TG119 Test Suite for VMAT
The Duke Experience
The Delivery Systems for RapidArc
Fang-Fang Yin, Ryan McMahon, Jennifer O’Daniel, Jackie Wu
• Objectives
– Understand clinical feasibility of using TG119 test suite
for RapidArc commissioning and QA
Varian 21EX
120 Millennium MLC
Static and Rotational IMRT
Static gantry IMRT
RapidArc/VMAT
NovalisTx
120 HD MLC
Acceptance Testing and Commissioning
One of the important component for VMAT
acceptance testing and commissioning is to
perform an end-to-end test for the process of
VMAT, including simulation, planning, QA,
localization and delivery.
TG119 useful for evaluating planning, QA, and
delivery
Multiple apertures
At each angle
One aperture
At each angle
1
TG119 Test Suite and RapidArc:
Initial Observations and Experience
• All TG119 tests are compatible with RapidArc
delivery
– Planning constraints met in all test cases
– Phantom geometries for chamber and film measurements
pose no problem
– Measurements only done for composite dose
distributions
Currently, we are only evaluating the test suite using single arc
treatment plans with full 360o gantry rotations
Comparison of Planning Results
TG119 Test Suite for RapidArc
Treatment Planning
• Arc arrangements will depend on your clinic’s
preferences
• We used single arcs with full gantry rotations,
• Our intent is to re-evaluate if we want to start using multiple arc
plans and/or partial gantry rotations.
• All TG119 planning constraints achievable with single–
arc RapidArc plans
• Doing Static Gantry IMRT plans in parallel with RapidArc plans
gives you an initial understanding of the advantages or
disadvantages of each technique.
Comparison of Planning Results
Prostate
MultiTarget
6000
Duke IMRT NTx
Duke IMRT 21Ex
TG119 Results
Duke IMRT NTx
9000
Duke IMRT 21Ex
8000
Duke RapidArc NTx
Duke RapidArc 21Ex
Duke RapidArc NTx
7000
Duke RapidArc 21Ex
4000
6000
Dose (cGy)
D ose (cG y)
5000
TG119 Results
3000
2000
5000
4000
3000
1000
2000
0
CentralTarget CentralTarget
D99
D10
Superior
Target D99
Superior
Target D10
Inferior Target Inferior Target
D99
D10
1000
0
Prostate D95 Prostate D5
Rectum D30 Rectum D10
Bladder D30
Bladder D10
2
Comparison of Planning Results
Head & Neck
Comparison of Planning Results
TG119 Results
C-Shape Easy
Duke IMRT NTx
Duke IMRT 21Ex
6000
Duke IMRT 21Ex
6000
5000
4000
4000
Duke RapidArc 21Ex
3000
2000
2000
1000
1000
0
0
PTV D90
PTV D99
PTV D20
Cord Maximum
Parotid D50
Comparison of Planning Results
C-Shape Hard
Duke IMRT 21Ex
Duke RapidArc NTx
6000
PTV D95
PTV D10
Core D10
Acceptance Testing Sample
TG119 Results
Duke IMRT NTx
7000
Duke RapidArc 21Ex
• Test 2.1: Accuracy of dMLC position vs.
gantry position
– Tolerance: + 1 mm
• Test 2.2: Accuracy of dMLC position during
arc
5000
Dose (cGy)
Duke RapidArc NTx
5000
Dose (cGy)
Dose (cGy)
Duke RapidArc 21Ex
3000
TG119 Results
Duke IMRT NTx
Duke RapidArc NTx
4000
– Tolerance: + 1 mm
3000
• Test 2.3: Ability to accurately detect MLC
position error
2000
– Criteria: detect sub-millimeter error in position
1000
0
PTV D95
PTV D10
Core D10
3
Acceptance Testing Sample
Commissioning RapidArc Delivery
• Next perform several iterations of patient specific QA.
• Test 2.4: Accuracy of dose rate and gantry
speed control during RapidArc
– Tolerance: + 2%
• Our procedure was:
• Ion chamber measurement in rectangular phantom
• Three film planes in solid water
• Axial, sagittal, coronal through high dose (PTV)
• Test 2.5: Ability to control leaf speed/position
during RapidArc
– Tolerance: + 2%
• TG119 procedure is:
• Ion chamber measurements in rectangular phantom
• Two film planes in solid water
• Coronal plane through high dose (PTV)
• Coronal plane through low dose (organ-at-risk)
TG119 Test Suite for RapidArc
Ion Chamber Measurements
No modification required. Chamber measurements done with
Ion Chambe
r High Dose Re gion
same phantom/chamber
for fixed-beam
IMRT and RapidArc
TG119 IMRT vs. RapidArc:
Planar Dose measurements
Current TG119 results include a wide range of standard
IMRT QA tools for planar dose/fluence verification
4
TG119 Results
Error (% relative to prescription)
3
Duke IMRT NTx
Duke RapidArc NTx
2
Local Confidence Interval:
3.1% (IMRT),
5.2% (RapidArc)
1
0
-1
Diode/Chamber
Array
-2
-3
TG119 Confidence Interval 4.5%
-4
-5
Multi Target
Prostate
Head & Neck
C-Easy
C-Hard
Film
EPID
These can be used for initial RapidArc/VMAT
commissioning, but many clinics will have new
devices for rotational IMRT QA.
4
How to Incorporate New Rotational
QA Devices into the Test Suite?
Angular Dependence of Planar
Measurement Devices
• Response of planar measurement devices can have a
substantial angular dependence.
– Potentially large source of uncertainty, particularly for treatment
plans containing partial arcs
• Solutions:
– Fix QA device to gantry (e.g. EPID)
• Potential to miss gantry position errors
– Angular calibration/correction
Delta 4
• Not currently available for some commercial QA devices
Matrixx
Sun Nuclear
TG119 Test Suite for RapidArc
Multi-planar Measurements
Coronal Plane (Film)
TG119 Test Suite for RapidArc
Multi-planar Measurements
Sagittal Plane (Film)
5
Remaining Issues, Future Directions
• Evaluate test suite using plans with:
• Partial arcs
• Multiple arcs
• Design phantom geometries and planning conditions that
are more applicable to delivery with a rotating gantry
• Organize multi-institutional analysis of the test suite’s
application to RapidArc/VMAT
• Build upon initial TG119 results
• How to deal with large variations between commercially available
VMAT QA devices
6