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X-Ray Computed Tomography and Nanomaterials as Contrast Agents for Tumor Diagnosis
Published in D. Sakthi Kumar, Aswathy Ravindran Girija, Bionanotechnology in Cancer, 2023
R. G. Aswathy, D. Sakthi Kumar
CT is based on the principle of X-ray [2]. For the generation of images based on X-rays, the X-rays penetrated through the body are either absorbed or attenuated at various intensities generating a profile or matrix of X-ray beams of different strengths. The X-ray profile is recorded on film, resulting in the development of an image. In CT imaging, a detector that quantifies the X-ray profile substitutes the film. CT is based on the density of tissue penetration by X-ray beam and its quantification from attenuation coefficient. Attenuation coefficient is determined by measuring how easily a material can be penetrated by the beam. It measures how much the beam is weakened by the material while it is penetrating through (attenuated). In CT, cross-sectional images (slices) of the body are generated and they are recreated from the attenuation coefficients of X-ray beams of the material under study. In CT, the X-ray emitter revolves around the subject and detector is positioned in diametrically opposite side of the emitter. Each time, the X-ray tube and detector make a 360° rotation around the object, the detector takes several shots (profiles) of the attenuated X-ray beam. To generate tomographic images from the data set in “raw” scan, the computer depends on complex mathematical algorithms for the reconstruction of image. Although images generated were in different planes, such as axial, transverse, or orthogonal, scanners reformat the data in many planes or as volumetric (3D) illustrations of the structures (Figure 6.1).
Understanding the Role of Existing Technology in the Fight Against COVID-19
Published in Ram Shringar Raw, Vishal Jain, Sanjoy Das, Meenakshi Sharma, Pandemic Detection and Analysis Through Smart Computing Technologies, 2022
CT also uses X-ray radiations like X-ray imaging, although the working principle is different in the two cases. In CT scans, cross-sectional images of the body are formed based on the X-ray interaction with the body. As stated earlier, the X-rays penetrate the body to different extent depending on the composition and density of the interacting material. While passing through a medium, all radiations tend to attenuate with distance. The attenuation coefficient defines the amount of radiations absorbed per unit thickness in a medium. The CT scans are constructed based on the measurement of the attenuation coefficients of the X-rays in the body. During a CT scan, the source and the detector are rotated around the body that results in capturing a 3D image of the interior rather than 2D image obtained in X-ray imaging. The image formation is done using complicated mathematical models.
Basic dosimetry and beam-quality characterization
Published in Gavin Poludniowski, Artur Omar, Pedro Andreo, Calculating X-ray Tube Spectra, 2022
Gavin Poludniowski, Artur Omar, Pedro Andreo
For a photon fluence Φ incident on a given target material of density ρ, the mean fraction of photons d interacting along a distance in the target defines the linear attenuation coefficient μ. Its unit is cm−1. The reciprocal of μ defines the mean free path or mean path length traversed by a photon between two consecutive interactions.1 As inferred from its definition, the linear attenuation coefficient depends strongly on the mass density of the material, a constraint removed by the mass attenuation coefficient, , which is defined as
Monte Carlo dosimetry using Fluka code and experimental dosimetry with Gafchromic EBT2 and XR-RV3 of self-built experimental setup for radiobiological studies with low-energy X-rays
Published in International Journal of Radiation Biology, 2020
Joanna Czub, Janusz Braziewicz, Adam Wasilewski, Anna Wysocka-Rabin, Paweł Wołowiec, Andrzej Wójcik
Effective energy was estimated by taking into account the first HVL (HVL1) value, using a method described by several authors (Khan and Gibbson 2014; Corrêa et al. 2016; Gotanda et al. 2016). In this procedure, the attenuation coefficient was calculated based on the Beer-Lambert law (Potts, 1992), which assume that when the thickness of the material is equal to HVL1, the subsequent radiation intensity is equal to half of the initial beam intensity (Khan and Gibbson 2014; Corrêa et al. 2016; Gotanda et al. 2016). The attenuation coefficient was then combined with the X-ray energy value using the dataset from (Hubbell and Seltzer 2004; Khan and Gibbson 2014; Corrêa et al. 2016; Gotanda et al. 2016). For this study, the effective energy calculated for HVL1=0.75 mmAl was 20 keV with a combined standard uncertainty equal to 0.1 keV. The combined standard uncertainties were calculated according to the instructions for (Joint Committee for Guides in Metrology [JCGM] 2008).
The interaction of gamma radiation with drugs used in cholinergic medications
Published in International Journal of Radiation Biology, 2020
Berna Oto, Gökhan Oto, Zekiye Madak, Esra Kavaz
When a material is exposed to photons, it is necessary to examine other important parameters that characterize the interaction of photons with the material. The mass attenuation coefficient (μρ), which characterizes the penetration effect of the photon radiation in the material, is a key parameter. μρ is used to calculate many other photon interaction parameters namely effective atomic number (Zeff) and electron densities (Nel). Zeff and Nel are remarkable parameters used to determine the radiation penetration of a multi-element material in medical radiation dosimetry. The values of Zeff provide precise information about the material which exposed to radiation and Zeff values of complex material are used in calculations of absorbed dose for radiotherapy (Aktas et al. 2019).
A case of carpal tunnel syndrome caused by giant gouty tophi: the usefulness of DECT for the diagnosis, preoperative planning and postoperative evaluation of atypical cases
Published in Modern Rheumatology Case Reports, 2019
Kazuhiro Maeda, Hiroyuki Chino, Tadashi Tokashiki, Jun Udaka, Yuya Okutsu, Mitsuhito Yukawa, Makoto Mitsuhashi, Naoya Inagaki, Hirofumi Osumi, Yuji Nagamine, Tetsuro Nishizawa, Tomohiro Kayama, Takeshi Fukuda, Kunihiko Fukuda, Hiroya Ojiri, Keishi Marumo
DECT is a CT method wherein a target is imaged with X-rays of two different energies. The technique of using the difference in the attenuation coefficient of each energy enables discrimination of materials. Discriminated materials can be colour-coded and overlaid onto CT images to assist the diagnosis and localization of the lesion [1,2]. The 2015 Gout Classification Criteria of the American College of Rheumatology-European League Against Rheumatism newly included ultrasound of the joint and DECT to the diagnostic criteria [10]. One advantage of DECT is that it enables visualization of the therapeutic effect for both surgical and conservative treatment. We found that DECT not only helps with the diagnosis of and surgical planning for atypical tophi but also is extremely useful for postoperative evaluation to determine whether the lesion was removed.