[Castor-users] Bug toolkits/castor-GATERootToCastor.cc

[Maxime Toussaint]

Greetings,

I was curious about your discovery and started to check it out. I am not totally sure but I think there is something else in this bug.

The tool castor-GATERootToCastor only require a projector object when evaluating attenuation coefficients. Since these coefficients are independent of TOF, the projector should not need TOF information. Worse, if the projector use the TOF information, the attenuation coefficients will be evaluated from a portion of the LOR which does not fit the reality. However, my previous statement might not be true for on-the-fly system matrix computing. I will leave it to more knowledgeable peers to confirm or infirm that part.

In short, my understanding is that TOF should be disabled for the tools castor-GATERootToCastor when evaluating attenuation coefficients (Using the SetIgnoreTOFFlag method, most likely) which should remove the error you observed.

On that note, I also like the idea that the variable m_TOFMeasurementRangeInPs can be user/scanner defined. While the current approach defined in castor-GATERootToCastor, which is data dependent(1), is efficient, it is true that we sometime want to fix that value for comparison or whatnot.

Have a nice day,
Maxime

(1) ((iDataFilePET*)Out_data_file)->SetTOFMeasurementRangeInPs(dt_max - dt_min);



________________________________
De : Castor-users <castor-users-bounces at lists.castor-project.org> de la part de Grahe, Jan <jan.grahe at pmi.rwth-aachen.de>
Envoyé : 23 janvier 2020 07:34
À : castor-users at lists.castor-project.org <castor-users at lists.castor-project.org>
Objet : [Castor-users] Bug toolkits/castor-GATERootToCastor.cc


Dear CASToR developers,



I tried converting a PET list-mode generated by GATE into the CASToR format using the castor-GATERootToCastor toolkit and obtained an error:



“….

sScannerManager::Initialize() -> From scanner PET_PHILIPS_VEREOS

iScannerPET::Initialize() -> Initialize remaining stuff for scanner to be ready

oProjectorManager::Initialize() -> Initialize projectors and projection lines

  --> Use TOF projector for listmode data

***** vProjector::CheckParameters() -> Inconsistent TOF related parameters !

***** oProjectorManager::ParseOptionsAndInitializeProjectors() -> A problem occurred while checking forward projector parameters !

***** oProjectorManager::Initialize() -> A problem occurred while parsing projector options and initializing it !”



Turns out, that the variable m_TOFMeasurementRangeInMm has a value of “-0.1498962” in the oProjectorManager, which caused the error in the vProjector::CheckParameters(). This variable is obtained from the vDataFile* Out_data_file using the method GetTOFMeasurementRangeInPs(). The datafile is initialized in the castor-GATERootToCastor.cc file and handed to the p_ProjectManager using the SetDataFile() method. However, the m_TOFMeasurementRangeInPs variable is set to -1 in the constructor and not set in the castor-GATERootToCastor toolkit before the oProjectorManager requires this variable to be set when calling it’s Initialize() function.



Therefore, to use the toolkit with TOF right now I added the red line in the toolkit (the block is approx. at line ~970 of the document):



“….

// Set ToF

      if(tof_reso>=0)

      {

        ((iDataFilePET*)Out_data_file)->SetTOFInfoFlag();

        ((iDataFilePET*)Out_data_file)->SetTOFResolutionInPs(tof_reso);

        ((iDataFilePET*)Out_data_file)->SetTOFMeasurementRangeInPs(myScannersTOFrange);

      }

”



This seems to solve the problem, but only with the general coincidence time window of the scanner instead of the longest coincidence time of all events in your datafile. Not sure if that is correct or a factor of e.g. 2 has to be applied. If there is no problem with that, you could fix this bug generally by getting the coincidence time window of the scanner and then later update it to the real variable when all the events have been processed.



As this only happens in version 3.0, can I still reconstruct images with CASToR 3.0 using datafiles generated with the CASToR 2.0 framework?



Thanks and I hope this helps!

Jan




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