I am scoring DOSEQLET for proton beams in a medium as a function of energy. As per manual, it will give absorbed dose X Q(LET). Now my queries are as below:
Whether it considers Effective Q value calculated based on the LET distribution of the the primary protons as well as the generated secondaries or it will simply take Q value corresponding to the LET of the incident proton energy.
In case it consider the LET distribution of the primary proton and the produced secondaries, then which formalism is used to calculate the effective Q values ?
Generally, the secondaries will have the Q(LET) values applied as well. The Q(LET) value is mainly contributing for hadrons or other heavy particles but not for electromagnetic particles. This means that you only see a non-negligible contribution if the impacting proton beam has a high enough energy, where it can create a hadronic shower.
The Q(LET) in FLUKA is calculated using the definition given in Table A-1 that can be found in the ICRP60 International Comission on Radiological Protection, ICRP Publication 60, Annals of the ICRP 21, 1-3 (1991), also discussed in this post.
The following statement is not clear to me:
“This means that you only see a non-negligible contribution if the impacting proton beam has a high enough energy, where it can create a hadronic shower.”
What I am understanding from this sentence is:
If I take high energy protons (GeV to TeV range) as incident, then this scorer will not give correct Q value. Am I correct ?
For understanding purpose, I did some auxiliary calculations using 50 GeV proton in water. Case 1: At a given depth, I calculated microdosimetric distributions at 1 um site size and using ICRP 60 and ICRU 40 formulations, I have calculated Q values. Both the ICRP 60 and ICRU 40-based Q values are comparable. Case 2: I have calculated DoseQLET and Dose at the same depth. Then I took ratio of DoseQLET to Dose to get the effective Q value. This Q value is around 35% lower as compared to those based on microdosimetric distributions.
I am not able to understand, why this much difference is there in the case of protons.
Can you please explain this. It will be helpful for me.
The following statement is not clear to me:
“This means that you only see a non-negligible contribution if the impacting proton beam has a high enough energy, where it can create a hadronic shower.”
Correction to my earlier reply:
“The Q(LET) value is contributed for all charged particles, i.e. for your incoming proton beam as well as for the delta rays it will produce, and nuclear reaction products.”
The original spirit was to imply that the higher the proton energy the higher the secondary (lower-energy particles) production rate, and therefore the higher the involved Q(LET) values.
What I am understanding from this sentence is:
If I take high energy protons (GeV to TeV range) as incident, then this scorer will not give correct Q value. Am I correct ?
No, this does not follow from the above considerations.
For understanding purpose, I did some auxiliary calculations using 50 GeV proton in water.
Case 1: At a given depth, I calculated microdosimetric distributions at 1 um site size and using ICRP 60 and ICRU 40 formulations, I have calculated Q values. Both the ICRP 60 and ICRU 40-based Q values are comparable.
Case 2: I have calculated DoseQLET and Dose at the same depth. Then I took ratio of DoseQLET to Dose to get the effective Q value. This Q value is around 35% lower as compared to those based on microdosimetric distributions.
Could you elaborate on how you proceeded for case 1?