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 data and allowing the development of reconstruction codes. At the same time the non-conventional design of AX-PET poses several challenges to the simulation and modeling tasks, mostly related to the light transport and distribution within the crystals and WLS strips, as well as the electronics readout. In this work we present a hybrid simulation tool based on an analytical model and a Monte-Carlo based description of the AX-PET demonstrator. It was extensively validated against experimental data, providing excellent agreement.
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http://dx.doi.org/10.1088/0031-9155/58/16/5495 | DOI Listing |
Cureus
December 2024
Department of Radiology, Aichi Medical University, Nagakute, JPN.
Purpose In linac-based stereotactic radiosurgery (SRS) utilizing a multileaf collimator (MLC) for brain metastases (BMs), a volumetric-modulated arc (VMA) technique is indispensable for generating a suitable dose distribution with efficient planning and delivery. However, the optimal calculation grid spacing (GS) and statistical uncertainty (SU) of the Monte Carlo algorithm for VMA optimization have yet to be determined. This planning study aimed to examine the impacts of GS and GU settings on VMA-based SRS planning and to find the optimal combination for templating.
View Article and Find Full Text PDFBackground: Uncertainty about optimal tranexamic acid (TXA) dosage has led to significant practice variation in hip arthroplasty. We aimed to identify the optimal i.v.
View Article and Find Full Text PDFAppl Radiat Isot
January 2025
Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Road, Hsinchu, 30013, Taiwan; Nuclear Science and Technology Development Center, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Road, Hsinchu, 30013, Taiwan. Electronic address:
In clinical boron neutron capture therapy (BNCT), the distribution of dose to a heterogeneous medium that is predicted by a treatment planning system (TPS) should be experimentally validated. A head phantom specifically developed for this purpose is described and demonstrated herein. The cylindrical phantom exhibits distinct regions made from four materials (polymethyl methacrylate, calcium phosphate, air, and boric acid) to approximate a head structure with explicitly defined skin, skull, and brain tissue with a cavity and tumor within.
View Article and Find Full Text PDFAppl Radiat Isot
January 2025
Department of Physics, Nuclear Physics and Techniques Team, Faculty of Science, Ibn Tofail University, Kenitra, Morocco.
Controlling the absorbed dose received by a target is a major challenge encountered during ionizing radiation applications. For experimentally measuring absorbed dose, dosimetric systems are used. On the other hand, in addition to experimental methods of dose measurement, there are other alternatives for calculating absorbed doses, these are numerical methods based on the Monte Carlo method which are very sophisticated and widely used throughout the world.
View Article and Find Full Text PDFBull Math Biol
January 2025
Section of Epidemiology, University of Copenhagen, Copenhagen, Denmark.
Using genetic data to infer evolutionary distances between molecular sequence pairs based on a Markov substitution model is a common procedure in phylogenetics, in particular for selecting a good starting tree to improve upon. Many evolutionary patterns can be accurately modelled using substitution models that are available in closed form, including the popular general time reversible model (GTR) for DNA data. For more complex biological phenomena, such as variations in lineage-specific evolutionary rates over time (heterotachy), other approaches such as the GTR with rate variation (GTR ) are required, but do not admit analytical solutions and do not automatically allow for likelihood calculations crucial for Bayesian analysis.
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