Abstract
The ultrasonic ‘phased tracking method’ (PTM) is a newly developed technique in which we can observe the phase difference of adjoining received RF signals. We aim to apply PTM—which enables precise measurement of the target’s velocity with 0.1 mm/s accuracy without restriction of transmitting wave length—for noninvasive measurements of fetal arterial diameter change, pulse wave velocity (PWV), and estimated fetal pulse pressure. We analyzed normal and growth-restricted fetuses using PTM. The fetal descending aorta was identified in the long axis direction using conventional B-mode with a convex array probe. Raw radiofrequency signals were recorded from the vessel wall of the descending aorta. Offline analysis was attempted for wall motion velocity waves. We employed PTM for measurement of pulsatile fine movement of the fetal descending aorta. Changes in internal diameter and PWV were analyzed. Pulse pressure was estimated from the transformed formula of Moens-Korteweg. PWVs were revealed to be significantly higher in growth-restricted fetuses. We could also demonstrate elevated estimated fetal pulse pressure in growth restriction. Measurement of fetal aortic diameter changes and fetal PWV using PTM is a feasible, noninvasive approach to evaluate fetal hemodynamics. Elevated PWV and estimated pulse pressure in growth-restricted fetuses suggest altered arterial wall compliance by histological remodeling that has already originated in the fetal period. Fetal PWV and estimated pulse pressure possibly distinguish cases at high risk for hypertensive complications later in life, which substantiates Developmental Origins of Health and Disease (DOHaD) theory.
