ring_artifact_apply — TOMOGRAPHY artifact op

• Data kinds: sinogram → sinogram

• Call: import tomography; tomography.ring_artifact_apply(sinogram, gain_sigma=0.02, seed=0, offsets=None) (or opstomography.get("ring_artifact_apply"))

Usage

Give the detector a per-bin gain error — the source of ring artefacts.

A detector bin whose gain is `g reports I = g I_true`, so after the

logarithm the line integral picks up a constant offset `-ln g` at that

bin, the same at every angle. Back-projecting a constant column smears it

around the rotation axis, and the reconstruction grows a ring at the radius

that bin's rays are tangent to. One bad pixel, one perfect circle.

The offsets are drawn once from `N(0, gain_sigma)` with a fixed *seed* and

applied to every row, because the whole point is that the error does not

vary with angle — that is what distinguishes a ring from noise, and what makes

:func:ring_artifact_remove possible.

:param sinogram: `(n_angles, n_detectors)`.

:param gain_sigma: standard deviation of the per-bin offset, `>= 0`.

:param seed: RNG seed; there is no `None` (determinism is a contract here).

:param offsets: explicit `(n_detectors,)` offsets; overrides the random draw.

:returns: `(n_angles, n_detectors)` float64 sinogram.

:raises ValueError: on a negative sigma, a non-int seed, or an *offsets* whose

length is not the detector count.

References (sample data, literature)

• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).

• Operator provenance and references — the sources of the research/methods this op family came from.

• The canonical algorithm (author, year) and its uses are named in the family usage guide above.

Runnable examples (verified samples that actually call this op)

• ct_reconstruction — py -3.11 examples/ct_reconstruction.py

Ops the type connects to (they accept sinogram as input)

backproject_sinogram · filtered_backprojection · sart_reconstruct · beam_hardening_apply · beam_hardening_correct · ring_artifact_remove · metal_trace_interpolate · sinogram_center_of_rotation

Same category (artifact)

beam_hardening_apply · beam_hardening_correct · ring_artifact_remove · metal_trace_interpolate

*Provenance: tomography.py — TOMOGRAPHY operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*

© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.