- Poster presentation
- Open Access
Cardiac MRI with concurrent physiological monitoring using MRI-compatible 12-lead ECG
© Tse et al; licensee BioMed Central Ltd. 2012
- Published: 1 February 2012
- Physiological Monitoring
- Scanner Gating
- Stroke Volume Estimation
- Gradient Ramp
- Switching Circuitry
High fidelity 12-lead ECG is important for physiological monitoring during cardiovascular interventions. A dominant ECG R-wave is essential for synchronizing cardiac MRI. Obtaining the real ECG in MRI is challenging due to a superimposed Magneto-Hydro-Dynamic (MHD) voltage (VMHD) , & strong induced voltages from MRI switched gradients. Detecting acute ischemia by S-T segment  is difficult due to VMHD peaks that occur during this period. We previously  presented (A) an adaptive MHD filtering procedure, based on 3 ECG training sets, & (B) R-wave detection based on 3-D ECG multichannel analysis. We extended our solution with (C) an electronic switching circuitry that blocks ECG transmission during Gradient Ramps and Radio-Frequency Transmission (GR&RF), providing; (1) 12-lead diagnostic-quality ECG free of MHD & GR&RF, (2) beat-to-beat stroke volumes (SV) estimated from VMHD, (3) accurately-gated cardiac MR images.
AF ECG processing during a GRE scan (Fig.1) (3): (a) Raw ECG V6 is dominated by GR&RF noise, which is removed (b) by the switching circuit, leaving real ECG + VMHD. VMHD is removed (c) using adaptive filters & QRS detection, also providing (d) SV estimation (irregular due to changes in ventricular-filling). In (c) S-T segment is preserved for ischemia monitoring. 3-D QRS R-wave detection is demonstrated (Fig.1) (4): (a) Sinus rhythm 3-D QRS shape is distinguishable from (b) 3D MHD shape, (c) even when MHD voltage dominates. 3D-QRS (Fig.1(5)) correctly detected the QRS in ECGs acquired at 1.5T & 3T in all 8 subjects. <5msec computational speed enabled accurate MRI triggering, permitting cine MRI in subjects (Fig.1 (6)) where 4-lead ECG failed due to a strong MHD peak.
The 12-lead ECG system acquired ECGs without MHD & GR&RF artifacts, preserving the S-T segment for ischemia monitoring, allowing SV estimation and robust ECG-gated cardiac MRI.
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