Dental Electronic Readout Device Will Lower X-Ray Exposure

February, 1995

Diane LaMacchia,

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

To develop the new technology, LBL has recently signed a $100,000 Cooperative Research and Development Agreement (CRADA) with Air Techniques, Inc., the nation's largest supplier of automatic dental film processors.

With the emergence of digital radiography, 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 coming 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 of the x-ray dosage 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.

Soon to be manufactured by Air Techniques, the alternative electronic technology developed at LBL 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 a better spatial resolution for a given sensitivity to x rays.

To make an x-ray-sensitive material, the LBL 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 collimated, and sideways spreading is minimized.

"The net result is that our x-ray-detecting devices are more efficient and more accurate than the commercial Kodak film combination," says Perez-Mendez.

To develop the scintillator for the electronic dental readout device, LBL and Air Techniques have signed a one-year CRADA. Although it is a small company, employing about 300 people in Hicksville, New York, Air Techniques is the major US supplier of dental film processors and also makes other dental clinical and laboratory equipment. Two scientists from Air Techniques, Claude Goodman and Daniel Wildermuth, are currently working full time at LBL to refine the scintillator manufacturing process; a prototype device is expected to be ready within the year.

Perez-Mendez, who is also a professor of radiology at the University of California, 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. We're starting small, making devices like this for dental radiography, because the electronics are easier to make."

Eventually, standard eleven by fourteen-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.

LBL is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California.