Proton Beam Therapy at Mayo Clinic - AAPM...
Transcript of Proton Beam Therapy at Mayo Clinic - AAPM...
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Proton Beam Therapy at Mayo Clinic
Jon J. Kruse, Ph.D.Mayo Clinic Dept. of Radiation Oncology
Rochester, MN
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History of Proton Therapy at Mayo
• 2002: Decided to consider particle therapy – analysis and education
• 2006: Initial meetings with manufacturers
• 2007: Initial RFP• Protons + Carbon• Scattered + Scanned beams
• 2008: Decision that the future was scanning particle beams
• 2/2010: Permission to Plan• RST + AZ
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History of Proton Therapy at Mayo
• 3/2010: Final RFP, protons only
• 11/2010: Board of Trustees approval
• 12/2010: Selected Hitachi as vendor
• 5/2011: Mayo/Hitachi contract signed
• 9/2011: RST groundbreaking
• 6/2013: Equipment installation began
• 3/2015: First RST Tx rooms accepted
• 6/2015: First Tx in RST
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Mayo Clinic Proton Beam Therapy Centers
• Two identical treatment facilities• Rochester, MN 2015• Phoenix, AZ 2016
• Synchrotron-based
• Four gantries (180 degrees)
• One fixed beam room
• All five nozzles in each facility are identical – optimized for scanning beam only
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Mayo Clinic Proton Beam Therapy Centers
• Design goals• Highest quality treatment available• High efficiency
• ~1200 patients per year, per facility
• Infrastructure for efficient treatment of complex disease sites• Radiographic imaging suites outside
treatment room• Remote anesthesia• Scanning beam nozzles
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Both Centers Adjacent to Photon Clinics
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Facility Layout
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Facility Layout
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Half Gantry Treatment Room
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10/15/2011
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03/09/20125/8/2012
Richard O. Jacobson Building
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05/03/20125/8/2012
Richard O. Jacobson Building
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5/8/2012
Richard O. Jacobson Building05/22/2012
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08/30/201210/08/2012
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11/12/2012
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Rochester Install 9-24-13
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Rochester G3 9-24-13
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Treating Cancer with Scattered Protons
Patient
Tumor
250 MeV Proton Beam
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Patient
Tumor
250 MeV Proton Beam
Treating Cancer with Scattered Protons
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Treating Cancer with Scattered Protons
Patient
Tumor
Reduced Energy Proton Beam
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Treating Cancer with Scattered Protons
Patient
Tumor
Add Double Scatterer
Tradeoff between field size and range
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Treating Cancer with Scattered Protons
Patient
Tumor
Add Field Aperture
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Treating Cancer with Scattered Protons
Patient
Tumor
Custom machined brass part must be changed
between fields
Nozzle must be very close to patient
And brass is expensive, and a potential source
of neutrons
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Treating Cancer with Scattered Protons
Patient
Tumor
Spread out peak with modulator wheel
Must accept maximum modulation width over
entire tumor
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Treating Cancer with Scattered Protons
Patient
Tumor
Match Distal Proton Range with Compensator
Compensator must be machined for each field,
and changed by hand
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250 MeV Proton Beam
Raster-scanned Proton BeamPatient
Tumor
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Treating Cancer with Scanned ProtonsPatient
Tumor
Variable EnergyProton Beam
Y-Scanning Magnets
X-Scanning Magnets
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Active Scanning Proton Beams
Passive Scattering Active Scanning
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Proton Developments at Mayo
• Hitachi has installed a scanning proton treatment room at M.D. Anderson
•Mayo’s facility is scanning beam only
• Redesign of many components• Synchrotron• Gantry • Nozzle• Console/HMI• IGRT
• Efficient treatment of complex cases
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MDA -> Mayo Synchrotron
Smaller Footprint24ft 18.5ft dia.
Fewer ComponentsLower CostLess PowerSimpler Maintenance
Fast Room SwitchSmaller Beam Spot
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Gantry~5M smaller
~60 tons lighterBetter patient
access
Gantry~5M smaller
~60 tons lighterBetter patient
access
MDA
Mayo
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Old Spot
New Spot
New Nozzle: Smaller Spot
10/08/2012 Richard O. Jacobson Building
TumorNormal Organ
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Scanning Nozzle RedesignMD Anderson Nozzle Mayo Nozzle
Gillin et al., Med Phys 37 (2010) p. 154
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New Console
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New HMI
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New HMI
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HMI Design w/ RTT in Omika
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~Monthly Design Meetings in Hitachi
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Mayo-Hitachi Design Teams at Hitachi Works
Mayo-Hitachi Omika Teams at Omika Works
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Facility Infrastructure for Complex Cases
Anesthesia SuiteImaging Rooms
Beam Matched Tx Rooms
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Why Do Active Scanning?
• Dosimetric advantages• No tradeoff between field size/depth• Variable modulation width• Higher resolution distal range
compensation• No hardware in the beam
• Easier planning• IMPT• Adaptive planning without new hardware
• Efficiency• Cycle through Tx fields from control room
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Why Not Do Active Scanning?
• Lateral penumbra• Scattered beams can achieve a very sharp
lateral penumbra, via brass aperture very close to the patient• With scanning beams, in some cases the
lateral penumbra is dominated by spot size in air – not as sharp as a collimated scattered beam
• Interplay• Time dependent dose delivery of a scanning
beam is problematic for moving tumors
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Interplay• Scattered beams irradiate entire target
volume with almost no time dependence• Traditional photon ‘ITV’ approach to
moving targets works fairly well
• Scanning beams scan through the target volume• ~mSec time scale for a single spot• ~100s to 1000s spots per layer• ~Several to dozens of layers per field• ~Seconds to change energy• 1 field may take tens of seconds to ~ 1 min• Some portions of target may be double
painted, others missed
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Interplay Effects
Bert et al., PMB 53 (2008) p. 2253
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Solutions for Moving Targets
• Optimized Planning Parameters
• Gating
• Breath hold
• Repainting
• Tracking
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Optimized Planning: Spot Spacing
Bert et al., IJROBP 73 (2009) p. 1270
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Optimized Planning: Scanning Direction
Static 1 cm parallel 1 cm orthogonal
Johnson et al., in preparation
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Delivery Options: Breath Hold
• Careful patient selection a must
• Feedback tools, coaching
• Reduced treatment time• Faster energy changes• Reduced number of energy levels
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Reducing Number of Energy Levels
Gillin et al., Med Phys 37 (2010) p. 154
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Reducing Number of Energy Levels
• Mini ridge filter introduces modest spatial dependence of beam energy
• Spatial component disappears quickly with phantom scatter
• Shallower dose falloff allows for fewer energy levels
• Decreased treatment time
• Higher dose/spotCournyea et al., AAPM 2013 Tues AM
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Treatment Times with Ridge Filter
• Standard plans: • 67 s (no MRF)• <30 s (w/ MRF)
• Stereotactic plans:• 95.4 s (no MRF)• 47.7 s (min)
• Diminishing gains as MRF thickness increased. MRF Thickness (cm)
0 0.5 1 1.5 2 2.5
Ave
rage
Tim
e/F
ield
(s)
0
20
40
60
80
100 SRσ2
SRσ3 SRσ4
σ2
σ3 σ4
SRσ2
SRσ3 SRσ4
σ2
σ3 σ4
Cournyea et al., AAPM 2013 Tues AM
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Delivery Options: Repainting
• Only a portion of the prescribed dose delivered in a single pass
• Repeat the delivery multiple times per fraction
• Individual hot/cold spots averaged out as number of repaints increases
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Delivery Options: Repainting
1 Scan 10 Scans
Furukawa et al., Med Phys 37 (2010) p. 4874
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IGRT in Mayo Clinic Half Gantry
• Fast Intra-Tx imaging at any gantry/couch position
• Fluoroscopy capable
• Large FOV
• No moving parts –stable imaging isocenter
• 6 DOF matching software
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IGRT in Mayo Clinic Half Gantry
• Limited to two imaging angles
• FOV is 30 cm x 30 cm at isocenter –may not see center of tumor volume for non-isocentric plans
• Not CBCT capable
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Utility of CBCT for Protons
• Bony anatomy is often a poor surrogate for target/critical anatomy
• Fiducials or CT localization required in cases where we expect movement of soft tissues relative to radiographically evident bony anatomy
• Photons: Place target tissue at isocenter, don’t worry about ‘upstream’ bony anatomy
• Protons: ??
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CT Localization for Protons: Pelvis
• Change in position of bony anatomy alters dose distribution
• CT localization may be of limited use
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• Change in position of rib causes minimal disturbance of dose distribution
• CT localization of lung tumors desirable for proton therapy
CT Localization for Protons: Lung
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CBCT for Lung?
•Mayo proton facilities will be scanning beam only
• Treatments of mobile tumors will probably require gating/breath hold
• Free-Breathing CBCT imaging a poor reference for gated/breath held treatment
• Gated/breath held CBCT not impossible, but not easy
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CBCT for Adaptive Protocols
• Proton dose calculation is extremely sensitive to CT number accuracy
• CT number accuracy / consistency not generally a priority in CBCT
• Increased scatter relative to helical CT degrades imaging performance
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Helical/CBCT Phantom Images
Helical CT
CBCT
Images Courtesy of T.J. Whitaker
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CT on Rails
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CT on Rails
• Robot moves patient to imaging isocenter
• CT translates over patient for imaging
• Robot moves patient back to treatment isocenter while CT registration is performed
• Helical CT image quality• Images for adaptive imaging
• Fast image acquisition
• 4D imaging capability