Dose Percentage

Dose percentage (D.p.) - the ratio of the values ​​of the absorbed dose D at two points (in one plane) of the irradiated body, expressed as a percentage. Used in radiation therapy, as well as in planning and conducting radiotherapy. In radiation therapy, D. point is calculated using the formula:
D. p. = (D2 - D1) / D2 * 100%, where D2 > D1;
i.e., the ratio of the difference in the values ​​of absorbed doses at two points to the highest value of the absorbed dose. Dp, calculated using this formula, is a relative measure of the uneven distribution of the absorbed dose in the patient's body.

The concept of “Dose” is one of the basic ones in physics and medicine. It refers to the amount of energy the body receives as a result of exposure to radiation. The dose is measured in Becquerels per kilogram (Bq/kg), but in medicine the SI units usually used are Gray (Gy). There are three main parameters that characterize the dose: the radiation beam, the distance between the source and the detection point, and the beam power. One of the important parameters used in dosimetry is the dose associated with the accumulation of radiation in the irradiated organ. This parameter is called absorbed dose (Sv) or gray dose (Gy). It is defined as a measure of energy per unit mass and corresponds to linear dose in SI units. Particular attention in dosimetry is paid to the dose associated with the characteristics of the distribution of radiation in the patient's body or the volume of exposure. A suitable measure, particularly useful for irradiation purposes of high body volume homogeneity (dose from head exposure), is body percentage dose, local dose, and relative dose, karma dose. In the practice of nuclear medicine, the terms “absolute local dose” and “target (focal) local dose” are used. They are associated with the local distribution of absorbed radiation over the area of ​​the body. **Absorption dose** in relative form takes into account the volumetric distribution of dose, while absolute dose refers to the dose accumulated in the organ (or other target organ structure). **Absolute skin dose** is a parameter that can be used to estimate the dose generated by intravenous irradiation. When calculating patient protection, the term “behavioral dose” is used, which considers the distribution of energy absorption in the body under the influence of several sources of radiation and the sequence of methods of introducing dose information and is the best parameter for determining the “red line” - a minimalistic dose that does not affect the effectiveness of prevention.