When an ultrasound isn’t enough: Making a case for fetal MRIs
Ultrasounds might be the modality of choice for diagnosing fetal conditions pre-delivery, but expectant mothers might benefit more from an MRI scan, a team of researchers reported in the American Journal of Roentgenology this month.
Despite the fact that ultrasounds are the go-to imaging tool for prenatal diagnosis, MRIs are often referred if a fetus presents with central nervous system or congenital abnormalities, Baltimore-based author Elizabeth Snyder, MD, and colleagues wrote. Combined with multidisciplinary input from specialists in pediatric radiology, fetal medicine and subspecialties, MRIs have been shown to influence parental counseling, as well as prenatal and postnatal care.
“With the increased use of fetal therapy techniques, MRI has had an expanded role in evaluating these patients both before and after therapy,” the authors said. “Although a few previous articles have addressed the role of MRI in specific pathologic conditions, the published literature has a paucity of reviews of the overall role of MRI in evaluation of the fetus in the age of fetal therapy.”
Snyder and her team aimed to highlight the added value of fetal MRIs in their study, focusing on MRI as a problem-solving tool in congenital cases of fetal chest, abdomen and pelvic anomalies.
In a woman’s first trimester of pregnancy, fetal MRIs are typically conducted exclusively for maternal indications, Snyder et al. wrote. Though MRI doesn’t pose any risk to a fetus during the first trimester, large quantities of amniotic fluid and the small size of the fetus mean motion artifacts are more likely. Still, the authors said, fetal MRI has the potential for higher inherent tissue-specific anatomic and functional imaging contrast.
At Charlotte R. Bloomberg’s Children Center, Snyder and the researchers looked at a number of anomalies in the context of both MRI and traditional ultrasound. These were some of their findings:
- Congenital pulmonary airway malformation. CPAM is the most common congenital lung lesion, the authors wrote, and it’s caused by developmental abnormalities in the lower respiratory tract. Prenatal ultrasounds are usually significant to diagnose and assess CPAM, but fetal MRI could aid in evaluating complex or equivocal cases.
- Congenital lobar overinflation. Ultrasounds can typically differentiate a case of CLO from CPAM, but MRIs are likely much more accurate indicators of disease. Using ultrasound alone to diagnose the condition “leads to underestimation of the clinical picture, which may affect planning for postnatal management,” Snyder and colleagues said.
- Congenital diaphragmatic hernia. CDH, a malformation of the diaphragm that’s linked to high mortality rates, can be diagnosed with an ultrasound, but a fetal MRI could shed light on specific contents of the hernia.
- Abdominal wall defects. Certain conditions like gastroschisis are sufficiently identified with an ultrasound, the authors said, but in cases where a diagnosis is uncertain, an MRI could clear up confusion.
- Abdominal masses. These might be rare, but missing an accurate diagnosis in the case of a congenital abdominal mass could mean delivery method and postnatal management suggestions are skewed. MRIs can more accurately identify the locations of these intraabdominal masses.
- Adrenal masses. Diagnosing neuroblastoma—the most common neonatal malignancy—is possible with an ultrasound, but fetal MRI could aid in differentiating the mass among other suprarenal masses and can help detect metastasis.
“A state-of-the-art fetal MRI protocol with pediatric radiologists present in the MRI suite at imaging ensures high-quality images and allows emphasis on patient-centered care, which maximizes the added value of fetal MRI,” Snyder and co-authors wrote. “As shown in these cases of complex thoracic, abdominal and pelvic anomalies of the fetus, MRI can serve as a problem-solving tool, guiding prenatal counseling and therapy after prenatal ultrasound, which remains the primary prenatal imaging tool.”
After graduating from Indiana University-Bloomington with a bachelor’s in journalism, Anicka joined TriMed’s Chicago team in 2017 covering cardiology. Close to her heart is long-form journalism, Pilot G-2 pens, dark chocolate and her dog Harper Lee.