Forensic Science, Medicine, and Pathology Copyright © 2007 Humana Press Inc. All rights of any nature whatsoever are reserved. ISSN 1547-769X/07/3:65–70/$30.00 (Online) 1556-2891 DOI: 10.1385/Forensic Sci. Med. Pathol.:3:1:65
RADIOLOGY REVIEW
The Use of CT Scanning in Forensic Autopsy Peter Mygind Leth Institute of Forensic Medicine, University of Southern Denmark, Odense, Denmark
Address for correspondence and reprints: Dr. Peter Mygind Leth Institute of Forensic Medicine University of Southern Denmark J.B. Winsløws Vej 17 DK-5000 Odense Denmark E-mail:
[email protected] Accepted for publication: December 20, 2006
Abstract Postmortem computed tomography (CT) is being used more frequently in forensic medicine. This review discusses 100 deceased individuals who underwent CT scanning, as well as a standard autopsy. The CT scan was performed and interpreted by a forensic medicine specialist. In 11 cases, important findings discovered during the CT scan were not found at autopsy, and in 58 cases, important findings revealed at autopsy were not uncovered during the CT-scan. The cause of death could be established by the CT scan and external examination in 27%; by CT scan, external examination, and forensic chemistry in 32%; and by autopsy in 95% of the cases. CT scanning was most useful in cases of traumatic death. CT is rarely a substitute for autopsy, but may contribute important new information in cases such as identifications (particularly following mass disasters), battered children, gunshot wounds, traffic accidents, and air embolisms. CT provides documentation in digital form, which is easily stored and permits review by others. CT also provides pictures that may be more suitable for presentation in court than autopsy photos. CT scanning also would be helpful during a medicolegal external examination (inquest) in the process of selecting cases for autopsy. Key Words: Forensic radiology; forensic science; autopsy; computed tomography; CT scanning imaging; postmortem imagining. (DOI: 10.1385/Forensic Sci. Med. Pathol.:3:1:65)
INTRODUCTION Examination of deceased individuals may benefit from modern imagining techniques such as computed tomography (CT) (1). The usefulness of this technique increases almost daily as a result of technical improvements and decreasing costs. Traditional autopsy remains the best method for postmortem examination and is the gold standard when evaluating postmortem imaging techniques. CT may, however, contribute important new information and may even, in some cases, be an acceptable substitute for an autopsy (2,3). CT scanning was introduced as a routine procedure at every autopsy at the Institute of Forensic Medicine, University of Southern Denmark in February 2006. This review includes a summary of the results of the first 100 cases.
BACKGROUND The Institute of Forensic Medicine at the University of Southern Denmark is the smallest of the three institutes of forensic medicine in Denmark. It consists of a Department
of Forensic Pathology, a Department of Forensic Chemistry, and a Department of Anthropology (mostly occupied with archaeological work), and provides forensic medical service for the population of 730,780 (as of January 2006) individuals who live on the island of Fyn and in the southernmost county of the Jutland peninsula at the Danish–German border. Two hundred medicolegal autopsies and 250 clinical forensic examinations of victims of violence and perpetrators are performed each year. The institute employs three forensic pathology specialists, and two doctors who are in training for forensic pathology. The institute is also a teaching and research facility.
MATERIAL The 100 cases presented in this review is a consecutive series of individuals autopsied at the Institute of Forensic Medicine, University of Southern Denmark, from February to June 2006. The cases included 62 men and 38 women. The median age was 46 years (range 0–88 years). There
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66 ______________________________________________________________________________________________Leth Table 1 Individuals Autopsied at the Institute of Forensic Medicine, University of Southern Denmark, February Through June 2006, Distributed After Cause of Death Cause of death
Number of cases
Cardiovascular disease Poisoning Severe trauma Gastrointestinal disease Traumatic suffocation Drowning Lung disease Central nervous system disease Sepsis Burns Exposure Unknown Total
27 22 13 8 6 5 5 3 2 1 1 7 100
Fig. 1. The computed tomography scanner at the Institute of Forensic Medicine, University of Southern Denmark.
CT FINDINGS COMPARED WITH AUTOPSY were 45 natural deaths, 39 accidents, 1 homicide, 9 suicides, and 6 unknown deaths. The causes of death are listed in Table 1.
CT SCANNING PROCEDURES The CT scanner used is a dual-slice Somatom Spirit spiral scanner from Siemens (Fig. 1). Dual-slice scanners have two parallel detector rows. The X-ray tube is air-cooled and needs a short pause for cooling between each scan. However, because of the small number of autopsies performed at the institute, this does not pose a problem. Facilities where larger numbers of autopsies are performed should use an oil-cooled X-ray tube. In each case, four separate scans are performed of the head, neck, thorax, and abdomen. In some cases, such as examination of the lower extremities of traffic accident victims, further scans may be necessary. This requires the body to be turned around on the table to allow the legs to be moved into the gantry opening. Routine scans take about 10 minutes, not including the handling of the body before and after the scanning. The scan operator is a forensic medicine specialist who has been trained to perform this procedure and who is also responsible for the evaluation of the images and the writing of the CT report. The forensic pathologist who performs the autopsy has no prior knowledge of the scan results, thus ensuring double-blinding of the data from the CT scan- and the autopsy. The forensic pathologist is informed of the CT findings before the organs are returned to the body, and the results from the CT scan are included in the final forensic report. The double-blind data from the CT scan and from the autopsy are entered into a computer database (SPSS) for further analysis and future research.
In 11 of the cases, important findings from the CT scan were not seen at autopsy. These included four extremity fractures, one pelvic fracture, two cases of bone metastases, two cases of pneumothorax, and two cases of severe compression of the heart by hydrothorax. In the latter two cases, the hydrothorax was found at the autopsy, but the full extent of the cardiac compression could not be appreciated. In one case, a pneumothorax thought to be present at autopsy was clearly not present at the CT scan. In 58 cases, important findings at autopsy were not found by the CT scan (Table 2). It remains to be seen whether these results can be improved as the pathologist gains experience in interpreting CT images. Postmortem CT-scanning suffers from the severe limitation that contrast cannot be used. The cause of death could be established by CT scan and external examination in 27% of the cases and by CT scanning, external examination, and forensic chemistry in 32%. In contrast, the cause of death was established in 95% of all autopsies. An often-raised question concerns how often an autopsy can be substituted with a CT scan. This question has become relevant because of decreasing autopsy frequency. In Denmark, this reduction has been from more than 65% of all deceased autopsied in the 1970s to less than 15% today (the number of medicolegal autopsies has not been decreasing). Two evaluations of this question were made, first before the autopsy, and then again after the autopsy, with additional investigations such as microscopy and toxicology.At the first evaluation, we found that the autopsy could be omitted in approximately one third of the cases. This, however, includes cases where the diagnosis of the cause of death depended on the toxicology, and where no suspicion of homicide was raised by the police investigation and the medicolegal external
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CT Scanning and Autopsy ___________________________________________________________________________67 Table 2 Individuals Autopsied at the Institute of Forensic Medicine, University of Southern Denmark, February Through June 2006, Distributed After Most Important Autopsy Finding Overlooked at Computed Tomography Scan Cause of death
Number of cases
Noncalcified severe coronary atherosclerosis (4), coronary thrombosis (4) Pulmonary embolism Emphysema aquosum (drowning) Peritonitis Myocardial infarction Liver or spleen contusion Bronchiectasis (2) and emphysema (1) Severe pulmonary edema Severe aspiration/bolus Fracture of cornu superior thyroideae Micronodular cirrhosis Metastases Rupture of atlanto-occipital ligament Nondislocated fracture of collumna thoracalis Fracture of cranial base Stress ulcer in ventricle (exposure) Small renal cell adenocarcinoma Bronchopneumonia Myocardial fibrotic scar Total
8
7 5 4 4 4 3 2 3 3 3 3 2 1 1 1 1 1 1 57
Note: In some cases more than one autopsy finding was overlooked by the CT scan, but only the most important diagnosis was selected for each case.
investigation. It remains to be seen whether it is advisable to omit the autopsy and rely exclusively on CT scanning in cases where the diagnosis depends on the toxicological examination, even when there is no prior suspicion of homicide. The result of the toxicology is usually not available until several weeks after the investigation, and at that time it would be too late to perform an autopsy should the toxicology turn out to be negative. More experience with CT scanning is needed before a conclusion can be reached in this matter. However, only in one case was the opinion regarding the need of an autopsy changed at the second evaluation after the results of the autopsy and supplementary investigations were available. In this case, a ring fracture in the cranial base was overlooked at the CT scanning. In which cases can CT scanning be used to establish the cause of death? Figure 2 shows a comparison between the groups where the cause of death could be established by CT scanning alone and those where an autopsy was needed. CT scanning seems to be most useful in cases of traumatic death.
Fig. 2. Individuals autopsied at the Institute of Forensic Medicine, University of Southern Denmark, February through June 2006. Causes of death in the groups where the cause of death could be established by CT scanning alone (light gray) compared to those where the autopsy was needed to establish the cause of death (dark gray). In each group, the distribution is given as a percentage within that group.
ADVANTAGES OF AUTOPSY AND CT SCANNING The autopsy has several important advantages compared to CT scanning. One advantage is the possibility of performing microscopy on tissue samples. Important microscopic findings were done in approximately one third of all cases and in one fifth of those cases where the cause of death could be established by CT scanning alone. This additional information is lost if an autopsy is not performed. Of course, it may be possible to take needle biopsies, but this seems to be a time-consuming procedure compared to an autopsy. On the other hand, the CT scan may contribute to the findings by providing new information that could not be obtained by an autopsy alone and allows investigation of anatomic regions that are not easily available by autopsy. Three-dimensional reconstruction of bone fractures as they appear in situ, before they are disturbed by an autopsy, is a good example (Fig. 3). CT scanning is also useful in cases of gunshot injuries. The projectile can easily be found, the bullet tract can often be visualized, and the shot angles can be measured (4,5). In cases where the deceased needs to be identified, CT scanning gives a quick overview of the body, revealing old fractures, transplants, dentition, and the like. CT scanning is especially useful in identification of mass-disaster victims (6,7). The Danish Defence has purchased a CT scanner that can be transported by air to the site of a mass disaster. The Army’s equipment also includes refrigerated containers, with room for 20 bodies each, and a field hospital in containers that may easily be converted to mobile autopsy rooms. These containers are also suitable for deployment in a harsh environment such as the North Atlantic (The Faeroe Islands and
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68 ______________________________________________________________________________________________Leth mechanically. The CT scanner was also used by a paleontologist who investigated the decomposition process of shrimps in small plexiglass containers with different seabed composition and different atmospheric and seawater conditions in order to shed light on the fascinating process of fossilization.
WHEN SHOULD CT SCANNING TAKE PLACE?
Fig. 3. Three-dimensional computed tomography reconstruction of a tibia fracture in a pedestrian hit by a car. There is an intermediary fragment, showing the direction of the trauma.
Greenland), where access to suitable autopsy room may be limited. CT scanning may be helpful in cases of terror bombings by allowing a quick evaluation of the distribution and type of shell fragments. CT scanning is also useful in cases of child abuse, revealing old and new fractures and intracranial bleedings. For this purpose, CT must be combined with conventional X-ray pictures. This is obviously a job for a specialist in radiology. CT scanning is superior to autopsy in visualizing air embolism (8). Finally, it should be mentioned that CT provides documentation in digital form that is easily stored and permits review by others, as well as providing pictures that may be more suitable for presentation in court than autopsy photos.
One could question at which point in the investigation of unnatural deaths CT scanning would be most useful. In Denmark, the medicolegal external examination or inquest in forensic cases is performed by the medical officer of public health in the county in question in coordination with a senior police officer. The police reports that are available at the inquest would include a description of the scene and interrogation of witnesses, including the family physician. The hospital records, if any, would also be made available. Based on this material, and on an external examination of the body performed by the medical officer, a decision is made as to whether or not a forensic autopsy is needed. Forensic autopsies are performed by the medical examiners at the Institute of Forensic Medicine. It is the police who decide whether an autopsy is needed. At present, the CT scan is performed immediately before the autopsy, but it might be preferable to perform the scan before the external medicolegal examination, that is, before a decision about the need for an autopsy is reached. It may then be found that some autopsies are not needed after all, but it could also be that an unexpected CT finding may lead to a decision of autopsy, in cases where an autopsy would otherwise not have been requested.
Educational Message 1. CT scanning can only be seen as a substitute for an autopsy in a minority of cases. 2. CT is helpful in many cases, such as identifications (including mass disasters), battered children, gunshot wounds, traffic accidents, air embolism, etc. 3. CT allows for investigation of anatomic regions that are not easily seen during autopsy. 4. CT allows fractures and inner organ to be seen in situ. 5. CT provides documentation in easily stored digital form, permits review by others, and provides pictures that may be more suitable for presentation in court than autopsy photos. 6. CT opens new fields of research.
RESEARCH The CT scanner may also be used for research. Among the research projects to date is the investigation of tooth eruption in children whose bodies were found at a medieval burial site. With this technique it is not necessary to dissect the old bones
The author has stated that he does not have a significant financial interest or other relationship with any product manufacturer or provider of services discussed in this article.
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