The role of magnetic resonance imaging in prenatal diagnosis of fetal anomalies

Magnetic resonance imaging (MR) has become a useful adjuvant in evaluating fetal structural anomalies when ultrasound (US) is equivocal. It has a significant promise in confirming a US suspected abnormality and providing new information that was previously not available.The first studies on prenatal MR were hindered by fetal motion and long acquisition times. This degraded imaging and, therefore, maternal or fetal sedation was needed. Since fast and ultrafast MR with scan times of <1 s have become available, the amount of motion artifacts is decreased and sedation is no longer needed.MR has proved to be especially beneficial in detecting CNS anomalies. Agenesis of the corpus callosum, migration abnormalities and abnormalities of the posterior fossa are better seen on MR. Masses in the fetal neck and thorax can be identified on MR, as some abdominal anomalies. However, the fetal skeletal is difficult to visualize with MR.In the future, it is most likely that real time MR will become clinically available which would improve MR imaging even more.     

Prenatal diagnosis of schizencephaly by fetal magnetic resonance imaging.

Schizencephaly is a neuronal migration anomaly characterized by gray matter lined clefts extending from the ventricle to the cortical surface leading to specific lesions, well demonstrated by imaging. The lips of the clefts can be fused or separated. Prognosis is related to the extend of the involved cortex. Both genetic and acquired factors can be responsible for this pathology. Three cases of antenatal diagnosed open schizencephaly are reported. Two cases are unilateral and one is bilateral. A cerebral anomaly has been detected in all cases by routine ultrasonography (US) revealing a ventricular dilatation with cortical associated abnormalities. Prenatal magnetic resonance imaging (MRI) permitted the diagnosis in the 3 cases. All cases had led to abortion because of the importance of the cortical defect. The aim of this report is to point out the importance of fetal MRI in the diagnosis of migration disorder and to discuss the medical implications. Indeed, MRI is better suited than US for the prenatal diagnosis of schizencephaly, being able to detect normal and abnormal brain cellular migration, especially with fast imaging (HASTE sequences). With its multiplanar imaging capability, MRI demonstrates the cleft extending from the pial surface to the ventricular ependyma and thus provides characteristic diagnosis of this disorder. Moreover, ventricular dilatation, a frequent anomaly detected by US should be completed with MRI in order to research a neuronal migration disorder.     

Hydrographic magnetic resonance imaging of the fetal eye

Previous work has shown that fetal hydrographic magnetic resonance imaging (MRI) provided additional information complementary to T2-weighted single-shot fast spin echo (ssFSE) images. The objective of this study was to determine if hydrographic MRI provides better conspicuity of fetal eye structures compared with ssFSE MRI. ssFSE and hydrographic images were retrospectively examined in 82 consecutive fetal studies with normal central nervous system without sensitivity encoding. Relative signal intensity values on ssFSE and hydrographic MRI were obtained for vitreous and sclera. Ratios of the signal intensity of vitreous to the signal intensity of sclera were calculated to determine conspicuity. Similar measurements were obtained in a smaller separate data set (n = 41) using hydrographic imaging with sensitivity encoding techniques. The hydrographic images significantly demonstrated greater conspicuity (ratio of vitreous to sclera) than ssFSE images. This was consistent for both sensitivity encoding and no-sensitivity encoding groups. The difference in conspicuity was on average approximately two times greater in the hydrographic images compared with ssFSE images. Hydrographic MRI of the fetal eye provides on average two times greater conspicuity of fetal eye structures than ssFSE imaging. This enhancement is not affected by gestational age or the use of sensitivity encoding parallel imaging techniques.     

Effect of fetal magnetic resonance imaging on fetal heart rate patterns

OBJECTIVE: Our aim was to record the fetal heart rate before and during magnetic resonance imaging to observe the effects of the magnetic resonance imaging process on fetal heart rate parameters during imaging. STUDY DESIGN: Fetal heart rate recordings were obtained in 10 pregnant volunteers at the time of magnetic resonance imaging. All the pregnant women were at term (37-41 weeks) with singleton fetuses in the cephalic presentation. The scanning was performed on a 0.5-T purpose-built superconductive magnet by use of echo-planar imaging. The fetal heart recordings were obtained with a modified Sonicaid Meridian 800 (Oxford) Doppler ultrasound monitor. Recordings of the fetal heart were made for a period of at least 15 minutes outside the magnet and then for at least 15 minutes inside the magnet. RESULTS: There were no significant changes in any fetal heart rate parameters before and during the magnetic resonance imaging, as determined by the Wilcoxon matched-pairs signed-ranks test (P >.3). CONCLUSION: This is the first report of fetal heart rate recording during magnetic resonance imaging of the fetus. Magnetic resonance imaging does not produce demonstrable effects on fetal heart rate patterns.     

Multilevel modeling of fetal and placental growth using echo-planar magnetic resonance imaging.

OBJECTIVE: To quantify longitudinal increases in fetal, fetal liver, and fetal brain volume using echo-planar magnetic resonance imaging and to quantify the results using appropriate statistical modeling. METHODS: Fifty-six singleton fetuses were studied using echo-planar (snap-shot) magnetic resonance imaging, between 19 weeks and term. They were assessed at a variety of different gestations and on a different number of occasions, thereby requiring multilevel statistical modeling to analyze the pattern of fetal growth. RESULTS: Fetal volume varied according to the following equation: square root (radical) [fetal volume]=-37.71+2.17 x gestational age (GA)-0.004 x GA(2). The equation for fetal liver volume was radical[fetal liver volume]=9.47+0.56 x GA-0.02 x GA(2), for fetal brain volume was radical[fetal brain volume]=15.50+0.69 x GA-0.014 x GA(2), and for placental volume radical[placental volume]=28.54+0.95 x GA-0.039 x GA(2), where GA is the gestational age in weeks -30. CONCLUSION: The assessment of fetal, fetal organ, and placental volume was feasible using echo-planar magnetic resonance imaging from 20 weeks to term. Multilevel statistical modeling can be applied to analyze sets of data with different measurements on different occasions. This information is useful clinically to assess abnormal fetal growth.     

Antepartum assessment of fetal cystic lymphangioma by magnetic resonance imaging

Few reports of fetal cystic lymphangioma have described assessment in utero by magnetic resonance imaging (MRI). We evaluated a fetus with cystic lymphangioma by this method. Complementing the characteristic features of cystic lymphangioma in ultrasonographic images, prenatal MRI provided a detailed view of anatomic relationships of cysts to surrounding tissues in this case. This anatomic evaluation facilitated planning of perinatal management and choice of manner of delivery. We found MRI very helpful in antepartum assessment of fetal cystic lymphangioma.     

Fetal magnetic resonance imaging.

Fast magnetic resonance imaging (MRI) has revolutionized our ability to image the fetus. Using fast scanning techniques, individual images are obtained in 300-400 ms, allowing for imaging of the fetus without sedation. MRI is most useful for evaluation of the anomalous fetal central nervous system, for further characterization of complex anomalies not fully elucidated by ultrasound and for evaluation of patients desiring fetal surgery. This review describes the history of fetal MRI, discusses current applications and mentions developments on the horizon.     

Osteogenesis imperfecta type II: fetal magnetic resonance imaging findings

We describe the prenatal magnetic resonance imaging (MRI) findings in a 25-week-old fetus with proven osteogenesis imperfecta type II. Fetal MRI findings are correlated with prenatal ultrasonography, conventional x-ray fetography and postpartal findings. Fetal MRI proves to be superior to conventional fetography in the evaluation of the skeletal findings. The high soft tissue resolution, the large field of view and the multiplanar imaging make it possible to study the non-ossified fetal skeleton in detail. Compared to prenatal ultrasonography, fetal MRI gives important additional information about the expected lung functionality by estimating fetal lung volume and signal intensity and rules out possible additional abnormalities of major fetal organs. These parameters may serve as valuable, additional prognostic markers in the prenatal diagnostic work-up.     

磁共振检查在脑室扩张胎儿产前诊断中的作用

目的:探讨磁共振成像(MRI)在超声提示脑室扩张胎儿产前诊断中的作用。方法:选择因超声提示单纯性脑室扩张而行MRI检查者,对MRI结果进行分析并随访妊娠结局。结果:1 MRI结果的准确性:入组病例MRI对超声的总补充诊断率为15.4%(38/247),其中脑积水11例,脑室扩张伴脑出血3例,脑室扩张伴胼胝体发育不全(ACC)9例,室管膜下囊肿(或蛛网膜囊肿)9例,DandyWalker等其他类型畸形6例。2胎儿脑室扩张的宫内转归及新生儿预后:63.2%(24/38)有结构畸形者选择引产,均未见染色体核型异常。正常分娩新生儿155例,新生儿随访无异常神经系统表现。结论:对于脑室扩张,尤其是重度脑室扩张,MRI对于超声有极高的补充诊断价值。     

Three-dimensional reconstruction of fetal abnormalities using ultrasonography and magnetic resonance imaging

Objective: We aimed to compare three-dimensional (3D) fetal malformation images obtained using ultrasonography (US) and magnetic resonance imaging (MRI) on the same day during the third trimester of pregnancy.

Methods: Total 33 fetuses were selected from cases evaluated for malformations. Morphological abnormalities were first scanned using 3DUS. MRI was used to confirm the previous preliminary 3DUS findings, and diagnoses were confirmed postnatally. 3DUS scans were performed transabdominally using an Rab (4–8?L) probe, Voluson 730 Pro/Expert and E8 (General Electric, Healthcare, Zipf, Austria). MRI was performed using a 1.5-T scanner (Magneton Avanto, Siemens, Erlangen, Germany) with a body coil. The 3D reconstruction of the structure of interest was manually performed from a True FISP sequence using an interactive pen tablet (Syngo multimodality 2009B, Siemens, Erlangen, Germany).

Results: Despite recent advancements in 3DUS, the quality of 3D images obtained from MRI was superior during the third trimester. 3DUS had certain limitations, such as being influenced by the fetal position, the volume of amniotic fluid, and maternal obesity. Fetal movements during image acquisition were one of the main challenges for MRI.

Conclusion: The quality of the 3D images obtained using MRI was superior to that of images obtained using US during the third trimester of pregnancy.     

The value of cardiovascular magnetic resonance in the diagnosis of fetal aortic arch anomalies

Background: Here we report our preliminary experience of using fetal cardiovascular magnetic resonance (CMR) imaging, particularly with transverse views at the level of the aortic arch, in the diagnosis of aortic arch anomalies.

Materials and methods: Between January 2013 and December 2015, routine prenatal obstetric ultrasound (US), echocardiography (Echo), and 1.5 T CMR were performed on approximately 600 pregnant women. CMR included balanced fast field echo and single-shot fast spin echo sequences. The images were analyzed using an anatomic segmental approach by two radiologists. The prenatal imaging findings were compared with postnatal diagnoses, from imaging or autopsy.

Results: A total of 22 cases with suspected aortic arch anomalies were found by prenatal Echo. These included the following: right aortic arch, 18 cases; double aortic arch, 2 cases; atrial isomerism, 3 cases including 2 with right aortic arch; and pulmonary atresia, aortic overriding and ventricular septal defect, 1 case. Fetal CMR diagnoses were: right aortic arch with aberrant left subclavian artery, 9 cases; right aortic arch with mirror-image branching, 8 cases; double aortic arch, 4 cases; left aortic arch with right aberrant subclavian artery, 1 case. 16 cases were born alive and subsequently underwent evaluation by Echo or MRI and 6 cases had autopsies. There were 23 aortic arch anomalies. Prenatal Echo misdiagnosed 5 of these (5/23), and missed the diagnosis in 4 cases (4/23). Consequently, the accuracy of prenatal Echo was 60.8% (14/23). Both prenatal Echo and CMR misdiagnosed the same single case as a double aortic arch. The correct diagnosis was found to be right aortic arch with aberrant subclavian artery. Consequently, the accuracy of fetal CMR was 95.6% (22/23).

Conclusion: Unlike prenatal Echo, fetal CMR is unaffected by fetal position. Fetal CMR with transverse views at the level of the aortic arch is a useful adjunct for the diagnosis of fetal aortic arch anomalies.     

Second-opinion magnetic resonance imaging for suspected fetal central nervous system abnormalities

OBJECTIVE: The purpose of this study was to evaluate the relationship of magnetic resonance imaging and gestational age in the setting of fetuses with suspected abnormalities of the central nervous system that were detected by ultrasound scanning. STUDY DESIGN: Multiplanar magnetic resonance studies were performed in fetuses with suspected central nervous system abnormalities on ultrasound scanning. Magnetic resonance imaging was evaluated for its ability to provide additional information, change the diagnosis, or impact obstetric treatment. Patients were grouped by gestational age at the time of magnetic resonance imaging. RESULTS: Magnetic resonance imaging provided additional information in 46 of 72 pregnancies (64%), changed the diagnosis in 20 of 72 pregnancies (28%), and potentially altered the timing or mode of delivery in 8 of 72 pregnancies (11%). Additional information increased with increasing gestational age groups (P =.03). CONCLUSION: Magnetic resonance imaging provided additional information in two thirds of the fetuses with central nervous system abnormalities, which was significantly increased with increasing gestation. Antenatal treatment was influenced by magnetic resonance imaging in 11% of the cases.     

Assessment of fetal well-being with magnetic resonance.

The application of magnetic resonance techniques in the assessment of fetal growth, fetal growth patterns and fetal health was assessed. Eighty-four sets of fetal images were obtained using a fast-scan magnetic resonance imaging technique. Measurements were made of fetal subcutaneous fat thickness, uterine cavity length and width, fetal and uterine cross-sectional areas and fetal volume. Fetal area and fetal volume measurements were found to correlate well with birth weight. Measurement of subcutaneous fat thickness may prove to be a means of differentiating between those fetuses who are constitutionally as opposed to pathologically large or small. Thirteen women had additional spectroscopic studies carried out. Twelve of the women had normal pregnancies. One woman had a twin pregnancy in which one twin died. 31P phosphorus spectra were obtained from seven of the normal pregnancies. In the remainder, the depth of the abdominal wall prevented spectra being obtained from the placenta. Differences in phosphorus metabolites were obtained from the placenta of the dead twin compared to those from the healthy pregnancies.