Fast Monte Carlo for Proton Therapy Andrew Green

Outline Things that happened in 2015 Update on Google Cloud work Algorithms work Geant4 development Thesis Progress The Job hunt

Things that happened in 2015 Attended MC2015 conference, presented work on Xeon Phi Well received, got some interesting questions Other talks very interesting, lots of good ideas about validation Had a good look round Nashville

Things that happened in 2015 Visited SLAC for two weeks, ostensibly for a two-day course on Xeon Phi – Also gave a seminar on my Cloud and Algorithms work Interesting course, but little material on Monte Carlo – Implicit admission that even Intel don’t think Xeon Phi is that good at it? Worst sunburn I have ever had (don’t worry, no pictures) Very productive, started a collaborative effort – Specialist Xeon Phi application for proton therapy – still working on that… Also learned a little bit about Hadronics (SLAC specialty)

Things that happened in 2015 Went to Geant4 collaboration meeting in Chicago Lots of interesting developments in version 10.2 – Improved Goudsmit-Saunderson Multiple scattering model – Better lateral correlation in Urban MCS model – Some hadronic model parameter tuning made available to users. Geant4 version 10.2 released on 4 th December – Should get about 5-10% speed improvement – Strange scaling: superlinear (i.e. 2 threads take less than half the time of one thread) – no-one understands this yet… Useful discussions about validation and performance issues relevant to medical Monte Carlo – Medical still not seen as a big player – Medical users need to make more noise

Google Cloud Work This time last year: – PYPE mostly written – Fast plan validation in the cloud using dummy plan – Plan validation I 6 minutes This time last week: – PYPE stable and reliable (mostly) – Able to validate actual plan from PSI in 10 minutes – Considerably more complex than proof of principle plan. Paper under review for submission to Medical Physics

Google Cloud Work Ran several large jobs using PYPE – Robustness study using two plans from PSI (approx 1 billion CPU seconds = 33 CPU years) – Full fraction of proton therapy – 100x109 protons Took longer to download the data than to produce it! – Roughly 3TB to download and analyse – Currently sat in UoM data storage in Salford. Analysis ongoing, hoping to publish in the new year

Algorithms Work Been very cagey up ‘til now, but almost ready to publish Technique known as ficticious interaction tracking, or Woodcock tracking – Used extensively in nuclear reactor codes. – Implemented in GATE for photons. Allows tracking of particles without having to consider boundary crossings – Perfect for medical physics There have been a couple of hiccoughs on the way though… – Where should the dose go? – Optimisation of the implementations – Migration to multithreaded mode Mostly solved now.

Tracking Algorithms PRESTAWoodcock

Woodcock vs PRESTA – no secondaries

Woodcock vs PRESTA – with secondaries

Secondary Production

Woodcock Applied to Secondaries

Validation Compare PRESTA algorithm produced Bragg peak to Woodcock produced Bragg peak Used Kolmogorov-Smirnov test to compare the two Found a problem, also found a solution! Still need to fully understand implications for simulation efficiency – At present, too much performance penalty – Profiling underway, think I have an idea what is wrong

Bragg peak Comparison

Validation Woodcock alone gives slightly different results – Barely visible in plot, visible in zoomed version Use step-limiting technique Kolmogorov-Smirnov results: – No step limit: D=0.465, p=1.06E-19 – With step limit: D=0.04, p= KS-test suggests the two are equivalent when step limiting is enabled.

Thesis Progress Comments back on one chapter, two more approaching readiness. Most of the actual work is now done Going pretty well (I think) Expect to have the next two chapters done soon after christmas Aiming to submit in March. This word cloud is here because I know it will annoy Hywel

Job Hunt Applications in a couple of places: – JSPS fellowship – one year in Japan at KEK, working on BNCT – As of this morning, KEK are looking for backup funding in case JSPS doesn’t pan out – Research Software Engineer at the Christie hospital – Integrated treatment planning and validation system – work with Marcel van Herk, should be pretty cool Not heard anything from any of these yet… Open to suggestions!

Next Year Finish thesis Get Job ???? Profit