Program for adding Gaussian noise to dynamic PET time-activity curve (TAC) or TACs using equations (1, 2): SD(t) = TAC(t) * sqrt(Pc/(TAC(t)*exp(-lambda*t)*deltat) TAC_noisy(t) = TAC(t) + SD(t)*G(0,1) , where Pc is the proportionality constant that determines the level of noise, TAC(t) is the mean activity concentration in the image frame, Deltat is the scan frame length, and G(0,1) is a pseudo random number from a Gaussian distribution with zero mean and SD of one. Usage: fvar4tac [Options] tacfile Pc isotope outputfile Options: -minsd=<SD> Set a minimum SD to add a minimum level of noise also to the time frames with little or no activity. -R=<nr of repeats> Specified number of output files (*_NNNN.*) with different set of noise are created. -common=<y|N> Common noise SD based on TAC mean is used (y), or SD is based on each TAC separately (n, default). -sd or -cv Noise is not added to TAC but calculated values of SD or CV (for noise) are saved instead in the output file. -sec If datafile does not contain time unit, times are by default assumed to be in minutes. Use this option to set time unit to sec. -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 data must contain frame start and end times (PMOD or DFT format). TACs are assumed to be decay corrected to zero time. Accepted isotope codes include at least O-15, C-11, F-18, Ga-68, N-13, Br-76, Rb-82, and Cu-62. Example: fvar4tac simulated.tac 5.0 C-11 noisy.tac References: 1. Chen K, Huang SC, Yu DC. Phys Med Biol 1991;36:1183-1200. 2. Varga J, Szabo Z. J Cereb Blood Flow Metab 2002;22:240-244. See also: fvar4img, var4tac, sim_3tcm, simframe, tacadd, avgttac Keywords: TAC, simulation, noise

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.