# Catenation of PET images or sinograms

When PET scanning has been performed in separate sessions, or scan was unintentionally interrupted, it is advisable to join the scans together into one dynamic image or sinogram before continuing the analysis. This will help, not only in the analysis steps, but also to ensure that the times and decay correction in the data are correct.

If there is only one scan which was started later than at injection time, then follow the procedure for correcting delayed scans.

## Correction procedure

DICOM images can be catenated using Carimas plug-in FrameConcatenationPlugin.

In case of ECAT 6 or 7 data, use the command-line program ecatcat to catenate the images or sinograms. You need to enter the file names of the images or sinograms to be catenated and the name for the catenated file. Program looks the scan start times and frame times in the file headers, and corrects automatically the frame times and the correction for physical decay when necessary. Do not apply any extra corrections before executing this program!

If PET scan was unintentionally interrupted, it may happen that the scan that was recorded during the failure contains one or more erroneous matrices in the end, which either look peculiar or cause an error during execution of ecatcat. In these cases, try to figure out what the erroneous matrices are for example by listing them using lmlist, and then extract the correct matrices using esplit or e63mreg.

After the catenation, you can check the frame times in the joined datafile using for example program eframe.

### Scan Information Files (SIF)

If SIF data are needed in weighting or when converting image data to Analyze or NIfTI format you need to catenate also the SIF data. Do this using sifcat.

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Updated at: 2018-05-26
Created at: 2010-10-29
Written by: Vesa Oikonen