1. Institute for Advanced Radiation Oncology
QA – LINAC
Daily, Monthly, Annual
Jack Yang, Ph.D., DABR
Institute for Advanced Radiation Oncology
Barnabas Health
Long Branch, NJ 07740
New Technologies in Modern Radiotherapy, Chulabhorn Research Institute, Bangkok, Thailand, August 22-25, 2012

2. Outlines
Definition of treatment delivery quality assurance for LINAC
Assure that the 5% final dose discrepancy can be achieved with the site specific QA process
Current QA protocols implemented in modern radiation oncology clinics with updated LINAC functionalities

3. Radiation Oncology Error Management
Clinical experience has shown that variations of 10% or more in the delivered dose can sharply reduce the probability of local tumor control.
ICRU Report 62 recommends that radiotherapy be delivered within 5% of the prescribed dose to ensure adequate tumor control.
The global aim is to achieve the desired tumor control while maintaining toxicities to normal tissues to a minimum
Are these endpoints achievable with current delivery technology?
Fig., Connor et al, IJROBP 1975

4. Linac QA Components: Dosimetric accuracy Mechanical Accuracy Safety
Frequency:
Daily
Monthly
Annually

5. The Early QA report (1994) AAPM TG-40 report Comprehensive QA program
QA of EXRT (External Beam Treatment) equipment
QA of RTP (Information and IT tools) system
Brachytherapy
Clinical practice

6. Periodic QA of Linear Accelerator (TG-40)
Frequency
Procedure
Tolerence (±)
Daily
X-ray & electron output constancy 3%
Localization lasers
2 mm
Safety interlocks (door)
functional
Monthly
X-ray & Electron output constancy 2%
Light/radiation field coincidence
X-ray flatness and symmetry
Electron flatness and symmetry
X-ray energy
2% in depth dose (2% in ionization ratio)
Electron energy
2 mm in R80 (2 mm in Rp)
Optical distance indicator
Field size indicators
Gantry angle indicator 1°
Collimator angle indicator
Cross-hair centering
1 mm
Annually
Full calibration
Isocenter shift
Collimator rotation
2 mm diameter
Gantry rotation
Couch rotation
Couch vertical travel
Tabletop sag

7. Radiation Isocenter Checks
Collimator » 2 mm diameter circle
Treatment table » 2 mm diameter circle
Gantry » 2 mm diameter circle

8. Misadministration Definition in US
For external beam (>3 fractions)
No written directive
Wrong patient
Wrong site
Weekly dose exceeds 30%
Total dose exceed 20%
Most of the LINACs are inspected and governed by the state government !!

9. Misadministration Definition in US
For Stereotactic radiosurgery/radiotherapy
(<= 3 fractions)
No written directive
Wrong patient
Wrong site
Total dose error exceeds 10%

10. Background of TG 142
Principles - TG-40 was the International Commission on Radiation Units and Measurements (ICRU) recommendation that the dose delivered to the patient be within ±5% of the prescribed dose.
The goal of a QA program for linear accelerators is to assure that the machine characteristics do not deviate significantly from their baseline values acquired at the time of acceptance and commissioning.

11. Rationales for Developing TG 142
New Technology since TG 40 MLC, as Asymmetric Jaws, Dynamic & virtual wedges, EPIDs…….
Imaging: kV and cone beam, Respiratory gating…..
Clinical procedures not emphasized in TG 40 with new modalities such SRS, SBRT, TBI, IMRT……
TG50, TG58, TG76 TG106, TG104, TG100 for various LINAC QAs

12. TG 142 fro Linear Accelerator QAs
What This Report Doesn’t cover (some special techniques)
Describe the techniques for performing QA tests
Accelerator beam data commissioning equipment and procedures – TG-106
QA for TomoTherapy –TG-148
QA for Robotic Radiosurgery – TG-135
QA for Non-Radiographic Radiotherapy Localization & Positioning Systems – TG-147
Does add Specific Recommendations / Supplements the Work of
Basic Applications of Multileaf Collimators – TG-50
Clinical use of electronic portal imaging - TG-58
Management of Respiratory Motion– TG-76
Kilovoltage localization in therapy – TG-104

13. MLC QA TG 50 (2001) - Update

14. EPID QA TG 58 (2001) - Update

15. TG-142 Testing Standards Acceptance Testing Procedure (ATP) Standards
Acceptance testing sets the baseline for future dosimetric measurements for beam performance constancy, verifies that the equipment is mechanically functional and operates within certain tolerances from absolute specified values.
Tolerances and Action Levels
Level 1 – Inspection Action
Level 2 – Scheduled Action
Level 3 – Immediate Action or Stop Treatment Action or Corrective Action
With these 3 action levels, there is an institutional need to specify the thresholds associated with Levels 2 and 3. Level 1 threshold isn’t a critical requirement but can lead to improvements in the QA program.

16. TG-142 Daily

17. TG-142 Daily (Continued)

18. TG-142: Monthly

19. TG-142 - Monthly (Continued)
Procedure
Tolerance
(non-IMRT
machines)
(IMRT
Stereotactic
machines

20. TG-142 - Monthly (Continued)
Procedure
Tolerance
(non-IMRT
machines)
(IMRT
Stereotactic
machines

21. TG-142: Annual

22. TG-142 – Annual (Continued)
Procedure
Tolerance
(non-IMRT
machines)
(IMRT
Stereotactic
machines

23. TG-142 – Annual (Continued)
Procedure
Tolerance (non-IMRT machines)
Tolerance (IMRT machines)
Tolerance Stereotactic machines

24. Wedge Verification (Not Physical)

25. MLC Verification

26. MLC - Annual Test

27. Imaging Equipment Test - Daily

28. Imaging Equipment Test - Monthly

29. Imaging Equipment Test - Annual

30. Conclusions
LINAC QA protocols have become extensive through modern LINAC development and implementation.
AAPM TG-40 report still function as the base lines.
AAPM TG-142 has gradually emerging into modern clinical practice (some of those testing are tedious and maybe not applicable to a busy clinic).
However, regulatory agencies still have hard time to follow due to manpower, training and budgeting constraints.
Annual report should include but not limited to the following: . (1) Dosimetry, (2) Mechanical, (3) Safety, (4) Imaging, and (5) Special Devices/Procedures.