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Cyberknife®
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- 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 • 6MVLINAC 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 VSI2010 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 • 3Dimage 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 pathsets -> 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 setof 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 • Beamalignment 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 traversalalgorithm->Robot only moves between nodes • Zero dose nodes- safety zone • 30-60 sec image interval • Large translations/rotation-> Treatment auto-pause
- 15. TREATMENT DELIVERY SYSTEMHARDWARE • 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
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- 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 IMAGINGSYSTEM: • 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 SYSTEMSOFTWARE • 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 ACQUISITIONALGORITHM • InTempo™ Adaptive Imaging System
- 26. • Synchrony Respiratorymotion 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.
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