Perfusion of the Placenta assessed using Arterial Spin Labeling and Ferumoxytol Dynamic Contrast Enhanced Magnetic Resonance Imaging in the Rhesus Macaque

Abstract

Purpose:

To investigate the correspondence between arterial spin labeling (ASL) flow-sensitive alternating inversion recovery (FAIR) and ferumoxytol dynamic contrast enhanced (DCE) magnetic resonance imaging (MRI) for the assessment of placental intervillous perfusion.

Methods:

Ten pregnant macaques in late 2 ^nd trimester were imaged at 3T using a 2D ASL FAIR, with and without outer volume saturation (OVS) pulses used to control the bolus width, and a 3D ferumoxytol DCE MRI acquisition. ASL tagged/control pairs were averaged, subtracted, and normalized to create perfusion ratio maps. Contrast arrival time and uptake slope were estimated by fitting DCE data to a sigmoid function. Macaques ( N=4) received interleukin-1β to induce inflammation and disrupt perfusion.

Results:

FAIR tag modification with OVS reduced median ASL ratio percentage compared to conventional FAIR (0.64±1.42% vs. 0.71±2.00%; p<0.05). Extended ferumoxytol arrival times (34±25sec) were observed across the placenta. No significant DCE signal change was measured in fetal tissue (−0.6±3.0%; p=0.52) or amniotic fluid (1.9±8.8%; p=0.59). High ASL ratio was significantly correlated with early arrival time and high uptake slope ( p<0.05) but ASL signal was not above noise in late-DCE-enhancing regions. No significant differences were observed in perfusion measurements between the interleukin-1β and controls ( p>0.05).

Conclusion:

ASL FAIR and ferumoxytol DCE MRI are feasible methods to detect early blood delivery to the macaque placenta. OVS reduced high macrovascular ASL signal. Interleukin-1β exposure did not alter placental intervillous perfusion. An endogenous-labeling perfusion technique is limited due to extended transit times for flow within the placenta beyond the immediate vicinity of the maternal spiral arteries.