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

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

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.

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)

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.

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

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

Thesis

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.

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.

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!

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.

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!

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