Image Artifacts in Concurrent Transcranial Magnetic Stimulation (TMS) and fMRI Caused by Leakage Currents: Modeling and Compensation

被引：35

作者：

Weiskopf, Nikolaus ^{[1
]}

Josephs, Oliver ^{[1
]}

Ruff, Christian C. ^{[1
,6
]}

Blankenburg, Felix ^{[1
,4
,5
,6
]}

Featherstone, Eric ^{[1
]}

Thomas, Anthony ^{[7
]}

Bestmann, Sven ^{[1
,3
]}

Driver, Jon ^{[1
,6
]}

Deichmann, Ralf ^{[1
,2
]}

机构：

[1] UCL, UCL Inst Neurol, Wellcome Trust Ctr Neuroimaging, London WC1N 3BG, England

[2] Univ Hosp, Brain Imaging Ctr, Frankfurt, Germany

[3] UCL, UCL Inst Neurol, Sobell Dept Motor Neurosci & Movement Disorders, London WC1N 3BG, England

[4] Charite Univ Med Berlin, Dept Neurol, Berlin, Germany

[5] Charite Univ Med Berlin, Bernstein Ctr Computat Neurosci, Berlin, Germany

[6] UCL, UCL Inst Cognit Neurosci, London WC1N 3BG, England

[7] Magstim Co Ltd, Whitland, Wales

来源：

JOURNAL OF MAGNETIC RESONANCE IMAGING | 2009年 / 29卷 / 05期

基金：

英国惠康基金; 英国医学研究理事会; 英国生物技术与生命科学研究理事会;

关键词：

transcranial magnetic stimulation; TMS; functional magnetic resonance imaging; fMRI; MR artifacts; leakage current; DISTORTION; CORTEX;

D O I：

10.1002/jmri.21749

中图分类号：

R8 [特种医学]; R445 [影像诊断学];

学科分类号：

1002 ; 100207 ; 1009 ;

摘要：

Purpose: To characterize and eliminate a new type of image artifact in concurrent transcranial magnetic stimulation and functional MRI (TMS-fMRI) caused by small leakage currents originating from the high-voltage capacitors in the TMS stimulator system. Materials and Methods: The artifacts in echo-planar images (EPI) caused by leakage currents were characterized and quantified in numerical simulations and phantom studies with different phantom-coil geometries. A relay-diode combination was devised and inserted in the TMS circuit that shorts the leakage current. Its effectiveness for artifact reduction was assessed in a phantom scan resembling a realistic TMS-fMRI experiment. Results: The leakage-current-induced signal changes exhibited a multipolar spatial pattern and the maxima exceeded 1% at realistic coil-cortex distances. The relay-diode combination effectively reduced the artifact to a negligible level. Conclusion: The leakage-current artifacts potentially obscure effects of interest or lead to false-positives. Since the artifact depends on the experimental setup and design (eg. amplitude of the leakage current, coil orientation, paradigm. EPI parameters), we recommend its assessment for each experiment. The relay-diode combination can eliminate the artifacts if necessary.

引用

页码：1211 / 1217

页数：7

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