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MRI PROVIDES MORE DETAILED INFORMATION THAN FETAL ULTRASOUND
CHICAGO -- Magnetic resonance imaging (MRI) is now being used as a follow-up to provide more information when fetal abnormalities are suspected at a prenatal ultrasound exam, according to the results of two studies being presented here today at the 85thScientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).
"Ultrasound is a wonderful tool, but it is sometimes limited in what it reveals," said Fergus Coakley, M.B.B.Ch., associate clinical professor of radiology at the University of California, San Francisco, and lead author of a study using MRI to assess potential fetal abnormalities. "If a radiologist says to an expectant couple, 'I don't like the way your fetus's brain is forming,' then they're terrified. MRI gives them a very powerful tool to provide more information. When the possibility is that the fetus ranges from near normal to being in devastatingly poor health, it means a lot."
"In some cases, MRI can tell parents not to worry, that everything is normal, even when an abnormality was suspected on ultrasound," said Mary C. Frates, M.D., assistant professor of radiology, Harvard Medical School, radiologist at Brigham & Women's Hospital and co-author of the second study, which focused on using MRI to assess central nervous system and genitourinary abnormalities.
Recently developed ultrafast MRI techniques now make it possible to routinely obtain high-quality diagnostic images of the fetus, without sedation or anesthesia. This was not possible previously, because fetal motion degraded the images using older and slower MRI techniques. Currently, it is only used in selected cases in which fetal abnormalities are suspected. Prior to MRI, parents given questionable or bad news after an ultrasound had no other options for further investigating the situation.
MRI, like ultrasound, is safe for fetuses; unlike X-ray, these imaging methods use no radiation. MRI creates images based on magnetic fields within the body. Currently, MRI is available to assess fetal abnormalities at many state-of-the-art imaging facilities.
Abnormalities can range from urinary tract deformities or hydrocephalus, known as "water on the brain," to complex problems, such as the two halves of the brain not being linked together or heart disorders.
MRI Can Help Couples Decide How to Manage Problematic Pregnancies
In the University of California, San Francisco, study, 45 pregnant women were referred for MRI to assess suspected fetal abnormalities detected on ultrasound. MRI findings agreed with ultrasound in 36 cases (80 percent) and added additional information in 12 of those cases (27 percent). MRI correctly clarified results when there was a discrepancy in the reading of the ultrasound in 4 cases (9 percent). MRI also provided information that was unclear on ultrasound in 2 cases (4 percent). Since the study, 19 women delivered without further interventions (four of the babies died after birth); intrauterine surgery was successfully performed on 6 fetuses; 6 pregnancies were terminated; and the outcome was unknown in 14 pregnancies. Information from MRI changed management of the pregnancy in 6 cases, said Dr. Coakley.
"MRI can play an invaluable role when couples are faced with an ultrasound diagnosis of a possibly life-threatening birth defect," said Dr. Coakley. "That is especially true when surgery may be an option, either in-utero or immediately after birth. The extra clarification available with an MRI can help parents and their doctors decide on a plan of action."
Central Nervous System And Genitourinary Problems Seen on MRI
In the Harvard Medical School study, 35 pregnant women were referred for MRI, and 13 of those were included in the study of fetal MRI. In 9 cases that involved suspected central nervous system disorders, MRI confirmed ultrasound findings in all 9 and provided additional information in 2 cases. In suspected genitourinary abnormalities, MRI agreed with the ultrasound diagnoses in all 4 cases, with additional information provided in 1 case. Two women had been referred because of a serious fetal brain problem in a prior pregnancy, and in both cases, the imaged fetus was healthy. One pregnancy was terminated. In the 12 other cases, the babies were delivered (two died shortly after birth) and MRI was correct in all but one genitourinary case early in the study, in which the absence of kidneys was missed by both MRI and ultrasound. The 22 cases not included in the fetal study involved questions about the mother's anatomy, including the uterus, placenta and ovaries.
"Brigham & Women's Hospital researchers are currently investigating an expanded role of MRI in less severe cases, for instance to assess intrauterine growth and to determine if fetal lungs are mature and baby is ready for delivery," said Dr. Frates.
Co-authors of a paper on the topic being presented by Dr. Coakley include: Hedvig Hricak, M.D., Ph.D.; Roy A. Filly, M.D.; Anthony J. Barkovich, M.D.; and Michael R. Harrison, M.D.
Co-authors of a paper on the topic being presented by Dr. Frates include: Clare M. Tempany, M.D.; Ada J. Kumar, M.D.; Valerie L. Ward, M.D.; Carol B. Benson, M.D.; Allan S. Nadel, M.D.; Peter M. Doubilet M.D., Ph.D; Carol Barnewolt, M.D.; and Diego Jaramillo, M.D.
The RSNA is an association of 31,000 radiologists and physicists in medicine dedicated to education and research in the science of radiology. The Society's headquarters are located at 820 Jorie Blvd., Oak Brook, Illinois 60523-2251.
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Note: Copies of 1999 RSNA news releases are available online at http://www.pcipr.com/rsna beginning Monday, Nov. 29.
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