Ohio River Valley Spring 2011

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Ohio River Valley Spring 2011

  1. 1. Quality Assurance Utilizing 3D DoseReconstruction for Stereotactic Lung Radiotherapy James Durgin, Michael Weldon, Nilendu Gupta Ohio River Valley AAPM Spring Educational Symposium March 5, 2011
  2. 2. Overview of Lung SBRT Program OSU Experience  Research Project  Began in 2008  41 plans  53 lesions, 43 patients  Both recurrences in  Mean/Mode Rx: 9GyX5 data set  1 biopsy-proven  Non-IMRT recurrence  No wedges  1 imaging-based  All heterogeneous recurrence calculations using AAA  Low toxicity profile in Eclipse  6MV Siemens Oncor accelerator The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 2
  3. 3. Compass Overview Plan Data Backprojected Measurements Forward Calculated Dose The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 3
  4. 4. PurposeHow effective are current QA procedures?
  5. 5. Clinical Challenges  Point calculations are less than ideal  Inhomogeneities  Scatter  Small field sizes  Detector arrays are calculated for homogenous materials  Effect of multiple entry points unknown The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 5
  6. 6. MethodsRetrospective point calculationsForward calculations with a collapsed cone algorithmBackprojected 3D reconstructed dose
  7. 7. Point Calculation Analysis Accessed point calculations in patient chart RadCalc software Utilized equivalent path length, field size scaling Calculated non-weighted field average Avg= -0.29% The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 7
  8. 8. Secondary Forward Calculation IBA’s Compass software TPS Dose Forward Calculated Dose Collapsed cone algorithm Incorporates heterogeneity calculations Subject to commissioning differences DVH Comparison Dose Difference Map The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 8
  9. 9. Compass Beam Model Commissioning Same input data/physicist commissioning as Eclipse Good agreement down to 3X3cm in solid water TPS Dose Forward Calculated Dose DVH Comparison Dose Difference Map The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 9
  10. 10. Backprojected 3D Dose IBA’s Compass software, Matrixx hardware used Mean PTV dose and DVH statistics analyzed TPS Dose Backprojected Dose DVH Comparison Dose Difference Map The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 10
  11. 11. Results
  12. 12. Comparison Methods Retrospective analysis using point measurements  Average point calculation vs. Eclipse prescription Comparison of calculation differences  Forward calculation vs. Eclipse for mean PTV Measured backprojected dose compared to TPS  Backprojection vs. Eclipse for mean PTV Within Compass differences  Backprojected vs. forward calculation for mean PTV The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 12
  13. 13. Percent Change from Eclipse Mean PTV 35 Point Calculation to TPS 30 25Number of Plans 20 15 10 5 0 -5 to -4 -4 to -3 -3 to -2 -2 to -1 -1 to 0 0 to +1 +1 to +2 +2 to +3 +3 to +4 +4 to +5 +5 to +6 Percent Difference The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 13
  14. 14. Percent Change from Eclipse Mean PTV 35 Point Calculation to TPS 30 Forward Calculated in Compass to TPS 25Number of Plans 20 15 10 5 0 -5 to -4 -4 to -3 -3 to -2 -2 to -1 -1 to 0 0 to +1 +1 to +2 +2 to +3 +3 to +4 +4 to +5 +5 to +6 Percent Difference The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 14
  15. 15. Percent Change from Eclipse Mean PTV 35 Point Calculation to TPS 30 Forward Calculated in Compass to TPS 25 Backprojected to TPSNumber of Plans 20 15 10 5 0 -5 to -4 -4 to -3 -3 to -2 -2 to -1 -1 to 0 0 to +1 +1 to +2 +2 to +3 +3 to +4 +4 to +5 +5 to +6 Percent Difference The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 15
  16. 16. Percent Change from Eclipse Mean PTV 35 Point Calculation to TPS 30 Forward Calculated in Compass to TPS 25 Backprojected to TPSNumber of Plans 20 Backprojected to Forward Calculated 15 10 5 0 -5 to -4 -4 to -3 -3 to -2 -2 to -1 -1 to 0 0 to +1 +1 to +2 +2 to +3 +3 to +4 +4 to +5 +5 to +6 Percent Difference The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 16
  17. 17. Mean PTVs Aren’t the Whole Story Though The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 17
  18. 18. OAR/Coverage Statistics for Backprojected Dose Compared to Eclipse OARs receiving >20% of Rx, dose maximum analyzed  Max dose for 2 spinal cord structures increased >5%  Max dose for 1 esophagus structure increased >5%  Max dose for 1 heart structure increased >5%  Max dose for 1 brachial plexus structure increased >5%  Max dose for 0 skin structures increased >5% Coverage of 95% isodose line  2 PTVs experienced a drop in 95% coverage of more than 5% The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 18
  19. 19. Conclusion
  20. 20. Summary QA is a process of constant improvement Ultimately TPS determines dose What to trust determines the success of QA Measurements/reconstructed dose have value, but resources must be used wisely 3D reconstructed dose provides variability analysis for plans that pass traditional QA procedures The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 20
  21. 21. The Ohio State University Comprehensive Cancer Center –The OhioG. James Cancer Hospital and Richard J.Center – Arthur State University Comprehensive Cancer SoloveArthur G. James Cancer Hospital and Richard J. Solove Research Institute Research Institute 21
  22. 22. References Per-beam, Planar IMRT QA Passing Rates Do Not Predict Clinically Relevant Patient Dose Errors, 2011 Comparison of DVH data from multiple radiotherapy treatment planning systems, 2010 US Patent Application: Radiation Therapy Dose Perturbation System and Method, 2009 The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 22
  23. 23. Bonus 1: 3DVH Sun Nuclear software using dose error kernels Compared Compass to TPS differences >3% for mean PTV Percent Change Between QA Methods 35 3DVH Measured to TPS 30 Compass Measured to Forward Calculated 25 Number of Plans Compass Measured to TPS 20 15 10 5 0 -5 to -4 -4 to -3 -3 to -2 -2 to -1 -1 to 0 0 to +1 +1 to +2 +2 to +3 +3 to +4 +4 to +5 +5 to +6 %Difference The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute 23

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