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Magnetic resonance spectroscopic imaging (MRSI) has proven to be a powerful tool for the metabolic characterization of prostate cancer in patients before and following therapy. The metabolites that are of particular interest are citrate and choline because an increased choline-to-citrate ratio can be used as a marker for cancer. High-field systems offer the advantage of improved spectral resolution as well as increased magnetization. Initial attempts at extending MRSI methods to 3 T have been confounded by the J-modulation of the citrate resonances. A new pulse sequence is presented that controls the J-modulation of citrate at 3 T such that citrate is upright, with high amplitude, at a practical echo time. The design of short (14 ms) spectral-spatial refocusing pulses and trains of nonselective refocusing pulses are described. Phantom studies and simulations showed that upright citrate with negligible sidebands is observed at an echo time of 85 ms. Studies in a human subject verified that this behavior is reproduced in vivo and demonstrated that the water and lipid suppression of the new pulse sequence are sufficient for application in prostate cancer patients.

In this study, we investigated the use of a single-shot fast spin-echo-based sequence to perform diffusion tensor imaging (DTI) with improved anatomic fidelity through the entire brain and the cervical spine. Traditionally, diffusion tensor images have been acquired by single-shot echo-planar imaging (EPI) methods in which large distortions result from magnetic susceptibility effects, especially near air-tissue interfaces. These distortions can be problematic, especially in anterior and inferior portions of the brain, and they also can severely limit applications in the spine. At higher magnetic fields these magnetic susceptibility artifacts are increased. The single-shot fast spin-echo (SSFSE) method used in this study utilizes radiofrequency rephasing in the transverse plane and thus provides diffusion images with negligible distortion even at 3 Tesla. In addition, the SSFSE sequence does not require multiple fast-receivers, which are not available on many magnetic resonance (MR) systems. Phased array coils were used to increase the signal-to-noise ratio of the images, offering a major inherent advantage in diffusion tensor imaging of the spine and brain. The mean diffusion measurements obtained with the SSFSE acquisition were not statistically different (p > 0.05) from EPI-based acquisitions. Compared to routine T(2)-weighted MR images, the DTI-EPI sequence showed up to 20% in elongation of the brain in the anterior-posterior direction on a sagittal image due to magnetic susceptibility distortions, whereas in the DTI-SSFSE, the image distortions were negligible. The diffusion tensor SSFSE method was also able to assess diffusion abnormalities in a brain stem hemorrhage, unaffected by the spatial distortions that limited conventional EPI acquisition.

In animal models, neonatal seizures (NS) alter hippocampal development and lead to long-term deficits. Whether NS similarly affect humans is not known. The goal of this study was to assess whether NS are associated with altered hippocampal microstructure in neonates with hypoxic ischemic encephalopathy. We included 6 neonates with and 27 without seizures. All were treated with therapeutic hypothermia after birth. Neonatal (median 5 days) and 6-month diffusion tensor imaging was used to measure apparent diffusion coefficient (ADC) from regions of interest (ROIs) in the hippocampus, basal ganglia, thalamus and frontal white matter. ADC was significantly lower on the 6-month scan as compared to the neonatal scan for all ROIs. There were no significant differences in ADC on the early scan when comparing neonates with and without seizures. At 6 months, infants with seizures as neonates had a 6% higher hippocampal ADC (95% confidence interval: 0–11%, p These preliminary results suggest that NS are associated with altered hippocampal structural development. Because the difference was seen only in the hippocampus, and on follow-up imaging but not the neonatal scan, we speculate that NS may have a negative effect on hippocampal development. However, these results could also be explained by unmeasured neoantal hypoxic-ischemic injury. The findings are in keeping with studies that suggest NS are an independent risk factor for adverse neurodevelopmental outcome. Further studies are needed to confirm whether seizures harm newborns. Acknowledgements NIH/NCRR (UL1 RR024131); NIH/NINDS P50NS035902.

A microwave imaging reflectometry system has been developed to visualize the density fluctuations on the HL-2A tokamak. This system is characterized by a quasi-optical system, a four frequency microwave transmitter, and a microwave quadrature receiver system with a 3D adjustable U-shaped horn antenna array, that generate 8 (poloidal) × 4 (radial) × 2 (toroidal) = 64 channel images of density fluctuations. Simulations and laboratory tests of the optical system have been conducted. The test results are in good agreement with the simulations.

Experiments with high-energy deuterium neutral beam (NB) injection were performed on the HL-2A tokamak. To obtain information on NB deposition and the slowing down of beam ions in HL-2A plasmas, very short-pulse deuterium NB injection, or the so-called ‘blip’ injection, was applied to MHD-quiescent ohmic deuterium plasmas. Analysis of neutron decay following the NB ‘blip’ injection indicates that tangentially injected beam ions are well confined, slowing down classically in the HL-2A tokamak. In contrast to the MHD-quiescent plasma, anomalous losses of beam ions were observed when a core-localized mode with a frequency up-chirping from 15 to 40 kHz appeared in the plasma. The core-localized mode was identified as a beta-induced Alfvén acoustic (BAAE) mode by its frequency sweeping behaviour and numerical calculation. Such a high energetic particle driven mode led to fast-ion loss, showing the strong influence of the core-localized fast-ion-driven BAAE mode on the fast-ion transport. Furthermore, a clear frequency splitting was first observed on the Alfvén-acoustic-type mode, and is found to be strongly linked to the effect of resonant wave–particle interaction, providing further insights into how frequency splitting structures are generated in the plasma.

Collisionless steady plasma sheath model is taken into account to study the interaction between dusty particles and plasma sheath as well as the density distributions of electrons, ions and dusty particles. Numerical simulation results are obtained, showing that the ability of an isolated charge to absorb electrons weakens with the increase of dusty particle density and its temperature, while the collective effect strengthens with the radius of dusty particle. Simultaneously, Bohm velocity and the sheath thickness are also greatly affected. The sheath potential decreases significantly and the E-field is stronger near the electrode. In addition, the densities of electrons and ions reduce exponentially but the dusty particle has a critical value. The three particles satisfy the quasi-neutrality condition.

The edge-localized modes (ELMs) are often excited in an H-mode plasma, and they are helpful for cleaning the H-mode plasma to sustain a steady state for a longer time by controlling plasma density and exhausting impurities, but energy and particles carried by ELM burst will badly damage the first-wall of fusion device, thus the characteristics of and the control and mitigation of ELM are studied necessarily prior to the basic operational regime operating on ITER. ELMs of different perturbation amplitudes are observed experimentally on HL-2A tokamak. The frequency of small perturbation amplitude ELM decreases with the increase of net heating power, and it is about 300-400 Hz, and energy loss induced by per ELM is usually less than 3% of the plasma energy. The small ELM is type Ⅲ ELM. While for large (type-I) ELM, besides that the energy loss induced by an ELM is generally more than 10%, they also exert an obvious perturbation on other plasma parameters, such as plasma current and electron density, and the tELM may be longer than 30 ms. ELM precursors are poloidally asymmetric, which can be measured by Mirnov probes on the low field side, but not on the high field side; the frequency of ELM precursors is about 45 kHz, and the longest precursors last approximately 10 ms prior to the ELM bursts.