By Jaimie McGlashan
According to the World Health Organisation, cancer has recently become the leading cause of death worldwide.
The devastating disease is responsible for 8.2 million deaths in 2012.
For my AMSI Vacation Research Project, I studied the Optimisation of Modulated Arc Therapy, a new form of radiotherapy.
Modulated Arc Therapy (mARC) differs from other forms of radiotherapy in that the sessions last 2-3 minutes as opposed to 15-20 minutes. Radiation beams are directed at a tumour at various angles or ‘control points’ from a rotating gantry, no radiation is delivered while the gantry moves. These beams pass through a multi-leaf collimator or MLC that is made up of rows containing left and right metal ‘leaves’. These leaves migrate horizontally to create an opening in a pre-determined specific shape.
In our project, we aim to optimise the treatment planning for mARC.
What does that mean?
Optimisation is a mathematical tool used to select the best solution to a problem while adhering to restrictions or constraints.
What is being optimised in a treatment plan? Our model will find the optimal angles (control points), MLC shapes and radiation intensity amounts for a collection of randomised samples.
An optimised treatment plan should deliver as much radiation as possible to the tumours in order to eliminate the cancer cells, whilst sparing the critical organs and tissues that surround the tumour as much as possible.
An optimisation model begins with an objective function.
In this case, it has been selected as maximising the number of voxels in a tumour that are receiving at least their desired dose.
There are a number of constraints that the solutions must obey. Including mARC machinery restrictions, MLC constraints and lower and upper dosage limits.
Once the constraints and the relevant variables and parameters are constructed mathematically, they are coded into an optimisation software with the accompanying data. This is where the optimal decisions are made.
Isn’t mathematics amazing!?
Jaimie McGlashan was one of the recipients of a 2013/14 AMSI Vacation Research Scholarship.