Winter 2006

MRI Provides Insights into Fetal Brain

Technological advancements have made it possible to produce detailed magnetic resonance imaging (MRI) of a fetus in the womb, making MRI an increasingly important clinical tool for diagnosing fetal abnormalities and understanding normal fetal development, UCSF physicians say.

"We often get patients referred to us when there is an abnormality detected on routine, prenatal ultrasound (such as mild ventriculomegaly)," says UCSF researcher Orit Glenn, M.D. "Referrals also come when the ultrasound is normal, but there is a family history of a neurological disorder or pregnancy complications such as monochorionic twinning."

MRI provides higher resolution images than ultrasound and can detect more subtle defects. "We look for additional abnormalities and try to use the additional information we get from MRI to make a specific diagnosis, which often influences prenatal counseling and genetic testing, as well as counseling for recurrence risk in future pregnancies," Glenn says.

To fully utilize the latest technologies in pediatric neuroscience, UCSF physicians and investigators are establishing the Comprehensive Center for Brain Development. The center will conduct multidisciplinary prenatal and postnatal evaluations. The center is being developed by Glenn along with colleagues Elliott Sherr, M.D., a pediatric neurologist; Mary Norton, M.D., director of Prenatal Diagnosis; and Ruth Goldstein, M.D., a radiologist.

Although referrals usually call for MRI scans of the brain, at other times images are requested of the spine, neck or body. UCSF radiologists perform MRI scans of the brain on about 100 fetuses a year, a figure that has grown over the years. Fetal MRI is usually done starting in the 22nd week of gestation, when the head has grown large enough to provide good resolution.

Getting good MR images of the fetus has become possible only in recent years, due to the development of new scanning techniques and software, Glenn says. Although some imaging technologies — like ultrasound and X-rays — work very quickly, MRI normally requires that the subject remain motionless for minutes while the scan is completed. In Europe during the 1980s, there were some clinicians who managed to get good images by injecting a paralytic agent into the umbilical cord, but U.S. researchers have never followed this course, she says.

What made the difference was a new generation of ultrafast MRI machines and changes in software that allow radiologists to adjust to movement on the fly. "Physicists from GE came to work with us to develop programs specifically for fetal MRI," Glenn says. Only a few other medical centers in the United States use this technology.

In the standard MRI system, a number of images have to be taken in a particular sequence and with particular orientations, a process that requires the fetus to be motionless for two to three minutes. If the fetus moves during this time, the whole sequence is halted, requiring a delay of several minutes while the sequence and the orientation of the machine are reset.

The new software allows radiologists to change the parameters of the scan in real time during the sequence without the need to reset the machine. If the fetus tilts its head, the orientation of the scan is adjusted and the imaging process continues.

"Real-time imaging has revolutionized how we image the fetus here at UCSF," Glenn says. "It means that imaging takes less time for the patients and less time for the technologists, while still providing high-resolution, useful images." The use of MRI also will assist researchers who want to understand normal fetal development, Glenn says.

Dr. Orit Glenn encourages referrals from physicians in clinical practice. For more information, contact her at orit.glenn@radiology.ucsf.edu

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