Intravascular Radiation Detectors to Detect Vulnerable Atheroma in the Coronary Arteries
Robert J. Gropler, David K. Glover, Albert J. Sinusas, Heinrich Taegtmeyer in Cardiovascular Molecular Imaging, 2007
Fabricating the radiation detector from materials optimized to sense charged particles rather than gamma or X-radiation makes the catheter insensitive to radioactivity concentrating outside the vessel. Charged particle radiation is emitted as a byproduct of nearly all radioactive decay, but is typically most abundant in radionuclides that decay by beta emission (either positrons or negatrons). Prototype catheters using a plastic scintillator mated to an optical fiber have been tested in the laboratory using the positron emitting radiopharmaceutical 18FDG. The catheter had sufficient sensitivity to detect lesions concentrating ~0.000001% of the typical 15 mCi dose of 18FDG. To increase the sensitivity and specificity of vulnerable plaque localization, multi-sensor catheters, capable of measuring several parameters simultaneously, are in development. Contemporaneous measurement of endothelial temperature (with a thermister), fluorescence emitted in proportion to local apoptosis (using optically labeled annexin), and glucose utilization (with 18FDG) with the same device, would enhance the likelihood of correct lesion characterization.
New Trends
Vlado Valković in Low Energy Particle Accelerator-Based Technologies and Their Applications, 2022
Now, however, about half of the population exposure is considered to originate from radon. This gaseous radioactive isotope is now recognized as being much more pervasive than previously acknowledged and a problem that was considered to be confined to special groups (such as uranium miners) has now confronted the community at large. Recognition that radon is more widespread than previously thought, along with a longstanding recognition of the biological effectiveness of alpha-particle radiation has led to estimates of significant numbers of human cancers being attributable to the alpha-particle irradiations from the breakdown of radon daughters. Such estimates are, however, fraught with considerable uncertainty and meaningful assessments of risk can only come about after a broad understanding of the biological effects of individual alpha particles over the LET range encompassed by the breakdown products of the radon daughters.
Micronutrients in Protecting Against Lethal Doses of Ionizing Radiation
Kedar N. Prasad in Micronutrients in Health and Disease, 2019
Ionizing radiation refers to photon energy that can knock out a negatively charged electron from the orbit of an atom, leaving it positively charged and thus creating an ion pair after every such interaction. The process of creating an ion pair is referred to as ionization. Ionization radiation has been divided into two categories, low energy transfer (LET) radiation and high LET radiation. The low LET radiation includes X-rays, gamma-rays, and beta-rays that cause cellular damage primarily (about two-third of damage) by generating free radicals during radiation exposure. The high LET radiation includes proton radiation, neutron radiation, alpha-particle radiation, and other heavy particle radiation that cause initial cellular damage primarily by ionization, while free radicals also play role in the progression of damage. High LET radiation is generally 5–20 times more effective than the low LET radiation in causing damage, depending upon the type of radiation and criteria of radiation injury. If radiation damage is not repaired, chronic inflammation sets in motion that releases additional free radicals, pro-inflammatory cytokines, complement proteins, and adhesion molecules, all of which are toxic to cells. Thus, increased oxidative stress and chronic inflammation together participate in the progression of acute and late effects of irradiation.
Construction and evaluation of an α-particle-irradiation exposure apparatus
Published in International Journal of Radiation Biology, 2021
Zacharenia Nikitaki, Evangelia Choulilitsa, Spyridon A. Kalospyros, Sofia Kaisaridi, Georgia I. Terzoudi, Mike Kokkoris, Alexandros G. Georgakilas
Ionizing radiation (IR) induces a variety of lesions in the DNA, like base or sugar damage, alkali-labile sites, single strand breaks (SSBs) and double-strand breaks (DSBs)-with the latter considered the most lethal ones. These lesions result from direct hit of the genetic molecule or indirectly due to free radicals attack (Georgakilas 2000; Boss 2014). Alpha particle radiation, characterized as a high LET -in contrast to low-LET X-rays- causes biological effects with less dependency on the dose rate or the cell cycle stage (NuPECC 2014). Additionally, the type of the DNA lesions caused by α- particles is less susceptible to the equivalent DNA repair mechanisms (NuPECC 2014). There is also plenty of evidence showing that IR and especially the high LET one such as α-particles, are capable of producing highly clustered (complex) DNA damage, which is closely connected to IR’s major lethal or mutagenic effects (Mavragani 2019). A cluster of lesions consisting of two or more types of damage in a small DNA region of a few base pairs, is widely considered to be more challenging to repair for the cell than individual lesions, and thus resulting in mutagenesis, genomic instability and cell death (Georgakilas 2013).
Role of DNA damage and repair in radiation cancer therapy: a current update and a look to the future
Published in International Journal of Radiation Biology, 2020
Jingya Liu, Kun Bi, Run Yang, Hongxia Li, Zacharenia Nikitaki, Li Chang
The most well-studied ionizing rays (photons) are the X- and γ-rays widely used for various technological or medical applications, as well as particle radiation like α particles, protons, carbon ions etc. Many years ago, it has been shown that 238Pu emitted α-particles (range of ∼20 μm; peak energy, 3.26 MeV; LET at the position of the cells, 121.4 keV/μm) induce presumably dense (clustered) DNA damage, complex genetic changes in irradiated human cells (Singleton et al. 2002). On the other hand, X- or γ- electromagnetic radiation, although causes ionizations quite easily, they are not so dense compared to those caused by particle radiation, but they are still destructive for any living matter, like cellular DNA (Sutherland et al. 2001, 2002). Steel, lead or concrete (or a combination) needs to be used for shielding electromagnetic IR. It is much more invasive than particle radiations and it poses a risk of external and internal exposure.
Isolation of the effects of alpha-related components from total effects of radium at low doses
Published in International Journal of Radiation Biology, 2022
Chandula Fernando, Soo Hyun Byun, Xiaopei Shi, Colin B. Seymour, Carmel E. Mothersill
At sub-lethal doses, survival greatly depends on repair mechanisms. Since the HaCaT cell line demonstrates hyper-radiosensitivity to acute gamma energy at low doses, high-LET alpha particle radiation may be able to produce sufficient genomic instability to induce radioresistance. In such instances, the ratio of biological damage caused by chronic alpha exposure is significantly lower compared with an equivalent dose of gamma energy alone, and as such a lower radiation weighting factor might be considered. However, while the CHSE-214 cell line demonstrates increased radioresistance to gamma energy, the concentrated nature of energy deposited causes increased lethality when exposed to alpha particles. These cases would suggest a higher radiation weighting factor, similar to what is currently recommended. Further study is required to isolate the effect of dose-rate at sub-lethal doses. In addition, further consideration is required to translate the observed in vitro results to in vivo effects.
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