|
Records |
Links |
|
Author |
Oliver, J.F.; Rafecas, M. |
|
|
Title |
Improving the singles rate method for modeling accidental coincidences in high-resolution PET |
Type |
Journal Article |
|
Year |
2010 |
Publication |
Physics in Medicine and Biology |
Abbreviated Journal |
Phys. Med. Biol. |
|
|
Volume |
55 |
Issue |
22 |
Pages |
6951-6971 |
|
|
Keywords |
|
|
|
Abstract |
Random coincidences ('randoms') are one of the main sources of image degradation in PET imaging. In order to correct for this effect, an accurate method to estimate the contribution of random events is necessary. This aspect becomes especially relevant for high-resolution PET scanners where the highest image quality is sought and accurate quantitative analysis is undertaken. One common approach to estimate randoms is the so-called singles rate method (SR) widely used because of its good statistical properties. SR is based on the measurement of the singles rate in each detector element. However, recent studies suggest that SR systematically overestimates the correct random rate. This overestimation can be particularly marked for low energy thresholds, below 250 keV used in some applications and could entail a significant image degradation. In this work, we investigate the performance of SR as a function of the activity, geometry of the source and energy acceptance window used. We also investigate the performance of an alternative method, which we call 'singles trues' (ST) that improves SR by properly modeling the presence of true coincidences in the sample. Nevertheless, in any real data acquisition the knowledge of which singles are members of a true coincidence is lost. Therefore, we propose an iterative method, STi, that provides an estimation based on ST but which only requires the knowledge of measurable quantities: prompts and singles. Due to inter-crystal scatter, for wide energy windows ST only partially corrects SR overestimations. While SR deviations are in the range 86-300% (depending on the source geometry), the ST deviations are systematically smaller and contained in the range 4-60%. STi fails to reproduce the ST results, although for not too high activities the deviation with respect to ST is only a few percent. For conventional energy windows, i.e. those without inter-crystal scatter, the ST method corrects the SR overestimations, and deviations from the true random rate are of the order of 1% or less. In addition, in the case of conventional energy window STi results reproduce ST results and therefore the former can be used to obtain the true random rate. |
|
|
Address |
[Oliver, Josep F.; Rafecas, Magdalena] Univ Valencia, CSIC, Inst Fis Corpuscular, IFIC, E-46003 Valencia, Spain, Email: josep.f.oliver@uv.es |
|
|
Corporate Author |
|
Thesis |
|
|
|
Publisher |
Iop Publishing Ltd |
Place of Publication |
|
Editor |
|
|
|
Language |
English |
Summary Language |
|
Original Title |
|
|
|
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
|
Series Volume |
|
Series Issue |
|
Edition |
|
|
|
ISSN |
0031-9155 |
ISBN |
|
Medium |
|
|
|
Area |
|
Expedition |
|
Conference |
|
|
|
Notes |
ISI:000283789700025 |
Approved |
no |
|
|
Is ISI |
yes |
International Collaboration |
no |
|
|
Call Number |
IFIC @ elepoucu @ |
Serial |
344 |
|
Permanent link to this record |
|
|
|
|
Author |
BABAR Collaboration (del Amo Sanchez, P. et al); Lopez-March, N.; Martinez-Vidal, F.; Milanes, D.A.; Oyanguren, A. |
|
|
Title |
Search for B+ meson decay to a(1)(+)(1260)K*(0)(892) |
Type |
Journal Article |
|
Year |
2010 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
|
|
Volume |
82 |
Issue |
9 |
Pages |
091101 - 8pp |
|
|
Keywords |
|
|
|
Abstract |
We present a search for the decay B+ -> a(1)(+)(1260)K*(0)(892). The data, collected with the BABAR detector at the SLAC National Accelerator Laboratory, represent 465 X 10(6)B (B) over bar pairs produced in e(+)e(-) annihilation at the energy of the gamma(4S). We find no significant signal and set an upper limit at 90% confidence level on the product of branching fractions B(B+ -> a(1)(+) (1260)K*(0)(892)) X B(a(1)(+)(1260) -> pi(+) pi(-) pi(+)) of 1.8 X 10(-6). |
|
|
Address |
[Sanchez, P. del Amo; Lees, J. P.; Poireau, V.; Prencipe, E.; Tisserand, V.] Univ Savoie, CNRS, IN2P3, Lab Annecy le Vieux Phys Particules LAPP, F-74941 Annecy Le Vieux, France |
|
|
Corporate Author |
|
Thesis |
|
|
|
Publisher |
Amer Physical Soc |
Place of Publication |
|
Editor |
|
|
|
Language |
English |
Summary Language |
|
Original Title |
|
|
|
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
|
Series Volume |
|
Series Issue |
|
Edition |
|
|
|
ISSN |
1550-7998 |
ISBN |
|
Medium |
|
|
|
Area |
|
Expedition |
|
Conference |
|
|
|
Notes |
ISI:000283773400001 |
Approved |
no |
|
|
Is ISI |
yes |
International Collaboration |
yes |
|
|
Call Number |
IFIC @ elepoucu @ |
Serial |
345 |
|
Permanent link to this record |
|
|
|
|
Author |
CDF Collaboration (Aaltonen, T. et al); Cabrera, S. |
|
|
Title |
Measurement of the WW plus WZ Production Cross Section Using the lepton plus jets Final State at CDF II |
Type |
Journal Article |
|
Year |
2010 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
|
|
Volume |
104 |
Issue |
10 |
Pages |
101801 - 8pp |
|
|
Keywords |
|
|
|
Abstract |
We report two complementary measurements of the WW + WZ cross section in the final state consisting of an electron or muon, missing transverse energy, and jets, performed using p (p) over bar collision data at root s = 1.96 TeV collected by the CDF II detector. The first method uses the dijet invariant mass distribution while the second more sensitive method uses matrix-element calculations. The result from the second method has a signal significance of 5.4 sigma and is the first observation of WW + WZ production using this signature. Combining the results gives sigma(WW+WZ) = 16.0 +/- 3.3 pb, in agreement with the standard model prediction. |
|
|
Address |
[Aaltonen, T.; Mehtala, P.; Orava, R.; Osterberg, K.; Saarikko, H.; van Remortel, N.] Univ Helsinki, Div High Energy Phys, Dept Phys, FIN-00014 Helsinki, Finland |
|
|
Corporate Author |
|
Thesis |
|
|
|
Publisher |
Amer Physical Soc |
Place of Publication |
|
Editor |
|
|
|
Language |
English |
Summary Language |
|
Original Title |
|
|
|
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
|
Series Volume |
|
Series Issue |
|
Edition |
|
|
|
ISSN |
0031-9007 |
ISBN |
|
Medium |
|
|
|
Area |
|
Expedition |
|
Conference |
|
|
|
Notes |
ISI:000275543500009 |
Approved |
no |
|
|
Is ISI |
yes |
International Collaboration |
yes |
|
|
Call Number |
IFIC @ pastor @ |
Serial |
293 |
|
Permanent link to this record |
|
|
|
|
Author |
Aguiar, P.; Rafecas, M.; Ortuño, J.E.; Kontaxakis, G.; Santos, A.; Pavia, J.; Rosetti, M. |
|
|
Title |
Geometrical and Monte Carlo projectors in 3D PET reconstruction |
Type |
Journal Article |
|
Year |
2010 |
Publication |
Medical Physics |
Abbreviated Journal |
Med. Phys. |
|
|
Volume |
37 |
Issue |
11 |
Pages |
5691-5702 |
|
|
Keywords |
3D PET; iterative reconstruction; list-mode reconstruction; ray-tracing techniques; Monte Carlo simulation; system response matrix |
|
|
Abstract |
Purpose: In the present work, the authors compare geometrical and Monte Carlo projectors in detail. The geometrical projectors considered were the conventional geometrical Siddon ray-tracer (S-RT) and the orthogonal distance-based ray-tracer (OD-RT), based on computing the orthogonal distance from the center of image voxel to the line-of-response. A comparison of these geometrical projectors was performed using different point spread function (PSF) models. The Monte Carlo-based method under consideration involves an extensive model of the system response matrix based on Monte Carlo simulations and is computed off-line and stored on disk. Methods: Comparisons were performed using simulated and experimental data of the commercial small animal PET scanner rPET. Results: The results demonstrate that the orthogonal distance-based ray-tracer and Siddon ray-tracer using PSF image-space convolutions yield better images in terms of contrast and spatial resolution than those obtained after using the conventional method and the multiray-based S-RT. Furthermore, the Monte Carlo-based method yields slight improvements in terms of contrast and spatial resolution with respect to these geometrical projectors. Conclusions: The orthogonal distance-based ray-tracer and Siddon ray-tracer using PSF image-space convolutions represent satisfactory alternatives to factorizing the system matrix or to the conventional on-the-fly ray-tracing methods for list-mode reconstruction, where an extensive modeling based on Monte Carlo simulations is unfeasible. |
|
|
Address |
[Aguiar, Pablo] Univ Santiago de Compostela, Dept Fis Particulas, Complexo Hosp Univ Santiago de Compostela, Fdn IDICHUS IDIS, Santiago De Compostela, Spain, Email: pablo.aguiar.fernandez@sergas.es |
|
|
Corporate Author |
|
Thesis |
|
|
|
Publisher |
Amer Assoc Physicists Medicine Amer Inst Physics |
Place of Publication |
|
Editor |
|
|
|
Language |
English |
Summary Language |
|
Original Title |
|
|
|
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
|
Series Volume |
|
Series Issue |
|
Edition |
|
|
|
ISSN |
0094-2405 |
ISBN |
|
Medium |
|
|
|
Area |
|
Expedition |
|
Conference |
|
|
|
Notes |
ISI:000283747600015 |
Approved |
no |
|
|
Is ISI |
yes |
International Collaboration |
no |
|
|
Call Number |
IFIC @ elepoucu @ |
Serial |
338 |
|
Permanent link to this record |
|
|
|
|
Author |
Wagner, C.; Verde, L.; Boubekeur, L. |
|
|
Title |
N-body simulations with generic non-Gaussian initial conditions I: power spectrum and halo mass function |
Type |
Journal Article |
|
Year |
2010 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
|
|
Volume |
10 |
Issue |
10 |
Pages |
022 - 24pp |
|
|
Keywords |
power spectrum; cosmological simulations; initial conditions and eternal universe; galaxy clusters |
|
|
Abstract |
We address the issue of setting up generic non-Gaussian initial conditions for N-body simulations. We consider inflationary-motivated primordial non-Gaussianity where the perturbations in the Bardeen potential are given by a dominant Gaussian part plus a non-Gaussian part specified by its bispectrum. The approach we explore here is suitable for any bispectrum, i.e. it does not have to be of the so-called separable or factorizable form. The procedure of generating a non-Gaussian field with a given bispectrum (and a given power spectrum for the Gaussian component) is not univocal, and care must be taken so that higher-order corrections do not leave a too large signature on the power spectrum. This is so far a limiting factor of our approach. We then run N-body simulations for the most popular inflationary-motivated non-Gaussian shapes. The halo mass function and the non-linear power spectrum agree with theoretical analytical approximations proposed in the literature, even if they were so far developed and tested only for a particular shape (the local one). We plan to make the simulations outputs available to the community via the non-Gaussian simulations comparison project web site http://icc.ub.edu/similar to liciaverde/NGSCP.html. |
|
|
Address |
[Wagner, Christian; Verde, Licia] Univ Barcelona, ICCUB IEEC, E-08028 Barcelona, Spain, Email: cwagner@icc.ub.edu |
|
|
Corporate Author |
|
Thesis |
|
|
|
Publisher |
Iop Publishing Ltd |
Place of Publication |
|
Editor |
|
|
|
Language |
English |
Summary Language |
|
Original Title |
|
|
|
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
|
Series Volume |
|
Series Issue |
|
Edition |
|
|
|
ISSN |
1475-7516 |
ISBN |
|
Medium |
|
|
|
Area |
|
Expedition |
|
Conference |
|
|
|
Notes |
ISI:000283577600013 |
Approved |
no |
|
|
Is ISI |
yes |
International Collaboration |
no |
|
|
Call Number |
IFIC @ elepoucu @ |
Serial |
339 |
|
Permanent link to this record |