Mid-esophageal LV views without foreshortening (Figure 2 & 3)
After inverting the z-axis and moving the MPR crosshairs into the
esophageal lumen, we simulate “turn to the left” by rotating the
sagittal MPR line counterclockwise on the axial MPR plane to make the
sagittal plane cross the LV apex. Then we can easily use the sagittal
plane to discern that at different level of esophagus, different degrees
of retroflex are needed to avoid LV foreshortening. With a LV image
without foreshortening, we can rotate the reference plane on the coronal
MPR plane to obtain LV 4-chamber, 2-chamber, bi-commissural and
long-axis images.
Orthogonal interrogation of ultrasound beams obtains the highest
reflection to deserve the most precise resolution. As a result, by
acquiring the mid-esophageal LV views with the ideal orientation, the
imagers can reconstruct the high-resolution 3D mitral valve en face
views. However, if the LV axis crossing from the center of mitral valve
to LV apex is not contained in the plane of ultrasound scanning beams,
there will be configural differences between TEE and CT imaging. On CT
TEE simulation, we can easily discern such configural differences by
investigating whether the sagittal MPR line on the axial plane crosses
the center of mitral valve or not (Figure 3C). Sometimes a little “flex
to the right” can partially ameliorate the configural differences. This
effect can also be easily realized by CT simulation as a parallel
movement of the sagittal line of sector from lateral annulus toward the
center of mitral valve on the axial plane. It is important for the
operators to understand such configural differences or they will be
confused by intraoperative TEE imaging, because the more the configural
differences appear, the higher the possibility that the devices make
out-of-plane motion on TEE imaging.