TY  - JOUR
A1  - Frauenrath, Tobias
A1  - Hezel, Fabian
A1  - Renz, Wolfgang
A1  - de Geyer d'Orth, Thibaut
A1  - Dieringer, Matthias
A1  - von Knobelsdorf-Brenkenhoff, Florian
A1  - Prothmann, Marcel
A1  - Schulz-Menger, Jeanette
A1  - Niendorf, Thoralf
T1  - Acoustic cardiac triggering: a practical solution for synchronization and gating of cardiovascular magnetic resonance at 7 Tesla
JF  - Journal of Cardiovascular Magnetic Resonance
N2  - Background
To demonstrate the applicability of acoustic cardiac triggering (ACT) for imaging of the heart at ultrahigh magnetic fields (7.0 T) by comparing phonocardiogram, conventional vector electrocardiogram (ECG) and traditional pulse oximetry (POX) triggered 2D CINE acquisitions together with (i) a qualitative image quality analysis, (ii) an assessment of the left ventricular function parameter and (iii) an examination of trigger reliability and trigger detection variance derived from the signal waveforms.

Results
ECG was susceptible to severe distortions at 7.0 T. POX and ACT provided waveforms free of interferences from electromagnetic fields or from magneto-hydrodynamic effects. Frequent R-wave mis-registration occurred in ECG-triggered acquisitions with a failure rate of up to 30% resulting in cardiac motion induced artifacts. ACT and POX triggering produced images free of cardiac motion artefacts. ECG showed a severe jitter in the R-wave detection. POX also showed a trigger jitter of approximately Δt = 72 ms which is equivalent to two cardiac phases. ACT showed a jitter of approximately Δt = 5 ms only. ECG waveforms revealed a standard deviation for the cardiac trigger offset larger than that observed for ACT or POX waveforms.

Image quality assessment showed that ACT substantially improved image quality as compared to ECG (image quality score at end-diastole: ECG = 1.7 ± 0.5, ACT = 2.4 ± 0.5, p = 0.04) while the comparison between ECG vs. POX gated acquisitions showed no significant differences in image quality (image quality score: ECG = 1.7 ± 0.5, POX = 2.0 ± 0.5, p = 0.34).

Conclusions
The applicability of acoustic triggering for cardiac CINE imaging at 7.0 T was demonstrated. ACT's trigger reliability and fidelity are superior to that of ECG and POX. ACT promises to be beneficial for cardiovascular magnetic resonance at ultra-high field strengths including 7.0 T.
KW  - Interval Time Series
KW  - Image Quality Score
KW  - Image Quality Assessment
KW  - Sound Pressure Level
KW  - Cardiovascular Magnetic Resonance
Y1  - 2010
U6  - https://doi.org/10.1186/1532-429X-12-67
SN  - 1532-429X
VL  - 12
IS  - 1
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - von Knobelsdorf-Brenkenhoff, Florian
A1  - Frauenrath, Tobias
A1  - Prothmann, Marcel
A1  - Dieringer, Matthias A.
A1  - Hezel, Fabian
A1  - Renz, Wolfgang
A1  - Kretschel, Kerstin
A1  - Niendorf, Thoralf
A1  - Schulz-Menger, Jeanette
T1  - Cardiac chamber quantification using magnetic resonance imaging at 7 Tesla—a pilot study
N2  - Objectives
Interest in cardiovascular magnetic resonance (CMR) at 7 T is motivated by the expected increase in spatial and temporal resolution, but the method is technically challenging. We examined the feasibility of cardiac chamber quantification at 7 T.

Methods
A stack of short axes covering the left ventricle was obtained in nine healthy male volunteers. At 1.5 T, steady-state free precession (SSFP) and fast gradient echo (FGRE) cine imaging with 7 mm slice thickness (STH) were used. At 7 T, FGRE with 7 mm and 4 mm STH were applied. End-diastolic volume, end-systolic volume, ejection fraction and mass were calculated.

Results
All 7 T examinations provided excellent blood/myocardium contrast for all slice directions. No significant difference was found regarding ejection fraction and cardiac volumes between SSFP at 1.5 T and FGRE at 7 T, while volumes obtained from FGRE at 1.5 T were underestimated. Cardiac mass derived from FGRE at 1.5 and 7 T was larger than obtained from SSFP at 1.5 T. Agreement of volumes and mass between SSFP at 1.5 T and FGRE improved for FGRE at 7 T when combined with an STH reduction to 4 mm.

Conclusions
This pilot study demonstrates that cardiac chamber quantification at 7 T using FGRE is feasible and agrees closely with SSFP at 1.5 T.
Y1  - 2010
U6  - https://doi.org/10.1007/s00330-010-1888-2
SN  - 0938-7994
VL  - 20
SP  - 2844
EP  - 2852
PB  - Springer
CY  - Berlin, Heidelberg
ER  -