# \[Castor--users\] image reconstruction using GATE simulation data for attenuation and normalization correction

**URL:** <https://castor-project.discourse.group/t/castor-users-image-reconstruction-using-gate-simulation-data-for-attenuation-and-normalization-correction/83>\
**Category:** General Discussions\
**Created:** [January 28, 2019, 10:18am UTC](https://castor-project.discourse.group/t/castor-users-image-reconstruction-using-gate-simulation-data-for-attenuation-and-normalization-correction/83 "2019-01-28T10:18:17Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![user1](https://avatars.discourse-cdn.com/v4/letter/u/5daacb/32.png) [@user1](https://castor-project.discourse.group/u/user1)\
**Post date:** [January 28, 2019, 10:18am UTC](https://castor-project.discourse.group/t/castor-users-image-reconstruction-using-gate-simulation-data-for-attenuation-and-normalization-correction/83/1 "2019-01-28T10:18:17Z")

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Dear CASToR users,

I obtained the image of the gate simulation data using the castor program.

What data should I use to make attenuation and normalization correction for the image?

I want to use the -atn command. Can you explain the example sentence?

The current data is obtained by using jaszczak phantom. Do you need additional uniform phantom data for image correction?

And I keep getting the error below. Could you tell me the cause and how to fix it?

 ![image.png](https://global.discourse-cdn.com/free1/uploads/castor_project/original/1X/f128d08856e7968339c99ec5e88f05cc0339d41d.png)

How can we solve it?

Any help I would really appreciate it.

Best regards,

Yeongkyeong KIM

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**Author:** ![tmerlin](https://yyz2.discourse-cdn.com/free1/user_avatar/castor-project.discourse.group/tmerlin/32/216_2.png) [@tmerlin](https://castor-project.discourse.group/u/tmerlin)\
**Post date:** [January 28, 2019, 6:43pm UTC](https://castor-project.discourse.group/t/castor-users-image-reconstruction-using-gate-simulation-data-for-attenuation-and-normalization-correction/83/2 "2019-01-28T18:43:21Z")

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Dear Yeongkyeong,

Regarding attenuation correction, you should provide an attenuation image (interfile format) of the jaszczak phantom in cm-1 unit to the _castor-recon_ executable (assuming your GATE data has been converted to list-mode, which is selected by default for data converted from GATE). Note that the conversion utility (_castor-GATERootToCastor_) also contains an _-atn_ option, which is only to use if you want an histogram dataset.

There is currently no tools to automatically compute normalization correction factors. You could generate a normalization datafile (see [the documentation](http://www.castor-project.org/sites/default/files/2018-11/CASToR_general_documentation.pdf), section 6.1.2) for your GATE data using this kind of method: [https://ieeexplore.ieee.org/document/6153804](https://ieeexplore.ieee.org/document/6153804). Alternatively, you could directly generate a sensitivity image containing normalization corrections using a GATE simulation of an uniform object spanning the whole field of view of your system. Then, you provide this image to _castor-recon_ using _-sens_ _path/to/your\_sensitivity\_image.hdr_ to bypass the sensitivity image generation step and use your image instead). However, this approach should be less accurate.

Finally the error you get means the code can’t find the scanner repository, which is apparently located at \*/GATE/castor\_v.2.0.2/\*_castor\_v2.0.2/config/scanner_ in your system. You should check if the path is correct (no typo?).

Hope this helps!

Best regards,

Thibaut

 ![image.png](https://global.discourse-cdn.com/free1/uploads/castor_project/original/1X/f128d08856e7968339c99ec5e88f05cc0339d41d.png)