Fetal curarization for prenatal magnetic resonance imaging

Magnetic resonance imaging of the monkey fetal brain in utero

Non-human primates (NHPs) are the closest living relatives of the human and play a critical role in investigating the effects of maternal viral infection and consumption of medicines, drugs, and alcohol on fetal development. With the advance of contemporary fast MRI techniques with parallel imaging, fetal MRI is becoming a robust tool increasingly used in clinical practice and preclinical studies to examine congenital abnormalities including placental dysfunction, congenital heart disease (CHD), and brain abnormalities non-invasively. Because NHPs are usually scanned under anesthesia, the motion artifact is reduced substantially, allowing multi-parameter MRI techniques to be used intensively to examine the fetal development in a single scanning session or longitudinal studies. In this paper, the MRI techniques for scanning monkey fetal brains in utero in biomedical research are summarized. Also, a fast imaging protocol including T2-weighted imaging, diffusion MRI, resting-state functional MRI (rsfMRI) to examine rhesus monkey fetal brains in utero on a clinical 3T scanner is introduced.

An ode to fetal, infant, and toddler neuroimaging: Chronicling early clinical to research applications with MRI, and an introduction to an academic society connecting the field

Fetal, infant, and toddler neuroimaging is commonly thought of as a development of modern times (last two decades). Yet, this field mobilized shortly after the discovery and implementation of MRI technology. Here, we provide a review of the parallel advancements in the fields of fetal, infant, and toddler neuroimaging, noting the shifts from clinical to research use, and the ongoing challenges in this fast-growing field. We chronicle the pioneering science of fetal, infant, and toddler neuroimaging, highlighting the early studies that set the stage for modern advances in imaging during this developmental period, and the large-scale multi-site efforts which ultimately led to the explosion of interest in the field today. Lastly, we consider the growing pains of the community and the need for an academic society that bridges expertise in developmental neuroscience, clinical science, as well as computational and biomedical engineering, to ensure special consideration of the vulnerable mother-offspring dyad (especially during pregnancy), data quality, and image processing tools that are created, rather than adapted, for the young brain.

La risonanza magnetica del feto

La RM fetale si candida come metodica di approfondimento nella diagnostica per immagini prenatale, dopo il classico approccio ecografico entrato ormai nel depistage di massa delle anomalie fetali. Il ricorso alla RM fetale ha una storia breve ma l'interesse dei vari autori a questa metodica è risultato crescente nell'ultimo decennio.

In questo lavoro viene presentata una breve revisione critica dei dati della letteratura con alcune annotazioni sulle diverse soluzioni tecniche proposte. Viene soprattutto discusso il problema legato ai movimenti fetali che tendono a degradare l'immagine RM dando particolare risalto alle manovre eco-guidate di curarizzazione fetale. Vengono quindi riportati i risultati su una casistica di 27 pazienti gravide in epoca gestazionale compresa tra il secondo ed il terzo trimestre, 22 delle quali sottoposte a curarizzazione fetale. In particolare sono presentati i diversi risultati RM in relazione al diverso dosaggio e al diverso agente curaro-simile impiegato e alcuni dettagli tecnici sull'esecuzione della RM fetale. In questa prima parte del nostro lavoro viene infine discussa l'anatomia normale del cervello fetale all'RM.

Fetal MRI: A Technical Update with Educational Aspirations

Fetal magnetic resonance imaging (MRI) examinations have become well-established procedures at many institutions and can serve as useful adjuncts to ultrasound (US) exams when diagnostic doubts remain after US. Due to fetal motion, however, fetal MRI exams are challenging and require the MR scanner to be used in a somewhat different mode than that employed for more routine clinical studies. Herein we review the techniques most commonly used, and those that are available, for fetal MRI with an emphasis on the physics of the techniques and how to deploy them to improve success rates for fetal MRI exams. By far the most common technique employed is single-shot T2-weighted imaging due to its excellent tissue contrast and relative immunity to fetal motion. Despite the significant challenges involved, however, many of the other techniques commonly employed in conventional neuro- and body MRI such as T1 and T2*-weighted imaging, diffusion and perfusion weighted imaging, as well as spectroscopic methods remain of interest for fetal MR applications. An effort to understand the strengths and limitations of these basic methods within the context of fetal MRI is made in order to optimize their use and facilitate implementation of technical improvements for the further development of fetal MR imaging, both in acquisition and post-processing strategies.

Mapping fetal brain development in utero using magnetic resonance imaging: the Big Bang of brain mapping

The development of tools to construct and investigate probabilistic maps of the adult human brain from magnetic resonance imaging (MRI) has led to advances in both basic neuroscience and clinical diagnosis. These tools are increasingly being applied to brain development in adolescence and childhood, and even to neonatal and premature neonatal imaging. Even earlier in development, parallel advances in clinical fetal MRI have led to its growing use as a tool in challenging medical conditions. This has motivated new engineering developments encompassing optimal fast MRI scans and techniques derived from computer vision, the combination of which allows full 3D imaging of the moving fetal brain in utero without sedation. These promise to provide a new and unprecedented window into early human brain growth. This article reviews the developments that have led us to this point, examines the current state of the art in the fields of fast fetal imaging and motion correction, and describes the tools to analyze dynamically changing fetal brain structure. New methods to deal with developmental tissue segmentation and the construction of spatiotemporal atlases are examined, together with techniques to map fetal brain growth patterns.

Indikationen zur fetalen Magnetresonanztomographie

Indications to perform fetal magnetic resonance imaging (MRI) are composed of common ones related to methodological problems of ultrasound (US) assessment (such as for instance hydramnios) and special ones. The latter are related to MR capability of high-resolution soft tissue contrast and an extended field of view that allows visualization of the whole fetus, even in later stages of pregnancy. The most important indications include confirmation of US findings, work-up of malformations with respect to individual prognosis and genetic background, differentiation between acquired conditions and malformations, visualization of pathologies that have to be treated surgically immediately after birth, and morphological changes of the placenta.

MR imaging of fetal central nervous system abnormalities

Ultrasound is the screening modality of choice for fetal imaging. However, when additional information regarding fetal anatomy or pathology is needed, fast MR imaging is increasingly being used as a correlative imaging modality. Performances of high quality sonographic and MR examinations as well as interpretation by individuals familiar with prenatal diagnosis are important factors for optimal parental counseling. MR imaging frequently adds additional information regarding fetal central nervous system anomalies beyond that available with ultrasound. This information commonly changes patient counseling, and at times patient management.

Magnetic resonance imaging in prenatal diagnosis

Ultrasound is the screening modality of choice for fetal imaging. However, when additional information regarding fetal anatomy or pathology is needed, fast magnetic resonance (MR) imaging is being used increasingly as a correlative imaging modality because it uses no ionizing radiation, provides excellent soft tissue contrast, has multiple planes for reconstruction, and a large field of view. Sonographic examination of the fetus is still important for selecting the appropriate fetuses for MR examination and to guide the protocol of the examination. Performance of high quality sonographic and MR examinations, as well as interpretation by individuals familiar with prenatal diagnosis, are important factors for optimal parental counseling. Magnetic resonance imaging frequently adds additional information beyond that available with ultrasound. This information commonly changes patient counseling, and at times patient management.

Obstetric MR imaging

The surge in the development of fast magnetic resonance (MR) techniques has revolutionized our ability to image the pregnant patient and the fetus. Fast MR imaging techniques provide excellent resolution for imaging the maternal and fetal anatomies without the need for sedation. This article addresses the use of fast MR imaging techniques in the evaluation of the pregnant patient for adnexal masses, pelvimetry, hydroureteronephrosis of pregnancy, and placenta accreta. In addition, fetal anomalies for which MR imaging has proved useful, such as ventriculomegaly, arachnoid cysts, and abdominal masses, are described.

Magnetic resonance imaging of the fetus: a study of 20 cases performed without curarization

Twenty patients underwent magnetic resonance imaging (MRI) at a mean gestational age of 32 weeks. There were 12 patients with suspected fetal brain abnormality and four with intrauterine growth retardation (IUGR), while the remaining four cases were studied for other reasons. The MRI examinations were performed on a 0.5 Tesla machine, with surface coils. One minute acquisition time T1 sequences were used. All the studies were performed without fetal curarization, and only under maternal sedation using flunitrazepam given per os 1 h before MRI examination. Three examinations were incomplete because of fetal movement artefacts. In the remaining cases, MRI allowed the examination of fetal brain anatomy. In five cases, it helped to differentiate isolated hydrocephalus and corpus callosum agenesis. Sub-ependymal nodules were depicted in a case of fetal tuberous sclerosis. One suspected arachnoid cyst was proved to be an ultrasound artefact. Decreased fetal fat on MR images was correlated with low birth weight in cases of IUGR. Due to its better spatial resolution, ultrasonography was more accurate for the diagnosis of facial and lumbar anomalies. Fetal MRI may be performed without curarization. Surface coils allow the detailed analysis of brain parenchyma, and thus MRI is especially useful in the difficult prenatal diagnosis of fetal brain abnormalities.

Prenatal diagnosis of fetal cerebral abnormalities by ultrasonography and magnetic resonance imaging

We found magnetic resonance imaging (MRI) of the fetal brain to be effective in confirming or denying diagnosis of fetal cerebral defects when ultrasonography was inconclusive or incomplete. In this paper we describe 31 cases in which ultrasonographic evidence of fetal brain defects was verified by MRI. MRI was performed after curarization of the fetus. In 21 cases, ultrasonographic evidence was confirmed by histological study of the fetus or postnatal radiological examination. In 10 cases, ultrasonographic diagnosis was denied by MRI and healthy infants were born. In one case of cerebral toxoplasmosis, ultrasonography detected periventricular calcifications but MRI was normal. In 20 cases MRI ascertained or further documented the ultrasonographic findings. However in 4 of these 20 cases autopsy of the fetus was required to determine the exact nature of the lesion.

In vivo MRI of the fetal brain

We report MRI of the brain in 45 fetuses; the findings were confirmed by pathological examination or postnatal neuroradiological studies. MRI necessitates medication to eliminate fetal motion; curare was injected into the umbilical cord, and MRI is therefore limited to cases in which umbilical cord puncture is indicated. T1-weighted images were obtained in axial, sagittal and coronal planes; the last of these were generally as the most useful as regards morphology. We demonstrated cerebral malformations (n = 13), brain haemorrhage (n = 1), a facial angioma (n = 1), a facial mass (n = 1), hydrocephalus (n = 5), unilateral ventricular enlargement (n = 1), atrophy (n = 4), a porencephalic cyst (n = 1) and normal appearances of the brain in 18 cases. Twenty-two of the fetuses were born alive, and the clinical and/or neuroradiological examination confirmed the antenatal findings. The diagnosis was also confirmed in 8 cases in which a neuropathological examination was possible.

Fast-scan magnetic resonance imaging in fetal visualization

Magnetic resonance imaging has potential as an imaging technique in obstetrics. Its application has been limited by the amount of image degradation that occurs as a result of fetal movement during the long imaging times. By use of a fast-scan imaging technique good images are obtained of fetal anatomy in 3 to 14 seconds per image, depending on the setting used. Different organs could be visualized by varying the setting. Magnetic resonance imaging complements the role of ultrasonography in fetal visualization. It also allows clear fetal imaging in such high-risk situations as maternal obesity and oligohydramnios, where it may be difficult to produce clear images by ultrasonography. This technique will allow wider application of magnetic resonance imaging in obstetrics and give additional information about the developing fetus.

[Fetal curarization by umbilical cord puncture during pregnancy]

Two cases of foetal neuromuscular blockade carried out to obtain foetal immobility during long procedures (in utero foetal exchange transfusion, foetal imaging) are reported. The blockade was carried out in the operating theatre, the mother being awake. Foetal weight had been estimated according to usual echographic parameters. After a long needle had been inserted in the umbilical vein under the guidance of ultrasonography, 0.1 mg.kg-1 vecuronium was injected. Muscle paralysis lasted for about 2 hours in both cases, foetal movements returning spontaneously. There were no side effects due to this technique, a transient foetal bradycardia excepted. Foetal neuromuscular blockade by direct cord injection of muscle relaxants seems to be a simpler, and perhaps safer, technique than obtaining foetal immobility by maternal anaesthesia.

Holoprosencephaly: prenatal diagnosis by sonography and magnetic resonance imaging

Magnetic resonance (MR) imaging was performed on two women at the 33rd and 34th pregnancy week, respectively, after ultrasonographic detection of a brain malformation. Fetal neuromuscular blockade was induced by pancuronium bromide injected into the umbilical vein under continuous ultrasound (US) guidance. MR images supported the echotomographic diagnosis of holoprosencephaly, improving the image quality and offering additional information in such cases of difficult differential fetal diagnosis. Holoprosencephaly was finally confirmed by neonatal US and autopsy (case 1), US, CT and MR (case 2).

The use of magnetic resonance imaging for the diagnosis of fetal intracranial anomalies

While fetal cranial sonography has been used for the sensitive detection of ventriculomegaly, ancillary imaging techniques may be needed for precise delineation of structural abnormalities. This report outlines the radiologic and clinical results using maternal magnetic resonance imaging (MRI) in ten patients with suspected fetal intracranial anomalies. Imaging was accomplished at 17-39 weeks gestational age, using spin-echo, a multislice technique with intramuscular morphine sulfate for sedation. In four cases, MRI significantly clarified the sonographic diagnosis, while in two cases the scan agreed with the sonographic findings. In one patient, MRI failed to image a lumbar meningomyelocele associated with the Chiari II malformation. In two patients with the Chiari II malformation, both sonography and MRI failed to delineate the anatomic pathology completely. Optimal imaging resolution was achieved in the third trimester. Four patients died in the perinatal period. All the surviving patients required shunting to treat intracranial hypertension: only two patients were meeting cognitive milestones. We conclude that due to the high incidence of multiple anomalies in the fetus with ventriculomegaly, precision in neuroradiological diagnosis is essential. MRI can be a useful adjunct to cranial sonography for the specific delineation of abnormalities of the fetal central nervous system.

Schizencephaly: prenatal diagnosis by computed sonography and magnetic resonance imaging

Magnetic resonance (MR) imaging was performed at 29 weeks of pregnancy after ultrasonographic detection of an abnormal cleft in the fetal brain. Fetal neuromuscular blockade was induced by pancuronium bromide injected into the umbilical vein under continuous ultrasound (US) guidance. MR images supported the echotomographic diagnosis of schizencephaly improving the visualization of symmetrical broad clefts connecting the lateral ventricles with the subarachnoid space. Schizencephaly was finally confirmed by neonatal US, computed tomography, and MR.