Changes in version CAT26.0

Changes in the preprocessing pipeline that affect your results compared to CAT12.9

The cortical surface extraction pipeline has been substantially revised, resulting in faster execution and more robust cortical thickness estimation. The initial surface reconstruction now uses an improved Marching Cubes implementation that directly produces topologically correct surfaces, thereby avoiding downstream topology correction issues. Cortical thickness is again estimated using the projection-based thickness (PBT) approach instead of the FreeSurfer-like distance measure used in CAT12.7–12.9, and is now additionally corrected for folding-related bias. Thickness values are therefore not directly comparable to CAT12.9, so please do not mix versions within a study.
The VBM pipeline has been comprehensively updated to improve stability and robustness, particularly for challenging acquisitions such as MP2RAGE. These improvements also enhance the accuracy and reliability of the initial affine registration.
The quality assessment framework has been updated according to the methods described in Dahnke et al., 2025. The former IQR metric has been replaced by SIQR.

A new versioning scheme has been introduced, aligned with the year-based system adopted in recent SPM releases. In contrast to SPM, only the release year is used, followed by semantic versioning. The new series therefore starts with CAT26.0.
Consistent with the new naming convention, the toolbox directory within spm/toolbox has been renamed from cat12 to CAT. CAT offers to remove an old cat12 folder on first start. Please update any scripts that refer to the old path.
BIDS output is now enabled by default: if your data follow the BIDS layout (sub-*/[ses-*/]anat), all results are written to derivatives/CAT… in the dataset root instead of next to the input files. Non-BIDS data are still written to the usual mri, surf, report, … subfolders. The output structure can be changed in the BIDS output options of the batch.
The standalone version is now based on MATLAB Runtime R2023b (v232) for all platforms and is additionally available natively for Apple Silicon (ARM64). Please install the matching Runtime (see README).

The long-awaited and much-requested surface area estimation is finally available. It follows FreeSurfer's sum-preserving per-vertex area estimation and can be used as an alternative measure of surface folding. Use Extract Additional Surface Parameters to access the new functionality.
New DICOM2BIDS batch to convert DICOM data into a BIDS dataset, including protocol-based filtering, anonymization and a basic image quality check. This requires dcm2niix to be installed. See DCM2BIDS/DZPG3T for an example configuration.
New BIDS: Data selection batch to select input files directly from a BIDS dataset root, with filtering by participants, sessions and participants.tsv. Subjects with multiple sessions are automatically passed on to the longitudinal pipeline.
A new batch has been added under Volume Tools > Rescan Average to average rescans either in BIDS format or from manually selected images. This can be used, for example, to minimize motion artifacts. It can also be started directly from the CAT menu.
To run SPM ImCalc on multiple images (e.g., to compute T1w/T2w ratios for all subjects), use the batch available under Volume Tools > Multi-Subject Image Calculator.
New atlases: JulichBrain 3.1 (207 regions, volume and surface; replaces the previous JulichBrain atlas) and a hypothalamus atlas.
The CAT manual now offers a search function.

This is the final release and mainly contains bug fixes and further improvements to the surface pipeline.