Fast track for quantitative isolation of lignosulfonates from spent sulfite liquors

In this study, a novel approach for isolation and purification of lignosulfonates from spent sulfite liquor was established.

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

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 achieve a DSI scan in less than 5 min. To augment this accelerated imaging approach we developed a 64-channel, tight-fitting brain array coil and show its performance benefit compared to a commercial 32-channel coil at all locations in the brain for these accelerated acquisitions. The technical challenges of developing the over-all system are discussed as well as results from SNR comparisons, ODF metrics and fiber tracking comparisons. The ultra-high gradients yielded substantial and immediate gains in the sensitivity through reduction of TE and improved signal detection and increased efficiency of the DSI or HARDI acquisition, accuracy and resolution of diffusion tractography, as defined by identification of known structure and fiber crossing.

The FDAM method: determination of carboxyl profiles in cellulosic materials by combining group-selective fluorescence labeling with GPC

A novel method for accurate determination of the carboxyl content in cellulosic materials by fluorescence labeling with 9H-fluoren-2-yl-diazomethane (FDAM) has been developed. The procedure can readily be implemented into a GPC system with RI and MALLS detectors, requiring additional fluorescence detection. The labeling conditions were optimized by means of sugar acid model compounds and were transferred to the cellulose case. Kinetics of the labeling and the influence of reaction parameters were comprehensively studied. For the first time, carboxyl profiles of cellulosics, i.e., the carboxyl content relative to the molecular weight distribution, were obtained.

32-channel 3 Tesla receive-only phased-array head coil with soccer-ball element geometry

A 32-channel 3T receive-only phased-array head coil was developed for human brain imaging. The helmet-shaped array was designed to closely fit the head with individual overlapping circular elements arranged in patterns of hexagonal and pentagonal symmetry similar to that of a soccer ball. The signal-to-noise ratio (SNR) and noise amplification (g-factor) in accelerated imaging applications were quantitatively evaluated in phantom and human images and compared with commercially available head coils. The 32-channel coil showed SNR gains of up to 3.5-fold in the cortex and 1.4-fold in the corpus callosum compared to a (larger) commercial eight-channel head coil. The experimentally measured g-factor performance of the helmet array showed significant improvement compared to the eight-channel array (peak g-factor 59% and 26% of the eight-channel values for four- and fivefold acceleration). The performance of the arrays is demonstrated in high-resolution and highly accelerated brain images.

Comparison of physiological noise at 1.5 T, 3 T and 7 T and optimization of fMRI acquisition parameters

Previous studies have shown that under some conditions, noise fluctuations in an fMRI time-course are dominated by physiological modulations of the image intensity with secondary contributions from thermal image noise and that these two sources scale differently with signal intensity, susceptibility weighting (TE) and field strength. The SNR of the fMRI time-course was found to be near its asymptotic limit for moderate spatial resolution measurements at 3 T with only marginal gains expected from acquisition at higher field strengths. In this study, we investigate the amplitude of image intensity fluctuations in the fMRI time-course at magnetic field strengths of 1.5 T, 3 T, and 7 T as a function of image resolution, flip angle and TE. The time-course SNR was a similar function of the image SNR regardless of whether the image SNR was modulated by flip angle, image resolution, or field strength. For spatial resolutions typical of those currently used in fMRI (e.g., 3 x 3 x 3 mm(3)), increases in image SNR obtained from 7 T acquisition produced only modest increases in time-course SNR. At this spatial resolution, the ratio of physiological noise to thermal image noise was 0.61, 0.89, and 2.23 for 1.5 T, 3 T, and 7 T. At a resolution of 1 x 1 x 3 mm(3), however, the physiological to thermal noise ratio was 0.34, 0.57, and 0.91 for 1.5 T, 3 T and 7 T for TE near T2*. Thus, by reducing the signal strength using higher image resolution, the ratio of physiologic to image noise could be reduced to a regime where increased sensitivity afforded by higher field strength still translated to improved SNR in the fMRI time-series.

Eight-channel phased array coil and detunable TEM volume coil for 7 T brain imaging

An eight-channel receive-only brain coil and table-top detunable volume transmit coil were developed and tested at 7 T for human imaging. Optimization of this device required attention to sources of interaction between the array elements, between the transmit and receive coils and minimization of common mode currents on the coaxial cables. Circular receive coils (85 mm dia.) were designed on a flexible former to fit tightly around the head and within a 270-mm diameter TEM transmit volume coil. In the near cortex, the array provided a fivefold increase in SNR compared to a TEM transmit-receive coil, a gain larger than that seen in comparable coils at 3 T. The higher SNR gain is likely due to strong dielectric effects, which cause the volume coil to perform poorly in the cortex compared to centrally. The sensitivity and coverage of the array is demonstrated with high-resolution images of the brain cortex.

Normal and abnormal pulmonary ventilation: visualization at hyperpolarized He-3 MR imaging

To assess the feasibility of helium-3 magnetic resonance (MR) imaging with a three-dimensional fast low-angle shot (FLASH) sequence, He-3 gas (volume, 300 mL; pressure, 3 x 10(5) Pa; polarized up to 45% by means of optimal pumping) was inhaled by five healthy volunteers and five patients with pulmonary diseases. All breath-hold examinations (22-42 seconds) were completed successfully. Normal ventilation was depicted with homogeneous high signal intensity, lesions were depicted as causing defects, and obstructive lung disease was depicted with severely inhomogeneous signal intensity.