BROOKHAVEN AND SCHERING AG COLLABORATE ON IMPROVED MEDICAL IMAGING METHOD
23 September 2004 - DOE/Brookhaven National Laboratory

"The new agent should improve the safety of X-ray radiographic contrast imaging in general, and thereby extend the applicability of these procedures to patients that are currently excluded from these tests due to certain health conditions," says Dr. F. Avraham Dilmanian, a medical physicist who heads the project at Brookhaven. "It should also lead to an improvement in X-ray radiography systems that, when combined with the new contrast agent, will offer a much better image quality and a smaller radiation dose to the patients."

X-ray radiography contrast agents are dyes that absorb X-rays, making the organs containing them visible in contrast to the surrounding tissue. "However, the traditional, injectable radiography contrast agents, which are all based on the contrast element iodine, can produce severe adverse reactions in patients with allergies, asthma, kidney diseases, diabetes, or poor general health," says Dr. Harold L. Atkins, a senior BNL radiologist working on the study. Also, says Dilmanian, "The iodine agents are not very efficient at absorbing the high-energy portion of the X-ray spectrum used today for radiographic imaging, so they don't produce ideal contrast."

Brookhaven and Schering aim to create a contrast agent based on lanthanides (e.g., the element gadolinium), which are heavier and better able to absorb high-energy X-rays than iodine, and combine it with a device to select the narrow, high-energy portion of the X-ray spectrum that would be absorbed most efficiently by this agent.

The work will proceed in two stages. First, Schering, under the direction of Dr. Hanns-Joachim Weinmann, will develop lanthanide-based contrast agents. The element gadolinium has been used with relatively little risk in contrast agents for magnetic resonance imaging. Standard agents, however, are not concentrated enough for X-ray radiography. Brookhaven scientists will test these more concentrated agents using the very narrow-energy-spectra X-rays available at the Lab's National Synchrotron Light Source.

Simultaneously, the Brookhaven scientists will develop a monochromator, a crystal device that selects a narrow spectrum of X-rays, to be used with conventional X-ray sources.

"This monochromator will be tailor-made to select X-rays in an energy range that is best absorbed by gadolinium," says Dr. Zhong Zhong, of the NSLS. The monochromator will be tested with the new contrast agent(s) using conventional X-ray sources at the State University of New York at Stony Brook's Radiology Department, in collaboration with Dr. Terry M. Button. (Implementation of the method in clinical radiology will eventually require the use of more intense X-ray tubes.)

If an X-ray beam has an energy spectrum tailored to the contrast agent, all the energy of a given X-ray dose contributes to the image. Thus, the patient is only exposed to X-rays within this "useful" band. "So we end up exposing the patient less because the energy absorption is optimal," Dilmanian says. Alternatively, he says, for the same dose, you'd get a better image.

Schering AG, based in Germany, is the world's largest manufacturer of contrast agents, including the one most commonly used for MRI.
Brookhaven's participation in this CRADA is funded by the DOE's Office of Science, Laboratory Technology Research Program.

http://www.bnl.gov

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