Absorbed dose, expression

The extent of damage from radiation depends mainly on two factors. These are the amount of radiation absorbed and the type of radiation. The former is commonly expressed in rads (radiation absorbed dose). A rad corresponds to the absorption of 10 z J of energy per kilogram of tissue ... 

Absorbed dose It is the amount of energy [30] imparted to the matter. Its unit is expressed in rad, or gray (Gy). The main units are interrelated by the following relation ... 

Absorbed dose rate This is the absorbed dose per unit time expressed in grays per unit time (kGy/s or kGy/min). Dose rate (Dr) for an electron accelerator [48] can be written in terms of beam current (I) and irradiation field area (A) as follows ... 

For the majority of drugs, the preferred administration route is by oral ingestion which requires good intestinal absorption of drug molecules. Intestinal absorption is usually expressed as fraction absorbed (FA), expressing the percentage of initial dose appearing in a portal vein [15]. 

Absorbed Dose, Chemical—The amount of a substance that is either absorbed into the body or placed in contact with the skin. For oral or inhalation routes, this is normally the product of the intake quantity and the uptake fraction divided by the body weight and, if appropriate, the time, expressed as mg/kg for a single intake or mg/kg/day for multiple intakes. For dermal exposure, this is the amount of material applied to the skin, and is normally divided by the body mass and expressed as mg/kg. 

Dose Equivalent (DE)—A quantity used in radiation safety practice to account for the relative biological effectiveness of the several types of radiation. It expresses all radiations on a common scale for calculating the effective absorbed dose. It is defined as the product of the absorbed dose in rad and certain modifying factors. (The unit of dose equivalent is the rem. In SI units, the dose equivalent is the sievert, which equals 100 rem.)... 

Dose, Radiation—The amount of energy imparted to matter by ionizing radiation per unit mass of the matter, usually expressed as the unit rad, or in SI units, the gray. 100 rad 1 gray (Gy) (see Absorbed Dose). 

Tissue Dose—Absorbed dose received by tissue in the region of interest, expressed in rad (see Dose, Gray, and Rad). 

Quality Factor (Q)—The linear-energy-transfer-dependent factor by which absorbed doses are multiplied to obtain (for radiation protection purposes) a quantity that expresses - on a common scale for all ionizing radiation - the approximate biological effectiveness of the absorbed dose. 

Sievert (Sv)—The SI unit of any of the quantities expressed as dose equivalent. The dose equivalent in sieverts is equal to the absorbed dose, in gray, multiplied by the quality factor (1 sievert equals 100 rem). 

Dose equivalent or rem is a special radiation protection quantity that is used, for administrative and radiation safety purposes only, to express the absorbed dose in a manner which considers the difference in biological effectiveness of various kinds of ionizing radiation. The ICRU has defined the dose equivalent, H, as the product of the absorbed dose, D, and the quality factor, Q, at the point of interest in biological tissue. This relationship is expressed as H = D x Q. The dose equivalent concept is applicable only to doses that are not great enough to produce biomedical effects. 

Absorbed Dose. In comparing different types of radiation and various chemical systems, the observed effect Is usually expressed... 

Rem (Roentgen equivalent in man) Special unit of any quantity expressed as a dose equivalent the dose equivalent in rems is equal to the absorbed dose in rads multiplied by the quality factor (1 rem = 0.01 Sv). 

In contrast to skeletal bone and dentine, which accumulate fluoride throughout life and whose levels are proportional to the absorbed dose of fluoride, fluoride in enamel is not an appropriate biomarker, because most of its fluorine was taken up during tooth formation [2]. The post-eruptive fluoride uptake of enamel is expressed only in the outer layer and depends on the concentration of fluoride in the oral cavity [6]. 

In this expression, z, termed specific energy, is the energy imparted per unit mass to a volume F the expected value of z (see below) is the absorbed dose D. It follows that, on average ... 

Mass production poses strict requirements on resist materials, most important of which are sensitivity, spatial resolution, contrast, and etch resistance. The sensitivity of the next-generation resists is required to be less than 10 pC/cm (EB), 100 mJ/cm (x-ray), and 25 mJ/cm (EUV) [89]. It should be noted that the resist sensitivity is traditionally expressed not by absorbed dose but exposure charge or energy per unit area. As for the spatial resolution, 45 nm is needed for the production of dynamic random access memory (DRAM) in 2010 [89]. Although resist patterns below 10 nm are presently fabricated by some kinds of resists, they do not have enough sensitivity required for the mass production [90,91]. 

In the field of the reprocessing, radiation energy released from radionuclides in the solution is normally expressed in a unit of W hr/1. If all the energy is absorbed in the medium, the absorbed dose can be calculated as ... 

G(s) and G(x) are defined as the number of scissons and the number of crosslinks produced when the polymer absorbs 100 eV. of ene and R is the radiation dose expressed in Mrads. JTable I lists values of M , and M measured for irradiated MP20 samples. A plot of M, and M vs. radiation dose is shown in Figure 1. The solid lines in Figure 1 are linear least-squares fits to the data in Table I. Values for G(s) and G(x) were determined from the slopes of these lines to be 6.8 0.9 and 0.3 0.3, respectively. 

Contemporary radiation protection systems (ICRP, 1977a 1991 NCRP, 1987 1993) include dose limits expressed in such a quantity. To obtain the quantity, absorbed doses are first multiplied by a quality factor (ICRP, 1977a) or a radiation weighting factor (ICRP, 1991), selected for the type and energy of the radiation incident upon the body, yielding, respectively, the dose equivalent in the tissue (ICRP, 1977a) or equivalent dose in the tissue (ICRP, 1991). Therefore ... 

Dose Equivalent The amount of effective radiation when modifying factors have been taken into account. The product of absorbed dose multiplied by a quality factor multiplied by a distribution factor, expressed numerically in units of REMS. 

Thin film dosimeters are essentially dyed or undyed plastics films, which, when irradiated, irreversibly change their optical absorbance in proportion to the absorbed dose. They are also referred to as radiachromic films or chips5 (see also Section 9.2.3). To minimize errors due to variation in the film thickness, the dosimeter response is usually expressed as the radiation-induced change in absorbance divided by the dosimeter film thickness. A partial list of currently available EB dosimeters is shown in Table 9.1. The appropriate test procedures are described in several ASTM standards.6... 

Given radiation chemical yields expressed as G values, it is possible to calculate the concentrations of oxidative and reductive species in pure water at a known absorbed dose. The SI unit of dose is the gray (Gy), which equals an energy deposition of 1 J kg-1. For example, the concentration of OH-produced in pure, neutral water by absorbing 1 kGy is ... 

A relevant simple model was used to estimate the maximum absorbable dose (MAD) [162], It takes into account the permeability, expressed in terms of a first-order rate constant ka, the solubility cs of the drug, and two physiological variables, the dissolution-intestinal volume V arbitrarily set to 250 ml, and the duration of gastrointestinal absorption ta for 6h ... 

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