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Friday, 25 November 2011

Getting the picture of how someone died

By screening people who have died with full-body computed tomography or magnetic resonance imaging, doctors can often determine the cause of death without an autopsy, British researchers report November 22 in the Lancet. Further combining a CT scan with a quick heart test might result in a solid determination of cause of death in up to half of cases referred for autopsy, says study coauthor Ian Roberts, a pathologist at the University of Oxford.

Autopsies are invasive and sometimes inconclusive, and some people object to the procedure on cultural or religions grounds. The new data suggest that imaging may provide an alternative in some cases, adding to post-mortem accuracy and easing the burden of grieving survivors, says Roberts. Whether imaging would save money is unknown, he says.

At their essence, autopsies have changed little in the past century but remain the gold standard post-mortem exam. In recent years, some coroners and medical examiners have considered the use of medical imaging with MRI or CT scans, but few labs or hospitals have adopted the technologies because little research data existed to document their utility in this setting.

For the new study, Roberts and his colleagues examined 182 deceased people whose cause of death wasn’t known. All underwent a CT scan and MRI. Radiologists analyzed those results separately and combined, arriving at a cause of death from each set of images. The radiologists also ranked how much confidence they had in each cause-of-death conclusion — definite, probable, possible or uncertain. Pathologists then performed autopsies on all of the bodies.

The radiologists’ cause-of-death determinations based on CT scans agreed with the more definitive autopsy findings 68 percent of the time. Conclusions based on MRI were accurate 57 percent of the time.

In cases where the radiologists ranked the cause of death from a CT scan as “definite,” the diagnosis agreed with the autopsy 84 percent of the time. But such “definite” determinations accounted for only one-third of all CT scan results.

The CT scan wasn’t particularly effective in spotting heart problems, which are common, Roberts says. But other data suggest that performing a heart angiogram after a CT scan could enable radiologists to pinpoint the cause of death in up to half of all cases, with just a slight error rate — less than that seen on most death certificates. An angiogram takes about 15 minutes, he says, and involves injecting a dye near the heart to visualize coronary vessels.

Some post-mortem scanning is done in Sweden and Australia, but making the procedure routine elsewhere would require labs to purchase CT scanners and train medical personnel to use them. Post-mortem scans look different from scans of live people. “As soon as you die, the body starts to change,” says Angela Levy, a radiologist at Georgetown University Hospital in Washington, D.C., who has done imaging on deceased members of the U.S. armed forces. “There’s a steep learning curve,” she says. Radiologists must read many scan results “to reset what they think of as normal.”

The British researchers scanned 10 cadavers and analyzed the results as training before beginning their research. “I think this is a well-done study,” Levy says.

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