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

Visualising uncertainty: Examining women's views on the role of Magnetic Resonance Imaging (MRI) in late pregnancy

Prenatal screening occupies a prominent role within sociological debates on medical uncertainty. A particular issue concerns the limitations of routine screening which tends to be based on risk prediction. Computer assisted visual technologies such as Magnetic Resonance Imaging (MRI) are now starting to be applied to the prenatal realm to assist in the diagnosis of a range of fetal and maternal disorders (from problems with the fetal brain to the placenta). MRI is often perceived in popular and medical discourse as a technology of certainty and truth. However, little is known about the use of MRI as a tool to confirm or refute the diagnosis of a range of disorders in pregnancy. Drawing on qualitative research with pregnant women attending a fetal medicine clinic in the North of England this paper examines the potential role that MRI can play in mediating pregnancy uncertainty. The paper will argue that MRI can create and manage women's feelings of uncertainty during pregnancy. However, while MRI may not always provide women with unequivocal answers, the detailed information provided by MR images combined with the interpretation and communication skills of the radiologist in many ways enables women to navigate the issue. Our analysis of empirical data therefore highlights the value of this novel technological application for women and their partners. It also seeks to stress the merit of taking a productive approach to the study of diagnostic uncertainty, an approach which recognises the concepts dual nature.

Fetal magnetic resonance imaging and ultrasound

Magnetic resonance imaging (MRI) has been increasingly adopted in obstetrics practice in the past three decades. MRI aids prenatal ultrasound and improves diagnostic accuracy for selected maternal and fetal conditions. However, it should be considered only when high-quality ultrasound cannot provide certain information that affects the counseling, prenatal intervention, pregnancy course, and delivery plan. Major indications of fetal MRI include, but are not restricted to, morbidly adherent placenta, selected cases of fetal brain anomalies, thoracic lesions (especially in severe congenital diaphragmatic hernia), and soft tissue tumors at head and neck regions of the fetus. For fetal anatomy assessment, a 1.5-Tesla machine with a fast T2-weighted single-shot technique is recommended for image requisition of common fetal abnormalities. Individual judgment needs to be applied when considering usage of a 3-Tesla machine. Gadolinium MRI contrast is not recommended during pregnancy. MRI should be avoided in the first half of pregnancy due to small fetal structures and motion artifacts. Assessment of fetal cerebral cortex can be achieved with MRI in the third trimester. MRI is a viable research tool for noninvasive interrogation of the fetus and the placenta.

'You're looking for different parts in a jigsaw': foetal MRI (magnetic resonance imaging) as an emerging technology in professional practice

Magnetic resonance imaging (MRI) was first introduced into clinical practice during the 1980s. Originally used as a diagnostic tool to take pictures of the brain, spine, and joints, it is now used to visualise a range of organs and soft tissue around the body. Developments in clinical applications of the technology are rapid and it is often viewed as the 'gold standard' in many areas of medicine. However, most existing sociological work on MRI tends to focus on the profession of radiology, little is known about the impact of MRI on a broader range of clinical practice. This article focuses on MRI use in pregnancy, a relatively new application of the technology. Drawing on empirical research with a range of health professionals (from radiologists to pathologists) in the North of England, this article asks: how do different types of health professionals engage with the technology and to what end? It will argue that MRI use in pregnancy offers an increasingly important piece of the diagnostic jigsaw, often acting as a bridging technology between medical specialties. The implications of this will be explored in the context of broader sociological debates on the 'visualisation' of medicine and its impact on professionals.

Standardized fetal anatomical examination using magnetic resonance imaging: a feasibility study

OBJECTIVE

To determine whether a standard complete fetal anatomical survey, as recommended for ultrasound examination guidelines, is feasible using a standardized magnetic resonance imaging (MRI) protocol.

METHODS

Based on guidelines for ultrasound examination, we created a specific MRI protocol for fetal anatomical survey. This protocol was then tested prospectively in 100 women undergoing fetal MRI examination for various specific indications at a median gestational age of 30 weeks. The feasibility of using MRI to perform the fetal anatomical survey was analyzed by two reviewers (A and B) based on 26 predefined anatomical criteria, yielding a score ranging from 0 to 26 (26 meaning successful complete anatomical study). Reproducibility was analyzed using percentage agreement and modified kappa statistics.

RESULTS

The mean score for the standardized MRI anatomical survey was 24.6 (SD, 1.4; range, 15-26) for Reviewer A and 24.2 (SD, 1.7; range, 15-26) for Reviewer B (P = 0.1). Twenty-two, two and two criteria could be assessed in > 95%, 80-95% and < 80% of cases by Reviewer A and 19, four and three criteria could be assessed in > 95%, 80-95% and < 80% of cases by Reviewer B. For both reviewers, the two most difficult criteria to evaluate were aorta and pulmonary artery. Inter-reviewer agreement was above 90% for 22 of the 26 anatomical criteria and adjusted kappa coefficients for each criterion demonstrated good, moderate and poor agreement for 22, two and two criteria, respectively.

CONCLUSION

Our data support the hypothesis that standardized fetal anatomical examination might be achieved and reproducible using MRI, although improvement is required for the cardiac part of the examination.

Techniques, terminology, and indications for MRI in pregnancy

Fetal MRI is now a well-established imaging modality for the diagnostic evaluation of fetuses with congenital anomalies. In this article, the authors provide a brief overview of the physical principles involved in fetal MRI imaging, the sequences that are used in clinical practice today, current indications, and limitations. A review of current evidence supports the following indications for fetal MRI: suspected central nervous system anomalies, neck and oropharyngeal masses, diaphragmatic hernia, abdominal masses or bowel pathology not fully characterized by ultrasonography, and suspected fetal infection. Other indications should be decided on a case-by-case basis with close collaboration between the departments of maternal-fetal medicine and radiology. More research is needed to determine the role of fetal MRI in functional neuroimaging at higher magnetic field strengths (3T).

Ultrasound diagnosis of fetal neck masses: a case series

Fetal neck masses are rare and may not be apparent during the second trimester fetal anomaly screening scan. It is essential to distinguish the different pathologies as it influences prenatal counseling, antenatal, and postnatal management. Furthermore, some causes may be amenable to in utero treatment. Others have a poor prognosis due to their association with congenital syndromes and aneuploidies. Differentiating the various neck masses and reaching an accurate diagnosis are a challenge. This requires a systematic approach, time and patience, together with an experienced sonographer. Ancillary investigations like karyotyping and magnetic resonance imaging may be used as well. It is important to attain an accurate diagnosis and to follow up the fetus with serial scans as this affects antenatal counselling and prognosis as well as the mode of delivery. Here, we present four cases of fetal neck masses that were seen at our antenatal diagnostic centre and highlight the distinguishing ultrasound features of each. This will enable one to approach the ultrasound diagnosis of fetal neck masses in a methodical and logical manner.

Magnetic resonance imaging in the evaluation of the fetal spinal canal contents

Ultrasonography (US) remains the first method in the evaluation of fetal central nervous system (CNS) abnormalities but in case of the spinal canal and cord it is often insufficient since the bony structures may obscure these structures. Prenatal magnetic resonance imaging (MRI) is therefore the final noninvasive tool for the assessment of these malformations allowing for correction of sonographic findings, revealing the full extent of complex lesions and choosing the candidates for in utero treatment. The authors present the most frequent anomalies of spinal canal and spinal cord in the consecutive phases of pregnancy, illustrated with their own MR images, with reference to the literature and own experience. In 58 out of 252 fetuses examined due to suspicion of CNS anomalies (23.0%) the spinal canal and spinal cord abnormalities were found on MRI. The cases of diastematomyelia, myelomeningocele, tethered cord, caudal regression syndrome, anterior meningocele, cystic sacrococcygeal teratoma and syringohydromyelia are demonstrated.

Magnetic Resonance Imaging of the Fetal Central Nervous System in Singapore

The dual energy CT (DECT) technology has been recently employed in the form of two X-ray sources of different energies to enhance the contrast between adjacent structures. Its use in the cardiac arena has been widely highlighted due to the higher temporal resolution. However, it may also be used in the craniocervical and peripheral vasculature for better differentiation between contrast-enhanced vascular lumina and calcified plaques, in the characterisation of ureteric stones, and in the evaluation of hepatic lesions. The objective of this paper is to revisit DECT physics, review the literature and discuss its use in CT neuroangiography with case illustrations from our institution, and impact on dose savings. Key words: Craniocervical CT angiography, Intracranial aneurysms, Radiation dosage, Vascular stenosis

Fetal central nervous system malformations on MR images

Sonography is the method of choice for prenatal malformation screening but it does not always provide sufficient information for correct diagnosis or adequate abnormality evaluation. Fetal magnetic resonance imaging (MRI) is considered as a valuable second line imaging tool for confirmation, completion and correction of sonographic findings. Fetal MRI has proven its value in the evaluation of central nervous system pathologies, especially of midline and posterior fossa malformations. The role of MRI is not only to confirm or exclude possible lesions but also to define their full extent, aiding in their characterization, and to demonstrate associated abnormalities. The authors describe the most common anomalies of CNS revealed by fetal MRI in a chronological way related to the age of pregnancy, with a review of own MR images and with reference to the literature and own experience.

Fetal Magnetic Resonance Imaging as a Complement to Fetal Ultrasonography

Ultrasonography is the screening method of choice for the evaluation of the fetus. It is safe, inexpensive, and easily performed. However, it is operator dependent, and evaluation may be limited because of fetal position, maternal obesity, overlying bone, and/or oligohydramnios. Magnetic resonance imaging is an alternative modality that uses no ionizing radiation, has excellent tissue contrast and a large field of view, is not limited by obesity or overlying bone, and can image the fetus in multiple planes, no matter the fetal lie. Faster scanning techniques allow studies to be performed without sedation in the second and third trimester with minimal motion artifact.

Foetal magnetic resonance imaging and echogenic bowel

OBJECTIVES

To evaluate how foetal magnetic resonance imaging (MRI) may change the diagnosis in cases of ultrasound (U/S) findings of echogenic bowel (EB).

METHODS

Seventeen foetuses with EB underwent serial U/S examinations, foetal MRI, cystic fibrosis screening and maternal viral serologic tests. MRI protocol included T2-weighted half-Fourier acquired single-shot turbo spin-echo (HASTE) sequence and gradient echo (GE) T1-weighted images. Foetal abdominal MRI analyzed patterns were size and signal of small bowel, colon and rectum, ascites and abdominal mass. All neonates had complete clinical examination, abdominal sonography, and a 6 months clinical follow-up.

RESULTS

Eleven foetuses with isolated EB had normal MRI and normal outcome. In comparison, all the 6 foetuses whose U/S patterns showed associated signs had abnormal MRI (p < 0.001). Five had proven pathology (83.3%: 5/6) and only 1 (16.7%: 1/6) had no proven pathology and normal postnatal outcome (p = 0.001). For those five, foetal MRI showed bowel abnormalities with one case of bowel duplication and four cases of bowel obstruction. Two out of the four cases of bowel obstruction were genetically diagnosed as cystic fibrosis. The two remaining cases were diagnosed as ileal atresia.

CONCLUSION

MRI could provide additive information in cases of EB associated with bowel dilatation.

Dynamic motion analysis of fetuses with central nervous system disorders by cine magnetic resonance imaging using fast imaging employing steady-state acquisition and parallel imaging: a preliminary result

OBJECT

The authors present a novel cine magnetic resonance (MR) imaging, two-dimensional (2D) fast imaging employing steady-state acquisition (FIESTA) technique with parallel imaging. It achieves temporal resolution at less than half a second as well as high spatial resolution cine imaging free of motion artifacts for evaluating the dynamic motion of fetuses in utero. The information obtained is used to predict postnatal outcome.

METHODS

Twenty-five fetuses with anomalies were studied. Ultrasonography demonstrated severe abnormalities in five of the fetuses; the other 20 fetuses constituted a control group. The cine fetal MR imaging demonstrated fetal head, neck, trunk, extremity, and finger as well as swallowing motions. Imaging findings were evaluated and compared in fetuses with major central nervous system (CNS) anomalies in five cases and minor CNS, non-CNS, or no anomalies in 20 cases. Normal motility was observed in the latter group. For fetuses in the former group, those with abnormal motility failed to survive after delivery, whereas those with normal motility survived with functioning preserved. The power deposition of radiofrequency, presented as specific absorption rate (SAR), was calculated. The SAR of FIESTA was approximately 13 times lower than that of conventional MR imaging of fetuses obtained using single-shot fast spin echo sequences.

CONCLUSIONS

The following conclusions are drawn: 1) Fetal motion is no longer a limitation for prenatal imaging after the implementation of parallel imaging with 2D FIESTA, 2) Cine MR imaging illustrates fetal motion in utero with high clinical reliability, 3) For cases involving major CNS anomalies, cine MR imaging provides information on extremity motility in fetuses and serves as a prognostic indicator of postnatal outcome, and 4) The cine MR used to observe fetal activity is technically 2D and conceptually three-dimensional. It provides four-dimensional information for making proper and timely obstetrical and/or postnatal management decisions.

Liver, meconium, haemorrhage: the value of T1-weighted images in fetal MRI

BACKGROUND

Ultrafast T2-weighted (T2-W) MRI sequences are currently considered a routine technique for fetal MR imaging. Limited experience exists with fetal T1-weighted (T1-W) imaging techniques.

OBJECTIVE

To determine MRI patterns of some fetal abdominal or haemorrhagic disorders with particular respect to the diagnostic value of T1-W images.

MATERIALS AND METHODS

In addition to standard T2-W single-shot sequences, T1-W single-shot and/or multislice sequences were employed in 25 MR examinations performed in 23 fetuses between 20 and 36 weeks of gestation for more detailed assessment of liver, meconium-filled digestive tract, haemorrhage, or further characterization of a fetal abdominal mass. Diagnostic value and presence of motion artefacts on T1-W images was recorded in each case.

RESULTS

T1-W images enabled superior delineation of fetal liver and large intestine. They provided additional diagnostic information in 9 (39%) of 23 fetuses. One false-positive and one false-negative MRI diagnosis of malrotation anomaly were encountered. Use of single-shot T1-W sequences reduced the occurrence of motion artefacts in 64%.

CONCLUSION

Our results suggest that the specific signal properties of methaemoglobin, meconium and liver are sufficiently important for T1-W sequences to become a routine part of fetal MRI protocols when dealing with digestive tract anomalies, diaphragmatic and abdominal wall defects, intraabdominal masses, and fetal haemorrhage.

Rhabdomyoma of the Head and Neck Demonstrated by Prenatal Magnetic Resonance Imaging

A case of fetal rhabdomyoma (myxoid type) of the head and neck demonstrated on prenatal magnetic resonance imaging (MRI) is presented. This benign tumor of skeletal muscle is uncommon and should not be confused with its malignant counterpart-rhabdomyosarcoma. With the increasing use of ultrafast MRI, the radiologist is more likely to encounter head and neck masses in the fetus.

Neuroimaging in cerebral palsy

Parents and clinicians concerned about high-risk infants and children with motor delay or cerebral palsy seek information on cause, treatment, prognosis, and recurrence risk. Used in combination with history and examination, neuroimaging studies can improve diagnosis and management. In premature infants, cranial ultrasound is a reliable, noninvasive diagnostic modality. Nuclear magnetic resonance techniques including magnetic resonance imaging and diffusion weighted imaging can be used effectively in neonatal encephalopathies. In children with motor delay and cerebral palsy syndromes including spastic diplegia, quadriplegia, hemiplegia, and extrapyramidal movement disorders, conventional magnetic resonance imaging has become an important determinant of diagnosis and management. The aim of this article is to help clinicians select and interpret imaging studies of benefit in clinical care.

Fetal liver magnetic resonance imaging in anterior body wall defects: a study of specimens from the museum of pathology

PURPOSE

The purpose of the study was to evaluate the appearance of liver anatomy in fetuses with complex anterior body wall defects (ABWD) using magnetic resonance imaging (MRI).

METHODS

Nineteen specimens from the National Museum of Pathological Anatomy (Vienna) with a wide range of ABWD were studied on a 1.5-T MR scanner (T1- and T2-weighted sequences) with special focus on the liver and the relationship between the large lesion and the adjacent structures.

RESULTS

The contrast of T2-weighted sequences was superior to that of the T1-weighted images. The liver was found in an intraabdominal location in 3 cases and in a completely extraabdominal location in 11 fetuses. Five fetuses had a very special configuration or position of the liver. Furthermore, the images showed an anteriorly located confluence of hepatic veins into the inferior vena cava in 5 specimens. Associated malformations of the complexly structured malformations involved the urogenital tract, the central nervous system (CNS), the cardiac system and the musculoskeletal system. Prenatal fast magnetic resonance imaging (MRI) in one fetus confirmed the liver in a both inside/outside position, whereas the diagnosis at fetal ultrasound scan (US) in this case had been uncertain.

CONCLUSIONS

These results show that MRI may play an important part in antenatal diagnosis of ABWD, complementary to prenatal US. Prenatal fast MRI should be considered if fetal US yields ambiguous findings.

Prenatal diagnosis of a prolapsed ureterocele with magnetic resonance imaging

Ectopic ureterocele with ureteral duplication is the most common type of ureterocele found in children. Early accurate diagnosis is desirable to decrease the risk of urosepsis and renal damage. Prenatal imaging with ultrasonography detects the vast majority of ureteroceles; however, in some cases, the diagnosis may remain in doubt. We report on the use of magnetic resonance imaging to clarify the prenatal diagnosis of a prolapsed ureterocele.

Intracranial hemorrhage progressing to porencephaly as a result of congenitally acquired cytomegalovirus infection?an illustrative report

OBJECTIVE

To report ultrasound and magnetic resonance imaging (MRI) findings in a fetus with intracranial hemorrhage and porencephaly, presumed secondary to intrauterine cytomegalovirus (CMV) infection.

METHODS

A 20-year-old, G2, P1 woman presented at 28.6 weeks' gestation after ultrasound examination demonstrated apparently isolated fetal ascites. Evaluation included maternal serology, amniocentesis, and repeated ultrasound examinations. Fetal MRI evaluation was also performed. The infant was born at 35 weeks' gestational age.

RESULTS

Maternal serology was positive for CMV IgG. Intrauterine CMV infection was confirmed using polymerase chain reaction (PCR). At 31.6 weeks' gestation, ultrasound demonstrated borderline lateral cerebral ventriculomegaly. MRI of the fetal brain on the same day demonstrated parenchymal hemorrhage in the right posterior temporal and parietal regions along with mild ventricular enlargement. Sonography one day before delivery revealed brain parenchymal cystic change consistent with porencephaly of the right posterior temporal and parietal region. Postnatal ultrasound, computed tomography (CT), and MRI confirmed the diagnosis of a porencephalic cyst communicating with the posterior body of the right lateral ventricle. Placental pathology was consistent with CMV infection.

CONCLUSION

This case report illustrates that fetal MRI is a useful adjunct in the evaluation of intrauterine infection with CMV.

Prenatal imaging of facial clefts by magnetic resonance imaging with emphasis on the posterior palate

OBJECTIVE

To evaluate the role of Magnetic Resonance Imaging (MRI) in the prenatal diagnosis of facial clefts.

MATERIALS AND METHODS

Six fetuses with a sonographic diagnosis of cleft lip and palate underwent MRI at a median age of 30 weeks (range 28-32). The defect was bilateral in two cases.

RESULTS

Fetal MRI confirmed the presence of a cleft involving at least the anterior palate in all cases. Distinction between unilateral and bilateral clefts could be made in all cases and was always confirmed after birth. Sagittal views of the fetal face were found to be particularly useful in identifying the degree of extension of the cleft into the palate. The diagnosis was confirmed after birth.

CONCLUSION

Our results suggest that MRI may be ancillary to ultrasound in prenatal investigation of a fetus with cleft lip, allowing a better staging of the lesion by demonstrating the degree of involvement of the palate.