Philosophy and Theory · Cause-and-Effect Diagram Responsibility of physicist Responsibility of...
Transcript of Philosophy and Theory · Cause-and-Effect Diagram Responsibility of physicist Responsibility of...
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Error Analysis & Reduction Error Analysis & Reduction Philosophy and TheoryPhilosophy and Theory
Todd Pawlicki, Ph.D.Department of Radiation OncologyStanford University School of Medicine
48th Annual Meeting of the AAPMOrlando Florida: July 30 – August 3, 2006
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Outline
• Error reduction and quality control
• The ‘system view’ and variation
• Tools for error reduction
• Summary and future directions
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Definition of Medical Errors• The failure of a planned action to be
completed as intended or the use of a wrong plan to achieve an aim
• A factor contributing to errors is the fragmented nature of the health care delivery system – or ‘nonsystem’
To Err Is Human: Building a Safer Health System. 1999: NationalAcademies Press (www.nap.edu/catalog/9728.html).
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Definition of Quality• The quality of a product or service is the
loss that product or service causes to the patient after it is used for treatment
• What is the meaning of loss?– Loss caused by variability of function– Loss caused by harmful side effects
• Quality can not be viewed as a value
G Taguchi. Introduction to Quality Engineering: Designing Quality into Products and Processes. 1986: Asian Productivity Organization.
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Error Reduction and Quality
• Both are concerned with reducing the two types of losses that may be caused to the patient after treatment– Variability of function– Harmful side effects
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Health Care Progress• During the past half-century, progress in
health care has been made by medical science and technology breakthroughs
• The quality revolution taking place in medicine will provide new remarkable opportunities to improve health care
B Sadler. To the Class of 2005: Will you be ready for the quality revolution? J on Quality and Patient Safety. 2006;32(1):51-55.
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Taguchi Loss Function (TLF)
f(x)
TX
L(x)[ ( )] ( ) ( )
all x
E L x L x f x dx= ∫Average loss per unit of production
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TLF Applied to RadiotherapyF = 1 − [TCP·(1−NTCP)]
0.0
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40.0 50.0 60.0 70.0 80.0
Dose (Gy)
0.00
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0.20RT Failure Function (F)Quality Distribution
Expected Failures E<F>
Figure 2
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TLF Applied to Radiotherapy
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-6.0% -4.0% -2.0% 0.0% 2.0% 4.0% 6.0% 8.0%
Per cent deviation from prescription dose
Expe
cted
radi
othe
rapy
failu
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0.5Gy SD1.0Gy SD2.0Gy SD3.0Gy SD4.0Gy SD
Figure 3
0.5 σ
4.0 σ
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Summary Thus Far
• Error reduction and quality control are intimately related
• Improving quality will reduce errors
• Improving quality may increase survival and decrease complications
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The System View and Variation• Appreciation of a system
• A network of interdependent components that work together to try to accomplish the aim of the system
• Knowledge of variation– Every system (or process) displays variation– Variation can be predictable or unpredictable
E Deming. The New Economics. 1993: MIT, Center for Advanced Engineering Study.
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E Deming. The New Economics. 1993: MIT, Center for Advanced Engineering Study.
ASSESSMENT
PRESCRIPTION
TREATMENT PLANNING
TREATMENT DELIVERY
FOLLOW-UPPatient Treatment Viewed As A System
Oncologists Radiologist Pathologists
Oncologist
Suppliers of information
Research Randomize trials
MD Peer Review
Physics QA
Dosimetrist
Therapists
Nurse
Oncologists Radiologist Pathologists
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System View• Every system or process creates data
• Every data set contains noise– To detect a signal, first filter out the noise
• Data do not have meaning apart from their context– The order in any sequence of observed
results helps physical interpretation
D Wheeler. Understanding Variation: The Key to Managing Chaos. 1993: SPC Press.
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Knowledge of Variation
• It is easy to appreciate variation in your personal life – What about variation in the workplace?
• Failing to appreciate variation in processes can lead to obvious and not so obvious problems
Carey and Lloyd. Measuring Quality Improvement in Healthcare. 2001: ASQ Quality Press Publications.
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Without an Understanding of Variation…
• Difficult to understand past performance– No ability to predict the future and make
improvements in a process
• Blame or give credit to others for things over which they have little control
• You see trends where none exist
Carey and Lloyd. Measuring Quality Improvement in Healthcare. 2001: ASQ Quality Press Publications.
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Importance of Time-Ordered Data
Chamber Readings - Random Ordered
1.930
1.935
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1.945
1.950
0 5 10 15 20 25 30
Reading number
Cha
mbe
r re
adin
g
Chamber Readings - Time Ordered
1.930
1.935
1.940
1.945
1.950
0 5 10 15 20 25 30
Reading number
Cham
ber r
eadi
ng
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Generic vs Critical ProcessesGeneric
Design
Statistical evaluation
Deployment
Design Improvement
Single-case boring
Design Improvement
Design
FTA
Deployment
Mistake-Proofing
PDPC
FMEA/EMEA
Critical
D Hutchison. Chaos Theory, Complexity Theory, and Health Care Quality Management. Quality Progress. 1994:69-72. Figure 1.
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Tools For QC & Error Reduction
• Project planning and implementation (2)
• Data collection and analysis (7)
• Management and planning tools (7)
• Idea Creation (4)• Cause analysis (3)• Evaluation and
decision-making (2)• Process analysis (3)
http://www.asq.org/learn-about-quality/quality-tools.html (accessed April 21, 2006)
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Idea Creation
• Nominal group technique– Structured brainstorming session that
encourages contributions from everyone
• Affinity diagram– Organize a large number of ideas into their
natural relationship
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Nominal Group Technique• When to use
– Ideas are coming slowly– Some members are more vocal than others
• General method– 10 minutes of individual idea generation– Each person states one idea aloud per round– Facilitator records each idea on a flipchart– After all ideas are out – then discuss each– Prioritize the ideas using multi-voting
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Affinity Diagram• When to use
– Many facts or ideas that seem unrelated– Issues seem too complex
• General method– Generate ideas – one per notecard– Spread all notecards on large surface– Group the notecards that are related– Discuss patterns of groups – changes are ok– Choose a title that captures each group
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Cause Analysis• Cause-and-effect (fishbone) diagram
– Identifies many possible causes for an effect or problem
• Pareto chart– Visual depiction of most significant
components or situations• Root cause analysis
– Study of the original reason for nonconformance with a process
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Cause-and-Effect Diagram• When to use
– To identify possible causes of a problem– Team thinking is in a rut
• General method– Describe the problem– List categories for causes of the problem– List possible causes of the problem– Continue to ask, “Why does this happen?” to
uncover sub-causes
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Cause-and-Effect DiagramResponsibility of physicist Responsibility of dosimetrist
Patient’s CT for planning is complete
Responsibility of physician
Treatment plan not
ready on time
Contours not drawn
No M
R s
can
Rx not communicatedDosi not notified
Plan not approvedNo
goo
d pl
ans
Rx c
hang
e
New patient info
QA not done Post-approval work not done
Plan not finishedFusion not done O
verworked
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Pareto Chart• When to use
– To analyze the frequency of problems– To focus on the most significant problems
• General method– Decide on categories, measurements, and
period of time– Subtotal the measurements for each
category– Plot as a bar graph from largest to smallest
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Pareto Chart
0.00
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Contou
rs no
t don
e
Plan no
t revie
wed
Wait
ing fo
r othe
r info
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nge
QA not d
one
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eptab
le pla
nsOthe
r
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Root Cause Analysis (RCA)• When to use
– To identify what, how and why something has happened to prevent recurrence
• General method– Data collection– Causal factor charting– Root cause identification– Recommendation and implementation
Rooney and Vanden Heuvel. Root Cause Analysis for Beginners. Quality Progress. 2004:45-53.
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Evaluation and Decision Making• Decision matrix
– Evaluates and prioritizes a list of options– Uses pre-determined weighted criteria
• Multi-voting– Narrows a large list of possibilities to a final
selection– Allows an item that is favored by all, but
not the top choice of any, to be selected
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Decision Matrix• When to use
– A list of options must be narrowed to one– The decision is made on the basis of several
criteria• General method
– Determine the evaluation criteria– Assign a relative weight to each criterion– Create a matrix that give a final highest
weight to one criterion
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Decision MatrixPossible Treatment Plans
Criteria Weight 3DCRT IMRT 1 IMRT 2
Rating Score Rating Score Rating Score
Target Coverage 8 9 72 10 80 8 64
Target Homogen 2 9 18 5 10 7 14
NT Sparing 7 1 7 9 63 9 63
Tx Time 5 9 45 4 20 5 25
Error Free 3 7 21 9 27 9 27
Decision 163 200 193
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Process Analysis• FMEA
– Systematic method of analyzing and ranking the risks associated with various modes of failure
• Mistake-proofing– A method that either makes it impossible
for an error to occur or makes the error immediately obvious once it occurs
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Failure Modes & Effects AnalysisFMEA – TG100
• When to use– When a process or equipment is being
applied in a new way– When a process or equipment is being
designed or redesigned– When analyzing failures of an existing
process or use of equipment• General method
– Please visit Medical Errors II– Wednesday, August 2. Rm 230A, 10-Noon.
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Mistake-Proofing• When to use
– At a hand-off step in a process– When the consequences of an error are
dangerous• General method
– Create flowchart of the process– Find source of each potential error– Elimination, Replacement, or Facilitation– Test it, then implement it (inspection)
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Data Collection and Analysis• Statistical Process Control (SPC)
– Monitor and control variation in a process or product over time
– Strikes a balance between two types of mistakes we can make in quality control
• Looking for problems when they do not exist• Not looking for problems when the do
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Process Control• A definition of control
– A process will be said to be predictable when, through the use of past experience, we can describe, at least within limits, how the process will behave in the future.
• SPC is concerned with practical methods to satisfy this definition
W.A. Shewhart. Economic Control of Quality of Manufactured Product. 1931:ASQ Quality Press Publications.
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Process Control• Every measurable phenomenon or
process displays variation
• There are 2 types of causes of variation– Exceptional variation
• Assignable cause(s) exist and once removed will reduce variation
– Routine variation• No readily assignable cause(s) exist
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Process Control• Process behavior charts
– Use a sequence of data for predictions of what will occur in the future
– Subgroups from a time-ordered stream of data are used to describe process behavior
• A process is predictable when it is in a state of statistical control
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Process Behavior Charts
X
2
3 RXd n
+One chart for the subgroup mean
Ave
rage
2
3 RXd n
−
Sample number or Time
Ran
ge
R
3
2
1 3 d Rd
⎛ ⎞+⎜ ⎟
⎝ ⎠
3
2
1 3 d Rd
⎛ ⎞−⎜ ⎟
⎝ ⎠
One chart for the subgroup range
Sample number or Time
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Project Planning/Implementation
• Models to carry out change and continued improvement– Plan-do-study-act (PDSA)– Define, Measure, Analyze, Improve and
Control (DMAIC)
• Design for Six-sigma (DFSS)– Answers the question, “How much risk is in
my design?”
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PDSA• Plan – Do – Study – Act • Shewhart cycle for learning and improvement
A
S D
P
Plan a change aimed at improvement
Adopt the change or abandon it
Study the results
What did we learn? What went wrong?
Carry out the change
E Deming. The New Economics. 1993: MIT, Center for Advanced Engineering Study. Figure 13.
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DMAIC• Define – Measure – Analyze – Improve – Control • Data-driven strategy for improving processes
DefineWhat problem to solve?
MeasureWhat is the process capability?
AnalyzeWhen & where do defects occur?
ImproveGo after root causes.
ControlControl process to sustain gains.
Redesign
Optimization
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Design for Six-Sigma (DFSS)• A process of predicting response
variation– Calculate variance due to specific noise
• Can answer the question; How much risk is in my design?
• Methods include – Deterministic– Stochastic
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Philosophy Paradigms• Six-Sigma
– Disciplined methodology of improving products and processes
• Lean– Processes are continually evaluated for waste
• Total Quality Management (TQM), Business Process Reengineering (BPR), etc…
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What Have We Omitted
Gage R&R
Fault Tree AnalysisCp
Cp,k
Scatter DiagramCheck Sheet
Stratification
BrainstormingRelations Diagram
Tree Diagram
Matrix DiagramArrow Diagram
PDPC Hypothesis Testing
HistogramsSurvey
Benchmarking
Gnatt Chart
Situational Awareness
DCOVList Reduction
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Summary
• Quality/error reduction innovations may not seem technologically significant but are extremely important for our patients
• Increased efforts should be aimed at reducing errors and chronic sources of defects from clinical processes
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Summary• Our best efforts are not good enough
– We can’t do everything we think of– We have to assess risk and choose our
focus carefully (TG100!)• Quantitative quality control techniques
require training and practice• Leadership must make quality a priority
(AAPM / ASTRO)
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Proposals for AAPM• Physicists should champion error
reduction and quality control
• Future AAPM meetings should have a specific research session for error/cost reduction and quality control
• Create a working group/task group charged to understand and describe the vast amount of quality techniques
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Some Further Reading• W.E. Deming. On Probability as a Basis for Action. The American
Statistician, 29(4):146-52, 1975.• Six part series on Quality of Health Care. The New England Journal of
Medicine, 335(12-17), 1996.• S.J. Goetsch. Risk Analysis of Leksell Gamma Knife Model C with
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