Department of Radiation Oncology

High resolution liquid filled array for routine pre-treatment HDR brachytherapy QA

The Division of Medical Physics (Chair: Prof. Dr. Dimos Baltas), Department of Radiation Oncology, is offering a Master thesis for a Master of Science student (Physics, Informatics, Engineering) to evaluate the use of a high resolution liquid filled array for routine pre-treatment high dose rate brachytherapy quality assurance (QA).

High dose rate (HDR) brachytherapy is a radiotherapy technique which employs a radioactive source (192Ir, 60Co) to apply therapeutic radiation doses by means of applicators or needles implanted directly into the tumour bed. The radioactive source traverses those applicators or needles according to a predefined time distribution (dwell time distribution), calculated on the basis of image guided (CT or ultrasound) treatment planning. Currently there is no commercially available solution to perform an independent dosimetric verification of individual treatment plans.

Our group has previously demonstrated the applicability of a high resolution liquid filled ionisation chamber array to perform commissioning of brachytherapy applicators and needles. Moreover, we have developed the workflow to perform a dosimetric pre-treatment verification of patient plans using the same array. The project involves verification of individual treatment plans using the array, evaluation of the robustness of the verification technique to various systematic errors such as positional shift and changes to the dwell time distribution, as well as determining its overall suitability to the routine clinical workflow. If time permits there is the possibility of extending the scope of the project to perform time resolved analysis of the array measurement.

Figure: Key steps in methodology

i) exemplary axial slice of patient plan comprising ring-tandem applicator and six interstitial plastic needles (upper left pane)

ii) experimental set-up showing sensitive area of array 110 mm x 110 mm and steel needles (upper right pane)

iii) recalculation of patient plan after transfer to measurement geometry (lower left pane)

iv) comparison of measured and calculated dose distributions (lower right pane)

We are looking for a student to conduct a Master thesis on the evaluation and validation of a pre-treatment QA for high dose rate brachytherapy. Are you ready for this challenge and interested in working in an international and interdisciplinary team? Let’s talk about it!

Prerequisites:
- Master of Science student (Physics, Informatics, Engineering)
- Highly self-motivated
- Interest in medical informatics and solving medical related problems

Nice-To-Have:
- Good programming skills (MATLAB,C++)
- Good mathematical background

Duration: 6 months
Starting date: 2019

Supervisor: Dr. Mark Gainey, mark.gainey@uniklinik-freiburg.de