MRICloudCalculateCBF
====================

**Purpose.** Compute **absolute (aCBF)** and **relative (rCBF)** maps in native perfusion space using MRICloud equations.

Workflow
--------

- Uses ``r{asl}_diff.nii`` (difference), ``M0map.nii``, and the two brain masks.
- Handles PCASL and PASL timing (PLD/TI, slice timing, labeling duration).
- Applies background suppression scaling (``alpha``).

Inputs
------

- ``r{asl}_diff.nii`` from :doc:`mricloud_calculate_diffmap`
- ``M0map.nii``, ``brnmsk_dspl.nii``, ``brnmsk_clcu.nii`` from :doc:`mricloud_calculate_m0`
- Timing and acquisition fields in ``data_descrip``:
  - ``ArterialSpinLabelingType`` (``PCASL``/``PASL``), ``PLDList``, ``SliceDuration``,
    ``MRAcquisitionType`` (``2D``/``3D``), ``LabelingDuration`` (PCASL),
    ``BolusCutOffDelayTime`` (PASL), background suppression metadata.

Outputs
-------

- ``{asl}_aCBF_native.nii`` — absolute CBF (clipped to [0, 200])
- ``{asl}_rCBF_native.nii`` — relative CBF (normalized by global mean over ``brnmsk_clcu``)

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

=================  ===================  ==========================================
Key                Type / Default       Meaning
=================  ===================  ==========================================
``t1_blood``       int / ``1650``       Blood T1 (ms)
``part_coef``      float / ``0.9``      Partition coefficient (λ)
``bgs_eff``        float / ``0.93``     Background suppression efficiency
=================  ===================  ==========================================

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

.. code-block:: yaml

    modules:
      - name: MRICloudCalculateCBF
        params:
          t1_blood: 1650
          part_coef: 0.9
          bgs_eff: 0.93