fit_feng - tpcclib 0.8.1 © 2025 by Turku PET Centre

Non-linear fitting of the exponential based function suggested by
Feng et al (1993) to the PET plasma or blood time-activity curve (TAC).
 
Function:
  when t<=dt : f(t) = 0 
  when t>dt  : f(t) = (p1*(t-dt)-p3-p5)*exp(p2*(t-dt)) 
                     + p3*exp(p4*(t-dt)) + p5*exp(p6*(t-dt))
 
Usage: fit_feng [Options] tacfile [parfile]
 
Options:
 -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.
     Without file name the default values are printed on screen.
 -integ[ral]
     Given datafile contains the AUC of TAC as function of time.
 -wf
     Weight by sampling interval.
 -n=<2|3|4|A>
     The nr of exponential functions; A=determined automatically.
     Default is 3; changing the default may lead to a bad fit.
 -ss
     Function approaches steady level; last exponent term is a constant,
     i.e. either p6 or p8 is 0.
 -delay=<time>
     Delay time (dt) is constrained to specified value (>=0).
 -MRL
     Error is returned if MRL check is not passed.
 -fast or -safe
     Speed up the fitting but increase the chance of failure, or
     increase the reliability at the cost of computing time
 -res=<Filename>
     Fitted parameters are also written in result file format.
 -svg=<Filename>
     Fitted and measured TACs are plotted in specified SVG file.
 -svg1=<Filename>
     Initial part of fitted and measured TACs are plotted in SVG file
 -svg2=<Filename>
     Lower part of fitted and measured TACs are plotted in 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 two columns, sample times in the first,
and concentrations of TACs in the following columns.
To obtain a good fit, TAC should be corrected for physical decay and any
circulating metabolites.
Function parameters (p1, ..., dt) will be written in the parfile.
 
References:
1. Feng D, Huang S-C, Wang X. Models for computer simulation studies of input
   functions for tracer kinetic modeling with positron emission tomography.
   Int J Biomed Comput. 1993;32:95-110.
 
See also: fit2dat, fit_sinf, fit_exp, fit_dexp, fit_ratf, extrapol
 
Keywords: curve fitting, input, modelling, simulation