## fit_gvar - tpcclib 0.7.8 © 2022 by Turku PET Centre

Non-linear fitting of Gamma variate bolus plus recirculation function
with time delay term to plasma and tissue time-activity curves (TACs).
Function:
| 0 , t < p1
f(t) = |
| p2*((t-p1)^p3)*exp(-(t-p1)/p4) , t >= p1
| + p5*(1-exp(-(t-p1)/p4))*exp(-(t-p1)/p6)
Usage: fit_gvar [Options] tacfile [fitfile]
Options:
-recirc=<Y|n>
Fit recirculation terms p5 and p6 (y, default), or fit only
gamma variate function setting p5=p6=0 (n).
-lim[=<filename>]
Specify the constraints for function parameters;
This file with default values can be created by giving this
option as the only command-line argument to this program.
-w1
All weights are set to 1.0 (no weighting); by default, weights in
data file are used, if available.
-wf
Weight by sampling interval.
-stoptime=<Fit end time>
All data with sample time > stoptime is excluded from the fit.
-thr=<Threshold%>
If sample value after the peak is less than Threshold% of the peak,
then that sample and all samples after that are omitted from the fit.
Hint: try to set threshold close to 100, e.g. 99%, to get a good
estimate of tracer appearance time.
-auto
Automatically sets the fit range from 0 to peak + at least one
sample more, until WSS/(sum of weights) gets worse.
-svg=<Filename>
Fitted and measured TACs are plotted in specified SVG file.
-fit=<Filename>
Fitted TACs are written in TAC format.
-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.
TAC file must contain at least 2 columns, sample times and
concentrations.
Weights can be specified as usual if data is in DFT format.
Program writes the fit start and end times, nr of points, WSS,
and parameters (p1, p2, ...) of the fitted function to the fit file.
See also: fit2dat, fit_sinf, fit_exp, fit_ratf, fit_hiad
Keywords: curve fitting, TAC, simulation