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Principles and Basic Concepts in Radiation Dosimetry
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
The unit of absorbed dose is the gray (Gy), which is equal to 1 Joule per kilogram (J kg−1). ICRU (2011) defines the energy imparted, ε, as the sum of all energy deposits (see later) in the volume.
Radiation Therapy and Radiation Safety in Medicine
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
A different unit, the absorbed dose (or dose), is used to measure the energy absorbed during radiation therapy and imaging procedures. It also gives a useful means for evaluating radiation safety levels. The absorbed dose characterizes how much energy was deposited into each kilogram of tissue exposed to ionizing radiation of any kind. (Note that the absorbed dose can be used to describe any type of ionizing radiation and it does not distinguish between different types of radiation.) The reason the mass of tissue is taken into account is that the absorbed dose measures how concentrated a dose was received: if a given number of gamma rays, for example, were concentrated into a tumor, then the dose is higher than if the same amount were spread throughout the entire body. There are two units for measuring absorbed dose: the gray and the rad. The gray (Gy) is equal to one joule of radiation energy per kilogram of body mass (1 J/kg). All doses mentioned in this chapter are given in Gy. To express the same dose in rads, a smaller unit of dose, multiply the dose in Gy by 100. For example, as an approximate rule of thumb, a 1-roentgen exposure to x-rays or gamma rays results in a dose of about 0.01 Gy (1 rad) to soft tissue.
Radiation safety in the cardiac catheterisation laboratory
Published in John Edward Boland, David W. M. Muller, Interventional Cardiology and Cardiac Catheterisation, 2019
Assessment of dose from radiation exposure is based on special dosimetric quantities that have been adopted by the system of radiological protection. The dosimetric quantities are designed to provide a system to quantify the relationship between radiation exposure or dose and radiation risk. Radiation dosimetry has a fundamental quantity called absorbed dose that is based on measurement of the energy deposited in organs and tissues of the human body.1 Radiation dose is then related to radiation risk by modifying the absorbed dose to account for the biological impact of different radiations and the sensitivity of organs and tissues to radiation.1 This modification process gives rise to equivalent dose and effective dose, which can be assessed from measured operational radiation quantities. These dose quantities are summarised as follows.
Dosimetry and uncertainty approaches for the million person study of low-dose radiation health effects: overview of the recommendations in NCRP Report No. 178
Published in International Journal of Radiation Biology, 2022
Lawrence T. Dauer, André Bouville, Richard E. Toohey, John D. Boice, Harold L. Beck, Keith F. Eckerman, Derek Hagemeyer, Richard W. Leggett, Michael T. Mumma, Bruce Napier, Kathy H. Pryor, Marvin Rosenstein, David A. Schauer, Sami Sherbini, Daniel O. Stram, James L. Thompson, John E. Till, R. Craig Yoder, Cary Zeitlin
Within the framework of an epidemiologic study evaluating the health effect attributed to a radiation dose, the quantity of interest is the annual absorbed dose to the organ or tissue (organ dose) that is assumed to be the origin of the radiation-induced cancer. For example, active bone-marrow dose is of interest if leukemia is the disease being considered in the epidemiologic study. Organ doses in most of the organs and tissues of the body can be calculated using relationships with measured or estimated personal dose equivalent [Hp(10)] values (in the case of external irradiation) or with unit of activity intakes of radionuclides (in the case of internal irradiation) that can be derived from ICRP publications. However, these relationships are not available for all organs and tissues of the body, so that a surrogate organ or tissue is sometimes used to estimate the organ dose to the organ or tissue that is assumed to be the origin of the radiation-induced cancer.
Using biodosimetry to enhance the public health response to a nuclear incident
Published in International Journal of Radiation Biology, 2021
L. K. Wathen, P. S. Eder, G. Horwith, R. L. Wallace
In a mass-casualty event, clinicians typically rely on various pieces of information for the management of patients. Estimates of absorbed dose can be made by various methods that may include external dosimetry that links location of a victim with levels of radiation in his or her immediate environment or biological dosimetry that uses laboratory results and clinical signs and symptoms for evaluations. A panel of global experts recommends that clinicians use as many methods of dose and predicting severity of ARS as they have to design treatment strategies (Dainiak et al. 2011). If one or more of the biodosimetry tests currently under investigation reach a high level of clinical maturity, perhaps the medical community will have additional individualized patient data to consider in a radiation response effort. Hopefully, in the future even newer strategies will be implemented that move beyond absorbed dose to more sophisticated predictive approaches to clinical outcomes (Port et al. 2019; Abend and Port 2018) and more innovative biodosimetry tools.
Occam’s broom and the dirty DSB: cytogenetic perspectives on cellular response to changes in track structure and ionization density
Published in International Journal of Radiation Biology, 2021
Most of the important biological effects associated with the exposure to ionizing radiations are mirrored by effects at the cytogenetic level. These include changes in biological response corresponding to changes in absorbed dose, dose rate, and radiation quality. To the extent this is true, the following discussion relating to the effects of LET on RBE for the production of chromosomal aberrations will also apply in general to the effects of principal concern. It has long been universally accepted that a (G1) chromosome is ‘uninemic’, meaning it is composed of a single strand of DNA, with antiparallel complementary strands running in a 3′→5′ direction from telomere to telomere. As such, it strains the imagination not to view exchange aberrations as being the products of two radiogenic DSBs coming together in an act of illicit recombination. In biophysical parlance, this general feature of exchange formation may be described as resulting from lesion-lesion interaction (henceforth called lesion-interaction). This idea finds harmony with well-known molecular mechanisms of DNA repair, specifically nonhomologous endjoining (NHEJ) (Cornforth 1998; Richardson and Jasin 2000a; Cornforth et al. 2017).