Energy deposited per unit mass (absorbed dose) in a medium is proportional to its mass to some extent. But if the medium changes its density also plays a role. I wonder whether there is a direct relationship in absorbed dose and mass attenuation coefficient?
There isn't quite a direct relationship between mass-attenuation coefficient and dose, since not every attenuated photon deposits all it's energy in the medium (e.g. for Compton or Rayleigh scattering). There is a related quantity called the mass energy-absorption coefficient that can be multiplied by the photon fluence to calculate the dosimetric quantity kerma (see the link below). Kerma is closely related to dose, but not exactly the same either. So the short answer to your question is "no".
http://physics.nist.gov/PhysRefData/XrayMassCoef/chap3.html
There is a relationship between absorbed dose and Stopping Power (dT/dx).
The book Introduction To Radiological Physics and Radiation
Dosimetry of Frank H. Attix its a great reference.
Best regards!
Dear Deepak, I guess that in the background of your question could be an image obtained from Xray examination, where more dense structures can be easily recognized (because of differences in attenuation of X rays). However doses absorbed by those various structures are quite similar, because as you mentioned dose is “normalized” to the mass of the absorber.
Anyway Jack is right that in details the dose is more tightly connected with the mass absorption coefficient. But for some materials composed of similar elements (close Z numbers) and for moderate photons energy the ratio of the mass absorption to the mass attenuation coefficient stays almost the same. So in such case one can approximately presume the dose absorbed in material is proportional to its mass attenuation coefficient.
I was thinking like energy deposited is proportional to exp(mu*t)/(density*volume).
Like Jack already stated, there is in general no direct relationship between dose and attenuation. To get dose you have to absorb energy in a given volume. Without further information of your set up, there is no simple answer.
If you use low energy X-rays and high Z materials the dominating process is photoeffect, The secondary particles (photo electrons) are stopped in the direct surrounding of the location of the interaction. In this case (omitting the flourescent radiation) you indeed can estimate the dose by a formula like you wrote it. But you need a conversion factor for your denominator where you transfer the number of photons to an energy term. Very complicated for a X-ray spectrum. No problem if you use monoenergetic low energy gammas. But remember, only approxiamation for photoeffect and no fluorescent photons.
If you use low Z materials, dominating effect will be compton effect with only a special part of local energy transfer. Again only approximation.
As a result I would either prefer the energy absorption coefficient mu-en and the photon fluence, which you surely don´t know like Jack already proposed or better measure your dose.
Therefore my summary is calculation using the attenuation or transfer or absorption coefficient: "No".
From the discussion the reply seems that there is no direct relationship can be established between absorbed dose and mass attenuation/absorption coefficient.
So, the knowledge/use of mass attenuation coefficient is not sufficient to predict absorbed dose in a medium.
is my conclusion true?
Attenuation of a photon beam refers to the intensity loss as the beam transverses a thickness of medium. The inverse is the amount of energy lost for each unit of distance. The attenuation is defined for a very small thickness and refers to the original beam intensity.
Energy deposited in the material if very thin, as in the definition, can be nearly equal to energy lost by the beam. A real, thick material will have energy deposited by build up and scatter. Build up and scatter are energy dependent.
Energy deposited can be predicted from the mass attenuation coefficient, density of the material, energy of the beam, and thickness of the material. It cannot be predicted from mass attenuation coefficient, alone.
hi,I think if The mass attenuation coefficient increase according to this formula I=I.e^-ux where I. is the initial beam intensity and I is the residual beam intensity when the radiation beam transit of thickness x and u is the linear attenuation coefficient and relationship between this coefficient and mass attenuation coefficient are equal Um=u/p.conclusion if the mass attenuation coefficient
increase, the medium
Will be able to absorb more beam and absorb dose.
There is no direct relationship yet is a related quantity between two terms.
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