GelDosimetryAnalysis is a 3D Slicer extension for optical CT and MR-based gel dosimetry analysis. This extension provides a streamlined workflow for image registration, dose calibration, and dose comparison. The optical CT and MR workflows are available as two separate, independently loadable modules (GelDosimetryAnalysis and GelDosimetryAnalysisMR) that can be installed and used together, and both have been updated to be compatible with Slicer 5.12 and later.