Evaluation of a Portable Doppler Ultrasound Gating Device for Fetal Cardiac MR Imaging: Initial Results at 1.5T and 3T

Abstract

Purpose:Fetal cardiac MRI has the potential to play an important role in the assessment of fetal cardiac pathologies, but it is up to now not feasible due to a missing gating method. The purpose of this work was the evaluation of Doppler ultrasound (DUS) for external fetal cardiac gating with regard to compatibility, functionality, and reliability. Preliminary results were assessed performing fetal cardiac MRI.Methods:An MRI conditional DUS device was developed to obtain a gating signal from the fetal heart. The MRI compatibility was evaluated at 1.5T and 3T using B1 field maps and gradient echo images. The quality and sensitivity of the DUS device to detect the fetal heart motion for cardiac gating were evaluated outside the MRI room in 15 fetuses. A dynamic fetal cardiac phantom was employed to evaluate distortions of the DUS device and gating signal due to electromagnetic interferences at 1.5T and 3T. In the first in vivo experience, dynamic fetal cardiac images were acquired in four-chamber view at 1.5T and 3T in two fetuses.Results:The maximum change in the B1 field and signal intensity with and without the DUS device was <6.5% for 1.5T and 3T. The sensitivity of the DUS device to detect the fetal heartbeat was 99.1%. Validation of the DUS device using the fetal cardiac phantom revealed no electromagnetic interferences at 1.5T or 3T and a high correlation to the simulated heart frequencies. Fetal cardiac cine images were successfully applied and showed good image quality.Conclusion:An MR conditional DUS gating device was developed and evaluated revealing safety, compatibility, and reliability for different field strengths. In a preliminary experience, the DUS device was successfully applied for in vivo fetal cardiac imaging at 1.5T and 3T.

MR imaging of the fetal heart

“…34 This portable Doppler ultrasound gating device has proven to be safe, MRI-compatible, and reliable for different field strengths when applied in human fetuses. 35,36 Dynamic fetal cardiac MRI using cardiotocographic gating allows evaluation of cardiac anatomy in fetuses with CHD, yielding good agreement with fetal echocardiography in terms of the dimensions of structures and cardiac diagnosis. 37…”

“…Based on the cardiotocographic monitoring commonly used by obstetricians in clinical practice, an alternative technology to obtain triggered acquisitions involves measurement of the fetal cardiac cycle by using Doppler ultrasound via an MR‐compatible transducer placed over the maternal abdomen . This portable Doppler ultrasound gating device has proven to be safe, MRI‐compatible, and reliable for different field strengths when applied in human fetuses . Dynamic fetal cardiac MRI using cardiotocographic gating allows evaluation of cardiac anatomy in fetuses with CHD, yielding good agreement with fetal echocardiography in terms of the dimensions of structures and cardiac diagnosis …”

Seeing the fetus from a DOHaD perspective: discussion paper from the advanced imaging techniques of DOHaD applications workshop held at the 2019 DOHaD World Congress

“…First, a non-imaging Doppler ultrasound probe that is MRI compatible and enables detection of signals related to the fetal cardiac cycle has been developed. 149,150 These are then relayed to the MRI scanner to provide prospective cardiac gating. Second, retrospective cardiac gating has been performed by multiple MR research groups using the raw MR signal.…”

Fetal Cardiac MRI

“…The most mature device for this purpose uses an MR-compatible Doppler Ultrasound Gating (DUS) probe placed over the maternal abdomen. 37,38 This nonimaging device monitors motions associated with the fetal cardiac cycle, such as blood flow and cardiac contraction, based on a Doppler waveform. Triggers derived from this waveform are supplied to the MRI scanner to synchronize data acquisition.…”