ABSTRACT
These volume data sets can be thought of as ‘digital specimens ’ of the fetal heart, akin to actual heart specimens that are examined by pathologists during a necropsy. The ‘digital heart ’ can be oriented on the screen to be displayed in a standardized position, after which standard planes of section are obtained with the use of ‘digital scalpel ’ tools. Moreover, sophisticated three-dimensional rendering techniques can be applied to display ‘digital casts ’ of cardiac chambers and great vessels that look very similar to postmortem casts obtained by injecting silicone rubber into cardiovascular structures. 19,30 Advantages of the ‘digital specimen ’ when compared to the ‘actual specimen ’ include: (1) functional information is preserved since heart beats are included in the volume data set; (2) the direction of blood flow can be analyzed in volume data sets acquired with color or power Doppler; and (3) if the examiner accidentally makes a mistake during the review of the volume data set, the ‘digital specimen ’ is not damaged forever, and all that it takes to begin the examination all over again is to reset it to its original state with the click of a button. Therefore, 4DUS of the fetal heart may help to overcome the dependency on operator skills which is characteristic of fetal echocardiography performed by conventional 2DUS, and eventually improve the prenatal characterization of complex congenital cardiac defects. 7-12,31
In this chapter, we will review several techniques that can be used to examine the fetal heart by 4DUS with STIC in normal fetuses as well as in those with congenital heart disease.
