cyberknife at saint raphael’s campus_revb

CYBERKNIFE At Saint Raphael’s Campus

Presented by: Justin Vinci M.S. DABR

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

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

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

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

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)

CYBERKNIFE SYSTEM OVERVIEW Isocentric Beam Treatment

Non-coplanar beam treatment to a single target coordinate

Small spherical lesions

CYBERKNIFE SYSTEM OVERVIEW Conformal Beam Treatment

Non-isocentric “Dose Painting” delivery Multiple target coordinates

CYBERKNIFE EXPERIENCE AT SRC

Installed May 2008 Re-commissioned 2010 with IRIS upgrade

Total Intracranial Patients Treated 466Total Extracranial Patients Treated 272 TOTAL PATIENTS TREATED 738


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)


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

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

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

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)

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

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

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)

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

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)

SYNCHRONYBreathing 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

SYNCHRONY

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

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

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

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

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

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

IRIS

2 banks of 6 tungsten blocks Dodocegonal Beam Penumbra periodicity

30° at 80% 60° at low isodoses (<20%)

BEAM DATA TPR (Coll, d)

BEAM DATA OCR (Coll, d, r)

BEAM DATA OF (Coll, SAD)

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

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

DOSE CALCULATIONS – RAY TRACING Calibration Conditions:

dmax = 15 mm 800 SAD 60 mm Fixed Collimator

),(),(800

),,()/(2

800 SADcollDMDFSTPRSAD

DRcollOCRMUD effeff

SAD

RR SAD

800800

800

SADCollFS

)800,60()15,60(800

800)15,0,60()/(

2

DMTPROCRMUD

11111)/( 2 MUD

800 mm SAD

cGy/MU

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

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 36.25Trigeminal Neuralgia 1 60 60Vestibular Schwannoma 3 7 21Brain mets 3 8 24 1 18 18Meningioma 5 5 25Liver 5 7 35Spine 5 6 30Lung Ray-Trace 3 20 60Lung Monte Carlo 3 18 54

Trigeminal Neuralgia Case

6D Skull Tracking

Spine CaseXsight Spine

Tracking


Proximity Detection Program (PDP)Site

head body

Fixed

Dynamic

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

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°

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

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

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

Planned Dose

Delivered Dose

Legend

Dose falloff near

brainstemPrescription Isodose line

Trigeminal Neuralgia Case

6D Skull Tracking

Planned Dose

Delivered Dose

Legend

Dose falloff near spinal cord verified

Spine CaseXsight Spine

Tracking

REFERENCESToru 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

REFERENCESFurweger 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

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 GuideAccuray Treatment Planning ManualAccuray Treatment Planning ManualTechnical Training for Radiation TherapistsAccuray Technical Training for Physicians: Full Body Course

ACKNOWLEDGEMENTS

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

cyberknife at saint raphael’s campus_revb

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