Cyberknife, Accuray Inc, Sunnyvale, CA PPT on Specifications, Treatment planning,Treatment Delivery, Hardware, Software

1. CYBERKNIFE®
DR.PRAVEEN KUMAR M

3. OVERVIEW
• CYBERKNIFE:
• INTRODUCTION
• SYSTEM OVERVIEW
• TREATMENT: Planning,Delivery
• TREATMENT DELIVERY SYSTEM HARDWARE
• TREATMENT DELIVERY SYSTEM SOFTWARE
• ADAPTIVE IMAGE ACQUISITION ALGORITHMS

4. INTRODUCTION
 John R. Adler-Neurosurgeon at Stanford University-1990
 Accuray Inc.,Sunnyvale,CA
 First patient treated in 1994
 FDA approved- 2001

5. BASIC PRINCIPLE
• 6MV LINAC mounted on a robotic manipulator delivering many
independently targeted (non-isocentric) and non-coplanar treatment
beams with high precision under continual X-ray image guidance

7. SYSTEM OVERVIEW
CYBERKNIFE VSI 2010
Robotic manipulator precision 0.12mm
Overall targeting accuracy(static target) Max ≤0.95mm
Overall targeting accuracy(target with organ motion) Max ≤1.5mm
Beam collimation Variable aperture/fixed circular collimators
Dose-rate 1000MU/min
Image detectors Amorphous silicon flat panel detectors with pixel size
0.4x0.4mm
Dose calculation algorithm Monte-Carlo, Ray tracing
Robot path traversal Nodes selected during planning
Patient positioning system Fully integrated 5-DOF standard treatment couch
Image registration and tracking methods 6D skull, Xsight spine, Fiducial, Synchrony, Xsight
lung

8. Treatment Planning
• 3D image acquisition- Target and OAR delineation
• Transferred to MultiPlan® TPS
• Beam-> Vector->Source point and direction point
• Source point-> Position of LINAC focal spot
• Direction point-> Within target volume
• Each source point is a node
• The complete set of nodes is a path set

10. • Different path sets -> range of non-coplanar beam directions
• Direction points based on beam generation mode-isocentric or non-
isocentric
• Isocentric mode -> Pseudo-isocentres within the patient model
resulting in one candidate beam from each node to each pseudo-
isocentre.
• Circular collimators-> isocentric mode-> spherical dose clouds
• Non-isocentric->multiple beams -> modulated fluence pattern->
independent field size and beam weight

12. • Optimal set of relative weighting factors for the candidate beam set
(i.e the dose delivered per beam) is obtained by inverse planning
• After optimization and approval-> plan transferred to the treatment
delivery system via the database server.

13. TREATMENT DELIVERY
• Beam alignment at time of treatment based on automatic registration
of DRRs generated from 3D patient model with live images acquired
using X-ray imaging system in the treatment room
• Live images and DRR combined and converted into a 3D
transformation by geometric backprojection.
• Image guidance system determines additional translational and
rotational corrections.

14. • Path traversal algorithm->Robot only moves between nodes
• Zero dose nodes- safety zone
• 30-60 sec image interval
• Large translations/rotation-> Treatment auto-pause

15. TREATMENT DELIVERY SYSTEM HARDWARE
• LINAC: X-band cavity magnetron, a standing wave, side-coupled
accelerating waveguide
• No bending magnet, no flattening filter
• Secondary collimation-> 12 fixed circular collimators with diameters
0.5-6cm.
• Iris™ Variable Aperture Collimator- same set of 12 field sizes with a
single variable aperture-> flexibility to apply any field size at any
beam position without the need to swap collimators during treatment

16. IRIS COLLIMATOR

17. • ROBOTIC MANIPULATOR: LINAC mounted on a KR240-2(Series
2000) robotic manipulator (Kuka Roboter GmbH,Augsburg,
Germany)
• Robot allows beam to be directed at unique points in space,i.e no
isocentre, also no coplanar constraints on beam geometry.
• Corrections relayed to the robotic manipulator->fine alignment is
achieved uniquely by adjusting the beam position and orientation
relative to the patient and not the patient relative to the beam

18. • X-Ray IMAGING SYSTEM:
• Two diagnostic X-ray sources in ceiling illuminate two X-ray
detectors by projecting square X-ray fields at 45° from vertical.
• Field size15 × 15 cm.(app)
• The flat panel X-ray detectors, consist of cesium-iodide scintillator
deposited directly on amorphous silicon photodiodes and generate
high-resolution digital images (1,024 × 1,024 pixels with 16-bit
resolution).
• STEREO CAMERA SYSTEM(Synchrony®)

19. TREATMENT DELIVERY SYSTEM SOFTWARE
• 6D SKULL:
• Image registration using high contrast bone information

21. • X-SIGHT SPINE:
• Based on high contrast bone information with image processing filters
• Tumors in spine, near the spine
• ROI: Vertebra of interest+2 adjacent vertebra

22. • XSIGHT LUNG:
• Global alignment-> spine alignment centre->tumor treatment centre.
• Direct tumor tracking is performed by matching image intensity
pattern of the tumor region in the DRRs to the corresponding region
in the treatment x-ray images.
• Image intensity pattern-> T>15mm diameter, located in peripheral,
apex lung regions

23. • FIDUCIAL TRACKING:
• For soft tissue targets not fixed relative to skull/spine eg. Prostate,
Pancreas, Liver, Lung ( Xsight unsuitable)
• Cylindrical gold seeds 0.8-1.2mm diameter, 3-6mm length
• 3-5 markers spaced atleast 1cm apart, 4-7 days for migration to settle
• Image registration based on alignment of these known DRR positions
with the marker locations extracted from treatment X-ray images.

25. ADAPTIVE IMAGE ACQUISITION ALGORITHM
• InTempo™ Adaptive Imaging System

26. • Synchrony Respiratory motion Tracking:
• Real time tracking for tumors that move with respiration
• No need for breath-holding, beam is dynamic throughout treatment
• Tumor position determined at multiple discrete time points by
acquiring orthogonal X-ray images
• A correlation model is generated by fitting the tumor positions at
different phases of breathing cycle to simultaneous external marker
position.

28. HASTA LA VISTA