A beam of hope

In 2012 a 15-year-old Dr Jessie Posar had a conversation that would change the trajectory of her future.

Her science teacher at Camden High School told Dr Posar that she was really focused and curious in class during the physics topics and should consider studying the discipline as she moved into her senior years.

“My teacher was trained in physics and she was fantastic. She was also female, and she really challenged the stereotype I had at the time of what a physicist could be,” Dr Posar said.

“At the time, I didn’t really know what physics was or the potential career pathways, but I thought I would give it a go, and then I discovered that I really enjoyed it. I wasn’t necessarily gifted in physics but I was passionate to learn.”

“This passion and curiosity for how the world works is what still motivates me to continue my career in physics.”

Transforming lives

Now, just 12 years later, Dr Posar is leading an international research team that is exploring whether wearable organic x-ray sensors could be the answer towards safer radiotherapy protocols for cancer patients.

“Our research team has been exploring the behaviour of wearable organic x-ray sensors and we’re hopeful our findings will lead to the development of safer radiotherapy protocols,” Dr Posar, from the said.

“It’s significant because more than 400 people are diagnosed with cancer every day in Australia and 50 per cent of these people will go on to be treated with radiotherapy. The side-effects of cancer treatment, including radiation, can be debilitating.”

The researchers’ latest findings were revealed in their new paper ‘Flexible Organic X-Ray Sensors: Solving the Key Constraints of PET Substrates’, which was published in Advanced Functional Materials (22 November 2024).

“With the external beam [of radiation therapy] hitting the body, you don’t want to hit other vital body parts. You want to target the tumour, not the areas around it. The novel materials I have been working on are flexible, and they sit on the patient during treatment,” Dr Posar said.

The researchers examined advancements in wearable organic x-ray sensors and found they could potentially transform future treatment options for cancer patients.

“Unlike traditional silicon-based detectors, organic semiconductors are inexpensive, lightweight, printable, stretchable and offer the first biocompatible response to ionising radiation due to their carbon-based composition,” Dr Posar said.

“These sensors can directly monitor radiation exposure of the body, allowing real-time adjustments during cancer treatments, minimising damage to healthy tissues. However, the behaviour of organic x-ray sensors is still unknown and that’s what our team wanted to explore.”

^{Professor Marco Petasecca, Dr Jessie Posar and Proffesor Attila Mozer}

The researchers delved into the electronic performance and radiation stability of organic x-ray sensors under clinical radiation beams.

“Under conventional radiotherapy conditions we have demonstrated that organic sensors can detect incident x-rays with no dependence on the energy or dose-rate of the incoming beam, while transmitting 99.8 per cent of the beam,” Dr Posar said.

“This means it can be worn on a patient to monitor x-ray exposure without impacting treatment protocol to improve safety and clinical outcomes.”

The power of collaboration

The researchers worked with the Australia's Nuclear Science and Technology Organisation’s (ANSTO) Australian Synchrotron, one of only two places in the world developing a radiation therapy treatment modality. Termed Microbeam Radiation Therapy, the modality aims to treat otherwise untreatable tumours including brain cancer.

Dr Posar said while it has shown promising treatment outcomes, there is no detector capable of providing quality assurance, limiting treatment efficacy and patient safety.

“Our study demonstrated that flexible organic sensors can detect microbeam x-rays with a precision of 2 per cent and that they exhibit similar radiation tolerance to silicon-based detectors ensuring reliable and long-term use under these dangerous radiation fields,” Dr Posar said.

“There is still a lot of unknown physics to explore. But our work shows that organic semiconductors exhibit the ideal properties for wearable and personalised x-ray sensing to improve the accuracy and safety in oncology towards tailored radiation delivery that maximises therapeutic effectiveness and reduces harm to healthy tissues.

“This innovation could revolutionise personalised radiation therapy, offering a new level of safety and effectiveness in patient care.”

A rapid trajectory

The work Dr Posar is at the forefront of today is an extension of the research she undertook while completing her PhD at UOW, just a few short years ago.

“I completed my thesis under the supervision of Associate Professor Marco Petasecca. He was such wonderful mentor,” Dr Posar said.

In 2023, she was awarded a research fellowship by the Office of National Intelligence to develop her expertise in organic electronics,

“To see this work now published in a high impact academic journal is a special moment for me, and to be the senior author on this work feels like a great achievement and demonstration of the leader I have become in my field.”

Before completing her PhD Dr Posar studied a Bachelor of Science Advanced at UOW, a four-year degree with honours that gave her an understanding of how to conduct research in the academic world.

Much like her research success, Dr Posar’s academic journey and career trajectory is exceptional in many ways – she was the first in her family to attend university.

“I did not know other people that attended or were aspiring to go to university. And because I was the first in my family to go to university, navigating it all was a daunting, but rewarding, experience.”

^{Dr Posar has had a profound impact on the research students she supervises}

Dr Posar excelled during her time as a student at UOW. For her PhD thesis, titled ‘Characterisation of Organic Semiconductors for Ionising Radiation Dosimetry in Medical Applications’, Dr Posar was awarded the Australian Institute of Nuclear Science and Engineering (AINSE) Scholar Gold Medal.

Dr Posar also received the Materials Research Society (MRS) Gold Recipient Graduate Award for exceptional ability and promise for significant future achievement in materials research. MRS was awarded in the United States where Dr Posar presented the research alongside other graduates from MIT, Stanford, CalTech and Oxford. It was a huge honour for Dr Posar, and one she never imagined would become a reality.

“As a PhD student, you’re just taking each small step at a time, you never question if you’re good at it or if anyone else recognises the value. So, it was a nice recognition that the work I was doing was important and had an impact.”

Dr Posar has had a profound impact on the research students she supervises. The paper’s first author is UOW PhD student Aishah Bashiri. Her thesis topic is on novel radiation detectors for dosimetry in advanced radiotherapy techniques.

“The experience and skills I developed in the lab under Dr. Posar's guidance allowed me to fabricate these novel organic sensors entirely from scratch," Ms Bashiri said.

"I am profoundly grateful to my supervisors and the research team for their invaluable training, guidance, and access to essential facilities, which allowed me to gain the knowledge and experience necessary for conducting this research.”

What’s next

As for what’s next Dr Posar says the research will involve data science approaches to accelerate the discovery and translation to real work applications.

Dr Posar said continued international collaboration will be instrumental in current and future developments in this space. Her colleague and mentor, Professor Marco Petasecca from UOW’s School of Physics, reiterated the importance of collaboration.

“Our team has a long track record of collaboration, which reaches out nationally and internationally with the best groups in the world in the field of developing of organic sensors,” Professor Petasecca said.

“We regularly collaborate with Professor Paul Sellin at the University of Surrey; Professor Beaturice Fraboni at the University of Bologna; Professor  Ian Hill and Assistant Professor Alasdair Syme at the University of Dalhousie; Dr Bronson Philippa at James Cook University; Associate Professor Matthew Griffith at the University of South Australia; the Centre for Organic Electronics and the Australian National Fabrication Facility Hub at the University of Newcastle.”

Professor Attila Mozer from the Intelligent Polymer Research Institute at UOW said being involved in this research has been an un-learning journey to discover something new.

“The performance of organic diodes exposed to natural sunlight as increased by almost 600 per cent over the last two decades, because of the work of tens of thousands of scientists and hundreds of millions of dollars in funding across the globe over that time,” Professor Mozer said.

“When we started using essentially the same materials for radiation detection, we needed to un-learn most of the well-established paradigms to make the progress we have presented today. It’s been a really fascinating aspect of this research.”