Smarter scanning

Radiology has been used in forensics since the late 1800s. In recent years, there has been increasing interest in the use of computed tomography (CT), which scientists believe can yield valuable unnatural findings and ultimately the cause of death. Damian Small reports.

The East Midlands Forensic Pathology Unit has virtually stopped using conventional radiological technology such as plain X-ray and fluoroscopy for post-mortem work due to the privileged access it has had to CT scanners in the University Hospitals of Leicester NHS Trust since 2002.

“The CT scanners have proved a valuable tool in the field of forensic pathology,” said Professor Guy Rutty, head of the Forensic Pathology Unit at the University of Leicester.

Prof Rutty has been using mobile CT scanners for both research and practical work. “We find that CT can provide rapid whole body imaging equalling that of plain radiography, with the addition of detailed axial images and three-dimensional (3-D) reconstructions,” he said

Another benefit of CT scanning, said Prof Rutty, is that less manipulation and manual handling is required as the body can be viewed in multiple planes without prior removal from a sealed body bag.

“This reduces the risk of evidence contamination and traumatic stress to inexperienced staff.”

Prof Rutty said a major advantage of CT pre-autopsy screening is that it provides important clinical diagnostic information for investigative and court purposes.

Pathology and the cause of death

To date, Prof Rutty and his team have examined a wide spectrum of natural and unnatural pathologies, from spontaneous subarachnoid haemorrhages (a serious, potentially life-threatening condition, which happens when an artery close to the brain surface ruptures) to stabbings, from strangulations to shootings to explosives.

“CT comes into its own in the assessment of traumatic deaths,” said Prof Rutty. “It is particularly helpful in the evaluation of skeletal trauma and also showing complications resulting from a traumatic injury.”

CT scanning allows the entirety of the body including the soft tissues, organs and skeleton to be viewed in two-dimensional (2-D) and 3-D revealing fractures that may not be found at postmortem, such as undisplaced fractures to the spine, limbs and scapulae.

The image quality however is dependent upon the scanner’s detector number. The Leicester unit is moving up to 64 detector imaging, which will open a new era in forensic radiological imaging.

“In cases where a specialist neuropathological examination would not be sought,” said Prof Rutty, “CT scanning can provide far more detailed information about the cranial cavity and brain than the macroscopic examination of an unfixed specimen in the mortuary.

“In this way in decomposed bodies, the brain can be examined prior to opening the skull that has the all too common consequence of trying to catch the liquid brain,” added Prof Rutty.

Not only has the team investigated the use of CT with human cadavers in traditional static and mobile (mass fatality) circumstances, it has also gone on to consider other forensic applications of CT beyond postmortem examination.

Ballistics

The team has examined a wide range of weapons including traditional firearms, arrows, crossbows and tasers, looking at the weapons, the ammunition and the consequences of the projectiles within the body.

Traditionally, terminal ballistics analysis has involved the firing of projectiles into a soft tissue stimulant such as gelatine blocks and the subsequent examination of the temporary cavity produced.

Prof Rutty said: “This may involve the production of plaster cast of the cavity and necessitate destruction of the stimulant to release the cast.

“CT scanning of the stimulant allows visualisation of the cavity in all planes with measurements, the production of virtual casts of the cavity, virtual slicing of the blocks and tunnelling, or fly-through images of the cavity