1. CYBERKNIFE
At Saint Raphael’s Campus
Presented by: Justin Vinci M.S. DABR

2. SUMMARY
 Cyberknife System Overview
 Cyberknife Concept
 Cyberknife Components
 Cyberknife Experience at SRC
 Tracking Modalities
 Collimation
 Fixed Stereotactic Cones
 IRIS Variable aperture
 Treatment Planning
 Optimization
 Dose Calculation
 Physics QA

3. CYBERKNIFE SYSTEM OVERVIEW
 Cyberknife Concept
 Robotic Radiosurgery System
 Non-coplanar beam arrangement
 Theoretically able to achieve a better treatment plan
 Conformality
 Homogeneity
 Critical structure avoidance
 Stereotactic alignment accuracy
 Room based stereotactic kV X-ray imaging system
 < 1 mm targeting accuracy
 Inter and Intrafraction Motion Management
 kV X-rays taken throughout treatment
 Synchrony respiratory motion tracking

4. CYBERKNIFE SYSTEM OVERVIEW
 Cyberknife Components
 Manipulator
 KUKA robot with 6 axes of rotation
 < 0.2 mm Mechanical precision
 Manual control with “teach pendant”
 Programmable robot positions
 Linac
 6 MV
 No flattening filter
 Dose Rate = 800 cGy/Min
 Sealed ion chambers (since 2010)
 Collimation system
 12 Fixed cones or IRIS variable collimator
 Collimator exchange table

5. CYBERKNIFE SYSTEM OVERVIEW
 Cyberknife Components
 Robocouch
 6 degrees of motion
 kV X-ray Target Location System
 Floor mounted flat panel imagers
 Perkin Elmer ASi panels
 1024 x 1024 pixels
 41 x 41 cm physical dimensions
 Ceiling mounted X-ray tubes
 Oil cooled
 2.5 mm Al filtration
 up to 125 kV, 320 mA, 500 ms
 Synchrony Respiratory Tracking System
 Ceiling mounted LED camera array
 Treatment Planning System
 Multi-Plan V3.5

6. CYBERKNIFE SYSTEM OVERVIEW

7. CYBERKNIFE SYSTEM OVERVIEW
 Treatment Paths
 Site dependent
 Set of nodes
 Nodes
 Positions where the robot stops in
robotic workspace
 12 beams per node. (12 angles)
 Head
 1pathhead (130 nodes, 800 SAD)
 Shortpath (69nodes, 800 SAD)
 Trigeminal (117 nodes, 650-750 SAD)
 Body
 1pathbody (117 nodes, 900-1000 SAD)
 ShortpathBody(62 nodes, 900-1000 SAD)
 Prostate path (114 nodes, 900-1000 SAD)

8. CYBERKNIFE SYSTEM OVERVIEW
 Isocentric Beam Treatment
 Non-coplanar beam treatment to a single target coordinate
 Small spherical lesions

9. CYBERKNIFE SYSTEM OVERVIEW
 Conformal Beam Treatment
 Non-isocentric “Dose Painting” delivery
 Multiple target coordinates

10. CYBERKNIFE SYSTEM OVERVIEW

11. CYBERKNIFE EXPERIENCE AT SRC
 Installed May 2008
 Re-commissioned 2010 with IRIS upgrade
Total Intracranial Patients Treated 466
Total Extracranial Patients Treated 272
TOTAL PATIENTS TREATED 738

12. CYBERKNIFE EXPERIENCE AT SRC
 Installed May 2008
 Re-commissioned 2010 with IRIS upgrade
AVM/AVOM 1 Breast Met to Brain 41
Trigeminal Neuralgia 62 Renal Met to Brain 12
Vestibular Schwannoma 39 Colon Met to Brain 8
Meningioma 85 Melanoma Met to Brain 6
Pituitary Adenoma 18 Ovarian Met to Brain 1
Glioblastoma 15 Other Metastatic Tumor to Brain 14
Craniopharyngioma 1 Glomus Tumor 3
Hemangioblastoma 2 Astrocytoma/Glioma/GBM 4
Schwannoma 8 Oligodendroglioma/Medulloblastoma 3
Other/Vas/Func Benign Tumors 1 Other Glial Tumors/Other/Unknown 1
Lung Met to Brain 141 Total Intracranial Patients Treated 466
 Data Intracranial (5/2008 – 2/2013)

13. CYBERKNIFE EXPERIENCE AT SRC
 Data Extracranial
C-spine 8
T-spine 36
L/S-spine 15
Lung 87
Liver 15
Pancreas 5
Head/Neck/ENT 12
Prostate 67
Nasopharynx 1
Other 26
Total Extracranial Patients Treated 272

14. TRACKING MODALITIES
 6D Skull
 Cranial Lesions
 Brain Mets
 Trigeminal Neuralgia
 Benign Meningiomas
 Fiducial Tracking
 Body
 Prostate
 Synchrony
 Fiducial Tracking with
respiratory motion
correction
 Lung, Liver
 X-sight Spine
 S,L,T,C Spine
 Anything < 5 cm
from spine
 X-sight Lung
 Lesions >1.5 cm in
periphery of lung

15. 6D SKULL
 Alignment center is always set to the center of the skull
 Library of 33 pairs of DRRs generated about alignment center
 6D correction determined from comparison between live X-rays and DRRS
 Similarity measure and rigid transformation based on bony anatomy
Fu et al.: A fast, accurate, and automatic 2D-3D image registration for
image-guided cranial radiosurgery, Med. Phys. 35 (5), May 2008

16. 6D SKULL
 6D couch correction is
calculated based on kV X-
rays
 Robocouch couch
automatically moves to the
correct position
 The Cyberknife robot
adjusts beam targeting
during treatment based
intra-fraction images
(limits: 10 mm, 1.5 degrees)

17. FIDUCIAL TRACKING
 Several fiducials surgically implanted in or nearby the tumor
 6D tracking requires at least 3 fiducials
 20 mm separation, 15°, non-co-linear,
 < 5 cm from target
 We typically use 0.8 x 3 mm coupled gold markers
 18 gauge needle
 Fiducials are identified on the CT in MultiPlan and used for
alignment

18. FIDUCIAL TRACKING
 “Blobs” are Identified in live X-ray images and compared to a
library of DRRs from the reference CT using a fiducial based
image registration methodology
 Intensity thresholds set to live images to bring out blobs
 Set of blobs is refined based on expected shape, size, etc.
 Ranked by likelyhood
 Refine by Inferior Superior location
 Blobs with the same I-S position = Same source
 Backward project from 2D to 3D space
 All potential fiducial configuration candidates compared
to the reference fiducial configuration from the CT
 Configurations are ranked and the best fit is used for
alignment
Saw et al.: Implementation of fiducial-based image
registration in the Cyberknife robotic system, Med Dos.
33 (2), 2008

19. FIDUCIAL TRACKING
 3 or more fiducial markers are placed inside the tumor with adequate separation
 Fiducial pattern is recognized by the Cyberknife imaging system. Marker
locations in the Live X-ray images are compared to expected locations. The
robotic couch automatically repositions the patient.
 The Cyberknife makes 6D (X,Y,Z; α,θ,φ) corrections to beam targeting using a
rigid transformation algorithm
 Live X-ray images taken during the treatment allows for semi-continuous
monitoring of intra-fraction motion (when not using Synchrony)

20. FIDUCIAL TRACKING
 Fiducial Tracking Parameters
 Rigid-body distance threshold 1.5 mm
 Fiducial spacing threshold 20.0 mm
 Colinearity Threshold 15.0°
 X-Axis Pairing Tolerance 2.5 mm
 Confidence Threshold 60 %
 Tracking Range 40 mm

21. SYNCHRONY
 Fiducial positions tracked at
discrete points in time
 LED Markers monitored in
real time by a camera system
 Synchrony establishes a
correlation between external
and internal moments
 Robot adjusts beam based on
Synchrony model (translations
only)

22. SYNCHRONY
Breathing Trace
Correlation
Graphs
Coverage of
Breathing
Cycle
Correlation Error
Graph
Nioutsikou et al.: Dosimetric investigation of lung tumor motion compensation with a
robotic respiratory tracking system: An experimental study, Med. Phys. 35 (4), April 2008
Pepin et al.: Correlation and prediction uncertainties in the Cyberknife Synchrony
respiratory tracking system, Med. Phys. 38 (7), July 2011

23. SYNCHRONY

24. XSIGHT SPINE
 Inherent problems aligning spinal anatomy:
 Vertebrae can move independent of one another
 Rigid transformation may be invalid
 Risks associated with surgical fiducial placement
 Xsight spine solution: Deformable registration
technique for spine alignment

25. XSIGHT SPINE
 Image enhancement
 Enhance skeletal structures, suppress soft tissue
 DRR generation (17 pairs of DRRs)
 ROI placement
 Maximum bone information
 Skeletal mesh overlayed on spine
 2D-3D registration
 Spatial transformation base on similarity measure
 Local displacement field calculated at each node (81)
 3D target location calculated
Maucevic et al.: Technical description, phantom accuracy, and clinical feasibility for
fiducial –free frameless real-time image guided spinal radiosurgery, J. Neurosurg
Spine, 5 October 2006
Furweger et al.: Advances in fiducial-free image-guidance for spinal radiosurgery with
Cyberknife – a phantom study, J. Applied Clinical Med. Phys. 12, (2), Spring 2011

26. XSIGHT SPINE
 Difference in spinal anatomy detected between acquired Live X-
ray images and planned DRR images
 6D Treatment Couch corrections (X,Y,Z; α,θ,φ) are applied for
initial setup.
 The Cyberknife robot adjusts beam targeting during treatment
based intra-fraction images

27. XSIGHT LUNG
 Fiducial-less lung tumor tracking
 Tracking based on imaging of
the lesion directly
 Patient Selection
 Target > 15 mm in each axis
 Peripherally located
 Not obstructed by skeletal
structures
 Tracking volume is contoured for
a visual reference
 Synchrony used for respiratory
tracking

28. XSIGHT LUNG
 Fiducial-less lung tumor tracking
 Tracking based on imaging of
the lesion directly
 Patient Selection
 Target > 15 mm in each axis
 Peripherally located
 Not obstructed by skeletal
structures
 Tracking volume is contoured for
a visual reference
 Synchrony used for respiratory
tracking

29. XSIGHT LUNG
 Fiducial-less lung tumor tracking
 Tracking based on imaging of
the lesion directly
 Patient Selection
 Target > 15 mm in each axis
 Peripherally located
 Not obstructed by skeletal
structures
 Tracking volume is contoured for
a visual reference
 Synchrony used for respiratory
tracking

30. XSIGHT LUNG
 Initial patient alignment with Xsight spine
 “go to Xsight Lung” Robocouch moves to align to target
 Visually confirm that the system truly detects lesion
 Build a Synchrony respiratory correlation model
 Begin Treatment
 Cyberknife adjusts beam targeting during treatment based on
Synchrony and intra-fraction images

31. COLLIMATION TYPES
 Stereotactic cone sizes:
5, 7.5, 10, 12.5, 15 20, 25,
30, 35, 40, 50, 60 mm
(defined at 80 cm)
 Variable aperture sizes:
5, 7.5, 10, 12.5, 15, 20, 25,
30, 35, 40, 50, 60 mm
(defined at 80 cm)
Fixed IRIS

32. IRIS
 2 banks of 6 tungsten blocks
 Dodocegonal Beam
 Penumbra periodicity
 30° at 80%
 60° at low isodoses (<20%)

33. IRIS

34. IRIS

35. BEAM DATA
 TPR (Coll, d)

36. BEAM DATA
 OCR (Coll, d, r)

37. BEAM DATA
 OF (Coll, SAD)

38. TREATMENT PLANNING
 MultiPlan Version 3.5
 Import Image Sets for Planning
 CT, MR, PET
 Fuse and create contours
 Define parameters
 Tracking method
 Collimation
 Conformal vs. Isocentric
 Pathset
 Optimization and beam reduction
 Dose Calculation
 Ray trace/Monte Carlo

39. OPTIMIZATION
 MU/beam, MU/node
 Create shells
 VOI Limits
 Set global max doses for structures
 Objective Steps
 Target
 Optimize Minimum Dose
 Optimize Coverage
 Optimize Homogeneity
 Critical Structures
 Optimize Max Dose
 Optimize Mean Dose

40. DOSE CALCULATIONS – RAY TRACING
 Calibration Conditions:
 dmax = 15 mm
 800 SAD
 60 mm Fixed Collimator
),(),(
800
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2
800 SADcollDMDFSTPR
SAD
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
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


SAD
RR SAD
800
800 
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
800
SAD
CollFS
)800,60()15,60(
800
800
)15,0,60()/(
2
DMTPROCRMUD 
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11111)/( 2
MUD
800 mm SAD
cGy/MU

41. DOSE CALCULATIONS – MONTE CARLO
 Ray Trace overpredicts dose to PTV
 Monte Carlo simulates particle transport and energy
deposition in the patient
 Much more accurate dose in presence of heterogeneities
Deng et al.: Commissioning 6 MV photon beams of a stereotactic radiosurgery system for Monte Carlo
treatment planning, Med Phys. 30 (12), December 2003
Wilcox et al.: Comparison of planned dose distributions calculated by monte carlo and ray-trace algorithms
for the treatment of lung tumors with Cyberknife: A preliminary study in 33 patients, Int. J. Radiation
Oncology Biol. Phys. 2009
Wilcox et al.: Stereotactic radiosurgery-radiotherapy: Should Monte Carlo treatment planning be used for all
sites? Practical Radiation Oncology (2011)1, 25

42. EXAMPLE PRESCRIPTION DOSES
Grimm et al.: Dose tolerance limits and dose volume
histogram evaluation for stereotactic body radiotherapy, J.
Applied Clinical Med. Phys. 12, (2), Spring 2011
CRITICAL STRUCTURE TOLERANCE DOSES
Fractions Gy/Fraction Total Dose (Gy)
Prostate 5 7.25 36.25
Trigeminal Neuralgia 1 60 60
Vestibular Schwannoma 3 7 21
Brain mets 3 8 24
1 18 18
Meningioma 5 5 25
Liver 5 7 35
Spine 5 6 30
Lung Ray-Trace 3 20 60
Lung Monte Carlo 3 18 54

43. Trigeminal Neuralgia
Case
6D Skull Tracking

44. Spine Case
Xsight Spine Tracking

45. CYBERKNIFE SYSTEM OVERVIEW
 Proximity Detection Program (PDP)
 Site
head
body
 Fixed
 Dynamic

46. PHYSICS QA
 AQA
 End to End Tests (E2E)
 Head phantom, Ballcube II
 Spine, mini-ballcube
 Synchrony motion phantom
 Xsight Lung motion phantom
 Dose Output, TG-51
 Daily
 Monthly
 Patient Specific QA (PSQA)
 IRIS aperture size check

47. AQA
 Daily QA check of robot
mastering
 Winston Lutz-ish
 Concentric circles
 AP and Lateral beams
targeted to metal sphere
 Aligned with fiducial
tracking
Example EBT3 film Example thresholded images
AQA film
phantom
0°
90°

48. E2E
 End to End test
 Center ball contoured on CT
 70% isodose is centered on the
ball in Multiplan (< 0.1 mm)
 Analysis software provided by
Accuray
 Delta-Man Adjustments
 6D Skull
 Fiducial
 Xsight spine

49. DOSE CALIBRATION AND QA
 TG-51 in water
 Atypical TG-51 conditions
 Determination of kq
 Ref: Toru et al.: Reference
dosimetry condition and
beam quality correction
factor for Cyberknife beam,
Med Phys. 35 (10), October
2008
 Monthly calibration check
 A14 in solid water phantom
 Daily
 Birdcage output check

50. PATIENT SPECIFIC QA
 Patient-Specific QA performed for
nearly every patient
 Patient’s treatment plan (dose rescaled)
delivered to a film-measurement
phantom
 Delivered dose is analyzed in RIT and
compared to the prescribed plan by
physics staff and approved prior to
treatment
 Verification of Cyberknife targeting and
dose delivery accuracy
 Gamma criteria:
5% 1 mm agreement
3% 1 mm in the future with
improved film techniques
Laser-Cut EBT3 gafchromic film
CIRS Anthropomorphic head
phantom with Ballcube II film
insert

51. Planned Dose
Delivered Dose
Legend
Dose falloff
near brainstem
Prescription Isodose line
Trigeminal Neuralgia
Case
6D Skull Tracking

52. Planned Dose
Delivered Dose
Legend
Dose falloff near spinal
cord verified
Spine Case
Xsight Spine Tracking

53. Planned Dose
Delivered Dose
Legend
Dose falloff near spinal
cord verified
Spine Case
Xsight Spine Tracking

54. REFERENCES
Toru et al.: Reference dosimetry condition and beam quality correction factor for
Cyberknife beam, Med Phys. 35 (10), October 2008
Deng et al.: Commissioning 6 MV photon beams of a stereotactic radiosurgery
system for Monte Carlo treatment planning, Med Phys. 30 (12), December 2003
Nioutsikou et al.: Dosimetric investigation of lung tumor motion compensation
with a robotic respiratory tracking system: An experimental study, Med. Phys. 35
(4), April 2008
Sharma et al.: Commissioning and acceptance testing of a Cyberknife linear
accelerator, J. Applied Clinical Med. Phys. 8, (3), Summer 2007
Saw et al.: Implementation of fiducial-based image registration in the
Cyberknife robotic system, Med Dos. 33 (2), 2008
Maucevic et al.: Technical description, phantom accuracy, and clinical feasibility
for fiducial –free frameless real-time image guided spinal radiosurgery, J.
Neurosurg Spine, 5 October 2006

55. REFERENCES
Furweger et al.: Advances in fiducial-free image-guidance for spinal radiosurgery
with Cyberknife – a phantom study, J. Applied Clinical Med. Phys. 12, (2), Spring
2011
Grimm et al.: Dose tolerance limits and dose volume histogram evaluation for
stereotactic body radiotherapy, J. Applied Clinical Med. Phys. 12, (2), Spring 2011
Pepin et al.: Correlation and prediction uncertainties in the Cyberknife
Synchrony respiratory tracking system, Med. Phys. 38 (7), July 2011
Wilcox et al.: Comparison of planned dose distributions calculated by monte
carlo and ray-trace algorithms for the treatment of lung tumors with Cyberknife:
A preliminary study in 33 patients, Int. J. Radiation Oncology Biol. Phys. 2009
Wilcox et al.: Stereotactic radiosurgery-radiotherapy: Should Monte Carlo
treatment planning be used for all sites? Practical Radiation Oncology (2011)1, 25
Chang et al.: An analysis of the accuracy of the CyberKnife: A robotic frameless
stereotactic radiosurgical system, Neurosurgery 52(1)2003

56. REFERENCES
Fu et al.: A fast, accurate, and automatic 2D-3D image registration for image-
guided cranial radiosurgery, Med. Phys. 35 (5), May 2008
Fu et al.: Fiducial-free Lung Tumor Tracking for Cyberknife Radiosurgery, I.J.
Radiation Oncology Biol. Phys. 72 (1), 2979, 2008
Adler, J.R., Chang, S.D., Murphy, M.J., Doty, J., Geis, P., & Hancock,
S.L. (1997). The CyberKnife: A frameless robotic system for radiosurgery.
Stereotactic and Functional Neurosurgery, 69(1–4 Pt. 2),
124–128.
Additional Information and Images taken from:
Accuray Physics Essentials Guide
Accuray Treatment Planning Manual
Accuray Treatment Planning Manual
Technical Training for Radiation Therapists
Accuray Technical Training for Physicians: Full Body Course

57. ACKNOWLEDGEMENTS
Thanks to Saint Raphael’s Cyberknife Team – Physics,
Dosimetry, and Radiation Therapy staff, and the
Smilow Physics group for having me.