Fix VFA validation for NumPy flip angles

osipy/dce/t1_mapping/vfa.py

@@ -149,16 +149,23 @@ def _compute_t1_vfa_impl(
         raise DataValidationError(msg)
 
     params = dataset.acquisition_params
-    if not params.flip_angles:
+
+    if params.flip_angles is None:
         msg = "VFA T1 mapping requires flip_angles in acquisition_params"
         raise DataValidationError(msg)
 
+    flip_angles = np.atleast_1d(np.asarray(params.flip_angles))
+
+    if flip_angles.size == 0:
+        msg = "VFA T1 mapping requires at least one flip angle"
+        raise DataValidationError(msg)
+
     if params.tr is None:
         msg = "VFA T1 mapping requires TR in acquisition_params"
         raise DataValidationError(msg)
 
     xp = get_array_module(dataset.data)
-    flip_angles = xp.asarray(params.flip_angles)
+    flip_angles = xp.asarray(flip_angles)
     tr = params.tr
 
     # Check data dimensions match flip angles

tests/unit/dce/test_t1_mapping.py

@@ -13,6 +13,7 @@
 from osipy.common.types import DCEAcquisitionParams, Modality
 from osipy.dce.t1_mapping.binding import BoundLookLockerModel, BoundSPGRModel
 from osipy.dce.t1_mapping.models import LookLockerSignalModel, SPGRSignalModel
+from osipy.dce.t1_mapping.vfa import compute_t1_vfa
 
 # ---------------------------------------------------------------------------
 # Helpers for synthetic data generation
@@ -407,7 +408,6 @@ class TestVFAFitting:
 
     def test_vfa_linear_recovers_t1(self) -> None:
         """VFA linear fit recovers known T1 from synthetic data."""
-        from osipy.dce.t1_mapping.vfa import compute_t1_vfa
 
         t1_true = 1000.0
         m0_true = 100.0
@@ -429,7 +429,6 @@ def test_vfa_linear_recovers_t1(self) -> None:
 
     def test_vfa_nonlinear_recovers_t1(self) -> None:
         """VFA nonlinear fit recovers known T1 from synthetic data."""
-        from osipy.dce.t1_mapping.vfa import compute_t1_vfa
 
         t1_true = 1000.0
         m0_true = 100.0
@@ -450,7 +449,6 @@ def test_vfa_nonlinear_recovers_t1(self) -> None:
 
     def test_vfa_array_interface(self) -> None:
         """VFA fitting works with individual arrays (no dataset)."""
-        from osipy.dce.t1_mapping.vfa import compute_t1_vfa
 
         t1_true = 800.0
         m0_true = 150.0
@@ -469,9 +467,33 @@ def test_vfa_array_interface(self) -> None:
         t1_mean = np.nanmean(result.t1_map.values[result.quality_mask])
         np.testing.assert_allclose(t1_mean, t1_true, rtol=0.01)
 
+    def test_vfa_accepts_numpy_flip_angles(self) -> None:
+        """VFA fitting accepts NumPy arrays for flip_angles in the dataset."""
+
+        t1_true = 1000.0
+        m0_true = 100.0
+        tr = 5.0
+
+        flip_angles = np.array([2.0, 5.0, 10.0, 15.0, 20.0])
+
+        dataset = _make_vfa_dataset(
+            t1=t1_true,
+            m0=m0_true,
+            flip_angles=flip_angles.tolist(),
+            tr=tr,
+        )
+
+        # Replace the list with a NumPy array to reproduce the reported bug
+        dataset.acquisition_params.flip_angles = flip_angles
+
+        result = compute_t1_vfa(dataset, method="linear")
+
+        t1_mean = np.nanmean(result.t1_map.values[result.quality_mask])
+
+        np.testing.assert_allclose(t1_mean, t1_true, rtol=0.01)
+
     def test_vfa_invalid_method_raises(self) -> None:
         """Unknown VFA method raises DataValidationError."""
-        from osipy.dce.t1_mapping.vfa import compute_t1_vfa
 
         dataset = _make_vfa_dataset(1000.0, 100.0, [2.0, 5.0, 10.0], 5.0)
         with pytest.raises(DataValidationError, match="Unknown VFA method"):