Time-of-flight neutron rejection to improve prompt gamma imaging for proton range verification: a simulation study

Biegun, A.; Seravalli, Enrica; Lopes, P. Cambraia; Rinaldi, I.; Pinto, M.; Oxley, D.C.; Dendooven, P.; Verhaegen, Frank; Parodi, Katia; Crespo, Paulo; Schaart, Dennis R.

doi:10.1088/0031-9155/57/20/6429

Cited by 64 publications

(79 citation statements)

References 46 publications

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“…The number of simulated particles was per beam, producing -emitters in each 30 min PET scan. In both cases, the amount of and simulated and the number of -emitters produced correspond to realistic numbers found in a treatment beam, which correspond to an average number of particles sent to generate a spread-out Bragg peak of 2 Gy [24], [25]. Considering the activity density produced by the particle (600 for , 200 for ), the induced -activity density is typical of that produced by therapeutic dose fractions (from 0.5-2 Gy).…”

Section: A Simulation Setupmentioning

confidence: 95%

PET Reconstruction From Truncated Projections Using Total-Variation Regularization for Hadron Therapy Monitoring

Cabello

Torres-Espallardó

Gillam

et al. 2013

IEEE Trans. Nucl. Sci.

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Hadron therapy exploits the properties of ion beams to treat tumors by maximizing the dose released to the target and sparing healthy tissue. With hadron beams, the dose distribution shows a relatively low entrance dose which rises sharply at the end of the range, providing the characteristic Bragg peak that drops quickly thereafter. It is of critical importance in order not to damage surrounding healthy tissues and/or avoid targeting underdosage to know where the delivered dose profile ends-the location of the Bragg peak. During hadron therapy, short-lived -emitters are produced along the beam path, their distribution being correlated with the delivered dose. Following positron annihilation, two photons are emitted, which can be detected using a positron emission tomography (PET) scanner. The low yield of emitters, their short half-life, and the wash out from the target region make the use of PET, even only a few minutes after hadron irradiation, a challenging application. In-beam PET represents a potential candidate to estimate the distribution of -emitters during or immediately after irradiation, at the cost of truncation effects and degraded image quality due to the partial rings required of the PET scanner. Time-of-flight (ToF) information can potentially be used to compensate for truncation effects and to enhance image contrast. However, the highly demanding timing performance required in ToF-PET makes this option costly. Alternatively, the use of maximum-a-posteriori-expectation-maximization (MAP-EM), including total variation (TV) in the cost function, produces images with low noise, while preserving spatial resolution. In this paper, we compare data reconstructed with maximum-likelihood-expectation-maximization (ML-EM) and MAP-EM using TV as prior, and the impact of including ToF information, from data acquired with a complete and a partial-ring PET scanner, of simulated hadron beams interacting Manuscript with a polymethyl methacrylate (PMMA) target. The results show that MAP-EM, in the absence of ToF information, produces lower noise images and more similar data compared to the simulated distributions than ML-EM with ToF information in the order of 200-600 ps. The investigation is extended to the combination of MAP-EM and ToF information to study the limit of performance using both approaches.Index Terms-Hadron therapy, in-beam PET, maximuma-posteriori-expectation-maximization (MAP-EM) reconstruction, time-of-flight positron emission tomography (PET), total variation.

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Section: A Simulation Setupmentioning

confidence: 95%

PET Reconstruction From Truncated Projections Using Total-Variation Regularization for Hadron Therapy Monitoring

Cabello

Torres-Espallardó

Gillam

et al. 2013

IEEE Trans. Nucl. Sci.

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“…The actual background is difficult to model and depends on the incident proton energy, the target composition, as well as the detector location and other elements in the treatment room. Based on previous measurements in a clinical scenario [21], [45], [46] as well as simulations [34,Fig. 6], the average ratio between overall events and prompt γ-rays can be roughly estimated with k γ ≈ 2.5 for the current setup in coaxial orientation and without collimator, cf.…”

Section: E Radiation Backgroundmentioning

confidence: 76%

“…We assume an analytical One-Dimensional (1D) model of the prompt γ-ray emission (including all energies) characterized by a flat profile and a sharp distal falloff near the proton range R w . This is a coarse approximation of the energyintegrated depth-emission profile [34,Fig. 6], [35,Fig.…”

Section: A Emissionmentioning

confidence: 99%

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Compact Method for Proton Range Verification Based on Coaxial Prompt Gamma-Ray Monitoring: A Theoretical Study

Hueso-González

Bortfeld

2020

IEEE Trans. Radiat. Plasma Med. Sci.

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Range uncertainties in proton therapy hamper treatment precision. Prompt gamma-rays were suggested 16 years ago for real-time range verification, and have already shown promising results in clinical studies with collimated cameras. Simultaneously, alternative imaging concepts without collimation are investigated to reduce the footprint and price of current prototypes. In this manuscript, a compact range verification method is presented. It monitors prompt gamma-rays with a single scintillation detector positioned coaxially to the beam and behind the patient. Thanks to the solid angle effect, proton range deviations can be derived from changes in the number of gammarays detected per proton, provided that the number of incident protons is well known. A theoretical background is formulated and the requirements for a future proof-of-principle experiment are identified. The potential benefits and disadvantages of the method are discussed, and the prospects and potential obstacles for its use during patient treatments are assessed. The final milestone is to monitor proton range differences in clinical cases with a statistical precision of 1 mm, a material cost of 25000 USD and a weight below 10 kg. This technique could facilitate the widespread application of in vivo range verification in proton therapy and eventually the improvement of treatment quality.

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“…From [20], we estimate that a detector placed perpendicularly to and at a distance of 30 cm from a 200-MeV proton beam is hit by 2 × 10 −5 neutrons per cm 2 per proton stopped. In the framework of establishing the Groningen Proton Therapy Center, the number of protons delivered to one gantry treatment room was estimated to be about 10 15 per year, assuming a realistic patient mix and a total of 380 patients.…”

Section: Introductionmentioning

confidence: 99%

Radiation hardness of dsipm sensors in a proton therapy radiation environment

Diblen

Buitenhuis

Solf

et al. 2017

IEEE Trans. Nucl. Sci.

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Abstract-In vivo verification of dose delivery in proton therapy by means of positron emission tomography (PET) or prompt gamma imaging is mostly based on fast scintillation detectors. The digital silicon photomultiplier (dSiPM) allows excellent scintillation detector timing properties and is thus being considered for such verification methods. We present here the results of the first investigation of radiation damage to dSiPM sensors in a proton therapy radiation environment. Radiation hardness experiments were performed at the AGOR cyclotron facility at the KVI-Center for Advanced Radiation Technology, University of Groningen. A 150-MeV proton beam was fully stopped in a water target. In the first experiment, bare dSiPM sensors were placed at 25 cm from the Bragg peak, perpendicular to the beam direction, a geometry typical for an in situ implementation of a PET or prompt gamma imaging device. In the second experiment, dSiPM-based PET detectors containing lutetium yttrium orthosilicate scintillator crystal arrays were placed at 2 and 4 m from the Bragg peak, perpendicular to the beam direction; resembling an in-room PET implementation. Furthermore, the experimental setup was simulated with a Geant4-based Monte Carlo code in order to determine the angular and energy distributions of the neutrons and to determine the 1-MeV equivalent neutron fluences delivered to the dSiPM sensors. A noticeable increase in dark count rate (DCR) after an irradiation with about 10 8 1-MeV equivalent neutrons/cm 2 agrees with observations by others for analog SiPMs, indicating that the radiation damage occurs in the single photon avalanche diodes and not in the electronics integrated on the sensor chip. It was found that in the in situ location, the DCR becomes too large for successful operation after the equivalent of a few weeks of use in a proton therapy treatment room (about 5×10 13 protons). For PET detectors in an in-room setup, detector performance was unchanged even after an irradiation equivalent to three years of use in a treatment room (3 × 10 15 protons). Manuscript

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Time-of-flight neutron rejection to improve prompt gamma imaging for proton range verification: a simulation study

Cited by 64 publications

References 46 publications

PET Reconstruction From Truncated Projections Using Total-Variation Regularization for Hadron Therapy Monitoring

PET Reconstruction From Truncated Projections Using Total-Variation Regularization for Hadron Therapy Monitoring

Compact Method for Proton Range Verification Based on Coaxial Prompt Gamma-Ray Monitoring: A Theoretical Study

Radiation hardness of dsipm sensors in a proton therapy radiation environment

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