Velocity resolution improvement for high temporal resolution ultrasonic transducer

In epicardial ultrasound, the myocardial tissue velocity will generally increase with depth, as the endocardial tissue usually moves at higher velocity than the epicardial tissue. Higher velocity resolution is therefore required in the epicardial region, while a higher maximum detectable velocity is needed in the endocardial region. This study introduces a method to balance this requirement, processing the lines slightly differently at epi- and endo-cardium. The method is based on two velocity estimates: Velocity V
₁
from the cross-correlation between successive scanlines, and V
₂
from the cross-correlation between every second scanline. The tissue velocity V was assigned to V
₁
and V
₂
at endo- and epi-cardial region, respectively. In the transition region, V was calculated as a weighted average between V
₁
and V
₂
along the depth. The results show that myocardial layer tracking was improved by combining the good resolution of V
₂
at the epicardium with the higher maximum detectable velocity of V
₁
at the endocardium. Finer details were captured by V
₂
while fast motion was captured by V
₁
.