artifact op• 資料種類:sinogram → sinogram
• 呼叫: import fullseye as fs; fs.ledger.metal_trace_interpolate(sinogram, angles_deg=None, image_threshold=None, mask=None, size=None)(要直接呼叫實作,import tomography; tomography.metal_trace_interpolate(sinogram, angles_deg=None, image_threshold=None, mask=None, size=None);從台帳取用則 opstomography.get("metal_trace_interpolate"))
線性插值的金屬偽影抑制(LI-MAR)。
> 以下的詳細說明為原文 —— 摘要與標題已翻譯。
A metal implant attenuates so strongly that its detector bins carry almost no photons; the measured line integrals there are dominated by scatter and by the noise floor of the logarithm, and back-projecting them lays down the dark bands and bright streaks between dense objects that make a slice unreadable.
The oldest working answer, and still the baseline every newer method is compared against: declare the affected bins *missing* and fill them by linear interpolation along the detector axis, per angle. The result is not the truth — it is a smooth guess with the streaks removed — and it blurs whatever was genuinely behind the metal.
How the affected bins are found matters more than the interpolation, and the obvious way is measurably worse than doing nothing. The metal trace is located the way LI-MAR actually does it: reconstruct once with filtered_backprojection, threshold the *image* at mean + 3*std, forward-project that binary mask, and treat the bins it touches as missing. Thresholding the sinogram directly is the shortcut that suggests itself, and on the Shepp-Logan phantom with a 6-px implant it goes wrong in the direction that is hardest to notice — it flags the densest *legitimate* structure (the skull, seen edge-on) and interpolates it away:
implant density uncorrected sinogram threshold image threshold
x8 0.0487 0.0626 0.0255
x30 0.1583 0.2249 0.0255
x100 0.5214 0.7127 0.0257
(normalised RMS error against the metal-free truth, outside the implant footprint; the metal-free reconstruction itself scores 0.0250.) The image route recovers essentially all of the damage at every density. The sinogram route makes it 1.3-1.4x *worse* than not correcting at all, at every density, while still producing a picture with fewer visible streaks — which is why the shortcut is not offered as an option here rather than merely discouraged.
Inside the implant footprint the reconstruction is now wrong on purpose: the metal is gone. Clinical practice puts it back from the thresholded reconstruction afterwards; that step is not implemented.
:param sinogram: (n_angles, n_detectors). :param angles_deg: view angles; None -> uniform [0, 180). Used for the
internal reconstruction and re-projection, so a wrong angle set here
misplaces the trace.
:param image_threshold: image-domain metal threshold; None ->
mean + 3*std of the internal reconstruction.
:param mask: explicit boolean (n_angles, n_detectors) metal trace. When
given, no reconstruction is done and *image_threshold* is ignored — this
is the route to use when the trace comes from a segmentation you trust.
:param size: side of the internal reconstruction; None -> the inscribed
square.
:returns: (n_angles, n_detectors) float64 sinogram. :raises ValueError: if the mask shape disagrees with the sinogram, if the mask
is not boolean, if nothing is left to interpolate from, or if any *row* is
entirely masked.
• 範例資料目錄(下載 URL / 授權) —— 2-D 用 skimage.data(BSD/公有領域)加合成圖,3-D 給出真實資料源(Stanford/PDS 等)的下載 URL。
• 運算子來歷與參考文獻 —— 該運算子族所依據的研究/方法出處。
• 演算法的正典(作者、年份)與用途見上面的族使用指南。
• ct_reconstruction — py -3.11 examples/ct_reconstruction.py
sinogram 作為輸入)backproject_sinogram · filtered_backprojection · sart_reconstruct · beam_hardening_apply · beam_hardening_correct · ring_artifact_apply · ring_artifact_remove · sinogram_center_of_rotation
artifact)beam_hardening_apply · beam_hardening_correct · ring_artifact_apply · ring_artifact_remove
*Provenance: tomography.py — TOMOGRAPHY 運算子登記表。本條目由 tools/opdocs.py md 自動產生(請勿手動編輯)。*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.