Most neurological damage occurs to fetuses prior to the onset of labor. Developing a screening tool to detect this damage is one of the goals of a new fetal monitoring system developed by researchers at the University of Arkansas for Medical Sciences in Little Rock.

The high-tech device, nicknamed SARA (Squid Array for Reproductive Assessment), relies on an array of 151 sensors that detect and record extremely weak signals generated from naturally occurring magnetic fields in the body. The system provides a graph that shows the changes in fetal heart rate, brain activity, and other vital functions as well as changes in the mother’s uterus.

Over the last two decades researchers have used SQUID arrays to assess adult brain activity. The technique of recording magnetic signals from the brain is called magnetoencephalography (MEG). Signals captured by the arrays are superimposed over images produced from imaging modalities such as computed tomography and magnetic resonance to give a complete picture of the adult brain and neuromuscular system.

In their research with SARA, Dr. Curtis Lowery, director, division of Maternal-Fetal Medicine, University of Arkansas for Medical Sciences and his colleague Hari Eswaran, director of the SARA Laboratory, University of Arkansas for Medical Sciences, found that the brain and heart signal patterns of healthy fetuses are far more complex than those of fetuses with problems. They have followed 70 patients since they began their fetal MEG research in 2005. "In theory high-risk fetuses produce less complex and more predictable signals than a healthy fetus," explains Lowery. "We now have some evidence that healthy fetuses produce very complex signals."

NIBIB support has allowed the researchers to fine tune SARA’s signal processing capabilities to produce a more complete picture of maternal/fetal heart/brain activity and their relation to uterine activity. "Normally [researchers] record brain and heart activity separately and then correlate it," says Lowery. "With SARA we record both activities on the same computer system so the correlation is easier."

Tracking Brain and Heart Activity

SARA has the potential to provide an array of monitoring capabilities. For instance, the researchers have mapped fetal brain function in response to sound and light stimuli. Early results show that normal fetuses produce responses to these stimuli from a small area of the cortex while spontaneous brain activity involves the whole brain. The investigators also discovered that healthy fetuses can discriminate between two different sound frequencies while neurologically impaired fetuses cannot.

The system’s ability to track heart function has enabled the researchers to study cardiac development as well as to monitor therapeutic drug interventions. A popular drug used to treat abnormal fetal heart rhythms is administered to the mother and crosses the placenta. One of the drug’s drawbacks is widening of a critical heart interval. With SARA, clinicians can monitor the mother and fetus and, if the complication arises, quickly stop the drug.

The researchers have completed recording data on normal mothers and fetuses and have turned their attention to mothers at high risk including those with pre-eclampsia, diabetes, and those who smoke. A key goal of the project is to extract three-dimensional data for both mother and fetus using ultrasound and electrical signaling. "Ultimately we would like to combine both structural and functional information," says Eswaran. "It seems simple but it means mapping two different coordinate systems." To produce a 3D image, the researchers must develop new algorithms or mathematical formulas so that the ultrasound and electrical signals can be combined in the same spatial dimension.

Lowery notes that a SARA system will be installed in Tuebingen, Germany in 2007 and he anticipates more widespread use in the next three years as SARA gains attention in the research community. "This is a research tool with clinical applications but we need multiple applications for widespread use," he says. Other potential applications include noninvasive bladder and digestive tract studies as well as reproductive studies in nonpregnant women.

In addition to support from NIBIB, the research is supported by the National Institute of Neurological Diseases and Stoke.

References:

Eswaran H, et al., Fetal magnetoencephalography—a multimodal approach. Developmental Brain Research 154: 57-62, 2005.

Preissl H, et al., Fetal magnetoencephalography: current progress and trends. Experimental Neurology 190: S28-S36, 2004.

Researchers recorded a fetus at 36 weeks responding to sound stimuli and monitoring spontaneous brain activity. (Left): A cartoon indicates the intrauterine fetal position at the time of the study obtained using ultrasound. (Bottom left): The location of spontaneous brain activity and responses to sound are shown over SARA's 151 sensor array. (Bottom right): A color-coded map shows the magnetic field distribution for brain activity and sound response. The color-coding is based on the intensity and the direction of the magnetic fields at a given time point. Images courtesy of Hari Eswaran, University of Arkansas for Medical Sciences.