FILM MEASUREMENTS Timo Ikonen 1 , Antti Kulmala 2 , Christopher - - PowerPoint PPT Presentation

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FILM MEASUREMENTS Timo Ikonen 1 , Antti Kulmala 2 , Christopher - - PowerPoint PPT Presentation

Feb 26, 2023 279 likes •437 views

GEANT4 MODELING OF VARIAN TRUEBEAM & COMPARISON TO FILM MEASUREMENTS Timo Ikonen 1 , Antti Kulmala 2 , Christopher Boylan 1 , Viljo Petj 1 , Daren Sawkey 1 1 Varian Medical Systems 2 Clinical Research Institute HUCH Ltd. MCMA2017, NAPOLI,

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SLIDE 1

GEANT4 MODELING OF VARIAN TRUEBEAM & COMPARISON TO FILM MEASUREMENTS

Timo Ikonen1, Antti Kulmala2, Christopher Boylan1, Viljo Petäjä1, Daren Sawkey1

1 Varian Medical Systems 2 Clinical Research Institute HUCH Ltd.

MCMA2017, NAPOLI, ITALIA 17 OCTOBER 2017

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SLIDE 2

Motivation: model improvement

Measurements Eclipse TPS Monte Carlo

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SLIDE 3

Motivation: model improvement

Measurements Eclipse TPS Monte Carlo

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SLIDE 4
  • Measurements with

3 different matched TrueBeam machines at Kotka and Helsinki, Finland

  • Measured on

GafChromic EBT2 dosimetry film inside an RW3 plastic water phantom

Measurements overview

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SLIDE 5

Film calibration and response correction

Film absolute dose calibration

Select middle sheet

  • f the film stack

Irradiate Scan Dose calibration curve

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SLIDE 6

Film calibration and response correction

Lateral and longitudinal response correction

Irradiate with

  • pen field

Scan Compare with known profiles Get correction curves

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SLIDE 7
  • TrueBeam treatment head

geometry implemented in Varian’s VirtuaLinac platform

  • Can be run in an Amazon cloud
  • Local implementation at the

computer cluster of VMS applied research department

  • Physics and MC algorithms

by Geant4

  • QGSP_BIC_EMZ
  • Beam parameters from

experiments (e.g. spot size)

  • r fitted to reference data

(e.g., electron energy)

Monte Carlo model

MLC Jaws Target / photon source

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SLIDE 8

Comparison of MC and measurements

Irradiation plan

  • Step-and-shoot IMRT
  • 6FFF field, 2 segments
  • Millennium 120 MLC

Measured Monte Carlo Difference Tips Edges

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SLIDE 9
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SLIDE 10
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SLIDE 11
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SLIDE 12

Corrugations due to MLC leaf tips

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SLIDE 13

Differences in MLC leaf tip modeling

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SLIDE 14
  • Varian has created a Monte Carlo simulation platform

based on Geant4 for the simulation of the TrueBeam linac

  • The Monte Carlo model can be used to interpret

measurements and other computational results

  • Initial results are encouraging and point to potential

improvements in the computational in-house algorithms and the photon source model

Summary and outlook

Also thanks to:

Petri Hiltunen, Petri Kokkonen, Martin Ruprecht, Tuomas Torsti

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SLIDE 15

Questions?