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X-Ray-Computed Tomography: Implementation and Applications
Published in Richard A. Robb, Three-Dimensional Biomedical Imaging, 2017
where the variance, σ2(µ), due to noise in the reconstructed value of the linear attenuation coefficient at any given point in the body, is directly proportional to the “transmissivity”, T, of the subject (a general term which is the inverse of attenuation and incorporates the composition and distribution of tissues in the beam path), and is inversely proportional to the slice thickness, t, the cube of the attenuation element size, d, and the X-ray dose R. (k is the factor to convert from incident (skin) dose R to the absorbed dose at any given point.)
Advanced technologies for beam’s eye view imaging
Published in Ross I. Berbeco, Beam’s Eye View Imaging in Radiation Oncology, 2017
An alternative scintillator is sintered GOS which is commonly used in diagnostic CT detectors (van Eijk 2002). Breitback et al. (2011) studied ceramic GOS for imaging at 6 MV using a pixelated array of area 40 cm × 10 cm and thickness of 1.8 mm. A modest 2.5× sensitivity increase was achieved when compared to Cu-GOS performance. Although suitable for lower energy systems, the low-optical transmissivity of the ceramic material may restrict the construction of pixels with high aspect ratios as are required for high-energy applications.
A public-private partnership for the express development of antiviral leads: a perspective view
Published in Expert Opinion on Drug Discovery, 2021
The risk of emergent pandemic diseases falls into two categories: a) Seasonal highly infectious diseases with typically low mortality that mutate into more lethal strains, while retaining high transmissivity and b) highly lethal diseases gaining transmissivity, altering the tropisms and therefore – the propagation paths. The example of the category (a) are influenza, coronaviruses, measles. The example of highly lethal pathogens with non-air-born transmission is smallpox and/or hemorrhagic fevers. Fortunately, the pathogens of the path (b) were not observed so far, but the theoretical possibility of such shifts remains an open question. The currently known cases of air-born infections for the group (b) are observed only in artificial conditions or in confined spaces [12–15].
Bridging the gap between fundamental research and product development of long acting injectable PLGA microspheres
Published in Expert Opinion on Drug Delivery, 2022
Xun Li, Zhanpeng Zhang, Alan Harris, Lin Yang
PLGA microspheres can also be industrially prepared by phase separation method [87,88]. In the phase separation method, firstly, PLGA is dissolved in organic solvent, and then the encapsulated drug is suspended into the PLGA polymer phase. Subsequently, by adding the suitable non-solvent for PLGA with a specific rate, a liquid-liquid phase separation process is induced, causing the formation of a polymer-poor phase (Continuous phase) and a polymer-rich phase (Dispersed phase). With the solvent extraction and exchange, the drug gradually encapsulated into PLGA matrix. The formed microspheres are then mixed with a hardening agent for solidification process. After rinsing to remove adhering non-solvent or drug, the microparticles are then dried and sieved. The whole process of phase separation is low in energy input and easy to perform. PLGA microspheres with specific internal structures and morphologies can be achieved by optimizing the non-solvent type and solvent feeding rate [89,90]. Although in the past, there were commercial PLGA products which were prepared by the phase separation method, the lack of process robustness is still the major drawback, with a high tendency toward microsphere agglomeration upon transfer to the hardening bath [87]. Therefore, the critical process parameters, critical material attributes in phase separation method are still ambiguous which indicate that the in-process control and better understanding of the complex, multi-step is required. Recently, to increase lot-to-lot reproducibility, some studies used Crystalline® (Technobis Crystallization Systems, Netherlands) for monitoring the whole phase separation process which may occur in a short time window. With a camera installed perpendicular to the cell, images can be taken automatically every several seconds. The transmissivity of the sample can be measured continuously. Images can be analyzed with Image J to find out the time point of phase separation.