imglhlk3 0.3.1 © 2003,2005 by Turku PET Centre
Estimation of three-compartment model term lambda*k3 for irreversible
PET tracers [2, 4] from dynamic PET images in ECAT 6.3 or 7.x format.
A modification of the method of Blomqvist [1] is applied and Lawson-Hanson
non-negative least squares (NNLS) [3] is used to solve the resulting
general linear least squares functions for Ki and K1.
Lambda*k3 is solved as lambda*k3 = Ki*K1/(K1-Ki) [2]. Ki/K1 is constrained
to <0.9.
Lambda*k3 is more robust parameter than k3, because
-like lambda=K1/k2 it is independent of blood flow [2]
-it is independent of nonspecific binding which appears in both k2 and k3
and is cancelled out in k3/k2 [4]
However, lambda*k3 is dependent on plasma protein binding [4].
Program parameters:
1) Plasma file (times in minutes!)
2) Dynamic image file
3) Parametric lambda*k3 image file
4) Parametric Vb image file (optional)
Options:
-T=<threshold%>
Pixels with AUC less than (threshold/100 x mean AUC) are set to zero.
Default is 0 %
-Ki=<filename>
Parametric Ki image is saved.
-K1=<filename>
Parametric K1 image is saved.
-F Remove parametric pixel values that are over 4x higher than
their closest neighbours.
-E=<Fit end time (min)>
Use data from 0 to end time; by default, model is fitted to all frames.
e.g.: imglhlk3 ua2917ap.kbq ua2917dy1.v ua2917lk3.v -K1=ua2917k1.v
The vascular volume is considered in the model setting only if filename
for Vb image is given. Otherwise the contribution of vasculature to the
total radioactivity concentration is assumed to be negligible.
Note that this model can correctly estimate Vb only if
-plasma does not contain any labelled metabolites
-plasma and blood curves are similar in shape.
The units of pixel values in the parametric images are ml/(min*ml) for
lambda*k3, Ki and K1, and ml/ml for Vb.
References:
1. Blomqvist G. On the construction of functional maps in positron
emission tomography. J Cereb Blood Flow Metab 1984;4:629-632.
2. Fowler JS, Volkow ND, Cilento R, Wang G-J, Felder C, Logan J.
Comparison of brain glucose metabolism and monoamine oxidase B (MAO B)
in traumatic brain injury. Clin Pos Imag 1999;2:71-79.
3. Lawson CL & Hanson RJ. Solving least squares problems.
Prentice-Hall, 1974.
4. Logan J, Fowler JS, Ding Y-S, Franceschi D, Wang G-J, Volkow ND,
Felder C, Alexoff D. Strategy for the formation of parametric images
under conditions of low injected radioactivity applied to PET studies
with the irreversible monoamine oxidase A tracers [11C]clorgyline and
deuterium-substituted [11C]clorgyline. J Cereb Blood Flow Metab 2002;
22:1367-1376.
See also:
imglhk3,
ecat2tif,
lhsolvk3,
lhsolk3
Keywords: image, modelling, irreversible uptake