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Principles behind Computed Tomography (CT)
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Mikael Gunnarsson, Kristina Ydström
With the exception of the two-layer detector that can separate two energies, no information is obtained on the energy of the absorbing photons with existing scintillation detectors. Research and development of semiconductor detectors with energy resolution for CT, so-called photon counters, is under development. By using different thresholds for the pulse readout, two or more energies can be determined. One of the challenges is managing and reading the high flow of photons, the so-called count rate. Potential benefits of photon counters are improved image contrast, increased contrast loading of iodine, reduction of beam-hardening artefacts, improved resolution, and elimination of electronic noise.
Radiation Protection of Staff and the Public
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Mike Rosenbloom, W. P. M. Mayles
It is important that after installation, a full survey is conducted to verify the design calculations and to ensure that builders have followed instructions.* The first step in this process is to choose the correct survey instrument. In the case of linear accelerators*, the pulsed nature of the radiation can give erroneous results with equipment such as Geiger–Müller tubes that count photons, in contrast to ionisation-based instruments that measure charge (see Section 16.2.2). Scintillation detectors can be used, provided that their response to pulsed radiation is verified. Radiation monitoring badges using thermoluminescent dosimeters (TLDs) (see Section 17.2) or Al2O3 (see Section 17.5) can be used for longer-term environmental surveys. Neutron measurements will be needed if the energy of the machine is above 8 MeV.
Nuclear Medicine Imaging and Therapy
Published in Debbie Peet, Emma Chung, Practical Medical Physics, 2021
David Towey, Lisa Rowley, Debbie Peet
Scintillation Crystal: It is a Sodium Iodide crystal, doped with thallium. Incident gamma photons excite electrons in the crystal, causing scintillation. Scintillation photons are then detected and amplified by photomultiplier tubes (PMTs). Solid-state cameras are becoming increasingly common but are generally more expensive than scintillation detectors.
Prostate-specific membrane antigen-directed imaging and radioguided surgery with single-photon emission computed tomography: state of the art and future outlook
Published in Expert Review of Medical Devices, 2022
Luca Filippi, Barbara Palumbo, Viviana Frantellizzi, Susanna Nuvoli, Giuseppe De Vincentis, Angela Spanu, Orazio Schillaci
As the present paper is focused on gamma-emitting PSMA-targeting tracers, we briefly describe the main characteristics of the two types of handheld devices employed as gamma-probes: the scintillation and the semiconductor-ionization detectors [28]. Scintillation probes are made up of some components: scintillation crystal – most commonly, thallium-activated sodium iodide/NaI(Tl) -, a light guide, a photomultiplier tube (PMT) and associated electronic: incident photon is absorbed by the scintillator crystal, producing visible light that, in its turn, is converted into electric pulse by the PMT. In the semiconductor-ionization detector-based probes, the main components are: semiconductor crystal, a pre-amplifier and its associated electronic; in this type of gamma-probes, incident photons determine ionization in the semiconductor crystal producing free electrons that are collected as electric pulse. It is still an open debate which type of intraoperative probe (scintillation vs semiconductor ones) performs better: while semiconductor probes, in fact, are generally characterized by higher energy and spatial resolution, scintillation detectors present higher sensitivity, especially for high and medium-energy photons [29,30].
Preparation and characterization of bee venom-loaded PLGA particles for sustained release
Published in Pharmaceutical Development and Technology, 2018
Min-Ho Park, Hye-Suk Jun, Jong-Woon Jeon, Jin-Kyu Park, Bong-Joo Lee, Guk-Hyun Suh, Jeong-Sook Park, Cheong-Weon Cho
FT-IR spectroscopy was conducted using a Thermo Nicolet 380 Spectrophotometer and the spectrum was recorded in the wavelength region of 4000 to 500 cm−1. The procedure consisted of dispersing the samples in potassium bromide and compressing them into discs by applying pressure. The pellet was placed in the light path and the spectrum was obtained. In order to assess changes in the solid state, DSC was performed on the bee venom-loaded PLGA particles. Weighed samples (2 mg) were analyzed in aluminum pans on a differential scanning calorimeter (DSC S-650; SCINCO, Daejeon, Korea). DSC was conducted from 20 to 250 °C and backwards at a rate of 10 °C/min. The change of crystallinity was observed by XRD, using a D8 DISCOVER (Bruker AXS, Karlsruhe, Germany) with Cu radiation. A dynamic scintillation detector was used as the detector system. Data were collected over an angular range comprised between 5° and 80°, with a step size of 0.01°.
Characterization, kinetics and thermodynamics of biosynthesized uranium nanoparticles (UNPs)
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Mervate Aly Abostate, Youssry Saleh, Hamed Mira, Maysa Amin, Maha Al Kazindar, Basma Mahmoud Ahmed
The contents of the main radio elements; U, Th, Ra (ppm) and K (%) in the collected samples were radiometrically determined using high-efficiency multichannel analyzer of gamma-ray spectrometry with sodium iodine detector. The system consists of Bicron Scintillation detector, NaI (Tl) crystal 76 × 76 mm, hermatically sealed with a photomultiplier tube in aluminum housing, which manufactured by Saint-Gobain Crystals and Detectors. The detector is protected by a copper cylindrical protection (0.6 cm thickness) against induced X-ray and the chamber of lead bricks against the environmental radiations and then the detector is covered by a lead shield (5 cm thickness). It is connected with Nuclear Enterprises main shaping amplifier, Model NE-4658, and tennelec high-voltage power supply, Model, TC 952 with HV digital display. It is also connected with Nucleas PCA-8000 computer, 8192 multichannel analyzer with color graphical display of spectra and high-level technical operation features and Epson LX-80 printer. This technique of γ-ray spectrometry is characterized by high-efficiency but low resolving power relative to the HP-Ge detector. It is used for measurement of concentration of four radionuclides U, Th, Ra and K by measuring the activity of γ-rays emitted from these radionuclides and their daughters. Reference standard samples have been provided by International Atomic Energy Agency (IEAE) [15].