Please go for the paper:

Estimation of effective dose and lifetime attributable risk from

multiple head CT scans in ventriculoperitoneal shunted children

J. Aw-Zoretica,, D. Sethb, G. Katzmanb, and S. Sammetb

Eur J Radiol. 2014 October ; 83(10): 1920–1924.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4623705/pdf/nihms729929.pdf

Best of luck.

mGy is the physical dose, and mSv is the physical dose multiplied by a relative effect value.  E.g., Low energy neutrons are more carcinogenic than the same dose of high energy X rays by a certain factor.  If one multiplies by the factor, then mGy is converted to mSv.  It's always best to state both; the physical dose and the equivalent dose, and cite the source and value of the conversion factor

.   

Maybe my question is not very clear. What I meant was whether I should use organ dose D (mGy) or the equivalent dose (Ht=Wt.D) absorbed by tissue?

How I can estimate LAR for high radiation dose for ex: 20 Gy