Saving face

The same technology used to make functional prototypes and production components in engineering research is now being applied in the medical field.

Rapid prototyping specialist, 3T RPD, based in Newbury, Berkshire, is using two 3D modelling techniques — Selective Laser Sintering (SLS) and Direct Metal Laser Sintering (DMLS) — to produce patient-specific instrumentation and custom medical devices.

SLS works by fusing together layers of powder such as nylon or glass-filled nylon into a 3D model with a laser. DMLS spreads a thin layer of metallic powder over a platform. The powder is fused by a laser beam and controlled by a computer using shape data from a CAD system. The 3D geometry is reconstructed layer by layer in every detail, building up highly complex parts and tools.

The goal of these technologies is to dramatically speed up the time it takes to get products to market. While SLS and DMLS are often used in many engineering applications, 3T RPD saw an opportunity to bring the technologies into the medical arena.

The company is involved with a DTI-funded project Facemaker, which aims to create an alternative method for developing facial prosthetics using digital scanning, design and manufacturing techniques.

The project, which concludes in March of this year, has the potential to make a big impact. According to one of the project partners, Loughborough University, 30,000 patients a year in the UK require maxillofacial therapies because of cancer, congenital conditions, surgery or trauma.

The Facemaker collaboration, which also includes Nottingham University Hospital Trust and Delcam, believes that a digital method will remove the need for directly contacting the skin of patients when making prosthetics and rehabilitation aids.

Traditional techniques require making direct facial moulds that are often heavy, time consuming and sometimes painful to the patient. From these moulds, prostheses experts sculpt a replica of the patient’s missing skin and bone to create a prosthetic match that is as close as possible to the original part.

The Facemaker team has made significant advancements from this technique by using FastSCAN Cobra, a laser scanner that has been produced by US company Polhemus. The hand-held device projects a fan of laser light that is manually swept over a patient’s face in a way similar to spray painting. The scanner’s camera views the laser to record cross-sectional depth profiles. Its embedded electromagnetic tracker measures the position and orientation of the scanner as it moves.

While direct moulds of the face have the potential to be distorted, the FastSCAN Cobra uses a reference receiver that enables scanning moving objects. The receiver can be attached to a headband worn by the patient.

FastSCAN relays the data to a computer and enables prostheses experts to reproduce the missing part using Delcam’s CopyCAD software. They then create a mirror image of the remaining parts to generate a prosthesis template for the defect site.

The template, which is manufactured using one of 3T’s SLS machines, is used to finally sculpt a new prosthesis. The prosthesis must be adapted to accurately fit the patient.

The Facemaker team claims that this non-contact method will also have significant benefits for patients who have suffered facial burns and require pressure therapy splints or head radiotherapy immobilisation splints. Manufacturers of these splints require a facial mould of the patient. These impressions are traditionally created with large amounts of a rubbery face-moulding material called alginate.

The new non-contact scanning process measures the position of thousands of discrete points over the surface of a patient’s face at a particular resolution. The collection of these digitised 3D points in space is known as a ‘cloud of points’.

These points are processed using Delcam’s CopyCAD software. With this 3D scan data, 3T RPD claims it can produce an SLS model in just a few days that is much more accurate than the traditional impression-based models.

The Facemaker team believes that its technique also has the potential to assist doctors planning surgeries for babies with cleft lips and palates. Usually, it is extremely difficult to obtain 3D images of a baby’s affected areas, unless the child is sedated. Facemaker, however, can produce a surface scan in a few seconds.

While 3T has found a niche application for its SLS technology in the healthcare sector, there are still many other uses for SLS and other rapid prototyping techniques in the market. 3T predicts the use of prototyping will flourish in the future as surgeries and medical treatments become more and more complex and the demand for bespoke devices increases.

The Facemaker team hopes that the project will highlight opportunities for the use of these techniques within the healthcare sector and lead to improvements in future patient care capabilites in the medical market.