imgki 1.5.6 © 2003-2012 by Turku PET Centre
Estimation of influx constant (Ki) from dynamic PET images in ECAT 6.3
or 7.2 format applying multiple time graphical analysis (MTGA) approach of
Gjedde [1] and Patlak & Blasberg [2, 3] for irreversible tracer uptake.
Simple non-iterative perpendicular line fitting algorithm [4] is applied.
Parameters:
1) Input file (Plasma or Reference region TAC; times in minutes)
2) Dynamic image file
3) Linear fit start time in minutes (0 for automatic determination)
4) Parametric image file
Options:
-Ca=<value>
Concentration of native substrate in arterial plasma (mM),
e.g. glucose in [18F]FDG studies.
With this option the metabolic rate (umol/(min*100 g)) is calculated.
-LC=<value>
Lumped Constant; default is 0.52.
This or default LC is used in calculation of metabolic rate.
-density=<value>
Tissue density; default is 1.04 g/ml.
This or default density is used only in calculation of metabolic rate.
-thr=<threshold%>
Pixels with AUC less than (threshold/100 x max AUC) are set to zero.
Default is 0 %.
-max=<Max value>
Upper limit for Ki values.
-filter
Remove parametric pixel values that are over 4x higher than
their closest neighbours.
-end=<Fit end time (min)>
Never use data after fit end time.
-v=<filename>
Y axis intercepts are written as an image in specified file.
-n=<filename>
Numbers of selected plot data points are written as an image.
-h or --help
Print this message and exit.
-v, --version or --build
Print software build information and exit.
--silent
Program works silently, printing only error and warning messages.
Example 1. Calculation of Ki image, starting linear fit from 20 minutes:
imgki ua2918ap.kbq ua2918dy1.v 20 ua2918ki.v
Example 2. Calculation of glucose uptake image, when tissue density is 1.02,
plasma glucose concentration is 5.2 mM, lumped constant is 1.0,
starting linear fit from 10 minutes after radiotracer injection:
imgki -density=1.02 -Ca=5.2 -LC=1.0 s8642ap.kbq s8642dy1.v 10 s8642ki.v
Format of the input data file is specified in
http://www.turkupetcentre.net/analysis/doc/format_dft.html
The unit of pixel values in the parametric (Ki) image is
(mL plasma)/(min*(mL tissue)) by default, and umol/(min*100 g) in metabolic
rate image.
To calculate Ki images from [18F]FDOPA studies with plasma input:
subtract reference region TAC from dynamic image before using this program.
References:
1. Gjedde A. Calculation of cerebral glucose phosphorylation from brain
uptake of glucose analogs in vivo: a re-examination. Brain Res. 1982;
257:237-274.
2. Patlak CS, Blasberg RG, Fenstermacher JD. Graphical evaluation of
blood-to-brain transfer constants from multiple-time uptake data.
J Cereb Blood Flow Metab 1983;3:1-7.
3. Patlak CS, Blasberg RG. Graphical evaluation of blood-to-brain transfer
constants from multiple-time uptake data. Generalizations
J Cereb Blood Flow Metab 1985;5:584-590.
4. Varga J & Szabo Z. Modified regression model for the Logan plot.
J Cereb Blood Flow Metab 2002; 22:240-244.
See also:
imgfur,
imgbound,
imglhki,
ecat2tif,
patlak
Keywords: image, modelling, irreversible uptake, metabolic rate
This program comes with ABSOLUTELY NO WARRANTY. This is free software, and
you are welcome to redistribute it under GNU General Public License.