Search

International audience; State-of-the-art techniques for phase retrieval in propagation based X-ray phase-contrast imaging are aiming to solve an underdetermined linear system of equations. They commonly employ Tikhonov regularization - an L2-norm regularized deconvolution scheme - despite some of its limitations. We present a novel approach to phase retrieval based on Total Variation (TV) minimization. We incorporated TV minimization for deconvolution in phase retrieval using a variety of the most common linear phase-contrast models. The results of our TV minimization was compared with Tikhonov regularized deconvolution on simulated as well as experimental data. The presented method was shown to deliver improved accuracy in reconstructions based on a single distance as well as multiple distance phase-contrast images corrupted by noise and hampered by errors due to nonlinear imaging effects. (C) 2013 Optical Society of America

International audience; The reconstruction problem in in-line X-ray Phase-Contrast Tomography is usually approached by solving two independent linearized sub-problems: phase retrieval and tomographic reconstruction. Both problems are often ill-posed and require the use of regularization techniques that lead to artifacts in the reconstructed image. We present a novel reconstruction approach that solves two coupled linear problems algebraically. Our approach is based on the assumption that the frequency space of the tomogram can be divided into bands that are accurately recovered and bands that are undefined by the observations. This results in an underdetermined linear system of equations. We investigate how this system can be solved using three different algebraic reconstruction algorithms based on Total Variation minimization. These algorithms are compared using both simulated and experimental data. Our results demonstrate that in many cases the proposed algebraic algorithms yield a significantly improved accuracy over the conventional L2-regularized closed-form solution. This work demonstrates that algebraic algorithms may become an important tool in applications where the acquisition time and the delivered radiation dose must be minimized. (C) 2013 Optical Society of America

Made available in DSpace on 2014-12-03T13:08:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-08-07Bitstream added on 2014-12-03T13:24:38Z : No. of bitstreams: 1 WOS000323109700082.pdf: 1393704 bytes, checksum: 25bc393488fc34ae69a2e38b45a346c2 (MD5) NPRP grant from the Qatar National Research Fund (a member of Qatar foundation) NCF (Netherlands Computer Facility Foundation) NWO (Nederlandse Organisatie voor Wetenschappelijk Onderzoek) Odo van Vloten Foundation Over the past two decades, several fungal outbreaks have occurred, including the high-profile 'Vancouver Island' and 'Pacific Northwest' outbreaks, caused by Cryptococcus gattii, which has affected hundreds of otherwise healthy humans and animals. Over the same time period, C. gattii was the cause of several additional case clusters at localities outside of the tropical and subtropical climate zones where the species normally occurs. In every case, the causative agent belongs to a previously rare genotype of C. gattii called AFLP6/VGII, but the origin of the outbreak clades remains enigmatic. Here we used phylogenetic and recombination analyses, based on AFLP and multiple MLST datasets, and coalescence gene genealogy to demonstrate that these outbreaks have arisen from a highly-recombining C. gattii population in the native rainforest of Northern Brazil. Thus the modern virulent C. gattii AFLP6/VGII outbreak lineages derived from mating events in South America and then dispersed to temperate regions where they cause serious infections in humans and animals. CBS KNAW Fungal Biodivers Ctr, Dept Yeast & Basidiomycete Res, Utrecht, Netherlands Canisius Wilhelmina Hosp, Dept Med Microbiol & Infect Dis, Nijmegen, Netherlands Univ Sao Paulo State, Dept Phytopathol, UNESP, Ilha Solteira, Brazil Hadassah Hebrew Univ Med Ctr, Dept Clin Microbiol & Infect Dis, Jerusalem, Israel Univ Birmingham, Sch Biosci, Birmingham, W Midlands, England Univ Ghent, Fac Pharmaceut Sci, Lab Pharmaceut Biotechnol, B-9000 Ghent, Belgium Ctr Genom Regulat, Barcelona, Spain UPF Doctor Aiguader, Barcelona, Spain Netherlands Inst Ecol NIOO KNAW, Ctr Limnol, Wageningen, Netherlands Ctr Wiskunde & Informat, Amsterdam, Netherlands Vrije Univ Amsterdam, Dept Operat Res, Amsterdam, Netherlands Univ British Columbia, Sch Environm Hlth, Vancouver, BC V5Z 1M9, Canada Inst Nacl Salud, Microbiol Grp, Bogota, Colombia Fiocruz MS, Fundacao Oswaldo Cruz, Lab Micol, Inst Pesquisa Clin Evandro Chagas, BR-21045900 Rio De Janeiro, Brazil Univ Sydney, Westmead Hosp, Ctr Infect Dis & Microbiol,Sydney Emerging Dis &, Mol Mycol Res Lab,Westmead Millennium Inst,Sydney, Westmead, NSW 2145, Australia Radboud Univ Nijmegen, Med Ctr, Dept Med Microbiol, NL-6525 ED Nijmegen, Netherlands Second Mil Med Univ, Changzheng Hosp, Shanghai Key Lab Mol Med Mycol, Shanghai, Peoples R China Univ Med Ctr, Dept Internal Med & Infect Dis, Utrecht, Netherlands Univ Sao Paulo State, Dept Phytopathol, UNESP, Ilha Solteira, Brazil NPRP grant from the Qatar National Research Fund (a member of Qatar foundation)5-298-3-06