The Contribution of Common Surgically Implanted Hardware to Functional MR Imaging Artifacts

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The authors calculated the BOLD-dependent MR imaging artifact impact arising from surgically implanted hardware through a retrospective analysis of fMRIs acquired from 2006–2014. Mean artifact volume associated with intracranial hardware was 4.3 cubic centimeters. The mean artifact volume from extracranial hardware in patients with cerebrovascular disease was 28.4 cubic centimeters. Artifacts had no-to-mild effects on clinical interpretability in all patients with intracranial implants. Extracranial hardware artifacts had no-to-moderate impact on clinical interpretability. The exceptions to interpretability in the face of hardware were ventriculoperitoneal shunts, particularly those with programmable valves and siphon gauges, and large numbers of KLS-Martin maxDrive screws.

Abstract

A representative patient (patient 3) with an intracranial implant. Signal drop-out from a left MCA Pharos Vitesse stent (Codman Neurovascular) is apparent on the magnitude BOLD fMRI image (A, white arrow), resulting in a total artifact volume of 2.1 cm3, which only mildly affected clinical interpretation of the examination. The patient was evaluated 2 years following implantation of the Pharos Vitesse stent in a stenosed left MCA. DSA (B) shows in-stent restenosis (black arrow), with corresponding decreased cerebrovascular reactivity (normalized CVR: voxel CVR normalized to cerebellar CVR) in the left MCA territory (C). In contrast, there is relative symmetry of the temporal signal-to-noise ratio (tSNR) map (D), suggesting that the asymmetric hemodynamic findings are not attributable to artifacts.
A representative patient (patient 3) with an intracranial implant. Signal drop-out from a left MCA Pharos Vitesse stent (Codman Neurovascular) is apparent on the magnitude BOLD fMRI image (A, white arrow), resulting in a total artifact volume of 2.1 cm3, which only mildly affected clinical interpretation of the examination. The patient was evaluated 2 years following implantation of the Pharos Vitesse stent in a stenosed left MCA. DSA (B) shows in-stent restenosis (black arrow), with corresponding decreased cerebrovascular reactivity (normalized CVR: voxel CVR normalized to cerebellar CVR) in the left MCA territory (C). In contrast, there is relative symmetry of the temporal signal-to-noise ratio (tSNR) map (D), suggesting that the asymmetric hemodynamic findings are not attributable to artifacts.

BACKGROUND AND PURPOSE

Blood oxygenation level–dependent MR imaging is increasingly used clinically to noninvasively assess cerebrovascular reactivity and/or language and motor function. However, many patients have metallic implants, which will induce susceptibility artifacts, rendering the functional information uninformative. Here, we calculate and interpret blood oxygenation level–dependent MR imaging artifact impact arising from surgically implanted hardware.

MATERIALS AND METHODS

A retrospective analysis of all blood oxygenation level–dependent MRIs (n = 343; B0 = 3T; TE = 35 ms; gradient echo EPI) acquired clinically (year range = 2006–2014) at our hospital was performed. Blood oxygenation level–dependent MRIs were most commonly prescribed for patients with cerebrovascular disease (n = 80) or patients undergoing language or motor localization (n = 263). Artifact volume (cubic centimeters) and its impact on clinical interpretation were determined by a board-certified neuroradiologist.

RESULTS

Mean artifact volume associated with intracranial hardware was 4.3 ± 3.2 cm3 (range = 1.1–9.4 cm3). The mean artifact volume from extracranial hardware in patients with cerebrovascular disease was 28.4 ± 14.0 cm3 (range = 6.1–61.7 cm3), and in patients with noncerebrovascular disease undergoing visual or motor functional mapping, it was 39.9 3± 27.0 cm3 (range = 6.9–77.1 cm3). The mean artifact volume for ventriculoperitoneal shunts was 95.7 ± 39.3 cm3 (range = 64.0–139.6 cm3). Artifacts had no-to-mild effects on clinical interpretability in all patients with intracranial implants. Extracranial hardware artifacts had no-to-moderate impact on clinical interpretability, with the exception of 1 patient with 12 KLS-Martin maxDrive screws with severe artifacts precluding clinical interpretation. All examined ventriculoperitoneal shunts resulted in moderate-to-severe artifacts, limiting clinical interpretation.

CONCLUSIONS

Blood oxygenation level–dependent MR imaging yields interpretable functional maps in most patients beyond a small (30–40 cm3) artifact surrounding the hardware. Exceptions were ventriculoperitoneal shunts, particularly those with programmable valves and siphon gauges, and large numbers of KLS-Martin maxDrive screws.

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The Contribution of Common Surgically Implanted Hardware to Functional MR Imaging Artifacts
jross
Jeffrey Ross • Mayo Clinic, Phoenix

Dr. Jeffrey S. Ross is a Professor of Radiology at the Mayo Clinic College of Medicine, and practices neuroradiology at the Mayo Clinic in Phoenix, Arizona. His publications include over 100 peer-reviewed articles, nearly 60 non-refereed articles, 33 book chapters, and 10 books. He was an AJNR Senior Editor from 2006-2015, is a member of the editorial board for 3 other journals, and a manuscript reviewer for 10 journals. He became Editor-in-Chief of the AJNR in July 2015. He received the Gold Medal Award from the ASSR in 2013.