NLLSQ estimation of R1 (=K1/K1'), k2, and k3 applying the reduced reference tissue compartment model, RRTM (1). This model is based on the reference tissue compartment model (2, 3), but here it is assumed that the binding or metabolism of tracer is irreversible (k4=0) during the PET scanning. Usage: fit_rrtm [Options] ttacfile reference endtime resultfile TTAC file can be in DFT or PMOD format. Sample times must be in minutes. If TTAC file contains weights, those are used in the NLLSQ fitting. Reference region TAC can be given separate TAC file or as the name or number of the reference region in TTAC file. Options: -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. -SD[=<y|N>] Standard deviations are calculated and saved in results (y), or not calculated (n). -CL[=<y|N>] 95% Confidence limits are calculated and saved in results (y), or not calculated (n). -w1 All weights are set to 1.0 (no weighting); by default, weights in TTAC file are used, if available. -wf Weight by sampling interval. -fit=<Filename> Fitted regional TACs are written in file. -svg=<Filename> Fitted and measured TACs are plotted in specified SVG file. -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. Values of R1, k2, and k3 are written in the specified result file. Fitted curves are written in DFT format, if file name is given. Example 1: file a789.dft contains regions-of-interest and reference region, with name 'cereb'. The whole time range is used in the fit. Fitted TACs are plotted in SVG format. fit_rrtm -svg=a789rrtm.svg a789.dft cereb 999 a789.res Example 2: Reference region TAC is in a separate file, a789ref.dft. Standard deviations and confidence limits are also estimated. TAC data from injection to 60 min is used in the fitting. fit_rrtm -SD=y -CL=y a789.dft a789ref.dft 60 a789.res Example 3a: Create a file containing default parameter limits: fit_rrtm -lim=rrtm.lim Example 3b: Apply user-defined parameter constraints specified in rrtm.lim: fit_rrtm -lim=rrtm.lim a789.dft cereb 999 a789.res References: 1. Oikonen V. Model equations for reference tissue compartmental models. http://www.turkupetcentre.net/reports/tpcmod0002.pdf 2. Cunningham VJ, Hume SP, Price GR, Ahier RG, Cremer JE, Jones AKP. Compartmental analysis of diprenorphine binding to opiate receptors in the rat in vivo and its comparison with equilibrium data in vitro. J Cereb Blood Flow Metab 1991;11:1-9. 3. Lammertsma AA, Hume SP. Simplified reference tissue model for PET receptor studies. NeuroImage 1996;4:153-158. See also: patlak, fitk3, tacweigh, rescoll, sim_rtcm, fit_trtm Keywords: TAC, modelling, irreversible uptake, RTCM, reference input