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3D IMRT Dosimetry
Stephen Gajdos, MSJeremy Donaghue, MS
Conflict of Interest
• None
Outline
• Intro to Compass
• Validation tests
• Clinical examples
Compass
• 3-D Patient QA analysis package
• Quasi-TPS with dose engine (CC S/C)
• Treatment verification as well as patient dose analysis
• Uses patient’s CT dataset
• Can compare DVH and ROI dose statistics
Compass
• Fluence computation is possible from TPS plan + beam model– DICOM RT import
• Compass performs independent dose calc
• Also can use corrected measured response from MatriXX
Compass
Compass
Compass
• Recent publications show 2-D methods might not show impact of delivery errors
• Also relevance of information
• Language that Radoncdosimetric team can understand
Compass
IMRT QA• Per patient (composite or field normal)
• Nelms et al., 2011:– TPS ability to calculate dose accurately
– Delivery system’s ability to deliver dose accurately
• TG-119 IMRT Commissioning (2009)– RPC in 2008: 28% failed to meet accuracy
criteria for H&N phantom
– Quantify overall performance of IMRT system
IMRT QA• Nelms et al., 2011
– Can accepted methods (2D)/performance metrics (3%/3mm) predict clinically relevant patient dose errors?
– Can abiding by these standards mitigate risk?
– Magnitude and location of errors matter more than quantity of errors
– Weak to moderate correlation between performance metrics and clinically relevant dose differences
IMRT QA• Takes a lot of time/effort
• Analysis based on phantom geometry
• Complacency
• Are we really detecting significant errors?– Less than 5% incidents detected
– NY misadministration
– Failed delivery due to machine limitations• Varian or Elekta
– Initial physics check
Validation
• Elekta Syn-S– 6 MV– FS 21 X 16 cm2
– Secondary collimator is fixed
– Leaf width: 4mm• TG-119 test cases
– APPA; Bands (APPA)– Cylinders– Prostate– H and N– C-shape
Validation
• Accepted in 9/2011
• Data accrual start in 12/2011
• AP, FS 16 cm2, 100 MU
• TG-119 9/2012
• MatriXX scanned with buildup.
• ROI
Validation TG-119
Validation
Validation
TPS Computed Diff Indirect 2σ Diff TPS Computed Diff Indirect 2σ Diff Computed Indirect 2σTotal Dose
32.72 32.39 0.990 33.47 0.44 1.023 0.17 0.20 0.02
FS 20 plane
67.03 67.13 1.001 67.81 0.89 1.012 3.56 2.12 0.60 4.72 0.07 1.325 0.24 0.24 0.05
Mid Chambers
164.1 165.3 1.007 164.1 2.02 1.000 161.9 162.8 1.006 161.6 2.00 0.998 0.20 0.15 0.16
average dose D95 γ (3%/3 mm)
AP
Validation
Validation TG-119
Average Gamma3%/3mm
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
Computed 09/04/12 12:04 09/07/12 12:25 09/14/12 18:43 9/20/2012 19:19
Date
Total Dose FS 20 Plane Mid_Chambers
Average Dose to ROINormalized to TPS dose
0.900
0.950
1.000
1.050
1.100
Computed 09/04/12 12:04 09/07/12 12:25 09/14/12 18:43 9/20/2012 19:19
Date
Total Dose FS 20 plane Mid_Chambers
Validation TG-119
Average Dose to ROINormalized to TPS dose
0.90
0.95
1.00
1.05
1.10
Computed 08/28/12 17:17 09/04/12 12:07 09/14/12 18:36 9/20/2012 19:24
Date
Total Dose Total_Dose3 Total_DoseVar FS 20 plane FS_20 plane3 FS_20 planeVar Mid_Chambers Mid_Chambers3 Mid_ChambersVar
Validation TG-119
Average Gamma3%/3mm
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Computed 08/28/12 17:17 09/04/12 12:07 09/14/12 18:36 9/20/2012 19:24
Date
Total Dose Total_Dose3 Total_DoseVar FS 20 plane FS_20 plane3 FS_20 planeVar Mid_Chambers Mid_Chambers3 Mid_ChambersVar
Validation TG-119
TPS Computed Diff Indirect 2� Diff TPS Computed Diff Indirect 2� Diff Computed Indirect 2�Total Dose
34.94 34.15 0.977 35.00 0.25 1.002 0.15 0.12 0.01
FS 20 plane
75.48 74.99 0.994 75.53 0.53 1.001 4.24 2.94 0.69 4.86 0.04 1.146 0.21 0.17 0.01
Mid Chambers 101.81 102.3 1.005 102.0 0.59 1.002 100.01 100.6 1.006 100.2 0.57 1.001 0.07 0.05 0.05
TPS Computed Diff Indirect 2� Diff TPS Computed Diff Indirect 2� Diff Computed Indirect 2�Total Dose
35.81 0.24 1.025 0.16 0.01
FS 20 plane
77.25 0.50 1.023 5.03 0.04 1.187 0.26 0.03
Mid Chambers
103.0 0.56 1.011 100.5 0.59 1.005 0.16 0.07
TPS Computed Diff Indirect 2� Diff TPS Computed Diff Indirect 2� Diff Computed Indirect 2�Total Dose
35.45 0.23 1.014 0.14 0.01
FS 20 plane
76.48 0.50 1.013 5.00 0.11 1.178 0.22 0.05
Mid Chambers
102.7 1.08 1.009 100.4 0.83 1.001 0.13 0.13
D95 (cGy) (3%/3 mm)
average dose (cGy) D95 (cGy) � (3%/3 mm)
Bands
Bands3
average dose (cGy)
BandsVar
average dose (cGy) D95 (cGy) (3%/3 mm)
Validation TG-119
Validation TG-119
TPS Computed Diff Indirect Diff Computed Indirect Computed IndirectCenter 5113.5 5185.0 1.014 5144.18 1.006 0.43 0.22 0.07 0.00Superior 2991.8 2966.1 0.991 2949.35 0.986 0.23 0.25Inferior 1807.6 1772.1 0.980 1815.7 1.004 0.28 0.14
TPS Computed Diff Indirect Diff Computed Indirect Computed IndirectProstate 7790.4 7944.7 1.020 7879.87 1.011 0.62 0.38PTV 7773.8 7897.1 1.016 7845.29 1.009 0.53 0.37 0.12 0.02Rectum 5789.2 5649.3 0.976 5637.62 0.974 0.31 0.34Bladder 4143.8 4033.9 0.973 4105.9 0.991 0.07 0.00
TPS Computed Diff Indirect Diff Computed Indirect Computed IndirectPTV 5104.2 5050.9 0.990 5087.29 0.997 0.32 0.34 0.11 0.54Cord 2894.8 2786.4 0.963 2879.92 0.995 0.41 0.27 0.15 0.00
Rt Parotid 1858.3 1748.3 0.941 1792.67 0.965 0.00 0.00
Lt Parotid 2043.4 1885.2 0.923 1928.8 0.944 0.38 0.26
TPS Computed Diff Indirect Diff Computed Indirect Computed IndirectTarget 5276.8 5026.8 0.953 5205.42 0.986 0.96 0.34 41.79 1.13Core 2070.4 1908.1 0.922 2082.6 1.006 0.46 0.28
TPS Computed Diff Indirect Diff Computed Indirect Computed IndirectTarget 5333.8 4827.8 0.905 5105.72 0.957 1.44 0.74 89.24 25.62Core 1132.3 929.5 0.821 1127.1 0.995 0.52 0.28
C_shape (hard)
C_shape (easy)
average dose (cGy) � (3%/3 mm) Vol @ � = 1 (%)
average dose (cGy) ♦ (3%/3 mm) Vol @ ♦ = 1 (%)
average dose (cGy) � (3%/3 mm)
H_N
Vol @ � = 1 (%)
Cylinders
average dose (cGy) ♦ (3%/3 mm)
average dose (cGy) � (3%/3 mm)
Prostate
Vol @ � = 1 (%)
Vol @ � = 1 (%)
Clinical Example
Conclusion
• 3D patient QA is beneficial
• IMRT QA more clinically relevant
• Time management
• Consider doing TG-119 tests
• “Joint expertise leads to better outcomes”