# Resampling to Isotropic: Signal Processing Theory

**URL:** https://discourse.itk.org/t/resampling-to-isotropic-signal-processing-theory/1403
**Category:** Algorithms
**Created:** [November 7, 2018, 8:04pm UTC](https://discourse.itk.org/t/resampling-to-isotropic-signal-processing-theory/1403 "2018-11-07T20:04:33Z")
**Posts on this page:** 1
**Showing post:** 16

<div class="post-metadata">

### Author: ![grothausmann.roman](https://discourse.itk.org/user_avatar/discourse.itk.org/grothausmann.roman/32/582_2.png) [@grothausmann.roman](https://discourse.itk.org/u/grothausmann.roman)
#### Post date: [June 10, 2020, 4:09pm UTC](https://discourse.itk.org/t/resampling-to-isotropic-signal-processing-theory/1403/16 "2020-06-10T16:09:31Z")

</div>

Since WBIR2020 is postponed, continuing the discussion here.  
I found this article from Cardoso M.J., Modat M., Vercauteren T., Ourselin S. (2015) Scale Factor Point Spread Function Matching: Beyond Aliasing in Image Resampling – MICCAI 2015 [https://doi.org/10.1007/978-3-319-24571-3\_81](https://doi.org/10.1007/978-3-319-24571-3_81) [PDF](http://discovery.ucl.ac.uk/1469251/1/scale-factor-point-5.pdf) which provides the formula `sigma= sqrt((isoSpacing^2 - inputSpacing[0]^2)/(2*sqrt(2*ln(2)))^2)`, which is not a function of the difference but based on difference and also leads to sigma= 0 in case input and output spacing are equal.  
@dzenanz @matt.mccormick What do you think? Is its application appropriate in the discussed case, i.e. is its use in my [resample-iso](https://github.com/romangrothausmann/ITK-CLIs/blob/3165433931a5d75d7014567920fad136fd4555a0/resample-iso.cxx#L65-L146) correct?

---

_[View the full topic](https://discourse.itk.org/t/resampling-to-isotropic-signal-processing-theory/1403)._