Proton and Heavier-Ion Therapy: Past, Present, and Future Richard A. Amos, FIPEM Associate Professor of Proton Therapy Research Lead for Translational Proton Therapy Physics Department of Medical Physics and Biomedical Engineering University College London [email protected]
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Proton and Heavier-Ion Therapy:Past, Present, and Future
Richard A. Amos, FIPEM
Associate Professor of Proton TherapyResearch Lead for Translational Proton Therapy Physics
Department of Medical Physics and Biomedical EngineeringUniversity College London
• Member of TAE Life Sciences’ Scientific Advisory Board.
Disclosures:
Rationale for particle beam radiotherapy
Brief history of Proton Beam Therapy
1946: Therapeutic use of proton beams first proposed by Robert Wilson1
1Wilson RR. Radiological use of fast protons. Radiology. 1946;47:487-491
1954: First patient treated at the UC Lawrence Berkeley Laboratory (LBL)– Treated the pituitary gland with beams passing entirely through the brain.
– Studied other ions
1957: Proton radiosurgical techniques for brain tumors developed at the Gustaf-Werner Institute, Uppsala, Sweden
– First to use range modulation
1961: Radiosurgery of small intercranial targets at the Harvard Cyclotron Laboratory (HCL)
70s – 80s: Physics facilities worldwide – notably, the Paul Scherrer Institute (PSI) in Switzerland
1990: The world’s first hospital-based high-energy proton beam therapy facility opened at Loma Linda University Medical Center, California
2001: Clinical program moved from HCL to Massachusetts General Hospital, Boston– First to use commercially available proton therapy system
2000s - : Rapid growth in number of proton facilities internationally
Personal US experience in proton beam therapy
2002 – 2005: 2005 – 2013:
•First hospital-based high-energy proton therapy facility in the world.•First patient treated in 1990•18,362 patients treated by end of 2014*
•World-leading cancer treatment and research center.•Proton Therapy Center opened in 2006•First in the USA to treat with PBS in 2008•5,838 patients treated by end of 2014*
*Int J Particle Ther. 2015;2(1):50-54
•250 MeV synchrotron developed in collaboration with Fermi National Accelerator Laboratory•3 gantries (passive scattering)•1 fixed clinical beamline (passive scattering)•1 fixed ocular beamline (passive scattering)•1 fixed experimental beamline (passive scattering)
Zakrzewska P, Pitt M, Amos RA, D’Souza D & Ahmed T.
Application of building information modelling (BIM) in the design, construction, and operations
management of a complex proton beam therapy facility in central London.
Proceedings of PTCOG 54. Int J Particle Ther. 2015;2(1):331-332
Cyclotron Synchrotron
Single-room proton therapy system:
Gantry-mounted 250 MeV synchrocyclotron
Capital cost:• Increased access to proton
therapy for patients• More clinical data
• Increased availability of research facilities
• Detector development• Radiobiological data• ….
Compact/modularity:• Construction and installation• Ease of maintenance
Reduced shielding:• Space and cost
Performance characteristics:• Motion mitigation techniques• Fast adaptive delivery• …..
Patient treatment in seated position?
CT scanner
Beam delivery system: Passive scattering
Beam delivery system: Pencil beam scanning
The PTV problem for proton beams
•Concept of GTV and CTV are the same for protons as they are for photons.
•Individual photon beams can only be geometrically conformed to the target in the plane perpendicular to the beam axis.
•Individual proton beams can be conformed to the target in three dimensions:
•Perpendicular to beam axis – aperture
•Parallel to beam axis – range and SOBP
•PTV concept does not directly apply to proton therapy planning.
•Single PTV is possible with multiple 2D projections
•Beam specific PTV’s necessary for protons
•Concept of treated and irradiated volumes remain consistent for both modalities, however their shape will differ.
Beam-specific distal margins (DM) and proximal margins (PM) giving rise to the concept of a “beam-specific PTV (bsPTV)” for each field.
Lateral margins (LM) for both fields, similar in concept to the standard photon PTV.
“Beam-specific PTV” concept
Advantages of scanned beam delivery
1. Can “paint” any physically possible dose distribution.
2. Uses protons very efficiently as compared to passive scattering in which more than 50% of protons have to be “thrown away”.
3. Generally requires no patient-specific hardware.
4. The neutron background is substantially reduced as a result of points (2) and (3).
5. Allows the implementation of IMRT with protons – termed intensity-modulated proton therapy (IMPT)
Disadvantages of scanned beam delivery
1. The need to overcome “interplay effects” (Bortfeld, 2002)* induced by organ motion.
*Bortfeld T et al. (2002) Effects of intra-fraction motion on IMRT dose delivery: Statistical analysis and simulation. Phys Med Biol 47:2203-2220
Pencil beam scanning
Single Field Optimization (SFO)
Multi-Field Optimization (MFO)
Single Field Uniform Dose (SFUD)
Single Field Integrated Boost (SFIB)
Intensity Modulated Proton Therapy (IMPT)
VMAT IMPT
VMAT technique: 2 full arcs;5mm PTV expansion from CTV.
IMPT technique: Multi-field optimization (MFO) with 2 pencil beam scanning fields;positional uncertainty of 5mm & range uncertainty of 3% to robustly cover CTV.
Proceedings 55th International Conference of the Particle Therapy Co-Operative Group. Int J Particle Ther. Summer 2016, 3(1), 231
Advantages of scanned beam delivery
1. Can “paint” any physically possible dose distribution.
2. Uses protons very efficiently as compared to passive scattering in which more than 50% of protons have to be “thrown away”.
3. Generally requires no patient-specific hardware.
4. The neutron background is substantially reduced as a result of points (2) and (3).
5. Allows the implementation of IMRT with protons – termed intensity-modulated proton therapy (IMPT)
Disadvantages of scanned beam delivery
1. The need to overcome “interplay effects” (Bortfeld, 2002)* induced by organ motion.
*Bortfeld T et al. (2002) Effects of intra-fraction motion on IMRT dose delivery: Statistical analysis and simulation. Phys Med Biol 47:2203-2220
Positional uncertainty and anatomical variation over course of treatment