Gamma Function

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Gamma Function

The blood and plasma activity concentrations require interpolation procedures for kinetic modeling, as described above.

Operational Model Curve

The Gamma Function model is defined by the following functional form:


describing a sharp peak governed followed by a quick decay towards zero.


Parameter Fitting

The Gamma Function model includes a Begin time parameter for positioning the peak. The factor A scales the curve, the exponent B governs the rise and constant C the decay towards zero. Use the Fit plasma activity or Fit whole blood button to fit the operational model curve to the measurements. Note that all samples are considered, not only the ones after Begin.

The form of the curve reacts very sensitively to changes of the parameters. The example above illustrates the inability to fit model a peak followed by a moderate to slow decay appropriately. This model may therefore be more suited for simulations rather than actual data processing.

The Delay parameter serves for correcting a timing offset between tissue and blood data. Positive delays correspond to delayed blood information and hence shift the blood curve to earlier times (to the left). The Delay is only relevant during the fitting of the tissue model where it can be fitted as an additional parameter to the parameters of the kinetic model.