Far beyond rapid prototyping

It’s been said that Australia’s industry has been a little slow to adopt additive manufacturing. However, local medical applications using various methods of 3D printing have gained global attention, and some are arguably world-leading.

Last month’s ABC 730 story on a titanium alloy vertebrae replacement, saving a patient from paralysis and eventual death, made news around the world. Other reported world-firsts in the last two years include a titanium heelbone replacement (saving a man’s leg) and last September’s sternum-and-ribcage implant created by CSIRO and Melbourne’s Anatomics.

One pocket of excellence in Australian metal Additive Manufacturing, RMIT, has also gained international attention, with its revolutionary just-in-time (JIT) titanium bone implant technology.

One of the co-authors of the provisional patent, Dr Martin Leary (alongside Professor Milan Brandt and Darpan Shidid, whose PhD work the JIT method is based on) said the University is currently using 3D printing to tackle another clinical area: radiation dosimetry.

As with bone implants, there is a great potential benefit in the method, largely around the patient specificity offered by additive fabrication.

 “It basically means that we can use 3D printing to simulate complicated clinical cases, and safely trial how the radiation interacts with a person,” Dr Leary told Manufacturers’ Monthly.  “Meaning that when they actually do treat the patient, they can do it with a higher degree of confidence.”

The 18-month-old project involves examining how radiation phantoms – models on which radiation therapy is tested to examine how radiation will be absorbed and scattered by the body’s organs – can be made better using polymer 3D printing. The effort came about through work with Melbourne’s Peter MacCallum Cancer Centre’s principal research physicist, Professor Tomas Kron.

Radiation phantoms are used where the reaction of tissue to radiation is of interest, according to a paper by Dr Leary, Prof. Kron and others published last year, including: diagnosis and treatment, studying effects on tissue, minimising health risks from radiation, and using radiation to kill cancerous cells.

Radiation phantoms come in different forms, and can represent a patient’s body or a section of their anatomy, but are often simple shapes from an engineering point of view, said Dr Leary.  “It really comes down to the fact that they're expensive to make, so it's often useful to have a standard, inexpensive geometry like a plastic cylinder or chamber block,” he added.

The more customised and close to reacting like a patient’s actual anatomy, the more effective such phantoms are in clinical applications. 3D printing had been examined there “in a forms and fixtures way” before the RMIT / Peter Mac team decided to systematically test how 3D printing polymers behave when exposed to radiation.

Eventually, the research led to ways to mimic the response of tissue to radiation, using a photopolymer Objet Connex machine and different combinations of clear, white, and frangible support materials.

 “We found that, if we mixed them in a strategic way, we could actually make something that looked like a human under CT scan” said Dr Leary.

STL files – the standard format for 3D printing objects – can be created directly from CT data, and the automated process and programming have been engineered so that clinicians don’t require specific knowledge of additive manufacturing processes.

As with many of the uses of 3D printers, this application was likely never imagined by the makers of the machines, originally used to make prototyping easier and faster in the automotive industry.

And as with many areas of medicine where personalised options offers a superior solution, there are numerous parties chasing effective 3D printed dosimetry phantoms.

RMIT, for its part, is developing the idea further, among other things, to better emulate lung and other more complicated tissue types.

The work represents another instance of medical technology collaboration in an area of particular strength in Australia. Victoria contains 13 medical research institutes, 11 teaching hospitals and nine universities, with the focus of these in Melbourne.

For the RMIT Advanced manufacturing Precinct (AMP), led by Professor Milan Brandt, there are strong links between its expertise in 3D printing and St Vincent’s team, led by renowned orthopaedic surgeon Professor Peter Choong.

Major medical manufacturers are very interested in the patient-specific surgical innovation in Additive Manufacturing – such as the JIT implant method – being pioneered by Professors Brandt and Choong.

“The best orthopaedic surgeon in the world [Professor Choong], the most experienced medical implant manufacturers in the world: they're all at the table and RMIT is right there front and centre involved in building these implants” said Dr Leary.

 

Images

RMIT and http://www.javelin-tech.com/solution/3d-printer/trade-in/stratasys-3d-printers.htm