4D RF-based cardiac strain imaging in healthy children: Initial in vivo experience

Most studies concerning 3D strain imaging of the heart report on 3D speckle tracking techniques, using the envelope data for tissue tracking. In this study, an RF-based 3D strain imaging technique was applied to 3D (+t) RF-data of the left ventricle. RF-data are not commercially available but have proven to yield a higher strain accuracy in all directions. The data were acquired in 6 young healthy children (6 14 yrs). A 3D free-shape coarse-to-fine displacement tracking algorithm was applied to the 3D RF-data, yielding the frame-to-frame 3D displacement fields. A 3D ellipsoidal function was fit through several manually segmented slices of the 3D volume. This 3D ellipsoid was tracked over the entire cardiac cycle, yielding the cumulative radial, circumferential and longitudinal strains. Results show 3D strain (radial, circumferential and longitudinal) within the entire left ventricle for different phases of the cardiac cycle. The shapes of the averaged strain curves are in well accordance with published curves. The image quality in the inferior and anterior wall seems to be less optimal for accurate strain imaging, leading to reduced strain values in these regions. In conclusion, 3D (+t) strain imaging is on the rise, and RF-based tracking will play an important role in the near future.