Diagnostic Imaging and Radiology

Exploration of the developing brain

13JUL16CatherineLBlogImage

Common, lifelong health conditions like diabetes and hypertension have footprints that can be traced back to the womb. With advanced fetal MRI we seek to understand as much as possible about brain development during the time in utero. Non-invasive imaging technology helps us to identify signs of abnormal fetal development that may facilitate earlier diagnoses of chronic conditions and intervention.

We’re exploiting both the power and safety of MRI to develop ways to pick up early signs and signals in fetuses whose brain development may be veering off in the wrong direction. Using this advanced technology we can begin to detect varying signals or other signs of distress. These signs of distress may appear in the form of a brain chemical imbalance or a structural brain abnormality that is too subtle to be seen by an ultrasound or other scan. We now have the ability to leverage magnetic resonance imaging to examine the brain in utero for even the most subtle derailments that can lead to lifelong consequences.

The first nine months of life, when a fetus is in the womb, is a time of unparalleled growth and a critical time for fetal brain development. As we examine the maturation of the fetal brain, we know that each and every cortical fold represents future function lost or gained and lays the fundamental background or platform from which critical functions will emerge such as language and social and behavioral development.

We are developing technology that can quickly and reliably pick up early signals of a fetal brain that’s going off route to provide the ability to access therapeutic windows that are currently inaccessible. Earlier identification and intervention can improve the quality of life for children and potentially could even reverse the abnormality.

Early identification of fetal distress is critical. To be able to provide an intervention you must first be able to know that a fetus is getting into trouble, and you must be able to identify the problem early enough, in order to intervene before it has already caused injury to the fetus.

About the Author

Catherine LimperopoulosCatherine Limperopoulos, Ph.D.
Director, MRI Research of the Developing Brain; Director, Diagnostic Imaging and Radiology/Fetal and Transitional Medicine
Research interests:
Fetal neonatal brain injury

Sharp images key to spotting the earliest signs of compromised pregnancies

Fetuses wiggle. They waggle. Some pirouette within the womb, amniotic fluid easing their spins. Pregnant mothers’ meals and beverages from hours earlier wend their way through their digestive systems. On top of that, mother and offspring may breathe out of sync and their hearts may beat in time to different drummers.

In short, there’s a whole lot of movement going on in the womb.

As anyone trying to capture a photograph with a digital camera knows, sudden movements are the enemy of a sharp image. The challenge is the same for fetal researchers aiming to capture crisp functional magnetic resonance imaging (fMRI) of the developing brains of fetuses who are always on the move.

Over two years, a Children’s National Health System research team led by Wonsang You, a research associate in the Developing Brain Research Laboratory, worked out complex mathematical algorithms to account for independent fetal and placental motions, to erase those noise artifacts, and to validate the accuracy of the technique.

“[M]otion correction is optimized to the experimental paradigm, and it is performed separately in each phase as well as in each region of interest (ROI), recognizing that each phase and organ experiences different types of motion. To obtain the averaged [blood oxygen level-dependent] BOLD signals for each ROI, both misaligned volumes and noisy voxels are automatically detected and excluded, and the missing data are then imputed by statistical estimation based on local polynomial smoothing,” You and colleagues wrote in a technical article published recently by the Journal of Medical Imaging and spotlighted on the journal’s website as a featured article.

To underscore the work’s clinical utility, they analyzed differences in fetal motion by acquiring BOLD fMRI data from eight pregnant women with healthy fetuses and comparing them with eight women whose fetuses had been diagnosed with congenital heart disease (CHD) between 25 to 40 weeks of gestational age. The team focused on changes in oxygenation of the fetal brain and placenta during maternal hyperoxia, an oxygen challenge test during which both groups of pregnant women received 100 percent oxygen via face mask for four to six minutes. Measurements were then taken to determine whether there were differences in how the fetuses and the placentas responded to the oxygen challenge test.

Recognizing compromised fetuses in utero – and understanding the subtle but important ways they deviate from the trajectory of normal fetuses – opens a critical window of opportunity to intervene through nutritional, pharmaceutical, or surgical means – before brain injury is consolidated, says Catherine Limperopoulos, PhD, Director, MRI Research of the Developing Brain at Children’s National, and the paper’s senior author.“

Our goal is to exploit the power of MRI, a non-invasive imaging technique, to detect the earliest signs of the fetus getting into trouble before it runs into serious problems,” Limperopoulos says. “We needed the technical development described in this foundational work to allow us to reliably measure the fMRI BOLD response in the fetal brain and placenta.”

The BOLD signal can be degraded by the independent and collective movements of the mother and fetus. Traditional motion correction makes assumptions, such as treating all moving objects like the fetal brain, which is solid, rigid, and has a high range of motion. The traditional approach also fails to account for such subtleties as the placenta’s low range of motion and its flexing in response to maternal and fetal movements.

The research team employed four-step pre-processing – which included correcting bias magnetic field, correcting for global and local motion, and rejecting outliers – and followed with data imputation, an alphabet soup of letters and Latin symbols that mathematically accounts for objects (placenta and fetal brain) that move independently.“

We showed that the proposed preprocessing pipeline can be effectively employed to characterize fetal motion in healthy controls and CHD fetuses. Our preliminary data suggest that the degree of fetal motion tends to increase during hyperoxia in CHD fetuses (but not significantly). In addition, the motion of the fetal brain in CHD cases showed higher variance during hyperoxia compare[d] to controls,” You and colleagues write. “These observations suggest that the CHD fetus may be more responsive to maternal hyperoxia. However, these pilot data need to be validated on a larger cohort of healthy and high-risk CHD fetuses.”

Related resources: Research at a Glance

Using 3-D MRI for fetal brain imaging during high-risk pregnancies

3DMRI

What’s Known
The placenta plays an essential role in the growth of a healthy fetus and, among other critical tasks, it ferries in oxygen and nutrients. During pregnancies complicated by fetal growth restriction (FGR), the failing placenta cannot support the developing fetus adequately. FGR is a major cause of stillbirth and death, and newborns who do survive face numerous risks for multiple types of ailments throughout their lives. In fact, studies have shown that nutrient depravation during gestation can have lasting consequences that may manifest themselves years or decades later in life. These risks can also cross generations, affecting future pregnancies.

What’s New
A team of researchers applied an advanced imaging technique, three-dimensional (3-D) MRI, to study brain development in these high-risk pregnancies. They are the first to report regional, tissue-specific volume delays for the developing fetal brain in FGR-affected pregnancies. The team compared overall fetal brain volume as well as regional brain volumes for a control group of healthy young pregnant women with a group of young women whose pregnancies were complicated by FGR. While fetuses in both groups grew exponentially as pregnancies progressed, the researchers began to see dramatic differences when they compared the volumes of specific regions of the brain, including the cerebellum, which coordinates balance and smooth movement; the deep gray matter, which also is involved in complex functions, such as memory and emotion; and the white matter, which is made up of millions of nerve fibers that connect to neurons in different regions. Because there are no biomarkers to spot early brain failure, 3-D MRI imaging may fill this knowledge gap.

Questions for Future Research
Q: Certain regions of the brains of FGR-affected infants show accelerated volume. Are these differences regional or global?
Q: Is accelerated brain volume in FGR-affected infants a result of heightened stress that these fetuses experience in the womb?
Q: How do differences in regional brain volume relate to later neurodevelopmental impairment that some FGR-affected infants experience?

Source: “Impaired Global and Tissue-Specific Brain Development in the Growth-Restricted Fetus.N. Andescavage, J. Cruz, M. Metzler, A. du Plessis, and C. Limperopoulos. Presented during the 2016 Pediatric Academic Societies Annual Meeting, Baltimore, MD. May 2, 2016.

Congenital Zika Viral Infection Linked to Significant Fetal Brain Abnormalities

mosquito

What’s Known
According to the Centers for Disease Control and Prevention, Zika viral transmission is occurring extensively throughout Central and South America. Like other mosquito-borne viruses, Zika virus can be passed by pregnant women to developing fetuses. Unlike these other viruses, Zika has been implicated in a growing number of cases of Brazilian infants born with microcephaly, a condition characterized by undersized heads and severe brain damage. The precise strategy that the Zika virus uses to elude the immune system and the reason why fetal brain cells are particularly vulnerable remain unknown.

What’s New
A 33-year-old Finnish woman was 11 weeks pregnant when she and her husband traveled on vacation to Mexico, Guatemala, and Belize in late November 2015. The pair was bitten by mosquitoes during their trip, particularly in Guatemala. One day after returning to their Washington, DC home, the woman got sick, experiencing eye pain, muscle pain, a mild fever, and a rash. A series of early ultrasounds showed no sign of microcephaly or brain calcifications. A fetal ultrasound at the 19th week and a fetal MRI at the 20th week, however, revealed severe brain damage.

The brain of the 21-week-old aborted fetus weighed only 30 grams. Zika RNA, viral particles, and infectious virus were detected, and Zika virus isolated from the fetal brain remained infectious when tested. The concentration of virus was highest in the fetal brain, umbilical cord, and placenta. The mother remained infected with Zika virus at 21 weeks, some 10 weeks after her initial infection.

Questions for Future Research

  • Could serial measurements and blood tests more accurately detect and, ultimately, predict fetal abnormalities following Zika virus infection?
  • Why does the Zika virus replicate with ease within the womb?
  • At which stage of pregnancy are fetuses most vulnerable?
  • Which specific brain cells does Zika target?

Source:Zika Virus Infection with Prolonged Maternal Viremia and Fetal Brain Abnormalities.” R.W. Driggers, C.Y. Ho, E.M. Korhonen, S. Kuivanen, A.J. Jääskeläinen, T. Smura, D.A. Hill, R. DeBiasi, G. Vezina, J. Timofeev, F.J. Rodriguez, L. Levanov, J. Razak, P. Iyengar, A. Hennenfent, R. Kennedy, R. Lanciotti, A. du Plessis, and O. Vapalahti. The New England Journal of Medicine. June 2, 2016.

Drs. DeBiasi and du Plessis

Suspected domestic zika virus infection in Florida underscores the importance of ongoing vigilance

Drs. DeBiasi and du Plessis

Federal health officials continue to investigate the first possible cases of domestic Zika virus transmission in Florida. In light of the growing number of Zika infections, the vast majority of which have been associated with foreign travel, vigilance for additional cases is warranted – particularly as summer heat intensifies and mosquito populations grow. The Centers for Disease Control and Prevention (CDC) now advises that all pregnant women in the continental United States and U.S. territories be evaluated for Zika infection at each prenatal care visit. The CDC also recognizes that Zika-exposed infants will require long-term, multidisciplinary care.

In mid-May, Children’s National Health System Fetal Medicine Institute and Division of Pediatric Infectious Disease announced the formation of a Congenital Zika Virus Program to serve as a dedicated resource for referring clinicians and for pregnant women to receive counseling and science-driven answers about the impact of the Zika virus on pregnancies and newborns. Children’s clinicians have consulted on 30 pregnancies or births with potential Zika virus exposure and/or infection. As of Aug. 31, eight were Zika-positive or probable. One of the pregnancies was the subject of an article published by The New England Journal of Medicine.

”While we’re hopeful there are few local cases, the Congenital Zika Virus Program has been developing emergency response plans in collaboration with local departments of health to prepare for any eventuality,” says Roberta DeBiasi, MD, MS, Chief of the Division of Infectious Disease and Congenital Zika Virus Program co-leader.

Over the years, Children’s National has invested in equipment and highly trained personnel, building world-class expertise in infectious diseases, pediatric neurology, pediatric cardiology, genetics, neurodevelopment, and other specialties. Children’s clinicians are recognized leaders in next-generation imaging techniques, such as fetal MRI, which detects more subtle and earlier indications of impaired brain growth. A variety of divisions work together to offer multidisciplinary support and coordinated care to infants born with special needs. As the nation braces for the possible expansion of Zika virus infection to other states, Children’s National is facilitating the multi-step process of testing blood, urine, and tissue with state health departments, helping to ensure timely and precise information. Children’s National specialists guide Zika-affected pregnancies through the fetal period and are able to oversee and coordinate the care of Zika-affected infants after delivery. Care and clinical support is provided by a multidisciplinary team of pediatric neurologists, ophthalmologists, audiologists, physical and occupational therapists, infectious disease experts, and neurodevelopmental physicians.

The Children’s National multidisciplinary team includes:

  • Adre du Plessis, M.B.Ch.B., Director of the Fetal Medicine Institute, Chief of the Fetal and Transitional Medicine Division, and Congenital Zika Virus Program co-leader;
  • Roberta DeBiasi, M.D., M.S., Chief of the Division of Infectious Disease and Congenital Zika Virus Program co-leader;
  • Cara Biddle, M.D., M.P.H., Medical Director, Children’s Health Center, and a bilingual expert on complex care;
  • Dorothy Bulas, M.D., Radiologist in the Division of Diagnostic Imaging and Radiology;
  • Taeun Chang, M.D., Director, Neonatal Neurology Program in the Division of Neurophysiology, Epilepsy and Critical Care Neurology;
  • Sarah Mulkey, M.D., Ph.D., Fetal-Neonatal Neurologist, Fetal Medicine Institute;
  • Lindsay Pesacreta, M.S., F.N.P.-B.C., Board-Certified Family Nurse Practitioner; and
  • Gilbert Vezina, M.D., attending Radiologist in the Division of Diagnostic Imaging and Radiology and Director of the Neuroradiology Program.

Related Resources: Research at a Glance | Guidelines for Referring Clinicians
[Updated Sept. 13, 2016]

New program provides science-driven answers about zika virus’s impact on pregnancies

Drs. DeBiasi and du Plessis

Each week, as temperatures rise, the likelihood increases that the United States will experience domestic Zika virus transmission. Indeed, such domestic Zika transmission already is occurring in Puerto Rico and the U.S. Virgin Islands. The Children’s National Health System Fetal Medicine Institute and Division of Pediatric Infectious Disease announced the formation of a Congenital Zika Virus Program to serve as a dedicated resource for referring clinicians and for pregnant women to receive counseling and science-driven answers about the impact of the Zika virus on their pregnancies.

Over years, Children’s National has invested in equipment and highly trained personnel, building expertise in infectious diseases, pediatric neurology, pediatric cardiology, genetics, neurodevelopment, and other specialties. Children’s clinicians are recognized as national leaders in next-generation imaging techniques, such as fetal MRI, and a variety of divisions work together to offer multidisciplinary support and coordinated care to infants born with special needs. As the nation prepares for the Zika virus, Children’s National is facilitating the multi-step process of blood testing, helping to ensure timely and precise information. Children’s National specialists are able to guide Zika-affected pregnancies through the fetal period and can oversee the care of Zika-affected infants after delivery. Care and clinical support is provided by a multidisciplinary team of pediatric neurologists, physical therapists, infectious disease experts, and neurodevelopmental physicians.

Some functional brain connectivity altered in fetuses with CHD

chd_fetus

What’s Known
Congenital heart disease (CHD), a structural problem with the heart at birth, is the most common birth defect and impacts 8 of every 1,000 newborns.

While many infants with mild disease require no intervention, others have complex CHD that necessitates specialized treatment shortly after birth. Complex defects change how blood flows through the heart and to other organs—including the brain.

What’s New
Newborns with this diagnosis are at an elevated risk for neurodevelopmental disabilities, underscoring the importance of monitoring fetal brain development and function to identify which newborns need additional surveillance and medical intervention. Neuroimaging research in recent years has shown that resting-state functional magnetic resonance imaging (rs-fMRI) can provide critical insights into how the brain functions, at rest. The research team in the Developing Brain Research Laboratory at Children’s National Health System successfully measured brain function in 90 different brain regions in healthy resting fetuses and pregnancies complicated by CHD. The team reports for the first time that there was robust functional connectivity between hemispheres in both fetuses diagnosed with CHD and controls matched by gestational age. The Children’s researchers and clinicians, however, found that some functional connections were weakened in the association and paralimbic regions of the brain that are involved in attention, emotions, and behaviors.

Questions for Future Research
Q: Does decreased regional connectivity in these association and paralimbic brain regions in CHD-complicated pregnancies influence infants’ neurodevelopment after birth?
Q: Can rs-fMRI be used to identify early disturbances in brain development in CHD-complicated pregnancies, and can the imaging technique lead to improved surveillance and more timely therapeutic intervention?

Source: “Functional Brain Connectivity Is Altered in Fetuses With Congenital Heart Disease.” J. De Asis-Cruz, A. Yarish, M. Donofrio, G. Vezina, A. du Plessis, and C. Limperopoulos. Presented during the 2016 American Society of Neuroradiology Annual Meeting, Washington, DC. May 25 2016.

Catherine Limperopoulos

Connection between abnormal placenta and impaired growth of fetuses discovered

CLimperopoulous

A team of researchers used 3-D volumetric magnetic resonance imaging (MRI) in an innovative study that reported that when the placenta fails to grow adequately in a fetus with congenital heart disease (CHD), it contributes to impaired fetal growth and premature birth. Fetal CHD involves an abnormality of the heart and is associated with increased risk for neurodevelopmental morbidity.Until now, CHD in the fetus and its relationship to placental function has been unknown. But the advanced fetal imaging study has shown for the first time that abnormal growth in the fetus with CHD relates to impaired placental growth over the third trimester of pregnancy. Catherine Limperopoulos, PhD, Director of Children’s National Developing Brain Research Laboratory in the Division of Diagnostic Imaging and Radiology, is the senior author of the study published in the September 2015 issue of the journal Placenta, “3-D Volumetric MRI Evaluation of the Placenta in Fetuses With Complex Heart Disease.”

Specifically, the decreased 3-D volumetric MRI measurements of pregnant women reported in this study suggest placental insufficiency related to CHD. The placenta nourishes and maintains the fetus, through the delivery of food and oxygen. Its volume and weight can determine fetal growth and birth weight.

Abnormality in placental development may contribute to significant morbidity in this high risk-population. This study shows impaired placental growth in CHD fetuses is associated with the length of the pregnancy and weight at birth. Nearly 1 in every 100 babies is born in the United States with a congenital heart defect.

Developing the capacity to examine the placenta non-invasively using advanced MRI is needed to identify early markers of impaired placental structure and function in the high-risk pregnancy. This is a critical first step towards developing strategies for improved fetal monitoring and management, Dr. Limperopoulos says.

“We are trying to develop the earliest and most reliable indicators of placental health and disease in high-risk pregnancies. Our goal is to bring these early biomarkers into clinical practice and improve our ability to identify placental dysfunction,” Dr. Limperopoulos says. “If we can develop the capacity to reliably identify when things begin to veer off course, we then have a window of opportunity to develop therapies to restore function.”

The study used in-vivo 3-D MRI studies and explored placental development and its relationship to neonatal outcomes by comparing placental volumetric growth in healthy pregnancies and pregnancies complicated by CHD.

While mortality rates continue to decrease steadily in newborns diagnosed with complex CHD, long-term neurodevelopmental impairments are recognized with increasing frequency in surviving infants, Dr. Limperopoulos says.

“Our goal is to better support the developing fetus with CHD. We can best accomplish this if we develop technology that can allow us to safely and effectively monitor the fetal-placental unit as a whole throughout pregnancy,” Dr. Limperopoulos says.

“This is the new frontier, not only to ensure survival but to safeguard the fetus and to ensure the best possible quality of life,” she says.