Fit time-activity curves with this program. fit_sinf can fit the time-activity curve (TAC) of PET tracer in plasma or blood to a four-to-ten parameter function.
This function may be applied when PET tracer is introduced into venous blood as a short infusion. Function: f(t)= if tTa and t=Ta+Ti : (1/Ti)*Sum[i=1..n, (Ai/Li)*(exp(-Li*(t-Ta-Ti)) - exp(-Li*(t-Ta)))].

Command-line arguments:
1) TAC filename
2) Filename for fitted function parameters (optional)

TAC data must be in DFT format (2). For a good fit, (radioactivity) concentrations should be corrected for physical decay and circulating metabolites.
Function parameters will be written in the parameter file (3).

Command-line options:
-fast or -safe
Speed up the fitting but increase the chance of failure, or increase the reliability at the cost of computing time.
-fit=<Filename>
Fitted TACs are written in DFT 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
-tau1=<Dispersion time constant (s)>
-tau2=<2nd dispersion time constant (s)>
Dispersion is added to function, also to saved curve and plot; curve without dispersion can be calculated from function parameters.
-wf
Weight by sampling interval.
-min=<SS|ABS>
Sum-of-squares (SS) is minimized by default, but optionally sum of absolute deviations can be selected.
-h or --help
Print this message and exit
--version or --build
Print software build information and exit
--silent
Program works silently, printing only error and warning messages
--verbose
Program prints more information about what it is doing

Options for constraining the fit:
-lim=<filename>
Specify the constraints for model parameters; This file with default values can be created by giving this option as the only command-line argument to this program.
-Ti=<infusion time>
Duration of tracer infusion; 0, if short bolus.
-Ta=<appearance time>
Time when tracer concentration starts ascending.
-n=<1|2|3|4|5|A> The nr of summed functions; A=determined by AIC (default).
2 or 3 is usually recommended (much faster).

The license of this software is Freeware, you can free download and free use this calculator software.