Hi Seyyed,
- Calibration factor is a voxelwise global factor to convert the counts into activity values or any value with a more physical meaning. You can have a look at the following topic for more about the image units, calibration factor and quantification:
2&3. Normalization should integrate any kind of multiplicative factors for the data channels, e.g detector efficiency, dead-time, some geometric factors depending on the system, etc…
In list-mode they are used during the generation of the sensitivity image through the back-projection of all possible LORs.
For list-mode, the event can be a single LOR or a group of LORs (in case of compression). Providing the normalization factor related to each recorded event is not enough as we need the factors from any possible LORs in order to properly generate the sensitivity images, so this is why there is a specific normalization datafile, which can also include ACFs. If you don’t provide this file, the sensitivity image will be generated from the system geometry assuming uniform detector efficiency, so only some geometric distortions will be corrected (which could be enough for some type of simulated data).
- I don’t really understand what you mean by “Is there any other reason than being more flexible to define a PET normalization mode?”
Best,
Thibaut