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Dr Emily Her; Combining radiology and radiotherapy to help cure prostate cancer

On this page we are introducing another high achiever UWA graduate, Dr. Emily Her.

Emily started her part time PhD study in Medical Physics in 2015 and completed it in 2020 while she was working as a scientific officer in the Medical Physics and Biomedical Engineering Department at Royal Perth Hospital. Emily then started the TEAP program in Diagnostic Imaging Medical Physics (DIMP) in 2021.

Her research project was on “Biological optimisation of prostate radiotherapy using tumour biology distributions derived from multiparametric magnetic resonance imaging” supervised by Adj/Prof. Martin Ebert, Prof. Annette Haworth, and Dr. Pejman Rowshanfarzad.



Here is what Emily’s principal supervisor, Adj/Prof. Martin Ebert, had to say about her performance:

"Emily took a very humble approach to her work, never pretending to be the “expert”. And yet, through her work, Emily has become an expert internationally in the use of “dose-painting” radiotherapy, a new experimental technique to use radiological imaging (in particular, MRI) to tell us where to put radiotherapy treatment dose and how much to put there. In collaboration with a team spanning Perth, Sydney, Melbourne and Auckland, Emily developed a way of quantifying such an approach in prostate cancer. Emily found that treatment with this approach can be much more efficient than the “traditional” approach of putting a uniform dose throughout the entire region to be treated. This positive outcome has now led to the next stage of using this technique, whereby a new PhD student will develop the method to transform Emily’s technique into a real-world clinical situation. Emily drove most of this work herself and should be credited with paving the way for this new treatment approach. We have been very grateful to have Emily as a PhD student and are now grateful that she is maintaining contact with us due to her interest to be involved in the ongoing progress of the project."


And here are comments from Emily’s coordinating supervisor, Dr. Pejman Rowshanfarzad:

"It was a pleasure to be the coordinating supervisor of Emily’s PhD project. She performed very well and managed to be ahead of timeline for her research. She routinely sent updates to supervisors and managed to publish 4 peer reviewed publications in leading medical physics journals. Emily kept in contact with our group and is a member of the UWA medical physics advisory panel. I wish her all the best in the TEAP training program and am sure she will be one of the best clinical medical physicists in the field."


Emily 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 Emily and I completed PhD at UWA in 2020. I am currently working as a Diagnostic Imaging Medical Physicist (DIMP) at Royal Perth and Fiona Stanley Hospital, also working towards DIMP TEAP certification in Nuclear Medicine.


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

UWA’s reputation as one of few universities that offer quality Medical Physics program was pretty much the only thing I knew about Perth before I moved from New Zealand. I enjoyed walking around the campus surrounded by beautiful architecture and along Swan River between classes. While I didn’t get to contribute much face-to-face time to the Medical Physics research group once I upgraded to PhD, I’ve always felt supported by Martin and Pejman in all aspects. I am also grateful that I was given opportunities to meet and work with leading researchers around the world.


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

1. Ability to apply physics to real world problems

2. Offers good work-life balance

3. Work with brilliant minds in a multi-disciplinary environment


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

My research investigated the potential benefit of utilising patient-specific tumour biology information derived from multiparametric magnetic resonance imaging to guide personalised prostate cancer radiotherapy. While it has only been tested in silico so far, I hope to have contributed towards evidence to support validation in clinical trial setting and ultimately improve treatment outcome.


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

Be open-minded and ask questions – you never know what kind of opportunities they might bring!



Here is the abstract of Emily’s thesis:

ABSTRACT

Traditional prostate radiotherapy involves conformal delivery of a spatially-uniform radiation dose to the whole prostate gland. While applying a focal dose escalation to macroscopic tumour identified on imaging is becoming popular, the dose prescription does not account for tumour biology heterogeneity. Biofocused radiotherapy (BiRT) has been proposed to optimise radiotherapy treatment planning using a tumour control probability (TCP) model and image-derived, patient-specific tumour biology maps to inform the model. Biologically-optimised plans are hypothesised to result in favourable treatment outcomes than conventional dose-based planning. This thesis aimed to apply the BiRT principles to prostate intensity-modulated radiotherapy (IMRT) and investigate the potential dosimetric benefits of biological optimisation using patient-specific, image-derived tumour biology distributions.

Recommendations for TCP model parameters to be used in prostate radiotherapy

A significant limitation in the clinical application of the BiRT principles is the uncertainties in the model parameters. Using a large low-dose-rate brachytherapy outcomes data set, recommendations for the selection of radiobiological parameters for prostate radiotherapy were made. A previously published set of parameters was recommended based on the results from external validation and parameter estimation performed on the clinical data. From the sensitivity analysis, it was highlighted that the TCP model was most sensitive to the population distribution parameters for radiosensitivity, demonstrating the importance of deriving accurate estimates of these parameters for future clinical implementations of BiRT.

Application of the BiRT approach to prostate IMRT

A framework for biological optimisation of prostate IMRT was developed to incorporate the TCP model in treatment planning optimisation. The main objective was to maximise the TCP while satisfying dose constraints for toxicity. The TCP was calculated using the recommended model parameter set and tumour location and cell density prediction maps derived from multiparametric magnetic resonance imaging (mpMRI), whilst accounting for geometric errors. Biologically-optimised plans demonstrated the potential to improve tumour control as well as reduce the rectal and bladder doses compared to uniform-dose plans.

Application of the BiRT approach to hypofractionated prostate IMRT

The BiRT approach was applied to prostate IMRT for two commonly used hypofractionation schedules. Hypofractionated treatment allowed a lower biologically equivalent dose to the rectum and bladder compared to conventional fractionation. The normal tissue sparing effect was more pronounced in extremely-hypofractionated plans, supporting further clinical investigations. From the robustness test against geometric errors, it was found that the plans become more sensitive to uncertainties with a reduced number of fractions as expected.

Application of the BiRT approach to hypoxia-targeting prostate IMRT

Tumour hypoxia has previously been identified as a prognostic factor for poor prostate radiotherapy outcome. Using mpMRI-derived hypoxia information, the BiRT principles were applied to hypoxia-targeting prostate IMRT. Compared to focal dose escalation methods, hypoxia-targeting BiRT allowed a lower dose to the rectum and bladder but in exchange for an increase in patient skin dose.



Publications and manuscripts arising from this thesis:

  1. Her, Emily J., Haworth, A., Rowshanfarzad, P., & Ebert, M. A. (2020). Progress towards Patient-Specific, Spatially-Continuous Radiobiological Dose Prescription and Planning in Prostate Cancer IMRT: An Overview. Cancers, 12(4), 854.

  2. Her, Emily J., Reynolds, H. M., Mears, C., Williams, S., Moorehouse, C., Millar, J. L., Ebert, M. A., & Haworth, A. (2018). Radiobiological parameters in a tumour control probability model for prostate cancer LDR brachytherapy. Physics in Medicine and Biology, 63(13), 135011.

  3. Her, Emily J., Haworth, A., Sun, Y., Reynolds, H. M., Panettieri, V., Bangert, M., Williams, S., & Ebert, M. A. (2020). Voxel-level biological optimisation of prostate IMRT using patient-specific tumour location and clonogen density derived from mpMRI. Radiation Oncology, 15(1), 172.

  4. Her, Emily J., Ebert, M. A., Kennedy, A., Reynolds, H. M., Sun, Y., Williams, S., & Haworth, A. (2020). Standard versus hypofractionated intensity-modulated radiotherapy for prostate cancer: Assessing the impact on dose modulation and normal tissue effects when using patient-specific cancer biology. Physics in Medicine and Biology, doi: 10.1088/1361-6560/ab9354.


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