Novel spatial-temporal image correlation derived indices of tissue vascular impedance: A variability study

Area of Science:

• Obstetrics and Gynecology
• Medical Imaging
• Fetal Medicine

Background:

• 4D (3D + time) tissue impedance indices using power Doppler (PD) ultrasound (US) can be measured with spatial-temporal image correlation (STIC) imaging.
• Assessing placental vascularity is crucial for monitoring fetal well-being.

Purpose of the Study:

• To evaluate the repeatability of 4D PD indices.
• To assess the influence of US machine settings (specifically wall motion filter - WMF) on these indices.
• To investigate regional variability of these indices within the placenta.

Main Methods:

• 46 healthy pregnant women (20-34 weeks gestation) were recruited.
• 9940 3D frames from 644 4D datasets were analyzed for 3D and 4D vascularity indices.
• Comparisons were made across different WMF settings, cardiac cycle phases, and placental regions.

Main Results:

• 3D and 4D indices decreased significantly with increasing WMF (P < 0.001), impacting repeatability.
• Repeatability was lower at the maternal placental aspect compared to the fetal aspect.
• 4D indices showed good repeatability centrally but poor repeatability peripherally; 3D indices were consistently repeatable across regions.

Conclusions:

• The 'low1' WMF setting with PD is recommended for reliable 4D indices.
• HD Flow may enhance 3D Doppler signal sensitivity.
• The fetal plate and central placental regions provide more repeatable 4D PD indices, offering a standardized measure of localized impedance.