Unveiling Success: Marsha Chin's Remarkable Journey as a UWA Graduate

In this page, we are going to introduce Marsha Chin, a UWA Medical Physics masters graduate. Marsha started her Masters in 2021 and completed the course in 2022. She started working as a Diagnostic Imaging Medical Physics Scientific Officer at Royal Perth Hospital (RPH) right after graduation and is going to start the ACPSEM Training, Education, and Assessment Program (TEAP) in Diagnostic Imaging at RPH soon.

Title of Marsha’s masters project was: “Dosimetric evaluation of an intraoperative radiotherapy system: a measurement-based and Monte-Carlo modelling investigation”

Here are some comments from Marsha’s coordinator and research supervisor Dr. Pejman Rowshanfarzad about her performance at UWA.

“Marsha's quality of study and work was one of the best among our graduates. She managed to complete her masters in 3 semesters with a high-quality research project, and soon after published her research outcome in a peer-reviewed journal.

Marsha is a great communicator. She managed to complete her research project in a multidisciplinary team involving physicists, mathematicians, and radiation oncologists. Marsha’s reports including assignments, exams, and her final thesis were always impressive.

While she was a student, Marsha regularly volunteered to attend activities at MT&P department at SCGH. Her interest and commitment to learning the clinical tasks was quite obvious since the very early days of masters education.

Marsha showed effective teamwork during masters. She was amazing in prioritizing tasks based on the advice from supervisors. During her research project, Marsha resolved a number of issues independently. I am sure that she will be a fantastic DIMP after completion of clinical training in TEAP”.

Marsha has kindly accepted to answer a few questions about her experience in the UWA Medical Physics Research Group, and provided advice for future students.

Introduction and your current position and role:

"I’m Marsha and I currently work as a diagnostic imaging medical physicist at Royal Perth Hospital and Fiona Stanley Hospital. I’m about to start my DIMP TEAP clinical training."

What did you enjoy most about UWA, and Medical Physics research group?

"Pejman, who is the UWA medical physics program coordinator, made my Master’s journey stimulating, challenging and enjoyable. I loved that it was an environment where the students helped build each other up, and where we could learn from one another, rather than just compete for grades. I stepped into the workplace feeling well-equipped.

The UWA campus is also really nice – lots of greenery, baby ducklings, and stunning peacocks!"

Can you give us your top three reasons to study Medical Physics?

I love that my job allows me to keep doing physics and help people with it.
I love the diversity of my tasks at work. My duties range from checking X-ray machines to giving patients radioactive pills.
There is always more to learn.

How do you feel you have made a difference in your field of research?

"My research involved evaluating the radiation dose distribution from an intraoperative X-ray machine, the Intrabeam. This allowed the physicists at Sir Charles Gairdner Hospital to better visualise dose deposition from the Intrabeam, and gave them deeper knowledge with which to treat patients.

My Master’s research project equipped me with invaluable practical and Monte Carlo skills that can be used for future research in the workplace."

What is your best advice to current students and Medical Physics applicants?

"Try to understand things rather than memorise them, don’t compare your journey to anyone else’s, and don’t take the privilege of learning for granted."

Here is the abstract of Marsha’s thesis:

Introduction: Radiotherapy is one of the principal modalities of cancer treatment; the others being surgery and chemotherapy. Intraoperative radiotherapy (IORT) is a specialised subset of radiotherapy, where a high radiation dose is delivered to a surgically exposed tumour bed in order to eradicate any remaining cancer cells invisible to the eye. The Zeiss Intrabeam is a type of IORT machine with a maximum X-ray energy of 50 kV. The Intrabeam contains an electron source which propagates down a probe and strikes a gold target to produce bremsstrahlung photons. These photons should ideally be emitted in an isotropic manner. The research objective of this thesis was to examine the dose distribution of the Intrabeam, by conducting physical, dosimetric measurements as well as via Monte Carlo (MC) simulation.

Materials and methods: The EGSnrc software toolkit was used to perform MC simulations of the Intrabeam X-ray source and spherical applicators (1.5 cm to 5 cm in diameter, in increments of 0.5 cm). The electron source was modelled with a Gaussian energy distribution with mean 50 keV and full width half maximum 5 keV. Geometry design, dose scoring methods and simulation parameters are described in detail. Dosimetric measurements involved a PTW 34013 soft X-ray parallel-plate ionisation chamber in the Zeiss water tank. The Zeiss dosimetry protocol was used to determine the dose to water. Percentage depth dose data from chamber meausrements were used to verify MC results. Having verified MC results, energy spectra, isodose curves and average photon energies were extracted from MC. In addition, EBT3 Gafchromic film was used to examine 2D dose distribution for various applicators.

Results: MC and IC PDDs were fairly similar, with most differences within around 3 %. The maximum MC uncertainties was 6.48 % (coverage factor of k = 3) with simulations using 109 histories. The bare probe energy spectrum showed good agreement with literature with the same bare probe design, and clearly demonstrated the impact of neglecting particularprobe coatings. The energy spectra for the spherical applicators demonstrate a general trend of greater attenuation with larger applicators. However, the aluminium filter in the smaller applicators (1.5 cm to 3 cm) clearly makes a difference, as expected. The applicator order with the highest fluence peak to the lowest is: 3.5, 4, 4.5, 1.5, 5, 2, 2.5 and 3 cm. The mean energy of the bare probe was found to be 21.19 keV. The mean photon energy from applicators ranged from 29.00 to 30.85 keV. The MC isodose curves depict the steeper radial dose fall-off with the bare probe and smaller applicators. Results from the irradiated film demonstrate the same effect.

Conclusion: These results of this study provide greater insight into the dose distribution of the Zeiss Intrabeam and may be useful for treatment planning at Sir Charles Gairdner Hospital, as each individual machine may differ slightly due to manufacturing variations. The effects of spherical applicators on the dose distribution were evaluated in depth. The MC phase space file obtained will allow for more efficient simulations in the future, whether for further research or treatment planning.

Here is Marsha’s recorded final research project presentation.