2003-05-08 Vesa Oikonen

Logan plot for regional analysis:

reference region input


Logan plot with reference region input is used to calculate the DVR values, which are related to the binding potential values: BP=DVR-1.

 

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 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.

2. Computing the DV

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

  1. regional tissue TAC file
  2. name of reference region in the datafile
  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.

With reference region input, the (population) average reference region k2 should be used to correct for the (small) time dependence of the ROI/reference ROI -ratio [Logan et al. 1996]. This correction can be made with option -k2=X, where X is the average k2 value determined from studies with plasma input. For some tracers, e.g. [11C]raclopride, this correction is not necessary [Logan et al. 1996].

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.

Logan J, Fowler JS, Volkow ND, Wang G-J, Ding Y-S, Alexoff DL. Distribution volume ratios without blood sampling from graphical analysis of PET data. J Cereb Blood Flow Metab 1996; 16: 834-840.