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Using 3D Printers to create Surgical Simulators

Whether we like to admit it or not, the days of a virtual reality interface being able to recreate our natural senses in all their glory, are still a long way off. We can get fairly close, but getting fairly close costs large sums of money – usually on the order of many millions of dollars or euros. So, if you wish to create a lifelike surgical simulator, one which responds as well as a human might, an actually simulated one is virtually beyond consideration for most hospitals.

Now, patient simulators of all manner, type and size are nothing new in physical medicine, but this one in particular is something new; a brain surgery simulator. As such the head is all that is required. That means no moving parts. No respiratory system, no cardiovascular system, no joints or eye movements required. Just a collection of static pieces. They still have to behave like their organic counterparts of course, but the basic construction is relatively straightforward.

If you then take things to their logical conclusion and utilise a 3D printer to make them, they also become rather cheap to produce. That is what a team of researchers from three universities in two countries set out to do.

From Malaysia, the primary impetuous for the work came from a research team working out of the University of Malaya. From the United Kingdom, two teams split between the University of Portsmouth and the University of Oxford brought their work to fruition, using the latest generation of multi-material 3D printers.

The reasoning behind having cheap to produce, effectively mass-produced models of the brain for use by trainee neurosurgeons is abundantly clear: Neurosurgeons must train for upwards of a decade to master the complexities of the brain and the physical attributes of the same. They must master deftly cutting into patient's heads and removing abnormalities whilst leaving as much functionality as possible, intact. Traditionally, it is somewhat hard to find living human heads to purely practice their skills on, and natural chemical changes in dead human heads change the way the tissue behaves. If they could have easy access to something that behaves just like a living human head, skull and brain, that feels the same and responds the same, it would make their training considerably easier as well as much more comprehensive.

Beginning with the team at the University of Malaya, the researchers created a two-part model so the same head can simulate a wide variety of pathological conditions. To do this, the head and the brain are actually separate models, one fitting inside the other. In this way the brain can have tumours and complications located in different positions, different shapes and sizes, whilst the separate head model can concentrate on the difficult to replicate exact stretchiness and pliability of the skin, and outer soft tissues as well as the hardness of the skull.

In fact the artificial skin has to behave exactly like the organic counterpart; it must be pliable enough to be cut by a scalpel and repaired by sutures, yet sturdy enough to be held by a retractor. The artificial bone likewise must be strong enough for the trainee to obtain experience using bone perforators and cutters, and the dura mater – the membrane under the skull, must be thin and pliable - just like the real thing. On top of the surgical requirements, all three must be made out of materials that a modern multi-material 3D printer can easily handle, and relatively cheap to produce.

The other segment fits inside the head piece, and itself is composed of two materials, each of which has both a different consistency and a different colour. This is of course the brain. It consists of normal brain tissue coloured a light yellow for easy identification, and a tumour which can be anywhere in the brain, of any size or shape, and is coloured a dark orange for easy contrast.

As it currently stands, blood and cerebrospinal fluid is not simulated. The practice is geared towards navigation, identification and extraction, as opposed to the messy additional factors of an actual operation. These will be added in later when the neurosurgeon performs actual operations.

Of the two pieces, the skull piece is designed to be used again and again, with sufficient detail to make the face recognisable, and attention to detail on the contour of the head. It can be reskinned and redrilled many times, compensating for it being the more expensive piece to create. The brain on the other hand is one-use throwaway quality, and whilst all the major structures are in place, and in the right places the same care in attention to detail is not present. These can then be printed out fairly quickly, to give a quick turn around on use.

The UK research teams came into play once the basic models were constructed. Several of the UK's neurosurgeons were tapped by these two universities, and minor adjustments in form made based on the feedback the neurosurgeons gave as they operated on a head and brain pairing as if it was a real patient. Three neurosurgeons and one expert in surgical simulations in total, with one 'fair' and three ' good' ratings as to how well the model performed, relative to the feeling of cutting into an actual human head.

The team estimate the production cost of the head will be 2,000 USD, or around 1,500 Euros. The brain segment on the other hand, will cost an estimated 800 USD or around 580 Euro. Remember this brain piece is to be thrown away after each practice session (as the tumour will be extracted from it). So, to sweeten the deal, the Malaysian research team are keen to point out that an effectively infinite variety of these brains can be produced from actual patient data.

In conclusion

As an idea, it is certainly not a bad one. Prior to this point, no actual surgical simulators for neurosurgery existed, with even the VR-based surgical simulators on the market, all geared for general operations rather than a specific type. The price is relatively high for a single practice surgery, meaning it is still not something a trainee neurosurgeon could practice on outside of their normal course hours. However that said, it is still leagues ahead of any other purpose-specific simulator currently around.

As the researchers themselves are overly keen to point out, the construction costs will drop as multi-material printers mature, and of course the same basic concept could be used for surgical procedures elsewhere in the body. Although of course, there they face competition from the many other types of surgical simulator currently on the market.


Multimaterial 3D printers create realistic hands-on models for neurosurgical training

Utility of multimaterial 3D printers in creating models with pathological entities to enhance the training experience of neurosurgeons (Paper)

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