3. John C. Flickinger, MD
Professor of Radiation Oncology
Physician, UPMC Presbyterian Gamma
Knife and Shadyside Hospital
10/30/2020 3
HISTORY…………….
4. HISTORY
• 23 year female
• ECOG-1
• Sudden onset headache
• Weakness of left upper and lower limb
• Evaluated outside
• Images not available
10/30/2020 4
5. • Right parasaggital and parafalcine T2 hyper
intense
• Flair [ central hypo and peripheral hyper]
• DWI- no restriction
• S/o- infarct
MRI FINDING
10/30/2020 5
6. 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 by10/30/2020 6
POST BLEED AND POST EMBOLIZATION AVM SRS
7. • 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
10/30/2020 7
12. 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
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13. 23rd NOV 2020/BRAINL. Dade Lunsford
ANALYSING ANEURYSMS IN AVM BEOFORE SRS
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.
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23. 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
10/30/2020 23
26. 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
10/30/2020 26
28. • 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
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29. PIE SCORE - POST SRS INJURY EXPRESSION
JOHN C. FLICKINGER/IJROBP/1998
Related to location – Higher PIE is
associated with higher likelihood of injury
10/30/2020
30. 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
10/30/2020 30
33. 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
10/30/2020 33
34. L. Dade Lunsford
IS EMBOLIZATION NEEDED BEFORE RADIOSURGERY IN AVM?
1. The goal was to decrease the volume of the
AVM to make it more effective for radiosurgery
2. However, embolization can be effective only if it
permanently reduces the nidus volume.
3. Reduction in flow from an AVM does not provide
improvement in radiosurgical outcome data
4. 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.
5. Our most recent analysis suggests that
radiosurgical embolization had a negative effect
on AVM obliteration rates.
6. 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
10/30/2020 34
35. 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.
10/30/2020 35
37. 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
10/30/2020 37
38. • Planned for SRS
• Single fraction
• 18Gy/1# marginal dose
Radiation tumor board
10/30/2020 38
41. 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
10/30/2020 41
42. • 1mm slice
• Contrast
• Vertex to neck
• With SRS mask
• CT contrast and ANGIO
Planning CT
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43. Basics of target delineation
10/30/2020 43
• 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
54. • 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
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57. 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
10/30/2020 57
58. • FORMULA
• VOLUME OF PRESCRIPTION ISODOSE/PTV VOLUME
• 10.67/9.97=1.07
• DESIRABLE=1
[Sonja Petkovska
Proceedings of the Second
Conference on Medical Physics and
Biomedical Engineering]
RTOG conformity index
10/30/2020 58
59. • FORMULA
(VOLUME OF PRESCRIPTION ISODOSE IN AREA OF INTEREST)2
PTV VOLUME X VOLUME OF PRESCRIPTION ISODOSE
• Here- 0.88
• IDEAL= > 0.85. AND <1
Michael Torrens,/J Neurosurg (Suppl 2)/2014
Paddick conformity index
10/30/2020 59
60. • FORMULA
• MAXIMUM DOSE/PRESCRIPTION DOSE
• 22.97Gy/18Gy=1.27
• DESIRABLE = 1.1-1.3
HOMOGENITY index
10/30/2020 60
61. • Dose fall off observation is very much needed in this
evaluation under headings
• Gradient index
• Difference between various isodose lines
• e.g between 80% and 60%- ideal- <2mm
• Between 80% and 40%- ideal- < 8mm
• For that reason we have to calculate equivalent
radius
Dose fall off
10/30/2020 61
62. • To evaluate dose gradient we have to find out
difference between radius of various isodose line
• But none is iso spherical
• We have to find out equivalent radius from formula
• First find out the specified isodose volume
• Then calculate the radius
• V=4/3 πr3
• r= (3V/4π)1/3
Equivalent radius
10/30/2020 62
64. • FORMULA
– Difference of equivalent radius of prescription
isodose and equivalent radius of 50% isodose
• 1.37mm-2.0mm=0.63mm
• It should be between 0.3 to 0.9
Gradient index
10/30/2020 64
65. • BETWEEN 80% AND 60%- IDEAL-<2mm
– HERE- 1.61-1.85=0.14mm
• BETWEEN 80% AND 40%- IDEAL- <8mm
– HERE- 1.61-2.19=0.58mm
EORTC-22952-26001
Distance between various isodose lines
10/30/2020 65
73. • MECHANICAL ISOCENTER CHECK
– WINSTON LUTZ TEST
• POINT DOSE VERIFICATION
• TOLERANCE-1MM
Travis R. Denton/JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS/2015
QA part
10/30/2020 73
77. 18th NOV 2020/BRAINL. 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
10/30/2020 77
78. 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
10/30/2020 78
79. 31st OCT 2020/BRAINSYMEON MISS IOS/NEUROSURG FOCUS/2014
FOLLOW UP IN POST SRS AVM
1. Patients were evaluated with MRI at
6, 12, 24, and 36 months after RS,
when possible.
2. In the case of adverse radiation
events, imaging was performed with
increased frequency.
3. After 3 years, if MRI demonstrated
likely obliteration of the AVM nidus,
angiography was recommended.
4. Arteriovenous malformation
obliteration was defined as a lack of
blood flow through the AVM nidus
without signs of early draining vein
on angiography.
5. If residual nidus was visualized, then
patients were typically
recommended to undergo a second
treatment.
10/30/2020 79
81. DOCTORS
• Dr P S Bhattacharya
• Dr C R Kundu
• Dr V K Reddy
• Dr Sajal Kakkar
• Dr Deepak Gupta
PHYSICISTS
• MR A C PRABU
• MR A SRINU
• MR PRASAD
• DR ANIL KUMAR
TECHNOLOGIST TEAM
Acknowledgments
10/30/2020 81
