CT Metal Artifact Reduction in the Spine: Can an Iterative Reconstruction Technique Improve Visualization?

Kotsenas, Amy L.; Michalak, Gregory J.; DeLone, David R.; Diehn, Felix E.; Grant, Katharine L.; Halaweish, Ahmed F.; Krauß, A.; Raupach, Rainer; Schmidt, Bernhard; McCollough, Cynthia H.; Fletcher, Joel G.

doi:10.3174/ajnr.a4416

Cited by 62 publications

(52 citation statements)

References 17 publications

(23 reference statements)

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“…These reports focused on hip arthroplasties, 5,10,14-18 shoulder arthroplasties, 13 internal fixation hardware, 12 dental hardware 14,19 and spinal hardware. 20,21 Our findings are consistent with those of previous studies. Furthermore, our findings demonstrate the utility of using iMAR in the post-operative phase and show that additional findings can be discovered after artefact reduction.…”

Section: Discussionsupporting

confidence: 93%

Clinical evaluation of the iterative metal artefact reduction algorithm for post-operative CT examination after maxillofacial surgery

Hakim

Slotboom

Lieger

et al. 2017

Dentomaxillofacial Radiology

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Objectives: Metal artefacts present challenges to both radiologists and clinicians during postoperative imaging. Such artefacts reduce the diagnostic effectiveness of CT scans and mask findings that could be vital for patient management. Thus, a powerful artefact reduction tool is necessary when imaging patients with metal implants. Our aim was to test the recently introduced iterative metal artefact reduction (iMAR) algorithm in patients with maxillofacial implants. Methods: Images from 17 patients with diverse maxillofacial metal implants who had undergone CT scans were qualitatively and quantitatively analyzed before and after metal artefact reduction with iMAR. Results: After iMAR application, images exhibited decreased artefacts and improved image quality, leading to detection of lesions that were previously masked by artefacts. The application of iMAR did not affect image quality in regions distant from the metal implants. Conclusions: The application of iMAR to CT examinations of patients with maxillofacial metal implants leads to artefact reduction, improvement of image quality and increased diagnostic utility. Routine implementation of iMAR during imaging of patients with metal hardware implants could add diagnostic value to their CT examinations.

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Section: Discussionsupporting

confidence: 93%

Clinical evaluation of the iterative metal artefact reduction algorithm for post-operative CT examination after maxillofacial surgery

Hakim

Slotboom

Lieger

et al. 2017

Dentomaxillofacial Radiology

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“…The neuroradiologists also examined the anatomic structure most compromised by the artifacts (identified by the PI, as above) and assigned a soft-tissue visualization score on a six-point scale (0 = totally obscured, no structures identifiable; 1 = marked artifacts, questionable recognition; 2 = faint anatomic recognition; 3 = anatomic recognition with low confidence; 4 = anatomic recognition with medium confidence; 5 = anatomic recognition with high confidence in a potential diagnosis), similar to a previously reported scale (2). Soft-tissue visualization scores were calculated by subtracting the score of the wFBP images from the score for the IMAR images, such that positive values reflected improvement with IMAR and negative values reflected degradation.…”

Section: Methodsmentioning

confidence: 87%

“…The IMAR images were reconstructed using a prototype three-dimensional (3D) IMAR algorithm (see Kotsenas et al. (2) for a detailed description) and a B40 kernel. The IMAR algorithm is an iterative frequency split technique, which is designed to reduce blurring of the anatomical structures near the metal objects and to suppress the “streaking” that emanates from metal structures in CT images.…”

Section: Methodsmentioning

confidence: 99%

“…Several investigators have proposed post-processing methods for decreasing the extent of metal-related artifacts in CT (1–9). Several of these publications have focused on the head and neck (1,8,9), comparing the current uncorrected clinical standard, weighted filtered back projection (wFBP) to linear interpolation metal artifact reduction, and iterative metal artifact reduction (IMAR).…”

Section: Introductionmentioning

confidence: 99%

“…In a study evaluating artifact reduction associated with spinal hardware (2), the use of an IMAR algorithm (Siemens Healthcare, Forchheim, Germany) minimized artifacts tangential to high-contrast regions on the basis of spatial frequency, recovering detail close to metallic objects. Thus, IMAR theoretically allows for retention of important anatomic information relative to the original images.…”

Section: Introductionmentioning

confidence: 99%

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CT Dental Artifact: Comparison of an Iterative Metal Artifact Reduction Technique with Weighted Filtered Back-Projection

Diehn

Michalak

DeLone

et al. 2017

Acta Radiologica Open

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BackgroundDental hardware produces streak artifacts on computed tomography (CT) images reconstructed with the standard weighted filtered back projection (wFBP) method.PurposeTo perform a preliminary evaluation of an iterative metal artifact reduction (IMAR) technique to assess its ability to improve anatomic visualization over wFBP in patients with dental amalgam or other hardware.Material and MethodsCT images from patients with dental hardware were reconstructed using wFBP and IMAR software and soft-tissue or bone window/level settings. The anatomy most affected by metal artifacts was identified. Two neuroradiologists determined subjective and objective imaging features, including overall metal artifact score (1 = severe artifacts, 5 = no artifacts), soft-tissue visualization score of the most-compromised structure, and artifact length along the skin surface. CT numbers were used to quantify artifact severity.ResultsTwenty-four patients were included. IMAR improved overall metal artifact score in 18/24 cases (median =2 ± 0.9 vs. 1 ± 0.6, P < 0.001). Mean CT number in the most-affected anatomical structure significantly improved with IMAR (94.6 vs. 219 HU, P = 0.002) and length of affected skin surface decreased (40.4 mm vs. 118.7 mm, P < 0.001). However, osseous/dental artifactual defects were found in 22/24 cases with IMAR vs. 11/24 with wFBP.ConclusionIMAR software reduced metal artifact both subjectively and objectively and improved visualization of adjacent soft tissues. However, it produced a higher rate of artifactual defects in the teeth and bones than wFBP. Our findings support the use of IMAR as a valuable complement to, but not a replacement for, standard wFBP image reconstruction.

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Evaluation of projection‐ and dual‐energy‐based methods for metal artifact reduction in CT using a phantom study

Long

Bruesewitz

DeLone

et al. 2018

J Applied Clin Med Phys

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ObjectivesBoth projection and dual‐energy (DE)‐based methods have been used for metal artifact reduction (MAR) in CT. The two methods can also be combined. The purpose of this work was to evaluate these three MAR methods using phantom experiments for five types of metal implants.Materials and MethodsFive phantoms representing spine, dental, hip, shoulder, and knee were constructed with metal implants. These phantoms were scanned using both single‐energy (SE) and DE protocols with matched radiation output. The SE data were processed using a projection‐based MAR (iMAR, Siemens) algorithm, while the DE data were processed to generate virtual monochromatic images at high keV (Mono+, Siemens). In addition, the DE images after iMAR were used to generate Mono+ images (DE iMAR Mono+). Artifacts were quantitatively evaluated using CT numbers at different regions of interest. Iodine contrast‐to‐noise ratio (CNR) was evaluated in the spine phantom. Three musculoskeletal radiologists and two neuro‐radiologists independently ranked the artifact reduction.ResultsThe DE Mono+ at high keV resulted in reduced artifacts but also lower iodine CNR. The iMAR method alone caused missing tissue artifacts in dental phantom. DE iMAR Mono+ caused wrong CT numbers in close proximity to the metal prostheses in knee and hip phantoms. All musculoskeletal radiologists ranked SE iMAR > DE iMAR Mono+ > DE Mono+ for knee and hip, while DE iMAR Mono+ > SE iMAR > DE Mono+ for shoulder. Both neuro‐radiologists ranked DE iMAR Mono+ > DE Mono+ > SE iMAR for spine and DE Mono+ > DE iMAR Mono+ > SE iMAR for dental.ConclusionsThe SE iMAR was the best choice for the hip and knee prostheses, while DE Mono+ at high keV was best for dental implants and DE iMAR Mono+ was best for spine and shoulder prostheses. Artifacts were also introduced by MAR algorithms.

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CT Metal Artifact Reduction in the Spine: Can an Iterative Reconstruction Technique Improve Visualization?

Cited by 62 publications

References 17 publications

Clinical evaluation of the iterative metal artefact reduction algorithm for post-operative CT examination after maxillofacial surgery

Clinical evaluation of the iterative metal artefact reduction algorithm for post-operative CT examination after maxillofacial surgery

CT Dental Artifact: Comparison of an Iterative Metal Artifact Reduction Technique with Weighted Filtered Back-Projection

Evaluation of projection‐ and dual‐energy‐based methods for metal artifact reduction in CT using a phantom study

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