RT-3DE examination
The 4V probe captured 3D full volume images in wide-angle mode when holding the breath at the end of exhalation. Five fan-shaped images were obtained through five consecutive cardiac cycles, and the volume ratio of each sector image was set to about 40 Hz, which triggered ECG R wave acquisition. Then, these datasets were stored and transferred to a computer for offline analysis[18, 19]. The 3D datasets are displayed as multiplanar reconstruction images, which correspond to apical 2- and 4-chamber views and three short-axis levels. And then though the four-dimensional LV analysis software calculated LV end-systolic volume (ESV), LV end-diastolic volume (EDV), LVEF and other parameters. (Figure 1)
2D and 3D STE examination
We used the same ultrasound machine to collect 2D and 3D speckle-tracking images and stored all the datasets digitally in raw data of this machine. The machine was equipped with the commercially available software (4D Auto LVQ software, GE Healthcare) for online quantification of 2D-derived GLS and 3D STE analysis. For 2D strain, apical four-chamber, three-chamber and two-chamber images were simultaneously collected by three-dimensional probe multi-plane mode in the same cardiac cycle. For 3D strain, Image acquisition is the same as real-time 3D full volume imaging. And then we could digitally send the collected data to a separate workstation (EchoPAC PC, 201.1.1) for subsequent offline analysis. The endocardial and epicardial border were traced automatically, and the region of interest was determined by the workstation. The machine automatically obtains 2D-STE and 3D-STE related parameters of the left ventricle[10]. (Figure 2)
If there are any of the following situations in the image, they will be excluded from the statistics: (1) the image quality is poor, and 3 of the 17 segments of the left ventricular wall are rejected. (2) an essential part of the left ventricular wall (> 25%) is outside the ultrasonic sector. (3) there is a volume rate lower than 40% of the heart rate in the collected data. (4) the collection contains ”suture” artefacts or serious reverb artefacts[20, 21].