Theoretical detection threshold of the proton‐acoustic range verification technique

Ahmad, Moiz; Xiang, Liangzhong; Yousefi, Siavash; Li, Xing

doi:10.1118/1.4929939

Cited by 40 publications

(61 citation statements)

References 30 publications

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“…Simulations confirmed previous intuition, and later systematic studies by Albul et al., that through time‐of‐flight calculations the detector‐to‐Bragg‐peak distance may be calculated by multiplying the γ ‐wave arrival time by the speed of sound in the medium . Further simulation work showed that the central frequency of the proton‐induced acoustic spectrum is <400 kHz, and predicted that the acoustic waves induced by a single proton pulse depositing on the order of 10 1 −10 2 mGy are detectable by 5 cm diameter transducers even in the presence of thermal noise …”

Section: Proton Therapy Range Verificationsupporting

confidence: 79%

“…60 Further simulation work showed that the central frequency of the proton-induced acoustic spectrum is <400 kHz, and predicted that the acoustic waves induced by a single proton pulse depositing on the order of 10 1 À10 2 mGy are detectable by 5 cm diameter transducers even in the presence of thermal noise. 61 As described in Eq. (15), thermoacoustic pressure waves depend on the temporal shape of the excitation pulse.…”

Section: B Recent Workmentioning

confidence: 99%

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Ionizing radiation‐induced acoustics for radiotherapy and diagnostic radiology applications

et al. 2018

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Acoustic waves are induced via the thermoacoustic effect in objects exposed to a pulsed beam of ionizing radiation. This phenomenon has interesting potential applications in both radiotherapy dosimetry and treatment guidance as well as low-dose radiological imaging. After initial work in the field in the 1980s and early 1990s, little research was done until 2013 when interest was rejuvenated, spurred on by technological advances in ultrasound transducers and the increasing complexity of radiotherapy delivery systems. Since then, many studies have been conducted and published applying ionizing radiation-induced acoustic principles into three primary research areas: Linear accelerator photon beam dosimetry, proton therapy range verification, and radiological imaging. This review article introduces the theoretical background behind ionizing radiation-induced acoustic waves, summarizes recent advances in the field, and provides an outlook on how the detection of ionizing radiationinduced acoustic waves can be used for relative and in vivo dosimetry in photon therapy, localization of the Bragg peak in proton therapy, and as a low-dose medical imaging modality. Future prospects and challenges for the clinical implementation of these techniques are discussed.

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Section: Proton Therapy Range Verificationsupporting

confidence: 79%

Section: B Recent Workmentioning

confidence: 99%

Ionizing radiation‐induced acoustics for radiotherapy and diagnostic radiology applications

et al. 2018

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“…A rectangular region‐of‐interest (ROI) (77 × 141 pixels) comprising the Bragg peak was selected. The pressure distribution, p δ ( r , 0) [unit: Pa] at a given position r and time t = 0, due to thermoelastic expansion can be related to the dose distribution through:

p_{δ} (r, 0) = ρ (boldr) Γ (boldr) D_{δ} false(boldr, 0 false)

where ρ [unit: kg/m 3 ] is the mass density, Γ = α V c 2 / C p is the dimensionless Grüneisen coefficient dependent on the volumetric thermal expansion coefficient, α V [unit: K −1 ], the speed of sound, c [unit: m/s], and the isobaric specific heat capacity, C p [unit: J/(K kg)]. Due to tissue heterogeneity, these physical parameters ( ρ , α V , c and C p ) for pressure distribution calculation at each pixel need to be converted through calibration curves (see Section 2.B).…”

Section: Methodsmentioning

confidence: 99%

“…PGs are high energy gamma rays created by inelastic interactions between incident proton and target nuclei. PGs are emitted with decay time less than 1 ps and a broad energy spectrum (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). This approach faces two main challenges: (a) low detection efficiency due to the high energy of gamma rays; and (b) discrimination of PG signals from background noise originating from secondary neutrons.…”

Section: Introductionmentioning

confidence: 99%

Simulation studies of time reversal‐based protoacoustic reconstruction for range and dose verification in proton therapy

Yu¹,

Li²,

Zhang³

et al. 2019

Medical Physics

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Purpose In vivo range verification in proton therapy is a critical step to help minimize range and dose uncertainty. We propose to employ a time reversal (TR)‐based approach using proton‐induced acoustics (protoacoustics) to reconstruct pressure/dose distribution in heterogeneous tissues. Methods The dose distribution of mono‐energetic proton pencil beam in a CT‐based patient phantom was calculated by Monte Carlo simulation. K‐wave toolbox was used to investigate protoacoustic pressurization, propagation and reconstruction in 2D. To address the tissue heterogeneity effect, a number of physical parameters, including mass density (ρ), speed of sound (c), volumetric thermal expansion coefficient (αV), isobaric specific heat capacity (Cp) and attenuation power law prefactor (α0), were empirically converted from CT number. The performance was evaluated using two figures of merit: mean square error (MSE) of pressure profiles and Bragg peak localization error (ΔBP). The impact of six parameters of the TR inversion was examined, including number of sensors, sampling duration, sampling timestep, spill time, noise level and number of iterations. Results The quantitative accuracy of TR reconstruction and its dependency on the selected parameters is presented. Under optimum conditions, the positioning accuracy of the Bragg peak can be controlled below 1 mm. For instance, MSE is 0.0123 and ΔBP is 0.59 mm under the following conditions (32 sensors, sampling duration: 600 µs, sampling timestep: 40 ns, spill time: 1 µs, no noise). Conclusions The feasibility of TR‐based protoacoustic reconstruction in 2D for proton range verification was first demonstrated. The approach is not only applicable to pencil beam, but also has potential to be extended to passive scattering systems.

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“…Basic science experiments performed at national laboratories in the 1970s transitioned to clinically driven benchwork and clinical testing by the 1990s. Recently, measurements by individual receivers with lateral and distal offsets from the Bragg peak were simulated with an eye towards range verification. A mathematically complete set of measurements including both lateral and distal offsets was simulated to demonstrate feasibility of dosimetry for ion therapy, and for x‐rays .…”

Section: Introductionmentioning

confidence: 99%

Two‐stage ionoacoustic range verification leveraging Monte Carlo and acoustic simulations to stably account for tissue inhomogeneity and accelerator–specific time structure – A simulation study

et al. 2017

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Ionoacoustic range verification may improve current practice. Ionoacoustic range estimates can be inherently co-registered to ultrasound images of underlying anatomy. To ensure estimates are robust in clinical practice, dose maps based upon the planning CT should be overlaid onto ultrasound volumes acquired at time of treatment and acoustic simulations re-computed to provide a database of control points and corresponding thermoacoustic emissions. Computation times for beamformed estimates are already fast enough for online range verification, but are not accurate enough for a measurement aperture limited to the surface of a transrectal ultrasound probe. Accelerated acoustic simulations will be required to enable online two-stage correction, but offline calculation is already suitable for adaptive planning.

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Theoretical detection threshold of the proton‐acoustic range verification technique

Cited by 40 publications

References 30 publications

Ionizing radiation‐induced acoustics for radiotherapy and diagnostic radiology applications

Ionizing radiation‐induced acoustics for radiotherapy and diagnostic radiology applications

Simulation studies of time reversal‐based protoacoustic reconstruction for range and dose verification in proton therapy

Two‐stage ionoacoustic range verification leveraging Monte Carlo and acoustic simulations to stably account for tissue inhomogeneity and accelerator–specific time structure – A simulation study

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