- Oral presentation
- Open Access
Cardiac imaging at 7.0 T: comparison of pulse oximetry, electrocardiogram and phonocardiogram triggered 2D-CINE for LV-function assessment
Journal of Cardiovascular Magnetic Resonance volume 12, Article number: O15 (2010)
One important development which is looming on the (pre)clinical research horizon is the move towards CMR at 7.0 T . At (ultra)highfields, the sensitivity of ECG recordings to interference from electromagnetic fields and to magneto-hydrodynamic effects increases and with it the ECG failure rate together with the motivation for a robust, practical gating/triggering alternative. Realizing the constraints of conventional ECG, an MR-stethoscope has been proposed to meet the demands of cardiac triggered MRI .
Motivated by the challenges and limitations of conventional ECG together with the advantages of acoustic cardiac triggering (ACT), this study compares phonocardiogram, electrocardiogram and pulse oximetry triggered MRI for LV-function assessment at 7.0 T. For this purpose, breath-held 2D-CINE imaging in conjunction with a retrospective triggering regime was conducted.
The acoustic gating device comprises three main components: an acoustic sensor, an acoustic wave guide and a signal processing unit . Short axis views of the heart were acquired with a 2D-CINE-FLASH technique (TE = 2 ms, TR = 4 ms, matrix = 256 × 192, FOV = 36 cm2, 25 cardiac phases, slice thickness) on a 7.0 T MR-system (Siemens, Erlangen, Germany) using a dedicated 4-element TX/RX cardiac coil array. Vector-ECG, pulse oximetry and ACT traces were recorded simultaneously.
ECG waveforms were susceptible to severe T-wave elevation which was pronounced at the isocenter of the 7.0 T magnet (Fig. 1). The MR-stethoscope provided phonocardiograms at 7.0 T free of interferences from electromagnetic fields or magneto-hydraulic effects (Fig. 1) even in the isocenter. This renders ACT suitable for reliable synchronization at ultrahigh fields as demonstrated in Fig. 2. Conversely, R-wave mis-registration occurred in ECG-triggered acquisitions with a failure rate of appr. 50% which manifest itself in a severe jitter of the R-wave recognition tickmarks (Fig. 2b). Failure to detect the onset of the cardiac cycle was reduced for pulse oximetry, though a temporal inaccuracy of the triggering of app. 20% of a R-R-interval was observed (Fig. 2). Acoustically triggered CINE imaging at 7.0 T produced images free of motion artifacts (Fig. 3a). In contrast, ECG triggered CINE imaging was prone to severe cardiac motion artifacts if R-wave misregistration occurred (Fig. 1a). Pulse oximetry triggered 2D-CINE imaging was found to be less sensitive to cardiac motion effects although the jitter in the pulse-oximetry recognition constituted a synchronization problem.
This work examined the feasibility of LV-function assessment at 7.0 T using acoustically triggered 2D-CINE imaging. ACT's superior robustness has been demonstrated by eliminating the frequently-encountered difficulty of mis-triggering due to ECG-waveform distortions or temporal jittering in the pulse-oximetry synchronization.
Vaughan JT, Snyder CJ, DelaBarre LJ, Bolan PJ, Tian J, Bolinger L, Adriany G, Andersen P, Strupp J, Ugurbil K: Whole-body imaging at 7 T: preliminary results. Magnetic resonance in medicine: official journal of the Society of Magnetic Resonance in Medicine/Society of Magnetic Resonance in Medicine. 2009, 61: 244-248.
Frauenrath T, Hezel F, Heinrichs U, Kozerke S, Utting JF, Kob M, Butenweg C, Boesiger P, Niendorf T: Feasibility of cardiac gating free of interference with electro-magnetic fields at 1.5 Tesla, 3.0 Tesla and 7.0 Tesla using an MR-stethoscope. Investigative radiology. 2009, 44: 539-547. 10.1097/RLI.0b013e3181b4c15e.
Frauenrath T, Niendorf T, Kob M: Acoustic method for synchronization of Magnetic Resonance Imaging (MRI). Acta Acustica united with Acustica. 2008, 148-155. 10.3813/AAA.918017.
Rights and permissions
Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
About this article
Cite this article
Frauenrath, T., Renz, W., Patel, N. et al. Cardiac imaging at 7.0 T: comparison of pulse oximetry, electrocardiogram and phonocardiogram triggered 2D-CINE for LV-function assessment. J Cardiovasc Magn Reson 12 (Suppl 1), O15 (2010). https://doi.org/10.1186/1532-429X-12-S1-O15
- Pulse Oximetry
- Cardiac Motion
- Signal Processing Unit
- Cardiac Motion Artifact
- Temporal Jittering