helical_fdk#

diffct.reconstruction.helical_fdk(sinogram, trajectory, volume_shape, angles, *, isocenter, detector_spacing=1.0, voxel_spacing=1.0, window='ram-lak', pad_factor=2, projection_weights=None, view_weights=None, filter_response=None)[source]#

Approximate axial helical FDK with one complete angular turn per slice.

Filters detector U once, then applies helical_view_weights() inside the analytical gather. isocenter is required in physical coordinates. Source heights and unwrapped angles must agree with the actual helix; finite scans must cover a full turn around every requested slice. view_weights replaces the complete (D,views) window/quadrature stage. Projection/filter replacements follow fbp(). Custom tensors retain autograd and are not normalized or clamped. Detector truncation is not corrected. This native-cone approximation does not implement cone-parallel rebinning, 3D conjugate weights or exact Katsevich inversion.