ubbed Dextroscope, the medical tool invented by Volume Interactions Pte Ltd, a recent Kent Ridge Digital Labs (KRDL) spinoff, allows a doctor to practise difficult surgical manoeuvres by providing three-dimensional (3D) images of the diseased organ from all angles.

The Dextroscope assists visualisation. It is able to combine data from various imaging techniques such as magnetic resonance imaging (MRI), computerised tomography (CT) and magnetic resonance angiography (MRA) to produce the image. The surgeon can then plan the least invasive route for the operation.

Dr Luis Serra, President and Chief Technology Officer of the company, says that instead of an unwieldy keyboard-and-mouse interface, surgeons can use natural and intuitive two-handed movements to manipulate the image. A control handle detects position while a stylus manoeuvres the image.

The images of the patient's organ, soft tissues and blood vessels obtained by the various imaging techniques are downloaded into the computer. These are then merged by the system into a single image. With a pair of stereoscopic glasses, the user looks at a mirror to view the virtual image generated by the computer.

The user can reach into the virtual work space and achieve precise hand-eye coordination by manipulating the control handle and stylus. The Dextroscope also acts as a consultative tool to facilitate discussion of operative strategies among groups of surgeons who can be remotely linked up.

The uniqueness of this technology stems from its ergonomics, real-time volumetric rendering, and the architecture built on a cross-platform software toolkit available for Windows NT and Unix from SGI, a US-based high-performance computing firm. It is technology based on off-the-shelf components such as a PC, 3D devices, mirrored display and stereoscopic glasses, a generic toolkit, and several software applications.

The first product based on the Dextroscope is NeuroDexter, a neurosurgical planning and simulation system. The work on NeuroDexter is led by a medical doctor, Dr Ralf Kockro, who is Vice-President of Medical Systems at Volume Interactions. He is also attached as a Clinical Fellow to the Department of Neurosurgery at the National Neuroscience Institute in Singapore.

Volume Interactions took more than three years to develop the system, with input from Dr Yeo Tseng Tsai and Dr Sitoh Yih Yian from the Singapore National Neuroscience Institute, and Dr Chumpon Chan of the Singapore General Hospital.

Dr Peter Munzel, a medical doctor-turned-businessman, has been appointed CEO of Volume Interactions to bring the company and its developments to market.

The NeuroDexter is already installed at the Johns Hopkins Hospital and Mayo Clinic in the US. One successful pilot project was its use by the Johns Hopkins Hospital paediatric department in planning the separation of a pair of Siamese twins joined at the head in 1997.

The neurosurgical flagship has a useful feature that 'peels' away different parts of the brain to reveal structures hidden beneath, to give as comprehensive an idea as possible of the problem. This is ideal for training and visualising various structures. Blood vessels, the skull and soft tissues can be displayed separately or embedded in the surrounding structure. The colour and transparency of each segment can be changed as required.

Another product offered is the MK Toolkit. This toolkit, the development of which was led by Mr Ng Hern, Vice-President of Research & Development of Volume Interactions, provides programming tools for visualisation and interaction with volumetric data. It allows programmers to develop C++ and OpenGL programs on either Windows NT or SGI Unix workstations. Dextroscope applications such as NeuroDexter and the forthcoming XtalDexter were created with this toolkit.

The MK Toolkit provides predefined virtual tools and predefined 3D widgets (such as slider, buttons and curve controls), so that programmers can quickly start building applications. The kit offers a real-time volume rendering module over the Windows NT and SGI Unix operating systems by supporting 2D and 3D texture technology.

Though the initial focus of Volume Interactions is on surgery planning and interventional radiology in the medical field, the Dextroscope can be extended to support specialties such as cardiothoracic, orthopaedic and hepato-biliary surgery.

Serra describes other exciting possible areas where it can be applied. In cell biology, the tool could provide visualisation and annotation of dynamic 3D images coming from laser scanning confocal microscopes, allowing live cells to be observed. Applied to volumetric seismic data, the Dextroscope facilitates decision making in locating mineral and oil deposits, as well as planning in the mining or drilling industry.

The Dextroscope can also be used in reverse engineering to reveal the internal structure of machinery, for general public education as an interactive teaching aid, and even for entertainment.

Volume Interactions is currently collaborating with The Scripps Research Institute in San Diego, US, to develop XtalDexter, reveals Serra. It will be used in crystallography to interact with electron density maps for the identification of protein structure.

Professor Duncan McRee, a crystallographer at The Scripps Research Institute, commented: "The view used by the Dextroscope, a voxel-based view, is a truer and most importantly, more easily perceived, view of the map. Where the Dextroscope becomes most useful though is the manipulation of the electron density map. The user can move it in three dimensions just as he would a real object. He can also use two hands, one for holding the map and moving it, and a second to hold a tool to work on the map.

"Other systems for three-dimensional visualisation exist. The one feature of the Dextroscope that attracted me to it most was the advanced software toolkit ... Good hardware is needed and necessary, but so also is good software. Without a good software toolkit, the development process is arduous and complicated."

The biggest challenge for Volume Interactions now is to get the right team for the young company, Serra says. There is also the need to break down the mental barrier for those used to the traditional way of doing things in their specialised fields, and convince them to try out new methods.

For further information, contact Dr Luis Serra at: lserra@volumeinteractions.com, or check out the company website at: www.volumeinteractions.com