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 !!