Using Task Group 137 to Prescribe and Report Dose. Vrinda Narayana. Department of Radiation Oncology University of Michigan. The

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1 Using Task Group 137 to Prescribe and Report Dose Vrinda Narayana The Department of Radiation Oncology University of Michigan

2 TG137 AAPM Recommendations on Dose Prescription and Reporting Methods for Permanent Interstitial Brachytherapy for Prostate Cancer R. Nath W. S. Bice W. M. Butler Z. Chen A. Meigooni V. Narayana M. J. Rivard Y. Yu 2016 AAPM Spring 2

3 TG 137 Charge Review Prescription Reporting Radiobiological models Consensus Min requirements for prescription and reporting Pre implant Post implant Recommend Optimal requirements for prescription and reporting Pre implant Post implant 2016 AAPM Spring 3

4 Outline Permanent Prostate Implants Impact of dose reporting based upon Imaging modalities Timing of imaging study Treatment planning approaches Interoperative planning strategies Biophysical models BED EUD TCP 2016 AAPM Spring 4

5 History Dose Prescription Bladde r Prostate Rectum Nomogram based on a modified peripheral loading Zheng et al., Medical Dosimetry, 28, (2003) AAPM Spring 5

6 History Dose Reporting D 99 Dose to 99% of target mpd minimum Peripheral Dose Bladde r Prostate Rectum Volume % US PROSTATE DVH Isodose Surface Implant too deep Implant too shallow Best Fit 0.5 cm superior 1.0 cm superior 0.5 cm inferior 1.0 cm inferior Dose Gy 2016 AAPM Spring 6

7 Plan evaluation today V100 Vol that receives 100% of dose 90 % excellent implant D90 Dose to 90 % of the volume Prescribed dose 2016 AAPM Spring 7

8 Today D 90 Dose to 90% of target V Volume that receives Rx dose V 100 Rx D AAPM Spring 8

9 Dose calculation Imaging 2016 AAPM Spring 9

10 Today D 90 Dose to 90% of target V Volume that receives Rx dose V 100 Rx IDS V 100 D 90 Rx D AAPM Spring 10

11 D90 issue False Decrease D90 False Increase D90 CT Prostate MR prostate 2016 AAPM Spring 11

12 Impact of Imaging Modality on Dose Reporting Ultrasound Imaging CT Imaging MR Imaging Recommendations on Imaging modality 2016 AAPM Spring 12

13 Imaging modalities Target delineation www 2016 AAPM Spring 13

14 Prostate Anatomy 2016 AAPM Spring 14

15 2016 AAPM Spring 15

16 Imaging Modalities Plane CT MRI TRUS films * Identification * Localization Prostate Delineation Critical St Delineation Comfort Cost & Convenience AAPM Spring 16

17 Ultrasound Prostate Urethra Rectal wall 2016 AAPM Spring 17

18 Ultrasound Apex / GUD Transition Prostate Apex GUD external sphincter Bulbourethral Gland H shaped External sphincter 2016 AAPM Spring 18

19 MRI Coronal vs. CT Coronal 2016 AAPM Spring 19

20 MR Anatomy Prostate Urethra Rectal wall Corpus Cavernosum Pudendal Arteries Sphincter Neurovascular bundle 2016 AAPM Spring 20

21 CT Prostate Apex when do you stop Base bladder neck oblitaration 2016 AAPM Spring 21

22 2016 AAPM Spring 22

23 Intra - lumen bladder density-small gland 2016 AAPM Spring 23

24 Figure AAPM Spring 24

25 Bladder Neck Obliteration 2016 AAPM Spring 25

26 MRI Coronal vs. CT Coronal 2016 AAPM Spring 26

27 MRI Coronal vs. CT Coronal 2016 AAPM Spring 27

28 CT Prostate post implant Apex when do you stop Base bladder neck obliteration Seminal vesicles Rectal surface 2016 AAPM Spring 28

29 Axial CT without Contour Axial MRI without Contour Axial CT with Contour Axial MRI with Contour 2016 AAPM Spring 29

30 Variations without a Standard (Lee) Observer 1 Observer 2 Observer 3 Vol 39 cc 48 cc 32 cc D Gy 123 Gy 155 Gy V100 93% 86% 99% 2016 AAPM Spring 30

31 Perils of CT contouring Bladder Anterior CT base Prostate Rectum CT apex Saggital McLaughlin et. al AAPM Spring 31

32 CT Prostate Outer Rectum Inner Rectum de-expansion 5 mm Urethra Foley Penile Bulb Urethra Prostate Rectum Axial 2016 AAPM Spring 32

33 Why MR? EXPECT VARIATION 2016 AAPM Spring 33

34 CT contouring / 6 national experts McLaughlin 2016 AAPM Spring et. 34 al.

35 CT contouring 3.00 Wide margin implants Observer/Std Volume Study Observer/Std V Observer/Std D Study Narayana et. al Study AAPM Spring

36 Deviation from a Standard (6 experts) MRI Observer 1 Observer 2 36cc 34cc 38cc Prostate Volume Agreement 2016 AAPM Spring 36

37 Deviation from a Standard (6 experts) MRI Observer 1 Observer Gy 153 Gy 143 Gy D90 Agreement 2016 AAPM Spring 37

38 Deviation from a Standard (6 experts) MRI Observer 1 Observer 2 95% 98% 92% V100 Agreement 2016 AAPM Spring 38

39 bladder seminal vesicle bone prostate rectum external sphincter Proximal penis Prostate side view: Note labels on right. Prostate is not enlarged and does not extend into the bladder. Urethra opening from the bladder is open (yellow arrow). Sphincter is normal length and there is no bony restriction note space between the bone and prostate (purple arrows) 2016 AAPM Spring 39

40 Central = transition zone (TZ) = dark Peripheral zone (PZ) = light normal prostate - normal appearance with light peripheral zone where tumors form and the dark central area called the transition zone this enlarges with age 2016 AAPM Spring 40

41 Multiparameter Imaging T2 DCE DWI 2016 AAPM Spring 41

42 Right side of the gland panel is normal prostate with clear PZ and TZ. On the left side (red) note the dark area that extends into the TZ and from front to back. This is tumor 2016 AAPM Spring 42

43 with contrast the area of concern on the left side of the panel is clearly seen, with a suggestion of extension beyond the gland (arrow) AAPM Spring 43

44 Note the tumor on the left side of the panel (red) and possible extension beyond the capsule 2016 AAPM Spring 44

45 Imaging Recommendations CT 2/3 mm cuts Prostate mindful of pitfalls Rectum outer 1 cm sup and inf Rectal wall cm contraction Urethra Foley Day 0 Foley Optional later scans Penial Bulb 2016 AAPM Spring 45

46 Imaging Guidelines MR T2 3 mm cuts (no rectal coil) immediately before or after CT Axial, coronal, sagittal Rectum 1 cm above & below Bladder axial MR Urethra axial and Sag MR Register CT-MR around prostate only CT seed positions 2016 AAPM Spring 46

47 Impact of timing of imaging on dose reporting Prostate edema Source displacement with time Optimal timing for post implant dosimetry Recommendations on timing of imaging 2016 AAPM Spring 47

48 Edema? Needle insertion? Bleeding needle pentration? General inflamation 2016 AAPM Spring 48

49 Edema Model Volume V max V T V 0 T 0 T max T Time 2016 AAPM Spring 49

50 Edema Model? T max? Different imaging modalities? Prostate Volumes 2016 AAPM Spring 50

51 Edema US 80% 1m CT1 14d CT2 150% CT3 120% Narayana et. al AAPM Spring 51

52 Edema CT 130% US 14 d MR 101% McLaughlin et. al 2016 AAPM Spring 52

53 MR edema 3 w MR 130% MR Implant 3 w Chung et. al 2016 AAPM Spring 53

54 Edema Model Max 1 day Longer to resolve than initial swelling Quick resolution - 2 weeks Slow resolution 2 to 4 weeks T1/2 ~ 10 d (4 to 25 days) 2016 AAPM Spring 54

55 Effect on post implant dosimetry Day 1 edema large underestimate dose Day 100 edema resolved overestimate dose 2016 AAPM Spring 55

56 Edema Model Assumes seeds move with the prostate Seeds inside the prostate? Stranded seeds 2016 AAPM Spring 56

57 McLaughlin et. al AAPM Spring 57

58 2016 AAPM Spring 58

59 2016 AAPM Spring 59

60 2016 AAPM Spring 60

61 2016 AAPM Spring 61

62 By how much? Timing of imaging Magnitude of prostate swelling Rate of resolution Radioactive T 1/2 Short T1/2 & low energy 2016 AAPM Spring 62

63 Optimal time 131 Cs 10+2 days 103 Pd 16+2 days 125 I 42+2 days 2016 AAPM Spring 63

64 Recommendation Timing of imaging Pre-Implant prostate volume Implant day dosimetry US immediate CT/MR 2 to 4 h Post-Implant dosimetry 131 Cs 10+2 days 103 Pd 16+2 days 125 I 1month+1week 2016 AAPM Spring 64

65 The optimal timing for post implant dosimetry is 20% 1. Immediately following the implant 20% 20% 20% 20% 2. 2 weeks after the implant 3. 1 month after the implant 4. 10, 16 and 42 days for 131 Cs, 103 Pd, 125 I respectively 5. No post implant dosimetry is required 10

66 The optimal timing for post implant dosimetry is 20% 1. Immediately following the implant 20% 20% 20% 20% 2. 2 weeks after the implant 3. 1 month after the implant 4. 10, 16 and 42 days for 131 Cs, 103 Pd, 125 I respectively 5. No post implant dosimetry is required Answer: 4 Reference: AAPM TG137, Nath et. al

67 Post implant prostate volume under- or overestimation is a result of 20% 1. The timing of dosimetry 20% 20% 20% 20% 2. Magnitude of preimplant prostate swelling 3. The rate of edema resolution 4. The radioactive decay half-life 5. All of the above 10

68 Post implant prostate volume under- or overestimation is a result of 20% 1. The timing of dosimetry 20% 20% 20% 20% 2. Magnitude of preimplant prostate swelling 3. The rate of edema resolution 4. The radioactive decay half-life 5. All of the above Answer: 5 Reference: AAPM TG137, Nath et. al

69 Impact of treatment planning approaches on dose reporting Planning techniques Choice of isotope Choice of source strength Calculation Algorithm Dose indices for target and normal tissue Recommendations for planning and dose reporting 2016 AAPM Spring 69

70 Peripheral loading? Volume % Prostate, with error Nomogram Differential Periphery Spike Volume % Prostate cm margin, with error Nomogram Differential Periphery Spike Dose (Gy) Narayana et. al Dose (Gy) 2016 AAPM Spring 70

71 Loose seeds vs strands Loose Seeds Expand with the prostate Migrate to the lung Strands No migration May not track with the prostate 2016 AAPM Spring 71

72 Seed Drop off Stranded preloaded Mick applicator Thin stranded seeds Preloaded cartridge 2016 AAPM Spring 72

73 Seed Drop off Prostate V100 % Prostate D90 Gy Rec wall D1cc Gy Rec wall D2cc Gy Urethra D10 Gy Rapid Strand Mick applicator Thin strand Preloaded cartridge AAPM Spring 73

74 Choice of Isotope 131 Cs 103 Pd 125 I 2016 AAPM Spring 74

75 I125 I-125 vs. Pd Vol + Error Ideal I Vol + Error Error Pd-103 Volume % Volume % Ideal Error Relative Prescription Dose Relative Prescription Dose Narayana et. al 2016 AAPM Spring 75

76 Seed Drop off Prostate V100 % Prostate D90 Gy Rec wall D1cc Gy Rec wall D2cc Gy Urethra D10 Gy Rapid Strand Mick applicator Thin strand Preloaded cartridge AAPM Spring 76

77 Source strength? Prospective Randomized Trial high vs. low mci No sig diff Transition Zone 2mm exp Prostate Narayana et. al Rectum Axial 2016 AAPM Spring 77

78 Calculation Algorithm 2016 AAPM Spring 78

79 GTV Recommendations CTV no posterior expansion PTV=CTV OAR Urethra Rectum Penile bulb 2016 AAPM Spring 79

80 Recommendations Dose clinical decision 131 Cs 115 Gy? ( Gy) 103 Pd 125 Gy 125 I 145 Gy 2016 AAPM Spring 80

81 CTV Recommendations Planning criteria V100> 95% of CTV D90 > 100 % of Rx V150 < 50% of CTV Rectum D2cc < Rx dose Urethra D10 < 150% Rx dose D30< 130% of Rx dose Penile bulb - investigational 2016 AAPM Spring 81

82 Recommendations Dose Reporting DVH for target Primary, D90,V100, V150 Secondary V200, V90,D100 Urethra D10 Secondary: D0.4cc, D30, D5 Rectum D2cc, Secondary: D0.1 cc, V AAPM Spring 82

83 Primary dose parameters for prostate implant that should always be 20% 1. D 90 reported are 20% 20% 20% 20% 2. V D 90 & V D 90 V 100 & V D 90 D 100 V 90 V 100 & V

84 Primary dose parameters for prostate implant that should always be 20% 1. D 90 reported are 20% 20% 20% 20% 2. V D 90 & V D 90 V 100 & V D 90 D 100 V 90 V 100 & V 150 Answer: 4 Reference: AAPM TG137, Nath et. al

85 Intraoperative treatment planning strategies Intraoperative preplanning Interactive planning Dynamic dose calculations Recommendations on Intraoperative planning and evaluation 2016 AAPM Spring 85

86 Pre vs. OR planning Pre 2 procedures Reproducible setup OR Target Volume Stress Time pressure # of seeds ordered 2016 AAPM Spring 86

87 Techniques Intraoperative Creation of plan in OR just before the implant Immediate execution Interactive Stepwise refinement Computerized dose calculations based on image feedback Dynamic Calculations constantly updated using continuous deposited-seed-position feed back 2016 AAPM Spring 87

88 Recommendations Enhanced implant quality Post implant dosimetry Edema Seed migration 2016 AAPM Spring 88

89 Sector anaylsis Research setting 2016 AAPM Spring 89

90 Biophysical Models BED for prostate implants EUD calculations TCP Recommendations for reporting radiobiological response 2016 AAPM Spring 90

91 . BED BED = D[ 1+ D /( α / β )] BED = D( T ) RE( T ) eff eff ln 2 T α eff T p RE( T ) = 1+ D 1 ( ) α ( µ λ) 1 e β 2λT ( µ + λ ) T {1 e 2λ (1 e µ + λ 0 eff eff λt eff )} T eff = T ln[ α D avg T p T 1/ 2 ] 2016 AAPM Spring 91

92 BED for inhomogeneous dose BED 1 = ln( α i ν e i α BED i ) Teff 1 D( T ) ( ) ln 2 = ln( eff RE T ν eff ie αt α p i α BED i ) 2016 AAPM Spring 92

93 Equivalent uniform EBRT dose EUD d = α + ln( β d i γ ν i e α BED ln 2 /( d i ) T p ) 2016 AAPM Spring 93

94 TCP TCP( D) = ( TCD / D) k 50 TCP = exp[ N exp( α BED)] AAPM Spring 94

95 Example Indices Radionuclide 125 I 103 Pd 131 Cs Dose (Gy) BED (Gy) EUD (Gy) TCP (%) T eff (day) Calculated with: α = 0.15 Gy -1, β = 0.05 Gy -2, α/β = 3.0 Gy, T p = 42 days, repair half-life of 0.27 hour, and N 0 = 5x AAPM Spring 95

96 Linear Quadratic Model ERD Nd 1 + N= # fx D = dose/fx α/β = 3Gy d = α β 2016 AAPM Spring 96

97 Linear Quadratic Model ERD NRt 1 + R = dose rate t = time Rt = G α β 2016 AAPM Spring 97

98 Linear Quadratic Model G LDR = 2 µ t 1 ( ) 1 e µ t µ t µ = repair rate const Rt ERD = NRt 1 + G α β 2016 AAPM Spring 98

99 Linear Quadratic Model ERD = R / λ IMP 1 + R ( ) µ + λ α β R = dose rate λ = decay constant µ = repair rate constant α/β = tissue specific parameter 2016 AAPM Spring 99

100 Linear Quadratic Model Beam? d = 2 Gy/fx α/β = 3Gy Brachy R = 4.4 cgy/h λ = 0.693/59.4 d -1 α/β = 3Gy µ =.4 h -1 d = D + α β ERD 1 R ERD = R / λ 1+ eq ( ) µ + λ α β 2016 AAPM Spring 100

101 Recommendations Adequate information BED EUD TCP Other 2016 AAPM Spring 101

102 Recommendation Model parameters should be specified All parameters required to calculate the biodose should be specified Encourage vendors to provide models 2016 AAPM Spring 102

103 What is the cause of most inconsistencies in dose reporting? 20% 1. Identification of source positions 20% 20% 20% 20% 2. Dose calculations 3. Target delineation 4. Timing of the imaging study 5. Type of isotope used 10

104 What is the cause of most inconsistencies in dose reporting? 20% 1. Identification of source positions 20% 20% 20% 20% 2. Dose calculations 3. Target delineation 4. Timing of the imaging study 5. Type of isotope used Answer: 3 Reference: AAPM TG137, Nath et. al