View source: R/kinfitr_mrtm2.R
mrtm2 | R Documentation |
Function to fit MRTM2 of Ichise et al. (2003) to data. This model is often used alongside MRTM1: MRTM1 is run on a high-binding region to obtain an estimate of k2prime, and this k2prime value is used for MRTM2.
mrtm2(
t_tac,
reftac,
roitac,
k2prime,
tstarIncludedFrames = NULL,
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 MRTM1 of SRTM, or set at a specified value. If using SRTM to estimate this value, it is equal to k2 / R1. |
tstarIncludedFrames |
Optional. The number of frames to be used in the
multiple regression. 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$tstarIncludedFrames
.
Granville J Matheson, mathesong@gmail.com
@references Ichise M, Liow JS, Lu JQ, Takano A, Model K, Toyama H, Suhara T, Suzuki K, Innis RB, Carson RE. Linearized Reference Tissue Parametric Imaging Methods: Application to [11C]DASB Positron Emission Tomography Studies of the Serotonin Transporter in Human Brain. Journal of Cerebral Blood Flow & Metabolism. 2003 Sep 1;23(9):1096-112.
data(simref)
t_tac <- simref$tacs[[2]]$Times
reftac <- simref$tacs[[2]]$Reference
roitac <- simref$tacs[[2]]$ROI1
weights <- simref$tacs[[2]]$Weights
dur <- simref$tacs[[2]]$Duration
fit <- mrtm2(t_tac, reftac, roitac, 0.1, weights = weights)
fit_dur <- mrtm2(t_tac, reftac, roitac, 0.1, weights = weights, dur = dur)
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