When the blood concentration in the Logan graphical method is replaced by a reference region concentration C'(t), the following linear regression equation is obtained.
k2' represents he average tissue-to-plasma clearance of the reference tissue. The equation contains the distribution volume ratio (DVR = BPnd+1) as the slope, and an intercept int' which becomes constant after an equilibration time t*. The method does not require a particular (1-tissue compartment model) structure of the data.