refPatlak: Patlak Reference Tissue Model

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

Patlak Reference Tissue Model

Description

Function to fit the Patlak Reference Tissue Model of Patlak & Blasbert (1985) to data.

Usage

refPatlak(
  t_tac,
  reftac,
  roitac,
  tstarIncludedFrames,
  weights = NULL,
  dur = NULL,
  frameStartEnd = NULL
)

Arguments

t_tac	Numeric vector of times for each frame in minutes. We use the time halfway through the frame as well as a zero. If a time zero frame is not included, it will be added.
reftac	Numeric vector of radioactivity concentrations in the reference tissue for each frame. We include zero at time zero: if not included, it is added.
roitac	Numeric vector of radioactivity concentrations in the target tissue for each frame. We include zero at time zero: if not included, it is added.
tstarIncludedFrames	The number of frames to be used in the regression model, i.e. the number of frames for which the function is linear after pseudo-equilibrium is reached. This is a count from the end of the measurement, so a value of 10 means that last 10 frames will be used. This value can be estimated using refPatlak_tstar.
weights	Optional. Numeric vector of the weights assigned to each frame in the fitting. We include zero at time zero: if not included, it is added. If not specified, uniform weights will be used.
dur	Optional. Numeric vector of the time durations of the frames. If not included, the integrals will be calculated using trapezoidal integration.
frameStartEnd	Optional: This allows one to specify the beginning and final frame to use for modelling, e.g. c(1,20). This is to assess time stability.

Value

A list with a data frame of the fitted parameters out$par, the model fit object out$fit, a dataframe containing the TACs of the data out$tacs, a dataframe containing the TACs of the fitted values out$fitvals, a vector of the weights out$weights, and the specified tstarIncludedFrames value out$tstarIncludedFrames

Author(s)

Granville J Matheson, [e-mail]

References

Patlak CS, Blasberg RG. Graphical evaluation of blood-to-brain transfer constants from multiple-time uptake data. Generalizations. Journal of Cerebral Blood Flow & Metabolism. 1985 Dec 1;5(4):584-90.

Examples

# Note: Reference region models, and irreversible binding models, should not
# be used for PBR28 - this is just to demonstrate function

data(pbr28)

t_tac <- pbr28$tacs[[2]]$Times / 60
reftac <- pbr28$tacs[[2]]$CBL
roitac <- pbr28$tacs[[2]]$STR
weights <- pbr28$tacs[[2]]$Weights

fit <- refPatlak(t_tac, reftac, roitac, tstarIncludedFrames = 10, weights = weights)

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