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It is assumed that the time-course of the tracer activity in whole blood has been loaded with Kinetic/Load Whole Blood Activity.To configure the interpolation model of whole blood please select the Blood tab, and set the Whole blood radio button. A list of model functions is available which can be shown with the arrow button indicated below.
Default is Lin. Interpolation, which just represents linear interpolation between sample times. To replace linear interpolation by a smoother function select an appropriate definition from the Whole Blood model list. The model functions are described in the reference section. As soon as a model function is selected, the parameters are updated in the Standard pane, and a corresponding model curve is shown in the curve window as Whole blood model.
In the example above the model has not yet been fitted so that the distinction between the measurement and the model (sum of exponentials) is clearly visible. The parameters of the blood model can be configured for fitting purposes by enabling the check boxes. Activating the Fit whole blood button starts a fitting process which adjusts the model parameters such that the interpolation curve comes into optimal agreement with the measurements. Fitting works exactly in the same way as is explained for the tissue models here.
Replace activity data will replace the actual data samples by the current model values at the original sampling times. This functionality is mostly useful for replacing a blood curve by its dispersion-correction as described in a separate section.
The Blood Delay Parameter
All standard blood models have a Delay parameter to correct for a timing error between tissue and blood data. Positive delays represent delayed blood information and hence shift the blood curves to earlier times (to the left). This parameter is only relevant for fitting of the tissue model. Therefore, when fitting the shape of the blood curve with Fit whole blood, it is automatically disabled. When fitting the kinetic tissue model, however, it can be allowed for fitting.