acknowledgements rapidarc: clinical implementation · 1 rapidarc: clinical implementation fang-fang...
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1
RapidArc: Clinical
Implementation
Fang-Fang Yin, PhD
Q. Jackie Wu, PhD
Duke University Medical Center
Acknowledgements
• Team efforts from staff at Duke Radiation
Oncology, especially to Dr. J Chang, Dr. J
O’Daniel for providing slide information
• Technical and financial supports from Varian
Medical Systems
Clinical Implementation of VMAT
• Fundamentals for RapidArc
• Infrastructure/Installation
• Acceptance testing/commissioning
• Planning
• Delivery
• Quality assurance
• Fundamentals for RapidArc
Fundamentals for VMAT
• Intensity Modulated arc therapy (VMAT)
– An arc-based approach to IMRT
– To be delivered on a conventional linear
accelerator with a conventional MLC
– During an arc, the leaves of the MLC
move and dose rate changes
continuously as the gantry rotates
• RapidArc is one format of VMAT
2
The Principle of IMRT: Dose Painting
Beam ProfilePTV
OAR
Conventional 3-field RT Expected 3-field IMRT
PTV
OAR
Typical dose
distribution
Static and Rotational IMRT
One aperture
At each angle
VMAT
Multiple apertures
At each angle
Static gantry IMRT
One arc from 179o 181o
Count-clockwise
Rotational IMRTStatic Gantry IMRT
Field1 @180o
One of 7 fields
The Format of Cone-Beam IMRT Volumetric Rotational IMRT Options
• Existing Planning Systems• Eclipse (Varian) – Duke choice
• ERGO++/Monaco (Elekta)
• Pinnacle SmartArc (Philips)
• Prowess (Prowess)
• Existing Delivery Systems• RapidArc (Varian) – Duke choice
• VMAT (Elekta)
• Cone-beam Therapy (Siemens) (WIP)
• Existing QA Systems• Matrixx – Duke choice for routine QA
• Film – Duke choice for commission
• SunNuclear
• Delta 4 – Duke choice for future QA device
• Optical Scanner ……
3
Where Are We (Duke)?
• Started investigation in June 2008
– A research RapidArc planning station from Varian
• Clinical installation in October
– Acceptance testing, commissioning, QA programs
– Single arc, no couch rotation, partial arc
• First patient treatment
– December 2008
• New versions in August 2009 and May 2011
– Allow multiple arcs, couch rotation, partial blocking, etc.
Clinical Implementation of RapidArc
• Fundamentals for RapidArc
• Infrastructure/Installation
• Acceptance testing/commissioning
• Planning
• Delivery
• Quality assurance
• Infrastructure/Installation
Infrastructure/Installation
• Staff (dedicated and trained)
• Existing machines:
– 21EX machine with 120-leaf millennium MLC
– NovalisTx with 120-leaf HD MLC (SRS, SRT,SBRT)
• ARIA version 8.6 or above (v10 now)
• Eclipse planning station (hardware and software)
• QA equipment
Clinical Implementation of RapidArc
• Fundamentals for RapidArc
• Infrastructure/Installation
• Acceptance testing/commissioning
• Planning
• Delivery
• Quality assurance
• Acceptance testing/commissioning
4
Acceptance Testing
• Machine readiness
• Verification of installation against items included in the
purchase order
• Inspections of safety and quality of installation and
components
• VMAT performance
• Testing of functionality of each component and system
performance against specifications.
• End-to-end testing
• Dry-runs for a few test case from simulation to delivery
Acceptance Testing Sample
• Test 1.1: Gantry Angle Calibration
– Tolerance: + 0.5°
• Test 1.2: Isocenter Calibration
– Tolerance: + 1 mm
• Test 1.3: General Arc Dosimetry
– Range: 0.2 MU/° to 5.0 MU/°
– Tolerance: + 1%
Acceptance Testing Sample
• Test 1.4
• dMLC Dosimetry
• 0.5cm MLC slit sliding over 4 cm range
• Gantry:0°, 90°, 270°, 180°
• Tolerance: + 2% (over mean value)
Acceptance Testing Sample
• Test 2.1:
• Accuracy of dMLC position vs. gantry position
• Tolerance: + 1 mm
5
Acceptance Testing Sample
• Test 2.2:
• Accuracy of dMLC position during arc
• Tolerance: + 1 mm
Acceptance Testing Sample
2.1: Picket Fence vs. Gantry Angle (static)
Acceptance Testing Sample
2.1: Picket Fence vs. Gantry Angle (static)
Acceptance Testing Sample
6
Acceptance Testing Sample
• Test 2.3:
• Ability to accurately detect MLC position error
• Criteria: detect sub-millimeter error in position
Acceptance Testing Sample
2.3: Picket Fence with Errors
• Test 2.4:
• Accuracy of dose rate and gantry speed control during RapidArc
• Tolerance: + 2%
Acceptance Testing Sample
• Test 2.5:
• Ability to control leaf speed/position during RapidArc
• Tolerance: + 2%
Acceptance Testing Sample
7
Acceptance Testing Sample
-200 -150 -100 -50 0 50 100 150 2001.00
1.02
1.04
1.06
1.08
1.10
1.12
1.14
1.16
1.18
1.20
Off x-axis Position (mm)
Rela
tive
Do
se
Off y-axis : -100 mmOff y-axis : 0 mmOff y-axis : 100 mm
Gantry speed
vs.
Dose rate
(Tolerance 2%)
Acceptance Testing Sample
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
Perc
en
t D
evia
tio
n (
%)
-60 -40 -20 0 20 40 60
Off X-axis Position (mm)
Off y-axis: -100 mmOff y-axis: 0 mmOff y-axis: 100 mm
Variation of gantry speed and dose
rate (tolerance 2%)
Commissioning
• Validate that VMAT is capable of delivering
radiation beams as good as SG-IMRT could
• Define the limitations of planning optimization,
gantry rotation, beam blocking, couch rotation,
and leaf speed, collimator settings
• Develop treatment process and
documentation
Workflow for RapidArc Treatment
Planning/prescription
Treatment/validation
Quality assurance
Target localization
Immobilization/simulation
Case selection
8
Clinical Implementation of RapidArc
• Fundamentals for RapidArc
• Infrastructure/Installation
• Acceptance testing/commissioning
• Planning
• Delivery
• Quality assurance
• Planning
Planning - Process
SG-IMRT RapidArc
Planning - Preparation
• Site-specific, for each site
– 10 cases from previous IMRT
– Develop RapidArc plan with different options
– Comparison between IMRT vs. RapidArc
• Constraint/optimization
– Optimization algorithm
– Constraints sensitivity
Planning - Strategy
• Selected site-specific planning strategy
– 1 arc: prostate only, prostate bed, prostate+SV,
brain lesions
– 2 arcs: prostate+SV+LN, spinal, brain lesions
– Multiple arcs: Head and neck, brain lesions, anal-
rectal
– Partial arcs: partial breast, liver, …
9
Planning - Optimization
• Key challenge
– interconnectivity of the beam shapes within consecutive
VMAT gantry positions
• Constraints
– Target and normal structures
– Mechanicals
• Optimization algorithms
– More parameters
– Aperture based objectives and algorithms
Planning – Quality and Efficiency
• MLC segments
– Number of segments: IMRT RapidArc
– Plan quality is comparable if same segments
– More segments: slow gantry rotation for RapidArc
– More segments: long treatment time
• Planner experience
– Understand algorithm
– Understand limitations
Planning - Logistics
• Training – multiple people involved in the
planning
• Gaining experience
• Develop planning protocols
• Last ~ 3 months before patients start
Clinical Implementation of RapidArc
• Fundamentals for RapidArc
• Infrastructure/Installation
• Acceptance testing/commissioning
• Planning
• Delivery
• Quality assurance
• Delivery
10
Delivery - Tolerances
• MLC leaf motion
• Leaf motion limit: 2.5 cm/s, 5 mm/degree
• Dose rate and gantry rotation speed
• One arc = one field
• MU, doserate, gantry speed linked
• Larger MU max doserate varying gantry speed
• Smaller MU max gantry speed varying doserate
• Middle varying gantry speed and doserate
Delivery – Sample Parameters
RapidArc Delivery Limits
• Variable gantry speed
– 0.5 – 5.6 degree/sec
• Variable dose rate
– 0 – 600 MU/min (0 -1000 Novalis Tx)
• Variable dose per degree
– 0.2 – 20 MU/degree
• Variable MLC speed
– 0 –2.5 cm/s
Delivery - Efficiency
• Plan quality
• The quality of plan number of apertures
• Single arc – 177 apertures
• Complexity structures:
• more apertures/arcs
• multiple arcs
• Delivery time
• Single arc – less time (< 2 mins) but sometimes
inferior quality
• Multiple arcs – better quality but longer time
11
Delivery – Treatment Time
• Treatment time = Patient set-up time + Delivery time
• Delivery time=beam-on time+between beam=on time
• Patient setup time: no reduction
• Beam-on time: 20-60% reduction (less MUs)
• Between beam-on time:
• 100% saving for single arc
• 20-60% saving for multiple arcs
Delivery – Partial Arc
• Mechanical collision
• If isocenter is close to
center
• full arc
• If isocenter is close to
peripheral
• partial arc
• Partial blocking is
also available
Partial RapidArc for Liver SBRT
RapidArc MU = 714
IMRT Total MU = 1572
Time: 1.3 min
Multiple Arcs vs. Single Arc
Single arc
Multiple arcs
12
VMAT For Large Size PTV
• Large field size -> sometimes IMRT beam has triple
beam splits
• Multi-sections (parts) of the PTV, large variation of
PTV shape, OARs and their constraints
• Beam orientation selection is part of IMRT planning,
is often not used for RapidArc (i.e. full arc)
VMAT For Large PTV
17cm Field Size << PTV in some
directions
3 Arcs, 1000 degree rotation
VMAT For Large Size PTV
IMRT VMAT17cm
VMAT For Large PTV
IMRT VMAT17cm
13
VMAT For Large PTV
IMRT VMAT17cm
VMAT For Large PTV
VMAT26CM VMAT 17cm
VMAT For Large PTV
VMAT17cm VMAT23cm
Field Size Effect On VMAT
Planning Quality
100
110
120
130
140
150
160
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0
D1%
(%
)
Projected Field Size X (cm)
PTV Hot Spot (D1%)
Collimator 30
Collimator 45
14
VMAT For Head-and-Neck
Field Thru
Shoulder Field Thru
Shoulder
VMAT For Head-and-Neck
VMATVMAT IMRT
VMAT For Head-and-Neck
VMAT IMRT
RapidArc For Head-and-Neck
PharynxLt Parotid
Rt Parotid
Oral CavityCord
15
VMAT For Head-and-Neck
Segments Thru Shoulder
Clinical Implementation of RapidArc
• Fundamentals for RapidArc
• Infrastructure/Installation
• Acceptance testing/commissioning
• Planning
• Delivery
• Quality assurance• Quality assurance
Quality Assurance
• The QA program for the VMAT is similar to SG-IMRT
in principle but with different measurement
approaches due to its dynamic nature that, during
VMAT delivery,
– MLC leaves are moving
– Gantry is rotating
– Dose rate is changing
Quality Assurance
• The QA program: validate the functionality
and performance of accepted features
• For each planned delivery
– Patient specific QA
– Machine specific QA
16
Quality Assurance
• Machine specific QA
– accuracy of the MLC leaf positions during VMAT
delivery
– ability of the system to accurately vary the dose
rate and gantry speed during VMAT delivery
– ability of the system to accurately vary the MLC
leaf speed during VMAT delivery
• Tolerances: Acceptance baselines
Machine QA Chart
• Daily– Standard linac QA
– Standard MLC QA
– Rotational delivery of dose to an ion chamber phantom
• Monthly– Leaf motion
– Gantry rotation
– Dose output
• leaf motion
• gantry motion
• dose rate changes
Patient Specific QA
• Hybrid QA technique
– Plan to phantom
– Dose measurement to phantom
• Rotational nature
– Not to single plan
• Phantoms
• Instruments
– Ion chamber
– 2-D array (ion chamber, diodes, film, …)
Patient Specific QA
• Data analysis
– Multiple planes (axial, coronal, sagittal)
– Profiles
– Points
– Gamma analysis
• Collision check
– Before patient on the couch
– When patient on the couch
17
RapidArc QA vs. IMRT QA
• More complex treatment delivery
– Varying gantry angle, gantry speed, dose rate, and
MLC leaf motion
• ImSure does not calculate dose for RapidArc
delivery
• Current IMRT technique: Portal dosimetry
• RapidArc technique: Ion chamber, film, and
Matrixx
QA Measurements
• Ion chamber– Absolute dose: (meas – calc) / calc < 3%
• Film (coronal, sagittal, and axial planes)– Optional
• Matrixx (coronal and sagittal planes)
• 3-6 hrs/patient
“Gold Standard” QA Tools
Ion ChamberFilm
Ion Chamber
• Equipment
– 0.13cc or 0.01cc ion
chamber
• Calibration
– 10x10cm2, 100SSD, depth
= dmax, 200MU
– cGy/nC correction factor
• RA delivery
– Center of 30cm x 30cm x
20cm solid water
phantom
– Compare to Eclipse
calculation
• 39 VMAT plans
18
Film
• Equipment
– Kodak EDR2 film
– OmniPro ImRT
• Calibration
– 12 2cm x 2cm squares
– 0 – 300cGy
• RA delivery
– MultiCube (IBA dosimetry)
– Coronal, sagittal, and axial planes
– Compare to Eclipse calculation
– Gamma analysis
• 8 MAT plans
Verification with “Gold Standard” QA
• Ion chamber:
– Median: +1.7%
– Range: -0.9% - 2.8%
• Film
– 24/24 > 93% passing rate
– 23/24 > 95% passing rate
– 20/24 > 97% passing rate
Ion chamber array vs. Eclipse
3%, 3mm DTA, 5% threshold
Ion Chamber vs. Eclipse Result: Axial Film vs. Eclipse
Film
Eclipse
19
Film vs. Eclipse
60
65
70
75
80
85
90
95
100
1 2 3 4 5 6 7 8
Plan #
% P
ixels
Pass
ing
Ga
mm
a (
<1
)
Coronal
Sagittal
Axial
14 15 23 24 32
3%, 3mm DTA, 5% threshold
Film vs. Eclipse
3%, 3mm, axial thresholds up to 40%
Film vs. Eclipse
60
65
70
75
80
85
90
95
100
1 2 3 4 5 6 7 8
Plan #
% P
ixels
Pass
ing
Ga
mm
a (
<1
)
Coronal
Sagittal
Axial
14 15 23 24 32
3%, 3mm DTA, 5% threshold Sagittal and Coronal, 40% threshold Axial
Film vs. Eclipse
Validation of 2D Ion Chamber Array
• MatriXX Evolution (IBA Dosimetry)
• 1020 ionization chambers– 0.07 cm3 sensitive volume
– 0.4cm diameter
• 24 x 24 cm2 grid
• 7.6mm spacing
• Automatic temperature-pressure correction
Herzen et al., PMB 2007; 52: 1197-1208
Angular Dependency:
-1.7% 15x
-1.8% 15x
+2.0% 15x
+2.2% 15x
+3.2% 15x-2.0% 6x
-3.5% 6x
+2.8% 6x
+3.0% 6x
+3.7% 6x
Fro
nt
Back
Measured/Calculated (%)
Future solution from IBA:
Gantry angle sensor
Apply correction
factor to each ion
chamber based on
angularity
20
Matrixx QAMatrixx vs Eclipse
88
90
92
94
96
98
100
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34
RapidArc (Plan #)
%P
ixels
Passin
g (
Gam
ma <
= 1
)
MatrixxCoronal
MatrixxSagittal
Results Patient Specific QA
3%, 3mm, axial thresholds up to 5%
Fig. 1: Ion Chamber vs. Eclipse and Matrixx vs. Eclipse
-6%
-4%
-2%
0%
2%
4%
6%
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Plan #
%D
iffe
ren
ce f
rom
Ecl
ipse
Ca
lcu
latio
n
IC
IC Array
BrainProstate
BedProstate
Prostate
+ SV Spine
Ion Chamber vs. Eclipse & ICA vs. Eclipse Film vs. Ion Chamber Array
88
90
92
94
96
98
100
0 1 2 3 4 5 6 7 8 9
Plan #
%P
ixe
ls P
ass
ing
Ga
mm
a (
<1
)
Coronal
Sagittal Gamma = 3%, 3mm, 5% threshold
Film vs. Ion Chamber Array
1 2 3 14 15 23 24 32
21
Effective vs. Efficient
• Stage 1: Intensive QA
– Ion chamber, film in 3 planes, ion chamber array in
2 planes, 3D polymer gel dosimetry
• Stage 2: Rigorous QA
– Ion chamber, ion chamber array in 2 planes
• Stage 3: Effective and Efficient QA
– Ion chamber, ion chamber array in 1 plane
– Ion chamber array only
Preparation Delivery Analysis
Ion chamber – 1st 15 15 5
Film – 1st 15 20 20
Ion chamber array – 1st 15 15 5
Ion chamber – additional 15 7 5
Film – additional 15 10 10
Ion chamber array –
additional
15 7 5
IC + 3 Film + 2 ICA 90 77 55
IC + 2 ICA 45 37 15
IC + ICA 30 30 10
Effective vs. Efficient
• When implementing a new technology
– Perform intensive patient-specific QA for the first
group of patients
– Rely on QA “gold standards”
– 3D QA very useful
– Use “gold standard” QA technology to transition to
newer QA devices
• Goal: Effective QA
Effective vs. Efficient Conclusion
• RapidArc is one format of rotational IMRT for dose
painting
• Implementation of RapidArc requires careful
planning, testing, and verifications.
• Thoroughly testing and commissioning are
necessary prior to patient treatment
• QA is a critical step, always compare with static field
IMRT plan in the early phase
• RapidArc should be judged by its
accuracy, safety, efficiency, applicability, integration
, and adaptation