imgflow 0.8.6 © 2003-2010 by Turku PET Centre
Estimation of rate constants K1, k2 and Va from dynamic PET image in
ECAT 6.3 or 7.x file format using linearized two-compartment model [1].
Lawson-Hanson non-negative least squares (NNLS) [2] are 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].
Parameters:
1) Blood file (corrected for decay and delay, times in seconds!)
2) Dynamic image file
3) Fit time (s)
4) Parametric K1 (flow) image file
Options:
-k2=<filename>
Parametric k2 image is saved.
-Va=<filename>
Parametric Va image is saved.
Set -Va=NONE, if Va=0 is assumed; otherwise Va is always fitted.
-DV=<filename>
Parametric K1/k2 image is saved.
-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 or --help
Print this message and exit.
-v, --version, or --build
Print software build information and exit.
--silent
Program works silently, printing only warnings and error messages.
--verbose
Program prints lots of information about what it is doing.
Example 1. Calculation of perfusion and arterial blood volume image,
stopping fit at 180 s:
imgflow -Va=s2345va.img s2345abfit.kbq s2345dy1.v 180 s2345flow.v
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.
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:
fit_h2o,
b2t_h2o,
imglhdv,
fitdelay,
ecat2tif,
ecatcalc
Keywords: image, modelling, perfusion, blood flow
This program comes with ABSOLUTELY NO WARRANTY. This is free software, and
you are welcome to redistribute it under GNU General Public License.
