Researchers image the human brain using ultrasonic sound and laser light

Researchers from Caltech and the University of Southern California have demonstrated a new technology that is able to image the human brain using laser light and ultrasonic sound waves. The technology is known as photoacoustic computerized tomography or PACT. Previous versions of PACT technology have been used to image the internal structure of a rat in a laboratory.

PACT can perform other medical uses, including detecting tumors in human breasts, presenting a possible alternative to mammograms. The technology was recently improved by Caltech professor Lihong Wang enhancing its precision. Researchers on the project say the new improvements make the technology so precise and sensitive it can detect minute changes in the amount of blood traveling through a very tiny blood vessel.

The technology can also be used to detect oxygenation levels in the brain. Researchers on the project say that showing blood concentration and oxygenation changes can help researchers and medical professionals monitor brain activity and is known as functional imaging. When imaging breasts, the researchers want to see the blood vessels because they reveal the presence of tumors.

Tumors have chemicals that stimulate blood vessel formation. However, measuring the functional change in imaged brain activity that varies only by a few percent compared to the baseline is very difficult. In the past, functional measuring was only conducted using fMRI machines that rely on radio waves and magnetic fields that are 100,000 times stronger than the Earth's magnetic field. The problem with those devices is they are very expensive.

However, the new technology developed by the researchers is simple, inexpensive, and compact. Notably, the technology developed by Wang and the other researchers doesn't require patients to be placed inside the machine. It shines a pulse of laser light into the head, and the light shines through the scalp, and the skull scattering to the brain and is absorbed by hemoglobin molecules in the red blood cells.

The hemoglobin molecules vibrate ultrasonically when they pick up the energy. The vibrations travel to the tissue, where they are picked up by an array of 1024 ultrasonic sensors placed around the outside of the head. The data creates a 3D map of blood flow and oxygenation in the brain after being processed by a computer algorithm.