# Thick slab reconstruction does not work with MicroCT

**URL:** <https://discourse.slicer.org/t/thick-slab-reconstruction-does-not-work-with-microct/38311>\
**Category:** Development\
**Tags:** volume, gui\
**Created:** [September 10, 2024, 12:28pm UTC](https://discourse.slicer.org/t/thick-slab-reconstruction-does-not-work-with-microct/38311 "2024-09-10T12:28:45Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![cpinter](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/cpinter/32/7995_2.png) [@cpinter](https://discourse.slicer.org/u/cpinter)\
**Post date:** [September 10, 2024, 12:28pm UTC](https://discourse.slicer.org/t/thick-slab-reconstruction-does-not-work-with-microct/38311/1 "2024-09-10T12:28:45Z")

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Hi all,

I noticed when working with MicroCT data that the thick slab reconstruction is not really meant for this modality. The minimum thickness is set to 1mm, which makes it basically unusable for volumes with very small voxel spacings.

Here’s a video illustrating this:

Here’s the volume I was using for this test:  
[microbumps\_FDK cropped.nrrd](https://1drv.ms/u/s!Ao_a-dPPX98Zh-lE2xThOTUH53A4RA?e=3KtOHG)

And here’s the line that I think would be the simplest place to fix this:

> <https://github.com/Slicer/Slicer/blob/c28ce0c16593fd6c494ceef4f65e3e4ee2d4d65c/Libs/MRML/Widgets/qMRMLSliceControllerWidget.cxx#L1612>

However, simply decreasing this would not be the best solution, because then we’d need to also decrease the single step value, which would make it unusable on normal patient volumes. (I also did not look into any similar limitation on the logic level, I just assumed that the constraint comes from this single place.)

What could be a good solution for this?

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [September 10, 2024, 12:50pm UTC](https://discourse.slicer.org/t/thick-slab-reconstruction-does-not-work-with-microct/38311/2 "2024-09-10T12:50:27Z")

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It sounds like the step size and range should adapt to the geometry of the volumes in the view. If it’s not possible to do this automatically, perhaps a menu item to select a reference volume to use for determining the values.

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [September 11, 2024, 9:27pm UTC](https://discourse.slicer.org/t/thick-slab-reconstruction-does-not-work-with-microct/38311/3 "2024-09-11T21:27:54Z")

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First of all, it should not be a `ctkDoubleSpinBox` but a `qMRMLSpinBox`, with unit set to `length`. That would display the unit correctly, and could use application defaults for precision and user could hit Ctrl - + to see more digits.

Minimum of the range can be set to 0.

Computing the step size dynamically from the spacing as @pieper suggested would be nice (similarly to how the slider’s step size is computed from the volume spacing), but it should be acceptable to have a hardcoded value there, as user can still type any number or drag-and-dropping the handles in slice view to adjust the value.