Mouse based mannequin enhances virtual heart

Tom Shelley reports on an amazing and potentially life saving application of animated computer graphics for the medical market



A mannequin based on computer mouse technology now augments a virtual reality heart in the training of medical staff in transoesophageal echocardiography (TOE), an ultrasonic scanning technique that uses a probe pushed down the oesophagus.
The virtual heart project arose from a chance meeting at a dinner party, which led three clinicians – Dr Bruce Martin, Dr Andrew Smith and Dr Sue Wright, all from University College London Hospitals – to contact London based computer graphics company Glassworks to create a virtual heart as a teaching aid. The aid would allow students of TOE to visualise clearly the relationship between 2D TOE images and the underlying 3D anatomy of the heart.
The latest enhancements to the technology were demonstrated and described by Glassworks’ ceo Hector Mcleod at Autodesk’s “3December” event in London. He explained the project came about because it is a ‘rare option’ for cardiac clinicians to learn their skills on live human patients because of concerns about litigation if things go wrong. So there was a real need to find a virtual reality substitute.
The virtual model was based on a scanned in Latex print of the left and right ventricles of a dead human heart. Autodesk Softimage XSI software was used to construct and animate the model, but a lot of the software used has been developed by, and is proprietary to, Glassworks.
McLeod said there were all kinds of problems to overcome. For example, when they started testing the simulated ultrasonic echo images against those produced using real patients, the development team had to ‘go back’ because the initial volume models did not match those of a living heart – the dead heart had partially collapsed.
There were many consultations with medical specialists during the course of the development and three members of the Glassworks team witnessed an open heart operation in order to obtain reference images and to experience of what a real beating heart looks like.
The result is a realistic representation of a beating heart with a time line so different parts of the pumping cycle can be studied. It also offers the ability to investigate the internals using a 3D CAD movable image plane technique. There are, in addition, 130 structures that can be associated with additional information, plus the ability to show how the 3D model matches simulated ultrasonic scans.
The latest enhancement is a full sized model human torso and simulated probe, made by model maker Asylum. In this, a probe can be inserted in the oesophagus and the resulting simulated scans compared with what the ultrasound is interacting with. The interaction is achieved by making the model probe interact with the model torso in a manner McLeod described as a ‘glorified mouse’.
Attendees at the presentation wanted to know whether there were any plans to enhance the model to simulate diseased hearts and other organs. Mcleod replied that various options were being looked at. He said: “The company is always looking for bespoke projects and this was the most major project we have ever done.”
The virtual heart is now the property of spinoff company Heartworks and a number of virtual hearts have been produced for teaching purposes at University College London hospitals. The first overseas order has recently been received from Harvard Medical School in Boston.

Pointers

* Software usually used for modelling in games, entertainment and advertising has been employed in the building of a simulation of a realistic virtual heart simulation for medical training

* An interactive model human torso and ultrasound probe interact with the virtual model using computer mouse technology

Author
Tom Shelley

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