2H-6 Tissue Doppler Gated (TDOG) Real-Time Stitching in Three-Dimensional Fetal Echocardiography

Three-dimensional (3D) fetal echocardiography is a promising technique for assessment of fetal cardiac structure and function, but suffers from lower temporal resolution than ultrasound imaging in two dimensions. Real-time, ECG-gated volume stitching is a known method in adult echocardiography, used to increase the spatial and/or temporal resolution of volumetric cardiac scans. In fetal echocardiography however, stitching has been impossible due to lack of ECG data for gating. A real-time gating signal for fetal echocardiography is suggested in this work. An ultrasound system was set up to acquire 3D gray-scale data and 3D tissue Doppler data simultaneously, with only the gray-scale data visible to the sonographer. Derived from the Doppler data, a gating signal, denoted the tissue Doppler gating (TDOG) signal, was calculated in real-time. The TDOG trigger events were used to induce changes in the geometry setup of the 3D gray-scale scan, ensuring that data from consecutive cardiac cycles were captured from separate parts of the total volumetric scan. A scan setup with six disjoint subvolumes was used, and the system could in real-time assemble and display volume data sets with data from the six most resent heart cycles. In-vivo data ware recorded from 5 pregnant women with fetuses aged 20-24 weeks, utilizing a matrix transducer with a center frequency of 3 MHz. TDOG signals from several different tissue Doppler scan geometries are presented: 5deg and 10deg planar sector scans and 8deg times 8deg volumetric scans. Volumetric, assembled scans acquired with TDOG gated stitching are shown, and both good and poor match between subvolumes are demonstrated. We conclude that the TDOG technique provides real-time gating of fetal cardiac cycles and it can be used to acquire stitched, 3D fetal echocardiographic data with high frame rate