# Registration CT images with Ants Rregistration or Elastix

**URL:** https://discourse.slicer.org/t/registration-ct-images-with-ants-rregistration-or-elastix/30408
**Category:** Support
**Tags:** registration
**Created:** [July 5, 2023, 3:04pm UTC](https://discourse.slicer.org/t/registration-ct-images-with-ants-rregistration-or-elastix/30408 "2023-07-05T15:04:20Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![Chiararp](https://avatars.discourse-cdn.com/v4/letter/c/e99b99/32.png) [@Chiararp](https://discourse.slicer.org/u/Chiararp)
#### Post date: [July 5, 2023, 3:04pm UTC](https://discourse.slicer.org/t/registration-ct-images-with-ants-rregistration-or-elastix/30408/1 "2023-07-05T15:04:20Z")

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Hi everyone,  
I have a problem with the registration of two abdominal CT scans. In particular, the two cases have different sizes and different characteristics that I show below.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/f/b/fb55b5b611ed8e51773c3919293cb50f6b212675.jpeg)

My goal is to accurately register the two CT because I want the kidney stones (which are shown in the basal ct) inside the calyxes of the kidney (shown in the late ct).

When I do the registration with Elastix or ANTS registration the result is not accurate.

I show the segmentations of the two volumes to emphasize how the two ct are distant from each other before registration.  
(yellow: late, purple: basal)  
 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/7/3/73d97a38e2a7446b18d98368891e3dea1b3c100a.png)  
Then I do the registration with Ants registration, rigid+affine (or Elastix, the final result is the same). It’s clear that the registration is not accurate. I show you how the kidney stones are outside the calyxes.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/e/f/ef64ccbbc7da79d33172aae959ac0a963c948d65.jpeg)  
Is there something I’m doing wrong? Do you have any suggestions for improving my work? Do I have to do some kind of manual pre-registration?  
Thank you all