CreateMask
==========

**Purpose.** Produce a binary brain mask from perfusion images using simple intensity thresholding.

Inputs
------

- For each ASL base name ``{asl}``, reads ``derivatives/<sub>/perf/srmean{asl}.nii``.

Outputs & filenames
-------------------

- Writes ``derivatives/<sub>/perf/{asl}_mask_perf_cbf.nii`` (int16).

Configuration
-------------

=================  ================  ==========================================
Key                Type / Default    Meaning
=================  ================  ==========================================
``thres``          float / ``0.1``   Threshold as a fraction of the image max
=================  ================  ==========================================

YAML example
------------

.. code-block:: yaml

    modules:
      - name: CreateMask
        config:
          thres: 0.15