New Device Lowers Radiation Exposure During Dental X-rays

Thanks to a new electronic readout device being developed by scientists at Berkeley Lab, dental patients will soon be exposed to as little as one-tenth of the x-ray radiation they typically receive now.

The new technology, known as digital radiography, means patients will still have to "open wide" and "bite down," but in place of dental film they will be closing their mouths around electronic sensors. Instead of the trip to the developing tank, dentist and patient will watch images come up on a computer screen seconds after the device is inserted into the patient's mouth. The images will be higher resolution than film images and will be conveniently stored in computer memory, from which they can be easily retrieved, combined, and manipulated to supply more information. The chemical waste associated with film processing will be eliminated. Most significantly, patients will be exposed to much less x-ray dosage than typically delivered today.

The conventional way to x-ray teeth is with a piece of thick film that is moderately sensitive to x-rays. To increase its efficiency and lower the required dosage of x-rays, the film can be sandwiched between sheets of plastic called intensifying screens. The disadvantage of using the screens is that they scatter radiation, resulting in decreased spatial resolution and accuracy.

To develop the new technology, Berkeley Lab has recently signed a Cooperative Research and Development Agreement (CRADA) with Air Techniques, Inc., the nation's largest supplier of automatic dental film processors. Two scientists from Air Techniques, Claude Goodman and Daniel Wildermuth, are currently working full time at Berkeley Lab to refine the scintillator manufacturing process, and a prototype device is expected to be ready within the year.

Soon to be manufactured by Air Techniques, the alternative electronic technology developed at Berkeley lab by physicists Victor Perez-Mendez, John Drewery, and graduate student Tao Jing involves a light-emitting material, or scintillator. It differs from other dental digital radiographic devices that have recently come on the market in that it provides better spatial resolution for a given sensitivity to x-rays.

To make an x-ray-sensitive material, researchers use a technique called vacuum evaporation in which a scintillator, cesium iodide, is deposited on raised pucks dotting the surface of a patterned piece of high-temperature plastic. In the process of evaporation, the cesium iodide forms columns on the plastic pucks. When x-rays hit these columns, the material emits light (scintillation) which is partially lined up. Sideways spreading is minimized, making the devices more efficient and more accurate than the commercial Kodak film combination.

Perez-Mendez, who is also a professor of radiology at UC San Francisco, says the next step in the development of the technology will be to make larger digital devices for mammography or heart imaging."The ultimate aim," he says, "is to avoid the use of film for medical x-ray imaging."

Eventually, standard 11 by 14-inch radiology film and developing tanks will be replaced by electronic detectors, high definition display screens, and computer-stored data. These technologies, says Perez-Mendez, will simplify procedures in a hospital's radiology department, and patients will be exposed to much lower doses of radiation.