<p>Positron emission tomography scanners are commonly characterized by their photon sensitivity. Scanner design often requires Monte Carlo simulations to probe different geometries and materials. However, the computational load of such simulations can be significant and costly. Furthermore, the applicability of the Monte Carlo approach in optimization loops is limited as each instance, such as source position or scanner dimensions, has to be simulated independently.</p> <p>In this work, Monte Carlo results have been accurately replicated by an analytical model that uses characteristics of the foreseen cylindrical scanner and returns the sensitivity profile following NEMA guidelines. BGO and LYSO bulk materials and several metascintillator scenarios have been used. The mean absolute error (MAE), mean absolute percentage error (MAPE) and standard deviation of the error (SDE) are as low as 0.49%, 2.22% and 0.26% when no energy window is used, respectively. With an energy window applied, the analytical model presents the lowest values of MAE and SDE, with MAPE value being 8.19%. A normalization factor has been used to compensate for the scattered events included in the 350-650 keV window. This work facilitates significantly the development of cylindrical scanners, allowing direct probing of their axial sensitivity profiles.</p>
<p>Positron emission tomography scanners are commonly characterized by their photon sensitivity. Scanner design often requires Monte Carlo simulations to probe different geometries and materials. However, the computational load of such simulations can be significant and costly. Furthermore, the applicability of the Monte Carlo approach in optimization loops is limited as each instance, such as source position or scanner dimensions, has to be simulated independently.</p> <p>In this work, Monte Carlo results have been accurately replicated by an analytical model that uses characteristics of the foreseen cylindrical scanner and returns the sensitivity profile following NEMA guidelines. BGO and LYSO bulk materials and several metascintillator scenarios have been used. The mean absolute error (MAE), mean absolute percentage error (MAPE) and standard deviation of the error (SDE) are as low as 0.49%, 2.22% and 0.26% when no energy window is used, respectively. With an energy window applied, the analytical model presents the lowest values of MAE and SDE, with MAPE value being 8.19%. A normalization factor has been used to compensate for the scattered events included in the 350-650 keV window. This work facilitates significantly the development of cylindrical scanners, allowing direct probing of their axial sensitivity profiles.</p>
The capabilities of the personal computers allow the application of Monte Carlo methods to simulate very complex problems that involve the transport of particles through matter. Among the several codes commonly employed in nuclear physics problems, the GEANT4 has received great attention in the last years, mainly due to its flexibility and possibility to be improved by the users. Differently from other Monte Carlo codes, GEANT4 is a toolkit written in object oriented language (C++) that includes the mathematical engine of several physical processes, which are suitable to be employed in the transport of practically all types of particles and heavy ions. GEANT4 has also several tools to define materials, geometry, sources of radiation, beams of particles, electromagnetic fields, and graphical visualization of the experimental setup. After a brief description of the GEANT4 toolkit, this presentation reports investigations carried out by our group that involve simulations in the areas of dosimetry, nuclear instrumentation and medical physics. The physical processes available for photons, electrons, positrons and heavy ions were used in these simulations.
Traditionally, pulse processing in Positron Emission Tomography (PET) has been based on analog or discrete circuits forming a decentralized processing system. However, there is a convergence for digital and integrated implementations due to the characteristics of the modern electronic devices which are real-time processing capable, such as Application-Specific Integrated Circuit (ASIC) and Field Programmable Gate Array (FPGA) with fast Analog to Digital Converters (ADC). However, FPGA can provide fast implementation at relatively low cost and also enables the development of sophisticated digital pulse processing algorithms to improve energy, position and time resolutions in PET systems. Our group has developed and evaluated one energy calculation and three timing pick-off methods for implementation onto an FPGA-based system. For a typical PET detector setup, our charge integration method presents energy resolution similar to previously designed PET detectors. The best performance for timing pick-off was achieved by the Initial Rise Interpolation (IRI) method, where a coincidence time resolution of around 440 ps is suitable for Time of Flight (TOF) PET. Future works include embedding the proposed algorithms in a FPGA-based data acquisition system under development by our group which will be employed in a PET prototype.
<p>Recent trends in Positron Emission Tomography (PET) use the time-of-flight (ToF) information in the image reconstruction process to improve the signal-to-noise ratio and the positioning of the annihilation event. One of the components that most contributes to the accuracy of the ToF-PET is the scintillation crystal. The metascintillator approach has been proposed to overcome the time resolution limits of commonly used scintillators. The metascintillator is an engineered composition of small units that combines and optimizes several features in a single scintillator heterostructure. In this work, metascintillator-based brain PET systems were modeled using the GATE Monte Carlo toolkit and compared with designs based on bulk LYSO or BGO. Sensitivity, noise equivalent count rate and scatter fraction were evaluated following the NEMA guidelines. Only data in the list mode format was used for comparison purposes to avoid dependence on the image reconstruction algorithm. To achieve the same peak sensitivity of a system based on a 15 mm thick bulk BGO, the metascintillator-based scanners using BGO/BaF2 , BGO/EJ232, LYSO/BaF2 and LYSO/EJ232 must have thicknesses of 23.2 mm, 22.5 mm, 29.7 mm and 31.1 mm, respectively. The objective of this work is to determine the clinical value of using metascintillator-based detectors in brain PET.</p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.