[Castor-users] Issues about the List-mode normalization

[Zipai Wang]

Dear CASToR developers and users,

I am trying to apply normalization to a simulated PET scanner but meet some
issues, any help is highly appreciated!

First I successfully applied the normalization by feeding the normalization
file (all LORs with norm&attenuation factors) into the CASToR for the
computation of the sensitivity image. The CASToR gives me artefact free
images in this way.

However, the normalization doesn't work when I embed the factors into the
List-mode binary datafile:

1. When I feed the list-mode data (with normalization factors and flag on)
to CASToR, it give me the following error:
*oSensitivityGenerator::InitializeNormalizationFiles() -> Normalization
correction is included in the data file while it is not in the sensitivity
computation!*
In order to bypass this error, I use *-sens* to provide a precomputed
sensitivity image (Not normalized) to CASToR. Is this the proper way to do
it? If not, what should I feed to CASToR instead?

2. After feeding precomputed sensitivity image, the CASToR can run
reconstruction with no issues, but the image with embedded LM
normalization factors is identical to the image without normalization
factors. Then I assign all the events with the same normalization factor of
0.1,1,10, respectively. But the reconstructed images have the same pixel
intensities, which means I did something wrong and the LM normalization
factors is not doing its job at all in my case.

The version I am using is CASToR v 3.0.1.

Here is one of the header files:
Data filename: PET_Sim_LMNorm.Cdf
Number of events: 13755984
Data mode: list-mode
Data type: PET
Start time (s): 0
Normalization correction flag: 1
Duration (s): 1500
Scanner name: D04_sim_1ring
Calibration factor: 1
Isotope: unknown

Here is some examples of the I generated list-mode data: (I assgin all the
time frames to 0 and  norm factors to 1)
0000 0000 0000 803f ba22 0000 c005 0000
0000 0000 0000 803f 9a15 0000 9e19 0000
0000 0000 0000 803f e20e 0000 fa0b 0000
0000 0000 0000 803f f51f 0000 6a05 0000
0000 0000 0000 803f 971a 0000 1203 0000
0000 0000 0000 803f e91f 0000 d719 0000
0000 0000 0000 803f 211d 0000 3721 0000
0000 0000 0000 803f f906 0000 7105 0000
0000 0000 0000 803f 4c20 0000 f014 0000
0000 0000 0000 803f 8e1e 0000 a607 0000
0000 0000 0000 803f a821 0000 1a19 0000
0000 0000 0000 803f e81a 0000 8514 0000
0000 0000 0000 803f 6913 0000 e525 0000


Thank you very much!
--
Zipai Wang
Biomedical Engineering PhD student
Stony Brook University
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.castor-project.org/pipermail/castor-users/attachments/20220221/9cb43553/attachment.html>