0000000000114076
AUTHOR
Werner Lustermann
A Demonstrator for a new Axial PET Concept
In PET imaging, improving sensitivity while maintaining very good spatial resolution is crucial. To achieve this goal, we propose a novel concept of PET scanner, with axially arranged crystals, providing a high sensitivity and a 3D reconstruction of the gamma interaction point. The trans-axial coordinate is given by the crystal hit, while the z coordinate is reconstructed by the weighted distribution of light escaping the crystal and entering into an array of Wave Length Shifting (WLS) strips interleaving the crystal layers. This novel configuration allows full identification of Compton interactions in the crystals that can be included in image reconstruction thus enhancing the sensitivity.…
Real-time computation of parameter fitting and image reconstruction using graphical processing units
Abstract In recent years graphical processing units (GPUs) have become a powerful tool in scientific computing. Their potential to speed up highly parallel applications brings the power of high performance computing to a wider range of users. However, programming these devices and integrating their use in existing applications is still a challenging task. In this paper we examined the potential of GPUs for two different applications. The first application, created at Paul Scherrer Institut (PSI), is used for parameter fitting during data analysis of μ SR (muon spin rotation, relaxation and resonance) experiments. The second application, developed at ETH, is used for PET (Positron Emission T…
The AX-PET demonstrator—Design, construction and characterization
Abstract Axial PET is a novel geometrical concept for Positron Emission Tomography (PET), based on layers of long scintillating crystals axially aligned with the bore axis. The axial coordinate is obtained from arrays of wavelength shifting (WLS) plastic strips placed orthogonally to the crystals. This article describes the design, construction and performance evaluation of a demonstrator set-up which consists of two identical detector modules, used in coincidence. Each module comprises 48 LYSO crystals of 100 mm length and 156 WLS strips. Crystals and strips are readout by Geiger-mode Avalanche Photo Diodes (G-APDs). The signals from the two modules are processed by fully analog front-end …
Performance of the AX-PET Demonstrator
The goal of the AX-PET project is to build and test a demonstrator for a high resolution, high sensitivity PET scanner, based on a novel geometrical concept of long axially oriented crystals. The demonstrator comprises two PET modules used in coincidence. The two modules have been constructed and characterized (both individually and in coincidence) in dedicated test setups, with point-like sources. Good performance in terms of energy, spatial and timing resolution have been demonstrated. First measurements with extended phantoms filled with FDG-radiotracers have been recently performed.
Development of a High Precision Axial 3-D PET for Brain Imaging
We describe a PET device based on a novel method to extract the coordinates of the interaction point of the 511keV γ rays from 100 mm long and thin LYSO (Lutetium Yttrium OxyorthoSilicate) scintillator bars, positioned axially in the tomograph. The coordinate along the hit crystal is measured by using a hodoscope of Wave Length Shifting (WLS) plastic strips mounted perpendicularly to each plane of scintillators. As photodetectors, new Geiger mode Avalanche PhotoDetectors (G-APDs) with integrated electronics are being used to detect both the hit crystal in a block (x and y coordinates) and the interaction point in the crystal (z coordinate) through the light escaping from the crystal and tra…
AX-PET: Concept, proof of principle and first results with phantoms
AX-PET is a novel PET concept based on long crystals axially arranged and orthogonal Wavelength shifter (WLS) strips, both individually readout by Geiger-mode Avalanche Photo Diodes (G-APD). Its design was conceived in order to reduce the parallax error and simultaneously improve spatial resolution and sensitivity. The assessment of the AX-PET concept and potential was carried out through a set of measurements comprising individual module characterizations and scans in coincidence mode of point-like and extended sources. The estimated energy and spatial resolutions from point-like measurements are R FWHM =11.6% (at 511 keV) and 1.7–1.9 mm (FWHM) respectively as measured with point-like sour…
Search forBs0→μ+μ−andB0→μ+μ−Decays with CDF II
A search has been performed for B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup -} and B{sup 0} {yields} {mu}{sup +}{mu}{sup -} decays using 7 fb{sup -1} of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron collider. The observed number of B{sup 0} candidates is consistent with background-only expectations and yields an upper limit on the branching fraction of {Beta}(B{sup 0} {yields} {mu}{sup +}{mu}{sup -}) < 6.0 x 10{sup -9} at 95% confidence level. We observe an excess of B{sub s}{sup 0} candidates. The probability that the background processes alone could produce such an excess or larger is 0.27%. The probability that the combination of background and the expe…
The AX-PET Concept: New Developments And Tomographic Imaging
The Axial PET (AX-PET) concept proposes a novel detection geometry for PET, based on layers of long scintillating crystals axially aligned with the bore axis. Arrays of wavelength shifting (WLS) strips are placed orthogonally and underneath the crystal layers; both crystals and strips are individually readout by G-APDs. The axial coordinate is obtained from the WLS signals by means of a Center-of-Gravity method combined with a cluster algorithm. This design allows spatial resolution and sensitivity to be decoupled and thus simultaneously optimized. In this work we present the latest results obtained with the 2-module AX-PET scanner prototype, which consists of 6 radial layers of 8 LYSO crys…
Observation of the rare B(s)(0) + decay from the combined analysis of CMS and LHCb data.
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported licence.-- et al.
A Monte-Carlo based model of the AX-PET demonstrator and its experimental validation
AX-PET is a novel PET detector based on axially oriented crystals and orthogonal wavelength shifter (WLS) strips, both individually read out by silicon photo-multipliers. Its design decouples sensitivity and spatial resolution, by reducing the parallax error due to the layered arrangement of the crystals. Additionally the granularity of AX-PET enhances the capability to track photons within the detector yielding a large fraction of inter-crystal scatter events. These events, if properly processed, can be included in the reconstruction stage further increasing the sensitivity. Its unique features require dedicated Monte-Carlo simulations, enabling the development of the device, interpreting …
AX-PET: A novel PET detector concept with full 3D reconstruction
We describe the concept and first experimental tests of a novel 3D axial Positron Emission Tomography (PET) geometry. It allows for a new way of measuring the interaction point in the detector with very high precision. It is based on a matrix of long Lutetium-Yttrium OxyorthoSilicate (LYSO) crystals oriented in the axial direction, each coupled to one Geiger Mode Avalanche Photodiode (G-APD) array. To derive the axial coordinate, Wave Length Shifter (WLS) strips are mounted orthogonally and interleaved between the crystals. The light from the WLS strips is read by custom-made G-APDs. The weighted mean of the signals in the WLS strips has proven to give very precise axial resolution. The ach…
Long axial crystals for PET applications: The AX-PET demonstrator and beyond
The usage of long, axially oriented scintillator crystals in a PET scanner has been shown by the AX-PET Demonstrator as a possible solution for a high resolution and high sensitivity PET detector. In the AX-PET implementation, arrays of wavelength shifting (WLS) strips, placed orthogonally behind every crystal layer, are used to define the axial coordinate. After extensive characterization measurements, the AX-PET Demonstrator has been successfully used for the reconstruction of several phantoms and a few rodents. Possible extensions of the AX-PET concept towards Time Of Flight capabilities have been investigated, using Philips digital SiPMs as alternative photodetector. Promising CRT value…
AX-PET: A novel PET concept with G-APD readout
Abstract The AX-PET collaboration has developed a novel concept for high resolution PET imaging to overcome some of the performance limitations of classical PET cameras, in particular the compromise between spatial resolution and sensitivity introduced by the parallax error. The detector consists of an arrangement of long LYSO scintillating crystals axially oriented around the field of view together with arrays of wave length shifter strips orthogonal to the crystals. This matrix allows a precise 3D measurement of the photon interaction point. This is valid both for photoelectric absorption at 511 keV and for Compton scattering down to deposited energies of about 100 keV. Crystals and WLS s…