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In-Room Imaging Devices Used for Treatment
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Principles of operation: Compton electrons are produced in the 1.5 mm copper plate.The electrons produce light photons in the phosphor material. The phosphor materials that can be used include gadolinium oxysulphide (Gd2O2S) and thallium-doped caesium iodide (CsI:Tl). The screen is either glued using transparent glue or mechanically pressed onto the light sensor system.The light sensor detector pixels are comprised of photodiodes and thin-film transistors (TFTs) that are connected to the readout and scanning electronics. The diodes initially are at 5 V bias before irradiation. During irradiation, the TFTs are non-conducting; the light photons discharge the diodes. On readout, the TFTs are made conducting to recharge the diodes. The charging is carried out row by row, and the charge required to re-bias the diodes is proportional to the light reaching the photodiode.
Principles of Radiation Detection and Image Formation
Published in Ken Holmes, Marcus Elkington, Phil Harris, Clark's Essential Physics in Imaging for Radiographers, 2021
There are a few phosphors/scintillators that may be used by manufacturers, such as gadolinium oxisulphide (Gd2O2S) or caesium iodide (CsI). There are advantages and disadvantages with any scintillator, but generally speaking the materials are subclassified as being either structured or non-structured.
X-ray Vision: Diagnostic X-rays and CT Scans
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
While this basic process can indeed be used to create a radiograph, by itself photographic film is not especially sensitive to x-rays due to the low x-ray absorption in the thin layer of the photographic emulsion. However, the sensitivity can easily be increased by placing the film in proximity to one or two thin intensifying screens of fluorescent material, forming what is called a film–screen combination. In such a system, an x-ray photon hits an intensifying screen, which then emits visible photons; these visible photons finally hit and expose the film emulsion. Phosphors in the screens efficiently absorb x-rays and re-emit their energy as visible light (Figure 5.18a). For example, one 50-keV x-ray photon can be converted into roughly 2000 photons of visible light in this way. Because photographic film is much more sensitive to visible light than it is to x-rays, this means that the combined detection system registers a much higher fraction of the x-rays hitting it than would film alone. To improve the detection efficiency yet further, the x-ray film can be made with an emulsion on both sides. The entire system finally is encased in a light-tight cassette for handling.
Current and emerging pharmacotherapy for the treatment of childhood acute myeloid leukemia
Published in Expert Opinion on Pharmacotherapy, 2022
Branko Cuglievan, David McCall, Lindsay Robusto, M. Estela Mireles, Suzanne C. Gettys
Quizartinib (AC220) is a second-generation FLT3 inhibitor. Quizartinib provides greater potency and selectivity in vivo when compared with first-generation inhibitors and demonstrates nanomolar potency against FLT3-WT, c-KIT PDGFR, and RET [42]. Adult phase 1 and 2 studies of quizartinib in relapsed and refractory cases of AML showed the drug to be safe. A high rate of durable responses enabling resistant AML patients to be bridged to HSCT was also seen [43]. Since then, quizartinib has been explored in adults in combination with chemotherapy and hypomethylating agents. In pediatrics, The Therapeutic Advances in Childhood Leukemia/Lymphoma (TACL) consortium conducted a phase 1 study of quizartinib with cytarabine and etoposide in relapsed/refractory leukemias [44]. Quizartinib provided notorious efficacy and sustained phosphor-FLT3 inhibition without dose-limiting toxicity. Despite its effectiveness, quizartinib treatment is hindered by the development of resistance due to TKD mutations or activation of distinct signaling pathways. The open-label, multicenter, single-arm, phase 1/2 study (NCT03793478) will provide further data on this drug in pediatrics [45].
One small step in time, one giant leap for DMPK kind – a CRO perspective of the evolving core discipline of drug development
Published in Xenobiotica, 2022
John S. Kendrick, Colin Webber
Phosphor imaging technology has transformed QWBA studies by providing high-definition images of the distribution and related concentrations of drug-derived radioactivity within the organs and tissues of laboratory animals. It may be used to provide whole body distribution data for rodents and other smaller species or extended to larger species in a more focussed way to provide data specific to the dose site (e.g. for intra-articular doses) or other regions of interest. The related technique of microautoradiography (MARG) has also increased in popularity in the past decade and is used to generate data revealing the cellular localisation of radiolabeled material by overlaying a histological preparation (Figure 5), thereby providing greater insights into the cellular localisation of test item-derived radioactivity, which could support the mechanism of action assessment, or mechanism of downstream toxicity effects noted during development.
Steering light in fiber-optic medical devices: a patent review
Published in Expert Review of Medical Devices, 2022
Merle S. Losch, Famke Kardux, Jenny Dankelman, Benno H. W. Hendriks
Four patents describe cylindrical diffuser tip designs that generate light scattering by several reflection events within a volume surrounded by reflective surfaces [78,87–89]. A basic example is given by Henriksson [87]. This diffuser tip consists of two or more materials with different refractive indices. Therefore, there are at least two interfaces: one between the two materials and another between the outer material and the surrounding tissue. Light is reflected several times between these interfaces before refracting into the tissue. This results in a scattered light beam that leaves the diffuser tip in several directions, see Figure 3h. In addition, one of the reflective surfaces within the diffuser tip can also have a rough texture to increase light diffusion [78,89]. Kikuchi and Kobayashi [88] describe a special diffuser tip. In this device, light that is scattered in several reflection events passes through a phosphor layer before leaving the diffuser tip, generating photoluminescence in random directions.