Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 1
Tools and Techniques for process based safety
M. Saiful Huq, Ph.D., FAAPM, FInstP Professor and DirectorDepartment of Radiation Oncology
University of Pittsburgh Cancer Institute ; UPMC CancerCenterPittsburgh, Pennsylvania, USA
6%
29%
16%16%
5%
9%
6%7% 6%
Procedures
Decision
Professional errorComminication
Instrument
OtherInterpre tation
Training
Supervision
Source: IAEA - Safety Report Series No 17
90 % human errors
Main causes of radiotherapy accidents
2Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
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Human failure18%
Lack of standardized procedures
18%Inadequate
training15%
Inadequate resources
13%
Hardware/software failures
13%
Lack of communication
11%
Design failure4%
Commissioning 4%
Others4%
TG-100 analysis of causes of failure for IMRT treatment
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 2
Challenges with current QA paradigm….
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• Current RT QA guidance is focused on equipment performance even though most RT events have resulted from human performance failures rather than equipment failure
• Different from a process centric QM approach which should be designed to mitigate all failures with detectable impact on patients, not just the ones resulting from equipment failure
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
2008
2008
2009
Recent reports
5
2000
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
6
• As technology & processes changeØ Retrospective approaches are not
sufficientØ All-inclusive QC checks may not be
feasibleØ Develop proactive approaches to
anticipation of failure modesØ Evaluate risks from each failure mode
ICRP 112 Conclusions and recommendations
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
• QM program should be based on risk assessment
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 3
Risk assessment
7
• Many risk assessment and analysis tools/techniques exist in industry
• These tools can be easily adapted to RT to enhance safety and quality of treatment process
• Risk assessment is the process of analyzing the hazards involved in a process
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Risk assessment tools
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• Failure Modes and Effects Analysis (FMEA)
• Fault Tree Analysis (FTA)
• Process Tree (Mapping)
• Establishment of a risk based QM program
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
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Process tree
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
• Graphically illustrates the relationship between the different steps in a process
• Delineate and then understand the steps in the process to be evaluated
• Demonstrates the flow of steps from process start to end
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 4
10
Patient database information entered
Immobilization and positioning
CT simulation
Other pre-treatment imaging
Transfer images and other DICOM data
Initial treatment planning directive
RTP anatomy contouring
Treatment planning
Plan approval
Plan preparation
Initial tx(Day 1)
Subsequent tx(Day N)
End of txStart of tx
Example: IMRT process tree
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Verify patientsetup
Register EPID andpseudo radiograph
LoadEPID
LoadPseudo-
radiograph
Determine patientShifts and rotations
Reimage if necessary a
Verify beam outlinesSelect beam in record & verify
Image
SetparametersVerify clearance
and achievabilityRegister beamoutline c plan
Repeat for each beam b
b
Approval to treat
Review setup images
Review beam images
Approve treatmentif good
Day 1 imaging verification
EPID imagingfor localization
Place patient on table
Align mold marks
Pt in mold
Align allmarks
Make AP imageSetmu
Set gantryMakeexposure Set field size
Set machineMake lateral image
Setmu
Set gantryMakeexposure
Set machineVerify images are adequate
Approve patient position
a
11
Process Tree
11
Day 1 imaging verification
EPID imagingfor localization
Place patient on table
Align mold marks
Pt in mold
Align allmarks
Make AP imageSetmu
Set gantryMakeexposure Set field size
Set machineMake lateral image
Setmu
Set gantryMakeexposure
Set machineVerify images are adequate
Approve patient position
a
11
Process Tree
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Day 1 imaging verification
EPID imagingfor localization
Place patient on table
Align mold marks
Pt in mold
Align allmarks
Make AP imageSet
mu
Set gantryMakeexposure Set field size
Set machineMake lateral image
Setmu
Set gantryMakeexposure
Set machineVerify images are adequate
Verify patientsetup
Register EPID andpseudo radiograph
LoadEPID
LoadPseudo-
radiograph
Determine patientShifts and rotations
Reimage if necessary
Approve patient position
a
a
Verify beam outlinesSelect beam in record & verify
Image
SetparametersVerify clearance
and achievabilityRegister beamoutline c plan
Repeat for each beam b
b
Approval to treat
Review setup images
Review beam images
Approve treatmentif good
11
Process Tree
12Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 5
A Process Tree
21%
21%
18%
22%
18%
Saiful Huq - Tools and techniques for process based safety
1. Cannot be used as a risk assessment tool2. Is a visual display of various stages of a
process3. Cannot be used to develop a QM program in
radiation therapy
4. Is a tool used by industrial engineers only5. Cannot represent the radiation treatment
process of a patient
Correct answer: 2
2. Is a visual display of various stages of a process
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
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• Assess potential risks involved in the process
• FMEA assesses the likelihood of errors in a process and considers the effects of such error
FMEA
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 6
Ø What could possibly go wrong (potential failure mode)
Ø How could that happen (what are the causes that result in a failure mode)
Ø What effects would such a failure produce (potential effects of failure)
Ø The overall risk of each identified failure mode is then scored and prioritized according to RPN
Ø A good FMEA then identifies corrective actions to prevent failure from reaching the patient
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• FMEA looks at each process and at each step asks the questions:
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
FMEA
• First day of Tx: Patient maybe positioned incorrectly relative to the isocenter
Example of FMEA
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Failure mode:
• Tx machine or simulator laser misalignment• Therapist error due to inattention• Poor instruction or setup documentation in the chart• Inadequate immobilization• Organ motion or tumor growth
Causes of failure:
• The magnitude of the displacement from planned isocenter• Tx technique (stereotactic, 3D conformal or large fields)• Proximity of critical structures and when in the course of tx the
error was detected
Consequences: severity depends on:
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Steps to perform a quantitative FMEA
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• Identify all of the potential causes for each FM
• Determine the impact of each FM on the outcome of the process assuming the failure is not detected and corrected in subsequent steps
• Identify all possible failure modes (FM)
• Establish a risk based QM program
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 7
Step Potential failure modes
Potential causes of failure
Potential effects
of failure
O S D RPN Comment
FMEAFor a given sub-process:
RPN = O x S x D [ 1 ≤ RPN ≤ 1000 ]
Examples of FMEA
Step Potential Failure Modes
Potential Cause of Failure
Potential Effects of Failure
O S D RPN Comments
Import images into RTP system data base
Wrong patient’s images
MiscommunicationUser error
Wrong dose distributionWrong volume
3 9 5 135
Wrong imaging study (correct patient)Viz.; wrong phase of 4D CT selected for planning; wrong MR for target volume delineation
Ignorance of available imaging studiesAmbiguous labeling of image setsInadequate training MiscommunicationUser error
Wrong dose distributionWrong volume
7 8 7 392
File(s) corrupted
Network problem Lost imagesWrong dose distributionWrong volume
43
39
24
24108
File probably would not open
Sub-process: RTP planning
20Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Examples of FMEA
Step Potential Failure Modes
Potential Cause of Failure
Potential Effects of Failure
O S D RPN Comments
Import images into RTP system data base
Wrong patient’s images
MiscommunicationUser error
Wrong dose distributionWrong volume
3 9 5 135
Wrong imaging study (correct patient)Viz.; wrong phase of 4D CT selected for planning; wrong MR for target volume delineation
Ignorance of available imaging studiesAmbiguous labeling of image setsInadequate training MiscommunicationUser error
Wrong dose distributionWrong volume
7 8 7 392
File(s) corrupted
Network problem Lost imagesWrong dose distributionWrong volume
43
39
24
24108
File probably would not open
Sub-process: RTP planning
21Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 8
Examples of FMEA
Step Potential Failure Modes
Potential Cause of Failure
Potential Effects of Failure
O S D RPN Comments
Import images into RTP system data base
Wrong patient’s images
MiscommunicationUser error
Wrong dose distributionWrong volume
3 9 5 135
Wrong imaging study (correct patient)Viz.; wrong phase of 4D CT selected for planning; wrong MR for target volume delineation
Ignorance of available imaging studiesAmbiguous labeling of image setsInadequate training MiscommunicationUser error
Wrong dose distributionWrong volume
7 8 7 392
File(s) corrupted
Network problem Lost imagesWrong dose distributionWrong volume
43
39
24
24108
File probably would not open
Sub-process: RTP planning
22Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Examples of FMEA
Step Potential Failure Modes
Potential Cause of Failure
Potential Effects of Failure
O S D RPN Comments
Import images into RTP system data base
Wrong patient’s images
MiscommunicationUser error
Wrong dose distributionWrong volume
3 9 5 135
Wrong imaging study (correct patient)Viz.; wrong phase of 4D CT selected for planning; wrong MR for target volume delineation
Ignorance of available imaging studiesAmbiguous labeling of image setsInadequate training MiscommunicationUser error
Wrong dose distributionWrong volume
7 8 7 392
File(s) corrupted
Network problem Lost imagesWrong dose distributionWrong volume
43
39
24
24108
File probably would not open
Sub-process: RTP planning
23Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
What are O, S and D’s?
• O : Probability that a specific cause will result in a failure mode
• S: Severity of the effects resulting from a specific failure mode if it is not detected or corrected
• D: Probability that the failure will not be detected
• Risk priority number RPN = O*S*D
• For O, S and D one assigns values from 1 to 10.
• TG100 has developed scales for O,S, and D indices that are tied to radiotherapy outcomes and observations
24Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 9
TG-100 O, S, and D values used for FMEARank Occurrence Severity Detectability
Qualitative Frequency Qualitative Categorization Estimated Probability of
going undetected in %
1 Failure unlikely 1/10,000 No effect 0.012 2/10,000 Inconvenience Inconvenience 0.23 Relatively few
failures5/10,000 0.5
4 1/1,000 Minor dosimetric error
Suboptimal plan or treatment
1.0
5 <0.2% Limited toxicity or under-dose
Wrong dose, dose distribution,
location or volume
2.06 Occasional
failures<0.5% 5.0
7 <1% Potentially serious toxicity or under-
dose
108 Repeated
failures<2% 15
9 <5% Possible very serious toxicity
Very wrong dose, dose distribution, location or volume
20
10 Failures inevitable
>5% Catastrophic >20
25Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
FMEA- mark process map
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• Shows if potential failures are uniformly distributed through the processes or clustered
• If clustered, should consider the major step as a hazard
• Prioritize the potential failure modes based on RPN and severity function
• Mark the highest rank steps on the process map
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
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Major Processes Step Potential Failure
Modes Potential Causes of Failure Potential Effects of Failure AVG O AVG S AVG D AVG RPN
4 - Other pretreatment imaging for
CTV localization
6. Images correctly
interpreted (e.g. windowing for
FDG PET)
Incorrect interpretation of tumor or normal
tissue.
User not familiar with modality or inadequately
trained)(Poor inter-disciplinary
communication)
Wrong volume 6.50 7.44 8.00 387.75
7 - RTP Anatomy
Delineate GTV/CTV (MD)
and other structures for planning and optimization
>3*sigma error contouring
errors: wrong organ, wrong site,
wrong expansions
User error
Inattention, lack of time, failure to review own work
Very wrong dose distributionsVery wrong volumes.
5.29 8.43 7.86 366.00
12 - Day N Treatment
Treatment delivered
LINAC hardware failures/wrong dose per MU;
MLC leaf motions inaccurate,
flatness/symmetry, energy – all the
things that standard physical
QA is meant to prevent.
Poor hardware design Poor hardware maintenance
Inadequate department policy (weak physics QA
process)Poorly trained personnel
Wrong dose Wrong dose distribution
Wrong locationWrong volume
5.44 8.22 7.22 354.00
FMEA by RPN (TG-100)
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 10
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Process map marking I wouldn’t try to read it…will hurt your eyes
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
FMEA
20%
21%
21%
19%
19%
Saiful Huq - Tools and techniques for process based safety
1. Identifies unknown potential failure modes in a process
2. Prioritizes the identified failure modes according to RPN only
3. Identifies the causes and effects of each failure mode
4. Provides only qualitative means to evaluates the risks associated with a process
5. Cannot provide for problem follow-up and corrective action
Correct answer: 3
3. Identifies the causes and effects of each failure mode
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 11
Fault tree (FT)
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• Evaluate propagation of failures using a FT analysis
• FT gives a visual representation of the propagation of failure in the procedure
• It helps identify intervention strategies to mitigate the risks which have been identified
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
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Errorin data
Errorin QC
Error in data input
Errorin QC
Error in Calculation algorithm
Errorin QC
Error in prescription
Errorin QC
Error in calculation
Errorin QA
Error in Calculated value for patient
• Fault tree compliments process tree
• Begins on the left with something that could possibly go wrong (failure mode)
• Works backwards in time (to the right) to study what could possibly cause that error
Fault tree
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Design of QM program
• Use the FTA and FMEA risk and process oriented information to design a QM program for the process being investigated
• Example (From TG-100 IMRT analysis)Ø Sub-process: RTP anatomyØ Step: Delineate GTV/CTV and other structuresØ FM: › 3σ contouring error, wrong organ, site, or expansionsØ RPN = 366Ø Rank: #2
33Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 12
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Rank RPN Step# Process Step
#2 366 58 7. RTP Anatomy Delineate GTV/CTV (MD) and other structures
FM: > 3σ contouring error, wrong organ, site, or expansions
2nd ranked Failure Mode
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
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Segment of RTP anatomy Fault Tree w/o QM placement
Step Failure Mode
Causes of failure
Effect of failure
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
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Segment of RTP anatomy Fault Tree with QM placement
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 13
37
Segment of RTP anatomy Fault Tree with QM placement
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
A Fault Tree analysis
21%
18%
21%
19%
20%
Saiful Huq - Tools and techniques for process based safety
1. Focuses on identifying the root factors that could cause a failure
2. Is unnecessary to design a process based QM program in radiation therapy
3. Diagram uses only “AND gate” and never any “OR gate”
4. Cannot help determine corrective action required to prevent or control the causes
5. Is only useful for designing a QM program
Correct answer: 1
1.Focuses on identifying the root factors that could cause a failure
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 14
Summary
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• QA/QM should be more process centric
• Should be based on rigorous sensitive analyses of all components of radiotherapy process
• Be based on industrial engineering approaches of risk analysis and mitigation
• Will be infrastructure dependent and may shed light on how much QA is enough for a given institution
• Risk analysis gives guidance for developing a QM program
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
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It is useful to report all accidents before consequences appear
Our job is not to prevent errors, but to keep the errors from injuring the patients.
Lucian Leape
It is impossible to make anything foolproof because fools are so ingenious.
Artur Bloch, Murphy’s law
Courtesy: Josef Novotny
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Major Processes Step Potential
Failure ModesPotential Causes of
FailurePotential Effects
of Failure AVG O AVG S AVG D AVG RPN
12 - Day N Treatment
Treatment delivered
Gantry or other LINAC
hardware (e.g. OBI) collides with patient
Carelessness Poor departmental
policy
Non-radiation-related physical
injury3.33 9.11 5.44 162.78
10 - Plan Preparation
Prepare e-chart
1. Incorrect Txinfo, 2. Wrong
Rx, 3. Wrong
patient/plan
Manual entry: Large error
Inadequate standard/ procedure / practice
Used incorrectly procedure/practice
Inadequate training/orientation
Very wrong dose Very wrong dose
distributionVery wrong
locationVery wrong
volume
5.44 8.89 5.56 272.89
11 - Day 1 Treatment
Gather patient
treatment information
3. Incorrect treatment data Hardware failure
Very wrong dose Very wrong
volume2.33 8.89 4.78 102.89
FMEA by Severity (S) (TG-100)
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 15
43
Process tree (map) I wouldn’t try to read it…will hurt your eyes
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
44
Process tree (map) I wouldn’t try to read it…will hurt your eyes
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
ICRP 112 definition of risk
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• Risk can be regarded as some function of the probability of an event’s occurring and the severity of the consequences for the patient should the event occur
Saiful Huq - Tools and techniques for process based safety 2012 AAPM annual meeting, July 29 - August 2
Recommendations of TG100
M. Saiful Huq - Recommendations of TG100 16
Top 6 RPN (TG-100)Major Sub-Processes Step Potential Failure Modes Potential Causes of Failure
1
Other pretreatment imaging for CTV localization
Images correctlyinterpreted (e.g.
windowing for FDG PET)
Incorrect interpretation of tumor or normal tissue
Inadequate training (user not familiar with modality
Lack of communication (inter-disciplinary)
2 RTP Anatomy
Delineate GTV/CTV (MD) and other structures for planning and optimization
Contouring errors: wrong organ, wrong site, wrong expansions
Lack of standardized procedures; Hardware failure (Defective materials/tools/equipment); Human failure(Inattention; failure to review work); Lack of staff
3 Day N treatment Treatment delivered
Linac hardware failure/wrong dose per MU; MLC leaf motion inaccurate; flatness/symmetry, energy – all the things that standard physical QA is meant to prevent
Poor hardware design; Inadequate maintenance; software failure; Lack of standardized procedures; Human failure; standard linac performance QM failure; Inadequate training
4Initial treatment planning directive (from MD)
Retreatment, previous treatment, brachy etc
Wrong summary of other treatments, Other treatments not documented
Lack of staff; Human failure (inattention; reconstructing previous treatment; wrong info obtained); information not available; Lack of communication
5 RTP anatomy
Delineate GTV/CTV (MD) and other structures for planning and optimization
Excessive delineation error resulting in ˂3σ segmentation errors
Lack of standardized procedures; Availability of defective materials/tools/equipment; Human failure (inattention; Failure to review work; etc); Inadequate training
6 RTP Anatomy PTV construction
Margin width protocol for PTV construction is inconsistent with actual distribution of patient setup errors
Lack of standardized procedures; Lack of communication; Inadequate training; Human failure (inattention; failure to review work; etc)
46