# dose

(redirected from MTD)
Also found in: Dictionary, Thesaurus, Medical, Acronyms, Wikipedia.

## dose

1. Med a specific quantity of a therapeutic drug or agent taken at any one time or at specified intervals
2. Physics the total energy of ionizing radiation absorbed by unit mass of material, esp of living tissue; usually measured in grays (SI unit) or rads
3. a small amount of syrup added to wine, esp sparkling wine, when the sediment is removed and the bottle is corked

## Dose

the energy of ionizing radiation absorbed by a unit of mass of irradiated matter (the absorbed dose Da). The absorbed energy is expended in the heating and the chemical and physical transformation of matter. The magnitude of the dose depends on the type of radiation (for example, X-ray or neutron flux), the energy of its particles, the density of their flux, and the composition of the irradiated matter. All other things being equal, the longer the time of irradiation, the greater the dose. Thus, doses accumulate with time. The dose per unit time is called the dose rate.

In addition to the absorbed dose there are the concepts of the exposure dose and the dose equivalent. The exposure dose, a measure of the ionization of air under the action of Xand y-radiation, is measured by the number of charges formed. Coulombs per kg is the unit of exposure dose in the system. An exposure dose of 1 coulomb per kg means that the total charge of all ions of the same sign formed in one kilogram of air is equal to one coulomb. The roentgen is a subsidiary that is widely used for exposure dose; 1 roentgen = 2.57976 x 10-4 coulombs per kg, which corresponds to the formation of 2.08 x 109 pairs of ions in 1 cu cm of air (at 0°C and 760 mm mercury). In order to create that number of ions it is necessary to expend energy equal to 0.114 ergs per cu cm, or 88 ergs per g. Thus, 88 ergs per g is the energy equivalent of the roentgen. The absorbed dose of X-radiation or y radiation in any substance can be calculated from the magnitude of the exposure dose. In order to do this it is necessary to know the composition of the substance and the photon energy.

Thus, the radiation danger to which a human being is subjected under any form of radiation corresponds to the same magnitude of dose equivalent. Natural sources of ionizing radiation (cosmic rays, the natural radioactivity of soil, water, air, and the human body) produce an average equivalent dose rate of 125 millirems per year. A dose equivalent of 400-500 rems received in a short time during irradiation of the whole body may, without special treatment, lead to death. However, the same dose equivalent received evenly during the course of one’s life leads to no perceptible changes. A dose equivalent of 5 rems per year is considered the maximum permissible exposure (MPE) in occupational irradiation.

The minimum dose of γ-radiation that will suppress the reproductive capacity of certain cells after a single irradiation is 5 rems. Inceptive changes in the blood are observed with prolonged daily doses of 0.02-0.05 rems, tumor formation, with 0.11 rems. The long-term consequences of irradiation are judged according to the increase in the frequency of mutation in the offspring. The dosage that will double the frequency of spontaneous mutation in man probably does not exceed 100 rems per generation. With local irradiation—that is, for the purpose of treating malignant tumors—high doses (6,000-10,000 rems in three or four weeks) of X-radiation or γ-radiation are used (carefully shielding the rest of the body).

Radiobiology distinguishes the following doses that lead sooner or later to death in animals: a dose that causes the death of 50 percent of the animals in 30 days (a lethal dose— LD30/50) with single-exposure unilateral X-radiation or γ-radiation is 300 rems for guinea pigs and 1,000 rems for rabbits; the minimum absolute lethal dose (MALD) with general γ-radiation is approximately 600 rems for man. With increases in dosage, the survival time is reduced to 2.8-3.5 days; further increases in dosage do not change that period. Only doses higher than 10,000-20,000 rems shorten the survival time to one day, and with subsequent irradiation, to a few hours. With a dose of 15,000-25,000 rems, cases of “death under the ray” are noted. Particular forms of radiation injury correspond to each dosage range. A number of invertebrate animals, plants, and microorganisms have considerably lower sensitivity.

Dosimeters are used in measuring radiation doses in order to predict radiation effects.

### REFERENCES

GOST 8848-63: Edinitsy radioaktivnosti i ioniziruiushchikh izluchenii. Moscow, 1964.
GOST 12631-67. Koeffitsient kachestva ioniziruiushchikh izluchenii. Moscow, 1967.
Ivanov, V. I. Kurs dozimetrii, 2nd ed. Moscow, 1970.
Golubev, B. P. Dozimetriia i zashchita ot ioniziruiushchikh izluchenii, 2nd ed. Moscow, 1971.

V. I. IVANOV and N. G. DARENSKAIA

## dose

[dōs]
(medicine)
The measure, expressed in number of roentgens, of a property of x-rays at a particular place; used in radiology.
(nucleonics)
References in periodicals archive ?
Similarly, exports from the chemical industry sector grew by 18.3% from 1,876.3 MTD to 2,218.8 MTD in year 2016.
Executives and senior managers account for 30.3 MTD and 31.1 MTD respectively, i.e.
They went down from 0.086 MTD in 2015 to 0.070 MTD in 2016.
Meanwhile, reported investments in chemical industries fell 10.7% with 205.1 MTD in the first nine months of 2017 against 229.6 MTD after the expansion in 2016 of an export-oriented artificial fertilisers unit (60 MTD).
Same for reported service projects where the amount of reported investment rose from 1,406.8 MTD in 2015 to 1,628.9 MTD In 2016, thus posting an increase of 15.8%.
As for non-principal expenditure on debt, they reached 18.929 MTD at the end of the first eight months of 2017, an increase of 2.313 MTD compared to the achievements of August 2016, due in particular to the increase in operating expenses , which totaled 13.075 MTD (against 11.766 MTD a year earlier).
The same goes for imports of agricultural products and basic foodstuffs that climbed 33.3% as a result of higher purchases of soft wheat (318.9 MTD against 272 MTD), raw materials and semi-finished products (21.6%), capital goods (8.8%), mining, phosphate and by-products (8.5%).
The same holds for net foreign currency assets, which declined by 148 MTD on December 29, 2016 from 13,226.3 MTD in 2015 to 13,078.3 MTD by 2016, i.e.
The value of exports stood at 16,072.3 MTD against 14, 255.3 MTD in the same period last year.
Foreign investment in agriculture increased by 123.4% from 9.3 million MTD at the end of November 2015 to 20.8 MTD in 2016.
Actually, exports were 7.4% higher than last year, ie a value of 7,532.6 MTD against 7,015.6 MTD, while imports showed a large increase for a value of 11,411.5 MTD in comparison with 9,482.0 MTD during the same period last year.
As for investment, the flow reached 2,707.4 MTD in 2013 against 3,391.7 MTD in 2011, i.e.

Full browser ?
Site: Follow: Share:
Open / Close