Post on 24-May-2015
0 9 / 1 7 / 2 0 0 8 – 1 1 / 1 4 / 2 0 0 8
M E N T O R S : T I M W A L D R O N A N D D R . J O E M O D R I C K
B Y
V I B H A C H A S W A L
Linear Accelerator Acceptance, Commissioning and Annual QA
Expectations
I Linear Accelerator Acceptance/Testing a. Fundamental concepts of linear accelerators, beam
production and control b. Medical Linear Accelerator Safety features c. The acceptance testing process
II Radiotherapy Beam data Collection for Commissioning a. Data Definitions b. Measurement techniques and underlying principles
III Medical Radiotherapy Equipment QA a. Linac QA b. Other treatment machine QA (?)
Interpretation
Understand: Working of Linac, especially beam-line and beam
characteristics Importance or Acceptance Testing Procedure: “that signature means you are stuck with the machine for next
10-15 years” Importance of Commissioning “Quality of your treatment beams for life-time of the machine” Difference between both – effort Measurements for Commissioning Annual Constancy check of Linac - Procedures
Lectures Data measurements Annual QA Reading Reading
Linac Beam Line
Beam line: Electron gun>Wave-Guide>Bending Magnet> Target > Flattening filter/Scattering foils > Monitoring chamber > Collimation
High Z target
Flattening filter
Patient treated at CEIGRT at UIHC RadOnc
Bending Magnet assembly
Waveguide
Diode gun injector
IG = Gun current I = Intrinsic current IB = Beam Current
IG IIN
IB
Photon Beam Produc2on mode
Bending Magnet assembly
Primary foil
Secondary foil
Patient treated at CEIGRT at UIHC RadOnc
Waveguide
Diode gun injector IG IIN
IB
Electron Beam Produc2on mode
Beam Characteristics
Energy: RF, BMI, Gun current Fluence: Gun Current, RF Flatness: Flattening filter Symmetry: Flattening filter
Acceptance: Verifying Specifications
AAPM TG – 45 Procedure starts at Installation, or even before while
making purchase agreement Importance Order in which tests should be performed Relative importance of some tests Procedures of preliminary calibration, isocenter
verification, end effect measurement Seemingly un-important tasks/tests that are absolutely
essential – (Oh! The electron mold kit doesn’t have the frame for 25x25 cone)
Commissioning
Much more effort! How much effort? – what is the minimum amount of
data you would require to commission a beam for your CLINIC REQUIREMENTS.
Beam characteristics important for treatment types performed most commonly.
Data measured.
AND ………..ANNUAL QA
Oncor D with Sarah AAPM TG-40 Techniques for Acceptance Procedures and
Commissioning data measurements - 3D water tank and Linear array for profiles and
PDDs - Gantry, Collimator and Table star-shots - Mechanicals
End effect Virtual Source for 12 meV and 15 MeV electrons on
Oncor B
Thank you !!