ABSTRACT
OBJECTIVE: To assess placental perfusion with magnetic resonance imaging (MRI) and superparamagnetic iron oxide (SPIO) in a rat model of intrauterine growth restriction (IUGR). DESIGN: Experimental animal study. SETTING: The study complied with US National Institutes of Health recommendations for animal care. POPULATION: Thirty-two rats at day 16 of gestation underwent surgical ligation of the left uterine vessel to induce IUGR. METHODS: Eighteen rats were examined by MRI 3 days later, after bolus injection of ferucarbotran. MAIN OUTCOME MEASURE: Signal intensities were measured in the maternal left ventricle and in the placentas of the two horns. Quantitative microcirculation parameters were calculated and compared between the placentas of the two horns. RESULTS: Fifty-four kinetic curves of placental perfusion were obtained in 11 rats. The mean placental blood flow was significantly lower in the ligated horns than in the normal horns (108.1 versus 159.4 ml/minute/100 ml, p = 0.0004). The mean fractional volume of the maternal vascular placental compartment did not differ significantly between the pathological (42.8%) and normal placentas (39.2%). CONCLUSIONS: Placental perfusion, including changes during experimental IUGR, can be measured in rats by using MRI with SPIO. These findings could have implications for human studies of placental microcirculation and for the management of disorders related to placental dysfunction.
Subject(s)
Fetal Growth Retardation/physiopathology , Microcirculation/physiology , Placental Circulation/physiology , Animals , Contrast Media , Dextrans , Disease Models, Animal , Female , Magnetic Resonance Angiography/methods , Magnetite Nanoparticles , Pregnancy , Rats , Rats, Sprague-DawleyABSTRACT
The placenta constitutes a complex circulatory interface between the mother and fetus, but the relationship between the maternal and fetal circulation is still very difficult to study in vivo. There is growing evidence that magnetic resonance imaging (MRI) is useful and safe during pregnancy, and MRI is increasingly used for fetal and placental anatomical imaging. MRI functional imaging is now a modern obstetric tool and has the potential to provide new insights into the physiology of the human placenta. Placental perfusion has been studied during the first pass of an MR contrast agent, by arterial spin labeling, diffusion imaging, T1 and T2 relaxation time measurement using echo-planar imaging, and by a combination of magnetization transfer with established stereological methods. The BOLD (blood oxygen level-dependent) effect offers new perspectives for functional MRI evaluation of the placenta.
