a wideband incoherent source. Utilizing the time-lens focusing mechanism mediated by a narrow-band pulse source, this approach allows generation of a wideband incoherent source, with the spectral efficiency enhanced by a factor of 18. As a proof-of-principle demonstration, time-stretch imaging with the scan rate as high as MHz and diffraction-limited resolution is achieved based on the wideband incoherent source. We note that the concept of time-wavelength sequence reconstruction from wideband incoherent source can also be generalized to any high-speed optical real-time measurements, where wavelength is acted as the information carrier

Investigations on the pulse operation of YAYOI

International Nuclear Information System (INIS)

1977-04-01

This report is composed of ten independent documents concerning the pulse operation of YAYOI, which were prepared in the period between July, 1976, and March, 1977. The titles of the documents included in this report are: (1) the operational sequence of the linac neutron generating facility, (2) safety systems of linac pulse operation and the treatment and preservation of neutron generating targets, (3) nuclear calculation concerning linac pulse operation, (4) simulated natural uranium core, (5) linac neutron target system, (6) computer processing accompanying linac pulse operation, (7) fundamental concept of electron beam generation within the reactor room, (8) reactor room shielding requirements for the linac neutron source, (9) TOF measuring room, and (10) utilization of low energy neutrons from P-YAYOI operation. (Aoki, K.)

Direct generation of all-optical random numbers from optical pulse amplitude chaos.

Science.gov (United States)

Li, Pu; Wang, Yun-Cai; Wang, An-Bang; Yang, Ling-Zhen; Zhang, Ming-Jiang; Zhang, Jian-Zhong

2012-02-13

We propose and theoretically demonstrate an all-optical method for directly generating all-optical random numbers from pulse amplitude chaos produced by a mode-locked fiber ring laser. Under an appropriate pump intensity, the mode-locked laser can experience a quasi-periodic route to chaos. Such a chaos consists of a stream of pulses with a fixed repetition frequency but random intensities. In this method, we do not require sampling procedure and external triggered clocks but directly quantize the chaotic pulses stream into random number sequence via an all-optical flip-flop. Moreover, our simulation results show that the pulse amplitude chaos has no periodicity and possesses a highly symmetric distribution of amplitude. Thus, in theory, the obtained random number sequence without post-processing has a high-quality randomness verified by industry-standard statistical tests.

Design of Optical Pulse Position Modulation (PPM) Translating Receiver

Energy Technology Data Exchange (ETDEWEB)

Mendez, A J; Hernandez, V J; Gagliardi, R M; Bennett, C V

2009-06-19

M-ary pulse position modulation (M-ary PPM) signaling is a means of transmitting multiple bits per symbol in an intensity modulated/direct detection (IM/DD) system. PPM is used in applications with average power limitations. In optical communication systems, PPM becomes challenging to implement at gigabit rates and/or large M, since pulsed signaling requires higher electronic processing bandwidths than the fundamental transmission rate. they have thus been exploring techniques for PPM communications using optical processing. Previous work described a transmitter algorithm that directly translates a bit sequence of N digital bits to the optical pulse position m for any M = 2{sup N}. It has been considerably more difficult to define a similar receiver algorithm that translates the received optical pulse position directly back to a bit sequence with minimal electronic processing. Designs for specific Ms (e.g., 4-ary) have been shown and implemented, but are difficult to scale to larger M. In this work, they present for the first time a generalized PPM translating receiver that is applicable to all M and data rates.

Pulsed laser-assisted focused electron-beam-induced etching of titanium with XeF2: enhanced reaction rate and precursor transport.

Science.gov (United States)

Noh, J H; Fowlkes, J D; Timilsina, R; Stanford, M G; Lewis, B B; Rack, P D

2015-02-25

In order to enhance the etch rate of electron-beam-induced etching, we introduce a laser-assisted focused electron-beam-induced etching (LA-FEBIE) process which is a versatile, direct write nanofabrication method that allows nanoscale patterning and editing. The results demonstrate that the titanium electron stimulated etch rate via the XeF2 precursor can be enhanced up to a factor of 6 times with an intermittent pulsed laser assist. The evolution of the etching process is correlated to in situ stage current measurements and scanning electron micrographs as a function of time. The increased etch rate is attributed to photothermally enhanced Ti-F reaction and TiF4 desorption and in some regimes enhanced XeF2 surface diffusion to the reaction zone.

Enhancement of mosquito trapping efficiency by using pulse width modulated light emitting diodes

Science.gov (United States)

Liu, Yu-Nan; Liu, Yu-Jen; Chen, Yi-Chian; Ma, Hsin-Yi; Lee, Hsiao-Yi

2017-01-01

In this study, a light-driving bug zapper is presented for well controlling the diseases brought by insects, such as mosquitoes. In order to have the device efficient to trap the insect pests in off-grid areas, pulse width modulated light emitting diodes (PWM-LED) combined with a solar power module are proposed and implemented. With specific PWM electric signals to drive the LED, it is found that no matter what the ability of catching insects or the consumed power efficiency can be enhanced thus. It is demonstrated that 40% of the UV LED consumed power and 25.9% of the total load power consumption can be saved, and the trapped mosquitoes are about 250% increased when the PWM method is applied in the bug zapper experiments.

The diagnostic value of dual energy virtual non-contrast images of dual-source CT in the diagnosis of com-mon benign liver diseases%双源CT双能量虚拟平扫对肝脏常见良性病变的诊断价值

Institute of Scientific and Technical Information of China (English)

刘盼; 王凤; 李邦国; 罗显丽; 王梦; 王荣品

2017-01-01

Objective To investigate the diagnostic value and limitations of dual-energy virtual non-con-trast images of dual-source CT in common benign liver diseases. Methods Dual-source CT was performed on 226 upper abdomen pathogenesis patients. The conventional non-contrast (CNC) scan was performed with single-energy mode, the arterial phase and portal phase scans were performed with dual-energy mode. The virtual non-contrast (VNC) images were derived from the portal data using liver virtual non-contrast software. 117 patients with common benign liver diseases were retrospectively analyzed in CNC and VNC. The lesion detectability, effective radiation doses for single-energy mode and dual-energy mode were compared. Results Among 117 patients, there were 28 (73.6%) hemangiomas, 58 (85.3%) calcifications or stones in VNC, but the hemangiomas, calcifications or stones in CNC were 37 (97.3%) and 68 (100%), respectively. The hemangiomas, calcifications or stones in VNC and CNC were significantly different (P 0.05). The CTDIvol, DLP and ED of dual-energy mode were obviously lower than those of single-energy mode (P 0.05);双能模式下CTDI、DLP及ED均低于单能模式,差异有统计学意义(P<0.05).结论:虚拟平扫对血管瘤、钙化或结石的检出低于常规平扫,对囊肿及脂肪肝的检出无差异.VNC技术可减低CT检查的辐射剂量,具有潜在的临床应用价值.

Dynamic MRI of tumours in head and neck with a contrast-enhanced FLASH-2D sequence

International Nuclear Information System (INIS)

Maeurer, J.; Rausch, M.; Richter, W.S.; Boeck, J.C.; Steinkamp, H.J.; Vogl, T.J.; Felix, R.

1995-01-01

The purpose of this study was to evaluate the utility of a dynamic contrast enhanced FLASH-2D sequence for differential diagnosis of tumours in head and neck in 93 patients. Initially, the localization of the lesion and the selection of four representative slices for the dynamic study were obtained by a T2-weighted spin-echo sequence (TR 2000-3000 ms; TE 25/90 ms). After IV bolus injection of the contrast agent 10 images were acquired during a period of 3 min by a FLASH-2D sequence (TR 60 ms; TE 6 ms; flip angle 40 ; matrix 256 x 256; one acquisition). The percentage signal intensity (SI) increase (r) and the slope (S) of the curve were calculated on the basis of the SI time curve of the pathological lesion and of muscle. Inflammatory processes could be differentiated from malignant or benign tumours by means of a higher contrast enhancement. The time of the maximum SI was not specific for the different lesions. In comparison with muscle the maximum SI change was achieved earlier in a pathological process. (orig.)

Pulse-dilation enhanced gated optical imager with 5 ps resolution (invited)

Energy Technology Data Exchange (ETDEWEB)

Hilsabeck, T. J.; Kilkenny, J. D. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Hares, J. D.; Dymoke-Bradshaw, A. K. L. [Kentech Instruments Ltd., Wallingford, Oxfordshire OX10 (United Kingdom); Bell, P. M.; Koch, J. A.; Celliers, P. M.; Bradley, D. K.; McCarville, T.; Pivovaroff, M.; Soufli, R.; Bionta, R. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2010-10-15

A 5 ps gated framing camera was demonstrated using the pulse-dilation of a drifting electron signal. The pulse-dilation is achieved by accelerating a photoelectron derived information pulse with a time varying potential [R. D. Prosser, J. Phys. E 9, 57 (1976)]. The temporal dependence of the accelerating potential causes a birth time dependent axial velocity dispersion that spreads the pulse as it transits a drift region. The expanded pulse is then imaged with a conventional gated microchannel plate based framing camera and the effective gating time of the combined instrument is reduced over that of the framing camera alone. In the drift region, electron image defocusing in the transverse or image plane is prevented with a large axial magnetic field. Details of the unique issues associated with rf excited photocathodes were investigated numerically and a prototype instrument based on this principle was recently constructed. Temporal resolution of the instrument was measured with a frequency tripled femtosecond laser operating at 266 nm. The system demonstrated 20x temporal magnification and the results are presented here. X-ray image formation strategies and photometric calculations for inertial confinement fusion implosion experiments are also examined.

Laser beam welding of titanium nitride coated titanium using pulse-shaping

Directory of Open Access Journals (Sweden)

Milton Sergio Fernandes de Lima

2005-09-01

Full Text Available A new welding method which allows the assembly of two titanium nitride coated titanium parts is proposed. The welding procedure utilizes the possibility for pulse-shaping in order to change the energy distribution profile during the laser pulse. The pulse-shaping is composed of three elements: a a short high power pulse for partial ablation at the surface; b a long pulse for thermal penetration; and c a quenching slope for enhanced weldability. The combination of these three elements produces crack-free welds. The weld microstructure is changed in comparison to normal welding, i.e. with a rectangular pulse, as the nitrogen and the microhardness are more homogenously distributed in the weld under pulse-shaping conditions. This laser pulse dissolves the TiN layer and allows nitrogen to diffuse into the melt pool, also contributing to an enhanced weldability by providing suitable thermal conditions.

Efficacy of the fluid attenuated inversion recovery (FLAIR) sequence of MRI as a preoperative diagnosis of hippocampal sclerosis

International Nuclear Information System (INIS)

Morioka, Takato; Nishio, Shunji; Mihara, Futoshi; Muraishi, Mitsuteru; Hisada, Kei; Hasuo, Kanehiro; Fukui, Masashi

1998-01-01

A newly advanced MRI pulse sequence, the FLAIR (fluid attenuated inversion recovery) imaging, in which a long TE spin echo sequence is used with suppression of the CSF with an inversion pulse, displays the CSF space as a no-signal intensity area. There have been only a few reports on the FLAIR pulse sequence of temporal lobe epilepsy (TLE) as yet. We examined 9 cases of intractable TLE by FLAIR images and analyzed the advantages and disadvantages of the FLAIR pulse sequence for decision making on temporal lobectomy. All patients underwent anterior temporal lobectomy with hippocampectomy, and the diagnoses were confirmed histologically after surgery. Abnormally high T2 signals (HT2S) were more conspicuous with the FLAIR sequence than with any of the conventional sequences. Tilted axial plane, orientated along to the long axis of the hippocampal body, clearly demonstrated hippocampal atrophy (HA). Selection of a FLAIR sequence into the routine MR examination of patients with TLE is recommended. (author)

Liver acquisition with acceleration volume acquisition gadolinium-enhanced magnetic resonance combined with T2 sequences in the diagnosis of local recurrence of rectal cancer.

Science.gov (United States)

Cao, Wuteng; Li, Fangqian; Gong, Jiaying; Liu, Dechao; Deng, Yanhong; Kang, Liang; Zhou, Zhiyang

2016-11-22

To investigate the efficacy of liver acquisition with acceleration volume acquisition (LAVA) gadolinium-enhanced magnetic resonance (MR) sequences and to assess its added accuracy in diagnosing local recurrence (LR) of rectal cancer with conventional T2-weighted fast spin echo (FSE) sequences. Pelvic MRI, including T2-weighted FSE sequences, gadolinium-enhanced sequences of LAVA and T1-weighted FSE with fat suppression, was performed on 225 patients with postoperative rectal cancer. Two readers evaluated the presence of LR according to "T2" (T2 sequences only), "T2 + LAVA-Gad" (LAVA and T2 imaging), and "T2 + T1-fs-Gad" (T1 fat suppression-enhanced sequence with T2 images). To evaluate diagnostic efficiency, imaging quality with LAVA and T1-fs-Gad by subjective scores and the signal intensity (SI) ratio. In the result, the SI ratio of LAVA was significantly higher than that of T1-fs-Gad (p = 0.0001). The diagnostic efficiency of "T2 + LAVA-Gad" was better than that of "T2 + T1-fs-Gad" (p = 0.0016 for Reader 1, p = 0.0001 for Reader 2) and T2 imaging only (p = 0.0001 for Reader 1; p = 0.0001 for Reader 2). Therefore, LAVA gadolinium-enhanced MR increases the accuracy of diagnosis of LR from rectal cancer and could replace conventional T1 gadolinium-enhanced sequences in the postoperative pelvic follow-up of rectal cancer.

A Novel Transcranial Magnetic Stimulator Inducing Near Rectangular Pulses with Controllable Pulse Width (cTMS)

Science.gov (United States)

Jalinous, Reza; Lisanby, Sarah H.

2013-01-01

A novel transcranial magnetic stimulation (TMS) device with controllable pulse width (PW) and near rectangular pulse shape (cTMS) is described. The cTMS device uses an insulated gate bipolar transistor (IGBT) with appropriate snubbers to switch coil currents up to 7 kA, enabling PW control from 5 μs to over 100 μs. The near-rectangular induced electric field pulses use 22–34% less energy and generate 67–72% less coil heating compared to matched conventional cosine pulses. CTMS is used to stimulate rhesus monkey motor cortex in vivo with PWs of 20 to 100 μs, demonstrating the expected decrease of threshold pulse amplitude with increasing PW. The technological solutions used in the cTMS prototype can expand functionality, and reduce power consumption and coil heating in TMS, enhancing its research and therapeutic applications. PMID:18232369

Arbitrary digital pulse sequence generator with delay-loop timing

Science.gov (United States)

Hošák, Radim; Ježek, Miroslav

2018-04-01

We propose an idea of an electronic multi-channel arbitrary digital sequence generator with temporal granularity equal to two clock cycles. We implement the generator with 32 channels using a low-cost ARM microcontroller and demonstrate its capability to produce temporal delays ranging from tens of nanoseconds to hundreds of seconds, with 24 ns timing granularity and linear scaling of delay with respect to the number of delay loop iterations. The generator is optionally synchronized with an external clock source to provide 100 ps jitter and overall sequence repeatability within the whole temporal range. The generator is fully programmable and able to produce digital sequences of high complexity. The concept of the generator can be implemented using different microcontrollers and applied for controlling of various optical, atomic, and nuclear physics measurement setups.

Pulse patterning effect in optical pulse division multiplexing for flexible single wavelength multiple access optical network

Science.gov (United States)

Jung, Sun-Young; Kim, Chang-Hun; Han, Sang-Kook

2018-05-01

A demand for high spectral efficiency requires multiple access within a single wavelength, but the uplink signals are significantly degraded because of optical beat interference (OBI) in intensity modulation/direct detection system. An optical pulse division multiplexing (OPDM) technique was proposed that could effectively reduce the OBI via a simple method as long as near-orthogonality is satisfied, but the condition was strict, and thus, the number of multiplexing units was very limited. We propose pulse pattern enhanced OPDM (e-OPDM) to reduce the OBI and improve the flexibility in multiple access within a single wavelength. The performance of the e-OPDM and patterning effect are experimentally verified after 23-km single mode fiber transmission. By employing pulse patterning in OPDM, the tight requirement was relaxed by extending the optical delay dynamic range. This could support more number of access with reduced OBI, which could eventually enhance a multiple access function.

Clinical Comparison of Pulse and Chirp Excitation

DEFF Research Database (Denmark)

Pedersen, Morten Høgholm; Misaridis, T.; Jensen, Jørgen Arendt

2002-01-01

Coded excitation (CE) using frequency modulated signals (chirps) combined with modified matched filtering has earlier been presented showing promising results in simulations and in-vitro. In this study an experimental ultrasound system is evaluated in a clinical setting, where image sequences...... and short pulse excitation to simultaneously produce identical image sequences using both techniques. Nine healthy male volunteers were scanned in abdominal locations. All sequences were evaluated by 3 skilled medical doctors, blinded to each other and to the technique used. They assessed the depth (1...

Nanosecond time-resolved EPR in pulse radiolysis via the spin echo method

International Nuclear Information System (INIS)

Trifunac, A.D.; Norris, J.R.; Lawler, R.G.

1979-01-01

The design and operation of a time-resolved electron spin echo spectrometer suitable for detecting transient radicals produced by 3 MeV electron radiolysis is described. Two modes of operation are available: Field swept mode which generates a normal EPR spectrum and kinetic mode in which the time dependence of a single EPR line is monitored. Techniques which may be used to minimize the effects of nonideal microwave pulses and overlapping sample tube signals are described. The principal advantages of the spin echo method over other time-resolved EPR methods are: (1) Improved time resolution (presently approx.30--50 nsec) allows monitoring of fast changes in EPR signals of transient radicals, (2) Lower susceptibility to interference between the EPR signal and the electron beam pulse at short times, and (3) Lack of dependence of transient signals on microwave field amplitude or static field inhomogeneity at short times. The performance of the instrument is illustrated using CIDEP from acetate radical formed in pulsed radiolysis of aqueous solutions of potassium acetate. The relaxation time and CIDEP enhancement factor obtained for this radical using the spin echo method compare favorably with previous determinations using direct detection EPR. Radical decay rates yield estimates of initial radical concentrations of 10 -4 10 -3 M per electron pulse. The Bloch equations are solved to give an expression for the echo signal for samples exhibiting CIDEP using arbitrary microwave pulse widths and distributions of Larmor frequencies. Conditions are discussed under which the time-dependent signal would be distorted by deviations from an ideal nonselective 90 0 --tau--180 0 pulse sequence

Contrast enhanced MR imaging of postoperative medulloblastoma in childhood: emphasis on meningeal enhancement

Energy Technology Data Exchange (ETDEWEB)

Choi, Choong Gon; Kim, In One; Kim, Woo Sun; Kim, Ho Chul; Yeon, Kyung Mo [College of Medicine, Seoul National University, Seoul (Korea, Republic of)

1993-03-15

To differentiate the postoperative changes from the recurrence of tumor and to evaluate MR imaging of early postoperative leptomeningeal seeding in medulloblastoma, We have retrospectively analysed 34 cases of MR images of 17 patients who were confirmed as medulloblastoma by histopathology. Noncontrast and postcontrast T1 weighted MR images were obtained in all patients. In 11 patients follow-up MR was done more than once (average: 1.5 times) and average interval of MR imaging was 6 months. The timing of 34 MR images was as follow: 6 case within 2 months, 9 cases between 2 months and 1 year, 19 cases more than 1 year after surgery respectively. MR images within 2 month after surgery revealed contrast enhancement at operation site and adjacent meninges, hemorrhage, residual tumor. In patients who had no evidence of tumor recurrence, these early postoperative changes were markedly decreased within 6 month after surgery. MR images obtained more than 1 year after surgery showed no abnormal contrast enhancement or mild focal dural enhancement at operation site. Diffuse moderate dural enhancement was noted in one patient who had the history of post-surgical subdural hemorrhage. In six patients with tumor recurrences which were detected from as early as 9 months to 6 years after surgery, the findings of recurrence included leptomeningeal enhancement of brain stem and cerebellar surface at early stage, variable sized enhancing leptomeningeal nodules, linear or irregular sulcus obliterating enhancing lesions, enhancing mass at primary or metastatic site. We have concluded that leptomeningeal enhancement detected after 6 months of surgery is an important MR finding suggesting the possibility of tumor recurrence. Small nodular and linear enhancement of leptomeninges at brainstem or cerebellar surface is considered as the early manifestation of intracranial tumor seeding.

Contrast enhanced MR imaging of postoperative medulloblastoma in childhood: emphasis on meningeal enhancement

International Nuclear Information System (INIS)

Choi, Choong Gon; Kim, In One; Kim, Woo Sun; Kim, Ho Chul; Yeon, Kyung Mo

1993-01-01

To differentiate the postoperative changes from the recurrence of tumor and to evaluate MR imaging of early postoperative leptomeningeal seeding in medulloblastoma, We have retrospectively analysed 34 cases of MR images of 17 patients who were confirmed as medulloblastoma by histopathology. Noncontrast and postcontrast T1 weighted MR images were obtained in all patients. In 11 patients follow-up MR was done more than once (average: 1.5 times) and average interval of MR imaging was 6 months. The timing of 34 MR images was as follow: 6 case within 2 months, 9 cases between 2 months and 1 year, 19 cases more than 1 year after surgery respectively. MR images within 2 month after surgery revealed contrast enhancement at operation site and adjacent meninges, hemorrhage, residual tumor. In patients who had no evidence of tumor recurrence, these early postoperative changes were markedly decreased within 6 month after surgery. MR images obtained more than 1 year after surgery showed no abnormal contrast enhancement or mild focal dural enhancement at operation site. Diffuse moderate dural enhancement was noted in one patient who had the history of post-surgical subdural hemorrhage. In six patients with tumor recurrences which were detected from as early as 9 months to 6 years after surgery, the findings of recurrence included leptomeningeal enhancement of brain stem and cerebellar surface at early stage, variable sized enhancing leptomeningeal nodules, linear or irregular sulcus obliterating enhancing lesions, enhancing mass at primary or metastatic site. We have concluded that leptomeningeal enhancement detected after 6 months of surgery is an important MR finding suggesting the possibility of tumor recurrence. Small nodular and linear enhancement of leptomeninges at brainstem or cerebellar surface is considered as the early manifestation of intracranial tumor seeding

Non-contrast CT at comparable dose to an abdominal radiograph in patients with acute renal colic; impact of iterative reconstruction on image quality and diagnostic performance

OpenAIRE

McLaughlin, P. D.; Murphy, K. P.; Hayes, S. A.; Carey, K.; Sammon, J.; Crush, L.; O’Neill, F.; Normoyle, B.; McGarrigle, A. M.; Barry, J. E.; Maher, M. M.

2014-01-01

Objectives The aim was to assess the performance of low-dose non-contrast CT of the urinary tract (LD-CT) acquired at radiation exposures close to that of abdominal radiography using adaptive statistical iterative reconstruction (ASiR). Methods Thirty-three patients with clinically suspected renal colic were prospectively included. Conventional dose (CD-CT) and LD-CT data sets were contemporaneously acquired. LD-CT images were reconstructed with 40 %, 70 % and 90 % ASiR. Image quality was sub...

MR-Guided Pulsed High-Intensity Focused Ultrasound Enhancement of Gene Therapy Combined With Androgen Deprivation and Radiotherapy for Prostate Cancer Treatment

Science.gov (United States)

2009-09-01

ultrasound . J. Acoust. Soc.Am. 72 1926-1932, (1982) (7) Neppiras E A. Acoustic cavitation . Physics reports 61(3): 159-251, (1980) (8) ter Haar G R, Daniels...Guided Pulsed High-Intensity Focused Ultrasound Enhancement of 5b. GRANT NUMBER W81XWH-08-1-0469 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT...failing to This work is aimed to study MR guided high intensity focused ultrasound (MRgHIFU) enhancement of gene therapy for Prostate Cancer. The

Optimal time-domain technique for pulse width modulation in power electronics

Directory of Open Access Journals (Sweden)

I. Mayergoyz

2018-05-01

Full Text Available Optimal time-domain technique for pulse width modulation is presented. It is based on exact and explicit analytical solutions for inverter circuits, obtained for any sequence of input voltage rectangular pulses. Two optimal criteria are discussed and illustrated by numerical examples.

Generation of isolated attosecond pulses using a plasmonic funnel-waveguide

International Nuclear Information System (INIS)

Choi, Joonhee; Kim, Seungchul; Park, In-Yong; Lee, Dong-Hyub; Han, Seunghwoi; Kim, Seung-Woo

2012-01-01

We theoretically investigated the possibility of generating attosecond pulses by means of plasmonic field enhancement induced in a nano-structured metallic funnel-waveguide. This study was motivated by our recent experimental demonstration of ultrashort extreme-ultraviolet (EUV) pulses using the same type of three-dimensional waveguides. Here, with emphasis on generation of isolated attosecond pulses, the finite-domain time-difference method was used to analyze the funnel-waveguide with respect to the geometry-dependent plasmonic features such as the field enhancement factor, enhanced plasmonic field profile and hot-spot location. Then an extended semi-classical model of high-order harmonic generation was adopted to predict the EUV spectra generated from the funnel-waveguide in consideration of the spatial inhomogeneity of the plasmonic field within the hot-spot volume. Our simulation finally proved that isolated attosecond pulses can be produced at fast repetition rates directly from a few-cycle femtosecond laser or by synthesizing a two-color laser consisting of two multi-cycle pulses of cross-polarized configuration. (paper)

As-grown enhancement of spinodal decomposition in spinel cobalt ferrite thin films by Dynamic Aurora pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Debnath, Nipa [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Physics, Jagannath University, Dhaka 1100 (Bangladesh); Kawaguchi, Takahiko; Kumasaka, Wataru [Department of Electronics and Materials Science, Shizuoka University, Hamamatsu 432-8561 (Japan); Das, Harinarayan [Materials Science Division, Atomic Energy Centre, Dhaka 1000 (Bangladesh); Shinozaki, Kazuo [School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo 152-8550 (Japan); Sakamoto, Naonori [Department of Electronics and Materials Science, Shizuoka University, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8561 (Japan); Suzuki, Hisao [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Electronics and Materials Science, Shizuoka University, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8561 (Japan); Wakiya, Naoki, E-mail: wakiya.naoki@shizuoka.ac.jp [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Electronics and Materials Science, Shizuoka University, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8561 (Japan)

2017-06-15

Highlights: • As-grown enhancement of spinodal decomposition (SD) in Co{sub x}Fe{sub 3−x}O{sub 4} film is observed. • Magnetic-field-induced ion-impingement enhances SD without any post-annealing. • The enhancement of SD is independent of the lattice-mismatch-induced strain. • This approach can promote SD in any thin film without post-deposition annealing. - Abstract: Cobalt ferrite Co{sub x}Fe{sub 3−x}O{sub 4} thin films with composition within the miscibility gap were grown using Dynamic Aurora pulsed laser deposition. X-ray diffraction patterns reveal as-grown phase separation to Fe-rich and Co-rich phases with no post-deposition annealing. The interconnected surface microstructure of thin film shows that this phase separation occurs through spinodal decomposition enhanced by magnetic-field-induced ion-impingement. The lattice parameter variation of the thin films with the magnetic field indicates that the composition fluctuations can be enhanced further by increasing the magnetic field. Results show that spinodal decomposition enhancement by magnetic-field-induced ion-impingement is independent of the lattice-mismatch-induced strain. This approach can promote spinodal decomposition in any thin film with no post-deposition annealing process.

Pulse height model for deuterated scintillation detectors

International Nuclear Information System (INIS)

Wang, Haitang; Enqvist, Andreas

2015-01-01

An analytical model of light pulse height distribution for finite deuterated scintillation detectors is created using the impulse approximation. Particularly, the energy distribution of a scattered neutron is calculated based on an existing collision probability scheme for general cylindrical shaped detectors considering double differential cross-sections. The light pulse height distribution is analytically and numerically calculated by convoluting collision sequences with the light output function for an EJ-315 detector from our measurements completed at Ohio University. The model provides a good description of collision histories capturing transferred neutron energy in deuterium-based scintillation materials. The resulting light pulse height distribution details pulse compositions and their corresponding contributions. It shows that probabilities of neutron collision with carbon and deuterium nuclei are comparable, however the light pulse amplitude due to collisions with carbon nuclei is small and mainly located at the lower region of the light pulse distribution axis. The model can explore those neutron interaction events that generate pulses near or below a threshold that would be imposed in measurements. A comparison is made between the light pulse height distributions given by the analytical model and measurements. It reveals a significant probability of a neutron generating a small light pulse due to collisions with carbon nuclei when compared to larger light pulse generated by collisions involving deuterium nuclei. This model is beneficial to understand responses of scintillation materials and pulse compositions, as well as nuclei information extraction from recorded pulses.