Selective palladium-catalyzed amination of the heterocyclic core of variolins

A new and selective palladium-catalyzed amination of the pyrido[3′,3′:4,5]pyrrolo[1,2-c]pyrimidine nucleus, the heterocyclic core of the variolin alkaloids, is described. The method allows the introduction of amino and aryl- and alkylamino substituents on the C9 position in advanced precursors of variolin B and deoxyvariolin.We acknowledge financial support from the Spanish Ministerio de Educación y Ciencia (project CTQ2005/011060), Comunidad de Madrid (CAM) and Universidad de Alcalá (UAH) (project CAM/UAH-2005/044) and a grant (A.B.) from the Ministerio de Educación y Ciencia

Investigation of Different Sparsity Transforms for the PICCS Algorithm in Small- Animal Respiratory Gated CT

Data Availability Statement: All relevant data are available from the Zenodo database, under the DOI: http://dx.doi.org/10.5281/zenodo.15685.Respiratory gating helps to overcome the problem of breathing motion in cardiothoracic small-animal imaging by acquiring multiple images for each projection angle and then assigning projections to different phases. When this approach is used with a dose similar to that of a static acquisition, a low number of noisy projections are available for the reconstruction of each respiratory phase, thus leading to streak artifacts in the reconstructed images. This problem can be alleviated using a prior image constrained compressed sensing (PICCS) algorithm, which enables accurate reconstruction of highly undersampled data when a prior image is available. We compared variants of the PICCS algorithm with different transforms in the prior penalty function: gradient, unitary, and wavelet transform. In all cases the problem was solved using the Split Bregman approach, which is efficient for convex constrained optimization. The algorithms were evaluated using simulations generated from data previously acquired on a micro-CT scanner following a high-dose protocol (four times the dose of a standard static protocol). The resulting data were used to simulate scenarios with different dose levels and numbers of projections. All compressed sensing methods performed very similarly in terms of noise, spatiotemporal resolution, and streak reduction, and filtered back-projection was greatly improved. Nevertheless, the wavelet domain was found to be less prone to patchy cartoon-like artifacts than the commonly used gradient domain.This work was partially funded by the RICRETIC network (RD12/0042/0057) from the Ministerio de Economía y Competitividad (www.mineco.gob.es/) and projects TEC2010-21619-C04-01 and PI11/00616 from Ministerio de Ciencia e Innovación (www.micinn.es/). The research leading to these results was supported by funding from the Innovative Medicines Initiative (www.imi.europa.eu) Joint Undertaking under grant agreement n°115337, the resources of which comprise financial contributions from the European Union's Seventh Framework Programme (FP7/2007-2013) and EFPIA companies ("in kind contribution"). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Expanding the dynamic range of flat-panel detectors used in small-animal cone-beam CT: an automated dual-exponsure technique

[Poster] 4th European Molecular Imaging Meeting, Barcelona, Spain, May 27 - 30, 2009This work is supported in part by Ministerio de Ciencia e Innovación (TEC2008-06715 and TEC2007-64731), EU-FP7 project FMTXCT-201792 and CD-TEAM project (CENIT program).Publicad

Corrección empírica de primer y segundo orden del artefacto de endurecimiento de haz en imágenes de micro-TAC

Actas de: XXIX Congreso Anual de la Sociedad Espñaola de Ingeniería Biomédica (CASEIB 2011). Cáceres, 16-18 Noviembre 2011.Los artefactos más comunes producidos por el fenómeno físico de endurecimiento de haz en imágenes obtenidas en un tomógrafo de rayos X son: "cupping", en volúmenes homogéneos y bandas oscuras, en presencia de objetos densos. Este trabajo presenta un esquema de corrección completa para ambos artefactos: un primer paso implementa una corrección de "cupping" por medio de un método de corrección de primer orden: linealización sobre los datos de proyección; en un segundo paso, se aplica un algoritmo de corrección de segundo orden sobre la imagen ya reconstruida para eliminar las bandas oscuras. En todo el proceso se elimina la necesidad de conocer el espectro de la fuente de rayos X. Ambos métodos han sido validados en maniquíes homogéneos y heterogéneos compuestos por dos materiales distintos, además de estudios de pequeño animal (ratas y ratones de laboratorio) adquiridos en un tomógrafo de rayos X para pequeños animales (micro-TAC) diseñado en el laboratorio. Los resultados demuestran la validez del esquema de corrección.Este trabajo ha sido financiado por el Ministerio de Ciencia e Innovación (proyectos CENIT AMIT, TEC 2008-06715-C02-1, RD07/0014/2009, TRA2009 0175 y Red RECAVA) y por la Comunidad de Madrid y Fondos FEDER (programa ARTEMIS S2009DPI-1802).Publicad

Automatic Monte-Carlo Based Scatter correction for X-ray Cone Beam CT using General Purpose Graphic Processing Units (GP-GPU): a Feasibility study

Proceedings of: 2011 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC). Valencia, Spain, 23-29 October 2011Scattered photons highly degrade the quality of X-ray images and their effect has become more important due to the increasing interest in cone-beam geometry for the acquisition of CT (CBCT) and micro-CT data. The random nature of scatter events and the great influence of the sample suggest that the most accurate methods for their estimation are Monte Carlo (MC) techniques, but their use is usually hampered by the large computation time required to obtain an acceptable estimation of the scattered radiation. We present an approach for scatter correction in CBCT by MC estimation, speeding up the computation by means of general purpose graphic processing units (GPGPU) and developing a framework for the automatic correction and reconstruction of projection data. The method consists of five stages: FDK reconstruction of the original data; histogram based automatic segmentation of the volume assigning a material and density to each voxel; fast MC estimation of the scatter signal; denoising of the independent scatter components and subtraction from original data; and FDK reconstruction of the corrected data. Every stage runs in a GPGPU using Nvidia CUD A. The MC stage is based on the MC-GPU code. To simulate polychromatic X-ray beams, the Spektr model is used to generate the source spectrum. Photon scattering is forced in order to reduce the number of events needed to obtain an acceptable scatter image weighting the photon histories to assure the correctness of the result. Further reduction in the variance is obtained by split the photon in several virtual photons which are forced point to the detector and are transported with no further interaction to the detector's surface. Furthermore, the divergence of the execution path of GPGPU kernels has been minimized. These techniques achieve a reduction of the variance of the scatter signal of two orders of magnitude and the final efficiency is improved by a factor of ~30.This work has been partially funded by the Spain Ministry of Education, FPU program; Spain Ministry of Science and Innovation, projects TEC2008-06715 and TEC2007-64731; CDTI under the CENIT Programme (AMIT Project); Comunidad de Madrid (ARTEMIS S2009/DPI-1802); and EU-FP7, FMTXCT-201792Publicad

Simulation of mechanical misalignments in a cone-beam micro-CT system

Proceeding of: 2008 IEEE Nuclear Science Symposium Conference Record (NSS '08), Dresden, Germany, 19-25 October 2008X-ray CT images usually show artefacts due not only to physical effects -e.g., beam hardening-, but also to misalignments that remain after mechanical calibration. These artefacts become particularly noticeable in the case of high spatial resolution systems and in hybrid systems, such as PETCT, SPECT-CT scanners, which rely on a correct registration of emission and CT data. Hence, slight mechanical misalignments affect the quality of the CT images and any attenuation correction methods or further quantification based on them. We implemented a computer simulator of these artefacts on a conebeam, flat-panel based micro-CT scanner. Using this simulator, we studied the effect of these different misalignments (pitch and roll tilts, skew and shifts) on reconstructed images.This work is partially funded by the CD-TEAM Project, CENIT Program, Spanish Ministerio de Industria, and with grants from the Ministerio de Educaci6n y Ciencia, projects TEC200764731 and TEC2008-06715-C02-01

A new algorithm for ring artifact reduction in cone-beam computed tomography: preliminary results

[Abstract] 22nd International Congress and Exhibition, Barcelona, Spain, June 25-28, 2008In this work we present a new method for ring artifact compensation, suitable for cone beam data. Starting from the idea of Sijbers et al., we have developed an improved procedure that operates on the projection data before the reconstruction and does not require interpolations, thus avoiding image degradation and reducing the computational burden. Results on phantoms and rodent studies are presentedPublicad

Isokinetic trunk flexion–extension protocol to assess trunk muscle strength and endurance: Reliability, learning effect, and sex differences

PurposeThe purpose of this study was to examine the reliability and the learning effect of an isokinetic trunk flexion–extension protocol designed to simultaneously assess trunk muscle strength and endurance. In addition, the effect of the participants' sex on the reliability data was examined.MethodsFifty-seven healthy and physically active young men (n = 28) and women (n = 29) performed the isokinetic protocol 5 times, separated by a week between each of the first 4 sessions and by a month between the last 2 sessions. The protocol consisted of performing 4 trials of 15 maximum flexion–extension concentric exertions at 120°/s (range of trunk motion = 50°). The absolute and relative peak torque and total work were calculated to assess trunk flexion and extension strength. In addition, endurance ratio, modified endurance ratio, fatigue final ratio, recovery ratio, and modified recovery ratio variables were used for the assessment of trunk muscle endurance in both directions.ResultsRegarding the absolute reliability, no relevant changes were found between paired-comparison sessions for most strength and endurance variables, except for total work and relative total work variables in the flexion movement in both sexes. In addition, the typical error of the isokinetic variables was lower than 10% in both males and females, and minimum detectable changes ranged from 7%–20%, with a tendency to be higher in females and in endurance variables. The strength variables showed high intraclass correlation coefficients (ICC; >0.74); however, for the endurance variables only the endurance ratio and the modified endurance ratio obtained moderate to high ICC values (0.57 < ICC < 0.82). In addition, the analysis of the variance reported no significant differences between consecutive pairs of sessions for most variables in both sexes.ConclusionOverall, these findings provide clinicians, trainers, and researchers with a 10-min single-session protocol to perform a reliable muscle strength and endurance evaluation of trunk flexor and extensor muscles, all within the same protocol

Palladium-mediated C-N, C-C, and C-O functionalization of azolopyrimidines: a new total synthesis of variolin B

A new total synthesis of the alkaloid variolin B is achieved by a selective and sequential palladium-mediated functionalization of a\ud trihalo-substituted pyrido[30\ud ,20\ud :4,5]pyrrolo[1,2-c]pyrimidine. This intermediate is obtained by a new heterocyclization reaction between\ud an appropriate bromomethyl azaindole and N-tosylmethyl dichloroformimide. The methodology may be effective for the synthesis of\ud some analogs by substitution on the relatively unexplored C4 and C9 positions of the alkaloid.The authors acknowledge financial support from the\ud Spanish Ministerio de Educación y Ciencia (project\ud CTQ2005/011060/BQU), Comunidad de Madrid (CAM),\ud and Universidad de Alcalá (UAH) (project CCG-UAH/\ud SAL-0660) and a grant from the Ministerio de Educación\ud y Ciencia (A.B.)

Statistical 4D reconstruction of dynamic CT images: preliminary results

[Poster] 4th European Molecular Imaging Meeting, Barcelona, Spain, May 27 - 30, 2009Preliminary results are presented of a 4d reconstruction algorithm for dynamic contrast enhanced CT, in a micro-CT based on cone beam geometry. The method is based on modelling the spatial and temporal distribution of the contrast inside the field of view. The use of non-uniform time sampling with b-splines yielded smooth time-activity curves that captured the relatively fast rise and fall of contrast in the aorta, as well as the uptake and retention of contrast in the kidneysThis work is supported by Ministerio de Ciencia e innovación (TeC2008-06715-C02-01 and TeC2007-64731/TCM), Ministerio de industria (CdTeaM, Programa CeniT), and the reCaVa-reTiC network.Publicad