metab_sigmoid: Fit a sigmoid function for Parent Fraction.

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

Fit a sigmoid function for Parent Fraction.

Description

This function fits the sigmoid function by Guo et al. (2013) to parent fraction data.

Usage

metab_sigmoid(
  time,
  parentFraction,
  fit_ppf0 = FALSE,
  fit_delay = FALSE,
  lower = list(a = 0, b = 0, c = 0, ppf0 = 0.8, delay = -30),
  upper = list(a = 100, b = 100, c = 100, ppf0 = 1.1, delay = 30),
  multstart_lower = NULL,
  multstart_upper = NULL,
  multstart_iter = 100
)

Arguments

time	Time in seconds.
parentFraction	Measured values of parent fraction.
fit_ppf0	Should the starting plasma parent fraction be fitted? Otherwise, it is set to 1. Defaults to FALSE.
fit_delay	Should the delay of the plasma parent fraction be fitted? Otherwise, it is set to 0. Defaults to FALSE.
lower	Named list of the lower limits.
upper	Named list of the upper limits.
multstart_lower	Named list of the lower starting limits.
multstart_upper	Named list of the upper starting limits.
multstart_iter	Number of fits to perform before deciding on an optimal.

Value

An nls fit object.

References

Guo Q, Colasanti A, Owen DR, et al. Quantification of the specific translocator protein signal of 18F-PBR111 in healthy humans: a genetic polymorphism effect on in vivo binding. J Nucl Med 2013; 54: 1915–1923.

Examples

## Not run: 
pf <- bd_getdata(blooddata, output = "parentFraction")
metab_sigmoid(pf$time, pf$parentFraction)

## End(Not run)

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