Chapter

Efeitos biológicos e proteção contra radiações ionizantes

March 2023

In book: Radiologia e Imaginologia Odontológica (pp.55-64)
Edition: 1
Chapter: 4
Publisher: SAGAH, 2022

Authors:

Cesar Augusto Viana de Araujo

Faculdade IDOR de Ciências Médicas

Entre o final do século XIX e o início do XX foi o período em que a humanidade conheceu as radiações. A descoberta dos raios X (1895) pelo físico alemão Wilhelm Conrad Röentgen, a radioatividade por Henri Becquerel (1896), o rádio pelo famoso casal Curie (1898) e as partículas alfa e beta por Ernest Rutherford (1902) são exemplos de como as radiações ficaram mais próximas da sociedade (LIMA; PIMENTEL; AFONSO, 2011). Desde então, podemos observar o uso das radiações nas mais diversas áreas como na medicina, na odontologia, na veterinária, na indústria e na agricultura, por exemplo. Neste capítulo, você vai estudar sobre a radioatividade e como diferenciar as radiações ionizantes das não ionizantes. Além disso, você vai conhecer os efeitos da interação da radiação com a matéria e as formas de proteção radiológica.

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Estimation of relative biological effectiveness of Ac compared to Lu during [Ac]Ac-PSMA and [Lu]Lu-P...

September 2023 · EJNMMI Physics

Aim Over recent years, [²²⁵Ac]Ac-PSMA and [¹⁷⁷Lu]Lu-PSMA radiopharmaceutical therapy have evolved as a promising treatment option for advanced prostate cancer. Especially for alpha particle emitter treatments, there is still a need for improving dosimetry, which requires accurate values of relative biological effectiveness (RBE). To achieve that, consideration of DNA damages in the cell nucleus ... [Show full abstract] and knowledge of the energy deposition in the location of the DNA at the nanometer scale are required. Monte Carlo particle track structure simulations provide access to interactions at this level. The aim of this study was to estimate the RBE of ²²⁵Ac compared to ¹⁷⁷Lu. The initial damage distribution after radionuclide decay and the residual damage after DNA repair were considered. Methods This study employed the TOol for PArtcile Simulation (TOPAS) based on the Geant4 simulation toolkit. Simulation of the nuclear DNA and damage scoring were performed using the TOPAS-nBio extension of TOPAS. DNA repair was modeled utilizing the Python-based program MEDRAS (Mechanistic DNA Repair and Survival). Five different cell geometries of equal volume and two radionuclide internalization assumptions as well as two cell arrangement scenarios were investigated. The radionuclide activity (number of source points) was adopted based on SPECT images of patients undergoing the above-mentioned therapies. Results Based on the simulated dose–effect curves, the RBE of ²²⁵Ac compared to ¹⁷⁷Lu was determined in a wide range of absorbed doses to the nucleus. In the case of spherical geometry, 3D cell arrangement and full radionuclide internalization, the RBE based on the initial damage had a constant value of approximately 2.14. Accounting for damage repair resulted in RBE values ranging between 9.38 and 1.46 for ²²⁵Ac absorbed doses to the nucleus between 0 and 50 Gy, respectively. Conclusion In this work, the consideration of DNA repair of the damage from [²²⁵Ac]Ac-PSMA and [¹⁷⁷Lu]Lu-PSMA revealed a dose dependency of the RBE. Hence, this work suggested that DNA repair is an important aspect to understand response to different radiation qualities.

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September 2023 · EJNMMI Radiopharmacy and Chemistry

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Diamond-like carbon generation from graphene oxide by ion irradiation

August 2023 · Applied Physics A

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First measurement of discrimination between helium and electron recoils in liquid xenon for low-mass...

August 2023

We report the first measurement of discrimination between low-energy helium recoils and electron recoils in liquid xenon. This result is relevant to proposed low-mass dark matter searches which seek to dissolve light target nuclei in the active volume of liquid-xenon time projection chambers. Low-energy helium recoils were produced by degrading $\alpha$ particles from $^{210}$Po with a gold foil ... [Show full abstract] situated on the cathode of a liquid xenon time-projection chamber. The resulting population of helium recoil events is well separated from electron recoils and is also offset from the expected position of xenon nuclear recoil events.

Last Updated: 02 Apr 2023