Construction of Castor histogram data file

General Discussions
1

Hi Castor developers and users,

A few moths ago I got the code for saving the forward projections (castor-proj) and I have used this a lot to generate PET-data so far.
I try to manually put Gaussian blur over the sinogram data to simulate the poorer resolution of PET data by PSF. I want to do this by putting a Gaussian blur on every single 2D-sinogram. In order to do this, I need to understand how the sinogram datafile is constructed and this has not become very clear to me yet. I know that every 16 bytes (for my data) describe one bin in the sinogram, but I don’t know in what order this dat is stored and whether I can properly separate the sinograms here to apply Gaussian blur.
Is it possible to provide more clarity on how the sinogram datafiles are constructed when formed with castor-proj?

Many thanks in advance,
Inge

2

Hi Inge,

To be generic and to allow for any possible geometry, no assumption are made.

This means that CASToR is using histograms and not sinograms, because sinograms are based on a specific geometry organisation.

The current solution for you is to use a blur in the image space.

In the future, a generic sinogram-based virtual scanner will be added in CASToR, so that for any modality (PET, SPECT or CT), a scanner could be described as a sinogram instead of describing the detector arrangement.

In this case, sinogram PSF blur will be allowed.

Best

Simon

3

Hi Simon,

Thank you very much for your response.
I understand, then I will blur the images during reconstruction.

Alle the best,
Inge