Brain Mapping

NIRS technology is uniquely positioned to help identify areas of the brain involved in a range of functions and tasks - an area of study called "brain mapping," which has important applications in and far-reaching implications for a number of fields, from basic science research to diagnosis and treatment of schizophrenia and other psychiatric disorders.

Computerized tomography (CT), functional magnetic resonance imaging (fMRI), positron emission tomography (PET), electroencephalography (EEG) and magnetoencephalography (MEG) are among the most prominent of the technologies used for brain imaging studies. However, these modalities typically suffer from relatively low temporal resolution (CT, fMRI, PET) or spatial resolution (EEG, MEG). Computed tomography and positron emission tomography have the added drawback of deploying ionizing radiation.

NIRS can measure hemodynamic changes reflecting the metabolic demands of tumors during formation, and therefore can identify tumors before they are visible by x-ray. In addition, it can spot tumors that might be hidden on x-rays (in dense breasts, for example) and differentiate between tumors and non-cancerous masses such as cysts - thus helping to avoid unnecessary biopsies, which can be particularly traumatic for patients.

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Breast Imaging

The most common type of invasive cancer in women, breast cancer accounted for 458,503 deaths worldwide in 2008 (13.7% of all cancer deaths in women; 6.0% of all cancer deaths for women and men together). Ongoing research and advances in breast cancer screening have helped to fight the disease, but there is still a need to catch more cancers earlier. NIRS holds considerable promise in this area.

X-ray mammography has long been the gold standard for breast cancer detection, offering a means to identify non-palpable tumors with fairly high sensitivity. The technique depends on structural changes within the breast, however, and for this reason cannot detect cancers at very early stages, before they are structurally evident.

Researchers have been working to develop near-infrared spectroscopy and diffuse optical tomography for breast cancer detection since the late 1990s. Many of these efforts have focused on multimodal imaging with NIRS providing functional information about the formation and growth of tumors and x-ray offering structural guidance. Early trials have proved very successful, as can be seen in a number of papers on the Publications page.

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NIRS-EEG and Epilepsy Research

Roughly 50 million people worldwide suffer from epilepsy, with onset occurring most often in infants and the elderly. Patients recovering from brain surgery can also be prone to epileptic seizures, which manifest as spontaneous hyperactive and hyper-synchronous neuronal activity in the brain.

When coupled with EEG, near-infrared spectroscopy enables significant insights in the study of epilepsy. EEG alone has long been the gold standard in the study and diagnosis of epileptic conditions, but it can be limited in application. In many cases, changes in electrical potential at the scalp do not accurately reflect the activity of cortical neurons, and the technique provides little information about the possibly damaging effects of epileptic discharges on the surrounding brain tissue.

Researchers have reported use of simultaneous EEG and BOLD-fMRI in the study of epilepsy. Here as well, though, there are limitations to the approach: for example, the relatively short amount of time an epileptic patient can undergo measurements - 1-2 hours - which hampers the ability to study the transient, spontaneous phenomena that characterize epilepsy.

Using NIRS in conjunction with EEG can help to overcome these limitations. Because it is portable and can be applied for days at a time, the technique is well suited to study the transient, spontaneous phenomena. At the same time, NIRS provides a measure of changes in both oxy- and deoxy-hemoglobin concentrations (and therefore of changes in blood volume and oxygen saturation), and enables estimates of localized changes in oxygen metabolism. Generally, NIRS-EEG allows for the study of the spatial, temporal, hemodynamic and metabolic characteristics of both ictal and inter-ictal epileptic events, and thus offers a promising tool for research in this area.

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Cognitive Development

Behavioral researchers studying cognitive development have long sought to establish different kinds of cognitive processes that come online across development time. For example, a popular technique for use with infants is "preferential looking,” in which infants are habituated to one stimulus and then presented with another to test whether they can discriminate between the two. The challenge with this approach is that infants sometimes show a preference for what they already know - a familiarity effect - and other times for the new stimulus - a novelty effect. It's difficult to predict when an infant is going to show one or the other, as well as what factors contribute to one or the other bias. This underscores the fact that behavioral measures are often used as a proxy for cognition.

In research on cognitive processing in adults, the desire to move past external measures led to an explosion of imaging work when fMRI became a viable lab technique. Functional magnetic resonance imaging has indeed provided a window into the ways cortical regions coordinate, both in general and over developmental time; however, there is a lower age limit to the use of this technology. MR imaging is quite challenging to do with infants and toddlers. Movement becomes an issue when a young child is put in an MRI scanner - only very young infants allow researchers to swaddle them for motion control, and they inevitably fall asleep - while active tasks can present a challenge in the MRI environment.

For these reasons, NIRS is very attractive to researchers working with infants and young children. Using the technology, they can have the child perform an active task and then look at how the behavioral outcomes couple with the hemodynamic and other physiological indicators of the processing that underlies the outcome. Before NIRS, this simply wasn't possible.

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