Virtual autopsy has moved into civilian forensics as well. In Melbourne, Australia, postmortem CT scanning has been part of legal investigations of deaths since 2005. In the U.S., at least two state medical examiners' offices, in New Mexico and Maryland, routinely use it. The Maryland office, according to Chief Medical Examiner David Fowler, applies CT to roughly half its autopsies, which amounts to about 2,000 cases a year. Imaging has proved invaluable, he says, for “pediatric cases, motor vehicle collisions and drownings” and has revealed causes of death in cases where dissection would destroy evidence, such as air sucked into blood vessels during trauma or dialysis and sports injuries to the vertebral artery, which snakes through the bones of the neck.

In hospitals, the value seems more mixed. Two 2009 research reviews by teams in the U.K. and the Netherlands found that virtual autopsies differed widely in accuracy, depending on whether the deceased was an infant, child or adult and on whether the cause of death was trauma or an infectious or chronic disease.

This past January a study conducted among intensive care unit patients in Germany compared diagnoses made before death with the results of both traditional and virtual autopsy in 47 patients and with only virtual autopsy in another 115 whose families refused standard autopsy. Virtual autopsies confirmed 88 percent of diagnoses made before death, not far behind the 93 percent rate for traditional postmortem exams. Although virtual autopsies tended to miss fatal heart attacks and blood clots in the lung and major blood vessels, traditional autopsies were not perfect either: they missed important fractures, fluid around the heart and collapsed lungs.

Dominic Wichmann, a specialist in internal medicine at University Medical Center Hamburg-Eppendorf in Germany and the study's first author, says the large number of instances where postmortem exams were refused underlines a situation in which virtual autopsy is essential: cases where cause of death is uncertain, but a standard autopsy violates religious rules.

Although no one keeps comparative records, the U.S. institution with the most virtual-autopsy experience may be Massachusetts General Hospital, which has conducted more than 125 procedures since 2010 under the direction of Mannudeep Kalra. He says that virtual autopsies help to establish frank causes of death such as air embolisms. Its biggest apparent shortcoming—failure to identify cardiovascular disease—is easily explained, he says: there is no circulation to move around the contrast medium that illuminates blood vessels from the inside. To solve this problem, several research teams are contemplating using heart-lung machines or similar pumps.

On the Table

Mass general, a teaching hospital of Harvard Medical School, is one of various academic medical centers to invest in the latest iteration of postmortem imaging technology: a virtual-autopsy table—essentially a giant iPad—that transforms the data from the scans into a 3-D animated image that doctors can “dissect” layer by layer with hand gestures. The Case Western Reserve University School of Medicine uses a virtual-autopsy table built by Swedish firm Sectra AB, while Harvard, Stanford University, the University of Texas at Austin and the University of Wisconsin–Madison have bought tables built by Silicon Valley–based Anatomage.

The biggest barrier to wider adoption of virtual autopsy is the cost of equipment and personnel. Virtual-autopsy tables are expensive; Anatomage's costs $60,000. The scanners used for MRI and CT cost hundreds of thousands of dollars, but most medical centers already have them. The true challenge is finding ways to pay technicians because autopsies—real or virtual—are not reimbursed procedures.

“I think compensation is going to be the rate-limiting step,” says Gregory Davis, a pathology professor at the University of Kentucky College of Medicine. Hospital radiology departments, he points out, already have hectic schedules full of appointments with paying patients. Establishing a virtual-autopsy program often requires staff and faculty to work outside standard hours and obtain scarce grants or donate their time.

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