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Medical Imaging Informatics
Published in Arvind Kumar Bansal, Javed Iqbal Khan, S. Kaisar Alam, Introduction to Computational Health Informatics, 2019
Arvind Kumar Bansal, Javed Iqbal Khan, S. Kaisar Alam
The PET scan uses liquid radionuclides such as 18F that contain a fast decay (110 minutes for 18F) radioactive isotope in a compound instead of oxygen and are absorbed into the cells like glucose. However, due to the absence of oxygen, metabolism does not progress further, and the radioactive isotope is trapped inside the cells until it decays. The radioactive material is traced to image the metabolic activity.
Special Problems of Internal Radioactive Materials
Published in George W. Casarett, Radiation Histopathology, 2019
Radioactive isotopes, with their nonuniform irradiation of lung tissue, including regions of high dose, appear to be more carcinogenic in lung than radiation from external sources. Similarly, alpha emitters appear to be more effective than beta emitters. Point sources of radiation have yielded relatively high incidence of lung carcinomas. Inhaled or intratracheally administered insoluble radionuclides are retained in the lungs longer than soluble radionuclides and therefore tend to be more effective in carcinogenesis of the lung.
Quantification in Nuclear Preclinical Imaging
Published in George C. Kagadis, Nancy L. Ford, Dimitrios N. Karnabatidis, George K. Loudos, Handbook of Small Animal Imaging, 2018
Due to their potential of being highly quantitative, this chapter focuses on nuclear imaging modalities. The underlying physical principle of the measurement is simple: every molecule labeled with a radioactive isotope emits some form of radiation. The emitted radiation may be detected directly in SPECT or indirectly via an intermediate process (annihilation) in PET. In nuclear imaging modalities, the acquisition process has no impact on the underlying processes of radioactive decay. Moreover, these isotopes are unlikely to be found in the body prior to injection, and gamma photons are likely to penetrate the object. During the scanning process, regions containing more radioactivity produce proportionally more photons, which may be detected by the scanner. So with these modalities, collected counts from a region used to produce images may be a linear function of the concentration of the tracer in the tissue, which greatly contributes to being quantitative. Moreover, these techniques are very sensitive compared to MRI and CT. From an imaging agent viewpoint, there is approximately 7–10 orders of magnitude difference between MRI and PET/SPECT sensitivity: while in the case of MRI 10−3–10−5 M concentration is necessary for detection, for nuclear techniques it is only 10−10–10−12 M (James and Gambhir 2012). As a result, only a small amount of tracer needs to be injected, which is unlikely to perturb the system.
Chromosome aberrations, micronucleus frequency, and catalase concentration in a population chronically exposed to high levels of radon
Published in International Journal of Radiation Biology, 2023
Dwi Ramadhani, Sofiati Purnami, Devita Tetriana, Irawan Sugoro, Viria Agesti Suvifan, Nastiti Rahadjeng, Septelia Inawati Wanandi, Heri Wibowo, Ikuo Kashiwakura, Tomisato Miura, Mukh Syaifudin
More than 60% of the total ionizing radiation a person gets each year can be attributed to natural sources; radon and its breakdown products account for more than 50% of these natural sources of radiation (Sinitsky and Druzhinin 2014). Radon, an odorless and colorless radioactive gas, is produced during the series of transformations in the uranium (U-238) decay chain. Specifically, radon (Rn-222) is the direct decay product of radium (Ra-226). As the decay chain continues, alpha (α) and beta (β) radioactive isotopes are produced. Alpha particles, have the ability to ionize and damage biomolecules in living cells (Walczak et al. 2019; Grzywa-Celińska et al. 2020). Ionizing radiation in the form of alpha particles can cause DNA damage, leading to double-strand DNA breaks and chromosomal aberrations (CA) (Robertson et al. 2013; Yanxiao et al. 2019). This type of radiation can also elicit damage to biomolecules (e.g. DNA, proteins, and lipids) indirectly by inducing the generation of reactive oxygen species (ROS). Several oxidant molecules are classified as ROS, including free radicals, such as superoxide (O2•–) and hydroxyl (OH•) radicals, and non-radical species, such as singlet oxygen (1O2) and hydrogen peroxide (H2O2). These highly reactive species are controlled by different mechanisms in the human body. One of them is the action of enzymatic antioxidants, such as superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) (Kuciel-Lewandowska et al. 2018).
Oral formulation of Prussian blue with improved efficacy for prophylactic use against thallium
Published in Drug Development and Industrial Pharmacy, 2023
Nidhi Sandal, Vivek Kumar, Pooja Sharma, Mahendra Yadav
Cs and Tl enters the body through ingestion, inhalation, or contaminated wound and distributed throughout the body. Once Cs or Tl enters the body, it closely follows potassium and is uniformly distributed throughout the system; with higher concentrations found in the liver, kidney, and skeletal muscles [5]. Cs and Tl are well absorbed orally and follow first-order kinetics during elimination. These ions are eliminated mainly through the kidneys and about 10% through fecal excretion [6,7]. The physiological half-life of Cs excretion in humans is 50–150 days and that of Tl is 10–12 days. The radioactive isotopes of these metal ions cause severe toxicity internally depending on the source of exposure and the degree of exposure. Internal contamination with these radioisotopes is extremely harmful even in very small amounts (in micrograms), although the strategy for removing these ions depends only on their chemical properties [8].
“They Are Invasive in Different Ways.”: Stakeholders’ Perceptions of the Invasiveness of Psychiatric Electroceutical Interventions
Published in AJOB Neuroscience, 2023
Robyn Bluhm, Marissa Cortright, Eric D. Achtyes, Laura Y. Cabrera
Further evidence that the distinction between invasive and noninvasive interventions has rhetorical power comes from Gaillard’s (2018) analysis of the way these terms are used to describe neurotechnologies in expert reports created by advisory bodies. He found that the boundary between invasive and noninvasive technologies can vary with context, including which technologies are being compared. For example, he found that positron emission tomography (PET) imaging is classified as noninvasive when it is compared with animal studies or with surgical procedures, but as invasive when it is compared with functional magnetic resonance imaging (fMRI), because the latter does not require the injection of radioactive isotopes. In the context of medical interventions, Cousins, Blencowe, and Blazeby (2019) found that the terms “surgery” and “interventional procedure” are used inconsistently in the literature, which also had implications for which procedures get counted as invasive.