Kinetic model-based factor analysis of dynamic sequences for 82-rubidium cardiac positron emission tomography

Purpose: Factor analysis has been pursued as a means to decompose dynamic cardiac PET images into different tissue types based on their unique temporal signatures to improve quantification of physiological function. In this work, the authors present a novel kinetic model-based (MB) method that includes physiological models of factor relationships within the decomposition process. The physiological accuracy of MB decomposed 82Rb cardiac PET images is evaluated using simulated and experimental data. Precision of myocardial blood flow (MBF) measurement is also evaluated. Methods: A gamma-variate model was used to describe the transport of 82Rb in arterial blood from the right to left ventricle, and a one-compartment model to describe the exchange between blood and myocardium. Simulations of canine and rat heart imaging were performed to evaluate parameter estimation errors. Arterial blood sampling in rats and 11CO blood pool imaging in dogs were used to evaluate factor and structure accuracy. Variable infusion duration studies in canine were used to evaluate MB structure and global MBF reproducibility. All results were compared to a previously published minimal structure overlap (MSO) method. Results: Canine heart simulations demonstrated that MB has lower root-mean-square error (RMSE) than MSO for both factor (0.2% vs 0.5%, p<0.001 MB vs MSO, respectively) and structure (3.0% vs 4.7%, p<0.001) estimations, as with rat heart simulations (factors: 0.2% vs 0.9%, p<0.001 and structures: 3.0% vs 6.7%, p<0.001). MB blood factors compared to arterial blood samples in rats had lower RMSE than MSO (1.6% vs 2.2%, p=0.025). There was no difference in the RMSE of blood structures compared to a 11CO blood pool image in dogs (8.5% vs 8.8%, p=0.23). Myocardial structures were more reproducible with MB than with MSO (RMSE=3.9% vs 6.2%, p<0.001), as were blood structures (RMSE=4.9% vs 5.6%, p=0.006). Finally, MBF values tended to be more reproducible with MB compared to MSO (CV=10% vs 18%, p=0.16). The execution time of MB was, on average, 2.4 times shorter than MSO (p<0.001) due to fewer free parameters. Conclusions: Kinetic model-based factor analysis can be used to provide physiologically accurate decomposition of 82Rb dynamic PET images, and may improve the precision of MBF quantification

Measurement of the B0s lifetime and study of B0s-B0s oscillations using Dsℓ events

Lifetime and oscillations of B0s mesons have been studied in events with a large transverse momentum lepton and a Ds of opposite electric charge in the same hemisphere, selected from about, 3.6 million hadronic Z0 decays accumulated by DELPHI between 1992 and 1995. The B0s lifetime and the fractional width difference between the two physical B0s states have been found to be: τB0s = (1.42+0.14-0.13(stat.) ± 0.03(syst.)) ps ΔΓB0s/ΓB0s &amp;lt; 0.46 at the 95% C.L. In the latter result it has been assumed that τB0s = τB0d. Using the same sample, a limit on the mass difference between the physical B0s states has been set: ΔmB0s &amp;gt; 7.4 ps-1 at the 95% C.L. with a corresponding sensitivity equal to 8.1 ps-1

Cross-sections and leptonic forward-backward asymmetries from the Z0 running of LEP

During 1993 and 1995 LEP was run at 3 energies near the Z0 peak in order to give improved measurements of the mass and width of the resonance. During 1994, LEP operated only at the Z0 peak. In total DELPHI accumulated data corresponding to an integrated luminosity of approximately 116 pb-1. Analyses of the hadronic cross-sections and of the cross-sections and forward-backward asymmetries in the leptonic channels used the most precise evaluations of the LEP energies. In the dimuon channel, events with a photon radiated from the initial state have been used to probe the cross-sections and asymmetries down to PETRA energies. Model independent fits to all DELPHI lineshape and asymmetry data from 1990 to 1995 have been carried out giving values of the resonance parameters: MZ = 91.1863 ± 0.0028 GeV ΓZ = 2.4876 ± 0.0041 GeV σ0 = 41.578 ± 0.069 nb R1 = 20.730 ± 0.060 AFB0 = 0.0187 ± 0.0019. These values are significantly more precise than those previously published. The results are interpreted in terms of the Standard Model

Searches for neutral Higgs bosons in e+e- collisions around √s = 189 GeV

Searches for neutral Higgs bosons in the Standard Model and the MSSM have been performed using data collected by the DELPHI experiment at a centre-of-mass energy of 188.7 GeV, corresponding to an integrated luminosity of 158 pb-1. These analyses are used, in combination with our results from lower energies, to set new 95% confidence level lower mass bounds on the Standard Model Higgs boson (94.6 GeV/c2) and on the lightest neutral scalar (82.6 GeV/c2) and neutral pseudoscalar (84.1 GeV/c2) Higgs bosons in a representative scan of the MSSM parameters. The results are also interpreted in the framework of a general two-Higgs doublet model