imgflow - tpcclib 0.8.0 © 2023 by Turku PET Centre

Estimation of rate constants K1, k2 and Va from dynamic PET image in
ECAT 6.3, ECAT 7.x, NIfTI-1, or Analyze 7.5 file format using
linearized two-compartment model [1].
Lawson-Hanson non-negative least squares (NNLS) method [2] is used to solve
general linear least squares functions.
 
When applied to dynamic [O-15]H2O studies, the resulting K1 image
equals perfusion (blood flow) image. K1 image can be divided by tissue
density (g/mL) (option -density) and multiplied by 100 (option -dL)
to achieve the blood flow image in units (mL blood)/((100 g tissue) * min).
 
When applied to dynamic [O-15]O2 brain studies, the resulting K1 image
can be converted to oxygen consumption image by multiplying it by
arterial oxygen concentration [3] (ml O2 / dL blood) to get the
parametric image in units mL O2 / ((100 ml tissue) * min).
The model assumptions hold only when oxygen consumption is 1-6.7
mL O2/(100g * min) and fit time is set to 300 s or less [3].
 
Arterial blood TAC must be corrected for decay and delay, with sample times
in seconds. Dynamic PET image must be corrected for decay.
 
Usage: imgflow [Options] btacfile imgfile flowfile
 
Options:
 -end=<Fit end time (sec)>
     Use data from 0 to end time; by default, all of it.
 -k2=<filename>
     Parametric k2 image is saved; in some situations perfusion calculation
     from k2 can be more accurate than the default assumption of f=K1.
     Perfusion can be calculated from k2 using equation f=k2*pH2O, where
     pH2O is the physiological partition coefficient of water in tissue.
 -Va=<filename>
     Parametric Va image is saved.
     Set -Va=0, if Va=0 is assumed; otherwise Va is always fitted.
 -thr=<threshold%>
     Pixels with AUC less than (threshold/100 x max AUC) are set to zero.
     Default is 5%.
 -max=<Max value>
     Upper limit for flow values in final units.
 -filter
     Remove parametric pixel values that are over 4x higher than
     their closest neighbours.
 -noneg
     Pixels where K1 estimates are negative are fitted again with
     constraint Va=0.
 -mL or -dL
     Units in flow and Va images will be given per mL or per dL,
     respectively. By default, units are per mL.
 -density[=<value>]
     With option -density the flow is calculated per gram or 100g tissue.
     Tissue density can be changed from the default 1.04 g/ml.
 -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.
 
By default, the units of pixel values in the flow (K1) image is
(mL blood)/((mL tissue) * min), in DV image (mL blood)/(mL tissue),
in k2 image 1/min, and in Va image (mL blood/mL tissue),
but the flow and Va units can be changed with above listed options.
 
Example 1. Calculation of perfusion and arterial blood volume image,
           stopping fit at 180 s:
  imgflow -Va=s2345va.v -end=180 s2345abfit.kbq s2345dy1.v s2345flow.v
 
Example 2. Dynamic image is precorrected for vascular activity,
           and all available data is used:
  imgflow -Va=0 s2345abfit.kbq s2345dy1_vacorr.v s2345flow.v
 
References:
1. Blomqvist G. On the construction of functional maps in positron
   emission tomography. J Cereb Blood Flow Metab. 1984;4:629-632.
2. Lawson CL & Hanson RJ. Solving least squares problems.
   Prentice-Hall, 1974.
3. Ohta S, Meyer E, Thompson CJ, Gjedde A. Oxygen consumption of the
   living human brain measured after a single inhalation of positron
   emitting oxygen. J Cereb Blood Flow Metab. 1992;12:179-192.
 
See also: imgflowm, imgbfh2o, imgcbv, fit_h2o, b2t_h2o, imglhdv, fitdelay
 
Keywords: image, modelling, perfusion, blood flow, radiowater, NNLS