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Topic: Absorbed dose


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SI

  
  Low Dose Radiation Research Program
Dose: The absorbed dose, given in rads (or in SI units, (Gy) grays), that represents the energy in ergs or Joules absorbed from the radiation per unit mass of tissue.
Furthermore, the biologically effective dose or dose equivalent, given in rem or sieverts, is a measure of the biological damage to living tissue from radiation exposure.
A calculated dose of radiation or a chemical substance that is expected to kill 50% of a population.
lowdose.tricity.wsu.edu /glossary.htm   (8933 words)

  
 Whole Body Scanning Using Computed Cotomography (CT) - Radiation Quantities and Units
Absorbed dose - The fundamental quantity for describing the effects of radiation in a tissue or organ is the absorbed dose.
Absorbed dose is the energy deposited in a small volume of matter (tissue) by the radiation beam passing through the matter divided by the mass of the matter.
Thus, for CT, the absorbed dose in a tissue, in Gy, is equal to the equivalent dose in Sv.
www.fda.gov /cdrh/ct/rqu.html   (568 words)

  
 ICRU News   (Site not responding. Last check: 2007-10-08)
Absorbed dose in enamel can be due to various sources of radiation including natural radiation, medical exposures and possibly accidental radiation events.
At typical diagnostic X-ray energies, the ratio of dose to the outer portion of the tooth versus that to the inner portion of the tooth was approximately 2 to 1.
Where quartz is to be measured, the proportion of absorbed dose due to natural background radiation is reduced by etching grains in HF acid to remove the outer volume of the grain in which the alpha particles are absorbed.
www.icru.org /n_001_2.htm   (4441 words)

  
 Absorbed dose - Wikipedia, the free encyclopedia
Absorbed dose is a measure of the energy deposited in a medium by ionizing radiation.
Note that the absorbed dose is not a good indicator of the likely biological effect.
The risk of stochastic effects due to radiation exposure can be quantified using the effective dose, which is a weighted average of the equivalent dose to each organ depending upon its radiosensitivity.
en.wikipedia.org /wiki/Absorbed_dose   (204 words)

  
 Units of Radioactivity and Dose
The absorbed dose, sometimes also known as the physical dose, defined by the amount of energy deposited in a unit mass in human tissue or other media.
This dose reflects the fact that the biological damage caused by a particle depends not only on the total energy deposited but also on the rate of energy loss per unit distance traversed by the particle (or "linear energy transfer").
The biological impact is specified by the dose equivalent H, which is the product of the absorbed dose D and the quality factor Q: H = Q D. The unit for the dose equivalent is the rem if the absorbed dose is in rads and the sievert (Sv) if the absorbed dose is in grays.
www.lbl.gov /abc/wallchart/chapters/15/2.html   (415 words)

  
 G Akabani, RE McLendon, DD Bigner, MR Zalutsky   (Site not responding. Last check: 2007-10-08)
Methods: The tumor-to-normal tissue mean absorbed dose ratio, TND, model calculates the ratio between the absorbed dose in the tumor and normal tissue for a given activity concentration in the tumor and normal tissue.
The radiation dose to the salivary glands found for a number of radiopharmaceuticals in ICRP80 were derived from a simple anatomic model of the glands using the nodule module of MIRDOSE3.1.
The radiation dose estimates for intravenous injection of the Tl RPs were obtained using a human body phantom by the MIRD method and our data on the radiation exposure of the human body.
www.doseinfo-radar.com /3-pos.htm   (2360 words)

  
 Radiation Safety-
The units of absorbed dose are the gray, or Gy, and the rad.
The dose equivalent in rem is equal to the absorbed dose in rads multiplied by the quality factor (one rem = 0.01 Sv).
The dose equivalent in sieverts is equal to the absorbed dose in grays multiplied by the quality factor.
www.ehs.ohio-state.edu /index.asp?PAGE=radsafe.faq   (1107 words)

  
 Absorbed dose - an invalid concept
Arguments against the validity of absorbed dose as a quantifier for the biological effects of ionizing radiations have been broached since the early 1970's.
Use of dose alone for measurement of the effectiveness of electrons implicitly assumes that the bio-effect per unit dose is independent of the LET which is manifestly not true.
If absorbed dose is agreed to be not only inappropriate but actually invalid for describing radiation effects then priority action, possibly in EC Fifth Framework programme, should by taken to examine the consequences for the future.
www.llrc.org /wobblyscience/subtopic/absorbed_dose.htm   (1590 words)

  
 Exposure, air kerma and absorbed dose
For volumes which are large compared to the tracklength, the kerma and absorbed dose are virtually identical, especially since absorbed dose also includes energy deposition within the volume by electrons set in motion outside the volume.
Because of this, absorbed dose to water (which closely resembles human tissue but is well defined) is the quantity which is used to specify the amount of radiation to be used in clinical practice.
Absorbed dose has the further advantage that it is directly measurable in a variety of ways.
www.irs.inms.nrc.ca /inms/irs/papers/pic/node3.html   (724 words)

  
 Radiological Fundamentals
The body absorbs the light (energy), and in some cases the absorption of the light energy may cause noticeable heating in the body tissue.
The important point is, the source of the exposure is relatively unimportant, once the dose has been measured in a standard unit, it can be compared to other doses, added to other doses, or used in risk comparisons regarding non-radiation risks.
Therefore, it can be used as a measure of energy absorbed by the body, but not as a measure of the relative biological effect (harm or risk) to the body.
www.jlab.org /div_dept/train/rad_guide/fund.html   (2120 words)

  
 EFMR   (Site not responding. Last check: 2007-10-08)
Absorbed dose is often expressed in terms of hundredths of a gray, or centi-grays.
Equivalent dose using rems is often expressed in terms of thousandths of a rem, or millirem.
To determine equivalent dose (rem), you multiply absorbed dose (RAD) by a quality factor (Q) that is unique to the of incident radiation.
www.efmr.org /RADALERT.htm   (1371 words)

  
 How to go from mAs to krad
This is a unit of absorbed dose, which in turn is the amount of energy absorbed per unit mass by the irradiated object (in this case, your sample of seeds).
The absorbed dose (krad) to the sample (seeds) is the important factor for your experiment.
For example, if the dose rate was specified for a 1-meter distance, the dose rate would be 1/4 as great if the sample were irradiated at a 2-meter distance and would be four times as high if the sample were placed at a 0.5-meter distance.
www.hps.org /publicinformation/ate/q610.html   (1013 words)

  
 The University of Michigan Health Physics Web Site: Basic Terms
In a general sense, dose is a measure of the amount of energy from an ionizing radiation deposited in a mass of some material.
Dose is affected by the TYPE of radiation, the amount of radiation and the physical properties of the material itself.
Absorbed doses are normally measured in units of Gray (RAD), and effective and equivalent doses in Sievert (Rem).
www.umich.edu /~radinfo/introduction/terms.htm   (1341 words)

  
 Radiation Risk
The rad is a unit of absorbed radiation dose in terms of the energy actually deposited in the tissue.
To assess the risk of radiation, the absorbed dose is multiplied by the relative biological effectiveness of the radiation to get the biological dose equivalent in rems or sieverts.
The biologically effective dose in rems is the radiation dose in rads multiplied by a "quality factor" which is an assessment of the effectiveness of that particular type and energy of radiation.
hyperphysics.phy-astr.gsu.edu /hbase/nuclear/radrisk.html   (430 words)

  
 What is Dose? What Units are Used for Dose?
In radiation protection, "dose" has a more specific meaning—it is the energy of ionizing radiation absorbed per unit mass of any material.
Special units exist for dose, including the "rad," which is defined as 100 erg/g, and the "gray" (Gy), which is defined as absorption of 1 J/kg.
These doses may be received from exposures to sources outside of the body (external dose) or radioactive material which may enter the body by being inhaled or swallowed (internal dose).
hps.org /publicinformation/ate/faqs/dose.html   (942 words)

  
 How Do We Measure the Biological Effects of External Radiation?
Someone absorbing 1 gray (100 rad) in a small amount of tissue, such as a thyroid gland, will absorb much less total energy than someone absorbing 1 gray (100 rad) throughout his or her entire body.
Thus, when speaking of absorbed dose, it is crucial to know the amount of tissue being exposed, not simply the number of gray or rad.
Multiplying the absorbed dose (in rad or gray) by the quality factor (also known as the radiation weighting factor) produces what is called the equivalent dose.
www.eh.doe.gov /ohre/roadmap/achre/intro_9_6.html   (740 words)

  
 Total Ionizing Dose
In either case, TID can be measured in terms of the absorbed dose, which is a measure of the energy absorbed by matter.
Absorbed dose is quantified using either a unit called the rad (an acronym for radiation absorbed dose) or the SI unit which is the gray (Gy); 1 Gy = 100 rads = 1 J/kg.
In low earth orbit (LEO), the main dose source is from electrons and protons (inner belt); and in geostationary earth orbit (GEO), the primary source is from electrons (outer belt) and solar protons.
www.eas.asu.edu /~holbert/eee460/tiondose.html   (907 words)

  
 A system based on absorbed-dose standards
The first generation of primary standards for absorbed dose were based on graphite calorimeters in which a small disk of graphite was thermally isolated from the surrounding graphite phantom and its temperature rise was measured when irradiated.
The only problem with this system is that the measured absorbed dose to graphite must be converted to an absorbed dose to water, but this can be done in several ways with an accuracy of better than 1%.
To summarize, there are several major approaches to primary standards for absorbed dose to water (besides the two described) and various on-going comparisons between national primary standards labs suggest that they are in agreement at the 1% level or better[10][9].
www.irs.inms.nrc.ca /papers/pic/node7.html   (678 words)

  
 Selective irradiation of the vascular endothelium has no effect on the survival of murine intestinal crypt stem cells ...
absorbed dose in the microvasculature was increased relative
The triangles and squares represent irradiation conditions where the dose to the microvasculature was increased relative to the rest of the mouse by a factor of 2 or 3, respectively.
absorbed doses of a whole-body epithermal neutron beam: 5.7
www.pnas.org /cgi/content/full/103/10/3787   (4533 words)

  
 RECORDING INFORMATION IN THE PATIENT'S MEDICAL RECORD THAT IDENTIFIES THE POTENTIAL FOR SERIOUS X-RAY-INDUCED SKIN ...
The purpose of the recommendation is to encourage identification of those areas of the skin which are irradiated at levels of absorbed dose that approach or exceed a threshold for injury.
For example, the sum of all exposures occurring in an entire procedure is likely to be a significant overestimate of the cumulative absorbed dose to a specific area of skin, except in the event that the x-ray beam is stationary during most of the procedure.
Therefore, a facility may wish to include in the recor a statement of the uncertainty in the estimate of cumulative absorbed dose recorded in the patient record or derivable from data in the record.
www.fda.gov /cdrh/xrayinj.html   (960 words)

  
 New Page 3   (Site not responding. Last check: 2007-10-08)
The conventional unit of measuring absorbed dose is the rad (radiation absorbed dose).
The quality factor is the factor by which the absorbed dose (rad or gray) is to be multiplied to obtain a quantity that expresses, on a common scale for all ionizing radiation, the biological damage (rem or sievert) to an exposed individual.
Dose equivalent is the product of absorbed dose (H) in tissue multiplied by a quality factor (Q), and then sometimes multiplied by other necessary modifying factors (N) at the location of interest.
www.dtc.dla.mil /radpro/measure/measuremain.htm   (877 words)

  
 WHO | What is Ionizing Radiation?
The international (SI) unit of measure for absorbed dose is the gray (Gy), which is defined as 1 joule of energy deposited in 1 kilogram of mass.
Equivalent dose – the biological effect depends not only on the amount of the absorbed dose but also on the intensity of ionisation in living cells caused by different type of radiations.
The unit of equivalent dose is the sievert (Sv).
www.who.int /ionizing_radiation/about/what_is_ir/en/index2.html   (266 words)

  
 Equivalent dose - Wikipedia, the free encyclopedia
Equivalent dose is therefore a less fundamental quantity than radiation absorbed dose, but is more biologically significant.
Dose equivalent (H) presents the absorbed dose at a specific location in tissue weighted by a distribution of quality factors (Q).
Equivalent dose (E) is calculated by multiplying the absorbed dose (D) with the evaluation factor.
en.wikipedia.org /wiki/Equivalent_dose   (299 words)

  
 How Is Ionizing Radiation Measure? RER-23
The extent of the damage depends, in part, on the amount of ionizing radiation that is absorbed by the tissue (i.e., the dose).
The absorbed dose is multiplied by a factor which takes into account the different biological effects of the various types of ionizing radiation.
This converts the absorbed dose to the equivalent dose which is of interest to most people, and it is the one that will be discussed in the remainder of this fact sheet.
ohioline.osu.edu /~rer/rerhtml/rer_23.html   (926 words)

  
 IEER: Energy & Security #4: Health Risks of Ionizing Radiation
The dose at which half the exposed population would die in sixty days without medical treatment is called the LD50 dose (LD for lethal dose, and 50 for 50 percent).
Because the main effect of low-dose radiation is the induction of cancer, and cancer is a common disease with many causes, it is not yet possible to verify the linear no-threshold model; nevertheless, there is considerable radiobiological evidence for this theory and it is generally used for public health protection purposes, such as setting standards.
Radiation doses at which biological effects cannot be immediately observed are classified under the general rubric of "low-level radiation." Since different physical effects are observed at different radiation levels, this has given rise to some confusion about what levels constitute low-level radiation.
www.ieer.org /ensec/no-4/main.html   (1729 words)

  
 Fm 101-5-1 Operational Terms and Graphics, Chapter 1, R
(DOD) The term radiation dose is often used in the sense of the exposure dose expressed in roentgens, which is a measure of the total amount of ionization that the quantity of radiation could produce in air.
This could be distinguished from the absorbed dose, also given in rads, which represents the energy absorbed from the radiation per gram of specified body tissue.
Further, the biological dose, in rems, is a measure of the biological effectiveness of the radiation exposure.
www.fas.org /man/dod-101/army/docs/fm101-5-1/f545-r.htm   (5077 words)

  
 Absorbed dose behind eye shields during kilovoltage photon radiotherapy -- Baker et al. 75 (896): 685 -- The British ...
The absorbed dose at the position of the lens of the eye under
is the dose at the centre of the field in the absence of the shield, and D
Equation (1)) and measured percentage dose under small (1.7 cm diameter) and medium (2.2 cm diameter) eye shields relative to dose in the centre of the field in the absence of the shield.
bjr.birjournals.org /cgi/content/full/75/896/685   (1360 words)

  
 Change in Tumor-absorbed Dose due to Decrease in Mass during Fractionated Radioimmunotherapy in Lymphoma Patients -- ...   (Site not responding. Last check: 2007-10-08)
Y, for which the absorbed dose was calculated.
an accurate estimation of the mean absorbed dose to the tumor.
A study of its frequency and estimation of absorbed doses in diagnosis and therapy.
clincancerres.aacrjournals.org /cgi/content/full/9/10/4003S   (2013 words)

  
 Absorbed dose definition - Medical Dictionary definitions of popular medical terms
Absorbed dose: In radiology, the amount of energy that is deposited in any material by ionizing radiation.
The unit of absorbed dose, the rad, is a measure of energy absorbed per gram of material.
An alternative unit of absorbed dose is the gray.
www.medterms.com /script/main/art.asp?articlekey=9640   (93 words)

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