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Written By

Bianca de Loryn


College of Science and Engineering

Publish Date

19 December 2023

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Hands-on work in physics

For medical physicist Dr Marcus Powers, working in physics is all about helping people in regional Australia survive cancer. Marcus has recently finished his PhD focusing on a new kind of radiation therapy that may be gentler on the body and that can identify and track tumours that are almost invisible on x-ray images.

Growing up in Mount Isa, Queensland, Marcus knew that he had to move elsewhere if he wanted to go to university. “I decided to move to Townsville, and I fell in love with it,” he says. “I studied a Bachelor of Science, majoring in Mathematics and Physics and thoroughly enjoyed that. I especially wanted to study Physics because you're not restricted to being a physicist if you do a physics degree.”

Even though finance companies were already looking for future Physics graduates during his Honours year, Marcus learned from a fellow Physics student that he did not have to pursue finance or leave Townsville if he was looking for work in his field.

“My friend explained that he was working in the medical physics department at the Townsville Cancer Centre. About two or three weeks later, I was sitting down with his boss,” Marcus says. “I started volunteering at the Cancer Centre and then went on to do my PhD in medical physics because of that.”

Marcus says that the hands-on aspect of medical physics is something that he really enjoys. “Medical physics is all about the physics of treating cancers with radiation,” he says. “So, my job is about quality assurance, commissioning and providing scientific and safety advice around radiation therapy.”

Ariadne Shoobridge and Marcus Powers (supplied by Marcus Powers).

Radiotherapy: A proven way to treat cancer

For more than 60 years, radiation therapy (also called ‘radiotherapy’) has been delivered by tried and trusted Linear Accelerators, also known as ‘Linacs’ for short. When treating a patient with radiotherapy using Linacs, finding the exact size and location of the tumour can be difficult, Marcus says.

"When there’s a tumour and you’re treating it with the radiation from the Linac, it’s like you’re trying to hit an invisible target with an invisible bullet,” Marcus says.

“The radiotherapy team can’t see in real-time what they are trying to treat. So, the team needs to take an x-ray snapshot of your anatomy a few minutes before the radiation treatment to make sure the tumour is exactly where they think it is.”

As radiotherapy is usually administered across 20-25 sessions over five to six weeks, just as many x-rays need to be taken because the tumour may change size and location over time. These repeated x-rays, however, may slightly increase the risk of secondary cancers.

New approaches to radiotherapy

So, when Marcus had just started his PhD research focusing on cancer treatments using Linacs, he was excited to hear that an innovative new machine named the MR-Linac had been ordered for the Townsville University Hospital that promised cancer treatments without requiring ongoing x-ray images.

“When the machine arrived in Townsville in 2019, it was the 25th or 26th Clinical one in the world. And it was the first one in the southern hemisphere ,” Marcus says.

The MR-Linac machine is a two-in-one device for cancer treatments. In addition to providing regular Linac radiation treatments, it also takes the necessary pre-treatment images using Magnetic Resonance Imaging (MRI). This entirely removes the need for x-ray images and avoids the potential risk of developing secondary cancers.

Not only was the new technology gentler on the body, an MR-Linac has also other benefits, Marcus says. “We know that some tumours can move in the body. So, we need to put a margin around what we’re treating to make sure we definitely target the tumour when we treat it,” Marcus says.

It’s important that the margin around the tumour doesn’t unnecessarily include healthy tissue that will be targeted by the radiotherapy as this can increase the risk of toxicity. “We need to reduce that margin as much as possible,” Marcus says. “The MR-Linac can provide that smaller margin around the tumour.”

Marcus Powers.
Marcus Powers.
Marcus Powers being interviewed in Cairns (left, © James Cook University 2023) and at work in the Townsville Cancer Centre (supplied).

Making the invisible visible

Marcus says that people who suffer cancers in certain parts of the body, such as the uterus, pancreas, or liver, may especially benefit from radiation treatment with an MR-Linac. “It’s quite hard to see soft tissue structures on an x-ray image. On an MRI image, soft tissue structures such as the pancreas, uterus or liver are highlighted really well. On an x-ray image, tumours within them would have been nearly invisible.”

Marcus also focused his PhD research on improving some of the treatment processes using the MR-Linac machine. “During the radiotherapy, the irradiation of air particles gives off electrons, and those electrons spiral in the magnetic field and hit protruding surfaces.”

Some of these spiralling contaminant electrons could penetrate the patient’s skin and potentially create tumours. Marcus's research investigated a useful solution, utilising patches of gelatine to protect patients from stray electrons.

“It's essentially just jelly. So, you make up a patch of gelatine, about one to two centimetres thick. The electrons will interact with that jelly, and the patient is protected,” Marcus says.

Working with the radiotherapy team in Townsville

Marcus finished his PhD in 2022, and he is now assisting in the operation of the MR-Linac full-time. He works with his colleagues in the radiotherapy team to make sure that patients of the Townsville Cancer Centre receive the best possible cancer treatment and can recover as soon as possible.

Marcus says that even though many people may think that physics is very theoretical, jobs like his prove that physics can be a very hands-on field that involves working with many people.

Physicists are problem-solvers

Outside of medical physics, Marcus says, physics graduates have a diverse range of opportunities to find meaningful work around North Queensland. “What employers are looking for is the problem-solving and critical thinking skills that you gain in a Physics degree. You could work in the mining industry or in geophysics or meteorology, for instance,” he says.

Marcus says he was happy that he could study Physics in Townsville. “Physics at JCU certainly was the right choice for me. I had absolutely fantastic lecturers and supervisors along the way,” he says. “The Physics and Mathematics staff are very approachable. If it weren’t for them, I wouldn't be in the position that I'm in right now.”

He says that many of his colleagues at the Townsville University Hospital have studied at JCU. Being around the right kind of people might be another reason why someone might want to study physics, he says. “The people here, they are just brilliant and very passionate. So, if you enjoy physics, you'll have a great time working in this field.”

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