Technology: Foam model gives surgeons a spitting image

2019-02-28 07:02:06

THIS MADE-TO-MEASURE skull is a precise image of its real counterpart. A technique developed in the Netherlands enables surgeons to model skulls, hip joints and other parts of the body so that the time needed to operate on the affected part can be dramatically reduced. People suffering from severe facial injuries, congenital deformities and distortions caused by tumours are among those who will benefit. Frans Zonneveld, a physicist at Philips Medical Systems, developed the system with doctors at Utrecht University Hospital. The model is based on three-dimensional screen images built up from scans of the body part, using computerised tomography. CT scans analyse thin ‘slices’ through the body, from back to front and from side to side. The slices are combined and digitised by a computer to form a full, three-dimensional image on screen. The computer then instructs a precise milling machine, which produces a real image out of rigid polyurethane foam. The accuracy of the technique depends on producing sufficiently thin slices in the CT scan. Zonneveld says that the slices must be no more than 1.5 millimetres thick, and contiguous. The only milling machine and software to suit the job comes from a West German firm, MEK, based in Kiel. Surgeons have used 3-D screen images of the body for some time, but the difference with the new technique is that it enables them to handle the model and familiarise themselves with it. They can also use it as a template to measure and cut prosthetic implants to exact size,