How to integrate normalization and scatter into reconstruction?

General Discussions
1

Hello:

At present, I hope to integrate normalization and scatter in my reconstruction task. I’ve carefully consulted the general guidebook and some related topic in this forum, but I still have some questions. If someone could give me some advice, I would greatly appreciate it.

For normalization: According to the instructions on pages 30~33 of the guidebook, I need to add the ‘Normalization correction flag’ field in the Cdh header file and extend the ‘normalization factor’ for each LOR calculated by myself in the Cdf datafile, right? In addition to these two modifications, do I need to provide an extra normalization datafile, as described in Table 4 of the guidebook?

For scatter: How should I calculated the ‘Un-normalized scatter intensity rate of the corresponding event (count/s)’ for list-mode TOF event? The relevant introduction on page 32 of the guidebook is as follows：

‘For (almost) continuous list-mode TOF measurement, the scatter should be estimated as a (almost) continuous function. This estimation can be done by some scatter estimation methods, or it can be approximated from TOF bin scatter estimation by dividing each TOF bin scatter estimation by the spatial width of the TOF bin.’

Firstly, I should divide the entire TOF measurement range into several virtual TOF bins, and then estimate the scatter sinogram for each virtual TOF compartment. Finally, I should divide each TOF bin scatter estimation by the spatial width of the TOF bin. Is it right? BTW, what is ‘the spatial width of the TOF bin’? Is it the (time) width of the TOF bin multiplied by the speed of light?

Thanks a lot!

2

The answers in the text.

Claude COMTAT
BioMaps
Service Hospitalier Frédéric Joliot
91401 Orsay, France
www.biomaps.universite-paris-saclay.fr

3

The answers in the text.

4

At present, I hope to integrate normalization and scatter in my reconstruction task. I’ve carefully consulted the general guidebook and some related topic in this forum, but I still have some questions. If someone could give me some advice, I would greatly appreciate it.

For normalization: According to the instructions on pages 30~33 of the guidebook, I need to add the ‘Normalization correction flag’ field in the Cdh header file and extend the ‘normalization factor’ for each LOR calculated by myself in the Cdf datafile, right?

YES

In addition to these two modifications, do I need to provide an extra normalization datafile, as described in Table 4 of the guidebook?

If your data are in list mode format, as opposed to histogram, yes : you need to provide an extra normalization datafile.

For scatter: How should I calculated the ‘Un-normalized scatter intensity rate of the corresponding event (count/s)’ for list-mode TOF event? The relevant introduction on page 32 of the guidebook is as follows：

‘For (almost) continuous list-mode TOF measurement, the scatter should be estimated as a (almost) continuous function. This estimation can be done by some scatter estimation methods, or it can be approximated from TOF bin scatter estimation by dividing each TOF bin scatter estimation by the spatial width of the TOF bin.’

Firstly, I should divide the entire TOF measurement range into several virtual TOF bins, and then estimate the scatter sinogram for each virtual TOF compartment.

YES

Finally, I should divide each TOF bin scatter estimation by the spatial width of the TOF bin. Is it right? BTW, what is ‘the spatial width of the TOF bin’? Is it the (time) width of the TOF bin multiplied by the speed of light?

Divided by 2:

In src/projector/oProjectorManager.cc, line 289 : m_TOFBinSizeInMm = p_pet_datafile->GetTOFBinSizeInPs() * SPEED_OF_LIGHT_IN_MM_PER_PS * 0.5;

  • sizeInMm = sizeInPs*speedOfLightInMmPerPs/2

Thanks a lot!