# SlicerRT built from source cannot start

**URL:** <https://discourse.slicer.org/t/slicerrt-built-from-source-cannot-start/43792>\
**Category:** Support\
**Tags:** build\
**Created:** [July 21, 2025, 8:52am UTC](https://discourse.slicer.org/t/slicerrt-built-from-source-cannot-start/43792 "2025-07-21T08:52:11Z")\
**Posts on this page:** 1\
**Showing post:** 3

<div class="post-metadata">

**Author:** ![ferhue](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/ferhue/32/82557_2.png) [@ferhue](https://discourse.slicer.org/u/ferhue)\
**Post date:** [July 21, 2025, 11:12am UTC](https://discourse.slicer.org/t/slicerrt-built-from-source-cannot-start/43792/3 "2025-07-21T11:12:05Z")

</div>

If I run `/home/user/builds/build-Slicer_src-Desktop-Debug/Slicer-build/bin/./SlicerApp-real --additional-module-paths /opt/SlicerRT_bld/inner-build/lib/Slicer-5.9/qt-scripted-modules /opt/SlicerRT_bld/inner-build/lib/Slicer-5.9/qt-loadable-modules /opt/SlicerRT_bld/inner-build/lib/Slicer-5.9/cli-modules --no-splash --verbose-module-discovery`

the GUI pops up, but with some warnings:

```auto
  File "<string>", line 5, in <module>
  File "<string>", line 5, in <module>
ModuleNotFoundError: No module named 'ctk'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
NameError: name 'getSlicerRCFileName' is not defined
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'slicer'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'slicer'
qSlicerScriptedLoadableModuleFactory - Failed to import module "NA" python extensions
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "<frozen importlib._bootstrap_external>", line 999, in exec_module
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed
  File "/home/user/builds/build-Slicer_src-Desktop-Debug/Slicer-build/lib/Slicer-5.9/qt-scripted-modules/AddManyMarkupsFiducialTest.py", line 3, in <module>
    import ctk
....

Loading module "ExternalBeamPlanning"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/opt/SlicerRT_bld/inner-build/lib/Slicer-5.9/qt-scripted-modules/DoseEngines/ __init__.py", line 1, in <module>
    from .AbstractScriptedDoseEngine import *
  File "/opt/SlicerRT_bld/inner-build/lib/Slicer-5.9/qt-scripted-modules/DoseEngines/AbstractScriptedDoseEngine.py", line 2, in <module>
    import vtk, qt, ctk, slicer, logging
ModuleNotFoundError: No module named 'vtk'

....

```

and DICOM import and many other things are not working.

This looks very similar to [2018-10-15 Windows nightly build "unable to import VTK"](https://discourse.slicer.org/t/2018-10-15-windows-nightly-build-unable-to-import-vtk/4403) so maybe @jcfr has an idea on what’s happening.

---

_[View the full topic](https://discourse.slicer.org/t/slicerrt-built-from-source-cannot-start/43792)._