is zero (i.e., k4=0). the calculation of ki 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 (ki), and cannot measure the individual kinetic parameters, k1, k2, k3, or k4. 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 c b o n e ( t ) c p l a s m a ( t ) = k i ∗ ∫ 0 t c p l a s m a ( t ) d t c p l a s m a ( t ) + v o (t)}(t)}}=k_*^c_(t)dt}(t)}}+v_ where, within the tissue region-of-interest from the pet image, cbone(t) is the bone tissue activity concentration of tracer (in units: mbq/ml) at any time t, cplasma(t) is the plasma concentration of tracer (in units: mbq/ml) at time t, vo is the fraction of the roi occupied by the ecf compartment, and ∫ 0 t c p l a s m a ( t ) d t ^c_(t)dt} 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 y = m ∗ x + c patlak analysis where a linear regression is fitted between the data on y- and x-axis to obtain the estimates of the ki, which is the slope of the fitted regression line. 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 ki and c is the y-intercept of the regression line representing vo. siddique–blake method the calculation of ki using arterial input function, time-activity curve, and hawkins model was limited to a small skeletal region covered by the narrow field-of-view of the pet scanner while acquiring a dynamic scan. however, siddique et al. showed in 2012 that it is possible to measure ki values in bones using static naf pet scans. blake et al. later showed in 2019 that the ki obtained using the siddique–blake method has precision errors of less than 10%. the siddique–blake approach is based on the combination of the patlak method, the semi-population based arterial input function, and the information that vo does not significantly change post-treatment. this method uses the information that a linear regression line can be plotted using the data from a minimum of two time-points, to obtain m and c as explained in the patlak method. however, if vo is known or fixed, only one single static pet image is required to obtain the second time-point to measure m, representing the ki value. this method should be applied with great caution to other clinical areas where these assumptions may not hold true. suv vs ki the most fundamental difference between suv and ki values is that suv is a simple measure of uptake, which is normalized to body weight and injected activity. the suv does not take into consideration the tracer delivery to the local region of interest from where the measurements are obtained, therefore, affected by the physiological process consuming naf elsewhere in the body. on the other hand, ki measures the plasma clearance to bone mineral, taking into account the tracer uptake elsewhere in the body affecting the delivery of tracer to the region of interest from where the measurements are obtained. the difference in the measurement of ki and suv in bone tissue using naf are explained in more detail by blake et al. it is critical to note that most of the methods for calculating ki require dynamic pet scanning over an hour, except, the siddique–blake methods. dynamic scanning is complicated and costly. however, the calculation of suv requires a single static pet scan performed approximately 45–60 minutes post-tracer injection at any region imaged within the skeleton. many researchers have shown a high correlation between suv and ki values at various skeletal sites. however, suv and ki methods can contradict for measuring response to treatment. since suv has not been validated against the histomorphometry, its usefulness in bone studies measuring response to treatment and disease progression is uncertain.