Fetal magnetic resonance imaging

Neurological and clinical outcomes in infants and children with a fetal diagnosis of asymmetric ventriculomegaly, interhemispheric cyst, and dysgenesis of the corpus callosum

OBJECTIVE

Advances in prenatal imaging have facilitated improvements in the fetal diagnosis of congenital anomalies. Asymmetric ventriculomegaly, interhemispheric cyst, and dysgenesis of the corpus callosum (AVID) is a constellation of congenital anomalies reported in fetal imaging. However, few data are available regarding postnatal outcomes of infants and children with a fetal diagnosis of AVID. The authors sought to report the neurodevelopmental outcomes of patients diagnosed with AVID before birth at a single institution.

METHODS

An institutional fetal imaging database was queried to identify cases with ventriculomegaly, interhemispheric cyst, and dysgenesis of the corpus callosum over a 10-year study period from 2000 to 2019. Overall, 41 maternal-infant dyads who met imaging criteria for AVID were identified; medical records were reviewed for prenatal variables including gestational age at birth, perinatal complications including fetal demise, and postnatal variables including demographics, mortality, hydrocephalus diagnosis and management, epilepsy, and neurodevelopmental outcomes at 2 years or the last follow-up.

RESULTS

Among 41 patients, 25 (61%) were male. A slight majority of patients (55%) were born before 36 weeks of gestational age, and 27 patients (68%) were delivered via cesarean section because their head size precluded vaginal delivery. There were 8 incidences of fetal demise, 1 pregnancy was terminated, and 32 patients were born alive. Neonatal or early infant death occurred in 5 patients. Two children died during follow-up after the neonatal period (ages 7 months and 7 years). Twenty-six children survived to at least the 2-year follow-up, all of whom required treatment for hydrocephalus. Of those 26 children, 12 (46%) had a diagnosis of epilepsy, 14 (54%) could sit independently, 4 (16%) were in mainstream school, 16 (62%) had expressive language, and 7 (28%) had near-normal development without seizures.

CONCLUSIONS

Among 41 maternal-fetal dyads with AVID, a majority of children survived to the 2-year follow-up, although all developed hydrocephalus. Many continued to have seizures, but expressive language use, attendance at mainstream school, and near-normal development without seizures were not infrequent. These data are critical for prenatal counseling and to establish the natural history of a diagnosis with limited outcome data.

Prenatal prediction of postnatal survival in fetuses with congenital diaphragmatic hernia using MRI: lung volume measurement, signal intensity ratio, and effect of experience

Objective: To evaluate various signal intensity ratios in isolated congenital diaphragmatic hernia (CDH) and to compare their potential in predicting survival with that of the observed-to-expected (O/E) ratio of total fetal lung volume (TFLV) using magnetic resonance imaging (MRI) measurements. Our second objective was to evaluate the impact of operator's experience in comparing the prediction of postnatal survival by O/E-TFLV.Methods: In 75 conservatively managed CDH fetuses and in 50 who underwent fetoscopic endoluminal tracheal occlusion (FETO), the fetal lung-to-amniotic fluid, lung-to-liver, lung-to-muscle, lung-to-spinal fluid signal intensity ratios, respectively LAFSIR, LLSIR, LMSIR, and LSFSIR, were measured, as was O/E-TFLV. Receiver operating characteristic (ROC) curves were constructed and used to compare the various signal intensity ratios with O/E-TFLV in the prediction of postnatal survival. In 72 MRI lung volumes assessed by the referring radiologists in Paris and Lille and secondarily by our expert radiologist in Brussels (M.M.C.) using the same MRI examinations, ROC curves were constructed and used to compare the value of O/E-TFLV determined by the two centers in the prediction of postnatal survival.Results: In the total cohort of CDH fetuses, O/E-TFLV and LLSIR were predictive of postnatal survival whereas in the conservatively managed group O/E-TFLV, LLSIR, and LMSIR predicted postnatal survival. O/E-TFLV predicted postnatal survival far better than the signal intensity ratios: area under the ROC curve for prediction by O/E-TFLV in the total cohort was 0.866 (p < .001; standard error = 0.031). The area under the ROC curve for prediction of postnatal survival using O/E-TFLV by MRI evaluated at the referral centers was 0.640 (p = 102; standard error = 0.085), and with O/E-TFLV reevaluated by M.M.C., it was 0.872 (p < .001; standard error = 0.061). Pairwise comparison showed a significant difference between the areas under the ROC curves (difference = 0.187, p = .012; standard error = 0.075).Conclusion: In fetuses with CDH with/without FETO, LLSIR was significantly correlated with the prediction of postnatal survival. However, measurement of O/E-TFLV was far better in predicting postnatal outcome. Operator experience in measurement of lung volumes using MRI seem to play a role in the predictive value of the technique.

PVR: Patch-to-Volume Reconstruction for Large Area Motion Correction of Fetal MRI

In this paper, we present a novel method for the correction of motion artifacts that are present in fetal magnetic resonance imaging (MRI) scans of the whole uterus. Contrary to current slice-to-volume registration (SVR) methods, requiring an inflexible anatomical enclosure of a single investigated organ, the proposed patch-to-volume reconstruction (PVR) approach is able to reconstruct a large field of view of non-rigidly deforming structures. It relaxes rigid motion assumptions by introducing a specific amount of redundant information that is exploited with parallelized patchwise optimization, super-resolution, and automatic outlier rejection. We further describe and provide an efficient parallel implementation of PVR allowing its execution within reasonable time on commercially available graphics processing units, enabling its use in the clinical practice. We evaluate PVR's computational overhead compared with standard methods and observe improved reconstruction accuracy in the presence of affine motion artifacts compared with conventional SVR in synthetic experiments. Furthermore, we have evaluated our method qualitatively and quantitatively on real fetal MRI data subject to maternal breathing and sudden fetal movements. We evaluate peak-signal-to-noise ratio, structural similarity index, and cross correlation with respect to the originally acquired data and provide a method for visual inspection of reconstruction uncertainty. We further evaluate the distance error for selected anatomical landmarks in the fetal head, as well as calculating the mean and maximum displacements resulting from automatic non-rigid registration to a motion-free ground truth image. These experiments demonstrate a successful application of PVR motion compensation to the whole fetal body, uterus, and placenta.

Coexistent Congenital Diaphragmatic Hernia with Extrapulmonary Sequestration

Bronchopulmonary foregut malformations are a heterogeneous but interrelated group of abnormalities that may contain more than one histologic feature. It is helpful to be familiar with the presentation and imaging features of bronchopulmonary foregut malformations presenting as a congenital mass or mass-like lesion, as imaging plays a central role in the evaluation of these lesions since, when symptomatic, clinical features are usually nonspecific. With imaging, the presence of other associated lesions can be determined, facilitating appropriate management to prevent the potential complications. We report a case of coexisting extralobar pulmonary sequestration and ipsilateral diaphragmatic hernia in a term neonate.

Surface reconstructions of foetal brain abnormalities using ultrafast steady state 3D acquisitions

MRI of the foetal brain in utero is performed in routine clinical practice using sequences that produce two-dimensional (2D) images. Recent developments in image post-processing have allowed the construction of three-dimensional (3D) volume data sets from 2D images acquired in different anatomical planes, but these have limitations due to the unpredictable nature of foetal movement. These limitations have been overcome by development of several different advanced computer techniques, which require specialist knowledge, software, and processing methods, which are rarely available in routine clinical settings. Our aim was to develop a technique that can be used in routine clinical situations without the need for custom-developed or expensive software by utilizing MRI sequences that can produce a 3D data set in "ultrafast" timescales. The 3D dataset, combined with versatile image post-processing and visualization techniques, has resulted in the production of high-resolution images of foetal brain surfaces in utero. The aim of this paper is to demonstrate our methods and early results by way of a pictorial review illustrating a range of developmental brain disease in utero.

Motion corrected 3D reconstruction of the fetal thorax from prenatal MRI

In this paper we present a semi-automatic method for analysis of the fetal thorax in genuine three-dimensional volumes. After one initial click we localize the spine and accurately determine the volume of the fetal lung from high resolution volumetric images reconstructed from motion corrupted prenatal Magnetic Resonance Imaging (MRI). We compare the current state-of-the-art method of segmenting the lung in a slice-by-slice manner with the most recent multi-scan reconstruction methods. We use fast rotation invariant spherical harmonics image descriptors with Classification Forest ensemble learning methods to extract the spinal cord and show an efficient way to generate a segmentation prior for the fetal lung from this information for two different MRI field strengths. The spinal cord can be segmented with a DICE coefficient of 0.89 and the automatic lung segmentation has been evaluated with a DICE coefficient of 0.87. We evaluate our method on 29 fetuses with a gestational age (GA) between 20 and 38 weeks and show that our computed segmentations and the manual ground truth correlate well with the recorded values in literature.

MRI and ultrasound fusion imaging for prenatal diagnosis

OBJECTIVE

A combination of magnetic resonance imaging (MRI) images with real time high-resolution ultrasound known as fusion imaging may improve prenatal examination. This study was undertaken to evaluate the feasibility of using fusion of MRI and ultrasound (US) in prenatal imaging.

STUDY DESIGN

This study was conducted in a tertiary referral center. All patients referred for prenatal MRI were offered to undergo fusion of MRI and US examination. All cases underwent 1.5 Tesla MRI protocol including at least 3 T2-weighted planes. The Digital Imaging and Communications in Medicine volume dataset was then loaded into the US system for manual registration of the live US image and fusion imaging examination.

RESULTS

Over the study period, 24 patients underwent fusion imaging at a median gestational age of 31 (range, 24-35) weeks. Data registration, matching and then volume navigation was feasible in all cases. Fusion imaging allowed superimposing MRI and US images therefore providing with real time imaging capabilities and high tissue contrast. It also allowed adding a real time Doppler signal on MRI images. Significant fetal movement required repeat-registration in 15 (60%) cases. The average duration of the overall additional scan with fusion imaging was 10 ± 5 minutes.

CONCLUSION

The combination of fetal real time MRI and US image fusion and navigation is feasible. Multimodality fusion imaging may enable easier and more extensive prenatal diagnosis.

Early second-trimester diagnosis of body stalk anomaly by fetal magnetic resonance imaging

We report a case of body stalk anomaly detected prenatally by fetal magnetic resonance imaging (MRI) at 14 weeks' gestation. A 29-year-old woman was followed during her first pregnancy. At 11-12 weeks' gestation, our sonographic images showed multiple fetal deformities. An abdominal wall defect was suspected. The exteriorized abdominal contents and the lower limb appeared within the extraembryonic celom with an intact amniotic membrane. Fetal MRI at 14 weeks' gestation confirmed a large anterior wall defect with herniation of the liver and bowel. In addition, abnormally rotated lower limb and scoliosis could be demonstrated. The fetus was prenatally diagnosed with body stalk anomaly, expected to be lethal in nature. The parents decided to terminate the pregnancy at 15 weeks' gestation. Prenatal diagnosis of body stalk anomaly is usually based on sonographic findings. As far as we are aware, this is the first case report of body stalk anomaly satisfactorily diagnosed by fetal MRI in the early second trimester. Fetal MRI scans should provide ground for a precise antenatal diagnosis of body stalk anomaly from early gestation.

Identification of fetal precentral gyrus on diffusion weighted MRI

To investigate the association of the diffusion-weighted MR imaging characteristics of fetal preCG and gestational age. Forty-four fetuses with normal brain MRI findings were included in the study. Gestational ages ranged from 18 to 36 weeks (mean 25.2 weeks). All exams were performed with a 1.5-T scanner using a body array coil during free maternal breathing without sedation. Precentral gyrus was defined as the hyperintense strip anterior to the central sulcus, on the superior section of axial brain images at the level of superior frontal cortex. The presence of preCG hyperintensity was noted as observed/subtle/not observed at different b values (500, 1000 s/mm(2)) and on apparent diffusion coefficient (ADC) maps and compared to the imaging characteristics of the superior frontal cortex. Precentral gyrus was first detected at 25 weeks as a hyperintense strip on DWI and hypointense strip on ADC maps. Display of preCG b 1000 s/mm(2) images were better than b 500 s/mm(2). Between 25 and 27 weeks, in 40% of fetuses preCG was observed on one hemisphere, and it was evident bilaterally in 60% of cases. Starting from the 28th week, preCG was observed on both hemispheres in 100% of cases. Diffusion weighted imaging helps better understanding of the evolution of fetal preCG. The hyperintense preCG strip starts to appear at 25 weeks, and when interpreting fetal DWI after 28 weeks this may be a sign to be sought for in all fetuses and an indicator for normal development.

Prenatal diagnosis by 3D ultrasound and MRI of an unusual malformation of cortical development with brain-in-brain appearance

A 31-year-old pregnant woman was referred for isolated mild ventriculomegaly and failure to visualize the left lateral ventricle's anterior horn on second trimester sonography (US). Three-dimensional US suspected a frontal lesion deviating the midline. MRI revealed a mass compressing the ventricle. Follow-up MRI described a "brain-in-brain" malformation: infolded microgyric cortex and white matter in frontal lobe extending to frontal horn and midline, irrorated by hypertophic Heubner artery. Conservative approach was chosen. Neurodevelopment at 1 year is normal.

The usefulness of fetal MRI for prenatal diagnosis

PURPOSE

Fast MRI has provided detailed and reproducible fetal anatomy. This study was performed to evaluate the usefulness of fetal MRI for prenatal diagnosis.

MATERIALS AND METHODS

Fifty-six fetuses with congenital abnormalities on ultrasonography were evaluated by fetal MRI from 2001 to 2004 in Severance Hospital. Final diagnosis was made by postnatal pathology, postnatal MRI, and other modalities (such as ultrasound, retrograde pyelogram). A 1.5-Tesla superconductive MR imaging unit was used to obtain half-Fourier acquisition single-shot turbo spin images.

RESULTS

Of the 56 fetuses, intracranial abnormalities were found in 26 fetuses, intraabdominal abnormalities in 17 fetuses, intrathoracic in 6 fetuses, head and neck in 5 fetuses, and other sites in 2 fetuses. There were six cases in which the diagnoses of fetal MRI and ultrasonography differed. In such cases, fetal MRI provided more exact diagnosis than ultrasonography (5 vs. 0). Three fetuses with intracranial abnormalities on ultrasonography were diagnosed as normal by fetal MRI and in postnatal diagnosis.

CONCLUSION

Although ultrasonography is known as a screening modality of choice in the evaluation of fetus because of the cost-effectiveness and safety, the sonographic findings are occasionally inconclusive or insufficient for choosing the proper management. Thus, in this study, we suggest that fetal MRI is more useful than ultrasonography for the evaluation of intracranial abnormalities in some instances. For prenatal counseling and postnatal treatment planning, fetal MRI can be informative when prenatal ultrasonography is inadequate and doubtful.

Diagnosis of pentalogy of cantrell in the fetus using magnetic resonance imaging and ultrasound

We report two cases of pentalogy of Cantrell diagnosed in utero using a combination of fetal echocardiography and magnetic resonance imaging. The cardiac component consisted of tetralogy of Fallot in the first fetus and ventricular septal defect in the second fetus. Whereas fetal echocardiography allowed accurate delineation of the cardiac anatomy, prenatal magnetic resonance imaging allowed clearer delineation of the extent of the thoracic and abdominal wall defects. Fetal magnetic resonance imaging in conjunction with prenatal echocardiography allows optimal assessment of the fetus with ectopia cordis, which has significant implications from the standpoint of preoperative planning and providing prognostic information. This report represents the first description of applying magnetic resonance imaging in combination with echocardiography toward a better understanding of this clinical entity in the fetus.

Prenatal diagnosis of fetal exencephaly associated with amniotic band sequence at 17 weeks of gestation by fetal magnetic resonance imaging

We report a fetus with exencephaly diagnosed by fetal magnetic resonance imaging (MRI) at 17 weeks of gestation. Fetal ultrasound performed at 13 and 17 weeks of gestation suggested occipital encephalocele. However, the fetal MRI done at 17 weeks of gestation showed exencephaly and suggested amniotic bands as the cause. By providing early and precise information regarding the abnormality and the possible etiology, the fetal MRI enabled us to provide the couple and their families with accurate information regarding the low recurrence risk of this condition.

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.

Registration-based approach for reconstruction of high-resolution in utero fetal MR brain images

RATIONALE AND OBJECTIVES

This paper describes a novel approach to forming high-resolution MR images of the human fetal brain. It addresses the key problem of fetal motion by proposing a registration-refined compounding of multiple sets of orthogonal fast two-dimensional MRI slices, which are currently acquired for clinical studies, into a single high-resolution MRI volume.

MATERIALS AND METHODS

A robust multiresolution slice alignment is applied iteratively to the data to correct motion of the fetus that occurs between two-dimensional acquisitions. This is combined with an intensity correction step and a super-resolution reconstruction step, to form a single high isotropic resolution volume of the fetal brain.

RESULTS

Experimental validation on synthetic image data with known motion types and underlying anatomy, together with retrospective application to sets of clinical acquisitions, are included.

CONCLUSION

Results indicate that this method promises a unique route to acquiring high-resolution MRI of the fetal brain in vivo allowing comparable quality to that of neonatal MRI. Such data provide a highly valuable window into the process of normal and abnormal brain development, which is directly applicable in a clinical setting.

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.

MRI supported diagnosis and counselling in a family with a probably autosomal recessive form of pachygyria

OBJECTIVES

To describe the use of fetal MRI as an adjunct to high-resolution ultrasound in parental counselling in a family with a central nervous system (CNS) abnormality, resembling the agyria-pachyria complex, of probably autosomal recessive inheritance.

METHODS

Description of the use of fetal MRI as an adjunct to high-resolution ultrasound in three consecutive pregnancies in a family with a CNS abnormality.

RESULTS

Fetal MRI, by showing more detailed abnormalities of the CNS, proved to be very useful in parental counselling because of the definitive diagnosis available early in pregnancy. In the first two pregnancies, ultrasound examination revealed mild pyelectasis, megacystis and an enlarged posterior fossa with small cerebellum. MRI at 22-33 weeks confirmed these abnormalities, but also showed pachygyria. In the third pregnancy, MRI at 19 weeks showed no abnormalities, a finding of decisive importance for counselling.

CONCLUSION

Fetal MRI was useful both for early diagnosis and prenatal management in this family with an agyria-pachyria complex CNS abnormality.

Prenatal diagnosis of fetal hydrometrocolpos secondary to a cloacal anomaly by magnetic resonance imaging

Fetal female urogenital anomalies are often difficult to evaluate by ultrasonography, especially in late gestation. We report a case of fetal hydrometrocolpos detected at 35 weeks of gestation. Ultrasonography revealed a large retrovesical septate hypoechogenic mass in the fetal abdomen, however the sonographic findings were inconclusive. Magnetic resonance imaging (MRI) confirmed that the abdominal mass was fluid-filled with a mid-plane septum in the midline posterior to the bladder, and showed a connection to the dilated uterus that was duplicated. These findings were consistent with a diagnosis of hydrometrocolpos with septate vagina and uterus didelphys. The neonate showed abdominal distension, ambiguous genitalia and anal atresia with a single perineal opening. Hydrometrocolpos was secondary to a urethral type of cloacal anomaly. Aspiration of the mass and a colostomy were performed on the first postnatal day, followed by anorectoplasty at 19 months of age. MRI is a useful complementary tool for assessing fetal urogenital anomalies when ultrasonography is inconclusive.

Cross-fused ectopic multicystic dysplastic kidney with associated ureterocele

We describe a case of the unique congenital anomaly of cross-fused ectopic multicystic dysplastic kidney with associated ureterocele and demonstrate the usefulness of magnetic resonance imaging in fetal imaging.

Current status of fetal surgery

The allure of fetal surgery is the possibility of interrupting in utero progression of an otherwise treatable condition. In spite of advances in prenatal diagnosis and refinements in surgical techniques, this field has not yet got off the ground because the risks to the mother and fetus, during and after the procedure far outweigh the benefits, and the infrastructure required to support such activity is prohibitively expensive. The various surgical conditions in which fetal surgery has been attempted and the present status of this specialty are discussed.

A novel approach to high resolution fetal brain MR imaging

This paper describes a novel approach to forming high resolution MR images of the human fetal brain. It addresses the key problem of motion of the fetus by proposing a registration refined compounding of multiple sets of orthogonal fast 2D MRI slices, that are currently acquired for clinical studies, into a single high resolution MRI volume. A robust multi-resolution slice alignment is applied iteratively to the data to correct motion of the fetus that occurs between 2D acquisitions. This is combined with an intensity correction step and a super resolution reconstruction step, to form a single high isotropic resolution volume of the fetal brain. Experimental validation on synthetic image data with known motion types and underlying anatomy, together with retrospective application to sets of clinical acquisitions are included. Results indicate the method promises a unique route to acquiring high resolution MRI of the fetal brain in vivo allowing comparable quality to that of neonatal MRI. Such data is highly valuable in allowing a clinically applicable window into the process of normal and abnormal brain development.