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Range Verification Methods in Particle Therapy: Underlying Physics and Monte Carlo Modeling.

Kraan AC - Front Oncol (2015)

Bottom Line: Currently, uncertainties in particle range lead to the employment of safety margins, at the expense of treatment quality.We include research studies and clinically applied methods.For each of the techniques, we point out advantages and disadvantages, as well as clinical challenges still to be addressed, focusing on MC simulation aspects.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, National Institute for Nuclear Physics (INFN), University of Pisa , Pisa , Italy.

ABSTRACT
Hadron therapy allows for highly conformal dose distributions and better sparing of organs-at-risk, thanks to the characteristic dose deposition as function of depth. However, the quality of hadron therapy treatments is closely connected with the ability to predict and achieve a given beam range in the patient. Currently, uncertainties in particle range lead to the employment of safety margins, at the expense of treatment quality. Much research in particle therapy is therefore aimed at developing methods to verify the particle range in patients. Non-invasive in vivo monitoring of the particle range can be performed by detecting secondary radiation, emitted from the patient as a result of nuclear interactions of charged hadrons with tissue, including β (+) emitters, prompt photons, and charged fragments. The correctness of the dose delivery can be verified by comparing measured and pre-calculated distributions of the secondary particles. The reliability of Monte Carlo (MC) predictions is a key issue. Correctly modeling the production of secondaries is a non-trivial task, because it involves nuclear physics interactions at energies, where no rigorous theories exist to describe them. The goal of this review is to provide a comprehensive overview of various aspects in modeling the physics processes for range verification with secondary particles produced in proton, carbon, and heavier ion irradiation. We discuss electromagnetic and nuclear interactions of charged hadrons in matter, which is followed by a summary of some widely used MC codes in hadron therapy. Then, we describe selected examples of how these codes have been validated and used in three range verification techniques: PET, prompt gamma, and charged particle detection. We include research studies and clinically applied methods. For each of the techniques, we point out advantages and disadvantages, as well as clinical challenges still to be addressed, focusing on MC simulation aspects.

No MeSH data available.


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Measured and simulated (TOPAS) energy spectra at the end of range of a monoenergetic 160 MeV proton pencil beam impinging along the central axis of a cylindrical PMMA target. Experimental setup (A) together with measured and simulated energy spectra for different collimator configurations (B–F). “Opening difference” is Collimator Open minus Collimator Closed, and “Wall-difference” means No Collimator minus Collimator closed, i.e., a configuration in which neutron background is subtracted. Measurements from Smeets et al. (154). Figure reproduced from Ref. (154, 155), with permission.
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Figure 12: Measured and simulated (TOPAS) energy spectra at the end of range of a monoenergetic 160 MeV proton pencil beam impinging along the central axis of a cylindrical PMMA target. Experimental setup (A) together with measured and simulated energy spectra for different collimator configurations (B–F). “Opening difference” is Collimator Open minus Collimator Closed, and “Wall-difference” means No Collimator minus Collimator closed, i.e., a configuration in which neutron background is subtracted. Measurements from Smeets et al. (154). Figure reproduced from Ref. (154, 155), with permission.

Mentions: As discussed in Sections 2.2.2–2.2.4, prompt gammas are emitted as a result of nuclear reactions during particle delivery along much of the particle path, with energies varying from 0 to about 10 MeV (for typical spectra see Figure 12, to be discussed below). We first briefly discuss the detectors, then describe MC validation studies with prompt gammas, and finally some clinical challenges.


Range Verification Methods in Particle Therapy: Underlying Physics and Monte Carlo Modeling.

Kraan AC - Front Oncol (2015)

Measured and simulated (TOPAS) energy spectra at the end of range of a monoenergetic 160 MeV proton pencil beam impinging along the central axis of a cylindrical PMMA target. Experimental setup (A) together with measured and simulated energy spectra for different collimator configurations (B–F). “Opening difference” is Collimator Open minus Collimator Closed, and “Wall-difference” means No Collimator minus Collimator closed, i.e., a configuration in which neutron background is subtracted. Measurements from Smeets et al. (154). Figure reproduced from Ref. (154, 155), with permission.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493660&req=5

Figure 12: Measured and simulated (TOPAS) energy spectra at the end of range of a monoenergetic 160 MeV proton pencil beam impinging along the central axis of a cylindrical PMMA target. Experimental setup (A) together with measured and simulated energy spectra for different collimator configurations (B–F). “Opening difference” is Collimator Open minus Collimator Closed, and “Wall-difference” means No Collimator minus Collimator closed, i.e., a configuration in which neutron background is subtracted. Measurements from Smeets et al. (154). Figure reproduced from Ref. (154, 155), with permission.
Mentions: As discussed in Sections 2.2.2–2.2.4, prompt gammas are emitted as a result of nuclear reactions during particle delivery along much of the particle path, with energies varying from 0 to about 10 MeV (for typical spectra see Figure 12, to be discussed below). We first briefly discuss the detectors, then describe MC validation studies with prompt gammas, and finally some clinical challenges.

Bottom Line: Currently, uncertainties in particle range lead to the employment of safety margins, at the expense of treatment quality.We include research studies and clinically applied methods.For each of the techniques, we point out advantages and disadvantages, as well as clinical challenges still to be addressed, focusing on MC simulation aspects.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, National Institute for Nuclear Physics (INFN), University of Pisa , Pisa , Italy.

ABSTRACT
Hadron therapy allows for highly conformal dose distributions and better sparing of organs-at-risk, thanks to the characteristic dose deposition as function of depth. However, the quality of hadron therapy treatments is closely connected with the ability to predict and achieve a given beam range in the patient. Currently, uncertainties in particle range lead to the employment of safety margins, at the expense of treatment quality. Much research in particle therapy is therefore aimed at developing methods to verify the particle range in patients. Non-invasive in vivo monitoring of the particle range can be performed by detecting secondary radiation, emitted from the patient as a result of nuclear interactions of charged hadrons with tissue, including β (+) emitters, prompt photons, and charged fragments. The correctness of the dose delivery can be verified by comparing measured and pre-calculated distributions of the secondary particles. The reliability of Monte Carlo (MC) predictions is a key issue. Correctly modeling the production of secondaries is a non-trivial task, because it involves nuclear physics interactions at energies, where no rigorous theories exist to describe them. The goal of this review is to provide a comprehensive overview of various aspects in modeling the physics processes for range verification with secondary particles produced in proton, carbon, and heavier ion irradiation. We discuss electromagnetic and nuclear interactions of charged hadrons in matter, which is followed by a summary of some widely used MC codes in hadron therapy. Then, we describe selected examples of how these codes have been validated and used in three range verification techniques: PET, prompt gamma, and charged particle detection. We include research studies and clinically applied methods. For each of the techniques, we point out advantages and disadvantages, as well as clinical challenges still to be addressed, focusing on MC simulation aspects.

No MeSH data available.


Related in: MedlinePlus