high-density diffuse optical tomography (DOT)

Radiologists Use Light To Scan The Inner Workings Of The Brain
December 1, 2007 — Radiologists have developed a new device to understand brain activity. It is a collection of fiber optic cables attached to a flexible cap placed atop the head. The cables send near-infrared light through the skull and into the brain, where it is diffused or scattered before it is collected by receiver cables. The device is able to interpret the light to measure blood circulation and the amount of oxygen in that blood, which helps explain brain activity.

When doctors want to find out what's going on inside a baby's brain it usually requires, noisy or dangerous equipment and babies sitting completely still.
But, new technology is now giving researchers a fascinating look inside an infant’s brain in a much easier way.
Radiologists are using a new technique to see what parts of a baby’s brain are working during any given task. Their method is baby-friendly with no exposure to radiation or loud machines.
“It has a more wearable cap so it can be placed in infants heads while they sit in their parents lap,” Joseph Culver, Ph.D., Washington University Medical School said. Culver and his colleagues improved a brain imaging technique called high-density diffuse optical tomography.
It measures how much blood and oxygen are in the brain.
“It’s similar to taking a flashlight and putting it on one side of your hand and looking at the light come through your hand so the light has traveled through your hand and the light that you detect on the other side tells you something about what’s inside your hand,” Dr. Culver said. Fiber optic cables on the cap shine light on the baby’s brain. The light scatters revealing blood flow related to brain activity in a 3D tomographic image. You can see it in action, when a patient watches a flickering light; a similar rotating pattern shows up in the brain’s blood flow.
“There’s an increase in blood flow to that area and that allows us to map that neuron activity,” Dr. Culver said.
Future uses for the cap include researching brain development in the tiniest of babies … or monitoring a baby’s brain during surgery.
BACKGROUND: Researchers have developed a new brain imaging technique for infants called high-density diffuse optical tomography which helps them to study the developing infant brain. This should help treat infant brain injuries by being able to monitor them in their incubators, and help scientists learn important basics about developing brains. The new scanner is quieter, and portable because it is much smaller – about the size of a small refrigerator – than typical MRI or CT scan machines. The developers are working to make the unit even smaller, about the size of a microwave.
THE PROBLEM: Scientists have been able to study brain scans of infants while they are asleep or sedated using functional MRI (magnetic resonance imaging). Ideally researchers would like to scan their brains while sitting on a parent’s lap or interacting with their environment. fMRI requires the patient to be inserted into a tightly confined passage through a large, noisy magnet; most infants find it upsetting and difficult to sit still in that environment. In the same way CT scans involve large, loud equipment, and also expose patients to levels of x-rays considered unsafe for infants.
HOW IT WORKS: The high-density diffuse optical tomography (DOT) uses harmless light from the near-infrared light spectrum. Unlike X-rays or ultrasound, near-infrared light passes through bone easily, so scientists can use the diffusing light to determine blood flow and oxygenation in the blood vessels of the brain. When these characteristics increase, it indicates that the area of the brain they are scanning is contributing to a mental task. To scan a patient, scientists attach a flexible cap that covers the exterior of the head above the region of interest. Inside the cap are fiber optic cables. Some of those cables shine light on the head and by determining the way the light is scattered, researchers can learn more about brain activity. Light passes out of one fiber optic cable, goes through the tissue, and is received by another cable. Based on its interpretation of the diffusion data, the machine creates a 3D image based on whether the red blood cells have lots of oxygen or less oxygen to determine brain activity.
WHAT IS fMRI: Magnetic resonance imaging uses radio waves and a strong magnetic field to take clear and detailed pictures of internal organs and tissues. fMRI uses this technology to identify regions of the brain where blood vessels are expanding, chemical changes are taking place, or extra oxygen is being delivered. These are indications that a particular part of the brain is processing information and giving commands to the body. As a patient performs a particular task, the metabolism will increase in the brain area responsible for that task, changing the signal in the MRI image. So by performing specific tasks that correspond to different functions, scientists can locate the part of the brain that governs that function.
The American Association of Physicists in Medicine and The Optical Society of America contributed to the information contained in the TV portion of this report.