02 igrt for india jan 2013 (cancer ci 2013) avraham eisbruch

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02 igrt for india jan 2013 (cancer ci 2013) avraham eisbruch

  1. 1. IGRT in Head andNeck Cancer { Avraham Eisbruch University of Michigan
  2. 2. Two goals for IGRT  1. Assess and correct set-up uncertainties using imaging:  2D imaging or CT  2. Assess and correct changes in tumors and critical organs during the course of therapy:  CT
  3. 3. Using 2D imaging for set-up corrections
  4. 4. {
  5. 5. {
  6. 6. {
  7. 7. {
  8. 8. Cone-beam CT-based : Correction for setup(Translate only based on C2)
  9. 9. Cone-beam CT-based : Correction for setup (Translate only based on C2)Correction for setup(Translate only based on C2)
  10. 10. How often should we image to minimize set-up deviations? Zeidan OA et al, IJROBP 67:670, 2007 Imaging every day if PTV margins are 3 mm, every other day if 5 mm
  11. 11. How should we image? CBCT vs 2D portal imaging The differences are mostly within 0-2 mm. Wu QJ et al, IJROBP 2007The frequency of imaging is more important than the mode of imaging
  12. 12. How can we correct rotational errors?
  13. 13. Correcting rotationalerrors 1. Re-positioning and re-making the mask 2. re-planning on the new rotated position 3. Correct the rotation using a rotating couch
  14. 14. IJROBP 2007
  15. 15. Barker et al. IJROBP 59(4) 2004
  16. 16. Registration
  17. 17. Registration accuracy
  18. 18. Planning Fraction 3 CT Fraction 8Fraction 13 Fraction 18 Fraction 23
  19. 19. GTV change over time Barker et al. IJROBP 59(4) 2004
  20. 20. L.N. change over time Barker et al. IJROBP 59(4) 2004
  21. 21. PTV70 : Max<77Gy, Min>70Gy 80 Max(1%) 75 70 EUD 65 Min(1%) Gy 60 55 50 45 40 0 5 10 15 20 25 30 35 Fx#
  22. 22. PTV59: Max<69Gy, Min>59Gy 80 75 70 Max(1%) 65 EUD Gy 60 55 Min(1%) 50 45 40 0 5 10 15 20 25 30 35 Fx#
  23. 23. Tumor shrinkage during RTMedian 70% GTV loss at the completion of therapy Barker et al, IJROBP ’04; Should we modify the treatment plan during RT? Mohan et al, IJROBP 2005
  24. 24. fx0 fx35
  25. 25. Building a cumulative actually delivered dosemap  Need to outline each target and organ on each during-treatment CT in order to calculate the doses each day, then to combine all doses to achieve cumulated DVHs.  Outlining the targets and organs manually on each CT is not practical
  26. 26. Deformable Registration
  27. 27. Dose Accumulation Using DeformableRegistration
  28. 28. Dose Accumulation Using DeformableRegistration
  29. 29. Difference between Planned and Delivered Mean Parotid Dose: University of Michigan10.00 8.00 6.00 4.00 2.00 0.00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36-2.00-4.00-6.00 Hunter et al, ASTRO 2012
  30. 30. Re-assessment of parotid doses during IMRT (no re-planning) The dose changes are higher in patients losing wt Robar JL, et al, IJROBP 2007
  31. 31. Patient Lost 35 lbs Planning CT Weekly DTD Plan on generated CT35
  32. 32. Decrease Parotid Volume andIncreased Mean Parotid Dose 100 90 Red= Planned Left Parotid Green = Planned Right Partoid Mean Dose to Left 80 Blue = Accumulated Left Parotid Orange = Accumulated Right Parotid Parotid increased by 70 2.3 Gy with 26% decrease in volume. 60Volume (%) Mean Dose to Right 50 Parotid increased by 40 6.1 Gy with 40% decrease in volume. 30 20 10 0 0 10 20 30 40 50 60 70 80 Dose (Gy)
  33. 33. Anatomy Change Without Dose Change {
  34. 34. Dose Gradient Effect Planning CT Weekly DTD Plan on generated CT35
  35. 35. Patient Lost 41 lbs. 100 90  Mean Dose to Left 80 Parotid increased by 70 1.6 Gy with 32% decrease in volume. 60Volume (%) 50  Mean Dose to Right 40 Parotid decreased by 30 0.6 Gy with 24% 20 decrease in volume. Red= Planned Left Parotid Green = Planned Right Partoid 10 Blue = Accumulated Left Parotid Orange = Accumulated Right Parotid 0 0 10 20 30 40 50 60 70 80 Dose (Gy)
  36. 36. Dose Changewithout AnatomyChange {
  37. 37. 100 Red= Planned Left Parotid Green = Planned Right Partoid 90 Blue = Accumulated Left Parotid Orange = Accumulated Right Parotid  Mean Dose to 80 Left Parotid 70 increased by 7.1 60 Gy with 3% decrease inVolume (%) 50 volume. 40 30  Mean Dose to Right Parotid 20 decreased by 1.2 10 Gy with 6% decrease in 0 volume. 0 10 20 30 40 50 60 70 80 Dose (Gy)
  38. 38. Alignment to the posterior body of C2 usingCBCT
  39. 39. The effect of rotations onparotid gland doses
  40. 40. DVH without rotation 100 Red= Planned Left Parotid Green = Planned Right Partoid 90 Blue = Accumulated Left Parotid Orange = Accumulated Right Parotid 80 70 60 Volume (%) 50 40 30 20 10 0 0 10 20 30 40 50 60 70 80 Dose (Gy)
  41. 41. Selective parotid flow measurements pre and Post-RT
  42. 42. Saliva output vs mean doses to the parotid glands:Saliva vs planned dose and saliva vs actually delivered doses Saliva flow by dose administered at month 6 1.6 1.5 Planned Dose 1.4 1.3 Delivered Dose 1.2Stimulated Saliva Flow (ml/min) 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 20 30 40 50 60 70 Mean Dose (Gy) Hunter K et al, ASTRO 2012
  43. 43. High correlation between dose deviations in the first treatment and the cumulative dose deviations 10(delivered – planned) dose on first day of treatment 8 Correlation = 0.92(<0.001) 6 4 2 0 -2 -4 -6 -8 -10 -10 -8 -6 -4 -2 0 2 4 6 8 10 (delivered – planned) dose for the entire treatment The main reason for the deviations: rotations
  44. 44. Conclusions Rotations can be a significant factor in the difference between planned dose and actual dose received. Managing rotations by robust planning and/or rapid monitoring and correction may reduce parotid toxicity with minimal impact on plan quality
  45. 45. Tumor shrinkage duringRT  Should we re-draw the GTV and re-plan for a smaller PTV?
  46. 46. Neoadjuvant chemo: Its tumor effect is trivial even if clinical CRis achieved.Similar effect is likely at mid-course of RT even if tumorshrank according to re-CT. OR: partial RT course After Ian Tannock
  47. 47. Adaptive Therapy?Changes in mass and position of the parotid glands during RT Medial shift of the parotid, correlates with wt loss: Higher doses than planned are actually delivered Barker et al, IJROBP 2004 Reduce weight loss during RT!
  48. 48. Who may need re-planning?  Patients with shrinkage of bulky tumors  Patients with significant weight reduction  Both lose mask fitting in addition to anatomical changes For other patients: The benefits of re-planning need more study

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