Complementary Roles of Sonography and Magnetic Resonance Imaging in the Assessment of Fetal Urinary Tract Anomalies

Objective. The purpose of our study was to determine whether fetal magnetic resonance imaging (MRI) provides additional information that might affect the obstetric management of pregnancies complicated by sonographically diagnosed fetal urinary tract anomalies. Methods. Fetal MRI and sonography were used to study 39 women with suspected fetal urinary tract anomalies in the second and third trimesters of pregnancy. Results. In 24 of 39 cases (61%), fetal MRI confirmed the sonographic diagnosis. In 14 cases (36%), fetal MRI modified the initial sonographic diagnosis and counseling but did not change obstetric management. In 1 case (3%), the addition of fetal MRI resulted in a substantial change in the management of the pregnancy. Conclusions. During the second and third trimesters of pregnancy, fetal MRI showed fetal urinary tract anomalies in excellent anatomic detail. Fetal MRI is a useful complementary tool in the assessment of sonographically diagnosed fetal urinary tract anomalies. In a small percentage of cases, it can have a substantial impact on obstetric management.     

Fetal magnetic resonance imaging in the evaluation of fetuses referred for sonographically suspected abnormalities of the corpus callosum.

OBJECTIVE: Fetal magnetic resonance imaging (MRI) has been shown to be useful in assessing the developing central nervous system. However, its utility in specific brain disorders has not been well investigated. We hypothesized that fetal MRI can better assess the integrity of the brain in cases with sonographically suspected callosal abnormalities. METHODS: We retrospectively reviewed fetal MRI and prenatal sonographic studies of 10 fetuses referred for MRI for sonographically suspected callosal abnormalities. RESULTS: An abnormal corpus callosum was identified on fetal MRI in 80% of cases. The type of callosal abnormality (complete or partial agenesis) was similar on both prenatal sonography and fetal MRI in all cases. All sonographically identified additional brain abnormalities were detected on fetal MRI, with the exception of choroid plexus cysts. Furthermore, in 63% (5 of 8) of cases with a callosal abnormality on both sonography and fetal MRI, additional brain abnormalities were detected on fetal MRI that were not apparent on sonography. These sonographically occult findings were confirmed on postnatal MRI or autopsy in 3 of 5 patients. CONCLUSIONS: Fetal MRI is an important adjunct to sonography in assessing the corpus callosum and other aspects of brain development when agenesis of the corpus callosum is suspected. It can identify frequent additional findings that are not visible on sonography such as abnormal sulcation. In light of the association between additional brain abnormalities and worse neurodevelopmental outcome, the potential of fetal MRI as an important adjunctive prognostic imaging test in fetuses with callosal agenesis can now be tested.     

The role of magnetic resonance imaging in the evaluation of isolated mild ventriculomegaly.

OBJECTIVE: Isolated mild ventriculomegaly is defined as dilatation of the lateral ventricle from 10 to 15 mm, with no other structural abnormalities observed at the time of diagnosis. Its reported frequency is between 1 per 50 and 1 per 700 deliveries. There are no universal recommendations for evaluation of isolated mild ventriculomegaly. Targeted sonography, karyotype analysis, and viral antigen testing, particularly for cytomegalovirus, are most often used for further investigation of this finding. We studied the role of magnetic resonance imaging as part of the prenatal evaluation of isolated mild ventriculomegaly. METHODS: Thirty-six pregnant women were referred to 2 Hadassah hospitals between 1999 and 2002 for evaluation of isolated mild ventriculomegaly. They underwent targeted sonography to exclude other anomalies, genetic amniocentesis for fetal karyotype, and serologic cytomegalovirus tests. Mild ventriculomegaly was the only pathologic finding diagnosed. Fetal brain magnetic resonance imaging was performed to evaluate the correlation between sonographic and magnetic resonance imaging findings and the additional contribution of magnetic resonance imaging in evaluating isolated mild ventriculomegaly. RESULTS: Thirty-six magnetic resonance imaging studies were performed. All tests were adequate for evaluation. In 3 (8.3%) of 36 cases, magnetic resonance imaging showed additional findings: in a severely obese woman, ventricular dilatation up to 18 mm and periventricular cystic lesions with abnormal sulcation suggestive of diffuse parenchymal abnormality were diagnosed, and in 2 cases, bleeding in germinal centers was found. On subsequent sonographic examination, no other finding but isolated mild ventriculomegaly was diagnosed. In the remaining 33 women (91.7%), magnetic resonance imaging studies correlated well with sonographic findings. Further sonographic follow-up in this subgroup failed to reveal any other pathologic findings. CONCLUSIONS: Our study supports the view that magnetic resonance imaging should be considered as part of the evaluation of isolated mild ventriculomegaly, especially when objective difficulties preclude detailed sonographic examination.     

Fine‐tuning the Diagnosis of Fetal Scalp Cysts

Objective. The purpose of this series is to emphasize the importance of an exhaustive and appropriately conducted sonographic examination in the correct diagnosis of fetal cystic scalp lesions and the place of magnetic resonance imaging (MRI) in the diagnostic sequence. Methods. Transabdominal and transvaginal 2‐ and 3‐dimensional sonography with color and power Doppler imaging as well as 3‐dimensional rendering techniques such as inversion and Doppler angiography were used. In 1 case, an MRI study was performed. Results. In 1 case, the MRI missed and the different sonographic techniques correctly made the diagnosis of a meningocele. In the second case, sonography was sufficient to establish the diagnosis of an epidermal cyst. Conclusions. These 2 cases show the value of going the distance with the newly available high‐frequency sonography. Ultimately, the correct diagnoses were made with the tools offered by sonography without the need for any other imaging modality.     

The use of high resolution magnetic resonance imaging in the prenatal diagnosis of fetal nuchal tumors.

Fetal magnetic resonance imaging (fetal MRI) is an important adjunct to antenatal imaging especially when neonatal surgery is contemplated. We report two cases of fetal nuchal tumors, which were diagnosed incidentally on an ultrasound scan and had fetal MRI to aid diagnosis, prognosis, counseling and management planning. In the first case, fetal MRI aided diagnosis and prenatal multidisciplinary management of a cervical teratoma. Tracheal involvement could not be excluded and an ex-utero intrapartum treatment procedure was planned. Postnatal MRI and angiography provided further information prior to surgery. In the second case, fetal MRI assisted thorough counseling following the finding of a cervical lesion thought to be a cervical teratodermoid, a multicystic hygroma or congenital lymphectasia. The parents opted for termination of the pregnancy. Postmortem findings confirmed the extent of involvement of surrounding structures diagnosed prenatally. The mass was found to be a hamartomatous hemangiolymphangioma.     

Fetal Hands: A Comprehensive Review of Prenatal Assessment and Diagnosis Over the Past 40 Years

Fetal skeletal dysplasias involving limbs and hands are rare congenital malformations. Prenatal two-dimensional ultrasound diagnosis of fetal limb defects has a sensitivity of about 30%; however, an increased detection rate may be obtained using three-dimensional (3-D) ultrasound in the rendering mode. 3-D ultrasound may be used as a complementary method providing additional information. Currently, magnetic resonance imaging (MRI), with the emergence of ultrafast imaging techniques and new sequences, allows for better diagnosis of several fetal skeletal dysplasias such as limb reduction defects and neuromuscular disorders. 3-D volumetric images from ultrasound or MRI scan data allow 3-D ultrasound reconstructions of virtual/physical models, and virtual reality can help researchers to improve our understanding of both normal and abnormal fetal limb/hand anatomy. In this article, we review the embryological development of fetal hands and their main anomalies including prenatal diagnostic methods, genetic counseling, the role of orthopedic and plastic surgery reconstruction, and new perspectives in fetal surgery.     

Prenatal diagnosis of herniated Dandy-Walker cysts.

OBJECTIVE: The purpose of this series is to describe the prenatal diagnosis and pregnancy outcome of fetuses affected with Dandy-Walker malformation in which a posterior cyst herniated through a bony defect of the occipital skull, foramen magnum, or both. METHODS: Two- and 3-dimensional sonography were used to examine 2 fetuses with poorly delineated cerebellar structures and a large posterior cystic neck mass. Fetal magnetic resonance imaging (MRI) was added to this evaluation as a complementary diagnostic modality. RESULTS: Three-dimensional sonography helped characterize the precise site of cyst herniation through the occipital skull or foramen magnum. Fetal MRI confirmed the sonographic findings. Neonatal MRI studies identified heterotopic gray matter as evidence of a neuronal migration disorder in both fetuses. The second fetus also had agenesis of the corpus callosum. Retrospective review of the fetal MRI (25.9 weeks' menstrual age) and 3-dimensional sonographic (18.7 weeks' menstrual age) studies confirmed ventricular wall nodularity involving the occipital horns of the second fetus. CONCLUSIONS: The antenatal detection of a large posterior cystic neck mass and a poorly defined or nonvisualized cerebellar vermis suggest Dandy-Walker malformation with a herniated cyst. Three-dimensional sonography and fetal MRI are important adjunctive methods that can be used to evaluate the herniation site and a possible neuronal migrational disorder.     

Congenital cardiovascular malformations: noninvasive imaging by MRI in neonates

Owing largely to advances in fetal echocardiography, in most developed countries the diagnosis of severe congenital heart disease (CHD) is now made during gestation, and delivery is electively planned in hospitals that have the facilities and expertise to manage these patients, with magnetic resonance (MR) imaging performing an important complementary role. MR imaging as a sole imaging modality for comprehensive presurgical evaluation is also increasingly being explored. This article focuses on the imaging of neonatal CHD by MR, followed by a brief discussion of the safety of gadolinium-based contrast agents in this age group.     

Fetal magnetic resonance imaging in the prenatal diagnosis of cerebellar hemorrhage.

We report the case of a fetus with a sonographic mid-gestation diagnosis of hyperechogenic cerebellum suspected to be of hemorrhagic origin on fetal brain magnetic resonance imaging (MRI). No etiological factors for fetal hemorrhage were found other than a maternal heterozygocity for factor V Leiden. Following termination of the pregnancy, autopsy confirmed the prenatal diagnosis of massive cerebellar hemorrhage without underlying vascular anomaly. As an additional tool to ultrasonography, fetal brain MRI can affirm the hemorrhagic origin of hyperechogenic cerebellar lesions, especially by showing a high signal on T1-weighted images.     

Imaging Features of Fetal Chest Lesions With a Focus on Ultrasound and Magnetic Resonance Imaging

Congenital lung anomalies vary in origin with numerous theories about overall formation. While many of these lesions may be asymptomatic or incidentally detected, on occasion these can have potentially life-threatening effects such as mass effect on adjacent structures and pulmonary hypoplasia. Prenatal diagnosis is advantageous to help direct prenatal counseling and perinatal care. Ultrasound and magnetic resonance imaging (MRI) are the most widely used modalities for fetal imaging and provide complementary information. This review describes congenital fetal chest lesions with a focus on differentiating imaging features.     

Magnetic resonance imaging of the intrauterine fetal genitourinary tract

Although ultrasonography (US) remains the most widely used diagnostic imaging modality for routine evaluation of the fetus, magnetic resonance (MR) imaging has become an invaluable complement to US in all cases in which additional information is desirable. While the ability of US to detect fetal abnormalities is limited in cases such as maternal obesity, oligohydramnios, and in certain fetal positions, MR using fast and ultrafast pulse sequences enables high-quality fetal images to be acquired regardless of the mothers physical condition or fetal position. Fetal genitourinary disorders are the most common intrauterine abnormalities detected by US, accounting for approximately 30% of all antenatally detected anomalies. Although they usually occur in isolation, these defects can form part of more complex syndromes or chromosomopathies, and MR is indicated to rule out associated abnormalities. In some severe genitourinary disorders, there is a severe deficit of amniotic fluid; these cases are associated with other fetal anomalies such as pulmonary hypoplasia and very poor prognosis. In other cases, the amniotic fluid is not compromised, yet the further detection, localization, and characterization of prenatal disorders will have an impact on postnatal follow-up. This article reviews the role of fetal MR in urogenital tract disorders.     

What Does Magnetic Resonance Imaging Add to the Prenatal Sonographic Diagnosis of Ventriculomegaly?

OBJECTIVE: The purpose of this study was to determine the contribution of magnetic resonance imaging (MRI) in evaluating fetuses with the sonographic diagnosis of ventriculomegaly (VM). METHODS: Over 4 years, consecutive fetuses with the sonographic diagnosis of VM at 1 facility who underwent prenatal MRI at a second facility were included. The roles of MRI and follow-up sonography were tabulated. The patients were analyzed in 2 groups based on the presence or absence of other central nervous system (CNS) abnormalities. RESULTS: Twenty-six fetuses with a gestational age range of 17 to 37 weeks had sonographically detected VM (atria > or =10-29 mm), including 19 with mild VM (atria 10-12 mm). In group 1, 14 had isolated VM, 6 of which reverted to normal by the third trimester. Magnetic resonance imaging showed cerebellar hypoplasia not shown by sonography in 1 fetus and an additional finding of a mega cisterna magna in a second fetus. In group 2, 12 fetuses had VM and other CNS anomalies on sonography. Additional findings were seen with MRI in 10 of these fetuses, including migrational abnormalities (n = 4), porencephaly (n = 4), and 1 diagnosis each of abnormal myelination, hypoplasia of the corpus callosum, microcephaly, a kinked brain stem, cerebellar hypoplasia, and congenital infarction. There were significantly more fetuses with additional CNS anomalies found by MRI among those in group 2 compared with those in group 1 (Fisher exact test, P = .001). CONCLUSIONS: Although sonography is an accurate diagnostic modality for the evaluation of fetuses with VM, MRI adds important additional information, particularly in fetuses in whom additional findings other than an enlarged ventricle are seen sonographically.     

MR imaging in chronic hepatitis and cirrhosis.

The role of magnetic resonance imaging (MRI) in the evaluation of diffuse parenchymal abnormalities of the liver has been expanded by recent technical advances of MR systems as well as the evolution of intravenous contrast media. Currently, MR is undoubtedly the most useful imaging modality for detecting the presence of chronic liver disease. Tailored sequences allow acurate depiction of specific disorders, including steatohepatitis and iron-overload states. Morphologic changes and signal intensity effects not only facilitate the diagnosis of chronic liver disease with MRI but they also help to distinguish between different etiologies, and they assist in staging the histologic severity of certain chronic conditions. Moreover, the faster MRI scanning techniques presently available permit the dynamic assessment of contrast enhancement, which permits improved characterization of focal hepatic lesions, including regenerative nodules, dysplastic nodules, and hepatocellular carcinoma (HCC). Although overlap in MRI findings still may exist among different types of chronic liver disease and among focal liver lesions, familiarity with certain specific imaging features may be diagnostic in the proper clinical setting. Finally, comprehensive MRI examination, including MR angiography and MR cholangiography, is the most sensitive and cost-effective technique for detecting extrahepatic disease, diagnosing vascular disorders, and evaluating the patient before or after liver transplantation. This article focuses on the current role of MR imaging in patients with chronic liver disease. The subjects covered include the detection and characterization of chronic hepatitis and cirrhosis, specific findings seen in steatohepatitis and certain metabolic diseases, the evaluation of extrahepatic vascular complications of cirrhosis, and patient assessment before and after liver transplantation. The characterization of hepatic masses is also included briefly. This subject is covered in greater depth elsewhere in this issue.     

Fusion of contrast-enhanced breast MR and mammographic imaging data

Increasing use is being made of Gd-DTPA contrast-enhanced magnetic resonance imaging for breast cancer assessment since it provides 3D functional information via pharmacokinetic interaction between contrast agent and tumour vascularity, and because it is applicable to women of all ages as well as patients with post-operative scarring. Contrast-enhanced MRI (CE-MRI) is complementary to conventional X-ray mammography, since it is a relatively low-resolution functional counterpart of a comparatively high-resolution 2D structural representation. However, despite the additional information provided by MRI, mammography is still an extremely important diagnostic imaging modality, particularly for several common conditions such as ductal carcinoma in situ (DCIS) where it has been shown that there is a strong correlation between microcalcification clusters and malignancy. Pathological indicators such as calcifications and fine spiculations are not visible in CE-MRI and therefore there is clinical and diagnostic value in fusing the high-resolution structural information available from mammography with the functional data acquired from MRI imaging. This paper presents a novel data fusion technique whereby medial-lateral oblique (MLO) and cranial-caudal (CC) mammograms (2D data) are registered to 3D contrast-enhanced MRI volumes. We utilise a combination of pharmacokinetic modelling, projection geometry, wavelet-based landmark detection and thin-plate spline non-rigid 'warping' to transform the coordinates of regions of interest (ROIs) from the 2D mammograms to the spatial reference frame of the contrast-enhanced MRI volume. Of key importance is the use of a flexible wavelet-based feature extraction technique that enables feature correspondences to be robustly determined between the very different image characteristics of X-ray mammography and MRI. An evaluation of the fusion framework is demonstrated with a series of clinical cases and a total of 14 patient examples.     

Prenatal Diagnosis of Torcular Herophili Thrombosis

Prenatally diagnosed thrombosis of the torcular herophili is very rare, and it is sometimes misdisgnosed due to unfamiliarity. Sonography with color Doppler imaging is the key imaging modality for prenatal diagnosis of torcular herophili thrombosis. Typical prenatal sonographic findings include a well‐defined triangular anechoic collection in the occipital region and an echogenic structure within the collection, which represents the thrombus. Fetal magnetic resonance imaging is usually used as an adjunctive modality for prenatal diagnosis, as it confirms the diagnosis by providing more precise anatomic information and better characterization of the lesion. We present 2 cases of thrombosis of an ectatic torcular herophili with serial sonographic and magnetic resonance imaging examinations, as well as a review of the literature regarding the prenatal diagnosis of torcular herophili thrombosis.     

Fetal diffusion imaging: pearls and solutions

ABSTRACT: Recently, diffusion-weighted (DWI) magnetic resonance imaging of the fetus has evolved from a basic research application to an important diagnostic imaging tool in fetal magnetic resonance imaging. Although technically challenging and still plagued with several sources of artifacts, DWI can add clinically important information, which cannot be provided by any other prenatal imaging modality. Its potential to noninvasively probe tissue structures on the basis of Brownian molecular motion enables the detection of early changes associated with acute fetal diseases, as well as structural alterations of functionally diverse compartments of different fetal organs. In this article, the current clinical applications of fetal brain and body DWI are outlined, as well as its current limitations.     

Fetal MR imaging

Ultrasonography is the primary prenatal screening modality used in the evaluation of the fetus and the maternal pelvis. However, fetal MR imaging plays a complementary role to prenatal ultrasound in the evaluation of the fetus with suspected abnormalities. MR imaging's role includes confirming or excluding possible lesions, defining their full extent, aiding in their characterization, and demonstrating other associated abnormalities. As newer techniques such as diffusion imaging, MR spectroscopy, and functional studies are used more widely, it is hoped that additional information will be made available by this modality to physicians evaluating and taking care of fetuses.     

MR imaging of the placenta: what a radiologist should know

Imaging of the placenta can have a profound impact on patient management, owing to the morbidity and mortality associated with various placental conditions. Placental conditions affecting the mother and fetus include molar pregnancies, placental hematoma, abruption, previa, accreta, vasa previa, chorioangioma, and retained products of conception. Although uncommon, abnormalities of the placenta are important to recognize owing to the potential for maternal and fetal morbidity and mortality. Sonography remains the first imaging modality for evaluation of the placenta. Magnetic resonance (MR) imaging has many unique properties that make it well-suited for imaging of the placenta: the multi-planar capabilities, the improved tissue contrast that can be obtained using a variety of pulse sequences and parameters and the lack of ionizing radiation; MR imaging can be of added diagnostic value when further characterization is required. In this article, we review the appearances and the role of MRI in diagnosis and management of these conditions. We present our clinical perspective on diagnosing these challenging problems with MRI and review the imaging findings that can lead to a correct diagnosis.     

乳腺1H磁共振波谱

对比增强MRI已经成为重要的乳腺成像手段,但是该手段并不总能提供确切的病理.在动态增强MRI基础上增加活体MRS的初步研究显示的结果很具前景,越来越多的研究小组将MRS加入乳腺MR检查序列.本文阐明了进行MRS检查的预期检查结果,并列举了其中的一些缺陷.