s davidson 1 , r popple 2 , g ibbott 1 , d followill 1
DESCRIPTION
A Comprehensive Study on the Heterogeneity Dose Calculation Accuracy in IMRT using an Anthropomorphic Thorax Phantom. S Davidson 1 , R Popple 2 , G Ibbott 1 , D Followill 1 1 The University of Texas M. D. Anderson Cancer Center, Houston, TX 2 University of Alabama Birmingham, Birmingham, AL. - PowerPoint PPT PresentationTRANSCRIPT
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A Comprehensive Study on the Heterogeneity Dose Calculation Accuracy in IMRT using an Anthropomorphic Thorax Phantom
S Davidson1, R Popple2, G Ibbott1, D Followill1
1The University of Texas M. D. Anderson Cancer Center,
Houston, TX2University of Alabama Birmingham, Birmingham, AL
2
Purpose
• Survey the accuracy of several commercial dose calculations
• Check the consistency of superposition-convolution implementations
• Baseline: RPC anthropomorphic thorax phantom
3
Methods & Materials
• IMRT Treatment Planning Systems (TPS)• Superposition-Convolution
• Pinnacle• Eclipse AAA• TomoTherapy
• Pencil-beam w/ effective pathlength correction• Corvus• Eclipse
4
Methods & Materials
TPS Beams MLC
Pinnacle • 5 beams• 4 coplanar beams
(35°, 90°, 150°, 190°)• 1 non-coplanar beam
(90° couch kick, 30° gantry angle)
Static
Corvus Static
Eclipse, AAA Dynamic
Eclipse, pencil-beam
Dynamic
TomoTherapy Helical; pitch 0.3, field-width 2.5cm
5
Methods & Materials
Corvus TPS
Corvus delivery:MLC & MU
Corvus calculation
Pinnacle re-calculation
Eclipse TPS
Eclipse delivery:MLC & MU
Eclipse PB
Eclipse AAA
6
Methods & Materials• Radiological Physics Center (RPC)
Anthropomorphic Thoracic Phantom• CIRS Lung insert (cylinder) with embedded tumor
• Fitted for TLD (tumor, heart, cord) and Radiochromic Film (tumor/lung)
S
LL
A
Dimensions (cm): 40W x 30H x 30DDisassembled Lung Insert
FilmSlits
Tumor (TLD)
Lung
Tumor(TLD)
Heart
Cord
Lung
LR
7
Methods & Materials
• TLD • Corrected for daily output
• Radiochromic Film • TLD normalization
• All plans repeated 3 times
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Dose Calculation
Delivery MLC & MU
IMRT QA IC correction
factor (calc-to-meas)
Pinnacle Pinnacle 1.027
Corvus 1.055
Pinnacle 1.043
Eclipse, PB 1.007
Eclipse, AAA 0.993
TomoTherapy TomoTherapy 1.016
Eclipse
Corvus
• IMRT QA: IC in water phantom
• Corvus beyond 5% in IMRT QA
Results & Discussion
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• Tumor Point Dose Comparison (corrected)
• All calculations corrected in response to IMRT QA
Dose Calculation
Delivery MLC & MU
corrected ratio of
calc/meas
Pinnacle Pinnacle 0.992
Corvus 1.050
Pinnacle 1.009
Eclipse, PB 1.049
Eclipse, AAA 1.036
TomoTherapy TomoTherapy 1.025
Corvus
Eclipse
Results & Discussion
10
Results & Discussion• Dose Profiles, Pinnacle
Pinnacle Calculation and Delivery Medial-Left Lateral Profile
0
500
1000
1500
2000
2500
-40 -20 0 20 40 60 80
Distance (mm)
Abs
olut
e D
ose
(cG
y)
Film Avg
Pinnacle
-5% or 3mm
+5% or 3mm
GTV
PTV
11
Corvus Calculation and Delivery Medial to Left Lateral Profile
0
500
1000
1500
2000
2500
-40 -20 0 20 40 60 80Distance (mm)
Ab
solu
te D
ose
(cG
y)
Film Avg
Corvus
-5% or 3mm
+5% or 3mm
GTV
PTV
Results & Discussion• Dose Profiles, Corvus
12
Pinnacle Calculation with Corvus MLC files Medial to Left Lateral Profile
0
500
1000
1500
2000
2500
-40 -20 0 20 40 60 80
Distance (mm)
Abs
olut
e D
ose
(cG
y)
Film Avg
Pinnacle-Corvus(MLC)
-5% or 3mm
+5% or 3mm
GTV
PTV
Results & Discussion• Dose Profiles, Pinn. Re-calc/Corvus Beams
13
Eclipse-AAA Calculation and Delivery Medial-Left Lateral Profile
0
100
200
300
400
500
600
700
800
-40 -20 0 20 40 60 80
Distance (mm)
Ab
solu
te D
ose
(cG
y)
Film Avg
Helios-AAA
-5% or 3mm
+5% or 3mm
GTV
PTV
Results & Discussion• Dose Profiles, Eclipse AAA
14
Eclipse PB Calculation and Delivery Medial-Left Lateral Profile
0
100
200
300
400
500
600
700
800
-40 -20 0 20 40 60 80
Distance (mm)
Dos
e (c
Gy)
Film Avg
Eclipse PB
+5% or 3mm
-5% or 3mm
GTV
PTV
Results & Discussion• Dose Profiles, Eclipse pencil-beam
15
TOMO Calculation and Delivery Medial-Left Lateral Profile
0
100
200
300
400
500
600
700
-40 -20 0 20 40 60 80
Distance (mm)
Abs
olut
e D
ose
(cG
y)
Film Avg
TOMO
-5% or 3mm
+5% or 3mm
GTV
PTV
Results & Discussion• Dose Profiles, TomoTherapy
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Results & Discussion• Binary Agreement Maps:
GTV
GTV GTVGTVGTV
Pinnacle Corvus Pinnacle calc/Corvus
Color Code
not testedFails all criteria
±7%/7mm±5%/3mmTest Criteria
Color Code
not testedFails all criteria
±7%/7mm±5%/3mmTest Criteria
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Results & Discussion• Binary Agreement Maps:
GTV
GTV GTVGTVGTV
Color Code
not tested
Fails all criteria
±7%/7mm±5%/3mmTest Criteria
Eclipse AAA Eclipse PB TomoTherapy
GTV
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Percentage of pixels passing criteria
79
99
66
96100100
85
50
9097
61
96
0
20
40
60
80
100
Pin
nacl
e, S
C
Cor
vus,
PB
Pin
nacl
e(C
orvu
sde
liver
y)
Ecl
ipse
AA
A,
SC
Ecl
ipse
, PB
Tom
oThe
rapy
,S
C
±7%/7mm
±5%/3mm
Results & Discussion• Binary Agreement Maps: Summary
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Conclusions
• The accuracy of dose calculations from several common IMRT TPSs was evaluated. • Superposition convolution based- algorithms met
the ±5%/3 mm criteria• Pencil-beam with an effective pathlength
correction did not meet the criteria
• Pinnacle, Eclipse AAA, and TomoTherapy apply superposition convolution accurately.
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References1 S. Davidson, K. Prado, G. Ibbott, and D. Followill, "SU-FF-T-255:
Hetergeneity Dose Calculation Accuracy in IMRT Using An Anthropomorphic Thorax Phantom," Medical Physics 33 (6), 2106 (2006).
2 N. Papanikolaou, J. J. Battista, A. L. Boyer, C. Kappas, E. E. Klein, T. R. Mackie, M. Sharpe, and J. Van Dyk, "Tissue Inhomogeneity Corrections for Megavoltage Photon Beams," AAPM Task Group #65 Radiation Therapy Commitee (2004).