In vivo intravoxel incoherent motion measurements in the human placenta using echo-planar imaging at 0.5 T

Abstract

This paper presents the first in vivo measurements of intravoxel incoherent motion in the human placenta, obtained using the pulsed gradient spin echo (PGSE) sequence. The aims of this study were two-fold. The first was to provide an initial estimate of the values of the IVIM parameters in this organ, which are currently unknown. The second aim was then to use these results to optimize the sequence timings for future studies. The moving blood fraction (f), diffusion coefficient (D), and pseudodiffusion coefficient (D*) were measured. The average value of f was 26 ؎ 6 % (mean ؎ SD), D was 1.7 ؎ 0.5 ؋ 10 ؊3 mm 2 /sec, and D* was 57 ؎ 41 ؋ 10 ؊3 mm 2 /sec. For the optimized values of b, the expected percentage uncertainty in the fitted values of f, D, and D* for the placenta were f/f ‫؍‬ 14.9%, D/D ‫؍‬ 14.3%, D*/D* ‫؍‬ 44.9%, for an image signal-to-noise of 20:1, and a total imaging time of 800 sec. Magn Reson Med 43:295-302, 2000.

SPIO‐enhanced magnetic resonance imaging study of placental perfusion in a rat model of intrauterine growth restriction

“…of placenta in this study, a value very similar to that obtained in our previous studies (128-180 ml/minute/ 100 ml of placenta), 10,12,13,15,16 and to that calculated by other teams using techniques such as EPI (176 ml/minute/ 100 ml). 14 Our MRI-based compartmental model showed a significant reduction in placental blood flow (108 ml/minute/ 100 ml) after uterine artery ligation, which is associated with an increased risk of intrauterine death and growth restriction, as confirmed here.…”

“…[9][10][11][12][13] Perfusion can be measured in several ways with MRI, including arterial spin labelling (ASL), echo planar imaging (EPI), and intravoxel incoherent motion (IVIM). [14][15][16] We have previously described a novel MRI-based approach to study placental function in a living mouse model, based on the use of gadolinium contrast agents and dynamic contrast enhancement (DCE) MRI. This has the capacity to measure placental perfusion and permeability in both physiological and pathological settings; 10,[12][13][14][15][16] however, gadolinium is not recommended for use during human pregnancy.…”

Magnetic resonance imaging‐estimated placental perfusion in fetal growth assessment

“…However, MRI can also provide physiological information such as the perfusion fraction, an in‐vivo estimate of the volume fraction of perfused tissue13, 14, 15, the examination for which can be performed within minutes. Previous studies have investigated the placental perfusion fraction in vivo 16, 17, 18, 19. One study showed that a small placental perfusion fraction in the second trimester was strongly associated with delivering a small‐for‐gestational age (SGA) neonate17.…”

Major mouse placental compartments revealed by diffusion-weighted MRI, contrast-enhanced MRI, and fluorescence imaging

“…Particularly promising in this regard are intravoxel incoherent motions methods, which attempt to distinguish between diffusion and perfusion of fluids (17,18). These methodologies have been previously applied to assess placentas in normal and pathological conditions, both in human and in rat models (19)(20)(21)(22).…”

“…Therefore, diffusion analyses are based on "ultrafast" methods such as spin-echo echo-planar imaging (SE-EPI) (15,(20)(21)(22), capable of delivering the 2D imaging information being sought in a single shot. EPI's capabilities, however, are limited when applied to imaging internal organs, subject to unavoidable motions and sizable magnetic field distortions (23)(24)(25)(26).…”