3D Printing in Radiotherapy

Hi, I’m Hannah (one of the co-editors!) and I’m in my first year of Route 2 training to become a Clinical Scientist in Radiotherapy Physics in Belfast, Northern Ireland!

My training is a little different from the STP. I already have an MSc and I’m primarily completing clinical training to build a portfolio that demonstrates equivalence to the training done through the STP! I will hopefully be sharing more about Route 2 training on this blog, sharing alternative routes to Clinical Scientist registration and providing a platform for other Route 2 trainees to connect!

3D printing in Radiotherapy really interests me and that’s why I’ve chosen to focus on it. It’s also an area that has been gaining momentum in the world of radiotherapy research in recent years.

Before I dive too deep into some of the really cool applications of 3D printing, I think it’s important I provide a brief introduction to both 3D printing and radiotherapy for context!

Radiotherapy is the treatment of cancer using radiation, this can be using externally-produced radiation (known as external-beam radiotherapy) or using small radioactive sources in a technique known as brachytherapy (sources are placed either directly in to, or in close proximity to a tumour). The main aim of radiotherapy is to kill cancer cells through irreparable biological damage, while minimising damage inflicted on nearby healthy tissues and organs.

So, what exactly is 3D printing? There are actually several types of 3D printing and each of them have their own associated pros and cons. But I’m going to discuss the technique which is currently more common in radiotherapy: Fused Deposition Modelling (FDM). This 3D printing technique produces 3D structures by extruding melted thermoplastic through a narrow nozzle, which then cools in a layer-by-layer fashion. (I’ve linked a video below too!) The amazing thing about 3D printing is that you can create any structure you’d like to print (for example; using computer aided-design software) and you can manipulate printing settings to achieve different outcomes (more on this later!).

Okay, so now that we know what 3D printing is; how exactly can this be used in radiotherapy? Depending on the radiotherapy technique used, there can be additional pieces of equipment that are required as a part of the treatment. For example: if we are aiming to irradiate a really specific area, the positioning of the patient becomes really important, immobilisation equipment might be required. Or to assist in the process of quality control, ensuring treatment machines are operating safely and accurately.

There is interest in creating models (phantoms) which mimic human tissues to be used in dose-measurements, as dose cannot directly be measured in patients. To achieve this, the physical and radiological properties of materials used in 3D printing need to be quantified; do they respond to irradiation in a similar way to the tissue they are mimicking? These properties can be altered by changing printing settings!

Figure 1: 3D Printed heart. This was printed to test printing with two materials simultaneously. The heart printed with Polyvinyl Alcohol (PVA), which is water-soluble, as the supporting structure. The PVA is then dissolved, leaving behind a hollowed structure which is ultimately the part we want.

My experience with 3D Printing

Last summer, I had the privilege of completing a short research placement at Cedar’s Sinai hospital in Los Angeles. I was able to observe how 3D printing was used clinically within their skin brachytherapy service (I will refer anyone interested in brachytherapy to this great post by Kieran (The Source (or Seed) of Hope for Cancer Patients – Brachytherapy – STP Perspectives). Patients with small, shallow skin legions were suitable for this treatment modality. As mentioned, it is where a radioactive source attached to a cable is driven close to the tumour site using an afterloader machine. 3D printing was utilised to create patient-specific moulds, which would fit tight to a patient’s anatomy and include channels for the radioactive source to be driven through to dwell above the lesion for defined periods of time. It was a really great experience to see the process of creating a bespoke patient mould for this treatment and observing some of the challenges involved in the fabrication process.

Before I began my Route 2 training, I worked as a research assistant through a university where I was lucky enough to participate in a multi-centre 3D printing project. The project was to produce a phantom to assist in daily checks of six-degree-of-freedom couches. They’re used for some radiotherapy treatments and can move in three translational and three rotational directions.

This project resulted in the clinical implementation of a phantom, which is now utilised in routine quality control. It also gave me my first ever opportunity to present research on a national scale (very daunting but also very rewarding experience!). If you’re interested in learning more about this work, we published an article in Physica Medica late last year! (Evaluation of a novel phantom for the quality assurance of a six-degree-of-freedom couch 3D-printed at multiple centres – ScienceDirect )

Currently, there is a need for greater guidance on how 3D printing can be used in clinical environments in the UK. This is including quality control of prints for different radiotherapy applications and ensuring that medical device legislation is adhered to. I was involved in the process of developing a local quality management system for 3D printing, to address some of the concerns regarding quantifying printing settings, geometrical output of prints and the full workflow of 3D printing in a clinical environment. I hope the completion of this quality system will allow for greater scope of use for 3D printing locally, which I’m hoping to get involved in!

I think that 3D printing in radiotherapy is a very exciting area of breakthrough research with many useful clinical applications, it is certainly something to look out for in the future!

There is also an IPEM event exactly on this topic linked here. It’ll be held just outside of London on the 21^st of May!