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Borate Phosphors for Radiation Dosimetery
Published in S. K. Omanwar, R. P. Sonekar, N. S. Bajaj, Borate Phosphors, 2022
Absorbed dose is the quantity that expresses the concentration of radiation energy absorbed at a specific point within the body tissue. Since an X-ray beam is attenuated by absorption as it passes through the body, all tissues within the beam will not absorb the same dose. The absorbed dose will be much greater for the tissues near the entrance surface than for those deeper within the body. Absorbed dose is defined as the quantity of radiation energy absorbed per unit mass of tissue.
Radiation Hazards
Published in Dag K. Brune, Christer Edling, Occupational Hazards in the Health Professions, 2020
The special unit of absorbed dose is the gray (abbreviated Gy): 1Gy=1J/kg(=100rad)
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
The absorbed dose cannot be measured directly, but it can be inferred from other measurable quantities. Radiation dosimetry involves methods developed to assess and control the doses delivered during therapeutic and diagnostic imaging procedures. For beam sources of radiation used in radiography and therapy, the exposure in roentgens can be measured directly, using an ionization detector. This then can be converted into an absorbed dose, using appropriate correction factors to go between the measured quantity (ionization of air) to the desired one (the absorbed dose). For imaging or therapy performed with radionuclides, the absorbed dose from a procedure (the dose commitment) must be computed from the administered source activity, half-life, and exposure time.
Everything you wanted to know about space radiation but were afraid to ask
Published in Journal of Environmental Science and Health, Part C, 2021
Jeffery Chancellor, Craig Nowadly, Jacqueline Williams, Serena Aunon-Chancellor, Megan Chesal, Jayme Looper, Wayne Newhauser
The biological effect of the radiation dose depends on physical and biological factors, e.g., multiple particle and energy-specific factors, dose rate per exposure and the frequency of multiple exposures. The (physical) absorbed dose is the energy absorbed per mass (J/Kg, Gy). For a dose-based system of radiation protection and for the determination of occupational dose limits, it is necessary to attempt summing the total risk of radiation from multiple sources (e.g., SPE protons, GCR, etc.).33 At a given ion velocity, LET increases with atomic number. Thus, for ground-based research, it is key to have the correct abundances and energy distributions of each ion present in the space radiation environment. As charged particles lose energy successively through material interactions, each energy loss event can result in damage to the biological tissue. In addition, as charged particles near the end of their track (i.e., as they slow down and are nearly stopped) the LET rises sharply, creating the so-called “Bragg peak”.34 This is demonstrated in Figure 3. The phenomenon of the Bragg peak is exploited in cancer therapy in order to concentrate the dose at the target tumor while minimizing impact to the surrounding tissue. This is demonstrated in Figure 3 where the relative dose deposition in tissue for various radiation types utilized in space radiobiology studies is plotted versus depth in tissue. The gray shaded area is the average width of a mouse model. Also shown are the average diameters of Yucatan mini-pigs and humans. Gamma and X-ray radiations deposit most of the energy at or near the surface, while in contrast, charged particles such as protons, carbon, iron, etc., have distinct Bragg peaks. In each example, the Bragg peak is located outside the body mass of the mouse, indicating the difficulty in replicating the relative organ dose distribution of a GCR exposure incurred by humans during spaceflight.
Radioactivity investigation of water and aerosols in Sharjah, United Arab Emirates
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Muhammad Zubair, Amrou Ismail, Hamad Mohammed, Sayed Azam, Ahmed Ishag
Absorbed dose is a physical dose quantity (D) representing the mean energy absorbed to matter per unit mass by ionizing radiation (Clemenin et al. 2012). The dose is calculated as:
Comprehensive strategies to minimize radiation exposure during Interventional electrophysiology procedures: state-of-the-art review
Published in Expert Review of Medical Devices, 2020
Miraj Desai, Omar Kahaly, Adil Aslam, Jonnie Saifa-Bonsu, Maham Usmani, Toshimasa Okabe, Muhammad R. Afzal, Mahmoud Houmsse
In order to properly recognize the detrimental effects of radiation exposure and minimizing these effects, it will be important to familiarize oneself with the definition and dose metrics that were highlighted by the Expert on Optimal Use of Ionizing Radiation in Cardiovascular Imaging-Best Practices for Safety and Effectiveness [2]. Absorbed dose is the amount of energy deposition per unit body mass. It is measured in grays (Gy).Effective dose is the measurement of the total body amount of radiation compared to potential risk of complications. It is measured in millisieverts (mSv). Effective dose >100 mSv will result in radiation complication including future development of cancer.ED50 is the median effective dose (ED50) of radiation to prevent from unwanted adverse effects of these procedures.ALARA (As Low As Reasonably Achievable) is a concept has been used to lower radiation exposure to prevent from accumulative long-term risk of cancer.Air kerma (AK) is the energy/dose delivered from an x-ray beam to a specific volume of air. KERMA stands for kinetic energy released per unit mass (of air). It is used clinically to estimate the energy/dose delivered to a specific point (typically skin surface) and is a measure of deterministic risk and absorbed dose. A point that is far from the radiation source will have a lower AK value, a point close to the radiation source will have a higher AK. It is measured in grays (Gy) [3,4].Dose-area product (DAP) is a measure of the total amount of x-ray energy delivered to the entire area being irradiated. Unlike AK, DAP does not vary with location, it is a clinical estimate of the total radiation dose delivered to the patient. DAP can be calculated by multiplying the average AK value in the irradiated field by the cross-sectional area of the x-ray beam. Thus, the units are Gy*cm2. DAP is also occasionally referred to as the kerma area product (KAP). DAP is a measure of stochastic risk and can be used to estimate effective doses and organ doses [3,4].