Search results for "positron"
showing 10 items of 1346 documents
Positron detrapping from defects: A thermodynamic approach
1981
The rate of positron detrapping in thermal equilibrium from lattice defects has been calculated by relating it to the specific trapping rate. The results for vacancies, dislocations and surfaces each show a different temperature dependence for the escape rate. For vacancies a measure of the importance of the detrapping can be obtained from the ratio of the vacancy formation energy to the positron binding energy in the defect. The positronium desorption rate from a surface is also calculated and agreement with experimental results is found.
Positronen-Emissions-Tomographie zum präoperativen Staging des Ösophaguskarzinoms
2002
BACKGROUND AND OBJECTIVE Exact preoperative staging is a prerequisite for the indication as well as the choice of the appropriate operative technique for patients with esophageal carcinoma. In this prospective study we assessed whether positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) increases the accuracy of staging compared to standard computer tomography (CT) and leads to a different therapeutic approach. PATIENTS AND METHODS 30 patients (25 men, 5 women, median age 63 years) with histologically identified carcinoma of the esophagus (n =29) and the cardia (n = 1), respectively, were studied. All patients underwent FDG-PET imaging of the neck, chest, and abdomen as w…
Discovery and validation of small-molecule heat-shock protein 90 inhibitors through multimodality molecular imaging in living subjects.
2012
Up-regulation of the folding machinery of the heat-shock protein 90 (Hsp90) chaperone protein is crucial for cancer progression. The two Hsp90 isoforms (α and β) play different roles in response to chemotherapy. To identify isoform-selective inhibitors of Hsp90(α/β)/cochaperone p23 interactions, we developed a dual-luciferase (Renilla and Firefly) reporter system for high-throughput screening (HTS) and monitoring the efficacy of Hsp90 inhibitors in cell culture and live mice. HTS of a 30,176 small-molecule chemical library in cell culture identified a compound, N -(5-methylisoxazol-3-yl)-2-[4-(thiophen-2-yl)-6-(trifluoromethyl)pyrimidin-2-ylthio]acetamide (CP9), that binds to Hsp90(α/β) an…
72/74As-labeling of HPMA based polymers for long-term in vivo PET imaging
2010
Abstract In the context of molecular imaging, various polymers based on the clinically approved N-(2-hydroxypropyl)-methacrylamide (HPMA) have been radio-labeled using longer-living positron emitters 72As t1/2 = 26 h or 74As t1/2 = 17.8 d. This approach may lead to non-invasive determination of the long-term in vivo fate of polymers by PET (positron emission tomography). Presumably, the radio label itself will not strongly influence the polymer structure due to the fact that the used nuclide binds to already existing thiol moieties within the polymer structure. Thus, the use of additional charges or bulky groups can be avoided.
Comparison of basis functions for 3D PET reconstruction using a Monte Carlo system matrix.
2012
In emission tomography, iterative statistical methods are accepted as the reconstruction algorithms that achieve the best image quality. The accuracy of these methods relies partly on the quality of the system response matrix (SRM) that characterizes the scanner. The more physical phenomena included in the SRM, the higher the SRM quality, and therefore higher image quality is obtained from the reconstruction process. High-resolution small animal scanners contain as many as 103?104 small crystal pairs, while the field of view (FOV) is divided into hundreds of thousands of small voxels. These two characteristics have a significant impact on the number of elements to be calculated in the SRM. …
Precision electroweak measurements on the Z resonance
2005
We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLD experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, $\MZ$ and $\GZ$, and its couplings to fermions, for example the $\rho$ parameter and the effective electroweak mixing angle, are precisely measured. The number of light neutrino species is determined to be 2.9840…
Electroweak measurements in electron-positron collisions at W-boson-pair energies at LEP
2013
The ALEPH, DELPHI, L3, OPAL collaborations and LEP Electroweak Working Group.-- arXiv:1302.3415
Generator-based PET radiopharmaceuticals for molecular imaging of tumours: on the way to THERANOSTICS.
2011
Generator-derived radionuclides for PET/CT imaging are promising for optimizing targeted radiotherapy by an individual patient-based approach, applying pre-therapeutic evaluation, as well as dosimetric calculations, and for measuring treatment response after radionuclide therapy.
Normal and Abnormal Tissue Classification in Positron Emission Tomography Oncological Studies
2018
Positron Emission Tomography (PET) imaging is increasingly used in radiotherapy environment as well as for staging and assessing treatment response. The ability to classify PET tissues, as normal versus abnormal tissues, is crucial for medical analysis and interpretation. For this reason, a system for classifying PET area is implemented and validated. The proposed classification is carried out using k-nearest neighbor (KNN) method with the stratified K-Fold Cross-Validation strategy to enhance the classifier reliability. A dataset of eighty oncological patients are collected for system training and validation. For every patient, lesion (abnormal tissue) and background (normal tissue around …
Reconstrucción on-line con algoritmos Modo Lista para equipos PET de cristal continuo
2014
En la presente memoria se estudia la obtención on-line de imágenes PET en equipos de cristal continuo a partir de algoritmos de reconstrucción Modo Lista. Estos algoritmos presentan una característica fundamental para conseguir el objetivo deseado, a saber, la capacidad de iniciar la reconstrucción una vez que ha sido adquirido el primer evento. Además, como están orientados al cálculo de las probabilidades de emisión ad-hoc, resultan especialmente atractivos para equipos PET de cristal continuo, permitiendo hacer uso de las reducidas dimensiones en el pixelado virtual sobre el detector. Para llevar a cabo el estudio, se realizó inicialmente una adaptación de las normativas NEMA NU 2-2007 y…