Reduction of Artifacts Caused by Deep Brain Stimulating Electrodes in Cranial Computed Tomography Imaging by Means of Virtual Monoenergetic Images, Metal Artifact Reduction Algorithms, and Their Combination

• Published in: Investigative radiology Vol. 53; no. 7; pp. 424 - 431
• Main Authors: Große Hokamp, Nils, Hellerbach, Alexandra, Gierich, Andreas, Jordan, David W, Visser-Vandewalle, Veerle, Maintz, David, Haneder, Stefan
• Format: Journal Article
• Language: English
• Published: United States Copyright Wolters Kluwer Health, Inc. All rights reserved 01-07-2018
• ISSN: 0020-9996; 1536-0210
• DOI: 10.1097/RLI.0000000000000460

OBJECTIVESThe aim of this study was to evaluate the reduction of artifacts from deep brain stimulation electrodes (DBS) using an iterative metal artifact reduction algorithm (O-MAR), virtual monoenergetic images (VMI), and both in combination in postoperative spectral detector computed tomography using a dual-layer detector (spectral detector computed tomography [SDCT]) of the head.
MATERIAL AND METHODSNonanthropomorphic phantoms with different DBS leads were examined on SDCT; in 1 phantom periprocedural bleeding was simulated. A total of 20 patients who underwent SDCT after DBS implantation between October 2016 and April 2017 were included in this institutional review board–approved retrospective study. Images were reconstructed using standard-of-care iterative reconstruction (CI) and VMI, each with and without O-MAR processing (IR and MAR). Artifacts were quantified by determining the percentage integrity uniformity in an annular region of 1.4 cm around the DBS lead; a percentage integrity uniformity of 100% indicates the absence of artifacts. In phantoms, conspicuity of blood was determined on a binary scale, whereas in patients, image quality, DBS lead assessment, and extent of artifact reduction were assessed on Likert scales by 2 radiologists. Statistical significance was assessed using analysis of variance and Wilcoxon tests; sensitivity and specificity were calculated.
RESULTSThe O-MAR processing significantly decreased artifacts in phantom and patients (P ≤ 0.05), whereas VMI did not reduce artifact burden compared with corresponding CI (P > 0.05)for example, CI-IR/MAR and 200 keV-IR/MAR for patients76.3%/90.7% and 75.9%/91.2%, respectively. Qualitatively, overall image quality was not improved (P > 0.05) and MAR improved DBS assessment (CI-IR/MAR2 [1–3]/3 [2–4]; P ≤ 0.05) and reduced artifacts significantly (P ≤ 0.05). The O-MAR processing increased sensitivity for bleeding by 160%. In some cases, new artifacts were induced through O-MAR processing, none of which impaired diagnostic image assessment.
DISCUSSIONThe investigated O-MAR algorithm reduces artifacts from DBS electrodes and should be used in the assessment of postoperative patients; however, combination with VMI does not provide an additional benefit.