The simple answer is energy of the radiation times dose conversion factor times intensity times time.

The question is very general. What is it you want to know. I can suggest references, including a chapter on measurement of effective dose.

There is a nice book on: Introduction to radiological physics and radiation dosimetry, by Frank H. Attix.

In eq. 2.4 he describes the Kerma ( kinetic energy released in material) as the energy fluence times the mass-energy absorption coefficient of the absorbing material. For homogenous media being sufficiently large the Kerma is equal to the absorbed energy dose.

Your energy fluence is calculated via the photon flux ( e.g. in photons per area and per time) times the photon energy. The mass energy absorption coeffcient(s) can be picked up by NIST:

https://physics.nist.gov/PhysRefData/XrayMassCoef/chap4.html

For non-monochromatic radiation you have to go for an integral.

I will send you the relevant page(s) of that book via RG messenger.

Good luck

Dear Sir, Thank you for your answer

The absorbed dose is simply calculated by taking into account the the specific energy emitted by the source × the corresponding $mu_en$ at that energy × fluence divided by the density of the tissue.

If you want to gain information about the Absorbed dose rate, then the fluence is replaced with Activity divided by square of distance source and the body reference.

However, this method is only valid for a crude calculation.

See attached file, and see also

https://www.nucleonica.com/wiki/index.php?title=Help:Dose_Rate_Constants%2B%2B

Thank you very much

just knowing the energy is not enough to estimate the absorbed dose.

the definition of absorbed dose (average energy imparted per unit mass) you need to know the amount of the energy imparted (absorbed) in a given mass . part of the energy given to a certain medium say water may be scattered, transfered or obsrbed. only the later is important in dose calculation

You are right. That is why the mass-energy absorption coefficient of the absorbing material is used in the calculations and not the linear mass attenuation coefficient ...

The absorbed dose is simply calculated by these equation

D(nGy.h )=0.462C Ra +0.604C Th +0.0417C K

Use the calculator below to estimate your yearly doseHelpdoseDose is defined as the amount of radiation or energy absorbed by a person's body. from the most significant sources of ionizing radiationHelpionizing radiationRadiation with so much energy it can knock electrons out of atoms. Ionizing radiation can affect the atoms in living things, so it poses a health risk by damaging tissue and DNA in genes.. Estimates are given in milliremHelpmilliremThe millirem is the U.S. unit used to measure effective dose. One millirem equals 0.001 rem. The international unit is milliSievert (mSv). (mrem)Helpmremone thousandth of a rem, the U.S. unit for effective dose. Effective dose is a measure of the amount of radiation absorbed by a person that accounts for the type of radiation received and the effects on particular organs. (The corresponding international unit for effective dose is the millisievert (mSv).)

According to the National Council on

according to the definition of absorbed dose rate: it is the amount of radiation energy deposited in the substance, which defined by the equation :

D = E/M ( J/Kg )

where E; the energy of radiation, M: the mass of a substance

firstly you have to know the mass of the substance and then you will calculate the absorbed dose easily.

Thanks. Dear All

Please tell me. How can I calculate the attunation coefficient of x ray of ct image using imageJ software?

Dear Tadelech Sisay Mekonin ,

if there is any calibration attached of the gray scale with respect to the Hounsfield units (HU), you might solve the HU scale definition for µ.

The HU scale is the per mille deviation of µ from the attenuation coefficient µH2O of water:

HU = 1000*(µ-µH2O)/µH2O

Some times a correction with respect to air is included. But that is only a very tiny modification...

https://en.wikipedia.org/wiki/Hounsfield_scale

The challenge of deriving µ from CT data is, that in general µ is energy dependent [ µ=µ(E) ] and thus the µ involved in CT is an average (or mean) value of µ(E).

This 'mean' is affected by

a) the primary x-ray tube spectrum ( target material, target angle, kVp setting),

b) filtration in use, and

c) overall sample attenuation (composition and thickness dependent).

So the µ derived from HU is only a rough measure of µ relative to that of water.

You have to bear in mind that, when taking further conclusions...

Best regards

G.M.

Dear. G.M

Thank you very much for your answer

How can I calculate attunation coefficient of any matterial?

Please tell me how to calculate the attunation coefficient of water?

Dear Tadelech Sisay Mekonin ,

you might use the NIST/XCOM data base.

https://physics.nist.gov/PhysRefData/Xcom/html/xcom1.html

This database will give you the energy dependence of the x-ray mass-attenuation coefficient µ/rho.

Thus multiplicate the µ/rho values with the density rho of the material of interest.

Pay attention:

a) the energy values are in MeV,

b) there is a decimal point in use , and

c) you may add additional energies by hand... (and skip the standard energy grid)

For a rough mean 'energy' estimation take about 2/3 of the kV value (of the tube setting) in keV.

Good luck and

best regards

G.M.

Dear G.M

First Thank you for your response.

I have only one question.

I have ct image file I collected this image using standard PMM phantom. How can I determine the attunation coefficient of the x-ray using imageJ .please tell me this quation.

Dear Tadelech Sisay Mekonin ,

if there is no relation given of gray scale to attenuation in the legend/caption of the image, there is no chance to extract the attenuation coefficient.

But, as I see, you have measured a phantom; so you should know the material (PMM) and thus the attenuation coeffcient via NIST/XCOM.

G.M.

Okay, thanks.

Dear.G.M

How to calculate the attunation coefficient of PMMA Philip phantom?

Thank.

Dear Tadelech Sisay Mekonin ,

please see for example section 2.2.1. at page 1873 of:

Article The relevance of image quality indices for dose optimization...

Here you will find the chemical formula ( C5H8O2) for PMMA

Density is 1,18g/cm3; ( see for example https://de.wikipedia.org/wiki/Polymethylmethacrylat ).

For 67keV, µ=0,224/cm is given there.

So please go to the NIST/XCOM link given above and calculate the mass-attenuation coefficient for your x-ray photon energies of interest.

Please insert the chemical formula with capital letters, as it is usually written...

The attenuation coeffcients may differ a bit between different data bases, but the deviation is in the very low % region. The NIST/XCOM data base will give 0,218/cm for µ at 67keV (=0.067MeV) compared to 0,224/cm mentioned above.

Best regards

G.M.

Dear G.M

Thanks very much

Dear G.M

Thanks very much

Dear G.M

Thanks you.

Dear G.M.

How are you?

XCOM database is the theoretical estimation of the x-ray attunation coefficient not expremental or by hand measurement of the x-ray attunation coefficient of PMNA phantom.please tell me how to calculate by hand or experimental measurement of x-ray attunation coefficient ?

Dear Tadelech Sisay Mekonin ,

data of NIST/XCOM database are well accepted data in the whole x-ray community.

Some of them were reproduced by myself...

among them was PMMA.

Measurement is done by taking a primary x-ray spectrum as well as transmission spectrum of a sample having wellknown thickness and then applying the Lambert-Beer law...

and solve for µ...

Dear G.M .

Thanks for your response.

How can I got the thickness of PMMA phantom? and. How can I calculate the incident intensity of x-ray photon and the transmitted intensity of x-ray photon?

Dear Tadelech Sisay Mekonin ,

a) measure the thickness d (or take it from a technical drawing),

b) measure the primary x-ray spectrum Io(E) and

c) measure the transmitted spectrum I(E);

Then calculate µ(E) = 1/d * ln[Io(E)/I(E)].

Even in the case if you have calculated for example any primary spectrum of an x-ray tube, you have to calculate the transmitted spectrum via the Lambert-Beer law. But in this case you need the µ(E) dependence of the PMMA and the thickness.

Here you are still at the beginning again...

So why not taking µ(E) from any database?

Dear G.M.

How I get attunation coefficient (E) for any database? I don't have energy of x-ray I have only tube potential 120KV and tube current 50-100-150-200-250-300mAs.how cal I calculate the x-ray energy? and how I used XCOM database ?

Dear.G.M

Using XCOM database for example 67kev =0.067Mev. In the data shit I can't got the attunation coefficient , but I got only density in g/cm3. Please tell me how can I got the attunation value in 1/cm?

Dear Tadelech Sisay Mekonin ,

with respect to the application of the NIST/XCOM data base please see my recent 'presentation' for the calculation of the linear x-ray attenuation coefficient :

Presentation How to use XCOM

With respect to the x-ray photon energy involved, there is only a rough estimate of the mean energy for an x-ray tube spectrum of given kV.

In the case of a 120kV tube spectrum one will have about 60keV in mean energy for a sample thickness of about 75mm PMMA and about 80keV for a 450mm PMMA sample *). The change in mean energy is due to the (so-called) hardening of the spectrum via increased sample attenuation.

So the 67keV, as mentioned above, fit into this range.

By the way: the current settings of a tube do not affect the spectrum...

*) via Philips (proprietary) tube spectrum calculator

Best regards

G.M.

Dear G.M

Thanks you very much

Dear G.M

I have only equation.

How to estimate the mean energy 60KeV above example the at 120KV tube spectrum sample thickness about75mm PMMA?

Dear.G.M

Please tell me

The characteristic ,thickness and behavior of this phantom material .

Dear Tadelech Sisay Mekonin ,

sorry, this phantom is unknown to me.

DearG.M.

I have only one question.

How to estimate the mean energy of 60 Kev the above example at 120 KV tub spectrum sample sample thickness about75mm? Please show me how to estimate the mean energy at 120 tube spectrum and 75 mm PMMA phantom thickness.

Dear Tadelech Sisay Mekonin ,

the mean energy has to be calculated via the following expression:

Emean = A/ B

with

A =integral [E*tubespectrum(E)*sampletransmission(E)*dE],

B= integral [tubespectrum(E)*sampletransmission(E)*dE],

sampletransmission = exp[-µPMMA(E)*d],

d= PMMA thickness

However you need the tube spectrum; but, unfortunately, I failed to execute properly tube spectrum calculators from the internet. So I cannot recommend you any free available calculators.

But with respect to the mean energy you may refer to the paper mentioned above.

The mean energy is a rough value, which depends on various parameters.

You may 'google' for the mean energy:

You will find some data, but they mainly refer to the primary spectrum, which is slightly filtered by the Be of the tube window and by some Al in the range of about 2 or 2,5mm; but a sample is not involved.

See for example:

Fig. 6 at:

https://pubs.rsna.org/doi/pdf/10.1148/radiographics.13.6.8290728

Fig. 9 at:

https://www.sciencedirect.com/science/article/pii/S1738573321004514

Dear, G.M.

Thank you for your responses.

I have only two CT scan parameter 120KV and 50-100-150-200mAs , I don't have E , tube spectrum, sample transmission and dE, how can I get or I calculate E,tub spectrum, sample transmission and dE? Please tell me

Dear Tadelech Sisay Mekonin ,

E is the x-ray photon energy; there is no necessity to calculate E. E is used as parameter here.

dE is the infinitesimal fraction of energy used for integrating an E-dependent function f(E) over E.

You should look at your basic math or physics courses for the calculation of an integral;

Tube spectrum is the challenge here; I cannot recommend a 'working' spectrum calculator from the internet.

Sample transmission T(E) is given above: T(E) = exp[-µ(E)*d]; d= sample thickness.

I

Dear GM

I have only x-ray tube potential 120kv ,but not x-ray photon energy, how can I got x-ray photon energy? I was doing laboratory work to estimate CTDI in phantom I was only fix x-ray tube potential 120kv and also estimate x-ray tube current 100mAs. How can I get x-ray photon energy ? I don't have fix this parameter.

Dear Tadelech Sisay Mekonin ,

we walk in a circle...

The simplest thing you can do, is to take the 67keV as mean energy for a 100kV spectrum, which is known from the paper given above for sufficient thick PMMA phantoms.

67keV is 2/3 of max photon energy of100keV (due to 100kV voltage).

So just scale the mean photon energy by the voltage (100kV --> 120kV).

You will end up with about 2/3*120keV = 80keV for your energy.

However, we all know, that these numbers are rough estimates. So for further calculations you may use attenuation coefficients up to 3 digits, but for presentation of final results you should restrict the numbers to 2 digits and add the term 'about'....

Best regards

G.M.

Dear G.M

Thanks very much.

My objective is the attenuation coefficient of x-ray photo for PMMA phantom the whole thickness of the PMMA body phantom is 32cm . we measure the attenuation coefficient of this phantom the thickness at the edeg from the centeral hole of the phantom is16 cm and the edge from the peripheral position of the phantom is I think 10mm. Which thickness is we used ? Both thickness ?

Dear Tadelech Sisay Mekonin ,

it depends on what you will measure:

a) the transmission, when the x-ray beam is passing the '16cm',

or that of the

b) '10 cm' section,

c) or both together, when these path lengths are in a straight line.

By the way; the attenuation coefficient itself is independet of the thickness d.

'd' is only involved when the transmission is involved:

transmission = I/Io= exp(-µ*d)

Final remark:

is there no colleague or tutor/supervisor at your institution, which can be partner of such discussions at your place?

I think, there should be someone.

Discussions by typing here on RG are very tough and in addition there may be a lot of misunderstanings here...

Best regards

G.M.

Dear G.M.

Thank you your answer and recommendation.

I am university teacher, parallel doing research work.

Dear G.M

How are you?

How can I calculate the xray attenuation coefficient for phantom material using grayscale value? I am using imageJ of CT image of phantom.

Please have a look at the header of the primary CT image file.

The data of the CT image are converted into gray values by ImageJ.

You may ask the operator of the CT about these issues...

Thanks

Dear G.M

i have one question ,

The dose is proportional to exp(mu*D)(asequare*sigmasquare*b*h) I got this expression you sent last days book. this book The relevance of image quality indices for dose optimization in abdominal multi-detector row

CT in children: experimental assessment with pediatric phantoms. please tell me the proportionality constant?

Sorry Tadelech Sisay Mekonin ,

I do not know.

Dear G.M.

Okay