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Overview of the RE-GP Processing in PXMOD
The preprocessing section of the Vt (RE-GP Analysis, Zhou) model serves for the specification of t* and the smoothing parameters. The user may specify an error criterion and fit t* for a representative tissue TAC, or directly enter t*. The t* resulting from preprocessing is applied for the pixel-wise fits.
For each pixel, the slope and intercept of the regression line to the Patlak plot are calculated. The resulting parametric maps are then smoothed. Finally, the regression line to the RE plot in each pixel is calculated in each pixel. Vt obtained from the RE plot is corrected using the smoothed outcome of the Patlak analysis according to
as explained above.
Acquisition and Data Requirements
Image Data |
A dynamic PET data from a receptor tracer with reversible binding. |
Blood Data |
The plasma activity from the time of injection until the end of the PET acquisition. |
Blood Preprocessing
Decay correction is the only blood correction option.
Model Preprocessing
t* |
Start time of the data segment used in the analysis. If t* is checked for fitting, the Max. Err. criterion will be applied to the RE plot of the specified tissue TAC. |
Max. Err. |
Maximum relative error ( (measured-predicted)/predicted ) allowed between the linear regression and the RE-transformed measurements in the segment starting from t*. |
Smooth |
Spatial smoothing window along z in number of pixels. A number of 1 means planar smoothing. |
Resampling |
Sampling increment applied during the basis function calculation. |
Threshold |
Discrimination threshold for background masking. |
Map Parameters
The example below shows a typical configuration for an irreversible mode (k4 = 0 fixed)
Vt-REGP |
Distribution volume of total ligand uptake in tissue. Insensitive to non-equilibration bias. |
Vt_RE |
Slope of the regression line to the RE plot and also a distribution volume estimate. If the equilibrium condition is not satisfied, this Vt estimate is biased. Default is therefore not to use Vt_RE, but it can enabled for inspection. |
RE Intercept |
y-Intercept of the regression line to the RE plot. |
Patlak Slope |
Slope of the regression line to the Patlak plot. |
Patlak Intercept |
y-Intercept of the regression line to Patlak plot |