I have some questions about the “USRBIN”, “DOSE“, and “DOSEQLET”.
The unit of both DOSE and DOSEQLET is (GeV/g·primary). If I use the REGION option in USRBIN, do I need to divide the output values of DOSE and DOSEQLET by the region volume (in cm^3) to obtain the unit (GeV/g·primary)? Is this correct?
To obtain the unit (Sv/primary) from the output value of DOSEQLET, should we apply the following conversion?
(output value of DOSEQLET / region volume)*1.602176462E-7
Is it correct?
Can we use the DOSEQLET to find the dose equivalent for “all particles” (i.e., photon, neutron, ions, etc)? Or do we need to use DOSE-EQ?
Are the results of DOSE-EQ and DOSEQLET equal to each other after applying the necessary conversion factors? Please explain.
Correct.
When using USRBIN with the REGION option, the results are normalised per primary only, not per unit volume. Therefore, to obtain the standard units:
for DOSE / DOSEQLET → GeV/g per primary
you must divide by the region volume (in cm³).
Correct.
After dividing by the region volume, the result is in GeV/g per primary, and you can convert it to dose units using:
1 GeV/g = 1.602176462 × 10⁻⁷ Gy
Since DOSEQLET already includes the quality factor, multiplying by this factor directly gives Sv per primary.
So your expression:
(DOSEQLET / region volume) × 1.602176462 × 10⁻⁷
is correct.
Not exactly.
For mixed radiation fields (photons, neutrons, protons, etc.), DOSE-EQ is generally preferred. It is based on fluence-to-dose-equivalent conversion coefficients (e.g. from ICRP 116).
DOSEQLET, instead, uses LET-dependent quality factors applied to the absorbed dose, and is more relevant when dealing with heavy ions, for which fluence conversion factors are not available. If this is not the case, it is better to use DOSE-EQ with suitable for your case conversion coefficients set, check AUXSCORE card.
No, they are not generally equal. DOSE-EQ and DOSEQLET are based on different physical approaches:
DOSE-EQ based on convoluting fluence with conversion coefficients
DOSEQLET based on multiplying dose by a LET-dependent quality factor
Could you please clarify what you mean by “all particles”?
If you refer to a typical mixed radiation field (e.g. photons + neutrons + charged hadrons), then DOSE-EQ is generally the appropriate and recommended estimator for radiation protection purposes.
Using DOSEQLET is not strictly wrong, but it is based on LET-dependent quality factors. Therefore, its use should be justified depending on your specific application.
They are conceptually different quantities.
It is up to you to decide which one is more appropriate for your case, but this choice should be guided by the underlying physics and the quantity you want to estimate.
For a deeper understanding, I recommend referring to publications of the ICRP (60, 103, 116), where the definitions of radiation weighting factors, protection and operational quantities are discussed in detail.