# Thresholding in DRR Image Computation module

**URL:** <https://discourse.slicer.org/t/thresholding-in-drr-image-computation-module/26118>\
**Category:** Support\
**Created:** [November 7, 2022, 7:23pm UTC](https://discourse.slicer.org/t/thresholding-in-drr-image-computation-module/26118 "2022-11-07T19:23:28Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![fieldr4](https://avatars.discourse-cdn.com/v4/letter/f/439d5e/32.png) [@fieldr4](https://discourse.slicer.org/u/fieldr4)\
**Post date:** [November 7, 2022, 7:23pm UTC](https://discourse.slicer.org/t/thresholding-in-drr-image-computation-module/26118/1 "2022-11-07T19:23:28Z")

</div>

Hi Slicer community,

Is the “Hounsfield unit threshold” applied in the “Plastimatch DRR image processing” submenu in the `DRR Image Computation` module represented in the “Plastimatch DRR command arguments (read only)” field?

 ![Thresholding in DRR Image Computation](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/b/6/b6456fc477182deb2367f1bca6c7d75b20caf0af.png)

This is a great functionality and it seems to be missing from the [Plastimatch DRR documentation](http://plastimatch.org/drr.html).

---

<div class="post-metadata">

**Author:** ![Mik](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mik](https://discourse.slicer.org/u/Mik)\
**Post date:** [November 8, 2022, 9:47am UTC](https://discourse.slicer.org/t/thresholding-in-drr-image-computation-module/26118/2 "2022-11-08T09:47:47Z")

</div>

No, it isn’t. It’s not a plastimatch feature, so it’s absent in the docs. It’s a part of “DRR generation” CLI module. The threshold filter is applied before any `plastimatch drr` functionality, some sort of preprocessing of original CT data if needed. May be something like than can be done with `plastimatch adjust` command, but i have never tried.

---

<div class="post-metadata">

**Author:** ![fieldr4](https://avatars.discourse-cdn.com/v4/letter/f/439d5e/32.png) [@fieldr4](https://discourse.slicer.org/u/fieldr4)\
**Post date:** [November 9, 2022, 3:01am UTC](https://discourse.slicer.org/t/thresholding-in-drr-image-computation-module/26118/3 "2022-11-09T03:01:23Z")

</div>

Plastimatch adjust worked perfectly! Thank you for the recommendation (and to Greg Sharp in the Plastimatch Google group).

For all those interested, --pw-linear “-inf,0,66,-1000,67,67,inf,1” maps all input intensities below 66 to -1000 and maps all values above 66 to themselves. Basically, like setting the thresholder slider in 3D Slicer to 66.