2003-06-01 Vesa Oikonen

Logan plot for regional analysis:

plasma input


Logan plot with plasma input is used to calculate the distribution volumes of tracer. If there exists a reference region with no specific binding, the DVR values can be calculated "manually" by dividing the DVs with the DV from reference region. There exists also an alternative multilinear method to calculate the DV using program lhsoldv.

 

Steps of calculation:

Any or all of of the following steps can be done in Solaris terminal window or MS Windows command prompt window on either SUN or PC platform. Currently, the Windows version is not installed or updated automatically.

1. Preparation of arterial plasma curve

The procedure is dependent on the tracer and study protocol. Detailed instructions on the preparation of input curves in given elsewhere. In short, if on-line detector was used to collect the blood curve during the early phase of the study, the blood curve must be corrected and converted to plasma TAC, and then combined to the manually sampled plasma curve. Fractions of metabolites must be corrected.

Logan plots are considered to be robust enough not to require corrections for delay or vascular volume fraction.

2. Preparation of regional tissue TAC data

This is explained in detail elsewhere. In short: draw ROIs and calculate regional TACs from dynamic images, and calculate averages over planes and regions if required. If you have regional TACs in old format (*.roi.kbq), convert those to DFT format using program nci2dft. Make sure that the reference tissue region is included in the datafile.

3. Computing the DV

The logan program can be run with at least the following command line parameters:

  1. regional tissue TAC file
  2. filename of metabolite corrected plasma TAC
  3. start time for the line fit (time where linear phase starts)
  4. end time for the line fit (time where linear phase ends, or end time of study)
  5. name for result file

In addition, the plot and line data can be saved in HTML table format by specifying filename for it as 6th parameter. This file can then be read into e.g. Excel or OpenOffice (and copied from there to Origin) for drawing the plots.

By default, logan fits the line using a method which assumed (correctly) that both of the plot coordinates contain variation. With option -c a traditional regression line can be used instead.