fitdt - tpcclib 0.8.2 © 2026 by Turku PET Centre

Estimate the time delay (dT) between PET tissue and blood curves.
Initial part of tissue curve is fitted with a range of input curves moved
in time (1, 2), using linearised one or two tissue compartment model
with blood volume term. The time that provides the best fit
(smallest sum-of-squares) is selected. Tissue heterogeneity, dispersion of
the blood curve, metabolites, and variable plasma-to-blood ratio may
only minimally impact the time delay estimate, if only the initial part
of the data is fitted with relatively complex model.
 
Usage: fitdt [options] btacfile ttacfile parfile [dcttacfile]
 
Options:
 -min=<Time (sec)> and -max=<Time (sec)>
     The range of time delays to be tested; by default -10 - +50 s.
 -end=<Fit end time (sec)>
     Use data from 0 to end time; by default, 300 s; at least 120 s.
     In case of short PET scan, end time may need to be reduced so that
     BTAC with negative delay extends to end time.
 -step=<dT step size (sec)>
     The step length for moving the input curve; by default 1 s.
 -model=<R1TCM | I2TCM | R2TCM>
     Reversible one-tissue (R1TCM, default), irreversible 2-tissue model
     (I2TCM), or reversible 2-tissue model (R2TCM) can be selected.
 -h, --help
     Display usage information on standard output and exit.
 -v, --version
     Display version and compile information on standard output and exit.
 -d[n], --debug[=n], --verbose[=n]
     Set the level (n) of debugging messages and listings.
 -q, --quiet
     Suppress displaying normal results on standard output.
 -s, --silent
     Suppress displaying anything except errors.
 
Delay times for each tissue curve are reported in parameter file.
File may also contain a median time delay as 'time_difference := time',
depending on the file format.
Positive delay time means that tissue curve is delayed as compared to
the input curve, and vice versa. Thus, input curve needs to be moved
by the delay time to match the tissue curve.
 
Optionally, delay corrected TTACs can be written in specified file.
 
References:
 1. Meyer. Simultaneous correction for tracer arrival delay and dispersion
    in CBF measurements by the H215O autoradiographic method and dynamic PET.
    J Nucl Med 1989; 30:1069-1078.
 2. van den Hoff et al. Accurate local blood flow measurements with
    dynamic PET: fast determination of input function delay and dispersion
    by multilinear minimization. J Nucl Med 1993; 34:1770-1777.
 
See also: fitdelay, imgdelay, tacmove, tactime, simdisp, tacframe
 
Keywords: TAC, modelling, time delay