Radiation Detection and Measurement
Shaheen A. Dewji, Nolan E. Hertel in Advanced Radiation Protection Dosimetry, 2019
Area monitoring is a basically different operation from individual monitoring. The purpose of area monitoring is to determine the exposure rate or dose equivalent rate at a place that may be occupied by a worker or other individual. This value is taken to represent the radiation intensity that could be received when a person is present. Its value will be posted at the entrance to an area where radiation may be present or may be produced, for example, by a radiation-generating device. The area monitored can also be much larger than a specific work area. Environmental monitoring may consist of measuring the dose equivalent rates in areas surrounding a nuclear power plant. Passive devices such as thermoluminescent dosimeters (TLDs) may be used for this purpose, along with active electronic instruments, such as high-sensitivity pressurized ionization chambers.
Artifacts
Pim J de Feyter, Gabriel P Krestin, Filippo Cademartiri, Carlos van Mieghem, Bob Meijboom, Nico Mollet, Koen Nieman, Denise Vrouenraets in Computed Tomography of the Coronary Arteries, 2008
The degree of contrast to differentiate between tissues with varying attenuation characteristics is defined as contrast resolution (Figure 22.3). Because CT has a much better contrast resolution than conventional radiography, tissues with only very small differences in density can be distinguished. The contrast resolution is affected by a number of fixed factors such as the detector sensitivity and patient size. Factors that can be influenced include the radiation intensity (the X-ray tube’s current and voltage), slice thickness, reconstruction filtering, and image noise. Additionally, the display of the tissue contrast is affected by the window settings. The display size and the distance between the observer and the screen influence the perception of contrast resolution. Image noise, which is the fluctuation of the measurement compared with the nominal density, affects contrast resolution. The amount of noise is related to a number of the factors mentioned above, including the radiation intensity, the slice thickness, and detector size.
Basics of Radiation and Radiotherapy
Prakash Srinivasan Timiri Shanmugam in Understanding Cancer Therapies, 2018
IMRT is an advanced mode of 3D conformal radiotherapy. It uses specialized software and computer-controlled x-ray accelerators to model the intensity of radiation delivered to the treatment volume. Treatment is planned by using 3D computed tomography (CT) images of the patient, followed by dose calculations to choose the radiation intensity pattern that will best cover the tumor shape. The shaping is achieved by combinations of several intensity-modulated fields coming from different beam directions. Because the dose delivered to normal tissue is significantly lower in comparison to conventional techniques, markedly higher and therefore more effective doses can be delivered to treatment volume with fewer side effects.
1,25-Dihydroxvitamin D3 attenuates the damage of human immortalised keratinocytes caused by Ultraviolet-B
Published in Cutaneous and Ocular Toxicology, 2023
Pingwei Wang, Dongge Liu, Jiajing Cui, Shuqi Yan, Yujun Liang, Qianqian Chen, Yanping Liu, Shuping Ren, Peng Chen
The HaCaT cells were plated in a 96-well plate with each well of 5 × 104 cells and cultured for 24h, aspirate the old culture solution, add PBS to wash the cells two times, add 20 μl of PBS to each well, move the cells to the UV lamp, open the lid of the 96-well plate, and then the cells were irradiated with UVB at the intensity of 5, 10, 20, 25, 30, 35, 40, 45 mJ/cm2, each intensity triple wells. Each different radiation dose is separately set with a 96-well plate for radiation to prevent mutual interference between different radiation dose groups. After irradiation, the cells were washed with PBS, then the cells were cultured in DMEM, 10 μL CCK-8 was added to the cells and incubated for 1h at 37 °C. The absorbance was determined at 450 nm wavelength. The viability of cells was calculated and the intensity of UVB was selected for the irradiation of the cells. (According to the calculation formula: radiation dose = radiation intensity × irradiation time, set the irradiation intensity to 220μw/cm2, according to 1 J = 2.778 × 10−7×kw × h. The irradiation time can be calculated for different UVB irradiation dose groups.)
New approach of controlling the area affected in brain tumour treatment by LITT
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Sadegh Amini, Hossein Ahmadikia
In order to compute laser intensity distribution in the medium, it is necessary to solve photon transportation Equation (Niemz 2007). This equation is solved by a discrete ordinate method in order to gain photon distribution in the tissue. Integral-differential form of Equation (1) is solved by numerical methods to gain radiation intensity I, in position r and direction Ω. C, t, μt, μs and f are light speed in the medium, time, attenuation factor, scattering factor and frequency, respectively (Niemz 2007). Two left terms are change of radiation intensity in the small volume element of tissue. The first term on the right hand of the equation is amount of light that is absorbed or scattered by tissue and it reduces the light power. The second term on the right hand side states the amount of light, which is scattered from other direction (such as Ω′) into the Ω direction. The last term is a light source term such as florescence. In order to compute absorbed density of energy per unit volume of tissue, it is necessary to sum radiation in all directions in the whole tumor: Equation (3) is solved and temperature distribution in the tissue will be obtained.
Areca nut procyanidins prevent ultraviolet light B-induced photoaging via suppression of cyclooxygenase-2 and matrix metalloproteinases in mouse skin
Published in Drug and Chemical Toxicology, 2022
Chia-Ling Weng, Chih-Chiang Chen, Han-Hsing Tsou, Tsung-Yun Liu, Hsiang-Tsui Wang
UVB irradiation was performed based on a previously described method with several modifications (Park et al.2006). Briefly, mice were randomly divided into the blank control group, UVB group, EGCG + UVB group, ANP 10 (10 mg/kg) + UVB group or ANP 20 (20 mg/kg) + UVB group. The hair growth cycle is generally recognized to comprise phases of growth (anagen), regression (catagen), and rest (telogen) (Stenn et al.1996). To make sure hair did not influence the UVB irradiation, hair from all mouse groups was synchronized for 24 d. First, mice were deeply anesthetized with Zoletil 50 and Rompun (4:1, v/v) and waxed to remove all back hair. After 24 d, hair had grown back and entered the telogen phase in all groups. After that, EGCG (20 mg/kg, Sigma) or ANP (10 or 20 mg/kg) was given by oral gavage 10 d before the start of UVB irradiation and continued until 24 h after the last UVB exposure. Mice were shaved to remove back hair and the dorsal skin was exposed to UVB radiation (290–320 nm). The UVB radiation intensity 30 cm from the light source was 1.0 mW cm−2 monitored using a UV radiometer (National Biological Corporation UVB-500C). Initially, we determined the minimal erythemal dose (MED) of mouse dorsal skin. MED is defined as the minimum amount of radiation exposure required to produce erythema with sharp margins after 24 h. Irradiation was performed three times per week (Monday, Wednesday and Friday) and the UV dose was 1 MED (1 MED = 130 mJ/cm2) for 3 weeks.
Related Knowledge Centers
- Radiometry
- Radiant Flux
- Irradiance
- Radiant Exitance
- Intensity
- Lambertian Reflectance
- Lambert'S Cosine Law