ranoise.c File Reference

PET noise estimation. More...

#include "tpcclibConfig.h"
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#include <string.h>
#include "tpcisotope.h"

Go to the source code of this file.

Functions
double	noiseSD4Frame (double y, double t1, double dt, int isotope, double a)

Detailed Description

PET noise estimation.

Definition in file ranoise.c.

Function Documentation

noiseSD4Frame()

double noiseSD4Frame	(	double	y,
		double	t1,
		double	dt,
		int	isotope,
		double	a )

Calculate the standard deviation (SD) of noise for PET radioactivity concentration.

SD of noise can be used in simulations. Reference: Varga & Szabo. J Cereb Blood Flow Metab 2002;22(2):240-244.

See also

isotopeIdentify, drandGaussian, simC3s, simC3p, simRTCM

Returns

Returns the SD, or NaN in case of an error.

Parameters

y	Sample radioactivity concentration (decay corrected to zero time).
t1	Radioactivity measurement (frame) start time in minutes.
dt	Radioactivity measurement (frame) duration in minutes.
isotope	Isotope code as enum or index of isotope in isotope table; enter ISOTOPE_UNKNOWN if not to be considered.
a	Proportionality factor. Note that it should be in relation to the unit of y.

Definition at line 26 of file ranoise.c.

  {
  /* Frame start time must be >=0 and frame duration must be >0 */
  if(isnan(y) || !(t1>=0.0) || !(dt>0.0) || !(a>=0.0)) return(nan(""));
  /* If concentration is not positive, then its SD is zero */
  if(!(y>0.0)) return(0.0);
 
  /* Calculate decay factor (<=1) */
  double df;
  if(isotope==ISOTOPE_UNKNOWN) {
    df=1.0;
  } else {
    df=1.0/decayCorrectionFactorFromIsotope(isotope, t1, dt);
    if(!(df>0.0 && df<=1.0)) return(nan(""));
  }
 
  /* Calculate SD */
  return(sqrt((a*y)/(dt*df)));
}