Metal artifact reduction from surgical clips for intracranial aneurysms in photon-counting detector CT angiography

To identify conditions that reduce metal artifacts from surgical clips for intracranial aneurysms while preserving parent vessel visualization in CT angiography (CTA) by using a reconstruction method combining virtual monoenergetic image (VMI) and a metal artifact reduction (MAR) algorithm.

Patients who underwent CTA after clipping surgery using photon-counting detector CT (PCD-CT) in 2023-2025 were included. Images were reconstructed as conventional polychromatic 120kVp images (T3D) and 40, 70, 100, 130, 160, and 190 keV using VMI; we created images applying the MAR algorithm to each. Hyperdense/ hypodense artifacts, the artifact index (AI), and the contrast-to-noise ratio (CNR) were quantitatively measured by two neuroradiologists. Hyperdense/ hypodense artifacts, noise, parent vessel visualization, blooming, and new artifacts generated with the MAR algorithm were qualitatively assessed by four neuroradiologists.

28 patients (median 64 [53-72] years, 15 men) were included. Quantitatively, hyperdense artifacts decreased at ≥ 70 keV (68.4H.U.) versus T3D (82.7) (P < 0.001). Hypodense artifacts and AI decreased at ≥ 100 keV (-2.3H.U. and 21.6) (P < 0.001). CNRs decreased at ≥ 70 keV (20.1) and further decreased when the MAR was applied (13.6) (P < 0.001). Qualitatively, hyperdense/ hypodense artifacts decreased at ≥ 100 keV and further decreased slightly with the MAR (P < 0.001). Noise decreased at ≥ 100 keV. The parent vessel visualization after clipping improved at 70 and 100 keV but decreased with the MAR (P < 0.001). Clip blooming did not occur at ≥ 100 keV (P < 0.001) regardless of the use/nonuse of the MAR (P > 0.500). New artifacts decreased at ≥ 100 keV-MAR versus T3D-MAR (P < 0.001).

The optimal setting for reducing metal artifacts while preserving vascular information was 100 keV.