text: Patlak method is based on the assumption that the backflow of tracer from bone mineral to bone ECF is zero (i.e., k=0). The calculation of K using Patlak method is simpler than using non-linear regression (NLR) fitting the arterial input function and the tissue time-activity curve data to the Hawkins model. It is crucial to note that Patlak method can only measure bone plasma clearance (K), and cannot measure the individual kinetic parameters, K, k, k, or k.
  The concentration of tracer in tissue region-of-interest can be represented as a sum of concentration in bone ECF and the bone mineral. It can be mathematically represented as
  where, within the tissue region-of-interest from the PET image, C(T) is the bone tissue activity concentration of tracer (in units: MBq/ml) at any time T, C(T) is the plasma concentration of tracer (in units: MBq/ml) at time T, V is the fraction of the ROI occupied by the ECF compartment, and  is the area under the plasma curve is the net tracer delivery to the tissue region of interest (in units: MBq.Sec/ml) over time T. The Patlak equation is a linear equation of the form 
  Therefore, linear regression is fitted to the data plotted on Y- and X-axis between 4–60 minutes to obtain m and c values, where m is the slope of the regression line representing K and c is the Y-intercept of the regression line representing V.