Computed Tomography Angiography Improves Quality of Postmortem Exams
The imaging technique detects 90 percent of all findings, compared to 61 percent for autopsy alone.
A high-quality postmortem examination is important for forensic cases as well as for medical quality control. A recent study showed that postmortem computed tomography angiography is superior to autopsy alone, but combining both methods leads to the best results. As reported in the May issue of the journal Radiology, autopsy missed nearly one quarter of forensically essential findings, compared with 10 percent for the angiography technique, which they call PMCTA.
"This method could -- in many cases -- be an alternative to invasive autopsy if such an opening of the body is not possible," said first author Silke Grabherr of the University Center of Legal Medicine Lausanne-Geneva in Switzerland. "This offers new investigation possibilities, for example, in countries where a conventional autopsy is not accepted or in cases where family members can refuse it."
Computed tomography is a widely used imaging technique in modern postmortem examinations. But it has a relatively low soft-tissue contrast and poor ability to visualize the vascular system, making conventional autopsy more suitable for investigations of cardiovascular death. To address these limitations, various postmortem angiographic techniques have been developed, and PMCTA was recently introduced into forensic investigations.
In a previous study, Grabherr and her team showed that PMCTA is more sensitive than conventional autopsy at identifying skeletal and vascular lesions. Moreover, PMCTA can increase the sensitivity of CT alone from 65 percent to 81 percent, which is comparable to the 83 percent sensitivity of conventional autopsy. But this single-center study involved only 50 human corpses, so Grabherr and her collaborators set out to validate the technique in a multi-center study involving a larger number of cases.
In the new study, the researchers compared the performance of postmortem CT, PMCTA and autopsy on 500 human corpses at nine centers. Among a total of 18,654 findings for all types of lesions, 61 percent were identified by autopsies, compared with 76 percent for CT and 90 percent for PMCTA. If only CT had been performed, 38 percent of findings essential for the forensic investigation would have remained unreported. While CT detected only 73 percent of soft-tissue findings and 53 percent of vascular lesions, PMCTA detected 86 percent and 95 percent, respectively.
In particular, PMCTA was far better than autopsy at identifying bone lesions (95 percent versus 47 percent) and vascular lesions (95 versus 69 percent). "The combination of bone lesions and vascular lesions is especially seen in cases of traumatic death, such as falls from height, traffic accidents, ballistic trauma and sharp trauma in homicides and suicides," Grabherr said. "This means that PMCTA is an excellent choice to investigate such cases and can be combined with or even used independently of conventional autopsy for investigating these cases."
The best results were achieved when autopsy was combined with CT and PMCTA, especially in cases of natural death and malpractice. In some cases, the interpretation of the autopsy results regarding the cause of death and events leading to death would have been incomplete or simply wrong if CT and PMCTA had not been performed.
“When we conduct forensic investigations, it is critical that methods used are valid with known error. This study starts this process for the use of PMCT and PMCT angiography,” said Daniel Wescott, director of the Forensic Anthropology Center at Texas State University in San Marcos, who was not involved in the study. “It clearly shows that more features critical to cause of death interpretation are observed with CT angiography, especially when the cause of death is vascular in nature. The study also makes a strong case for medical examiners to use CT angiography as part of their autopsy toolkit in postmortem examinations.”
In the future, Grabherr and her team plan to study the combination of post-mortem angiography with MRI in order to quantify the potential increase in sensitivity of findings related to organs such as the brain and liver.