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Sample records for 3he diffusion mri

  1. In vivo lung morphometry with hyperpolarized 3He diffusion MRI: Theoretical background

    NASA Astrophysics Data System (ADS)

    Sukstanskii, A. L.; Yablonskiy, D. A.

    2008-02-01

    MRI-based study of 3He gas diffusion in lungs may provide important information on lung microstructure. Lung acinar airways can be described in terms of cylinders covered with alveolar sleeve [Haefeli-Bleuer, Weibel, Anat. Rec. 220 (1988) 401]. For relatively short diffusion times (on the order of a few ms) this geometry allows description of the 3He diffusion attenuated MR signal in lungs in terms of two diffusion coefficients—longitudinal (D) and transverse (D) with respect to the individual acinar airway axis [Yablonskiy et al., PNAS 99 (2002) 3111]. In this paper, empirical relationships between D and D and the geometrical parameters of airways and alveoli are found by means of computer Monte Carlo simulations. The effects of non-Gaussian signal behavior (dependence of D and D on b-value) are also taken into account. The results obtained are quantitatively valid in the physiologically important range of airway parameters characteristic of healthy lungs and lungs with mild emphysema. In lungs with advanced emphysema, the results provide only "apparent" characteristics but still could potentially be used to evaluate emphysema progression. This creates a basis for in vivo lung morphometry—evaluation of the geometrical parameters of acinar airways from hyperpolarized 3He diffusion MRI, despite the airways being too small to be resolved by direct imaging. These results also predict a rather substantial dependence of 3He ADC on the experimentally-controllable diffusion time, Δ. If Δ is decreased from 3 ms to 1 ms, the ADC in normal human lungs may increase by almost 50%. This effect should be taken into account when comparing experimental data obtained with different pulse sequences.

  2. 3D MRI of non-Gaussian 3He gas diffusion in the rat lung

    NASA Astrophysics Data System (ADS)

    Jacob, Richard E.; Laicher, Gernot; Minard, Kevin R.

    2007-10-01

    In 3He magnetic resonance images of pulmonary air spaces, the confining architecture of the parenchymal tissue results in a non-Gaussian distribution of signal phase that non-exponentially attenuates image intensity as diffusion weighting is increased. Here, two approaches previously used for the analysis of non-Gaussian effects in the lung are compared and related using diffusion-weighted 3He MR images of mechanically ventilated rats. One approach is model-based and was presented by Yablonskiy et al., while the other approach utilizes the second order decay contribution that is predicted from the cumulant expansion theorem. Total lung coverage is achieved using a hybrid 3D pulse sequence that combines conventional phase encoding with sparse radial sampling for efficient gas usage. This enables the acquisition of nine 3D images using a total of only ˜1 L of hyperpolarized 3He gas. Diffusion weighting ranges from 0 s/cm 2 to 40 s/cm 2. Results show that the non-Gaussian effects of 3He gas diffusion in healthy rat lungs are directly attributed to the anisotropic geometry of lung microstructure as predicted by the Yablonskiy model, and that quantitative analysis over the entire lung can be reliably repeated in time-course studies of the same animal.

  3. Quantitative in vivo assessment of lung microstructure at the alveolar level with hyperpolarized 3He diffusion MRI

    NASA Astrophysics Data System (ADS)

    Yablonskiy, Dmitriy A.; Sukstanskii, Alexander L.; Leawoods, Jason C.; Gierada, David S.; Bretthorst, G. Larry; Lefrak, Stephen S.; Cooper, Joel D.; Conradi, Mark S.

    2002-03-01

    The study of lung emphysema dates back to the beginning of the 17th century. Nevertheless, a number of important questions remain unanswered because a quantitative localized characterization of emphysema requires knowledge of lung structure at the alveolar level in the intact living lung. This information is not available from traditional imaging modalities and pulmonary function tests. Herein, we report the first in vivo measurements of lung geometrical parameters at the alveolar level obtained with 3He diffusion MRI in healthy human subjects and patients with severe emphysema. We also provide the first experimental data demonstrating that 3He gas diffusivity in the acinus of human lung is highly anisotropic. A theory of anisotropic diffusion is presented. Our results clearly demonstrate substantial differences between healthy and emphysematous lung at the acinar level and may provide new insights into emphysema progression. The technique offers promise as a clinical tool for early diagnosis of emphysema.

  4. Probing lung microstructure with hyperpolarized 3He gradient echo MRI.

    PubMed

    Sukstanskii, Alexander L; Quirk, James D; Yablonskiy, Dmitriy A

    2014-12-01

    In this paper we demonstrate that gradient echo MRI with hyperpolarized (3)He gas can be used for simultaneously extracting in vivo information about lung ventilation properties, alveolar geometrical parameters, and blood vessel network structure. This new approach is based on multi-gradient-echo experimental measurements of hyperpolarized (3)He gas MRI signal from human lungs and a proposed theoretical model of this signal. Based on computer simulations of (3)He atoms diffusing in the acinar airway tree in the presence of an inhomogeneous magnetic field induced by the susceptibility differences between lung tissue (alveolar septa, blood vessels) and lung airspaces, we derive analytical expressions relating the time-dependent MR signal to the geometrical parameters of acinar airways and the blood vessel network. Data obtained on eight healthy volunteers are in good agreement with literature values. This information is complementary to the information obtained by means of the in vivo lung morphometry technique with hyperpolarized 3He diffusion MRI previously developed by our group, and opens new opportunities to study lung microstructure in health and disease. PMID:24920182

  5. Assessment of the lung microstructure in patients with asthma using hyperpolarized 3He diffusion MRI at two time scales: Comparison with healthy subjects and patients with COPD

    PubMed Central

    Wang, Chengbo; Altes, Talissa A.; Mugler, John P.; Miller, G. Wilson; Ruppert, Kai; Mata, Jaime F.; Cates, Gordon D.; Borish, Larry; de Lange, Eduard E.

    2010-01-01

    Purpose To investigate short- and long-time-scale 3He diffusion in asthma. Materials and methods A hybrid MRI sequence was developed to obtain co-registered short- and long-time-scale ADC maps during a single breath-hold. Study groups: asthma (n=14); healthy (n=14); COPD (n=9). Correlations were made between mean-ADC and %ADC-abn (%pixels with ADC>mean+2SD of healthy) at both time-scales, and spirometry. Sensitivities were determined using ROC analysis. Results For asthmatics, the short- and long-time-scale group-mean ADC were 0.254±0.032 cm2/s and 0.0237±0.0055 cm2/s, respectively, representing a 9% and 27% (p=0.038 and p=0.005) increase compared to healthy group. The group-mean %ADC-abn were 6.4%±3.7% and 17.5%±14.2%, representing a 107% and 272% (p=0.004 and p=0.006) increase. For COPD much greater elevations were observed. %ADC-abn provided better discrimination than mean-ADC between asthmatic and healthy subjects. In asthmatics ADC did not correlate with spirometry. Conclusion With long-time-scale 3He diffusion magnetic resonance imaging (MRI) changes in lung microstructure were detected in asthma that were more conspicuous regionally than at the short time scale. The hybrid diffusion method is a novel means of identifying small airway disease. PMID:18581381

  6. Perspectives of hyperpolarized noble gas MRI beyond 3He

    PubMed Central

    Lilburn, David M.L.; Pavlovskaya, Galina E.; Meersmann, Thomas

    2013-01-01

    Nuclear Magnetic Resonance (NMR) studies with hyperpolarized (hp) noble gases are at an exciting interface between physics, chemistry, materials science and biomedical sciences. This paper intends to provide a brief overview and outlook of magnetic resonance imaging (MRI) with hp noble gases other than hp 3He. A particular focus are the many intriguing experiments with 129Xe, some of which have already matured to useful MRI protocols, while others display high potential for future MRI applications. Quite naturally for MRI applications the major usage so far has been for biomedical research but perspectives for engineering and materials science studies are also provided. In addition, the prospects for surface sensitive contrast with hp 83Kr MRI is discussed. PMID:23290627

  7. Models and Applications of in Vivo Lung Morphometry with Hyperpolarized 3He MRI in a Mild COPD Population

    NASA Astrophysics Data System (ADS)

    Quirk, James D.; Sukstanskii, Alexander L.; Gierada, David S.; Woods, Jason C.; Conradi, Mark S.; Yablonskiy, Dmitriy A.

    2008-12-01

    Hyperpolarized 3He diffusion MRI is increasingly used to non-invasively quantify local alveolar structure changes, such as those from Chronic Obstructive Pulmonary Disease (COPD). Previously, we described an in vivo lung morphometry technique that decouples the helium apparent diffusion coefficient (ADC) into components oriented along the longitudinal (DL) and transverse (DT) axes of the acinar airways. Herein, we discuss our recent expansion of this theory, which relates the anisotropy of the MRI diffusion signal to the geometrical parameters of the acinar airways. We demonstrate the utility of this model in human studies and compare the measured airway radii with prior ex vivo experiments.

  8. Phase-Contrast MRI and CFD Modeling of Apparent 3He Gas Flow in Rat Pulmonary Airways

    SciTech Connect

    Minard, Kevin R.; Kuprat, Andrew P.; Kabilan, Senthil; Jacob, Rick E.; Einstein, Daniel R.; Carson, James P.; Corley, Richard A.

    2012-08-01

    Phase-contrast (PC) magnetic resonance imaging (MRI) with hyperpolarized 3He is potentially useful for developing and testing patient-specific models of pulmonary airflow. One challenge, however, is that PC-MRI provides apparent values of local 3He velocity that not only depend on actual airflow but also on gas diffusion. This not only blurs laminar flow patterns in narrow airways but also introduces anomalous airflow structure that reflects gas-wall interactions. Here, both effects are predicted in a live rat using computational fluid dynamics (CFD), and for the first time, simulated patterns of apparent 3He gas velocity are compared with in-vivo PC-MRI. Results show (1) that correlations (R2) between measured and simulated airflow patterns increase from 0.23 to 0.79 simply by accounting for apparent 3He transport, and that (2) remaining differences are mainly due to uncertain airway segmentation and partial volume effects stemming from relatively coarse MRI resolution. Higher-fidelity testing of pulmonary airflow predictions should therefore be possible with future imaging improvements.

  9. Phase-Contrast MRI and CFD Modeling of Apparent 3He Gas Flow in Rat Pulmonary Airways

    PubMed Central

    Minard, Kevin R.; Kuprat, Andrew P.; Kabilan, Senthil; Jacob, Richard E.; Einstein, Daniel R.; Carson, James P.; Corley, Richard A.

    2012-01-01

    Phase-contrast (PC) magnetic resonance imaging (MRI) with hyperpolarized 3He is potentially useful for developing and testing patient-specific models of pulmonary airflow. One challenge, however, is that PC-MRI provides apparent values of local 3He velocity that not only depend on actual airflow but also on gas diffusion. This not only blurs laminar flow patterns in narrow airways but also introduces anomalous airflow structure that reflects gas-wall interactions. Here, both effects are predicted in a live rat using computational fluid dynamics (CFD), and for the first time, simulated patterns of apparent 3He gas velocity are compared with in-vivo PC-MRI. Results show 1) that correlations (R2) between measured and simulated airflow patterns increase from 0.23 to 0.79 simply by accounting for apparent 3He transport, and 2) that remaining differences are mainly due to uncertain airway segmentation and partial volume effects stemming from relatively coarse MRI resolution. Higher-fidelity testing of pulmonary airflow predictions should therefore be possible with future imaging improvements. PMID:22771528

  10. Longitudinal assessment of treatment effects on pulmonary ventilation using 1H/3He MRI multivariate templates

    NASA Astrophysics Data System (ADS)

    Tustison, Nicholas J.; Contrella, Benjamin; Altes, Talissa A.; Avants, Brian B.; de Lange, Eduard E.; Mugler, John P.

    2013-03-01

    The utitlity of pulmonary functional imaging techniques, such as hyperpolarized 3He MRI, has encouraged their inclusion in research studies for longitudinal assessment of disease progression and the study of treatment effects. We present methodology for performing voxelwise statistical analysis of ventilation maps derived from hyper­ polarized 3He MRI which incorporates multivariate template construction using simultaneous acquisition of IH and 3He images. Additional processing steps include intensity normalization, bias correction, 4-D longitudinal segmentation, and generation of expected ventilation maps prior to voxelwise regression analysis. Analysis is demonstrated on a cohort of eight individuals with diagnosed cystic fibrosis (CF) undergoing treatment imaged five times every two weeks with a prescribed treatment schedule.

  11. Effects of Diffusion Time on Short-Range Hyperpolarized 3He Diffusivity Measurements in Emphysema

    SciTech Connect

    Gierada, David S.; Woods, Jason C.; Bierhals, Andrew J.; Bartel, Seth T.; Ritter, Jon H.; Choong, Cliff K.; Das, Nitin A.; Hong, Cheng; Pilgram, Thomas K.; Chang, Yulin V.; Jacob, Rick E.; Hogg, James C.; Battafarano, Richard J.; Cooper, Joel D.; Meyers, Bryan F.; Patterson, G Alexander; Yablonskiy, Dmitriy A.; Conradi, Mark S.

    2009-09-28

    Purpose: To characterize the effect of diffusion time on short-range hyperpolarized 3He MR diffusion measurements across a wide range of emphysema severity. Materials and Methods: 3He diffusion MR imaging was performed on 19 lungs or lobes resected from 18 subjects with varying degrees of emphysema using 3 diffusion times (1.6 msec, 5 msec, and 10 msec) at constant b value. Emphysema severity was quantified as the mean apparent diffusion coefficient (ADC) and as the percentage of pixels with ADC higher than multiple thresholds from 0.30-0.55 cm2/sec (ADC index). Quantitative histology (mean linear intercept) was obtained in 10 of the lung specimens from 10 of the subjects. Results: The mean ADCs with diffusion times of 1.6, 5.0, and 10.0 msec were 0.46, 0.40, and 0.37 cm2/sec, respectively (P <0.0001, ANOVA). There was no relationship between the ADC magnitude and the effect of diffusion time on ADC values. Mean linear intercept correlated with ADC (r=0.91-0.94, P<0.001) and ADC index (r=0.78-0.92, P<0.01) at all diffusion times.

  12. Magnetization and spin diffusion of liquid {sup 3}He in aerogel

    SciTech Connect

    Sauls, J. A.; Bunkov, Yu.M.; Collin, E.; Godfrin, H.; Sharma, P.

    2005-07-01

    We report theoretical calculations and experimental measurements of the normal-state spin diffusion coefficient of {sup 3}He in aerogel, including both elastic and inelastic scattering of {sup 3}He quasiparticles, and compare these results with data for {sup 3}He in 98% porous silica aerogel. This analysis provides a determination of the elastic mean free path within the aerogel. Measurements of the magnetization of the superfluid phase in the same aerogel samples provide a test of the theory of pairbreaking and magnetic response of low-energy excitations in the 'dirty' B phase of {sup 3}He in aerogel. A consistent interpretation of the data for the spin-diffusion coefficient, magnetization, and superfluid transition temperature is obtained by including correlation effects in the aerogel density.

  13. Diffusion MRI

    NASA Astrophysics Data System (ADS)

    Fukuyama, Hidenao

    Recent advances of magnetic resonance imaging have been described, especially stressed on the diffusion sequences. We have recently applied the diffusion sequence to functional brain imaging, and found the appropriate results. In addition to the neurosciences fields, diffusion weighted images have improved the accuracies of clinical diagnosis depending upon magnetic resonance images in stroke as well as inflammations.

  14. Linking Ventilation Heterogeneity Quantified via Hyperpolarized 3He MRI to Dynamic Lung Mechanics and Airway Hyperresponsiveness

    PubMed Central

    Lui, Justin K.; Parameswaran, Harikrishnan; Albert, Mitchell S.; Lutchen, Kenneth R.

    2015-01-01

    Advancements in hyperpolarized helium-3 MRI (HP 3He-MRI) have introduced the ability to render and quantify ventilation patterns throughout the anatomic regions of the lung. The goal of this study was to establish how ventilation heterogeneity relates to the dynamic changes in mechanical lung function and airway hyperresponsiveness in asthmatic subjects. In four healthy and nine mild-to-moderate asthmatic subjects, we measured dynamic lung resistance and lung elastance from 0.1 to 8 Hz via a broadband ventilation waveform technique. We quantified ventilation heterogeneity using a recently developed coefficient of variation method from HP 3He-MRI imaging. Dynamic lung mechanics and imaging were performed at baseline, post-challenge, and after a series of five deep inspirations. AHR was measured via the concentration of agonist that elicits a 20% decrease in the subject’s forced expiratory volume in one second compared to baseline (PC20) dose. The ventilation coefficient of variation was correlated to low-frequency lung resistance (R = 0.647, P < 0.0001), the difference between high and low frequency lung resistance (R = 0.668, P < 0.0001), and low-frequency lung elastance (R = 0.547, P = 0.0003). In asthmatic subjects with PC20 values <25 mg/mL, the coefficient of variation at baseline exhibited a strong negative trend (R = -0.798, P = 0.02) to PC20 dose. Our findings were consistent with the notion of peripheral rather than central involvement of ventilation heterogeneity. Also, the degree of AHR appears to be dependent on the degree to which baseline airway constriction creates baseline ventilation heterogeneity. HP 3He-MRI imaging may be a powerful predictor of the degree of AHR and in tracking the efficacy of therapy. PMID:26569412

  15. Posture-Dependent Human 3He Lung Imaging in an Open Access MRI System: Initial Results

    PubMed Central

    Tsai, L. L.; Mair, R. W.; Li, C.-H.; Rosen, M. S.; Patz, S.; Walsworth, R. L.

    2008-01-01

    Rationale and Objectives The human lung and its functions are extremely sensitive to orientation and posture, and debate continues as to the role of gravity and the surrounding anatomy in determining lung function and heterogeneity of perfusion and ventilation. However, study of these effects is difficult. The conventional high-field magnets used for most hyperpolarized 3He MRI of the human lung, and most other common radiological imaging modalities including PET and CT, restrict subjects to lying horizontally, minimizing most gravitational effects. Materials and Methods In this paper, we briefly review the motivation for posture-dependent studies of human lung function, and present initial imaging results of human lungs in the supine and vertical body orientations using inhaled hyperpolarized 3He gas and an open-access MRI instrument. The open geometry of this MRI system features a “walk-in” capability that permits subjects to be imaged in vertical and horizontal positions, and potentially allows for complete rotation of the orientation of the imaging subject in a two-dimensional plane. Results Initial results include two-dimensional lung images acquired with ~ 4 × 8 mm in-plane resolution and three-dimensional images with ~ 2 cm slice thickness. Conclusion Effects of posture variation are observed, including posture-related effects of the diaphragm and distension of the lungs while vertical. PMID:18486009

  16. Interspecies Ion Diffusion Studies using DT, DT(3He), and DT(H) Implosions

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Herrmann, H. W.; Schmitt, M. J.; Kagan, G.; McEvoy, A. M.; Hoffman, N. M.; Gales, S.; Leatherland, A.; Gatu Johnson, M.; Frenje, J.; Glevov, V. Yu; Forrest, C.

    2015-11-01

    Anomalous ICF yield degradation has been observed from gas fills containing mixtures (i.e., D(3He), DT(3He), D(Ar), and even DT). Interspecies ion diffusion theory has been suggested as a possible cause resulting from gradient-driven diffusion (i.e., pressure, electric potential, and temperature) which forces lower mass ions away from core and higher mass ions toward core. The theory predicts hydrogen addition to deuterium or tritium should result in increased yield compared to expected yield, which is opposite to 3He addition. At Omega laser facility, we have tested hydro-equivalent fills of DT, DT(3He), and DT(H) with the assumption that same fuel mass and particle pressure will provide identical convergence. Preliminary results verify a factor of 2 yield reduction relative to scaling when 3He added to DT. At DT(H) case, however, no significant yield degradation or a slight yield enhancement was observed which agrees with the interspecies ion diffusion theory. Detailed experiment results and simulation are needed to confirm the initial observation.

  17. Diffusive transfer of polarized 3He gas through depolarizing magnetic gradients

    NASA Astrophysics Data System (ADS)

    Maxwell, J. D.; Epstein, C. S.; Milner, R. G.

    2015-03-01

    Transfer of polarized 3He gas across spatially varying magnetic fields will facilitate a new source of polarized 3He ions for particle accelerators. In this context, depolarization of atoms as they pass through regions of significant transverse field gradients is a major concern. To understand these depolarization effects, we have built a system consisting of a Helmholtz coil pair and a solenoid, both with central magnetic fields of order 30 gauss. The atoms are polarized via metastability exchange optical pumping in the Helmholtz coil and are in diffusive contact via a glass tube with a second test cell in the solenoid. We have carried out measurements of the spin relaxation during transfer of polarization in 3He at 1 torr by diffusion. We explore the use of measurements of the loss of polarization taken in one cell to infer the polarization in the other cell.

  18. Spin Diffusion Coefficient of A1-PHASE of Superfluid 3He at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Afzali, R.; Pashaee, F.

    The spin diffusion coefficient tensor of the A1-phase of superfluid 3He at low temperatures and melting pressure is calculated using the Boltzmann equation approach and Pfitzner procedure. Then considering Bogoliubov-normal interaction, we show that the total spin diffusion is proportional to 1/T2, the spin diffusion coefficient of superfluid component D\\uparrowxzxz is proportional to T-2, and the spin diffusion coefficient of super-fluid component D\\uparrowxxxx (=D\\uarrowxyxy) is independent of temperature. Furthermore, it is seen that superfluid components play an important role in spin diffusion of the A1-phase.

  19. Apparent diffusion coefficient of hyperpolarized (3)He with minimal influence of the residual gas in small animals.

    PubMed

    Carrero-González, L; Kaulisch, T; Ruiz-Cabello, J; Pérez-Sánchez, J M; Peces-Barba, G; Stiller, D; Rodríguez, I

    2012-09-01

    The apparent diffusion coefficient (ADC) of hyperpolarized (HP) gases is a parameter that reflects changes in lung microstructure. However, ADC is dependent on many physiological and experimental variables that need to be controlled or specified in order to ensure the reliability and reproducibility of this parameter. A single breath-hold experiment is desirable in order to reduce the amount of consumed HP gas. The application of a positive end-expiratory pressure (PEEP) causes an increase in the residual gas volume. Depending on the applied PEEP, the ratio between the incoming and residual gas volumes will change and the ADC will vary, as long as both gases do not have the same diffusion coefficient. The most standard method for human applications uses air for breathing and a bolus of pure HP (3)He for MRI data acquisition. By applying this method in rats, we have demonstrated that ADC values are strongly dependent on the applied PEEP, and therefore on the residual gas volume in the lung. This outcome will play an important role in studies concerning certain diseases, such as emphysema, which is characterized by an increase in the residual volume. Ventilation with an oxygen-helium mixture (VOHeM) is a proposed single breath-hold method that uses two different gas mixtures (O(2)-(4)He for ventilation and HP (3)He-N(2) for imaging). The concentration of each gas in its respective mixture was calculated in order to obtain the same diffusion coefficient in both mixtures. ADCs obtained from VOHeM are independent of PEEP, thus minimizing the effect of the different residual volumes. PMID:22275333

  20. An Open-Access, Very-Low-Field MRI System for Posture-Dependent 3He Human Lung Imaging

    PubMed Central

    Tsai, L. L.; Mair, R. W.; Rosen, M. S.; Patz, S.; Walsworth, R. L.

    2008-01-01

    We describe the design and operation of an open-access, very-low-field, magnetic resonance imaging (MRI) system for in-vivo hyperpolarized 3He imaging of the human lungs. This system permits the study of lung function in both horizontal and upright postures, a capability with important implications in pulmonary physiology and clinical medicine, including asthma and obesity. The imager uses a bi-planar B0 coil design that produces an optimized 65 G (6.5 mT) magnetic field for 3He MRI at 210 kHz. Three sets of bi-planar coils produce the x, y, and z magnetic field gradients while providing a 79-cm inter-coil gap for the imaging subject. We use solenoidal Q-spoiled RF coils for operation at low frequencies, and are able to exploit insignificant sample loading to allow for pre-tuning/matching schemes and for accurate pre-calibration of flip angles. We obtain sufficient SNR to acquire 2D 3He images with up to 2.8 mm resolution, and present initial 2D and 3D 3He images of human lungs in both supine and upright orientations. 1H MRI can also be performed for diagnostic and calibration reasons. PMID:18550402

  1. An open-access, very-low-field MRI system for posture-dependent 3He human lung imaging

    NASA Astrophysics Data System (ADS)

    Tsai, L. L.; Mair, R. W.; Rosen, M. S.; Patz, S.; Walsworth, R. L.

    2008-08-01

    We describe the design and operation of an open-access, very-low-field, magnetic resonance imaging (MRI) system for in vivo hyperpolarized 3He imaging of the human lungs. This system permits the study of lung function in both horizontal and upright postures, a capability with important implications in pulmonary physiology and clinical medicine, including asthma and obesity. The imager uses a bi-planar B0 coil design that produces an optimized 65 G (6.5 mT) magnetic field for 3He MRI at 210 kHz. Three sets of bi-planar coils produce the x, y, and z magnetic field gradients while providing a 79-cm inter-coil gap for the imaging subject. We use solenoidal Q-spoiled RF coils for operation at low frequencies, and are able to exploit insignificant sample loading to allow for pre-tuning/matching schemes and for accurate pre-calibration of flip angles. We obtain sufficient SNR to acquire 2D 3He images with up to 2.8 mm resolution, and present initial 2D and 3D 3He images of human lungs in both supine and upright orientations. 1H MRI can also be performed for diagnostic and calibration reasons.

  2. Response to Commentary on "The influence of lung airways branching structure and diffusion time on measurements and models of short-range 3He gas MR diffusion".

    PubMed

    Parra-Robles, Juan; Wild, Jim M

    2014-02-01

    Our extensive investigation of the cylinder model theory through numerical modelling and purpose-designed experiments has demonstrated that it does produce inaccurate estimates of airway dimensions at all diffusion times currently used. This is due to a variety of effects: incomplete treatment of non-Gaussian effects, finite airway size, branching geometry, background susceptibility gradients and diffusion time dependence of the (3)He MR diffusion behaviour in acinar airways. The cylinder model is a good starting point for the development of a lung morphometry technique from (3)He diffusion MR but its limitations need to be understood and documented in the interest of reliable clinical interpretation. PMID:24342570

  3. A Variability Study of Regional Alveolar Oxygen Tension Measurement in Humans Using Hyperpolarized 3He MRI

    PubMed Central

    Hamedani, Hooman; Kadlecek, Stephen J.; Ishii, Masaru; Emami, Kiarash; Kuzma, Nicholas N.; Xin, Yi; Rossman, Milton; Rizi, Rahim R.

    2013-01-01

    To presents the first systematic reproducibility measurement of alveolar partial pressure of oxygen (pAO2) in the human lung, regional variability is defined in terms of an intraclass correlation coefficient (ICC) between co-localized, same-subject measurements separated by one-week or couple of minutes (short-term). In addition, the repeatability of the average lung pAO2 is compared to that of the standard pulmonary function tests (PFT). PFT and pAO2 imaging were performed on eight subjects: 4 nonsmokers (1 man, 3 women; 56 ± 1.7 years), 4 smokers (1 woman, 3 men; 52 ± 7.5 years) in three visits during two weeks. Regional variability was assessed based on a mixed-effects model and an ICC. The coefficient of variation (CV) of mean and standard deviation of pAO2 in three days was also compared to CV of PFT results. Short-term regional reproducibility based on ICC was 0.71 and 0.63 for nonsmokers and smokers; respectively. The one-week variability was lower (ICC=0.59 and 0.47; respectively). The CV of whole-lung average pAO2 was significantly higher than that of FVC(forced vital capacity; P=0.02) but not from DLCO (diffusing capacity). The smoker group shows more variability in pAO2 measurements both between experiments and in each individual pAO2 maps. pAO2 had a similar repeatability to DLCO. PMID:23382040

  4. Gas exchange dependency on diffusion coefficient: direct /sup 222/Rn and /sup 3/He comparisons in a small lake

    SciTech Connect

    Torgersen, T.; Mathieu, G.; Hesslein, R.H.; Broecker, W.S.

    1982-01-20

    A direct field comparison was conducted to determine the dependency of gas exchange coefficient (k/sub x/) on the diffusion coefficient (D/sub x/). The study also sought to confirm the enhanced vertical exchange properties of limnocorrals and similar enclosures. Gas exchange coefficients for /sup 222/Rn and /sup 3/He were determined in a small northern Ontario lake, using a /sup 226/Ra and /sup 3/H spike to gain the necessary precision. The results indicate that the gas exchange coefficient is functionally dependent on the diffusion coefficient raised to the 1.22/sub -35//sup + > 12/ power (k/sub x/ = f(D/sub x//sup 1.22)), clearly supporting the stagnant film model of gas exchange. Limnocorrals were found to have gas exchange rates up to 1.7 times higher than the whole lake in spite of the observation of more calm surface conditions in the corral than in the open lake. 33 references, 6 figures, 8 tables.

  5. Development and application of methods to quantify spatial and temporal hyperpolarized 3He MRI ventilation dynamics: preliminary results in chronic obstructive pulmonary disease

    NASA Astrophysics Data System (ADS)

    Kirby, Miranda; Wheatley, Andrew; McCormack, David G.; Parraga, Grace

    2010-03-01

    Hyperpolarized helium-3 (3He) magnetic resonance imaging (MRI) has emerged as a non-invasive research method for quantifying lung structural and functional changes, enabling direct visualization in vivo at high spatial and temporal resolution. Here we described the development of methods for quantifying ventilation dynamics in response to salbutamol in Chronic Obstructive Pulmonary Disease (COPD). Whole body 3.0 Tesla Excite 12.0 MRI system was used to obtain multi-slice coronal images acquired immediately after subjects inhaled hyperpolarized 3He gas. Ventilated volume (VV), ventilation defect volume (VDV) and thoracic cavity volume (TCV) were recorded following segmentation of 3He and 1H images respectively, and used to calculate percent ventilated volume (PVV) and ventilation defect percent (VDP). Manual segmentation and Otsu thresholding were significantly correlated for VV (r=.82, p=.001), VDV (r=.87 p=.0002), PVV (r=.85, p=.0005), and VDP (r=.85, p=.0005). The level of agreement between these segmentation methods was also evaluated using Bland-Altman analysis and this showed that manual segmentation was consistently higher for VV (Mean=.22 L, SD=.05) and consistently lower for VDV (Mean=-.13, SD=.05) measurements than Otsu thresholding. To automate the quantification of newly ventilated pixels (NVp) post-bronchodilator, we used translation, rotation, and scaling transformations to register pre-and post-salbutamol images. There was a significant correlation between NVp and VDV (r=-.94 p=.005) and between percent newly ventilated pixels (PNVp) and VDP (r=- .89, p=.02), but not for VV or PVV. Evaluation of 3He MRI ventilation dynamics using Otsu thresholding and landmark-based image registration provides a way to regionally quantify functional changes in COPD subjects after treatment with beta-agonist bronchodilators, a common COPD and asthma therapy.

  6. Helium diffusion coefficient measurements in R7T7 nuclear glass by 3He(d,α) 1H nuclear reaction analysis

    NASA Astrophysics Data System (ADS)

    Chamssedine, F.; Sauvage, T.; Peuget, S.; Fares, T.; Martin, G.

    2010-05-01

    The immobilization of fission products and minor actinides by vitrification is the reference process for industrial management of high-level radioactive wastes generated by spent fuel reprocessing. Radiation damage and radiogenic helium accumulation must be specifically studied to evaluate the effects of minor actinide alpha decay on the glass long-term behavior under repository conditions. A specific experimental study was conducted for a comprehensive evaluation of the behavior of helium and its diffusion mechanisms in borosilicate nuclear waste glass. Helium production was simulated by external implantation with 3He ions at a concentration (≈1 at.%) 30 times higher than obtained after 10,000 years of storage. Helium diffusion coefficients as a function of temperature were extracted from the depth profiles after annealing. The 3He(d,α) 1H nuclear reaction analysis (NRA) technique was successfully adopted for low-temperature in situ measurements of depth profiles. Its high depth resolution revealed helium mobility at temperatures as low as 253 K and the presence of a trapped helium fraction. The diffusion coefficients of un-trapped helium atoms follow an Arrhenius law between 253 K and 323 K. An activation energy of 0.55 ± 0.03 eV was determined, which is consistent with a process controlled by diffusion in the glass free volume.

  7. Diffusion MRI and its role in neuropsychology

    PubMed Central

    Mueller, Bryon A; Lim, Kelvin O; Hemmy, Laura; Camchong, Jazmin

    2015-01-01

    Diffusion Magnetic Resonance Imaging (dMRI) is a popular method used by neuroscientists to uncover unique information about the structural connections within the brain. dMRI is a non-invasive imaging methodology in which image contrast is based on the diffusion of water molecules in tissue. While applicable to many tissues in the body, this review focuses exclusively on the use of dMRI to examine white matter in the brain. In this review, we begin with a definition of diffusion and how diffusion is measured with MRI. Next we introduce the diffusion tensor model, the predominant model used in dMRI. We then describe acquisition issues related to acquisition parameters and scanner hardware and software. Sources of artifacts are then discussed, followed by a brief review of analysis approaches. We provide an overview of the limitations of the traditional diffusion tensor model, and highlight several more sophisticated non-tensor models that better describe the complex architecture of the brain’s white matter. We then touch on reliability and validity issues of diffusion measurements. Finally, we describe examples of ways in which dMRI has been applied to studies of brain disorders and how identified alterations relate to symptomatology and cognition. PMID:26255305

  8. Diffusion MRI and its Role in Neuropsychology.

    PubMed

    Mueller, Bryon A; Lim, Kelvin O; Hemmy, Laura; Camchong, Jazmin

    2015-09-01

    Diffusion Magnetic Resonance Imaging (dMRI) is a popular method used by neuroscientists to uncover unique information about the structural connections within the brain. dMRI is a non-invasive imaging methodology in which image contrast is based on the diffusion of water molecules in tissue. While applicable to many tissues in the body, this review focuses exclusively on the use of dMRI to examine white matter in the brain. In this review, we begin with a definition of diffusion and how diffusion is measured with MRI. Next we introduce the diffusion tensor model, the predominant model used in dMRI. We then describe acquisition issues related to acquisition parameters and scanner hardware and software. Sources of artifacts are then discussed, followed by a brief review of analysis approaches. We provide an overview of the limitations of the traditional diffusion tensor model, and highlight several more sophisticated non-tensor models that better describe the complex architecture of the brain's white matter. We then touch on reliability and validity issues of diffusion measurements. Finally, we describe examples of ways in which dMRI has been applied to studies of brain disorders and how identified alterations relate to symptomatology and cognition. PMID:26255305

  9. Quantification of regional fractional ventilation in human subjects by measurement of hyperpolarized 3He washout with 2D and 3D MRI.

    PubMed

    Horn, Felix C; Deppe, Martin H; Marshall, Helen; Parra-Robles, Juan; Wild, Jim M

    2014-01-15

    Multiple-breath washout hyperpolarized (3)He MRI was used to calculate regional parametric images of fractional ventilation (r) as the ratio of fresh gas entering a volume unit to the total end inspiratory volume of the unit. Using a single dose of inhaled hyperpolarized gas and a total acquisition time of under 1 min, gas washout was measured by dynamic acquisitions during successive breaths with a fixed delay. A two-dimensional (2D) imaging protocol was investigated in four healthy subjects in the supine position, and in a second protocol the capability of extending the washout imaging to a three-dimensional (3D) acquisition covering the whole lungs was tested. During both protocols, subjects were breathing comfortably, only restricted by synchronization of breathing to the sequence timings. The 3D protocol was also successfully tested on one patient with cystic fibrosis. Mean r values from each volunteer were compared with global gas volume turnover, as calculated from flow measurement at the mouth divided by total lung volume (from MRI images), and a significant correlation (r = 0.74, P < 0.05) was found. The effects of gravity on R were investigated, and an average decrease in r of 5.5%/cm (Δr = 0.016 ± 0.006 cm(-1)) from posterior to anterior was found in the right lung. Intersubject reproducibility of r imaging with the 2D and 3D protocol was tested, and a significant correlation between repeated experiments was found in a pixel-by-pixel comparison. The proposed methods can be used to measure r on a regional basis. PMID:24311749

  10. Biomimetic phantom for cardiac diffusion MRI

    PubMed Central

    Teh, Irvin; Zhou, Feng‐Lei; Hubbard Cristinacce, Penny L.; Parker, Geoffrey J.M.

    2015-01-01

    Purpose Diffusion magnetic resonance imaging (MRI) is increasingly used to characterize cardiac tissue microstructure, necessitating the use of physiologically relevant phantoms for methods development. Existing phantoms are generally simplistic and mostly simulate diffusion in the brain. Thus, there is a need for phantoms mimicking diffusion in cardiac tissue. Materials and Methods A biomimetic phantom composed of hollow microfibers generated using co‐electrospinning was developed to mimic myocardial diffusion properties and fiber and sheet orientations. Diffusion tensor imaging was carried out at monthly intervals over 4 months at 9.4T. 3D fiber tracking was performed using the phantom and compared with fiber tracking in an ex vivo rat heart. Results The mean apparent diffusion coefficient and fractional anisotropy of the phantom remained stable over the 4‐month period, with mean values of 7.53 ± 0.16 × 10‐4 mm2/s and 0.388 ± 0.007, respectively. Fiber tracking of the 1st and 3rd eigenvectors generated analogous results to the fiber and sheet‐normal direction respectively, found in the left ventricular myocardium. Conclusion A biomimetic phantom simulating diffusion in the heart was designed and built. This could aid development and validation of novel diffusion MRI methods for investigating cardiac microstructure, decrease the number of animals and patients needed for methods development, and improve quality control in longitudinal and multicenter cardiac diffusion MRI studies. J. MAGN. RESON. IMAGING 2016;43:594–600. PMID:26213152

  11. Radiation-damage-controlled He diffusion and 4He/3He spectra in apatite: an example of mutually consistent results from the Grand Canyon (Invited)

    NASA Astrophysics Data System (ADS)

    Farley, K. A.; Flowers, R. M.

    2009-12-01

    Recent work indicates that He diffusion from apatite is impeded by the accumulation of radiation damage from actinide decay. Supporting evidence includes laboratory diffusion measurements as well as (U-Th)/He dates positively correlated with effective uranium (eU) concentration in certain geologic situations. Here we investigate whether the radiation damage effect can be identified in 4He concentration profiles, as it must be if the system behaves as we anticipate. Apatites from nearby igneous basement samples in the Upper Gorge of the Grand Canyon showing a strong date-eU correlation were proton irradiated, step-heated, and analyzed for 4He/3He spectra. The low eU apatites with younger He dates yielded nearly flat spectra, while the high eU apatites with older He dates yielded highly rounded spectra (see Figure). This implies that the higher eU apatites were partially retaining He while the lower eU apatites were still acting as an open system. Using the RDAAM kinetic model (Flowers et al. 2009) and local geologic constraints we confirm that this behavior is consistent with the observed differences in date and eU, providing compelling evidence that both the He dates and the 4He profiles are sensitive to radiation damage accumulation. Equally importantly, the combination of multiple samples with differing eU and thus differing 4He/3He spectra yields remarkably tight constraints on the time-temperature path experienced by these rocks, from ~90oC down to < 30oC.

  12. Response to Commentary on “The influence of lung airways branching structure and diffusion time on measurements and models of short-range 3He gas MR diffusion”

    NASA Astrophysics Data System (ADS)

    Parra-Robles, Juan; Wild, Jim M.

    2014-02-01

    Our extensive investigation of the cylinder model theory through numerical modelling and purpose-designed experiments has demonstrated that it does produce inaccurate estimates of airway dimensions at all diffusion times currently used. This is due to a variety of effects: incomplete treatment of non-Gaussian effects, finite airway size, branching geometry, background susceptibility gradients and diffusion time dependence of the 3He MR diffusion behaviour in acinar airways. The cylinder model is a good starting point for the development of a lung morphometry technique from 3He diffusion MR but its limitations need to be understood and documented in the interest of reliable clinical interpretation.

  13. Gibbs Ringing in Diffusion MRI

    PubMed Central

    Veraart, Jelle; Fieremans, Els; Jelescu, Ileana O.; Knoll, Florian; Novikov, Dmitry S.

    2016-01-01

    Purpose To study and reduce the effect of Gibbs ringing artifact on computed diffusion parameters. Methods We reduce the ringing by extrapolating the k-space of each diffusion weighted image beyond the measured part by selecting an adequate regularization term. We evaluate several regularization terms and tune the regularization parameter to find the best compromise between anatomical accuracy of the reconstructed image and suppression of the Gibbs artifact. Results We demonstrate empirically and analytically that the Gibbs artifact, which is typically observed near sharp edges in magnetic resonance images, has a significant impact on the quantification of diffusion model parameters, even for infinitesimal diffusion weighting. We find the second order total generalized variation to be a good choice for the penalty term to regularize the extrapolation of the k-space, as it provides a parsimonious representation of images, a practically full suppression of Gibbs ringing, and the absence of staircasing artifacts typical for total variation methods. Conclusions Regularized extrapolation of the k-space data significantly reduces truncation artifacts without compromising spatial resolution in comparison to the default option of window filtering. In particular, accuracy of estimating diffusion tensor imaging and diffusion kurtosis imaging parameters improves so much that unconstrained fits become possible. PMID:26257388

  14. Diffusion-MRI in neurodegenerative disorders.

    PubMed

    Goveas, Joseph; O'Dwyer, Laurence; Mascalchi, Mario; Cosottini, Mirco; Diciotti, Stefano; De Santis, Silvia; Passamonti, Luca; Tessa, Carlo; Toschi, Nicola; Giannelli, Marco

    2015-09-01

    The ability to image the whole brain through ever more subtle and specific methods/contrasts has come to play a key role in understanding the basis of brain abnormalities in several diseases. In magnetic resonance imaging (MRI), "diffusion" (i.e. the random, thermally-induced displacements of water molecules over time) represents an extraordinarily sensitive contrast mechanism, and the exquisite structural detail it affords has proven useful in a vast number of clinical as well as research applications. Since diffusion-MRI is a truly quantitative imaging technique, the indices it provides can serve as potential imaging biomarkers which could allow early detection of pathological alterations as well as tracking and possibly predicting subtle changes in follow-up examinations and clinical trials. Accordingly, diffusion-MRI has proven useful in obtaining information to better understand the microstructural changes and neurophysiological mechanisms underlying various neurodegenerative disorders. In this review article, we summarize and explore the main applications, findings, perspectives as well as challenges and future research of diffusion-MRI in various neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease and degenerative ataxias. PMID:25917917

  15. Commentary on “The influence of lung airways branching structure and diffusion time on measurements and models of short-range 3He gas MR diffusion”

    NASA Astrophysics Data System (ADS)

    Yablonskiy, Dmitriy A.; Sukstanskii, Alexander L.; Conradi, Mark S.

    2014-02-01

    In a recently published paper by Parra-Robles and Wild [1], the authors challenge the in vivo lung morphometry technique (based on hyperpolarized gas diffusion MRI) developed by our Washington University research group. In this Commentary we demonstrate that the main conclusion of Parra-Robles and Wild, that our MRI-based lung morphometry technique “produces inaccurate estimates of the airway dimensions”, does not have any scientific basis and is not in agreement with the considerable body of peer-reviewed scientific reports as well as with Parra-Robles and Wild's own data. On the contrary, our technique has a strong theoretical background, is validated, and provides accurate 3D tomographic information on lung microstructural parameters previously available only from invasive biopsy specimens. This technique has already produced a number of results related to lung morphology and function that were not previously available. In our Commentary we also discuss a number of other incorrect statements in and shortcomings of Parra-Robles and Wild's paper.

  16. ^3He Spin Pump

    NASA Astrophysics Data System (ADS)

    Yamaguchi, A.; Ishimoto, H.; Kojima, H.

    2009-03-01

    The superfluid component of ^3He A1 phase is spin-polarized. The process of forcing the superfluid component through a spin filtering structure, in a manner of mechano-magnetic effect, can be used to increase the spin polarization beyond the equilibrium under a given applied magnetic field. We have constructed a test cell in which a glass capillary array acts as the spin (and entropy) filter and an electrostatically actuated diaphragm forces the superfluid flow through it. Preliminary results show that a maximum relative increase of polarization by 50 % could be achieved. The maximum increase in polarization appears to be limited by the critical superfluid flow through the channels in the glass capillary array. The dependence of the observed effects on temperature, pressure and magnetic field will be presented.

  17. 3D He-3 diffusion MRI as a local in vivo morphometric tool to evaluate emphysematous rat lungs

    SciTech Connect

    Jacob, Rick E.; Minard, Kevin R.; Laicher, Gernot J.; Timchalk, Charles

    2008-08-21

    In this work, we validate 3He magnetic resonance imaging as a non-invasive morphometric tool to assess emphysematous disease state on a local level. Emphysema was induced intratracheally in rats with 25U/100g body weight of porcine pancreatic elastase dissolved in 200 μL saline. Rats were then paired with saline-dosed controls. Nine three-dimensional 3He diffusion-weighted images were acquired at one-, two-, or three-weeks post-dose, after which the lungs were harvested and prepared for histological analysis. Recently introduced indices sensitive to the heterogeneity of the airspace size distribution were calculated. These indices, D1 and D2, were derived from the moments of the mean equivalent airway diameters. Averaged over the entire lung, it is shown that the 3He diffusivity (Dave) and anisotropy (Dan) both correlate with histology (R = 0.85, p < 0.0001 and R = 0.88, p < 0.0001, respectively). By matching small (0.046 cm2) regions in 3He images with corresponding regions in histological slices, Dave and Dan each correlate significantly with both D1 and D2 (R = 0.93, p < 0.0001). It is concluded that 3He MRI is a viable non-invasive morphometric tool for localized in vivo emphysema assessment.

  18. Zircon 4He/3He thermochronometry

    NASA Astrophysics Data System (ADS)

    Tripathy-Lang, Alka; Fox, Matthew; Shuster, David L.

    2015-10-01

    Multiple thermochronometric methods are often required to constrain time-continuous rock exhumation for studying tectonic processes or development of km-scale topography at Earth's surface. Here, we explore 4He/3He thermochronometry of zircon as a method for constraining continuous time-temperature (t-T) paths of individual samples through a temperature range that is complementary to methods such as 40Ar/39Ar thermochronometry of K-feldspar and 4He/3He thermochronometry of apatite. For different cooling rates and diffusion domain size, the temperature sensitivity of zircon 4He/3He thermochronometry ranges from slightly less than 100 °C to slightly greater than 250 °C; a typical sample provides continuous thermal constraints over ∼100 °C within that range. Outside these temperatures, 4He in zircon will either be quantitatively retained or completely lost by volume diffusion. As proof-of-concept, we present stepwise release 4He/3He spectra and associated U and Th concentration maps measured by laser ablation ICP-MS analysis of individual crystal aliquots of Fish Canyon Tuff (FCT) zircon and of a more complex setting in the Sierra Nevada batholith that experienced reheating from a proximal basaltic intrusion, the Little Devil's Postpile (LDP). The FCT zircon 4He/3He release spectra are consistent with a 4He spatial distribution dominated by alpha-ejection from crystal surfaces. The spatial distributions of U and Th measured in the same crystals do not substantially influence 4He/3He release spectra that are predicted for the known thermal history, even when incorporating spatially variable diffusivity due to accumulation of radiation damage. Conversely, the LDP 4He/3He release spectra are strongly influenced by the observed parent nuclide zonation. A three-dimensional (3D) numerical model of 4He production and diffusion, which incorporates crystal geometry, U and Th zonation, and spatially variable He diffusion kinetics, substantially improves the fit between

  19. The 3He Supply Problem

    SciTech Connect

    Kouzes, Richard T.

    2009-05-01

    One of the main uses for 3He is in gas proportional counters for neutron detection. Radiation portal monitors deployed for homeland security and non-proliferation use such detectors. Other uses of 3He are for research detectors, commercial instruments, well logging detectors, dilution refrigerators, for targets or cooling in nuclear research, and for basic research in condensed matter physics. The US supply of 3He comes almost entirely from the decay of tritium used in nuclear weapons by the US and Russia. A few other countries contribute a small amount to the world’s 3He supply. Due to the large increase in use of 3He for homeland security, the supply has dwindled, and can no longer meet the demand. This white paper reviews the problems of supply, utilization, and alternatives.

  20. Neutron polarizers based on polarized ^3He

    NASA Astrophysics Data System (ADS)

    Gentile, T. R.; Jones, G. L.; Thompson, A. K.; Fei, X.; Keith, C. D.; Rich, D.; Snow, W. M.; Penttila, S.

    1997-10-01

    Research is underway at NIST, Indiana Univ., and LANL to develop neutron polarizers and analyzers based on polarized ^3He. Such devices, which rely on the strong spin dependence of the neutron capture cross section by polarized ^3He, have applications in weak interaction physics and materials science. In addition, the technology for polarized ^3He production is directly applicable to polarized gas MRI of lungs, and polarized targets. Our program, which includes both the spin-exchange and metastability-exchange optical pumping methods, will be reviewed. Spin-exchange has been used to analyze a polarized cold neutron beam at NIST, and also for lung imaging in collaboration with the Univ. of Pennsylvania. In the metastable method, the ^3He is polarized at low pressure, and must be substantially compressed. A piston compressor has been designed for this goal at Indiana Univ. and is under construction. At NIST we have compressed polarized gas using an apparatus that is based on a modified commercial diaphragm pump.

  1. White Matter Development during Adolescence as Shown by Diffusion MRI

    ERIC Educational Resources Information Center

    Schmithorst, Vincent J.; Yuan, Weihong

    2010-01-01

    Previous volumetric developmental MRI studies of the brain have shown white matter development continuing through adolescence and into adulthood. This review presents current findings regarding white matter development and organization from diffusion MRI studies. The general trend during adolescence (age 12-18 years) is towards increasing…

  2. IEC-^3He Breeder for D-^3He Satellite Systems.

    NASA Astrophysics Data System (ADS)

    Chacon, L.; Miley, G. H.

    1996-11-01

    D-^3He fusion minimizes neutrons and maximizes charged fusion products, enabling increased energy recovery efficiency by direct conversion. However, scarce ^3He terrestrial resources have deterred R&D on this alternative. Here, we explore ^3He production through Inertial Electrostatic Confinement^1 (IEC) D-breeders, which supply ^3He to FRC D-^3He satellite reactors.^2 Favorable features for the IEC breeder include simplicity, low cost, easy extraction of fusion products, and compatibility with direct conversion. The breeder-satellite system energy balance is analyzed taking the net energy gain of the overall system, Q_N, as the figure of merit. Breeding is applicable for systems where the satellite Q-value, Q_S, > the breeder Q-value, Q_B. For improved performance, i.e., for high Q_N, QS >= QB >> 1 is needed; however, lower QB values (typical of the IEC) are permissible and still offer sufficient Q_N. An economic study determined breeding produces ^3He at a cost comparable to lunar ^3He, already shown to lead to competitive power.^3 The cost of electricity (COE) for the breeder-satellite complex was compared with the ARTEMIS COE,^4 using lunar ^3He fuel: assuming one satellite (1000 MWe)/breeder (170 MWe), the ratio of the breeding system COE to the lunar mining base COE is ~ 1.2. However, economic breeding is driven by large IEC breeder powers, i.e., increased ^3He breeding rates. Thus, the COE ratio approaches unity with two or three satellites/breeder, requiring increased breeder size and power (340 MWe for 2 satellites, 510 MWe for 3 satellites). Such systems potentially provide a ``bridge'' to a future lunar ^3He economy. 1. G.H. Miley et al., Dense Z-pinches, AIP Conf. 299, AIP Press, 675-689 (1994). 2. G.H. Miley, Nucl. Instrum. Methods, A271, 197-202 (1988). 3. L.J. Wittenberg et al., Fusion Technol., 10, 167-178 (1986). 4. H. Momota et al., Fusion Technol., 21, 2307-2323 (1992).

  3. Diffusion MRI on lymph node staging of gastric adenocarcinoma

    PubMed Central

    Akcakaya, Adem; Memmi, Naim; Turkmen, Ihsan; Cipe, Gokhan; Yildiz, Pelin; Arici, Dilek Sema; Muslumanoglu, Mahmut

    2015-01-01

    Objective The purpose of this study was to evaluate the accuracy of diffusion weighted magnetic resonance imaging (MRI) in preoperative assessment of metastatic lymph nodes of gastric cancer. Methods A total of 23 gastric cancer patients with a mean age of 59.4±10.9 years were analyzed. Lymph nodes were grouped as perigastric lesser curvature (Group Ia), perigastric greater curvature (Group Ib), D1+/D2 lymph nodes (Group II). Identification of histologically metastatic lymph nodes by diffusion weighted MRI was regarded as the main outcome. Results A total of 1,056 lymph nodes including 180 histologically proven metastatic lymph nodes were dissected. Although diffusion weighted MRI could identify the metastatic lymph nodes in 18 out of 23 patients (77.8%), only 69 of total 1,056 nodes (6.53%), either metastatic or non-metastatic, could be detected. There was no correlation between histopathology and diffusion weighted MRI with regard to lymph node groups (P>0.05 for all). Overall accuracy was calculated as 69.56, 65.21 and 52.17 for Groups II, Ib and Ia lymph nodes, respectively. Apparent diffusion coefficient (ADC) values could not be helpful to differentiate metastatic lymph nodes (P=0.673). Conclusions Diffusion weighted MRI has low accuracy to detect or to differentiate metastatic and non-metastatic lymph nodes based on their ADC values in gastric cancer. PMID:26029642

  4. Sparse and optimal acquisition design for diffusion MRI and beyond

    PubMed Central

    Koay, Cheng Guan; Özarslan, Evren; Johnson, Kevin M.; Meyerand, M. Elizabeth

    2012-01-01

    Purpose: Diffusion magnetic resonance imaging (MRI) in combination with functional MRI promises a whole new vista for scientists to investigate noninvasively the structural and functional connectivity of the human brain—the human connectome, which had heretofore been out of reach. As with other imaging modalities, diffusion MRI data are inherently noisy and its acquisition time-consuming. Further, a faithful representation of the human connectome that can serve as a predictive model requires a robust and accurate data-analytic pipeline. The focus of this paper is on one of the key segments of this pipeline—in particular, the development of a sparse and optimal acquisition (SOA) design for diffusion MRI multiple-shell acquisition and beyond. Methods: The authors propose a novel optimality criterion for sparse multiple-shell acquisition and quasimultiple-shell designs in diffusion MRI and a novel and effective semistochastic and moderately greedy combinatorial search strategy with simulated annealing to locate the optimum design or configuration. The goal of the optimality criteria is threefold: first, to maximize uniformity of the diffusion measurements in each shell, which is equivalent to maximal incoherence in angular measurements; second, to maximize coverage of the diffusion measurements around each radial line to achieve maximal incoherence in radial measurements for multiple-shell acquisition; and finally, to ensure maximum uniformity of diffusion measurement directions in the limiting case when all the shells are coincidental as in the case of a single-shell acquisition. The approach taken in evaluating the stability of various acquisition designs is based on the condition number and the A-optimal measure of the design matrix. Results: Even though the number of distinct configurations for a given set of diffusion gradient directions is very large in general—e.g., in the order of 10232 for a set of 144 diffusion gradient directions, the proposed search

  5. Relaxation time of 3He

    NASA Astrophysics Data System (ADS)

    Gao, Hayian

    2004-10-01

    The next generation of searches for the neutron electric dipole moment using ultra cold neutrons will use polarized ^3He as a co-magnetometer. The first such experiment has been proposed, with a goal of improving the current limit on the neutron EDM by two orders of magnitude. This experiment requires a systematic study of the properties of polarized ^3He at cryogenic temperatures under actual experimental conditions. These experimental conditions include polarized ^3He mixed in a bath of superfluid ^4He in low magnetic field and held in an acrylic cell which is coated with deuterated TetraphenylButadiene . Parts of these systematic studies will be done at Duke University using a newly built, novel refillable double cell ^3 He polarizer based on spin exchange optical pumping with Rubidium vapor. The polarimetry for this apparatus is done with a NMR polarimeter using the adiabatic fast passage method. An alternate polarimeter using free induction decay method is also being built. This apparatus is being used to study the relaxation time and other critical properties of polarized ^3He at temperatures ranging from 2.3 - 4.2 K, under simulated experimental conditions. We will present details about this novel polarizer and show preliminary results of our measurements.

  6. Mathematical Methods for Diffusion MRI Processing

    PubMed Central

    Lenglet, C.; Campbell, J.S.W.; Descoteaux, M.; Haro, G.; Savadjiev, P.; Wassermann, D.; Anwander, A.; Deriche, R.; Pike, G.B.; Sapiro, G.; Siddiqi, K.; Thompson, P.

    2009-01-01

    In this article, we review recent mathematical models and computational methods for the processing of diffusion Magnetic Resonance Images, including state-of-the-art reconstruction of diffusion models, cerebral white matter connectivity analysis, and segmentation techniques. We focus on Diffusion Tensor Images (DTI) and Q-Ball Images (QBI). PMID:19063977

  7. Diffusion MRI at 25: Exploring brain tissue structure and function

    PubMed Central

    Bihan, Denis Le; Johansen-Berg, Heidi

    2013-01-01

    Diffusion MRI (or dMRI) came into existence in the mid-1980s. During the last 25 years, diffusion MRI has been extraordinarily successful (with more than 300,000 entries on Google Scholar for diffusion MRI). Its main clinical domain of application has been neurological disorders, especially for the management of patients with acute stroke. It is also rapidly becoming a standard for white matter disorders, as diffusion tensor imaging (DTI) can reveal abnormalities in white matter fiber structure and provide outstanding maps of brain connectivity. The ability to visualize anatomical connections between different parts of the brain, non-invasively and on an individual basis, has emerged as a major breakthrough for neurosciences. The driving force of dMRI is to monitor microscopic, natural displacements of water molecules that occur in brain tissues as part of the physical diffusion process. Water molecules are thus used as a probe that can reveal microscopic details about tissue architecture, either normal or in a diseased state. PMID:22120012

  8. COMPARISON OF THE COMPLETE FOURIER DIRECT MRI WITH EXISTING DIFFUSION WEIGHTED MRI METHODS

    PubMed Central

    Özcan, Alpay

    2011-01-01

    The Complete Fourier Direct (CFD) MRI method introduced in earlier work for modeling the diffusion weighted MRI signal is compared with the existing methods. The preservation of Hermitian symmetry in the diffusion weighted MRI signal without affecting its energy is the key point that differentiates CFD–MRI from the existing methods. By keeping the correct Fourier relationship intact, the joint distribution function is represented ‘as it is’, without any constraints, e.g. being symmetric. The necessity to model or assume models for spin motion and try to fit the model to the samples of the Fourier transform as in case of model matching methods is not required because the Discrete Fourier Transform applied to correctly processed signal in CFD–MRI gives more accurate results. PMID:21918715

  9. Diffusion and perfusion MRI of the lung and mediastinum.

    PubMed

    Henzler, Thomas; Schmid-Bindert, Gerald; Schoenberg, Stefan O; Fink, Christian

    2010-12-01

    With ongoing technical improvements such as multichannel MRI, systems with powerful gradients as well as the development of innovative pulse sequence techniques implementing parallel imaging, MRI has now entered the stage of a radiation-free alternative to computed tomography (CT) for chest imaging in clinical practice. Whereas in the past MRI of the lung was focused on morphological aspects, current MRI techniques also enable functional imaging of the lung allowing for a comprehensive assessment of lung disease in a single MRI exam. Perfusion imaging can be used for the visualization of regional pulmonary perfusion in patients with different lung diseases such as lung cancer, chronic obstructive lung disease, pulmonary embolism or for the prediction of postoperative lung function in lung cancer patients. Over the past years diffusion-weighted MR imaging (DW-MRI) of the thorax has become feasible with a significant reduction of the acquisition time, thus minimizing artifacts from respiratory and cardiac motion. In chest imaging, DW-MRI has been mainly suggested for the characterization of lung cancer, lymph nodes and pulmonary metastases. In this review article recent MR perfusion and diffusion techniques of the lung and mediastinum as well as their clinical applications are reviewed. PMID:20627435

  10. Dipy, a library for the analysis of diffusion MRI data.

    PubMed

    Garyfallidis, Eleftherios; Brett, Matthew; Amirbekian, Bagrat; Rokem, Ariel; van der Walt, Stefan; Descoteaux, Maxime; Nimmo-Smith, Ian

    2014-01-01

    Diffusion Imaging in Python (Dipy) is a free and open source software project for the analysis of data from diffusion magnetic resonance imaging (dMRI) experiments. dMRI is an application of MRI that can be used to measure structural features of brain white matter. Many methods have been developed to use dMRI data to model the local configuration of white matter nerve fiber bundles and infer the trajectory of bundles connecting different parts of the brain. Dipy gathers implementations of many different methods in dMRI, including: diffusion signal pre-processing; reconstruction of diffusion distributions in individual voxels; fiber tractography and fiber track post-processing, analysis and visualization. Dipy aims to provide transparent implementations for all the different steps of dMRI analysis with a uniform programming interface. We have implemented classical signal reconstruction techniques, such as the diffusion tensor model and deterministic fiber tractography. In addition, cutting edge novel reconstruction techniques are implemented, such as constrained spherical deconvolution and diffusion spectrum imaging (DSI) with deconvolution, as well as methods for probabilistic tracking and original methods for tractography clustering. Many additional utility functions are provided to calculate various statistics, informative visualizations, as well as file-handling routines to assist in the development and use of novel techniques. In contrast to many other scientific software projects, Dipy is not being developed by a single research group. Rather, it is an open project that encourages contributions from any scientist/developer through GitHub and open discussions on the project mailing list. Consequently, Dipy today has an international team of contributors, spanning seven different academic institutions in five countries and three continents, which is still growing. PMID:24600385

  11. Dipy, a library for the analysis of diffusion MRI data

    PubMed Central

    Garyfallidis, Eleftherios; Brett, Matthew; Amirbekian, Bagrat; Rokem, Ariel; van der Walt, Stefan; Descoteaux, Maxime; Nimmo-Smith, Ian

    2014-01-01

    Diffusion Imaging in Python (Dipy) is a free and open source software project for the analysis of data from diffusion magnetic resonance imaging (dMRI) experiments. dMRI is an application of MRI that can be used to measure structural features of brain white matter. Many methods have been developed to use dMRI data to model the local configuration of white matter nerve fiber bundles and infer the trajectory of bundles connecting different parts of the brain. Dipy gathers implementations of many different methods in dMRI, including: diffusion signal pre-processing; reconstruction of diffusion distributions in individual voxels; fiber tractography and fiber track post-processing, analysis and visualization. Dipy aims to provide transparent implementations for all the different steps of dMRI analysis with a uniform programming interface. We have implemented classical signal reconstruction techniques, such as the diffusion tensor model and deterministic fiber tractography. In addition, cutting edge novel reconstruction techniques are implemented, such as constrained spherical deconvolution and diffusion spectrum imaging (DSI) with deconvolution, as well as methods for probabilistic tracking and original methods for tractography clustering. Many additional utility functions are provided to calculate various statistics, informative visualizations, as well as file-handling routines to assist in the development and use of novel techniques. In contrast to many other scientific software projects, Dipy is not being developed by a single research group. Rather, it is an open project that encourages contributions from any scientist/developer through GitHub and open discussions on the project mailing list. Consequently, Dipy today has an international team of contributors, spanning seven different academic institutions in five countries and three continents, which is still growing. PMID:24600385

  12. Hyperpolarized (3)He magnetic resonance imaging-derived pulmonary pressure-volume curves.

    PubMed

    Choy, Stephen; Wheatley, Andrew; McCormack, David G; Parraga, Grace

    2010-08-01

    We aimed to evaluate the potential for the use of hyperpolarized helium-3 magnetic resonance imaging (MRI) apparent diffusion coefficient (ADC) surrogates of alveolar size, together with literature-based morphological parameters in a theoretical model of lung mechanics to simulate noninvasive transpulmonary pressure-volume curves. Fourteen ex-smokers with chronic obstructive pulmonary disease (COPD) (n = 8 stage II, n = 6 stage III/IV COPD) and five age-matched never-smokers, provided written, informed consent and were evaluated at baseline and 26 + or - 2 mo later (n = 15 subjects) using plethysmography, spirometry, and (3)He MRI at 3.0 T. Total lung capacity, residual volume, and literature-based morphological parameters were used with alveolar volumes derived from (3)He ADC to simulate noninvasive pressure-volume curves. The resultant anterior-posterior transpulmonary pressure gradient was significantly decreased for stage II COPD (P < 0.01) and stage III COPD subjects (P < 0.001) compared with healthy volunteers. Both COPD subgroups showed increased alveolar radius compared with healthy subjects (P < 0.01, stage II COPD; P < 0.001, stage III COPD). In addition, surface area and surface tension were significantly increased in stage III COPD compared with healthy volunteers (P < 0.01). These results suggest that (3)He MRI provides a potential noninvasive approach to evaluate lung mechanics regionally and further supports the use of ADC values as a regional noninvasive probe of pulmonary microstructure and compliance. PMID:20538846

  13. Hyperpolarized Gas Diffusion MRI for the Study of Atelectasis and Acute Respiratory Distress Syndrome

    PubMed Central

    Cereda, Maurizio; Xin, Yi; Kadlecek, Stephen; Hamedani, Hooman; Rajaei, Jennia; Clapp, Justin; Rizi, Rahim R.

    2014-01-01

    Considerable uncertainty remains about the best ventilator strategies for the mitigation of atelectasis and associated airspace stretch in patients with acute respiratory distress syndrome (ARDS). In addition to several immediate physiological effects, atelectasis increases the risk of ventilator-associated lung injury (VALI), which has been shown to significantly worsen ARDS outcomes. A number of lung imaging techniques have made substantial headway in clarifying the mechanisms of atelectasis. This paper reviews the contributions of CT, PET, and conventional MRI to understanding this phenomenon. In doing so, it also reveals several important shortcomings inherent to each of these approaches. Once these shortcomings have been made apparent, we describe how hyperpolarized gas magnetic resonance imaging (HP MRI)—a technique that is uniquely able to assess responses to mechanical ventilation and lung injury in peripheral airspaces—is poised to fill several of these knowledge gaps. The HP-MRI-derived apparent diffusion coefficient (ADC) quantifies the restriction of 3He diffusion by peripheral airspaces, thereby obtaining pulmonary structural information at an extremely small scale. Lastly, this paper reports the results of a series of experiments that measured ADC in mechanically ventilated rats in order to investigate (i) the effect of atelectasis on ventilated airspaces; (ii) the relationship between positive end-expiratory pressure (PEEP), hysteresis, and the dimensions of peripheral airspaces; and (iii) the ability of PEEP and surfactant to reduce airspace dimensions after lung injury. An increase in ADC was found to be a marker of atelectasis-induced overdistension. With recruitment, higher airway pressures were shown to reduce stretch rather than worsen it. Moving forward, HP MRI has significant potential to shed further light on the atelectatic processes that occur during mechanical ventilation. PMID:24920074

  14. Diffusion MRI/NMR magnetization equations with relaxation times

    NASA Astrophysics Data System (ADS)

    de, Dilip; Daniel, Simon

    2012-10-01

    Bloch-Torrey diffusion magnetization equation ignores relaxation effects of magnetization. Relaxation times are important in any diffusion magnetization studies of perfusion in tissues(Brain and heart specially). Bloch-Torrey equation cannot therefore describe diffusion magnetization in a real-life situation where relaxation effects play a key role, characteristics of tissues under examination. This paper describes derivations of two equations for each of the y and z component diffusion NMR/MRI magnetization (separately) in a rotating frame of reference, where rf B1 field is applied along x direction and bias magnetic field(Bo) is along z direction. The two equations are expected to further advance the science & technology of Diffusion MRI(DMRI) and diffusion functional MRI(DFMRI). These two techniques are becoming increasingly important in the study and treatment of neurological disorders, especially for the management of patients with acute stroke. It is rapidly becoming a standard for white matter disorders, as diffusion tensor imaging (DTI) can reveal abnormalities in white matter fibre structure and provide models of brain connectivity.

  15. Formation ages and thermal histories of fracture-filling hematite and Mn-oxide in Precambrian basement from (U-Th)/He dating and 4He/3He diffusion experiments

    NASA Astrophysics Data System (ADS)

    Reiners, P. W.; Shuster, D. L.; Evenson, N.

    2015-12-01

    Secondary Fe- and Mn-oxides in bedrock form from fluid flow associated with events that may not be preserved in stratigraphic records. (U-Th)/He chronometry is well suited for dating these phases but potential diffusive loss of 4He can complicate interpretations. Here we show that measuring He diffusion kinetics of dated samples can resolve whether ages record formation or cooling. Proterozoic (1.6 Ga) volcanics in Aravaipa Canyon, southern Arizona, contain 1.4-1.6-Ga quartz-vein-hosted hematite, as well as 1.0-1.1-Ga hematite precipitated on fractures and overlain by 20-30-Ma Mn-oxide. Hematite 4He/3He age spectra and multi-domain (MD) diffusion models are consistent with a small proportion (4-10%) of domains between 1-500 nm, larger proportions (5-15%) of 1-10 μm domains, and a majority (60-75%) of domains of 80-150 μm. Although the smallest domains would have extremely low He retentivity, models predict bulk "closure temperatures" of 180-200 °C. The 1.4-1.6-Ga quartz-vein hematite likely formed soon after eruption of its host rock, and has not been hotter than ~250 °C for Ma durations. The 1.0-1.1 Ga age of the fracture-fill hematite likely also records the timing of precipitation, but from fluids associated with nearby diabase of the same age. In contrast, the 4He/3He MD model of the 20-30-Ma Mn-oxide requires ~80% of 1-100 nm domains and 20% between 1-10 μm. Although the Mn-oxide likely formed at the same time as the hematite it coats, its age records transient heating from overlying 28-Ma volcanics. In all cases, approximate crystal sizes observed in SEM images are consistent with the predictions of MD modeling, and support the assumed kinetics of He diffusion (~147-157 kJ/mol and ~2.2×10-4 cm2/s for hematite, and ~134 kJ/mol and ~4×10-3 cm2/s for Mn-oxide).These results suggest that specular hematite can have bulk He closure temperatures at least as high as 200 °C and in some cases record precipitation; this is supported by our results on specularite

  16. Estimation of Bounded and Unbounded Trajectories in Diffusion MRI

    PubMed Central

    Ning, Lipeng; Westin, Carl-Fredrik; Rathi, Yogesh

    2016-01-01

    Disentangling the tissue microstructural information from the diffusion magnetic resonance imaging (dMRI) measurements is quite important for extracting brain tissue specific measures. The autocorrelation function of diffusing spins is key for understanding the relation between dMRI signals and the acquisition gradient sequences. In this paper, we demonstrate that the autocorrelation of diffusion in restricted or bounded spaces can be well approximated by exponential functions. To this end, we propose to use the multivariate Ornstein-Uhlenbeck (OU) process to model the matrix-valued exponential autocorrelation function of three-dimensional diffusion processes with bounded trajectories. We present detailed analysis on the relation between the model parameters and the time-dependent apparent axon radius and provide a general model for dMRI signals from the frequency domain perspective. For our experimental setup, we model the diffusion signal as a mixture of two compartments that correspond to diffusing spins with bounded and unbounded trajectories, and analyze the corpus-callosum in an ex-vivo data set of a monkey brain. PMID:27064745

  17. On 3He bolometer systems

    NASA Technical Reports Server (NTRS)

    Houck, J. R.

    1983-01-01

    A 3He cryostat which was constructed to cool a germanium bolometer for use as an infrared detector at submillimeter wavelength is discussed. The system had better sensitivity than any other existing system for these wavelengths; the system could be improved if better optical coupling could be achieved between the bolometer and the incoming photon stream. Considerable effort was expended to improve this coupling. Even the best results however, fell short of an ideal system by a factor of nearly 5 in coupling efficiency.

  18. A multipurpose 3He refrigerator

    NASA Astrophysics Data System (ADS)

    Pizzo, L.; Dall'Oglio, G.; Martinis, L.; Sabbatini, L.

    2006-10-01

    We introduce a mini 3He refrigerator, operating at ˜300 mK starting from 4.2 K without pumping on the main 4He bath. The innovative idea is that the present one is suitable for a very fast operation; for its use, it is sufficient a storage 4He Dewar. In this way we drastically reduce the time required to cool it down, because there is no need for a classic cryostat. This prototype is particularly aimed for all those operations in which it is necessary to test a large number of samples that do not require long duration measurements at low temperature.

  19. Hard Photodisintegration of 3He

    NASA Astrophysics Data System (ADS)

    Granados, Carlos

    2011-02-01

    Large angle photodisintegration of two nucleons from the 3He nucleus is studied within the framework of the hard rescattering model (HRM). In the HRM the incoming photon is absorbed by one nucleon's valence quark that then undergoes a hard rescattering reaction with a valence quark from the second nucleon producing two nucleons emerging at large transverse momentum . Parameter free cross sections for pp and pn break up channels are calculated through the input of experimental cross sections on pp and pn elastic scattering. The calculated cross section for pp breakup and its predicted energy dependency are in good agreement with recent experimental data. Predictions on spectator momentum distributions and helicity transfer are also presented.

  20. Conventions and nomenclature for double diffusion encoding NMR and MRI.

    PubMed

    Shemesh, Noam; Jespersen, Sune N; Alexander, Daniel C; Cohen, Yoram; Drobnjak, Ivana; Dyrby, Tim B; Finsterbusch, Jurgen; Koch, Martin A; Kuder, Tristan; Laun, Fredrik; Lawrenz, Marco; Lundell, Henrik; Mitra, Partha P; Nilsson, Markus; Özarslan, Evren; Topgaard, Daniel; Westin, Carl-Fredrik

    2016-01-01

    Stejskal and Tanner's ingenious pulsed field gradient design from 1965 has made diffusion NMR and MRI the mainstay of most studies seeking to resolve microstructural information in porous systems in general and biological systems in particular. Methods extending beyond Stejskal and Tanner's design, such as double diffusion encoding (DDE) NMR and MRI, may provide novel quantifiable metrics that are less easily inferred from conventional diffusion acquisitions. Despite the growing interest on the topic, the terminology for the pulse sequences, their parameters, and the metrics that can be derived from them remains inconsistent and disparate among groups active in DDE. Here, we present a consensus of those groups on terminology for DDE sequences and associated concepts. Furthermore, the regimes in which DDE metrics appear to provide microstructural information that cannot be achieved using more conventional counterparts (in a model-free fashion) are elucidated. We highlight in particular DDE's potential for determining microscopic diffusion anisotropy and microscopic fractional anisotropy, which offer metrics of microscopic features independent of orientation dispersion and thus provide information complementary to the standard, macroscopic, fractional anisotropy conventionally obtained by diffusion MR. Finally, we discuss future vistas and perspectives for DDE. PMID:26418050

  1. D-BRAIN: Anatomically Accurate Simulated Diffusion MRI Brain Data.

    PubMed

    Perrone, Daniele; Jeurissen, Ben; Aelterman, Jan; Roine, Timo; Sijbers, Jan; Pizurica, Aleksandra; Leemans, Alexander; Philips, Wilfried

    2016-01-01

    Diffusion Weighted (DW) MRI allows for the non-invasive study of water diffusion inside living tissues. As such, it is useful for the investigation of human brain white matter (WM) connectivity in vivo through fiber tractography (FT) algorithms. Many DW-MRI tailored restoration techniques and FT algorithms have been developed. However, it is not clear how accurately these methods reproduce the WM bundle characteristics in real-world conditions, such as in the presence of noise, partial volume effect, and a limited spatial and angular resolution. The difficulty lies in the lack of a realistic brain phantom on the one hand, and a sufficiently accurate way of modeling the acquisition-related degradation on the other. This paper proposes a software phantom that approximates a human brain to a high degree of realism and that can incorporate complex brain-like structural features. We refer to it as a Diffusion BRAIN (D-BRAIN) phantom. Also, we propose an accurate model of a (DW) MRI acquisition protocol to allow for validation of methods in realistic conditions with data imperfections. The phantom model simulates anatomical and diffusion properties for multiple brain tissue components, and can serve as a ground-truth to evaluate FT algorithms, among others. The simulation of the acquisition process allows one to include noise, partial volume effects, and limited spatial and angular resolution in the images. In this way, the effect of image artifacts on, for instance, fiber tractography can be investigated with great detail. The proposed framework enables reliable and quantitative evaluation of DW-MR image processing and FT algorithms at the level of large-scale WM structures. The effect of noise levels and other data characteristics on cortico-cortical connectivity and tractography-based grey matter parcellation can be investigated as well. PMID:26930054

  2. D-BRAIN: Anatomically Accurate Simulated Diffusion MRI Brain Data

    PubMed Central

    Perrone, Daniele; Jeurissen, Ben; Aelterman, Jan; Roine, Timo; Sijbers, Jan; Pizurica, Aleksandra; Leemans, Alexander; Philips, Wilfried

    2016-01-01

    Diffusion Weighted (DW) MRI allows for the non-invasive study of water diffusion inside living tissues. As such, it is useful for the investigation of human brain white matter (WM) connectivity in vivo through fiber tractography (FT) algorithms. Many DW-MRI tailored restoration techniques and FT algorithms have been developed. However, it is not clear how accurately these methods reproduce the WM bundle characteristics in real-world conditions, such as in the presence of noise, partial volume effect, and a limited spatial and angular resolution. The difficulty lies in the lack of a realistic brain phantom on the one hand, and a sufficiently accurate way of modeling the acquisition-related degradation on the other. This paper proposes a software phantom that approximates a human brain to a high degree of realism and that can incorporate complex brain-like structural features. We refer to it as a Diffusion BRAIN (D-BRAIN) phantom. Also, we propose an accurate model of a (DW) MRI acquisition protocol to allow for validation of methods in realistic conditions with data imperfections. The phantom model simulates anatomical and diffusion properties for multiple brain tissue components, and can serve as a ground-truth to evaluate FT algorithms, among others. The simulation of the acquisition process allows one to include noise, partial volume effects, and limited spatial and angular resolution in the images. In this way, the effect of image artifacts on, for instance, fiber tractography can be investigated with great detail. The proposed framework enables reliable and quantitative evaluation of DW-MR image processing and FT algorithms at the level of large-scale WM structures. The effect of noise levels and other data characteristics on cortico-cortical connectivity and tractography-based grey matter parcellation can be investigated as well. PMID:26930054

  3. Joint brain connectivity estimation from diffusion and functional MRI data

    NASA Astrophysics Data System (ADS)

    Chu, Shu-Hsien; Lenglet, Christophe; Parhi, Keshab K.

    2015-03-01

    Estimating brain wiring patterns is critical to better understand the brain organization and function. Anatomical brain connectivity models axonal pathways, while the functional brain connectivity characterizes the statistical dependencies and correlation between the activities of various brain regions. The synchronization of brain activity can be inferred through the variation of blood-oxygen-level dependent (BOLD) signal from functional MRI (fMRI) and the neural connections can be estimated using tractography from diffusion MRI (dMRI). Functional connections between brain regions are supported by anatomical connections, and the synchronization of brain activities arises through sharing of information in the form of electro-chemical signals on axon pathways. Jointly modeling fMRI and dMRI data may improve the accuracy in constructing anatomical connectivity as well as functional connectivity. Such an approach may lead to novel multimodal biomarkers potentially able to better capture functional and anatomical connectivity variations. We present a novel brain network model which jointly models the dMRI and fMRI data to improve the anatomical connectivity estimation and extract the anatomical subnetworks associated with specific functional modes by constraining the anatomical connections as structural supports to the functional connections. The key idea is similar to a multi-commodity flow optimization problem that minimizes the cost or maximizes the efficiency for flow configuration and simultaneously fulfills the supply-demand constraint for each commodity. In the proposed network, the nodes represent the grey matter (GM) regions providing brain functionality, and the links represent white matter (WM) fiber bundles connecting those regions and delivering information. The commodities can be thought of as the information corresponding to brain activity patterns as obtained for instance by independent component analysis (ICA) of fMRI data. The concept of information

  4. Joint brain connectivity estimation from diffusion and functional MRI data

    NASA Astrophysics Data System (ADS)

    Chu, Shu-Hsien; Lenglet, Christophe; Parhi, Keshab K.

    2015-03-01

    Estimating brain wiring patterns is critical to better understand the brain organization and function. Anatomical brain connectivity models axonal pathways, while the functional brain connectivity characterizes the statistical dependencies and correlation between the activities of various brain regions. The synchronization of brain activity can be inferred through the variation of blood-oxygen-level dependent (BOLD) signal from functional MRI (fMRI) and the neural connections can be estimated using tractography from diffusion MRI (dMRI). Functional connections between brain regions are supported by anatomical connections, and the synchronization of brain activities arises through sharing of information in the form of electro-chemical signals on axon pathways. Jointly modeling fMRI and dMRI data may improve the accuracy in constructing anatomical connectivity as well as functional connectivity. Such an approach may lead to novel multimodal biomarkers potentially able to better capture functional and anatomical connectivity variations. We present a novel brain network model which jointly models the dMRI and fMRI data to improve the anatomical connectivity estimation and extract the anatomical subnetworks associated with specific functional modes by constraining the anatomical connections as structural supports to the functional connections. The key idea is similar to a multi-commodity flow optimization problem that minimizes the cost or maximizes the efficiency for flow configuration and simultaneously fulfills the supply-demand constraint for each commodity. In the proposed network, the nodes represent the grey matter (GM) regions providing brain functionality, and the links represent white matter (WM) fiber bundles connecting those regions and delivering information. The commodities can be thought of as the information corresponding to brain activity patterns as obtained for instance by independent component analysis (ICA) of fMRI data. The concept of information

  5. Motion Detection in Diffusion MRI via Online ODF Estimation

    PubMed Central

    Caruyer, Emmanuel; Aganj, Iman; Lenglet, Christophe; Sapiro, Guillermo; Deriche, Rachid

    2013-01-01

    The acquisition of high angular resolution diffusion MRI is particularly long and subject motion can become an issue. The orientation distribution function (ODF) can be reconstructed online incrementally from diffusion-weighted MRI with a Kalman filtering framework. This online reconstruction provides real-time feedback throughout the acquisition process. In this article, the Kalman filter is first adapted to the reconstruction of the ODF in constant solid angle. Then, a method called STAR (STatistical Analysis of Residuals) is presented and applied to the online detection of motion in high angular resolution diffusion images. Compared to existing techniques, this method is image based and is built on top of a Kalman filter. Therefore, it introduces no additional scan time and does not require additional hardware. The performance of STAR is tested on simulated and real data and compared to the classical generalized likelihood ratio test. Successful detection of small motion is reported (rotation under 2°) with no delay and robustness to noise. PMID:23509445

  6. Focal nodular hyperplasia: characterisation at gadoxetic acid-enhanced MRI and diffusion-weighted MRI

    PubMed Central

    An, H S; Kim, Y J; Jung, S I; Jeon, H J

    2013-01-01

    Purpose: The aim of this study was to assess the enhancement patterns of hepatic focal nodular hyperplasia (FNH) on gadoxetic acid-enhanced MRI and diffusion-weighted (DW) MRI. Methods: This retrospective study had institutional review board approval. Gadoxetic acid-enhanced and DW MR images were evaluated in 23 patients with 30 FNHs (26 histologically proven and 4 radiologically diagnosed). The lesion enhancement patterns of the hepatobiliary phase images were classified as heterogeneous or homogeneous signal intensity (SI), and as dominantly high/iso or low SI compared with those of adjacent liver parenchyma. Heterogeneous (any) SI lesions and homogeneous low SI lesions were categorised into the fibrosis group, whereas homogeneous high/iso SI lesions were categorised into the non-fibrosis group. Additionally, lesion SI on T2 weighted images, DW images and apparent diffusion coefficient (ADC) values were compared between the two groups. Results: The lesions showed heterogeneous high/iso SI (n=16), heterogeneous low SI (n=5), homogeneous high/iso SI (n=7) or homogeneous low SI (n=2) at the hepatobiliary phase MR images. The fibrosis group lesions were more likely to show high SI on DW images and T2 weighted images compared with those in the non-fibrosis group (p<0.05). ADC values tended to be lower in the fibrosis group than those in the non-fibrosis group without significance. Conclusion: FNH showed variable enhancement patterns on hepatobiliary phase images during gadoxetic acid-enhanced MRI. SI on DW and T2 weighted images differed according to the fibrosis component contained in the lesion. Advances in knowledge: FNH shows a wide spectrum of imaging findings on gadoxetic acid-enhanced MRI and DW MRI. PMID:23873903

  7. A 4-channel 3 Tesla phased array receive coil for awake rhesus monkey fMRI and diffusion MRI experiments

    PubMed Central

    Khachaturian, Mark Haig

    2010-01-01

    Awake monkey fMRI and diffusion MRI combined with conventional neuroscience techniques has the potential to study the structural and functional neural network. The majority of monkey fMRI and diffusion MRI experiments are performed with single coils which suffer from severe EPI distortions which limit resolution. By constructing phased array coils for monkey MRI studies, gains in SNR and anatomical accuracy (i.e., reduction of EPI distortions) can be achieved using parallel imaging. The major challenges associated with constructing phased array coils for monkeys are the variation in head size and space constraints. Here, we apply phased array technology to a 4-channel phased array coil capable of improving the resolution and image quality of full brain awake monkey fMRI and diffusion MRI experiments. The phased array coil is that can adapt to different rhesus monkey head sizes (ages 4–8) and fits in the limited space provided by monkey stereotactic equipment and provides SNR gains in primary visual cortex and anatomical accuracy in conjunction with parallel imaging and improves resolution in fMRI experiments by a factor of 2 (1.25 mm to 1.0 mm isotropic) and diffusion MRI experiments by a factor of 4 (1.5 mm to 0.9 mm isotropic). PMID:21243106

  8. Rotationally invariant clustering of diffusion MRI data using spherical harmonics

    NASA Astrophysics Data System (ADS)

    Liptrot, Matthew; Lauze, François

    2016-03-01

    We present a simple approach to the voxelwise classification of brain tissue acquired with diffusion weighted MRI (DWI). The approach leverages the power of spherical harmonics to summarise the diffusion information, sampled at many points over a sphere, using only a handful of coefficients. We use simple features that are invariant to the rotation of the highly orientational diffusion data. This provides a way to directly classify voxels whose diffusion characteristics are similar yet whose primary diffusion orientations differ. Subsequent application of machine-learning to the spherical harmonic coefficients therefore may permit classification of DWI voxels according to their inferred underlying fibre properties, whilst ignoring the specifics of orientation. After smoothing apparent diffusion coefficients volumes, we apply a spherical harmonic transform, which models the multi-directional diffusion data as a collection of spherical basis functions. We use the derived coefficients as voxelwise feature vectors for classification. Using a simple Gaussian mixture model, we examined the classification performance for a range of sub-classes (3-20). The results were compared against existing alternatives for tissue classification e.g. fractional anisotropy (FA) or the standard model used by Camino.1 The approach was implemented on both two publicly-available datasets: an ex-vivo pig brain and in-vivo human brain from the Human Connectome Project (HCP). We have demonstrated how a robust classification of DWI data can be performed without the need for a model reconstruction step. This avoids the potential confounds and uncertainty that such models may impose, and has the benefit of being computable directly from the DWI volumes. As such, the method could prove useful in subsequent pre-processing stages, such as model fitting, where it could inform about individual voxel complexities and improve model parameter choice.

  9. Evaluating the accuracy of diffusion MRI models in white matter.

    PubMed

    Rokem, Ariel; Yeatman, Jason D; Pestilli, Franco; Kay, Kendrick N; Mezer, Aviv; van der Walt, Stefan; Wandell, Brian A

    2015-01-01

    Models of diffusion MRI within a voxel are useful for making inferences about the properties of the tissue and inferring fiber orientation distribution used by tractography algorithms. A useful model must fit the data accurately. However, evaluations of model-accuracy of commonly used models have not been published before. Here, we evaluate model-accuracy of the two main classes of diffusion MRI models. The diffusion tensor model (DTM) summarizes diffusion as a 3-dimensional Gaussian distribution. Sparse fascicle models (SFM) summarize the signal as a sum of signals originating from a collection of fascicles oriented in different directions. We use cross-validation to assess model-accuracy at different gradient amplitudes (b-values) throughout the white matter. Specifically, we fit each model to all the white matter voxels in one data set and then use the model to predict a second, independent data set. This is the first evaluation of model-accuracy of these models. In most of the white matter the DTM predicts the data more accurately than test-retest reliability; SFM model-accuracy is higher than test-retest reliability and also higher than the DTM model-accuracy, particularly for measurements with (a) a b-value above 1000 in locations containing fiber crossings, and (b) in the regions of the brain surrounding the optic radiations. The SFM also has better parameter-validity: it more accurately estimates the fiber orientation distribution function (fODF) in each voxel, which is useful for fiber tracking. PMID:25879933

  10. Evaluating the Accuracy of Diffusion MRI Models in White Matter

    PubMed Central

    Rokem, Ariel; Yeatman, Jason D.; Pestilli, Franco; Kay, Kendrick N.; Mezer, Aviv; van der Walt, Stefan; Wandell, Brian A.

    2015-01-01

    Models of diffusion MRI within a voxel are useful for making inferences about the properties of the tissue and inferring fiber orientation distribution used by tractography algorithms. A useful model must fit the data accurately. However, evaluations of model-accuracy of commonly used models have not been published before. Here, we evaluate model-accuracy of the two main classes of diffusion MRI models. The diffusion tensor model (DTM) summarizes diffusion as a 3-dimensional Gaussian distribution. Sparse fascicle models (SFM) summarize the signal as a sum of signals originating from a collection of fascicles oriented in different directions. We use cross-validation to assess model-accuracy at different gradient amplitudes (b-values) throughout the white matter. Specifically, we fit each model to all the white matter voxels in one data set and then use the model to predict a second, independent data set. This is the first evaluation of model-accuracy of these models. In most of the white matter the DTM predicts the data more accurately than test-retest reliability; SFM model-accuracy is higher than test-retest reliability and also higher than the DTM model-accuracy, particularly for measurements with (a) a b-value above 1000 in locations containing fiber crossings, and (b) in the regions of the brain surrounding the optic radiations. The SFM also has better parameter-validity: it more accurately estimates the fiber orientation distribution function (fODF) in each voxel, which is useful for fiber tracking. PMID:25879933

  11. Minimal mass size of a stable {sup 3}He cluster

    SciTech Connect

    Guardiola, R.; Navarro, J.

    2005-03-01

    The minimal number of {sup 3}He atoms required to form a bound cluster has been estimated by means of a diffusion Monte Carlo procedure within the fixed-node approximation. Several importance sampling wave functions have been employed in order to consider different shell-model configurations. The resulting upper bound for the minimal number is 32 atoms.

  12. The effect of Gibbs ringing artifacts on measures derived from diffusion MRI.

    PubMed

    Perrone, Daniele; Aelterman, Jan; Pižurica, Aleksandra; Jeurissen, Ben; Philips, Wilfried; Leemans, Alexander

    2015-10-15

    Diffusion-weighted (DW) magnetic resonance imaging (MRI) is a unique method to investigate microstructural tissue properties noninvasively and is one of the most popular methods for studying the brain white matter in vivo. To obtain reliable statistical inferences with diffusion MRI, however, there are still many challenges, such as acquiring high-quality DW-MRI data (e.g., high SNR and high resolution), careful data preprocessing (e.g., correcting for subject motion and eddy current induced geometric distortions), choosing the appropriate diffusion approach (e.g., diffusion tensor imaging (DTI), diffusion kurtosis imaging (DKI), or diffusion spectrum MRI), and applying a robust analysis strategy (e.g., tractography based or voxel based analysis). Notwithstanding the numerous efforts to optimize many steps in this complex and lengthy diffusion analysis pipeline, to date, a well-known artifact in MRI--i.e., Gibbs ringing (GR)--has largely gone unnoticed or deemed insignificant as a potential confound in quantitative DW-MRI analysis. Considering the recent explosion of diffusion MRI applications in biomedical and clinical applications, a systematic and comprehensive investigation is necessary to understand the influence of GR on the estimation of diffusion measures. In this work, we demonstrate with simulations and experimental DW-MRI data that diffusion estimates are significantly affected by GR artifacts and we show that an off-the-shelf GR correction procedure based on total variation already can alleviate this issue substantially. PMID:26142273

  13. Brain MRI in patients with diffuse psychiatric/neuropsychological syndromes in systemic lupus erythematosus

    PubMed Central

    Arinuma, Yoshiyuki; Kikuchi, Hirotoshi; Wada, Tatsuhiko; Nagai, Tatsuo; Tanaka, Sumiaki; Oba, Hiroshi; Hirohata, Shunsei

    2014-01-01

    Background Manifestations in neuropsychiatric systemic lupus erythematosus (NPSLE), especially active diffuse NPSLE syndromes, are some of the most difficult complications of the disease. For the evaluation and the diagnosis of central nervous system manifestations, including NPSLE, MRI is a very useful tool to detect the various abnormalities. However, the relationship between brain MRI findings and clinical variables has not yet been clarified in patients with diffuse NPSLE. Objectives The aim of this study is to investigate the pathogenesis of diffuse NPSLE, by comparing various parameters such as serum autoantibodies and cytokines in cerebrospinal fluid (CSF) with abnormal findings revealed on brain MRIs in patients with diffuse NPSLE. Methods Fifty-three patients with diffuse NPSLE admitted to our University Hospital from 1992 to 2012 were exhaustively enrolled in this study. Their medical charts and brain MRI scans were reviewed. The relationship of MRI abnormalities with various parameters was analysed. Results As many as 25 of 53 patients (47.2%) had abnormal MRI findings. MRI findings improved after treatment in 10 of 17 patients for whom follow-up studies were available. MRI abnormalities were not correlated with age at the onset of diffuse NPSLE. However, the disease duration of SLE was significantly longer in patients with abnormal MRI findings (p=0.0009). MRI abnormalities were not significantly associated with serum autoantibodies. However, there were significant elevations of the CSF protein level (p=0.0106) and the CSF interleukin 6 level (p=0.0225) in patients with abnormal MRI findings. Patients with MRI abnormalities showed significantly higher overall mortality (p=0.0348). Conclusions The results revealed that MRI abnormalities in diffuse NPSLE might be heterogeneous with regard to their reversibility. These data also indicate that patients with diffuse NPSLE and MRI abnormalities have more severe inflammation in the central nervous system

  14. Molecular imaging of water binding state and diffusion in breast cancer using diffuse optical spectroscopy and diffusion weighted MRI

    PubMed Central

    Yu, Hon; Su, Min-Ying; Cerussi, Albert E.; Tromberg, Bruce J.

    2012-01-01

    Abstract. Tissue water content and molecular microenvironment can provide important intrinsic contrast for cancer imaging. In this work, we examine the relationship between water optical spectroscopic features related to binding state and magnetic resonance imaging (MRI)-measured water diffusion dynamics. Broadband diffuse optical spectroscopic imaging (DOSI) and MR images were obtained from eight patients with locally-advanced infiltrating ductal carcinomas (tumor size=5.5±3.2  cm). A DOSI-derived bound water index (BWI) was compared to the apparent diffusion coefficient (ADC) of diffusion weighted (DW) MRI. BWI and ADC were positively correlated (R=0.90, p-value=0.003) and BWI and ADC both decreased as the bulk water content increased (R=−0.81 and −0.89, respectively). BWI correlated inversely with tumor size (R=−0.85, p-value=0.008). Our results suggest underlying sensitivity differences between BWI and ADC to water in different tissue compartments (e.g., extracellular vs cellular). These data highlight the potential complementary role of DOSI and DW-MRI in providing detailed information on the molecular disposition of water in breast tumors. Because DOSI is a portable technology that can be used at the bedside, BWI may provide a low-cost measure of tissue water properties related to breast cancer biology. PMID:22894465

  15. Transport in ultradilute solutions of 3He in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Baym, Gordon; Beck, D. H.; Pethick, C. J.

    2015-07-01

    We calculate the effect of a heat current on transporting 3He dissolved in superfluid 4He at ultralow concentration, as will be utilized in a proposed experimental search for the electric dipole moment of the neutron (nEDM). In this experiment, a phonon wind will be generated to drive (partly depolarized) 3He down a long pipe. In the regime of 3He concentrations ≲10-9 and temperatures ˜0.5 K, the phonons comprising the heat current are kept in a flowing local equilibrium by small angle phonon-phonon scattering, while they transfer momentum to the walls via the 4He first viscosity. On the other hand, the phonon wind drives the 3He out of local equilibrium via phonon-3He scattering. For temperatures below 0.5 K, both the phonon and 3He mean free paths can reach the centimeter scale, and we calculate the effects on the transport coefficients. We derive the relevant transport coefficients, the phonon thermal conductivity, and the 3He diffusion constants from the Boltzmann equation. We calculate the effect of scattering from the walls of the pipe and show that it may be characterized by the average distance from points inside the pipe to the walls. The temporal evolution of the spatial distribution of the 3He atoms is determined by the time dependent 3He diffusion equation, which describes the competition between advection by the phonon wind and 3He diffusion. As a consequence of the thermal diffusivity being small compared with the 3He diffusivity, the scale height of the final 3He distribution is much smaller than that of the temperature gradient. We present exact solutions of the time dependent temperature and 3He distributions in terms of a complete set of normal modes.

  16. Longitudinal, Noninvasive Monitoring of Compensatory Lung Growth in Mice after Pneumonectomy via 3He and 1H Magnetic Resonance Imaging

    PubMed Central

    Wang, Wei; Nguyen, Nguyet M.; Guo, Jinbang

    2013-01-01

    In rodents and some other mammals, partial pneumonectomy (PNX) of adult lungs results in rapid compensatory lung growth. In the past, quantification of compensatory lung growth and realveolarization could only be accomplished after killing the animal, removal of lungs, and histologic analysis of lungs at single time points. Hyperpolarized 3He diffusion magnetic resonance imaging (MRI) allows in vivo morphometry of human lungs; our group has adapted this technique for application to mouse lungs. Through imaging, we can obtain maps of lung microstructural parameters that allow quantification of morphometric and physiologic measurements. In this study, we employed our 3He MRI technique to image in vivo morphometry at baseline and to serially assess compensatory growth after left PNX of mice. 1H and hyperpolarized 3He diffusion MRI were performed at baseline (pre-PNX), 3-days, and 30-days after PNX. Compared with the individual mouse’s own baseline, MRI was able to detect and serially quantify changes in lung volume, alveolar surface area, alveolar number, and regional changes in alveolar size that occurred during the course of post-PNX lung growth. These results are consistent with morphometry measurements reported in the literature for mouse post-PNX compensatory lung growth. In addition, we were also able to serially assess and quantify changes in the physiologic parameter of lung compliance during the course of compensatory lung growth; this was consistent with flexiVent data. With these techniques, we now have a noninvasive, in vivo method to serially assess the effectiveness of therapeutic interventions on post-PNX lung growth in the same mouse. PMID:23763461

  17. DNP for polarizing liquid {sup 3}He

    SciTech Connect

    Uemtasu, H.; Iwata, T.; Kato, S.; Michigami, T.; Ohizumi, S.; Shishido, T.; Tanaka, A.; Toyama, K.; Tajima, Y.; Yoshida, H. Y.; Kuriyama, N.

    2008-02-06

    Using DNP with zeolite powders and TEMPO, we have developed a method to enhance polarization of liquid {sup 3}He. At magnetic field of 2.5 T and a temperature of around 1.5 K, we have obatined polarization enhancement of liquid {sup 3}He, 2.34 and -1.59 for positive and negative enhancements, respectively.

  18. Dynamics of vortex nucleation in sup 3 He- A flow

    SciTech Connect

    Kopnin, N.B.; Soininen, P.I.; Salomaa, M.M. )

    1992-03-01

    Quantum phase slippage in superfluid {sup 3}He flow is simulated numerically in rectangular slab geometries. Assuming that the flow is confined to a channel having horizontal surfaces close to each other, the spatial problem reduces to the two transverse dimensions; we report time-dependent computer simulations of superfluid {sup 3}He flow in 2+1 dimensions using the time-dependent Ginzburg-Landau equations. The quantum-dynamic processes of phase slippage in {sup 3}He are demonstrated to be associated with superfluid vortex nucleation; we thus confirm Anderson's assumption for phase slippage through vortex motion in superfluids. We also find several other phase-slip scenarios involving vortices, phase-slip lines, and combinations thereof for the coupled multicomponent order-parameter amplitudes. We consider both diffuse and specular boundary conditions at the side walls and demonstrate that our results are essentially independent of the boundaries. We compute the critical current for vortex nucleation as a function of the channel width, and compare it with existing theories of vortex nucleation; we also discuss our calculations in connection with experiments on phase slippage in {sup 3}He flow. One of our most important results is that the superfluid order parameter for the vortices generated in the computer simulations does not vanish anywhere; i.e., the vortices possess superfluid core structures; hence the processes of phase slip for superfluid {sup 3}He are nonlocal in space-time.

  19. Vortices in rotating superfluid 3He.

    PubMed

    Lounasmaa, O V; Thuneberg, E

    1999-07-01

    In this review we first present an introduction to 3He and to the ROTA collaboration under which most of the knowledge on vortices in superfluid 3He has been obtained. In the physics part, we start from the exceptional properties of helium at millikelvin temperatures. The dilemma of rotating superfluids is presented. In 4He and in 3He-B the problem is solved by nucleating an array of singular vortex lines. Their experimental detection in 3He by NMR is described next. The vortex cores in 3He-B have two different structures, both of which have spontaneously broken symmetry. A spin-mass vortex has been identified as well. This object is characterized by a flow of spins around the vortex line, in addition to the usual mass current. A great variety of vortices exist in the A phase of 3He; they are either singular or continuous, and their structure can be a line or a sheet or fill the whole liquid. Altogether seven different types of vortices have been detected in 3He by NMR. We also describe briefly other experimental methods that have been used by ROTA scientists in studying vortices in 3He and some important results thus obtained. Finally, we discuss the possible applications of experiments and theory of 3He to particle physics and cosmology. In particular, we report on experiments where superfluid 3He-B was heated locally by absorption of single neutrons. The resulting events can be used to test theoretical models of the Big Bang at the beginning of our universe. PMID:10393895

  20. Vortices in rotating superfluid 3He

    PubMed Central

    Lounasmaa, Olli V.; Thuneberg, Erkki

    1999-01-01

    In this review we first present an introduction to 3He and to the ROTA collaboration under which most of the knowledge on vortices in superfluid 3He has been obtained. In the physics part, we start from the exceptional properties of helium at millikelvin temperatures. The dilemma of rotating superfluids is presented. In 4He and in 3He-B the problem is solved by nucleating an array of singular vortex lines. Their experimental detection in 3He by NMR is described next. The vortex cores in 3He-B have two different structures, both of which have spontaneously broken symmetry. A spin-mass vortex has been identified as well. This object is characterized by a flow of spins around the vortex line, in addition to the usual mass current. A great variety of vortices exist in the A phase of 3He; they are either singular or continuous, and their structure can be a line or a sheet or fill the whole liquid. Altogether seven different types of vortices have been detected in 3He by NMR. We also describe briefly other experimental methods that have been used by ROTA scientists in studying vortices in 3He and some important results thus obtained. Finally, we discuss the possible applications of experiments and theory of 3He to particle physics and cosmology. In particular, we report on experiments where superfluid 3He-B was heated locally by absorption of single neutrons. The resulting events can be used to test theoretical models of the Big Bang at the beginning of our universe. PMID:10393895

  1. Diffusion-weighted MRI derived apparent diffusion coefficient identifies prognostically distinct subgroups of pediatric diffuse intrinsic pontine glioma.

    PubMed

    Lober, Robert M; Cho, Yoon-Jae; Tang, Yujie; Barnes, Patrick D; Edwards, Michael S; Vogel, Hannes; Fisher, Paul G; Monje, Michelle; Yeom, Kristen W

    2014-03-01

    While pediatric diffuse intrinsic pontine gliomas (DIPG) remain fatal, recent data have shown subgroups with distinct molecular biology and clinical behavior. We hypothesized that diffusion-weighted MRI can be used as a prognostic marker to stratify DIPG subsets with distinct clinical behavior. Apparent diffusion coefficient (ADC) values derived from diffusion-weighted MRI were computed in 20 consecutive children with treatment-naïve DIPG tumors. The median ADC for the cohort was used to stratify the tumors into low and high ADC groups. Survival, gender, therapy, and potential steroid effects were compared between the ADC groups. Median age at diagnosis was 6.6 (range 2.3-13.2) years, with median follow-up seven (range 1-36) months. There were 14 boys and six girls. Seventeen patients received radiotherapy, five received chemotherapy, and six underwent cerebrospinal fluid diversion. The median ADC of 1,295 × 10(-6) mm(2)/s for the cohort partitioned tumors into low or high diffusion groups, which had distinct median survivals of 3 and 13 months, respectively (log-rank p < 0.001). Low ADC tumors were found only in boys, whereas high ADC tumors were found in both boys and girls. Available tissue specimens in three low ADC tumors demonstrated high-grade histology, whereas one high ADC tumor demonstrated low-grade histology with a histone H3.1 K27M mutation and high-grade metastatic lesion at autopsy. ADC derived from diffusion-weighted MRI may identify prognostically distinct subgroups of pediatric DIPG. PMID:24522717

  2. Complete fourier direct magnetic resonance imaging (CFD-MRI) for diffusion MRI

    PubMed Central

    Özcan, Alpay

    2013-01-01

    The foundation for an accurate and unifying Fourier-based theory of diffusion weighted magnetic resonance imaging (DW–MRI) is constructed by carefully re-examining the first principles of DW–MRI signal formation and deriving its mathematical model from scratch. The derivations are specifically obtained for DW–MRI signal by including all of its elements (e.g., imaging gradients) using complex values. Particle methods are utilized in contrast to conventional partial differential equations approach. The signal is shown to be the Fourier transform of the joint distribution of number of the magnetic moments (at a given location at the initial time) and magnetic moment displacement integrals. In effect, the k-space is augmented by three more dimensions, corresponding to the frequency variables dual to displacement integral vectors. The joint distribution function is recovered by applying the Fourier transform to the complete high-dimensional data set. In the process, to obtain a physically meaningful real valued distribution function, phase corrections are applied for the re-establishment of Hermitian symmetry in the signal. Consequently, the method is fully unconstrained and directly presents the distribution of displacement integrals without any assumptions such as symmetry or Markovian property. The joint distribution function is visualized with isosurfaces, which describe the displacement integrals, overlaid on the distribution map of the number of magnetic moments with low mobility. The model provides an accurate description of the molecular motion measurements via DW–MRI. The improvement of the characterization of tissue microstructure leads to a better localization, detection and assessment of biological properties such as white matter integrity. The results are demonstrated on the experimental data obtained from an ex vivo baboon brain. PMID:23596401

  3. Spin Duality on the Neutron (^3He)

    SciTech Connect

    Solvignon, Patricia

    2007-02-01

    Thomas Jefferson National Accelerator Facility experiment E01-012 measured the 3He spin structure functions and virtual photon asymmetries in the resonance region in the momentum transfer range 1.0 < Q2 < 4.0 (GeV/c)2. Our date, when compared with existing deep inelastic scattering data, can be used to test quark-hadron duality in g1 and A1 for 3He and the neutron. Preliminary results for A{sub 1}{sup {sup 3}He} are presented, as well as some details about the experiment.

  4. Multishot diffusion-weighted SPLICE PROPELLER MRI of the abdomen.

    PubMed

    Deng, Jie; Omary, Reed A; Larson, Andrew C

    2008-05-01

    Multishot FSE (fast spin echo)-based diffusion-weighted (DW)-PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) MRI offers the potential to reduce susceptibility artifacts associated with single-shot DW-EPI (echo-planar imaging) approaches. However, DW-PROPELLER in the abdomen is challenging due to the large field-of-view and respiratory motion during DW preparation. Incoherent signal phase due to motion will violate the Carr-Purcell-Meiboom-Gill (CPMG) conditions, leading to destructive interference between spin echo and stimulated echo signals and consequent signal cancellation. The SPLICE (split-echo acquisition of FSE signals) technique can mitigate non-CPMG artifacts in FSE-based sequences. For SPLICE, spin echo and stimulated echo are separated by using imbalanced readout gradients and extended acquisition window. Two signal families each with coherent phase properties are acquired at different intervals within the readout window. Separate reconstruction of these two signal families can avoid destructive phase interference. Phantom studies were performed to validate signal phase properties with different initial magnetization phases. This study evaluated the feasibility of combining SPLICE and PROPELLER for DW imaging of the abdomen. It is demonstrated that DW-SPLICE-PROPELLER can effectively mitigate non-CPMG artifacts and improve DW image quality and apparent diffusion coefficient (ADC) map homogeneity. PMID:18429036

  5. A new generation of 3He refrigerators

    NASA Astrophysics Data System (ADS)

    Graziani, A.; DalĺOglio, G.; Martinis, L.; Pizzo, L.; Sabbatini, L.

    2003-12-01

    The characteristics and performance of a new class of 3He refrigerators are discussed. We introduce a 3He refrigerator, which allows a temperature of 296 m K to be reached with a starting point of 4.2 K, without pumping on the main 4He bath. The operating principle is based on the single-expansion helium liquefier: gas cooling by isothermal compression and adiabatic expansion.

  6. Development of polarized 3He ion source

    NASA Astrophysics Data System (ADS)

    Tanaka, M.; Takahashi, Y.; Shimoda, T.; Yasui, S.; Yosoi, M.; Takahisa, K.; Shimakura, N.

    2007-02-01

    A long history on the polarized 3He ion source developed at RCNP is presented. We started with an "OPPIS" (Optical Pumping Polarized Ion Source) and later found the fundamental difficulties in the OPPIS. To overcome them an "EPPIS" (Electron Pumping Polarized Ion Source) was proposed and its validity was experimentally proven. However, a serious technical disadvantage was also found in the EPPIS. To avoid this disadvantage we proposed a new concept, "SEPIS" (Spin Exchange Polarized Ion Source), which uses an enhanced spin-exchange cross section theoretically expected at low 3He+ incident energies for the 3He+ + Rb system. Next, we describe the present status of the SEPIS development; construction of a bench test device allowing the measurements of not only the spin-exchange cross sections σse but also the electron capture cross sections σec for the 3He+ + Rb system. The latest experimental data on σec are presented and compared with other previous experimental data and the theoretical calculations. A design study of the SEPIS for practical use in nuclear (cyclotron) and particle physics (synchrotron) is shortly mentioned. Finally, we mention possibility to polarize ions heavier than 3He as an application of SEPIS. The theoretical calculation showed that σse comparable to that for the 3He+ + Rb is expected for the Li2+ + Rb system, which suggests that the SEPIS will hopefully be a general tool to polarize any heavy ions.

  7. Dislocation motion in solid hcp 3He

    NASA Astrophysics Data System (ADS)

    Beamish, John; Cheng, Zhi Gang

    At temperatures above about 100 mK, dislocations reduce the shear modulus of hcp 4He by as much as 90 %. This occurs when dislocations thermally unbind from the 3He impurities that pin them, becoming extraordinarily mobile. The elastic softening is accompanied by a thermally activated dissipation peak due to the 3He impurities. At higher temperatures the dissipation has an ωT4 dependence caused by scattering of thermal phonons from moving dislocations. Previous measurements on the fermi solid, hcp 3He, showed a similar dislocation softening, but the corresponding dissipation was not measured. We have extended these measurements by measuring the temperature, amplitude and frequency dependence of both the shear modulus and the dissipation in hcp 3He. The dissipation behavior is very different from that of hcp 4He. Neither the impurity unbinding peak associated with the elastic softening, nor the high temperature phonon scattering dissipation, were observed. Instead, there is a large and non-thermally activated dissipation which is largest at low frequencies. We believe that this unexpected dissipation is associated with a new dislocation damping mechanism in 3He, perhaps associated with spin rearrangements caused by moving dislocations. This work was supported by a grant from NSERC Canada.

  8. Major mouse placental compartments revealed by diffusion-weighted MRI, contrast-enhanced MRI, and fluorescence imaging

    PubMed Central

    Solomon, Eddy; Avni, Reut; Hadas, Ron; Raz, Tal; Garbow, Joel Richard; Bendel, Peter; Frydman, Lucio; Neeman, Michal

    2014-01-01

    Mammalian models, and mouse studies in particular, play a central role in our understanding of placental development. Magnetic resonance imaging (MRI) could be a valuable tool to further these studies, providing both structural and functional information. As fluid dynamics throughout the placenta are driven by a variety of flow and diffusion processes, diffusion-weighted MRI could enhance our understanding of the exchange properties of maternal and fetal blood pools—and thereby of placental function. These studies, however, have so far been hindered by the small sizes, the unavoidable motions, and the challenging air/water/fat heterogeneities, associated with mouse placental environments. The present study demonstrates that emerging methods based on the spatiotemporal encoding (SPEN) of the MRI information can robustly overcome these obstacles. Using SPEN MRI in combination with albumin-based contrast agents, we analyzed the diffusion behavior of developing placentas in a cohort of mice. These studies successfully discriminated the maternal from the fetal blood flows; the two orders of magnitude differences measured in these fluids’ apparent diffusion coefficients suggest a nearly free diffusion behavior for the former and a strong flow-based component for the latter. An intermediate behavior was observed by these methods for a third compartment that, based on maternal albumin endocytosis, was associated with trophoblastic cells in the interphase labyrinth. Structural features associated with these dynamic measurements were consistent with independent intravital and ex vivo fluorescence microscopy studies and are discussed within the context of the anatomy of developing mouse placentas. PMID:24969421

  9. Major mouse placental compartments revealed by diffusion-weighted MRI, contrast-enhanced MRI, and fluorescence imaging.

    PubMed

    Solomon, Eddy; Avni, Reut; Hadas, Ron; Raz, Tal; Garbow, Joel Richard; Bendel, Peter; Frydman, Lucio; Neeman, Michal

    2014-07-15

    Mammalian models, and mouse studies in particular, play a central role in our understanding of placental development. Magnetic resonance imaging (MRI) could be a valuable tool to further these studies, providing both structural and functional information. As fluid dynamics throughout the placenta are driven by a variety of flow and diffusion processes, diffusion-weighted MRI could enhance our understanding of the exchange properties of maternal and fetal blood pools--and thereby of placental function. These studies, however, have so far been hindered by the small sizes, the unavoidable motions, and the challenging air/water/fat heterogeneities, associated with mouse placental environments. The present study demonstrates that emerging methods based on the spatiotemporal encoding (SPEN) of the MRI information can robustly overcome these obstacles. Using SPEN MRI in combination with albumin-based contrast agents, we analyzed the diffusion behavior of developing placentas in a cohort of mice. These studies successfully discriminated the maternal from the fetal blood flows; the two orders of magnitude differences measured in these fluids' apparent diffusion coefficients suggest a nearly free diffusion behavior for the former and a strong flow-based component for the latter. An intermediate behavior was observed by these methods for a third compartment that, based on maternal albumin endocytosis, was associated with trophoblastic cells in the interphase labyrinth. Structural features associated with these dynamic measurements were consistent with independent intravital and ex vivo fluorescence microscopy studies and are discussed within the context of the anatomy of developing mouse placentas. PMID:24969421

  10. The influence of restricted geometry of diamagnetic nanoporous media on 3He relaxation

    NASA Astrophysics Data System (ADS)

    Alakshin, E. M.; Gazizulin, R. R.; Zakharov, M. Yu.; Klochkov, A. V.; Morozov, E. V.; Salikhov, T. M.; Safin, T. R.; Safiullin, K. R.; Tagirov, M. S.; Shabanova, O. B.

    2015-01-01

    This is an experimental study of the spin kinetics of 3He in contact with diamagnetic samples of inverse opals SiO2, and LaF3 nanopowder. It is demonstrated that the nuclear magnetic relaxation of the absorbed 3He occurs due to the modulation of dipole-dipole interaction by the quantum motion in the two-dimensional film. It is found that the relaxation of liquid 3He occurs through a spin diffusion to the absorption layer, and that the restricted geometry of diamagnetic nanoporous media has an influence on the 3He relaxation.

  11. Polarization of3He and3He-4He mixtures with the castaing-nozieres method

    NASA Astrophysics Data System (ADS)

    van Woerkens, C. M. C. M.; Remeijer, P.; Steel, S. C.; Jochemsen, R.; Frossati, G.

    1996-01-01

    We describe experiments employing a strongly improved technique to prepare highly polarized3He and3He-4He mixtures. The polarization is obtained with the rapid melting method. A novel design cell using Vespel SP-1 (a sintered form of polyimide) can reach relative volume changes of 17%, which is required to decompress a completely solid3He-4He mixture to a completely liquid state at 23 bar.

  12. Coherent Photoproduction of pi^+ from 3/^He

    SciTech Connect

    Rakhsha Nasseripour, Barry Berman

    2011-03-01

    We have measured the differential cross section for the $\\gamma$$^3$He$\\rightarrow \\pi^+ t$ reaction. This reaction was studied using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. Real photons produced with the Hall-B bremsstrahlung tagging system in the energy range from 0.50 to 1.55 GeV were incident on a cryogenic liquid $^3$He target. The differential cross sections for the $\\gamma$$^3$He$\\rightarrow \\pi^+ t$ reaction were measured as a function of photon-beam energy and pion-scattering angle. Theoretical predictions to date cannot explain the large cross sections except at backward angles, showing that additional components must be added to the model.

  13. Photoproduction of eta-mesic 3He.

    PubMed

    Pfeiffer, M; Ahrens, J; Annand, J R M; Beck, R; Caselotti, G; Cherepnya, S; Föhl, K; Fog, L S; Hornidge, D; Janssen, S; Kashevarov, V; Kondratiev, R; Kotulla, M; Krusche, B; McGeorge, J C; MacGregor, I J D; Mengel, K; Messchendorp, J G; Metag, V; Novotny, R; Rost, M; Sack, S; Sanderson, R; Schadmand, S; Thomas, A; Watts, D P

    2004-06-25

    The photoproduction of eta-mesic 3He has been investigated using the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI. The total inclusive cross section for the reaction gamma3He-->etaX has been measured for photon energies from threshold to 820 MeV. The total and angular differential coherent eta cross sections have been extracted up to energies of 745 MeV. A resonancelike structure just above the eta production threshold with an isotropic angular distribution suggests the existence of a resonant quasibound state. This is supported by studies of a competing decay channel of such a quasibound eta-mesic nucleus into pi(0)pX. A binding energy of (-4.4+/-4.2) MeV and a width of (25.6+/-6.1) MeV is deduced for the quasibound eta-mesic state in 3He. PMID:15244998

  14. Hyperfine structure of /sup 3/He

    SciTech Connect

    Druzbick, J.; Williams, H.T.

    1987-01-01

    Relativistic contribution to the hyperfine structure of /sup 3/He are reexamined in order to resolve inconsistencies in published values. The orbit-orbit and diamagnetic screening contributions are recomputed and are found to contribute less than one part per million (ppm), contrary to previous results. A new value (318 ppm compared to the perturbation result of 327 ppm) is obtained for the relativistic velocity correction using recently available relativistic Hartree-Fock wave functions. New values of the hyperfine-structure splitting of /sup 3/He in the 1S2S state and the /sup 3/He ion in the 1S and 2S states are presented. Comparison with experiment suggests that the relativistic velocity correction should be 323 ppm and the nuclear structure correction should be 184.2 ppm.

  15. Nuclear electric dipole moment of 3He

    SciTech Connect

    Stetcu, Ionel; Friar, J L; Hayes, A C; Liu, C P; Navratil, P

    2008-01-01

    In the no-core shell model (NCSM) framework, we calculate the {sup 3}He electric dipole moment (EDM) generated by parity- and time-reversal violation in the nucleon-nucleon interaction. While the results are somehow sensitive to the interaction model chosen for the strong two- and three-body interactions, we demonstrate the pion-exchange dominance to the EDM of {sup 3}He, if the coupling constants for {pi}, {rho} and {omega}-exchanges are of comparable magnitude, as expected. Finally, our results suggest that a measurement of {sup 3}He EDM would be complementary to the currently planned neutron and deuteron experiments, and would constitute a powerful constraint to the models of the pion P- and T-violating interactions.

  16. Resolution of early diffusion-weighted and FLAIR MRI abnormalities in a patient with TIA.

    PubMed

    Lecouvet, F E; Duprez, T P; Raymackers, J M; Peeters, A; Cosnard, G

    1999-03-23

    We report a patient with a clinical history and neurologic examination consistent with acute stroke. Diffusion-weighted and fast fluid-attenuated inversion recovery MRI obtained 4 hours after stroke onset detected focal abnormalities suggestive of acute ischemic brain damage. The neurologic deficit and the imaging abnormalities both resolved completely at follow-up. This patient illustrates complete resolution of early changes observed with diffusion-weighted MRI at the hyperacute phase in a TIA. PMID:10102438

  17. Influence of BOLD Contributions to Diffusion fMRI Activation of the Visual Cortex

    PubMed Central

    Williams, Rebecca J.; Reutens, David C.; Hocking, Julia

    2016-01-01

    Reliance on the hemodynamic response as a surrogate marker of neural activity imposes an intrinsic limit on the spatial specificity of functional MRI. An alternative approach based on diffusion-weighted functional MRI (DfMRI) has been reported as a contrast less reliant on hemodynamic effects, however current evidence suggests that both hemodynamic and unique neural sources contribute to the diffusion signal. Here we compare activation patterns obtained with the standard blood oxygenation level-dependent (BOLD) contrast to DfMRI in order to gain a deeper understanding of how the BOLD proportion contributes to the observable diffusion signal. Both individual and group-level activation patterns obtained with DfMRI and BOLD to a visual field stimulation paradigm were analyzed. At the individual level, the DfMRI contrast showed a strong, positive relationship between the volumes of cortex activated in response to quadrant- and hemi-field visual stimulation. This was not observed in the corresponding BOLD experiment. Overall, the DfMRI response indicated less between-subject variability, with random effects analyses demonstrating higher statistical values at the peak voxel for DfMRI. Furthermore, the spatial extent of the activation was more restricted to the primary visual region for DfMRI than BOLD. However, the diffusion signal was sensitive to the hemodynamic response in a manner dependent on experimental manipulation. It was also limited by its low signal-to-noise ratio (SNR), demonstrating lower sensitivity than BOLD. Together these findings both support DfMRI as a contrast that bears a closer spatial relationship to the underlying neural activity than BOLD, and raise important caveats regarding its utilization. Models explaining the DfMRI signal change need to consider the dynamic vascular contributions that may vary with neural activity. PMID:27445654

  18. Diffuse Axonal Injury at Ultra-High Field MRI

    PubMed Central

    Moenninghoff, Christoph; Kraff, Oliver; Maderwald, Stefan; Umutlu, Lale; Theysohn, Jens M.; Ringelstein, Adrian; Wrede, Karsten H.; Deuschl, Cornelius; Altmeppen, Jan; Ladd, Mark E.; Forsting, Michael; Quick, Harald H.; Schlamann, Marc

    2015-01-01

    Objective Diffuse axonal injury (DAI) is a specific type of traumatic brain injury caused by shearing forces leading to widespread tearing of axons and small vessels. Traumatic microbleeds (TMBs) are regarded as a radiological marker for DAI. This study aims to compare DAI-associated TMBs at 3 Tesla (T) and 7 T susceptibility weighted imaging (SWI) to evaluate possible diagnostic benefits of ultra-high field (UHF) MRI. Material and Methods 10 study participants (4 male, 6 female, age range 20-74 years) with known DAI were included. All MR exams were performed with a 3 T MR system (Magnetom Skyra) and a 7 T MR research system (Magnetom 7 T, Siemens AG, Healthcare Sector, Erlangen, Germany) each in combination with a 32-channel-receive coil. The average time interval between trauma and imaging was 22 months. Location and count of TMBs were independently evaluated by two neuroradiologists on 3 T and 7 T SWI images with similar and additionally increased spatial resolution at 7 T. Inter- and intraobserver reliability was assessed using the interclass correlation coefficient (ICC). Count and diameter of TMB were evaluated with Wilcoxon signed rank test. Results Susceptibility weighted imaging revealed a total of 485 TMBs (range 1-190, median 25) at 3 T, 584 TMBs (plus 20%, range 1-262, median 30.5) at 7 T with similar spatial resolution, and 684 TMBs (plus 41%, range 1-288, median 39.5) at 7 T with 10-times higher spatial resolution. Hemorrhagic DAI appeared significantly larger at 7 T compared to 3 T (p = 0.005). Inter- and intraobserver correlation regarding the counted TMB was high and almost equal 3 T and 7 T. Conclusion 7 T SWI improves the depiction of small hemorrhagic DAI compared to 3 T and may be supplementary to lower field strengths for diagnostic in inconclusive or medicolegal cases. PMID:25793614

  19. The n3He Experiment: Current Status

    NASA Astrophysics Data System (ADS)

    McCrea, Mark; n3He Collaboration

    2014-09-01

    The n3He experiment aims to make a high precision measurement of the hadronic weak interaction in the reaction n-> +3 He --> p + T by measuring the parity violating asymmetry in the direction of proton emission relative to the neutron polarization direction. As the weak interaction is the only interaction to violate parity this allows us to extract the much smaller weak interaction effects from the larger strong interaction effects. The range of the asymmetry is estimated to be (- 9 . 5 --> 2 . 5) ×10-8 . The goal is to measure this asymmetry with an accuracy of 2 ×10-8 to provide a benchmark for modern effective field theory calculations. n3He will run at the SNS Fundamental Neutron Physics Beamline. The combined target and detector is a multiwire 3He ionization chamber. A super mirror polarizer will be used to polarize the incoming cold neutron beam, and a spin flipper will reverse the spin in a sequence to control for systematic effects.

  20. Applications of {sup 3}He neutron detectors

    SciTech Connect

    Testov, D. A.; Briancon, Ch.; Dmitriev, S. N.; Yeremin, A. V.; Penionzhkevich, Yu. E.; Pyatkov, Yu. V.; Sokol, E. A.

    2009-01-15

    Neutron detectors with {sup 3}He-filled proportional counters are described. The use of these detectors in measuring the probability of neutron emission (in particular, multiparticle neutron emission) after the {beta} decay of neutron-rich nuclei and in studying rare events of spontaneous fission of superheavy nuclei is considered.

  1. CT and MRI of diffuse lobar involvement pattern in liver pathology.

    PubMed

    Karçaaltincaba, Muşturay; Sirlin, Claude B

    2011-12-01

    Focal, segmental, and diffuse liver pathologies have been described in the literature. This article describes a pattern in which liver pathology is confined to a lobe. This lobar pattern has not been described previously to our knowledge. Herein, we illustrate computed tomography (CT) and magnetic resonance imaging (MRI) findings of diffuse lobar involvement patterns in various liver conditions. Diffuse lobar involvement can be observed in benign (steatosis, hepatic iron overload, cholestasis, perfusion alterations, infarction, alveolar hydatid cysts, trauma, and hemangiomas) and primary malignant (hepatocellular carcinoma) pathologies. Diffuse lobar involvement in metastatic disease appears to be rare. Due in part to their potentially unusual appearances, the diagnosis of lobar pathologies using imaging can be challenging, and entities with lobar patterns can cause diagnostic confusion. Liver MRI can be used as a problem-solving tool for diffuse lobar pathologies detected on ultrasonography and CT. Inand out-of-phase MRI can help in the assessment of lobar fat accumulation. PMID:21053176

  2. Pomeranchuk cell for hyperpolarized 3He based on the brute force method

    NASA Astrophysics Data System (ADS)

    Makino, Seiji; Tanaka, Masayoshi; Ueda, Kunihiro; Fujiwara, Mamoru; Fujimura, Hisako; Yosoi, Masaru; Ohta, Takeshi; Frossati, Giorgio; de Waard, Arlette; Rouille, Gerard

    2014-09-01

    MRI (Magnetic Resonance Imaging) has been used for the medical diagnosis as a radiation-free imaging equipment. Since the proton has been mainly used for medical MRI, usefulness has been rather restrictive. As an example for expanding the range of applicability, MRI with hyperpolarized 3He gas has been used for the lung disease. Here, ``hyperpolarized'' means ``polarized higher than the thermal equilibrium polarization.'' For producing a large amount of hyperpolarized 3He gas at a time, we have been developing a hyperpolarization technique based on the brute force method which uses an ultralow temperature of a few mK and a strong magnetic field around 17 T in combination with the principle of the Pomeranchuk cooling. The Pomeranchuk cell made with non-metallic materials of small heat capacity is attached to the 3He/4He dilution refrigerator using a sintered silver allowing large heat conduction. After the sensors to monitor the temperature and pressure of 3He are calibrated and the Pomeranchuk cell is constructed, the system is tested. Then, the solidification of 3He and the measurement of NMR (Nuclear Magnetic Resonance) signals of 3He under the magnetic field of 17 T are carried out. The current status is reported in this talk.

  3. Data on the verification and validation of segmentation and registration methods for diffusion MRI.

    PubMed

    Esteban, Oscar; Zosso, Dominique; Daducci, Alessandro; Bach-Cuadra, Meritxell; Ledesma-Carbayo, María J; Thiran, Jean-Philippe; Santos, Andres

    2016-09-01

    The verification and validation of segmentation and registration methods is a necessary assessment in the development of new processing methods. However, verification and validation of diffusion MRI (dMRI) processing methods is challenging for the lack of gold-standard data. The data described here are related to the research article entitled "Surface-driven registration method for the structure-informed segmentation of diffusion MR images" [1], in which publicly available data are used to derive golden-standard reference-data to validate and evaluate segmentation and registration methods in dMRI. PMID:27508235

  4. Validation of diffuse correlation spectroscopy for muscle blood flow with concurrent arterial spin labeled perfusion MRI

    NASA Astrophysics Data System (ADS)

    Yu, Guoqiang; Floyd, Thomas F.; Durduran, Turgut; Zhou, Chao; Wang, Jiongjiong; Detre, John A.; Yodh, Arjun G.

    2007-02-01

    Calf blood flow was measured simultaneously in healthy human subjects (n = 7) during cuff inflation and deflation using near-infrared diffuse correlation spectroscopy (DCS) and arterial spin labeled perfusion MRI (ASL-MRI). The DCS and ASL-MRI data exhibited highly correlated absolute and relative dynamic flow responses in each individual (p < 0.001). Peak flow variations during hyperemia were also significantly correlated, though more for relative (p = 0.003) than absolute (p = 0.016) flow. Repeated measurement variation was less than 8% for both modalities. The results provide much needed quantitative blood flow validation of the diffuse optical correlation method in humans.

  5. Does diffusion MRI tell us anything about the white matter? An overview of methods and pitfalls

    PubMed Central

    O’Donnell, Lauren J.; Pasternak, Ofer

    2014-01-01

    One key pitfall in diffusion magnetic resonance imaging (dMRI) clinical neuroimaging research is the challenge of understanding and interpreting the results of a complex analysis pipeline. The sophisticated algorithms employed by the analysis software, combined with the relatively non-specific nature of many diffusion measurements, lead to challenges in interpretation of the results. This paper is aimed at an intended audience of clinical researchers who are learning about dMRI or trying to interpret dMRI results, and who may be wondering “Does dMRI tell us anything about the white matter?” We present a critical review of dMRI methods and measures used in clinical neuroimaging research, focusing on the most commonly used analysis methods and the most commonly reported measures. We describe important pitfalls in every section, and provide extensive references for the reader interested in more detail. PMID:25278106

  6. Neutron Polarizers Based on Polarized 3He

    SciTech Connect

    William M. Snow

    2005-05-01

    The goal of this work, which is a collaborative effort between Indiana University, NIST, and Hamilton College, is to extend the technique of polarized neutron scattering into new domains by the development and application of polarized 3He-based neutron spin filters. After the IPNS experiment which measured Zeeman sp[litting in surface scattered neutrons using a polarized 3He cell as a polarization analyzer transporterd by car from Bloomington to Chicago, the Indiana work focused on technical developments to improve the 3He polarization of the Indiana compression system. The compression system was rebuilt with a new valve system which allows gas trapped in the dead volume of the compressors at the end of the piston stroke to be exhausted and conducted back to the optical pumping cell where it can be repolarized. We also incorporated a new intermediate storage volume made at NIST from 1720 glass which will reduce polarization losses between the compressors. Furthermore, we improved the stability of the 1083 nm laser by cooling the LMA rod. We achieved 60% 3he polarization in the optical pumping cell and 87% preservation of the polarization during compression. In parallel we built a magnetically-shielded transport solenoid for use on neutron scattering instruments such as POSY which achieves a fractional field uniformity of better than 10-3 per cm. The field was mapped using an automated 3D field mapping system for in-situ measurement of magnetic field gradients Diluted magnetic semiconductors offer many exciting opportunities for investigation of spintronic effects in solids and are certain to be one of the most active areas of condensed matter physics over then next several years. These materials can act as efficient spin injectors for devices that make use of spin-dependent transport phenomena. We just (late July 2002) finished a neutron reflectivity experiment at NIST on a GaMnAs trilayer film. This material is a ferromagnetic semiconductor which is of interest

  7. Development of spatial-temporal ventilation heterogeneity and probability analysis tools for hyperpolarized 3He magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Choy, S.; Ahmed, H.; Wheatley, A.; McCormack, D. G.; Parraga, G.

    2010-03-01

    We developed image analysis tools to evaluate spatial and temporal 3He magnetic resonance imaging (MRI) ventilation in asthma and cystic fibrosis. We also developed temporal ventilation probability maps to provide a way to describe and quantify ventilation heterogeneity over time, as a way to test respiratory exacerbations or treatment predictions and to provide a discrete probability measurement of 3He ventilation defect persistence.

  8. 3He Spin Filter for Neutrons

    PubMed Central

    Batz, M.; Baeßler, S.; Heil, W.; Otten, E. W.; Rudersdorf, D.; Schmiedeskamp, J.; Sobolev, Y.; Wolf, M.

    2005-01-01

    The strongly spin-dependent absorption of neutrons in nuclear spin-polarized 3He opens up the possibility of polarizing neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. This paper gives a report on the neutron spin filter (NSF) development program at Mainz. The polarization technique is based on direct optical pumping of metastable 3He atoms combined with a polarization preserving mechanical compression of the gas up to a pressure of several bar, necessary to run a NSF. The concept of a remote type of operation using detachable NSF cells is presented which requires long nuclear spin relaxation times of order 100 hours. A short survey of their use under experimental conditions, e.g. large solid-angle polarization analysis, is given. In neutron particle physics NSFs are used in precision measurements to test fundamental symmetry concepts. PMID:27308139

  9. Surface tension maximum of liquid 3He

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koichi; Hasegawa, Syuichi; Suzuki, Masaru; Okuda, Yuichi

    2000-07-01

    The surface tension of liquid 3He was measured using the capillary-rise method. Suzuki et al. have reported that its temperature dependence was almost quenched below 120 mK. Here we have examined it with higher precision and found that it has a small maximum around 100 mK. The amount of the maximum is about 3×10 -4 as a fraction of the surface tension at 0 K. The density of liquid 3He increases with temperature by about 5×10 -4 in Δ ρ/ ρ between 0 and 100 mK. This density change could be one of the reasons of the surface tension maximum around 100 mK.

  10. Dating degassed groundwater with 3H/3He

    NASA Astrophysics Data System (ADS)

    Visser, Ate; Broers, Hans Peter; Bierkens, Marc F. P.

    2007-10-01

    The production of gases in groundwater under contaminated locations by geochemical and biological processes is not uncommon. Degassing of these gases from groundwater and repartitioning of noble gases between water and gas phase distorts groundwater dating by 3H/3He. We observed noble gas concentrations below atmospheric equilibrium in 20 out of 34 groundwater samples from agriculturally polluted sandy areas in the Netherlands. From the absence of nitrate in degassed samples, we conclude that denitrification causes degassing. The 22Ne/20Ne ratios show that degassing had attained solubility equilibrium and had not caused isotopic fractionation by diffusion. To correct for the loss of tritiogenic 3He due to degassing, we present a single-step equilibrium degassing model. We use the total dissolved gas pressure at the monitoring screen to estimate the depth and timing of degassing, which is essential to estimate travel times from degassed samples. By propagating the uncertainties in the underlying measurements and assumptions through the travel time calculations, we found a travel time uncertainty of 3 years (a). We therefore conclude that 3H/3He dating can produce valuable information on groundwater flow even at sites with strong degassing.

  11. NMR Studies of 3He Films on Boron Nitride

    NASA Astrophysics Data System (ADS)

    Tang, Y.; Sullivan, N. S.

    2014-12-01

    We report the results of NMR studies of the dynamics of 3He adsorbed on hexagonal boron nitride. These studies can identify the phase transitions of the 2D films as a function of temperature. A thermally activated temperature dependence is observed for 2.6 < T < 8 K compared to a linear temperature dependence for 0.7 < T < 2.6 K. This linear dependence is consistent with that expected for thermal diffusion in a fluid for coverages of 0.4 - 0.6 of a monolayer.

  12. High-momentum response of liquid 3He.

    PubMed

    Mazzanti, F; Polls, A; Boronat, J; Casulleras, J

    2004-02-27

    A final-state-effects formalism suitable to analyze the high-momentum response of Fermi liquids is presented and used to study the dynamic structure function of liquid 3He. The theory, developed as a natural extension of the Gersch-Rodriguez formalism, incorporates the Fermi statistics explicitly through a new additive term which depends on the semidiagonal two-body density matrix. The use of a realistic momentum distribution, calculated using the diffusion Monte Carlo method, and the inclusion of this additive correction allows for good agreement with available deep-inelastic neutron scattering data. PMID:14995785

  13. Coupling between Solid 3He on Aerogel and Superfluid 3He in the Low Temperature Limit

    SciTech Connect

    Bradley, D. I.; Fisher, S. N.; Guenault, A. M.; Haley, R. P.; Pickett, G. R.; Tsepelin, V.; Whitehead, R. C. V.; Skyba, P.

    2006-09-07

    We have cooled liquid 3He contained in a 98% open aerogel sample surrounded by bulk superfluid 3He-B at zero pressure to below 120 {mu}K. The aerogel sample is placed in a quasiparticle blackbody radiator cooled by a Lancaster-style nuclear cooling stage to {approx}200 {mu}K. We monitor the temperature of the 3He inside the blackbody radiator using a vibrating wire resonator. We find that reducing the magnetic field on the aerogel sample causes substantial cooling of all the superfluid inside the blackbody radiator. We believe this is due to the demagnetization of the solid 3He layers on the aerogel strands. This system has potential for achieving extremely low temperatures in the confined fluid.

  14. Diffusion fMRI detects white-matter dysfunction in mice with acute optic neuritis

    PubMed Central

    Lin, Tsen-Hsuan; Spees, William M.; Chiang, Chia-Wen; Trinkaus, Kathryn; Cross, Anne H.; Song, Sheng-Kwei

    2014-01-01

    Optic neuritis is a frequent and early symptom of multiple sclerosis (MS). Conventional magnetic resonance (MR) techniques provide means to assess multiple MS-related pathologies, including axonal injury, demyelination, and inflammation. A method to directly and non-invasively probe white-matter function could further elucidate the interplay of underlying pathologies and functional impairments. Previously, we demonstrated a significant 27% activation-associated decrease in the apparent diffusion coefficient of water perpendicular to the axonal fibers (ADC⊥) in normal C57BL/6 mouse optic nerve with visual stimulation using diffusion fMRI. Here we apply this approach to explore the relationship between visual acuity, optic nerve pathology, and diffusion fMRI in the experimental autoimmune encephalomyelitis (EAE) mouse model of optic neuritis. Visual stimulation produced a significant 25% (vs. baseline) ADC⊥ decrease in sham EAE optic nerves, while only a 7% (vs. baseline) ADC⊥ decrease was seen in EAE mice with acute optic neuritis. The reduced activation-associated ADC⊥ response correlated with post-MRI immunohistochemistry determined pathologies (including inflammation, demyelination, and axonal injury). The negative correlation between activation-associated ADC⊥ response and visual acuity was also found when pooling EAE-affected and sham groups under our experimental criteria. Results suggest that reduction in diffusion fMRI directly reflects impaired axonal-activation in EAE mice with optic neuritis. Diffusion fMRI holds promise for directly gauging in vivo white-matter dysfunction or therapeutic responses in MS patients. PMID:24632420

  15. 3He lung morphometry technique: Accuracy analysis and pulse sequence optimization

    NASA Astrophysics Data System (ADS)

    Sukstanskii, A. L.; Conradi, M. S.; Yablonskiy, D. A.

    2010-12-01

    The 3He lung morphometry technique (Yablonskiy et al., JAP, 2009), based on MRI measurements of hyperpolarized gas diffusion in lung airspaces, provides unique information on the lung microstructure at the alveolar level. 3D tomographic images of standard morphological parameters (mean airspace chord length, lung parenchyma surface-to-volume ratio, and the number of alveoli per unit lung volume) can be created from a rather short (several seconds) MRI scan. These parameters are most commonly used to characterize lung morphometry but were not previously available from in vivo studies. A background of the 3He lung morphometry technique is based on a previously proposed model of lung acinar airways, treated as cylindrical passages of external radius R covered by alveolar sleeves of depth h, and on a theory of gas diffusion in these airways. The initial works approximated the acinar airways as very long cylinders, all with the same R and h. The present work aims at analyzing effects of realistic acinar airway structures, incorporating airway branching, physiological airway lengths, a physiological ratio of airway ducts and sacs, and distributions of R and h. By means of Monte-Carlo computer simulations, we demonstrate that our technique allows rather accurate measurements of geometrical and morphological parameters of acinar airways. In particular, the accuracy of determining one of the most important physiological parameter of lung parenchyma - surface-to-volume ratio - does not exceed several percent. Second, we analyze the effect of the susceptibility induced inhomogeneous magnetic field on the parameter estimate and demonstrate that this effect is rather negligible at B0 ⩽ 3T and becomes substantial only at higher B0 Third, we theoretically derive an optimal choice of MR pulse sequence parameters, which should be used to acquire a series of diffusion-attenuated MR signals, allowing a substantial decrease in the acquisition time and improvement in accuracy of the

  16. Pushing spatial and temporal resolution for functional and diffusion MRI in the Human Connectome Project

    PubMed Central

    Uğurbil, Kamil; Xu, Junqian; Auerbach, Edward J.; Moeller, Steen; Vu, An; Duarte-Carvajalino, Julio M.; Lenglet, Christophe; Wu, Xiaoping; Schmitter, Sebastian; Van de Moortele, Pierre Francois; Strupp, John; Sapiro, Guillermo; De Martino, Federico; Wang, Dingxin; Harel, Noam; Garwood, Michael; Chen, Liyong; Feinberg, David A.; Smith, Stephen M.; Miller, Karla L.; Sotiropoulos, Stamatios N; Jbabdi, Saad; Andersson, Jesper L; Behrens, Timothy EJ; Glasser, Matthew F.; Van Essen, David; Yacoub, Essa

    2013-01-01

    The human connectome project (HCP) relies primarily on three complementary magnetic resonance (MR) methods. These are: 1) resting state functional MR imaging (rfMRI) which uses correlations in the temporal fluctuations in an fMRI time series to deduce ‘functional connectivity’; 2) diffusion imaging (dMRI), which provides the input for tractography algorithms used for the reconstruction of the complex axonal fiber architecture; and 3) task based fMRI (tfMRI), which is employed to identify functional parcellation in the human brain in order to assist analyses of data obtained with the first two methods. We describe technical improvements and optimization of these methods as well as instrumental choices that impact speed of acquisition of fMRI and dMRI images at 3 Tesla, leading to whole brain coverage with 2 mm isotropic resolution in 0.7 second for fMRI, and 1.25 mm isotropic resolution dMRI data for tractography analysis with three-fold reduction in total data acquisition time. Ongoing technical developments and optimization for acquisition of similar data at 7 Tesla magnetic field are also presented, targeting higher resolution, specificity of functional imaging signals, mitigation of the inhomogeneous radio frequency (RF) fields and power deposition. Results demonstrate that overall, these approaches represent a significant advance in MR imaging of the human brain to investigate brain function and structure. PMID:23702417

  17. Structural and Functional Brain Remodeling during Pregnancy with Diffusion Tensor MRI and Resting-State Functional MRI

    PubMed Central

    Chan, Russell W.; Ho, Leon C.; Zhou, Iris Y.; Gao, Patrick P.; Chan, Kevin C.; Wu, Ed X.

    2015-01-01

    Although pregnancy-induced hormonal changes have been shown to alter the brain at the neuronal level, the exact effects of pregnancy on brain at the tissue level remain unclear. In this study, diffusion tensor imaging (DTI) and resting-state functional MRI (rsfMRI) were employed to investigate and document the effects of pregnancy on the structure and function of the brain tissues. Fifteen Sprague-Dawley female rats were longitudinally studied at three days before mating (baseline) and seventeen days after mating (G17). G17 is equivalent to the early stage of the third trimester in humans. Seven age-matched nulliparous female rats served as non-pregnant controls and were scanned at the same time-points. For DTI, diffusivity was found to generally increase in the whole brain during pregnancy, indicating structural changes at microscopic levels that facilitated water molecular movement. Regionally, mean diffusivity increased more pronouncedly in the dorsal hippocampus while fractional anisotropy in the dorsal dentate gyrus increased significantly during pregnancy. For rsfMRI, bilateral functional connectivity in the hippocampus increased significantly during pregnancy. Moreover, fractional anisotropy increase in the dentate gyrus appeared to correlate with the bilateral functional connectivity increase in the hippocampus. These findings revealed tissue structural modifications in the whole brain during pregnancy, and that the hippocampus was structurally and functionally remodeled in a more marked manner. PMID:26658306

  18. Numerical study of a cylinder model of the diffusion MRI signal for neuronal dendrite trees.

    PubMed

    Van Nguyen, Dang; Grebenkov, Denis; Le Bihan, Denis; Li, Jing-Rebecca

    2015-03-01

    We study numerically how the neuronal dendrite tree structure can affect the diffusion magnetic resonance imaging (dMRI) signal in brain tissue. For a large set of randomly generated dendrite trees, synthetic dMRI signals are computed and fitted to a cylinder model to estimate the effective longitudinal diffusivity D(L) in the direction of neurites. When the dendrite branches are short compared to the diffusion length, D(L) depends significantly on the ratio between the average branch length and the diffusion length. In turn, D(L) has very weak dependence on the distribution of branch lengths and orientations of a dendrite tree, and the number of branches per node. We conclude that the cylinder model which ignores the connectivity of the dendrite tree, can still be adapted to describe the apparent diffusion coefficient in brain tissue. PMID:25681802

  19. Numerical study of a cylinder model of the diffusion MRI signal for neuronal dendrite trees

    NASA Astrophysics Data System (ADS)

    Van Nguyen, Dang; Grebenkov, Denis; Le Bihan, Denis; Li, Jing-Rebecca

    2015-03-01

    We study numerically how the neuronal dendrite tree structure can affect the diffusion magnetic resonance imaging (dMRI) signal in brain tissue. For a large set of randomly generated dendrite trees, synthetic dMRI signals are computed and fitted to a cylinder model to estimate the effective longitudinal diffusivity DL in the direction of neurites. When the dendrite branches are short compared to the diffusion length, DL depends significantly on the ratio between the average branch length and the diffusion length. In turn, DL has very weak dependence on the distribution of branch lengths and orientations of a dendrite tree, and the number of branches per node. We conclude that the cylinder model which ignores the connectivity of the dendrite tree, can still be adapted to describe the apparent diffusion coefficient in brain tissue.

  20. Direct and fast detection of neuronal activation in the human brain with diffusion MRI

    PubMed Central

    Le Bihan, Denis; Urayama, Shin-ichi; Aso, Toshihiko; Hanakawa, Takashi; Fukuyama, Hidenao

    2006-01-01

    Using MRI, we found that a slowly diffusing water pool was expanding (1.7 ± 0.3%) upon activation on the human visual cortex at the detriment of a faster diffusing pool. The time course of this water phase transition preceded the activation-triggered vascular response detected by usual functional MRI by several seconds. The observed changes in water diffusion likely reflect early biophysical events that take place in the activated cells, such as cell swelling and membrane expansion. Although the exact mechanisms remain to clarify, access to such an early and direct physiological marker of cortical activation with MRI will provide opportunities for functional neuroimaging of the human brain. PMID:16702549

  1. The expanding landscape of diffusion-weighted MRI in prostate cancer.

    PubMed

    Wibmer, Andreas G; Sala, Evis; Hricak, Hedvig; Vargas, Hebert Alberto

    2016-05-01

    The added value of diffusion-weighted magnetic resonance imaging (DW-MRI) for the detection, localization, and staging of primary prostate cancer has been extensively reported in original studies and meta-analyses. More recently, DW-MRI and related techniques have been used to noninvasively assess prostate cancer aggressiveness and estimate its biological behavior. The present article aims to summarize the potential applications of DW-MRI for noninvasive optimization of pretherapeutic risk assessment, patient management decisions, and evaluation of treatment response. PMID:26814501

  2. A diffusion tensor MRI atlas of the postmortem rhesus macaque brain.

    PubMed

    Calabrese, Evan; Badea, Alexandra; Coe, Christopher L; Lubach, Gabriele R; Shi, Yundi; Styner, Martin A; Johnson, G Allan

    2015-08-15

    The rhesus macaque (Macaca mulatta) is the most widely used nonhuman primate for modeling the structure and function of the brain. Brain atlases, and particularly those based on magnetic resonance imaging (MRI), have become important tools for understanding normal brain structure, and for identifying structural abnormalities resulting from disease states, exposures, and/or aging. Diffusion tensor imaging (DTI)-based MRI brain atlases are widely used in both human and macaque brain imaging studies because of the unique contrasts, quantitative diffusion metrics, and diffusion tractography that they can provide. Previous MRI and DTI atlases of the rhesus brain have been limited by low contrast and/or low spatial resolution imaging. Here we present a microscopic resolution MRI/DTI atlas of the rhesus brain based on 10 postmortem brain specimens. The atlas includes both structural MRI and DTI image data, a detailed three-dimensional segmentation of 241 anatomic structures, diffusion tractography, cortical thickness estimates, and maps of anatomic variability among atlas specimens. This atlas incorporates many useful features from previous work, including anatomic label nomenclature and ontology, data orientation, and stereotaxic reference frame, and further extends prior analyses with the inclusion of high-resolution multi-contrast image data. PMID:26037056

  3. Nuclear Electric Dipole Moment of 3He

    SciTech Connect

    Stetcu, I; P.Liu, C; Friar, J L; Hayes, A C; Navratil, P

    2008-04-08

    A permanent electric dipole moment (EDM) of a physical system would require time-reversal (T) violation, which is equivalent to charge-conjugation-parity (CP) violation by CPT invariance. Experimental programs are currently pushing the limits on EDMs in atoms, nuclei, and the neutron to regimes of fundamental theoretical interest. Nuclear EDMs can be studied at ion storage rings with sensitivities that may be competitive with atomic and neutron measurements. Here we calculate the magnitude of the CP-violating EDM of {sup 3}He and the expected sensitivity of such a measurement to the underlying CP-violating interactions. Assuming that the coupling constants are of comparable magnitude for {pi}-, {rho}-, and {omega}-exchanges, we find that the pion-exchange contribution dominates. Finally, our results suggest that a measurement of the {sup 3}He EDM is complementary to the planned neutron and deuteron experiments, and could provide a powerful constraint for the theoretical models of the pion-nucleon P,T-violating interaction.

  4. Nuclear Electric Dipole Moment of ^{3}_He

    SciTech Connect

    Stetcu, I.; Liu, C.-P.; Friar, J. L.; Hayes, A. C.; Navratil, P.

    2008-01-01

    A permanent electric dipole moment (EDM) of a physical system would require time-reversal (T) violation, which is equivalent to charge-conjugation-parity (CP) violation by CPT invariance. Experimental programs are currently pushing the limits on EDMs in atoms, nuclei, and the neutron to regimes of fundamental theoretical interest. Nuclear EDMs can be studied at ion storage rings with sensitivities that may be competitive with atomic and neutron measurements. Here we calculate the magnitude of the CP-violating EDM of ^{3}_He and the expected sensitivity of such a measurement to the underlyng CP-violating interactions. Assuming that the coupling constants are of comparable magnitude for {\\pi}-, {\\rho}-, and {\\omega}-exchanges, we find that the pion-exchange contribution dominates. Our results suggest that a measurement of the ^{3}_He EDM is complementary to the planned neutron and deuteron experiments, and could provide a powerful constraint for the theoretical models of the pion-nucleon P,T-violating interaction.

  5. MR Scanner Systems Should Be Adequately Characterized in Diffusion-MRI of the Breast

    PubMed Central

    Giannelli, Marco; Sghedoni, Roberto; Iacconi, Chiara; Iori, Mauro; Traino, Antonio Claudio; Guerrisi, Maria; Mascalchi, Mario; Toschi, Nicola; Diciotti, Stefano

    2014-01-01

    Breast imaging represents a relatively recent and promising field of application of quantitative diffusion-MRI techniques. In view of the importance of guaranteeing and assessing its reliability in clinical as well as research settings, the aim of this study was to specifically characterize how the main MR scanner system-related factors affect quantitative measurements in diffusion-MRI of the breast. In particular, phantom acquisitions were performed on three 1.5 T MR scanner systems by different manufacturers, all equipped with a dedicated multi-channel breast coil as well as acquisition sequences for diffusion-MRI of the breast. We assessed the accuracy, inter-scan and inter-scanner reproducibility of the mean apparent diffusion coefficient measured along the main orthogonal directions () as well as of diffusion-tensor imaging (DTI)-derived mean diffusivity (MD) measurements. Additionally, we estimated spatial non-uniformity of (NU) and MD (NUMD) maps. We showed that the signal-to-noise ratio as well as overall calibration of high strength diffusion gradients system in typical acquisition sequences for diffusion-MRI of the breast varied across MR scanner systems, introducing systematic bias in the measurements of diffusion indices. While and MD values were not appreciably different from each other, they substantially varied across MR scanner systems. The mean of the accuracies of measured and MD was in the range [−2.3%,11.9%], and the mean of the coefficients of variation for and MD measurements across MR scanner systems was 6.8%. The coefficient of variation for repeated measurements of both and MD was < 1%, while NU and NUMD values were <4%. Our results highlight that MR scanner system-related factors can substantially affect quantitative diffusion-MRI of the breast. Therefore, a specific quality control program for assessing and monitoring the performance of MR scanner systems for diffusion-MRI of the breast is

  6. Comparison of 3D orientation distribution functions measured with confocal microscopy and diffusion MRI.

    PubMed

    Schilling, Kurt; Janve, Vaibhav; Gao, Yurui; Stepniewska, Iwona; Landman, Bennett A; Anderson, Adam W

    2016-04-01

    The ability of diffusion MRI (dMRI) fiber tractography to non-invasively map three-dimensional (3D) anatomical networks in the human brain has made it a valuable tool in both clinical and research settings. However, there are many assumptions inherent to any tractography algorithm that can limit the accuracy of the reconstructed fiber tracts. Among them is the assumption that the diffusion-weighted images accurately reflect the underlying fiber orientation distribution (FOD) in the MRI voxel. Consequently, validating dMRI's ability to assess the underlying fiber orientation in each voxel is critical for its use as a biomedical tool. Here, using post-mortem histology and confocal microscopy, we present a method to perform histological validation of orientation functions in 3D, which has previously been limited to two-dimensional analysis of tissue sections. We demonstrate the ability to extract the 3D FOD from confocal z-stacks, and quantify the agreement between the MRI estimates of orientation information obtained using constrained spherical deconvolution (CSD) and the true geometry of the fibers. We find an orientation error of approximately 6° in voxels containing nearly parallel fibers, and 10-11° in crossing fiber regions, and note that CSD was unable to resolve fibers crossing at angles below 60° in our dataset. This is the first time that the 3D white matter orientation distribution is calculated from histology and compared to dMRI. Thus, this technique serves as a gold standard for dMRI validation studies - providing the ability to determine the extent to which the dMRI signal is consistent with the histological FOD, and to establish how well different dMRI models can predict the ground truth FOD. PMID:26804781

  7. Current and future diagnostic tools for traumatic brain injury: CT, conventional MRI, and diffusion tensor imaging.

    PubMed

    Brody, David L; Mac Donald, Christine L; Shimony, Joshua S

    2015-01-01

    Brain imaging plays a key role in the assessment of traumatic brain injury. In this review, we present our perspectives on the use of computed tomography (CT), conventional magnetic resonance imaging (MRI), and newer advanced modalities such as diffusion tensor imaging. Specifically, we address assessment for immediately life-threatening intracranial lesions (noncontrast head CT), assessment of progression of intracranial lesions (noncontrast head CT), documenting intracranial abnormalities for medicolegal reasons (conventional MRI with blood-sensitive sequences), presurgical planning for post-traumatic epilepsy (high spatial resolution conventional MRI), early prognostic decision making (conventional MRI with diffusion-weighted imaging), prognostic assessment for rehabilitative planning (conventional MRI and possibly diffusion tensor imaging in the future), stratification of subjects and pharmacodynamic tracking of targeted therapies in clinical trials (specific MRI sequences or positron emission tomography (PET) ligands, e.g., diffusion tensor imaging for traumatic axonal injury). We would like to emphasize that all of these methods, especially the newer research approaches, require careful radiologic-pathologic validation for optimal interpretation. We have taken this approach in a mouse model of pericontusional traumatic axonal injury. We found that the extent of reduction in the diffusion tensor imaging parameter relative anisotropy directly correlated with the number of amyloid precursor protein (APP)-stained axonal varicosities (r(2)=0.81, p<0.0001, n=20 injured mice). Interestingly, however, the least severe contusional injuries did not result in APP-stained axonal varicosities, but did cause reduction in relative anisotropy. Clearly, both the imaging assessments and the pathologic assessments will require iterative refinement. PMID:25702222

  8. Formation of 3He droplets in dilute 3He-4He solid solutions

    NASA Astrophysics Data System (ADS)

    Huan, Chao; Candela, Don; Kim, Sung; Yin, Liang; Xia, Jiang-Sheng; Sullivan, Neil

    2015-03-01

    We review the different stages of the formation of 3He droplets in dilute solid 3He-4He solutions. The studies are interesting because the phase separation in isotopic helium mixtures is a first-order transition with a conserved order parameter. The rate of growth of the droplets as observed in NMR studies is compared with the rates expected for homogeneous nucleation followed by a period of coarsening known as Ostwald ripening. Work suported by the National Science Foundation - DMR-1303599 and DMR- 1157490 (National High Magnetic Field Laboratory).

  9. {sup 3}He melting pressure thermometry

    SciTech Connect

    Ni, W.; Xia, J.S.; Adams, E.D.

    1995-10-01

    High-precision measurements of the {sup 3}He melting pressure versus temperature have been made from 500 {mu}K to 25 mK using a {sup 60}Co nuclear orientation primary thermometer and a Pt NMR susceptibility secondary thermometer. Temperatures for the fixed points on the melting curve are: the superfluid A transition T{sub A}=2.505 mK, the A-B transition T{sub AB}=1.948 mK, and the solid ordering temperature T{sub N}=0.934 mK. These fixed points and a functional form for P(T) constitute a convenient temperature scale, based on a primary thermometer, usable to well below 1 mK.

  10. Degassing of 3H/ 3He, CFCs and SF 6 by denitrification: Measurements and two-phase transport simulations

    NASA Astrophysics Data System (ADS)

    Visser, Ate; Schaap, Joris D.; Broers, Hans Peter; Bierkens, Marc F. P.

    2009-01-01

    The production of N 2 gas by denitrification may lead to the appearance of a gas phase below the water table prohibiting the conservative transport of tracer gases required for groundwater dating. We used a two-phase flow and transport model (STOMP) to study the reliability of 3H/ 3He, CFCs and SF 6 as groundwater age tracers under agricultural land where denitrification causes degassing. We were able to reproduce the amount of degassing ( R2 = 69%), as well as the 3H ( R2 = 79%) and 3He* ( R2 = 76%) concentrations observed in a 3H/ 3He data set using simple 2D models. We found that the TDG correction of the 3H/ 3He age overestimated the control 3He/ 3He age by 2.1 years, due to the accumulation of 3He* in the gas phase. The total uncertainty of degassed 3H/ 3He ages of 6 years (± 2 σ) is due to the correction of degassed 3He* using the TDG method, but also due to the travel time in the unsaturated zone and the diffusion of bomb peak 3He*. CFCs appear to be subject to significant degradation in anoxic groundwater and SF 6 is highly susceptible to degassing. We conclude that 3H/ 3He is the most reliable method to date degassed groundwater and that two-phase flow models such as STOMP are useful tools to assist in the interpretation of degassed groundwater age tracer data.

  11. Assessment of bias for MRI diffusion tensor imaging using SIMEX.

    PubMed

    Lauzon, Carolyn B; Asman, Andrew J; Crainiceanu, Ciprian; Caffo, Brian C; Landman, Bennett A

    2011-01-01

    Diffusion Tensor Imaging (DTI) is a Magnetic Resonance Imaging method for measuring water diffusion in vivo. One powerful DTI contrast is fractional anisotropy (FA). FA reflects the strength of water's diffusion directional preference and is a primary metric for neuronal fiber tracking. As with other DTI contrasts, FA measurements are obscured by the well established presence of bias. DTI bias has been challenging to assess because it is a multivariable problem including SNR, six tensor parameters, and the DTI collection and processing method used. SIMEX is a modem statistical technique that estimates bias by tracking measurement error as a function of added noise. Here, we use SIMEX to assess bias in FA measurements and show the method provides; i) accurate FA bias estimates, ii) representation of FA bias that is data set specific and accessible to non-statisticians, and iii) a first time possibility for incorporation of bias into DTI data analysis. PMID:21995019

  12. Lunar source of /sup 3/He for commercial fusion power

    SciTech Connect

    Wittenberg, L.J.; Santarius, J.F.; Kulcinski, G.L.

    1986-09-01

    An analysis of astrophysical information indicates that the solar wind has deposited an abundant, easily extractable source of /sup 3/He onto the surface of the moon. Apollo lunar samples indicate that the moon's surface soil contains approx. =10/sup 9/kg of /sup 3/He. If this amount of /sup 3/He were to be used in a 50% efficient D-/sup 3/He fusion reactor, it would provide 10/sup 7/GW(electric) . yr of electrical power. The energy required to extract /sup 3/He from the lunar regolith and transport it to earth is calculated to be approx. =2400 GJ/kg. Since the D-/sup 3/He reaction produces 6 X 10/sup 5/ GJ of energy per kilogram of /sup 3/He, the energy payback ratio is approx. =250. Implications for the commercialization of D-/sup 3/He fusion reactors and for the development of fusion power are discussed.

  13. Examining Particle Transport in Multi-Spacecraft 3He-Rich SEP Events

    NASA Astrophysics Data System (ADS)

    Cohen, Christina; Giacalone, Joe; Wiedenbeck, Mark E.; Mason, Glenn

    2015-04-01

    One of the surprising outcomes of recent multi-spacecraft studies of solar energetic particle (SEP) events is that small 3He-rich events can have large longitudinal spans. Although their solar source region is typically quite small, individual 3He-rich SEP events have been detected by near-1AU spacecraft separated by as much as 136 degrees. Although bundles of magnetic field lines can expand from small areas (5-10 degrees) at the photosphere to larger (~60 degrees) regions at 2.5 RS, this is not sufficient to explain the wide 3He-rich events observed by well-separated spacecraft. One possible explanation of these events involves a combination of particle diffusion in the inner heliosphere and field line co-rotation with the Sun. We have examined the onsets of the elevated 3He intensities at ACE and both STEREO spacecraft for several wide 3He-rich SEP events. The timing of these onsets has been compared to that predicted by a diffusive transport model for particle propagation. These results and their implications for the conditions conducive to creating wide 3He-rich SEP events are discussed.

  14. Polarisation and compression of {sup 3}He for Magnetic Resonance Imaging purposes

    SciTech Connect

    Geurts, D. G.; Brand, J. F. J. van den; Bulten, H. J.; Poolman, H. R.; Ferro-Luzzi, M.; Nicolay, K.

    1998-01-20

    Magnetic Resonance Imaging is often used in medical science as a diagnostic tool for the human body. Conventional MRI uses the NMR signal from the protons of water molecules in tissue to image the interior of the patient's body. However, for certain areas such as the lungs and airways, the usage of a highly polarised gas yields better results. We are currently constructing an apparatus that uses polarised {sup 3}He gas to produce detailed images of those signal-deficient moyeties. We also plan to study possible uptake of polarised {sup 3}He gas by the circulatory system to image other organs.

  15. Numerical simulation of diffusion MRI signals using an adaptive time-stepping method.

    PubMed

    Li, Jing-Rebecca; Calhoun, Donna; Poupon, Cyril; Le Bihan, Denis

    2014-01-20

    The effect on the MRI signal of water diffusion in biological tissues in the presence of applied magnetic field gradient pulses can be modelled by a multiple compartment Bloch-Torrey partial differential equation. We present a method for the numerical solution of this equation by coupling a standard Cartesian spatial discretization with an adaptive time discretization. The time discretization is done using the explicit Runge-Kutta-Chebyshev method, which is more efficient than the forward Euler time discretization for diffusive-type problems. We use this approach to simulate the diffusion MRI signal from the extra-cylindrical compartment in a tissue model of the brain gray matter consisting of cylindrical and spherical cells and illustrate the effect of cell membrane permeability. PMID:24351275

  16. Limitations and Prospects for Diffusion-Weighted MRI of the Prostate

    PubMed Central

    Bourne, Roger; Panagiotaki, Eleftheria

    2016-01-01

    Diffusion-weighted imaging (DWI) is the most effective component of the modern multi-parametric magnetic resonance imaging (mpMRI) scan for prostate pathology. DWI provides the strongest prediction of cancer volume, and the apparent diffusion coefficient (ADC) correlates moderately with Gleason grade. Notwithstanding the demonstrated cancer assessment value of DWI, the standard measurement and signal analysis methods are based on a model of water diffusion dynamics that is well known to be invalid in human tissue. This review describes the biophysical limitations of the DWI component of the current standard mpMRI protocol and the potential for significantly improved cancer assessment performance based on more sophisticated measurement and signal modeling techniques. PMID:27240408

  17. Numerical simulation of diffusion MRI signals using an adaptive time-stepping method

    NASA Astrophysics Data System (ADS)

    Li, Jing-Rebecca; Calhoun, Donna; Poupon, Cyril; Le Bihan, Denis

    2014-01-01

    The effect on the MRI signal of water diffusion in biological tissues in the presence of applied magnetic field gradient pulses can be modelled by a multiple compartment Bloch-Torrey partial differential equation. We present a method for the numerical solution of this equation by coupling a standard Cartesian spatial discretization with an adaptive time discretization. The time discretization is done using the explicit Runge-Kutta-Chebyshev method, which is more efficient than the forward Euler time discretization for diffusive-type problems. We use this approach to simulate the diffusion MRI signal from the extra-cylindrical compartment in a tissue model of the brain gray matter consisting of cylindrical and spherical cells and illustrate the effect of cell membrane permeability.

  18. Limitations and Prospects for Diffusion-Weighted MRI of the Prostate.

    PubMed

    Bourne, Roger; Panagiotaki, Eleftheria

    2016-01-01

    Diffusion-weighted imaging (DWI) is the most effective component of the modern multi-parametric magnetic resonance imaging (mpMRI) scan for prostate pathology. DWI provides the strongest prediction of cancer volume, and the apparent diffusion coefficient (ADC) correlates moderately with Gleason grade. Notwithstanding the demonstrated cancer assessment value of DWI, the standard measurement and signal analysis methods are based on a model of water diffusion dynamics that is well known to be invalid in human tissue. This review describes the biophysical limitations of the DWI component of the current standard mpMRI protocol and the potential for significantly improved cancer assessment performance based on more sophisticated measurement and signal modeling techniques. PMID:27240408

  19. Impact of radial and angular sampling on multiple shells acquisition in diffusion MRI.

    PubMed

    Merlet, Sylvain; Caruyer, Emmanuel; Deriche, Rachid

    2011-01-01

    We evaluate the impact of radial and angular sampling on multiple shells (MS) acquisition in diffusion MRI. The validation of our results is based on a new and efficient method to accurately reconstruct the Ensemble Average Propagator (EAP) in term of the Spherical Polar Fourier (SPF) basis from very few diffusion weighted magnetic resonance images (DW-MRI). This approach nicely exploits the duality between SPF and a closely related basis in which one can respectively represent the EAP and the diffusion signal using the same coefficients. We efficiently combine this relation to the recent acquisition and reconstruction technique called Compressed Sensing (CS). Based on results of multi-tensors models reconstruction, we show how to construct a robust acquisition scheme for both neural fibre orientation detection and attenuation signal/EAP reconstruction. PMID:21995020

  20. 3He gas gap heat switch

    NASA Astrophysics Data System (ADS)

    Catarino, I.; Paine, C.

    2011-01-01

    Thermal control at 1 K is still demanding for heat switches development. A gas gap heat switch using 3He gas as the heat-transfer fluid was tested and characterized. The switch is actuated by a sorption pump, whose triggering temperatures were also characterized. Switching times were recorded for different thermalizations of the sorption pump. This paper presents the conductance results of such switch. The temperature scanning of the actuator is also presented. The effect of filling pressure is discussed as well as the thermalization of the sorption pump. About 60 μW/K OFF-state conductance and 100 mW/K ON-state conductance were obtained at 1.7 K. The actuation temperature is slightly adjustable upon the charging pressure of the working gas. Thermalization of the sorption pump at about 8-10 K is enough for producing an OFF state - it can be comfortably linked to a 4 K stage. Temperatures of 15-20 K at the sorption pump are required for reaching the viscous range for maximum ON conduction. Switching time dependence on the thermalization of the sorption pump is discarded.

  1. The spectra of mixed 3He-4He droplets.

    PubMed

    Fantoni, S; Guardiola, R; Navarro, J; Zuker, A

    2005-08-01

    The diffusion Monte Carlo technique is used to calculate and analyze the excitation spectrum of 3He atoms bound to a cluster of 4He atoms by using a previously determined optimum filling of single-fermion orbits with well-defined orbital angular momentum L, spin S, and parity quantum numbers. The study concentrates on the energies and shapes of the three kinds of states for which the fermionic part of the wave function is a single Slater determinant: maximum L or maximum S states within a given orbit, and fully polarized clusters. The picture that emerges is that of systems with strong shell effects, whose binding and excitation energies are essentially determined by averages over configuration at fixed number of particles and spin, i.e., by the monopole properties of an effective Hamiltonian. PMID:16108665

  2. Monitoring Chemotherapeutic Response by Hyperpolarized 13C-Fumarate MRS and Diffusion MRI

    PubMed Central

    Mignion, Lionel; Dutta, Prasanta; Martinez, Gary V.; Foroutan, Parastou; Gillies, Robert J.; Jordan, Bénédicte F.

    2015-01-01

    Targeted chemotherapeutic agents often do not result in tumor shrinkage, so new biomarkers that correlate with clinical efficacy are needed. In this study, we investigated noninvasive imaging protocols to monitor responses to sorafenib, a multikinase inhibitor approved for treatment of renal cell and hepatocellular carcinoma. Healthy cells are impermeable to fumarate, so conversion of this metabolite to malate as detected by 13C-magnetic resonance spectroscopy (MRS) has been suggested as one marker for cell death and treatment response in tumors. Diffusion MRI also has been suggested as a measure of therapy-induced cytotoxic edema because viable cells act as a diffusion barrier in tissue. For these reasons, we assessed sorafenib responses using hyperpolarized 13C-fumarate, diffusion-weighted MRI (DW-MRI) in a xenograft model of human breast cancer in which daily administration of sorafenib was sufficient to stabilize tumor growth. We detected signals from fumarate and malate following intravenous administration of hyperpolarized fumarate with a progressive increase in the malate-to-fumarate (MA/FA) ratio at days 2 to 5 after sorafenib infusion. The apparent diffusion coefficient (ADC) measured by DW-MRI increased in the treated group consistent with cytotoxic edema. However, the MA/FA ratio was a more sensitive marker of therapeutic response than ADC, with 2.8-fold versus 1.3-fold changes, respectively, by day 5 of drug treatment. Histologic analyses confirmed cell death in the sorafenib-treated cohort. Notably, 13C-pyruvate-to-lactate conversion was not affected by sorafenib in the breast cancer model examined. Our results illustrate how combining hyperpolarized substrates with DW-MRI can allow noninvasive monitoring of targeted therapeutic responses at relatively early times after drug administration. PMID:24285723

  3. Monitoring chemotherapeutic response by hyperpolarized 13C-fumarate MRS and diffusion MRI.

    PubMed

    Mignion, Lionel; Dutta, Prasanta; Martinez, Gary V; Foroutan, Parastou; Gillies, Robert J; Jordan, Bénédicte F

    2014-02-01

    Targeted chemotherapeutic agents often do not result in tumor shrinkage, so new biomarkers that correlate with clinical efficacy are needed. In this study, we investigated noninvasive imaging protocols to monitor responses to sorafenib, a multikinase inhibitor approved for treatment of renal cell and hepatocellular carcinoma. Healthy cells are impermeable to fumarate, so conversion of this metabolite to malate as detected by (13)C-magnetic resonance spectroscopy (MRS) has been suggested as one marker for cell death and treatment response in tumors. Diffusion MRI also has been suggested as a measure of therapy-induced cytotoxic edema because viable cells act as a diffusion barrier in tissue. For these reasons, we assessed sorafenib responses using hyperpolarized (13)C-fumarate, diffusion-weighted MRI (DW-MRI) in a xenograft model of human breast cancer in which daily administration of sorafenib was sufficient to stabilize tumor growth. We detected signals from fumarate and malate following intravenous administration of hyperpolarized fumarate with a progressive increase in the malate-to-fumarate (MA/FA) ratio at days 2 to 5 after sorafenib infusion. The apparent diffusion coefficient (ADC) measured by DW-MRI increased in the treated group consistent with cytotoxic edema. However, the MA/FA ratio was a more sensitive marker of therapeutic response than ADC, with 2.8-fold versus 1.3-fold changes, respectively, by day 5 of drug treatment. Histologic analyses confirmed cell death in the sorafenib-treated cohort. Notably, (13)C-pyruvate-to-lactate conversion was not affected by sorafenib in the breast cancer model examined. Our results illustrate how combining hyperpolarized substrates with DW-MRI can allow noninvasive monitoring of targeted therapeutic responses at relatively early times after drug administration. PMID:24285723

  4. Feature-based interpolation of diffusion tensor fields and application to human cardiac DT-MRI.

    PubMed

    Yang, Feng; Zhu, Yue-Min; Magnin, Isabelle E; Luo, Jian-Hua; Croisille, Pierre; Kingsley, Peter B

    2012-02-01

    Diffusion tensor interpolation is an important issue in the application of diffusion tensor magnetic resonance imaging (DT-MRI) to the human heart, all the more as the points representing the myocardium of the heart are often sparse. We propose a feature-based interpolation framework for the tensor fields from cardiac DT-MRI, by taking into account inherent relationships between tensor components. In this framework, the interpolation consists in representing a diffusion tensor in terms of two tensor features, eigenvalues and orientation, interpolating the Euler angles or the quaternion relative to tensor orientation and the logarithmically transformed eigenvalues, and reconstructing the tensor to be interpolated from the interpolated eigenvalues and tensor orientations. The results obtained with the aid of both synthetic and real cardiac DT-MRI data demonstrate that the feature-based schemes based on Euler angles or quaternions not only maintain the advantages of Log-Euclidean and Riemannian interpolation as for preserving the tensor's symmetric positive-definiteness and the monotonic determinant variation, but also preserve, at the same time, the monotonicity of fractional anisotropy (FA) and mean diffusivity (MD) values, which is not the case with Euclidean, Cholesky and Log-Euclidean methods. As a result, both interpolation schemes remove the phenomenon of FA collapse, and consequently avoid introducing artificial fiber crossing, with the difference that the quaternion is independent of coordinate system while Euler angles have the property of being more suitable for sophisticated interpolations. PMID:22154961

  5. Differentiation of Reactive and Tumor Metastatic Lymph Nodes with Diffusion-weighted and SPIO Enhanced MRI

    PubMed Central

    Zhang, Fan; Zhu, Lei; Huang, Xinglu; Niu, Gang; Chen, Siouan

    2012-01-01

    Objectives Determination of lymphatic metastasis is of great importance for both treatment planning and patient prognosis. We aim to distinguish tumor metastatic lymph nodes (TLNs) and reactive lymph nodes (RLNs) with diffusion-weighted and superparamagnetic iron oxide (SPIO) enhanced magnetic resonance imaging (MRI). Materials and methods Ipsilateral popliteal lymph node metastasis or lymphadenitis model was established by hock injection of either luciferase-expressing 4T1 murine breast cancer cells or Complete Freund Adjuvant (CFA) in male Balb/C mice. At different time points after inoculation, bioluminescence imaging, T2-weighted, diffusion-weighted and SPIO enhanced MRI were performed. Imaging findings were confirmed by histopathological staining. Results Size enlargement was observed in both TLNs and RLNs. At day 28, TLNs showed strong bioluminescence signal and bigger size than RLNs (p < 0.01). At early stages up to day 21, both TLNs and RLNs appeared homogeneous on diffusion-weighted imaging (DWI). At day 28, TLNs showed heterogeneous apparent diffusion coefficient (ADC) map with significantly higher average ADC value of 0.41 ± 0.03 × 10−3 mm2/s than that of RLNs (0.34 ± 0.02 10−3 mm2/s, p < 0.05). On SPIO enhanced MRI, both TLNs and RLNs showed distinct T2 signal reduction at day 21 after inoculation. At day 28, TLNs demonstrated partial uptake of the iron oxide particles, which was confirmed by Prussian blue staining. Conclusions Both diffusion-weighted and SPIO enhanced MRI can distinguish tumor metastatic lymph nodes from reactive lymph nodes. However, neither method is able to detect tumor metastasis to the draining lymph nodes at early stages. PMID:22588595

  6. Temporal scaling characteristics of diffusion as a new MRI contrast: Findings in rat hippocampus

    PubMed Central

    Özarslan, Evren; Shepherd, Timothy M.; Koay, Cheng Guan; Blackband, Stephen J.; Basser, Peter J.

    2012-01-01

    Features of the diffusion-time dependence of the diffusion-weighted magnetic resonance imaging (MRI) signal provide a new contrast that could be altered by numerous biological processes and pathologies in tissue at microscopic length scales. An anomalous diffusion model, based on the theory of Brownian motion in fractal and disordered media, is used to characterize the temporal scaling (TS) characteristics of diffusion-related quantities, such as moments of the displacement and zero-displacement probabilities, in excised rat hippocampus specimens. To reduce the effect of noise in magnitude-valued MRI data, a novel numerical procedure was employed to yield accurate estimation of these quantities even when the signal falls below the noise floor. The power-law dependencies characterize the TS behavior in all regions of the rat hippocampus, providing unique information about its microscopic architecture. The relationship between the TS characteristics and diffusion anisotropy is investigated by examining the anisotropy of TS, and conversely, the TS of anisotropy. The findings suggest the robustness of the technique as well as the reproducibility of estimates. TS characteristics of the diffusion-weighted signals could be used as a new and useful marker of tissue microstructure. PMID:22306798

  7. A System for Open-Access 3He Human Lung Imaging at Very Low Field

    PubMed Central

    RUSET, I.C.; TSAI, L.L.; MAIR, R.W.; PATZ, S.; HROVAT, M.I.; ROSEN, M.S.; MURADIAN, I.; NG, J.; TOPULOS, G.P.; BUTLER, J.P.; WALSWORTH, R.L.; HERSMAN, F.W.

    2010-01-01

    We describe a prototype system built to allow open-access very-low-field MRI of human lungs using laser-polarized 3He gas. The system employs an open four-coil electromagnet with an operational B0 field of 4 mT, and planar gradient coils that generate gradient fields up to 0.18 G/cm in the x and y direction and 0.41 G/cm in the z direction. This system was used to obtain 1H and 3He phantom images and supine and upright 3He images of human lungs. We include discussion on challenges unique to imaging at 50 –200 kHz, including noise filtering and compensation for narrow-bandwidth coils. PMID:20354575

  8. Diffusion and near-equilibrium distribution of MRI and CT contrast agents in articular cartilage.

    PubMed

    Silvast, Tuomo S; Kokkonen, Harri T; Jurvelin, Jukka S; Quinn, Thomas M; Nieminen, Miika T; Töyräs, Juha

    2009-11-21

    Charged contrast agents have been used both in vitro and in vivo for estimation of the fixed charge density (FCD) in articular cartilage. In the present study, the effects of molecular size and charge on the diffusion and equilibrium distribution of several magnetic resonance imaging (MRI) and computed tomography (CT) contrast agents were investigated. Full thickness cartilage disks (Ø = 4.0 mm, n = 64) were prepared from fresh bovine patellae. Contrast agent (gadopentetate: Magnevist((R)), gadodiamide: Omniscan, ioxaglate: Hexabrix or sodium iodide: NaI) diffusion was allowed either through the articular surface or through the deep cartilage. CT imaging of the samples was conducted before contrast agent administration and after 1, 5, 9, 16, 25 and 29 h (and with three samples after 2, 3, 4 and 5 days) diffusion using a clinical peripheral quantitative computed tomography (pQCT) instrument. With all contrast agents, the diffusion through the deep cartilage was slower when compared to the diffusion through the articular surface. With ioxaglate, gadopentetate and gadodiamide it took over 29 h for diffusion to reach the near-equilibrium state. The slow diffusion of the contrast agents raise concerns regarding the validity of techniques for FCD estimation, as these contrast agents may not reach the equilibrium state that is assumed. However, since cartilage composition, i.e. deep versus superficial, had a significant effect on diffusion, imaging of the nonequilibrium diffusion process might enable more accurate assessment of cartilage integrity. PMID:19864699

  9. Diffusion weighted MRI of the breast: Protocol optimization, guidelines for interpretation, and potential clinical applications

    PubMed Central

    Partridge, Savannah C.; McDonald, Elizabeth S.

    2013-01-01

    Synopsis There has been increasing interest in the use of diffusion weighted MRI (DWI) for breast imaging. This technique has shown promise for improving the positive predictive value of breast MRI for detection of breast cancer, evaluating tumor response to neoadjuvant chemotherapy, and as a non-contrast MRI alternative for breast cancer screening. However, there is currently no standardized approach to DWI of the breast and data quality varies widely. Prior to implementing DWI into clinical practice, it is important to understand the pertinent technical considerations and current evidence of clinical applications of DWI of the breast. This article provides an overview of basic principles of DWI, optimization of breast DWI protocols, imaging features of benign and malignant breast lesions, promising clinical applications, and potential future directions. PMID:23928248

  10. Advances in diffusion MRI acquisition and processing in the Human Connectome Project.

    PubMed

    Sotiropoulos, Stamatios N; Jbabdi, Saad; Xu, Junqian; Andersson, Jesper L; Moeller, Steen; Auerbach, Edward J; Glasser, Matthew F; Hernandez, Moises; Sapiro, Guillermo; Jenkinson, Mark; Feinberg, David A; Yacoub, Essa; Lenglet, Christophe; Van Essen, David C; Ugurbil, Kamil; Behrens, Timothy E J

    2013-10-15

    The Human Connectome Project (HCP) is a collaborative 5-year effort to map human brain connections and their variability in healthy adults. A consortium of HCP investigators will study a population of 1200 healthy adults using multiple imaging modalities, along with extensive behavioral and genetic data. In this overview, we focus on diffusion MRI (dMRI) and the structural connectivity aspect of the project. We present recent advances in acquisition and processing that allow us to obtain very high-quality in-vivo MRI data, whilst enabling scanning of a very large number of subjects. These advances result from 2 years of intensive efforts in optimising many aspects of data acquisition and processing during the piloting phase of the project. The data quality and methods described here are representative of the datasets and processing pipelines that will be made freely available to the community at quarterly intervals, beginning in 2013. PMID:23702418

  11. Advances in diffusion MRI acquisition and processing in the Human Connectome Project

    PubMed Central

    Sotiropoulos, Stamatios N; Jbabdi, Saad; Xu, Junqian; Andersson, Jesper L; Moeller, Steen; Auerbach, Edward J; Glasser, Matthew F; Hernandez, Moises; Sapiro, Guillermo; Jenkinson, Mark; Feinberg, David A; Yacoub, Essa; Lenglet, Christophe; Ven Essen, David C; Ugurbil, Kamil; Behrens, Timothy EJ

    2013-01-01

    The Human Connectome Project (HCP) is a collaborative 5-year effort to map human brain connections and their variability in healthy adults. A consortium of HCP investigators will study a population of 1200 healthy adults using multiple imaging modalities, along with extensive behavioral and genetic data. In this overview, we focus on diffusion MRI (dMRI) and the structural connectivity aspect of the project. We present recent advances in acquisition and processing that allow us to obtain very high-quality in-vivo MRI data, while enabling scanning of a very large number of subjects. These advances result from 2 years of intensive efforts in optimising many aspects of data acquisition and processing during the piloting phase of the project. The data quality and methods described here are representative of the datasets and processing pipelines that will be made freely available to the community at quarterly intervals, beginning in 2013. PMID:23702418

  12. Subject Based Registration for Individualized Analysis of Diffusion Tensor MRI

    PubMed Central

    Suri, Asif K.; Fleysher, Roman; Lipton, Michael L.

    2015-01-01

    Registration of subject and control brains to a common anatomical space or template is the basis for quantitatively delineating regions of abnormality in an individual brain. Normally, a brain atlas is chosen as the template. Limitations in the registration process result in persistent differences between individual subject brains and template, which can be a source of error in an analysis. We propose a new approach to the registration process where the subject of interest is the registration template. Through this change, we eliminate errors due to differences between a brain template and a subject’s brain. We applied this method to the analysis of FA values derived from DTI data of 20 individual mTBI patients as compared to 48 healthy controls. Subject-centered analysis resulted in identification of significantly fewer regions of abnormally low FA compared to two separate atlas-centered analyses, with subject-centered abnormalities essentially representing the common subset of abnormal low FA regions detected by the two atlas-centered methods. Whereas each atlas-centered approach demonstrated abnormalities in nearly every subject (19/20 and 20/20), the subject-centered approach demonstrated abnormalities in fewer than half the subjects (9/20). This reduction of diffusion abnormalities observed using the subject-centered approach is due to elimination of misregistration errors that occur when registering the subject of interest to a template. Evaluation of atlas-centered analyses demonstrated that 9.8% to 13.3% of subject GM and CSF was misregistered onto the WM of the brain atlas, resulting in the observation of additional low FA clusters compared to the subject-centered approach. Without careful evaluation, these misregistrations could be misinterpreted as pathology. An additional benefit of the subject-centered approach is that diffusion abnormalities can now be visualized directly in the subject’s anatomical space, rather than interpolating results from

  13. Heidenhain variant of Creutzfeldt-Jakob disease: diffusion-weighted MRI and PET characteristics.

    PubMed

    Tsuji, Yoshihisa; Kanamori, Hiroshi; Murakami, Gaku; Yokode, Masayuki; Mezaki, Takahiro; Doh-ura, Katsumi; Taniguchi, Ken; Matsubayashi, Kozo; Fukuyama, Hidenao; Kita, Toru; Tanaka, Makoto

    2004-01-01

    Creutzfeldt-Jakob disease (CJD) is characterized by rapidly progressive dementia with a variety of neurological disorders and a fatal outcome. The authors present a case with visual disturbance as a leading symptom and rapid deterioration in global cognitive functions. The cerebrospinal fluid was positive for 14-3-3 protein, and diffusion-weighted magnetic resonance imaging (MRI) showed marked hyperintensity in the parieto-occipital cortices, where hypometabolism was clearly detected on positron emission tomography (PET). Pattern-reversal visual evoked potentials showed prolonged P100 latencies and increased N/5/P100 amplitudes. All these findings supported a diagnosis of the Heidenhain variant of CJD, whereas a long clinical course, a lack of myoclonus, and an absence of periodic synchronous discharges on electroencephalography were atypical. Diffusion-weighted MRI and PE1 in combination with visual evoked potential recording and 14-3-3 protein detection may be useful for the early diagnosis of CJD. PMID:14748211

  14. Diffusion-Weighted MRI for the Assessment of Liver Fibrosis: Principles and Applications

    PubMed Central

    Attinà, Giancarlo; Fuccio Sanzà, Giovanni; Foti, Pietro Valerio; Ettorre, Giovanni Carlo; Milone, Pietro

    2015-01-01

    The importance of an early identification of hepatic fibrosis has been emphasized, in order to start therapy and obtain fibrosis regression. Biopsy is the gold-standard method for the assessment of liver fibrosis in chronic liver diseases, but it is limited by complications, interobserver variability, and sampling errors. Several noninvasive methods have been recently introduced into clinical routine, in order to detect liver fibrosis early. One of the most diffuse approaches is represented by diffusion-weighted liver MRI. In this review, the main technical principles are briefly reported in order to explain the rationale for clinical applications. In addition, roles of apparent diffusion coefficient, intravoxel incoherent motion, and relative apparent diffusion coefficient are also reported, showing their advantages and limits. PMID:25866819

  15. A compressed-sensing approach for super-resolution reconstruction of diffusion MRI

    PubMed Central

    Ning, Lipeng; Setsompop, Kawin; Michailovich, Oleg; Makris, Nikos; Westin, Carl-Fredrik; Rathi, Yogesh

    2015-01-01

    We present an innovative framework for reconstructing high-spatial-resolution diffusion magnetic resonance imaging (dMRI) from multiple low-resolution (LR) images. Our approach combines the twin concepts of compressed sensing (CS) and classical super-resolution to reduce acquisition time while increasing spatial resolution. We use sub-pixel-shifted LR images with down-sampled and non-overlapping diffusion directions to reduce acquisition time. The diffusion signal in the high resolution (HR) image is represented in a sparsifying basis of spherical ridgelets to model complex fiber orientations with reduced number of measurements. The HR image is obtained as the solution of a convex optimization problem which can be solved using the proposed algorithm based on the alternating direction method of multipliers (ADMM). We qualitatively and quantitatively evaluate the performance of our method on two sets of in-vivo human brain data and show its effectiveness in accurately recovering very high resolution diffusion images. PMID:26221667

  16. Cardiac Amyloidosis: Typical Imaging Findings and Diffuse Myocardial Damage Demonstrated by Delayed Contrast-Enhanced MRI

    SciTech Connect

    Sueyoshi, Eijun Sakamoto, Ichiro; Okimoto, Tomoaki; Hayashi, Kuniaki; Tanaka, Kyouei; Toda, Genji

    2006-08-15

    Amyloidosis is a rare systemic disease. However, involvement of the heart is a common finding and is the most frequent cause of death in amyloidosis. We report the sonographic, scintigraphic, and MRI features of a pathologically proven case of cardiac amyloidosis. Delayed contrast-enhanced MR images, using an inversion recovery prepped gradient-echo sequence, revealed diffuse enhancement in the wall of both left and right ventricles. This enhancement suggested expansion of the extracellular space of the myocardium caused by diffuse myocardial necrosis secondary to deposition of amyloid.

  17. Advantage of Adding Diffusion Weighted Imaging to Routine MRI Examinations in the Diagnostics of Scrotal Lesions

    PubMed Central

    Algebally, Ahmed Mohamed; Tantawy, Hazim Ibrahim; Yousef, Reda Ramadan Hussein; Szmigielski, Wojciech; Darweesh, Adham

    2015-01-01

    Summary Background The purpose of the study is to identify the diagnostic value of adding diffusion weighted images (DWI) to routine MRI examinations of the scrotum. Material/Methods The study included 100 testes of 50 patients with a unilateral testicular disease. Fifty normal contralateral testes were used as a control group. All patients underwent conventional MRI and DWI examinations of the scrotum. The results of MRI and DWI of the group of patients treated surgically were correlated with histopathological findings. The MRI and DWI results of non-surgical cases were correlated with the results of clinical, laboratory and other imaging studies. Comparison of the ADC value of normal and pathological tissues was carried out followed by a statistical analysis. Results There was a significant difference between ADC values of malignant testicular lesions and normal testicular tissues as well as benign testicular lesions (P=0.000). At a cut-off ADC value of ≤0.99, it had a sensitivity of 93.3%, specificity of 90%, positive predictive value of 87.5%, and negative predictive value of 94.7% in the characterization of intratesticular masses. Conclusions Inclusion of DWI to routine MRI has a substantial value in improving diagnosis in patients with scrotal lesions and consequently can reduce unnecessary radical surgical procedures in these patients. PMID:26491491

  18. Diffusion coefficients of articular cartilage for different CT and MRI contrast agents.

    PubMed

    Kulmala, K A M; Korhonen, R K; Julkunen, P; Jurvelin, J S; Quinn, T M; Kröger, H; Töyräs, J

    2010-10-01

    In contrast enhanced magnetic resonance imaging (MRI) and computed tomography (CT), the equilibrium distribution of anionic contrast agent is expected to reflect the fixed charged density (FCD) of articular cartilage. Diffusion is mainly responsible for the transport of contrast agents into cartilage. In osteoarthritis, cartilage composition changes at early stages of disease, and solute diffusion is most likely affected. Thus, investigation of contrast agent diffusion could enable new methods for imaging of cartilage composition. The aim of this study was to determine the diffusion coefficient of four contrast agents (ioxaglate, gadopentetate, iodide, gadodiamide) in bovine articular cartilage. The contrast agents were different in molecular size and charge. In peripheral quantitative CT experiments, penetration of contrast agent into the tissue was allowed either through the articular surface or through deep cartilage. To determine diffusion coefficients, a finite element model based on Fick's law was fitted to experimental data. Diffusion through articular surface was faster than through deep cartilage with every contrast agent. Iodide, being of atomic size, diffused into the cartilage significantly faster (q<0.05) than the other three contrast agents, for either transport direction. The diffusion coefficients of all clinical contrast agents (ioxaglate, gadopentetate and gadodiamide) were relatively low (142.8-253.7 μm(2)/s). In clinical diagnostics, such slow diffusion may not reach equilibrium and this jeopardizes the determination of FCD by standard methods. However, differences between diffusion through articular surface and deep cartilage, that are characterized by different tissue composition, suggest that diffusion coefficients may correlate with cartilage composition. Present method could therefore enable image-based assessment of cartilage composition by determination of diffusion coefficients within cartilage tissue. PMID:20594900

  19. Studies of 3He+3He, T+3He, and p +D nuclear reactions relevant to stellar or Big-Bang Nucleosynthesis using ICF plasmas at OMEGA

    NASA Astrophysics Data System (ADS)

    Zylstra, Alex; Gatu Johnson, Maria; Frenje, Johan; Li, Chikang; Seguin, Fredrick; Sio, Hong; Rosenberg, Michael; Rinderknecht, Hans; Petrasso, Richard; Herrmann, Hans; Kim, Yong Ho; Hale, Gerry; McNabb, Dennis; Sayre, Dan; Pino, Jesse; Brune, Carl; Bacher, Andy; Forrest, Chad; Glebov, Vladimir; Stoeckl, Christian; Janezic, Roger; Sangster, Craig

    2014-10-01

    The 3He+3He, T+3He, and p +D reactions directly relevant to Stellar or Big-Bang Nucleosynthesis (BBN) have been studied at the OMEGA laser facility using high-temperature low-density `exploding pusher' implosions. The advantage of using these plasmas is that they better mimic astrophysical systems than cold-target accelerator experiments. Measured proton spectra from the 3He3He reaction are used to constrain nuclear R-matrix modeling. The resulting T+3He γ-ray data rule out an anomalously-high 6Li production during BBN as an explanation to the high observed values in primordial material. The proton spectrum from the T+3He reaction is also being used to constrain the R-matrix model. Recent experiments have probed the p +D reaction for the first time in a plasma; this reaction is relevant to energy production in protostars, brown dwarfs and at higher CM energies to BBN. This work was partially supported by the US DOE, NLUF, LLE, and GA.

  20. Test-retest reliability of white matter structural brain networks: a multiband diffusion MRI study

    PubMed Central

    Zhao, Tengda; Duan, Fei; Liao, Xuhong; Dai, Zhengjia; Cao, Miao; He, Yong; Shu, Ni

    2015-01-01

    The multiband EPI sequence has been developed for the human connectome project to accelerate MRI data acquisition. However, no study has yet investigated the test-retest (TRT) reliability of the graph metrics of white matter (WM) structural brain networks constructed from this new sequence. Here, we employed a multiband diffusion MRI (dMRI) dataset with repeated scanning sessions and constructed both low- and high-resolution WM networks by volume- and surface-based parcellation methods. The reproducibility of network metrics and its dependence on type of construction procedures was assessed by the intra-class correlation coefficient (ICC). We observed conserved topological architecture of WM structural networks constructed from the multiband dMRI data as previous findings from conventional dMRI. For the global network properties, the first order metrics were more reliable than second order metrics. Between two parcellation methods, networks with volume-based parcellation showed better reliability than surface-based parcellation, especially for the global metrics. Between different resolutions, the high-resolution network exhibited higher TRT performance than the low-resolution in terms of the global metrics with a large effect size, whereas the low-resolution performs better in terms of local (region and connection) properties with a relatively low effect size. Moreover, we identified that the association and primary cortices showed higher reproducibility than the paralimbic/limbic regions. The important hub regions and rich-club connections are more reliable than the non-hub regions and connections. Finally, we found WM networks from the multiband dMRI showed higher reproducibility compared with those from the conventional dMRI. Together, our results demonstrated the fair to good reliability of the WM structural brain networks from the multiband EPI sequence, suggesting its potential utility for exploring individual differences and for clinical applications. PMID

  1. Kernel regression estimation of fiber orientation mixtures in diffusion MRI.

    PubMed

    Cabeen, Ryan P; Bastin, Mark E; Laidlaw, David H

    2016-02-15

    We present and evaluate a method for kernel regression estimation of fiber orientations and associated volume fractions for diffusion MR tractography and population-based atlas construction in clinical imaging studies of brain white matter. This is a model-based image processing technique in which representative fiber models are estimated from collections of component fiber models in model-valued image data. This extends prior work in nonparametric image processing and multi-compartment processing to provide computational tools for image interpolation, smoothing, and fusion with fiber orientation mixtures. In contrast to related work on multi-compartment processing, this approach is based on directional measures of divergence and includes data-adaptive extensions for model selection and bilateral filtering. This is useful for reconstructing complex anatomical features in clinical datasets analyzed with the ball-and-sticks model, and our framework's data-adaptive extensions are potentially useful for general multi-compartment image processing. We experimentally evaluate our approach with both synthetic data from computational phantoms and in vivo clinical data from human subjects. With synthetic data experiments, we evaluate performance based on errors in fiber orientation, volume fraction, compartment count, and tractography-based connectivity. With in vivo data experiments, we first show improved scan-rescan reproducibility and reliability of quantitative fiber bundle metrics, including mean length, volume, streamline count, and mean volume fraction. We then demonstrate the creation of a multi-fiber tractography atlas from a population of 80 human subjects. In comparison to single tensor atlasing, our multi-fiber atlas shows more complete features of known fiber bundles and includes reconstructions of the lateral projections of the corpus callosum and complex fronto-parietal connections of the superior longitudinal fasciculus I, II, and III. PMID:26691524

  2. Optical Pumping Spin Exchange {sup 3}He Gas Cells for Magnetic Resonance Imaging

    SciTech Connect

    Kim, W.; Stepanyan, S. S.; Kim, A.; Jung, Y.; Woo, S.; Yurov, M.; Jang, J.

    2009-08-04

    We present a device for spin-exchange optical pumping system to produce large quantities of polarized noble gases for Magnetic Resonance Imaging (MRI). A method and design of apparatus for pumping the polarization of noble gases is described. The method and apparatus enable production, storage and usage of hyperpolarized noble gases for different purposes, including Magnetic Resonance Imaging of human and animal subjects. Magnetic imaging agents breathed into lungs can be observed by the radio waves of the MRI scanner and report back physical and functional information about lung's health and desease. The technique known as spin exchange optical pumping is used. Nuclear magnetic resonance is implemented to measure the polarization of hyperpolarized gas. The cells prepared and sealed under high vacuum after handling Alkali metals into the cell and filling with the {sup 3}He-N{sub 2} mixture. The cells could be refilled. The {sup 3}He reaches around 50% polarization in 5-15 hours.

  3. Modeling 3H-3He Gas-Liquid Phase Transport for Interpretation of Groundwater Age

    NASA Astrophysics Data System (ADS)

    Carle, S. F.; Esser, B.; Moran, J. E.

    2009-12-01

    California’s Groundwater Ambient Monitoring and Assessment (GAMA) Program has measured many hundreds of tritium (3H) and helium-3 (3He) concentrations in well water samples to derive estimates of groundwater age at production and monitoring wells in California basins. However, a 3H-3He age differs from an ideal groundwater age tracer in several respects: (1) the radioactive decay of 3H results in the accumulation of 3He being first-order with respect to 3H activity (versus a zero-order age-mass accumulation process for an ideal tracer), (2) surface concentrations of 3H as measured in precipitation over the last several decades have not been uniform, and (3) the 3H-3He “clock” begins at the water table and not at the ground surface where 3H source measurements are made. To better understand how these non-idealities affect interpretation of 3H-3He apparent groundwater age, we are modeling coupled gas-liquid phase flow and 3H-3He transport including processes of radiogenic decay, phase equilibrium, and molecular diffusion for water, air, 3H, and 3He components continuously through the vadose zone and saturated zone. Assessment of coupled liquid-gas phase processes enables consideration of 3H-3He residence time and dispersion within the vadose zone, including partitioning of tritiogenic 3He to the gas phase and subsequent diffusion into the atmosphere. The coupled gas-liquid phase modeling framework provides direct means to compare apparent 3H-3He age to ideal mean or advective groundwater ages for the same groundwater flow conditions. Examples are given for common groundwater flow systems involving areal recharge, discharge to streams or long-screened wells, and aquifer system heterogeneity. The Groundwater Ambient Monitoring and Assessment program is sponsored by the California State Water Resources Control Board and carried out in cooperation with the U.S. Geological Survey. This work was performed under the auspices of the U.S. Department of Energy by

  4. Effects of Non-Local Diffusion on Structural MRI Preprocessing and Default Network Mapping: Statistical Comparisons with Isotropic/Anisotropic Diffusion

    PubMed Central

    Zuo, Xi-Nian; Xing, Xiu-Xia

    2011-01-01

    Neuroimaging community usually employs spatial smoothing to denoise magnetic resonance imaging (MRI) data, e.g., Gaussian smoothing kernels. Such an isotropic diffusion (ISD) based smoothing is widely adopted for denoising purpose due to its easy implementation and efficient computation. Beyond these advantages, Gaussian smoothing kernels tend to blur the edges, curvature and texture of images. Researchers have proposed anisotropic diffusion (ASD) and non-local diffusion (NLD) kernels. We recently demonstrated the effect of these new filtering paradigms on preprocessing real degraded MRI images from three individual subjects. Here, to further systematically investigate the effects at a group level, we collected both structural and functional MRI data from 23 participants. We first evaluated the three smoothing strategies' impact on brain extraction, segmentation and registration. Finally, we investigated how they affect subsequent mapping of default network based on resting-state functional MRI (R-fMRI) data. Our findings suggest that NLD-based spatial smoothing maybe more effective and reliable at improving the quality of both MRI data preprocessing and default network mapping. We thus recommend NLD may become a promising method of smoothing structural MRI images of R-fMRI pipeline. PMID:22066005

  5. Two and three-dimensional segmentation of hyperpolarized 3He magnetic resonance imaging of pulmonary gas distribution

    NASA Astrophysics Data System (ADS)

    Heydarian, Mohammadreza; Kirby, Miranda; Wheatley, Andrew; Fenster, Aaron; Parraga, Grace

    2012-03-01

    A semi-automated method for generating hyperpolarized helium-3 (3He) measurements of individual slice (2D) or whole lung (3D) gas distribution was developed. 3He MRI functional images were segmented using two-dimensional (2D) and three-dimensional (3D) hierarchical K-means clustering of the 3He MRI signal and in addition a seeded region-growing algorithm was employed for segmentation of the 1H MRI thoracic cavity volume. 3He MRI pulmonary function measurements were generated following two-dimensional landmark-based non-rigid registration of the 3He and 1H pulmonary images. We applied this method to MRI of healthy subjects and subjects with chronic obstructive lung disease (COPD). The results of hierarchical K-means 2D and 3D segmentation were compared to an expert observer's manual segmentation results using linear regression, Pearson correlations and the Dice similarity coefficient. 2D hierarchical K-means segmentation of ventilation volume (VV) and ventilation defect volume (VDV) was strongly and significantly correlated with manual measurements (VV: r=0.98, p<.0001 VDV: r=0.97, p<.0001) and mean Dice coefficients were greater than 92% for all subjects. 3D hierarchical K-means segmentation of VV and VDV was also strongly and significantly correlated with manual measurements (VV: r=0.98, p<.0001 VDV: r=0.64, p<.0001) and the mean Dice coefficients were greater than 91% for all subjects. Both 2D and 3D semi-automated segmentation of 3He MRI gas distribution provides a way to generate novel pulmonary function measurements.

  6. Recycling of 3He from lung magnetic resonance imaging.

    PubMed

    Salhi, Z; Grossmann, T; Gueldner, M; Heil, W; Karpuk, S; Otten, E W; Rudersdorf, D; Surkau, R; Wolf, U

    2012-06-01

    We have developed the means to recycle (3) He exhaled by patients after imaging the lungs using magnetic resonance of hyperpolarized (3) He. The exhaled gas is collected in a helium leak proof bag and further compressed into a steel bottle. The collected gas contains about 1-2% of (3) He, depending on the amount administered and the number of breaths collected to wash out the (3) He gas from the lungs. (3) He is separated from the exhaled air using zeolite molecular sieve adsorbent at 77 K followed by a cold head at 8 K. Residual gaseous impurities are finally absorbed by a commercial nonevaporative getter. The recycled (3) He gas features high purity, which is required for repolarization by metastability exchange optical pumping. At present, we achieve a collection efficiency of 80-84% for exhaled gas from healthy volunteers and cryogenic separation efficiency of 95%. PMID:22135249

  7. Non Local Spatial and Angular Matching: Enabling higher spatial resolution diffusion MRI datasets through adaptive denoising.

    PubMed

    St-Jean, Samuel; Coupé, Pierrick; Descoteaux, Maxime

    2016-08-01

    Diffusion magnetic resonance imaging (MRI) datasets suffer from low Signal-to-Noise Ratio (SNR), especially at high b-values. Acquiring data at high b-values contains relevant information and is now of great interest for microstructural and connectomics studies. High noise levels bias the measurements due to the non-Gaussian nature of the noise, which in turn can lead to a false and biased estimation of the diffusion parameters. Additionally, the usage of in-plane acceleration techniques during the acquisition leads to a spatially varying noise distribution, which depends on the parallel acceleration method implemented on the scanner. This paper proposes a novel diffusion MRI denoising technique that can be used on all existing data, without adding to the scanning time. We first apply a statistical framework to convert both stationary and non stationary Rician and non central Chi distributed noise to Gaussian distributed noise, effectively removing the bias. We then introduce a spatially and angular adaptive denoising technique, the Non Local Spatial and Angular Matching (NLSAM) algorithm. Each volume is first decomposed in small 4D overlapping patches, thus capturing the spatial and angular structure of the diffusion data, and a dictionary of atoms is learned on those patches. A local sparse decomposition is then found by bounding the reconstruction error with the local noise variance. We compare against three other state-of-the-art denoising methods and show quantitative local and connectivity results on a synthetic phantom and on an in-vivo high resolution dataset. Overall, our method restores perceptual information, removes the noise bias in common diffusion metrics, restores the extracted peaks coherence and improves reproducibility of tractography on the synthetic dataset. On the 1.2 mm high resolution in-vivo dataset, our denoising improves the visual quality of the data and reduces the number of spurious tracts when compared to the noisy acquisition. Our

  8. Quantified MRI and cognition in TBI with diffuse and focal damage☆

    PubMed Central

    Levine, Brian; Kovacevic, Natasa; Nica, Elena Irina; Schwartz, Michael L.; Gao, Fuqiang; Black, Sandra E.

    2013-01-01

    In patients with chronic-phase traumatic brain injury (TBI), structural MRI is readily attainable and provides rich anatomical information, yet the relationship between whole-brain structural MRI measures and neurocognitive outcome is relatively unexplored and can be complicated by the presence of combined focal and diffuse injury. In this study, sixty-three patients spanning the full range of TBI severity received high-resolution structural MRI concurrent with neuropsychological testing. Multivariate statistical analysis assessed covariance patterns between volumes of grey matter, white matter, and sulcal/subdural and ventricular CSF across 38 brain regions and neuropsychological test performance. Patients with diffuse and diffuse + focal injury were analyzed both separately and together. Tests of speeded attention, working memory, and verbal learning and memory robustly covaried with a distributed pattern of volume loss over temporal, ventromedial prefrontal, right parietal regions, and cingulate regions. This pattern was modulated by the presence of large focal lesions, but held even when analyses were restricted to those with diffuse injury. Effects were most consistently observed within grey matter. Relative to regional brain volumetric data, clinically defined injury severity (depth of coma at time of injury) showed only weak relation to neuropsychological outcome. The results showed that neuropsychological test performance in patients with TBI is related to a distributed pattern of volume loss in regions mediating mnemonic and attentional processing. This relationship holds for patients with and without focal lesions, indicating that diffuse injury alone is sufficient to cause significant neuropsychological disability in relation to regional volume loss. Quantified structural brain imaging data provides a highly sensitive index of brain integrity that is related to cognitive functioning in chronic phase TBI. PMID:24049744

  9. /sup 3/He functions in tokamak-pumped laser systems

    SciTech Connect

    Jassby, D.L.

    1986-10-01

    /sup 3/He placed in an annular cell around a tokamak fusion generator can convert moderated fusion neutrons to energetic ions by the /sup 3/He(n,p)T reaction, and thereby excite gaseous lasants mixed with the /sup 3/He while simultaneously breeding tritium. The total /sup 3/He inventory is about 4 kg for large tokamak devices. Special configurations of toroidal-field magnets, neutron moderators and beryllium reflectors are required to permit nearly uniform neutron current into the laser cell with minimal attenuation. The annular laser radiation can be combined into a single output beam at the top of the tokamak.

  10. Detection of electroporation-induced membrane permeabilization states in the brain using diffusion-weighted MRI

    PubMed Central

    Mahmood, Faisal; Hansen, Rasmus H.; Agerholm-Larsen, Birgit; Gissel, Hanne; Ibsen, Per

    2015-01-01

    Background Tissue permeabilization by electroporation (EP) is a promising technique to treat certain cancers. Non-invasive methods for verification of induced permeabilization are important, especially in deep-seated cancers. In this study we evaluated diffusion-weighted magnetic resonance imaging (DW-MRI) as a quantitative method for detecting EP-induced membrane permeabilization of brain tissue using a rat brain model. Material and methods Fifty-four anesthetized Sprague-Dawley male rats were electroporated in the right hemisphere, using different voltage levels to induce no permeabilization (NP), transient membrane permeabilization (TMP), and permanent membrane permeabilization (PMP), respectively. DW-MRI was acquired 5 minutes, 2 hours, 24 hours and 48 hours after EP. Histology was performed for validation of the permeabilization states. Tissue content of water, Na+, K+, Ca2+, and extracellular volume were determined. The Kruskal-Wallis test was used to compare the DW-MRI parameters, apparent diffusion coefficient (ADC) and kurtosis, at different voltage levels. The two-sample Mann- Whitney test with Holm's Bonferroni correction was used to identify pairs of significantly different groups. The study was approved by the Danish Animal Experiments Inspectorate. Results and conclusion Results showed significant difference in the ADC between TMP and PMP at 2 hours (p < 0.001) and 24 hours (p < 0.05) after EP. Kurtosis was significantly increased both at TMP (p < 0.05) and PMP (p < 0.001) 5 minutes after EP, compared to NP. Kurtosis was also significantly higher at 24 hours (p < 0.05) and 48 hours (p < 0.05) at PMP compared to NP. Physiological parameters indicated correlation with the permeabilization states, supporting the DW-MRI findings. We conclude that DW-MRI is capable of detecting EP-induced permeabilization of brain tissue and to some extent of differentiating NP, TMP and PMP using appropriate scan timing. PMID:25591820

  11. Auditory tracts identified with combined fMRI and diffusion tractography.

    PubMed

    Javad, Faiza; Warren, Jason D; Micallef, Caroline; Thornton, John S; Golay, Xavier; Yousry, Tarek; Mancini, Laura

    2014-01-01

    The auditory tracts in the human brain connect the inferior colliculus (IC) and medial geniculate body (MGB) to various components of the auditory cortex (AC). While in non-human primates and in humans, the auditory system is differentiated in core, belt and parabelt areas, the correspondence between these areas and anatomical landmarks on the human superior temporal gyri is not straightforward, and at present not completely understood. However it is not controversial that there is a hierarchical organization of auditory stimuli processing in the auditory system. The aims of this study were to demonstrate that it is possible to non-invasively and robustly identify auditory projections between the auditory thalamus/brainstem and different functional levels of auditory analysis in the cortex of human subjects in vivo combining functional magnetic resonance imaging (fMRI) with diffusion MRI, and to investigate the possibility of differentiating between different components of the auditory pathways (e.g. projections to areas responsible for sound, pitch and melody processing). We hypothesized that the major limitation in the identification of the auditory pathways is the known problem of crossing fibres and addressed this issue acquiring DTI with b-values higher than commonly used and adopting a multi-fibre ball-and-stick analysis model combined with probabilistic tractography. Fourteen healthy subjects were studied. Auditory areas were localized functionally using an established hierarchical pitch processing fMRI paradigm. Together fMRI and diffusion MRI allowed the successful identification of tracts connecting IC with AC in 64 to 86% of hemispheres and left sound areas with homologous areas in the right hemisphere in 86% of hemispheres. The identified tracts corresponded closely with a three-dimensional stereotaxic atlas based on postmortem data. The findings have both neuroscientific and clinical implications for delineation of the human auditory system in vivo

  12. Robust optimization of diffusion-weighted MRI protocols used for fiber reconstruction

    NASA Astrophysics Data System (ADS)

    Majumdar, S.; Udpa, S. S.; Raguin, L. G.

    2008-11-01

    Diffusion-weighted imaging (DWI) is a magnetic resonance imaging (MRI) technique that employs diffusion-encoding gradients to sensitize the signal to the diffusion of water molecules. DWI allows the noninvasive and quantitative probing of opaque structures such as fibrous soft tissues. Model-based DWI post-processing algorithms, such as diffusion tensor imaging (DTI), solve an inverse problem to estimate from a series of DWI data a set of model parameters representing the diffusion process and the environment of the water molecules. DWI models connect the model parameters (e.g., fiber orientations for fibrous soft tissues) with the experimental parameters (e.g., strengths and directions of the 3-D diffusion-encoding gradients). For spinal cord injuries and skeletal muscle characterization, the fiber orientations within the imaged region can be approximately known a priori using localizer images. Then, we propose and implement a model-based robust optimization framework for two axisymmetric diffusion models, producing robust DWI protocols with respect to the approximate knowledge of the fiber orientations within the images, thereby reducing the uncertainty in the parameter estimates caused by experimental noise. Our goal is to improve the yield of quantitative DWI diagnostics used in clinical and preclinical trials by minimizing the experimental uncertainty.

  13. Perfusion and diffusion MRI of glioblastoma progression in a four-year prospective temozolomide clinical trial

    SciTech Connect

    Leimgruber, Antoine; Ostermann, Sandrine; Yeon, Eun Jo; Buff, Evelyn; Maeder, Philippe P.; Stupp, Roger; Meuli, Reto A. . E-mail: Reto.Meuli@chuv.ch

    2006-03-01

    Purpose: This study was performed to determine the impact of perfusion and diffusion magnetic resonance imaging (MRI) sequences on patients during treatment of newly diagnosed glioblastoma. Special emphasis has been given to these imaging technologies as tools to potentially anticipate disease progression, as progression-free survival is frequently used as a surrogate endpoint. Methods and Materials: Forty-one patients from a phase II temolozomide clinical trial were included. During follow-up, images were integrated 21 to 28 days after radiochemotherapy and every 2 months thereafter. Assessment of scans included measurement of size of lesion on T1 contrast-enhanced, T2, diffusion, and perfusion images, as well as mass effect. Classical criteria on tumor size variation and clinical parameters were used to set disease progression date. Results: A total of 311 MRI examinations were reviewed. At disease progression (32 patients), a multivariate Cox regression determined 2 significant survival parameters: T1 largest diameter (p < 0.02) and T2 size variation (p < 0.05), whereas perfusion and diffusion were not significant. Conclusion: Perfusion and diffusion techniques cannot be used to anticipate tumor progression. Decision making at disease progression is critical, and classical T1 and T2 imaging remain the gold standard. Specifically, a T1 contrast enhancement over 3 cm in largest diameter together with an increased T2 hypersignal is a marker of inferior prognosis.

  14. Quantitative comparison of reconstruction methods for intra-voxel fiber recovery from diffusion MRI.

    PubMed

    Daducci, Alessandro; Canales-Rodríguez, Erick Jorge; Descoteaux, Maxime; Garyfallidis, Eleftherios; Gur, Yaniv; Lin, Ying-Chia; Mani, Merry; Merlet, Sylvain; Paquette, Michael; Ramirez-Manzanares, Alonso; Reisert, Marco; Reis Rodrigues, Paulo; Sepehrband, Farshid; Caruyer, Emmanuel; Choupan, Jeiran; Deriche, Rachid; Jacob, Mathews; Menegaz, Gloria; Prčkovska, Vesna; Rivera, Mariano; Wiaux, Yves; Thiran, Jean-Philippe

    2014-02-01

    Validation is arguably the bottleneck in the diffusion magnetic resonance imaging (MRI) community. This paper evaluates and compares 20 algorithms for recovering the local intra-voxel fiber structure from diffusion MRI data and is based on the results of the "HARDI reconstruction challenge" organized in the context of the "ISBI 2012" conference. Evaluated methods encompass a mixture of classical techniques well known in the literature such as diffusion tensor, Q-Ball and diffusion spectrum imaging, algorithms inspired by the recent theory of compressed sensing and also brand new approaches proposed for the first time at this contest. To quantitatively compare the methods under controlled conditions, two datasets with known ground-truth were synthetically generated and two main criteria were used to evaluate the quality of the reconstructions in every voxel: correct assessment of the number of fiber populations and angular accuracy in their orientation. This comparative study investigates the behavior of every algorithm with varying experimental conditions and highlights strengths and weaknesses of each approach. This information can be useful not only for enhancing current algorithms and develop the next generation of reconstruction methods, but also to assist physicians in the choice of the most adequate technique for their studies. PMID:24132007

  15. Tracking on the Product Manifold of Shape and Orientation for Tractography from Diffusion MRI*

    PubMed Central

    Wang, Yuanxiang; Salehian, Hesamoddin; Cheng, Guang; Vemuri, Baba C.

    2014-01-01

    Tractography refers to the process of tracing out the nerve fiber bundles from diffusion Magnetic Resonance Images (dMRI) data acquired either in vivo or ex-vivo. Tractography is a mature research topic within the field of diffusion MRI analysis, nevertheless, several new methods are being proposed on a regular basis thereby justifying the need, as the problem is not fully solved. Tractography is usually applied to the model (used to represent the diffusion MR signal or a derived quantity) reconstructed from the acquired data. Separating shape and orientation of these models was previously shown to approximately preserve diffusion anisotropy (a useful bio-marker) in the ubiquitous problem of interpolation. However, no further intrinsic geometric properties of this framework were exploited to date in literature. In this paper, we propose a new intrinsic recursive filter on the product manifold of shape and orientation. The recursive filter, dubbed IUKFPro, is a generalization of the unscented Kalman filter (UKF) to this product manifold. The salient contributions of this work are: (1) A new intrinsic UKF for the product manifold of shape and orientation. (2) Derivation of the Riemannian geometry of the product manifold. (3) IUKFPro is tested on synthetic and real data sets from various tractography challenge competitions. From the experimental results, it is evident that IUKFPro performs better than several competing schemes in literature with regards to some of the error measures used in the competitions and is competitive with respect to others. PMID:25531012

  16. A validation of the 3H/3He method for determining groundwater recharge

    NASA Astrophysics Data System (ADS)

    Solomon, D. K.; Schiff, S. L.; Poreda, R. J.; Clarke, W. B.

    1993-09-01

    Tritium and He isotopes have been measured at a site where groundwater flow is nearly vertical for a travel time of 100 years and where recharge rates are spatially variable. Because the mid-1960s 3H peak (arising from aboveground testing of thermonuclear devices) is well-defined, the vertical groundwater velocity is known with unusual accuracy at this site. Utilizing 3H and its stable daughter 3He to determine groundwater ages, we compute a recharge rate of 0.16 m/yr, which agrees to within about 5% of the value based on the depth of the 3H peak (measured both in 1986 and 1991) and two-dimensional modeling in an area of high recharge. Zero 3H/3He age occurs at a depth that is approximately equal to the average depth of the annual low water table, even though the capillary fringe extends to land surface during most of the year at the study site. In an area of low recharge (0.05 m/yr) where the 3H peak (and hence the vertical velocity) is also well-defined, the 3H/3He results could not be used to compute recharge because samples were not collected sufficiently far above the 3H peak; however, modeling indicates that the 3H/3He age gradient near the water table is an accurate measure of vertical velocities in the low-recharge area. Because 3H and 3He have different diffusion coefficients, and because the amount of mechanical mixing is different in the area of high recharge than in the low-recharge area, we have separated the dispersive effects of mechanical mixing from molecular diffusion. We estimate a longitudinal dispersivity of 0.07 m and effective diffusion coefficients for 3H (3HHO) and 3He of 2.4×10-5 and 1.3×10-4 m2/day, respectively. Although the 3H/3He age gradient is an excellent indicator of vertical groundwater velocities above the mid-1960s 3H peak, dispersive mixing and diffusive loss of 3He perturb the age gradient near and below the 3H peak.

  17. Spatially-constrained probability distribution model of incoherent motion (SPIM) for abdominal diffusion-weighted MRI.

    PubMed

    Kurugol, Sila; Freiman, Moti; Afacan, Onur; Perez-Rossello, Jeannette M; Callahan, Michael J; Warfield, Simon K

    2016-08-01

    Quantitative diffusion-weighted MR imaging (DW-MRI) of the body enables characterization of the tissue microenvironment by measuring variations in the mobility of water molecules. The diffusion signal decay model parameters are increasingly used to evaluate various diseases of abdominal organs such as the liver and spleen. However, previous signal decay models (i.e., mono-exponential, bi-exponential intra-voxel incoherent motion (IVIM) and stretched exponential models) only provide insight into the average of the distribution of the signal decay rather than explicitly describe the entire range of diffusion scales. In this work, we propose a probability distribution model of incoherent motion that uses a mixture of Gamma distributions to fully characterize the multi-scale nature of diffusion within a voxel. Further, we improve the robustness of the distribution parameter estimates by integrating spatial homogeneity prior into the probability distribution model of incoherent motion (SPIM) and by using the fusion bootstrap solver (FBM) to estimate the model parameters. We evaluated the improvement in quantitative DW-MRI analysis achieved with the SPIM model in terms of accuracy, precision and reproducibility of parameter estimation in both simulated data and in 68 abdominal in-vivo DW-MRIs. Our results show that the SPIM model not only substantially reduced parameter estimation errors by up to 26%; it also significantly improved the robustness of the parameter estimates (paired Student's t-test, p < 0.0001) by reducing the coefficient of variation (CV) of estimated parameters compared to those produced by previous models. In addition, the SPIM model improves the parameter estimates reproducibility for both intra- (up to 47%) and inter-session (up to 30%) estimates compared to those generated by previous models. Thus, the SPIM model has the potential to improve accuracy, precision and robustness of quantitative abdominal DW-MRI analysis for clinical applications. PMID

  18. Fast and accurate simulations of diffusion-weighted MRI signals for the evaluation of acquisition sequences

    NASA Astrophysics Data System (ADS)

    Rensonnet, Gaëtan; Jacobs, Damien; Macq, Benoît.; Taquet, Maxime

    2016-03-01

    Diffusion-weighted magnetic resonance imaging (DW-MRI) is a powerful tool to probe the diffusion of water through tissues. Through the application of magnetic gradients of appropriate direction, intensity and duration constituting the acquisition parameters, information can be retrieved about the underlying microstructural organization of the brain. In this context, an important and open question is to determine an optimal sequence of such acquisition parameters for a specific purpose. The use of simulated DW-MRI data for a given microstructural configuration provides a convenient and efficient way to address this problem. We first present a novel hybrid method for the synthetic simulation of DW-MRI signals that combines analytic expressions in simple geometries such as spheres and cylinders and Monte Carlo (MC) simulations elsewhere. Our hybrid method remains valid for any acquisition parameters and provides identical levels of accuracy with a computational time that is 90% shorter than that required by MC simulations for commonly-encountered microstructural configurations. We apply our novel simulation technique to estimate the radius of axons under various noise levels with different acquisition protocols commonly used in the literature. The results of our comparison suggest that protocols favoring a large number of gradient intensities such as a Cube and Sphere (CUSP) imaging provide more accurate radius estimation than conventional single-shell HARDI acquisitions for an identical acquisition time.

  19. Microfluidic laminate-based phantom for diffusion tensor-magnetic resonance imaging (DT-MRI)

    PubMed Central

    Samuel, R; Sant, H J; Jiao, F; Johnson, C R; Gale, B K

    2011-01-01

    This paper reports fabrication of a magnetic resonance imaging (MRI) phantom created by stacking of multiple thin polydimethylsiloxane (PDMS) layers. PDMS is spin coated on SU-8 molds to obtain the desired layer thickness and imprints of the microchannel patterns that define the phantom geometry. This paper also identifies the unique challenges related to the fabrication and assembly of multiple thin layers and reports for the first time assembly of a large number of thin laminates of this nature. Use of photolithography techniques allows us to create a wide range of phantom geometries. The target dimensions of the phantoms reported here are (i) a stack of 30 thin PDMS layers of 10 µm thickness (ii) curved 5 µm × 5 µm microchannels with 8.7 µm spacing, and (iii) straight 5 µm × 5 µm microchannels with 3.6 µm spacing. SEM scans of the assembled phantoms show open microchannels and a monolithic cross-section with no visible interface between PDMS layers. Based on the results of diffusion tensor magnetic resonance imaging (DT-MRI) scan, the anisotropic diffusion of water molecules due to the physical restriction of the microchannels was detected, which means that the phantom can be used to calibrate and optimize MRI instrumentation. PMID:22865956

  20. Microfluidic laminate-based phantom for diffusion tensor-magnetic resonance imaging (DT-MRI).

    PubMed

    Samuel, R; Sant, H J; Jiao, F; Johnson, C R; Gale, B K

    2011-09-01

    This paper reports fabrication of a magnetic resonance imaging (MRI) phantom created by stacking of multiple thin polydimethylsiloxane (PDMS) layers. PDMS is spin coated on SU-8 molds to obtain the desired layer thickness and imprints of the microchannel patterns that define the phantom geometry. This paper also identifies the unique challenges related to the fabrication and assembly of multiple thin layers and reports for the first time assembly of a large number of thin laminates of this nature. Use of photolithography techniques allows us to create a wide range of phantom geometries. The target dimensions of the phantoms reported here are (i) a stack of 30 thin PDMS layers of 10 µm thickness (ii) curved 5 µm × 5 µm microchannels with 8.7 µm spacing, and (iii) straight 5 µm × 5 µm microchannels with 3.6 µm spacing. SEM scans of the assembled phantoms show open microchannels and a monolithic cross-section with no visible interface between PDMS layers. Based on the results of diffusion tensor magnetic resonance imaging (DT-MRI) scan, the anisotropic diffusion of water molecules due to the physical restriction of the microchannels was detected, which means that the phantom can be used to calibrate and optimize MRI instrumentation. PMID:22865956

  1. Longitudinal change detection in diffusion MRI using multivariate statistical testing on tensors.

    PubMed

    Grigis, Antoine; Noblet, Vincent; Heitz, Fabrice; Blanc, Frédéric; de Sèze, Jérome; Kremer, Stéphane; Rumbach, Lucien; Armspach, Jean-Paul

    2012-05-01

    This paper presents a longitudinal change detection framework for detecting relevant modifications in diffusion MRI, with application to neuromyelitis optica (NMO) and multiple sclerosis (MS). The core problem is to identify image regions that are significantly different between two scans. The proposed method is based on multivariate statistical testing which was initially introduced for tensor population comparison. We use this method in the context of longitudinal change detection by considering several strategies to build sets of tensors characterizing the variability of each voxel. These strategies make use of the variability existing in the diffusion weighted images (thanks to a bootstrap procedure), or in the spatial neighborhood of the considered voxel, or a combination of both. Results on synthetic evolutions and on real data are presented. Interestingly, experiments on NMO patients highlight the ability of the proposed approach to detect changes in the normal-appearing white matter (according to conventional MRI) that are related with physical status outcome. Experiments on MS patients highlight the ability of the proposed approach to detect changes in evolving and non-evolving lesions (according to conventional MRI). These findings might open promising prospects for the follow-up of NMO and MS pathologies. PMID:22387171

  2. Fractality in the neuron axonal topography of the human brain based on 3-D diffusion MRI

    NASA Astrophysics Data System (ADS)

    Katsaloulis, P.; Ghosh, A.; Philippe, A. C.; Provata, A.; Deriche, R.

    2012-05-01

    In this work the fractal architecture of the neuron axonal topography of the human brain is evaluated, as derived from 3-D diffusion MRI (dMRI) acquisitions. This is a 3D extension of work performed previously in 2D regions of interest (ROIs), where the fractal dimension of the neuron axonal topography was computed from dMRI data. A group study with 18 subjects is here conducted and the fractal dimensions D f of the entire 3-D volume of the brains is estimated via the box counting, the correlation dimension and the fractal mass dimension methods. The neuron axon data is obtained using tractography algorithms on diffusion tensor imaging of the brain. We find that all three calculations of D f give consistent results across subjects, namely, they demonstrate fractal characteristics in the short and medium length scales: different fractal exponents prevail at different length scales, an indication of multifractality. We surmise that this complexity stems as a collective property emerging when many local brain units, performing different functional tasks and having different local topologies, are recorded together.

  3. Inter-site and inter-scanner diffusion MRI data harmonization.

    PubMed

    Mirzaalian, H; Ning, L; Savadjiev, P; Pasternak, O; Bouix, S; Michailovich, O; Grant, G; Marx, C E; Morey, R A; Flashman, L A; George, M S; McAllister, T W; Andaluz, N; Shutter, L; Coimbra, R; Zafonte, R D; Coleman, M J; Kubicki, M; Westin, C F; Stein, M B; Shenton, M E; Rathi, Y

    2016-07-15

    We propose a novel method to harmonize diffusion MRI data acquired from multiple sites and scanners, which is imperative for joint analysis of the data to significantly increase sample size and statistical power of neuroimaging studies. Our method incorporates the following main novelties: i) we take into account the scanner-dependent spatial variability of the diffusion signal in different parts of the brain; ii) our method is independent of compartmental modeling of diffusion (e.g., tensor, and intra/extra cellular compartments) and the acquired signal itself is corrected for scanner related differences; and iii) inter-subject variability as measured by the coefficient of variation is maintained at each site. We represent the signal in a basis of spherical harmonics and compute several rotation invariant spherical harmonic features to estimate a region and tissue specific linear mapping between the signal from different sites (and scanners). We validate our method on diffusion data acquired from seven different sites (including two GE, three Philips, and two Siemens scanners) on a group of age-matched healthy subjects. Since the extracted rotation invariant spherical harmonic features depend on the accuracy of the brain parcellation provided by Freesurfer, we propose a feature based refinement of the original parcellation such that it better characterizes the anatomy and provides robust linear mappings to harmonize the dMRI data. We demonstrate the efficacy of our method by statistically comparing diffusion measures such as fractional anisotropy, mean diffusivity and generalized fractional anisotropy across multiple sites before and after data harmonization. We also show results using tract-based spatial statistics before and after harmonization for independent validation of the proposed methodology. Our experimental results demonstrate that, for nearly identical acquisition protocol across sites, scanner-specific differences can be accurately removed using the

  4. Hepatocellular Carcinoma and Diffusion-Weighted MRI: Detection and Evaluation of Treatment Response.

    PubMed

    Gluskin, Jill S; Chegai, Fabrizio; Monti, Serena; Squillaci, Ettore; Mannelli, Lorenzo

    2016-01-01

    Differentiating between cancerous tissue and healthy liver parenchyma could represent a challenge with the only conventional Magnetic Resonance (MR) imaging. Diffusion weighted imaging (DWI) exploits different tissue characteristics to conventional Magnetic Resonance Imaging (MRI) sequences that enhance hepatocellular carcinoma (HCC) detection, characterization, and post-treatment evaluation. Detection of HCC is improved by DWI, infact this technology increases conspicuity of lesions that might otherwise not be identified due to obscuration by adjacent vessels or due to low contrast between the lesion and background liver. It is important to remember that DWI combined with contrast-enhanced MRI has higher sensitivity than DWI alone, and that some patients are not eligible for use of contrast on CT and MRI; in these patients DWI has a prominent role. MRI has advanced beyond structural anatomic imaging to now showing pathophysiologic processes. DWI is a promising way to characterize lesions utilizing the inherent contrast within the liver and has the benefit of not requiring contrast injection. DWI improves detection and characterization of HCC. Proposed clinical uses for DWI include: assessing prognosis, predicting response, monitoring response to therapy, and distinguishing tumor recurrence from treatment effect. Ideally, DWI will help risk stratify patients and will participate in prognostic modeling. PMID:27471573

  5. Hepatocellular Carcinoma and Diffusion-Weighted MRI: Detection and Evaluation of Treatment Response

    PubMed Central

    Gluskin, Jill S; Chegai, Fabrizio; Monti, Serena; Squillaci, Ettore; Mannelli, Lorenzo

    2016-01-01

    Differentiating between cancerous tissue and healthy liver parenchyma could represent a challenge with the only conventional Magnetic Resonance (MR) imaging. Diffusion weighted imaging (DWI) exploits different tissue characteristics to conventional Magnetic Resonance Imaging (MRI) sequences that enhance hepatocellular carcinoma (HCC) detection, characterization, and post-treatment evaluation. Detection of HCC is improved by DWI, infact this technology increases conspicuity of lesions that might otherwise not be identified due to obscuration by adjacent vessels or due to low contrast between the lesion and background liver. It is important to remember that DWI combined with contrast-enhanced MRI has higher sensitivity than DWI alone, and that some patients are not eligible for use of contrast on CT and MRI; in these patients DWI has a prominent role. MRI has advanced beyond structural anatomic imaging to now showing pathophysiologic processes. DWI is a promising way to characterize lesions utilizing the inherent contrast within the liver and has the benefit of not requiring contrast injection. DWI improves detection and characterization of HCC. Proposed clinical uses for DWI include: assessing prognosis, predicting response, monitoring response to therapy, and distinguishing tumor recurrence from treatment effect. Ideally, DWI will help risk stratify patients and will participate in prognostic modeling. PMID:27471573

  6. Evaluation of three inverse problem models to quantify skin microcirculation using diffusion-weighted MRI

    NASA Astrophysics Data System (ADS)

    Cordier, G.; Choi, J.; Raguin, L. G.

    2008-11-01

    Skin microcirculation plays an important role in diseases such as chronic venous insufficiency and diabetes. Magnetic resonance imaging (MRI) can provide quantitative information with a better penetration depth than other noninvasive methods, such as laser Doppler flowmetry or optical coherence tomography. Moreover, successful MRI skin studies have recently been reported. In this article, we investigate three potential inverse models to quantify skin microcirculation using diffusion-weighted MRI (DWI), also known as q-space MRI. The model parameters are estimated based on nonlinear least-squares (NLS). For each of the three models, an optimal DWI sampling scheme is proposed based on D-optimality in order to minimize the size of the confidence region of the NLS estimates and thus the effect of the experimental noise inherent to DWI. The resulting covariance matrices of the NLS estimates are predicted by asymptotic normality and compared to the ones computed by Monte-Carlo simulations. Our numerical results demonstrate the effectiveness of the proposed models and corresponding DWI sampling schemes as compared to conventional approaches.

  7. A new method for determining the 3He/4He ratio in the local interstellar medium

    NASA Astrophysics Data System (ADS)

    Lemoine, M.; Vidal-Madjar, A.; Ferlet, R.

    1993-06-01

    We propose here an original method for estimating the 3He/4 Heratio in the local diffuse interstellar medium at a low cost from an observational point of view. The main idea is to measure the shift in radial velocity of the 4He λ537Å and λ584Å lines due to the presence of 3He in the red wing of these lines, and to compare the observed shift to the shifts obtained through numerical simulations for different 3He/4He ratios. We performed such simulations in order to reveal the efficiency of this method, using typical astrophysical conditions and instrumental parameters corresponding to the Lyman-FUSE mission. We find that this method should yield the 3He/4He ratio with a 1 σ uncertainty ˜50% at a spectral resolving power R=30 000 and a signal-to-noise ratio S/N=50. This method thus appears more adapted to a forehand estimation of the interstellar 3He/4He ratio than the standard profile fitting method, which should yield a 1 σ uncertainty of 10% at R=30 000 and S/N ≃ 290 (Hurwitz & Bowyer, t985). Finally, our method should be able to settle the evolutionary status of 3He if 3He has been significantly enhanced or depleted in the last 4.6 Gyr. Combined with the measurement of the deuterium abundance on the same line of sight (already programmed on HST), this might yield very important constraint on Big-Bang nucleosynthesis consistency.

  8. Early Days of Superfluid ^3He: An Experimenter's View

    NASA Astrophysics Data System (ADS)

    Lee, David

    2010-03-01

    The formulation of the BCS theory led theorists to investigate possible non-S-wave pairing in liquid ^3He. Unfortunately as time went on, estimates for the pairing temperature became unattainably low. Nevertheless, the push to lower temperatures by experimentalists continued and was facilitated by the invention of the dilution refrigerator. Nuclear adiabatic demagnetization could then be used to cool liquid ^3He to ˜1 mK as demonstrated by Goodkind. An alternate approach, suggested by Pomeranchuk, involved adiabatic compression of liquid ^3He into the solid phase. Efforts to develop this technique at the Kapitza Institute, La Jolla and Cornell achieved success in demonstrating cooling of mixtures of liquid and solid ^3He to ˜ 1 mK following dilution refrigerator pre-cooling. Although there was great pessimism regarding the possible observation of pairing in liquid ^3He, the unsettled problem of magnetic ordering in solid ^3He beckoned. Ultimately two phase transition along the melting curve were observed by Osheroff et al at Cornell. Although first associated with solid ^3He, extensive NMR studies showed them to be two new phases of liquid ^3He. A brief history of experiments at various laboratories following the discovery is given, along with early interpretations given by Anderson and Morel and Balian and Werthamer. The key role of Leggett's spin dynamics is also discussed.

  9. MRI Quantification of Non-Gaussian Water Diffusion by Kurtosis Analysis

    PubMed Central

    Jensen, Jens H.; Helpern, Joseph A.

    2010-01-01

    Quantification of non-Gaussianity for water diffusion in brain by means of diffusional kurtosis imaging (DKI) is reviewed. Diffusional non-Gaussianity is a consequence of tissue structure that creates diffusion barriers and compartments. The degree of non-Gaussianity is conveniently quantified by the diffusional kurtosis and derivative metrics, such as the mean, axial, and radial kurtoses. DKI is a diffusion-weighted MRI technique that allows the diffusional kurtosis to be estimated with clinical scanners using standard diffusion-weighted pulse sequences and relatively modest acquisition times. DKI is an extension of the widely used diffusion tensor imaging method, but requires the use of at least 3 b-values and 15 diffusion directions. This review discusses the underlying theory of DKI as well as practical considerations related to data acquisition and post-processing. It is argued that the diffusional kurtosis is sensitive to diffusional heterogeneity and suggested that DKI may be useful for investigating ischemic stroke and neuropathologies, such as Alzheimer’s disease and schizophrenia. PMID:20632416

  10. Phase Diagram for 3He Films on Boron Nitride: NMR Studies

    NASA Astrophysics Data System (ADS)

    Tang, Yibing; Sullivan, Neil

    2014-03-01

    Recent studies of the thermodynamic properties of 3He films on graphite have revealed the existence of a previously undetected self-bound liquid phase at low density coverages. We report the results of NMR relaxation time studies for 3He adsorbed on hexagonal boron nitride designed to explore the dynamics of the adsorbed 3He atoms in order to identify the phase boundaries as a function of temperature. A steep thermally activated temperature dependence is observed at high temperatures (T > 2 . 6) K, followed by a linear dependence for 0 . 77 < T < 2 . 6 K. The linear dependence is consistent with that expected for thermal diffusion in the self-bound liquid state. The research was supported in part by a grant from the National Science Foundation, DMR-1303599.

  11. Modeling diffusion-weighted MRI as a spatially variant Gaussian mixture: Application to image denoising

    PubMed Central

    Gonzalez, Juan Eugenio Iglesias; Thompson, Paul M.; Zhao, Aishan; Tu, Zhuowen

    2011-01-01

    Purpose: This work describes a spatially variant mixture model constrained by a Markov random field to model high angular resolution diffusion imaging (HARDI) data. Mixture models suit HARDI well because the attenuation by diffusion is inherently a mixture. The goal is to create a general model that can be used in different applications. This study focuses on image denoising and segmentation (primarily the former). Methods: HARDI signal attenuation data are used to train a Gaussian mixture model in which the mean vectors and covariance matrices are assumed to be independent of spatial locations, whereas the mixture weights are allowed to vary at different lattice positions. Spatial smoothness of the data is ensured by imposing a Markov random field prior on the mixture weights. The model is trained in an unsupervised fashion using the expectation maximization algorithm. The number of mixture components is determined using the minimum message length criterion from information theory. Once the model has been trained, it can be fitted to a noisy diffusion MRI volume by maximizing the posterior probability of the underlying noiseless data in a Bayesian framework, recovering a denoised version of the image. Moreover, the fitted probability maps of the mixture components can be used as features for posterior image segmentation. Results: The model-based denoising algorithm proposed here was compared on real data with three other approaches that are commonly used in the literature: Gaussian filtering, anisotropic diffusion, and Rician-adapted nonlocal means. The comparison shows that, at low signal-to-noise ratio, when these methods falter, our algorithm considerably outperforms them. When tractography is performed on the model-fitted data rather than on the noisy measurements, the quality of the output improves substantially. Finally, ventricle and caudate nucleus segmentation experiments also show the potential usefulness of the mixture probability maps for

  12. Velocity, correlation time and diffusivity measurements in highly turbulent gas flow by an MRI method

    NASA Astrophysics Data System (ADS)

    Yang, Zhi; Newling, Ben

    2007-03-01

    We present non-invasive, quantitative MRI wind-tunnel measurements in flowing gas (velocity > 10 m/s) at high Reynolds numbers (Re > 10^5). Our measurement method is three-dimensional and has the potential for saving time over traditional pointwise techniques. The method is suitable for liquids and for gases. We demonstrate the use of the technique on different test sections (bluff obstruction, clark Y-wing and cylinder). The mean velocity of gas flowing past those sections has been measured. We also investigate methods to measure flow correlation times by changing the acquisition interval between excitation of the sample and detection of the signal. This may be accomplished by making separate measurements or by using a multiple-point acquisition method. A measurement of correlation time allows us to map turbulent diffusivity. The MRI data are compared with computational fluid dynamics.

  13. A survey of current trends in diffusion MRI for structural brain connectivity

    NASA Astrophysics Data System (ADS)

    Ghosh, Aurobrata; Deriche, Rachid

    2016-02-01

    In this paper, we review the state of the art in diffusion magnetic resonance imaging (dMRI) and we present current trends in modelling the brain's tissue microstructure and the human connectome. dMRI is today the only tool that can probe the brain's axonal architecture in vivo and non-invasively, and has grown in leaps and bounds in the last two decades since its conception. A plethora of models with increasing complexity and better accuracy have been proposed to characterise the integrity of the cerebral tissue, to understand its microstructure and to infer its connectivity. Here, we discuss a wide range of the most popular, important and well-established local microstructure models and biomarkers that have been proposed from these models. Finally, we briefly present the state of the art in tractography techniques that allow us to understand the architecture of the brain's connectivity.

  14. Diffusion and ideal MRI techniques to characterize limb-girdle muscular dystrophy

    NASA Astrophysics Data System (ADS)

    Hernández-Salazar, G.; Hidalgo-Tobon, S.; Vargas-Cañas, S.; Marrufo-Melendez, O.; Solis-Najera, S.; Taboada-Barajas, J.; Rodríguez, A. O.; Delgado-Hernández, R.

    2012-10-01

    Limb-girdle muscular dystrophies (LGMD) are a group of autosomal dominantly or recessively inherited muscular dystrophies that also present with primary proximal (limb-girdle) muscle weakness. In the thigh, muscles at the back are affected, with a tendency to preserve the tibialis anterior and gastrocnemius. The aim of this study was to compare quantitative MRI measurements from IDEAL-based imaging and DW imaging in the thigh muscles of adults with LGMDs and healthy volunteers(HC). Six women (three patients and three healthy volunteers) were examined. Imaging experiments were conducted on a 1.5T GE scanner (General Electric Medical Systems. Milwaukee). T1 IDEAL 2D images and diffusion images were acquired. Results demonstrated that the use of noninvasive MRI techniques may provide the means to characterize the muscle through quantitative methods to determine the percentage of fat and ADC values.

  15. A diffusion and T2 relaxation MRI study of the ovine lumbar intervertebral disc under compression in vitro

    NASA Astrophysics Data System (ADS)

    Drew, Simon C.; Silva, Pujitha; Crozier, Stuart; Pearcy, Mark J.

    2004-08-01

    The ovine lumbar intervertebral disc is a useful model for the human lumbar disc. We present preliminary estimates of diffusion coefficients and T2 relaxation times in a pilot MRI study of the ovine lumbar intervertebral disc during uniaxial compression in vitro, and identify factors that hamper the ability to accurately monitor the temporal evolution of the effective diffusion tensor at high spatial resolution.

  16. Degassing of 3H/3He, CFCs and SF6 by denitrification: measurements and two-phase transport simulations.

    PubMed

    Visser, Ate; Schaap, Joris D; Broers, Hans Peter; Bierkens, Marc F P

    2009-01-26

    The production of N2 gas by denitrification may lead to the appearance of a gas phase below the water table prohibiting the conservative transport of tracer gases required for groundwater dating. We used a two-phase flow and transport model (STOMP) to study the reliability of 3H/3He, CFCs and SF6 as groundwater age tracers under agricultural land where denitrification causes degassing. We were able to reproduce the amount of degassing (R2=69%), as well as the 3H (R2=79%) and 3He (R2=76%) concentrations observed in a 3H/3He data set using simple 2D models. We found that the TDG correction of the 3H/3He age overestimated the control 3He/3He age by 2.1 years, due to the accumulation of 3He in the gas phase. The total uncertainty of degassed 3H/3He ages of 6 years (+/-2 sigma) is due to the correction of degassed 3He using the TDG method, but also due to the travel time in the unsaturated zone and the diffusion of bomb peak 3He. CFCs appear to be subject to significant degradation in anoxic groundwater and SF6 is highly susceptible to degassing. We conclude that 3H/3He is the most reliable method to date degassed groundwater and that two-phase flow models such as STOMP are useful tools to assist in the interpretation of degassed groundwater age tracer data. PMID:19042054

  17. Quantitative evaluation of brain development using anatomical MRI and diffusion tensor imaging☆

    PubMed Central

    Oishi, Kenichi; Faria, Andreia V.; Yoshida, Shoko; Chang, Linda; Mori, Susumu

    2013-01-01

    The development of the brain is structure-specific, and the growth rate of each structure differs depending on the age of the subject. Magnetic resonance imaging (MRI) is often used to evaluate brain development because of the high spatial resolution and contrast that enable the observation of structure-specific developmental status. Currently, most clinical MRIs are evaluated qualitatively to assist in the clinical decision-making and diagnosis. The clinical MRI report usually does not provide quantitative values that can be used to monitor developmental status. Recently, the importance of image quantification to detect and evaluate mild-to-moderate anatomical abnormalities has been emphasized because these alterations are possibly related to several psychiatric disorders and learning disabilities. In the research arena, structural MRI and diffusion tensor imaging (DTI) have been widely applied to quantify brain development of the pediatric population. To interpret the values from these MR modalities, a “growth percentile chart,” which describes the mean and standard deviation of the normal developmental curve for each anatomical structure, is required. Although efforts have been made to create such a growth percentile chart based on MRI and DTI, one of the greatest challenges is to standardize the anatomical boundaries of the measured anatomical structures. To avoid inter- and intra-reader variability about the anatomical boundary definition, and hence, to increase the precision of quantitative measurements, an automated structure parcellation method, customized for the neonatal and pediatric population, has been developed. This method enables quantification of multiple MR modalities using a common analytic framework. In this paper, the attempt to create an MRI- and a DTI-based growth percentile chart, followed by an application to investigate developmental abnormalities related to cerebral palsy, Williams syndrome, and Rett syndrome, have been introduced

  18. Prediction of Selective Serotonin Reuptake Inhibitor Response Using Diffusion-Weighted MRI

    PubMed Central

    DeLorenzo, Christine; Delaparte, Lauren; Thapa-Chhetry, Binod; Miller, Jeffrey M.; Mann, J. John; Parsey, Ramin V.

    2013-01-01

    Pre-treatment differences in serotonergic binding between those who remit to antidepressant treatment and those who do not have been found using Positron Emission Tomography (PET). To investigate these differences, an exploratory study was performed using a second imaging modality, diffusion-weighted MRI (DW-MRI). Eighteen antidepressant-free subjects with Major Depressive Disorder received a 25-direction DW-MRI scan prior to 8 weeks of selective serotonin reuptake inhibitor treatment. Probabilistic tractography was performed between the midbrain/raphe and two target regions implicated in depression pathophysiology (amygdala and hippocampus). Average fractional anisotropy (FA) within the derived tracts was compared between SSRI remitters and non-remitters, and correlation between pre-treatment FA values and SSRI treatment outcome was assessed. Results indicate that average FA in DW-MRI-derived tracts to the right amygdala was significantly lower in non-remitters (0.55 ± 0.04) than remitters (0.61 ± 0.04, p < 0.01). In addition, there was a significant correlation between average FA in tracts to the right amygdala and SSRI treatment response. These relationships were found at a trend level when using the left amygdala as a tractography target. No significant differences were observed when using the hippocampus as target. These regional differences, consistent with previous PET findings, suggest that the integrity and/or number of white matter fibers terminating in the right amygdala may be compromised in SSRI non-remitters. Further, this study points to the benefits of multimodal imaging and suggests that DW-MRI may provide a pre-treatment signature of SSRI depression remission at 8 weeks. PMID:23508528

  19. Mapping mean axon diameter and axonal volume fraction by MRI using temporal diffusion spectroscopy

    PubMed Central

    Xu, Junzhong; Li, Hua; Harkins, Kevin D.; Jiang, Xiaoyu; Xie, Jingping; Kang, Hakmook; Does, Mark D.; Gore, John C.

    2014-01-01

    Mapping mean axon diameter and intra-axonal volume fraction may have significant clinical potential because nerve conduction velocity is directly dependent on axon diameter, and several neurodegenerative diseases affect axons of specific sizes and alter axon counts. Diffusion-weighted MRI methods based on the pulsed gradient spin echo (PGSE) sequence have been reported to be able to assess axon diameter and volume fraction non-invasively. However, due to the relatively long diffusion times used, e.g. > 20 ms, the sensitivity to small axons (diameter < 2 µm) is low, and the derived mean axon diameter has been reported to be overestimated. In the current study, oscillating gradient spin echo (OGSE) diffusion sequences with variable frequency gradients were used to assess rat spinal white matter tracts with relatively short effective diffusion times (1 – 5 ms). In contrast to previous PGSE-based methods, the extra-axonal diffusion cannot be modeled as hindered (Gaussian) diffusion when short diffusion times are used. Appropriate frequency-dependent rates are therefore incorporated into our analysis and validated by histology-based computer simulation of water diffusion. OGSE data were analyzed to derive mean axon diameters and intra-axonal volume fractions of rat spinal white matter tracts (mean axon diameter ~ 1.27 – 5.54 µm). The estimated values were in good agreement with histology, including the small axon diameters (< 2.5 µm). This study establishes a framework for quantification of nerve morphology using the OGSE method with high sensitivity to small axons. PMID:25225002

  20. Supratentorial and infratentorial damage in spinocerebellar ataxia 2: a diffusion-weighted MRI study.

    PubMed

    Salvatore, Elena; Tedeschi, Enrico; Mollica, Carmine; Vicidomini, Caterina; Varrone, Andrea; Coda, Anna Rita Daniela; Brunetti, Arturo; Salvatore, Marco; De Michele, Giuseppe; Filla, Alessandro; Pappatà, Sabina

    2014-05-01

    Spinocerebellar ataxia type 2 (SCA2) is an autosomal-dominant degenerative disorder that is neuropathologically characterized primarily by infratentorial damage, although less severe supratentorial involvement may contribute to the clinical manifestation. Diffusion-weighted imaging (DWI)-Magnetic Resonance Imaging (MRI) studies of SCA2 have enabled in vivo quantification of neurodegeneration in infratentorial regions, whereas supratentorial regions have been explored less thoroughly. We measured microstructural changes in both infratentorial and supratentorial regions in 13 SCA2 patients (9 men, 4 women; mean age, 50 ± 12 years) and 15 controls (10 men, 5 women; mean age, 49 ± 14 years) using DWI-MRI and correlated the DWI changes with disease severity and duration. Disease severity was evaluated using the International Cooperative Ataxia Rating Scale and the Inherited Ataxia Clinical Rating Scale. Cerebral diffusion trace ( D¯) values were generated, and regions of interest (ROIs) and voxel-based analysis with Statistical Parametric Mapping (SPM) were used for data analysis. In SCA2 patients, ROI analysis and SPM confirmed significant increases in D¯ values in the pons, cerebellar white matter (CWM) and middle cerebellar peduncles. Moreover, SPM analysis revealed increased D¯ values in the right thalamus, bilateral temporal cortex/white matter, and motor cortex/pyramidal tract regions. Increased diffusivity in the frontal white matter (FWM) and the CWM was significantly correlated with ataxia severity. DWI-MRI revealed that both infratentorial and supratentorial microstructural changes may characterize SCA2 patients in the course of the disease and might contribute to the severity of the symptoms. PMID:24375449

  1. The Quantitative Effects of Inclusion of Fat on Muscle Diffusion Tensor MRI Measurements

    PubMed Central

    Williams, Sarah E.; Heemskerk, Anneriet M.; Welch, E. Brian; Li, Ke; Damon, Bruce M.; Park, Jane H.

    2012-01-01

    Purpose To determine the minimum water percentage in a muscle region of interest that would allow diffusion tensor (DT-) MRI data to reflect the diffusion properties of pure muscle accurately. Materials and Methods Proton density-weighted images with and without fat saturation were obtained at the mid-thigh in four subjects. Co-registered DT-MR images were used to calculate the diffusion tensor’s eigenvalues and fractional anisotropy. Results The eigenvalues transitioned monotonically as a function of water signal percentage from values near to those expected for pure fat to those for pure muscle. Also, the fractional anisotropy transitioned monotonically from 0.50 (fat) to 0.20 (muscle). For water signal percentages >55%, none of the diffusion indices differed significantly from those for regions of >90% muscle. Conclusion Accounting for the T1 and T2 values of muscle and fat and the pulse sequence properties, it is concluded that, as a conservative estimate, regions must contain at least 76% muscle tissue to reflect the diffusion properties of pure muscle accurately. PMID:23418124

  2. Na and Li ion diffusion in modified ASTM C 1260 test by Magnetic Resonance Imaging (MRI)

    SciTech Connect

    Feng, X. Balcom, B.J.; Thomas, M.D.A.; Bremner, T.W.

    2008-12-15

    In the current study, MRI was applied to investigate lithium and sodium ion diffusion in cement paste and mortars containing inert sand and borosilicate glass. Paste and mortars were treated by complying with ASTM C 1260. Lithium and sodium distribution profiles were collected at different ages after different treatments. Results revealed that sodium ions had a greater diffusion rate than lithium ions, suggesting that Na reaches the aggregate particle surface before Li. Results also showed that Na and Li ions had a competitive diffusion process in mortars; soaking in a solution with higher [Li] favored Li diffusion but hindered Na diffusion. In mortars containing glass, a substantial amount of Li was consumed by the formation of ASR products. When [Li] in soaking solution was reduced to 0.37 N, a distinctive Na distribution profile was observed, indicating the free-state Na ions were continuously transformed to solid reaction products by ASR. Hence, in the modified ASTM C 1260 test, [Li] in the storage solution should be controlled at 0.74 N, in order to completely prevent the consumption of Na ions and thus stop ASR.

  3. The impact of gradient strength on in vivo diffusion MRI estimates of axon diameter

    PubMed Central

    Huang, Susie Y.; Nummenmaa, Aapo; Witzel, Thomas; Duval, Tanguy; Cohen-Adad, Julien; Wald, Lawrence L.; McNab, Jennifer A.

    2014-01-01

    Diffusion magnetic resonance imaging (MRI) methods for axon diameter mapping benefit from higher maximum gradient strengths than are currently available on commercial human scanners. Using a dedicated high-gradient 3 T human MRI scanner with a maximum gradient strength of 300 mT/m, we systematically studied the effect of gradient strength on in vivo axon diameter and density estimates in the human corpus callosum. Pulsed gradient spin echo experiments were performed in a single scan session lasting approximately 2 h on each of three human subjects. The data were then divided into subsets with maximum gradient strengths of 77, 145, 212, and 293 mT/m and diffusion times encompassing short (16 and 25 ms) and long (60 and 94 ms) diffusion time regimes. A three-compartment model of intra-axonal diffusion, extra-axonal diffusion, and free diffusion in cerebrospinal fluid was fitted to the data using a Markov chain Monte Carlo approach. For the acquisition parameters, model, and fitting routine used in our study, it was found that higher maximum gradient strengths decreased the mean axon diameter estimates by two to three fold and decreased the uncertainty in axon diameter estimates by more than half across the corpus callosum. The exclusive use of longer diffusion times resulted in axon diameter estimates that were up to two times larger than those obtained with shorter diffusion times. Axon diameter and density maps appeared less noisy and showed improved contrast between different regions of the corpus callosum with higher maximum gradient strength. Known differences in axon diameter and density between the genu, body, and splenium of the corpus callosum were preserved and became more reproducible at higher maximum gradient strengths. Our results suggest that an optimal q-space sampling scheme for estimating in vivo axon diameters should incorporate the highest possible gradient strength. The improvement in axon diameter and density estimates that we demonstrate from

  4. The Unusual Behavior of Solar Wind 3He++

    NASA Astrophysics Data System (ADS)

    Gloeckler, George; Fisk, L. A.; Geiss, J.

    2016-07-01

    The first measurements of the isotopic ratio of solar wind He by the Apollo SWC experiment revealed that 3He/4He is not constant, but varies from ˜~4•10-4 to ˜~5.5•10-4. Such variations are modest compared with the 3He/4He variations often seen in Helium-3 rich SEP events. Here we report and compare detailed measurements with ACE/SWICS of the densities, bulk speeds and thermal speeds of solar wind 1H+, 4He++ and 3He++ during one Carrington rotation (in January 2005). The most remarkable finding is the factor of ˜~100 variation in the solar wind 3He++/4He++ number density ratio from a low value of ˜~5•10-5 to a high value of ˜~6•10-3. The highest ratios occurred during four time intervals of one to two days each. Large ratios are observed during periods of low (< ˜~20 km/s) 3He++ thermal speeds and when the bulk speeds as well as the thermal speeds of 1H+, 4He++ and 3He++ are almost the same. Small ratios, on the other hand, were found when the spread between the thermal speeds as well as between the bulk speeds of 1H+, 4He++ and 3He++ was large. During times of small 3He++/4He++ ratios the thermal speed of 3He++ was above 20 km/s, and the proton and 4He++ thermal speeds exceeded ˜~50 km/s and ˜~35 km/s, respectively. We will examine additional time periods to determine whether the compositional variations of solar wind helium during this particular Carrington rotation are unusual or common, and will speculate on possible mechanisms that could produce the factor of 100 variations in the isotopic solar wind He ratio.

  5. Dressed spin of polarized {sup 3}He in a cell

    SciTech Connect

    Chu, P.-H.; Esler, A. M.; Peng, J. C.; Beck, D. H.; Chandler, D. E.; Clayton, S.; Williamson, S.; Yoder, J.; Hu, B.-Z.; Ngan, S. Y.; Sham, C. H.; So, L. H.

    2011-08-15

    We report a measurement of the modification of the effective precession frequency of polarized {sup 3}He atoms in response to a dressing field in a room-temperature cell. The {sup 3}He atoms were polarized using the metastability spin-exchange method. An oscillating dressing field was then applied perpendicular to the constant magnetic field. Modification of the {sup 3}He effective precession frequency was observed over a broad range of the amplitude and frequency of the dressing field. The observed effects are compared with calculations based on quantum optics formalism.

  6. Dressed spin of polarized 3He in a cell

    NASA Astrophysics Data System (ADS)

    Chu, P.-H.; Esler, A. M.; Peng, J. C.; Beck, D. H.; Chandler, D. E.; Clayton, S.; Hu, B.-Z.; Ngan, S. Y.; Sham, C. H.; So, L. H.; Williamson, S.; Yoder, J.

    2011-08-01

    We report a measurement of the modification of the effective precession frequency of polarized 3He atoms in response to a dressing field in a room-temperature cell. The 3He atoms were polarized using the metastability spin-exchange method. An oscillating dressing field was then applied perpendicular to the constant magnetic field. Modification of the 3He effective precession frequency was observed over a broad range of the amplitude and frequency of the dressing field. The observed effects are compared with calculations based on quantum optics formalism.

  7. Recent Advances of Polarized 3He Target at Jefferson Lab

    SciTech Connect

    Yi Qiang

    2011-10-01

    Polarized {sup 3}He target has been widely used in nuclear and particle experiments to study the neutron structure in the spin degree of freedom, as most of the {sup 3}He spin is carried by the unpaired neutron. Spin-Exchange Optical Pumping (SEOP) process is used in Jefferson Lab Hall A to polarize its {sup 3}He target. Through developments in recent years, both the performance and corresponding polarimetry of such a target were greatly improved. Several experiments recently carried out in Hall A benefited remarkably from this target for the record highest figure of merit.

  8. Neutron Detection Alternatives to 3He for National Security Applications

    SciTech Connect

    Kouzes, Richard T.; Ely, James H.; Erikson, Luke E.; Kernan, Warnick J.; Lintereur, Azaree T.; Siciliano, Edward R.; Stephens, Daniel L.; Stromswold, David C.; Van Ginhoven, Renee M.; Woodring, Mitchell L.

    2010-11-21

    One of the main uses for 3He is in gas proportional counters for neutron detection. Large radiation detection systems deployed for homeland security and proliferation detection applications use such systems. Due to the large increase in use of 3He for homeland security and basic research, the supply has dwindled, and can no longer meet the demand. This has led to the search for an alternative technology to replace the use of 3He-based neutron detectors. In this paper, we review the testing of currently commercially available alternative technologies for neutron detection in large systems used in various national security applications.

  9. Can musical training influence brain connectivity? Evidence from diffusion tensor MRI.

    PubMed

    Moore, Emma; Schaefer, Rebecca S; Bastin, Mark E; Roberts, Neil; Overy, Katie

    2014-01-01

    In recent years, musicians have been increasingly recruited to investigate grey and white matter neuroplasticity induced by skill acquisition. The development of Diffusion Tensor Magnetic Resonance Imaging (DT-MRI) has allowed more detailed investigation of white matter connections within the brain, addressing questions about the effect of musical training on connectivity between specific brain regions. Here, current DT-MRI analysis techniques are discussed and the available evidence from DT-MRI studies into differences in white matter architecture between musicians and non-musicians is reviewed. Collectively, the existing literature tends to support the hypothesis that musical training can induce changes in cross-hemispheric connections, with significant differences frequently reported in various regions of the corpus callosum of musicians compared with non-musicians. However, differences found in intra-hemispheric fibres have not always been replicated, while findings regarding the internal capsule and corticospinal tracts appear to be contradictory. There is also recent evidence to suggest that variances in white matter structure in non-musicians may correlate with their ability to learn musical skills, offering an alternative explanation for the structural differences observed between musicians and non-musicians. Considering the inconsistencies in the current literature, possible reasons for conflicting results are offered, along with suggestions for future research in this area. PMID:24961769

  10. Can Musical Training Influence Brain Connectivity? Evidence from Diffusion Tensor MRI

    PubMed Central

    Moore, Emma; Schaefer, Rebecca S.; Bastin, Mark E.; Roberts, Neil; Overy, Katie

    2014-01-01

    In recent years, musicians have been increasingly recruited to investigate grey and white matter neuroplasticity induced by skill acquisition. The development of Diffusion Tensor Magnetic Resonance Imaging (DT-MRI) has allowed more detailed investigation of white matter connections within the brain, addressing questions about the effect of musical training on connectivity between specific brain regions. Here, current DT-MRI analysis techniques are discussed and the available evidence from DT-MRI studies into differences in white matter architecture between musicians and non-musicians is reviewed. Collectively, the existing literature tends to support the hypothesis that musical training can induce changes in cross-hemispheric connections, with significant differences frequently reported in various regions of the corpus callosum of musicians compared with non-musicians. However, differences found in intra-hemispheric fibres have not always been replicated, while findings regarding the internal capsule and corticospinal tracts appear to be contradictory. There is also recent evidence to suggest that variances in white matter structure in non-musicians may correlate with their ability to learn musical skills, offering an alternative explanation for the structural differences observed between musicians and non-musicians. Considering the inconsistencies in the current literature, possible reasons for conflicting results are offered, along with suggestions for future research in this area. PMID:24961769

  11. Crease surfaces: from theory to extraction and application to diffusion tensor MRI.

    PubMed

    Schultz, Thomas; Theisel, Holger; Seidel, Hans-Peter

    2010-01-01

    Crease surfaces are two-dimensional manifolds along which a scalar field assumes a local maximum (ridge) or a local minimum (valley) in a constrained space. Unlike isosurfaces, they are able to capture extremal structures in the data. Creases have a long tradition in image processing and computer vision, and have recently become a popular tool for visualization. When extracting crease surfaces, degeneracies of the Hessian (i.e., lines along which two eigenvalues are equal) have so far been ignored. We show that these loci, however, have two important consequences for the topology of crease surfaces: First, creases are bounded not only by a side constraint on eigenvalue sign, but also by Hessian degeneracies. Second, crease surfaces are not, in general, orientable. We describe an efficient algorithm for the extraction of crease surfaces which takes these insights into account and demonstrate that it produces more accurate results than previous approaches. Finally, we show that diffusion tensor magnetic resonance imaging (DT-MRI) stream surfaces, which were previously used for the analysis of planar regions in diffusion tensor MRI data, are mathematically ill-defined. As an example application of our method, creases in a measure of planarity are presented as a viable substitute. PMID:19910665

  12. Shear Modulus and Dislocations in bcc Solid ^3He

    NASA Astrophysics Data System (ADS)

    Cheng, Zhi Gang; Souris, Fabien; Beamish, John

    2016-05-01

    The shear modulus of hcp ^4He decreases significantly above ˜ 200 mK, as ^3He impurities unbind from dislocations, unpinning them, and softening the crystal. Here we report shear modulus measurements on a fermi quantum solid: bcc ^3He. In contrast to previous low-frequency measurements, which did not show dislocation softening in this system, we have observed a drop in shear modulus, accompanied by a dissipation peak, which we attribute to the unpinning of dislocations as ^4He impurities unbind. For large stresses, impurities cannot pin the dislocations and the low temperature stiffening is suppressed. At high frequencies, the modulus changes and dissipation peaks shift to higher temperature, indicating that the unbinding is thermally activated. For a 58 bar bcc ^3He crystal, we find an activation energy of 0.27 K, smaller than the 0.7 K binding energy for ^3He impurities in hcp ^4He.

  13. Diffusion-Weighted MRI of Malignant versus Benign Portal Vein Thrombosis

    PubMed Central

    Ahn, Jhii-Hyun; Cho, Eun-Suk; Chung, Jae-Joon; Kim, Joo Hee; Kim, Ki Whang

    2016-01-01

    Objective To validate the diffusion-weighted MRI (DWI) for differentiation of benign from malignant portal vein thrombosis. Materials and Methods The Institutional Review Board approved this retrospective study and waived informed consent. A total of 59 consecutive patients (52 men and 7 women, aged 40–85 years) with grossly defined portal vein thrombus (PVT) on hepatic MRI were retrospectively analyzed. Among them, liver cirrhosis was found in 45 patients, and hepatocellular carcinoma in 47 patients. DWI was performed using b values of 50 and 800 sec/mm2 at 1.5-T unit. A thrombus was considered malignant if it enhanced on dynamic CT or MRI; otherwise, it was considered bland. There were 18 bland thrombi and 49 malignant thrombi in 59 patients, including 8 patients with simultaneous benign and malignant PVT. Mean apparent diffusion coefficients (ADCs) of benign and malignant PVTs were compared by using Mann-Whitney U test. Diagnostic accuracy was evaluated using receiver operating characteristic (ROC) curve analysis. Results The mean ADC ± standard deviation of bland and malignant PVT were 1.00 ± 0.39 × 10-3 mm2/sec and 0.92 ± 0.25 × 10-3 mm2/sec, respectively; without significant difference (p = 0.799). The area under ROC curve for ADC was 0.520. An ADC value of > 1.35 × 10-3 mm2/sec predicted bland PVT with a specificity of 94.6% (95% confidence interval [CI]: 84.9–98.9%) and a sensitivity of 22.2% (95% CI: 6.4–47.6%), respectively. Conclusion Due to the wide range and considerable overlap of the ADCs, DWI cannot differentiate the benign from malignant thrombi efficiently. PMID:27390544

  14. Prediction of background parenchymal enhancement on breast MRI using mammography, ultrasonography, and diffusion-weighted imaging

    PubMed Central

    Kawamura, Akiko; Satake, Hiroko; Ishigaki, Satoko; Ikeda, Mitsuru; Kimura, Reiko; Shimamoto, Kazuhiro; Naganawa, Shinji

    2015-01-01

    ABSTRACT This retrospective study assessed the effects of menopausal status and menstrual cycle on background parenchymal enhancement (BPE) of breast magnetic resonance imaging (MRI), and investigated whether the degree of BPE can be predicted by findings of mammography, ultrasonography (US), and diffusion-weighted MR imaging (DWI). There were 160 study patients (80 premenopausal, 80 postmenopausal). Degree of BPE was classified into minimal, mild, moderate, or marked. Mammographic density was classified into fatty, scattered, heterogeneously dense, and extremely dense. BP echotexture on US and BP intensity on DWI were visually classified as homogeneous or heterogeneous. Apparent diffusion coefficient (ADC) values of normal breast tissue were measured. Associations of the degree of BPE with menopausal status, menstrual cycle, or imaging features were evaluated by univariate and multivariate analyses. No significant correlation was found between mammographic density and BPE (p=0.085), whereas menopausal status (p=0.000), BP echotexture (p=0.000), and BP intensity on DWI (p= 0.000), and ADC values (p=0.000) showed significant correlations with BPE. Multivariate analysis showed that postmenopausal status was an independent predictor of minimal BPE (p=0.002, OR=3.743). In premenopausal women, there was no significant correlation between menstrual cycle and BPE, whereas BP echotexture was an independent predictor of whether BPE was less than mild or greater than moderate (p=0.001, OR=26.575). BPE on breast MRI is associated with menopausal status and the findings of US and DWI. Because premenopausal women with heterogeneous BP echotexture may be predicted to show moderate or marked BPE, scheduling of breast MRI should preferentially be adjusted to the menstrual cycle. PMID:26412889

  15. Regional MRI Diffusion, White-Matter Hyperintensities, and Cognitive Function in Alzheimer's Disease and Vascular Dementia

    PubMed Central

    Scrascia, Federica; Quattrocchi, Carlo Cosimo; Errante, Yuri; Gangemi, Emma; Curcio, Giuseppe; Ursini, Francesca; Silvestrini, Mauro; Maggio, Paola; Beomonte Zobel, Bruno; Rossini, Paolo Maria; Pasqualetti, Patrizio; Falsetti, Lorenzo; Vernieri, Fabrizio

    2016-01-01

    Background and Purpose An increase in brain water diffusivity as measured using magnetic resonance imaging (MRI) has been recently reported in normal-appearing white matter (NAWM) in patients affected by cognitive impairment. However, it remains to be clarified if this reflects an overt neuronal tissue disruption that leads to degenerative or microvascular lesions. This question was addressed by comparing the regional MRI apparent diffusion coefficients (ADCs) of NAWM in patients affected by Alzheimer's disease (AD) or vascular dementia (VaD). The relationships of ADCs with the white-matter hyperintensity (WMH) burden, carotid atherosclerosis, and cognitive performance were also investigated. Methods Forty-nine AD and 31 VaD patients underwent brain MRI to assess the WMH volume and regional NAWM ADCs, neuropsychological evaluations, and carotid ultrasound to assess the plaque severity and intima-media thickness (IMT). Results Regional ADCs in NAWM did not differ between VaD and AD patients, while the WMH volume was greater in VaD than in AD patients. The ADC in the anterior corpus callosum was related to the WMH volume, while a greater carotid IMT was positively correlated with the temporal ADC and WMH volume. The memory performance was worse in patients with higher temporal ADCs. Constructional praxis scores were related to ADCs in the frontal, and occipital lobes, in the anterior and posterior corpus callosum as well as to the WMH volume. Abstract reasoning was related to frontal, parietal, and temporal ADCs. Conclusions Our data show that higher regional ADCs in NAWM are associated with microcirculatory impairment, as depicted by the WMH volume. Moreover, regional ADCs in NAWM are differently associated with the neuropsychological performances in memory, constructional praxia, and abstract reasoning domains. PMID:27074295

  16. Diffusion-weighted MRI for imaging cell death after cytotoxic or apoptosis-inducing therapy

    PubMed Central

    Papaevangelou, E; Almeida, G S; Jamin, Y; Robinson, S P; deSouza, N M

    2015-01-01

    Background: Non-invasive serial imaging is desirable to detect processes such as necrotic and apoptotic cell death in cancer patients undergoing treatment. This study investigated the use of diffusion-weighted (DW-) magnetic resonance imaging (MRI) for imaging cell death induced by either a cytotoxic drug (irinotecan), or the apoptosis-inducing agent birinapant, in human tumour xenografts in vivo. Methods: Nude mice bearing human SW620 colon carcinoma xenografts were treated with vehicle, irinotecan (50 mg kg−1) or birinapant (30 mg kg−1) for up to 5 days. DW-MRI was performed prior to and on days 1, 3 and 5 during treatment. Assessment of tumour apoptosis and necrosis ex vivo was used to validate the imaging findings. Results: Both irinotecan and birinapant induced significant tumour growth delay. Irinotecan induced a small increase in the tumour apparent diffusion coefficient (ADC) after 1 day, with a 20 and 30% increase at days 3 and 5 respectively. ADC was unchanged in the vehicle- and birinapant-treated tumours despite a growth delay in the latter. Histological analysis showed that irinotecan increased necrosis at days 3 and 5, and induced apoptosis after 1 day, compared with vehicle. Birinapant induced apoptosis after day 3, but had no effect on tumour necrosis. Conclusions: Tumour ADC changes after irinotecan treatment were associated with the induction of a mixture of necrotic and apoptotic cell death, whereas induction of apoptosis alone with birinapant was not sufficient to induce changes in tissue microstructure that were detectable with DW-MRI. ADC is a useful non-invasive biomarker for early detection of response to cytotoxic drugs, but false negatives may arise while detecting apoptotic response to birinapant. PMID:25880014

  17. Apparent Diffusion Coefficient analysis of encephalitis: A comparative study with topographic evaluation and conventional MRI findings

    PubMed Central

    Katirag, Ahmet; Beker-Acay, Mehtap; Unlu, Ebru; Demirbas, Hayri; Demirturk, Nese

    2016-01-01

    Objective: Our purpose was to reveal the efficiency of diffusion weighted imaging (DWI) in the diagnosis of encephalitis, and to determine the relation between the apparent diffusion coefficient (ADC) values, the onset of the clinical symptoms, and the lesion extent. Methods: Conventional magnetic resonance imaging (MRI) was performed in 17 patients with encephalitis diagnosed on the basis of laboratory, clinical and radiologic findings during 2009 and 2015. Based on the duration between the onset of the symptoms and the brain MRI findings, the patients were divided into three groups. ADC values of the encephalitis lesion, the lesions’ topographic analysis score, deep gray matter involvement, patients’ clinical situation and the duration of the arrival to the clinic was examined. Results: Mean ADC values were 0,988±0,335 x10-3 mm2/s in group I (0-2 days), 1,045±0,347 x10-3 mm2/s in Group-II (3-7 days), 1,451±0,225 x10-3 mm2/s in Group-III (8 days and over). The relation between the ADC values and the duration of the arrival, topographic analysis score, the relation between the patients’ clinical situation and the deep gray matter involvement were found to be statistically significant. The deep gray matter involvement was demonstrated more clearly by FLAIR images when compared with DWI. Conclusion: Conventional MRI sequences may be insufficient in showing the encephalitis lesion. DWI must be added to the imaging modalities immediately in the cases suspected of having encephalitis. PMID:27375722

  18. Polar Phase of Superfluid (3)He in Anisotropic Aerogel.

    PubMed

    Dmitriev, V V; Senin, A A; Soldatov, A A; Yudin, A N

    2015-10-16

    We report the first observation of the polar phase of superfluid (3)He. This phase appears in (3)He confined in a new type of aerogel with a nearly parallel arrangement of strands which play the role of ordered impurities. Our experiments qualitatively agree with theoretical predictions and suggest that in other systems with unconventional Cooper pairing (e.g., in unconventional superconductors) similar phenomena may be found in the presence of anisotropic impurities. PMID:26550884

  19. Development of a Polarized 3He Ion Source for RHIC

    SciTech Connect

    Milner, Richard G.

    2013-01-15

    The goal of the project was to design and construct a source of polarized 3He atoms for injection into EBIS. This is the initial step in producing polarized 3He beams in RHIC in collaboration with physicists from Columbia University and Brookhaven National Laboratory. These beams can be used to probe the spin structure of the neutron in the existing RHIC complex as well as to measure precisely the Bjorken Sum Rule at a future eRHIC electron-ion collider.

  20. The non-local bootstrap--estimation of uncertainty in diffusion MRI.

    PubMed

    Yap, Pew-Thian; An, Hongyu; Chen, Yasheng; Shen, Dinggang

    2013-01-01

    Diffusion MRI is a noninvasive imaging modality that allows for the estimation and visualization of white matter connectivity patterns in the human brain. However, due to the low signal-to-noise ratio (SNR) nature of diffusion data, deriving useful statistics from the data is adversely affected by different sources of measurement noise. This is aggravated by the fact that the sampling distribution of the statistic of interest is often complex and unknown. In situations as such, the bootstrap, due to its distribution-independent nature, is an appealing tool for the estimation of the variability of almost any statistic, without relying on complicated theoretical calculations, but purely on computer simulation. In this work, we present new bootstrap strategies for variability estimation of diffusion statistics in association with noise. In contrast to the residual bootstrap, which relies on a predetermined data model, or the repetition bootstrap, which requires repeated signal measurements, our approach, called the non-local bootstrap (NLB), is non-parametric and obviates the need for time-consuming multiple acquisitions. The key assumption of NLB is that local image structures recur in the image. We exploit this self-similarity via a multivariate non-parametric kernel regression framework for bootstrap estimation of uncertainty. Evaluation of NLB using a set of high-resolution diffusion-weighted images, with lower than usual SNR due to the small voxel size, indicates that NLB is markedly more robust to noise and results in more accurate inferences. PMID:24683985

  1. Evaluating Contextual Processing in Diffusion MRI: Application to Optic Radiation Reconstruction for Epilepsy Surgery

    PubMed Central

    Tax, Chantal M. W.; Duits, Remco; Vilanova, Anna; ter Haar Romeny, Bart M.; Hofman, Paul; Wagner, Louis; Leemans, Alexander; Ossenblok, Pauly

    2014-01-01

    Diffusion MRI and tractography allow for investigation of the architectural configuration of white matter in vivo, offering new avenues for applications like presurgical planning. Despite the promising outlook, there are many pitfalls that complicate its use for (clinical) application. Amongst these are inaccuracies in the geometry of the diffusion profiles on which tractography is based, and poor alignment with neighboring profiles. Recently developed contextual processing techniques, including enhancement and well-posed geometric sharpening, have shown to result in sharper and better aligned diffusion profiles. However, the research that has been conducted up to now is mainly of theoretical nature, and so far these techniques have only been evaluated by visual inspection of the diffusion profiles. In this work, the method is evaluated in a clinically relevant application: the reconstruction of the optic radiation for epilepsy surgery. For this evaluation we have developed a framework in which we incorporate a novel scoring procedure for individual pathways. We demonstrate that, using enhancement and sharpening, the extraction of an anatomically plausible reconstruction of the optic radiation from a large amount of probabilistic pathways is greatly improved in three healthy controls, where currently used methods fail to do so. Furthermore, challenging reconstructions of the optic radiation in three epilepsy surgery candidates with extensive brain lesions demonstrate that it is beneficial to integrate these methods in surgical planning. PMID:25077946

  2. sup 3 He and methane in the Gulf of Aden

    SciTech Connect

    Jean-Baptiste, P.; Alaux, G. ); Belviso, S.; Nguyen, B.C.; Mihalopoulos, N. )

    1990-01-01

    During the OCEAT cruise (July, 1987), the vertical and spatial distributions of {sup 3}He and methane were measured at six stations over the West Sheba Ridge (Gulf of Aden). The results show significant {delta}{sup 3}He anomalies (up to 49%). The authors conclude that the origin of this signal is independent from the well known Red Sea hydrothermal {sup 3}He (of the Red Sea Brines). Thus, active hydrothermalism occurs in this extensional basin associated with spreading along an incipient mid-ocean ridge. The {sup 3}He input from the Gulf of Aden accounts for the S-N positive gradient in {sup 3}He concentration observed in the western part of the Indian Ocean. Several methane anomalies are also present (up to 664 nl/l,i.e., 25 times the regional methane background), but the CH{sub 4} and {sup 3}He signals are not systematically correlated, suggesting complex production and consumption mechanisms of methane in these areas. The authors results confirm previous observations in the South West Pacific Ocean.

  3. Oscillating gradient diffusion MRI reveals unique microstructural information in normal and hypoxia-ischemia injured mouse brains

    PubMed Central

    Wu, Dan; Martin, Lee J.; Northington, Frances J.; Zhang, Jiangyang

    2014-01-01

    Purpose We investigated whether oscillating gradient diffusion MRI (dMRI) can provide information on brain microstructural changes after formaldehyde fixation and after hypoxic-ischemic (HI) injury beyond that provided by conventional dMRI. Methods Pulsed gradient spin echo (PGSE) and oscillating gradient spin echo (OGSE) dMRI of the adult mouse brain was performed in vivo (50-200 Hz, b = 600 mm2/s), and a similar protocol was applied to neonatal mouse brains at 24 hours after unilateral hypoxia-ischemia. Animals were perfusion fixed with 4% paraformaldehyde for ex vivo dMRI and histology. Results Apparent diffusion coefficients (ADCs) measured in the live adult mouse brain presented tissue-dependent frequency-dependence. In vivo OGSE-ADC maps at high oscillating frequencies (>100Hz) showed clear contrast between the molecular layer and granule cell layer in the adult mouse cerebellum. Formaldehyde fixation significantly altered the temporal diffusion spectra in several brain regions. In neonatal mouse brains with HI injury, in vivo ADC measurements from edema regions showed diminished edema contrasts at 200 Hz compared to the PGSE results. Histology showed severe tissue swelling and necrosis in the edema regions. Conclusion The results demonstrate the unique ability of OGSE-dMRI in delineating tissue microstructures at different spatial scales. PMID:25168861

  4. A rapid method for the measurement and estimation of CO2 diffusivity in liquid hydrocarbon-saturated porous media using MRI.

    PubMed

    Zhao, Yuechao; Chen, Junlin; Yang, Mingjun; Liu, Yu; Song, Yongchen

    2016-05-01

    In this study, magnetic resonance imaging (MRI) was used to dynamically visualize the diffusion process of CO2 in porous media saturated with liquid hydrocarbon. Based on the assumption of semi-infinite media, effective CO2 diffusivity was obtained directly by the nonlinear fitting of one MR profile during the diffusion process. These experimental findings obtained based on MRI method showed a close agreement with the conventional pressure-volume-temperature method. The novel MRI-based technique is a time-saving approach that can reduce the duration of CO2 diffusivity measurement more than 90%, and realize rapid and accurate measurement and estimation of CO2 diffusivity. PMID:26707850

  5. Added value of diffusion-weighted MRI in detection of cervical cancer recurrence: comparison with morphologic and dynamic contrast-enhanced MRI sequences

    PubMed Central

    Lucas, Rita; Dias, João Lopes; Cunha, Teresa Margarida

    2015-01-01

    PURPOSE We aimed to evaluate the added value of diffusion-weighted imaging (DWI) to standard magnetic resonance imaging (MRI) for detecting post-treatment cervical cancer recurrence. The detection accuracy of T2-weighted (T2W) images was compared with that of T2W MRI combined with either dynamic contrast-enhanced (DCE) MRI or DWI. METHODS Thirty-eight women with clinically suspected uterine cervical cancer recurrence more than six months after treatment completion were examined with 1.5 Tesla MRI including T2W, DCE, and DWI sequences. Disease was confirmed histologically and correlated with MRI findings. The diagnostic performance of T2W imaging and its combination with either DCE or DWI were analyzed. Sensitivity, positive predictive value, and accuracy were calculated. RESULTS Thirty-six women had histologically proven recurrence. The accuracy for recurrence detection was 80% with T2W/DCE MRI and 92.1% with T2W/DWI. The addition of DCE sequences did not significantly improve the diagnostic ability of T2W imaging, and this sequence combination misclassified two patients as falsely positive and seven as falsely negative. The T2W/DWI combination revealed a positive predictive value of 100% and only three false negatives. CONCLUSION The addition of DWI to T2W sequences considerably improved the diagnostic ability of MRI. Our results support the inclusion of DWI in the initial MRI protocol for the detection of cervical cancer recurrence, leaving DCE sequences as an option for uncertain cases. PMID:26200480

  6. Integrative analysis of diffusion-weighted MRI and genomic data to inform treatment of glioblastoma.

    PubMed

    Jajamovich, Guido H; Valiathan, Chandni R; Cristescu, Razvan; Somayajula, Sangeetha

    2016-09-01

    Gene expression profiling from glioblastoma (GBM) patients enables characterization of cancer into subtypes that can be predictive of response to therapy. An integrative analysis of imaging and gene expression data can potentially be used to obtain novel biomarkers that are closely associated with the genetic subtype and gene signatures and thus provide a noninvasive approach to stratify GBM patients. In this retrospective study, we analyzed the expression of 12,042 genes for 558 patients from The Cancer Genome Atlas (TCGA). Among these patients, 50 patients had magnetic resonance imaging (MRI) studies including diffusion weighted (DW) MRI in The Cancer Imaging Archive (TCIA). We identified the contrast enhancing region of the tumors using the pre- and post-contrast T1-weighted MRI images and computed the apparent diffusion coefficient (ADC) histograms from the DW-MRI images. Using the gene expression data, we classified patients into four molecular subtypes, determined the number and composition of genes modules using the gap statistic, and computed gene signature scores. We used logistic regression to find significant predictors of GBM subtypes. We compared the predictors for different subtypes using Mann-Whitney U tests. We assessed detection power using area under the receiver operating characteristic (ROC) analysis. We computed Spearman correlations to determine the associations between ADC and each of the gene signatures. We performed gene enrichment analysis using Ingenuity Pathway Analysis (IPA). We adjusted all p values using the Benjamini and Hochberg method. The mean ADC was a significant predictor for the neural subtype. Neural tumors had a significantly lower mean ADC compared to non-neural tumors ([Formula: see text]), with mean ADC of [Formula: see text] and [Formula: see text] for neural and non-neural tumors, respectively. Mean ADC showed an area under the ROC of 0.75 for detecting neural tumors. We found eight gene modules in the GBM cohort. The

  7. Quantifying the effect of tissue deformation on diffusion-weighted MRI: a mathematical model and an efficient simulation framework applied to cardiac diffusion imaging.

    PubMed

    Mekkaoui, Imen; Moulin, Kevin; Croisille, Pierre; Pousin, Jerome; Viallon, Magalie

    2016-08-01

    Cardiac motion presents a major challenge in diffusion weighted MRI, often leading to large signal losses that necessitate repeated measurements. The diffusion process in the myocardium is difficult to investigate because of the unqualified sensitivity of diffusion measurements to cardiac motion. A rigorous mathematical formalism is introduced to quantify the effect of tissue motion in diffusion imaging. The presented mathematical model, based on the Bloch-Torrey equations, takes into account deformations according to the laws of continuum mechanics. Approximating this mathematical model by using finite elements method, numerical simulations can predict the sensitivity of the diffusion signal to cardiac motion. Different diffusion encoding schemes are considered and the diffusion weighted MR signals, computed numerically, are compared to available results in literature. Our numerical model can identify the existence of two time points in the cardiac cycle, at which the diffusion is unaffected by myocardial strain and cardiac motion. Of course, these time points depend on the type of diffusion encoding scheme. Our numerical results also show that the motion sensitivity of the diffusion sequence can be reduced by using either spin echo technique with acceleration motion compensation diffusion gradients or stimulated echo acquisition mode with unipolar and bipolar diffusion gradients. PMID:27385441

  8. Quantifying the effect of tissue deformation on diffusion-weighted MRI: a mathematical model and an efficient simulation framework applied to cardiac diffusion imaging

    NASA Astrophysics Data System (ADS)

    Mekkaoui, Imen; Moulin, Kevin; Croisille, Pierre; Pousin, Jerome; Viallon, Magalie

    2016-08-01

    Cardiac motion presents a major challenge in diffusion weighted MRI, often leading to large signal losses that necessitate repeated measurements. The diffusion process in the myocardium is difficult to investigate because of the unqualified sensitivity of diffusion measurements to cardiac motion. A rigorous mathematical formalism is introduced to quantify the effect of tissue motion in diffusion imaging. The presented mathematical model, based on the Bloch–Torrey equations, takes into account deformations according to the laws of continuum mechanics. Approximating this mathematical model by using finite elements method, numerical simulations can predict the sensitivity of the diffusion signal to cardiac motion. Different diffusion encoding schemes are considered and the diffusion weighted MR signals, computed numerically, are compared to available results in literature. Our numerical model can identify the existence of two time points in the cardiac cycle, at which the diffusion is unaffected by myocardial strain and cardiac motion. Of course, these time points depend on the type of diffusion encoding scheme. Our numerical results also show that the motion sensitivity of the diffusion sequence can be reduced by using either spin echo technique with acceleration motion compensation diffusion gradients or stimulated echo acquisition mode with unipolar and bipolar diffusion gradients.

  9. Zeeman relaxation of cold atomic iron and nickel in collisions with {sup 3}He

    SciTech Connect

    Johnson, Cort; Newman, Bonna; Kleppner, Daniel; Greytak, Thomas J.; Brahms, Nathan; Doyle, John M.

    2010-06-15

    We have measured the ratio {gamma} of the diffusion cross section to the angular momentum reorientation cross section in the colliding Fe-{sup 3}He and Ni-{sup 3}He systems. Nickel (Ni) and iron (Fe) atoms are introduced via laser ablation into a cryogenically cooled experimental cell containing cold (<1 K) {sup 3}He buffer gas. Elastic collisions rapidly cool the translational temperature of the ablated atoms to the {sup 3}He temperature. {gamma} is extracted by measuring the decays of the atomic Zeeman sublevels. For our experimental conditions, thermal energy is comparable to the Zeeman splitting. As a result, thermal excitations between Zeeman sublevels significantly impact the observed decay. To determine {gamma} accurately, we introduce a model of Zeeman-state dynamics that includes thermal excitations. We find {gamma}{sub Ni-}{sup 3}{sub He}=5x10{sup 3} and {gamma}{sub Fe-}{sup 3}{sub He{<=}}3x10{sup 3} at 0.75 K in a 0.8-T magnetic field. These measurements are interpreted in the context of submerged shell suppression of spin relaxation, as studied previously in transition metals and rare-earth-metal atoms [C. I. Hancox, S. C. Doret, M. T. Hummon, R. V. Krems, and J. M. Doyle, Phys. Rev. Lett. 94, 013201 (2005); C. I. Hancox, S. C. Doret, M. T. Hummon, L. Luo, and J. M. Doyle, Nature (London) 431, 281 (2004); A. Buchachenko, G. Chaasiski, and M. Szczniak, Eur. Phys. J. D 45, 147 (2007)].

  10. MRI

    MedlinePlus

    ... scan is an imaging test that uses powerful magnets and radio waves to create pictures of the ... in your eyes) Because the MRI contains strong magnets, metal objects are not allowed into the room ...

  11. Final state interaction in (3He, 2He) reactions

    NASA Astrophysics Data System (ADS)

    Congedo, T. V.; Lee-Fan, I. S.; Cohen, B. L.

    1980-09-01

    The two protons from 2He breakup following (3He, 2He) reactions were detected in coincidence, and energy and angular correlations between them were studied and compared with predictions of the final state interaction theories of Watson and Migdal and Phillips, Griffy, and Biedenharn. The angular correlation between the breakup protons drops off much faster than predicted by these theories; a final state interaction empirically derived to fit the angular correlation is sharply peaked at a breakup energy ~ 0.6 MeV and is quite narrow. Energy distributions of the protons have a dip at the center for small correlation angles which disappears at larger angles. This is well predicted by all final state interaction theories but the slopes of these distributions are much better fit by the empirical final state interaction than by Watson and Migdal or by Phillips, Griffy, and Biedenharn. By maintaining a constant small correlation angle (proton detectors close together), 2He angular distributions were measured and found to be in good agreement with distorted-wave Born approximation predictions. NUCLEAR REACTIONS 64Ni(3He, 2p), E=13 MeV; measured σ(θ), pp correlation; deduced pp FSI; calculated 2He detection efficiency. 9Be(3He, 2p), E=13 MeV; measured σ(θ). 27Al, 90Zr(3He, 2p) measured pp correlation. 51V, 65Cu, 89Y(3He, 2p), E=13 MeV, 17 MeV, measured σ(θ), DWBA analysis.

  12. 3He Films as Model Strongly Correlated Fermion Systems

    SciTech Connect

    Neumann, Michael; Casey, Andrew; Nyeki, Jan; Cowan, Brian; Saunders, John

    2006-09-07

    Helium films on graphite are atomically layered. This allows a wide variety of studies of strong correlations in two dimensions with density as a continuously tunable parameter. Studies of a monolayer of 3He adsorbed on graphite plated by a bi-layer of HD find a divergence of effective mass with increasing density, corresponding to a Mott-Hubbard transition between a 2D Fermi liquid and a quantum spin liquid phase. While the Fermi liquid survives in 2D, non-Fermi liquid features remain at finite T, recent theories find that this correction arises from the spin component of the backscattering amplitude. In another experiment a 3He film is grown on graphite plated by a bi-layer of 3He. The first 3He layer only solidifies in the presence of an overlayer. However in the regime in which the system comprises a 3He fluid bilayer, we observe a striking maximum in the temperature dependence of both heat capacity and magnetization. This feature is driven towards T = 0 with increasing film coverage, suggestive of a quantum critical point. Well below the maximum a linear temperature dependence of the heat capacity is recovered; the coverage dependence of the effective mass identifies a (bandwidth driven) Mott-Hubbard transition at 9.8 nm-2.

  13. Polarized 3He Spin Filters for Slow Neutron Physics

    PubMed Central

    Gentile, T. R.; Chen, W. C.; Jones, G. L.; Babcock, E.; Walker, T. G.

    2005-01-01

    Polarized 3He spin filters are needed for a variety of experiments with slow neutrons. Their demonstrated utility for highly accurate determination of neutron polarization are critical to the next generation of betadecay correlation coefficient measurements. In addition, they are broadband devices that can polarize large area and high divergence neutron beams with little gamma-ray background, and allow for an additional spin-flip for systematic tests. These attributes are relevant to all neutron sources, but are particularly well-matched to time of flight analysis at spallation sources. There are several issues in the practical use of 3He spin filters for slow neutron physics. Besides the essential goal of maximizing the 3He polarization, we also seek to decrease the constraints on cell lifetimes and magnetic field homogeneity. In addition, cells with highly uniform gas thickness are required to produce the spatially uniform neutron polarization needed for beta-decay correlation coefficient experiments. We are currently employing spin-exchange (SE) and metastability-exchange (ME) optical pumping to polarize 3He, but will focus on SE. We will discuss the recent demonstration of 75 % 3He polarization, temperature-dependent relaxation mechanism of unknown origin, cell development, spectrally narrowed lasers, and hybrid spin-exchange optical pumping. PMID:27308140

  14. Solar source regions of 3HE-rich particle events

    NASA Technical Reports Server (NTRS)

    Reames, D. V.; Stone, R. G.; Kahler, S. W.; Lin, R. P.; Liggett, M.

    1985-01-01

    Hydrogen alpha X-ray, and metric and kilometric radio data to examine the solar sources of energetic 3He-rich particle events observed near earth in association with impulsive 2 to 100 keV electron events were applied. Each 3He/electron event is associated with a kilometric type 3 burst belonging to a family of such bursts characterized by similar interplanetary propagation paths from the same solar active region. The 3He/electron events correlate very well with the interplanetary low frequency radio brightnesses of these events, but progressively worse with signatures from regions closer to the Sun. When H alpha brightnings can be associated with 3He/electron events, they have onsets coinciding to within 1 min of that of the associated metric type 3 burst but are often too small to be reported. The data are consistent with the earlier idea that many type 3 bursts, the 3He/electron events, are due to particle acceleration in the corona, well above the associated H alpha and X-ray flares.

  15. Probing region-specific microstructure of human cortical areas using high angular and spatial resolution diffusion MRI

    PubMed Central

    Aggarwal, Manisha; Nauen, David W.; Troncoso, Juan C.; Mori, Susumu

    2014-01-01

    Regional heterogeneity in cortical cyto- and myeloarchitecture forms the structural basis of mapping of cortical areas in the human brain. In this study, we investigate the potential of diffusion MRI to probe the microstructure of cortical gray matter and its region-specific heterogeneity across cortical areas in the fixed human brain. High angular resolution diffusion imaging (HARDI) data at an isotropic resolution of 92-μm and 30 diffusion-encoding directions were acquired using a 3D diffusion-weighted gradient-and-spin-echo sequence, from the prefrontal (Brodmann area 9), primary motor (area 4), primary somatosensory (area 3b), and primary visual (area 17) cortical specimens (n = 3 each) from three human subjects. Further, the diffusion MR findings in these cortical areas were compared with histological silver impregnation of the same specimens, in order to investigate the underlying architectonic features that constitute the microstructural basis of diffusion-driven contrasts in cortical gray matter. Our data reveal distinct and region-specific diffusion MR contrasts across the studied areas, allowing delineation of intracortical bands of tangential fibers in specific layers layer I, layer VI, and the inner and outer bands of Baillarger. The findings of this work demonstrate unique sensitivity of diffusion MRI to differentiate region-specific cortical microstructure in the human brain, and will be useful for myeloarchitectonic mapping of cortical areas as well as to achieve an understanding of the basis of diffusion NMR contrasts in cortical gray matter. PMID:25449747

  16. Hyperpolarized helium-3 mouse lung MRI: Studies of lung structure and function

    NASA Astrophysics Data System (ADS)

    Dugas, Joseph Paul

    Hyperpolarized 3He magnetic resonance imaging (MRI) of human and animal lungs has displayed promising and useful applications to studies of lung structure and function in both healthy and diseased lungs. Hyperpolarized 3He MRI allows the visualization of gas in the gas-exchange spaces of the lungs (as opposed to tissue) and has proven especially effective in studying diseases that are characterized by ventilation defects, such as emphysema. In particular, in-vivo measurements of the 3He apparent diffusion coefficient (ADC) can quantify lung structure by measuring its restrictive effects on the motion of 3He spins. This allows for detection and longitudinal tracking of changes in micro-architecture that result from disease destruction of alveolar walls. Due, in part, to the difficulties inherent in administering and imaging hyperpolarized 3He within the small (0.5 cc volume) mouse lung, applications of hyperpolarized 3He MRI techniques to laboratory mice are scarce. We have been able to implement and improve the techniques of hyperpolarized 3He mouse lung MRI and subsequently apply them to studies of several mouse models of disease, including elastase-induced emphysema, smoking-induced emphysema, and lung cancer. Here we detail the design, development, and implementation of a versatile, electronically-controlled, small animal ventilator that is capable of delivering tiny volumes of hyperpolarized 3He, mixed with oxygen, to the mouse and is also compatible with both the easily depolarized 3He gas and the highly magnetic environment within and around an imaging magnet. Also described are NM techniques developed to improve the signal-to-noise ratio of our images and effectively utilize the gas hyperpolarization. Applications of these technologies and techniques to small animal models of disease are presented wherein we have measured up to a 35% increase in 3He ADC in mice with elastase-induced emphysema as compared to healthy mice. We also demonstrate the potential

  17. Diffusion-weighted MRI with parallel imaging technique: apparent diffusion coefficient determination in normal kidneys and in nonmalignant renal diseases.

    PubMed

    Macarini, Luca; Stoppino, Luca Pio; Milillo, Paola; Ciuffreda, Pierpaolo; Fortunato, Francesca; Vinci, Roberta

    2010-01-01

    The purpose of the study was to assess the capability and the reliability of apparent diffusion coefficient (ADC) measurements in the evaluation of different benign renal abnormalities. Twenty-five healthy volunteers and 31 patients, divided into seven different groups (A-G) according to pathology, underwent diffusion-weighted magnetic resonance imaging (DW MRI) of the kidneys using 1.5-T system. DW images were obtained in the axial plane with a spin-echo echo planar imaging single-shot sequence with three b values (0, 300, and 600 s/mm²). Before acquisition of DW sequences, we performed in each patient a morphological study of the kidneys. ADC was 2.40±0.20×10⁻³ mm² s⁻¹ in volunteers. A significant difference was found between Groups A (cysts=3.39±0.51×10⁻³ mm² s⁻¹) and B (acute/chronic renal failure=1.38±0.40×10⁻³ mm² s⁻¹) and between Groups A and C (chronic pyelonephritis=1.53±0.21×10⁻³ mm² s⁻¹) (P<.05). An important difference was also observed among Group D (hydronephrosis=4.82±0.35×10⁻³ mm² s⁻¹) and Groups A, B, and C (P<.05), whereas no differences were found between Groups B and C (P>.05). A considerable correlation between glomerular filtration rate and ADC was found (P=.04). In conclusion, significant differences were detected among different patient groups, and this suggests that ADC measurements can be useful in differentiating normal renal parenchyma from most commonly encountered nonmalignant renal lesions. PMID:21092872

  18. A validation of the [sup 3]H/[sup 3]He method for determining groundwater recharge

    SciTech Connect

    Solomon, D.K. ); Schiff, S.L. ); Poreda, R.J. ); Clarke, W.B. )

    1993-09-01

    Tritium and He isotopes have been measured at a site where groundwater flow is nearly vertical for a travel time of 100 years and where recharge rates are spatially variable. Because the mid-1960s [sup 3]H peak (arising from aboveground testing of thermonuclear devices) is well-defined, the vertical groundwater velocity is known with unusual accuracy at this site. Utilizing [sup 3]H and its stable daughter [sup 3]He to determine groundwater ages, we compute a recharge rate of 0.16 m/yr, which agrees to within about 5% of the value based on the depth of the [sup 3]H peak (measured both in 1986 and 1991) and two-dimensional modeling in an area of high recharge. Zero [sup 3]H/[sup 3]He age occurs at a depth that is approximately equal to the average depth of the annual low water table, even though the capillary fringe extends to land surface during most of the year at the study site. In an area of low recharge (0.05 m/yr) where the [sup 3]H peak (and hence the vertical velocity) is also well-defined, the [sup 3]H/[sup 3]He results could not be used to compute recharge because samples were not collected sufficiently far above the [sup 3]H peak; however, modeling indicates that the [sup 3]H/[sup 3]He age gradient near the water table is an accurate measure of vertical velocities in the low-recharge area. Because [sup 3]H and [sup 3]He have different diffusion coefficients, and because the amount of mechanical mixing is different in the area of high recharge than in the low-recharge area, we have separated the dispersive effects of mechanical mixing from molecular diffusion. We estimate a longitudinal dispersivity of 0.07 m and effective diffusion coefficients for [sup 3]H ([sup 3]HHO) and [sup 3]He of 2.4 x 10[sup [minus]5] and 1.3 x 10[sup [minus]4] m[sup 2]/day, respectively. 26 refs., 8 figs., 1 tab.

  19. Spherical Deconvolution of Multichannel Diffusion MRI Data with Non-Gaussian Noise Models and Spatial Regularization.

    PubMed

    Canales-Rodríguez, Erick J; Daducci, Alessandro; Sotiropoulos, Stamatios N; Caruyer, Emmanuel; Aja-Fernández, Santiago; Radua, Joaquim; Yurramendi Mendizabal, Jesús M; Iturria-Medina, Yasser; Melie-García, Lester; Alemán-Gómez, Yasser; Thiran, Jean-Philippe; Sarró, Salvador; Pomarol-Clotet, Edith; Salvador, Raymond

    2015-01-01

    Spherical deconvolution (SD) methods are widely used to estimate the intra-voxel white-matter fiber orientations from diffusion MRI data. However, while some of these methods assume a zero-mean Gaussian distribution for the underlying noise, its real distribution is known to be non-Gaussian and to depend on many factors such as the number of coils and the methodology used to combine multichannel MRI signals. Indeed, the two prevailing methods for multichannel signal combination lead to noise patterns better described by Rician and noncentral Chi distributions. Here we develop a Robust and Unbiased Model-BAsed Spherical Deconvolution (RUMBA-SD) technique, intended to deal with realistic MRI noise, based on a Richardson-Lucy (RL) algorithm adapted to Rician and noncentral Chi likelihood models. To quantify the benefits of using proper noise models, RUMBA-SD was compared with dRL-SD, a well-established method based on the RL algorithm for Gaussian noise. Another aim of the study was to quantify the impact of including a total variation (TV) spatial regularization term in the estimation framework. To do this, we developed TV spatially-regularized versions of both RUMBA-SD and dRL-SD algorithms. The evaluation was performed by comparing various quality metrics on 132 three-dimensional synthetic phantoms involving different inter-fiber angles and volume fractions, which were contaminated with noise mimicking patterns generated by data processing in multichannel scanners. The results demonstrate that the inclusion of proper likelihood models leads to an increased ability to resolve fiber crossings with smaller inter-fiber angles and to better detect non-dominant fibers. The inclusion of TV regularization dramatically improved the resolution power of both techniques. The above findings were also verified in human brain data. PMID:26470024

  20. Spherical Deconvolution of Multichannel Diffusion MRI Data with Non-Gaussian Noise Models and Spatial Regularization

    PubMed Central

    Canales-Rodríguez, Erick J.; Caruyer, Emmanuel; Aja-Fernández, Santiago; Radua, Joaquim; Yurramendi Mendizabal, Jesús M.; Iturria-Medina, Yasser; Melie-García, Lester; Alemán-Gómez, Yasser; Thiran, Jean-Philippe; Sarró, Salvador; Pomarol-Clotet, Edith; Salvador, Raymond

    2015-01-01

    Spherical deconvolution (SD) methods are widely used to estimate the intra-voxel white-matter fiber orientations from diffusion MRI data. However, while some of these methods assume a zero-mean Gaussian distribution for the underlying noise, its real distribution is known to be non-Gaussian and to depend on many factors such as the number of coils and the methodology used to combine multichannel MRI signals. Indeed, the two prevailing methods for multichannel signal combination lead to noise patterns better described by Rician and noncentral Chi distributions. Here we develop a Robust and Unbiased Model-BAsed Spherical Deconvolution (RUMBA-SD) technique, intended to deal with realistic MRI noise, based on a Richardson-Lucy (RL) algorithm adapted to Rician and noncentral Chi likelihood models. To quantify the benefits of using proper noise models, RUMBA-SD was compared with dRL-SD, a well-established method based on the RL algorithm for Gaussian noise. Another aim of the study was to quantify the impact of including a total variation (TV) spatial regularization term in the estimation framework. To do this, we developed TV spatially-regularized versions of both RUMBA-SD and dRL-SD algorithms. The evaluation was performed by comparing various quality metrics on 132 three-dimensional synthetic phantoms involving different inter-fiber angles and volume fractions, which were contaminated with noise mimicking patterns generated by data processing in multichannel scanners. The results demonstrate that the inclusion of proper likelihood models leads to an increased ability to resolve fiber crossings with smaller inter-fiber angles and to better detect non-dominant fibers. The inclusion of TV regularization dramatically improved the resolution power of both techniques. The above findings were also verified in human brain data. PMID:26470024

  1. Diffusion MRI properties of the human uncinate fasciculus correlate with the ability to learn visual associations.

    PubMed

    Thomas, Cibu; Avram, Alexandru; Pierpaoli, Carlo; Baker, Chris

    2015-11-01

    The uncinate fasciculus (UF) is a cortico-cortico white matter pathway that links the anterior temporal and the orbitofrontal cortex (OFC). In the monkey, transection of the UF causes significant impairments in learning conditional visual-visual associations, while object discrimination remains intact, suggesting an important role for the UF in mediating the learning of complex visual associations. Whether this functional role extends to the human UF has not been tested directly. Here, we used diffusion tensor magnetic resonance imaging (dMRI) and behavioral experiments to examine the relation between learning visual associations and the structural properties of the human UF. In a group of healthy adults, we segmented the UF and the inferior longitudinal fasciculus (ILF) and derived dMRI measures of the structural properties of the two pathways. We also used a behavioral experiment adapted from the monkey studies to characterize the ability of these individuals to learn to associate a person's face with a group of specific scenes (conditional visual-visual association). We then tested whether the variability in the dMRI measures of the two pathways correlated with variability in the ability to rapidly learn the face-place associations. Our study suggests that in the human, the left UF may be important for mediating the rapid learning of conditional visual-visual associations whereas the right UF may play an important role in the immediate retrieval of visual-visual associations. These results provide preliminary evidence suggesting similarities and differences in the functional role of the UF in monkeys compared to humans. The findings presented here contribute to our understanding of the functional role of the UF in humans and the functional neuroanatomy of the brain networks involved in visual cognition. PMID:25742710

  2. Blood Pressure Reduction, Decreased Diffusion on MRI, and Outcomes After Intracerebral Hemorrhage

    PubMed Central

    Garg, Rajeev K; Liebling, Storm M; Maas, Matthew B; Nemeth, Alexander J; Russell, Eric J; Naidech, Andrew M

    2011-01-01

    Background Decreased diffusion (DD) consistent with acute ischemia may be detected on MRI after acute intracerebral hemorrhage (ICH), but its risk factors and impact on functional outcomes are not well defined. We tested the hypotheses that DD after ICH is related to acute blood pressure (BP) reduction and lower hemoglobin (HGB) and presages worse functional outcomes. Methods Patients who underwent MRI were prospectively evaluated for DD by certified neuroradiologists blinded to outcomes. HGB and BP data were obtained via electronic queries. Outcomes were obtained at 14 days and 3 months with the modified Rankin Scale (mRS), a functional scale scored from 0 (no symptoms) to 6 (dead). We used logistic regression for dependence or death (mRS 4 to 6). Results DD distinct from the hematoma was found on MRI in 36 of 95 patients (38%). DD was associated with greater BP reductions from baseline, and a higher risk of dependence or death at 3 months (OR 4.8, 95% CI 1.7 – 13.9, P=0.004) after correction for ICH Score (1.8 per point, 95%CI 1.2–3.1, P=0.01). Lower HGB was associated with worse ICH score, larger hematoma volume and worse outcomes, but not DD. Conclusions DD is common after ICH, associated with greater acute BP reductions, and associated with disability and death at 3 months in multivariate analysis. The potential benefits of acute BP reduction to reduce hematoma growth may be limited by DD. The prevention and treatment of cerebral ischemia manifested as DD is a potential method to improve outcomes. PMID:21980211

  3. Whole body MRI: Improved Lesion Detection and Characterization With Diffusion Weighted Techniques

    PubMed Central

    Attariwala, Rajpaul; Picker, Wayne

    2013-01-01

    Diffusion-weighted imaging (DWI) is an established functional imaging technique that interrogates the delicate balance of water movement at the cellular level. Technological advances enable this technique to be applied to whole-body MRI. Theory, b-value selection, common artifacts and target to background for optimized viewing will be reviewed for applications in the neck, chest, abdomen, and pelvis. Whole-body imaging with DWI allows novel applications of MRI to aid in evaluation of conditions such as multiple myeloma, lymphoma, and skeletal metastases, while the quantitative nature of this technique permits evaluation of response to therapy. Persisting signal at high b-values from restricted hypercellular tissue and viscous fluid also permits applications of DWI beyond oncologic imaging. DWI, when used in conjunction with routine imaging, can assist in detecting hemorrhagic degradation products, infection/abscess, and inflammation in colitis, while aiding with discrimination of free fluid and empyema, while limiting the need for intravenous contrast. DWI in conjunction with routine anatomic images provides a platform to improve lesion detection and characterization with findings rivaling other combined anatomic and functional imaging techniques, with the added benefit of no ionizing radiation. PMID:23960006

  4. A volumetric approach to quantifying region-to-region white matter connectivity in diffusion tensor MRI.

    PubMed

    Fletcher, P Thomas; Tao, Ran; Jeong, Won-Ki; Whitaker, Ross T

    2007-01-01

    In this paper we present a volumetric approach for quantitatively studying white matter connectivity from diffusion tensor magnetic resonance imaging (DT-MRI). The proposed method is based on a minimization of path cost between two regions, defined as the integral of local costs that are derived from the full tensor data along the path. We solve the minimal path problem using a Hamilton-Jacobi formulation of the problem and a new, fast iterative method that computes updates on the propagating front of the cost function at every point. The solutions for the fronts emanating from the two initial regions are combined, giving a voxel-wise connectivity measurement of the optimal paths between the regions that pass through those voxels. The resulting high-connectivity voxels provide a volumetric representation of the white matter pathway between the terminal regions. We quantify the tensor data along these pathways using nonparametric regression of the tensors and of derived measures as a function of path length. In this way we can obtain volumetric measures on white-matter tracts between regions without any explicit integration of tracts. We demonstrate the proposed method on several fiber tracts from DT-MRI data of the normal human brain. PMID:17633712

  5. Quark-Hadron Duality in Neutron (3He) Spin Structure

    SciTech Connect

    Solvignon, Patricia; Liyanage, Nilanga; Chen, Jian-Ping; Choi, Seonho; Aniol, Konrad; Averett, Todd; Boeglin, Werner; Camsonne, Alexandre; Cates, Gordon; Chang, C.; Chang, C.C.; Chang, C.; Chang, C.C.; Chudakov, Eugene; Craver, Brandon; Cusanno, Francesco; Deur, Alexandre; Dutta, Dipangkar; Ent, Rolf; Feuerbach, Robert; Frullani, Salvatore; Gao, Haiyan; Garibaldi, Franco; Gilman, Ronald; Glashausser, Charles; Gorbenko, Viktor; Hansen, Jens-Ole; Higinbotham, Douglas; Ibrahim, Hassan; Jiang, Xiaodong; Jones, Mark; Kelleher, Aidan; Kelly, J.; Keppel, Cynthia; Kim, Wooyoung; Korsch, Wolfgang; Kramer, Kevin; Kumbartzki, Gerfried; LeRose, John; Lindgren, Richard; Ma, Bin; Margaziotis, Demetrius; Markowitz, Pete; McCormick, Kathy; Meziani, Zein-Eddine; Michaels, Robert; Moffit, Bryan; Monaghan, Peter; Munoz-Camacho, Carlos; Paschke, Kent; Reitz, Bodo; Saha, Arunava; Sheyor, Ran; Singh, Jaideep; Slifer, Karl; Sulkosky, Vince; Sulkosky, Vincent; Sulkosky, Vince; Sulkosky, Vincent; Tobias, William; Urciuoli, Guido; Wang, Kebin; Wijesooriya, Krishni; Wojtsekhowski, Bogdan; Woo, Seungtae; Yang, Jae-Choon; Zheng, Xiaochao; Zhu, Lingyan

    2008-10-01

    We present experimental results of the first high-precision test of quark-hadron duality in the spin-structure function g_1 of the neutron and $^3$He using a polarized 3He target in the four-momentum-transfer-squared range from 0.7 to 4.0 (GeV/c)^2. Global duality is observed for the spin-structure function g_1 down to at least Q^2 = 1.8 (GeV/c)^2 in both targets. We have also formed the photon-nucleon asymmetry A_1 in the resonance region for 3He and found no strong Q^2-dependence above 2.2 (GeV/c)^2.

  6. Light-Front Dynamics and the {{3He}} Spectral Function

    NASA Astrophysics Data System (ADS)

    Pace, Emanuele; Del Dotto, Alessio; Kaptari, Leonid; Rinaldi, Matteo; Salmé, Giovanni; Scopetta, Sergio

    2016-07-01

    Two topics are presented. The first one is a novel approach for a Poincaré covariant description of nuclear dynamics based on light-front Hamiltonian dynamics. The key quantity is the light-front spectral function, where both normalization and momentum sum rule can be satisfied at the same time. Preliminary results are discussed for an initial analysis of the role of relativity in the EMC effect in {{3He}}. A second issue, very challenging, is considered in a non-relativistic framework, namely a distorted spin-dependent spectral function for {{3He}} in order to take care of the final state interaction between the observed pion and the remnant in semi-inclusive deep inelastic electron scattering off polarized {{3He}}. The generalization of the analysis within the light-front dynamics is outlined.

  7. Ultrasensitive 3He magnetometer for measurements of high magnetic fields

    NASA Astrophysics Data System (ADS)

    Nikiel, Anna; Blümler, Peter; Heil, Werner; Hehn, Manfred; Karpuk, Sergej; Maul, Andreas; Otten, Ernst; Schreiber, Laura M.; Terekhov, Maxim

    2014-11-01

    We describe a 3He magnetometer capable to measure high magnetic fields ( B> 0.1 T) with a relative accuracy of better than 10-12. Our approach is based on the measurement of the free induction decay of gaseous, nuclear spin polarized 3He following a resonant radio frequency pulse excitation. The measurement sensitivity can be attributed to the long coherent spin precession time T2 ∗ being of order minutes which is achieved for spherical sample cells in the regime of "motional narrowing" where the disturbing influence of field inhomogeneities is strongly suppressed. The 3He gas is spin polarized in situ using a new, non-standard variant of the metastability exchange optical pumping. We show that miniaturization helps to increase T2 ∗ further and that the measurement sensitivity is not significantly affected by temporal field fluctuations of order 10-4.

  8. Strong-Coupling and the Stripe Phase of ^3He

    NASA Astrophysics Data System (ADS)

    Wiman, Joshua J.; Sauls, J. A.

    2016-09-01

    Thin films of superfluid 3He were predicted, based on weak-coupling BCS theory, to have a stable phase which spontaneously breaks translational symmetry in the plane of the film. This crystalline superfluid, or "stripe" phase, develops as a one-dimensional periodic array of domain walls separating degenerate B phase domains. We report calculations of the phases and phase diagram for superfluid 3He in thin films using a strong-coupling Ginzburg-Landau theory that accurately reproduces the bulk 3He superfluid phase diagram. We find that the stability of the Stripe phase is diminished relative to the A phase, but the Stripe phase is stable in a large range of temperatures, pressures, confinement, and surface conditions.

  9. Nuclear electric dipole moment of {sup 3}He

    SciTech Connect

    Stetcu, I.; Friar, J. L.; Hayes, A. C.; Liu, C.-P.; Navratil, P.

    2009-01-28

    In the no-core shell model (NCSM) framework, we calculate the {sup 3}He electric dipole moment (EDM) generated by parity- and time-reversal violation in the nucleon-nucleon interaction. While the results are somehow sensitive to the interaction model chosen for the strong two- and three-body interactions, we demonstrate the pion-exchange dominance to the EDM of {sup 3}He, if the coupling constants for {pi}, {rho} and {omega}-exchanges are of comparable magnitude, as expected. Finally, our results suggest that a measurement of {sup 3}He EDM would be complementary to the currently planned neutron and deuteron experiments, and would constitute a powerful constraint to the models of the pion P- and T-violating interactions.

  10. Surface Waves on the Superfluids ^3He and ^4He

    NASA Astrophysics Data System (ADS)

    Manninen, M. S.; Ranni, A.; Rysti, J.; Todoshchenko, I. A.; Tuoriniemi, J. T.

    2016-06-01

    Free surface waves were examined both in superfluids ^3He and ^4He with the premise that these inviscid media would represent ideal realizations for this fluid dynamics problem. The work in ^3He is one of the first of its kind, but in ^4He, it was possible to produce a much more complete set of data for meaningful comparison with theoretical models. Most measurements were performed at the zero temperature limit, meaning T< 100 mK for ^4He and T˜ 100 μ K for ^3He. Dozens of surface wave resonances, including up to 11 overtones, were observed and monitored as the liquid depth in the cell was varied. Despite of the wealth of data, perfect agreement with the constructed theoretical models could not be achieved.

  11. Surface Waves on the Superfluids ^3 He and ^4 He

    NASA Astrophysics Data System (ADS)

    Manninen, M. S.; Ranni, A.; Rysti, J.; Todoshchenko, I. A.; Tuoriniemi, J. T.

    2016-04-01

    Free surface waves were examined both in superfluids ^3 He and ^4 He with the premise that these inviscid media would represent ideal realizations for this fluid dynamics problem. The work in ^3 He is one of the first of its kind, but in ^4 He, it was possible to produce a much more complete set of data for meaningful comparison with theoretical models. Most measurements were performed at the zero temperature limit, meaning T< 100 mK for ^4 He and T˜ 100 μ K for ^3 He. Dozens of surface wave resonances, including up to 11 overtones, were observed and monitored as the liquid depth in the cell was varied. Despite of the wealth of data, perfect agreement with the constructed theoretical models could not be achieved.

  12. Coherent photoproduction of {pi}{sup +} from {sup 3}He

    SciTech Connect

    Nasseripour, R.; Berman, B.L.; Briscoe, W.J.; Micherdzinska, A.M.; Munevar, E.; Adhikari, K.P.; Adikaram, D.; Hyde, C.E.; Klein, A.; Kuhn, S.E.; Mayer, M.; Seraydaryan, H.; Weinstein, L.B.; Anghinolfi, M.; Battaglieri, M.; De Vita, R.; Osipenko, M.; Ripani, M.; Ball, J.; Konczykowski, P.

    2011-03-15

    We have measured the differential cross section for the {gamma}{sup 3}He{yields}{pi}{sup +}t reaction. This reaction was studied using the Continuous Electron Beam Accelerator Facility (CEBAF) Large Acceptance Spectrometer (CLAS) at Jefferson Lab. Real photons produced with the Hall-B bremsstrahlung tagging system in the energy range from 0.50 to 1.55 GeV were incident on a cryogenic liquid {sup 3}He target. The differential cross sections for the {gamma}{sup 3}He{yields}{pi}{sup +}t reaction were measured as a function of photon-beam energy and pion-scattering angle. Theoretical predictions to date cannot explain the large cross sections except at backward angles, showing that additional components must be added to the model.

  13. Diagnostic significance of diffusion-weighted MRI in patients with cervical cancer: a meta-analysis.

    PubMed

    Hou, Bo; Xiang, Shi-Feng; Yao, Gen-Dong; Yang, Su-Jun; Wang, Yu-Fang; Zhang, Yi-Xin; Wang, Jun-Wei

    2014-12-01

    The aim of this meta-analysis is to demonstrate whether diffusion-weighted magnetic resonance imaging (DWI) could assist in the precise diagnosis of cervical cancer or not. Both English and Chinese electronic databases were searched for potential relevant studies followed by a comprehensive literature search without any language restriction. Two reviewers independently assessed the methodological quality of the included trials. Standardized mean difference (SMD) and its corresponding 95 % confidence interval (95 % CI) were calculated in this meta-analysis. We chose Version 12.0 STATA statistical software to analyze our statistical data. Thirteen eligible cohort studies were selected for statistical analysis, including 645 tumor tissues and 504 normal tissues. Combined SMD of apparent diffusion coefficient (ADC) suggested that the ADC value in cervical cancer tissues was significantly lower than that of normal tissue (SMD = 2.80, 95 % CI = 2.64 ~ 2.96, P < 0.001). Subgroup analysis stratified by ethnicity indicated a higher ADC value in the normal tissues compared to the cancer tissues in both the Asian and Caucasian subgroups (Asians: SMD = 2.83, 95 % CI = 2.64 ~ 3.02, P < 0.001; Caucasians: SMD = 2.73, 95 % CI = 2.45 ~ 3.01, P < 0.001, respectively). The results from the subgroup analysis by MRI machine type revealed a statistically significant difference in ADC value between normal cervical tissue and tumor tissues among all of the six MRI machine type subgroups (all P < 0.05). The main finding from our meta-analysis revealed that increased signal intensity on DWI and decreased signal on ADC seem to be useful in the diagnosis of cervical cancer. DWI could therefore be an important imaging tool in potentially identifying patients with cervical cancer. PMID:25168365

  14. Diffusion-weighted MRI in the evaluation of renal lesions: preliminary results.

    PubMed

    Cova, M; Squillaci, E; Stacul, F; Manenti, G; Gava, S; Simonetti, G; Pozzi-Mucelli, R

    2004-10-01

    The purpose of this study was to evaluate the capability and the reliability of diffusion-weighted MRI in the evaluation of normal kidney and different renal lesions. 39 patients (10 normal volunteers and 29 patients with known renal lesions) underwent MRI of the kidneys by using a 1.5 T superconducting magnet. Axial fat suppressed turbo spin echo (TSE) T(2) and coronal fast field echo (FFE) T(1) or TSE T(1) weighted images were acquired for each patient. Diffusion-weighted (DW) images were obtained in the axial plane during breath-hold (17 s) with a spin-echo echo planar imaging (SE EPI) single shot sequence (repetition time (TR)=2883 ms, echo time (TE)=61 ms, flip angle=90 degrees ), with b value of 500 s mm(-2). 16 slices were produced with slice thickness of 7 mm and interslice gap of 1 mm. An apparent diffusion coefficient (ADC) map was obtained at each slice position. The ADC was measured in an approximately 1 cm region of interest (ROI) within the normal renal parenchyma, the detected renal lesions and the collecting system if dilated. ADC values in normal renal parenchyma ranged from 1.72 x 10(-3) mm(2) s(-1) to 2.65 x 10(-3) mm(2) s(-1), while ADC values in simple cysts (n=13) were higher (2.87 x 10(-3) mm(2) s(-1) to 4.00 x 10(-3) mm(2) s(-1)). In hydronephrotic kidneys (n=6) the ADC values of renal pelvis ranged from 3.39 x 10(-3) mm(2) s(-1) to 4.00 x 10(-3) mm(2) s(-1). In cases of pyonephrosis (n=3) ADC values of the renal pelvis were found to be lower than those of renal pelvis of hydronephrotic kidneys (0.77 x 10(-3) mm(2) s(-1) to 1.07 x 10(-3) mm(2) s(-1)). Solid benign and malignant renal tumours (n=7) showed ADC values ranging between 1.28 x 10(-3) mm(2) s(-1) and 1.83 x 10(-3) mm(2) s(-1). In conclusion diffusion-weighted MR imaging of the kidney seems to be a reliable way to differentiate normal renal parenchyma and different renal diseases. Clinical experience with this method is still preliminary and further studies are required. PMID

  15. Evaluation of Hepatic Tumors Using Intravoxel Incoherent Motion Diffusion-Weighted MRI

    PubMed Central

    Wang, Mingjie; Li, Xudan; Zou, Jianxun; Chen, Xugao; Chen, Shuyan; Xiang, Wanqing

    2016-01-01

    Background This study aimed to evaluate the diagnostic value of the D value, D* value, and f magnitude for identifying benign and malignant hepatic tumors using intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI). Material/Methods Data of 89 cases (123 lesions) with hepatic tumor confirmed by surgical pathology and postoperative follow-up were retrospectively collected. Among these cases, 40 cases were benign hepatic tumors (57 lesions) and 49 cases were malignant hepatic tumors (66 lesions). All subjects underwent conventional MRI with T1WI, T2WI, multi-b-value DWI, and dynamic enhanced LAVA scan. Diffusion-weighted images with 11 b values (0, 10, 20, 30, 50, 80, 100, 200, 400, 800, and 1000 s/mm2) were obtained to calculate true molecular diffusion (D), perfusion-related diffusion coefficient (D*), and perfusion fraction (f). The diagnostic performance in differentiating between malignant and benign hepatic lesions was analyzed. Results Malignant lesions had a significantly lower D value ([1.04±0.34]×10−3 mm2/s) and D* value ([16.5±7.7]×10−3 mm2/s) compared to benign lesions (D value: [1.70±0.55]×10−3 mm2/s, P<0.01; D* value: [21.7±9.9]×10−3 mm2/s, P<0.01). There was no statistically significant difference in f values between malignant (23.3±9.5) and benign lesions (33.5±14.9, P=0.13). In addition, D exhibited a better diagnostic performance than D* in terms of the area under the curve, sensitivity, and specificity when identifying malignancies from benign lesions. Conclusions D and D* are significant parameters for diagnosing hepatic tumors. Moreover, the D value is a more reliable parameter in distinguishing benign and malignant hepatic tumors. PMID:26931063

  16. Parametric Representation of Multiple White Matter Fascicles from Cube and Sphere Diffusion MRI

    PubMed Central

    Scherrer, Benoit; Warfield, Simon K.

    2012-01-01

    The characterization of the complex diffusion signal arising from the brain remains an open problem. Many representations focus on characterizing the global shape of the diffusion profile at each voxel and are limited to the assessment of connectivity. In contrast, Multiple Fascicle Models (MFM) seek to represent the contribution from each white matter fascicle and may be useful in the investigation of both white matter connectivity and diffusion properties of each individual fascicle. However, the most appropriate representation of multiple fascicles remains unclear. In particular, a multiple tensor representation of multiple fascicles has frequently been reported to be numerically challenging and unstable. We provide here the first analytical demonstration that when using a diffusion MRI acquisition with only one non-zero b-value, such as in conventional single-shell HARDI acquisition, a co-linearity in model parameters makes the precise model estimation impossible. Motivated by this theoretical result, we propose the novel CUSP (CUbe and SPhere) optimal acquisition scheme to achieve multiple non-zero b-values. It combines the gradients of a single-shell HARDI with gradients in its enclosing cube, in which varying b-values can be acquired by modulation of the gradient strength, without modifying the minimum echo time. Compared to a multi-shell HARDI acquisition, our scheme has significantly increased signal-to-noise ratio. We propose a novel estimation algorithm that enables efficient, robust and accurate estimation of the parameters of a multi-tensor model. In conjunction with a CUSP acquisition, it enables full estimation of the multi-tensor model. We present an evaluation of CUSP-MFM on both synthetic phantoms and invivo data. We report qualitative and quantitative experimental evaluations which demonstrate the ability of CUSP-MFM to characterize multiple fascicles from short duration acquisitions. CUSP-MFM enables rapid and effective investigation of multiple

  17. Pitfalls in whole body MRI with diffusion weighted imaging performed on patients with lymphoma: What radiologists should know.

    PubMed

    Albano, Domenico; La Grutta, Ludovico; Grassedonio, Emanuele; Patti, Caterina; Lagalla, Roberto; Midiri, Massimo; Galia, Massimo

    2016-09-01

    The technological advances in radiological imaging and the relevance of a diagnostic tool that may reduce radiation-induced long-term effects have led to a widespread use of whole body magnetic resonance imaging (WB-MRI) with diffusion weighted imaging for oncologic patients. A lot of studies demonstrated the feasibility and reliability of WB-MRI as an alternative technique for lymphoma staging and response assessment during and after treatment. In this paper, taking advantage of our 2years of experience using WB-MRI for lymphoma, we discuss the main pitfalls and artifacts radiologists should know examining a WB-MRI performed on this typology of patients in order to avoid images misinterpretation. PMID:27114337

  18. Anisotropic phases of superfluid ^{3}he in compressed aerogel.

    PubMed

    Li, J I A; Zimmerman, A M; Pollanen, J; Collett, C A; Halperin, W P

    2015-03-13

    It has been shown that the relative stabilities of various superfluid states of ^{3}He can be influenced by anisotropy in a silica aerogel framework. We prepared a suite of aerogel samples compressed up to 30% for which we performed pulsed NMR on ^{3}He imbibed within the aerogel. We identified A and B phases and determined their magnetic field-temperature phase diagrams as a function of strain. From these results, we infer that the B phase is distorted by negative strain forming an anisotropic superfluid state more stable than the A phase. PMID:25815941

  19. A Study of 3He detectors for Active Interrogation

    SciTech Connect

    E.H. Seabury; D.L. Chichester

    2009-10-01

    3He proportional counters have long been used as neutron detectors for both passive and active detection of Special Nuclear Material (SNM). The optimal configuration of these detectors as far as gas pressure, amount of moderating material, and size are concerned is highly dependent on what neutron signatures are being used to detect and identify SNM. We present here a parametric study of the neutron capture response of 3He detectors, based on Monte Carlo simulations using the MCNPX radiation transport code. The neutron capture response of the detectors has been modeled as a function of time after an incident neutron pulse.

  20. Rotational quenching of CS in ultracold 3He collisions

    NASA Astrophysics Data System (ADS)

    Kaur, Rajwant; Dhilip Kumar, T. J.

    2016-08-01

    Quantum mechanical scattering calculations of rotational quenching of CS (v = 0) collision with 3He are performed at ultracold temperatures and results are compared with isotopic 4He collision. Rotational quenching cross sections and rate coefficients have been calculated in the ultracold region for rotational levels up to j = 10 using the He-CS potential energy surface computed at the CCSD(T)/aug-cc-pVQZ level of theory. The quenching cross sections are found to be two orders of magnitude larger for the 3He than the 4He isotope under ultracold conditions. Wigner threshold law is found to be valid below 10-3 K temperature.

  1. Temporal Evolution of Ischemic Lesions in Nonhuman Primates: A Diffusion and Perfusion MRI Study

    PubMed Central

    Zhang, Xiaodong; Tong, Frank; Li, Chun-Xia; Yan, Yumei; Kempf, Doty; Nair, Govind; Wang, Silun; Muly, E. Chris; Zola, Stuart; Howell, Leonard

    2015-01-01

    Background and Purpose Diffusion-weighted imaging (DWI) and perfusion MRI were used to examine the spatiotemporal evolution of stroke lesions in adult macaques with ischemic occlusion. Methods Permanent MCA occlusion was induced with silk sutures through an interventional approach via the femoral artery in adult rhesus monkeys (n = 8, 10–21 years old). The stroke lesions were examined with high-resolution DWI and perfusion MRI, and T2-weighted imaging (T2W) on a clinical 3T scanner at 1–6, 48, and 96 hours post occlusion and validated with H&E staining. Results The stroke infarct evolved via a natural logarithmic pattern with the mean infarct growth rate = 1.38 ± 1.32 ml per logarithmic time scale (hours) (n = 7) in the hyperacute phase (1–6 hours). The mean infarct volume after 6 hours post occlusion was 3.6±2.8 ml (n = 7, by DWI) and increased to 3.9±2.9 ml (n = 5, by T2W) after 48 hours, and to 4.7±2.2ml (n = 3, by T2W) after 96 hours post occlusion. The infarct volumes predicted by the natural logarithmic function were correlated significantly with the T2W-derived lesion volumes (n = 5, r = 0.92, p = 0.01) at 48 hours post occlusion. The final infarct volumes derived from T2W were correlated significantly with those from H&E staining (r = 0.999, p < 0.0001, n = 4). In addition, the diffusion-perfusion mismatch was visible generally at 6 hours but nearly diminished at 48 hours post occlusion. Conclusion The infarct evolution follows a natural logarithmic pattern in the hyperacute phase of stroke. The logarithmic pattern of evolution could last up to 48 hours after stroke onset and may be used to predict the infarct volume growth during the acute phase of ischemic stroke. The nonhuman primate model, MRI protocols, and post data processing strategy may provide an excellent platform for characterizing the evolution of acute stroke lesion in mechanistic studies and therapeutic interventions of stroke disease. PMID:25659092

  2. Multi-centre reproducibility of diffusion MRI parameters for clinical sequences in the brain.

    PubMed

    Grech-Sollars, Matthew; Hales, Patrick W; Miyazaki, Keiko; Raschke, Felix; Rodriguez, Daniel; Wilson, Martin; Gill, Simrandip K; Banks, Tina; Saunders, Dawn E; Clayden, Jonathan D; Gwilliam, Matt N; Barrick, Thomas R; Morgan, Paul S; Davies, Nigel P; Rossiter, James; Auer, Dorothee P; Grundy, Richard; Leach, Martin O; Howe, Franklyn A; Peet, Andrew C; Clark, Chris A

    2015-04-01

    The purpose of this work was to assess the reproducibility of diffusion imaging, and in particular the apparent diffusion coefficient (ADC), intra-voxel incoherent motion (IVIM) parameters and diffusion tensor imaging (DTI) parameters, across multiple centres using clinically available protocols with limited harmonization between sequences. An ice-water phantom and nine healthy volunteers were scanned across fives centres on eight scanners (four Siemens 1.5T, four Philips 3T). The mean ADC, IVIM parameters (diffusion coefficient D and perfusion fraction f) and DTI parameters (mean diffusivity MD and fractional anisotropy FA), were measured in grey matter, white matter and specific brain sub-regions. A mixed effect model was used to measure the intra- and inter-scanner coefficient of variation (CV) for each of the five parameters. ADC, D, MD and FA had a good intra- and inter-scanner reproducibility in both grey and white matter, with a CV ranging between 1% and 7.4%; mean 2.6%. Other brain regions also showed high levels of reproducibility except for small structures such as the choroid plexus. The IVIM parameter f had a higher intra-scanner CV of 8.4% and inter-scanner CV of 24.8%. No major difference in the inter-scanner CV for ADC, D, MD and FA was observed when analysing the 1.5T and 3T scanners separately. ADC, D, MD and FA all showed good intra-scanner reproducibility, with the inter-scanner reproducibility being comparable or faring slightly worse, suggesting that using data from multiple scanners does not have an adverse effect compared with using data from the same scanner. The IVIM parameter f had a poorer inter-scanner CV when scanners of different field strengths were combined, and the parameter was also affected by the scan acquisition resolution. This study shows that the majority of diffusion MRI derived parameters are robust across 1.5T and 3T scanners and suitable for use in multi-centre clinical studies and trials. PMID:25802212

  3. Multi-centre reproducibility of diffusion MRI parameters for clinical sequences in the brain

    PubMed Central

    Grech-Sollars, Matthew; Hales, Patrick W; Miyazaki, Keiko; Raschke, Felix; Rodriguez, Daniel; Wilson, Martin; Gill, Simrandip K; Banks, Tina; Saunders, Dawn E; Clayden, Jonathan D; Gwilliam, Matt N; Barrick, Thomas R; Morgan, Paul S; Davies, Nigel P; Rossiter, James; Auer, Dorothee P; Grundy, Richard; Leach, Martin O; Howe, Franklyn A; Peet, Andrew C; Clark, Chris A

    2015-01-01

    The purpose of this work was to assess the reproducibility of diffusion imaging, and in particular the apparent diffusion coefficient (ADC), intra-voxel incoherent motion (IVIM) parameters and diffusion tensor imaging (DTI) parameters, across multiple centres using clinically available protocols with limited harmonization between sequences. An ice–water phantom and nine healthy volunteers were scanned across fives centres on eight scanners (four Siemens 1.5T, four Philips 3T). The mean ADC, IVIM parameters (diffusion coefficient D and perfusion fraction f) and DTI parameters (mean diffusivity MD and fractional anisotropy FA), were measured in grey matter, white matter and specific brain sub-regions. A mixed effect model was used to measure the intra- and inter-scanner coefficient of variation (CV) for each of the five parameters. ADC, D, MD and FA had a good intra- and inter-scanner reproducibility in both grey and white matter, with a CV ranging between 1% and 7.4%; mean 2.6%. Other brain regions also showed high levels of reproducibility except for small structures such as the choroid plexus. The IVIM parameter f had a higher intra-scanner CV of 8.4% and inter-scanner CV of 24.8%. No major difference in the inter-scanner CV for ADC, D, MD and FA was observed when analysing the 1.5T and 3T scanners separately. ADC, D, MD and FA all showed good intra-scanner reproducibility, with the inter-scanner reproducibility being comparable or faring slightly worse, suggesting that using data from multiple scanners does not have an adverse effect compared with using data from the same scanner. The IVIM parameter f had a poorer inter-scanner CV when scanners of different field strengths were combined, and the parameter was also affected by the scan acquisition resolution. This study shows that the majority of diffusion MRI derived parameters are robust across 1.5T and 3T scanners and suitable for use in multi-centre clinical studies and trials. © 2015 The Authors NMR in

  4. Apatite 4He/3He and (U-Th)/He evidence for an ancient Grand Canyon.

    PubMed

    Flowers, R M; Farley, K A

    2012-12-21

    The Grand Canyon is one of the most dramatic features on Earth, yet when and why it was carved have been controversial topics for more than 150 years. Here, we present apatite (4)He/(3)He thermochronometry data from the Grand Canyon basement that tightly constrain the near-surface cooling history associated with canyon incision. (4)He/(3)He spectra for eastern Grand Canyon apatites of differing He date, radiation damage, and U-Th zonation yield a self-consistent cooling history that substantially validates the He diffusion kinetic model applied here. Similar data for the western Grand Canyon provide evidence that it was excavated to within a few hundred meters of modern depths by ~70 million years ago (Ma), in contrast to the conventional model in which the entire canyon was carved since 5 to 6 Ma. PMID:23196906

  5. Surface Scattering Effect and the Stripe Order in Films of the Superfluid3He B Phase

    NASA Astrophysics Data System (ADS)

    Aoyama, Kazushi

    2016-09-01

    Surface scattering effects in thin films of the superfluid 3He B phase have been theoretically investigated, with an emphasis on the stability of the stripe order with spontaneous broken translational symmetry in the film plane and quasiparticle excitations in this spatially inhomogeneous phase. Based on the Ginzburg-Landau theory in the weak coupling limit, we have shown that the stripe order, which was originally discussed for a film with two specular surfaces, can be stable in a film with one specular and one diffusive surfaces which should correspond to superfluid 3He on a substrate. It is also found by numerically solving the Eilenberger equation that due to the stripe structure, a midgap state distinct from the surface Andreev bound state emerges and its signature is reflected in the local density of states.

  6. Apatite 4He/3He and (U-Th)/He Evidence for an Ancient Grand Canyon

    NASA Astrophysics Data System (ADS)

    Flowers, R. M.; Farley, K. A.

    2012-12-01

    The Grand Canyon is one of the most dramatic features on Earth, yet when and why it was carved have been controversial topics for more than 150 years. Here, we present apatite 4He/3He thermochronometry data from the Grand Canyon basement that tightly constrain the near-surface cooling history associated with canyon incision. 4He/3He spectra for eastern Grand Canyon apatites of differing He date, radiation damage, and U-Th zonation yield a self-consistent cooling history that substantially validates the He diffusion kinetic model applied here. Similar data for the western Grand Canyon provide evidence that it was excavated to within a few hundred meters of modern depths by ~70 million years ago (Ma), in contrast to the conventional model in which the entire canyon was carved since 5 to 6 Ma.

  7. Pushing the limits of in vivo diffusion MRI for the Human Connectome Project

    PubMed Central

    Setsompop, K.; Kimmlingen, R.; Eberlein, E.; Witzel, T.; Cohen-Adad, J.; McNab, J.A.; Keil, B.; Tisdall, M.D.; Hoecht, P.; Dietz, P.; Cauley, S.F.; Tountcheva, V.; Matschl, V.; Lenz, V. H.; Heberlein, K.; Potthast, A.; Thein, H.; Van Horn, J.; Toga, A.; Schmitt, F.; Lehne, D.; Rosen, B.R.; Wedeen, V.; Wald, L.L.

    2013-01-01

    Perhaps more than any other “-omics” endeavor, the accuracy and level of detail obtained from mapping the major connection pathways in the living human brain with diffusion MRI depends on the capabilities of the imaging technology used. The current tools are remarkable; allowing the formation of an “image” of the water diffusion probability distribution in regions of complex crossing fibers at each of half a million voxels in the brain. Nonetheless our ability to map the connection pathways is limited by the image sensitivity and resolution, and also the contrast and resolution in encoding of the diffusion probability distribution. The goal of our Human Connectome Project (HCP) is to address these limiting factors by re-engineering the scanner from the ground up to optimize the high b-value, high angular resolution diffusion imaging needed for sensitive and accurate mapping of the brain’s structural connections. Our efforts were directed based on the relative contributions of each scanner component. The gradient subsection was a major focus since gradient amplitude is central to determining the diffusion contrast, the amount of T2 signal loss, and the blurring of the water PDF over the course of the diffusion time. By implementing a novel 4-port drive geometry and optimizing size and linearity for the brain, we demonstrate a whole-body sized scanner with Gmax = 300mT/m on each axis capable of the sustained duty cycle needed for diffusion imaging. The system is capable of slewing the gradient at a rate of 200 T/m/s as needed for the EPI image encoding. In order to enhance the efficiency of the diffusion sequence we implemented a FOV shifting approach to Simultaneous MultiSlice (SMS) EPI capable of unaliasing 3 slices excited simultaneously with a modest g-factor penalty allowing us to diffusion encode whole brain volumes with low TR and TE. Finally we combine the multi-slice approach with a compressive sampling reconstruction to sufficiently undersample q

  8. Pushing the limits of in vivo diffusion MRI for the Human Connectome Project.

    PubMed

    Setsompop, K; Kimmlingen, R; Eberlein, E; Witzel, T; Cohen-Adad, J; McNab, J A; Keil, B; Tisdall, M D; Hoecht, P; Dietz, P; Cauley, S F; Tountcheva, V; Matschl, V; Lenz, V H; Heberlein, K; Potthast, A; Thein, H; Van Horn, J; Toga, A; Schmitt, F; Lehne, D; Rosen, B R; Wedeen, V; Wald, L L

    2013-10-15

    Perhaps more than any other "-omics" endeavor, the accuracy and level of detail obtained from mapping the major connection pathways in the living human brain with diffusion MRI depend on the capabilities of the imaging technology used. The current tools are remarkable; allowing the formation of an "image" of the water diffusion probability distribution in regions of complex crossing fibers at each of half a million voxels in the brain. Nonetheless our ability to map the connection pathways is limited by the image sensitivity and resolution, and also the contrast and resolution in encoding of the diffusion probability distribution. The goal of our Human Connectome Project (HCP) is to address these limiting factors by re-engineering the scanner from the ground up to optimize the high b-value, high angular resolution diffusion imaging needed for sensitive and accurate mapping of the brain's structural connections. Our efforts were directed based on the relative contributions of each scanner component. The gradient subsection was a major focus since gradient amplitude is central to determining the diffusion contrast, the amount of T2 signal loss, and the blurring of the water PDF over the course of the diffusion time. By implementing a novel 4-port drive geometry and optimizing size and linearity for the brain, we demonstrate a whole-body sized scanner with G(max) = 300 mT/m on each axis capable of the sustained duty cycle needed for diffusion imaging. The system is capable of slewing the gradient at a rate of 200 T/m/s as needed for the EPI image encoding. In order to enhance the efficiency of the diffusion sequence we implemented a FOV shifting approach to Simultaneous MultiSlice (SMS) EPI capable of unaliasing 3 slices excited simultaneously with a modest g-factor penalty allowing us to diffusion encode whole brain volumes with low TR and TE. Finally we combine the multi-slice approach with a compressive sampling reconstruction to sufficiently undersample q-space to

  9. Automatic clustering of white matter fibers in brain diffusion MRI with an application to genetics

    PubMed Central

    Jin, Yan; Shi, Yonggang; Zhan, Liang; Gutman, Boris; de Zubicaray, Greig I.; McMahon, Katie L.; Wright, Margaret J.; Toga, Arthur W.; Thompson, Paul M.

    2014-01-01

    To understand factors that affect brain connectivity and integrity, it is beneficial to automatically cluster white matter (WM) fibers into anatomically recognizable tracts. Whole brain tractography, based on diffusion-weighted MRI, generates vast sets of fibers throughout the brain; clustering them into consistent and recognizable bundles can be difficult as there are wide individual variations in the trajectory and shape of WM pathways. Here we introduce a novel automated tract clustering algorithm based on label fusion – a concept from traditional intensity-based segmentation. Streamline tractography generates many incorrect fibers, so our top-down approach extracts tracts consistent with known anatomy, by mapping multiple hand-labeled atlases into a new dataset. We fuse clustering results from different atlases, using a mean distance fusion scheme. We reliably extracted the major tracts from 105-gradient high angular resolution diffusion images (HARDI) of 198 young normal twins. To compute population statistics, we use a point-wise correspondence method to match, compare, and average WM tracts across subjects. We illustrate our method in a genetic study of white matter tract heritability in twins. PMID:24821529

  10. Primary Pulmonary Diffuse Large B-Cell Lymphoma on FDG PET/CT-MRI and DWI

    PubMed Central

    Xu, Huiting; Xu, Kai; Wang, Ru; Liu, Xiaohua

    2015-01-01

    Abstract Primary pulmonary diffuse large B-cell lymphoma (PPDLBCL) directly arising from lung tissue is extremely rare. It may usually be misdiagnosed as inflammation including pulmonary tuberculosis, even lung cancer, because its clinical symptoms and signs are often nonspecific. The final diagnosis usually depends on lung biopsy. Herein, we report a case of PPDLBCL and review of diagnosis of this disease, particularly in radiology. A 44-year-old man presented with cough, sputum, and intermittent chest pain for 4 weeks. Multiple radiological examinations showed an irregular mass in the right upper lobe with ground-glass opacities around it and air-filled bronchi in the consolidation. Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography-magnetic resonance imaging (MRI) detected positive FDG uptake, and diffusion-weighted imaging indicated abnormal hyperintension in the lesion. Inflammation was suspected, but malignance cannot be excluded. Finally, ultrasound-guided fine-needle aspiration cytology was performed for histological examination and definitive diagnosis yielded lymphomatous cells infiltration in the right upper lobe. This report emphasizes the significance of multimodality radiological examinations. Multimodality imaging contributes to proper diagnosis, staging, and management of lymphomas. PMID:26200643

  11. Hyperpolarized 3He MR imaging of the lung: Effect of subject immobilization on the occurrence of ventilation defects

    PubMed Central

    Mata, Jaime; Altes, Talissa; Knake, Jeffrey; Mugler, John; Brookeman, James; de Lange, Eduard

    2008-01-01

    Purpose To investigate immobilization-induced ventilation defects when performing hyperpolarized 3He (H3He) MRI of the lung. Methods and Materials Twelve healthy subjects underwent MRI of the lungs following inhalation of H3He gas at three time points: 1) immediately after having been positioned supine on the MR scanner table, 2) at 45 minutes while remaining supine, 3) and immediately thereafter after having turned prone. All image sets were reviewed in random order by three independent, blinded readers who recorded number, location and size of H3He ventilation defects. Scores were averaged for each time point and comparisons were made to determine change in number, location and size of ventilation defects with time and positioning of the subject in the scanner. Results At baseline supine there were small numbers of defects in the dependent (posterior) and non-dependent (anterior) portions of the lung (p=0.625). At 45 minutes there was a significant increase in the mean number of ventilation defects/slice (VDS) for the dependent (p=0.005) and a decrease for the non-dependent lung portions (p=0.021). After subjects turned prone, mean VDS for posterior defects decreased significantly (p=0.011) while those for anterior defects increased (p=0.010). Most defects were less than 3 cm in diameter. Conclusion It was found that immobilization of the subject for an extended period of time led to increased number of H3He ventilation defects in the dependent portions of the lung. Therefore, after a subject is positioned in the scanner, H3He MR imaging should be performed quickly to avoid the occurrence of the immobilization-induced ventilation defects, and possible overestimation of disease. PMID:18206626

  12. Progress in Polarized 3He Ion Source at RCNP

    SciTech Connect

    Tanaka, M.; Takahashi, Y.; Shimoda, T.; Yasui, S.; Yosoi, M.; Takahisa, K.; Shimakura, N.; Plis, Yu. A.; Donets, E. D.

    2007-06-13

    A long history on the polarized 3He ion source developed at RCNP is presented. We started with an 'OPPIS' (Optical Pumping Polarized Ion Source) and later found the fundamental difficulties in the OPPIS. To overcome them an 'EPPIS' (Electron Pumping Polarized Ion Source) was proposed and its validity was experimentally proven. However, a serious technical disadvantage was also found in the EPPIS. To avoid this disadvantage we proposed a new concept, 'SEPIS' (Spin Exchange Polarized Ion Source), which uses an enhanced spin-exchange cross section theoretically expected at low 3He+ incident energies in the 3He+ + Rb system. Next, we describe the present status of the SEPIS development: construction of a bench test device allowing the measurements of not only the spin-exchange cross sections {sigma}se but also the electron capture cross sections {sigma}ec for the 3He+ + Rb system. The latest experimental data on {sigma}ec are presented and compared with other previous experimental data and the theoretical calculations.Finally, a design study of the SEPIS for practical use in nuclear (cyclotron) and particle physics (synchrotron) is shortly mentioned.

  13. Acoustic Spectroscopy of Superfluid 3He in Aerogel

    SciTech Connect

    Davis, J. P.; Choi, H.; Pollanen, J.; Halperin, W. P.

    2006-09-07

    We have designed an experiment to study the role of global anisotropic quasiparticle scattering on the dirty aerogel superfluid 3He system. We observe significant regions of two stable phases at temperatures below the superfluid transition at a pressure of 25 bar for a 98% aerogel.

  14. Flight performance of a rocket-borne 3He refrigerator

    NASA Astrophysics Data System (ADS)

    Duband, L.; Alsop, D.; Lange, A.; Hayata, S.; Matsumoto, T.; Sato, S.

    A self-contained, recyclable 3He refrigerator suitable for use in zero-gravity has been developed. This refrigerator successfully flew on 5 September 1989, as part of an S-520 sounding rocket payload designed to measure the spectrum of the cosmic submillimetre background. This paper presents the cryogenic performance of the refrigerator during flight.

  15. Summary of high field diffusion MRI and microscopy data demonstrate microstructural aberration in chronic mild stress rat brain.

    PubMed

    Khan, Ahmad Raza; Chuhutin, Andrey; Wiborg, Ove; Kroenke, Christopher D; Nyengaard, Jens R; Hansen, Brian; Jespersen, Sune Nørhøj

    2016-09-01

    This data article describes a large, high resolution diffusion MRI data set from fixed rat brain acquired at high field strength. The rat brain samples consist of 21 adult rat brain hemispheres from animals exposed to chronic mild stress (anhedonic and resilient) and controls. Histology from amygdala of the same brain hemispheres is also included with three different stains: DiI and Hoechst stained microscopic images (confocal microscopy) and ALDH1L1 antibody based immunohistochemistry. These stains may be used to evaluate neurite density (DiI), nuclear density (Hoechst) and astrocytic density (ALDH1L1). This combination of high field diffusion data and high resolution images from microscopy enables comparison of microstructural parameters derived from diffusion MRI to histological microstructure. The data provided here is used in the article (Jespersen, 2016) [1]. PMID:27508246

  16. Non-parametric representation and prediction of single- and multi-shell diffusion-weighted MRI data using Gaussian processes

    PubMed Central

    Andersson, Jesper L.R.; Sotiropoulos, Stamatios N.

    2015-01-01

    Diffusion MRI offers great potential in studying the human brain microstructure and connectivity. However, diffusion images are marred by technical problems, such as image distortions and spurious signal loss. Correcting for these problems is non-trivial and relies on having a mechanism that predicts what to expect. In this paper we describe a novel way to represent and make predictions about diffusion MRI data. It is based on a Gaussian process on one or several spheres similar to the Geostatistical method of “Kriging”. We present a choice of covariance function that allows us to accurately predict the signal even from voxels with complex fibre patterns. For multi-shell data (multiple non-zero b-values) the covariance function extends across the shells which means that data from one shell is used when making predictions for another shell. PMID:26236030

  17. Data for evaluation of fast kurtosis strategies, b-value optimization and exploration of diffusion MRI contrast.

    PubMed

    Hansen, Brian; Jespersen, Sune Nørhøj

    2016-01-01

    Here we describe and provide diffusion magnetic resonance imaging (dMRI) data that was acquired in neural tissue and a physical phantom. Data acquired in biological tissue includes: fixed rat brain (acquired at 9.4 T) and spinal cord (acquired at 16.4 T) and in normal human brain (acquired at 3 T). This data was recently used for evaluation of diffusion kurtosis imaging (DKI) contrasts and for comparison to diffusion tensor imaging (DTI) parameter contrast. The data has also been used to optimize b-values for ex vivo and in vivo fast kurtosis imaging. The remaining data was obtained in a physical phantom with three orthogonal fiber orientations (fresh asparagus stems) for exploration of the kurtosis fractional anisotropy. However, the data may have broader interest and, collectively, may form the basis for image contrast exploration and simulations based on a wide range of dMRI analysis strategies. PMID:27576023

  18. Data for evaluation of fast kurtosis strategies, b-value optimization and exploration of diffusion MRI contrast

    PubMed Central

    Hansen, Brian; Jespersen, Sune Nørhøj

    2016-01-01

    Here we describe and provide diffusion magnetic resonance imaging (dMRI) data that was acquired in neural tissue and a physical phantom. Data acquired in biological tissue includes: fixed rat brain (acquired at 9.4 T) and spinal cord (acquired at 16.4 T) and in normal human brain (acquired at 3 T). This data was recently used for evaluation of diffusion kurtosis imaging (DKI) contrasts and for comparison to diffusion tensor imaging (DTI) parameter contrast. The data has also been used to optimize b-values for ex vivo and in vivo fast kurtosis imaging. The remaining data was obtained in a physical phantom with three orthogonal fiber orientations (fresh asparagus stems) for exploration of the kurtosis fractional anisotropy. However, the data may have broader interest and, collectively, may form the basis for image contrast exploration and simulations based on a wide range of dMRI analysis strategies. PMID:27576023

  19. Serial diffusion MRI to monitor and model treatment response of the targeted nanotherapy CRLX101

    PubMed Central

    Ng, Thomas S.C.; Wert, David; Sohi, Hargun; Procissi, Daniel; Colcher, David; Raubitschek, Andrew A.; Jacobs, Russell E.

    2013-01-01

    Purpose Targeted nanotherapies are being developed to improve tumor drug delivery and enhance therapeutic response. Techniques that can predict response will facilitate clinical translation and may help define optimal treatment strategies. We evaluated the efficacy of diffusion-weighted magnetic resonance imaging to monitor early response to CRLX101 nanotherapy (formerly IT-101), and explored its potential as a therapeutic response predictor using a mechanistic model of tumor cell-proliferation. Experimental Design Diffusion MRI was serially performed following CRLX101 administration in a mouse lymphoma model. Apparent diffusion coefficients (ADC) extracted from the data were used as treatment response biomarkers. Animals treated with irinotecan (CPT-11) and saline were imaged for comparison. ADC data were also input into a mathematical model of tumor growth. Histological analysis using cleaved-caspase 3, TUNEL, Ki-67 and H&E were conducted on tumor samples for correlation with imaging results. Results CRLX101 treated tumors at day 2, 4, 7 post-treatment exhibited changes in mean ADC=16 ± 9%, 24 ± 10% 49 ± 17% and size (TV)=−5 ± 3%, −30 ± 4% and −45 ± 13% respectively. Both parameters were statistically greater than controls (p(ADC) ≤ 0.02, and p(TV) ≤ 0.01 at day 4 and 7), and noticeably greater than CPT-11 treated tumors (ADC=5 ± 5%, 14 ± 7% and 18 ± 6%, TV=−15 ± 5%, −22 ± 13% and −26 ± 8%). Model-derived parameters for cell-proliferation obtained using ADC data distinguished CRLX101 treated tumors from controls (p = 0.02). Conclusions Temporal changes in ADC specified early CRLX101 treatment response and could be used to model image-derived cell-proliferation rates following treatment. Comparisons of targeted and non-targeted treatments highlight the utility of non-invasive imaging and modeling to evaluate, monitor and predict responses to targeted nanotherapeutics. PMID:23532891

  20. White matter integrity, fiber count, and other fallacies: the do's and don'ts of diffusion MRI.

    PubMed

    Jones, Derek K; Knösche, Thomas R; Turner, Robert

    2013-06-01

    Diffusion-weighted MRI (DW-MRI) has been increasingly used in imaging neuroscience over the last decade. An early form of this technique, diffusion tensor imaging (DTI) was rapidly implemented by major MRI scanner companies as a scanner selling point. Due to the ease of use of such implementations, and the plausibility of some of their results, DTI was leapt on by imaging neuroscientists who saw it as a powerful and unique new tool for exploring the structural connectivity of human brain. However, DTI is a rather approximate technique, and its results have frequently been given implausible interpretations that have escaped proper critique and have appeared misleadingly in journals of high reputation. In order to encourage the use of improved DW-MRI methods, which have a better chance of characterizing the actual fiber structure of white matter, and to warn against the misuse and misinterpretation of DTI, we review the physics of DW-MRI, indicate currently preferred methodology, and explain the limits of interpretation of its results. We conclude with a list of 'Do's and Don'ts' which define good practice in this expanding area of imaging neuroscience. PMID:22846632

  1. A pitfall in the reconstruction of fibre ODFs using spherical deconvolution of diffusion MRI data.

    PubMed

    Parker, G D; Marshall, D; Rosin, P L; Drage, N; Richmond, S; Jones, D K

    2013-01-15

    Diffusion weighted (DW) MRI facilitates non-invasive quantification of tissue microstructure and, in combination with appropriate signal processing, three-dimensional estimates of fibrous orientation. In recent years, attention has shifted from the diffusion tensor model, which assumes a unimodal Gaussian diffusion displacement profile to recover fibre orientation (with various well-documented limitations), towards more complex high angular resolution diffusion imaging (HARDI) analysis techniques. Spherical deconvolution (SD) approaches assume that the fibre orientation density function (fODF) within a voxel can be obtained by deconvolving a 'common' single fibre response function from the observed set of DW signals. In practice, this common response function is not known a priori and thus an estimated fibre response must be used. Here the establishment of this single-fibre response function is referred to as 'calibration'. This work examines the vulnerability of two different SD approaches to inappropriate response function calibration: (1) constrained spherical harmonic deconvolution (CSHD)--a technique that exploits spherical harmonic basis sets and (2) damped Richardson-Lucy (dRL) deconvolution--a technique based on the standard Richardson-Lucy deconvolution. Through simulations, the impact of a discrepancy between the calibrated diffusion profiles and the observed ('Target') DW-signals in both single and crossing-fibre configurations was investigated. The results show that CSHD produces spurious fODF peaks (consistent with well known ringing artefacts) as the discrepancy between calibration and target response increases, while dRL demonstrates a lower over-all sensitivity to miscalibration (with a calibration response function for a highly anisotropic fibre being optimal). However, dRL demonstrates a reduced ability to resolve low anisotropy crossing-fibres compared to CSHD. It is concluded that the range and spatial-distribution of expected single

  2. Silent cerebral emboli following percutaneous closure of atrial septal defect in pediatric patients: a diffusion-weighted MRI study

    PubMed Central

    Koç, Gonca; Özyurt, Abdullah; Doğanay, Selim; Baykan, Ali; Görkem, S. Burcu; Doğan, M. Sait; Pamukçu, Özge; Üzüm, Kazım; Coşkun, Abdulhakim; Narin, Nazmi

    2016-01-01

    PURPOSE The aim of this prospective study was to investigate the incidence of silent cerebrovascular embolic events associated with percutaneous closure of atrial septal defect (ASD) in pediatric patients. METHODS A total of 23 consecutive pediatric patients (mean age, 10.4±3.8 years; range, 4–17 years) admitted for transcatheter closure of ASD were recruited in the study. The patients were scanned with a 1.5 Tesla clinical scanner. Two cranial magnetic resonance imaging (MRI) examinations were acquired before the procedure and within 24 hours following the catheterization. MRI included turbo spin-echo fluid-attenuated inversion recovery (FLAIR) sequence and diffusion-weighted imaging technique with single-shot echo-planar spin-echo sequence. The transcatheter closure of ASD was performed by three expert interventional cardiologists. Amplatzer septal occluder device was implemented for the closure of the defect. No contrast medium was administered in the course of the procedure. RESULTS None of the patients had diffusion restricted cerebral lesions resembling microembolic infarctions on postprocedural MRI. Preprocedural MRI of two patients revealed nonspecific hyperintense white matter lesions on FLAIR images with increased diffusion, which were considered to be older ischemic lesions associated with previously occurred paradoxical embolism. CONCLUSION The current study suggests that percutaneous closure of the ASD, when performed by experienced hands, may be free of cerebral microembolization in pediatric patients. However, due to the relatively small sample size, further studies with larger patient groups are needed for the validation of our preliminary results. PMID:26394443

  3. Investigation of Relationships Between Transverse Relaxation Rate, Diffusion Coefficient, and Labeled Cell Concentration in Ischemic Rat Brain Using MRI

    PubMed Central

    Athiraman, Hemanthkumar; Jiang, Quan; Ding, Guang Liang; Zhang, Li; Zhang, Zheng Gang; Wang, Lei; Arbab, Ali S.; Li, Qingjiang; Panda, Swayam; Ledbetter, Karen; Rad, Ali M.; Chopp, Michael

    2009-01-01

    MRI has been used to evaluate labeled cell migration and distribution. However, quantitative determination of labeled cell concentration using MRI has not been systematically investigated. In the current study, we investigated the relationships between labeled cell concentration and MRI parameters of transverse relaxation rate, R2, and apparent diffusion coefficient (ADC), in vitro in phantoms and in vivo in rats after stroke. Significant correlations were detected between iron concentration or labeled cell concentration and MRI measurements of R2, ADC, and ADC×R2 in vitro. In contrast, in vivo labeled cell concentration did not significantly correlate with R2, ADC, and ADC×R2. A major factor for the absence of a significant correlation between labeled cell concentration and MRI measurements in vivo may be attributed to background effects of ischemic tissue. By correcting the background effects caused by ischemic damage, ΔR2 (difference in R2 values in the ischemic tissue with and without labeled cells) exhibited a significant correlation to labeled cell concentration. Our study suggests that MRI parameters have the potential to quantitatively determine labeled cell concentration in vivo. PMID:19107898

  4. Emphysema Quantification in Inflation-Fixed Lungs Using Low-Dose Computed Tomography and 3He Magnetic Resonance Imaging

    SciTech Connect

    Gierada, David S.; Woods, Jason C.; Jacob, Rick E.; Bierhals, Andrew J.; Choong, Cliff K.; Bartel, Seth T.; Chang, Yulin V.; Das, Nitin A.; Hong, Cheng; Lutey, Barbara; Ritter, Jon H.; Pilgram, Thomas K.; Cooper, Joel D.; Patterson, G Alexander; Battafarano, Richard J.; Meyers, Bryan F.; Yablonskiy, Dmitriy A.; Conradi, Mark S.

    2010-09-02

    Abstract: Objective: To evaluate the use of inflation-fixed lung tissue for emphysema quantification with CT and 3He MR diffusion imaging. Methods: Fourteen subjects representing a range of chronic obstructive pulmonary disease severity who underwent complete or lobar lung resection were studied. CT measurements of lung attenuation and MR measurements of the hyperpolarized 3He apparent diffusion coefficient (ADC) in resected specimens fixed in inflation with heated formalin vapor were compared with measurements obtained before fixation. Results: The mean CT emphysema index was 56% ± 17% before and 58% ± 19% after fixation (P=0.77;R=0.76). Index differences correlated with differences in lung volume (R2=0.47). The mean 3He ADC was 0.40 ± 0.15 cm2/sec before and 0.39 ± 0.14 cm2/sec after fixation (P=0.03, R=0.98). The CT emphysema index and the 3He ADC were correlated before (R=0.89) and after fixation (R=0.79). Conclusion: Concordance of CT and 3He MR imaging measurements in unfixed and inflation-fixed lungs supports the use of inflation-fixed lungs for quantitative imaging studies in emphysema.

  5. q-Space diffusion MRI (QSI) of the disease progression in the spinal cords of the Long Evans shaker: diffusion time and apparent anisotropy

    PubMed Central

    Anaby, Debbie; Duncan, Ian D.; Smith, Chelsey M.; Cohen, Yoram

    2014-01-01

    q-Space diffusion MRI (QSI) was used to study the spinal cords of Long Evans shaker (les) rats, a model of dysmyelination, and their age-matched controls at different maturation stages. Diffusion was measured parallel and perpendicular to the fibers of the spinal cords of the two groups and at different diffusion times. The results showed that QSI is able to detect the dysmyelination process that occurs in this model in the different stages of the disease. The differences in the diffusion characteristics of the spinal cords of the two groups were found to be larger when the diffusion time was increased from 22 to 100 ms. We found that the radial mean displacement is a much better parameter than the QSI fractional anisotropy (FA) to document the differences between the two groups. We observed that the degree of myelination affects the diffusion characteristics of the tissues, but has a smaller effect on FA. All of the extracted diffusion parameters that are affected by the degree of myelination are affected in a diffusion time-dependent fashion, suggesting that the terms apparent anisotropy, apparent fractional anisotropy and even apparent root-mean-square displacement (rmsD) are more appropriate. PMID:24123305

  6. JET (3He)-D scenarios relying on RF heating: survey of selected recent experiments

    NASA Astrophysics Data System (ADS)

    Van Eester, D.; Lerche, E.; Andrew, Y.; Biewer, T. M.; Casati, A.; Crombé, K.; de la Luna, E.; Ericsson, G.; Felton, R.; Giacomelli, L.; Giroud, C.; Hawkes, N.; Hellesen, C.; Hjalmarsson, A.; Joffrin, E.; Källne, J.; Kiptily, V.; Lomas, P.; Mantica, P.; Marinoni, A.; Mayoral, M.-L.; Ongena, J.; Puiatti, M.-E.; Santala, M.; Sharapov, S.; Valisa, M.; JET EFDA contributors

    2009-04-01

    Recent JET experiments have been devoted to the study of (3He)-D plasmas involving radio frequency (RF) heating. This paper starts by discussing the RF heating efficiency theoretically expected in such plasmas, covering both relevant aspects of wave and of particle dynamics. Then it gives a concise summary of the main conclusions drawn from recent experiments that were either focusing on studying RF heating physics aspects or that were adopting RF heating as a tool to study plasma behavior. Depending on the minority concentration chosen, different physical phenomena are observed. At very low concentration (X[3He] < 1%), energetic tails are formed which trigger MHD activity and result in loss of fast particles. Alfvén cascades were observed and gamma ray tomography indirectly shows the impact of sawtooth crashes on the fast particle orbits. Low concentration (X[3He] < 10%) favors minority heating while for X[3He] Gt 10% electron mode conversion damping becomes dominant. Evidence for the Fuchs et al standing wave effect (Fuchs et al 1995 Phys. Plasmas 2 1637-47) on the absorption is presented. RF induced deuterium tails were observed in mode conversion experiments with large X[3He] (≈18%). As tentative modeling shows, the formation of these tails can be explained as a consequence of wave power absorption by neutral beam particles that efficiently interact with the waves well away from the cold D cyclotron resonance position as a result of their substantial Doppler shift. As both ion and electron RF power deposition profiles in (3He)-D plasmas are fairly narrow—giving rise to localized heat sources—the RF heating method is an ideal tool for performing transport studies. Various of the experiments discussed here were done in plasmas with internal transport barriers (ITBs). ITBs are identified as regions with locally reduced diffusivity, where poloidal spinning up of the plasma is observed. The present know-how on the role of RF heating for impurity transport is

  7. Heat Capacity of Dilute 3He-4He Monolayer Films

    NASA Astrophysics Data System (ADS)

    Morishita, Masashi

    2016-05-01

    The heat capacities of a small amount of 3He dissolved in monolayer 4He films are measured to clarify natures of monolayer 4He films. With increasing areal density, the measured heat capacities gradually increase and subsequently gradually decrease. With further increase in areal density, the measured heat capacity rapidly decreases to zero over a very narrow areal density range near that of the sqrt{3} × sqrt{3} phase. These slightly complex areal-density variations and dependence on 3He concentration are discussed from the viewpoint of the known properties of 4He films. The behaviors can be explained. However, the expected two-dimensional gas-liquid or gas-solid coexistence is not observed in this study.

  8. Hexapole magnet system for thermal energy 3He atom manipulation

    NASA Astrophysics Data System (ADS)

    Jardine, A. P.; Fouquet, P.; Ellis, J.; Allison, W.

    2001-10-01

    We present design and construction details for a novel high field, small bore permanent hexapole magnet. The design is intended for focusing atomic beams of 3He at thermal energies. The magnet uses an optimized polepiece design which includes vacuum gaps to enable its use with high intensity atomic and molecular beams. The 0.3 m long, 1 mm internal radius magnet achieves a polepiece tip field of 1.1 T using NdFeB permanent magnets and Permendur 49 polepieces. The polepiece shanks are designed to saturate so that the hexapole properties are determined predominantly by the shape of the polepiece tip. The performance of the hexapole assembly is demonstrated with an 8 meV 3He beam in the beam source of the Cambridge spin echo spectrometer and the measured focused beam results show excellent agreement with theoretical predictions and negligible beam attenuation.

  9. Nuclear spin heat capacity of 3He adsorbed on graphite

    NASA Astrophysics Data System (ADS)

    Greywall, Dennis S.

    1989-10-01

    The heat capacity of 3He adsorbed on graphite has been measured for films between one and five atomic layers and for temperatures between 2 and 200 mK. These results are compared with recent magnetization data which also show several anomalies in this coverage regime. Prior to third layer promotion the second layer is found to solidify into a registered structure with unusual propertis. This contradicts the model proposed to explain the NMR measurements.

  10. NOVEL CONCEPTS FOR ISOTOPIC SEPARATION OF 3HE/4HE

    SciTech Connect

    Roy, L.; Nigg, H.; Watson, H.

    2012-09-04

    The research outlined below established theoretical proof-of-concept using ab initio calculations that {sup 3}He can be separated from {sup 4}He by taking advantage of weak van der Waals interactions with other higher molecular weight rare gases such as xenon. To the best of our knowledge, this is the only suggested method that exploits the physical differences of the isotopes using a chemical interaction.

  11. Density of liquid 3He in 8 T magnetic field

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koichi; Hasegawa, Syuichi; Okuda, Yuichi

    2000-07-01

    We report a precise measurement of the density of liquid 3He in a 8 T field. Measurements performed at saturated vapour pressure between 30 and 300 mK show a field-induced increase of density. The relative change is about 1×10 -5 in this temperature range. These results are in agreement with a calculation based on a Maxwell relation and the pressure dependence of the susceptibility.

  12. Hard two-body photodisintegration of 3He.

    PubMed

    Pomerantz, I; Ilieva, Y; Gilman, R; Higinbotham, D W; Piasetzky, E; Strauch, S; Adhikari, K P; Aghasyan, M; Allada, K; Amaryan, M J; Anefalos Pereira, S; Anghinolfi, M; Baghdasaryan, H; Ball, J; Baltzell, N A; Battaglieri, M; Batourine, V; Beck, A; Beck, S; Bedlinskiy, I; Berman, B L; Biselli, A S; Boeglin, W; Bono, J; Bookwalter, C; Boiarinov, S; Briscoe, W J; Brooks, W K; Bubis, N; Burkert, V; Camsonne, A; Canan, M; Carman, D S; Celentano, A; Chandavar, S; Charles, G; Chirapatpimol, K; Cisbani, E; Cole, P L; Contalbrigo, M; Crede, V; Cusanno, F; D'Angelo, A; Daniel, A; Dashyan, N; de Jager, C W; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Dodge, G E; Doughty, D; Dupre, R; Dutta, C; Egiyan, H; El Alaoui, A; El Fassi, L; Eugenio, P; Fedotov, G; Fegan, S; Fleming, J A; Fradi, A; Garibaldi, F; Geagla, O; Gevorgyan, N; Giovanetti, K L; Girod, F X; Glister, J; Goetz, J T; Gohn, W; Golovatch, E; Gothe, R W; Griffioen, K A; Guegan, B; Guidal, M; Guo, L; Hafidi, K; Hakobyan, H; Harrison, N; Heddle, D; Hicks, K; Ho, D; Holtrop, M; Hyde, C E; Ireland, D G; Ishkhanov, B S; Isupov, E L; Jiang, X; Jo, H S; Joo, K; Katramatou, A T; Keller, D; Khandaker, M; Khetarpal, P; Khrosinkova, E; Kim, A; Kim, W; Klein, F J; Koirala, S; Kubarovsky, A; Kubarovsky, V; Kuleshov, S V; Kvaltine, N D; Lee, B; LeRose, J J; Lewis, S; Lindgren, R; Livingston, K; Lu, H Y; MacGregor, I J D; Mao, Y; Martinez, D; Mayer, M; McCullough, E; McKinnon, B; Meekins, D; Meyer, C A; Michaels, R; Mineeva, T; Mirazita, M; Moffit, B; Mokeev, V; Montgomery, R A; Moutarde, H; Munevar, E; Munoz Camacho, C; Nadel-Turonski, P; Nasseripour, R; Nepali, C S; Niccolai, S; Niculescu, G; Niculescu, I; Osipenko, M; Ostrovidov, A I; Pappalardo, L L; Paremuzyan, R; Park, K; Park, S; Petratos, G G; Phelps, E; Pisano, S; Pogorelko, O; Pozdniakov, S; Procureur, S; Protopopescu, D; Puckett, A J R; Qian, X; Qiang, Y; Ricco, G; Rimal, D; Ripani, M; Ritchie, B G; Rodriguez, I; Ron, G; Rosner, G; Rossi, P; Sabatié, F; Saha, A; Saini, M S; Sarty, A J; Sawatzky, B; Saylor, N A; Schott, D; Schulte, E; Schumacher, R A; Seder, E; Seraydaryan, H; Shneor, R; Smith, G D; Sokhan, D; Sparveris, N; Stepanyan, S S; Stepanyan, S; Stoler, P; Subedi, R; Sulkosky, V; Taiuti, M; Tang, W; Taylor, C E; Tkachenko, S; Ungaro, M; Vernarsky, B; Vineyard, M F; Voskanyan, H; Voutier, E; Walford, N K; Wang, Y; Watts, D P; Weinstein, L B; Weygand, D P; Wojtsekhowski, B; Wood, M H; Yan, X; Yao, H; Zachariou, N; Zhan, X; Zhang, J; Zhao, Z W; Zheng, X; Zonta, I

    2013-06-14

    We have measured cross sections for the γ(3)He → pd reaction at photon energies of 0.4-1.4 GeV and a center-of-mass angle of 90°. We observe dimensional scaling above 0.7 GeV at this center-of-mass angle. This is the first observation of dimensional scaling in the photodisintegration of a nucleus heavier than the deuteron. PMID:25165915

  13. Thermal Conductivity of Spin-Polarized Liquid {sup 3}He

    SciTech Connect

    Sawkey, D.; Puech, L.; Wolf, P.E.

    2006-06-02

    We present the first measurements of the thermal conductivity of spin-polarized normal liquid {sup 3}He. Using the rapid melting technique to produce nuclear polarizations up to 0.7, and a vibrating wire both as a heater and a thermometer, we show that, unlike the viscosity, the conductivity increases much less than predicted for s-wave scattering. We suggest that this might be due to a small probability for head-on collisions between quasiparticles.

  14. High Efficiency Spin Flipper for the n3He Experiment

    NASA Astrophysics Data System (ADS)

    Hayes, Christopher; n3He Collaboration

    2015-10-01

    The n3He experiment, constructed on the Fundamental Neutron Physics Beamline (FnPB) at the Spallation Neutron Source, is designed to measure the parity violating (PV) proton asymmetry Ap in the capture reaction n +3 He -->3 H + p + 765 keV The asymmetry has an estimated value Ap ~ - 1 ×10-7 and is directly related to the weak isospin conserved couplings hρ0 and ωρ0 which are of fundamental interest in the verification of the meson exchange model of low energy NN intereactions. Data production for the n3He experiment began in February 2015 and is scheduled to continue thru December 2015 - reaching a statistical sensitivity δAp ~10-8 or better. I will discuss the spin flipper which is designed using the theory of double cosine-theta coils, and capable of flipping neutron spins with an efficiency approaching its maximum value ɛsf = 1 . I will also discuss the theory of Spin Magnetic Resonance (SMR) and how it is employed by the spin flipper to flip 60 Hz pulses of cold neutrons over a range of wavelengths.

  15. Noise Studies of Polarimetry Systems for Polarized 3 He Targets

    NASA Astrophysics Data System (ADS)

    Katugampola, Sumudu K.; Matyas, Daniel J.; Nelyubin, Vladimir; Wang, Yunxiao; Cates, Gordon D.

    2015-04-01

    The NMR technique of adiabatic fast passage (AFP) plays an important role in 3 He targets polarized using spin-exchange optical pumping. Since AFP signals before amplification are generally small, identifying these signals amidst noise caused by external electromagnetic interference and micro-phonics can be challenging. When using thermally polarized water samples for absolute calibration of AFP signals, electromagnetic and micro-phonic noise can easily dominate. Although both types of interference have often been cited as the predominant sources of noise during AFP, few studies of these effects have been done under the conditions that are typical for a polarized 3 He target. This talk will describe studies of electromagnetic and micro-phonic noise using a small-scale prototype NMR system similar to those we use to study polarized 3 He targets. We will describe the effect of using aluminum metal shielding and other methods to minimize noise. We are using these studies to inform the design of a full-scale set up that will be used to test next-generation targets for use at Jefferson Lab, and measure atomic parameters relevant to polarimetry.

  16. Uranium Neutron Coincidence Collar Model Utilizing 3He

    SciTech Connect

    Siciliano, Edward R.; Rogers, Jeremy L.; Schweppe, John E.; Lintereur, Azaree T.; Kouzes, Richard T.

    2012-07-30

    The Department of Energy Office of Nuclear Safeguards (NA-241) is supporting the project 'Coincidence Counting With Boron-Based Alternative Neutron Detection Technology' at Pacific Northwest National Laboratory (PNNL) for development of an alternative neutron coincidence counter. The goal of this project is to design, build and demonstrate a boron-lined proportional tube based alternative system in a configuration typically used for 3He-based coincidence counter applications. The specific application selected for boron-lined tube replacement in this project was one of the Uranium Neutron Coincidence Collar (UNCL) designs. This report, providing results for model development of a UNCL, is a deliverable under Task 2 of the project. The current UNCL instruments utilize 3He tubes. As the first step in developing and optimizing a boron-lined proportional counter based version of the UNCL, models of eight different 3He-based UNCL detectors currently in use were developed and evaluated. A comparison was made between the simulated results and measured efficiencies for those systems with values reported in the literature. The reported experimental measurements for efficiencies and die-away times agree to within 10%.

  17. Enhancement of Magnetization in Liquid 3He at Aerogel Interface

    NASA Astrophysics Data System (ADS)

    Fukui, A.; Kondo, K.; Kato, C.; Obara, K.; Yano, H.; Ishikawa, O.; Hata, T.

    2013-05-01

    A novel feature of condensate state in liquid 3He is predicted theoretically, which consists of spin triplet s-wave Cooper pairs (Higashitani et al. in J. Low. Temp. Phys. 155:83-97, 2009). Such a spin triplet s-wave state will appear inside aerogel near the surface boundary contacting with superfluid 3He-B, and the enhancement of magnetization due to s-wave state is theoretically expected (Nagato et al. in J. Phys. Soc. Jpn. 78:123603, 2009; Higashitani et al. in Phys. Rev. B 85:024524, 2012). In order to detect this proximity effect, we made the interface in columnar glass tube which coated with 2.5 layer 4He, and set a saddle shape NMR coil very near the interface. At 7 bar, we found that superfluidity in liquid 3He inside aerogel never occurred, even at considerably low temperatures. At 24 bar below T/ T c =0.392, we observed no decrease of magnetization with decreasing temperatures. This phenomenon might be due to spin triplet s-wave Cooper pairs.

  18. The use of MRI apparent diffusion coefficient (ADC) in monitoring the development of brain infarction

    PubMed Central

    2011-01-01

    Background To study the rules that apparent diffusion coefficient (ADC) changes with time and space in cerebral infarction, and to provide the evidence in defining the infarction stages. Methods 117 work-ups in 98 patients with cerebral infarction (12 hyperacute, 43 acute, 29 subacute, 10 steady, and 23 chronic infarctions) were imaged with both conventional MRI and diffusion weighted imaging. The average ADC values, the relative ADC (rADC) values, and the ADC values or rADC values from the center to the periphery of the lesion were calculated. Results The average ADC values and the rADC values of hyperacute and acute infarction lesion depressed obviously. rADC values in hyperacute and acute stage was minimized, and increased progressively as time passed and appeared as "pseudonormal" values in approximately 8 to 14 days. Thereafter, rADC values became greater than normal in chronic stage. There was positive correlation between rADC values and time (P < 0.01). The ADC values and the rADC values in hyperacute and acute lesions had gradient signs that these lesions increased from the center to the periphery. The ADC values and the rADC values in subacute lesions had adverse gradient signs that these lesions decreased from the center to the periphery. Conclusion The ADC values of infarction lesions have evolution rules with time and space. The evolution rules with time and those in space can be helpful to decide the clinical stage, and to provide the evidence in guiding the treatment or judging the prognosis in infarction. PMID:21211049

  19. Microstructural parameter estimation in vivo using diffusion MRI and structured prior information

    PubMed Central

    Nagy, Zoltan; Weiskopf, Nikolaus; Alexander, Daniel C.; Clark, Chris A.

    2015-01-01

    Purpose Diffusion MRI has recently been used with detailed models to probe tissue microstructure. Much of this work has been performed ex vivo with powerful scanner hardware, to gain sensitivity to parameters such as axon radius. By contrast, performing microstructure imaging on clinical scanners is extremely challenging. Methods We use an optimized dual spin‐echo diffusion protocol, and a Bayesian fitting approach, to obtain reproducible contrast (histogram overlap of up to 92%) in estimated maps of axon radius index in healthy adults at a modest, widely‐available gradient strength (35 mT m −1). A key innovation is the use of influential priors. Results We demonstrate that our priors can improve precision in axon radius estimates—a 7‐fold reduction in voxelwise coefficient of variation in vivo—without significant bias. Our results may reflect true axon radius differences between white matter regions, but this interpretation should be treated with caution due to the complexity of the tissue relative to our model. Conclusions Some sensitivity to relatively large axons (3–15 μm) may be available at clinical field and gradient strengths. Future applications at higher gradient strength will benefit from the favorable eddy current properties of the dual spin‐echo sequence, and greater precision available with suitable priors. Magn Reson Med, 2015. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Magn Reson Med 75:1787–1796, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance. PMID:25994918

  20. Thalamic involvement in paroxysmal kinesigenic dyskinesia: a combined structural and diffusion tensor MRI analysis.

    PubMed

    Kim, Ji Hyun; Kim, Dong-Wook; Kim, Jung Bin; Suh, Sang-Il; Koh, Seong-Beom

    2015-04-01

    Alteration of basal ganglia-thalamocortical circuit has been hypothesized to play a role in the pathophysiology underlying paroxysmal kinesigenic dyskinesia (PKD). We investigated macrostructural and microstructural changes in PKD patients using structural and diffusion tensor magnetic resonance imaging (MRI) analyses. Twenty-five patients with idiopathic PKD and 25 control subjects were prospectively studied on a 3T magnetic resonance (MR) scanner. Cortical thickness analysis was used to evaluate cortical gray matter (GM) changes, and automated volumetry and shape analysis were used to assess volume changes and shape deformation of the subcortical GM structures, respectively. Tract-based spatial statistics (TBSS) was used to evaluate white matter integrity changes in a whole-brain manner, and region-of-interest (ROI) analysis of diffusion tensor metrics was performed in subcortical GM structures. Compared to controls, PKD patients exhibited a reduction in volume of bilateral thalami and regional shape deformation mainly localized to the anterior and medial aspects of bilateral thalami. TBSS revealed an increase in fractional anisotropy (FA) of bilateral thalami and right anterior thalamic radiation in patients relative to controls. ROI analysis also showed an increase in FA of bilateral thalami in patients compared to controls. We have shown evidence for thalamic abnormalities of volume reduction, regional shape deformation, and increased FA in patients with PKD. Our novel findings of concomitant macrostructural and microstructural abnormalities in the thalamus lend further support to previous observations indicating causal relationship between a preferential lesion in the thalamus and development of PKD, thus providing neuroanatomical basis for the involvement of thalamus within the basal ganglia-thalamocortical pathway in PKD. PMID:25504906

  1. Differences in early and late mild cognitive impairment tractography using a diffusion tensor MRI.

    PubMed

    Lee, Seung-Hak; Seo, Jongbum; Lee, Jong-min; Park, Hyunjin

    2014-12-01

    Diffusion tensor MRI tractography is an imaging tool that can provide information of in-vivo neuronal fiber tracts to assess progress for Alzheimer's disease (AD). In an effort to detect early AD progression, we focused on distinguishing subgroups within mild cognitive impairment (MCI): early MCI and late MCI. Tractography was applied not only to white matter regions but also neighboring gray matter regions known to be affected by AD. Nerve fibers touching the hippocampus, thalamus, and amygdala in both hemispheres were extracted to quantify limbic system fiber connectivity. Two fiber extraction algorithms, fiber assignment by continuous tracking and the Runge Kutta approach, were applied to an AD imaging database. We computed the number of fibers touching regions of interest as the imaging feature. The imaging feature could distinguish between the MCI subgroups. It was also significantly correlated with a known genetic marker for AD, the apolipoprotein E epsilon 4 allele. The number of fibers might be a useful imaging biomarker to complement conventional region of interest-based biomarkers for AD research. PMID:25325351

  2. Bingham-NODDI: Mapping anisotropic orientation dispersion of neurites using diffusion MRI.

    PubMed

    Tariq, Maira; Schneider, Torben; Alexander, Daniel C; Gandini Wheeler-Kingshott, Claudia A; Zhang, Hui

    2016-06-01

    This paper presents Bingham-NODDI, a clinically-feasible technique for estimating the anisotropic orientation dispersion of neurites. Direct quantification of neurite morphology on clinical scanners was recently realised by a diffusion MRI technique known as neurite orientation dispersion and density imaging (NODDI). However in its current form NODDI cannot estimate anisotropic orientation dispersion, which is widespread in the brain due to common fanning and bending of neurites. This work proposes Bingham-NODDI that extends the NODDI formalism to address this limitation. Bingham-NODDI characterises anisotropic orientation dispersion by utilising the Bingham distribution to model neurite orientation distribution. The new model estimates the extent of dispersion about the dominant orientation, separately along the primary and secondary dispersion orientations. These estimates are subsequently used to estimate the overall dispersion about the dominant orientation and the dispersion anisotropy. We systematically evaluate the ability of the new model to recover these key parameters of anisotropic orientation dispersion with standard NODDI protocol, both in silico and in vivo. The results demonstrate that the parameters of the proposed model can be estimated without additional acquisition requirements over the standard NODDI protocol. Thus anisotropic dispersion can be determined and has the potential to be used as a marker for normal brain development and ageing or in pathology. We additionally find that the original NODDI model is robust to the effects of anisotropic orientation dispersion, when the quantification of anisotropic dispersion is not of interest. PMID:26826512

  3. Human brain diffusion tensor imaging at submillimeter isotropic resolution on a 3 Tesla clinical MRI scanner

    PubMed Central

    Chang, Hing-Chiu; Sundman, Mark; Petit, Laurent; Guhaniyogi, Shayan; Chu, Mei-Lan; Petty, Christopher; Song, Allen W.; Chen, Nan-kuei

    2015-01-01

    The advantages of high-resolution diffusion tensor imaging (DTI) have been demonstrated in a recent post-mortem human brain study (Miller et al., NeuroImage 2011;57(1):167–181), showing that white matter fiber tracts can be much more accurately detected in data at submillimeter isotropic resolution. To our knowledge, in vivo human brain DTI at submillimeter isotropic resolution has not been routinely achieved yet because of the difficulty in simultaneously achieving high resolution and high signal-to-noise ratio (SNR) in DTI scans. Here we report a 3D multi-slab interleaved EPI acquisition integrated with multiplexed sensitivity encoded (MUSE) reconstruction, to achieve high-quality, high-SNR and submillimeter isotropic resolution (0.85 × 0.85 × 0.85 mm3) in vivo human brain DTI on a 3 Tesla clinical MRI scanner. In agreement with the previously reported post-mortem human brain DTI study, our in vivo data show that the structural connectivity networks of human brains can be mapped more accurately and completely with high-resolution DTI as compared with conventional DTI (e.g., 2 × 2 × 2 mm3). PMID:26072250

  4. Anatomical accuracy of brain connections derived from diffusion MRI tractography is inherently limited.

    PubMed

    Thomas, Cibu; Ye, Frank Q; Irfanoglu, M Okan; Modi, Pooja; Saleem, Kadharbatcha S; Leopold, David A; Pierpaoli, Carlo

    2014-11-18

    Tractography based on diffusion-weighted MRI (DWI) is widely used for mapping the structural connections of the human brain. Its accuracy is known to be limited by technical factors affecting in vivo data acquisition, such as noise, artifacts, and data undersampling resulting from scan time constraints. It generally is assumed that improvements in data quality and implementation of sophisticated tractography methods will lead to increasingly accurate maps of human anatomical connections. However, assessing the anatomical accuracy of DWI tractography is difficult because of the lack of independent knowledge of the true anatomical connections in humans. Here we investigate the future prospects of DWI-based connectional imaging by applying advanced tractography methods to an ex vivo DWI dataset of the macaque brain. The results of different tractography methods were compared with maps of known axonal projections from previous tracer studies in the macaque. Despite the exceptional quality of the DWI data, none of the methods demonstrated high anatomical accuracy. The methods that showed the highest sensitivity showed the lowest specificity, and vice versa. Additionally, anatomical accuracy was highly dependent upon parameters of the tractography algorithm, with different optimal values for mapping different pathways. These results suggest that there is an inherent limitation in determining long-range anatomical projections based on voxel-averaged estimates of local fiber orientation obtained from DWI data that is unlikely to be overcome by improvements in data acquisition and analysis alone. PMID:25368179

  5. Anatomically Informed Metrics for Connectivity-based Cortical Parcellation from Diffusion MRI

    PubMed Central

    Tungaraza, Rosalia L.; Mehta, Sonya H.; Haynor, David R.; Grabowski, Thomas J.

    2015-01-01

    Connectivity information derived from diffusion MRI can be used to parcellate the cerebral cortex into anatomically and functionally meaningful subdivisions. Acquisition and processing parameters can significantly affect parcellation results, and there is no consensus on best practice protocols. We propose a novel approach for evaluating parcellation based on measuring the degree to which parcellation conforms to known principles of brain organization, specifically cortical field homogeneity and inter-hemispheric homology. The proposed metrics are well behaved on morphologically-generated whole-brain parcels, where they correctly identify contralateral homologies, and give higher scores to anatomically versus arbitrarily generated parcellations. The measures show that individual cortical fields have characteristic connectivity profiles that are compact and separable, and that the topological arrangement of such fields is strongly conserved between hemispheres and individuals. The proposed metrics can be used to evaluate the quality of parcellations at the subject and group levels, and to improve acquisition and data processing for connectivity-based cortical parcellation. PMID:26080389

  6. A Simulation Framework for Quantitative Validation of Artefact Correction in Diffusion MRI.

    PubMed

    Graham, Mark S; Drobnjak, Ivana; Zhang, Hui

    2015-01-01

    In this paper we demonstrate a simulation framework that enables the direct and quantitative comparison of post-processing methods for diffusion weighted magnetic resonance (DW-MR) images. DW-MR datasets are employed in a range of techniques that enable estimates of local microstructure and global connectivity in the brain. These techniques require full alignment of images across the dataset, but this is rarely the case. Artefacts such as eddy-current (EC) distortion and motion lead to misalignment between images, which compromise the quality of the microstructural measures obtained from them. Numerous methods and software packages exist to correct these artefacts, some of which have become de-facto standards, but none have been subject to rigorous validation. The ultimate aim of these techniques is improved image alignment, yet in the literature this is assessed using either qualitative visual measures or quantitative surrogate metrics. Here we introduce a simulation framework that allows for the direct, quantitative assessment of techniques, enabling objective comparisons of existing and future methods. DW-MR datasets are generated using a process that is based on the physics of MRI acquisition, which allows for the salient features of the images and their artefacts to be reproduced. We demonstrate the application of this framework by testing one of the most commonly used methods for EC correction, registration of DWIs to b = 0, and reveal the systematic bias this introduces into corrected datasets. PMID:26221709

  7. Diffusion-weighted imaging and dynamic contrast-enhanced MRI in assessing response and recurrent disease in gynaecological malignancies.

    PubMed

    Hameeduddin, Ayshea; Sahdev, Anju

    2015-01-01

    Magnetic resonance imaging (MRI) has an established role in imaging pelvic gynaecological malignancies. It is routinely used in staging endometrial and cervical cancer, characterizing adnexal masses, selecting optimal treatment, monitoring treatment and detecting recurrent disease. MRI has also been shown to have an excellent performance and an evolving role in surveillance of patients after chemoradiotherapy in cervical cancer, post-trachelectomy, detecting early recurrence and planning exenterative surgery in isolated central recurrences in both cervical and endometrial cancer and in young patients on surveillance for medically managed endometrial cancer. However, conventional MRI still has limitations when the morphological appearance of early recurrent or residual disease overlaps with normal pelvic anatomy or treatment effects in the pelvis. In particular, after chemoradiotherapy for cervical cancer, distinguishing between radiotherapy changes and residual or early recurrent disease within the cervix or the vaginal vault can be challenging on conventional MRI alone. Therefore, there is an emerging need for functional imaging to overcome these limitations. The purpose of this paper is to discuss the emerging functional MRI techniques and their applications in predicting treatment response, detecting residual disease and early recurrent disease to optimize the treatment options available using diffusion-weighted imaging and dynamic contrast enhancement particularly in cervical and endometrial cancer. PMID:25889065

  8. Diffusion-Weighted MRI for Nodal Staging of Head and Neck Squamous Cell Carcinoma: Impact on Radiotherapy Planning

    SciTech Connect

    Dirix, Piet; Vandecaveye, Vincent; De Keyzer, Frederik; Op de beeck, Katya; Poorten, Vincent Vander; Delaere, Pierre; Verbeken, Eric; Hermans, Robert; Nuyts, Sandra

    2010-03-01

    Purpose: To evaluate the use of diffusion-weighted magnetic resonance imaging (DW-MRI) for nodal staging and its impact on radiotherapy (RT) planning. Methods and Materials: Twenty-two patients with locally advanced head and neck squamous cell carcinoma underwent contrast-enhanced computed tomography (CT), as well as MRI (with routine and DW sequences) prior to neck dissection. After topographic correlation, lymph nodes were evaluated microscopically with prekeratin immunostaining. Pathology results were correlated with imaging findings and an RT planning study was performed for these surgically treated patients. One set of target volumes was based on conventional imaging only, and another set was based on the corresponding DW-MRI images. A third reference set was contoured based solely on pathology results. Results: A sensitivity of 89% and a specificity of 97% per lymph node were found for DW-MRI. Nodal staging agreement between imaging and pathology was significantly stronger for DW-MRI (kappa = 0.97; 95% confidence interval [CI], 0.84-1.00) than for conventional imaging (kappa = 0.56; 95% CI, 0.16-0.96; p = 0.019, by McNemar's test). For both imaging modalities, the absolute differences between RT volumes and those obtained by pathology were calculated. Using an exact paired Wilcoxon test, the observed difference was significantly larger for conventional imaging than for DW-MRI for nodal gross tumor volume (p = 0.0013), as well as for nodal clinical target volume (p = 0.0415) delineation. Conclusions: These results suggest that DW-MRI is superior to conventional imaging for preradiotherapy nodal staging of head and neck squamous cell carcinoma, and provides a potential impact on organsparing and tumor control.

  9. Usefulness of diffusion-weighted MRI with echo-planar technique in the evaluation of cellularity in gliomas.

    PubMed

    Sugahara, T; Korogi, Y; Kochi, M; Ikushima, I; Shigematu, Y; Hirai, T; Okuda, T; Liang, L; Ge, Y; Komohara, Y; Ushio, Y; Takahashi, M

    1999-01-01

    The purpose of this study was to evaluate the utility of diffusion-weighted magnetic resonance imaging (MRI) with echo-planar imaging (EPI) technique in depicting the tumor cellularity and grading of gliomas. Twenty consecutive patients (13 men and 7 women, ranging in age from 13 to 69 years) with histologically proven gliomas were examined using a 1.5 T superconducting imager. Tumor cellularity, analyzed with National Institutes of Health Image 1.60 software on a Macintosh computer, was compared with the minimum apparent diffusion coefficient (ADC) and the signal intensity on the T2-weighted images. The relationship of the minimum ADC to the tumor grade was also evaluated. Tumor cellularity correlated well with the minimum ADC value of the gliomas (P = 0.007), but not with the signal intensity on the T2-weighted images. The minimum ADC of the high-grade gliomas was significantly higher than that of the low-grade gliomas. Diffusion-weighted MRI with EPI is a useful technique for assessing the tumor cellularity and grading of gliomas. This information is not obtained with conventional MRI and is useful for the diagnosis and characterization of gliomas. PMID:10030650

  10. Nuclear reaction analysis as a tool for the 3He thermal evolution in Li2TiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Carella, E.; Sauvage, T.; Bès, R.; Courtois, B.; González, M.

    2014-08-01

    Li2TiO3 ceramic is one of the promising solid breeding candidates for fuel generation in deuterium-tritium Fusion reactors. The Tritium (T) release characteristics consist of a complex combination of gas diffusion stages inside the solid. Considering that this ceramic will produce high concentration of gaseous transmutation products (3H and 4He) when exposed to high-energy neutrons, there are considerable interests in studying 3He thermal evolution for the fundamental understanding of the light ion behavior in breeder blanket materials under reactor conditions. 3He atoms used to simulate the 4He incorporation were implanted by a 600 keV ion beam at a fluence of 1017 at/cm2 and the 3He(d,α)1H nuclear reaction analysis (NRA) technique was subsequently used to study depth profiles evolution after different thermal annealing treatments. The release experiments showed that 3He outgassing is not effective at room temperature, remaining quite negligible till 300 °C. After this temperature, the 3He content in the sample reduces steadily with increasing the annealing temperature, and less than 5% of the initial 3He concentration was found at 900 °C after an isochronal annealing, without significant depth-profile broadening. Scanning and transmission electron microscopies characterization highlight the microstructural changes of the implanted and annealed ceramic within the nuclear cascades zone. The correlation of results obtained by electron microscopy and NRA technique leads to the conclusion that the helium release is governed by a transport mechanism that involves rapid migration/diffusion through interconnected gas cavities and resulting microcracks before reaching grain boundaries and opened pores.

  11. Spatially constrained incoherent motion method improves diffusion-weighted MRI signal decay analysis in the liver and spleen

    PubMed Central

    Taimouri, Vahid; Afacan, Onur; Perez-Rossello, Jeannette M.; Callahan, Michael J.; Mulkern, Robert V.; Warfield, Simon K.; Freiman, Moti

    2015-01-01

    Purpose: To evaluate the effect of the spatially constrained incoherent motion (SCIM) method on improving the precision and robustness of fast and slow diffusion parameter estimates from diffusion-weighted MRI in liver and spleen in comparison to the independent voxel-wise intravoxel incoherent motion (IVIM) model. Methods: We collected diffusion-weighted MRI (DW-MRI) data of 29 subjects (5 healthy subjects and 24 patients with Crohn’s disease in the ileum). We evaluated parameters estimates’ robustness against different combinations of b-values (i.e., 4 b-values and 7 b-values) by comparing the variance of the estimates obtained with the SCIM and the independent voxel-wise IVIM model. We also evaluated the improvement in the precision of parameter estimates by comparing the coefficient of variation (CV) of the SCIM parameter estimates to that of the IVIM. Results: The SCIM method was more robust compared to IVIM (up to 70% in liver and spleen) for different combinations of b-values. Also, the CV values of the parameter estimations using the SCIM method were significantly lower compared to repeated acquisition and signal averaging estimated using IVIM, especially for the fast diffusion parameter in liver (CVIV IM = 46.61 ± 11.22, CVSCIM = 16.85 ± 2.160, p < 0.001) and spleen (CVIV IM = 95.15 ± 19.82, CVSCIM = 52.55 ± 1.91, p < 0.001). Conclusions: The SCIM method characterizes fast and slow diffusion more precisely compared to the independent voxel-wise IVIM model fitting in the liver and spleen. PMID:25832079

  12. Nuclear Ordered Phases of Solid 3He in Silver Sinters

    NASA Astrophysics Data System (ADS)

    Schuberth, Erwin A.; Kath, Matthias; Bago, Simone

    2006-09-01

    To determine the exact spin structure of the nuclear magnetic ordered phases of solid 3He, the U2D2 low field and the high field phases above 0.4 T, a European Research and Training Network for neutron scattering from the ordered solid was established which consisted of a collaboration with the Hahn Meitner Institute, Berlin, and other European and US groups. For this experiment it is crucial to grow a single crystal within the sinter needed for cooling the solid to temperatures of the order of 500 μK and to keep it cold long enough to measure a magnetic neutron diffraction. The sinter is also necessary to absorb the major part (> 90%) of the heat generated by the neutron capture and decay reaction of the 3He nucleus. In this work we studied the growth of crystals in Ag sinters of different pore sizes and with different growth speeds to find an optimal way to obtain single crystalline samples, or at least samples with only a few grains. We used SQUID magnetometry and NMR to measure the magnetization in the ordered phases. They were indicated by the known drop of the intensity, both in the NMR signal and in the dc magnetization, for the U2D2 phase, and by an increase of about 30% for the high field phase. The best results for cooling were obtained with sinters made from 700 Å "Japanese powder" with a packing fraction of 50% which were annealed at 130 °C after sintering and then had a calculated particle size of about 4200 Å. In the dc magnetization we found a paramagnetic surface contribution from a few monolayers of 3He down to 500 μK in addition to the bulk magnetization.

  13. 3He Spin-Dependent Cross Sections and Sum Rules

    SciTech Connect

    Slifer, Karl; Amaryan, Moscov; Amaryan, Moskov; Auerbach, Leonard; Averett, Todd; Berthot, J.; Bertin, Pierre; Bertozzi, William; Black, Tim; Brash, Edward; Brown, D.; Burtin, Etienne; Calarco, John; Cates, Gordon; Chai, Zhengwei; Chen, Jian-Ping; Choi, Seonho; Chudakov, Eugene; Ciofi, Claudio; Cisbani, Evaristo; De Jager, Cornelis; Deur, Alexandre; DiSalvo, R.; Dieterich, Sonja; Djawotho, Pibero; Finn, John; Fissum, Kevin; Fonvieille, Helene; Frullani, Salvatore; Gao, Haiyan; Gao, Juncai; Garibaldi, Franco; Gasparian, Ashot; Gilad, Shalev; Gilman, Ronald; Glamazdin, Oleksandr; Glashausser, Charles; Glockle, W.; Golak, J.; Goldberg, Emma; Gomez, Javier; Gorbenko, Viktor; Hansen, Jens-Ole; Hersman, F.; Holmes, Richard; Huber, Garth; Hughes, Emlyn; Humensky, Thomas; Incerti, Sebastien; Iodice, Mauro; Jensen, S.; Jiang, Xiaodong; Jones, C.; Jones, G.; Jones, Mark; Jutier, Christophe; Kamada, H.; Ketikyan, Armen; Kominis, Ioannis; Korsch, Wolfgang; Kramer, Kevin; Kumar, Krishna; Kumbartzki, Gerfried; Kuss, Michael; Lakuriqi, Enkeleida; Laveissiere, Geraud; LeRose, John; Liang, Meihua; Liyanage, Nilanga; Lolos, George; Malov, Sergey; Marroncle, Jacques; McCormick, Kathy; McKeown, Robert; Meziani, Zein-Eddine; Michaels, Robert; Mitchell, Joseph; Nogga, Andreas; Pace, Emanuele; Papandreou, Zisis; Pavlin, Tina; Petratos, Gerassimos; Pripstein, David; Prout, David; Ransome, Ronald; Roblin, Yves; Rowntree, David; Rvachev, Marat; Sabatie, Franck; Saha, Arunava; Salme, Giovanni; SCOPETTA, S.; Skibinski, R.; Souder, Paul; Saito, Teijiro; Strauch, Steffen; Suleiman, Riad; Takahashi, Kazunori; Todor, Luminita; Tsubota, Hiroaki; Ueno, Hiroaki; Urciuoli, Guido; van der Meer, Rob; Vernin, Pascal; Voskanyan, Hakob; Witala, Henryk; Wojtsekhowski, Bogdan; Xiong, Feng; Xu, Wang; Yang, Jae-Choon; Zhang, Bin; Zolnierczuk, Piotr

    2008-07-01

    We present a measurement of the spin-dependent cross sections for the \\vec{^3He}(\\vec{e},e')X} reaction in the quasielastic and resonance regions at four-momentum transfer 0.1 < Q^2< 0.9 GeV^2. The spin-structure functions have been extracted and used to evaluate the nuclear Burkhardt--Cottingham and extended GDH sum rules for the first time. Impulse approximation and exact three-body Faddeev calculations are also compared to the data in the quasielastic region.

  14. Hard Photodisintegration of Proton Pairs in {sup 3}He

    SciTech Connect

    Piasetzky, Eli; Pomerantz, Ishay; Higinbotham, D.; Strauch, S.; Gilman, R.

    2008-10-13

    Hard deuteron photodisintegration has been investigated for 20 years, as its cross section follows the constituent counting rule and it provides insight into the interplay between hadronic and quark-gluon degrees of freedom in high-momentum transfer exclusive reactions. We have now measured for the first time hard pp-pair disintegration in the reaction {gamma}{sup 3}He{yields}pp+n, using kinematics corresponding to a spectator neutron. Cross sections were measured for 90 deg. c.m. at 8 beam energies, from 0.8 to 4.7 GeV. Preliminary results will be presented and compared to the hard deuteron photodisintegration data.

  15. High-pressure /sup 3/He gas scintillation neutron spectrometer

    SciTech Connect

    Derzon, M.S.; Slaughter, D.R.; Prussin, S.G.

    1985-10-01

    A high-pressure, /sup 3/He-Xe gas scintillation spectrometer has been developed for neutron spectroscopy on D-D fusion plasmas. The spectrometer exhibits an energy resolution of (121 +- 20 keV) keV (FWHM) at 2.5 MeV and an efficiency of (1.9 +- 0.4) x 10/sup -3/ (n/cm/sup 2/)/sup -1/. The contribution to the resolution (FWHM) from counting statistics is only (22 +- 3 keV) and the remainder is due predominantly to the variation of light collection efficiency with location of neutron events within the active volume of the detector.

  16. Isospin effects in the exclusive dp 3He reaction

    NASA Astrophysics Data System (ADS)

    Mielke, M.; Burmeister, I.; Chiladze, D.; Dymov, S.; Fritzsch, C.; Gebel, R.; Goslawski, P.; Hartmann, M.; Kacharava, A.; Khoukaz, A.; Kulessa, P.; Lorentz, B.; Mersmann, T.; Mikirtychiants, S.; Ohm, H.; Papenbrock, M.; Rausmann, T.; Serdyuk, V.; Ströher, H.; Täschner, A.; Valdau, Yu.; Wilkin, C.

    2014-06-01

    The differential cross section for the exclusive reaction has been measured with high resolution and large statistics over a large fraction of the backward 3He hemisphere at the excess energy 265 MeV using the COSY-ANKE magnetic spectrometer. Though the well-known ABC enhancement is observed in the spectrum, the differences detected between the and invariant-mass distributions show that there must be some isospin-one production even at relatively low excess energies. The invariant-mass differences are modeled in terms of the sequential decay.

  17. Fermion Monte Carlo Calculations on Liquid-3He

    SciTech Connect

    Kalos, M H; Colletti, L; Pederiva, F

    2004-03-16

    Methods and results for calculations of the ground state energy of the bulk system of {sup 3}He atoms are discussed. Results are encouraging: they believe that they demonstrate that their methods offer a solution of the ''fermion sign problem'' and the possibility of direct computation of many-fermion systems with no uncontrolled approximations. Nevertheless, the method is still rather inefficient compared with variational or fixed-node approximate methods. There appears to be a significant populations size effect. The situation is improved by the inclusion of ''Second Stage Importance Sampling'' and of ''Acceptance/Rejection'' adapted to their needs.

  18. Realistic simulation of artefacts in diffusion MRI for validating post-processing correction techniques.

    PubMed

    Graham, Mark S; Drobnjak, Ivana; Zhang, Hui

    2016-01-15

    In this paper we demonstrate a simulation framework that enables the direct and quantitative comparison of post-processing methods for diffusion weighted magnetic resonance (DW-MR) images. DW-MR datasets are employed in a range of techniques that enable estimates of local microstructure and global connectivity in the brain. These techniques require full alignment of images across the dataset, but this is rarely the case. Artefacts such as eddy-current (EC) distortion and motion lead to misalignment between images, which compromise the quality of the microstructural measures obtained from them. Numerous methods and software packages exist to correct these artefacts, some of which have become de-facto standards, but none have been subject to rigorous validation. In the literature, improved alignment is assessed using either qualitative visual measures or quantitative surrogate metrics. Here we introduce a simulation framework that allows for the direct, quantitative assessment of techniques, enabling objective comparisons of existing and future methods. DW-MR datasets are generated using a process that is based on the physics of MRI acquisition, which allows for the salient features of the images and their artefacts to be reproduced. We apply this framework in three ways. Firstly we assess the most commonly used method for artefact correction, FSL's eddy_correct, and compare it to a recently proposed alternative, eddy. We demonstrate quantitatively that using eddy_correct leads to significant errors in the corrected data, whilst eddy is able to provide much improved correction. Secondly we investigate the datasets required to achieve good correction with eddy, by looking at the minimum number of directions required and comparing the recommended full-sphere acquisitions to equivalent half-sphere protocols. Finally, we investigate the impact of correction quality by examining the fits from microstructure models to real and simulated data. PMID:26549300

  19. Dynamics of the connectome in Huntington's disease: A longitudinal diffusion MRI study

    PubMed Central

    Odish, Omar F.F.; Caeyenberghs, Karen; Hosseini, Hadi; van den Bogaard, Simon J.A.; Roos, Raymund A.C.; Leemans, Alexander

    2015-01-01

    Objectives To longitudinally investigate the connectome in different stages of Huntington's disease (HD) by applying graph theoretical analysis to diffusion MRI data. Experimental design We constructed weighted structural networks and calculated their topological properties. Twenty-two premanifest (preHD), 10 early manifest HD and 24 healthy controls completed baseline and 2 year follow-up scans. We stratified the preHD group based on their predicted years to disease onset into a far (preHD-A) and near (preHD-B) to disease onset group. We collected clinical and behavioural measures per assessment time point. Principle observations We found a significant reduction over time in nodal betweenness centrality both in the early manifest HD and preHD-B groups as compared to the preHD-A and control groups, suggesting a decrease of importance of specific nodes to overall network organization in these groups (FDR adjusted ps < 0.05). Additionally, we found a significant longitudinal decrease of the clustering coefficient in preHD when compared to healthy controls (FDR adjusted p < 0.05), which can be interpreted as a reduced capacity for internodal information processing at the local level. Furthermore, we demonstrated dynamic changes to hub-status loss and gain both in preHD and early manifest HD. Finally, we found significant cross-sectional as well as longitudinal relationships between graph metrics and clinical and neurocognitive measures. Conclusions This study demonstrates divergent longitudinal changes to the connectome in (pre) HD compared to healthy controls. This provides novel insights into structural correlates associated with clinical and cognitive functions in HD and possible compensatory mechanisms at play in preHD. PMID:26288754

  20. Diffusion tensor imaging in evaluation of posterior fossa tumors in children on a 3T MRI scanner

    PubMed Central

    Assis, Zarina Abdul; Saini, Jitender; Ranjan, Manish; Gupta, Arun Kumar; Sabharwal, Paramveer; Naidu, Purushotham R

    2015-01-01

    Context: Primary intracranial tumors in children are commonly located in the posterior fossa. Conventional MRI offers limited information regarding the histopathological type of tumor which is essential for better patient management. Aims: The purpose of the study was to evaluate the usefulness of advanced MR imaging techniques like diffusion tensor imaging (DTI) in distinguishing the various histopathological types of posterior fossa tumors in children. Settings and Design: DTI was performed on a 3T MRI scanner in 34 untreated children found to have posterior fossa lesions. Materials and Methods: Using third party software, various DTI parameters [apparent diffusion coefficient (ADC), fractional anisotropy (FA), radial diffusivity, planar index, spherical index, and linear index] were calculated for the lesion. Statistical Analysis Used: Data were subjected to statistical analysis [analysis of variance (ANOVA)] using SPSS 15.0 software. Results: We observed significant correlation (P < 0.01) between ADC mean and maximum, followed by radial diffusivity (RD) with the histopathological types of the lesions. Rest of the DTI parameters did not show any significant correlation in our study. Conclusions: The results of our study support the hypothesis that most cellular tumors and those with greater nuclear area like medulloblastoma would have the lowest ADC values, as compared to less cellular tumors like pilocytic astrocytoma. PMID:26752824

  1. Quantum Phase Transition of 3He in Aerogel at a Nonzero Pressure

    NASA Astrophysics Data System (ADS)

    Matsumoto, K.; Porto, J. V.; Pollack, L.; Smith, E. N.; Ho, T. L.; Parpia, J. M.

    1997-07-01

    We present evidence for a nonzero pressure, T = 0 superfluid phase transition of 3He in 98.2% open aerogel. Unlike bulk 3He which is a superfluid at T = 0 at all pressures (densities) between zero and the melting pressure, 3He in aerogel is not superfluid unless the 3He density exceeds a critical value ρc. About 90% of the 3He added above ρc contributes to the superfluid density.

  2. Effective theory of 3H and 3He

    NASA Astrophysics Data System (ADS)

    König, Sebastian; Grießhammer, Harald W.; Hammer, H.-W.; van Kolck, U.

    2016-06-01

    We present a new perturbative expansion for pionless effective field theory with Coulomb interactions in which at leading order (LO) the spin-singlet nucleon–nucleon channels are taken in the unitarity limit. Presenting results up to next-to-leading order for the Phillips line and the neutron–deuteron doublet-channel phase shift, we find that a perturbative expansion in the inverse {}1{S}0 scattering lengths converges rapidly. Using a new systematic treatment of the proton–proton sector that isolates the divergence due to one-photon exchange, we renormalize the corresponding contribution to the {}3{{H}} –{}3{He} binding energy splitting and demonstrate that the Coulomb force in pionless EFT is a completely perturbative effect in the trinucleon bound-state regime. In our new expansion, the LO is exactly isospin-symmetric. At next-to-leading order, we include isospin breaking via the Coulomb force and two-body scattering lengths, and find for the energy splitting {({E}B{(}3{He})-{E}B{(}3{{H}}))}{NLO}\\quad =(-0.86+/- 0.17)\\quad {MeV}.

  3. Simulation of detector signals in n+3 He --> p + t

    NASA Astrophysics Data System (ADS)

    Coppola, Christopher; n3He Collaboration

    2015-10-01

    The parity violating proton directional asymmetry from the capture of polarized neutrons on 3He is being measured with a pulsed neutron beam at the Spallation Neutron Source at Oak Ridge National Laboratory. The target is an ion chamber with 3He at approximately half an atmosphere. Signal wires at different locations in the chamber have different sensitivities to the physics asymmetry, which are determined by the geometry and configuration of the experiment. These geometry factors must be determined by simulation. In addition, a simulation can estimate the statistical precision of the experiment, optimize configuration variables, and assist with error analysis. To achieve the most accurate simulation of the detector signals, a custom simulation was written in C++ using weighted variables and taking advantage of parallel execution. The inputs used to construct the simulation came from measurements of the neutron phase space, ENDF cross sections, and PSTAR ionization data. A cell model was used to combine this physics to produce an accurate simulation of the experimental data. This simulation can be used to calculate accurate and tunable geometry factors, and to produce desired quanities for use in optimization and analysis.

  4. Source investigation of impulsive 3He-rich particle events

    NASA Astrophysics Data System (ADS)

    Tan, Chengming; Yan, Yihua

    We have investigated the source characteristic and coronal magnetic field structure of six impulsive solar energetic particle (SEP) events selected from Wang et al. [Wang, Y.-M., Pick, M., Mason, G.M. Coronal holes, jets, and the origin of 3He-rich particle events. ApJ 639, 495, 2006] and Pick et al. [Pick, M., Mason, G.M., Wang, Y.-M., Tan, C., Wang, L. Solar source regions for 3He-rich solar energetic particle events identified using imaging radio, optical, and energetic particle observations. ApJ 648, 1247, 2006]. Some results are obtained: first, 2 events are associated with wide (≈100°) CMEs (hereafter wide CME events), another 4 events are associated with narrow (⩽40°) CMEs (hereafter narrow CME events); second, the coronal magnetic field configuration of narrow CME events appear more simple than that of the wide CME events; third, the photospheric magnetic field evolutions of all these events show new emergence of fluxes, while one case also shows magnetic flux cancellation; fourth, the EUV jets usually occurred very close to the footpoint of the magnetic field loop, while meter type III bursts occurred near or at the top of the loop and higher than EUV jets. Furthermore, the heights of type III bursts are estimated from the result of the coronal magnetic field extrapolations.

  5. Liquid and Solid Phases of 3He on Graphite

    NASA Astrophysics Data System (ADS)

    Gordillo, M. C.; Boronat, J.

    2016-04-01

    Recent heat-capacity experiments show quite unambiguously the existence of a liquid 3He phase adsorbed on graphite. This liquid is stable at an extremely low density, possibly one of the lowest found in nature. Previous theoretical calculations of the same system, and in strictly two dimensions, agree with the result that this liquid phase is not stable and the system is in the gas phase. We calculated the phase diagram of normal 3He adsorbed on graphite at T =0 using quantum Monte Carlo methods. Considering a fully corrugated substrate, we observe that at densities lower than 0.006 Å-2 the system is a very dilute gas that, at that density, is in equilibrium with a liquid of density 0.014 Å-2 . Our prediction matches very well the recent experimental findings on the same system. On the contrary, when a flat substrate is considered, no gas-liquid coexistence is found, in agreement with previous calculations. We also report results on the different solid structures, and on the corresponding phase transitions that appear at higher densities.

  6. The 3H-3He Charge Radii Difference

    NASA Astrophysics Data System (ADS)

    Myers, L. S.; Arrington, J. R.; Higinbotham, D. W.

    2016-03-01

    The upcoming E12-14-009 [1] experiment at Jefferson Lab will determine the ratio of the electric form factors for the A=3 mirror nuclei 3He and 3H. The measurement will use a 1.1 GeV electron beam, a special collimator plate to allow for simultaneous optics measurements, and the low-activity tritium target being prepared for Jefferson Lab. By observing the dependence of the form factor ratio as a function of Q2 over 0.05-0.09 GeV2, the dependence of the radii extraction on the shape of the form factors is minimized. As a result, we anticipate the uncertainty of the extracted charge radii difference to be 0.03 fm, a reduction of 70% from the current measurement. Using precise measurements of the 3He charge radius from isotopic shift or μHe measurements [2-4], we can deduce the absolute 3H charge radius. The results will provide a direct comparison to recent calculations of the charge radii.

  7. Double-quantum vortex in superfluid 3He-A

    PubMed

    Blaauwgeers; Eltsov; Krusius; Ruohio; Schanen; Volovik

    2000-03-30

    Linear defects are generic in continuous media. In quantum systems they appear as topological line defects which are associated with a circulating persistent current. In relativistic quantum field theories they are known as cosmic strings, in superconductors as quantized flux lines, and in superfluids and low-density Bose-Einstein condensates as quantized vortex lines. A conventional quantized vortex line consists of a central core around which the phase of the order parameter winds by 27(pi)n, while within the core the order parameter vanishes or is depleted from the bulk value. Usually vortices are singly quantized (that is, have n = 1). But it has been theoretically predicted that, in superfluid 3He-A, vortex lines are possible that have n = 2 and continuous structure, so that the orientation of the multicomponent order parameter changes smoothly throughout the vortex while the amplitude remains constant. Here we report direct proof, based on high-resolution nuclear magnetic resonance measurements, that the most common vortex line in 3He-A has n = 2. One vortex line after another is observed to form in a regular periodic process, similar to a phase-slip in the Josephson effect. PMID:10761908

  8. Hard photodisintegration of a proton pair in {sup 3}He

    SciTech Connect

    Stanley Brodsky; Leonid Frankfurt; Ronald Gilman; J. R. Hiller; G. A. Miller; Eliezer Piasetzky; Misak Sargsian; Mark Strikman

    2003-05-01

    Hard photodisintegration of the deuteron has been extensively studied in order to understand the dynamics of the transition from hadronic to quark-gluon descriptions of the strong interaction. In this work, we discuss the extension of this program to hard photodisintegration of a pp pair in the {sup 3}He nucleus. Experimental confirmation of new features predicted here for the suggested reaction would advance our understanding of hard nuclear reactions. A main prediction, in contrast with low-energy observations, is that the pp breakup cross section is not much smaller than the one for pn break up. In some models, the energy-dependent oscillations observed for pp scattering are predicted to appear in the {gamma} {sup 3}He {yields} pp + n reaction. Such an observation would open up a completely new field in studies of color coherence phenomena in hard nuclear reactions. We also demonstrate that, in addition to the energy dependence, the measurement of the light-cone momentum distribution of the recoil neutron provides an independent test of the underlying dynamics of hard disintegration.

  9. First observation of two hyperfine transitions in antiprotonic 3He

    PubMed Central

    Friedreich, S.; Barna, D.; Caspers, F.; Dax, A.; Hayano, R.S.; Hori, M.; Horváth, D.; Juhász, B.; Kobayashi, T.; Massiczek, O.; Sótér, A.; Todoroki, K.; Widmann, E.; Zmeskal, J.

    2011-01-01

    We report on the first experimental results for microwave spectroscopy of the hyperfine structure of p¯3He+. Due to the helium nuclear spin, p¯3He+ has a more complex hyperfine structure than p¯4He+, which has already been studied before. Thus a comparison between theoretical calculations and the experimental results will provide a more stringent test of the three-body quantum electrodynamics (QED) theory. Two out of four super-super-hyperfine (SSHF) transition lines of the (n,L)=(36,34) state were observed. The measured frequencies of the individual transitions are 11.12559(14) GHz and 11.15839(18) GHz, less than 1 MHz higher than the current theoretical values, but still within their estimated errors. Although the experimental uncertainty for the difference of these frequencies is still very large as compared to that of theory, its measured value agrees with theoretical calculations. This difference is crucial to be determined because it is proportional to the magnetic moment of the antiproton. PMID:21822351

  10. Textural domain walls in superfluid 3He-B

    NASA Astrophysics Data System (ADS)

    Mizushima, Takeshi

    Owing to the richness of symmetry, the superfluid 3He serves as a rich repository of topological quantum phenomena. This includes the emergence of surface Majorana fermions and their quantum mass acquisition at the topological critical point. Furthermore, the marriage of the prototype topological superfluid with nanofabrication techniques brings about a rich variety of spontaneous symmetry breaking, such as the formation of the stripe order and nontrivial domain walls. In this work, we examine the possible formation of textural domain walls in the superfluid 3He-B confined to a thin slab with a sub-micron thickness. When an applied magnetic field is much higher than the dipolar field, two nearly degenerate ground states appear, which are characterized by the Ising order associated with the spontaneous breaking of a magnetic order-two symmetry, lcirc;z = + 1 and - 1 . We here discuss the structure of the textural domain wall formed by the spatial modulation of the Ising order, such as low-lying quasiparticle excitations and spontaneous spin current. We also report bosonic modes bound to the textural domain wall.

  11. 4-D segmentation and normalization of 3He MR images for intrasubject assessment of ventilated lung volumes

    NASA Astrophysics Data System (ADS)

    Contrella, Benjamin; Tustison, Nicholas J.; Altes, Talissa A.; Avants, Brian B.; Mugler, John P., III; de Lange, Eduard E.

    2012-03-01

    Although 3He MRI permits compelling visualization of the pulmonary air spaces, quantitation of absolute ventilation is difficult due to confounds such as field inhomogeneity and relative intensity differences between image acquisition; the latter complicating longitudinal investigations of ventilation variation with respiratory alterations. To address these potential difficulties, we present a 4-D segmentation and normalization approach for intra-subject quantitative analysis of lung hyperpolarized 3He MRI. After normalization, which combines bias correction and relative intensity scaling between longitudinal data, partitioning of the lung volume time series is performed by iterating between modeling of the combined intensity histogram as a Gaussian mixture model and modulating the spatial heterogeneity tissue class assignments through Markov random field modeling. Evaluation of the algorithm was retrospectively applied to a cohort of 10 asthmatics between 19-25 years old in which spirometry and 3He MR ventilation images were acquired both before and after respiratory exacerbation by a bronchoconstricting agent (methacholine). Acquisition was repeated under the same conditions from 7 to 467 days (mean +/- standard deviation: 185 +/- 37.2) later. Several techniques were evaluated for matching intensities between the pre and post-methacholine images with the 95th percentile value histogram matching demonstrating superior correlations with spirometry measures. Subsequent analysis evaluated segmentation parameters for assessing ventilation change in this cohort. Current findings also support previous research that areas of poor ventilation in response to bronchoconstriction are relatively consistent over time.

  12. Studies of 3He polarization losses during NMR and EPR measurment and Polarized 3He target cell lifetime

    NASA Astrophysics Data System (ADS)

    An, Peibo

    2014-09-01

    The 3He target cell polarized by spin-exchange optical pumping(SEOP) is used as a neutron substitute to study the inner structure of the neutron. In our lab, nuclear-magnetic-resonance(NMR) is used to measure the relative polarization and electron-paramagnetic-resonance(EPR) is used to measure the spin exchange EPR frequency shift parameter of potassium and rubidium in our target cell presented in magnetic fields. The alkali in the cell is used to facilitate the polarization of 3He. The first part of my work presents the study of the polarization losses of the cell during both NMR and EPR. With the help of improved RF coils, we keep the background noise received by pickup coils reasonably low, but three other kinds of losses are inevitable: losses during Adiabatic Fast Passage (AFP) sweep, losses due to flux change caused by different cell orientation with respect to RF fields and physical losses. Fortunately there is only flux change in NMR measurements. The second part of my work presents the study of cell lifetime improvement. The polarization decreases in a process called relaxation exponentially. The lifetime of a cell is how long it can keep its polarization. The typical lifetime of cells produced in our lab is about 22 hours. With a newly designed vacuum system. The 3He target cell polarized by spin-exchange optical pumping(SEOP) is used as a neutron substitute to study the inner structure of the neutron. In our lab, nuclear-magnetic-resonance(NMR) is used to measure the relative polarization and electron-paramagnetic-resonance(EPR) is used to measure the spin exchange EPR frequency shift parameter of potassium and rubidium in our target cell presented in magnetic fields. The alkali in the cell is used to facilitate the polarization of 3He. The first part of my work presents the study of the polarization losses of the cell during both NMR and EPR. With the help of improved RF coils, we keep the background noise received by pickup coils reasonably low, but

  13. MRI diffusion tensor tracking of a new amygdalo-fusiform and hippocampo-fusiform pathway system in humans

    PubMed Central

    Smith, Charles D.; Lori, Nicolas F.; Akbudak, Erbil; Sorar, Ertugrul; Gultepe, Eren; Shimony, Joshua S.; McKinstry, Robert C.; Conturo, Thomas E.

    2009-01-01

    Purpose To use MRI diffusion-tensor tracking (DTT) to test for the presence of unknown neuronal fiber pathways interconnecting mid-fusiform cortex and anteromedial temporal lobe in humans. Such pathways are hypothesized to exist because these regions co-activate in functional MRI (fMRI) studies of emotion-valued faces and words, suggesting a functional link that could be mediated by neuronal connections. Materials and Methods 15 normal human subjects were studied using unbiased DTT approaches designed for probing unknown pathways, including whole-brain seeding and large pathway-selection volumes. Several quality-control steps verified the results. Results Parallel amygdalo-fusiform and hippocampo-fusiform pathways were found in all subjects. The pathways begin/end at mid-fusiform gyrus above the lateral occipitotemporal sulcus bilaterally. The superior pathway ends/begins at the superolateral amygdala. The inferior pathway crosses medially and ends/begins at the hippocampal head. The pathways are left-lateralized, with consistently larger cross-sectional area, higher anisotropy, and lower minimum eigenvalue (D-min) on the left, where D-min assesses intrinsic cross-fiber diffusivity independent of curvature. Conclusion A previously-undescribed pathway system interconnecting mid-fusiform region with amygdala/hippocampus has been revealed. This pathway system may be important for recognition, memory consolidation, and emotional modulation of face, object, and lexical information, which may be disrupted in conditions such as Alzheimer's disease. PMID:19418556

  14. Mapping somatosensory connectivity in adult mice using diffusion MRI tractography and super-resolution track density imaging.

    PubMed

    Richards, Kay; Calamante, Fernando; Tournier, Jacques-Donald; Kurniawan, Nyoman D; Sadeghian, Farnoosh; Retchford, Alexander R; Jones, Gabriel Davis; Reid, Christopher A; Reutens, David C; Ordidge, Roger; Connelly, Alan; Petrou, Steven

    2014-11-15

    In this study we combined ultra-high field diffusion MRI fiber tracking and super-resolution track density imaging (TDI) to map the relay locations and connectivity of the somatosensory pathway in paraformaldehyde fixed, C57Bl/6J mouse brains. Super-resolution TDI was used to achieve 20 μm isotropic resolution to inform the 3D topography of the relay locations including thalamic barreloids and brainstem barrelettes, not described previously using MRI methodology. TDI-guided mapping results for thalamo-cortical connectivity were consistent with thalamo-cortical projections labeled using virus mediated fluorescent protein expression. Trigemino-thalamic TDI connectivity maps were concordant with results obtained using anterograde dye tracing from brainstem to thalamus. Importantly, TDI mapping overcame the constraint of tissue distortion observed in mechanically sectioned tissue, enabling 3D reconstruction and long-range connectivity data. In conclusion, our results showed that diffusion micro-imaging at ultra-high field MRI revealed the stereotypical pattern of somatosensory connectivity and is a valuable tool to complement histologic methods, achieving 3D spatial preservation of whole brain networks for characterization in mouse models of human disease. PMID:25087481

  15. Multi-modal pharmacokinetic modelling for DCE-MRI: using diffusion weighted imaging to constrain the local arterial input function

    NASA Astrophysics Data System (ADS)

    Hamy, Valentin; Modat, Marc; Shipley, Rebecca; Dikaios, Nikos; Cleary, Jon; Punwani, Shonit; Ourselin, Sebastien; Atkinson, David; Melbourne, Andrew

    2014-03-01

    The routine acquisition of multi-modal magnetic resonance imaging data in oncology yields the possibility of combined model fitting of traditionally separate models of tissue structure and function. In this work we hypothesise that diffusion weighted imaging data may help constrain the fitting of pharmacokinetic models to dynamic contrast enhanced (DCE) MRI data. Parameters related to tissue perfusion in the intra-voxel incoherent motion (IVIM) modelling of diffusion weighted MRI provide local information on how tissue is likely to perfuse that can be utilised to guide DCE modelling via local modification of the arterial input function (AIF). In this study we investigate, based on multi-parametric head and neck MRI of 8 subjects (4 with head and neck tumours), the benefit of incorporating parameters derived from the IVIM model within the DCE modelling procedure. Although we find the benefit of this procedure to be marginal on the data used in this work, it is conceivable that a technique of this type will be of greater use in a different application.

  16. Thymoma of the left thymic lobe with a contralateral small pleural implant successfully detected with diffusion-weighted MRI.

    PubMed

    Priola, Adriano Massimiliano; Priola, Sandro Massimo

    2015-01-01

    Thymoma is the most common primary neoplasm of the anterior mediastinum. At diagnosis, up to 40% of patients present with advanced disease. Because advanced thymomas receive neoadjuvant chemotherapy, diagnostic imaging is crucial to plan the correct treatment. For characterizing thymomas, CT is the first choice modality, whereas 18F-FDG/PET is reserved for questionable cases and MRI is not routinely employed. Hereby, we describe a case of thymoma with a single contralateral pleural implant in a 30-year-old woman. The small pleural thickening detected at CT was correctly interpreted as pleural seeding related to thymoma at diffusion-weighted (DW)-MRI after a negative 18F-FDG/PET scan, and was subsequently confirmed at surgery. Precise diagnosis and accurate preoperative staging are crucial in managing thymic epithelial tumours in order to design the appropriate treatment and improve prognosis. Indeed, when stage IVa for pleural seeding is diagnosed preoperatively, a multimodality approach including primary chemotherapy followed by surgery and postoperative radiotherapy/chemotherapy is recommended. This is the first report that used DW-MRI for the characterization of pleural seeding in thymoma and demonstrates that DW-MRI could be useful for the correct pre-operatory staging in thymoma patients, especially in cases with indeterminate pleural thickenings at CT, in order to define the correct management. PMID:25702681

  17. Estimation of the extraterrestrial 3He and 20Ne fluxes on Earth from He and Ne systematics in marine sediments

    NASA Astrophysics Data System (ADS)

    Chavrit, Déborah; Moreira, Manuel; Moynier, Frédéric

    2016-04-01

    Sediments contain interplanetary dust particles (IDPs) carrying extraterrestrial noble gases, such as 3He, which have previously been used to estimate the IDP accretion flux over time and the duration of past environmental events. However, due to its high diffusivity, He can be lost by diffusion either due to frictional heating during entry in the atmosphere, or once it has been incorporated in the sediments. Therefore the absolute values of 3He IDP fluxes cannot be known. Due to its lower diffusivity, Ne is less likely to be lost by diffusion than He and can potentially provide an absolute IDP flux value. Here, we studied the Ne and He isotopic composition of 21 sediments of different ages (3 to 38 Myr, 56 Myr and 183 Myr) in order to better constrain the retention of 3He in such deposits. The samples are carbonates from 2 sites of the Integrated Ocean Drilling Program (IODP), which previously showed evidence of detectable extraterrestrial 3He, and from the Sancerre core in the Paris basin. The 3He/4He, 20Ne/22Ne and 21Ne/22Ne ratios of decarbonated residues vary respectively from 0.09×10‑6 to 76.5×10‑6, 9.54±0.08 to 11.30±0.60 and from 0.0295±0.0001 to 0.0344±0.0003. These isotopic compositions can be explained by a mixing between two terrestrial components (atmosphere and radiogenic He and nucleogenic Ne present in the terrigenous fractions) and an extraterrestrial component. The linear relationship between 20Ne/22Ne and 3He/22Ne ratios shows that the extraterrestrial component has a unique composition and is similar to the He and Ne composition of implanted solar wind. This composition is different from the individual stratospheric IDPs for which the Ne and He isotopic compositions have been measured. We suggest that this difference is due to a bias in the sampling of the individual IDPs previously analyzed toward the largest ones that are more likely to lose He during entry in the atmosphere. Our data further constrains the size of the majority of

  18. Estimation of the extraterrestrial 3He and 20Ne fluxes on Earth from He and Ne systematics in marine sediments

    NASA Astrophysics Data System (ADS)

    Chavrit, Déborah; Moreira, Manuel A.; Moynier, Frédéric

    2016-02-01

    Sediments contain interplanetary dust particles (IDPs) carrying extraterrestrial noble gases, such as 3He, which have previously been used to estimate the IDP accretion flux over time and the duration of past environmental events. However, due to its high diffusivity, He can be lost by diffusion either due to frictional heating during entry in the atmosphere, or once it has been incorporated in the sediments. Therefore the absolute values of 3He IDP fluxes cannot be known. Due to its lower diffusivity, Ne is less likely to be lost by diffusion than He and can potentially provide an absolute IDP flux value. Here, we studied the Ne and He isotopic composition of 21 sediments of different ages (3 to 38 Myr, 56 Myr and 183 Myr) in order to better constrain the retention of 3He in such deposits. The samples are carbonates from 2 sites of the Integrated Ocean Drilling Program (IODP), which previously showed evidence of detectable extraterrestrial 3He, and from the Sancerre core in the Paris basin. The 3He/4He, 20Ne/22Ne and 21Ne/22Ne ratios of decarbonated residues vary respectively from 0.09 ×10-6 to 76.5 ×10-6, 9.54 ± 0.08 to 11.30 ± 0.60 and from 0.0295 ± 0.0001 to 0.0344 ± 0.0003. These isotopic compositions can be explained by a mixing between two terrestrial components (atmosphere and radiogenic He and nucleogenic Ne present in the terrigenous fractions) and an extraterrestrial component. The linear relationship between 20Ne/22Ne and 3He/22Ne ratios shows that the extraterrestrial component has a unique composition and is similar to the He and Ne composition of implanted solar wind. This composition is different from the individual stratospheric IDPs for which the Ne and He isotopic compositions have been measured. We suggest that this difference is due to a bias in the sampling of the individual IDPs previously analyzed toward the largest ones that are more likely to lose He during entry in the atmosphere. Our data further constrains the size of the majority

  19. A dynamic model for power deposition in 3He lasers pumped by 3He(n,p) 3H reactions

    NASA Astrophysics Data System (ADS)

    Çetin, Füsun

    2004-07-01

    The coupled variation of power density with gas density in a nuclear-pumped laser, which is excited by 3He(n,p) 3H reaction products, is considered. In the literature, volumetric excitation by reaction products of 3He(n,p) 3H is only considered for the case in which gas density is uniform and does not change during the pumping. In this work, a time-dependent model describing the coupled fluid dynamic and particle transport behaviour of the gas has been developed. In modelling charge particle transport behaviour, a previously reported energy deposition model for a constant gas density is extended for a variable gas density by taking into account variations in the particle range, macroscopic cross sections and neutron flux depending on density field of the gas. The coupled equations, which are obtained by using the power deposition density expression obtained for variable gas density in the acoustically filtered equations of motion of the gas, are solved numerically. Spatial and temporal variations of power deposition density and gas density during the pumping pulse are determined for various operating pressures ranging from 0.5 to 10 atm. In the calculations, the characteristics of I.T.U TRIGA Mark-II Reactor are used and it is assumed that laser tube is placed in the centre of the reactor core. Obtained results are presented and examined.

  20. Monitoring of gliomas in vivo by diffusion MRI and (1)H MRS during gene therapy-induced apoptosis: interrelationships between water diffusion and mobile lipids.

    PubMed

    Liimatainen, Timo; Hakumäki, Juhana M; Kauppinen, Risto A; Ala-Korpela, Mika

    2009-04-01

    The measurement of water diffusion by diffusion-weighted MRI (DWI) in vivo offers a non-invasive method for assessing tissue responses to anti-cancer therapies. The pathway of cell death after anti-cancer treatment is often apoptosis, which leads to accumulation of mobile lipids detectable by (1)H MRS in vivo. However, it is not known how these discrete MR markers of cell death relate to each other. In a rodent tumour model [i.e. ganciclovir-treated herpes simplex thymidine kinase (HSV-tk) gene-transfected BT4C gliomas], we studied the interrelationships between water diffusion (Trace{D}) and mobile lipids during apoptosis. Water diffusion and water-referenced concentrations of mobile lipids showed clearly increasing and interconnected trends during treatment. Of the accumulating (1)H MRS-visible lipids, the fatty acid --CH==CH-- groups and cholesterol compounds showed the strongest associations with water diffusion (r(2) = 0.30; P < 0.05 and r(2) = 0.48; P < 0.01, respectively). These results indicate that the tumour histopathology and apoptotic processes during tumour shrinkage can be interrelated in vivo by DWI of tissue water and (1)H MRS of mobile lipids, respectively. However, there is considerable individual variation in the associations, particularly at the end of the treatment period, and in the relative compositions of the accumulating NMR-visible lipids. The findings suggest that the assessment of individual treatment response in vivo may benefit from combining DWI and (1)H MRS. Absolute and relative changes in mobile lipids may indicate initiation of tumour shrinkage even when changes in tissue water diffusion are still small. Conversely, greatly increased water diffusion probably indicates that substantial cell decomposition has taken place in the tumour tissue when the (1)H MRS resonances of mobile lipids alone can no longer give a reliable estimate of tissue conditions. PMID:19009568

  1. {sup 3}He target for Hall C at CEBAF

    SciTech Connect

    Zeidman, B.; Zeuli, A.

    1995-08-01

    A major fraction of the physics program for Hall C involves scattering from cryogenic targets of the lightest nuclei, i.e. H, D, and {sup 3,4}He. Argonne is constructing the He target that will consist of a 4cm cylinder, operating at a pressure of 10 atmospheres and a temperature of {approximately}5.2 degrees Kelvin. CEBAF is currently constructing a cryo-target system for liquid H and D cells and the cooled, pressurized helium targets. The He target system includes cell loop, the He supply systems, and the additional equipment needed to ensure minimum loss of {sup 3}He in the event of target rupture. Some of the major components have been completed, while the balance of the system will be ready for installation this fiscal year.

  2. Event identification in 3He proportional counters using risetime discrimination

    NASA Astrophysics Data System (ADS)

    Langford, T. J.; Bass, C. D.; Beise, E. J.; Breuer, H.; Erwin, D. K.; Heimbach, C. R.; Nico, J. S.

    2013-07-01

    We present a straightforward method for particle identification and background rejection in 3He proportional counters for use in neutron detection. By measuring the risetime and pulse height of the preamplifier signals, one may define a region in the risetime versus pulse height space where the events are predominately from neutron interactions. For six proportional counters surveyed in a low-background environment, we demonstrate the ability to reject alpha-particle events with an efficiency of 99%. By applying the same method, we also show an effective rejection of microdischarge noise events that, when passed through a shaping amplifier, are indistinguishable from physical events in the counters. The primary application of this method is in measurements where the signal-to-background for counting neutrons is very low, such as in underground laboratories.

  3. Direct energy conversion system for D(3)-He fusion

    NASA Astrophysics Data System (ADS)

    Tomita, Y.; Shu, L. Y.; Momota, H.

    1993-11-01

    A novel and highly efficient direct energy conversion system is proposed for utilizing D(3)-He fueled fusion. In order to convert kinetic energy of ions, we applied a pair of direct energy conversion systems each of which has a cusp-type DEC and a traveling wave DEC (TWDEC). In a cusp-type DEC, electrons are separated from the escaping ions at the first line-cusp and the energy of thermal ion components is converted at the second cusp DEC. The fusion protons go through the cusp-type DEC and arrive at the TWDEC, which principle is similar to 'LINAC'. The energy of fusion protons is recovered to electricity with an efficiency of more than 70%. These DEC's bring about the high efficient fusion plant.

  4. Polarimetries for the Polarized 3 He Target at JLab

    NASA Astrophysics Data System (ADS)

    Ton, Nguyen; Jefferson Lab Polarized 3 He Target Collaboration

    2015-04-01

    At Jefferson Lab, a Polarized 3 He Target has been used as an effective polarized neutron target for studying nucleon spin structure. For the 12 GeV program at JLab, the first stage upgrade of the target aim to increase luminosity by a factor of 2 (to luminosity ~ 2 ×1036 cm-2s-1) while keep maximum in-beam polarization at 60 % with 30 μA beam current and reach a systematic uncertainty of polarimetry below 3 %. During the 6 GeV era, the target polarization was measured by two polarimetries: adiabatic fast passage-nuclear magnetic resonance (AFP-NMR) and electron paramagnetic resonance (EPR). With the upgrade, a new polarimetry, Pulse-NMR, is being studied in the lab for the up-coming metal coated target. In this talk, we will discuss the detail study of AFP-NMR, EPR, Pulsed-NMR measurements and their corresponding uncertainties.

  5. Electrodisintegration of 3He below and above deuteron breakup threshold

    SciTech Connect

    Marcucci, L. E.; Viviani, M.; Schiavilla, R.; Kievsky, A.; Rosati, S.

    2005-02-01

    Recent advances in the study of electrodisintegration of 3He are presented and discussed. The pair-correlated hyperspherical harmonics method is used to calculate the initial and final state wave functions, with a realistic Hamiltonian consisting of the Argonne v18 two-nucleon and Urbana IX three-nucleon interactions. The model for the nuclear current and charge operators retains one- and many-body contributions. Particular attention is made in the construction of the two-body current operators arising from the momentum-dependent part of the two-nucleon interaction. Three-body current operators are also included so that the full current operator is strictly conserved. The present model for the nuclear current operator is tested comparing theoretical predictions and experimental data of pd radiative capture cross section and spin observables.

  6. Stability of superfluid 3He-B in compressed aerogel.

    PubMed

    Li, J I A; Zimmerman, A M; Pollanen, J; Collett, C A; Gannon, W J; Halperin, W P

    2014-03-21

    In recent work, it was shown that new anisotropic p-wave states of superfluid (3)He can be stabilized within high-porosity silica aerogel under uniform positive strain. In contrast, the equilibrium phase in an unstrained aerogel is the isotropic superfluid B phase. Here we report that this phase stability depends on the sign of the strain. For a negative strain of ∼ 20% achieved by compression, the B phase can be made more stable than the anisotropic A phase, resulting in a tricritical point for A, B, and normal phases with a critical field of ∼ 100 mT. From pulsed NMR measurements, we identify these phases and the orientation of the angular momentum. PMID:24702386

  7. APT {sup 3}He target/blanket. Topical report

    SciTech Connect

    1995-03-01

    The {sup 3}He target/blanket (T/B) preconceptual design for the 3/8-Goal facility is based on a 1000-MeV, 200-mA accelerator to produce a high-intensity proton beam that is expanded and then strikes one of two T/B modules. Each module consists of a centralized neutron source made of tungsten and lead, a proton beam backstop region made of zirconium and lead, and a moderator made of D{sub 2}O. Helium-3 gas is circulated through the neutron source region and the blanket to create tritium through neutron capture. The gas is continually processed to extract the tritium with an online separation process.

  8. Reprint of “Quantitative evaluation of brain development using anatomical MRI and diffusion tensor imaging”☆

    PubMed Central

    Oishi, Kenichi; Faria, Andreia V.; Yoshida, Shoko; Chang, Linda; Mori, Susumu

    2015-01-01

    The development of the brain is structure-specific, and the growth rate of each structure differs depending on the age of the subject. Magnetic resonance imaging (MRI) is often used to evaluate brain development because of the high spatial resolution and contrast that enable the observation of structure-specific developmental status. Currently, most clinical MRIs are evaluated qualitatively to assist in the clinical decision-making and diagnosis. The clinical MRI report usually does not provide quantitative values that can be used to monitor developmental status. Recently, the importance of image quantification to detect and evaluate mild-to-moderate anatomical abnormalities has been emphasized because these alterations are possibly related to several psychiatric disorders and learning disabilities. In the research arena, structural MRI and diffusion tensor imaging (DTI) have been widely applied to quantify brain development of the pediatric population. To interpret the values from these MR modalities, a “growth percentile chart,” which describes the mean and standard deviation of the normal developmental curve for each anatomical structure, is required. Although efforts have been made to create such a growth percentile chart based on MRI and DTI, one of the greatest challenges is to standardize the anatomical boundaries of the measured anatomical structures. To avoid inter- and intra-reader variability about the anatomical boundary definition, and hence, to increase the precision of quantitative measurements, an automated structure parcellation method, customized for the neonatal and pediatric population, has been developed. This method enables quantification of multiple MR modalities using a common analytic framework. In this paper, the attempt to create an MRI- and a DTI-based growth percentile chart, followed by an application to investigate developmental abnormalities related to cerebral palsy, Williams syndrome, and Rett syndrome, have been introduced

  9. In vivo quantification of demyelination and recovery using compartment-specific diffusion MRI metrics validated by electron microscopy.

    PubMed

    Jelescu, Ileana O; Zurek, Magdalena; Winters, Kerryanne V; Veraart, Jelle; Rajaratnam, Anjali; Kim, Nathanael S; Babb, James S; Shepherd, Timothy M; Novikov, Dmitry S; Kim, Sungheon G; Fieremans, Els

    2016-05-15

    There is a need for accurate quantitative non-invasive biomarkers to monitor myelin pathology in vivo and distinguish myelin changes from other pathological features including inflammation and axonal loss. Conventional MRI metrics such as T2, magnetization transfer ratio and radial diffusivity have proven sensitivity but not specificity. In highly coherent white matter bundles, compartment-specific white matter tract integrity (WMTI) metrics can be directly derived from the diffusion and kurtosis tensors: axonal water fraction, intra-axonal diffusivity, and extra-axonal radial and axial diffusivities. We evaluate the potential of WMTI to quantify demyelination by monitoring the effects of both acute (6weeks) and chronic (12weeks) cuprizone intoxication and subsequent recovery in the mouse corpus callosum, and compare its performance with that of conventional metrics (T2, magnetization transfer, and DTI parameters). The changes observed in vivo correlated with those obtained from quantitative electron microscopy image analysis. A 6-week intoxication produced a significant decrease in axonal water fraction (p<0.001), with only mild changes in extra-axonal radial diffusivity, consistent with patchy demyelination, while a 12-week intoxication caused a more marked decrease in extra-axonal radial diffusivity (p=0.0135), consistent with more severe demyelination and clearance of the extra-axonal space. Results thus revealed increased specificity of the axonal water fraction and extra-axonal radial diffusivity parameters to different degrees and patterns of demyelination. The specificities of these parameters were corroborated by their respective correlations with microstructural features: the axonal water fraction correlated significantly with the electron microscopy derived total axonal water fraction (ρ=0.66; p=0.0014) but not with the g-ratio, while the extra-axonal radial diffusivity correlated with the g-ratio (ρ=0.48; p=0.0342) but not with the electron microscopy

  10. Exploration of kinetic and multiple-ion-fluids effects in D3He and T3He gas-filled ICF implosions using multiple nuclear reaction histories

    NASA Astrophysics Data System (ADS)

    Sio, Hong; Rinderknecht, Hans; Rosenberg, Michael; Zylstra, Alex; Séguin, Fredrick; Gatu Johnson, Maria; Li, Chikang; Petrasso, Richard; Hoffman, Nelson; Kagan, Krigory; Molvig, Kim; Amendt, Peter; Bellei, Claudio; Wilks, Scott; Stoeckl, Christian; Glebov, Vladimir; Betti, Riccardo; Sangster, Thomas; Katz, Joseph

    2014-10-01

    To explore kinetic and multi-ion-fluid effects in D3He and T3He gas-filled shock-driven implosions, multiple nuclear reaction histories were measured using the upgraded Particle Temporal Diagnostic (PTD) on OMEGA. For D3He gas-filled implosions, the relative timing of the DD and D3He reaction histories were measured with 20 ps precision. For T3He gas-filled implosions (with 1-2% deuterium), the relative timing of the DT and D3He reaction histories were measured with 10 ps precision. The observed differences between the reaction histories on these two OMEGA experiments are contrasted to 1-D single-ion hydro simulations for different gas-fill pressure and gas mixture. This work is supported in part by the U.S. DOE, LLNL, LLE, and NNSA SSGF.

  11. Choosing the polarity of the phase-encoding direction in diffusion MRI: Does it matter for group analysis?

    PubMed Central

    Kennis, M.; van Rooij, S.J.H.; Kahn, R.S.; Geuze, E.; Leemans, A.

    2016-01-01

    Notorious for degrading diffusion MRI data quality are so-called susceptibility-induced off-resonance fields, which cause non-linear geometric image deformations. While acquiring additional data to correct for these distortions alleviates the adverse effects of this artifact drastically – e.g., by reversing the polarity of the phase-encoding (PE) direction – this strategy is often not an option due to scan time constraints. Especially in a clinical context, where patient comfort and safety are of paramount importance, acquisition specifications are preferred that minimize scan time, typically resulting in data obtained with only one PE direction. In this work, we investigated whether choosing a different polarity of the PE direction would affect the outcome of a specific clinical research study. To address this methodological question, fractional anisotropy (FA) estimates of FreeSurfer brain regions were obtained in civilian and combat controls, remitted posttraumatic stress disorder (PTSD) patients, and persistent PTSD patients before and after trauma-focused therapy and were compared between diffusion MRI data sets acquired with different polarities of the PE direction (posterior-to-anterior, PA and anterior-to-posterior, AP). Our results demonstrate that regional FA estimates differ on average in the order of 5% between AP and PA PE data. In addition, when comparing FA estimates between different subject groups for specific cingulum subdivisions, the conclusions for AP and PA PE data were not in agreement. These findings increase our understanding of how one of the most pronounced data artifacts in diffusion MRI can impact group analyses and should encourage users to be more cautious when interpreting and reporting study outcomes derived from data acquired along a single PE direction. PMID:27158586

  12. Surface-based reconstruction and diffusion MRI in the assessment of gray and white matter damage in multiple sclerosis

    NASA Astrophysics Data System (ADS)

    Caffini, Matteo; Bergsland, Niels; LaganÃ, Marcella; Tavazzi, Eleonora; Tortorella, Paola; Rovaris, Marco; Baselli, Giuseppe

    2014-03-01

    Despite advances in the application of nonconventional MRI techniques in furthering the understanding of multiple sclerosis pathogenic mechanisms, there are still many unanswered questions, such as the relationship between gray and white matter damage. We applied a combination of advanced surface-based reconstruction and diffusion tensor imaging techniques to address this issue. We found significant relationships between white matter tract integrity indices and corresponding cortical structures. Our results suggest a direct link between damage in white and gray matter and contribute to the notion of gray matter loss relating to clinical disability.

  13. Theory of spin-exchange optical pumping of 3He and 129Xe

    NASA Astrophysics Data System (ADS)

    Appelt, S.; Baranga, A. Ben-Amar; Erickson, C. J.; Romalis, M. V.; Young, A. R.; Happer, W.

    1998-08-01

    We present a comprehensive theory of nuclear spin polarization of 3He and 129Xe gases by spin-exchange collisions with optically pumped alkali-metal vapors. The most important physical processes considered are (1) spin-conserving spin-exchange collisions between like or unlike alkali-metal atoms; (2) spin-destroying collisions of the alkali-metal atoms with each other and with buffer-gas atoms; (3) electron-nuclear spin-exchange collisions between alkali-metal atoms and 3He or 129Xe atoms; (4) spin interactions in van der Waals molecules consisting of a Xe atom bound to an alkali-metal atom; (5) optical pumping by laser photons; (6) spatial diffusion. The static magnetic field is assumed to be small enough that the nuclear spin of the alkali-metal atom is well coupled to the electron spin and the total spin is very nearly a good quantum number. Conditions appropriate for the production of large quantities of spin-polarized 3He or 129Xe gas are assumed, namely, atmospheres of gas pressure and nearly complete quenching of the optically excited alkali-metal atoms by collisions with N2 or H2 gas. Some of the more important results of this work are as follows: (1) Most of the pumping and relaxation processes are sudden with respect to the nuclear polarization. Consequently, the steady-state population distribution of alkali-metal atoms is well described by a spin temperature, whether the rate of spin-exchange collisions between alkali-metal atoms is large or small compared to the optical pumping rate or the collisional spin-relaxation rates. (2) The population distributions that characterize the response to sudden changes in the intensity of the pumping light are not described by a spin temperature, except in the limit of very rapid spin exchange. (3) Expressions given for the radio-frequency (rf) resonance linewidths and areas can be used to make reliable estimates of the local spin polarization of the alkali-metal atoms. (4) Diffusion effects for these high

  14. Incorporating 3-D parent nuclide zonation for apatite 4He/3He thermochronometry: An example from the Appalachian Mountains

    NASA Astrophysics Data System (ADS)

    Fox, Matthew; McKeon, Ryan E.; Shuster, David L.

    2014-11-01

    ability to constrain km-scale exhumation with apatite 4He/3He thermochronometry is well established and the technique has been applied to a range of tectonic and geomorphic problems. However, multiple sources of uncertainty in specific crystal characteristics limit the applicability of the method, especially when geologic problems require identifying small perturbations in a cooling path. Here we present new 4He/3He thermochronometric data from the Appalachian Mountains, which indicate significant parent nuclide zonation in an apatite crystal. Using LA-ICPMS measurements of U and Th in the same crystal, we design a 3-D model of the crystal to explore the effects of intracrystal variability in radiation damage accumulation. We describe a numerical approach to solve the 3-D production-diffusion equation. Using our numerical model and a previously determined time temperature path for this part of the Appalachians, we find excellent agreement between predicted and observed 4He/3He spectra. Our results confirm this time-temperature path and highlight that for complex U and Th zonation patterns, 3-D numerical models are required to infer an accurate time-temperature history. In addition, our results provide independent and novel evidence for a radiation damage control on diffusivity. The ability to exploit intracrystal differences in 4He diffusivity [i.e., temperature sensitivity) greatly increases the potential to infer complex thermal histories.

  15. Neutron Multiplicity Measurements With 3He Alternative: Straw Neutron Detectors

    DOE PAGESBeta

    Mukhopadhyay, Sanjoy; Wolff, Ronald S.; Meade, John A.; Detweiler, Ryan; Maurer, Richard J.; Mitchell, Stephen E.; Guss, Paul P.; Lacy, Jeffrey L.; Sun, Liang; Athanasiades, Athanasios

    2015-01-27

    Counting neutrons emitted by special nuclear material (SNM) and differentiating them from the background neutrons of various origins is the most effective passive means of detecting SNM. Unfortunately, neutron detection, counting, and partitioning in a maritime environment are complex due to the presence of high-multiplicity spallation neutrons (commonly known as “ship effect”) and to the complicated nature of the neutron scattering in that environment. In this study, a prototype neutron detector was built using 10B as the converter in a special form factor called “straws” that would address the above problems by looking into the details of multiplicity distributions ofmore » neutrons originating from a fissioning source. This paper describes the straw neutron multiplicity counter (NMC) and assesses the performance with those of a commercially available fission meter. The prototype straw neutron detector provides a large-area, efficient, lightweight, more granular (than fission meter) neutron-responsive detection surface (to facilitate imaging) to enhance the ease of application of fission meters. Presented here are the results of preliminary investigations, modeling, and engineering considerations leading to the construction of this prototype. This design is capable of multiplicity and Feynman variance measurements. This prototype may lead to a near-term solution to the crisis that has arisen from the global scarcity of 3He by offering a viable alternative to fission meters. This paper describes the work performed during a 2-year site-directed research and development (SDRD) project that incorporated straw detectors for neutron multiplicity counting. The NMC is a two-panel detector system. We used 10B (in the form of enriched boron carbide: 10B4C) for neutron detection instead of 3He. In the first year, the project worked with a panel of straw neutron detectors, investigated its characteristics, and developed a data acquisition (DAQ) system to collect

  16. Neutron multiplicity ,easurements With 3He alternative: Straw neutron detectors

    DOE PAGESBeta

    Mukhopadhyay, Sanjoy; Wolff, Ronald S.; Meade, John A.; Detweiler, Ryan; Maurer, Richard J.; Mitchell, Stephen E.; Guss, Paul P.; Lacy, Jeffrey L.; Sun, Liang; Athanasiades, Athanasios

    2015-01-27

    Counting neutrons emitted by special nuclear material (SNM) and differentiating them from the background neutrons of various origins is the most effective passive means of detecting SNM. Unfortunately, neutron detection, counting, and partitioning in a maritime environment are complex due to the presence of high-multiplicity spallation neutrons (commonly known as “ship effect”) and to the complicated nature of the neutron scattering in that environment. In this study, a prototype neutron detector was built using 10B as the converter in a special form factor called “straws” that would address the above problems by looking into the details of multiplicity distributions ofmore » neutrons originating from a fissioning source. This paper describes the straw neutron multiplicity counter (NMC) and assesses the performance with those of a commercially available fission meter. The prototype straw neutron detector provides a large-area, efficient, lightweight, more granular (than fission meter) neutron-responsive detection surface (to facilitate imaging) to enhance the ease of application of fission meters. Presented here are the results of preliminary investigations, modeling, and engineering considerations leading to the construction of this prototype. This design is capable of multiplicity and Feynman variance measurements. This prototype may lead to a near-term solution to the crisis that has arisen from the global scarcity of 3He by offering a viable alternative to fission meters. This paper describes the work performed during a 2-year site-directed research and development (SDRD) project that incorporated straw detectors for neutron multiplicity counting. The NMC is a two-panel detector system. We used 10B (in the form of enriched boron carbide: 10B4C) for neutron detection instead of 3He. In the first year, the project worked with a panel of straw neutron detectors, investigated its characteristics, and developed a data acquisition (DAQ) system to collect

  17. Clinical Implications of Diffuse Excessive High Signal Intensity (DEHSI) on Neonatal MRI in School Age Children Born Extremely Preterm

    PubMed Central

    Padilla, Nelly; Skiöld, Béatrice; Eklöf, Eva; Mårtensson, Gustaf; Vollmer, Brigitte; Ådén, Ulrika

    2016-01-01

    Objective Magnetic resonance imaging (MRI) of the brain carried out during the neonatal period shows that 55–80% of extremely preterm infants display white matter diffuse excessive high signal intensity (DEHSI). Our aim was to study differences in developmental outcome at the age of 6.5 years in children born extremely preterm with and without DEHSI. Study Design This was a prospective cohort study of 83 children who were born in Stockholm, Sweden, between 2004 and 2007, born at gestational age of < 27 weeks + 0 days and who underwent an MRI scan of their brain at term equivalent age. The outcome measures at 6.5 years included testing 66 children with the modified Touwen neurology examination, the Movement Assessment Battery for Children 2, the Wechsler Intelligence Scale for Children—Fourth Edition, Beery Visual-motor Integration test—Sixth Edition, and the Strengths and Difficulties Questionnaire. Group-wise comparisons were done between children with and without DEHSI using Student t-test, Mann Whitney U test, Chi square test and regression analysis. Results DEHSI was detected in 39 (59%) of the 66 children who were assessed at 6.5 years. The presence of DEHSI was not associated with mild neurological dysfunction, scores on M-ABC assessment, cognition, visual-motor integration, or behavior at 6.5 years. Conclusion The presence of qualitatively defined DEHSI on neonatal MRI did not prove to be a useful predictor of long-term impairment in children born extremely preterm. PMID:26886451

  18. Comparison of Diffusion MRI Acquisition Protocols for the In Vivo Characterization of the Mouse Spinal Cord: Variability Analysis and Application to an Amyotrophic Lateral Sclerosis Model

    PubMed Central

    Marcuzzo, Stefania; Bonanno, Silvia; Padelli, Francesco; Moreno-Manzano, Victoria; García-Verdugo, José Manuel; Bernasconi, Pia; Mantegazza, Renato; Bruzzone, Maria Grazia; Zucca, Ileana

    2016-01-01

    Diffusion-weighted Magnetic Resonance Imaging (dMRI) has relevant applications in the microstructural characterization of the spinal cord, especially in neurodegenerative diseases. Animal models have a pivotal role in the study of such diseases; however, in vivo spinal dMRI of small animals entails additional challenges that require a systematical investigation of acquisition parameters. The purpose of this study is to compare three acquisition protocols and identify the scanning parameters allowing a robust estimation of the main diffusion quantities and a good sensitivity to neurodegeneration in the mouse spinal cord. For all the protocols, the signal-to-noise and contrast-to noise ratios and the mean value and variability of Diffusion Tensor metrics were evaluated in healthy controls. For the estimation of fractional anisotropy less variability was provided by protocols with more diffusion directions, for the estimation of mean, axial and radial diffusivity by protocols with fewer diffusion directions and higher diffusion weighting. Intermediate features (12 directions, b = 1200 s/mm2) provided the overall minimum inter- and intra-subject variability in most cases. In order to test the diagnostic sensitivity of the protocols, 7 G93A-SOD1 mice (model of amyotrophic lateral sclerosis) at 10 and 17 weeks of age were scanned and the derived diffusion parameters compared with those estimated in age-matched healthy animals. The protocols with an intermediate or high number of diffusion directions provided the best differentiation between the two groups at week 17, whereas only few local significant differences were highlighted at week 10. According to our results, a dMRI protocol with an intermediate number of diffusion gradient directions and a relatively high diffusion weighting is optimal for spinal cord imaging. Further work is needed to confirm these results and for a finer tuning of acquisition parameters. Nevertheless, our findings could be important for the

  19. Comparison of Diffusion MRI Acquisition Protocols for the In Vivo Characterization of the Mouse Spinal Cord: Variability Analysis and Application to an Amyotrophic Lateral Sclerosis Model.

    PubMed

    Figini, Matteo; Scotti, Alessandro; Marcuzzo, Stefania; Bonanno, Silvia; Padelli, Francesco; Moreno-Manzano, Victoria; García-Verdugo, José Manuel; Bernasconi, Pia; Mantegazza, Renato; Bruzzone, Maria Grazia; Zucca, Ileana

    2016-01-01

    Diffusion-weighted Magnetic Resonance Imaging (dMRI) has relevant applications in the microstructural characterization of the spinal cord, especially in neurodegenerative diseases. Animal models have a pivotal role in the study of such diseases; however, in vivo spinal dMRI of small animals entails additional challenges that require a systematical investigation of acquisition parameters. The purpose of this study is to compare three acquisition protocols and identify the scanning parameters allowing a robust estimation of the main diffusion quantities and a good sensitivity to neurodegeneration in the mouse spinal cord. For all the protocols, the signal-to-noise and contrast-to noise ratios and the mean value and variability of Diffusion Tensor metrics were evaluated in healthy controls. For the estimation of fractional anisotropy less variability was provided by protocols with more diffusion directions, for the estimation of mean, axial and radial diffusivity by protocols with fewer diffusion directions and higher diffusion weighting. Intermediate features (12 directions, b = 1200 s/mm2) provided the overall minimum inter- and intra-subject variability in most cases. In order to test the diagnostic sensitivity of the protocols, 7 G93A-SOD1 mice (model of amyotrophic lateral sclerosis) at 10 and 17 weeks of age were scanned and the derived diffusion parameters compared with those estimated in age-matched healthy animals. The protocols with an intermediate or high number of diffusion directions provided the best differentiation between the two groups at week 17, whereas only few local significant differences were highlighted at week 10. According to our results, a dMRI protocol with an intermediate number of diffusion gradient directions and a relatively high diffusion weighting is optimal for spinal cord imaging. Further work is needed to confirm these results and for a finer tuning of acquisition parameters. Nevertheless, our findings could be important for the

  20. Comment on "Deep mixing of 3He: reconciling Big Bang and stellar nucleosynthesis".

    PubMed

    Balser, Dana S; Rood, Robert T; Bania, T M

    2007-08-31

    Eggleton et al. (Reports, 8 December 2006, p. 1580) reported on a deep-mixing mechanism in low-mass stars caused by a Rayleigh-Taylor instability that destroys all of the helium isotope 3He produced during the star's lifetime. Observations of 3He in planetary nebulae, however, indicate that some stars produce prodigious amounts of 3He. This is inconsistent with the claim that all low-mass stars should destroy 3He. PMID:17761865

  1. Diffusion and clearance of superparamagnetic iron oxide nanoparticles infused into the rat striatum studied by MRI and histochemical techniques

    NASA Astrophysics Data System (ADS)

    Wang, F. H.; Kim, D. K.; Yoshitake, T.; Johansson, S. M.; Bjelke, B.; Muhammed, M.; Kehr, J.

    2011-01-01

    The purpose of the present study was to investigate, by MRI and histochemical techniques, the diffusion and clearance abilities of superparamagnetic iron oxide nanoparticles (SPION) coated with dextran (Dextran-SPION) and gold (Au-SPION) following their local infusions into the rat brain. In separate groups of anesthetized rats, the Dextran-SPION and Au-SPION were infused at concentrations of 0.01, 0.1, 1 and 5 µg Fe/0.5 µl and at the flow rate of 0.5 µl min - 1 into the left and right striata, respectively. Repetitive T2-weighted spin-echo MRI scans were performed at time intervals of 1, 6, 12, 24, 48, 72 h, and one, two and eight weeks after inoculation. Following infusion of Dextran-SPION (0.1 µg and 1 µg Fe), the maximal distribution volume was observed at about 12-24 h after inoculation and two weeks later the Fe signals were undetectable for the lower dose. On the other hand, Au-SPION remained tightly localized in the closest vicinity of the infusion site as revealed by unchanged MRI signal intensities and strong histochemical staining of Fe2 + and Fe3 + ions in the corresponding brain slices. Immunohistochemical staining of astrocytic and microglial reactions revealed that there were no marked differences in GFAP, VIM or OX-42 labeling observed between the nanoparticle types, however the astrocytic reaction was more pronounced in rats receiving nanoparticles compared to the control (aCSF-infused) rats. In conclusion, the present data demonstrate that the viral-sized Dextran-SPION were able to diffuse freely through the interstitial space of the brain being progressively cleared out from the infusion site within two weeks. Thus, Dextran-SPION could be beneficially used in MRI-guided diagnostic applications such as in experimental oncology or as labels and carriers for targeted drug delivery, whereas Au-SPION could be used for labeling and tracking the transplanted stem cells in experimental MRI.

  2. Systematic optimization of MRI guided near infrared diffuse optical spectroscopy in breast

    NASA Astrophysics Data System (ADS)

    Zhao, Yan; Mastanduno, Michael A.; Jiang, Shudong; El-Ghussein, Fadi; Xu, Junqing; Gui, Jiang; Pogue, Brian W.; Paulsen, Keith D.

    2015-03-01

    A hybrid frequency domain (FD)-continuous wave (CW) MRI/NIRS system was validated in a clinical trial involving patients with at least ACR 4 radiologic findings in Xi'an, China. In this study, MRI guided nonlinear iterative reconstruction of near-infrared spectroscopy (NIRS) images with limited phase data is investigated. In addition, a systematic optimization of the system hardware design has been conducted as well. We are able to get less than 3% variation in tumor contrast to the surrounding normal tissue, by reducing the number of FD detectors from 16 to 6, showing the potential of reducing the FD detectors. Furthermore, a lookup table of the scattering properties has been made by averaging four MRI-identified breast density groups. By using this look-up table for the patient with the noisy phase data, similar AUCs and p-values are achieved for differentiating the malignant from benign patients.

  3. Equilibrium helical order in radially confined superfluid 3He

    NASA Astrophysics Data System (ADS)

    Wiman, Joshua; Sauls, J. A.

    An exciting prediction of confined superfluid 3He is the presence of spontaneously broken translational symmetry, resulting in a superfluid phase that has a different translational symmetry than that of the confining geometry. Such phases have been described theoretically in films, cylinders, and ribbons. We predict an inhomogeneous superfluid phase with helical order that is energetically stable within cylindrical channels of radius comparable to the Cooper pair coherence length. By incorporating extensions to standard Ginzburg-Landau (GL) strong-coupling theory that accurately reproduce the bulk phase diagram at high pressures and allow tuneable boundary conditions, we find this new phase to be stable at both high and low pressures and favored by boundary conditions with strong pairbreaking. We present superfluid phase diagrams as functions of pressure, temperature, and channel radius showing the regions of stability for this ``spiral'' phase relative to those phases previously predicted for the channel. Transverse NMR frequency shifts are a possible experimental signature of this phase, and we present calculations of these shifts as functions of rf pulse tipping angle, field orientation, and temperature. Supported by NSF Grant DMR-1508730.

  4. Hydrogen trapping in 3He-irradiated Fe

    NASA Astrophysics Data System (ADS)

    Takagi, Ikuji; Matsuoka, Kotaro; Tanaka, Toshiyuki; Akiyoshi, Masafumi; Sasaki, Takayuki

    2013-11-01

    The characteristics of irradiation-induced hydrogen (deuterium) traps in pure Fe were investigated for quantitative evaluation of tritium retention in fusion reactor components. The deuterium depth profiles of an Fe disk sample exposed to deuterium plasma were observed by means of nuclear reaction analysis (NRA) before and after irradiation with 0.8 MeV or 1.3 MeV 3He ions. Irradiation generated a number of traps, and deuterium retention was drastically increased subsequent to irradiation. Steady-state deuterium concentration in the trap and the solution sites were obtained by continuously charging the sample with deuterium during the NRA. Based on these values, the trapping energy, which is the enthalpy difference between the two sites, was estimated to be 0.38 eV. The number ratio of the trap to atomic displacement was 0.013. Some of the traps were annihilated around 523 K. The annihilation temperature, the trapping energy, and the equilibrium constant suggest that the trap is a dislocation loop introduced by the irradiation. It is deduced that the tritium inventory in the Fe components of a reactor should be drastically increased by neutron irradiation due to the formation of traps, but may be significantly reduced by high temperature operation of the components.

  5. Measurement of the Coherent Neutron Scattering Length of 3He

    PubMed Central

    Ketter, W.; Heil, W.; Badurek, G.; Baron, M.; Loidl, R.; Rauch, H.

    2005-01-01

    By means of neutron interferometry the s-wave neutron scattering length of the 3He nucleus was re-measured at the Institut Laue-Langevin (ILL). Using a skew symmetrical perfect crystal Si-interferometer and a linear twin chamber cell, false phase shifts due to sample misalignment were reduced to a negligible level. Simulation calculations suggest an asymmetrically alternating measuring sequence in order to compensate for systematic errors caused by thermal phase drifts. There is evidence in the experiment’s data that this procedure is indeed effective. The neutron refractive index in terms of Sears’ exact expression for the scattering amplitude has been analyzed in order to evaluate the measured phase shifts. The result of our measurement, b′c = (6.000 ± 0.009) fm, shows a deviation towards a greater value compared to the presently accepted value of b′c = (5.74 ± 0.07) fm, confirming the observation of the partner experiment at NIST. On the other hand, the results of both precision measurements at NIST and ILL exhibit a serious 12σ (12 standard uncertainties) deviation, the reason for which is not clear yet.

  6. Andreev reflection in rotating superfluid {sup 3}He-B

    SciTech Connect

    Eltsov, V. B.; Hosio, J. J.; Krusius, M. Mäkinen, J. T.

    2014-12-15

    Andreev reflection of quasiparticle excitations from quantized line vortices is reviewed in the isotropic B phase of superfluid {sup 3}He in the temperature regime of ballistic quasiparticle transport at T ≤ 0.20T{sub c}. The reflection from an array of rectilinear vortices in solid-body rotation is measured with a quasiparticle beam illuminating the array mainly in the orientation along the rotation axis. The result is in agreement with the calculated Andreev reflection. The Andreev signal is also used to analyze the spin-down of the superfluid component after a sudden impulsive stop of rotation from an equilibrium vortex state. In a measuring setup where the rotating cylinder has a rough bottom surface, annihilation of the vortices proceeds via a leading rapid turbulent burst followed by a trailing slow laminar decay, from which the mutual friction dissipation can be determined. In contrast to the currently accepted theory, it is found to have a finite value in the zero-temperature limit: α(T→0) = (5 ± 0.5) × 10{sup −4}.

  7. Optical interferometry in superfluid {sup 3}He-B

    SciTech Connect

    Alles, H.; Ruutu, J.P.; Babkin, A.V.; Hakonen, P.J.; Sonin, E.B.

    1996-03-01

    The authors report interferometric measurements in 0.1...1 mm thick films of superfluid {sup 3}He-B. The menisci of three different rotational states of the superfluid were observed and analyzed theoretically using two-fluid hydrodynamics: These are (i) the equilibrium vortex state in which the superfluid and the normal components corotate (solid body rotation), (ii) the vortex-free state (the Landau state), in which only the normal component rotates, and (iii) the quasistationary vortex state in which only the superfluid fraction rotates (pure superfluid rotation). The Landua state manifested itself by a reduced parabolic meniscus at rotation speeds below the critical angular velocity {Omega}{sub c}{approx_lt} 0.2 rad/s for vortex formation. Transition from the Landua state to the equilibrium vortex state yielded a sudden deepening of the meniscus when {Omega}{sub c} was exceeded. After a rapid halt of the cryostat, the authors observed a novel meniscus which was produced by the superfluid rotation while the normal component was at rest. The enhanced depth of this meniscus is governed by the reactive mutual friction parameter B{prime}. By employing laser light, both for imaging and for thermomechanical excitation, the authors measured the response of a thin superfluid layer to a heat pulse and analyzed it within the theory of two fluid hydrodynamics. The data were employed, using the dispersion relation for thin film oscillations, to deduce the second viscosity coefficient {zeta}{sub 3} close to T{sub c}.

  8. MR Imaging of Apparent 3He Gas Transport in Narrow Pipes and Rodent Airways

    SciTech Connect

    Minard, Kevin R.; Jacob, Rick E.; Laicher, Gernot; Einstein, Daniel R.; Kuprat, Andrew P.; Corley, Richard A.

    2008-10-01

    High sensitivity makes hyperpolarized 3He an attractive signal source for visualizing gas flow with magnetic resonance (MR) imaging. Its rapid Brownian motion, however, can blur observed flow lamina and alter measured diffusion rates when excited nuclei traverse shear-induced velocity gradients during data acquisition. Here, both effects are described analytically, and predicted values for measured transport during laminar flow through a straight, 3.2-mm-diameter pipe are validated using two-dimensional (2D) constant-time images of different binary gas mixtures. Results show explicitly how measured transport in narrow conduits is characterized by apparent values that depend on underlying gas dynamics and imaging time. In ventilated rats, this is found to obscure acquired airflow images. Flow splitting at airway branches is still evident, however, and use of 3D vector flow mapping is shown to provide a quantitative view of pulmonary gas supply that highlights the correlation of airflow dynamics with lung structure.

  9. MR Imaging of Apparent 3He Gas Transport in Narrow Pipes and Rodent Airways

    PubMed Central

    Minard, Kevin R.; Jacob, Richard E.; Laicher, Gernot; Einstein, Daniel R.; Kuprat, Andrew P.; Corley, Richard A.

    2013-01-01

    High sensitivity makes hyperpolarized 3He an attractive signal source for visualizing gas flow with magnetic resonance (MR) imaging. Its rapid Brownian motion, however, can blur observed flow lamina and alter measured diffusion rates when excited nuclei traverse shear-induced velocity gradients during data acquisition. Here, both effects are described analytically, and predicted values for measured transport during laminar flow through a straight, 3.2-mm-diameter pipe are validated using two-dimensional (2D) constant-time images of different binary gas mixtures. Results show explicitly how measured transport in narrow conduits is characterized by apparent values that depend on underlying gas dynamics and imaging time. In ventilated rats, this is found to obscure acquired airflow images. Nevertheless, flow splitting at airway branches is still evident and use of 3D vector flow mapping is shown to reveal surprising detail that highlights the correlation between gas dynamics and lung structure. PMID:18667344

  10. Detecting the subregion proceeding to infarction in hypoperfused cerebral tissue: a study with diffusion and perfusion weighted MRI.

    PubMed

    Liu, Y; Karonen, J O; Vanninen, R L; Nuutinen, J; Perkiö, J; Vainio, P A; Soimakallio, S; Aronen, H J

    2003-06-01

    Diffusion and perfusion weighted MRI have been widely used in ischaemic stroke. We studied 17 patients in whom ischaemic areas showed an ischaemic core, an area of infarct growth and hypoperfused but ultimately surviving tissue. Apparent diffusion coefficients (ADC) were measured on days 1, 2, and 8 in the three subregions and in contralateral control areas. Cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were measured in these regions on day 1 perfusion maps. On day 1, the ischaemic core had very low ADC and CBF and increased MTT. The ADC in the ischaemic core gradually increased during the week. The area of infarct growth on day 1 had slightly but significantly decreased ADC (96% of control, P=0.028), moderately decreased CBF and increased MTT. On day 1 the hypoperfused but surviving tissue had slightly but significantly increased ADC (103% of control, P=0.001), mildly decreased CBF and increased CBV and MTT. The ADC of the area of infarct growth decreased to the same level as in the ischaemic core on days 2 and 8. That of surviving tissue was still above normal on day 2 (103% of control), but had returned to the normal level by day 8. Measurement of ADC combined with perfusion MRI may help distinguish different subregions in acutely hypoperfused brain. PMID:12750863

  11. Multi-Scale Characterization of Lyotropic Liquid Crystals Using 2H and Diffusion MRI with Spatial Resolution in Three Dimensions

    PubMed Central

    Bernin, Diana; Koch, Vanessa; Nydén, Magnus; Topgaard, Daniel

    2014-01-01

    The ability of lyotropic liquid crystals to form intricate structures on a range of length scales can be utilized for the synthesis of structurally complex inorganic materials, as well as in devices for controlled drug delivery. Here we employ magnetic resonance imaging (MRI) for non-invasive characterization of nano-, micro-, and millimeter scale structures in liquid crystals. The structure is mirrored in the translational and rotational motion of the water, which we assess by measuring spatially resolved self-diffusion tensors and spectra. Our approach differs from previous works in that the MRI parameters are mapped with spatial resolution in all three dimensions, thus allowing for detailed studies of liquid crystals with complex millimeter-scale morphologies that are stable on the measurement time-scale of 10 hours. The data conveys information on the nanometer-scale structure of the liquid crystalline phase, while the combination of diffusion and data permits an estimate of the orientational distribution of micrometer-scale anisotropic domains. We study lamellar phases consisting of the nonionic surfactant C10E3 in O, and follow their structural equilibration after a temperature jump and the cessation of shear. Our experimental approach may be useful for detailed characterization of liquid crystalline materials with structures on multiple length scales, as well as for studying the mechanisms of phase transitions. PMID:24905818

  12. Pretreatment Diffusion-Weighted MRI Can Predict the Response to Neoadjuvant Chemotherapy in Patients with Nasopharyngeal Carcinoma

    PubMed Central

    Zhang, Guo-Yi; Wang, Yue-Jian; Liu, Jian-Ping; Zhou, Xin-Han; Xu, Zhi-Feng; Chen, Xiang-Ping; Xu, Tao; Wei, Wei-Hong; Zhang, Yang; Huang, Ying

    2015-01-01

    Purpose. To explore the potential of diffusion-weighted (DW) magnetic resonance imaging (MRI) using apparent diffusion coefficient (ADC) for predicting the response to neoadjuvant chemotherapy in nasopharyngeal carcinoma (NPC). Methods and Materials. Ninety-two consecutive patients with NPC who underwent three cycles of neoadjuvant chemotherapy were retrospectively analyzed. DW and anatomical MRI were performed before and after neoadjuvant chemotherapy prior to radiotherapy. Pretreatment ADCs and percentage increases in ADC after chemotherapy were calculated for the primary lesions and metastatic adenopathies. Receiver operating characteristic curve analysis was used to select optimal pretreatment ADCs. Results. Pretreatment mean ADCs were significantly lower for responders than for nonresponders (primary lesions, P = 0.012; metastatic adenopathies, P = 0.013). Mean percentage increases in ADC were higher for responders than for nonresponders (primary lesions, P = 0.008; metastatic adenopathies, P < 0.001). The optimal pretreatment primary lesion and metastatic adenopathy ADCs for differentiating responders from nonresponders were 0.897 × 10−3 mm2/sec and 1.031 × 10−3 mm2/sec, respectively. Conclusions. NPC patients with low pretreatment ADCs tend to respond better to neoadjuvant chemotherapy. Pretreatment ADCs could be used as a new pretreatment imaging biomarker of response to neoadjuvant chemotherapy. PMID:26413513

  13. Temporal Variability in the Accretion Rate of Interplanetary Dust Using (3)He as a Tracer

    NASA Technical Reports Server (NTRS)

    Farley, K. A.

    2005-01-01

    The research supported by this grant falls under three topics: 1) Weekly Interplanetary Dust Sampling via (3)He; 2) Extraterrestrial (3)He at Major Impact Boundaries; 3) Completing a Moderately-High Resolution Record of Extraterrestrial (3)He Flux: A Major Asteroidal Break up Event at 8.2 Ma.

  14. WE-G-18C-09: Separating Perfusion and Diffusion Components From Diffusion Weighted MRI of Rectum Tumors Based On Intravoxel Incoherent Motion (IVIM) Analysis

    SciTech Connect

    Tyagi, N; Wengler, K; Mazaheri, Y; Hunt, M; Deasy, J; Gollub, M

    2014-06-15

    Purpose: Pseudodiffusion arises from the microcirculation of blood in the randomly oriented capillary network and contributes to the signal decay acquired using a multi-b value diffusion weighted (DW)-MRI sequence. This effect is more significant at low b-values and should be properly accounted for in apparent diffusion coefficient (ADC) calculations. The purpose of this study was to separate perfusion and diffusion component based on a biexponential and a segmented monoexponential model using IVIM analysis Methods. The signal attenuation is modeled as S(b) = S0[(1−f)exp(−bD) + fexp(−bD*)]. Fitting the biexponetial decay leads to the quantification of D, the true diffusion coefficient, D*, the pseudodiffusion coefficient, and f, the perfusion fraction. A nonlinear least squares fit and two segmented monoexponential models were used to derive the values for D, D*,‘and f. In the segmented approach b = 200 s/mm{sup 2} was used as the cut-off value for calculation of D. DW-MRI's of a rectum cancer patient were acquired before chemotherapy, before radiation therapy (RT), and 4 weeks into RT and were investigated as an example case. Results: Mean ADC for the tumor drawn on the DWI cases was 0.93, 1.0 and 1.13 10{sup −3}×mm{sup 2}/s before chemotherapy, before RT and 4 weeks into RT. The mean (D.10{sup −3} × mm{sup 2}/s, D* 10{sup −3} × mm{sup 2}/s, and f %) based on biexponential fit was (0.67, 18.6, and 27.2%), (0.72, 17.7, and 28.9%) and (0.83,15.1, and 30.7%) at these time points. The mean (D, D* f) based on segmented fit was (0.72, 10.5, and 12.1%), (0.72, 8.2, and 17.4%) and (.82, 8.1, 16.5%) Conclusion: ADC values are typically higher than true diffusion coefficients. For tumors with significant perfusion effect, ADC should be analyzed at higher b-values or separated from the perfusion component. Biexponential fit overestimates the perfusion fraction because of increased sensitivity to noise at low b-values.

  15. Partial volume effect of cingulum tract in diffusion-tensor MRI

    NASA Astrophysics Data System (ADS)

    Cao, Ning; Gold, Brian T.; Zhang, Jun

    2008-03-01

    Diffusion tensor imaging (DTI) represents a promising tool for the early diagnosis of certain brain diseases. Many DTI studies have compared differences in local diffusivity in specific region-of- interest (ROI) between patient and control groups to find possible disease markers. However, local diffusivity results may be influenced by partial volume effects (PVE), particularly in small white matter tracts that border grey matter tissue. Here, we investigated the influence of PVE on local diffusivity measurements in a small but critical white matter tract, the cingulum. Results demonstrated significant variability in PVE that contribute to local diffusivity in the cingulum. Our results highlight the need for careful consideration of PVE when computing diffusivity of small tissues.

  16. Transfer Excitation Processes Observed in N3+-He and O3+-He Collisions at Elab = 33 eV

    NASA Astrophysics Data System (ADS)

    Itoh, Yoh

    2016-09-01

    We measured the relative state-selective differential cross sections (DCSs) for one-electron capture reactions using a crossed-beam apparatus. The scattering angle θlab studied in the laboratory frame ranged from -3.0 to 22° and the laboratory collision energy Elab was 33 eV. Only the transfer excitation processes, i.e., the electron capture reactions with the simultaneous excitation of the projectile, were observed. The DCSs were determined for the following reactions: N3+ (1s2 2s2 1S) + He (1s2 1S) → N2+ (1s2 2s2p2 2D) + He+ (1s 2S) + 10.3 eV, O3+ (1s2 2s2 2p 2P) + He (1s2 1S) → O2+ (1s2 2s 2p3 3P) + He+ (1s 2S) + 12.7 eV, and O3+ (1s2 2s2 2p 2P) + He (1s2 1S) → O2+ (1s2 2s 2p3 3D) + He+ (1s 2S) + 15.5 eV. In the N3+-He system, the DCSs for the reaction are zero at the center-of-mass angle θcm = 0 and show a peak at a certain angle and a shoulder at a larger angle. In the O3+-He system, the DCSs are again zero at θcm = 0. The capture process to the O2+ (1s2 2s 2p3 3P) state is mainly observed at smaller scattering angles, and the reaction to the O2+ (1s2 2s 2p3 3D) state becomes dominant with increasing scattering angle. A classical trajectory analysis within the two-state approximation based on the ab initio potentials for (NHe)3+ revealed that the transfer excitation of a two-electron process takes place through a single crossing of the relevant potentials.

  17. Electron screening and stellar rates in the {sup 3}He({sup 3}He,2p){sup 4}He and {sup 3}He(d,p){sup 4}He fusion reactions

    SciTech Connect

    Messahel, L.; Ouichaoui, S.; Belhout, A.; Fouka, M.; Trabelsi, A.

    2008-05-12

    The astrophysical S(E) factor experimental data available over the energy region E (C.M.)<1.0 MeV for the {sup 3}He({sup 3}He,2p){sup 4}He and {sup 3}He(d,p){sup 4}He fusion reactions are analyzed using a polynomial expression and the R-Matrix formalism, respectively. The reaction thermonuclear rates for bare nuclei are determined and compared to previous ones after a precise assessment of the electron screening factors. New level parameter values are deduced for the {sup 5}Li nucleus.

  18. Surface-Based fMRI-Driven Diffusion Tractography in the Presence of Significant Brain Pathology: A Study Linking Structure and Function in Cerebral Palsy

    PubMed Central

    Cunnington, Ross; Boyd, Roslyn N.; Rose, Stephen E.

    2016-01-01

    Diffusion MRI (dMRI) tractography analyses are difficult to perform in the presence of brain pathology. Automated methods that rely on cortical parcellation for structural connectivity studies often fail, while manually defining regions is extremely time consuming and can introduce human error. Both methods also make assumptions about structure-function relationships that may not hold after cortical reorganisation. Seeding tractography with functional-MRI (fMRI) activation is an emerging method that reduces these confounds, but inherent smoothing of fMRI signal may result in the inclusion of irrelevant pathways. This paper describes a novel fMRI-seeded dMRI-analysis pipeline based on surface-meshes that reduces these issues and utilises machine-learning to generate task specific white matter pathways, minimising the requirement for manually-drawn ROIs. We directly compared this new strategy to a standard voxelwise fMRI-dMRI approach, by investigating correlations between clinical scores and dMRI metrics of thalamocortical and corticomotor tracts in 31 children with unilateral cerebral palsy. The surface-based approach successfully processed more participants (87%) than the voxel-based approach (65%), and provided significantly more-coherent tractography. Significant correlations between dMRI metrics and five clinical scores of function were found for the more superior regions of these tracts. These significant correlations were stronger and more frequently found with the surface-based method (15/20 investigated were significant; R2 = 0.43–0.73) than the voxelwise analysis (2 sig. correlations; 0.38 & 0.49). More restricted fMRI signal, better-constrained tractography, and the novel track-classification method all appeared to contribute toward these differences. PMID:27487011

  19. Surface-Based fMRI-Driven Diffusion Tractography in the Presence of Significant Brain Pathology: A Study Linking Structure and Function in Cerebral Palsy.

    PubMed

    Reid, Lee B; Cunnington, Ross; Boyd, Roslyn N; Rose, Stephen E

    2016-01-01

    Diffusion MRI (dMRI) tractography analyses are difficult to perform in the presence of brain pathology. Automated methods that rely on cortical parcellation for structural connectivity studies often fail, while manually defining regions is extremely time consuming and can introduce human error. Both methods also make assumptions about structure-function relationships that may not hold after cortical reorganisation. Seeding tractography with functional-MRI (fMRI) activation is an emerging method that reduces these confounds, but inherent smoothing of fMRI signal may result in the inclusion of irrelevant pathways. This paper describes a novel fMRI-seeded dMRI-analysis pipeline based on surface-meshes that reduces these issues and utilises machine-learning to generate task specific white matter pathways, minimising the requirement for manually-drawn ROIs. We directly compared this new strategy to a standard voxelwise fMRI-dMRI approach, by investigating correlations between clinical scores and dMRI metrics of thalamocortical and corticomotor tracts in 31 children with unilateral cerebral palsy. The surface-based approach successfully processed more participants (87%) than the voxel-based approach (65%), and provided significantly more-coherent tractography. Significant correlations between dMRI metrics and five clinical scores of function were found for the more superior regions of these tracts. These significant correlations were stronger and more frequently found with the surface-based method (15/20 investigated were significant; R2 = 0.43-0.73) than the voxelwise analysis (2 sig. correlations; 0.38 & 0.49). More restricted fMRI signal, better-constrained tractography, and the novel track-classification method all appeared to contribute toward these differences. PMID:27487011

  20. Co-analysis of Brain Structure and Function using fMRI and Diffusion-weighted Imaging

    PubMed Central

    Phillips, Jeffrey S.; Greenberg, Adam S.; Pyles, John A.; Pathak, Sudhir K.; Behrmann, Marlene; Schneider, Walter; Tarr, Michael J.

    2012-01-01

    The study of complex computational systems is facilitated by network maps, such as circuit diagrams. Such mapping is particularly informative when studying the brain, as the functional role that a brain area fulfills may be largely defined by its connections to other brain areas. In this report, we describe a novel, non-invasive approach for relating brain structure and function using magnetic resonance imaging (MRI). This approach, a combination of structural imaging of long-range fiber connections and functional imaging data, is illustrated in two distinct cognitive domains, visual attention and face perception. Structural imaging is performed with diffusion-weighted imaging (DWI) and fiber tractography, which track the diffusion of water molecules along white-matter fiber tracts in the brain (Figure 1). By visualizing these fiber tracts, we are able to investigate the long-range connective architecture of the brain. The results compare favorably with one of the most widely-used techniques in DWI, diffusion tensor imaging (DTI). DTI is unable to resolve complex configurations of fiber tracts, limiting its utility for constructing detailed, anatomically-informed models of brain function. In contrast, our analyses reproduce known neuroanatomy with precision and accuracy. This advantage is partly due to data acquisition procedures: while many DTI protocols measure diffusion in a small number of directions (e.g., 6 or 12), we employ a diffusion spectrum imaging (DSI)1, 2 protocol which assesses diffusion in 257 directions and at a range of magnetic gradient strengths. Moreover, DSI data allow us to use more sophisticated methods for reconstructing acquired data. In two experiments (visual attention and face perception), tractography reveals that co-active areas of the human brain are anatomically connected, supporting extant hypotheses that they form functional networks. DWI allows us to create a "circuit diagram" and reproduce it on an individual-subject basis, for

  1. Nonlinear development of strong current-driven instabilities and selective acceleration of ^3He ions

    NASA Astrophysics Data System (ADS)

    Toida, Mieko; Okumura, Hayato

    2003-10-01

    In some solar flares, the abundance of high-energy ^3He ions is extremely increased. As a mechanism for these ^3He rich events, current-driven instabilities are believed to be important. Nonlinear development of the strong current-driven instabilities and associated energy transfer to ^3He ions are studied theoretically and numerically [1]. First, by means of a two-dimensional, electrostatic, particle simulation code, it is demonstrated that ^3He ions are selectively accelerated by fundamental H cyclotron waves with frequencies ω ≃ 2Ω_3He (Ω_3He is the cyclotron frequency of ^3He). Then, from the analysis of the dispersion relation of these waves, it is found that the ω ≃ 2 Ω_ 3He waves have the greatest growth rate, if Te > 10 T_H. Energies of the ^3He ions are also discussed. Theoretical expression for the maximum ^3He energy is presented, which is in good agreement with the simulation results. Based on this theory, it is shown that when the initial electron drift energy is of the order of 10 keV, many ^3He ions can be accelerated to energies of the order of MeV/n. [1] M. Toida and H. Okumura, J. Phys. Soc. Jpn. 72,1098 (2003)

  2. OBSERVATIONS OF SOLAR ENERGETIC PARTICLES FROM {sup 3}He-RICH EVENTS OVER A WIDE RANGE OF HELIOGRAPHIC LONGITUDE

    SciTech Connect

    Wiedenbeck, M. E.; Mason, G. M.; Haggerty, D. K; Cohen, C. M. S.; Nitta, N. V.; Gomez-Herrero, R.

    2013-01-01

    A prevailing model for the origin of {sup 3}He-rich solar energetic particle (SEP) events attributes particle acceleration to processes associated with the reconnection between closed magnetic field lines in an active region and neighboring open field lines. The open field from the small reconnection volume then provides a path along which accelerated particles escape into a relatively narrow range of angles in the heliosphere. The narrow width (standard deviation <20 Degree-Sign ) of the distribution of X-ray flare longitudes found to be associated with {sup 3}He-rich SEP events detected at a single spacecraft at 1 AU supports this model. We report multispacecraft observations of individual {sup 3}He-rich SEP events that occurred during the solar minimum time period from 2007 January through 2011 January using instrumentation carried by the two Solar Terrestrial Relations Observatory spacecraft and the Advanced Composition Explorer. We find that detections of {sup 3}He-rich events at pairs of spacecraft are not uncommon, even when their longitudinal separation is >60 Degree-Sign . We present the observations of the {sup 3}He-rich event of 2010 February 7, which was detected at all three spacecraft when they spanned 136 Degree-Sign in heliographic longitude. Measured fluences of {sup 3}He in this event were found to have a strong dependence on longitude which is well fit by a Gaussian with standard deviation {approx}48 Degree-Sign centered at the longitude that is connected to the source region by a nominal Parker spiral magnetic field. We discuss several mechanisms for distributing flare-accelerated particles over a wide range of heliographic longitudes including interplanetary diffusion perpendicular to the magnetic field, spreading of a compact cluster of open field lines between the active region and the source surface where the field becomes radial and opens out into the heliosphere, and distortion of the interplanetary field by a preceding coronal mass

  3. Lattice Relaxation of 4He with 3He Impurities: NMR Studies

    NASA Astrophysics Data System (ADS)

    Candela, D.; Huan, C.; Kim, S. S.; Yin, L.; Xia, J. S.; Sullivan, N. S.

    2014-12-01

    Measurements of the 3He nuclear spin relaxation times of dilute 3He impurities in solid 4He have been used to explore the unusual dynamics of solid 4He at low temperatures. The 3He impurities move through the lattice by quantum mechanical exchange with neighboring 4He atoms. Because of the larger zero point motion of the 3He atoms, there is an appreciable lattice distortion that accompanies the tunneling 3 He atom and the tunneling motion depends on the elastic properties of the 4He lattice. This motion modulates the 3He-3He nuclear dipole- dipole interactions and thus determines the NMR relaxation rates. We compare the observed temperature dependence of the NMR relaxation rates with that expected from the measurements of the shear modulus by Syshchenko et al. [Phys. Rev. Lett. 104, 195301 (2009)].

  4. Assessment of treatment response by total tumor volume and global apparent diffusion coefficient using diffusion-weighted MRI in patients with metastatic bone disease: a feasibility study.

    PubMed

    Blackledge, Matthew D; Collins, David J; Tunariu, Nina; Orton, Matthew R; Padhani, Anwar R; Leach, Martin O; Koh, Dow-Mu

    2014-01-01

    We describe our semi-automatic segmentation of whole-body diffusion-weighted MRI (WBDWI) using a Markov random field (MRF) model to derive tumor total diffusion volume (tDV) and associated global apparent diffusion coefficient (gADC); and demonstrate the feasibility of using these indices for assessing tumor burden and response to treatment in patients with bone metastases. WBDWI was performed on eleven patients diagnosed with bone metastases from breast and prostate cancers before and after anti-cancer therapies. Semi-automatic segmentation incorporating a MRF model was performed in all patients below the C4 vertebra by an experienced radiologist with over eight years of clinical experience in body DWI. Changes in tDV and gADC distributions were compared with overall response determined by all imaging, tumor markers and clinical findings at serial follow up. The segmentation technique was possible in all patients although erroneous volumes of interest were generated in one patient because of poor fat suppression in the pelvis, requiring manual correction. Responding patients showed a larger increase in gADC (median change = +0.18, range = -0.07 to +0.78 × 10(-3) mm2/s) after treatment compared to non-responding patients (median change = -0.02, range = -0.10 to +0.05 × 10(-3) mm2/s, p = 0.05, Mann-Whitney test), whereas non-responding patients showed a significantly larger increase in tDV (median change = +26%, range = +3 to +284%) compared to responding patients (median change = -50%, range = -85 to +27%, p = 0.02, Mann-Whitney test). Semi-automatic segmentation of WBDWI is feasible for metastatic bone disease in this pilot cohort of 11 patients, and could be used to quantify tumor total diffusion volume and median global ADC for assessing response to treatment. PMID:24710083

  5. Micro-imaging of the Mouse Lung via MRI

    NASA Astrophysics Data System (ADS)

    Wang, Wei

    Quantitative measurement of lung microstructure is of great significance in assessment of pulmonary disease, particularly in the earliest stages. Conventional stereological assessment of ex-vivo fixed tissue specimens under the microscope has a long and successful tradition and is regarded as a gold standard, but the invasive nature limits its applications and the practicality of use in longitudinal studies. The technique for diffusion MRI-based 3He lung morphometry was previously developed and validated for human lungs, and was recently extended to ex-vivo mouse lungs. The technique yields accurate, quantitative information about the microstructure and geometry of acinar airways. In this dissertation, the 3He lung morphometry technique is for the first time successfully implemented for in-vivo studies of mice. It can generate spatially-resolved maps of parameters that reveal the microstructure of mouse lung. Results in healthy mice indicate excellent agreement between in-vivo morphometry via 3He MRI and microscopic morphometry after sacrifice. The implementation and validation of 3He morphometry in healthy mice open up new avenues for application of the technique as a precise, noninvasive, in-vivo biomarker of changes in lung microstructure, within various mouse models of lung disease. We have applied 3He morphometry to the Sendai mouse model of lung disease. Specifically, the Sendai-virus model of chronic obstructive lung disease has demonstrated an innate immune response in mouse airways that exhibits similarities to the chronic airway inflammation in human COPD and asthma, but the effect on distal lung parenchyma had not been investigated. We imaged the time course and regional distribution of mouse lung microstructural changes in vivo after Sendai virus (SeV) infection with 1H and 3He diffusion MRI. 1H MR images detected the SeV-induced pulmonary inflammation in vivo and 3He lung morphometry showed modest increase in alveolar duct radius distal to airway

  6. Postmortem interval alters the water relaxation and diffusion properties of rat nervous tissue--implications for MRI studies of human autopsy samples.

    PubMed

    Shepherd, Timothy M; Flint, Jeremy J; Thelwall, Peter E; Stanisz, Greg J; Mareci, Thomas H; Yachnis, Anthony T; Blackband, Stephen J

    2009-02-01

    High-resolution imaging of human autopsy tissues may improve our understanding of in vivo MRI findings, but interpretation is complicated because samples are obtained by immersion fixation following a postmortem interval (PMI). This study tested the hypotheses that immersion fixation and PMI's from 0-24 h would alter the water relaxation and diffusion properties in rat cortical slice and spinal cord models of human nervous tissue. Diffusion data collected from rat cortical slices at multiple diffusion times (10-60 ms) and b-values (7-15,000 s/mm(2)) were analyzed using a two-compartment model with exchange. Rat spinal cords were characterized with standard diffusion tensor imaging (21 directions, b=1250 s/mm(2)). Switching from perfusion- to immersion-fixation at 0 h PMI altered most MRI properties of rat cortical slices and spinal cords, including a 22% decrease in fractional anisotropy (P<0.001). After 4 h PMI, cortical slice T(1) and T(2) increased 22% and 65% respectively (P<0.001), transmembrane water exchange decreased 23% (P<0.001) and intracellular proton fraction increased 25% (P=0.002). After 6 h PMI, spinal cord white matter fractional anisotropy had decreased 38% (P<0.001). MRI property changes were observed for PMIs up to 24 h. The MRI changes correlated with protease activity and histopathological signs of autolysis. Thus, immersion fixation and/or even short PMIs (4-6 h) altered the MRI properties of rat nervous tissue. This suggests comparisons between in vivo clinical MRI and MRI data from human autopsy tissues should be interpreted with caution. PMID:18996206

  7. 3He lung imaging in an open access, very-low-field human magnetic resonance imaging system.

    PubMed

    Mair, R W; Hrovat, M I; Patz, S; Rosen, M S; Ruset, I C; Topulos, G P; Tsai, L L; Butler, J P; Hersman, F W; Walsworth, R L

    2005-04-01

    The human lung and its functions are extremely sensitive to gravity; however, the conventional high-field magnets used for most laser-polarized (3)He MRI of the human lung restrict subjects to lying horizontally. Imaging of human lungs using inhaled laser-polarized (3)He gas is demonstrated in an open-access very-low-magnetic-field (<5 mT) MRI instrument. This prototype device employs a simple, low-cost electromagnet, with an open geometry that allows variation of the orientation of the imaging subject in a two-dimensional plane. As a demonstration, two-dimensional lung images were acquired with 4-mm in-plane resolution from a subject in two orientations: lying supine and sitting in a vertical position with one arm raised. Experience with this prototype device will guide optimization of a second-generation very-low-field imager to enable studies of human pulmonary physiology as a function of subject orientation. PMID:15799045

  8. WE-G-BRD-01: Diffusion Weighted MRI for Response Assessment of Inoperable Lung Tumors for Patients Undergoing SBRT Treatment

    SciTech Connect

    Tyagi, N; Wengler, K; Yorke, E; Hunt, M; Deasy, J; Rimner, A

    2014-06-15

    Purpose: To investigate early changes in tumor Apparent Diffusion Coefficients derived from diffusion weighted (DW)-MRI of lung cancer patients undergoing SBRT, as a possible early predictor of treatment response. Methods: DW-MRI scans were performed in this prospective phase I IRB-approved study of inoperable lung tumors at various time-points during the course of SBRT treatments. Axial DW scan using multi b-values ranging from 0–1000 s/mm{sup 2} were acquired in treatment position on a 3T Philips MR scanner during simulation, one hour after the first fraction (8 Gy), after a total of 5 fractions (40 Gy) and 4 weeks after SBRT delivery. A monoexponential model based on a least square fit from all b values was performed on a pixel-by-pixel basis and ADC was calculated. GTVs drawn on 4DCT for planning were mapped on the T2w MRI (acquired at exhale) after deformable registration. These volumes were then mapped on DWI scan for ADC calculation after rigid registration between the anatomical scan and diffusion scan. T2w scan on followup time points were deformably registered to the pretreatment T2 scan. Results: The first two patients in this study were analyzed. Median ADC values were 1.48, 1.48, 1.62 and 1.83 (10{sup −3}×) mm{sup 2}/s at pretreatment, after 8 Gy, after 40 Gy and 4 weeks posttreatment for the first patient and 1.57, 1.53, 1.66 and 1.72 (10{sup −3}×) mm{sup 2}/s for the second patient. ADC increased more significantly after 4 weeks of treatment rather than immediately post treatment, implying that late ADC value may be a better predictor of tumor response for SBRT treatment. The fraction of tumor pixels at high ADC values increased at 4 weeks post treatment. Conclusion: The observed increase in ADC values before the end of radiotherapy may be a surrogate for tumor response, but further patient accrual will be necessary to determine its value.

  9. ADC values in diffusion-weighted MRI and their relationship with age, gender and BMI in healthy people's pancreases

    PubMed Central

    Faeghi, F; Abdkarimi, M H; Asghari JafarAbadi, M

    2015-01-01

    Objective: The aim of this study is to use diffusion-weighted MRI to assess the apparent diffusion coefficient (ADC) values in head, body and tail sections of the pancreas in healthy subjects and the relationships between these values and age, gender and body mass index (BMI) of these cases. Methods: This study was conducted on 82 participants who were referred to the Tabesh Medical Imaging Center, Tabriz, Islamic Republic of Iran, during 2013. Echo-planar diffusion-weighted imaging of the pancreas was carried out with b-values of 50, 400 and 800 s mm−2, and ADC values were assessed for the head, body and tail sections of the pancreas. Results: The ADC values for the head, body and tail sections of the pancreas in female participants were significantly greater than those in male subjects (p < 0.05). ADC values for these parts among subjects with different BMI differed significantly (p < 0.05). Regarding age, there were no statistically meaningful differences among the ADC values for the three parts (p > 0.05). Conclusion: Gender and BMI effect the ADC values of the three sections of the pancreas. Thus, knowledge of the basic values based on gender and BMI can improve diagnostics. Having looked at age factor, it seems that the ADC values were not significantly different. Advances in knowledge: According to the results pancreatic ADC values appear to be influenced by gender and BMI but not by age. PMID:25471056

  10. Low-temperature instability of uniform spin precession in the B phase of pure {sup 3}He and {sup 3}He in an aerogel

    SciTech Connect

    Surovtsev, E. V. Fomin, I. A.

    2010-08-15

    The magnetic-field dependences of the threshold temperature of the low-temperature instability of uniform spin precession in pure {sup 3}He-B and {sup 3}He-B in an aerogel have been determined for the bulk mechanism. These dependences appear to be different. The theoretical dependence of the threshold temperature for the pure case has been compared with the experimental dependence. The threshold temperature of the instability for {sup 3}He in the aerogel has been estimated for typical experimental conditions.

  11. Evaluation of thermal and cryo lesions by diffusion-weighted MRI

    NASA Astrophysics Data System (ADS)

    Chen, Jing; Daniel, Bruce; Bouley, Donna; Sommer, Graham; Butts Pauly, Kim

    2007-02-01

    The purpose of this study is to further investigate the approach of DWI to estimate the cell viability immediately after treatment. In this work, we reported the result from 12 canine prostate experiments underwent cryoablation or hyperthermic therapy. The lesion detected by diffusion-weighted imaging was evaluated through apparent diffusion coefficient (ADC) value, image contrast, and lesion contour compared to contrast enhanced imaging and histology.

  12. Microanisotropy imaging: quantification of microscopic diffusion anisotropy and orientational order parameter by diffusion MRI with magic-angle spinning of the q-vector

    NASA Astrophysics Data System (ADS)

    Lasič, Samo; Szczepankiewicz, Filip; Eriksson, Stefanie; Nilsson, Markus; Topgaard, Daniel

    2014-02-01

    Diffusion tensor imaging (DTI) is the method of choice for non-invasive investigations of the structure of human brain white matter. The results are conventionally reported as maps of the fractional anisotropy (FA), which is a parameter related to microstructural features such as axon density, diameter, and myelination. The interpretation of FA in terms of microstructure becomes ambiguous when there is a distribution of axon orientations within the image voxel. In this paper, we propose a procedure for resolving this ambiguity by determining a new parameter, the microscopic fractional anisotropy (µFA), which corresponds to the FA without the confounding influence of orientation dispersion. In addition, we suggest a method for measuring the orientational order parameter (OP) for the anisotropic objects. The experimental protocol is capitalizing on a recently developed diffusion NMR pulse sequence based on magic-angle spinning of the q-vector. Proof-of-principle experiments are carried out on microimaging and clinical MRI equipment using lyotropic liquid crystals and plant tissues as model materials with high µFA and low FA on account of orientation dispersion. We expect the presented method to be especially fruitful in combination with DTI and high angular resolution acquisition protocols for neuroimaging studies of grey and white matter.

  13. The diffusion tensor imaging (DTI) component of the NIH MRI study of normal brain development (PedsDTI).

    PubMed

    Walker, Lindsay; Chang, Lin-Ching; Nayak, Amritha; Irfanoglu, M Okan; Botteron, Kelly N; McCracken, James; McKinstry, Robert C; Rivkin, Michael J; Wang, Dah-Jyuu; Rumsey, Judith; Pierpaoli, Carlo

    2016-01-01

    The NIH MRI Study of normal brain development sought to characterize typical brain development in a population of infants, toddlers, children and adolescents/young adults, covering the socio-economic and ethnic diversity of the population of the United States. The study began in 1999 with data collection commencing in 2001 and concluding in 2007. The study was designed with the final goal of providing a controlled-access database; open to qualified researchers and clinicians, which could serve as a powerful tool for elucidating typical brain development and identifying deviations associated with brain-based disorders and diseases, and as a resource for developing computational methods and image processing tools. This paper focuses on the DTI component of the NIH MRI study of normal brain development. In this work, we describe the DTI data acquisition protocols, data processing steps, quality assessment procedures, and data included in the database, along with database access requirements. For more details, visit http://www.pediatricmri.nih.gov. This longitudinal DTI dataset includes raw and processed diffusion data from 498 low resolution (3 mm) DTI datasets from 274 unique subjects, and 193 high resolution (2.5 mm) DTI datasets from 152 unique subjects. Subjects range in age from 10 days (from date of birth) through 22 years. Additionally, a set of age-specific DTI templates are included. This forms one component of the larger NIH MRI study of normal brain development which also includes T1-, T2-, proton density-weighted, and proton magnetic resonance spectroscopy (MRS) imaging data, and demographic, clinical and behavioral data. PMID:26048622

  14. Q-space trajectory imaging for multidimensional diffusion MRI of the human brain.

    PubMed

    Westin, Carl-Fredrik; Knutsson, Hans; Pasternak, Ofer; Szczepankiewicz, Filip; Özarslan, Evren; van Westen, Danielle; Mattisson, Cecilia; Bogren, Mats; O'Donnell, Lauren J; Kubicki, Marek; Topgaard, Daniel; Nilsson, Markus

    2016-07-15

    This work describes a new diffusion MR framework for imaging and modeling of microstructure that we call q-space trajectory imaging (QTI). The QTI framework consists of two parts: encoding and modeling. First we propose q-space trajectory encoding, which uses time-varying gradients to probe a trajectory in q-space, in contrast to traditional pulsed field gradient sequences that attempt to probe a point in q-space. Then we propose a microstructure model, the diffusion tensor distribution (DTD) model, which takes advantage of additional information provided by QTI to estimate a distributional model over diffusion tensors. We show that the QTI framework enables microstructure modeling that is not possible with the traditional pulsed gradient encoding as introduced by Stejskal and Tanner. In our analysis of QTI, we find that the well-known scalar b-value naturally extends to a tensor-valued entity, i.e., a diffusion measurement tensor, which we call the b-tensor. We show that b-tensors of rank 2 or 3 enable estimation of the mean and covariance of the DTD model in terms of a second order tensor (the diffusion tensor) and a fourth order tensor. The QTI framework has been designed to improve discrimination of the sizes, shapes, and orientations of diffusion microenvironments within tissue. We derive rotationally invariant scalar quantities describing intuitive microstructural features including size, shape, and orientation coherence measures. To demonstrate the feasibility of QTI on a clinical scanner, we performed a small pilot study comparing a group of five healthy controls with five patients with schizophrenia. The parameter maps derived from QTI were compared between the groups, and 9 out of the 14 parameters investigated showed differences between groups. The ability to measure and model the distribution of diffusion tensors, rather than a quantity that has already been averaged within a voxel, has the potential to provide a powerful paradigm for the study of

  15. Regional Heterogeneity of Chronic Obstructive Pulmonary Disease Phenotypes: Pulmonary (3)He Magnetic Resonance Imaging and Computed Tomography.

    PubMed

    Pike, Damien; Kirby, Miranda; Eddy, Rachel L; Guo, Fumin; Capaldi, Dante P I; Ouriadov, Alexei; McCormack, David G; Parraga, Grace

    2016-10-01

    Pulmonary ventilation may be visualized and measured using hyperpolarized (3)He magnetic resonance imaging (MRI) while emphysema and its distribution can be quantified using thoracic computed tomography (CT). Our objective was to phenotype ex-smokers with COPD based on the apical-to-basal distribution of ventilation abnormalities and emphysema to better understand how these phenotypes change regionally as COPD progresses. We evaluated 100 COPD ex-smokers who provided written informed consent and underwent spirometry, CT and (3)He MRI. (3)He MRI ventilation imaging was used to quantify the ventilation defect percent (VDP) for whole-lung and individual lung lobes. Regional VDP was used to generate the apical-lung (AL)-to-basal-lung (BL) difference (ΔVDP); a positive ΔVDP indicated AL-predominant and negative ΔVDP indicated BL-predominant ventilation defects. Emphysema was quantified using the relative-area-of-the-lung ≤-950HU (RA950) of the CT density histogram for whole-lung and individual lung lobes. The AL-to-BL RA950 difference (ΔRA950) was generated with a positive ΔRA950 indicating AL-predominant emphysema and a negative ΔRA950 indicating BL-predominant emphysema. Seventy-two ex-smokers reported BL-predominant MRI ventilation defects and 71 reported AL-predominant CT emphysema. BL-predominant ventilation defects (AL/BL: GOLD I = 18%/82%, GOLD II = 24%/76%) and AL-predominant emphysema (AL/BL: GOLD I = 84%/16%, GOLD II = 72%/28%) were the major phenotypes in mild-moderate COPD. In severe COPD there was a more uniform distribution for ventilation defects (AL/BL: GOLD III = 40%/60%, GOLD IV = 43%/57%) and emphysema (AL/BL: GOLD III = 64%/36%, GOLD IV = 43%/57%). Basal-lung ventilation defects predominated in mild-moderate GOLD grades, and a more homogeneous distribution of ventilation defects was observed in more advanced grade COPD; these differences suggest that over time, regional ventilation abnormalities become more homogenously distributed during

  16. A possible in situ 3H and 3He source in Earth's interior: an alternative explanation of origin of 3He in deep Earth.

    PubMed

    Jiang, Songsheng; Liu, Jing; He, Ming

    2010-07-01

    Origin of (3)He in the Earth is a mystery. Lacking a production mechanism, scientists assume (3)He was trapped in the Earth, when the Earth was formed. In contrast to this assumption, we have found (3)He and (3)H concentrations in excess of the atmospheric values in the deep waters of the volcanic Lakes Pavin (France), Laacher (Germany) and Nemrut (Turkey). This paper reports the result of finding (3)H in these three volcanic lakes that appear to originate from the mantle. Because (3)H has a half-life of 12.3 years, this (3)H and the resulting (3)He must have formed recently in the mantle and not be part of a primordial reservoir. The nuclear reactions that generate tritium might be a source of "missing" energy in the interior of the Earth. PMID:20502855

  17. Cortical restricted diffusion as the predominant MRI finding in sporadic Creutzfeldt-Jakob disease.

    PubMed

    Talbott, Sabrina D; Plato, Brian M; Sattenberg, Ronald J; Parker, John; Heidenreich, Jens O

    2011-04-01

    Creutzfeldt-Jakob disease is a rare and fatal neurodegenerative disorder with MR findings predominantly limited to the grey matter of the cortex and the basal ganglia. Sporadic Creutzfeldt-Jakob disease can produce a spectrum of MR imaging findings of the brain, most notably on DWI and FLAIR sequences. Involvement of the basal ganglia and neocortex is the most common finding, but isolated involvement of the cortex can also be seen. We describe the clinical history and MRI findings of three patients with sporadic Creutzfeldt-Jakob disease confirmed by brain biopsy or autopsy and review the literature of imaging manifestations of this disease. PMID:21498372

  18. The presence of two local myocardial sheet populations confirmed by diffusion tensor MRI and histological validation

    PubMed Central

    Kung, Geoff; Nguyen, Tom C.; Itoh, Aki; Skare, Stefan; Ingels, Neil B.; Miller, D. Craig; Ennis, Daniel B.

    2011-01-01

    Purpose To establish the correspondence between the two histologically observable and diffusion tensor magnetic resonance imaging (DTMRI) measurements of myolaminae orientation for the first time and show that single myolaminar orientations observed in local histology may result from histological artifact. Materials and Methods DTMRI was performed on six sheep left ventricles (LV), then corresponding direct histological transmural measurements were made within the antero-basal and lateral-equatorial LV. Secondary and tertiary eigenvectors of the diffusion tensor were compared to each of the two locally observable sheet orientations from histology. Diffusion tensor invariants were calculated to compare differences in microstructural diffusive properties between histological locations with one observable sheet population and two observable sheet populations. Results Mean difference ± one standard deviation between DTMRI and histology measured sheet angles was 8° ± 27°. Diffusion tensor invariants showed no significant differences between histological locations with one observable sheet population and locations with two observable sheet populations. Conclusion DTMRI measurements of myolaminae orientations derived from the secondary and tertiary eigenvectors correspond to each of the two local myolaminae orientations observed in histology. Two local sheet populations may exist throughout LV myocardium and one local sheet population observed in histology may be a result of preparation artifact. PMID:21932362

  19. Perinatal MRI diffusivity is related to early assessment of motor performance in preterm neonates.

    PubMed

    Navarra, Riccardo; Sestieri, Carlo; Conte, Emanuela; Salomone, Rita; Mattei, Peter A; Romani, Gian L; Domizio, Sergio; Caulo, Massimo

    2016-04-01

    Preterm neonates represent a high-risk population for abnormal neuropsychological development. But presently, an accurate method for identifying those at risk is not available. This study evaluated the association between the microstructural organization measured with Diffusion Tensor Imaging (DTI) in term-corrected preterm neonates and subsequent motor performance. Fractional anisotropy (FA), axial diffusion (AD), mean diffusivity (MD) and radial diffusivity (RD) were determined in two regions of interest (ROIs) corresponding to the posterior limb of the internal capsule (PLIC) and cortico-spinal tract (CST). The Griffiths Mental Developmental Scales (GMDS) were longitudinally administered at 3, 6 and 15 months; and correlations between the metrics of diffusivity and the motor subscale of the GMDS were assessed using the Spearman correlation. A statistically significant negative correlation was observed between the AD of PLIC of the left hemisphere and the 3-month GMDS Locomotor Subscale. These results suggested that AD is a valid indicator of the stage of maturation of the motor pathway in preterm neonates, but not of later motor outcome. PMID:26915895

  20. Polarized {sup 3}He gas compression system using metastability-exchange optical pumping

    SciTech Connect

    Hussey, D.S.; Rich, D.R.; Belov, A.S.; Tong, X.; Yang, H.; Bailey, C.; Keith, C.D.; Hartfield, J.; Hall, G.D.R.; Black, T.C.; Snow, W.M.; Gentile, T.R.; Chen, W.C.; Jones, G.L.; Wildman, E.

    2005-05-15

    Dense samples (10-100 bar cm) of nuclear spin polarized {sup 3}He are utilized in high energy physics, neutron scattering, atomic physics, and magnetic resonance imaging. Metastability exchange optical pumping can rapidly produce high {sup 3}He polarizations ({approx_equal}80%) at low pressures (few mbar). We describe a polarized {sup 3}He gas compressor system which accepts 0.26 bar l h{sup -1} of {sup 3}He gas polarized to 70% by a 4 W neodymium doped lanthanum magnesium hexaluminate (Nd:LMA) laser and compresses it into a 5 bar cm target with final polarization of 55%. The spin relaxation rates of the system's components have been measured using nuclear magnetic resonance and a model of the {sup 3}He polarization loss based on the measured relaxation rates and the gas flow is in agreement with a {sup 3}He polarization measurement using neutron transmission.

  1. A 3He Cryostat for Scientific Measurements in Pulsed High Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Wang, Shaoliang; Li, Liang; Liu, Mengyu; Zuo, Huakun; Peng, Tao

    A top loading 3He cryostat has been developed for scientific experiments with a 60 T pulsed magnetic field facility at Wuhan National High Magnetic Field Center. The cryostat consists of a 4He bath cryostat, a 3He insert and a closed circulation system for 3He gas handling. To eliminate the eddy current heating during the pulse, the tail of the 3He insert with a vacuum space at the bottom is made from fiberglass tubing coated with epoxy. The 3He bath is separated from the 4He bath with the vacuum space. The 4He bath cryostat provides cooling power to condense 3He gas by a neck tube on top of the tail. Experimental results have shown that the sample can be cooled down to 385 mK and kept cold for more than 150 second by one-shot cooling, which is sufficiently long for an experiment in a pulsed high magnetic field.

  2. Fabrication and tests of 3He and 2H targets for beam polarization measurement

    PubMed

    Naqvi; Aksoy; Nagadi; Al-Ohali; Kidwai; Fageeha

    2000-09-01

    3He and 2H targets were fabricated through implantation of 3He and 2H ions in 0.2-0.3 mm thick tantalum and titanium foils. The energy of 3He and 2H ions was 45-100 and 78 keV, respectively. Ions beams with typical current of 90-300 microA were used for implantation. Stability tests of 3He and 2H targets were carried out by monitoring the yield of 3He(d, p)4He and 2H(d, p)3H reactions. For the 3He target, the reaction yield was stable for both tantalum and titanium foils but the most stabilized maximum yield was observed for the 100 keV tantalum target. In the case of 2H targets, the yield increased with increasing total dose implanted on the target. PMID:10972150

  3. Quantification of fibrosis in infarcted swine hearts by ex vivo late gadolinium-enhancement and diffusion-weighted MRI methods

    NASA Astrophysics Data System (ADS)

    Pop, Mihaela; Ghugre, Nilesh R.; Ramanan, Venkat; Morikawa, Lily; Stanisz, Greg; Dick, Alexander J.; Wright, Graham A.

    2013-08-01

    Many have speculated that MRI signal characteristics can be used to identify regions of heterogeneous infarct associated with an arrhythmogenic substrate; however, direct evidence of this relationship is limited. The aim of this study was to demonstrate the remodelling characteristics of fibrosis by means of histology and high-resolution MR imaging. For this purpose, we performed whole-mount histology in heart samples (n = 9) collected from five swine at six weeks post-infarction and compared the extent of fibrosis in the infarcted areas delineated in these histological images with that obtained ex vivo by MRI using late gadolinium-enhancement (LGE) and diffusion-weighted imaging (DWI) methods. All MR images were obtained at a submillimetre resolution (i.e., voxel size of 0.6×0.6×1.2 mm3). Specifically, in the histology images, we differentiated moderate fibrosis (consisting of a mixture of viable and non-viable myocytes, known as border zone, BZ) from severe fibrosis (i.e., the dense scar). Correspondingly, tissue heterogeneities in the MR images were categorized by a Gaussian mixture model into healthy, BZ and scar. Our results showed that (a) both MRI methods were capable of qualitatively distinguishing sharp edges between dense scar and healthy tissue from regions of heterogeneous BZ; (b) the BZ and dense scar areas had intermediate-to-high increased values of signal intensity in the LGE images and of apparent diffusion coefficient in the DWI, respectively. In addition, as demonstrated by the Picrosirius Red and immunohistochemistry stains, the viable bundles in the BZ were clearly separated by thin collagen strands and had reduced expression of Cx43, whereas the core scar was composed of dense fibrosis. A quantitative analysis demonstrated that the comparison between BZ/scar extent in LGE and DWI to the corresponding areas identified in histology yielded very good correlations (i.e., for the scar identified by LGE, R2 was 0.96 compared to R2 = 0.93 for the

  4. Quantifying the Diffusion of a Fluid through Membranes by RemoteDetection MRI

    SciTech Connect

    Telkki, Ville-Veikko; Hilty, Christian; Garcia, Sandra; Harel,Elad; Pines, Alexander

    2006-10-24

    We present a method to measure self-diffusion acrossmembranes without the need for concentration or pressure gradients.Hyperpolarized xenon in combination with remote detection of NMR allowsthe measurement of membrane permeation, even in the gas phase. Theresulting images allow quantification of the amount of fluid diffusedthrough the membrane, and represent an alternative, potentially moreprecise way of measuring a membrane diffusion coefficient. The use ofremote detection of NMR allows for non-invasive signal encoding coupledto sensitive detection, making this approach ideal for the study ofdiffusion in intact devices such as fuel cells or separationsystems.

  5. Neural substrates of vulnerability to postsurgical delirium as revealed by presurgical diffusion MRI.

    PubMed

    Cavallari, Michele; Dai, Weiying; Guttmann, Charles R G; Meier, Dominik S; Ngo, Long H; Hshieh, Tammy T; Callahan, Amy E; Fong, Tamara G; Schmitt, Eva; Dickerson, Bradford C; Press, Daniel Z; Marcantonio, Edward R; Jones, Richard N; Inouye, Sharon K; Alsop, David C

    2016-04-01

    Despite the significant impact of postoperative delirium on surgical outcomes and the long-term prognosis of older patients, its neural basis has not yet been clarified. In this study we investigated the impact of premorbid brain microstructural integrity, as measured by diffusion tensor imaging before surgery, on postoperative delirium incidence and severity, as well as the relationship among presurgical cognitive performance, diffusion tensor imaging abnormalities and postoperative delirium. Presurgical diffusion tensor imaging scans of 136 older (≥70 years), dementia-free subjects from the prospective Successful Aging after Elective Surgery study were analysed blind to the clinical data and delirium status. Primary outcomes were postoperative delirium incidence and severity during the hospital stay, as assessed by the Confusion Assessment Method. We measured cognition before surgery using general cognitive performance, a composite score based on a battery of neuropsychological tests. We investigated the association between presurgical diffusion tensor imaging parameters of brain microstructural integrity (i.e. fractional anisotropy, axial, mean and radial diffusivity) with postoperative delirium incidence and severity. Analyses were adjusted for the following potential confounders: age, gender, vascular comorbidity status, and general cognitive performance. Postoperative delirium occurred in 29 of 136 subjects (21%) during hospitalization. Presurgical diffusion tensor imaging abnormalities of the cerebellum, cingulum, corpus callosum, internal capsule, thalamus, basal forebrain, occipital, parietal and temporal lobes, including the hippocampus, were associated with delirium incidence and severity, after controlling for age, gender and vascular comorbidities. After further controlling for general cognitive performance, diffusion tensor imaging abnormalities of the cerebellum, hippocampus, thalamus and basal forebrain still remained associated with delirium

  6. The Validation of Complete Fourier Direct MR Method for Diffusion MRI via Biological and Numerical Phantoms

    PubMed Central

    Özcan, Alpay; Quirk, James D.; Wang, Yong; Wang, Qing; Sun, Peng; Spees, William M.; Song, Sheng–Kwei

    2012-01-01

    The equations of the Complete Fourier Direct (CFD) MR model are explicitly derived for diffusion weighted NMR experiments. The CFD–MR theory is validated by comparing a biological phantom constructed from nerve bundles and agar gel with its numerical implementation. The displacement integral distribution function estimated from the experimental data is in high agreement with the numerical phantom. CFD–MR’s ability to estimate accurately and fully spin diffusion properties demonstrated here, provides the experimental validation of the theoretical CFD–MR model. PMID:22255156

  7. Polarization of 3He by Spin Exchange with Optically Pumped Rb and K Vapors

    NASA Astrophysics Data System (ADS)

    Ben-Amar Baranga, A.; Appelt, S.; Romalis, M. V.; Erickson, C. J.; Young, A. R.; Cates, G. D.; Happer, W.

    1998-03-01

    We report on extensive experimental measurements of the key rates that determine the efficiency for polarizing the nuclei of 3He by spin exchange with optically pumped Rb vapor. In agreement with recent theoretical predictions, we find a strong temperature dependence of the electron-spin loss rates due to 3HeRb collisions. We also find that the maximum possible efficiency for spin-exchange polarization of 3He by K is 10 times greater than for Rb.

  8. NMR Studies of Texture in the B-like Phase of 3He in Aerogel

    SciTech Connect

    Dmitriev, V. V.; Zavjalov, V. V.; Zmeev, D. E.; Mulders, N.

    2006-09-07

    Continuous wave NMR experiments have been performed in the B-like phase of 3He in a 98% open aerogel. The results allow us to get information about the texture of the 3He order parameter inside the aerogel. We conclude that in the B-like phase the boundary between the bulk 3He and the aerogel orients the vector of orbital anisotropy (L) parallel to it. Two stable textures and textural transition between them were observed in our sample.

  9. Detecting compartmental non-Gaussian diffusion with symmetrized double-PFG MRI.

    PubMed

    Paulsen, Jeffrey L; Özarslan, Evren; Komlosh, Michal E; Basser, Peter J; Song, Yi-Qiao

    2015-11-01

    Diffusion in tissue and porous media is known to be non-Gaussian and has been used for clinical indications of stroke and other tissue pathologies. However, when conventional NMR techniques are applied to biological tissues and other heterogeneous materials, the presence of multiple compartments (pores) with different Gaussian diffusivities will also contribute to the measurement of non-Gaussian behavior. Here we present symmetrized double PFG (sd-PFG), which can separate these two contributions to non-Gaussian signal decay as having distinct angular modulation frequencies. In contrast to prior angular d-PFG methods, sd-PFG can unambiguously extract kurtosis as an oscillation from samples with isotropic or uniformly oriented anisotropic pores, and can generally extract a combination of compartmental anisotropy and kurtosis. The method further fixes its sensitivity with respect to the time dependence of the apparent diffusion coefficient. We experimentally demonstrate the measurement of the fourth cumulant (kurtosis) of diffusion and find it consistent with theoretical predictions. By enabling the unambiguous identification of contributions of compartmental kurtosis to the signal, sd-PFG has the potential to help identify the underlying micro-structural changes corresponding to current kurtosis based diagnostics, and act as a novel source of contrast to better resolve tissue micro-structure. PMID:26434812

  10. Linear Transforms for Fourier Data on the Sphere: Application to High Angular Resolution Diffusion MRI of the Brain

    PubMed Central

    Haldar, Justin P.; Leahy, Richard M.

    2013-01-01

    This paper presents a novel family of linear transforms that can be applied to data collected from the surface of a 2-sphere in three-dimensional Fourier space. This family of transforms generalizes the previously-proposed Funk-Radon Transform (FRT), which was originally developed for estimating the orientations of white matter fibers in the central nervous system from diffusion magnetic resonance imaging data. The new family of transforms is characterized theoretically, and efficient numerical implementations of the transforms are presented for the case when the measured data is represented in a basis of spherical harmonics. After these general discussions, attention is focused on a particular new transform from this family that we name the Funk-Radon and Cosine Transform (FRACT). Based on theoretical arguments, it is expected that FRACT-based analysis should yield significantly better orientation information (e.g., improved accuracy and higher angular resolution) than FRT-based analysis, while maintaining the strong characterizability and computational efficiency of the FRT. Simulations are used to confirm these theoretical characteristics, and the practical significance of the proposed approach is illustrated with real diffusion weighted MRI brain data. These experiments demonstrate that, in addition to having strong theoretical characteristics, the proposed approach can outperform existing state-of-the-art orientation estimation methods with respect to measures such as angular resolution and robustness to noise and modeling errors. PMID:23353603

  11. Intraprocedural Diffusion-Weighted PROPELLER MRI to Guide Percutaneous Biopsy Needle Placement within Rabbit VX2 Liver Tumors

    PubMed Central

    Deng, Jie; Virmani, Sumeet; Yang, Guang-Yu; Tang, Richard; Woloschak, Gayle; Omary, Reed A.; Larson, Andrew C.

    2010-01-01

    Purpose To test the hypothesis that diffusion-weighted (DW)-PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) magnetic resonance imaging (MRI) can be used to guide biopsy needle placement during percutaneous interventional procedures to selectively target viable and necrotic tissues within VX2 rabbit liver tumors. Materials and Methods Our institutional Animal Care and Use Committee approved all experiments. In six rabbits implanted with 15 VX2 liver tumors, baseline DWPROPELLER images acquired prior to the interventional procedure were used for apparent diffusion coefficient (ADC) measurements. Next, intraprocedural DW-PROPELLER scans were performed with needle position iteratively adjusted to target viable, necrotic, or intermediate border tissue regions. DW-PROPELLER ADC measurements at the selected needle tip locations were compared with the percentage of tumor necrosis qualitatively assessed at histopathology. Results DW-PROPELLER images demonstrated intratumoral tissue heterogeneity and clearly depicted the needle tip position within viable and necrotic tumor tissues. Mean ADC measurements within the region-of-interest encompassing the needle tip were highly correlated with histopathologic tumor necrotic tissue assessments. Conclusion DW-PROPELLER is an effective method to selectively position the biopsy needle tip within viable and necrotic tumor tissues. The DW-PROPELLER method may offer an important complementary tool for functional guidance during MR-guided percutaneous procedures. PMID:19629976

  12. The role of pre-treatment diffusion-weighted MRI in predicting long-term outcome of colorectal liver metastasis

    PubMed Central

    Collins, D J; Brown, G; Chau, I; Cunningham, D; Leach, M O; Koh, D-M

    2013-01-01

    Objective: To determine the prognostic value of pre-treatment apparent diffusion coefficient (ADC) of colorectal liver metastases in predicting disease response, progression-free survival (PFS) and overall survival (OS). Methods: We retrospectively reviewed 102 patients who underwent pre-treatment diffusion-weighted MRI using a breath-hold (b=0, 150, 500) or a free-breathing (b=0, 50, 100, 250, 500, 750) technique. The mean ADC (b=0–500) and mean flow-insensitive ADC (ADChigh) values (breath-hold: b=150 and 500; free-breathing: b=100 and 500) of up to three hepatic lesions were evaluated in each patient. Clinical and laboratory parameters were recorded. Tumour response was assessed by Response Evaluation Criteria in Solid Tumors (RECIST) criteria at 12 weeks after treatment. Associations between tumour response, ADC values and clinical/laboratory parameters were examined by one-way analysis of variance. The relationship of ADC with PFS and OS was determined by Kaplan–Meier analysis. Results: 62 patients responded to chemotherapy at 12 weeks. The pre-treatment mean ADC and mean ADChigh were higher in the non-responding group than in the responding group (1.55 vs 1.36, p=0.033; 1.40 vs 1.16, p=0.024). However, the PFS and OS of the two groups of patients stratified by the median of mean ADC values or threshold derived by receiver operating characteristic analysis were not statistically significant. By multivariate Cox regression analysis, patients with ≤2 metastases and response to chemotherapy showed better PFS; white cell count ≤10 and surgical treatment were associated with better OS. Conclusion: Colorectal liver metastasis with higher pre-treatment mean ADC and mean ADChigh was associated with poorer response to chemotherapy. However, ADC and ADChigh values did not predict the patient outcome in this study cohort. Advances in knowledge: High mean ADC values of colorectal liver metastases on pre-treatment diffusion-weighted MRI is associated with poorer

  13. Longitudinal development in the preterm thalamus and posterior white matter: MRI correlations between diffusion weighted imaging and T2 relaxometry.

    PubMed

    Melbourne, Andrew; Eaton-Rosen, Zach; Orasanu, Eliza; Price, David; Bainbridge, Alan; Cardoso, M Jorge; Kendall, Giles S; Robertson, Nicola J; Marlow, Neil; Ourselin, Sebastien

    2016-07-01

    Infants born prematurely are at increased risk of adverse neurodevelopmental outcome. The measurement of white matter tissue composition and structure can help predict functional performance. Specifically, measurements of myelination and indicators of myelination status in the preterm brain could be predictive of later neurological outcome. Quantitative imaging of myelin could thus serve to develop biomarkers for prognosis or therapeutic intervention; however, accurate estimation of myelin content is difficult. This work combines diffusion MRI and multi-component T2 relaxation measurements in a group of 37 infants born very preterm and scanned between 27 and 58 weeks equivalent gestational age. Seven infants have longitudinal data at two time points that we analyze in detail. Our aim is to show that measurement of the myelin water fraction is achievable using widely available pulse sequences and state-of-the-art algorithmic modeling of the MR imaging procedure and that a multi-component fitting routine to multi-shell diffusion weighted data can show differences in neurite density and local spatial arrangement in grey and white matter. Inference on the myelin water fraction allows us to demonstrate that the change in diffusion properties of the preterm thalamus is not solely due to myelination (that increase in myelin content accounts for about a third of the observed changes) whilst the decrease in the posterior white matter T2 has no significant component that is due to myelin water content. This work applies multi-modal advanced quantitative neuroimaging to investigate changing tissue properties in the longitudinal setting. Hum Brain Mapp 37:2479-2492, 2016. © 2016 Wiley Periodicals, Inc. PMID:26996400

  14. Longitudinal development in the preterm thalamus and posterior white matter: MRI correlations between diffusion weighted imaging and T2 relaxometry

    PubMed Central

    Eaton‐Rosen, Zach; Orasanu, Eliza; Price, David; Bainbridge, Alan; Cardoso, M. Jorge; Kendall, Giles S.; Robertson, Nicola J.; Marlow, Neil; Ourselin, Sebastien

    2016-01-01

    Abstract Infants born prematurely are at increased risk of adverse neurodevelopmental outcome. The measurement of white matter tissue composition and structure can help predict functional performance. Specifically, measurements of myelination and indicators of myelination status in the preterm brain could be predictive of later neurological outcome. Quantitative imaging of myelin could thus serve to develop biomarkers for prognosis or therapeutic intervention; however, accurate estimation of myelin content is difficult. This work combines diffusion MRI and multi‐component T2 relaxation measurements in a group of 37 infants born very preterm and scanned between 27 and 58 weeks equivalent gestational age. Seven infants have longitudinal data at two time points that we analyze in detail. Our aim is to show that measurement of the myelin water fraction is achievable using widely available pulse sequences and state‐of‐the‐art algorithmic modeling of the MR imaging procedure and that a multi‐component fitting routine to multi‐shell diffusion weighted data can show differences in neurite density and local spatial arrangement in grey and white matter. Inference on the myelin water fraction allows us to demonstrate that the change in diffusion properties of the preterm thalamus is not solely due to myelination (that increase in myelin content accounts for about a third of the observed changes) whilst the decrease in the posterior white matter T2 has no significant component that is due to myelin water content. This work applies multi‐modal advanced quantitative neuroimaging to investigate changing tissue properties in the longitudinal setting. Hum Brain Mapp 37:2479–2492, 2016. © The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.. PMID:26996400

  15. Model formalism of liquid /sup 3/He-B at equilibrium

    SciTech Connect

    Goldstein, L.; Goldstein, J.C.

    1980-04-01

    The approximate formal treatment of the nuclear spin system of normal liquid /sup 3/He given some time ago is extended to the ordered /sup 3/He phase. The formalism leads to the prediction of normal thermal behavior of /sup 3/He-B at lower pressures and at temperatures approaching its phase-boundary temperatures. In contrast to the disordered normal liquid phase, which is thermally anomalous, the entropy of the /sup 3/He-B decreases on isothermal compression, or its isobaric volume expansion coefficient is positive. The equilibrium thermal behavior of ordered /sup 3/He-B is thus qualitatively different from that of disordered liquid /sup 3/He. Experimental control of these aspects of the liquid /sup 3/He phase transformation is lacking at the present time. Both early and new /sup 3/He-B paramagnetic susceptibility data, extended recently over a wide reduced-temperature range, disclose a fundamental competition between the spontaneous ordering mechanism responsible for the existence of /sup 3/He-B and the specific ordering process imposed upon this phase on application of an external constant and uniform magnetic field. As a consequence, magnetized /sup 3/He-B will be shown to increase its entropy on isothermal magnetization and to cool on adiabatic magnetization. The magnetocaloric effect is, however, only moderate. The competition of the ordering process leads to the delay or possibly even to the suppression of the formation of the ordered phase, a state of affairs foreseen in our earlier work. At low or moderate magnetic field strengths, the zero-field phase-boundary temperatures are shown to shift toward lower temperatures while, simultaneously, the order of the phase change decreases, from second order, in the absence of the field, to first order. Although of model-theoretic character, involving limitations of various types, the rich physical content of /sup 3/He-B at equilibrium clearly emerges in the present work.

  16. Segmentation of High Angular Resolution Diffusion MRI using Sparse Riemannian Manifold Clustering

    PubMed Central

    Wright, Margaret J.; Thompson, Paul M.; Vidal, René

    2015-01-01

    We address the problem of segmenting high angular resolution diffusion imaging (HARDI) data into multiple regions (or fiber tracts) with distinct diffusion properties. We use the orientation distribution function (ODF) to represent HARDI data and cast the problem as a clustering problem in the space of ODFs. Our approach integrates tools from sparse representation theory and Riemannian geometry into a graph theoretic segmentation framework. By exploiting the Riemannian properties of the space of ODFs, we learn a sparse representation for each ODF and infer the segmentation by applying spectral clustering to a similarity matrix built from these representations. In cases where regions with similar (resp. distinct) diffusion properties belong to different (resp. same) fiber tracts, we obtain the segmentation by incorporating spatial and user-specified pairwise relationships into the formulation. Experiments on synthetic data evaluate the sensitivity of our method to image noise and the presence of complex fiber configurations, and show its superior performance compared to alternative segmentation methods. Experiments on phantom and real data demonstrate the accuracy of the proposed method in segmenting simulated fibers, as well as white matter fiber tracts of clinical importance in the human brain. PMID:24108748

  17. Joint reconstruction of white-matter pathways from longitudinal diffusion MRI data with anatomical priors.

    PubMed

    Yendiki, Anastasia; Reuter, Martin; Wilkens, Paul; Rosas, H Diana; Fischl, Bruce

    2016-02-15

    We consider the problem of reconstructing white-matter pathways in a longitudinal study, where diffusion-weighted and T1-weighted MR images have been acquired at multiple time points for the same subject. We propose a method for joint reconstruction of a subject's pathways at all time points given the subject's entire set of longitudinal data. We apply a method for unbiased within-subject registration to generate a within-subject template from the T1-weighted images of the subject at all time points. We follow a global probabilistic tractography approach, where the unknown pathway is represented in the space of this within-subject template and propagated to the native space of the diffusion-weighted images at all time points to compute its posterior probability given the images. This ensures spatial correspondence of the reconstructed pathway among time points, which in turn allows longitudinal changes in diffusion measures to be estimated consistently along the pathway. We evaluate the reliability of the proposed method on data from healthy controls scanned twice within a month, where no changes in white-matter microstructure are expected between scans. We evaluate the sensitivity of the method on data from Huntington's disease patients scanned repeatedly over the course of several months, where changes are expected between scans. We show that reconstructing white-matter pathways jointly using the data from all time points leads to improved reliability and sensitivity, when compared to reconstructing the pathways at each time point independently. PMID:26717853

  18. The value of novel MRI techniques in Parkinson-plus syndromes: diffusion tensor imaging and anatomical connectivity studies.

    PubMed

    Tir, M; Delmaire, C; Besson, P; Defebvre, L

    2014-04-01

    Conventional MRI is a well-described, highly useful tool for the differential diagnosis of degenerative parkinsonian syndromes. Nevertheless, the observed abnormalities may only appear in late-stage disease. Diffusion tensor imaging (DTI) can identify microstructural changes in brain tissue integrity and connectivity. The technique has proven value in the differential diagnosis of multiple system atrophy (MSA), progressive supranuclear palsy (PSP) and Parkinson's disease (PD). Here, we performed a systematic review of the literature on the main corticosubcortical DTI abnormalities identified to date in the context of the diagnosis of MSA and PSP with diffusion-weighted imaging, diffusion tensor imaging and anatomical connectivity studies. In good agreement with the histological data, increased diffusivity in the putamen (in MSA and PSP), in the middle cerebellar peduncles (in MSA) and in the upper cerebellar peduncles (in PSP) has been reported. Motor pathway involvement is characterized by low fraction anisotropy (FA) in the primary motor cortex in MSA-P and PSP, a high apparent diffusion coefficient (ADC) and low FA in the supplementary motor area in PSP. We then outline the value of these techniques in differential diagnosis (especially with respect to PD). Anatomical connectivity studies have revealed a lower number of fibers in the corticospinal tract in MSA and PSP (relative to PD and controls) and fewer tracked cortical projection fibers in patients with PSP or late-stage MSA (relative to patients with early MSA or PD and controls). Lastly, we report the main literature data concerning the value of DTI parameters in monitoring disease progression. The observed correlations between DTI parameters on one hand and clinical scores and/or disease duration on the other constitute strong evidence of the value of DTI in monitoring disease progression. In MSA, the ataxia score was correlated with ADC values in the pons and the upper cerebellar peduncles, whereas both

  19. Imaging signatures of meningioma and low-grade glioma: a diffusion tensor, magnetization transfer and quantitative longitudinal relaxation time MRI study.

    PubMed

    Piper, Rory J; Mikhael, Shadia; Wardlaw, Joanna M; Laidlaw, David H; Whittle, Ian R; Bastin, Mark E

    2016-05-01

    Differentiation of cerebral tumor pathology currently relies on interpretation of conventional structural MRI and in some cases histology. However, more advanced MRI methods may provide further insight into the organization of cerebral tumors and have the potential to aid diagnosis. The objective of this study was to use multimodal quantitative MRI to measure the imaging signatures of meningioma and low-grade glioma (LGG). Nine adults with meningioma and 11 with LGG were identified, and underwent standard structural, quantitative longitudinal relaxation time (T1) mapping, magnetization transfer and diffusion tensor MRI. Maps of mean (〈D〉), axial (λAX) and radial (λRAD) diffusivity, fractional anisotropy (FA), magnetization transfer ratio (MTR) and T1 were generated on a voxel-by-voxel basis. Using structural and echo-planar T2-weighted MRI, manual region-of-interest segmentation of brain tumor, edema, ipsilateral and contralateral normal-appearing white matter (NAWM) was performed. Differences in imaging signatures between the different tissue types, both absolute mean values and ratios relative to contralateral NAWM, were assessed using t-tests with statistical significance set at p<0.05. For both absolute mean values and ratios relative to contralateral NAWM, there were significant differences in 〈D〉, λAX, λRAD, FA, MTR and T1 between meningioma and LGG tumor tissue, respectively. Only T1 and FA differed significantly between edematous tissue associated with the two tumor types. These results suggest that multimodal MRI biomarkers are significantly different, particularly in tumor tissue, between meningioma and LGG. By using quantitative multimodal MRI it may be possible to identify tumor pathology non-invasively. PMID:26708035

  20. Asymmetric Interhemispheric Transfer in the Auditory Network: Evidence from TMS, Resting-State fMRI, and Diffusion Imaging.

    PubMed

    Andoh, Jamila; Matsushita, Reiko; Zatorre, Robert J

    2015-10-28

    Hemispheric asymmetries in human auditory cortical function and structure are still highly debated. Brain stimulation approaches can complement correlational techniques by uncovering causal influences. Previous studies have shown asymmetrical effects of transcranial magnetic stimulation (TMS) on task performance, but it is unclear whether these effects are task-specific or reflect intrinsic network properties. To test how modulation of auditory cortex (AC) influences functional networks and whether this influence is asymmetrical, the present study measured resting-state fMRI connectivity networks in 17 healthy volunteers before and immediately after TMS (continuous theta burst stimulation) to the left or right AC, and the vertex as a control. We also examined the relationship between TMS-induced interhemispheric signal propagation and anatomical properties of callosal auditory fibers as measured with diffusion-weighted MRI. We found that TMS to the right AC, but not the left, resulted in widespread connectivity decreases in auditory- and motor-related networks in the resting state. Individual differences in the degree of change in functional connectivity between auditory cortices after TMS applied over the right AC were negatively related to the volume of callosal auditory fibers. The findings show that TMS-induced network modulation occurs, even in the absence of an explicit task, and that the magnitude of the effect differs across individuals as a function of callosal structure, supporting a role for the corpus callosum in mediating functional asymmetry. The findings support theoretical models emphasizing hemispheric differences in network organization and are of practical significance in showing that brain stimulation studies need to take network-level effects into account. PMID:26511249

  1. Staging of Primary Abdominal Lymphomas: Comparison of Whole-Body MRI with Diffusion-Weighted Imaging and 18F-FDG-PET/CT

    PubMed Central

    Stecco, Alessandro; Buemi, Francesco; Quagliozzi, Martina; Lombardi, Mariangela; Santagostino, Alberto; Sacchetti, Gian Mauro; Carriero, Alessandro

    2015-01-01

    Background. The purpose of this study was to compare the accuracy of whole-body MRI with diffusion-weighted sequences (WB-DW-MRI) with that of 18F-FDG-PET/CT in the staging of patients with primary gastrointestinal lymphoma. Methods. This retrospective study involved 17 untreated patients with primary abdominal gastrointestinal lymphoma. All patients underwent 18F-FDG-PET/CT and WB-DW-MRI. Histopathology findings or at least 6 months of clinical and radiological follow-up was the gold standard. The Musshoff-modified Ann Arbor system was used for staging, and diagnostic accuracy was evaluated on a per-node basis. Results. WB-DW-MRI exhibited 100% sensitivity, 96.3% specificity, and 96.1% and 100% positive and negative predictive values (PPV and NPV), respectively. The sensitivity, specificity, and PPV and NPV of PET/CT were 95.9%, 100%, and 100% and 96.4%, respectively. There were no statistically significant differences between the two techniques (p = 0.05). The weighted kappa agreement statistics with a 95% confidence interval were 0.97 (0.95–0.99) between the two MRI readers and 0.87 (0.82–0.92) between the two methods. Conclusions. WB-DW-MRI appears to have a comparable diagnostic value to 18F-FDG-PET/CT in staging patients with gastrointestinal lymphoma. PMID:26798331

  2. First detection of 3He+ in the planetary nebula IC 418

    NASA Astrophysics Data System (ADS)

    Guzman-Ramirez, L.; Rizzo, J. R.; Zijlstra, A. A.; García-Miró, C.; Morisset, C.; Gray, M. D.

    2016-07-01

    The 3He isotope is important to many fields of astrophysics, including stellar evolution, chemical evolution, and cosmology. The isotope is produced in low-mass stars which evolve through the planetary nebula (PN) phase. 3He abundances in PNe can help test models of the chemical evolution of the Galaxy. We present the detection of the 3He+ emission line using the single dish Deep Space Station 63, towards the PN IC 418. We derived a 3He/H abundance in the range 1.74 ± 0.8 × 10-3 to 5.8 ± 1.7 × 10-3, depending on whether part of the line arises in an outer ionized halo. The lower value for 3He/H ratio approaches values predicted by stellar models which include thermohaline mixing, but requires that large amounts of 3He are produced inside low-mass stars which enrich the interstellar medium (ISM). However, this overpredicts the 3He abundance in H II regions, the ISM, and protosolar grains, which is known to be of the order of 10-5. This discrepancy questions our understanding of the evolution of the 3He, from circumstellar environments to the ISM.

  3. Possible Dimensional Crossover to 1D of ^3He Fluid in Nanochannels Observed in Susceptibilities

    NASA Astrophysics Data System (ADS)

    Matsushita, Taku; Kurebayashi, Katsuya; Shibatsuji, Ryosuke; Hieda, Mitsunori; Wada, Nobuo

    2016-05-01

    Dimensional crossover to the one-dimensional (1D) state from higher dimensions has been studied for dilute ^3He fluid adsorbed in 2.4 nm ^4He-preplated nanochannels, by susceptibility measurements down to 70 mK using 4.29 MHz nuclear magnetic resonance. In nanochannels, since energy states of ^3He motion perpendicular to the channel axis are discrete, a genuine 1D ^3He fluid is expected when the Fermi energy is less than the first excitation Δ _{01} for azimuthal motion. The susceptibilities χ above 0.3 K show the Curie-law susceptibilities independent of the ^3He density, which are characteristic of nondegenerate fluid in higher dimensions. With decreasing the temperature, a significant reduction of χ T was observed from about 0.3 K for all ^3He densities. It is considered to be due to the dimensional crossover below Δ _{01}˜ 0.5 K to the 1D ^3He state in the semi-degenerate regime above the Fermi temperature. In the 1D state at lower temperatures, T-independent χ were observed for ^3He of 0.019 layers below 0.1 K. It suggests that the 1D ^3He fluid enters the quantum degenerate regime.

  4. Design of an Ion Source for {sup 3}He Fusion in a Low Pressure IEC Device

    SciTech Connect

    Piefer, Gregory R.; Santarius, John F.; Ashley, Robert P.; Kulcinski, Gerald L.

    2005-05-15

    Recent developments in helicon ion sources and Inertial Electrostatic Confinement (IEC) device performance at UW-Madison have enabled low pressure (< 50 {mu}torr, 6.7 mPa) operating conditions that should allow the {sup 3}He-{sup 3}He fusion reaction to be observed in an IEC device. An ion source capable of delivering a {approx} 10 mA {sup 3}He ion beam into an IEC device with minimal neutral gas flow has been designed and tested. Furthermore, a new IEC device that has never been operated with deuterium has been constructed to avoid D-{sup 3}He protons from obstructing the {sup 3}He-{sup 3}He reaction product spectrum, and to minimize Penning ionization of deuterium by excited helium, which in the past is suspected to have limited the ionized density of He. These developments make it possible to study beam-background {sup 3}He-{sup 3}He fusion reactions with > 300 mA recirculating ion currents.

  5. First Detection of 3He+ in the Planetary Nebula IC 418

    NASA Astrophysics Data System (ADS)

    Guzman-Ramirez, L.; Rizzo, J. R.; Zijlstra, A. A.; García-Miró, C.; Morisset, C.; Gray, M. D.

    2016-04-01

    The 3He isotope is important to many fields of astrophysics, including stellar evolution, chemical evolution, and cosmology. The isotope is produced in low-mass stars which evolve through the planetary nebula (PN) phase. 3He abundances in PNe can help test models of the chemical evolution of the Galaxy. We present the detection of the 3He+ emission line using the single dish Deep Space Station 63, towards the PN IC 418. We derived a 3He/H abundance in the range 1.74±0.8×10-3 to 5.8±1.7×10-3, depending on whether part of the line arises in an outer ionized halo. The lower value for 3He/H ratio approaches values predicted by stellar models which include thermohaline mixing, but requires that large amounts of 3He are produced inside low-mass stars which enrich the interstellar medium (ISM). However, this over-predicts the 3He abundance in H II regions, the ISM, and proto-solar grains, which is known to be of the order of 10-5. This discrepancy questions our understanding of the evolution of the 3He, from circumstellar environments to the ISM.

  6. Measurement of fast minority /sub 3/He/sup + +/ energy distribution during ICRF heating

    DOEpatents

    Post, D.E. Jr.; Grisham, L.R.; Medley, S.S.

    A method and means for measuring the fast /sub 3/He/sup + +/ distribution during /sub 3/He/sup + +/ minority Ion Cyclotron Resonance Frequency (ICRF) heating is disclosed. The present invention involves the use of 10 to 100 keV beams of neutral helium atoms to neutralize the fast /sub 3/He/sup + +/ ions in a heated plasma by double charge exchange (/sub 3/He/sup + +/ + /sub 4/He/sup 0/ ..-->.. /sub 3/He/sup 0/ + /sub 4/He/sup + +/). The neutralized fast /sub 3/He/sup 0/ atoms then escape from the hot plasma confined by a magnetic field and are detected by conventional neutral particle analyzing means. This technique permits the effectiveness of the coupling of the ion cyclotron waves to the /sub 3/He/sup + +/ minority ions to be accurately measured. The present invention is particularly adapted for use in evaluating the effectiveness of the intermediate coupling between the RF heating and the /sub 3/He/sup + +/ in an energetic toroidal plasma.

  7. Calculation of induced reactions of 3He-particles on natSb in 10-34MeV energy range.

    PubMed

    Gul, K

    2009-01-01

    Calculations for the excitation functions of the (121)Sb((3)He, xn) (121,122,123)I, and (123)Sb((3)He xn) (122,123,124,125)I reactions have been carried out using statistical and pre-equilibrium nuclear reaction models in 10-34MeV energy range. These excitation functions have been used to derive the excitation functions of the (nat)Sb((3)He, xn)(121,123,124)I reactions and compared with reported measurements. For studying the improvement with measurements two values of the diffuseness parameter a(w) equal to 0.9 and 0.7fm have been used in the calculations. The dependence of pre-equilibrium calculations on the initial exciton numbers has also been considered. PMID:18951811

  8. Performance of Apparent Diffusion Coefficient Values and Conventional MRI Features in Differentiating Tumefactive Demyelinating Lesions From Primary Brain Neoplasms

    PubMed Central

    Mabray, Marc C.; Cohen, Benjamin A.; Villanueva-Meyer, Javier E.; Valles, Francisco E.; Barajas, Ramon F.; Rubenstein, James L.; Cha, Soonmee

    2015-01-01

    OBJECTIVE Tumefactive demyelinating lesions (TDLs) remain one of the most common brain lesions to mimic a brain tumor, particularly primary CNS lymphoma (PCNSL) and high-grade gliomas. The purpose of our study was to evaluate the ability of apparent diffusion coefficient (ADC) values and conventional MRI features to differentiate TDLs from PCNSLs and high-grade gliomas. MATERIALS AND METHODS Seventy-five patients (24 patients with TDLs, 28 with PCNSLs, and 23 with high-grade gliomas) with 168 brain lesions (70 TDLs, 68 PCNSLs, and 30 high-grade gliomas) who underwent DWI before surgery or therapy were included in the study. Minimum ADC (ADCmin) and average ADC (ADCavg) values were calculated for each lesion. ANOVA and ROC analyses were performed. ROC analyses were also performed for the presence of incomplete rim enhancement and for the number of lesions. Multiple-variable logistic regression with ROC analysis was then performed to evaluate performance in multiple-variable models. RESULTS ADCmin was statistically significantly higher (p < 0.01) in TDLs (mean, 0.886; 95% CI, 0.802–0.931) than in PCNSLs (0.547; 95% CI, 0.496–0.598) and high-grade gliomas (0.470; 95% CI, 0.385–0.555). (All ADC values in this article are reported in units of × 10−3 mm2/s.) ADCavg was statistically significantly higher (p < 0.01) in TDLs (mean, 1.362; 95% CI, 1.268–1.456) than in PCNSLs (0.990; 95% CI, 0.919–1.061) but not in high-grade gliomas (1.216; 95% CI, 1.074–1.356). Multiple-variable models showed statistically significant individual effects and superior diagnostic performance on ROC analysis. CONCLUSION TDLs can be diagnosed on preoperative MRI with a high degree of specificity; MRI features of incomplete rim enhancement, high ADC values, and a large number of lesions individually increase the probability and diagnostic confidence that a lesion is a TDL. PMID:26496556

  9. Diffusion MRI and novel texture analysis in osteosarcoma xenotransplants predicts response to anti-checkpoint therapy.

    PubMed

    Foroutan, Parastou; Kreahling, Jenny M; Morse, David L; Grove, Olya; Lloyd, Mark C; Reed, Damon; Raghavan, Meera; Altiok, Soner; Martinez, Gary V; Gillies, Robert J

    2013-01-01

    Combinations of targeted drugs have been employed to treat sarcomas, however, response rates have not improved notably, therefore emphasizing the need for novel treatments. In addition, imaging approaches to assess therapeutic response is lacking, as currently measurable indices, such as volume and/or diameter, do not accurately correlate with changes in tumor biology. In this study, quantitative and profound analyses of magnetic resonance imaging (MRI) were developed to evaluate these as imaging biomarkers for MK1775 and Gem in an osteosarcoma xenotransplant model at early time-points following treatment. Notably, we showed that Gem and Gem+MK1775 groups had significantly inhibited tumor growth by day 4, which was presaged by elevations in mean ADC by 24 hours post treatment. Significant differences were also observed at later time points for the Gem+MK1775 combination and MK1775 therapy. ADC distribution and entropy (randomness of ADC values) were also elevated by 24 hours following therapy. Immunohistochemistry demonstrated that these treatment-related increases in ADC correlated with apoptosis and observed cell condensations (dense- and exploded bodies). These findings underline the role of ADC as a quantitative imaging biomarker for therapy-induced response and show promising clinical relevance in the sarcoma patient population. PMID:24358232

  10. Diffusion MRI and Novel Texture Analysis in Osteosarcoma Xenotransplants Predicts Response to Anti-Checkpoint Therapy

    PubMed Central

    Foroutan, Parastou; Kreahling, Jenny M.; Morse, David L.; Grove, Olya; Lloyd, Mark C.; Reed, Damon; Raghavan, Meera; Altiok, Soner; Martinez, Gary V.; Gillies, Robert J.

    2013-01-01

    Combinations of targeted drugs have been employed to treat sarcomas, however, response rates have not improved notably, therefore emphasizing the need for novel treatments. In addition, imaging approaches to assess therapeutic response is lacking, as currently measurable indices, such as volume and/or diameter, do not accurately correlate with changes in tumor biology. In this study, quantitative and profound analyses of magnetic resonance imaging (MRI) were developed to evaluate these as imaging biomarkers for MK1775 and Gem in an osteosarcoma xenotransplant model at early time-points following treatment. Notably, we showed that Gem and Gem+MK1775 groups had significantly inhibited tumor growth by day 4, which was presaged by elevations in mean ADC by 24 hours post treatment. Significant differences were also observed at later time points for the Gem+MK1775 combination and MK1775 therapy. ADC distribution and entropy (randomness of ADC values) were also elevated by 24 hours following therapy. Immunohistochemistry demonstrated that these treatment-related increases in ADC correlated with apoptosis and observed cell condensations (dense- and exploded bodies). These findings underline the role of ADC as a quantitative imaging biomarker for therapy-induced response and show promising clinical relevance in the sarcoma patient population. PMID:24358232

  11. First measurement of the helicity dependence of 3He photoreactions in the Δ(1232) resonance region

    NASA Astrophysics Data System (ADS)

    Costanza, Susanna

    2014-03-01

    The first measurement of the helicity dependence for several photo-reaction channels on 3He was carried out in the photon energy range between 150 and 500 MeV at the MAMI accelerator (Mainz). The experiment used the large acceptance Crystal Ball spectrometer, complemented by charged particle and vertex detectors, a circularly polarised tagged photon beam and a longitudinally polarised high-pressure 3He gas target. Results of the helicity dependent total inclusive photoabsorption cross section on 3He and of both the unpolarised and polarised partial cross sections for the pion photoproduction channels γ 3He → πX and for the γ 3He → ppn channel, measured for the first time at MAMI, will be shown. They can also be found in [1].

  12. Nuclear georeactor origin of oceanic basalt 3He/4He, evidence, and implications

    PubMed Central

    Herndon, J. Marvin

    2003-01-01

    Nuclear georeactor numerical simulation results yield substantial 3He and 4He production and 3He/4He ratios relative to air (RA) that encompass the entire 2-SD (2σ) confidence level range of tabulated measured 3He/4He ratios of basalts from along the global spreading ridge system. Georeactor-produced 3He/4He ratios are related to the extent of actinide fuel consumption at time of production and are high near the end of the georeactor lifetime. Georeactor numerical simulation results and the observed high 3He/4He ratios measured in Icelandic and Hawaiian oceanic basalts indicate that the demise of the georeactor is approaching. Within the present level of uncertainty, one cannot say precisely when georeactor demise will occur, whether in the next century, in a million years, or in a billion years from now. PMID:12615991

  13. Polarization Induced Spin Wave Damping in Spin Polarized Liquid 3He 4He

    NASA Astrophysics Data System (ADS)

    Perisanu, Sorin; Vermeulen, Gerard

    2007-08-01

    We have measured the temperature and polarization dependence of Silin spin wave spectra in a saturated 3He 4He mixture with a concentration of 9.4% at a pressure of 8 bars. The mixture has been cooled and polarized by a Leiden dilution refrigerator to temperatures in the range 10 15 mK and polarizations as high as 9.2% corresponding to 3.4 times the equilibrium polarization of 2.7% in the external magnetic field of 11.36 T. The analysis takes into account the dipolar interactions and results in the relaxation time τ ⊥ and spin diffusion constant D ⊥ . We find that τ ⊥ and D ⊥ are proportional to 1/(T2+mathcal{A}2T_{a0}2) where T is the temperature, mathcal{A} is the polarization enhancement factor and T a0 is the anisotropy temperature for the mixture at equilibrium in the external field. Our result T a0=3.66±0.14 mK is 30% higher than the theoretical prediction for very dilute mixtures and is evidence for the existence of polarization induced relaxation of transverse spin currents.

  14. Diffusion-Weighted MRI Reflects Proliferative Activity in Primary CNS Lymphoma

    PubMed Central

    Meyer, Jonas; Gawlitza, Matthias; Frydrychowicz, Clara; Müller, Wolf; Preuss, Matthias; Bure, Lionel; Quäschling, Ulf; Hoffmann, Karl-Titus; Surov, Alexey

    2016-01-01

    Purpose To investigate if apparent diffusion coefficient (ADC) values within primary central nervous system lymphoma correlate with cellularity and proliferative activity in corresponding histological samples. Materials and Methods Echo-planar diffusion-weighted magnetic resonance images obtained from 21 patients with primary central nervous system lymphoma were reviewed retrospectively. Regions of interest were drawn on ADC maps corresponding to the contrast enhancing parts of the tumors. Biopsies from all 21 patients were histologically analyzed. Nuclei count, total nuclei area and average nuclei area were measured. The proliferation index was estimated as Ki-67 positive nuclei divided by total number of nuclei. Correlations of ADC values and histopathologic parameters were determined statistically. Results Ki-67 staining revealed a statistically significant correlation with ADCmin (r = -0.454, p = 0.038), ADCmean (r = -0.546, p = 0.010) and ADCmax (r = -0.515, p = 0.017). Furthermore, ADCmean correlated in a statistically significant manner with total nucleic area (r = -0.500, p = 0.021). Conclusion Low ADCmin, ADCmean and ADCmax values reflect a high proliferative activity of primary cental nervous system lymphoma. Low ADCmean values—in concordance with several previously published studies—indicate an increased cellularity within the tumor. PMID:27571268

  15. Fitting parametric models of diffusion MRI in regions of partial volume

    NASA Astrophysics Data System (ADS)

    Eaton-Rosen, Zach; Cardoso, M. J.; Melbourne, Andrew; Orasanu, Eliza; Bainbridge, Alan; Kendall, Giles S.; Robertson, Nicola J.; Marlow, Neil; Ourselin, Sebastien

    2016-03-01

    Regional analysis is normally done by fitting models per voxel and then averaging over a region, accounting for partial volume (PV) only to some degree. In thin, folded regions such as the cerebral cortex, such methods do not work well, as the partial volume confounds parameter estimation. Instead, we propose to fit the models per region directly with explicit PV modeling. In this work we robustly estimate region-wise parameters whilst explicitly accounting for partial volume effects. We use a high-resolution segmentation from a T1 scan to assign each voxel in the diffusion image a probabilistic membership to each of k tissue classes. We rotate the DW signal at each voxel so that it aligns with the z-axis, then model the signal at each voxel as a linear superposition of a representative signal from each of the k tissue types. Fitting involves optimising these representative signals to best match the data, given the known probabilities of belonging to each tissue type that we obtained from the segmentation. We demonstrate this method improves parameter estimation in digital phantoms for the diffusion tensor (DT) and `Neurite Orientation Dispersion and Density Imaging' (NODDI) models. The method provides accurate parameter estimates even in regions where the normal approach fails completely, for example where partial volume is present in every voxel. Finally, we apply this model to brain data from preterm infants, where the thin, convoluted, maturing cortex necessitates such an approach.

  16. Diffusion-weighted MRI findings and clinical correlations in sporadic Creutzfeldt-Jakob disease.

    PubMed

    Gao, Ting; Lyu, Jin-Hao; Zhang, Jia-Tang; Lou, Xin; Zhao, Wei; Xing, Xiao-Wei; Yang, Ming; Yao, Yan; Tan, Qing-Che; Tian, Cheng-Lin; Huang, Xu-Sheng; Ma, Lin; Yu, Sheng-Yuan

    2015-06-01

    The objective of this study is to investigate the hyperintense lesions on diffusion-weighted magnetic resonance imaging (DWI) and its clinical correlation in sporadic Creutzfeldt-Jakob disease (sCJD). Patients who suffered from sCJD and followed up at the Department of Neurology at the General Hospital of the People's Liberation Army during the period of June 1, 2007 to July 1, 2014 were reviewed. The location of the hyperintense lesions on DWI, apparent diffusion coefficient (ADC) values of the hyperintense lesions were correlated with symptoms and clinical course. A total of 58 sCJD patients and ten healthy controls were included. Hyperintense lesions on DWI were observed in all the patients. The patients with basal ganglia (BG) hyperintense lesions on DWI had shorter disease duration and higher incidence of myoclonus (92 versus 44 %) than those without BG hyperintense lesions. The patients with occipital cortex hyperintense lesions on DWI had shorter disease duration between symptom onset and akinetic mutism than those without these lesions. The lower of the BG ADC value the faster presence of akinetic mutism and the shorter disease duration the patients will have. The presence of BG and occipital cortex hyperintense lesions on DWI and BG ADC values is correlated with the clinical course and clinical symptoms. PMID:25860342

  17. Utility of MRI Diffusion Tensor Imaging in Carpal Tunnel Syndrome: A Meta-Analysis.

    PubMed

    Wang, Hong; Ma, Jingxu; Zhao, Liping; Wang, Yunling; Jia, Xiaowen

    2016-01-01

    BACKGROUND After successful utilization of diffusion tensor imaging (DTI) in detecting brain pathologies, it is now being examined for use in the detection of peripheral neuropathies. The aim of this meta-analysis was to evaluate the diagnostic potentials of DTI in carpal tunnel syndrome (CTS). MATERIAL AND METHODS The literature search was performed in multiple electronic databases using a keyword search and final selection of the studies was based on predetermined inclusion and exclusion criteria. We performed a meta-analyses of mean differences in fractional anisotropy (FA) and apparent diffusion coefficient (ADC) between CTS patient and healthy subjects. Publication bias detection was done with Begg's test and sensitivity analyses were performed to explore the source/s of higher heterogeneity and the authenticity of results. RESULTS FA was significantly lower in CTS patients in comparison with healthy subjects (mean and the difference [95% confidence interval] was -0.06 [-0.10, -0.02] (p=0.003). The ADC was significantly higher in CTS patients (mean difference [95% CI] was 0.10 [0.02, 0.18], p=0.02). Overall sensitivity of FA-based diagnosis was 82.82%, with 77.83% specificity. CONCLUSIONS DTI can be a valuable tool in diagnosing CTS. PMID:26942911

  18. Myofiber ellipticity as an explanation for transverse asymmetry of skeletal muscle diffusion MRI in vivo signal.

    PubMed

    Karampinos, Dimitrios C; King, Kevin F; Sutton, Bradley P; Georgiadis, John G

    2009-12-01

    Due to its unique non-invasive microstructure probing capabilities, diffusion tensor imaging (DTI) constitutes a valuable tool in the study of fiber orientation in skeletal muscles. By implementing a DTI sequence with judiciously chosen directional encoding to quantify in vivo the microarchitectural properties in the calf muscles of three healthy volunteers at rest, we report that the secondary eigenvalue is significantly higher than the tertiary eigenvalue, a phenomenon corroborated by prior DTI findings. Toward a physics-based explanation of this phenomenon, we propose a composite medium model that accounts for water diffusion in the space within the muscle fiber and the extracellular space. The muscle fibers are abstracted as cylinders of infinite length with an elliptical cross section, the latter closely approximating microstructural features well documented in prior histological studies of excised muscle. The range of values of fiber ellipticity predicted by our model agrees with these studies, and the spatial orientation of the cross-sectional ellipses is consistent with local muscle strain fields and the putative direction of lateral transmission of stress between fibers in certain regions in three antigravity muscles (Tibialis Anterior, Soleus, and Gastrocnemius), as well as independent measurements of deformation in active calf muscles. As a metric, fiber cross-sectional ellipticity may be useful for quantifying morphological changes in skeletal muscle fibers with aging, hypertrophy, or sarcopenia. PMID:19763830

  19. Electron bubbles and Weyl fermions in chiral superfluid 3He-A

    NASA Astrophysics Data System (ADS)

    Shevtsov, Oleksii; Sauls, J. A.

    2016-08-01

    Electrons embedded in liquid 3He form mesoscopic bubbles with large radii compared to the interatomic distance between 3He atoms, voids of Nbubble≈200 3He atoms, generating a negative ion with a large effective mass that scatters thermal excitations. Electron bubbles in chiral superfluid 3He-A also provide a local probe of the ground state. We develop a scattering theory of Bogoliubov quasiparticles by negative ions embedded in 3He-A that incorporates the broken symmetries of 3He-A , particularly broken symmetries under time reversal and mirror symmetry in a plane containing the chiral axis l ̂. Multiple scattering by the ion potential, combined with branch conversion scattering by the chiral order parameter, leads to a spectrum of Weyl fermions bound to the ion that support a mass current circulating the electron bubble—a mesoscopic realization of chiral edge currents in superfluid 3He-A films. A consequence is that electron bubbles embedded in 3He-A acquire angular momentum, L ≈-(Nbubble/2 ) ℏ l ̂ , inherited from the chiral ground state. We extend the scattering theory to calculate the forces on a moving electron bubble, both the Stokes drag and a transverse force, FW=e/c v ×BW , defined by an effective magnetic field, BW∝l ̂ , generated by the scattering of thermal quasiparticles off the spectrum of Weyl fermions bound to the moving ion. The transverse force is responsible for the anomalous Hall effect for electron bubbles driven by an electric field reported by the RIKEN group. Our results for the scattering cross section, drag, and transverse forces on moving ions are compared with experiments and shown to provide a quantitative understanding of the temperature dependence of the mobility and anomalous Hall angle for electron bubbles in normal and superfluid 3He-A . We also discuss our results in relation to earlier work on the theory of negative ions in superfluid 3He.

  20. 3He and BF 3 neutron detector pressure effect and model comparison

    NASA Astrophysics Data System (ADS)

    Lintereur, Azaree; Conlin, Kenneth; Ely, James; Erikson, Luke; Kouzes, Richard; Siciliano, Edward; Stromswold, David; Woodring, Mitchell

    2011-10-01

    Radiation detection systems for homeland security applications must possess the capability of detecting both gamma rays and neutrons. The radiation portal monitor systems that are currently deployed use a plastic scintillator for detecting gamma rays and 3He gas-filled proportional counters for detecting neutrons. Proportional counters filled with 3He are the preferred neutron detectors for use in radiation portal monitor systems because 3He has a large neutron cross-section, is relatively insensitive to gamma-rays, is neither toxic nor corrosive, can withstand extreme environments, and can be operated at a lower voltage than some of the alternative proportional counters. The amount of 3He required for homeland security and science applications has depleted the world supply and there is no longer enough available to fill the demand. Thus, alternative neutron detectors are being explored. Two possible temporary solutions that could be utilized while a more permanent solution is being identified are reducing the 3He pressure in the proportional counters and using boron trifluoride gas-filled proportional counters. Reducing the amount of 3He required in each of the proportional counters would decrease the rate at which 3He is being used; not enough to solve the shortage, but perhaps enough to increase the amount of time available to find a working replacement. Boron trifluoride is not appropriate for all situations as these detectors are less sensitive than 3He, boron trifluoride gas is corrosive, and a much higher voltage is required than what is used with 3He detectors. Measurements of the neutron detection efficiency of 3He and boron trifluoride as a function of tube pressure were made. The experimental results were also used to validate models of the radiation portal monitor systems.

  1. Sparse Reconstruction Challenge for diffusion MRI: Validation on a physical phantom to determine which acquisition scheme and analysis method to use?

    PubMed

    Ning, Lipeng; Laun, Frederik; Gur, Yaniv; DiBella, Edward V R; Deslauriers-Gauthier, Samuel; Megherbi, Thinhinane; Ghosh, Aurobrata; Zucchelli, Mauro; Menegaz, Gloria; Fick, Rutger; St-Jean, Samuel; Paquette, Michael; Aranda, Ramon; Descoteaux, Maxime; Deriche, Rachid; O'Donnell, Lauren; Rathi, Yogesh

    2015-12-01

    Diffusion magnetic resonance imaging (dMRI) is the modality of choice for investigating in-vivo white matter connectivity and neural tissue architecture of the brain. The diffusion-weighted signal in dMRI reflects the diffusivity of water molecules in brain tissue and can be utilized to produce image-based biomarkers for clinical research. Due to the constraints on scanning time, a limited number of measurements can be acquired within a clinically feasible scan time. In order to reconstruct the dMRI signal from a discrete set of measurements, a large number of algorithms have been proposed in recent years in conjunction with varying sampling schemes, i.e., with varying b-values and gradient directions. Thus, it is imperative to compare the performance of these reconstruction methods on a single data set to provide appropriate guidelines to neuroscientists on making an informed decision while designing their acquisition protocols. For this purpose, the SPArse Reconstruction Challenge (SPARC) was held along with the workshop on Computational Diffusion MRI (at MICCAI 2014) to validate the performance of multiple reconstruction methods using data acquired from a physical phantom. A total of 16 reconstruction algorithms (9 teams) participated in this community challenge. The goal was to reconstruct single b-value and/or multiple b-value data from a sparse set of measurements. In particular, the aim was to determine an appropriate acquisition protocol (in terms of the number of measurements, b-values) and the analysis method to use for a neuroimaging study. The challenge did not delve on the accuracy of these methods in estimating model specific measures such as fractional anisotropy (FA) or mean diffusivity, but on the accuracy of these methods to fit the data. This paper presents several quantitative results pertaining to each reconstruction algorithm. The conclusions in this paper provide a valuable guideline for choosing a suitable algorithm and the corresponding

  2. The value of diffusion-weighted MRI in the diagnosis of malignant and benign urinary bladder lesions

    PubMed Central

    Avcu, S; Koseoglu, M N; Ceylan, K; Dbulutand, M; Unal, O

    2011-01-01

    Objectives To investigate the role of diffusion-weighted MRI (DWI) in the diagnosis of urinary bladder (UB) tumours by means of measuring apparent diffusion coefficient (ADC) values. Methods A total of 83 people aged between 18 and 86 years were included in the study: 63 patients with UB pathology (46 malignant, 17 benign) constituted the case group; 20 individuals without any UB pathology constituted the control group. DWI was applied to all individuals. The ADC values were measured based on the tissue of the UB mass entities and normal UB wall in the control group. Results The mean ADC value in the UB carcinoma group was significantly lower than that in the control group: 1.0684 ± 0.26 × 10−3 mm2 s–1 and 2.010 ± 0.11 × 10−3 mm2 s–1, respectively (p<0.01). There was a significant difference among the mean ADC values of different grades of malignant tumours, corresponding to 0.9185 ± 0.20 mm2 s–1 and 1.281 ± 0.18 mm2 s–1 in high-grade and low-grade malignant UB carcinomas, respectively (p<0.01). The ADC value in the carcinoma group was significantly lower than that in the benign lesion group: 1.0684 ± 0.26 × 10−3 mm2 s–1 and 1.803 ± 0.19 × 10−3 mm2 s–1, respectively (p<0.01). All 46 malignant lesions displayed a restriction in diffusion; 4 of the 17 benign lesions displayed a mild restriction in diffusion. The sensitivity, specificity and accuracy of DWI in the diagnosis of malignant UB lesions was 100%, 76.5% and 93.65%, respectively. Conclusion DWI can be beneficial in the differentiation of benign and malignant UB lesions, as well as of high-grade and low-grade UB carcinomas, using quantitative ADC measurements. PMID:21224296

  3. T(T,2n)4He and 3He(3He,2p)4He: The Reaction Mechanism from Solar Energies to 10 MeV

    NASA Astrophysics Data System (ADS)

    Bacher, A. D.; Brune, C. R.; Sayre, D. B.; Hale, G. M.; Frenje, J. A.; Gatu Johnson, M.

    2016-03-01

    We have studied the energy dependence of the reaction mechanism of the T(t,2n)4He reaction at stellar energies and of its charge symmetric analog reaction 3He(3He,2p)4He at energies up 10 MeV. We find that the reaction mechanism changes dramatically over this energy range in part due to the interference of the two identical fermions in the three-body final state. This contribution is dedicated to the memory of Tom Tombrello, my Ph.D. advisor at Cal Tech, who died in 2014.

  4. Search for anomalous deuterons in the reaction /sup 3/He+C. -->. d+X at p3He = 10. 8 GeV/c

    SciTech Connect

    Ableev, V.G.; Vorob'ev, G.G.; Gasparyan, A.P.; Grigalashvili, N.S.; Dzhmukhadze, S.V.; Zaporozhets, S.A.; Nomofilov, A.A.; Piskunov, N.M.; Sitnik, I.M.; Strokovskii, E.A.

    1985-07-01

    The Alpha apparatus in a beam of 10.78-GeV/c /sup 3/He nuclei has been used to search for anomalous deuterons (demons) in the reaction /sup 3/He+C ..-->.. d+X. The deuteron yield was measured at angles theta< or approx. =20 mrad as a function of the target thickness, which varied from 0.6 to 70 cm. The data obtained exclude the production of demons in this reaction over a wide range of expected values of the cross sections for their production and interaction with matter. The technique used can be applied also to beams of relativistic nuclei in experiments to search for anomalons.

  5. Contributions of bilateral white matter to chronic aphasia symptoms as assessed by diffusion tensor MRI

    PubMed Central

    Geva, Sharon; Correia, Marta M.; Warburton, Elizabeth A.

    2015-01-01

    Language reorganisation following stroke has been studied widely. However, while studies of brain activation and grey matter examined both hemispheres, studies of white matter changes have mostly focused on the left hemisphere. Here we examined the relationship between bilateral hemispheric white matter and aphasia symptoms. 15 chronic stroke patients with aphasia and 18 healthy adults were studied using Diffusion Weighted Imaging data. By applying histogram analysis, Tract-Based Spatial Statistics, tractography and lesion-tract overlap methods, it was found that damage to the left hemisphere in general, and to the arcuate fasciculus in particular, correlated with impairments on word repetition, object naming, sentence comprehension and homophone and rhyme judgement. However, no such relationship was found in the right hemisphere. It is suggested that while some language function in aphasia can be explained by damage to the left arcuate fasciculus, it cannot be explained by looking at the contra-lesional tract. PMID:26401977

  6. Broca's area and its striatal and thalamic connections: a diffusion-MRI tractography study

    PubMed Central

    Ford, Anastasia A.; Triplett, William; Sudhyadhom, Atchar; Gullett, Joseph; McGregor, Keith; FitzGerald, David B.; Mareci, Thomas; White, Keith; Crosson, Bruce

    2013-01-01

    In the recent decades structural connectivity between Broca's area and the basal ganglia has been postulated in the literature, though no direct evidence of this connectivity has yet been presented. The current study investigates this connectivity using a novel diffusion-weighted imaging (DWI) fiber tracking method in humans in vivo. Our findings suggest direct connections between sub-regions of Broca's area and the anterior one-third of the putamen, as well as the ventral anterior nucleus of the thalamus. Thus, we are the first to provide a detailed account of inferred circuitry involving basal ganglia, thalamus, and Broca's area, which would be a prerequisite to substantiate their support of language processing. PMID:23675324

  7. Sensitivity of Diffusion-Weighted STEAM MRI and EPI-DWI to Infratentorial Ischemic Stroke

    PubMed Central

    Hohenhaus, Marc; Kunze, Claudia; Schmidt, Wolf; Brunecker, Peter; Villringer, Kersten; Merboldt, Klaus-Dietmar; Frahm, Jens; Fiebach, Jochen B.

    2016-01-01

    Objectives To assess the sensitivity of stimulated echo acquisition mode diffusion weighted imaging (STEAM-DWI) to ischemic stroke in comparison to echo-planar imaging diffusion weighted imaging (EPI-DWI) in the infratentorial compartment. Methods Fifty-seven patients presenting with clinical features of infratentorial stroke underwent STEAM-DWI, high-resolution EPI-DWI (HR-DWI, 2.5 mm slice thickness) and low-resolution EPI-DWI (LR-DWI, 5 mm slice thickness). Four readers assessed the presence of ischemic lesions and artifacts. Agreement between sequences and interobserver agreement on the presence of ischemia were calculated. The sensitivities of the DWI sequences were calculated in 45 patients with a confirmed diagnosis of infratentorial stroke. Results Median time from symptom onset to imaging was 24 hours. STEAM-DWI agreed with LR-DWI in 89.5% of cases (kappa = 0.72, p<0.0001) and with HR-DWI in 89.5% of cases (kappa = 0.68, p<0.0001). STEAM-DWI showed fewer intraparenchymal artifacts (1/57) than HR-DWI (44/57) and LR-DWI (41/57). Ischemia was visible in 87% of cases for LR-DWI, 93% of cases for HR-DWI, and 89% of cases for STEAM-DWI. Interobserver agreement was good for STEAM-DWI (kappa = 0.62, p<0.0001). Conclusions Compared to the best currently available MR sequence for detecting ischemia (HR-DWI), STEAM-DWI shows fewer artifacts and a similar sensitivity to infratentorial stroke. PMID:27529697

  8. 3T diffusion-weighted MRI of the thyroid gland with reduced distortion: preliminary results

    PubMed Central

    Nagala, S; Priest, A N; McLean, M A; Jani, P; Graves, M J

    2013-01-01

    Objective: Single-shot diffusion-weighted (DW) echo planar imaging (EPI), which is commonly used for imaging the thyroid, is characterised by severe blurring and distortion. The objectives of this work were: 1, to show that a reduced-field of view (r-FOV) DW EPI technique can improve image quality; and 2, to investigate the effect of different reconstruction strategies on the resulting apparent diffusion coefficients (ADCs). Methods: We implemented a single-shot, r-FOV DW EPI technique with a two-dimensional radiofrequency excitation pulse for DW imaging of the thyroid at 3T. Images were reconstructed using root sum of squares (SOS) and an optimal-B1 reconstruction (OBR). Phantom and in vivo experiments were performed to compare r-FOV and conventional full-FOV DW EPI with root SOS and OBR. Results: r-FOV with OBR substantially improved image quality at 3T. In phantoms, r-FOV gave more accurate ADCs than full-FOV. In vivo r-FOV always gave lower ADC values with respect to the full-FOV technique irrespective of the reconstruction used and whether only two or multiple b-values were used to compute the ADCs. Conclusion: r-FOV DW EPI can reduce image blurring and distortion at the expense of a low signal-to-noise ratio. OBR is a promising reconstruction technique for accurate ADC measurements in lower signal-to-noise ratio regimes, although further studies are needed to characterise its performance. Advances in knowledge: DW imaging of the thyroid at 3T could potentially benefit from r-FOV acquisition strategies, such as the r-FOV DW EPI technique proposed in this paper. PMID:23770539

  9. Current concepts on magnetic resonance imaging (MRI) perfusion-diffusion assessment in acute ischaemic stroke: a review & an update for the clinicians.

    PubMed

    Roldan-Valadez, Ernesto; Lopez-Mejia, Mariana

    2014-12-01

    Recently, several medical societies published joint statements about imaging recommendations for acute stroke and transient ischaemic attack patients. In following with these published guidelines, we considered it appropriate to present a brief, practical and updated review of the most relevant concepts on the MRI assessment of acute stroke. Basic principles of the clinical interpretation of diffusion, perfusion, and MRI angiography (as part of a global MRI protocol) are discussed with accompanying images for each sequence. Brief comments on incidence and differential diagnosis are also included, together with limitations of the techniques and levels of evidence. The purpose of this article is to present knowledge that can be applied in day-to-day clinical practice in specialized stroke units or emergency rooms to attend patients with acute ischaemic stroke or transient ischaemic attack according to international standards. PMID:25758570

  10. PREFACE: JCNS Workshop on Modern Trends in Production and Applications of Polarized 3He

    NASA Astrophysics Data System (ADS)

    Ioffe, Alexander; Babcock, Earl; Gutberlet, Thomas

    2011-03-01

    Polarized neutron scattering techniques are an indispensable and highly requested tool for studying magnetic phenomena in condensed matter. The different coherent and incoherent scattering of isotopes such as protons and deuterons also allows applications of polarized neutrons in soft matter and biological studies of molecular and macromolecular dynamics. One method to polarize neutrons is to use polarized 3He gas which absorbs, or filters, one spin state of the neutron beam as it passes through it. Only about ten years ago, early polarized neutron scattering experiments using such 3He neutron spin filters (3He NSF) were being conducted using starting 3He polarizations of 55%. Currently there are two different commonly used methods to polarize high quantities of 3He. These methods both collisionally transfer spin polarization to ground state 3He nucleuses; one method uses optical pumping of an excited metastable state of 3He atoms, and the other uses optical pumping of the ground state of an alkali-metal vapour. Within the last decade immense progress in both methods has resulted in 3He polarizations of up to 80% being reported in atmosphere-pressure 3He cells by the world's leading labs. This progress in optical pumped 3He promises to give rise to much more efficient and novel polarized neutron scattering experiments as and also impacts other areas of science. Polarized 3He is additionally applied in research fields such as particle physics, fundamental studies and medicine. Thus not only the techniques and methods of polarization, but the research groups themselves exploring polarized 3He, have a large breadth and diversity spanning different fields of science and locations in the world. Given this diversity, it is rare for this community to meet as a group at any one meeting or conference. Because it is crucial to discuss new developments in 3He polarization in a multi-disciplinary international setting, an international workshop on "Modern Trends in Production

  11. The cosmological density of baryons from observations of 3He+ in the Milky Way.

    PubMed

    Bania, T M; Rood, Robert T; Balser, Dana S

    2002-01-01

    Primordial nucleosynthesis after the Big Bang can be constrained by the abundances of the light elements and isotopes 2H, 3He, 4He and 7Li (ref. 1). The standard theory of stellar evolution predicts that 3He is also produced by solar-type stars, so its abundance is of interest not only for cosmology, but also for understanding stellar evolution and the chemical evolution of the Galaxy. The 3He abundance in star-forming (H II) regions agrees with the present value for the local interstellar medium, but seems to be incompatible with the stellar production rates inferred from observations of planetary nebulae, which provide a direct test of stellar evolution theory. Here we develop our earlier observations, which, when combined with recent theoretical developments in our understanding of light-element synthesis and destruction in stars, allow us to determine an upper limit for the primordial abundance of 3He relative to hydrogen: 3He/H = (1.1 +/- 0.2) x 10(-5). The primordial density of all baryons determined from the 3He data is in excellent agreement with the densities calculated from other cosmological probes. The previous conflict is resolved because most solar-mass stars do not produce enough 3He to enrich the interstellar medium significantly. PMID:11780112

  12. Anomalous yield reduction in direct-drive DT implosions due to 3He addition

    SciTech Connect

    Herrmann, Hans W; Langenbrunner, James R; Mack, Joseph M; Cooley, James H; Wilson, Douglas C; Evans, Scott C; Sedillo, Tom J; Kyrala, George A; Caldwell, Stephen E; Young, Carlton A; Nobile, Arthur; Wermer, Joseph R; Paglieri, Stephen N; Mcevoy, Aaron M; Kim, Yong Ho; Batha, Steven H; Horsfield, Colin J; Drew, Dave; Garbett, Warren; Rubery, Michael; Glebov, Vladimir Yu; Roberts, Samuel; Frenje, Johan A

    2008-01-01

    Glass capsules were imploded in direct drive on the OMEGA laser [T. R. Boehly et aI., Opt. Commun. 133, 495, 1997] to look for anomalous degradation in deuterium/tritium (DT) yield (i.e., beyond what is predicted) and changes in reaction history with {sup 3}He addition. Such anomalies have previously been reported for D/{sup 3}He plasmas, but had not yet been investigated for DT/{sup 3}He. Anomalies such as these provide fertile ground for furthering our physics understanding of ICF implosions and capsule performance. A relatively short laser pulse (600 ps) was used to provide some degree of temporal separation between shock and compression yield components for analysis. Anomalous degradation in the compression component of yield was observed, consistent with the 'factor of two' degradation previously reported by MIT at a 50% {sup 3}He atom fraction in D{sub 2} using plastic capsules [Rygg et aI., Phys. Plasmas 13, 052702 (2006)]. However, clean calculations (i.e., no fuel-shell mixing) predict the shock component of yield quite well, contrary to the result reported by MIT, but consistent with LANL results in D{sub 2}/{sup 3}He [Wilson, et aI., lml Phys: Conf Series 112, 022015 (2008)]. X-ray imaging suggests less-than-predicted compression ofcapsules containing {sup 3}He. Leading candidate explanations are poorly understood Equation-of-State (EOS) for gas mixtures, and unanticipated particle pressure variation with increasing {sup 3}He addition.

  13. Third sound and stability of 3He-4He mixture films

    SciTech Connect

    Anderson, R. H.; Krotscheck, E.; Miller, M. D.

    2006-09-07

    We study third sound and the interaction between 3He adatoms in two thin 3He-4He mixture films from a first-principles, microscopic theory. Utilizing the variational, hypernetted-chain Euler-Lagrange (HNC-EL) theory as applied to inhomogeneous boson systems, we calculate chemical potentials for both the 4He superfluid film and the physisorbed 3He. Numerical density derivatives of the chemical potentials lead to the sought-after third sound speeds that clearly reflect a layered structure of at least seven oscillations. In this paper, we report third sound on model substrates: Nuclepore, and sodium. We find that the effect of the 3He depends sensitively on the particular 4He film coverage. Our most important result is that, with the addition of 3He, the third sound speed can either increase or decrease. In fact, in some regimes, the added 3He destabilizes the film and can drive ''layering transitions'', leading to fairly complicated geometric structures of the film in which the outermost layer is predicted to consist of phase-separated regions of 3He and 4He.

  14. Recent advances in polarized 3 He based neutron spin filter development

    NASA Astrophysics Data System (ADS)

    Chen, Wangchun; Gentile, Thomas; Erwin, Ross; Watson, Shannon; Krycka, Kathryn; Ye, Qiang; NCNR NIST Team; University of Maryland Team

    2015-04-01

    Polarized 3 He neutron spin filters (NSFs) are based on the strong spin-dependence of the neutron absorption cross section by 3 He. NSFs can polarize large area, widely divergent, and broadband neutron beams effectively and allow for combining a neutron polarizer and a spin flipper into a single polarizing device. The last capability utilizes 3 He spin inversion based on the adiabatic fast passage (AFP) nuclear magnetic resonance technique. Polarized 3 He NSFs are significantly expanding the polarized neutron measurement capabilities at the NIST Center for Neutron Research (NCNR). Here we present an overview of 3 He NSF applications to small-angle neutron scattering, thermal triple axis spectrometry, and wide-angle polarization analysis. We discuss a recent upgrade of our spin-exchange optical pumping (SEOP) systems that utilize chirped volume holographic gratings for spectral narrowing. The new capability allows us to polarize rubidium/potassium hybrid SEOP cells over a liter in volume within a day, with 3 He polarizations up to 88%, Finally we discuss how we can achieve nearly lossless 3 He polarization inversion with AFP.

  15. Multi-spacecraft observations of recurrent {sup 3}He-rich solar energetic particles

    SciTech Connect

    Bučík, R.; Innes, D. E.; Mall, U.; Korth, A.; Mason, G. M.; Gómez-Herrero, R.

    2014-05-01

    We study the origin of {sup 3}He-rich solar energetic particles (<1 MeV nucleon{sup –1}) that are observed consecutively on STEREO-B, Advanced Composition Explorer (ACE), and STEREO-A spacecraft when they are separated in heliolongitude by more than 90°. The {sup 3}He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE {sup 3}He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 {sup 3}He-rich events with the same sizeable active region (AR) producing X-ray flares accompanied by prompt electron events, when it was near the west solar limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous {sup 3}He enrichment, lacking solar energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged AR near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of (1) solar regions with long-lasting conditions for {sup 3}He acceleration and (2) solar energetic {sup 3}He that is temporarily confined/re-accelerated in interplanetary space.

  16. Cosmogenic 3He in terrestrial rocks: The summit lavas of Maui

    PubMed Central

    Craig, H.; Poreda, R. J.

    1986-01-01

    We have identified terrestrial cosmic rayproduced 3He in three lava flows on the crest of Haleakala Volcano on Maui, 3 km above sea level, and ≈0.5 million years old. Although these lavas, like all oceanic basalts, contain primordial 3He from the mantle, the “cosmogenic” component (3HeC) can be identified unambiguously because it is extractable only by high-temperature vacuum fusion. In contrast, a large fraction of the mantle helium resides in fluid inclusions and can be extracted by vacuum crushing, leaving a residual component with 3He/4He ratios as high as 75× those in the atmosphere, which can be liberated by melting the crushed grains. Cosmogenic 3He is present in both olivines and clinopyroxenes at 0.8-1.2 × 10-12 ml(STP)/g and constitutes 75% ± 5% of the total 3He present. The observed 3HeC levels require a cosmic ray exposure age of only some 64,000 years, much less than the actual age of the lavas, if there is no erosion. Using a model that includes effects of uplift or submergence as well as erosion, we calculate an apparent “erosion rate” of the order of 8.5 m/106 years for the western rim of the summit crater, as an example of the application of measurements of cosmogenic rare gases to terrestrial geological problems. PMID:16593671

  17. Gas cells for 3He hyperpolarized via spin-exchange optical pumping

    NASA Astrophysics Data System (ADS)

    Kim, W.; Stepanyan, S. S.; Kim, A.; Tan, J. A.; Woo, S.

    2016-01-01

    We present a device for the production of hyperpolarized 3He, which is widely used in spinrelated nuclear physics research. Spin-exchange optical pumping (SEOP) is employed to polarize 3He enclosed in a circular borosilicate glass cell suitable not only for the production of polarized gas but also for its storage. The portable glass cell can, thus, be transported to any other research facility. The glass cell can be refilled several times. Special attention is given to the preparation and the filling of the cell to minimize the impurities on its walls and in the gas. We employ glass tubes with shorter lengths and larger diameters in the gas-filling system to achieve the improvement in the air flow necessary to obtain purer polarized 3He samples. The cell is prepared, and after it has been filled with rubidium (Rb) and 3He-N2 mixture, it is sealed under high vacuum conditions. The cell containing the mixture is exposed to circularly-polarized laser light with a wavelength of 795 nm at temperatures of 180 - 220 °C for SEOP. The polarization of 3He is measured via nuclear magnetic resonance (NMR). We obtained 40% polarized 3He in less than 15 hours and 50% in about 25 hours. The longitudinal relaxation time T 1 of the polarized 3He we measured was about 58 hours.

  18. Connectivity‐based segmentation of the periaqueductal gray matter in human with brainstem optimized diffusion MRI

    PubMed Central

    Faull, Olivia Kate; Jbabdi, Saad; Pattinson, Kyle Thomas

    2015-01-01

    Abstract The periaqueductal gray matter (PAG) is a midbrain structure, involved in key homeostatic neurobiological functions, such as pain modulation and cardiorespiratory control. Animal research has identified four subdivisional columns that differ in both connectivity and function. Until now these findings have not been replicated in humans. This study used high‐resolution brainstem optimized diffusion magnetic resonance imaging and probabilistic tractography to segment the human PAG into four subdivisions, based on voxel connectivity profiles. We identified four distinct subdivisions demonstrating high spatial concordance with the columns of the animal model. The resolution of these subdivisions for individual subjects permitted detailed examination of their structural connectivity without the requirement of an a priori starting location. Interestingly patterns of forebrain connectivity appear to be different to those found in nonhuman studies, whereas midbrain and hindbrain connectivity appears to be maintained. Although there are similarities in the columnar structure of the PAG subdivisions between humans and nonhuman animals, there appears to be different patterns of cortical connectivity. This suggests that the functional organization of the PAG may be different between species, and as a consequence, functional studies in nonhumans may not be directly translatable to humans. This highlights the need for focused functional studies in humans. Hum Brain Mapp 36:3459–3471, 2015. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc. PMID:26138504

  19. Evaluation of mean diffusion and kurtosis MRI mismatch in subacute ischemic stroke: Comparison with NIHSS score.

    PubMed

    Guo, Yue-Lin; Zhang, Zhong-Ping; Zhang, Gui-Shan; Kong, Ling-Mei; Rao, Hai-Bing; Chen, Wei; Wang, Guang-Wen; Shen, Zhi-Wei; Zheng, Wen-Bin; Wu, Ren-Hua

    2016-08-01

    Neurological deterioration (ND) is a devastating complication following ischemic stroke. This study aimed to identify the differences in lesion characteristics in subacute ischemic stroke patients with and without ND using diffusional kurtosis imaging (DKI), as well as to confirm the responsible lesions that may lead to ND, as assessed by the National Institutes of Health Stroke Scale (NIHSS) score. Seventy-nine patients with subacute cerebral infarction were allocated to the ND (-) and ND (+) groups according to the NIHSS score and lesion number. The mean diffusion (MD) lesions were significantly larger than the mean kurtosis (MK) deficits in the ND (+) group (P<0.05); however, there was no significant difference in the ND (-) group (P>0.05). The MD and MK in the lesion recovered to normal levels over time; however, the recovery trends in the ND (+) group were substantially slower than the ND (-) group. The differences between the two groups were only significant regarding the MK (p<0.05). Furthermore, multiple infarction lesions exhibited good consistency in the ND (-) group, but were non-homogeneous in the ND (+) group. To the best of our knowledge, this is the first study to demonstrate that a significant MD/MK mismatch and heterogeneity of multiple ischemic lesions on MK in subacute ischemic stroke may represent a new expansion of an ischemic lesion or acute reinfarction, which is closely related to ND. PMID:27208488

  20. Quantitative Tractography Metrics of White Matter Integrity in Diffusion-Tensor MRI

    PubMed Central

    Correia, Stephen; Lee, Stephanie Y.; Voorn, Thom; Tate, David F.; Paul, Robert H.; Zhang, Song; Salloway, Stephen P.; Malloy, Paul F.; Laidlaw, David H.

    2009-01-01

    We present new quantitative diffusion-tensor imaging (DTI) tractography-based metrics for assessing cerebral white matter integrity. These metrics extend prior work in this area. Tractography models of cerebral white matter were produced from each subject's DTI data. The models are a set of curves (e.g., “streamtubes”) derived from DTI data that represent the underlying topography of the cerebral white matter. Nine metrics were calculated in whole brain tractography models and in three “tracts-of-interest” (TOI): transcallosal fibers, and the left and right cingulum bundles. The metrics included the number of streamtubes and several metrics based on the summed length of streamtubes in including some that were weighted by scalar anisotropy metrics and normalized for estimated intracranial volume. We then tested whether patients with subcortical ischemic vascular disease (i.e., vascular cognitive impairment or VCI) vs. healthy controls (HC) differed on the metrics. The metrics were significantly lower in the VCI group in whole brain and in transcallosal TOI but not in the left or right cingulum bundles. The metrics correlated significantly with cognitive functions known to be impacted by white matter abnormalities (e.g., processing speed) but not with those more impacted by cortical disease (e.g., naming). These new metrics help bridge the gap between DTI tractography and scalar analytical methods and provide a potential means for examining group differences in white matter integrity in specific tracts-of-interest. PMID:18617421

  1. Mapping of ApoE4 related white matter damage using diffusion MRI

    NASA Astrophysics Data System (ADS)

    Tsao, Sinchai; Gajawelli, Niharika; Hwang, Darryl H.; Kriger, Stephen; Law, Meng; Chui, Helena; Weiner, Michael; Lepore, Natasha

    2014-04-01

    ApoliopoproteinE Ɛ4 (ApoE-Ɛ4) polymorphism is the most well known genetic risk factor for developing Alzheimers Disease. The exact mechanism through which ApoE 4 increases AD risk is not fully known, but may be related to decreased clearance and increased oligomerization of Aβ. By making measurements of white matter integrity via diffusion MR and correlating the metrics in a voxel-based statistical analysis with ApoE-Ɛ4 genotype (whilst controlling for vascular risk factor, gender, cognitive status and age) we are able to identify changes in white matter associated with carrying an ApoE Ɛ4 allele. We found potentially significant regions (Puncorrected < 0:05) near the hippocampus and the posterior cingulum that were independent of voxels that correlated with age or clinical dementia rating (CDR) status suggesting that ApoE may affect cognitive decline via a pathway in dependent of normal aging and acute insults that can be measured by CDR and Framingham Coronary Risk Score (FCRS).

  2. Diffusion-weighted MRI for the detection of colorectal polyps: feasibility study.

    PubMed

    Leufkens, Anke M; Kwee, Thomas C; van den Bosch, Maurice A A J; Mali, Willem P Th M; Takahara, Taro; Siersema, Peter D

    2013-01-01

    The purpose of this study was to determine the feasibility of diffusion-weighted magnetic resonance imaging (DWI) for detecting colorectal polyps. DWI (high b-value of 1000 s/mm(2)) was prospectively performed in 26 symptomatic patients who were scheduled to undergo colonoscopy. DWI and colonoscopic findings were interpreted in a blinded manner. The sensitivity and positive predictive value (PPV) of DWI for the detection of clinically relevant polyps (≥6 mm) and colorectal cancer (CRC) were calculated on a per-lesion basis, using colonoscopy results as the standard of reference. Sensitivity, specificity, PPV and negative predictive value (NPV) on a per-patient basis were also calculated. Sensitivity and PPV on a per-lesion basis were 80.0% [95% confidence interval (CI): 49.0%-94.3%] and 72.7% (95% CI: 43.4%-90.3%) for polyps ≥6 mm and CRC. Sensitivity, specificity, PPV and NPV on a per-patient basis were 85.7% (95% CI: 48.7%-97.4%), 84.2% (95% CI: 62.4%-94.5%), 66.7% (95% CI: 35.4%-87.9%) and 94.1% (95% CI: 73.0%-99.0%) for polyps ≥6mm and CRC. In conclusion, DWI cannot yet be recommended in a clinical setting in which DWI is performed first and subsequent colonoscopy is only performed in patients with positive findings at DWI. Further (technical) developments are required to increase its diagnostic yield. PMID:22898697

  3. Comparison of EPI Distortion Correction Methods in Diffusion Tensor MRI Using a Novel Framework

    PubMed Central

    Wu, M.; Chang, L.-C.; Walker, L.; Lemaitre, H.; Barnett, A.S.; Marenco, S.; Pierpaoli, C.

    2016-01-01

    Diffusion weighted images (DWIs) are commonly acquired with Echo-planar imaging (EPI). B0 inhomogeneities affect EPI by producing spatially nonlinear image distortions. Several strategies have been proposed to correct EPI distortions including B0 field mapping (B0M) and image registration. In this study, an experimental framework is proposed to evaluation the performance of different EPI distortion correction methods in improving DT-derived quantities. A deformable registration based method with mutual information metric and cubic B-spline modeled constrained deformation field (BSP) is proposed as an alternative when B0 mapping data are not available. BSP method is qualitatively and quantitatively compared to B0M method using the framework. Both methods can successful reduce EPI distortions and significantly improve the quality of DT-derived quantities. Overall, B0M was clearly superior in infratentorial regions including brainstem and cerebellum, as well as in the ventral areas of the temporal lobes while BSP was better in all rostral brain regions. PMID:18982621

  4. Gaining insight of fetal brain development with diffusion MRI and histology.

    PubMed

    Huang, Hao; Vasung, Lana

    2014-02-01

    Human brain is extraordinarily complex and yet its origin is a simple tubular structure. Its development during the fetal period is characterized by a series of accurately organized events which underlie the mechanisms of dramatic structural changes during fetal development. Revealing detailed anatomy at different stages of human fetal brain development provides insight on understanding not only this highly ordered process, but also the neurobiological foundations of cognitive brain disorders such as mental retardation, autism, schizophrenia, bipolar and language impairment. Diffusion tensor imaging (DTI) and histology are complementary tools which are capable of delineating the fetal brain structures at both macroscopic and microscopic levels. In this review, the structural development of the fetal brains has been characterized with DTI and histology. Major components of the fetal brain, including cortical plate, fetal white matter and cerebral wall layer between the ventricle and subplate, have been delineated with DTI and histology. Anisotropic metrics derived from DTI were used to quantify the microstructural changes during the dynamic process of human fetal cortical development and prenatal development of other animal models. Fetal white matter pathways have been traced with DTI-based tractography to reveal growth patterns of individual white matter tracts and corticocortical connectivity. These detailed anatomical accounts of the structural changes during fetal period may provide the clues of detecting developmental and cognitive brain disorders at their early stages. The anatomical information from DTI and histology may also provide reference standards for diagnostic radiology of premature newborns. PMID:23796901

  5. Investigation of the {sup 3}He wave function by quasifree scattering

    SciTech Connect

    Jones, C.E.; Hansen, J.O.; Bloch, C.

    1995-08-01

    The analysis of the data from the CE25 experiment at IUCF, which measured the target and beam analyzing powers and the spin correlation parameter in {sup 3}He(p,2p) and {sup 3}He(p,pn) quasielastic scattering, is nearing completion. At low missing momentum, the extracted polarization of the neutron and proton in {sup 3}He are consistent with Faddeev calculations. Two papers, one reporting the physics results and one describing the experiment, were published. The data from this experiment indicates that for q {>=} 500 MeV/c the plane wave impulse approximation is valid.

  6. Polarized {sup 3}He{sup −} ion source with hyperfine state selection

    SciTech Connect

    Dudnikov, V.; Morozov, V.; Dudnikov, A.

    2015-04-08

    High beam polarization is essential to the scientific productivity of a collider. Polarized {sup 3}He ions are an essential part of the nuclear physics programs at existing and future ion-ion and electron-ion colliders such as BNL's RHIC and eRHIC and JLab's ELIC. Ion sources with performance exceeding that achieved today are a key requirement for the development of these next generation high-luminosity high-polarization colliders. The development of high-intensity high-brightness arc-discharge ion sources at the Budker Institute of Nuclear Physics (BINP) has opened up an opportunity for realization of a new type of a polarized {sup 3}He{sup −} ion source. This report discusses a polarized {sup 3}He{sup −} ion source based on the large difference of extra-electron auto-detachment lifetimes of the different {sup 3}He{sup −} ion hyperfine states. The highest momentum state of 5/2 has the largest lifetime of τ ∼ 350 µs while the lower momentum states have lifetimes of τ ~ 10 µs. By producing {sup 3}He{sup −} ion beam composed of only the |5/2, ±5/2> hyperfine states and then quenching one of the states by an RF resonant field, {sup 3}He{sup −} beam polarization of 90% can be achieved. Such a method of polarized {sup 3}He{sup −} production has been considered before; however, due to low intensities of the He{sup +} ion sources existing at that time, it was not possible to produce any interesting intensity of polarized {sup 3}He{sup −} ions. The high-brightness arc-discharge ion source developed at BINP can produce a high-brightness {sup 3}He{sup +} beam with an intensity of up to 2 A allowing for selection of up to ∼1-4 mA of {sup 3}He{sup −} ions with ∼90% polarization. The high gas efficiency of an arc-discharge source is important due to the high cost of {sup 3}He gas. Some features of such a PIS as well as prototype designs are considered. An integrated {sup 3}He{sup −} ion source design providing high beam polarization could be

  7. A polarized internal sup 3 He target using optical pumping of metastable atoms

    SciTech Connect

    McKeown, R.D.; Milner, R.G.; Woodward, C.E. )

    1989-05-05

    The design of a polarized internal {sup 3}He target for use in storage rings based on optical pumping of metastables is discussed. The target employs an infrared laser to polarize {sup 3}He atoms in a pyrex cell which is connected by a capillary to a windowless cell through which the stored beam passes. Using this technique it should be possible construct targets of 50% polarized {sup 3}He targets of thickness 10{sup 16} cm{sup {minus}2}. Small holding fields ({similar to}10 gauss) and resistance to beam-induced depolarization are desirable features of this target in a storage ring environment.

  8. Experimental investigation and theoretical calculation for 3He induced nuclear reactions on vanadium

    NASA Astrophysics Data System (ADS)

    Ali, B. M.; Al-Abyad, M.; Seddik, U.; El-Kameesy, S. U.; Ditrói, F.; Takács, S.; Tárkányi, F.

    2016-04-01

    Using stacked-foil activation technique and gamma-ray spectrometry, excitation functions for 3He induced nuclear reactions on natV were measured. Cross-sections for natV(3He, xn)52m,gMn and natV(3He, pxn)51Cr nuclear reactions were measured up to 27 MeV utilizing the MGC-20E cyclotron of ATOMKI. The measurements establish for the first time consistent excitation curves. Comparisons with results for values derived from different theoretical codes were included. Integral yield were calculated.

  9. Triple oxygen isotopic composition of the high-3He/4He mantle

    NASA Astrophysics Data System (ADS)

    Starkey, N. A.; Jackson, C. R. M.; Greenwood, R. C.; Parman, S.; Franchi, I. A.; Jackson, M.; Fitton, J. G.; Stuart, F. M.; Kurz, M.; Larsen, L. M.

    2016-03-01

    Measurements of Xe isotope ratios in ocean island basalts (OIB) suggest that Earth's mantle accreted heterogeneously, and that compositional remnants of accretion are sampled by modern, high-3He/4He OIB associated with the Icelandic and Samoan plumes. If so, the high-3He/4He source may also have a distinct oxygen isotopic composition from the rest of the mantle. Here, we test if the major elements of the high-3He/4He source preserve any evidence of heterogeneous accretion using measurements of three oxygen isotopes on olivine from a variety of high-3He/4He OIB locations. To high precision, the Δ17O value of high-3He/4He olivines from Hawaii, Pitcairn, Baffin Island and Samoa, are indistinguishable from bulk mantle olivine (Δ17OBulk Mantle - Δ17OHigh 3He/4He olivine = -0.002 ± 0.004 (2 × SEM)‰). Thus, there is no resolvable oxygen isotope evidence for heterogeneous accretion in the high-3He/4He source. Modelling of mixing processes indicates that if an early-forming, oxygen-isotope distinct mantle did exist, either the anomaly was extremely small, or the anomaly was homogenised away by later mantle convection. The δ18O values of olivine with the highest 3He/4He ratios from a variety of OIB locations have a relatively uniform composition (∼5‰). This composition is intermediate to values associated with the depleted MORB mantle and the average mantle. Similarly, δ18O values of olivine from high-3He/4He OIB correlate with radiogenic isotope ratios of He, Sr, and Nd. Combined, this suggests that magmatic oxygen is sourced from the same mantle as other, more incompatible elements and that the intermediate δ18O value is a feature of the high-3He/4He mantle source. The processes responsible for the δ18O signature of high-3He/4He mantle are not certain, but δ18O-87Sr/86Sr correlations indicate that it may be connected to a predominance of a HIMU-like (high U/Pb) component or other moderate δ18O components recycled into the high-3He/4He source.

  10. Influence of Bone Marrow Composition on Measurements of Trabecular Microstructure using Decay due to Diffusion in the Internal Field (DDIF) MRI: Simulations and Clinical Studies

    PubMed Central

    Sprinkhuizen, Sara M.; Ackerman, Jerome L.; Song, Yi-Qiao

    2014-01-01

    Purpose Decay due to Diffusion in the Internal Field (DDIF) MRI allows for measurements of microstructures of porous materials at low spatial resolution and thus has potential for trabecular bone quality measurements. In trabecular bone, solid bone changes (osteoporosis) as well as changes in bone marrow composition occur. The influence of such changes on DDIF MRI was studied by simulations and in vivo measurements. Methods Monte Carlo simulations of DDIF in various trabecular bone models were conducted. Changes in solid bone and marrow composition were simulated with numerical bone erosion and marrow susceptibility variations. Additionally, in vivo measurements were performed in the lumbar spine of healthy volunteers of ages 23 to 62 years. Results Simulations and in vivo results yielded that 1) DDIF decay times decrease with increasing marrow fat and 2) the marrow fat percentage needs to be incorporated in the DDIF analysis to discriminate between healthy and osteoporotic solid bone structures. Conclusions Bone marrow composition plays an important role in DDIF MRI: incorporation of marrow fat percentage into DDIF MRI allowed for differentiation of young and old age groups (in vivo experiments). DDIF MRI may develop into a means of assessing osteoporosis and disorders that affect marrow composition. PMID:24382681

  11. Feasibility and Diagnostic Accuracy of Ischemic Stroke Territory Recognition Based on Two-Dimensional Projections of Three-Dimensional Diffusion MRI Data

    PubMed Central

    Wrosch, Jana Katharina; Volbers, Bastian; Gölitz, Philipp; Gilbert, Daniel Frederic; Schwab, Stefan; Dörfler, Arnd; Kornhuber, Johannes; Groemer, Teja Wolfgang

    2015-01-01

    This study was conducted to assess the feasibility and diagnostic accuracy of brain artery territory recognition based on geoprojected two-dimensional maps of diffusion MRI data in stroke patients. In this retrospective study, multiplanar diffusion MRI data of ischemic stroke patients was used to create a two-dimensional map of the entire brain. To guarantee correct representation of the stroke, a computer-aided brain artery territory diagnosis was developed and tested for its diagnostic accuracy. The test recognized the stroke-affected brain artery territory based on the position of the stroke in the map. The performance of the test was evaluated by comparing it to the reference standard of each patient’s diagnosed stroke territory on record. This study was designed and conducted according to Standards for Reporting of Diagnostic Accuracy (STARD). The statistical analysis included diagnostic accuracy parameters, cross-validation, and Youden Index optimization. After cross-validation on a cohort of 91 patients, the sensitivity of this territory diagnosis was 81% with a specificity of 87%. With this, the projection of strokes onto a two-dimensional map is accurate for representing the affected stroke territory and can be used to provide a static and printable overview of the diffusion MRI data. The projected map is compatible with other two-dimensional data such as EEG and will serve as a useful visualization tool. PMID:26635717

  12. White matter structure and clinical characteristics of stroke patients: A diffusion tensor MRI study.

    PubMed

    Ueda, Ryo; Yamada, Naoki; Kakuda, Wataru; Abo, Masahiro; Senoo, Atsushi

    2016-03-15

    Fractional anisotropy has been used in many studies that examined post-stroke changes in white matter. This study was performed to clarify cerebral white matter changes after stroke using generalized fractional anisotropy (GFA). White matter structure was visualized using diffusion tensor imaging in 72 patients with post-stroke arm paralysis. Exercise-related brain regions were examined in cerebral white matter using GFA. The relationship between GFA and clinical characteristics was examined. Overall, the mean GFA of the lesioned hemisphere was significantly lower than that of the non-lesioned hemisphere (P<0.05), the white matter of the lesioned side was severely affected by stroke. A weak negative correlation between GFA and time since stroke onset was found in Brodmann area 5 of the non-lesioned hemisphere. Age correlated negatively with GFA in Brodmann areas 5 and 7 of the lesioned hemisphere. Though these results may be due to a decrease in the frequency of use of the paralyzed limb over time, GFA overall was significantly and negatively affected by the subject's age. The GFA values of patients with paralysis of the dominant hand were significantly different from those of patients with paralysis of the nondominant hand in Brodmann areas 4 and 6 of the non-lesioned hemisphere and Brodmann area 4 of the lesioned hemisphere (P<0.05). The stroke size and location were not associated with GFA differences. Differences between the GFA of the lesioned and non-lesioned hemispheres varied depending on the affected brain region, age at onset of paralysis, and paralysis of the dominant or non-dominant hand. PMID:26783693

  13. PGSE, OGSE, and sensitivity to axon diameter in diffusion MRI: Insight from a simulation study

    PubMed Central

    Zhang, Hui; Ianuş, Andrada; Kaden, Enrico; Alexander, Daniel C

    2015-01-01

    Purpose To identify optimal pulsed gradient spin‐echo (PGSE) and oscillating gradient spin‐echo (OGSE) sequence settings for maximizing sensitivity to axon diameter in idealized and practical conditions. Methods Simulations on a simple two‐compartment white matter model (with nonpermeable cylinders) are used to investigate a wide space of clinically plausible PGSE and OGSE sequence parameters with trapezoidal diffusion gradient waveforms. Signal sensitivity is measured as a derivative of the signal with respect to axon diameter. Models of parallel and dispersed fibers are investigated separately to represent idealized and practical conditions. Results Simulations show that, for the simple case of gradients perfectly perpendicular to straight parallel fibers, PGSE always gives maximum sensitivity. However, in real‐world scenarios where fibers have unknown and dispersed orientation, low‐frequency OGSE provides higher sensitivity. Maximum sensitivity results show that on current clinical scanners (G max = 60 mT/m, signal to noise ratio (SNR) = 20)