Once you do a traditional autopsy, it's difficult to look at the wounds—the skull fragments fall apart. On the CT scan, you can visualize the injury pattern or where the injury occurred. Commander Craig Mallak, M.D.

Virtual Autopsy Offers Noninvasive Postmortem Exam

Powerful new technologies are yielding postmortem images that allow medical examiners to comprehensively understand cause of death while avoiding some of the drawbacks of traditional scalpel autopsy.

In the past, determining cause of death meant careful examination of the body by dissection—a time-consuming, expensive procedure some cultures find objectionable.
On the other hand, virtual autopsy, as it is generally known, uses CT and MR imaging to capture detailed images of cadavers. Radiologists can then create 3D visualizations that enable pathologists, coroners and medical examiners to investigate the condition of the body for clues to the cause and manner of death.

Swiss pioneers of the technology have trademarked the name Virtopsy® to describe their unique forensic reconstruction strategy that combines different imaging methods—computed tomography (CT), MR imaging, image guided biopsy and postmortem angiography, among others— with special database and application software. These researchers have drawn the interest of the National Institutes of Health, which most recently included their work in the “Visible Proofs: Forensic Views of the Body” exhibition showing at the National Library of Medicine through February 16, 2008.

Postmortem imaging is not new, but the advent of 3D imaging technology has made it much more applicable to forensic medicine. Examiners now have options traditional scalpel autopsy could not offer.

“Diagnostic imaging is still underused in forensics, mainly due to unawareness of its potential and the lack of teaching and experience,” said Richard Dirnhofer, M.D., founder and manager of the Virtopsy Project at the University of Bern in Switzerland. Dr. Dirnhofer is the lead author of “VIRTOPSY: Minimally Invasive, Imaging-guided Virtual Autopsy,” appearing in the September-October issue of RadioGraphics.

Dr. Dirnhofer sees parallels between Virtopsy and the DNA research that began 20 years ago and recently culminated in sequencing the human genome. DNA sequencing was fraught with the same anxiety and hand-wringing over expense, said Dr. Dirnhofer, that he sees some colleagues experiencing about Virtopsy.

“We are now in the research phase, which is a difficult time for Virtopsy,” he said. The feasibility has been shown, he said, but now the technology must hold up to repeated testing. “As with DNA, it will be a step-by-step process,” he said.

Permanence and Ease are Advantages

Given that forensic evidence doesn’t last forever, virtual autopsy's most obvious advantage is that it creates a 3D image—a permanent record that can be studied, archived or sent on to others.

“It is easy to have objective documentation after a virtual autopsy,” said Anders Persson, M.D., Ph.D., director of the Center for Medical Image Science and Visualization (CMIV) at Sweden’s Linkoping University. “You can reproduce it, give it to a third party or look at it again in 10 years.”

Ease of documentation also makes virtual autopsy particularly well-suited for use as courtroom evidence, taking the place of graphic or disturbing photographs.

“You can also see different versions from different angles,” said Graham Segal, O.A.M.., an Australian barrister-at-law and chair of the first virtual autopsy conference, held late last year in Sydney. “For example, if you’re looking at the passage of a bullet, you can manipulate the image to enable a variety of understandings.”

Cultural Impact is Significant

Another key benefit of virtual autopsy is that it allows investigation without destroying the body, a procedure many people of different faiths and cultures find invasive or offensive. People of Jewish and Muslim faiths that believe most autopsies violate religious laws, said Segal, while others find the idea of autopsy on relatives distasteful or unnecessary. “You have the decorum of a funeral, interrupted by a slight detour to chopping block—that’s the way some people see it,” he said.

Segal also points to a variety of injuries and trauma—including facial fractures, drowning, strangulation and gunshot wounds—that are easier to identify through imaging rather than scalpel autopsy.

Added Dr. Persson, “Our software can amplify the very small fragments that you can’t see with the naked eye.”

Military Examiners Find Use

Virtual autopsy also is helping military examiners find the exact causes of death for soldiers killed in the line of duty. At the forefront is the U.S. Armed Forces Institute of Pathology (AFIP), which performs CT-assisted autopsy.

Commander Craig Mallak, M.D., an AFIP medical examiner, said he believes that CT helps examiners more quickly localize certain abnormalities than was possible using past procedures.

“In the old 2D days, we had no idea what plane a bullet was laying in without taking a series of x-rays,” he said. “Now, we run the body through a CT scanner and we know exactly where to look for the projectile.” CT-assisted autopsy also picks up a lot of subtle injuries not seen in traditional autopsy, he said. In certain areas that might not traditionally have been examined, the CT scan now guides the hands of the pathologist.

 Dr. Mallak said he believes virtual autopsy can sometimes offer better information than traditional autopsy, particularly in trauma cases. For example, imaging enhances the recovery of projectiles, which is often helpful with trauma such as severe head injuries, he said.
“Once you do a traditional autopsy, it's difficult to look at the wounds—the skull fragments fall apart,” Dr. Mallack said. “But on the CT scan, you can visualize the injury pattern or where the injury occurred.”

Despite its capabilities, few predict that imaging will completely replace the scalpel in the future. Most agree virtual autopsy works best as a supplement to traditional autopsy. Dr. Mallack noted that certain injuries are not well-visualized on CT, adding. “You can't get toxicology samples or recover bullets from a scan.”

Virtual Autopsy also a Triage Tool

Some also foresee virtual autopsy as a screening tool for mass casualties from natural disasters or terrorism.

“In a scenario where you have mass casualties and the medical examiner can't possibly autopsy every person, it can help you figure out which body needs an autopsy,” said Colonel Angela Levy, M.D., who works with Dr. Mallack at AFIP.

Dr. Mallak said Hurricane Katrina provides a potent example. “You had bodies that had decomposed and you couldn't tell whether they had suffered trauma or simply drowned,” he said. “Using a CT scan would be a good triage tool,” he said.

Many argue imaging, despite employing cutting-edge technology, is less expensive than traditional autopsies. Scanning the dead “is cheaper per case because it’s so much quicker,” said Segal. “It’s less labor intensive, so you need less staff at the morgue.”
 
Reading postmortem scans does present new challenges for radiologists. “It’s not the same as looking at the living,” said Dr. Persson. “One important issue is postmortem gas. After a day or so, you find gas in the skeleton, in the soft tissue; it’s popping up everywhere. It’s hard to see if it’s gas from bowels or from the wound.”

Radiologists can learn only by looking at many cases, said Dr. Persson. “There are no books; it’s a completely new area,” he said.

With that newness, however, comes continual discovery.

“You never know what you're going to find," said Dr. Mallak. "We've been surprised by what we’ve seen in the images, but that's good. This isn't fantasy anymore; it's reality.”     

To read the abstract for the article, “VIRTOPSY: Minimally Invasive, Imaging-guided Virtual Autopsy,” go to radiographics.rsnajnls.org/cgi/content/abstract/26/5/1305.

For more information about the “Visible Proofs: Forensic Views of the Body” exhibition at the National Library of Medicine, go to www.nlm.nih.gov/visibleproofs/exhibition/ .