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Basic dosimetry and beam-quality characterization
Published in Gavin Poludniowski, Artur Omar, Pedro Andreo, Calculating X-ray Tube Spectra, 2022
Gavin Poludniowski, Artur Omar, Pedro Andreo
The first half-value layer in aluminium or copper is probably the most widely used single x-ray beam quality specifier, frequently shortened to half-value layer. It has been shown, however, that x-ray beams generated with different tube potential and/or filtration may have the same HVL, rendering the use of this single parameter non-rigorous. Illustrative examples are shown in ref. [65] and in ICRU Report 74 [66]. The latter suggests using the combination of tube potential, HVL1 and HVL2, which is equivalent to including the homogeneity index in the beam quality specification given as the triplet (kV, HVL1, ), although for most practical dosimetry purposes the pair (kV, HVL1) is suitable for the beam quality specification of x-ray beams.
Reference Dose Determination under Reference Conditions
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Yet another difference lies in the way that kilovoltage beam quality is specified. This is done in terms of the half-value layer (HVL) (see Section 22.2.2), generally expressed in millimetres of aluminium or, at the top end of the energy range, copper. The HVL is that thickness of material that reduces the air kerma to half its value. It must be measured in narrow-beam geometry to eliminate the influence of photon scatter generated in the attenuating material (see Figure 22.4). Beams with widely differing generating potentials can have similar HVLs because of the marked effect of different filtrations (e.g. Knight and Nahum 1994 and Table 22.1). The user must measure the HVL of the clinical beam and then select the NK value for the calibrated chamber for that beam using the calibration curve supplied by the SDL.
California Radiation Control Regulations: Responsibility of the Supervisor and Operator
Published in Robert J. Parelli, Principles of Fluoroscopic Image Intensification and Television Systems, 2020
Half value layer is used in two different situations:Determining; the barrier thickness, which is the amount of shielding: needed to attenuate radiation to the required degree.Determining the quality that is the average penetrating ability of an x-ray beam.
Investigation of neutron and gamma radiation protective characteristics of synthesized quinoline derivatives
Published in International Journal of Radiation Biology, 2020
Bünyamin Aygün, Burak Alaylar, Kadir Turhan, Erdem Şakar, Mehmet Karadayı, Mohammed Ibrahim Abu Al-Sayyed, Emel Pelit, Medine Güllüce, Abdulhalik Karabulut, Zuhal Turgut, Bünyamin Alım
Radiation is widely used for energy production (power plant), in research applications, in the research and treatment of many diseases with nuclear medicine. Radiation leakage can be emitted from radioactive waste released into the environment during radiation use or as a result of a nuclear accident and war. These wastes can enter the tissues or cells. These radioactive wastes emit continuous radiation, causing great damage to these tissues and cells (Painuli and Kumar 2016). It has destructive effects on living things according to the sort of radiation, its energy, and the exposed dose rate. When radiation enters the human body, it interacts with tissues and cells and either completely loses its energy or produce secondary radiation (WHO 2016). Absorption of this radiated radiation by an agent is one of the most effective methods (Costa et al. 2014). These events can be estimated by shielding parameters such as effective interaction cross section (cm−1), mean free path (MFP), number of transmissions, and absorbed dose rate for neutron radiation (Aygün 2020). In addition to neutron radiation shielding characteristic must be determined for gamma radiation; half value layer (cm), MFP, mass attenuation coefficient (µ/ρ), linear attenuation coefficient (µ) and effective atomic numbers (Zeff) (Sayyed et al. 2018; Oto et al. 2020). There are three effective ways to prevent radiation damage to cells and tissues: First, protectors are the agents given before the radiation effect; the latter are attenuators, which are administered in or after an applied radiation treatment, before toxicity; the third one is the repairers given for the purpose of treatment after the damage.
Monte Carlo dosimetry using Fluka code and experimental dosimetry with Gafchromic EBT2 and XR-RV3 of self-built experimental setup for radiobiological studies with low-energy X-rays
Published in International Journal of Radiation Biology, 2020
Joanna Czub, Janusz Braziewicz, Adam Wasilewski, Anna Wysocka-Rabin, Paweł Wołowiec, Andrzej Wójcik
In the dose estimation process, it is important to determine half value layer (HVL). The HVL is the first, basic and key parameter that should be estimated for a newly constructed experimental system. This value is necessary to calibrate any detector and it can then be used in the dosimetry process (Hill et al. 2014). Usually, the calibration process is done by Secondary Standards Laboratory (SSL) in terms of kerma or absorbed dose (Hill et al. 2014; Iba 2015). Effective energy is the second essential factor to describe a fully experimental setup (Gotanda et al. 2016). In addition, Ma et al. (2001) showed that HVL values can have different numbers depending on the absorbent material, which was set at a standard distance of 50 cm from the X-ray tube during HVL measurement. Although aluminum is the most common substance that is used as an absorbent in measurements of HVL value, especially for low energy X-rays, but sometimes copper is also applied, mainly for high energy photons (IAEA 2009) and usually above 100 kV in the X-ray tube (Ma et al. 2001). The HVL values also depend on the energy of the X-ray beam (Saha 2013). The calculation of HVL values in this study had two aims. The first intention was to prepare a newly built experimental system to start the experimental dosimetry process, where the first step is the calibration of the detector by SSL. The second purpose was to compare the HVL values obtained by means of different detectors. To achieve these goals, four types of detectors were used. In addition, HVL values were determined for X-ray beam both with and without additional filtration. The HVL values and effective energies are new information for the low energy X-ray experimental system that is placed at Jan Kochanowski University in Kielce, Poland.