Characterization of a mammographic system based on single photon counting pixel arrays coupled to GaAs x-ray detectors.

The authors report on the imaging capabilities of a mammographic system demonstrator based on GaAs pixel detectors operating in single photon counting (SPC) mode. The system imaging performances have been assessed by means of the transfer functions: The modulation transfer function (MTF), the normalized noise power spectrum, and the detective quantum efficiency (DQE) have been measured following the guidelines of the IEC 62220-1-2 protocol. The transfer function analysis has shown the high spatial resolution capabilities of the GaAs detectors. The MTF calculated at the Nyquist frequency (2.94 cycles/mm) is indeed 60%. The DQE, measured with a standard mammographic beam setup (Mo/Mo, 28 kVp, with 4 mm Al added filter) and calculated at zero frequency, is 46%. Aiming to further improve the system's image quality, the authors investigate the DQE limiting factors and show that they are mainly related to system engineering. For example, the authors show that optimization of the image equalization procedure increases the DQE(0) up to 74%, which is better than the DQE(0) of most clinical mammographic systems. The authors show how the high detection efficiency of GaAs detectors and the noise discrimination associated with the SPC technology allow optimizing the image quality in mammography. In conclusion, the authors propose technological solutions to exploit to the utmost the potentiality of GaAs detectors coupled to SPC electronics.

MammoGrid--a prototype distributed mammographic database for Europe.

This paper describes the prototype for a Europe-wide distributed database of mammograms entitled MammoGrid, which was developed as part of an EU-funded project. The MammoGrid database appears to the user to be a single database, but the mammograms that comprise it are in fact retained and curated in the centres that generated them. Linked to each image is a potentially large and expandable set of patient information, known as metadata. Transmission of mammograms and metadata is secure, and a data acquisition system has been developed to upload and download mammograms from the distributed database, and then annotate them, rewriting the annotations to the database. The user can be anywhere in the world, but access rights can be applied. The paper aims to raise awareness among radiologists of the potential of emerging "grid" technology ("the second-generation Internet").

A comparison of some anthropometric parameters between an Italian and a UK population: "proof of principle" of a European project using MammoGrid.

AIM: To demonstrate the use of grid technology to produce a database of mammograms and supporting patient data, specifically using breast density as a biomarker of risk for breast cancer, for epidemiological purposes. METHOD: The cohort comprised 1737 women from the UK and Italy, aged 28-87 years, mean 54.7 years, who underwent mammography after giving consent to the use of their data in the project. Information regarding height, weight, and exposure data (mAs and kV) was recorded. The computer program Generate-SMF was applied to all films in the database to measure breast volume, dense breast volume, and thereby percentage density. Visual readings of density using a six-category classification system were also available for 596 women. RESULTS: The UK and Italian participants were similar in height, but the UK women were significantly heavier with a slightly higher body mass index (BMI), despite being younger. Both absolute and percentage breast density were significantly higher in the Udine cohort. Images from the medio-lateral projection (MLO) give a significantly lower percentage density than cranio-caudal (CC) images (p<0.0001). Total breast volume is negatively associated with percentage density, as are BMI and age (p<0.0001 for all), although 80% of the variability in percentage density remains unexplained. CONCLUSION: The study offers proof of principle that confederated databases generated using Grid technology provide a useful and adaptable environment for large quantities of image, numerical, and qualitative data suitable for epidemiological research using the example of mammographic density as a biomarker of risk for breast cancer.

Resolving clinicians' queries across a Grid's infrastructure.

OBJECTIVES: The past decade has witnessed order of magnitude increases in computing power, data storage capacity and network speed, giving birth to applications which may handle large data volumes of increased complexity, distributed over the internet. METHODS: Medical image analysis is one of the areas for which this unique opportunity likely brings revolutionary advances both for the scientist's research study and the clinician's everyday work. Grids [1] computing promises to resolve many of the difficulties in facilitating medical image analysis to allow radiologists to collaborate without having to co-locate. RESULTS: The EU-funded MammoGrid project [2] aims to investigate the feasibility of developing a Grid-enabled European database of mammograms and provide an information infrastructure which federates multiple mammogram databases. This will enable clinicians to develop new common, collaborative and co-operative approaches to the analysis of mammographic data. CONCLUSION: This paper focuses on one of the key requirements for large-scale distributed mammogram analysis: resolving queries across a grid-connected federation of images.

A real-time classification system of thalassemic pathologies based on artificial neural networks.

Thalassemias are pathologies that derive from genetic defects of the globin genes. The most common defects among the population affect the genes that are involved in the synthesis of alpha and beta chains. The main aspects of these pathologies are well explained from a biochemical and genetic point of view. The diagnosis is fundamentally based on hematologic and genetic tests. A genetic analysis is particularly important to determine the carriers of alpha-thalassemia, whose identification by means of the hematologic parameters is more difficult in comparison with heterozygotes for alpha-thalassemia. This work investigates the use of artificial neural networks (ANNs) for the classification of thalassemic pathologies using the hematologic parameters resulting from hemochromocytometric analysis only. Different combinations of ANNs are reported, which allow thalassemia carriers to be discriminated from normals with 94% classification accuracy, 92% sensitivity, and 95% specificity. On the basis of these results, an automated system that allows real-time support for diagnoses is proposed. The automated system interfaces a hemochromo analyzer to a simple PC.

Measurement of the top quark p(T) distribution.

We have measured the p(T) distribution of top quarks that are pair produced in pp collisions at sqrt[s] = 1.8 TeV using a sample of tt decays in which we observe a single high- p(T) charged lepton, a neutrino, and four or more jets. We use a likelihood technique that corrects for the experimental bias introduced due to event reconstruction and detector resolution effects. The observed distribution is consistent with the standard model prediction. We use these data to place limits on the production of high- p(T) top quarks suggested in some models of anomalous top quark pair production.

Search for neutral supersymmetric Higgs bosons in pp collisions at sqrt[s] = 1.8TeV.

We present the results of a search for neutral Higgs bosons produced in association with b quarks in pp-->bb(phi)-->bbb final states with 91+/-7 pb(-1) of pp collisions at sqrt[s] = 1.8 TeV recorded by the Collider Detector at Fermilab. We find no evidence of such a signal and the data are interpreted in the context of the neutral Higgs sector of the minimal supersymmetric extension of the standard model. With basic parameter choices for the supersymmetric scale and the stop-quark mixing, we derive 95% C.L. lower mass limits for neutral Higgs bosons for tan(beta) values in excess of 35.

First measurement of the ratio B(t --> Wb)/B(t --> Wq) and associated limit on the Cabibbo-Kobayashi-Maskawa element /V(tb)/.

We present the first measurement of the ratio of branching fractions R identical withB(t-->Wb)/B(t-->Wq) from p_p collisions at sqrt[s] = 1.8 TeV. The data set corresponds to 109 pb(-1) of data recorded by the Collider Detector at Fermilab during the 1992-95 Tevatron run. We measure R = 0.94(+0.31)(-0.24)(stat+syst) or R>0.61 (0.56) at 90% (95)% C.L., in agreement with the standard model predictions. This measurement yields a limit on the Cabibbo-Kobayashi-Maskawa quark mixing matrix element /V(tb)/ under the assumption of three generations and unitarity.

Production of chi(c1) and chi(c2) in pp collisions at sqrt[S] = 1.8 TeV.

We have measured the ratio of prompt production rates of the charmonium states chi(c1) and chi(c2) in 110 pb(-1) of pp collisions at sqrt[s] = 1.8 TeV. The photon from their decay into J/psi(gamma) is reconstructed through conversion into e+e- pairs. The energy resolution this technique provides makes the resolution of the two states possible. We find the ratio of production cross sections sigma(chi(c2))/sigma(chi(c1)) = 0.96+/-0.27(stat)+/-0.11(syst) for events with pT(J/psi) > 4.0 GeV/c, /eta(J/psi)/ < 0.6, and pT(gamma) > 1.0 GeV/c.

Search for scalar top and scalar bottom quarks in pp collisions at square root s=1.8 TeV.

We have searched for direct pair production of scalar top and scalar bottom quarks in 88 pb-1 of pp collisions at sqrt[s]=1.8 TeV with the CDF detector. We looked for events with a pair of heavy flavor jets and missing energy, consistent with scalar top (bottom) quark decays to a charm (bottom) quark and a neutralino. The numbers of events that pass our selections show no significant deviation from standard model expectations. We compare our results to the next-to-leading order scalar quark production cross sections to exclude regions in scalar quark-neutralino mass parameter space.

Search for a W' boson via the decay mode W'-->munumu in 1.8 TeV pp collisions.

We report the results of a search for a W' boson produced in pp collisions at a center-of-mass energy of 1.8 TeV using a 107 pb-1 data sample recorded by the Collider Detector at Fermilab. We consider the decay channel W'-->&munumu and search for anomalous production of high transverse mass munumu lepton pairs. We observe no excess of events above background and set limits on the rate of W' boson production and decay relative to standard model W boson production and decay using a fit of the transverse mass distribution observed. If we assume standard model strength couplings of the W' boson to quark and lepton pairs, we exclude a W' boson with invariant mass less than 660 GeV/c2 at 95% confidence level.

Measurement of J/psi and psi(2S) polarization in pp collisions at sqrt[s] = 1.8 TeV.

We have measured the polarization of J/psi and psi(2S) mesons produced in pp collisions at sqrt[s] = 1.8 TeV, using data collected at the Collider Detector at Fermilab during 1992-1995. The polarization of promptly produced J/psi [psi(2S)] mesons is isolated from those produced in B-hadron decay, and measured over the kinematic range 4 [5.5]

Measurement of b-Quark Fragmentation Fractions in pp[over ¯] Collisions at sqrt[s]=1.8 TeV.

We have studied the production of B hadrons in 1.8-TeV pp[over ¯] collisions. We present measurements of the fragmentation fractions, f_{u}, f_{d}, f_{s}, and f_{baryon}, of produced b quarks that yield B^{+}, B^{0}, B_{s}^{0}, and Λ[over ¯]_{b}^{0} hadrons. Reconstruction of five electron-charm final states yields f_{s}/( f_{u}+f_{d})=0.213±0.068 and f_{baryon}/( f_{u}+f_{d})=0.118±0.042, assuming f_{u}=f_{d}. If all B hadrons produced in pp[over ¯] collisions cascade to one of these four hadrons, we determine f_{u}=f_{d}=0.375±0.023, f_{s}=0.160±0.044, and f_{baryon}=0.090±0.029. If we do not assume f_{u}=f_{d}, we find f_{d}/f_{u}=0.84±0.16.

Classification and quantitation of 1H NMR spectra of alditols binary mixtures using artificial neural networks.

A pattern recognition method based on artificial neural networks (ANNs) to analyze and quantify the components of six alditol binary mixtures is presented. This method is suitable to classify the spectra of the 15 mixtures obtained from the six alditols and to produce quantitative estimates of the component concentrations. The system is user-friendly and is helpful in solving the problem of greatly overlapping signals, often encountered in NMR spectroscopy of carbohydrates. A "classification" ANN uses 200 intensity values of the 1H NMR spectrum in the range 3.5-4 ppm. When the correct mixture is identified, the quantification is solved by assigning a specific ANN to each mixture. These ANNs use the same 200 values of the spectrum and output the values of the two concentrations. The error in the ANN responses is studied, and a method is developed to estimate the accuracy in determining the concentrations. The networks' abilities to recognize previously unseen mixtures are tested. When the classification ANN (trained on the 15 binary mixtures) is exposed to complex (i.e., more than binary) mixtures of the six known alditols, it successfully identifies the components if their minimum concentration is 10%. Given the precision of the results and the small number of errors reported, we believe that the method can be used in all fields in which the recognition and quantification of components are necessary.

Spectroscopic identification and quantitative analysis of binary mixtures using artificial neural networks.

This work deals with the application of artificial neural networks to two common problems in spectroscopy: the identification of distorted UV-visible spectra of a specific class of organic compounds, and the quantitative determination of single components in binary mixtures of these compounds. The examined species were six organic indicators, whose spectra are very similar to each other; the trained networks have proven to be very powerful in both applications.