The document discusses quality assurance of 3D treatment planning systems for external photon and electron beams. It covers international reports on QA of TPS from organizations like IAEA, AAPM Task Group 53, and CAPCA. The presentation reviews aspects of TPS QA like system/software configuration, data entry, and evolution over time. It provides examples of important quality control checks for components like the CPU, digitizer, backups, CT transfer, and validating basic beam data. Tolerances for dose calculation accuracy are also addressed.

1. PRESENTER:
RAHIM GOHAR
Quality assurance of 3-D treatment
planning systems
for external photon and electron beams
Review
IAEA TRS -430
AAPM Task Group- 53
 Canadian Association of Provincial
Cancer Agencies(CAPCA)

2. overview
 Introduction
 IAEA TRS 430
 Task Group 53
 Canadian Association of Provincial Cancer Agencies(CAPCA)
(2nd part)
 What's going on in the TPS
 Eclipse
 Planning
 Limitations
 Current practices
 What needs to be done???

3. introduction
 Generally
“Quality assurance, is all those planned and
systematic actions necessary to provide adequate confidence
that a product or service will satisfy the given requirements
for quality (ISO 9000:1994).”

4. Quality Assurance in Radiotherapy
“QA of a TPS is a dynamic process which evolves with
time”
Purpose
 Proper functioning of TPS
 verification of dose calculations.
 Validation of planning algorithms
 to reduce uncertainties
 reduces the likelihood of accident
 inter-comparison of results
among different radiotherapy
centers,
 Patient safety (End Result)

5. Reports on QA of TPS
Early reports on QA of TPS
 AAPM Report TG-53
Recent reports on QA of TPS
 IAEA Report
 ESTRO (1998)

6. Aspects of TPS QA
We can categorize QA tests according to
 System and software
 Configuration process
 Data entry
Evolution of QA of a TPS
 Dynamic process
 Introduction of new software
Tolerances and accuracy
 Accuracy of treatment
 Tolerances in treatment planning http://blog.iactiveit.com/?p=224

7. Errors in Treatment Planning Process
 Input of patient anatomical data
 Treatment planning system (TPS)
 Dosimetric data for radiation beams
 Dose calculation algorithms
 Geometric data for treatment machines
 Patient and treatment data management & transfer
 Human errors

8. Quality Assurance in Treatment Planning
 Appropriate program
 Consultants, protocol implementation
 Error identification
 Expertise , mechanism
 Reduce the likelihood of unexpected dosimetric errors
 End Result
BUT……..

9. Periodic Quality Assurance
After commissioning
 Integrity of
o Hardware, software, data transfer
Upgrading of system
o subset of acceptance tests

10. Be careful

11. Some important QC checks
Central processing unit
 Purpose
o To check the functionality of CPU
 Procedure
o Restart or reboot the computer as recommended by the vendor or
as appropriate
o Observe onscreen messages
o Malfunctions(notice if any)

12. Some important QC checks
Digitizer
 Purpose
o Check the sensitivity, accuracy
 Procedure
 Input any contour of known dimension
 Use screen ruler for verification
 Deviation
 Within 1mm
B
A
1
0
C
6
7
5
D
E

13. Some important QC checks
Backup recovery
 To confirm that data that have been backed up can be
recovered.
 Restore data that have been recently backed up
 Check the integrity of the restored data.

14. Some important QC checks
Computed tomography transfer
 Purpose
 To check that CT transfer protocols
have not changed.
 Procedure
 Transfer four basic patient studies
• prone, supine, head first and feet first

15. Anatomical description
Basic patient entry
 Uniqueness of patient
Image conversion, input and use
 Import, patient orientation
 slice position

16. Some important QC checks
 Computed tomography density and geometry
 Purpose
 To check that the relationship between the CT number and density and
image geometry has not changed
 Procedure
 Scan a phantom with insertion
of some known density and geometry
 Transfer images to the TPS
 Comparison (0.2cm for distance,
0.02 for electron
density)
Tissue characterization phantom

17. Reverse verification of HU number
 Hounsfield unit
o Linear transformation attenuation coefficient measurement, by taking
water as reference medium
o Quantitative scale(not SI or derived quantity)
 The CT # of a medium is related to its
attenuation coefficient. They range
from -1000 (air) to “zero” (water) to
1000 (bone):
 H = [(µm - µw) ÷ µw] x 1000
Dosimetric error that would result from the uncertainties from in the HU calibration

18. Confirmation of the basic beam data

19. External beam revalidation
 Purpose
 To check the constancy of external beam dose calculations to
safeguard against inadvertent alteration or corruption.
 Procedure
 Check data files
 Review the directory
 Check the creation date
 TPS configuration
 Review calculation model
parameters and check against
the commissioning data.
 Test plans with and without
in-homogeinity

20. MONITOR UNIT/TIME CHECK
Standard geometrical set up
SSD = 95cm
Depth = 5cm
F.S = 10x10cm2
1 monitor unit =1cGy

21. Recommissioning or additional data
If a new machine is installed
 update the TPS data

22. MONITOR UNIT/TIME CHECK
Independent (redundant) check of the MUs/time
 Computer program
 Manual calculation
 Deviation
S
. R
SAD
100
dr
P
SSD
dm
S

23. Dose uniformity verification at field junction
 Creating junction
 Run the plan on 2-D Array
 Comparison in veri-soft
 Criteria

24. Photon-Photon field junction
 Beam profile across the junction
BEV

25. Electron-Electron field junction
 Beam profile across the junction

26. Electron-photon field junction
 Beam profile across the junction BEV

27. Electron-photon field junction

28. Measured electron-photon junction profile
using Gafchromatic films

29. Dose distribution verification using 2-D Array

30. Tolerances for the accuracy of photon beam dose calculations
of treatment planning systems
 Objectivity
 Precision
 Machine specific
 Reproducibility
 Accuracy
 Calculation Dependent
 Depends on several factors
Life itself is the second name of uncertainty

32. Thank you for your attention
Queries??
Comments
Note: “As you sow so shall you Reap”