Effect of different interpolation methods on the accuracy of the reconstruction of spiral k-space trajectories in MRI

[Poster] 4th European Molecular Imaging Meeting, Barcelona, Spain, May 27 - 30, 2009This work is supported in part by the projects CdTeaM (CeniT-ingenio 2010), Ministerio de Ciencia e innovación, and Ciber Cb07/09/0031 CiberSaM, Ministerio de Sanidad y Consumo.Publicad

High temperature internal friction in a Ti–46Al–1Mo–0.2Si intermetallic, comparison with creep behaviour

Advanced gamma-TiAl based intermetallics Mo-bearing have been developed to obtain the fine-grained microstructure required for superplastic deformation to be used during further processing. In the present work we have studied an alloy of Ti-46.8Al-1Mo-0.2Si (at%) with two different microstructures, ascast material with a coarse grain size above 300 mu m, and the hot extruded material exhibiting a grain size smaller than 20 mu m. We have used a mechanical spectrometer especially developed for high temperature internal friction measurements to study the defect mobility processes taking place at high temperature. The internal friction spectra at different frequencies has been studied and analyzed up to 1360 K in order to characterize the relaxation processes appearing in this temperature range. A relaxation peak, with a maximum in between 900 K and 1080 K, depending on the oscillating frequency, has been attributed to Ti-atoms diffusion by the stress-induced reorientation of Al-V-Ti-Al elastic dipoles. The high temperature background in both microstructural states, as-cast and extruded, has been analyzed, measuring the apparent activation parameters, in particular the apparent energies of E-cast(IF) = 4.4 +/- 0.05 eV and E-ext(IF) = 4.75 +/- 0.05 eV respectively. These results have been compared to those obtained on the same materials by creep deformation. We may conclude that the activation parameters obtained by internal friction analysis, are consistent with the ones measured by creep. Furthermore, the analysis of the high temperature background allows establish the difference on creep resistance for both microstructural states. (c) 2015 Acta Materialia Inc. Published by Elsevier Ltd.This work was supported by the Spanish MICINN project CONSOLIDER-INGENIO 2010 CSD2009-00013, as well as by the Consolidated Research Group IT-10-310 from the Education Department and the project ETORTEK ACTIMAT from the Industry Department of the Basque Governmen

Quantitative comparison of partial fourier reconstruction algorithms in MRI at 7T

[Poster] 4th European Molecular Imaging Meeting, Barcelona, Spain, May 27 - 30, 2009In this work we present a quantitative comparison at 7T of the most common partial fourier reconstruction algorithms: conjugate synthesis with phase correction, Margosian method, homodyne reconstruction, PoCS algorithm and iterative homodyne reconstructionThis work is supported in part by the projects CdTeaM (CeniT-ingenio 2010), Ministerio de Ciencia e innovación, and Ciber Cb07/09/0031 CiberSaM, Ministerio de Sanidad y Consumo.Publicad

Quantification of SPIO using T2* and phase imaging

Proceeding of: 17th Scientific Meeting, International Society for Magnetic Resonance in Medicine, 18-24 April, 2009, Honolulu, Hawai, USAPublicad

Small-animal PET registration method with intrinsic validation designed for large datasets

Proceeding of: 2007 IEEE Nuclear Science Symposium Conference Record (NSS'07), Honolulu, Hawaii, USA, Oct. 27 - Nov. 3, 2007We present a procedure to validate the results of small animal Positron Emission Tomography (PET) image registration by means of consistency measures. Small animal 2-Deoxy-2-[F-18]fluoro-D-glucose (FDG) PET studies do not show the same intensity distribution even for images acquired in similar conditions, as the resulting image is influenced by several variables which are not always completely under control. Because of these difficulties, the results from automatic registration methods have to be visually inspected to detect failures. We propose a method to automate this validation process. Two reference images from the dataset are selected by an expert user avoiding images with poor contrast, animal movement or low quality, and both are co-registered using anatomical landmarks. All the remaining images in the dataset are then registered to every reference with an automatic two-step algorithm based on Mutual Information. The known transformation relating both references allows measuring the registration consistency, which is a good estimator of the accuracy of the alignment process, for every image in the dataset. This value can be used to assess the quality of the registration and therefore detect the incorrect results. We have applied this validation process on a large dataset of 120 FDG-PET rat brain images obtained with a rotating PET scanner. The registration consistency was calculated for every image in the dataset and values below 1.65 mm (PET image resolution) were considered as successful registrations. 116 images were correctly registered with an average error of 0.839 mm, while in four images the proposed method detected a registration failure. Two of these failures were due to very low image quality and these studies were discarded from the study, while the other two were correctly aligned after applying a manual pre-alignment step. Our approach requires minimal user interaction and provides automatic assessment of the registration error, making it unnecessary to visually inspect and check every registration result.This work was supported by projects CIBER CB06/01/0079 (Ministerio de Sanidad y Consumo) and CDTEAM (CENIT program, Ministerio de Industria)

Compilation of parameterized seismogenic sources in Iberia for the SHARE European-scale seismic source model.

Abstract: SHARE (Seismic Hazard Harmonization in Europe) is an EC-funded project (FP7) that aims to evaluate European seismic hazards using an integrated, standardized approach. In the context of SHARE, we are compiling a fully-parameterized active fault database for Iberia and the nearby offshore region. The principal goal of this initiative is for fault sources in the Iberian region to be represented in SHARE and incorporated into the source model that will be used to produce seismic hazard maps at the European scale. The SHARE project relies heavily on input from many regional experts throughout the Euro-Mediterranean region. At the SHARE regional meeting for Iberia, the 2010 Working Group on Iberian Seismogenic Sources (WGISS) was established; these researchers are contributing to this large effort by providing their data to the Iberian regional integrators in a standardized format. The development of the SHARE Iberian active fault database is occurring in parallel with IBERFAULT, another ongoing effort to compile a database of active faults in the Iberian region. The SHARE Iberian active fault database synthesizes a wide range of geological and geophysical observations on active seismogenic sources, and incorporates existing compilations (e.g., Cabral, 1995; Silva et al., 2008), original data contributed directly from researchers, data compiled from the literature, parameters estimated using empirical and analytical relationships, and, where necessary, parameters derived using expert judgment. The Iberian seismogenic source model derived for SHARE will be the first regional-scale source model for Iberia that includes fault data and follows an internationally standardized approach (Basili et al., 2008; 2009). This model can be used in both seismic hazard and risk analyses and will be appropriate for use in Iberian- and European-scale assessments

Metalogenia del depósito de manganeso Santa Rosa, Baja California Sur, México

The Santa Rosa Mn-Ba deposit is located southwest of the town of San Nicolás and south of the Concepción Peninsula in Baja California Sur (Mexico). It consists of a manganese oxide vein-breccia striking NNW with a subvertical dip to the ENE that is exposed discontinuously over 500 m. The deposit is hosted in conglomerates that belong to the Los Volcanes member of the Pliocene age San Nicolas Formation. The mineralization is characterized mainly by banded and brecciated structures with manganese oxides (romanèchite and pyrolusite), along with barite, opal, quartz, calcite, magnetite-maghemite and minor goethite. The ore contains between 23.6 and 50.0 wt. % MnO, 13.3 and 32.4 wt. % SiO2, and 9.9 and 13.7 wt. % BaO. In addition, the ores are significantly enriched in Sr, Sb, As, Cu and Zn. The NASC normalized REE profles show a pronounced negative Eu anomaly and a more moderate negative Ce anomaly. The Fe/Mn and the Co/Zn ratios range between 0.01 and 0.16, and 0.17 and 0.34, respectively. Microthermometry suggests two fluid inclusion populations: one with an average Th of 136.5°C and estimated salinity of 4.2 wt. % equivalent NaCl, and the other with an average Th of 136°C and estimated salinity of 11.4 wt. % equivalent NaCl. The mineralogical and geochemical composition, together with the ore formation conditions and the geotectonic setting, suggest a genetic relation between the Santa Rosa deposit and the modern coastal hydrothermal systems of the Concepción Bay

Validity and reliability of transbronchial needle aspiration for diagnosing mediastinal adenopathies

<p>Abstract</p> <p>Background</p> <p>The aim is to assess the validity and reliability of transbronchial needle aspiration (TBNA) of mediastinal and hilar adenopathies and to evaluate factors predictive of TBNA outcome.</p> <p>Methods</p> <p>We performed an analysis of prospectively collected data of patients (n = 580) who underwent TBNA (n = 685) from January 1998 to December 2007 in our center. Validity and reliability were evaluated for the overall sample and according to specific pathology. Factors predicting the successful acquisition of diagnostic samples were analyzed by multivariate analysis.</p> <p>Results</p> <p>Overall sensitivity, specificity, accuracy, and positive and negative predictive (NPV) values for TBNA were 68%, 100%, 68.8%, 100%, and 10%, respectively. The most sensitive and accurate TBNAs were obtained for patients with small cell lung carcinoma and the worst results were for patients with lymphomas. NPV were similar for all pathologies. The most predictive factors of outcome were adenopathy size and the presence of indirect signs at the puncture site.</p> <p>Conclusion</p> <p>The sensitivity and accuracy of TBNA are high in small cell lung cancer, followed by other types of carcinoma, sarcoidosis, and tuberculosis, and low for lymphoproliferative diseases. The NPV of TBNA for all individual pathologies is low. The size of the adenopathy and the presence of indirect signs at the puncture site predict the achievement of diagnostic samples.</p