1. IMRT: Treatment Planning and Dosimetry Nesrin Dogan, Ph.D Department of Radiation Oncology Virginia Commonwealth University Medical College of Virginia Hospitals Richmond, VA, USA

9. Output Factor Small Fields D.A. Low et al. “Ionization chamber volume averaging effects in dynamic intensity modulated radiation therapy beams, Med.Phys.30(7): 1706-1711 (2003). Micro cham: 0.009cc PTW: 0.125cc Farmer:0.65cc

12. Courtesy of Jean Moran, Ph.D, UofMichigan Small 1-D Detectors 0.0019 NA NA 0.3 0.015 0.009 Volume (cm 3 ) 0.45 0.4 0.73 NA 0.2 0.6 Diameter (cm) < resolution than diodes, dose rate dependence, expensive Diamond Non-linear dose response for <30 cGy MOSFET Stereotactic diode p-type Si diode Over-respond to low energy photons Martens et al. 2000 Pinpoint chamber Poorer resolution than diodes Micro-chamber Disadvantages Detector

13. Pasma Med Phys 26: 2373-2378 (2376) 1999 Predicted EPID Ion Chamber + Discrepancies in the penumbra region (up to 10%) Overall: Good agreement 10 MV 25 MV EPID: DMLC measurements Courtesy of Jean Moran, UofMichigan

17. Dose Calculation Algorithms Calculation Speed Calculation Accuracy Pencil Beam Monte Carlo Superposition/Convolution Courtesy: Jeff Siebers, VCU

18. Comparison of SC and MC Comparison of a) Superposition-Convolution (SC) and b) MC dose calculations

19. Monte Carlo Pencil Beam Pawlicki et al., Med Dosim, 26 157 (2001) Comparison of PB and MC Pencil Beam Monte Carlo

20. Superposition Monte Carlo Slice 45 Monte Carlo Slice 55 Monte Carlo Slice 64 Comparison of SC and MC Superposition Superposition

22. DPE (same intensities) PB computed SC computed Make sure your final dose calculation is with an accurate algorithm 68 Gy 64 Gy 60 Gy 50 Gy 40 Gy 30 Gy

23. OCE (different intensities) SC optimization SC calc PB optimization SC calc 68 Gy 64 Gy 60 Gy 50 Gy 40 Gy 30 Gy

24. Conventional IMRT Optimization Process Create Leaf Sequence “ Deliverable” Dose Calculation Create Deliverable Intensities Optimization Leaf Sequencer Leaf positions do not exist Deliverable Plan

26. Comparison of Isodoses a) An optimized intensity distribution b) A deliverable distribution using DMLC calculated using Convolution/Superposition algorithm

27. Final dose is deliverable Deliverable IMRT Optimization Process combine optimization and delivery into one process Leaf Sequencing Initial Intensity (I I (x,y)) Evaluate Plan Objective Converged? Adjust I(x,y) Compute Dose (D O ) Optimized Intensity (I O (x,y)) and Dose D O = D D No Yes 1 3 4 5 2 Create Leaf Sequence 7 Create Deliverable Intensities (I D (x,y)) 8 6

28. Deliverable Optimization Deliverable optimization can restore original optimized plan Head and Neck IMRT plan Original SC opt Deliverable Plan SC MC of Deliverable MC opt (deliverable)

38. Target Nodes Spinal cord Avoidance tissue Avoidance tissue Gy 60 50 45 30 Gy 60 50 45 30 Courtesy of G. Ezzel, Ph.D., Mayo Clinic

41. Guidelines for Target Expansions Prostate CTV: Expand prostate by 0.5cm in all directions except posteriorly then + seminal vesicles (no expansion for seminal vesicles) Prostate PTV: Expand Prostate CTV by 0.5cm in all directions (3D expansion) Lymph Nodes CTV : Expand lymph nodes by 1.0 cm in anterior, posterior, right and left (2D expansion) with small bowel, bladder, rectum, bones, muscle, skin1cm and prostate PTV tissues being the limiting organs Lymph Nodes PTV : Expand Lymph Nodes CTV 0.5 cm in all directions (3D expansion) with only skin1cm and Prostate PTV as the limiting structures

43. CTV 1 = GTV t + GTV n + 1cm margin for subclinical disease PTV 1 = GTV t + GTV n + 0.5 setup uncertainty PTV 2 = CTV 1 + 0.5 setup uncertainty PTV 3 = CTV nodes + 0.5 setup uncertainty ≤ 5 70 Unspecified Tissue 0 60 Brachial Plexus 30 45 Esophagus 0 45 Larynx – if feasible ≤ 50 30 Parotids (L & R) – at least one of them 50 45 Oral Cavity 30 60 Mandible ≤ 0.03 cc 48 Cord + 0.5 cm 0 50 Brainstem + 0.5 cm ----- ----- PTV 3 35 95 56 PTV 2 35 97 < 20 70 77 PTV 1 Fraction size Volume (%) / cc Limiting Dose(Gy) Structures H&N IMRT Treatment Planning Instruction Form Department of Radiation Oncology, VCU Health Systems

44. 10 50 Unspecified Tissue 50 10 2 30 35 45 Skin1cm 50 10 2 25 45 50 Small Bowel 50 10 2 45 60 65 Bladder 50 10 2 45 55 60 Remaining rectum 50 10 2 55 63 65 Periprostatic rectum 50 10 2 35 40 45 Femurs (L&R) 28 95 50.4 PTV Nodes 28 97 63 PTV Fraction Size Volume (%) Limiting Dose(Gy) Structures Prostate IMRT Treatment Planning Instruction Form Department of Radiation Oncology, VCU Health Systems

45. General Principles for Beam Angle Selection

50. H&N: 5 Beam 9 Beam 7 Beam 15 Beam

53. Dose-Volume Based vs. EUD-Based Optimization – H&N Example EUD + tumor as “virtual normal tissue” 30 45 50 (c) 70 60 EUD unconstrained (b) 30 45 50 80 60 70 45 Dose-Volume (a) 30 50 60 70 45

55. Dose-Volume Based vs. EUD-Based Optimization – Prostate Example 60 50 70 40 (a) 80 40 80 60 70 50 (c) 90 80 40 90 60 50 70 (b) Bladder Target Bladder Target Bladder Rectum Dose-Volume EUD unconstrained EUD + tumor as “virtual normal tissue”

57. SIB IMRT Two-Phase IMRT Mean dose to nodes 59 Gy Mean dose to nodes 51 Gy Sequential vs. SIB 70 50 45 60 35 40 45 50 35 40 45 45 50 60 70 50

58. Non-Target Tissue Volumes Receiving Specified Dose

59. Minimize Number of Segments

60. Minimize Number of Segments Segments MU 50 550 75 582 100 604 150 619 200 631 50 Segments 75 Segments 100 Segments 150 Segments 200 Segments

61. Impact of Degree of Fluctuations (“Complexity”) in Intensity Patterns on MUs for IMRT 100 Total MUs= 100 100 Total MUs = 300 100 100 10 cm 10 cm 100 100 Total MUs = 200 10 cm Total MUs = 150 50 50 50 10 cm

62. Attention to Objective Function

63. Target Volumes Critical Structure TLDs in Target Volumes Radiochromic film through multiple plans Delivery is required by RTOG for participation in IMRT trials Removable Dry Insert Water Water Anthropomorphic: RPC Head Phantom Courtesy of Jean Moran, UofM

64. Anthropomorphic: RPC Head Phantom

65. Examples

67. This row might be used by the IMRT plan if the target is drawn too close to the isocenter plane Courtesy of G. Ezzel, Ph.D., Mayo Clinic Human planners sometimes have to trim IMRT beams…..

69. Nasopharynx Nasopharynx field arrangement 7 posterior fields

72. 7 beam field arrangement

74. Sinus DVH

78. Nasal cavity isodose lines

79. Prostate and Lymph Nodes 1. Prostate PTV+ Lymph Nodes PTV: 50.4 Gy / 28 fx Prostate PTV : 63 Gy ( BED = 70 Gy ) / 28 fx 2. Sequential 9 Gy IMRT Boost to Prostate PTV : 72 Gy ( BED = 80 Gy ) or Upfront 6 Gy HDR boost SIB-IMRT

80. Heart IM nodes Heart IM nodes Breast IMRT w/IM nodes

81. Breast IMRT W/regional Nodes

82. Breast IMRT W/regional Nodes

83. Lung IMRT

85. GYN Brachytherapy + IMRT IMRT+BRT Conventional 3DCRT+BRT Primary Tumor

86. Conventional 3DCRT+BRT vs. IMRT+BRT

88. Phantom Dose Verification Beams on Patient Beams on Phantom

89. Sample Film Dosimetry Results Other Analysis Distance to Agreement Gamma … Isodose Comparison Profiles Dose Differences

90. Compare isodoses (film) and absolute dose (chamber) Current Practice Courtesy of G. Ezzel, Ph.D., Mayo Clinic

91. Gamma Analysis Measured Film Adaptive Convolution Monte Carlo

92. Calculation to Measurement Comparison (b) Measured Calculated 54% of points have a dose difference <2% or a DTA <2 mm

93. MC to Measurement Comparison (b) (c) Measured Calculated Measurement and MC w transport through MLC 97% within 2%,2 mm Measurement and MC using Tx planning systems Intensity Matrix

94.  =10% Superposition Monte Carlo MC Verification

95. The percentage of points, averaged over all of the plan’s treatment fields for each patient with  ≥ 1 with 2% tolerance and 2 mm DTA. MC (8.1% ± 3.7% points failed; range = 4.9% – 18.4%) SC (16.7% ± 5.6% points failed; range = 11.3% – 30.7%) MC Verification of Prostate IMRT Plans

96. Courtesy of G. Ezzel, Ph.D., Mayo Clinic Check standard patterns for constancy

100. Acknowledgements Jeffrey Siebers – VCU Gary Ezzel – Mayo Clinic Mark Oldham – Duke University Jean Moran – U of Michigan Ivaylo Mihalov - UofArkansas