Development of array‐type prompt gamma measurement system for <i>in vivo</i> range verification in proton therapy

Min, Chul Hee; Lee, Han Rim; Kim, Chan Hyeong; Lee, Se Byeong

doi:10.1118/1.3694098

Cited by 96 publications

(71 citation statements)

References 18 publications

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“…This has led to a large amount of work to design new systems for PG measurements that are adequate for use in a clinical proton therapy environment (Frandes et al , 2010; Kang and Kim, 2009; Kim et al , 2009; Min et al , 2012; Smeets et al , 2012). These studies propose a wide range of detection methods for PG imaging based on either the total emission signal, or the signal from individual elemental emission lines measured during irradiation.…”

Section: Introductionmentioning

confidence: 99%

Detecting prompt gamma emission during proton therapy: the effects of detector size and distance from the patient

et al. 2014

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Recent studies have suggested that the characteristics of prompt gammas (PG) emitted from excited nuclei during proton therapy are advantageous for determining beam range during treatment delivery. Since PGs are only emitted while the beam is on, the feasibility of using PGs for online treatment verification depends greatly on the design of highly efficient detectors. The purpose of this work is to characterize how PG detection changes as a function of distance from the patient as a means of guiding the design and usage of clinical prompt gamma imaging detectors. Using a Monte Carlo model (GEANT4.9.4) we studied the detection rate (PGs per incident proton) of a high purity Germanium detector for both the total PG emission and the characteristic 6.13 MeV PG emission from 16O emitted during proton irradiation. The PG detection rate was calculated as a function of distance from the isocenter of the proton treatment nozzle for: (1) a water phantom irradiated with a proton pencil beam and (2) a prostate patient irradiated with a scanning beam proton therapy treatment field (lateral field size: ~6 cm × 6 cm, beam range: 23.5 cm). An analytical expression of the PG detection rate as a function of distance from isocenter, detector size, and proton beam energy was then developed. The detection rates were found to be 1.3 × 10−6 for oxygen and 3.9 × 10−4 for the total PG emission, respectively, with the detector placed 11 cm from isocenter for a 40 MeV pencil beam irradiating a water phantom. The total PG detection rate increased by ~85±3% for beam energies greater than 150 MeV. The detection rate was found to be approximately 2.1 × 10−6 and 1.7 × 10−3 for oxygen and total PG emission, respectively, during delivery of a single pencil beam during a scanning beam treatment for prostate cancer. The PG detection rate as a function of distance from isocenter during irradiation of a water phantom with a single proton pencil beam was described well by the model of a point source irradiating a cylindrical detector of a known diameter over the range of beam energies commonly used for proton therapy. For the patient studies, it was necessary to divide the point source equation by an exponential factor in order to correctly predict the falloff of the PG detection rate as a function of distance from isocenter.

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Section: Introductionmentioning

confidence: 99%

Detecting prompt gamma emission during proton therapy: the effects of detector size and distance from the patient

et al. 2014

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“…The collimator length (denoted by I in Fig. 1) was set to 160 mm, consistent with what was optimized by others [5].…”

Section: A Simulation Specifics and Data Analysismentioning

confidence: 98%

“…Although first results are encouraging, prompt-gamma detection is challenging to implement in practice, mainly due to (1) the amount of statistics of the prompt signal being limited by the number of particles delivered, as determined by the treatment plan, (2) interference of background radiation from other secondary products of the irradiation -especially for higher energy proton beams [5], [7] -, and (3) the characteristic high energy of the emitted prompt photons (up to a few tens of MeV). Neutrons play a major role in the creation of the background signal, as they are difficult to stop and may give rise to secondary gamma rays when interacting in the patient, collimator, and other materials.…”

Section: Introductionmentioning

confidence: 99%

“…Proposed approaches include the multi-slat collimator, also called multi-slit [5] or multi-parallel slit -an extension of the scanned single-parallel slit [4] -and the knife-edge-shaped slit [3] or slit-camera [6], [7]. On one side, the latter may be favorable in that it can in principle combine relatively high sensitivity with high resolution, especially when a large magnification factor is applied [3].…”

Section: Introductionmentioning

confidence: 99%

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Optimization of collimator designs for real-time proton range verification by measuring prompt gamma rays

Lopes

Pinto

Simoes

et al. 2012

2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)

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Precise monitoring of the particle range inside the body, preferably in real-time, is a primary interest in quality assurance of particle therapy. Prompt-gamma (PG) detection aims at this task, but such a system is technically challenging to implement. For mechanically collimated PG detection, neutron-induced background radiation originating in the collimator material is a major issue. We study by Monte-Carlo simulations (Geant4), the influence of different collimator designs and their geometric parameters -such as distance to source, size and septa thickness -on the correlation between transmitted PG profiles and the longitudinal depth-dose profile. The impact of background rejection by time-of-flight (TOF) is also addressed. A single-parallel-slit collimator scanned along the beam axis was primarily studied and results show that the background can be efficiently reduced by TOF discrimination. Due to reduced statistics, signal integration from neighbouring pencil-beams was further considered, accounting for typical clinical proton fluences. Furthermore, first direct-comparison results between multi-slat collimation and a knife-edge-slit collimator are presented, obtained both by simulation and analytical calculations of their geometric performances. Advantages and disadvantages of both approaches are highlighted and some design improvements are proposed. Energy thresholding was also addressed, showing that a low-energy threshold of 4 MeV increases the signal-to-background ratio in all simulation results, a factor mostly important if TOF rejection cannot be applied.

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“…Collimated cameras are of two types: on the one hand, knife-edge single-slit cameras [8,18] present the advantage of compactness, simple collimation and detection. On the other hand, multi-slit cameras enable non-restricted eld of view and potentially better spatial resolution [10,19].…”

Section: Device Developmentsmentioning

confidence: 99%

Prompt-Gamma Monitoring of Proton- and Carbon-Therapy. Combined Development of Time-of-Flight Collimated- and Compton-Cameras

et al. 2015

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Prompt-gamma imaging during ion therapy has proven its ability to control the ion range in real time. The achievable precision is of the order of the millimeter for a single spot in proton pencil beam scanning. Collimated gamma cameras have been developed, that are close to clinical application. The Compton cameras are also under development in various laboratories. Time of ight enables the reduction of the background due to other prompt radiations.

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Development of array‐type prompt gamma measurement system for in vivo range verification in proton therapy

Abstract: The results show that the array-type measurement system can measure prompt gamma distributions from a therapeutic proton beam within a short measurement time, and that the distal dose edge can be determined within a few millimeters of error without using any sophisticated analysis.

Cited by 96 publications

References 18 publications

Detecting prompt gamma emission during proton therapy: the effects of detector size and distance from the patient

Detecting prompt gamma emission during proton therapy: the effects of detector size and distance from the patient

Optimization of collimator designs for real-time proton range verification by measuring prompt gamma rays

Prompt-Gamma Monitoring of Proton- and Carbon-Therapy. Combined Development of Time-of-Flight Collimated- and Compton-Cameras

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