Radiosurgery: IndicationsRadiosurgery: Indications
Intra-cranial: Intra-cranial: 1.1.Brain metsBrain mets2.2.MeningiomaMeningioma3.3.Acaustic schwannomaAcaustic schwannoma4.4.AVMsAVMs5.5.TNTN
Extra-cranial: Extra-cranial: 1.1.Lung: Primary & metsLung: Primary & mets2.2.Liver: HCC & metsLiver: HCC & mets3.3.Inoperable pancreasInoperable pancreas4.4.ProstateProstate5.5.Bone metastasisBone metastasis
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Robotic RadiosurgeryHighly precise RT delivery system - Respiratory tracking - Fiducial based tracking system - Intra-fraction motion correction - Uncomparable dose distribution - X-ray based image verificationHypofractionated RT - High dose short course RT - Higher BED delivered to target
Ideal for moving targets
- Radiation source is mounted on a precisely controlled industrial robot.
- Image guidance system(continuous tracking system)
- Eliminates the need of gating techniques and restrictive head frames
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GTV= Gross tumour volumeCTV= Clinical target volume
IM= Internal marginSM= Setup margin
PTV= Planning target volume
PTV= IM+SM
ICRU 62
CyberKnife in liver tumour: NO IM & SM<1 mm
In Liver, PTV = GTV/ CTV+ 0-1 mm marginIn Liver, PTV = GTV/ CTV+ 0-1 mm margin Copyright @ www.radiosurgery-india.com
Robot is capable of delivering
radiation from different
100 nodes, with each node is
capable of giving a max 12
different beams.
Usage of these nodes depends
on the treatment room constraints
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Table consists of 12 fixed cones and housings of ‘Fixed’ and ‘Iris’ Collimator
Collimator sizes(mm): 5, 7.5, 10, 12.5, 15, 20, 25, 30, 35, 40, 50, 60
Laser Sensor
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Cyberknife treatment delivery is based on the following
tracking systems 6D_ Skull tracking system Fiducials tracking system Synchrony tracking system X_sight Spine tracking system X_sight Lung tracking system
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6D_ Skull tracking system:used for intra-cranial lesions up to C2Bony anatomy of the skull is used as
reference for tracking
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• Fiducial tracking system: used for soft tissues, where gold fiducials can be implanted. Minimum of 3 nos. to be implanted
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Respiratory-induced motion of tumors causes significant targeting uncertainty
Lung, liver, pancreas, Prostate, kidney
Traditional radiation therapy margins are not optimized for high-dose radiosurgery
Two features to form the basis for accuracy
Fiducials, implanted prior to treatment
Optical markers on a special patient vest
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Prior to treatment start: creation of dynamic correlation model
Markers are monitored in real time by a camera system
Imaging system takes positions of fiducials at discrete points of time
Prior to treatment start: creation of dynamic correlation model
Markers are monitored in real time by a camera system
Imaging system takes positions of fiducials at discrete points of time
time
disp
lace
men
t
disp
lace
men
t
time
This process repeats throughout the treatment, updating and correcting beam delivery based upon the patient’s current breathing pattern
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The mechanical accuracy of the system is 0.12 mm , according to Accuray
The system maintains sub-millimeter tracking accuracy, if the patient positions are within the following limitsLeft / Right (Lat) 10 mmAnt/ Post (Ver) 10 mmSup/ Inf ( Long) 10 mmRoll (Left / Right) 10
Pitch (Head Up / Down) 10
Yaw ( C.W / C.C.W) 30
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‘‘CyberKnife is an extension of Gamma-KnifeCyberKnife is an extension of Gamma-Knife’’
- Principles of ‘field arrangement’
- Dose distribution pattern
- Multiple isocentre
-Treatment principles
- Treatment delivery accuracy similar
- Delivered dose in single fractions
- Intra-cranial indications
CK & GK: SimilarityCK & GK: Similarity
‘CyberKnife treatment is as good as Gamma-Knife’ Dr Bernadt Wowra Copyright @ www.radiosurgery-india.com
Cyberknife Vs Gamma-Knife: Cyberknife Vs Gamma-Knife: DissimilarityDissimilarityGK CK Comments
Immobilization device
Rigid frame Orfit CK has favorable orfit
RT source Co60 6MV LA GK need to replace sources every 5/6 yrs
Planning No complex planning
Inverse planning Favorable dosimetry in CK
Planning method
Simple Complex Even neurosurgeons can plan in GK
Isodose pres Usually 50% Usually 80-95% GK: more dose heterogeniety
Fractions Single May treat multiple fraction
Radiobiology favorable in CK
Tumour size Only smaller lesions can be treated
Larger lesions also can be treated in fractionated schedule
Increased indications with CK
Energy source Radiation Electricity GK can work with less electricity
Verification Not possible Possible Even Intra-fraction movement can be corrected
Indications Only brain lesions Extra & intra cranial
CK more economical
SummarySummary
CyberKnife Radiosurgery is an ideal machine for both cranial & extracranial radiosurgery
Appropriate patient selection is the most important factor
CyberKnife is safe and patient friendly radiotherapy delivery system
Short course, precise, high dose RT may be beneficial in few indications However, the indications are limited and long-term data of most of the extra-cranial indication is still to be available
With more clinical data, indications are expanding
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