Scatter estimation happens in 2D, with using SSRB for ProjDataInfoCylindrical to reduce noise (for BlocksOnCylindrical, we just use seg 0).
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ScatterEstimation::make_2D_projdata_sptr(const shared_ptr<ProjData> in_3d_sptr) |
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{ |
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shared_ptr<ProjData> out_2d_sptr; |
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if (in_3d_sptr->get_proj_data_info_sptr()->get_scanner_sptr()->get_scanner_geometry() == "Cylindrical") |
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{ |
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shared_ptr<ProjDataInfo> out_info_2d_sptr( |
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SSRB(*in_3d_sptr->get_proj_data_info_sptr(), in_3d_sptr->get_num_segments(), 1, false)); |
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out_2d_sptr.reset(new ProjDataInMemory(in_3d_sptr->get_exam_info_sptr(), out_info_2d_sptr)); |
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SSRB(*out_2d_sptr, *in_3d_sptr, false); |
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} |
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else |
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{ |
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shared_ptr<ProjDataInfo> out_info_2d_sptr(in_3d_sptr->get_proj_data_info_sptr()->create_shared_clone()); |
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out_info_2d_sptr->reduce_segment_range(0, 0); |
For prompts, randoms and efficiencies, we use SSRB in its "adding" mode (do_normalisation=false). However, this is incorrect for the attenuation correction factors. (2D ACFs should correspond to exp(lineintegral(mu)), and hence should be very close to seg 0 of 3D ACFs, i.e we should use averaging, not adding)
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atten_projdata_2d_sptr = make_2D_projdata_sptr(tmp_atten_projdata_sptr, out_filename); |
git blame confirms that this bug was introduced in 852c10d when cleaning-up the SSRB lines to replace them with make_2D_projdata_sptr (in #1006, merged 27 Jun 2022, rel 5.1.0). Before this PR, all SSRBs were called with false (i.e. add), except for the 2D ACFs, where it uses true (i.e. average).
Scatter estimation happens in 2D, with using SSRB for
ProjDataInfoCylindricalto reduce noise (forBlocksOnCylindrical, we just use seg 0).STIR/src/scatter_buildblock/ScatterEstimation.cxx
Lines 165 to 179 in 5da26d8
For prompts, randoms and efficiencies, we use SSRB in its "adding" mode (
do_normalisation=false). However, this is incorrect for the attenuation correction factors. (2D ACFs should correspond to exp(lineintegral(mu)), and hence should be very close to seg 0 of 3D ACFs, i.e we should use averaging, not adding)STIR/src/scatter_buildblock/ScatterEstimation.cxx
Line 661 in 5da26d8
git blameconfirms that this bug was introduced in 852c10d when cleaning-up the SSRB lines to replace them withmake_2D_projdata_sptr(in #1006, merged 27 Jun 2022, rel 5.1.0). Before this PR, all SSRBs were called withfalse(i.e. add), except for the 2D ACFs, where it usestrue(i.e. average).