To complete my previous answer, doing a case-insensitive search returns the following:
$ rg -i regularization
186: - Acquisition geometry regularization option supports the creation of a nonlinear transform that corrects for things like missing slices or gantry tilt in the acquisition. See more information [here](https://github.com/Slicer/Slicer/commit/3328b81211cb2e9ae16a0b49097744171c8c71c0)
243:Scanners may create image volumes with varying image slice spacing. Slicer can represent such images in the scene by apply a non-linear transform. To enable this feature, go to menu: Edit / Application settings / DICOM and set *Acquisition geometry regularization* to *apply regularization transform*. Slice view, segmentation, and many other features work directly on non-linearly transformed volumes. For some other features, such as volume rendering, you need to harden the transform on the volume: go to Data module, in the row of the volume node, right-click on the transform column, and choose *Harden transform*.
665: # Get acquisition geometry regularization setting value
667: acquisitionGeometryRegularizationEnabled = (settings.value("DICOM/ScalarVolume/AcquisitionGeometryRegularization", "default") != "none")
688: if acquisitionGeometryRegularizationEnabled:
691: warningText += (" If loaded image appears distorted, enable 'Acquisition geometry regularization'"
88: " If no regularization is applied then image may appear distorted if it was acquired with irregular geometry.")
90: importFormatsComboBox.addItem(_("default (apply regularization transform)"), "default")
92: importFormatsComboBox.addItem(_("apply regularization transform"), "transform")
96: formLayout.addRow(_("Acquisition geometry regularization:"), importFormatsComboBox)
98: "DICOM/ScalarVolume/AcquisitionGeometryRegularization", importFormatsComboBox,
137: def acquisitionGeometryRegularizationEnabled(self):
139: return (settings.value("DICOM/ScalarVolume/AcquisitionGeometryRegularization", "default") != "none")
850: logging.warning(warningText + " Regularization transform is not added, as the option is disabled.")