From hospital to lab: tracing technetium
JOYCE MCBETH
method will remain limited to the 6 h half-life in real time. When usHydrologists have used radioactive lab. Gamma-camera imaging is exing low concentrations in the bioisotopes of the element technetium pensive and bulky, putting such geochemical experiments, they (Tc), produced in bulk by nuclear infrastructure out of the reach of added 10 megabecquerel (MBq) of facilities using uranium (U), as a 99m most academic researchers and tracer to follow groundwater. A Tc, equivalent to 10 × 10-12 M making it difficult to take into the short-lived isotope of Tc also serves of the tracer. They also tracked field, says the soil remediation exas a medical tracer in human bodhigh amounts of 99Tc, adding 15 pert, who is a professor at the Uniies. Scientists reporting in Environ. µM of ammonium pertechnetate versity of Tennessee, Sci. Technol. 2009, (DOI Knoxville. 10.1021/es802885r) have Glasauer says the technique united the two applications, has potential in the lab, but it showing how the medical needs more fine-tuning: packmethod can illuminate differing the soils into glass tubes ent Tc isotopes’ path and fate loses the heterogeneity natuin soils. rally present in the field, she The new method is a says, including the presence “novel use of what’s a stanof different-sized pore spaces dard medical technique to and naturally occurring chanlook at these soil samples,” nels in soils that serve as consays Susan Glasauer, a bioduits for water and geochemist and soil scientist contaminants. She says the at the University of Guelph technique may be better used (Canada). Reminiscent of takfor wider columns or natural ing CT scans to examine sediCo-authors Beverly Ellis and Richard Lawson of the soil cores, with more realistic ment cores, “that kind of Manchester Royal Infirmary injected soil columns with soil structures and settings, [interdisciplinary] thinking is 99mTc tracer to get images of the radioactive elesubsequently sliced up for really great,” continues Glament with a γ-ray camera. tracking Tc. Glasauer also sauer, who did not participate (or 60 kBq of the isotope) to a colnotes that lab experiments with the in the research but in the past has umn approximating anoxic soils for imaging method may be tied to worked with the corresponding auseveral weeks. using medical 99mTc, which could thor of the new method, Jonathan The team attempted to further R. Lloyd of the University of be too fast-decaying for mimicking substantiate what they saw using Manchester (UK). natural activity. TEM imaging with collaborators in Lloyd, lead-author Gavin Lear, The team’s results, which conLeeds. With the help of DNA analyand their colleagues, several of firm the bacterial immobilization of sis, they confirmed that certain miwhom hail from the university’s Tc in certain settings, might call crobes (particularly some bacteria nuclear medicine department, into question measurements in the from the family Geobacteraceae that turned gamma-ray (γ-ray) cameras field using 99Tc as a tracer for use ferric iron [Fe{III}] for energy) usually found in medical facilities groundwater or other soil movecan fix Tc in place in soils. Nearly to the task of finding Tc in soil ments. “That could be a problem all of the Tc stayed put when Fe(Isamples from Oak Ridge, TN. Manbecause [99Tc] could get hung up II) was present with these “ironmade fission of U has released tons on the iron” in natural settings, reducing” bacteria. This activity of Tc, the lightest normally radioacGlasauer says. Tc “may be too reacsuggests “a role for highly reactive tive element, from nuclear facilities tive to be used like that if what [Fe(II)] formed by these microorlike the one at Oak Ridge over the they are showing is correct.” ganisms in controlling [Tc] solubilpast decades. The element remains Either way, the team “opened ity and mobility,” says Lloyd. radioactive for thousands of years. the door for some new possibilities While these findings are not new, Back in their Manchester labs, in tracking the fate of radioactive use of the γ-camera to see Tc in a the researchers packed their contaminants undergoing gamma biogeochemical lab context is samples into thin glass columns, decay,” Glasauer says. She sees novel. Possible applications include spiked with the medical radiotracer some interesting potential in some 99m tracking how Fe and Tc move toof the researchers’ suggestions of Tc (m means the isotope is gether in soils under different conother apt radioactive isotopes, such metastable) or with the contamiditions, to inform future as mercury (Hg) and chromium nant 99Tc. By monitoring the γ-rays (Cr), as soil column tracers using emitted by the Tc in the samples, remediation techniques. this established medical method. the team could track the moveBaohua Gu of Oak Ridge Nament of the medical tracer with its —NAOMI LUBICK tional Laboratory notes that the 8 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / January 1, 2010
10.1021/es903566f
2010 American Chemical Society
Published on Web 12/30/2009
