Magnetic resonance imaging of fetal thoracic abnormalities

Isolated unilateral pulmonary agenesis and other fetal thoracic anomalies

IMPORTANCE

Although the diagnostic workup and management regimens for many of the common fetal thoracic lesions have been well described, the understanding of pulmonary agenesis is more limited. A better understanding of the published reports of this condition is essential to provide proper care for these complicated pregnancies.

OBJECTIVE

The aims of this study were to provide a better understanding of the difficulties in the diagnosis and management of fetal thoracic lesions and to consolidate what is known about unilateral pulmonary agenesis.

EVIDENCE ACQUISITION

We performed a review of the English medical literature covering the last 20 years (1993-2013) in PubMed, MEDLINE, and MD Consult using search terms pulmonary agenesis, pulmonary aplasia, unilateral pulmonary agenesis, unilateral pulmonary aplasia, lung agenesis, lung aplasia, unilateral lung agenesis, and unilateral lung aplasia.

RESULTS

Prenatal diagnosis of pulmonary agenesis and other fetal thoracic lesions can be particularly challenging given that many anomalies have similar appearance on ultrasound. Fetal magnetic resonance imaging has been used in several of the reported cases to clarify the diagnosis. Once confirmed, there are several important prognostic factors to consider in the management of unilateral pulmonary agenesis. Poor prognostic factors include right-sided agenesis, the presence of genetic abnormalities, and other associated congenital anomalies.

CONCLUSION AND RELEVANCE

Fetal magnetic resonance imaging can be a useful imaging modality when the diagnosis is unclear after ultrasound imaging. The management of cases with a poor prognosis should be guided by the nature of the associated anomalies. Cases of isolated pulmonary agenesis have an overall good prognosis and can be managed conservatively during pregnancy, with consideration of delivery at a tertiary care facility in case postnatal respiratory issues arise.

Fetal magnetic resonance imaging: a review

PURPOSE OF REVIEW

To describe advances in magnetic resonance technology and the current indications and advantages of magnetic resonance imaging that have led to increased utilization in fetal medicine.

RECENT FINDINGS

The article covers the most common uses of magnetic resonance imaging in fetal medicine. The advantages of magnetic resonance imaging for the diagnosis of fetal malformations are described, in particular the advantages of magnetic resonance imaging in central nervous system malformations not optimally diagnosed by ultrasound are described. These cases include malformations of migration, malformations of development, such as agenesis of the corpus callosum, and destructive lesions. Noncentral nervous system lesions include chest abnormalities, abdominal wall defects, gastrointestinal and genitourinary abnormalities and fetal neoplasms. Abnormalities of placentation and other maternal factors affecting pregnancy are shown.

SUMMARY

Recent studies have shown that magnetic resonance imaging can add significantly to the prenatal diagnosis and management of congenital abnormalities. In addition, placental abnormalities have been diagnosed with greater accuracy.

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.

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.

Imaging the fetal spine using in utero MR: diagnostic accuracy and impact on management

BACKGROUND

In-utero MR imaging (iuMR) has entered the clinical arena during the last decade. It is used mainly for imaging fetal brain abnormalities.

OBJECTIVE

To report our experience of imaging the fetal spine and spinal cord in fetuses with known or suspected abnormalities diagnosed on US imaging.

MATERIALS AND METHODS

Prospective imaging and retrospective analysis of the possible impact on management of 50 consecutive fetuses with spinal abnormalities detected by antenatal US imaging.

RESULTS

In 40 (80%) of 50 fetuses, iuMR and US imaging were in complete agreement. In the other 10 fetuses (20%), iuMR provided additional information or changed the diagnosis, including 8 fetuses where the iuMR could find no abnormality and was found to be correct by later follow-up.

CONCLUSION

IuMR is useful in fetuses with a suspected spinal abnormality. The clinical impact of iuMR may be numerically less than with brain abnormalities, but is still sufficient to warrant its use, especially if there is any uncertainty about the US imaging, and particularly as a relatively high proportion of diagnoses on US imaging are false-positives.

Fetal Lung Volume Measurements: Determination with MR Imaging—Effect of Various Factors

PURPOSE

To retrospectively determine the effect of gestational age (GA), imaging plane, section thickness, and inter- and intraobserver variability on fetal lung volume (FLV) measurements obtained with magnetic resonance (MR) imaging in a cohort of fetuses without thoracic abnormalities.

MATERIALS AND METHODS

Institutional review board approval was obtained. Informed consent for this retrospective cohort study was waived, and the conduct of this study was HIPAA compliant. FLV was measured in 30 fetuses (GA, 17-36 weeks) referred for MR imaging for indications other than pulmonary abnormalities. Measurements were made on single-shot fast spin-echo images by tracing free-form regions of interest on individual consecutive sections in the transverse, sagittal, and coronal planes. Measurements were performed twice by two observers independently. Correlations between FLV and GA, imaging plane, and section thickness were assessed, as were intra- and interobserver variability. Time to perform FLV was assessed in a subset of fetuses.

RESULTS

Total FLV ranged from 2 to 110 mL. Mixed-effects regression model showed significant quadratic trend in FLV with increasing GA, with comparable strength of correlation (r = 0.89-0.91) in the three imaging planes of measurement. Intraobserver agreement was good in all three planes (r = 0.65-0.83) and was highest in the transverse plane. Interobserver agreement was good in all three planes (r = 0.68-0.76). FLV showed no significant dependence on section thickness (P = .23) or imaging plane (P = .82). Mean time to obtain FLV measurements ranged from 48 seconds at GA of 21 weeks to 77 seconds at GA of 29-30 weeks.

CONCLUSION

GA-based FLV measurements obtained with MR images are independent of section thickness and imaging plane and can be performed with good inter- and intraobserver agreement in less than 2 minutes.

MRT des fetalen Abdomens

Magnetic resonance imaging (MRI) is an important diagnostic component for central nervous system and thoracic diseases during fetal development. Although ultrasound remains the method of choice for observing the fetus during pregnancy, fetal MRI is being increasingly used as an additional technique for the accurate diagnosis of abdominal diseases. Recent publications confirm the value of MRI in the diagnosis of fetal gastrointestinal tract and urogenital system diseases. The following report provides an overview of MRI-examination techniques for the most frequent diseases of the abdomen.

Fetal abdominal magnetic resonance imaging

This review deals with the in vivo magnetic resonance imaging (MRI) appearance of the human fetal abdomen. Imaging findings are correlated with current knowledge of human fetal anatomy and physiology, which are crucial to understand and interpret fetal abdominal MRI scans. As fetal MRI covers a period of more than 20 weeks, which is characterized not only by organ growth, but also by changes and maturation of organ function, a different MR appearance of the fetal abdomen results. This not only applies to the fetal intestines, but also to the fetal liver, spleen, and adrenal glands. Choosing the appropriate sequences, various aspects of age-related and organ-specific function can be visualized with fetal MRI, as these are mirrored by changes in signal intensities. Knowledge of normal development is essential to delineate normal from pathological findings in the respective developmental stages.

Three-dimensional volume rendering of fetal MR images for the diagnosis of congenital cystic adenomatoid malformation

RATIONALE AND OBJECTIVES

Great expertise is necessary to mentally compile a series of individual two-dimensional image sections into a three-dimensional (3D) composite view that can aid in differential diagnosis. The purpose of this study was to test 3D volume-rendering techniques for differentiating congenital cystic adenomatoid malformation from congenital diaphragmatic hernia.

MATERIALS AND METHODS

The authors acquired T2-weighted magnetic resonance (MR) images of a 27-week fetus in the sagittal plane and then applied the 3D volume-rendering method to the MR image data sets to obtain a composite 3D image.

RESULTS

It was unclear on the MR images whether the intestines were situated above or below the diaphragm. The composite image showed that the intestines were not herniated into the chest, and this facilitated a diagnosis of congenital cystic adenomatoid malformation rather than congenital diaphragmatic hernia.

CONCLUSION

The 3D volume-rendering techniques aided in the assessment of fetal organ structure and could be applied also to preoperative simulation and planning of fetal surgery.