WHY STEREOTATXY IN CRANIAL AVM / DR KANHU CHARAN PATRO

1. Why SRS for cranial AVM?
12/17/2023 1
Dr Kanhu Charan Patro
MD,DNB(Radiation Oncology),MBA,FICRO,FAROI(USA),PDCR,CEPC
HOD, Radiation Oncology
ISRo- Institute of Stereotactic Radiation oncology
Mahatma Gandhi Cancer Hospital & Research Institute, Visakhapatnam
drkcpatro@gmail.com /M- +91-9160470564/ www.drkanhupatro.com

2. 12/17/2023 2
What is AVM?

3. 12/17/2023 3
Location

4. Bleeding in the brain.
Reduced oxygen to brain tissue
Aneurysm formation
Brain damage
Stroke like pic due to hemmorage
12/17/2023 4
Why clinically important?

5. Treatment options
12/17/2023 5

6. • Observation
• Surgery
• Embolization
• SRS
• Combination
12/17/2023 6

7. Treatment Algorithm
12/17/2023 7

8. 12/17/2023 8

9. 12/17/2023 9
Grading of AVM

10. 12/17/2023 10

11. Why SRS?
• Noninvasive
• No incision
• Obliteration rates are comparable
• Eloquent areas
• Deep Location
• Residual after embolization
• Among the minimally invasive therapies for
nonsurgical AVMs.
• SRS alone can cure most of AVMs smaller than
2.5 cm in diameter or 10 cm3 in volume.
12/17/2023 11

12. Eloquent areas for AVM surgery
12/17/2023 12

13. 12/17/2023 13

14. RADIOLOGY
12/17/2023 14

15. DSA THE GOLD STANDARD
12/17/2023 15

16. CT/MR ANGIO
12/17/2023 16

17. 1. Number of AVM
2. Location of AVM
1. Eloquent vs. non eloquent
2. Parenchymal vs. dural
3. Size of AVM
4. Feeding artery and number
5. Draining vein and number
6. Associated aneurysm and location
7. Any clot
8. Size of nidus
9. Blood degradation product
10. Edema
11. Thrombosis
12. Venous ectasia or stenosis
13. Superficial or deep draining vein
14. Aneurysm and clips
15. Compact nidus vs. diffuse nidus
16. Early draining veins vs. not early
CHECKLIST IN AVM RADIOLOGY FINDING
12/17/2023 17

18. Mechanism of obliteration
12/17/2023 18

19. Timothy H. Ung/frontiers in human neuroscience/2022 12/17/2023 19

20. 12/17/2023 20

21. 12/17/2023 21

22. Dose SRS
12/17/2023 22

23. 12/17/2023 23

24. • Nidus volume-5.8cc
• K index formula- dose x cube root AVM volume
• K index usually kept at 27
• dose = 27/ cube root AVM volume
• =27/ cube root of 5.8
• =27/1.8
• =15Gy
The dose selection by K INDEX
12/17/2023 24

25. 12/17/2023 25

26. L. Dade Lunsford
OBLITERATION OF AVM-DOSE RESPONSE RELATIONSHIP
1. Using dosages at the
margin of 20 Gy
(median),we
documented AVM
obliteration in 73% of
those patients studied
by angiography and in
86% of those patients
studied by MRI alone.
2. Furthermore, we
believe that there is
approximately a 95%
accuracy that MRI-
detected obliteration
will be confirmed by
follow-up angiography.
12/17/2023 26

27. • The goal was to decrease the volume of the AVM to make it more
effective for radiosurgery
• However, embolization can be effective only if it permanently
reduces the nidus volume.
• Reduction in flow from an AVM does not provide improvement in
radiosurgical outcome data
• In a study of 47 patients who had radiosurgery and embolization
in comparison to 47 matched patients who were treated with
radiosurgery alone, nidus obliteration was achieved in 47% of the
embolization group but in 70% of the radiosurgery group.
• Our most recent analysis suggests that radiosurgical embolization
had a negative effect on AVM obliteration rates.
• Others have reported that up to 30% of patients who had AVM
embolization subsequently had an increase in the nidus volume
when a subsequent angiogram was performed at the time of
radiosurgical targeting.
• Do not embolize before radiation treatment since it can decrease
the apparent size of the AVM and can lead to inadequate
treatment because of geographic miss
12/17/2023 27
Is
embolization
needed
before
radiosurgery
in AVM?

28. 1. For those patients who have previously undergone embolization in an attempt to reduce flow or to
achieve volumetric reduction of the AVM, or for those who have had intracranial surgery or
hematoma evacuation, radiosurgery may be used as an adjuvant strategy rather than a primary
management.
2. We often perform radiosurgery once the patient has achieved stable neurologic improvement but
almost never within the first month after an ictal event, such as a bleed or embolization.
3. For patients who have had intracranial hemorrhages, we prefer to wait between 1 and 3 months
to see if there will be a regional clot reabsorption.
4. The AVM nidus should not be compressed by clot at the time of the radiosurgery.
5. Failure of radiosurgery can be traced in some ways to inadequate planning, inadequate
recognition of the 3D geometry of the AVM, reappearance of a component of the AVM previously
embolized, or reappearance of a component of the AVM that was previously compressed by
intracerebral hematoma.
12/17/2023 28
POST BLEED AND POST EMBOLIZATION AVM SRS

29. The obliteration rate of AVM after SRS
12/17/2023 29

30. Timothy H. Ung/frontiers in
human neuroscience/2022
12/17/2023 30

31. 12/17/2023 31

32. Case 1- parietal
12/17/2023 32

33. Case 2- posterior frontal
12/17/2023 33

34. Case 3 Lt. insular
12/17/2023 34

35. Case 4- Intraventricular
12/17/2023 35

36. 12/17/2023 36
Case 5

37. Pre SRS DSA
12/17/2023 37

38. 12/17/2023 38

39. Post SRS DSA
12/17/2023 39

40. 12/17/2023 40
Case 6

41. 12/17/2023 41

42. 12/17/2023 42
Case 7

43. Case 8- corpus callaosum
12/17/2023 43

44. 12/17/2023 44
Case 9 post. ventricular

45. 12/17/2023 45
Case 10- posterior frontal

46. 12/17/2023 46
Case 11- frontal

47. 47
12/17/2023
Staged SRS for
larger volume
Volume staged
Dose staged

48. Volume staged SRS
12/17/2023 48

49. 12/17/2023 49

50. 1. Patients who have a proximal unsecured aneurysm have an increased risk of post-
radiosurgical hemorrhage.
2. If the aneurysm is immediately proximal to the AVM, it will likely close as the AVM
obliterates.
3. We have not found that intranidal aneurysms increase the risk of bleeding during
the latency interval.
4. For those patients with aneurysms more than one arterial branch proximal to their
AVM, we believe that the aneurysm requires a different management algorithm that
should be determined based on those characteristics that guide whether surgery or
endovascular is the best management.
5. Such aneurysms generally do not go away at the time that the AVM is obliterated.
ANALYSING ANEURYSMS IN AVM BEOFORE SRS
50

51. BRAIN NECROSIS
51

52. PIE SCORE - POST SRS INJURY EXPRESSION
JOHN C. FLICKINGER/IJROBP/1998
Related to location – Higher PIE is
associated with higher likelihood of injury
12/17/2023

53. FLICKINGER CURVE -12Gy VOL. BASED ON LOCATION
JOHN C. FLICKINGER/IJROBP/2000
Symptomatic post SRS injury according to
location & 12-Gy-Volume for AVM in temporal,
parietal, cerebellar, corpus callosum, medulla,
and basal ganglia locations.
Symptomatic post SRS injury according to
location & 12-Gy-Volume for AVM in frontal,
intraventricular, cerebellar, occipital, thalamic,
and pons/midbrain locations
CHANCES OF NECROSIS
12/17/2023 53

54. RESPONSE EVALUATION
54
Six monthly follow up with MRA.
You can avoid more invasive DSA.
Radiation changes are also depicted by MRI.
Do confirmatory DSA if obliteration seen on MRI

55. DEFINITION
1. Stereotactic radiosurgery (SRS) is a non-
surgical radiation therapy used to treat
functional abnormalities and small tumors
of the brain.
2. It can deliver precisely-targeted radiation
in fewer high-dose treatments than
traditional therapy, which can help
preserve healthy tissue
12/17/2023 55

56. WHAT IS IT?
• Stereotactic (guiding) devices capable of
pinpointing targets within the brain.
• High dose of radiation
• Exact localization
• Imaging during radiation
12/17/2023 56

57. WHY WORD SURGERY?
12/17/2023 57

58. The spectrum
• SRS
– Smaller lesion usually less than 3 cm.
– Single fraction
• FRACTIONATED SRS
– Relatively larger tumor
– 1 to 5 fractions
• SRT
– Larger tumor usually more than 3 cm
– Close to vital structures
58

59. ADVANTAGES
• Decreased length of stay
• Decreased cost
• Rapid return to full employment
• Lower immediate post treatment morbidity
and mortality
12/17/2023 59

60. INVENTION-LARS LEKSELL
12/17/2023 60

61. Legend - AVM SRS history
12/17/2023 61

62. John C. Flickinger, MD
Professor of Radiation Oncology
Physician, UPMC Presbyterian Gamma
Knife and Shadyside Hospital
12/17/2023 62
HISTORY…………….

63. FRAME BASED
12/17/2023 63

64. FRAMELESS
12/17/2023 64

65. MACHINES
• GAMMA KNIFE
• PROTON RADIOSURGERY
• X- KNIFE
– CYBERKNIFE
– ELEKETA
– VARIAN
12/17/2023 65

66. GAMMA KNIFE
12/17/2023 66

67. Linear accelearator- X Knife
12/17/2023 67

68. X-KNIFE
• Treatment by high energy X rays
• Mostly non-invasive
• Equally effective
• Cheaper
• Availability
12/17/2023 68

69. Requirements?
• Cones- for subcentemeter tumors
• Agility head-more conformity for smaller
tumors
• Fraxion -non- invasive, frameless
comfortable mask
• Cone beam CT- online CT based correction
• Hexapod- extra degree of rotational
correction
12/17/2023 69

70. WHAT are the requirements?
• Micro MLC/cone
• Planning system
• Imaging
• Immobilization
• Respiratory Motion management system
• QA accessories
• CBCT
• Protocols
70

71. micro MLC
71

72. CONE
72

73. • CT
• MRI
• DSA
IMAGING
73

74. Planning system
74

75. Verification system
75

76. Hexapod
76

77. • MECHANICAL ISOCENTER CHECK
– WINSTON LUTZ TEST
• POINT DOSE VERIFICATION
• TOLERANCE-1MM
Travis R. Denton/JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS/2015
QUALITY ASSURANCE PART
77

78. SUITABLE CASES
• Any lesion benign or malignant less than 3cm
• Eloquent areas
12/17/2023 78

79. The duo
• High dose
• Strict immobilization
79

80. • Massive vascular damage causes indirect tumor death-it is endothelial cell
inflammation and apoptosis via the sphingomyelin pathway causing
subsequent microvascular dysfunction that are the triggers for tumor cell
death
• 4 r of radiobiology in different manner
• No Repair after ablative dose
• Treatment is for short period no chance of Repopulation
• No Reoxygenation of hypoxic cells due to massive vascular destruction by
SRS/SBRT
• Redistribution dose not happen as more cells die because of massive cell
death
• Massive immunogenic reaction
• Abscopal effect
RADIOBIOLOGY BEHIND STEROTAXY
80

81. 81
Guidelines we follow?

82. 82

83. 83

84. HISTORY
• 23 year female
• ECOG-1
• Sudden onset headache
• Weakness of left upper and lower limb
• Evaluated outside
• Images not available
12/17/2023 84

85. • Right parasaggital and parafalcine T2 hyper
intense
• Flair [ central hypo and peripheral hyper]
• DWI- no restriction
• S/o- infarct
MRI FINDING
12/17/2023 85

86. • Location-Right high posterior parietal vascular malformation
• Malformation size 3.4cm x 2.9cm x3.4cm
• Nidus size 1.6cm x 1.4cm
• Arterial supply- Pericollasal and collasomarginal branches of
right anterior cerebral artery
• Venous drainage- cortical veins along the right posterior
parietal region
• Hemoglobin degradation products with gliosis and
enchephalomalacia.
MRI and MR ANGIO after 3 months
12/17/2023 86

87. MR ANGIO after 3 months
12/17/2023 87

88. T1/T2- after 3 months
12/17/2023 88

89. AVM RIGHT PARIETAL LOBE
Final Diagnosis
12/17/2023 89

90. • NEUROSURGEON
• INTERVENTIONAL RADIOLOGIST
• RADIATION ONCOLOGIST
MULTI DISCIPLINARY DISCUSSION
12/17/2023 90

91. Tumor board decision
• After group discussion with neurosurgeon,
radiation oncologist and interventional
radiologist, board decided to plan for
stereotactic radiotherapy
• Patient was explained about complications
and outcome of the procedure
12/17/2023 91

92. STEREOTACTIC RADIOSURGERY
PLAN of treatment
12/17/2023 92

93. Patient discussion
• Discussed about the procedure
• Discussed about imaging and follow up
• Discussed about obliteration rate
• Discussed about the complications
• Discussed about the avoidance of pregnancy
for 3 years
• Discussed about the repeat SRS
• Discussed about post radiotherapy raised ICT
12/17/2023 93

94. • OBLITERATION RATE
• REBLEED
• SYMPTOMATIC RADIONECROSIS
Patient discussion
12/17/2023 94

95. • How it works?
• Is emobilization needed?
• What is obliteration rate?
• What is rebleed incidence?
• How will be the follow up
• Can I conceive?
• Complication and rates?
Answering patient specific questions
12/17/2023 95

96. 12/17/2023 96

97. Daniel Tonetti/J Neurosurg (Suppl 2)/2014
PREGNANCY AFTER AVM SRS
After SRS, pregnancy during the latency period
before AVM obliteration may be a risk factor for
AVM hemorrhage. Hence defer pregnancy till
obliteration has been achieved
Doctor, my SRS treatment was over . Can
I plan for a baby?
1. Hemorrhage during the
latency interval occurred at
an annual rate of 2.5% for
nonpregnant women and
11.1% for pregnant women.
2. The data suggest that
pregnancy might be a risk
factor for AVM hemorrhage
during the interval between
SRS and AVM obliteration
12/17/2023 97

98. Daniel Tonetti/J Neurosurg (Suppl 2)/2014
AVM SRS complications
1.Another malignancy
2.Bleed
3.Convulsion
4.Deficit
5.Raised ICT
12/17/2023 98

99. L. Dade Lunsford
CYST FORMATION IN POST RADIOSURGERY AVM
1. Risk of late cyst formation at the site of the obliterated nidus, and the long-
term risk for radiation-induced tumor.
2. Cyst formation after AVM radiosurgery was first reported by Japanese
investigators who had sent patients to receive Gamma Knife radiosurgery
in Sweden in the early years of radiosurgery.
3. Cyst formation has also been reported in other long-term follow-up studies.
4. In our 20 years of experience, we have detected 16 patients (1.7%) with
delayed cyst formation.
5. We also observed that patients who developed delayed cyst formation
were more likely to have had prior bleeds.
6. This raises the intriguing possibility that residual iron deposition in the brain
tissue may serve as a radiation sensitizer that could potentiate the effects
of radiosurgery on a long-term basis.
7. Such cysts have been managed with observation, simple drainage, cyst
shunting, or surgical fenestration.
8. Patients with perioperative T2 signal change without additional neurologic
problems do not require additional treatment
12/17/2023 99

100. • Planned for SRS
• Single fraction
• 18Gy/1# marginal dose
Radiation tumor board
12/17/2023 100

101. Simulation
12/17/2023 101

102. MRI protocol
• T1/T2/FLAIR sequence- Usual sequence
• MR ANGIO
• 3D FSPGR contrast- Normal anatomy
• 3D DSA
• 512x 512 matrix
• 1mm slice
• No gap
• No tilt
• Neutral neck
• FOV should include body contour nose,
eye and skull
12/17/2023 102

103. • 1mm slice
• Contrast
• Vertex to neck
• With SRS mask
• CT contrast and ANGIO
Planning CT
12/17/2023 103

104. Basics of target delineation
12/17/2023 104
• Delineate the nidus
• Do not include the vessels
• Exclude the hemorrhagic degradation product if any
• Take the help of interventional radiologist and
neurosurgeon
• If post emobilization take the residual nidus only

105. • Nidus is delineated
• VOLUME- 5.835cc
• Multiplanar evaluation
Target delineation nidus
12/17/2023 105

106. Nidus
12/17/2023 106

107. Image fusion
12/17/2023 107

108. Nidus MULTIPLANNAR
12/17/2023 108

109. PTV
1. 1mm
2. VOLUME-9.97CC
12/17/2023 109

110. Multiplanar nidus and PTV
12/17/2023 110

111. • VOLUME- 12.987CC
Brain-PTV
12/17/2023 111

112. Smooth your contour
12/17/2023 112

113. OAR DELINEATION
OAR delineation
12/17/2023 113

114. • VMAT
• D-ARC
• 3DCRT
• IMRT
Planning
12/17/2023 114

115. • Nidus volume-5.8cc
• K index formula- dose x cube root AVM volume
• K index usually kept at 27
• dose = 27/ cube root AVM volume
• =27/ cube root of 5.8
• =27/1.8
• =15Gy
The dose selection by K INDEX
12/17/2023 115

116. The beam arrangement
12/17/2023 116

117. SL NO PARAMETER VALUE
1 D MAX 22.97Gy
2 D95% 18.29Gy
3 D100% 16Gy
4 V95% 99.7%
5 V18 Gy[V100%] 97%
6 V19.8Gy[110%] 73.58% (7.322cc)
7 V21.60Gy[120%] 4.4% (0.438cc)
8 V130% 0%
1. Prescription Isodose level is usually not 100% PD covering 100% PTV
2. Often 95% PD covering 95% PTV or higher
3. Or 100% PD covering 95% PTV or higher.
Michael Torrens,/J Neurosurg (Suppl 2)/2014
PTV coverage index
12/17/2023 117

118. Isodose line
COLOUR ISODOSE LINE
Green PTV
Red 100%
orange 80%
Yellow 60%
pink 50%
Blue 40%
ISODOSE LINES
12/17/2023 118

119. 12/17/2023 119

120. SL NO ORGAN DESIRABLE ACHIEVED
1 RT. EYE MAX <22.5Gy <1Gy
2 LT. EYE MAX <22.5Gy <1Gy
3 RT. OPTIC NERVE MAX <22.5Gy <1Gy
4 LT. OPTIC NERVE MAX <22.5Gy <1Gy
5 OPTIC CHIASM MAX <22.5Gy 1.25Gy
8 BRAIN STEM MAX 23-31Gy 1.6Gy
9 RT. COCHLEA MEAN <25Gy <1Gy
10 LT. COCHLEA MEAN <25Gy <1Gy
GG HANNA/CLINICAL ONCOLOGY/2016
OAR coverage
12/17/2023 120

121. • MECHANICAL ISOCENTER CHECK
– WINSTON LUTZ TEST
• POINT DOSE VERIFICATION
• TOLERANCE-1MM
Travis R. Denton/JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS/2015
QA part
12/17/2023 121

122. • CBCT CORRECTIONS
Set-up verification
12/17/2023 122

123. 18th NOV 2020/BRAIN
L. Dade Lunsford
PERI PROCEDURE MEDICATION DURING AVM SRS
1.Patients with lobar AVMs were placed
prophylactically on anticonvulsants for a period of 2
to 4 weeks around the time of the procedure.
2.This has reduced the risk of a perioperative seizure
event from as high as 5% in year 1 of our 20-year
experience to a risk of 1% at the current time
3.At the conclusion of the procedure, patients receive
20 to 40 mg of methylprednisolone
Steroids
12/17/2023 123

124. PREMEDICATION
• Tab. Dexamethasone 8mg thrice daily starting day
before
• Tab. Ondansetron 8mg thrice daily starting day
before
• Tab. Pan 40 once daily starting day before
• Antiepileptic for 6-8 weeks
• Diabetes care if
• Taper the steroid over 3 weeks
• Anti emetics
• PPI
Peri medication
12/17/2023 124

125. PATIENT IS DOING WELL
2 YEAR FOLLOW UP
12/17/2023 125

126. SUMMARY
• Multidisciplinary decision
• Deep location
• Eloquent location
• Post embolization residual
• Noninvasive
• Single day procedure of 20 mins
• Established technique
12/17/2023 126