Calibration Experiment

The recommended practical calibration procedure is as follows:

1. Make sure the system time of the PET scanner and the twilite acquisition computer is synchronized.
2. Fill a PET phantom partially with water, add radioactivity, and shake to distribute the activity homogeneously. Fill the phantom entirely and shake again. The amount of activity should be such that a tracer concentration of 200-500 kBq/cc results.
3. Inlay the same catheter which will be used for the live experiment into the template, fill it with the phantom fluid, but don't yet insert it into the measuring head.
4. Position the phantom in the PET scanner.
5. Start data acquisition of the twilite without template inserted. A flat coincidence rate appears in the acquisition interface which corresponds to the background rate.
6. After 30 seconds, insert the template with the filled catheter into the tungsten head. In the acquisition interface the coincidence rate jumps up and the stays level, apart from the decay which depends on the isotope used.
7. Start the PET scanner and record the starting time.
8. After 5-10 minutes stop the twilite and the PET acquisitions.
9. Save the twilite raw data for the calibration procedure.
10. Reconstruct the PET image, including all corrections, outline a volume of interest (VOI) in the middle of the phantom and calculate the average activity concentration in the VOI in kBq/cc. This represents the reference, to which the twilite is going to be calibrated.