OC47: Placental functional MRI: a comprehensive mouse model

16th World Congress on Ultrasound in Obstetrics and Gynecology

Oral communication abstracts

of third ventricle (Group 2). Abnormal cerebral findings in group 2 were always identified at the first neurosonogram, usually within midgestation, and were subsequently confirmed by magnetic resonance. In group 1, ventriculomegaly improved during pregnancy and eventually disappeared at birth in 11/16. In one case ventriculomegaly worsened and the infant albeit developing normally is now under consideration for neurosurgery. In all the other cases, diagnostic imaging and neurodevelopment appeared normal after birth. Of the 4 fetuses in group 2, 2 were terminated and autopsy confirmed the postnatal findings, 1 is affected by cortical maldevelopment and cerebral palsy, one with dilatation of third ventricle is developing normally at 14 months. Conclusions: Expert neurosonography and/or MR allow to identify subtle cerebral findings that have prognostic value in seemingly isolated mild cerebral ventriculomegaly. In this group of fetuses, there was no overt advantage of MR over ultrasound. Abnormal findings were usually detected prior to fetal viability.

magnetic resonance imaging (MRI) for prenatal diagnosis of placenta accreta. Methods: A retrospective database and chart review of women at risk for placenta accreta who obtained both US and MRI prenatally was undertaken at three institutions. US and MRI results were compared to clinical outcome as determined by findings at delivery and pathology. Results: 30 patients who had both US and MRI prenatally were identified. Of these, 13 had a clinical and/or pathologic confirmation of placenta accreta. US correctly identified placenta accreta in 12/13 patients (92% sensitivity), but the absence of placenta accreta was correctly diagnosed in only 12/17 patients (71% specificity). MRI correctly identified placenta accreta in 11/13 patients (85% sensitivity), but the absence of placenta accreta was correctly diagnosed in only 11/17 patients (65% specificity). In 6/30 cases US and MRI had discordant diagnoses: US was correct in 4 cases and MRI was correct in 2. US and MRI both had equivocal readings in 3 and 6 cases, respectively. When one test was equivocal, the other test was able to make a correct diagnosis 67% of the time.

OC45 Third-trimester fetal MRI in isolated 10–12 mm ventriculomegaly: is it worth it? L. J. Salomon1 , J. Ouahba2 , A. L. Delezoide2 , E. Vuillard2 , J. F. Oury2 , G. Sebag2 , C. Garel2 1

Universit´e Versailles Saint-Quentin, Department of Obstetrics and Gynecology, France, 2 Hopital Robert Debr´e, AP-HP, France Objectives: The justification for MR in isolated mild ventriculomegaly remains controversial. This study was undertaken to evaluate the contribution of third-trimester MR in isolated 10–12 mm fetal ventriculomegaly. Methods: From February 2000 to May 2005 we prospectively collected data concerning fetuses referred to us for cerebral MR following detection of ventriculomegaly in US (n = 310). Among these, we identified and analysed those cases in which ventriculomegaly was isolated and did not exceed 12 mm on US examinations prior to MR scan (n = 185). Cases in which MR provided additional information that was likely to impact on prenatal management were detailed. Results: 310 MR were performed because of fetal ventriculomegaly. 185 were isolated 10–12 mm ventriculomegalies in US and formed our database. MR confirmed the 10–12 mm isolated fetal ventriculomegaly in 106 cases (57.3%), and found other abnormalities in 5 (4.7%) of these 106 cases. MR found ventricular measurement slightly below 10 mm in 43 cases (23.3%) and slightly above 12 mm in 36 cases (19.4%). Among these 36 fetuses with ventricles above 12mm, 6 (16.7%) had other abnormalities whereas MR did not find other abnormalities in the 43 cases with ventricles below 10 mm. Conclusion: MRI should remain an investigational tool, restricted to selected clinical situations in which the results are expected to modify case management. In 10–12 mm isolated ventriculomegaly, our data suggest that when the finding is confirmed with MRI this could be expected in around 5% of cases. Therefore the policy of routine MRI in such cases should mainly depend on resources allocation.

OC46 Prenatal diagnosis of placenta accreta by ultrasound and magnetic resonance imaging B. Dwyer1 , A. Rao1 , L. Tran2 , V. Belogolovkin3 , I. Carroll1 , R. Barth1 , U. Chitkara1 Stanford University, United States, 2 University of Washington, United States, 3 Mount Sinai Hospital, New York, United States

1

Objective: Prenatal diagnosis of placenta accreta allows for appropriate resources to be made available at delivery in order to minimize the complication rate. The purpose of this study was to compare the accuracy of transabdominal ultrasound (US) and

372

Table 1 US and MRI which were correct, not correct, and equivocal

US MRI

Correct

Not Correct

Equivocal

23 (77%) 19 (63%)

4 (13%) 5 (17%)

3 (10%) 6 (20%)

Conclusion: Both US and MRI have similar abilities for prenatal diagnosis of placenta accreta. Both US and MRI have fairly good sensitivity, despite a high number of false positive tests. When there was disagreement between the two tests, US was more often correct. Using US or MRI to evaluate patients at high risk for placenta accreta is warranted to allow the surgeon to be better prepared for the management of these patients. However, the use of both tests in every case may not clarify diagnosis or be cost effective.

OC47 Placental functional MRI: a comprehensive mouse model L. J. Salomon1 , N. Siauve2 , F. Taillieu2 , D. Balvay2 , C. Vayssettes2 , G. Frija2 , C. A. Cuenod2 , O. Clement2 , Y. Ville1 1

Universit´e Versailles Saint-Quentin, Department of Obstetrics and Gynecology, France, 2 Universit´e Paris Descartes, Laboratoire de Recherche en Imagerie, Facult´e de M´edecine, Paris, France

Objectives: This study was undertaken to develop a new model for placental perfusion and permeability assessment by using MRI with contrast agents in a mouse model. Methods: Balb/c pregnant mice at 16 days of gestation were studied. 2D Fast SPGR sequential MRI was used to analyze placental perfusion following contrast agent injection. Some mice were randomly selected to receive noradrenalin injection prior to perfusion measurement. A complete model for both perfusion and permeability assessment was then developed, based on a single-slice dual echo 2D FSPGR sequence. An original threecompartmental model was developed and used to calculate quantitative microcirculation parameters. Results: 133 mice were studied. Mean placental perfusion was 1.3 ml/min/g (± 0.6) with the simple perfusion model. There was a significant decrease in placental perfusion following noradrenalin injection. Using the complete model, placental perfusion was 1.80 ml/min/g (± 0.9) and permeability (PSr) was measured as well. Conclusion: This approach gives a non invasive access to placental microvascular parameters including the perfusion and the permeability. It shows promises to study mouse model of placental diseases. If this approach is feasible and safe in humans, it may have potential for investigating the origin and course of IUGR, and for the management of compromised pregnancies.

Ultrasound in Obstetrics & Gynecology 2006; 28: 359–411