Looking inside a closed box: forensic radiology

News item | 02-12-2024 | 10:37

‘Let’s start with the obvious: post-mortem radiology is when someone's dead and you use imaging to try and understand how that person died. But the radiological focus is different from the clinical radiology done in hospitals. For forensic radiology, we look at injuries and how to present them in a way that enables a judge or jury – depending on whichever legal system you've got - to understand what happened when a case goes to court.

In the state of Victoria, we have some 45,000 deaths per year. About 7000 of those are presented to the coroner and some 2500 cases get autopsies at our Institute. In Australia, the coroner decides which case needs an autopsy. We have a Coroner Act of Parliament, specifying that all deaths that fit a list of requirements must be sent to the coroner for a decision about what needs to be done to determine cause and manner of death. We call it the preliminary examination. It's ticking boxes, really. And one of those is a CT scan. Different experts working together as a team, combining post-mortem radiology, pathology and toxicology, providing the coroner with information: ‘Do we have a reasonable cause of death? Is there anything that needs to be investigated further? Does an autopsy need to be done?

So, the focus of post-mortem radiology is different from clinical radiology. The interpretation is different as well. The minute you die, your body changes. And you have to understand how those changes are manifested on imaging, or you will make mistakes. For instance, the body has no blood pressure. You don't have a beating heart, so a blood vessel that will be full of blood when you're living will look different i.e it collapses. This would be very abnormal in a living person but in a deceased person’s body, that's normal. It’s called an ‘artefact of death’. We see it as a normal process. The same is true for the way you use radiological tools. In a living person, you might inject a dye into an arm and the heart will pump the fluid around in the body. But when you're dead, you stick a needle in a vessel and nothing is going to happen, unless you infuse it in with a pump. You basically have to use a machine in place of the heart.’

How did forensic radiology start in Australia?

‘Forensic radiology as we know it today originated in Switzerland but it really started in Israel during the 1970s, partly because of Judaism that as a religion that is resistant to performing autopsies. For Australia, the story is that of the Bali bombing of December 2002, which killed more than 200 people. Bali is a common tourist destination for Australians. Usually, young people go there for holiday. That was Australia's first experience of terrorism in a mass scale bombing of a bar where there were many Australian patrons. The Australian authorities became heightened to the possibility of further acts of mass terrorism. A couple of years later Melbourne was due to host the Commonwealth Games and the government was concerned about a possible terrorist attack in our city leading to mass casualties. I put forward a submission that if we had a CT scanner, we could rapidly identify the victims using CT. The government said ‘yes’, providing a CT scanner and the whole setup. Every state in Australia saw what we were doing and wanted a scanner as well. There are now 12 forensic departments in Australia, out of which 8 have CT scanner in their mortuary.’

Sharing forensic information thus plays a key role

‘Absolutely. It has always been our objective to use all available data the best way we can. As soon as we started, in April 2005, we made a conscious decision to build up a permanent repository of all the information we were collecting. Anything that comes to us as biological tissue, we scan and images are stored forever. We have amassed a huge database of over 100,000 different cases, that we share with others. And they do the same elsewhere such as in the state of New Mexico in the USA. They don’t get as broad variety of cases as we do, but they do make them freely available on the web. Researchers can submit an application and get access to a thousand head injuries, or whatever they want to investigate. They just type in some keywords and the data comes through. That is helpful from a research point of view, or for analysis of a particularly unusual case. In New Mexico, common causes of death are gunshot and handgun injuries as well as massive numbers of motor vehicle accidents. So, if you want to know more about those kinds of cases, for example because you are reporting on a particular case where you want to better understand specific injury patterns, there's a huge repository that can be freely used to compare with your case(s). It's unlimited, really.

In Victoria, we get doctors from all over the world coming to work with us to learn PMCT. They are often from countries where families prefer not to allow autopsies, like Israel, the UAE, Indonesia and Malaysia. For religious reasons in these countries they believe that the body should remain whole after death. In an Islamic country like Malaysia, whole-body CT, or an PMCT angiogram is allowed, as long as no tissue is removed. Post-mortem radiology offers a way to see pathology in the body without having to do an autopsy. We look “inside the box without opening the box”. We can often get to tell the story of what happened in death.’

How do you deal with uncertainty?

‘If you only look at the outside of the body, you may have a lot of doubt about cause and manner of death. But if you look at the outside of the body and do an additional CT scan, combined with toxicological analysis, review of medical records of the deceased and information from the police, you get information from multiple perspectives. That’s why we work as a multidisciplinary team. You cannot achieve the same result in isolation. We still do autopsies in some cases, and we can't work out what happened in each and every case. But working together as a team is the best way, with everyone contributing to a final diagnosis, drawn up by the pathologist.

But the fact remains: you don't know what you don't know. When police are called in and find a dead person, they may initially be led to think: ‘Nothing suspicious’, because they don't know what has occurred on the inside the body. Let me give you a classic example. A guy sits in a room in his workshop. He's sitting in a chair; some blood is coming out of his mouth. He's yellowish in color, jaundiced. The police and the ambulance are called in. They try to resuscitate him, but the guy dies. So, they look at the body. There's nothing to indicate that anything is wrong. No knife wounds. No gunshot. Nothing. So the police statement says: ‘The guy looks yellow, like jaundice. He probably suffered from a liver disease or something. No suspicious circumstances.’ I guess in the Netherlands, a forensic medical examiner would be called in by the police and the diagnose would be the same: ‘The guy’s yellow. Nothing suspicious. Probable liver disease, causing a natural death.’

This is where radiology makes a difference. By definition in Victoria, because the guy has died unexpectedly, the body must be presented to the coroner come to the Institute. The first thing that happens is we do a CT scan, and finding a nail in the back of his mouth, entering into his brain. So, we go back to the police and say: ‘This happened in a workshop, right? Are there any tools lying around?’ And they say: ’There's a nail gun on the floor. One of those tools that fires nails.’ And we do the autopsy. This nail is going straight through the brainstem, which is the base of the brain. So, this is a suicide. The guy put the nail gun in his mouth. But he didn't die straightaway. He drops the gun and it falls to the ground, but it’s a workshop and there are lots of tools lying around all over the place. The guy sits down and dies. The case would have been called a natural death without imaging, but it becomes a suicide. Is that relevant? I believe it is. We need to know how many people are killing themselves. The family has the right to know what happened. There are reasons why it's important to try and be as accurate as you possibly can. Without CT, you would not have had any indication of events. The point I'm trying to make is ‘You don't know what you don't know’. You wouldn’t be thinking about a nail gun when you find a dying guy sitting in a seat. It's only when you do something like a CT scan that you discover these things.’

Radiology makes it possible to do a CT scan and get it analyzed somewhere else. What is your opinion on that?

‘Radiology is digital data with a universal language (DICOM), which can be seen anywhere via the Internet, at any time. No problem, as long as you can get the necessary legal clearance. Radiology is therefore a job without borders, because CT is the same all over the world. In fact, CT scanners are all standardized. There are only 4 or 5 companies that make the scanning equipment and all the information their scanners accumulate is basically the same. The companies use ‘phantoms’, which are a sort of spheres in which they put certain liquids. If I took a phantom for my scanner in Australia and brought it here, the CT scan would be standardized to give the same outcome. Philips in the Netherlands, Siemens in Germany, General Electric in the United States or Canon in Japan: you could use the same phantom on their scanners and get the same result.

Is there still room for improvement in radiology?

‘At the moment it's all about CT. It is the scanning technique that most people are using because it's quick and easy. But MRI (Magnetic Resonance Imaging) is the next chapter in innovation for forensic purposes. MRI is much harder to interpret and much more expensive than CT scanning, but it gives answers that are not available on CT such as soft tissue, the heart and particularly the brain . I think, CT will be always be used as a standard test. And then, based on what we see or what we suspect, MRI will be used for additional information, not of the whole body but of particular organs, such as the brain or the heart. The technology will also be helpful for full body scans on babies because they are difficult to interpret on CT. Another area is the spine. There are certain spinal areas in which a CT scan doesn’t provide sufficient information. We know that we're getting things wrong on CT and we think we can try and get it better on MRI.

On the judicial side, new technology help us to take the CT scan and animate it, creating an “avatar” of the body after death. Our Supreme Court in Melbourne has facilities that allow the projection of images in 3-D. Participants in Courts love this stuff. They love pictures although it is highly technical, requiring a lot of computer knowledge and potentially could bring about tension between a written report and a image presentation, which is relevant in a jury system. I believe that if I show the avatar in 3-D, the jury can be led to reconstruct in their own imagination all the events that I believe happened, whereas written scientific data does not always irrevocably lead to that correct interpretation being portrayed in a courtroom. One problem is that the avatar is so seductive, especially with goggles and 3D, that defense counsel might suggest that the imagery is prejudicial.

You know, you can really recreate amazing images, but you might be making a lot of assumptions to get to that final production. So that is a potential area of concern. We can demonstrate incredible cases, such as 2 guys entering a room, firing 27 bullets. Who shot whom? It's like a Hollywood movie, very convincing as a reenactment of what might have happened, and very hard for a defense team to counter. ‘Well, that's not what actually happened they might say.’ So how would they create doubt, or present an alternative scenario which is not as alluring as a 3D Hollywood movie? That is something we should be thinking about, too.’