Radioactive sprinkles keep machines true

Peter Weiss

Radioactivity-detecting medical scanners, such as positron emission tomography (PET) imagers, are becoming so sharp-eyed that it's more challenging than ever to find the limits of the machines' vision. Doing this requires uniform radiation sources smaller than the minimum-size object the scanners are supposed to discern. Without such verification, uncertainty about the resolution of the machines' detectors could lead to misinterpretations of scans.

Medical physicists have made test items for scanners by irradiating fine metal wires or other objects in nuclear reactors or particle accelerators, but that's not cheap or convenient.

Now, an Australian team has come up with a promising alternative. Dale L. Bailey and his colleagues at the Royal North Shore Hospital in Sydney have created radioactive balls the size of candy sprinkles by dipping porous beads into a saline solution containing the radioisotope technetium-99m. The beads themselves are commercially available spheres of zeolite—a class of porous compounds of silicon, aluminum, and oxygen (SN: 5/17/03, p. 318: Available to subscribers at http://www.sciencenews.org/articles/ 20030517/note18.asp).

"The beauty of [these] sources … is that they're cheap and easy to make in the hospital or lab," Bailey says. He and his colleagues describe their work in the Feb. 7 Physics in Medicine and Biology.

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References:

Bailey, D.L., et al. 2004. The use of molecular sieves to produce point sources of radioactivity. Physics in Medicine and Biology 49(Feb. 7):N21–N29. Abstract available at http://dx.doi.org/10.1088/0031-9155/49/3/N02.

Further Readings:

2003. Growing zeolite crystals in space may show how nature makes some of its tiniest traps and help researchers learn how to grow better crystals for a multitude of uses on Earth. NASA/Office of Biological and Physical Research news release. Feb. 5. Available at http://spaceresearch.nasa.gov/research_projects/zeolites_02-2003_lite.html.

Gorman, J. 2003. Zeolites get an organic makeover. Science News 163(May 17):318. Available to subscribers at http://www.sciencenews.org/articles/20030517/note18.asp.

For further information on Single Photon Emission Computed Tomography (SPECT), go to http://www.bae.ncsu.edu/bae/courses/bae590f/1995/scarfone/.

For further information on zeolites, go to http://www.bza.org/zeolites.html.

Sources:

Dale L. Bailey
Department of Nuclear Medicine
Royal North Shore Hospital
St. Leonards, NSW, Sydney
Australia

From Science News, Volume 165, No. 11, March 13, 2004, p. 173.