blmod_exp_startpars: Create starting parameters for an exponential blood model

In mathesong/kinfitr: Kinetic Modelling of PET Time Activity Curves

Create starting parameters for an exponential blood model

Description

This function guesses reasonable starting parameters for exponential blood models. I use the suggestions from page 515 of Pinheiro & Bates Mixed-Effects Models in S and S-PLUS for creating the exponential starting parameters.

Usage

blmod_exp_startpars(
  time,
  activity,
  fit_exp3 = TRUE,
  expdecay_props = c(1/60, 0.1)
)

Arguments

time	The time of each measurement.
activity	The radioactivity of each measurement.
fit_exp3	Should a third exponential be fitted, or is a bi-exponential fit desired? Default is TRUE.
expdecay_props	What proportions of the decay should be used for choosing starting parameters for the exponential decay. Defaults to 1/60 and 1/10, i.e. start to 1/60, 1/60 to 1/10 and 1/10 to end. If fitting only two exponentials, the second value will be used.

Value

A list of the starting parameters

Author(s)

Granville J Matheson, [e-mail]

Examples

blooddata <- pbr28$blooddata[[1]]
blooddata <- bd_blood_dispcor(blooddata)
aif <- bd_extract(blooddata, output = "AIF")
start <- blmod_exp_startpars(aif$time,
                           aif$aif)

mathesong/kinfitr documentation built on Jan. 15, 2024, 11:07 p.m.