In this post we are going to introduce Sini Abraham, one of our successful graduates. Sini completed her BSc and MSc in Physics in 2006 . She started a Master of Physics (Medical Physics) at UWA and received her degree in 2019.

Sini’s research project title was: “Independent Ray-Tracing dose calculation for CyberKnife radiotherapy plans with fixed and iris collimators: A 3D voxel-based dose calculation software on the MATLAB platform”.

Sini was offered a position at Royal Perth Hospital in WA as a scientific officer right after graduation. Later, she started working as a DIMP TEAP registrar at Fiona Stanley Hospital.

Here are some comments from Sini’s research supervisor Adj/Prof. Martin Ebert: “Sini entered the UWA Masters course after having established a family and juggled family responsibility with the rigour of the course, including the commitment to undertaking a clinically-relevant research project. Sini stepped up to this with confidence and well demonstrated her ability to understand new concepts. Sini developed computer code to undertake independent calculation of the doses to be received by a patient undergoing treatment with a CyberKnife robotic radiotherapy device. Sini was able to use the code to replicate the dose calculation performed by the commercial planning system, providing a valuable part of the process of quality assurance for patient treatment. Sini has subsequently moved on to applying her developed skills in several clinical environments. I was very glad to have played a small part in Sini’s journey.”

Sini kindly accepted to answer a few questions about her experience in the UWA Medical Physics Research Group.

Introduction and your current position and role:

My name is Sini and I graduated from UWA in 2019. I am currently a Registrar Medical Physicist at Royal Perth and Fiona Stanley Hospital and working towards DIMP TEAP certification in Nuclear Medicine.

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

I just found UWA an incredibly inspirational and motivating place. UWA Medical Physics research group is a close-knit group of people who have the similar passion and interests in Medical Physics and a place where you learn and grow as a researcher. Discussions at the weekly research meetings really helped to speed the pace of my research, make it more efficient and gave insight into my work. It also added a strong auditory dimension to my learning experience. The broader ideas shared, and the wide base of professional and interpersonal skills developed through these research meetings are useful in the professional life.

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

  1. Always liked physics and medicine and Medical Physics is a perfect amalgamation of these two.
  2. A career where you apply principles of physics to manage the safety and technical side of radiation use in medicine, whether diagnostic or therapeutic.
  3. Challenging but highly rewarding career

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

Radiation treatment planning process is complex and involves multiple steps and involves a number of technologies. The rapid development in the technology of radiation oncology and the complexity of 3-D treatment planning necessitates a quality assurance procedures that ensures confidence that each patient will receive the optimal treatment as planned and that no errors will occur in the process of using the TPS or in the clinical implementation of the treatment plan. With the help of my supervisors we developed an independent dose calculation software on MATLAB platform to check the accuracy of Cyberknife™ treatment planning system Precision™ that has the potential to be implemented clinically.

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

Take advantage of all practical sessions and shadow medical physicist in different specialities. It’s a great way to get an idea of what it’s like to be a Medical Physicist and also a great way to network within the medical physics community. Manage your time, listen to your lecturers and don’t be afraid to ask for help.

In the end, you will find yourself in one of the most rewarding career fields out there that worth all the effort.

Here is the abstract of Sini’s thesis:

Aim: Precision and accuracy are of high importance in radiotherapy. Due to the fact that CyberKnife® treatments involve steep dose gradients, tight margins, and small fields, an independent dose calculation is highly recommended to ensure the dose calculation in the treatment planning system (TPS) is sufficiently accurate for the safe and effective treatment of the patient. This study aimed to develop a 3D voxel-based independent dose calculation (IDC) software on the Matlab platform for CyberKnife® (fixed and iris) treatments planned with the Precision TPS.

Method: The IDC framework developed on the MATLAB platform (originally developed by Pavel Dvorak of the University Hospital Vinohrady, Prague, and generously supplied for this work) is capable of reconstructing the patient model and structures using DICOM CT images and a DICOM RT structure set. It also uses XML treatment plan and patient data as exported from the TPS. CyberKnife beam data like output factor, tissue phantom ratio and off-center ratio for fixed cones and the iris collimator are stored independently in the framework. Dose calculation is performed on selected voxels using a simple factor-based ray tracing technique with a 1D inhomogeneity correction based on equivalent path length (EPL). The dose is calculated typically at the voxel of global dose maximum and center of mass voxel of each selected structure. Though the framework is capable of calculating dose on all voxels in the selected structure, and indeed the whole CT set, the number of calculated voxels are restricted to increase calculation speed. In addition, the contribution of all beams at the reference point voxel is calculated and also compared with the plan-specific beam data file exported from TPS.

Results: Mu calculations for 14 randomly-selected clinical treatment plans were verified using the newly developed IDC framework. The dose comparisons values were represented as a percentage difference between IDC calculated dose and the reference TPS calculated dose. For each given case, a text file was generated with a dose comparison for all voxels evaluated in the selected structure and a comparison of individual beam dose contributions to the reference point. The IDC calculated dose of selected voxels were displayed on reference CT image set along with TPS dose. The percentage deviation of the dose was also represented graphically.

Conclusion: An IDC framework capable of voxel-based dose calculation is developed unlike the commercial software used for independent dose/MU check procedure for CyberKnife® that only calculates individual beam contributions to a single reference point, IDC software developed in this study can perform dose calculation in any voxel within a selected structure. The level of independence is also high as IDC calculates key parameters for dose/MU calculation such as depth, equivalent depth, and off-axis distance independently from the TPS.

Here is Sini’s recorded final research project presentation.

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