Search results for "positron"

Evidence forB0→ρ0ρ0Decays and Implications for the Cabibbo-Kobayashi-Maskawa Angleα

2007

We search for the decays B(0) --> rho(0)rho(0), B(0) --> rho(0)f(0)(980), and B(0) --> f(0)(980)f(0)(980) in a sample of about 384 x 10(6) Upsilon(4S) --> BB[over] decays collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at Stanford Linear Accelerator Center. We find evidence for B(0) --> rho(0)rho(0) with 3.5 sigma significance and measure the branching fraction B = (1.07 +/- 0.33 +/- 0.19) x 10(-6) and longitudinal polarization fraction f(L) = 0.87 +/- 0.13 +/- 0.04, where the first uncertainty is statistical, and the second is systematic. The uncertainty on the Cabibbo-Kobayashi-Maskawa quark-mixing matrix unitarity angle alpha due to penguin contributio…

Do the Quark Masses Run? Extractingm¯b(mZ)from CERN LEP Data

1997

We present the first results of next-to-leading order QCD corrections to three-jet heavy quark production at the CERN ${e}^{+}{e}^{\ensuremath{-}}$ collider LEP including mass effects. Among other applications, this calculation can be used to extract the bottom-quark mass from LEP data and, therefore, to test the running of masses as predicted by QCD.

Dimensional reduction methods in QCD

1994

We apply the technique of dimensional reduction to massless quantum chromodynamics. It is shown that compared to conventional dimensional regularization methods calculations of radiative corrections at the one-loop level are less involved. We discuss the use of helicity methods within this framework and as an application we evaluate the one-loop corrections to the parity-violating cross sections and to the quark forwardbackward asymmetric polarization in\(e^ + e^ - \to V \to q\bar q(g)\). Finally, we demonstrate that further simplifications occur in the computation of structure functions including the parity-violating structure function in quark- and gluoninitiated electroproduction process…

Longitudinal contribution to the alignment polarization of quarks produced in e + e - -annihilation: an O (α s ) effect

1996

We calculate the longitudinal contribution to the alignment polarization Pl of quarks produced in e+e− annihilation. In the Standard Model, the longitudinal alignment polarization vanishes at the Born term level and thus receives its first non-zero contribution from the O(αs) tree graph process. We provide analytical and numerical results for the longitudinal alignment polarization of massless and massive quarks, in particular for the recently discovered top quark.

Impact of prompt gamma emission of 44Sc on quantification in preclinical and clinical PET systems

2021

Abstract 44Sc is an increasingly investigated positron emitter for use in positron emission tomography (PET) imaging. However, 44Sc is a non-pure positron emitter, since prompt photons are co-emitted during the decay process. This study investigates coincidence energy spectra of 44Sc and its impact on PET quantification on a preclinical and clinical PET system in comparison with 18F. The raw data of the coincidence events revealed characteristic differences comparing the photon energy distribution of 44Sc and 18F. Due to prompt gamma emission of 44Sc, activity recovery is underestimated on PET systems. However, clinical PET imaging of 44Sc with acceptable quantitative accuracy appears feasi…

A new method for radiochemical separation of arsenic from irradiated germanium oxide.

2005

Abstract Radioarsenic labelled radiopharmaceuticals could be a valuable asset to Positron Emission Tomography (PET). In particular, the long half-lives of 72 As ( T 1/2 =26 h) and 74 As ( T 1/2 =17.8 d) allow to investigate slow physiological or metabolical processes, like the enrichment and distribution of antibodies in tumor tissue. This work describes the direct production of no-carrier-added (nca) arsenic isotopes *As, with *=71, 72, 73, 74 or 77, the reaction to [*As]AsI 3 and its radiochemical separation from the irradiated solid germanium oxide via polystyrene-based solid-phase extraction. The germanium oxide target, irradiated at a cyclotron or a nuclear reactor, is dissolved in con…

Post-elution processing of 44Ti/44Sc generator-derived 44Sc for clinical application

2009

The (44)Ti/(44)Sc (T(1/2)(44)Ti=60a) generator provides cyclotron-independent access to positron-emitting (44)Sc (T(1/2)=3.97d) for PET imaging. This work aims to post-elution processing of initial (44)Sc generator eluates in order to reduce its volume, HCl concentration and remove the oxalate anions. The on-line adsorption of (44)Sc on cationic resin AG 50W-X8 (200-400 mesh, H(+)-form) is achieved with >98% efficacy. Subsequently, the purified (44)Sc is desorbed by using 3ml of 0.25M ammonium acetate (pH=4.0). The post-processing takes 10min. The overall yield of the post-processing reached 90%, which is referred to the (44)Sc obtained from the (44)Ti/(44)Sc generator. In addition to the c…

Joint image and motion reconstruction for PET using a B-spline motion model.

2012

We present a novel joint image and motion reconstruction method for PET. The method is based on gated data and reconstructs an image together with a motion function. The motion function can be used to transform the reconstructed image to any of the input gates. All available events (from all gates) are used in the reconstruction. The presented method uses a B-spline motion model, together with a novel motion regularization procedure that does not need a regularization parameter (which is usually extremely difficult to adjust). Several image and motion grid levels are used in order to reduce the reconstruction time. In a simulation study, the presented method is compared to a recently propos…

2017

In the context of radiopharmacy and molecular imaging, the concept of theranostics entails a therapy-accompanying diagnosis with the aim of a patient-specific treatment. Using the adequate diagnostic radiopharmaceutical, the disease and the state of the disease are verified for an individual patient. The other way around, it verifies that the radiopharmaceutical in hand represents a target-specific and selective molecule: the “best one” for that individual patient. Transforming diagnostic imaging into quantitative dosimetric information, the optimum radioactivity (expressed in maximum radiation dose to the target tissue and tolerable dose to healthy organs) of the adequate radiotherapeutica…

A fully automatic approach for multimodal PET and MR image segmentation in gamma knife treatment planning

2017

The aim of this study is to combine Biological Target Volume (BTV) segmentation and Gross Target Volume (GTV) segmentation in stereotactic neurosurgery.Our goal is to enhance Clinical Target Volume (CTV) definition, including metabolic and morphologic information, for treatment planning and patient follow-up.We propose a fully automatic approach for multimodal PET and MR image segmentation. This method is based on the Random Walker (RW) and Fuzzy C-Means clustering (FCM) algorithms. A total of 19 brain metastatic tumors, undergone stereotactic neuro-radiosurgery, were retrospectively analyzed. A framework for the evaluation of multimodal PET/MRI segmentation is presented, considering volume…