1. IGRT in Head andNeck Cancer{ Avraham Eisbruch University of Michigan

2. Two goals for IGRT 1. Assess and correct set-upuncertainties using imaging: 2D imaging or CT 2. Assess and correct changes intumors and critical organs duringthe course of therapy: CT 3. Using 2D imaging for set-up corrections 4. { 5. { 6. { 7. { 8. Cone-beam CT-based : Correction for setup(Translate only based on C2) 9. Cone-beam CT-based : Correction for setup (Translate only based on C2)Correction for setup(Translate only based on C2) 10. How often should we image to minimize set-up deviations? Zeidan OA et al, IJROBP 67:670, 2007Imaging every day if PTV margins are 3 mm, every other day if 5 mm 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. How can we correct rotational errors? 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. IJROBP 2007 15. Barker et al. IJROBP 59(4) 2004 16. Registration 17. Registration accuracy 18. Planning Fraction 3 CT Fraction 8Fraction 13 Fraction 18 Fraction 23 19. GTV change over time Barker et al. IJROBP 59(4) 2004 20. L.N. change over timeBarker et al. IJROBP 59(4) 2004 21. PTV70 : Max70Gy80 Max(1%)7570 EUD65 Min(1%) Gy6055504540 0 5 10 15 20 25 30 35 Fx# 22. PTV59: Max59Gy807570 Max(1%)65 EUD Gy6055 Min(1%)504540 0 5 10 15 20 25 30 35 Fx# 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. fx0 fx35 25. Building a cumulative actually delivered dosemap Need to outline each target and organ on eachduring-treatment CT in order to calculate thedoses each day, then to combine all doses toachieve cumulated DVHs. Outlining the targets and organs manually oneach CT is not practical 26. Deformable Registration 27. Dose Accumulation Using DeformableRegistration 28. Dose Accumulation Using DeformableRegistration 29. Difference between Planned and Delivered Mean Parotid Dose: University of Michigan10.00 8.00 6.00 4.00 2.00 0.001 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 36-2.00-4.00-6.00Hunter et al, ASTRO 2012 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. Patient Lost 35 lbs Planning CT Weekly DTD Plan on generated CT35 32. Decrease Parotid Volume andIncreased Mean Parotid Dose 10090 Red= Planned Left Parotid Green = Planned Right Partoid Mean Dose to Left80 Blue = Accumulated Left Parotid Orange = Accumulated Right Parotid Parotid increased by70 2.3 Gy with 26% decrease in volume.60Volume (%) Mean Dose to Right50 Parotid increased by40 6.1 Gy with 40% decrease in volume.302010 0 0 10 20 3040 50 6070 80Dose (Gy) 33. Anatomy Change Without Dose Change{ 34. Dose Gradient Effect Planning CT Weekly DTD Plan on generated CT35 35. Patient Lost 41 lbs. 10090 Mean Dose to Left80Parotid increased by701.6 Gy with 32%decrease in volume.60Volume (%)50 Mean Dose to Right40Parotid decreased by300.6 Gy with 24%20decrease in volume. Red= Planned Left Parotid Green = Planned Right Partoid10 Blue = Accumulated Left Parotid Orange = Accumulated Right Parotid 0 01020 3040 50 60 70 80Dose (Gy) 36. Dose Changewithout AnatomyChange { 37. 100 Red= Planned Left Parotid Green = Planned Right Partoid90 Blue = Accumulated Left Parotid Orange = Accumulated Right Parotid Mean Dose to80Left Parotid70increased by 7.160Gy with 3%decrease inVolume (%)50volume.4030 Mean Dose toRight Parotid20decreased by 1.210Gy with 6%decrease in 0volume. 0 10 20 3040 5060 7080Dose (Gy) 38. Alignment to the posterior body of C2 usingCBCT 39. The effect of rotations onparotid gland doses 40. DVH without rotation100Red= Planned Left ParotidGreen = Planned Right Partoid 90 Blue = Accumulated Left ParotidOrange = Accumulated Right Parotid 80 70 60 Volume (%) 50 40 30 20 1000 10 20 3040 50607080 Dose (Gy) 41. Selective parotid flow measurements pre and Post-RT 42. Saliva output vs mean doses to the parotid glands:Saliva vs planned dose and saliva vs actually delivered dosesSaliva flow by dose administered at month 61.61.5Planned Dose1.41.3Delivered Dose1.2Stimulated Saliva Flow (ml/min)1.11.00.90.80.70.60.50.40.30.20.10.020 3040 50 6070 Mean Dose (Gy)Hunter K et al, ASTRO 2012 43. High correlation between dose deviations in the first treatment and the cumulative dose deviations 10(delivered planned) dose on first day of treatment8Correlation = 0.92(