1. BDSIM for proton therapy gantry simulation
Accelerator Group Christmas Meeting
Andrew Green

2. About Me Recently finished my PhD (2012 – 2016)
Did my Manchester too (2007 – 2012)
Lots of work on proton therapy
Specifically Monte Carlo
Now Christie in Marcel van Herk’s group

3. Proton Therapy Uses protons to treat tumours Protons stop
Most of the time in the right place
Should be able to spare quite a lot of normal tissue.
However…
Obligatory Bragg Peak plot.
All talks discussing proton therapy are required by law to have at least one plot showing how much better than X-rays protons are.

4. Proton therapy Protons don’t always go where you expect them to.
Monte Carlo will be needed for treatment planning.
But…
...it’s far too slow.
Pencil beam algorithm (left) vs Monte Carlo (right). The arrow indicates a range difference due to multiple Coulomb Scattering. Adapted from Paganetti (2008)

5. My Work Tried a few tricks to make Monte Carlo faster
Supercomputer
Intel Xeon Phi
Modified transport algorithm
Cloud computing
Also developed a different technique for dose comparisons.

6. The Woodcock Algorithm
Took the full 4 years to develop
Seemed like a good idea at the time
Discovered two things:
Most tracking time is for secondaries
Depositing CSDA losses properly is really hard

7. Thesis Hardest part of PhD One piece of advice:
Start writing early.
Even if it’s shit.
It can be quite fun when you get into it

8. Thesis

9. The title said something about BDSM..
BDSIM is a wrapper for Geant4 to do accelerator tracking
We’ve been tracking through a research beamline which is going to be installed at the Christie proton therapy centre
Also looking at tracking through an RF cavity to look at losses.

10. Tracking losses through the cavity (in progress!)
Previously used a ‘homebrew’ tracking model plus iris radii
Gives approximate beam loss, but not subsequent radiation shower
Working on a combined beam tracking/loss calculation in GEANT4
Uses BDSIM framework
We added CAD import
Field map import in progress
We added improved tracking algorithm
We added some parallelisation tools
A good general tool for proton therapy centre design, e.g. losses, shielding etc.

11. Optics Validation Does BDSIM correctly model the focusing of the beam?
Use well known accelerator code MADX to get optics functions.
Try to replicate them in BDSIM
Looks good!

12. Optics Validation Not everything works out of the box
Something odd going on with units?
Pretty sure the beam isn’t 1.5 m!
Should be fixed fairly easily.

13. Loss Maps CAD import linac structure: BDSIM uses ROOT to collect data
For now, simulate separate to other geometry
BDSIM uses ROOT to collect data
Easy(ish) to produce histograms of primary loss
Very very preliminary!
The cavity was 10x too small!

14. The Future Tracking through a gantry Not been done before
We will need a gantry optics file
Not been done before
Can we track from the accelerator into the patient?
Include degraders, beam transport and gantry, then deposit dose in the patient
Probably do a mashup of everything used so far