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

This program comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome

to redistribute it under GNU General Public License.

Source codes are available in https://gitlab.utu.fi/vesoik/tpcclib.git.