Post on 29-Nov-2014
description
ROTATION 5: TPS MODELING AND BEAM COMMISSIONING at UIHC Radia9on
Oncology Mentors: John Bayouth, Ph.D.
(04/23/09 – 06/11/09)
By Vibha Chaswal
Goals
• Model 1 photon beam -‐ Know parameters and their effects
• Model 1 electron beam
-‐ Know parameters and their effect
• Model Wedges
• Validate the beams modeled
• Understand the nuances of TPS modeling
Photon beams: data requirements
• Pdds • Profiles • Calibra9on output factor • Rela9ve output factors Data For Valida9on! -‐ A subset of above -‐ Sc and Sp -‐ Dosimetric tests, match computed and measured dose distribu9ons
Data collected for assumed clinical applica9on
TPS modeling: The Machine
TPS Modeling: The machine
TPS Modeling: The Radia9on Beam
• Fine tuning Profiles -‐ Effec9ve source size for Penumbra matching
-‐ Gaussian width and height of FF scacer source for tails
-‐ Transmission factors of Jaw and MLC for tails region
Energy Spectrum
Energy Spectrum: Build-‐up region
In-‐field Region: FF acenua9on using cone model
With Off-‐axis Soeening factor
In-‐field Region: FF acenua9on using arbitrary profile
With Off-‐axis Soeening factor
Off-‐axis soeening
Out-‐of field regions: Penumbra and tails
Out-‐of field modeling parameters
Beam Valida9on: PDDs
Result: All Pdds pass within 2% or 2mm
Beam Valida9on: Profiles
Result: Within 3% or 3mm except outliers in tail regions
Beam Valida9on tests: MU verifica9on
Beam valida9on: R and V import
Rela9ve Decision Maps: error Limit = 3 %, dta Limit = 3 mm
TPS Modeling: The machine, Collimator rota9on incorrect
Electron beams: Data required
Electron Beam Parameters
Two adjustable parameters
- Off-axis ratios, and
- The scatter correction factor (FMCS), dose spread out in media relative to air.
Electron Beam modeling
Electron PDD
Thank you!!!!!