Search results for "computed tomography"
showing 10 items of 713 documents
Beta-delayed neutron emission from93?100Rb to excited states in the residual Sr isotopes
1982
Beta-delayed neutron emission from the precursors93–100Rb to excited states in the residual nuclei92–99Sr has been measured by means ofγ-ray and neutron spectroscopy. In general, considerable neutron feeding of excited final states is observed. The experimental branching ratios (P ) are compared to predictions from statistical model calculations. It is demonstrated that the main parameter affecting theP -values is the shape of theβ-strength function (S β). For several Rb isotopes hindrance, respectively enhancement of neutron branches to specific final states is observed giving evidence for the persistence of intermediate structure of the neutron-emitting states. By the example of98Rb it is…
The neutron long counter NERO for studies of neutron emission in the r-process
2010
Abstract The neutron long counter NERO was built at the National Superconducting Cyclotron Laboratory (NSCL), Michigan State University, for measuring β -delayed neutron-emission probabilities. The detector was designed to work in conjunction with a β -delay implantation station, so that β decays and β -delayed neutrons emitted from implanted nuclei can be measured simultaneously. The high efficiency of about 40%, for the range of energies of interest, along with the small background, are crucial for measuring β -delayed neutron emission branchings for neutron-rich r-process nuclei produced as low intensity fragmentation beams in in-flight separator facilities.
Preliminary assessment of the imaging capability of the YAP–(S)PET small animal scanner in neuroscience
2006
The new and fully engineered version of the YAP–(S)PET small animal scanner has been tested at the University of Mainz for preliminary assessment of its imaging capability for studies related to neuropharmacology and psychiatry. The main feature of the scanner is the capability to combine PET and SPECT techniques. It allows the development of new and interesting protocols for the investigation of many biological phenomena, more effectively than with PET or SPECT modalities alone. The scanner is made up of four detector heads, each one composed of a 4 � 4c m 2 of YAlO3:Ce (or YAP:Ce) matrix, and has a field of view (FOV) of 4 cm axially � 4c m + transaxially. In PET mode, the volume resoluti…
MONSTER: a TOF Spectrometer for beta-delayed Neutron Spectroscopy
2014
β-delayed neutron (DN) data, including emission probabilities, Pn, and energy spectrum, play an important role in our understanding of nuclear structure, nuclear astrophysics and nuclear technologies. A MOdular Neutron time-of-flight SpectromeTER (MONSTER) is being built for the measurement of the neutron energy spectra and branching ratios. The TOF spectrometer will consist of one hundred liquid scintillator cells covering a significant solid angle. The MONSTER design has been optimized by using Monte Carlo (MC) techniques. The response function of the MONSTER cell has been characterized with mono-energetic neutron beams and compared to dedicated MC simulations.
Estimating accidental coincidences for pixelated PET detectors and singles list-mode acquisition
2007
We have studied the validity of random estimation techniques for various low energy thresholds (LETs) and single list-mode data sets in small animal PET. While a LET below 255 keV helps to increase the sensitivity, it also results in an increase of random coincidences and inter-crystal scatter (ICS). The study is carried out for MADPET-II, a dual-layer positron emission tomography (PET) scanner prototype consisting of LSO crystals read out individually by APDs. The data are acquired in singles list-mode format, and coincidences are computed post-acquisition. To estimate randoms, we have used the delayed coincidence window method (DW), and the singles rate model (SR). Various phantoms were s…
The neutron binding energy in the neutron-rich nucleus93Sr
1980
The neutron binding energy in93Sr has been determined to (5230±6) keV from energy correspondences between levels defined by γ-ray transitions and β-delayed neutron emission.
Validation of the Monte Carlo Simulation of a Siemens Biograph mCT PET
2016
Geant4 Application for Tomography Emission (GATE) is a simulation platform based on GEANT4. It is designed to perform numerical simulations in medical imaging and radiotherapy. It is also used to simulate Emission Tomography (Positron Emission Tomography, PET and Single Photon Emission Computed Tomography, SPECT), Computed Tomography (CT) and Radiotherapy experiments. The purpose of this study is to validate a GATE model of the commercial PET/CT Siemens Biograph, the latest acquisition of the Clinical Hospital of Salamanca. The geometry of the system has been implemented in GATE, including the detector ring, the crystal blocks, the PMTs etc. Radionuclides for all measurements shall be \(^{1…
First coincidences in pre-clinical Compton camera prototype for medical imaging
2003
Abstract Compton collimated imaging may improve the detection of gamma rays emitted by radioisotopes used in single photon emission computed tomography (SPECT). We present a crude prototype consisting of a single 500 μm thick, 256 pad silicon detector with pad size of 1.4×1.4 mm 2 , combined with a 15×15×1 cm 3 NaI scintillator crystal coupled to a set of 20 photo multipliers. Emphasis is placed on the performance of the silicon detector and the associated read-out electronics, which has so far proved to be the most challenging part of the set-up. Results were obtained using the VATAGP3, 128 channel low-noise self-triggering ASIC as the silicon detector's front-end. The noise distribution (…
Enhancedγ-Ray Emission from Neutron Unbound States Populated inβDecay
2015
Total absorption spectroscopy is used to investigate the β-decay intensity to states above the neutron separation energy followed by γ-ray emission in (87,88)Br and (94)Rb. Accurate results are obtained thanks to a careful control of systematic errors. An unexpectedly large γ intensity is observed in all three cases extending well beyond the excitation energy region where neutron penetration is hindered by low neutron energy. The γ branching as a function of excitation energy is compared to Hauser-Feshbach model calculations. For (87)Br and (88)Br the γ branching reaches 57% and 20%, respectively, and could be explained as a nuclear structure effect. Some of the states populated in the daug…
High performance 3D CZT spectro-imager for BNCT-SPECT: preliminary characterization
2018
The National Institute of Nuclear Physics (INFN) is supporting the 3CaTS project with the aim of developing a new Single Photon Emission Computed Tomography (SPECT) system for real time 10 B therapeutic dose monitoring in the binary experimental hadron therapy called Boron Neutron Capture Therapy (BNCT). BNCT is a highly selective tumour treatment based on the neutron capture reaction 10 B(n,α) 7 Li. The secondary particles have a high LET with ranges in tissues of the order of 10 μm (thus less than the mean cell diameter of few tens μm). Targeting the 10 B delivery towards cancer, the released energy lethally damages only the malignant cells sparing the normal tissues, thus enabling a cell…