add TOF mashing to SSRB

[KrisThielemans]

Some pointers to enable this.

The ProjDataInfo code:

• this would need be deleted
  

  STIR/src/buildblock/SSRB.cxx

  Lines 50 to 51 in 8ced2d7

  	if (num_tof_bins_to_combine != 1)
  	error("SSRB: num_tof_bins_to_combine (%d) currently needs to be 1", num_tof_bins_to_combine);

• This looks fine
  

  STIR/src/buildblock/SSRB.cxx

  Lines 134 to 140 in 8ced2d7

  	if (num_tof_bins_to_combine != 1)
  	{
  	if (num_tof_bins_to_combine < 1)
  	error("SSRB: num_tof_bins_to_combine needs to be at least 1");
  	const int new_tof_mash_factor = in_proj_data_info_sptr->get_tof_mash_factor() * num_tof_bins_to_combine;
  	out_proj_data_info_sptr->set_tof_mash_factor(new_tof_mash_factor);
  	}

The actual rebinning code:

• compute num_tof_bins_to_combine like for views
• add in and out_timing_pos_num in various places when constructing the sinos
• loop over out_timing_pos_num here
• loop over in_timing_pos_num here
• add num_tof_bins_to_combine in the normalisation step
  

  STIR/src/buildblock/SSRB.cxx

  Line 277 in 8ced2d7

  out_sino /= static_cast<float>(num_in_ax_pos * num_views_to_combine);

[NicoleJurjew]

Hello Kris, thanks for the detailed instructions! I've implemented them (as best as I could) here, but I have a few questions/remarks (normalisation is currently incorrect, I've not touched that yet).

The code compiles and I have used it on some 3D Vision TOF data to get 2D Vision TOF data out. That "worked" (at least the output dimensions are correct, no further testing performed so far), with the following command:
SSRB det_effs_test.hs detection_efficiencies_SIRF.hs 9

Now I'm having trouble to call the command such that it tries to combine TOF bins. From this here:

STIR/src/include/stir/SSRB.h

Lines 104 to 111 in 8ced2d7

	void SSRB(const std::string& output_filename,
	const ProjData& in_projdata,
	const int num_segments_to_combine,
	const int num_views_to_combine = 1,
	const int num_tangential_poss_to_trim = 0,
	const bool do_normalisation = true,
	const int max_in_segment_num_to_process = -1,
	const int num_tof_bins_to_combine = 1);

I thought that SSRB det_effs_test.hs detection_efficiencies_SIRF.hs 9 1 0 1 -1 33 should do the trick, but that just prompts the help docstring (which never mentions tof-bins). Could you please tell me how I need to do this? Do I need to change something in the code?

Other thoughts:

• Don't we always want to have an odd number of TOF-bin? So, as for views, the num_tof_bins_to_combine must not be even then? Or is it more complicated?
• I guess we need a check to make sure that non-TOF data is not called with a num_TOF_bins_to_combine greater than 1, but that's just a side note, can do that.

Thank you!

[KrisThielemans]

great!

Looks like you will need to adjust the utility as well, i.e. here and usage message etc.

• Don't we always want to have an odd number of TOF-bin? So, as for views, the num_tof_bins_to_combine must not be even then? Or is it more complicated?

At present, the output number of TOF bins need to be odd, but @danieldeidda is addressing that in #1334 . I wouldn't put any checks in here, except for saying that it needs to divide (e.g. org_num_tof_bins % num_tof_bins_to_combine == 0)

• I guess we need a check to make sure that non-TOF data is not called with a num_TOF_bins_to_combine greater than 1, but that's just a side note, can do that.

yes, the above check could handle that, but likely it needs another one like org_num_tof_bins >= num_tof_bins_to_combine)