Assessing Heterogeneity Correction Algorithms Using the Radiological Physics Center Anthropomorphic Thorax Phantom David Followill, Ph.D. Associate Director Radiological Physics Center
RPC History Lesson Formed by agreement between AAPM and Committee for Radiotherapy Studies (CRTS) chaired by G. Fletcher Founded in 1968 to monitor institution participation in clinical trials Funded continuously by NCI as structure of cooperative group programs have changed Now 43 years of experience of monitoring institutions and reporting findings to study groups and community
Mission Assure NCI and cooperative groups that institutions participating in clinical trials deliver prescribed doses that are comparable and consistent. (Minimize dose uncertainty) Help institutions to make any corrections that might be needed. Report findings to the community.
Clinical Trial Participants Number of Active Institutions 1,650 ~3,300 megavoltage machines ~20,000 active megavoltage beams # of Institutions # of Machines 3500 1700 3000 1600 2500 1500 0 1 1500 1000 1300 500 1 0 1100 1000 1970 1973 1976 1979 Active Machines Active Institutions 1982 1985 1988 1998 1999 0 1 2 3 4 5 6 7 8 9 Year Year 1991 1994 1997 0 3 6 9
Purpose of Credentialing Educate Evaluate ability to deliver dose using advanced technologies Improve understanding of protocol Reduce deviation rate
Credentialing Technique Previous patients treated with technique Facility Questionnaire Knowledge Assessment Questionnaire Benchmark Case Electronic data submission Protocol patient dosimetry review Rapid Review Phantom Irradiation (end to end test)
What are Advanced Technologies in clinical trials? TRACKING TPS IMRT DOSE PAINTING HETERO CORRECTION IGRT KV OR MV IMRT Respiratory Control GATING SBRT
IMRT/SBRT Planning and Delivery - QA required at each step Positioning and Immobilization Image Acquisition (CT, MR) Structure Segmentation Black Box IMRT/SBRT treatment planning and dose calc. File transfer and management Plan validation Position verification treatment delivery What You See Is NOT What You Always Get
Delivery Plan OAR PTV Cord/bone
4 SRS phantoms RPC Phantoms family 10 prostate phantoms (IMRT) 10 thorax phantoms (SBRT) 30 H&N phantoms (IMRT) 3 Spine phantoms 2 liver phantoms (SBRT)
RPC Lung phantom
RPC Phantom Design Anthropomorphic shape Water filled Plastic inserts containing targets and organs at risk (heterogeneity) The phantom is to be Point dose treated (TLD) and planar as if (radiochromic it were film) a dosimeters patient. Purpose is to evaluate the complete treatment process 1. Imaging and transfer of images to planning computer 2. Development of treatment plan 3. Phantom set up on treatment couch 4. Dose delivery
Some institutions go overboard!!
Dose distribution - CERR
Phantom Analysis Development Electronic TLD analysis Electronic film analysis Import and view digital data Gamma calculation
Initial Phantom Results TPS Precise BrainLab Eclipse Ergo RenderPlan Pinnacle XiO Dose Calc. Algorithm # irradiations Center of Tumor TPS D hetero /D homo Scatter Int. Clarkson 2 1.19 ± 2.6% Clarkson & Pencil beam 5 1.20 ± 2.2% Pencil Beam 5 1.18 ± 4.3% 3D Convol.. Pencil Beam 2 1.19 ± 0.1% Change in primary attenuation 1 1.20 Adaptive convolve 10 1.13 ± 2.1% Superposition/Convolution 5 1.11 ± 2.3% Clearly, there are two groupings
PTV Periphery and Lung Points PTV = Tumor (CTV) + 0.5 cm in axial plane + 1 cm in longitudinal plane. Lung constraint: points 2 cm from the PTV X PTV Periphery X CTV X X X CTV X Lung points Axial Plane Longitudinal Plane
Initial Phantom Results (PTV Periphery) TPS TPS Dose Calc. Algorithm # irradiation D hetero/ D homo Axial plane Precise BrainLab Eclipse Ergo Pinnacle XiO Scatter Int. Clarkson 2 1.20 ± 3.2% Clarkson & Pencil beam 2 1.17 ± 1.6% Pencil Beam 5 1.17 ± 4.3% 3D Convol.. Pencil Beam 2 1.18 ± 1.3% Adaptive convolve 10 1.06 ± 4.2% Superposition/Convol Convol. 3 1.08 ± 5.3% Two separate groupings again
Initial Phantom Results (PTV Periphery) Measurements TPS Precise Dose Calc. Algorithm # irradiation PTV Periphery measured D TLD/film /D hetero Scatter Int. Clarkson 2 0.88 BrainLab Eclipse Ergo Pinnacle XiO Clarkson & Pencil beam 2 0.84 Pencil Beam 5 0.87 3D Convol.. Pencil Beam 2 0.84 Adaptive convolve 10 0.97 Superposition/Convol Convol. 3 0.95 Two separate groupings again
Initial Phantom Results (Lung points) TPS TPS Dose Calc. Algorithm # irradiation D hetero/ D homo Axial plane Precise BrainLab Eclipse Ergo Pinnacle XiO Scatter Int. Clarkson 2 1.19 ± 4.2% Clarkson & Pencil beam 2 1.22 ± 5.5% Pencil Beam 5 1.19 ± 8.3% 3D Convol.. Pencil Beam 2 1.20 ± 5.3% Adaptive convolve 10 1.12 ± 5.8% Superposition/Convol Convol. 3 1.12 ± 6.4% Two separate groupings again
Eclipse AAA Profile 8 Left Right 6 Dose (Gy) 4 2 PTV 0-6 -5-4 -3-2 -1 0 Distance (cm) 1 2 3 4 5 6 RPC Film Institution values AAA
Eclipse Pencil-Beam Profile Left 8 Right 6 Dose (Gy) 4 2 PTV 0-6 -5-4 -3-2 -1 0 Distance (cm) 1 2 3 4 5 6 RPC Film Institution values PB
Gamma Analysis results Pass 99.7% Pass 60.6%
Pinnacle Convolution R-L Profile Left Right Left Profile Axial plane Righ Average displacement Left side: on: 3 mm off: 1 mm Prescribed D 30 20 Average displacement Rigth side: on: 1 mm off: 5 mm Dose (Gy) D2cm 10 PTV 0-7 -6-5 -4-3 -2-1 0 1 2 3 4 5 6 7 Distance (cm) RPC Film ITC off ITC on RPC Regression Institution Regression
Brain Lab Pencil-Beam Profile Right Left Profile Axial plane Left 30 Right Average displacement Left side: on: -2 mm off: -6 mm Prescribed D 20 Average displacement Right side: on: -5 mm off: -2 mm Dose (Gy) D2cm 10 PTV 0-7 -6-5 -4-3 -2-1 0 1 2 3 4 5 6 7 Distance (cm) RPC Film ITC off ITC on RPC Regression Institution Regression
Pinnacle Calculation and Delivery Medial-Left Lateral Profile Pinnacle Absolute Dose (cgy) 2500 0 1500 1000 GTV PTV Film Avg Pinnacle -5% or 3mm +5% or 3mm 500 0-40 -20 0 20 40 60 80 Distance (mm) ISODOSE: Pinnacle, Axial, Film #2 16 Jul 7 Anterior to Posterior (mm) Medial to Distal (mm) 0 20 40 60 80 100 120 0 20 40 60 80 100 120 1000 1950 1950 1500 1000 GTV 1950 1000 1950 2050 1000 1500 1950 1500 700 1500 1000 700 1000 1000 700 700 700 Measured Calculated GTV 96% PASS ±5%/3mm >99% PASS ±7%/7mm FAIL
Eclipse AAA Calculation and Delivery Medial-Left Lateral Profile Eclipse AAA Absolute Dose (cgy) 800 700 600 500 300 GTV PTV Film Avg Helios-AAA -5% or 3mm +5% or 3mm 100 0-40 -20 0 20 40 60 80 Distance (mm) ISODOSE: Eclipse AAA, Axial, Film #5 16 Jul 7 Anterior to Posterior (mm) Medial to Distal (mm) 0 20 40 60 80 100 120 0 300 100 20 40 60 80 100 120 650 0 550 700 550 650 700 700 700 GTV 700 650 650 550 300 550 300 300 100 100 100 0 GTV Measured Calculated
500 TOMO Calculation and Delivery Medial-Left Lateral Profile TomoTherapy Absolute Dose (cgy) 700 600 500 300 GTV PTV Film Avg TOMO -5% or 3mm +5% or 3mm 100 0-40 -20 0 20 40 60 80 Distance (mm) ISODOSE: TomoTherapy, Axial, Film #2 16 Jul 7 Anterior to Posterior (mm) Medial to Distal (mm) 0 20 40 60 80 100 120 0 300 20 600 600 600 300 40 600 GTV 600 60 500 500 80 100 120 100 600 500 600 600 300 300 300 GTV Measured Calculated
Eclipse PB Calculation and Delivery Medial-Left Lateral Profile Eclipse PB Dose (cgy) 800 700 600 500 300 GTV Film Avg Eclipse PB +5% or 3mm -5% or 3mm PTV 100 0-40 -20 0 20 40 60 80 Distance (mm) ISODOSE: Eclipse PBC, Axial, Film #5 16 Jul 7 Anterior to Posterior (mm) Medial to Distal (mm) 0 20 40 60 80 100 120 0 600700 100 20 40 60 80 100 500 600 700 740 600 700 700 500 500 GTV 700 740 740 600 300 700 500 600 500 300 300 300 100 GTV 120 300 Measured Calculated
CyberKnife ray-tracing GTV Film 1 Film 2 Film 3 Film Avg TPS +5%/3mm -5%/3mm Initial results were not good with ray-tracing algorithm PTV TLD measured doses in the center of the PTV to be ~13% low compared to calculated values. Profiles were correct shape, but wrong absolute dose.
CyberKnife 11 Left Average displacement Left side: 1 mm Prescribed D Right-Left Profile Axial plane 8 Right Average displacement Right side: 2 mm Monte Carlo 6 Dose (Gy) D 2cm 4 Average TLD RPC/Inst = 0.985 2 PTV 0-7 -6-5 -4-3 -2-1 0 1 2 3 4 5 6 7 Distance (cm)
Binary Agreement Map Analysis 100 80 60 40 20 0 96 94 90 86 85 61 50 31 Percent of pixels passing ±5%/3mm criteria Pinnacle SC Eclipse AAA Eclipse PB XiO SC TomoTherapy SC MultiPlan MC MultiPlan PB Corvus PB
Stationary vs. Motion lung target No difference in the results New criteria are ±5% dose to TLD and average percent of pixels passing 5%/5 mm must be 85% and no single film with < 80% of pixels passing
Phantom Results Comparison between institution s plan and delivered dose. Phantom Thorax Irradiations 237 Pass 178 Fail 59 (25%) Criteria 5%/5mm Year introduced 4
Phantom Results Comparison between institution s plan and delivered dose. Phantom Thorax Irradiations 237 237 Pass 178 116 Fail 59 (25%) 121 (51%) Criteria 5%/5mm 5%/3mm Year introduced 4 4
More Good News >80% Pass Rate RPC H&N and Lung Phantoms Percent of Passing Irradiations 100 80 60 40 H&N lung 20 3 4 5 6 7 8 9 2010 Year
Acceptable Brain Lab / Monte Carlo Eclipse / AAA Pinnacle / Collapsed Cone Convolution Adaptive Convolve XiO / Superposition Fast Superposition Helax / Collapsed Cone TomoTherapy / Convolution Superposition Corvus / Monte Carlo Multiplan / Monte Carlo In House TPS / Monte Carlo Unacceptable Brain Lab / Pencil Beam Eclipse / Pencil Beam Pinnacle / Fast Convolve XiO / Modified Clarkson Convolution Helax / Pencil Beam Corvus / Pencil Beam Multiplan / Ray Tracing In House TPS / Pencil Beam or Clarkson base
Phantom Accomplishments Use of heterogeneity corrections for modern algorithms Test ability to hit a moving target(s) Corrected many dosimetry errors that might have impacted on patient doses Testing proton therapy planning and dose calculations (in development)
Thank You Questions?