imgtrtm 0.1.3 © 2010 by Turku PET Centre
Computation of parametric images of k3 from dynamic PET images in
ECAT or Analyze format applying transport-limited reference
tissue model for irreversible uptake, TRTM (1). This model
is based on the reference tissue compartment model (2,3), but here it is
assumed that in reference tissue k3'>>k2', and thus the uptake in it is
limited only by transport into tissue (4,5).
______ K1' ____________________
| | --> | k3'| | Assumptions:
| | <-- | Crf ------> Crb | k3'>>k2'
| | k2'|___________|________| R1=K1/k2=K1'/k2'
| | ____________________ Equation:
| Cp | K1 | k3 | | dCt(t)=R1*dCr(t)+R1*k3*Cr(t)
| | --> | Cf -------> Cb | -(k2+k3)*Ct(t)
| | <-- | | |
|______| k2 |___________|________|
The model is transformed to general linear least squares functions (6),
which are solved using Lawson-Hanson non-negative least squares (NNLS)
algorithm (7).
Parameters:
1) Dynamic image file (corrected for decay)
2) Reference region TAC file
3) Parametric BPnd image file
Options:
-R1=<filename>
Program computes also an R1 image
-k2=<filename>
Program computes also a k2 image
-k2s=<filename>
Program computes also a k2' image
-DV=<filename>
Parametric R1*k2/(k2+k3) image is saved
-rp=<filename>
Program writes regression parameters in the specified image file
-dual=<filename> or -du=<filename>
Program writes number of i in set p in NNLS dual solution vector in
the specified image file
-thr=<threshold%>
Pixels with AUC less than (threshold/100 x ref AUC) are set to zero
default is 0%
-thrR1=<threshold>
Pixels with R1 less than specified threshold value are set to zero in
parametric maps. By default, this threshold is not applied.
-thrDV=<threshold%>
DV (=R1*k2/(k2+k3)) and k3 in pixels with DV less than
(threshold/100 x DVmax) are set to zero.
By default, this threshold is not applied.
-end=<Fit end time (min)>
Use data from 0 to end time; by default, model is fitted to all frames
-h or --help
Print this message and exit
--version or --build
Print software build information and exit
--silent
Program works silently, printing only error and warning messages
--verbose
Program prints more information about what it is doing.
Example 1: k3 map is computed with default settings
imgtrtm ua5212dy1.v ua5212put.dft ua5212k3.v
Example 2: Pixel values in k3 map are set to zero when R1 is lower than
the specified R1 threshold level:
imgtrtm -thrR1=0.7 -R1=ua5212r1.v ua5212dy1.v ua5212put.dft ua5212k3.v
Example 3: k3 pixel values are set to zero when TAC AUC is less than 5% of
reference region AUC, or when DV is less than 10% of DVmax:
imgtrtm -thr=5 -thrdv=10 ua5212dy1.v ua5212put.dft ua5212k3.v
References:
1. Oikonen V. Model equations for reference tissue compartmental models.
http://www.turkupetcentre.net/reports/tpcmod0002.pdf
2. Cunningham VJ, Hume SP, Price GR, Ahier RG, Cremer JE, Jones AKP.
Compartmental analysis of diprenorphine binding to opiate receptors
in the rat in vivo and its comparison with equilibrium data in vitro.
J Cereb Blood Flow Metab 1991;11:1-9.
3. Lammertsma AA, Hume SP. Simplified reference tissue model for PET
receptor studies. NeuroImage 1996;4:153-158.
4. Herholz K, Lercher M, Wienhard K, Bauer B, Lenz O, Heiss W-D.
PET measurement of cerebral acetylcholine esterase activity without
blood sampling. Eur J Nucl Med 2001;28:472-477.
5. Nagatsuka S, Fukushi K, Shinotoh H, Namba H, Iyo M, Tanaka N, Aotsuka A,
Ota T, Tanada S, Irie T. Kinetic analysis of [11C]MP4A using a high-
radioactivity brain region that represents an integrated input function
for measurement of cerebral acetylcholinesterase activity without
arterial blood sampling. J Cereb Blood Flow Metab 2001; 21: 1354-1366.
6. Blomqvist G. On the construction of functional maps in positron emission
tomography. J Cereb Blood Flow Metab 1984;4:629-632.
7. Lawson CL & Hanson RJ. Solving least squares problems.
Prentice-Hall, 1974.
See also:
fit_trtm,
lhtrtm,
imglhk3,
ecat2tif,
ecatunit
Keywords: image, modelling, irreversible uptake, reference tissue
This program comes with ABSOLUTELY NO WARRANTY. This is free software, and
you are welcome to redistribute it under GNU General Public License.
