Novel real-time R-wave detection algorithm based on the vectorcardiogram for accurate gated magnetic resonance acquisitions

Electrocardiograph (ECG) triggered or gated magnetic resonance methods are used in many imaging applications, Therefore, a reliable trigger signal der ived from to the R-wave of the ECG is essential, especially in cardiac imag ing. However, currently available methods often fail mainly due to the arti facts in the ECG generated by the MR scanner itself, such as the magnetohyd rodynamic effect and gradient switching noise. The purpose this study was t o characterize the accuracy of selected R-wave detection algorithms in an M R environment, and to develop novel approaches to eliminate imprecise trigg ering. Vectorcardiograms (VCG) in 12 healthy volunteers exposed to 1.5 T ma gnetic field were digitized and used as a reference data set including manu ally corrected onsets of R-waves, To define the magnetohydrodynamic effect, the VCGs were characterized in time, frequency, and spatial domains. The s elected real-time R-wave detection algorithms, and a new "target-distance" VCG-based algorithm were applied either to standard surface leads calculate d from the recorded VCG or to the VCG directly. The flow related artifact w as higher in amplitude than the R-wave in 28% of the investigated VCGs whic h yielded up to 9-16%false positive detected QRS complexes for traditional algorithms. The "target-distance" R-wave detection algorithm yielded a scor e of 100% for detection with 0.2% false positives and was superior to all t he other selected methods, Thus, the VCG of subjects exposed to a strong ma gnetic field can be use to separate the magnetohydrodynamic artifact and th e actual R-wave, and markedly improves the trigger accuracy in gated magnet ic resonance scans. Magn Reson Med 42:361-370, 1999. (C) 1999 Wiley-Liss, I nc.