Figure 1

(A) Artifacts on 12-lead ECG traces during an SSFP sequence with the heart at iso-center. (a) ECG traces acquired in the MRI without the sequence running, (b) traces acquired during the sequence, which are overlaid with strong gradient-induced voltages, since the hardware switching is disabled, and (c) traces obtained during the sequence, and with the hardware switching enabled, demonstrating the quality of gradient-induced voltage removal. Black arrows indicate regions of largest voltages, which were removed by hardware. Note the similarity of the cleaned ECG traces in (c) with those acquired without imaging in (a). (B) The magnitude of the gradient-induced voltages (sampled at 32 KHz) on the limb leads (channels I-III) can be very large, reaching 1800 mV peak-to-peak (mV p-p) for SSFP with the heart at iso-center (and far larger voltages with peripheral organs, such as the nose, at iso-center). The temporal extent of the largest induced voltages, in microseconds (μs), which is used to tune the sample-and-hold circuits, is listed. These large artifacts are removed by the 12-lead system. (C) Volunteer 12-lead ECG acquired inside the MRI during imaging. Lower row triangles depict location of QRS triggers sent to the MRI scanner’s gating interface. (D) Breath-held volunteer ECG-triggered BB-TSE (TR/TE=2100 ms/46 ms, ETL=9, 192 × 256, 29 × 36, 5 mm sw, 14s/sl., 2 avg.). Acquisition was prospectively triggered by the 12-lead VCG. (E) 12 frames from 25 frame/R-R breath-held volunteer ECG-triggered SSFP cine (TR/TW/flip=3.5 ms/1,2 ms/28deg, 26 × 32, 216 × 256, 5 mm sw, 10s/sl., 2 avg.). Acquisition was retrospectively triggered by the 12-lead VCG.