71.211.166.234: /* MPC and nature of country */

2014-11-16T22:14:14Z

MPC and nature of country

2601:7:F80:995:3084:53E6:1BF9:AB12: /* MPC and nature of country */

2014-01-26T21:37:48Z

MPC and nature of country

← Older revision		Revision as of 23:37, 26 January 2014
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	~~The name~~ of the ~~author~~ is ~~probably Gabrielle Lattimer~~. ~~For years she's been working compared to~~ a ~~library assistant~~. For a ~~while she's only been~~ in ~~Massachusetts~~. As a ~~woman what lindsay really likes~~ is ~~mah jongg but she have~~ not ~~made~~ a ~~dime with it~~. ~~She~~ is ~~without a doubt running~~ and ~~maintaining~~ the ~~best blog here~~: http://~~prometeu~~.~~net~~<br><br>~~My blog:~~ [http://~~prometeu~~.~~net clash~~ of ~~clans cheat~~ no ~~survey~~]		[[File:Dose units.jpg\|400px\|right\|Graphical relationship of radiation dose units]]
			'''Absorbed dose''' (also known as '''total ionizing dose''', TID) is a measure of the energy deposited in a medium by [[ionizing radiation]] per unit mass, which may be measured as joules per kilogram when it is represented by the equivalent SI unit, [[Gray (unit)\|gray]] (Gy). The [[Centimetre gram second system of units\|CGS]] units, [[rad (unit)\|rad]] and [[roentgen equivalent physical\|rep]] are also used.

			The absorbed dose from a given level of incident radiation depends on the absorbing medium. For instance, a soft X-ray beam may deposit four times more dose in bone than in air, or none at all in a vacuum.

			==Uses==
			Absorbed dose is of fundamental importance as a step in [[dosimetry]] calculations. However, the absorbed dose alone is not an adequate indicator of the likely health effects in humans, and consideration must be given to the type of radiation, the affected tissues, and other factors. These are taken into account when the [[equivalent dose]] and the [[Effective dose (radiation)\|effective dose]] are calculated for a given situation.

			For example, 1 Gy of [[alpha particle\|alpha]] radiation would carry a much greater risk of cancer than 1 Gy of [[photon]] radiation, and the weighting factor used reflects this. Further calculation can be performed to find the [[equivalent dose]] for the irradiation of the whole body, the [[effective dose (radiation)\|effective dose]] for irradiation of specific parts of the body, or the [[committed dose]] for internal radiation exposures. These adjusted doses, measured in units of [[sievert]] (Sv), or [[rem (unit)\|rem]], are representative of the stochastic risks to human health.

			Absorbed dose is used to estimate the risk of [[acute radiation syndrome]], and to rate the survivability of devices such as electronic components in ionizing radiation environments.

			==Computation==

			The absorbed dose is equal to the [[kerma (physics)\|kerma]] of the radiation beam multiplied by the ionization energy of the medium to be ionized.

			For example, the ionization energy of dry air at 20°C and 101.325 kPa of pressure is 33.97 ± 0.06 J/C.<ref>{{cite book\|title=Radiation Oncology Physics: A Handbook for Teachers and Students\|year=2005\|publisher=International Atomic Energy Agency\|location=Vienna\|isbn=92-0-107304-6\|url=http://www-pub.iaea.org/mtcd/publications/pdf/pub1196_web.pdf\|editor=Podgorsak, E. B.\|accessdate=25 November 2012}}</ref>{{rp\|305}} (33.97 eV per ion pair) Therefore a beam kerma of 2.58×10<sup>−4</sup> C/kg (1 [[roentgen (unit)\|roentgen]]) would deposit an absorbed dose of 8.76×10<sup>−3</sup> J/kg (0.00876 Gy or 0.876 rad) in dry air at those conditions.

			When the absorbed dose is not uniform, or when it is only applied to a portion of a body or object, an absorbed dose representative of the entire item can be calculated by taking a mass-weighted average of the absorbed doses at each point.

			More precisely,<ref name="ICRP103">{{cite journal\|title=The 2007 Recommendations of the International Commission on Radiological Protection\|journal=Annals of the ICRP\|year=2007\|volume=37\|series=ICRP publication 103\|issue=2-4\|url=http://www.icrp.org/publication.asp?id=ICRP%20Publication%20103\|accessdate=17 May 2012\|isbn=978-0-7020-3048-2}}</ref>

			<math>\bar{D_T}=\frac{\int_{T}D(x,y,z)\rho(x,y,z)dV}{\int_{T}\rho(x,y,z)dV}</math>

			Where
			:<math>\bar{D_T}</math> is the mass-averaged absorbed dose of the entire item T
			:<math>T</math> is the item of interest
			:<math>D(x,y,z)</math> is the absorbed dose as a function of location
			:<math>\rho(x,y,z)</math> is the density as a function of location
			:<math>V</math> is volume

			Non-uniform absorbed dose is common for soft radiations such as low energy x-rays or beta radiation. Self-shielding means that the absorbed dose will be higher in the tissues facing the source than deeper in the body.

			The mass average can be important in evaluating the risks of radiotherapy treatments, since they are designed to target very specific volumes in the body, typically a tumour. For example, if 10% of a patient's bone marrow mass is irradiated with 10 Gy of radiation locally, then the absorbed dose in bone marrow overall would be 1 Gy. Bone marrow makes up 4% of the body mass, so the whole-body absorbed dose would be 0.04 Gy. The first figure (10 Gy) is indicative of the local effects on the tumour, while the second and third figure (1 Gy and 0.04 Gy) are better indicators of the overall health effects on the whole organism. Additional dosimetry calculations would have to be performed on these figures to arrive at a meaningful effective dose, which is needed to estimate the risk of cancer or other stochastic effects.

			When ionizing radiation is used to treat cancer, the doctor will usually prescribe the [[radiotherapy]] treatment in units of gray. [[Medical imaging]] doses may be described in units of [[coulomb]] per [[kilogram]], but when [[radiopharmaceutical]]s are used, they will usually be administered in units of [[becquerel]]. When health risk from ionizing radiation is being discussed, the [[sievert]] would be used. There is no universally applicable conversion constant between these different units because they measure different things.

			==See also==
			[[File:Radiation (xkcd).png\|thumb\|Radiation dose chart from [[XKCD]]]]
			* [[Specific absorption rate]]
			* [[Equivalent dose]]
			* [[Effective dose (radiation)\|Effective dose]]
			* [[kerma (physics)]]
			* [[Sievert]]

			==References==
			{{reflist}}

			==External links==
			* [http://www.ornl.gov/info/reports/1982/3445603573381.pdf ''Specific Gamma-Ray Dose Constants for Nuclides Important to Dosimetry and Radiological Assessment'', Laurie M. Unger and D. K . Trubey, Oak Ridge National Laboratory, May 1982] - contains gamma-ray dose constants (in tissue) for approximately 500 radionuclides.

			[[Category:Physical quantities]]
			[[Category:Radiobiology]]

208.118.191.66: /* MPC and nature of country */

2012-08-08T21:34:37Z

MPC and nature of country

New page

The name of the author is probably Gabrielle Lattimer. For years she's been working compared to a library assistant. For a while she's only been in Massachusetts. As a woman what lindsay really likes is mah jongg but she have not made a dime with it. She is without a doubt running and maintaining the best blog here: http://prometeu.net<br><br>My blog: [http://prometeu.net clash of clans cheat no survey]

Marginal propensity to consume - Revision history

71.211.166.234: /* MPC and nature of country */

2601:7:F80:995:3084:53E6:1BF9:AB12: /* MPC and nature of country */

208.118.191.66: /* MPC and nature of country */