View source: R/kinfitr_reflogan.R
refLogan | R Documentation |
Function to fit the non-invasive Logan plot model of Logan et al. (1996) to data.
refLogan(
t_tac,
reftac,
roitac,
k2prime,
tstarIncludedFrames,
weights = NULL,
dur = NULL,
frameStartEnd = NULL
)
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. |
k2prime |
Value of k2prime to be used for the fitting, i.e. the average tissue-to-plasma clearance rate. This can be obtained from another model, or set at a specified value. If using SRTM to estimate this value, it is equal to k2 / R1. |
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 |
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. |
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$weights
, the specified k2prime value out$k2prime
, and the specified
tstarIncludedFrames value out$tstarIncludedFrames
Granville J Matheson, mathesong@gmail.com
Logan J, Fowler JS, Volkow ND, Wang GJ, Ding YS, Alexoff DL. Distribution volume ratios without blood sampling from graphical analysis of PET data. Journal of Cerebral Blood Flow & Metabolism. 1996 Sep 1;16(5):834-40.
data(simref)
t_tac <- simref$tacs[[2]]$Times
reftac <- simref$tacs[[2]]$Reference
roitac <- simref$tacs[[2]]$ROI1
weights <- simref$tacs[[2]]$Weights
fit <- refLogan(t_tac, reftac, roitac, k2prime = 0.1, tstarIncludedFrames = 15, weights = weights)
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