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Brain Imaging for Global Health

Elwell, Clare E. PhD

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Journal of Neurosurgical Anesthesiology: July 2020 - Volume 32 - Issue 3 - p 188-190
doi: 10.1097/ANA.0000000000000685
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“Addressing an unmet clinical need with innovative physics and engineering solutions” is a mantra often quoted when explaining the work of Medical Physicists and Biomedical Engineers. In the field of brain imaging, this usually means striving for improved spatial or temporal resolution, contrast, specificity or sensitivity. Our efforts are often directed at making high tech even higher tech. As a consequence, we surround ourselves with costly imaging suites housed in specialist facilities that are reliant on teams of technical experts to staff and maintain them. There’s no doubt of the benefit that these facilities afford, but while developing ever more complex and expensive methods and instrumentation it is all too easy to overlook the needs of those whose access to any type of brain imaging is severely limited or nonexistent.

Each year, 250 million children in low- and middle-income countries fail to reach basic milestones in their cognitive or socioemotional development.1 In these settings, lack of essential nutrients, exposure to infectious diseases, pollution, and poor living conditions in the early days, weeks, and months of life create a toxic environment for the developing brain which can have long-lasting consequences well into adulthood.2

Current methods for understanding infant brain development in resource-poor settings are limited. Most studies rely upon behavioral assessments, such as the Bayley Scales for Infant and Toddler Assessment,3 to chart developmental milestones. With a few exceptions, the majority of these assessments have been developed for use in highresource settings and their translation (linguistic and cultural) to other populations is nontrivial. And, by default, they can only be used once an infant’s behavior actually becomes observable—restricting their value in the earliest stages of development when some of the most rapid and important changes in the brain are taking place. There is, therefore, a clearly identifiable unmet need for infant brain imaging which can be implemented from birth in poor resource settings.

The gold standard of neuroimaging—magnetic resonance imaging (MRI)—can be used to image new-born infants (and fetuses).4 Despite the emergence of sustainable low-field MRI technologies,5 the cost of installing and running these facilities in rural and remote settings in developing countries remains a limiting factor for their widespread use in global health studies. To address this unmet need, researchers are turning towards portable neuroimaging methodologies to create mobile neuroimaging laboratories which can be established with the bear minimum of infrastructure and deployed in a wide range of resource-poor settings. One such neuroimaging methodology is functional near-infrared spectroscopy (fNIRS), which uses low levels of light to image the hemodynamic response to neuronal activation (the same response measured by the BOLD functional MRI signal). Because of its noninvasive nature and infant friendly hardware, fNIRS has found widespread application in neurodevelopment studies.6 In addition, fNIRS technology is portable, low cost, and requires minimal setup and training.

In February 2012, with funding from the Bill and Melinda Gates Foundation, a team of physicists and neurodevelopmental psychologists from University College London and Birkbeck, University of London transported an fNIRS system to a field station in Keneba in rural Gambia, part of the Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine. Within a few hours, the team had established an fNIRS neuroimaging lab within the field station and successfully imaged the brain of a 4-month-old—the first image of brain function acquired from an infant in Africa.7

This study proved the feasibility of using fNIRS for infant testing in a resource-poor setting (Fig. 1) and led to the establishment of the Brain Imaging for Global Health (BRIGHT) project,8 which is generating brain function for age curves across the first 2 years of life in Gambian and UK infants. The BRIGHT project incorporates a range of brain imaging (fNIRS and electroencephalography), behavioral (including Mullen Scales of Early Learning, eye tracking, parent-child interaction, language environment analysis), growth, health, and socioeconomic measures to characterize typical and atypical brain development from birth in low-resource and high-resource settings. A total of 222 Gambian infants and 62 UK infants have been recruited to this study with data collection due to be completed on both sites by June 2020. fNIRS neuroimaging has been performed longitudinally in each infant at 1, 5, 8, 12, 18, and 24 months to understand the trajectory of typical and atypical infant brain development in these 2 settings and to inform targeted interventions to protect against the impact of early adversity.

Functional near-infrared spectroscopy studies in rural Gambia. A, New-born infant. B, Twelve-month-old infant.

Preliminary results are demonstrating the value of conducting brain imaging from birth by showing differences in response to habituation and novelty from the first few months of life in Gambian and UK infants, and the emergence of associations between risk factors in low-resource settings and neurodevelopmental outcomes.9,10 Further analysis is being focused on the extraction of robust markers of brain activation to provide early predictors of the impact of adversity on cognitive function—way before behavioral signs are evident—so that interventions, nutritional or otherwise, can be targeted in the prenatal and postnatal periods to have maximum effect on protecting the rapidly developing brain.

Following the successful demonstration of fNIRS in measuring infant brain development in rural Gambia, the author established the Global fNIRS initiative8 to encourage the application of fNIRS technology to address the unmet need for infant brain imaging in global health. Since then, this research field has rapidly expanded to encompass projects investigating the impact of biological and psychosocial hazards in urban Bangladesh,11 the development of visual working memory over the first 4 years of life in rural India,12 nutritional supplementation in Guinea-Bissau,13 child labor in the Ivory Coast,14 and malnutrition in Colombia.15

As technological developments drive forward the availability and applicability of wearable and portable fNIRS systems,16 our ambitions for how, when and where we can image the brain will continue to expand, as should our ambition to ensure that we are responding to needs in populations across the globe.

Clare E. Elwell, PhD
Department of Medical Physics and Biomedical Engineering, University College London, London, UK


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