POST-MORTEM IMAGING: RADIOLOGY AND PHOTOGRAPHY

• Jurisdiction: Australia

Introduction ................................................................................................... [33B.100]

The purpose of autopsy imaging .................................................................. [33B.110]

Post-mortem radiology .................................................................................. [33B.120]

Post-mortem CT scanning ............................................................................ [33B.130]

Cause of death and CT scanning ................................................................. [33B.140]

CT scans and inheritable disease ................................................................ [33B.150]

CT scans in trauma....................................................................................... [33B.160]

CT scans in tissue donation ......................................................................... [33B.170]

Limitations of CT scanning ........................................................................... [33B.180]

CT scan case studies ................................................................................... [33B.190]

Post-mortem CT angiography ....................................................................... [33B.200]

Conclusions ................................................................................................... [33B.210]

[33B.100] Introduction

The Webster's New International Dictionary with reference history (circa 1930s) defined an autopsy, in the medical sense, as the "dissection of a dead body for the purpose of ascertaining the cause, seat, or nature of a disease; a post-mortem examination". This definition has stood the test of time. However, the rapid evolution of imaging technology now means that one does not necessarily have to conduct a physical dissection of the deceased to address the medico-legal issues involved in a particular death investigation. The dictionary also has a more general definition of autopsy that is derived from the Greek words for "self" and "seen". The general definition states that an autopsy is a "personal observation or examination; seeing with one's own eyes; an ocular view".

Today forensic pathologists are considerably more flexible in deciding what type of "autopsy" is indicated for each individual case. Although autopsy has traditionally meant the direct observation of the macroscopic findings during a conventional post-mortem dissection, today "seeing with one's own eyes" can just as easily refer to the examination of a radiograph, a video, a photograph or a CT image on a computer screen.

Photography is the main stay of post-mortem imaging and is a specialist forensic discipline in its own right. (Aspects of photography are discussed earlier in this chapter — Part A - at [33A.810] and [33A.820].) Photographs help to document findings and can also reveal features of a body that may be difficult or impossible to see with the naked eye. Infrared and ultraviolet photography use the non-visible parts of the spectrum and have particular advantages in aspects of photography of the skin. Infrared photography may help to reveal hidden bruises and tattoos while ultraviolet imaging may reveal other forms of skin pigmentation and staining of the skin surface. However, the rendering of a three-dimensional shape in a two-dimensional photograph can lead to misrepresentation of observations. For this reason, professionally trained photographers are needed to properly document autopsy findings.

Today post-mortem computer tomography (CT) scans have become a normal part of the "autopsy" in many jurisdictions and it has added the medical radiologist to the medical pathology specialists who are involved with death investigation. The forensic pathologist must understand "to see" what is illustrated on the CT images. This may require the forensic pathologist to refer post-mortem CT images to their radiological colleagues for an expert medical opinion.

To some, the introduction of routine CT scanning to death investigations has the potential to reduce the importance of the forensic pathologist.¹ Such a narrow view of death investigation is misconceived. The skillset of most medical radiologists relates to the examination of the living and as a result, clinical radiologists may have little understanding of post-mortem changes in the body or the radiological appearances to which they give rise. In addition, and as mentioned above, the role of the pathologist in death investigations involves far more than just dissecting a body to determine a cause of death. It is by integrating a range of medical investigation modalities that we can best carry out effective and efficient death investigations.

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¹ The percentage of death investigations involving a full internal dissection of the body has reduced from around 80% to just under 50% since the introduction of CT scanning of all individuals admitted to the Victorian Institute of Forensic Medicine mortuary.

[33B.110] The purpose of autopsy imaging

The principal purposes of autopsy imaging are:

• to record the process of the death investigation;
• to record the following critical observations:

- features of body identification,
- the characteristics of injuries (location, nature, size),
- the presence and nature of staining of the body surface,
- the presence and absence of clothing, jewellery and foreign material and
- the major internal findings on dissection (natural disease and injury);

• to reveal features hidden from naked eye observation;
• to support visible comparison of body characteristics with photographs taken in life;
• to document wound paths and wound directions in relation to the environment and clothing; and
• to facilitate case audit and case consultation with other medical specialists.

Radiographs, CT and magnetic resonance imaging (MRI) scanning provide an effective means of documenting some aspects of the visible findings and can also reveal features of the body that may be difficult to identify during routine dissection. There is value in being able to visualise the interior of the body prior to dissection, since the process of opening the body is naturally associated with displacement of the major organs. A CT scan performed prior to dissection makes the relationship between external and internal injuries easier to explore. Such a volumetric three-dimensional digital model of the body forms a permanent virtual volumetric record that can be subject to further exploration and analysis by others in the future.

The importance of forensic imaging is particularly clear when the identity of the deceased is unknown or when the body has been subject to missile injury and may contain foreign material. Comparison of post-mortem radiographs with clinical radiographs taken in life can result in identity being established with a high degree of certainty. The shape of the frontal sinuses and dental structures are highly individual features and make post-mortem radiography of the head almost mandatory in autopsies on unknown individuals. The presence of medical prosthetic devices and other metallic implants may prove useful in suggesting the identity of a corpse, as these may correlate with ante-mortem medical records.

Post-mortem radiology may well be a crucial element of the investigation and management of multiple deaths in a natural disaster or terrorist incident (O'Donnell, Lino, Mansharan et al, 2010). Radiography may reveal skeletal features, which can assist in determining the age of a deceased person. The closure of epiphyses in adolescents, the development of dental structures within the jaws of children and morphometry of specific bone components may help to provide information about the age of an individual, and in the case of foetal remains, the accuracy of this technique may allow the degree of gestation to be determined to within a few days. (See also Part F.)It is important to coordinate the photographic and radiological examination with the remainder of the autopsy procedures to minimise the risk of one process interfering with another. For example, if the head is first opened with a saw, later radiographs of the frontal sinuses of the skull will be much more difficult to interpret. Similarly, the process of embalming a body may cause trauma artefacts and introduce air and fluids into body cavities, changing the radiological appearance (as well as interfering with toxicological analysis of body fluids).

Radiographs are also useful for the identification of fractures in the areas of the body that might not be routinely subject to physical dissection at autopsy. It is difficult to identify some fractures at autopsy, particularly fractures in the internal aspects of the mid-facial skeleton or in the inner aspects of joints. Such fractures may be more easily revealed in special radiological views or by utilising CT scans.

Conversely, there are some fractures that are difficult to identify in plain radiographs and are more easily revealed by direct dissection of the relevant area of the body. Subtle fractures of the base of the skull are a good example of fractures which are more easily identified during the autopsy dissection.

The identification of foreign material within the body is another way in which radiographs are used in post-mortem examinations. Bullets, bomb fragments, fire debris and penetrating objects such as knife blades or portions of aircraft or motor vehicles may be detected in this way. The radiographs become important records of the presence of such objects. Other foreign material may also be identified in particular body structures. The identification of gas within blood vessels in the body may be more easily detected by...