# Isotropic Volume with B-Spline Interpolation

**URL:** <https://discourse.slicer.org/t/isotropic-volume-with-b-spline-interpolation/16933>\
**Category:** Support\
**Created:** [April 2, 2021, 8:27pm UTC](https://discourse.slicer.org/t/isotropic-volume-with-b-spline-interpolation/16933 "2021-04-02T20:27:26Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Fluvio\_Lobo](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/fluvio_lobo/32/81262_2.png) [@Fluvio\_Lobo](https://discourse.slicer.org/u/Fluvio_Lobo)\
**Post date:** [April 2, 2021, 8:27pm UTC](https://discourse.slicer.org/t/isotropic-volume-with-b-spline-interpolation/16933/1 "2021-04-02T20:27:26Z")

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Hello,

I am trying to understand what is exactly happening when I use the **crop volume** function with the **isotropic spacing** and **B-spline interpolation** flags on. This is mostly for a discussion section on a publication and my own sanity 😅

The **isotropic spacing** is ensuring that the shape of the voxels of the new volume are almost identical in size (say +/- 5-10%). And, in the directions in which the difference is greater than a set limit, say this 5-10%, a **B-Spline** interpolation is used to approximate the voxels in between???

Is this correct? 😅 close?

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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:** [April 2, 2021, 8:30pm UTC](https://discourse.slicer.org/t/isotropic-volume-with-b-spline-interpolation/16933/2 "2021-04-02T20:30:32Z")

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If you set “isotropic spacing” then the voxel spacing of the output volume will be exactly the same along all 3 axes. B-spline interpolation is used to get voxel values of the new volume.