Grids and Collimators Produce
Better X-ray and Nuclear Images

A grid as little as three millimeters tall could save lives by helping X-rays and radiotracers provide clearer diagnostic images of the human body. These X-ray anti-scatter grids and nuclear collimators were developed by scientists at Argonne National Laboratory and Creatv MicroTech, Inc. “The two areas where it's important for medical imaging are mammography and gamma ray imaging,” said developer Derrick Mancini of Argonne's Center for Nanoscale Materials. “Both of them are critically important for early detection of cancer and other diseases. The impact, therefore, is saving lives.”

X-rays, create an image based on the density of the matter. However, before a beam of X-rays hits the target, the X-rays are attenuated and scattered. Scattered X-rays modify and cloud the image, which can lead to medical misdiagnoses. Anti-scatter grids are placed between the target and the imager to greatly reduce or eliminate this X-ray scattering.
"The basic concept of an anti-scatter grid is not new," said Cha-Mei Tang, president of Creatv MicroTech, "but our method can make two-dimensional grids that reduce scatter to less than one percent. This is far more effective than one-dimensional grids currently on the market, which reduce scattering to about 10 percent."

The anti-scatter grids developed by Argonne and Creatv MicroTech, however, are superior to existing anti-scatter grids because they are made using a method called LIGA, a German acronym that refers to lithography, electroforming and molding.

Argonne's Advanced Photon Source (APS) is normally used to analyze materials. The LIGA produced anti-scattering grid is the first time that the APS was used in the fabrication of an industrial product. Grids produced in 2006 were shown to be highly effective in improving X-ray images. To make an anti-scatter X-ray grid in the LIGA method X-rays from the APS burn a deep grid pattern into a thick polymer. After placing the exposed polymer in a developer, the polymer mold for the grid pattern is obtained. The grid mold is filled with metal by electroplating, and when the polymer is removed, a grid results.

X-ray anti-scatter grids and nuclear collimators can help save lives

While many previous anti-scatter grids were one-dimensional, the LIGA grids consist of two-dimensional cells. These cells are divided by walls as thin as 25 microns (millionths of a meter), a thinness that cannot be achieved with other methods for making anti-scatter grids, such as casting, foil folding and chemical etching. For one-dimensional grids, the measured transmission of primary X-rays is 72 percent. A competing cellular grid transmits 80 percent, but the LIGA grid transmits the highest proportion of primary X-rays: 87 percent.