The transformation of the plasma activity curve into the input curve is governed by the configuration on the Metabolites tab. Two cases are to be distinguished.
Measured Parent Fraction Data is available
If a parent fraction curve has been loaded, it is shown in the curve area. Initially, the parent fraction model is set to Measured so that linear interpolation between the samples is used to calculated intermediate parent fractions. The model selection choice allows to select smoother models, and fit them to the measurements using the Fit parent fraction button as illustrated below.
No Parent Fraction Data available
If no data parent fraction data have been loaded, the parent fraction model is set to Fix with a free parent fraction f_{p}=1. This is adequate for all tracers which do not require metabolite correction, and for cases when the metabolite correction has already been applied to the plasma data prior to loading them with Load Plasma Curve.
In the case of a tracer which shows a characteristic buildup of the metabolites it may be possible to derive an average parent fraction curve and fit a model to it. To apply a metabolite correction the user can then simply select the appropriate model function and enter the demographic parameter values, as illustrated below. To apply a demographic correction, it must be ensured that time zero of plasma data always represents the time of tracer injection. Naturally, no fit will be possible in this situation.
Parent Fraction Models
The following parent fraction models are available. All of them include the constant f_{p} which must be determined externally and which is set to 1 per default. For information about the fitting options please refer to fitting of kinetic models.

Fix 
The concentration of free tracer is proportional to the concentration of the loaded plasma curve. There is nothing to fit with the Fix model. 

Measured 
The ratio unchanged/total tracer in plasma has been experimentally determined and loaded. Linear interpolation is used for the calculation of intermediate fraction values. There is nothing to fit with the Measured model. 

Hill 
The parent fraction is described by a Hill function with a delay t_{0}, and 0<A<=1, B>0, C>0. The delay allows for an initial phase during the infusion without tracer metabolites. This function was used with 11CWAY100635 data [53]. 

Watabe 
The functional form introduced by Watabe for 11CMDL100907 data [54]: with a delay t_{0}. 

1Exponential 
The functional form described by Wu et al for 11CWAY100635 data [55]: with a delay t_{0}. f_{parent}(t) is forced to f_{p} at time t_{0}. 

2Exponential 
The functional form described by Wu et al for 11CWAY100635 data [55]: with a delay t_{0}. f_{parent}(t) is forced to f_{p} at time t_{0}. 

3Exponential 
Sum of three decaying exponentials with a delay t_{0}. There is no restriction that f_{parent}(t) equals f_{p }at time t_{0}. 
Note: The metabolite correction is applied to the plasma curve using the original plasma sampling times. The assumption is that the parent fraction and the plasma curve have a common time scale. Only after the metabolite correction has been applied is the input curve shifted by the blood sampling time delay.
Default Values of Model Parameters
Each model has default values. Initially, they are factory settings, but they can be redefined by the user if he wants to establish a default configurations which is more adequate from him. Note that the configurations are valid per PMOD login, so different logins could be prepared for processing types of data requiring different initial parameter values.
Saves the current configuration of the model as the new default. Included are the values, the fit flags, and the restrictions of all parameters. 

Retrieves the default configuration of the model. 