Shelley HuaLei Zhang1, Zion Tsz Ho Tse2, Charles L Dumoulin3, Raymond Y Kwong4, William G Stevenson4, Ronald Watkins5, Jay Ward6, Wei Wang1, Ehud J Schmidt1. 1. Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts, USA. 2. Department of Engineering, University of Georgia, Athens, Georgia, USA. 3. Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA. 4. Department of Cardiology, Brigham and Women's Hospital, Boston, Massachusetts, USA. 5. Department of Radiology, Stanford University, Stanford, California, USA. 6. E-TROLZ Inc, North Andover, Massachusetts, USA.
Abstract
PURPOSE: To restore 12-lead electrocardiographic (ECG) signal fidelity inside MRI by removing magnetic field gradient-induced voltages during high gradient duty cycle sequences. THEORY AND METHODS: A theoretical equation was derived to provide first- and second-order electrical fields induced at individual ECG electrodes as a function of gradient fields. Experiments were performed at 3T on healthy volunteers using a customized acquisition system that captured the full amplitude and frequency response of ECGs, or a commercial recording system. The 19 equation coefficients were derived via linear regression of data from accelerated sequences and were used to compute induced voltages in real-time during full resolution sequences to remove ECG artifacts. Restored traces were evaluated relative to ones acquired without imaging. RESULTS: Measured induced voltages were 0.7 V peak-to-peak during balanced steady state free precession (bSSFP) with the heart at the isocenter. Applying the equation during gradient echo sequencing, three-dimensional fast spin echo, and multislice bSSFP imaging restored nonsaturated traces and second-order concomitant terms showed larger contributions in electrodes further from the magnet isocenter. Equation coefficients are evaluated with high repeatability (ρ = 0.996) and are dependent on subject, sequence, and slice orientation. CONCLUSION: Close agreement between theoretical and measured gradient-induced voltages allowed for real-time removal. Prospective estimation of sequence periods in which large induced voltages occur may allow hardware removal of these signals.
PURPOSE: To restore 12-lead electrocardiographic (ECG) signal fidelity inside MRI by removing magnetic field gradient-induced voltages during high gradient duty cycle sequences. THEORY AND METHODS: A theoretical equation was derived to provide first- and second-order electrical fields induced at individual ECG electrodes as a function of gradient fields. Experiments were performed at 3T on healthy volunteers using a customized acquisition system that captured the full amplitude and frequency response of ECGs, or a commercial recording system. The 19 equation coefficients were derived via linear regression of data from accelerated sequences and were used to compute induced voltages in real-time during full resolution sequences to remove ECG artifacts. Restored traces were evaluated relative to ones acquired without imaging. RESULTS: Measured induced voltages were 0.7 V peak-to-peak during balanced steady state free precession (bSSFP) with the heart at the isocenter. Applying the equation during gradient echo sequencing, three-dimensional fast spin echo, and multislice bSSFP imaging restored nonsaturated traces and second-order concomitant terms showed larger contributions in electrodes further from the magnet isocenter. Equation coefficients are evaluated with high repeatability (ρ = 0.996) and are dependent on subject, sequence, and slice orientation. CONCLUSION: Close agreement between theoretical and measured gradient-induced voltages allowed for real-time removal. Prospective estimation of sequence periods in which large induced voltages occur may allow hardware removal of these signals.
Authors: Zion Tsz Ho Tse; Charles L Dumoulin; Gari D Clifford; Jeff Schweitzer; Lei Qin; Julien Oster; Michael Jerosch-Herold; Raymond Y Kwong; Gregory Michaud; William G Stevenson; Ehud J Schmidt Journal: Magn Reson Med Date: 2014-03 Impact factor: 4.668
Authors: Adrienne E Campbell-Washburn; Mohammad A Tavallaei; Mihaela Pop; Elena K Grant; Henry Chubb; Kawal Rhode; Graham A Wright Journal: J Magn Reson Imaging Date: 2017-05-11 Impact factor: 4.813
Authors: T Stan Gregory; John Oshinski; Ehud J Schmidt; Raymond Y Kwong; William G Stevenson; Zion Tsz Ho Tse Journal: Circ Cardiovasc Imaging Date: 2015-12 Impact factor: 7.792
Authors: Ehud J Schmidt; Ronald D Watkins; Menekhem M Zviman; Michael A Guttman; Wei Wang; Henry A Halperin Journal: Circ Cardiovasc Imaging Date: 2016-10 Impact factor: 7.792
Authors: Ehud J Schmidt; Hassan Elahi; Eric S Meyer; Ryan Baumgaertner; Luca Neri; Ronald D Berger; Harikrishna Tandri; David W Hunter; Steven P Cohen; Matt T Oberdier; Henry R Halperin Journal: Heart Rhythm Date: 2022-02-28 Impact factor: 6.779