January 28, 2008

CT Autopsy
By Kathy Hardy
Radiology Today
Vol. 9 No. 2 P. 20

Medical examiners see its value, but cost could derail widespread use.

Medical examiners and forensic pathologists could benefit from a virtual point of view, according to a recent CT autopsy study. The study reveals how scanning a decedent’s body can enhance conventional autopsy procedures that document specific injuries related to certain accidental deaths. However, it remains to be seen whether adoption of this technological advancement will become a reality for a public sector in which the number of bodies is greater than the number of medical professionals assigned to examine them. Also, the tool’s cost could be prohibitive to its mainstream use.

Barry Daly, MD, professor of radiology at the University of Maryland School of Medicine in Baltimore, presented early study results at RSNA 2007 in November suggesting a role for high-resolution multidetector CT imaging autopsy in the forensic investigation of nonaccidental deaths or traumatic accidents. Daly says the study was conducted to show the feasibility of performing routine CT autopsies, especially in cases of severe accidental trauma.

“A CT autopsy can reveal forensic evidence much faster than a conventional autopsy,” Daly says. “It may also show better detail of bone and spine injuries and air embolisms. This noninvasive procedure is very good for looking at severe trauma in such areas as the brain, spine, and pelvis. A reason not to use CT autopsy would be where the cause of death is likely to be cardiac in nonaccidental deaths where autopsy is mandatory.”

The study investigators also reported certain advantages of CT autopsy over conventional autopsy. For example, in cases of suspicious death, the noninvasive exam does not damage vital forensic evidence, as can happen during a conventional autopsy. In addition, CT can be used in situations where autopsy may be prohibited by religious or cultural beliefs.

Triage Tool
For those medical personnel involved in the study, as well as forensic pathology professionals, the current potential for CT autopsy is seen as more of a triage tool to determine if a full autopsy is necessary.

In this study, 20 cadavers underwent CT scans and conventional autopsies at the University of Maryland Medical Center and the state’s chief medical examiner’s office within 24 hours of death by blunt or penetrating trauma. Among the subjects scanned, 14 suffered blunt trauma injuries, and six were victims of penetrating wounds caused by a knife, gunshot, or other ballistic weapon.

Conducting a CT scan on a corpse has its unique characteristics, Daly says. Technicians can use a higher radiation dose on a dead body, and very thin sections can be captured. However, there is no opportunity for using intravenous or oral contrast postmortem since there is no blood circulation.

Two radiologists conducted and interpreted the scans, the results of which were compared with those of conventional autopsies performed by state forensic medical examiners. The findings were evaluated as comparable with, a helpful adjunct to, or as providing no additive value to the conventional autopsy findings.

The study results showed that CT imaging correctly identified 92 major findings and all 14 causes of death in the cases of blunt trauma. In the cases of penetrating trauma, imaging correctly discovered 36 major findings and five of six causes of death.

Radiologists and forensic medical examiners evaluated the CT findings as comparable with conventional autopsy in 13 of the 14 blunt trauma cases and as a helpful adjunct in five of the six penetrating wound cases. Six major false-negative CT findings included lacerations of the bronchus, right heart, ascending aorta, and liver. In addition, CT scans localized all 26 major ballistic fragments recovered from the victims during conventional autopsy; however, 13 known pathways were incompletely identified or unidentified, especially where no fragments remained.

“Autopsy is mandatory in deaths involving gunshot wounds, but CT can serve as a powerful adjunct to the conventional exam,” Daly said in a prepared statement. “Performing CT imaging first may speed up a conventional autopsy, especially when it comes to locating multiple ballistic fragments, which are so important to criminal investigations.”

Traumatic Death
Overall, the study results suggest that CT shows promise as a sensitive tool for the detection of major injuries and cause of death after accidental blunt trauma. In nonaccidental traumatic deaths, CT can be a valuable adjunct to mandatory autopsy for detecting injuries.

“A CT scan would be helpful in certain cases, particularly those involving a victim with multiple gunshot wounds,” says forensic pathologist Joseph Prahlow, MD, associate professor of pathology at the Indiana University School of Medicine in South Bend. “In cases where the victim was shot multiple times or where there are numerous small caliber bullets, CT scan would be a tremendous help in locating those bullets in the body.”

However, Prahlow points out that in this study, not all evidence was detected with the CT scan. A small injury that is not detected with CT isn’t necessarily insignificant to the overall evidence-gathering process. “Also, a very important part of an autopsy is the external exam,” he says. “In most cases, you would still need to do an external exam.”

Prahlow, who is also the president of the National Association of Medical Examiners, also works for the South Bend Medical Foundation as a forensic pathologist, where he performs autopsies for area hospitals and coroners. Prahlow agrees that CT autopsy would be a useful tool in any medical examiner’s office. “There’s probably not a forensic pathologist in the United States who would say ‘no’ if offered a free CT scanner,” he says.

Cost Issues
However, Prahlow doesn’t see the technology replacing traditional autopsy procedures in the near future. This is mostly because of the expense of adding CT technology to the average medical examiner’s department.

“If a medical examiner’s office is faced with the cost of a CT scanner and the radiologist to interpret the scan vs. the cost of opening another office or hiring another medical examiner to handle increased workload, they would chose the latter,” he says.

Increased workload is an issue for forensic pathologists. All states require autopsies in cases of sudden and unexplained death. There are two types of autopsies. Medical autopsies are most often performed with deaths considered to be by natural cause and are done in hospitals. Forensic autopsies are performed for legal reasons, with each state defining requirements for the procedure. The number of cases requiring forensic autopsy is increasing, and the number of medical examiners and forensic pathologists is not keeping pace, which creates a backlog. For example, the state of Maryland reported more than 8,000 sudden and unexplained deaths referred to the chief medical examiner in 2006, with approximately one half requiring full autopsies.

Daly says that getting CT scanners into medical examiners’ offices is key to the technology’s adoption. But for more widespread acceptance, there needs to be a demonstrated economical advantage to adding CT to a forensic pathologist’s toolkit. A CT scan takes less time than a traditional autopsy and could reduce the cost by at least 50%. A forensic medical examiner requires several hours to conduct a full autopsy, while CT scanning and interpretation can be completed in approximately 30 minutes.

Prahlow also foresees a problem in attracting the increased staff required to handle the operation of CT scanners within a medical examiner’s office. Forensic pathologists, hired by local and county governments to run their medical examiners’ offices, receive salaries at a lower rate than general pathologists due to the nature of local and county government budgetary restrictions. Therefore, fewer pathologists take the extra steps required to specialize in forensic examinations.

“You would run into the same situation trying to hire a new subspecialty of radiologists to interpret scans for forensic work,” Prahlow says. “You have more training and a lower salary.”

Another staffing issue involves which personnel within the medical examiner’s office would conduct CT scans. Some large offices may employ radiologic technologists, but most have autopsy assistants, he says. While autopsy assistants have been trained to take x-rays, they don’t have training in conducting CT scans.

“We would have to train autopsy assistants to perform the CT scans,” he says. “We would also have to find a radiologist to consult on a case for interpretation of the scan’s findings. In most cases, forensic pathologists don’t require radiologists to interpret x-rays. We’re different from those medical professionals who work with live patients. If we’re looking for a bullet, we locate the bullet and we recover it. There’s less interpretation required. But, in something like a case of alleged child abuse, we will ask for interpretation of x-rays. The evidence is more subtle.”

Training Radiologists
Daly adds that there are plans to initiate training for radiologists in this new subspecialty of forensic interpretation of CT scans. “With PACS and teleradiology, a few medical centers with trained radiologists could easily provide consultations nationwide,” he says.

The U.S. military has been routinely implementing CT-assisted autopsies for three years at the world’s largest mortuary, the Charles C. Carson Center for Mortuary Affairs at Dover Air Force Base in Delaware. It is at this facility that the remains of U.S. service members who die overseas are autopsied and prepared for burial. According to Col Angela D. Levy of the U.S. Army Medical Corps, CT scans have been part of the autopsy process for each body that has passed through the Dover mortuary since 2004 to assist in determining cause of death.

Levy, who is also professor of radiology and nuclear medicine with Uniformed Services University of the Health Sciences in Bethesda, Md., says imaging is a useful tool but not yet a replacement for conventional autopsy. “We’re looking for the reason why a person died,” she says. “We’re looking for abnormalities. Imaging is a complement to conventional autopsy procedures, but I don’t see a situation yet where you could only do imaging as a form of autopsy.”

She says there is a particular learning curve when interpreting CT autopsy scans, just as there is with the introduction of any new imaging technology in a particular medical field. “There needs to be more time for validation of the technology,” she says, “and with more experience, that time will come.”

Once more people are comfortable with the technology, Levy says, the information gathered via CT scan is helpful in determining cause of death. “It has helped us, and I can see where it could help in many other situations,” she says.

— Kathy Hardy is a freelance writer and editor based in Phoenixville, Pa.