Summary
Background
Foetal echocardiography has been used to diagnose congenital heart disease. However, conventional echocardiography can only display two-dimensional (2D) structural images of the intricate three-dimensional (3D) foetal heart.
Aim
The purpose of this study was to report the first use of a new transabdominal xMATRIX array transducer and to describe its ability to perform all 3D modalities: intelligent spatiotemporal image correlation (iSTIC) acquisition, xPlane imaging and 3D surface imaging.
Methods
Eighty foetuses without congenital heart disease were included consecutively, with a gestational age between 20 and 37 weeks. 2D and 3D scans were performed with a transabdominal xMATRIX array transducer. Cardiac-STIC volume datasets were acquired and postprocessed with new automatic software (the ‘Fetal Heart Navigator’).
Results
A total of 224 iSTIC acquisitions were performed (mean time for each, 2 seconds). Only 78 iSTIC acquisitions (35%) were able to detect the ductal arch automatically. ‘Fetal Heart Navigator’ feasibility varied according to foetal position, including the descending aorta. Live xPlane imaging had excellent feasibility regardless of foetal position; using rotation, lateral and vertical tilts, all cardiac structures were identified from a unique reference plane. Live 3D surface imaging had variable feasibility depending on the target structure. Only 10% of the volume dataset offered comprehensive imaging of intracardiac views.
Conclusion
The new xMATRIX transabdominal transducer allows a multimodality approach to the foetal heart. Further studies that include foetuses with cardiac malformations are required.
Résumé
Contexte
L’échocardiographie fœtale permet de dépister les malformations cardiaques chez le fœtus. Néanmoins, les ultrasons conventionnels sont limités à des coupes 2D.
Objectif
Notre but a été de rapporter la 1 re utilisation d’une sonde matricielle 3D transabdominale chez le fœtus.
Méthodes
Quatre-vingt fœtus sans malformations cardiaque d’âge gestationnel de 20 à 37 semaines d’aménorrhée ont été inclus incluant des acquisitions 2D et 3D (iSTIC, xPlan et imagerie de surface 3D). Un nouveau processeur automatique des données STIC ( fetal heart navigator ) a été utilisé.
Résultats
Deux cent vingt-quatre acquisitions iSTIC ont été réalisées (temps moyen de deux secondes). Seulement 78 acquisitions iSTIC (35 %) ont été exploitables par le fetal heart navigator (nécessité d’inclure l’aorte descendante). Le xPlan avait une bonne faisabilité indépendante de la position du fœtus. À partir d’une image de référence, après rotation ou inclinaison latérale et verticale tilts, toutes les structures cardiaques ont pu être identifiées. L’imagerie de surface 3D n’a donné une image exploitable que dans 10 % des fœtus.
Conclusion
La nouvelle sonde matricielle xMATRIX transabdominale permet une approche multimodale du cœur fœtal. D’autres études sont nécessaires pour démontrer son intérêt dans le dépistage des malformations cardiaques.
Background
Congenital heart disease (CHD) is one of the most common congenital anomalies and is the leading cause of neonatal and infant mortality. Prenatal diagnosis of CHD has benefits for parental counselling, decision making during pregnancy, prenatal interventions, site and mode of delivery, and postnatal management . The detection rate of prenatal cardiac lesions has increased significantly during the past two decades with the improvement in foetal echocardiography . Two-dimensional (2D) foetal echocardiography has been used to screen, diagnose, monitor and treat congenital heart defects and rhythm abnormalities . However conventional echocardiography can only display 2D structural images of the intricate three-dimensional (3D) foetal heart. 3D echocardiography has been shown to enhance the diagnosis of CHD in children . Spatiotemporal image correlation (STIC) was first introduced for 3D foetal echocardiography using mechanical transducers . STIC acquires a series of volume data that can be displayed in any plane. However, postprocessing of the volume dataset requires expertise . Real-time 3D echocardiography in the foetus was recently introduced with the development of the cardiac xMATRIX array transducer . This type of transducer enables visualization and examination of the pulsating foetal heart in real time, without the need for gating, and is unaffected by motion artefacts. Live 3D surface and xPlane imaging are modalities of this new technology . However, STIC and live 3D imaging have never been produced by the same ultrasound system.
We report for the first time on a new transabdominal xMATRIX array transducer. Our aim was to describe its ability to perform the three modalities of 3D imaging: STIC acquisition, xPlane imaging and 3D surface imaging. New automatic software for displaying STIC planes was tested.
Methods
Eighty women with singleton pregnancies (gestational age between 20 and 37 weeks) were studied consecutively at Toulouse University Hospital from July to October 2012. All patients had undergone previous 2D ultrasound examinations that excluded any malformations. Informed consent was obtained in all cases.
Transabdominal real-time 3D echocardiography was performed using an iU22 ultrasound machine (Philips Medical Systems, Bothell, WA, USA) equipped with an x6-1 PureWave xMATRIX array transducer ( Fig. 1 ). All 3D echocardiography was performed by two experienced operators (P.A. and C.V.). Three modalities of 3D imaging were performed.
Intelligent STIC (iSTIC) acquisition
With the full volume angle set at 20° and an acquisition time of only 3 seconds, this fast acquisition is obtained thanks to the electronic phasing of the x6-1 xMATRIX transducer ( versus 10 seconds with the conventional STIC method on a mechanical transducer). The acquisition was started from a four-chamber view during a foetal quiescent period. Two to three sets of volume data were collected for each case and saved on the hard disk of the machine. All volume datasets were analysed off-line using dedicated software by two independent observers (L.B. and M.G.). Postprocessing was performed using the ‘Fetal Heart Navigator’ (FHN) software (plug-in within QLAB 9.0 software; Philips Medical Systems, Bothell, WA, USA; 2011). The FHN software automatically detects the ductal arch as the initial view no matter what position the iSTIC data set or STIC data set is acquired in ( Fig. 2 ). For the next step, the user was guided in obtaining the views recommended by the ISUOG guidelines on foetal cardiac screening: the four-chamber view and the left and right ventricular outflow tract views . At the end of the protocol, all four views were displayed on one screen.
Live xPlane imaging
The xMATRIX array transducer allows the simultaneous display by using a split-screen format of two high-resolution real-time views: a primary reference imaging plane and a secondary imaging plane selected by electronic rotation of the ultrasound beam ( Fig. 3 ). A rotation through a full 360° was applied from the reference image plane. A lateral tilt from −45° to +45° was added to the rotated image plane. From the reference plane, an elevation tilt was performed from −30° to +30°.
