Changed flip angles in dce tutorial to list

[dsmits]

I found a small mistake in the DCE tutorial. The flip angles in there are defined as a numpy array (which is very reasonable). However, the _compute_t1_vfa_impl function has been written with only lists in mind.

The call osipy.compute_t1_map(vfa_data, method="vfa") in the DCE-MRI analysis tutorial fails when the flip angles are defined as numpy arrays (see stacktrace below). Since the type hint states it should be a list anyways I thought it would be reasonable enough to only fix the documentation.

Stacktrace

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[13], line 8
      4     tr=tr, flip_angles=flip_angles
      5 )
      6 
      7 # Compute T1 map using Variable Flip Angle method
----> 8 t1_result = osipy.compute_t1_map(vfa_data, method="vfa")
      9 
     10 # The result is a T1MappingResult with t1_map (ParameterMap) and quality_mask
     11 t1_values = t1_result.t1_map.values

File [~/projects/OSIPY/osipy-test/.venv/lib/python3.14/site-packages/osipy/dce/t1_mapping/__init__.py:59](http://localhost:8888/home/dsmits/projects/OSIPY/osipy-test/.venv/lib/python3.14/site-packages/osipy/dce/t1_mapping/__init__.py#line=58), in compute_t1_map(dataset, method)
     29 """Compute T1 map from multi-flip-angle or Look-Locker data.
     30 
     31 Parameters
   (...)     56 >>> print(f"Mean T1: {result.t1_map.statistics()['mean']:.0f} ms")
     57 """
     58 t1_func = get_t1_method(method)
---> 59 return t1_func(dataset)

File [~/projects/OSIPY/osipy-test/.venv/lib/python3.14/site-packages/osipy/dce/t1_mapping/vfa.py:380](http://localhost:8888/home/dsmits/projects/OSIPY/osipy-test/.venv/lib/python3.14/site-packages/osipy/dce/t1_mapping/vfa.py#line=379), in compute_t1_vfa(dataset, method, signal, flip_angles, tr, mask)
    370     # Create temporary dataset
    371     dataset = PerfusionDataset(
    372         data=signal,
    373         affine=np.eye(4),
   (...)    377         quality_mask=mask,
    378     )
--> 380 return _compute_t1_vfa_impl(dataset, method)

File [~/projects/OSIPY/osipy-test/.venv/lib/python3.14/site-packages/osipy/dce/t1_mapping/vfa.py:152](http://localhost:8888/home/dsmits/projects/OSIPY/osipy-test/.venv/lib/python3.14/site-packages/osipy/dce/t1_mapping/vfa.py#line=151), in _compute_t1_vfa_impl(dataset, method)
    149     raise DataValidationError(msg)
    151 params = dataset.acquisition_params
--> 152 if not params.flip_angles:
    153     msg = "VFA T1 mapping requires flip_angles in acquisition_params"
    154     raise DataValidationError(msg)

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

[ltorres6]

Thanks Djura! Approving so that the example works. We have another PR open to ensure that this is properly handled on the backend (I would like to handle both arrays and lists). I think we are converging on a solution there.