Half fan CBCT reconstruction

Hi all,
I am attempting CBCT reconstruction using python TIGRE’s OSSART algorithm, but I am consistently getting a prominent ring artifact and a diagonal streak in the reconstructed images.

I am using the following geometry:

```
geo= tigre.geometry_default(high_resolution=True) # base`
geo.DSO = float(921)
geo.DSD = float(1690)
geo.nDetector = np.array([col_det,row_det],dtype=np.int32)
geo.dDetector = np.array([0.278,0.278], dtype=np.float32)
geo.sDetector = geo.nDetector * geo.dDetector
geo.mode = "cone"
geo.angles = angles
n_proj = angles.size
geo.nVoxel = np.array([400,400,400], dtype=np.int32)
geo.dVoxel = np.array([1,1,1], dtype=np.float32)
geo.sVoxel = geo.nVoxel * geo.dVoxel
geo.offOrigin = np.array([0, 0, 0], dtype=np.float32)
geo.offDetector = np.array([-195,0])
geo.rotDetector = np.array([0, 0, 0])
geo.accuracy = 0.5
geo.COR = `0``
```

Any guidance on how to refine the geometry setup or reconstruction parameters to reduce these streaks would be greatly appreciated.

Start by reproducing the reconstruction with the posted geometry_default setup, detector offsets, angles, and OSSART call, then inspect how geometry and reconstruction parameters are passed into TIGRE. Compare results while isolating geometry values from algorithm settings; done means identifying a reproducible cause or documenting a validated configuration that removes the ring and diagonal streak artifacts.

Written by the indexing model from the issue text.