July 16, 2007

Advance in Brain Imaging

Side view of blue, stylized human brain on black background

Brain imaging is becoming an increasingly important tool in many research areas, including sleep, addiction and other behaviors, and in diseases such as autism, Alzheimer's disease and Parkinson's disease. Its expanding use is driving the development of new, more flexible tools. Researchers have now developed a high-performance, portable system that offers unique advantages over current brain imaging systems.

The large scanners currently in use make brain imaging difficult in many situations — for example, with patients in intensive care units, research subjects performing complex tasks, or for infants and young children who need sedation. Diffuse optical imaging (DOI) is a mobile system that uses a small, flexible imaging cap. In contrast to positron emission tomography (PET), which uses ionizing radiation, DOI uses safe, infrared light for imaging. DOI detects blood dynamics in a manner similar to functional MRI (fMRI), which primarily measures levels of one form of hemoglobin, the molecule that carries oxygen in our blood. DOI can measure levels of hemoglobin both when it is carrying oxygen and when it isn't, enabling researchers to form a more complete picture of blood activity in the brain. Despite these advantages, however, DOI has been limited by its low resolution, lack of ability to measure area volumes and the complexity of the equipment.

A research team led by Dr. Joseph Culver of the Washington University School of Medicine set out to develop a more advanced optical imaging system with improved image quality. Their work was supported in part by NIH's National Institute of Neurological Disorders and Stroke (NINDS) and National Institute of Biomedical Imaging and Bioengineering (NIBIB). In the online edition of Proceedings of the National Academy of Sciences on July 6, 2007, they reported the development of a high-performance, high-density diffuse optical tomography (DOT) system.

The researchers demonstrated their system by functionally mapping the adult human visual cortex. This brain region is ideal for testing new brain imaging techniques because its structure and function have already been comprehensively mapped using other methods. The results from the high-density DOT system were consistent with previous fMRI and PET mappings of the visual cortex.

The study demonstrated that high-density DOT can be a practical and powerful tool for functional brain mapping. The system is also scalable, which will allow for mapping larger brain regions. The researchers anticipate that this advance will open the path for a wide range of new studies of both developing and diseased brains.

— by Harrison Wein, Ph.D.