Recoil-gated plunger lifetime measurements in 188Pb

Electromagnetic transition probabilities were measured using the recoil distance Doppler-shift technique and the 40Ca(152Sm,4n) 188Pb reaction at a beam energy of 805 MeV to investigate shape coexistence in 188Pb. For the first time, a plunger was combined with Gammasphere and the Argonne Fragment Mass Analyzer. It was possible to measure the lifetimes of two states in the prolate band of 188Pb and, thus, provide for the first time evidence for the collectivity of this band. A three-level mixing calculation revealed that the first 2+ state is predominantly of prolate character

Investigation of the Spatial Correlation in Human White Matter and the Influence of Age Using 3-Dimensional Variography Applied to MP-RAGE Data

A novel method for the quantification of heterogeneity and spatial correlation in 3D MP-RAGE images of white matter is presented. The technique is based on the variogram, a tool commonly used in geosciences for the analysis of spatial data, and was tailored to the special requirements of MR image analysis. Influences from intensity non-uniformities, noise and arbitrary greyscale were quantified and considered in the calculations. The obtained variograms were fitted with spherical model functions to infer parameters that quantify heterogeneity and size of the correlation structures of the tissue. Numerically generated samples with well-defined correlation properties were employed to validate the estimation process and to provide an interpretation of the parameters obtained. It is shown that the method gives reliable results in an interval of correlation structures sized between 2mm and 20mm. The method was applied to 24 MP-RAGE datasets of healthy female volunteers ranging in age from 19 to 73years. White matter was found to have two prominent correlation structures with sizes of approximately 3mm and 23mm. The heterogeneity of the smaller structure increases significantly with age (r=0.83, p<10(-6))

Automatic segmentation of tissue sections using the multielement information provided by LA-ICP-MS imaging and k-means cluster analysis

Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) is an established and powerful tool to analyse the distribution of elements in tissue sections. Among other applications, the technique is expected to play a central role in the understanding of normal and pathological element distributions in brain tissue.In order to interpret the distribution of elements such as the bio-metals Cu, Zn, Fe and Mn and proceed to an element-based comparison between groups of samples, it is necessary to anatomically parcel the tissue section into regions-of-interest and to average element signals across these regions. This categorization, also termed segmentation, can be done manually, but the support of automated procedures is highly desirable, especially in order to (1) identify groups of pixels with similar elemental fingerprint, termed clusters, and to determine which degree of discrimination is reasonable; (2) segment anatomical structures known to exhibit substructure but without clearly defined borders, such as the healthy cortex, zones of tumours or ischemic lesions, in an observer-independent way; and (3) to investigate correlation between the distribution of elements in tissue and phenomena which incorporate contributions from several elements in a convoluted way, such as the origin of contrast in magnetic resonance imaging (MRI) experiments.The multi-parametric information provided by LA-ICP-MS lends itself naturally to multivariate analysis. This study provides a new way to synthesise the information distributed over many element images by demonstrating the possibility to segment tissue sections into biologically meaningful substructures. This data-driven, observer-independent categorization was based on k-means clustering. The optimal number of clusters was determined based on the silhouette method.Segmentation of healthy tissue resulted in a set of substructures in perfect congruence to the anatomical architecture. Segmentation of ischemic lesions identified a number of regions with different fingerprints of C, P. Fe, Cu and Zn deposits. Clustering provides a promising way of combining the information present in several element images and reveals structure which is not entirely present in any isolated image.As a useful by-product of this study we have found a promising method for investigating the optimal line length within the process of image reconstruction from the continuous stream of raw data points. Images were characterized by their tensor of inertia, in image- as well as in Fourier dual-space (k-space) and changes in the ratio of the intrinsic moments of inertia or the orientation of the principal axes were found to closely describe the optimum orientation. The first results look very encouraging, but the method must be extensively tested before it can be used as an automatic procedure.In conclusion, cluster analysis of mass spectrometric imaging data allows one to define the fingerprint element distribution of different anatomically or functionally distinct regions and opens a new way for the study of correlation between the element distribution and related phenomena. (C) 2011 Elsevier B.V. All rights reserved

Non-Gaussian diffusion in brain tissue at high b-factors as examined by a combined diffusion kurtosis and biexponential diffusion tensor analysis

Diffusion tensor imaging (DTI) permits non-invasive probing of tissue microstructure and provides invaluable information in brain diagnostics. Our aim was to examine approaches capable of capturing more detailed information on the propagation mechanisms and underlying tissue microstructure in comparison to the conventional methods. In this work, we report a detailed in vivo diffusion study of the human brain in an extended range of the b-factors (up to 7000 s mm(-2)) performed on a group of 14 healthy volunteers at 3T. Combined diffusion kurtosis imaging (DKI) and biexponential diffusion tensor analysis (BEDTA) were applied to quantify the attenuation curves. New quantitative indices are suggested as map parameters and are shown to improve the underlying structure contrast in comparison to conventional DTI. In particular, fractional anisotropy maps related to the slow diffusion tensor are shown to attain significantly higher values and to substantially improve white matter mapping. This is demonstrated for the specified regions of the frontal and occipital lobes and for the anterior cingulate. The findings of this work are substantiated by the statistical analysis of the whole slice histograms averaged over 14 subjects. Colour-coded directional maps related to the fast and slow diffusion tensors in human brain tissue are constructed for the first time and these demonstrate a high degree of axial co-alignment of the two tensors in the white matter regions. It is concluded that a combined DKI and BEDTA offers a promising framework for monitoring tissue alteration during development and degeneration or as a consequence of the neurological disease

In vivo imaging of the human brain at 1.5 T with 0,6-mm isotropic resolution

We present high-resolution in vivo anatomical scans with 3D whole-brain coverage and an isotropic resolution of 0.6 mm, obtained at a clinical field of 1.5 T. The data are acquired in 10 independent scans over two sessions using a 3D magnetization-prepared, gradient echo sequence, modified to output phase images in addition to magnitude images. The independent scans are coregistered to correct for head motion, prior to performing complex averaging. The resolution of the final, averaged image, is found to be equal to the nominal one. The separation between the distribution of gray-scale values characterizing the gray and white matter, respectively, is substantially improved over single-scan images. Complex and magnitude averaging are compared and found to deliver similar results for regions with a high initial signal-to-noise ratio (SNR) within the brain. However, complex averaging is strongly recommended for quantitative applications or for studies where regions of low initial SNR are important. To summarize, a method for high-resolution in vivo anatomical imaging at a clinical field strength is demonstrated and is recommended for brain mapping. The method can also be applied at higher fields with a reduced acquisition time

Comparison of O-(2-[18F]fluoroethyl)-L-tyrosine and L-[3H]-methionine uptake in cerebral hematomas

Radiolabeled amino acids are useful for brain tumor diagnosis, but unspecific uptake near the cerebral hematoma may complicate the differentiation of a neoplastic from a nonneoplastic origin of the hematoma. The aim of this study was to investigate the pattern and time course of O-(2-(18)F-fluorethyl)-l-tyrosine ((18)F-FET) and l-(3)H-methionine ((3)H-MET) uptake in rats with cerebral hematomas.Intracerebral hematomas were induced in the striatum of 25 Fischer 344 CDF rats by inoculation of bacterial collagenase. (18)F-FET and (3)H-MET were injected intravenously at different times up to 4 wk after bleeding. One hour after tracer injection, brains were cut in coronal sections and evaluated by dual-tracer autoradiography. Lesion-to-brain (L/B) ratios were calculated by dividing maximal uptake near the hematomas and mean uptake in normal brain tissue. An L/B ratio greater than 1.5 was considered as indicative of pathologic uptake. The autoradiograms were compared with histology and immunostainings for astrogliosis (glial fibrillary acidic protein) and macrophage infiltration (CD68).(18)F-FET exhibited significantly increased uptake near the hematomas between 3 and 14 d after bleeding. The time course of pathologic (3)H-MET uptake was similar, but after 3-4 wk there was still borderline uptake in single animals. The L/B ratios exceeded the cutoff level of 1.5 in 10 of 23 animals for (18)F-FET and in 12 of 22 animals for (3)H-MET but did not exceed a value of 3. Immunostainings indicated that increased uptake of both tracers correlated with reactive astrogliosis, whereas (3)H-MET uptake was additionally increased in areas with macrophage infiltration.(18)F-FET, like (3)H-MET, may exhibit significantly increased uptake near cerebral hematomas, especially during the first 2 wk after bleeding, complicating the differentiation between a neoplastic and a nonneoplastic origin of cerebral hematomas