Highlights
- •Reducing penumbra of Scanning proton therapy by using multi-leaf collimator (MLC) is investigated.
- •The increasing of neutron dose due to proton interaction with MLC is studied.
- •Neutron dose in scanning with MLC is lower than wobbling therapy, but higher than scanning without MLC.
Abstract
Purpose
Scanning proton therapy has dosimetric advantage over passive treatment, but has a
large penumbra in low-energy region. This study investigates the penumbra reduction
when multi-leaf collimators (MLCs) are used for line scanning proton beams and secondary
neutron production from MLCs.
Methods
Scanning beam plans with and without MLC shaping were devised. Line scanning proton
plan of 36 energy layers between 71.2 and 155.2 MeV was generated. The MLCs were shaped
according to the cross-sectional target shape for each energy layer. The two-dimensional
doses were measured through an ion-chamber array, depending on the presence of MLC
field, and Monte Carlo (MC) simulations were performed. The plan, measurement, and
MC data, with and without MLC, were compared at each depth. The secondary neutron
dose was simulated with MC. Ambient neutron dose equivalents were computed for the
line scanning with 10 × 10 × 5 cm3 volume and maximum proton energy of 150 MeV, with and without MLCs, at lateral distances
of 25–200 cm from the isocenter. The neutron dose for a wobbling plan with 10 × 10 × 5 cm3 volume was also evaluated.
Results
The lateral penumbra width using MLC was reduced by 23.2% on average, up to a maximum
of 32.2%, over the four depths evaluated. The ambient neutron dose equivalent was
18.52% of that of the wobbling beam but was 353.1% larger than the scanning open field.
Conclusions
MLC field shaping with line scanning reduced the lateral penumbra and should be effective
in sparing normal tissue. However, it is important to investigate the increase in
neutron dose.
Keywords
To read this article in full you will need to make a payment
Purchase one-time access:
Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online accessOne-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:
Subscribe to Physica Medica: European Journal of Medical PhysicsAlready a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
References
- Spot scanning system for proton radiotherapy.Med Phys. 1980; 7: 365-369
- The 200-MeV proton therapy project at the Paul Scherrer Institute: conceptual design and practical realization.Med Phys. 1995; 22: 37-53
- The PSI gantry 2: a second generation proton scanning gantry.Z Med Phys. 2004; 14: 25-34
- Treatment planning and verification of proton therapy using spot scanning: initial experiences.Med Phys. 2004; 31: 3150-3157
- Commissioning of the discrete spot scanning proton beam delivery system at the University of Texas M.D. Anderson Cancer Center, Proton Therapy Center, Houston.Med Phys. 2010; 37: 154-163
- Preliminary analysis for integration of spot-scanning proton beam therapy and real-time imaging and gating.Phys Med. 2014; 30: 555-558
- Proton microbeam radiotherapy with scanned pencil-beams – Monte Carlo simulations.Phys Med. 2015; 31: 621-626
- Characterization of commercial scintillation detector for 2-D dosimetry in scanned proton and carbon ion beams.Phys Med. 2017; 34: 48-54
- Impact of physiological breating motion for breast cancer radiotherapy with proton beam scanning – an in silico study.Phys Med. 2017; (39-88-94)
- Dose conformation of intensity-modulated stereotactic photon beams, proton beams, and intensity-modulated proton beams for intracranial lesions.Int J Radiat Oncol Biol Phys. 2004; 60: 1314-1324
- Proton radiotherapy for childhood ependymoma: Initial clinical outcomes and dose comparisons.Int J Radiat Oncol Biol Phys. 2008; 71: 979-986
- Intensity-modulated proton therapy reduces the dose to normal tissue compared with intensity-modulated radiation therapy or passive scattering proton therapy and enables individualized radical radiotherapy for extensive state IIIB non-small-cell lung cancer: a virtual clinical study.Int J Radiat Oncol Biol Phys. 2009; 77: 357-366
- Potential benefits of scanned intensity-modulated proton therapy versus advanced photon therapy with regard to sparing of the salivary glands in oropharyngeal cancer.Int J Radiat Oncol Biol Phys. 2011; 79: 1216-1224
- Dosimetric comparison of three-dimensional conformal proton radiotherapy, intensity-modulated proton therapy, and intensity-modulated radiotherapy for treatment of pediatric craniopharyngiomas.Int J Radiat Oncol Biol Phys. 2012; 82: 643-652
- Comparison of surface doses from spot scanning and passively scattered proton therapy beams.Phys Med Biol. 2009; 54: N295-N302
- Secondary neutron dose during proton therapy using spot scanning.Int J Radiat Oncol Biol Phys. 2002; 53: 244-251
- Secondary neutron doses for several beam configurations for proton therapy.Int J Radiat Oncol Biol Phys. 2009; 74: 260-265
- Comparison between the lateral penumbra of a collimated double-scattered beam and uncollimated scanning beam in proton radiotherapy.Phys Med Biol. 2008; 53: 1729-1750
- Monte Carlo study of the potential reduction in out-of-field dose using a patient-specific aperture in pencil beam scanning proton therapy.Phys Med Biol. 2012; 57: 2829-2842
- Therapeutic step and shoot proton beam spot-scanning with a multi-leaf collimator: a Monte Carlo study.Radiat Prot Dosim. 2005; 115: 164-169
- Characterization of a mini-multileaf collimator in a proton beamline.Med Phys. 2009; 36: 1886-1894
- A dynamic collimation system for penumbra reduction in spot-scanning proton therapy: proof of concept.Med Phys. 2014; 41 (091701-1-091701-9)
- Ambient neutron dose equivalent during proton therapy using wobbling scanning system: measurements and calculations.Radiat Phys Chem. 2017; 140: 290-294
- Broad beam three-dimensional irradiation for proton radiotherapy.Med Phys. 1983; 10: 344-346
- Broad-beam three-dimensional irradiation system for heavy-ion radiotherapy at HIMAC.Nucl Instr Meth Phys Res A. 1999; 430: 143-153
- Treatment planning for the layer-stacking irradiation system for three-dimensional conformal heavy-ion radiotherapy.Med Phys. 2002; 29: 2823-2829
- Commissioning of a conformal irradiation system for heavy-ion radiotherapy using a layer-stacking method.Med Phys. 2006; 33: 2989-2997
- Clinical characterization of a proton beam continuous uniform scanning system with dose layer stacking.Med Phys. 2008; 35: 4945-4954
- Comprehensive clinical commissioning and validation of the RayStation treatment planning system for proton therapy with active scanning and passive treatment techniques.Phys Med. 2017; 43: 15-24
- GEANT4 – a simulation toolkit.Nucl Instr Meth Phys Res A. 2003; 506: 250-303
- Assessment of organ-specific neutron equivalent doses in proton therapy using computational whole-body age-dependent voxel phantoms.Phys Med Biol. 2008; 53: 693-717
- Comparison of the neutron ambient dose equivlanet and ambient absorbed dose calculations with different GEANT4 physics lists.Radiat Phys Chem. 2017; 139: 179-183
- Proton range verification in inhomogeneous tissue: treatment planning vs. measurement vs. Monte Carlo simulation.PLoS ONE. 2018; 13 (e0193904)
International Commission on Radiological Protection. Conversion coefficients for use in radiological protection against external radiation, ICRP Publ 74 Ann ICRT, 26 (3-4), 1996.
- A model for the lateral penumbra in water of a 200 MeV proton beam devoled to clinical applications.Med Phys. 1997; 24: 1599-1604
- Effects of spot size and spot spacing on lateral penumbra reduction when using a dynamic collimation system for spot scanning proton therapy.Phys Med Biol. 2014; 59: N187-N196
- Monte Carlo study of neutron dose equivalent during passive scattering proton therapy.Phys Med Biol. 2007; 52: 4481-4496
- Paganetti H. Reduction of the secondary neutron dose in passively scattered proton radiotherapy, using an optimized pre-collimator/collimator.Phys Med Biol. 2009; 54: 6065-6078
Article info
Publication history
Accepted:
October 8,
2018
Received in revised form:
September 8,
2018
Received:
March 28,
2018
Identification
Copyright
© 2018 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
