Introduction
Introduced as a promising tool, volumetry of the fetal heart using spatial-temporal image correlation (STIC) has been shown to enable obtaining in-depth information retrieved from large volume data sets of the fetal heart and proven to be of additional value in offline analysis for multidisciplinary consultation, facilitating a more detailed understanding of the complex fetal anatomy and reducing operator dependency1,2. Multiplanar navigation and the application of a number of imaging algorithms are of particular value in evaluation of cardiovascular integrity or function (in combination with color Doppler or M-mode). Nevertheless, quite a number of publications have stated that these techniques have rather poor reliability in clinical practice and have consequently faced limited use despite their widespread availability for more than 15 years3. Thus, the major disadvantages of STIC interrogation include the following: professional experience has been shown to be the most limiting factor in the image quality of acquired volumes, and orientation within the volume is cumbersome and remains challenging for most operators, precluding its use in a screening setting4. This illustrates the urgent need for a concept to standardize 4D echocardiography and aid targeted navigation in STIC volume data sets.
In 2013, fetal intelligent navigation echocardiography (FINE) emerged as a novel semiautomatic technique to dissect fetal cardiac anatomy after a STIC volume has been acquired. This intelligent navigation technology is based on manual selection of key anatomical landmarks, allowing the system to automatically realign the volume, reorientate and standardize the anatomical position to find, extract, and display specific diagnostic cardiac planes5. Recent studies have demonstrated that the FINE method is able to successfully generate all nine standard views for complete fetal echocardiography in 96–100 % of 2nd and 3rd trimester fetuses. It has also been shown that detection of an altered cardiac morphology in case of congenital heart defects (CHDs) is feasible with high sensitivity (98 %) and specificity (93 %)6.
In this two-part manuscript, we aimed to scrutinize the advantages of workflow-based semiautomatic postprocessing of STIC volumes for detailed prenatal assessment of cardiovascular anatomy in fetuses affected by congenital heart disease (CHD). Despite the fact that from a physiological perspective left and right ventricular performance are strictly related to that of the other (ventricular interdependence), for teaching purposes, we focused on predominantly right- and left-sided anomalies separately. We highlight the educational value of standardized reconstruction of both cross-sectional and longitudinal cardiac planes in order to aid in establishing correct diagnoses in index cases of normal and anomalous fetal hearts assessed during mid- and third trimester targeted ultrasound.