### Linear Interpolation of Plasma/Whole-blood Fraction

The sequential steps for converting blood measurements to an input curve are explained in a dedicated section. The current plasma fraction model serves for converting a whole-blood activity curve into a plasma-activity curve.

It is assumed that a curve representing the measured fractions of plasma/whole-blood activity has been loaded with **Load Plasma/WB Fraction**.

The **Lin. Interpolation **model interpolates linearly between the measured fraction values. Outside the measured values the following interpolation rules apply:

- The fraction at time t=0 is assumed to equal 1.
- The fraction is assumed to remain constant after the last measured fraction.

For incomplete fraction data it is therefore recommended to replace the tail of the measurements by a fitted tri-exponential model.

Parameter Fitting

There is nothing to fit with the **Lin. Interpolation **model.