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Instead of cutting into a dead body to determine the cause of death, some coroners are already calling in a radiologist. But can CT (computed tomography) and MRI (magnetic-resonance imaging) tests accurately assess the recently deceased?

Formal autopsies have been on the decline for decades, due in part to tightening budgets. In the U.S. less than a quarter of deaths are followed with an autopsy, and previous research has shown that about a third of deaths have an incorrect causes listed on the death certificate. To lower cost and to help families whose religions prohibit post-mortem dissection, non-invasive imaging technology has been gaining favor. Some evidence had suggested, however, that CTs and MRIs are not quite as reliable as a traditional autopsy.

A new U.K. study of 182 adult deaths shows that more than half the time, a radiologist could pinpoint the cause of death with just a scan. But in 42 percent of CT scans and 32 percent of MRIs (and 30 percent of cases that used both), the radiologists' assessments differed from those from a full autopsy. The research was led by Ian Roberts, of the cellular pathology department at John Radcliffe Hospital in Oxford, and the results were published online Monday in The Lancet.

"Post-mortem imaging cannot yet be regarded as a universal substitute for autopsy," James Underwood, of the University of Sheffield, wrote in an essay in the same issue of the journal.

Imaging analyses were particularly poor at picking up certain common causes of death, including artery blockage (pulmonary embolism) and pneumonia. But they surpassed autopsy in a few areas, such as collapsed lungs and some bone fractures. Another benefit would be their longevity, remaining available for re-analysis long after tissue samples would have been discarded.

Even with mixed reviews, imaging techniques could help determine when a full autopsy might not be needed. The researchers noted that the imaging approach could be used more for pre-autopsy screening, which could weed out the cases that don't require further investigation—and for those that do, the information gleaned from CT scans or MRIs could help guide later dissections. CT scans can also be cheaper than a traditional autopsy, and by using machines that they already own, medical institutions could keep costs down, noted the research team.

Underwood concluded that for now, the best use of imaging might indeed be to lessen the demand on coroners' time by keeping traditional autopsies to "those cases in which the cause of death cannot be arrived at in any other way."