This article from the Economist Dec 10th 2009 .
PERFORMING a postmortem on a murder victim can take days, delaying any criminal investigation. Moreover, pathologists sometimes get only one chance to look for clues when dissecting a body. But Anders Persson, director of Linköping University’s centre for medical image science and visualisation in Sweden, hopes to change that. Along with his colleagues Thomas Rydell and Anders Ynnerman of the Norrköping Visualisation Centre, they have created a virtual autopsy system.
The body needing to be examined is first scanned using a computed tomography (CT) machine, a process which takes about 20 seconds and creates up to 25,000 images, each one a slice through the body. Different tissues, bodily substances and foreign objects (such as bullets) absorb the scanner’s X-rays in varying amounts. The software recognises these and assigns them a density value. These densities are then rendered with the aid of an NVIDiA graphics card, of a type used for high-speed gaming, into a 3-D visualisation of different colours and opacities. Air pockets are shown as blue, soft tissues as beige, blood vessels as red and bone as white. A pathologist can then peel through layers of virtual skin and muscle with the click of a computer mouse.
To make the process easier, Dr Persson and his colleagues have also created a virtual autopsy table. This is a large touch-sensitive LCD screen which stands like a table in an operating room, displaying an image of the body. Up to six people can gather around the table and, with a swipe of a finger, remove layers of muscle, zoom in and out of organs and slice through tissue with a virtual knife.
The Swedish police have already used the researchers’ virtual-autopsy technology to investigate nearly 350 cases. It has proved capable of detecting crucial but difficult-to-spot pieces of evidence, such as the angle of a bullet’s trajectory, air pockets in the wrong place in the body and bone fractures in a burns victim. The virtual autopsy can also be used to determine the cause of death in a few hours. And unlike a physical autopsy it does not alter evidence, enabling investigators to revisit a cadaver for additional clues if necessary. Television detectives everywhere will have them soon.
