Visit the PSII website. One of only two machines in the world of its type, the microbeam analyzes speech patterns by tracking small pellets placed in the subject's tongue, teeth and nose. The tracking is accomplished by a very narrow x-ray beam passing through the subject area and detected by a sodium iodide crystal located behind the head. The dense pellets block the x-rays from reaching the crystal. The microbeam allows study of speech patterns in real time.
More detail is available.
Visit the Microbeam website.