more questions about the Scherrer formula

[Miguel Hesiquio Garduno]

When I use the pseudo-Voigt function corrected by Thompson-CoX-Hastings
in the Rietveld software the calculations for size and strain  are make
with fwhm instead
integral breadth, is this a mistake?  or  can I calculate the
values for integral breadth and then apply to the formulas for
size/strain?   

thanks in advance
Miguel Hesiquio