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known_issues.md

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Known issues related to using STIR and SIMIND together

To test: do density map dimensions need to be isotropic/match source map dimensions? (indices 34, 78, 81)

To test: do pixel sizes need to be isotropic in density maps? (index 31)

To test: do pixel sizes need to be isotropic in source maps? (index 28(?))

To test: do parameters on page 1 defining source and phantom length/width/height have any impact when simulating voxelwise data? (indices 2, 3, 4, 5, 6, 7)

Conclusion: Indices 2 and 5 are important for voxelwise data (3,4,6,7 can be set to zero)

To test: non-circular orbits (elliptical orbit, or orbit based on density map –index 42, index-35 and index-56 will be relevant)

Conclusion: For elliptical orbit, set Index-42 to define ratio between major and minor axes. Index-12 defines the horizontal [z-axis according to SIMIND coordinate system] radius (tested for values >1 and between 0 and 1)

Conclusion: For non-circular orbits, the SIMIND header states “orbit := noncircular”, but STIR understands only “orbit := Non-circular”. Then need to copy values from *.cor file, multiply by 10 to convert to mm, and insert into “Radii := {values from *.cor file}”

Conclusion: For non-circular orbits based on density map, set Index-42 to < 0. Index-35 is important and needs to be <1 for water (i.e. lower than the g/cm value defining the relevant border). The absolute value of Index-42 then adds an airgap between the defined border and the surface of the detector (assume this means front of collimator).

Note: confirmed with Michael Ljungberg regarding Index-42 "surface of the
detector" in SIMIND corresponds to the shortest distance to the overall device (detector meaning overall device, so could be collimator surface, Aluminium cover, or crystal, depending on how device is set up [emailed RG 22/11/22]

Conclusion: Index-56 does not seem to have an effect on RoR for density-based orbits

separate .awk and .sh files have been written to convert SIMIND headers from non-circular orbit data to a STIR-readable version

To test: Does SIMIND require Uint16 [0 to 65535] or signed int 16 [-32768 to +32767]

To test: z-slice order (and general conversion between SIMIND's Fortran order {2, 1, 0} and STIR's C++ order {0, 1, 2})

note: binary (input) data could be read in anyway

To do: RG to check where “signed integer” vs “integer” makes a difference (one is OK for STIR, but not for SIMIND)

Conclusion: STIR needs "signed integer" (or "unsigned integer") when defining data types, doesn't recognise "integer"

To test: check how to get directory referencing to work for all systems (currently can get mixed up with runtime switches)

To test: is it possible to read in DICOM data directly?