Comparison of the space bubble detector response to space-like neutron spectra and high energy protons

Miller, Alexander L.; Machrafi, R.; Benton, E. R.; Kitamura, Hisashi; Kodaira, Satoshi

doi:10.1016/j.actaastro.2018.05.035

Cited by 4 publications

(4 citation statements)

References 8 publications

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“…Detection of proton radiation in the vicinity of the Bragg peak with superheated drops was reported by several groups (Green et al 2005, D'Errico and Egger 1994, Guo et al 2002, indicating that the threshold for proton detection lies between s = 0.35 and s = 0.42, corresponding to an LET threshold of 70-90 keV/µm, typically reached by protons at the end of their range. Proton irradiation of bubble detectors with lower degrees of superheat revealed that high-LET nuclear reaction products (heavy recoils) induce uniform vaporization tracks (Green et al 2005, D'Errico et al 1997, Miller et al 2018, Takada et al 2004. nanodroplets employed in this study are comprised of a perfluorobutane (C4F10, boiling point of -2°C) liquid core encapsulated by a polymerizable fatty acid monolayer of 10,12-pentacosadiynoic acid (PCDA).…”

Section: Theory Of Nucleation Induced By Ionizing Radiationmentioning

confidence: 99%

Proton range verification with ultrasound imaging using injectable radiation sensitive nanodroplets: a feasibility study

et al. 2020

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Technologies enabling in vivo range verification during proton therapy are actively sought as a means to reduce the clinical safety margins currently adopted to avoid tumor underdosage. In this contribution, we applied the semi-empirical theory of radiation-induced vaporization of superheated liquids to coated nanodroplets. Nanodroplets are injectable phase-change contrast agents that can vaporize into highly echogenic microbubbles to provide contrast in ultrasound images. We exposed nanodroplet dispersions in aqueous phantoms to monoenergetic proton beams of varying energies and doses. Ultrasound imaging of the phantoms revealed that radiation-induced droplet vaporization occurred in regions proximal to the proton Bragg peak. A statistically significant increase in contrast was observed in irradiated regions for doses as low as 2 Gy and found to be proportional to the proton fluence. The absence of enhanced response in the vicinity of the Bragg peak, combined with theoretical considerations, suggest that droplet vaporization is induced by high linear energy transfer (LET) recoil ions produced by nuclear reactions with incoming protons. Vaporization profiles were compared to non-elastic cross sections and LET characteristics of oxygen recoils. Shifts between the ultrasound image contrast drop and the expected proton range showed a sub-millimeter reproducibility. These early findings confirm the potential of superheated nanodroplets as a novel tool for proton range verification.

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Section: Theory Of Nucleation Induced By Ionizing Radiationmentioning

confidence: 99%

Proton range verification with ultrasound imaging using injectable radiation sensitive nanodroplets: a feasibility study

et al. 2020

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“…The detection of charged particles, among which are protons, can be achieved in superheated liquids (D 'Errico 2001;Felizardo et al 2013;Miller et al 2018), which can remain in a metastable liquid phase above their boiling point owing to the removal of heterogeneous nucleation sites (Apfel 1979). The only mechanism remaining for vaporization is homogeneous nucleation, occurring when a gas embryo grows larger than a critical size (Mountford and Borden 2016).…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal Distribution of Nanodroplet Vaporization in a Proton Beam Using Real-Time Ultrasound Imaging for Range Verification

Collado-Lara

Heymans

Rovituso³

et al. 2022

Ultrasound in Medicine & Biology

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The potential of proton therapy to improve the conformity of the delivered dose to the tumor volume is currently limited by range uncertainties. Injectable superheated nanodroplets have recently been proposed for ultrasound-based in vivo range verification, as these vaporize into echogenic microbubbles on proton irradiation. In previous studies, offline ultrasound images of phantoms with dispersed nanodroplets were acquired after irradiation, relating the induced vaporization profiles to the proton range. However, the aforementioned method did not enable the counting of individual vaporization events, and offline imaging cannot provide real-time feedback. In this study, we overcame these limitations using high-frame-rate ultrasound imaging with a linear array during proton irradiation of phantoms with dispersed perfluorobutane nanodroplets at 37˚C and 50˚C. Differential image analysis of subsequent frames allowed us to count individual vaporization events and to localize them with a resolution beyond the ultrasound diffraction limit, enabling spatial and temporal quantification of the interaction between ionizing radiation and nanodroplets. Vaporization maps were found to accurately correlate with the stopping distribution of protons (at 50˚C) or secondary particles (at both temperatures). Furthermore, a linear relationship between the vaporization count and the number of incoming protons was observed. These results indicate the potential of real-time high-frame-rate contrast-enhanced ultrasound imaging for proton range verification and dosimetry.

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“…26,32 For the past half century, this principle has been exploited by bubble chambers and superheated drop detectors in a variety of fields ranging from radiation spectrometry and dosimetry to space applications and dark matter search. [33][34][35][36][37] Furthermore, it was envisioned for in vivo applications two decades ago. 38 To apply this concept to in vivo noninvasive radiation dosimetry and proton range verification, the aforementioned emulsions were downscaled to phase-change nanodroplets and stabilized by a lipidic shell.…”

Section: Introductionmentioning

confidence: 99%

“…These highly echogenic bubbles can then be detected via optical, acoustic, or volume measurements 26,32 . For the past half century, this principle has been exploited by bubble chambers and superheated drop detectors in a variety of fields ranging from radiation spectrometry and dosimetry to space applications and dark matter search 33–37 . Furthermore, it was envisioned for in vivo applications two decades ago 38…”

Section: Introductionmentioning

confidence: 99%

Modulating ultrasound contrast generation from injectable nanodroplets for proton range verification by varying the degree of superheat

et al. 2021

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Purpose: Despite the physical benefits of protons over conventional photon radiation in cancer treatment, range uncertainties impede the ability to harness the full potential of proton therapy. While monitoring the proton range in vivo could reduce the currently adopted safety margins, a routinely applicable range verification technique is still lacking. Recently, phase-change nanodroplets were proposed for proton range verification, demonstrating a reproducible relationship between the proton range and generated ultrasound contrast after radiation-induced vaporization at 25°C. In this study, previous findings are extended with proton irradiations at different temperatures, including the physiological temperature of 37°C, for a novel nanodroplet formulation. Moreover, the potential to modulate the linear energy transfer (LET) threshold for vaporization by varying the degree of superheat is investigated, where the aim is to demonstrate vaporization of nanodroplets directly by primary protons. Methods: Perfluorobutane nanodroplets with a shell made of polyvinyl alcohol (PVA-PFB) or 10,12-pentacosadyinoic acid (PCDA-PFB) were dispersed in polyacrylamide hydrogels and irradiated with 62 MeV passively scattered protons at temperatures of 37°C and 50°C. Nanodroplet transition into echogenic microbubbles was assessed using ultrasound imaging (gray value and attenuation analysis) and optical images. The proton range was measured independently and compared to the generated contrast. Results: Nanodroplet design proved crucial to ensure thermal stability, as PVA-shelled nanodroplets dramatically outperformed their PCDA-shelled counterpart. At body temperature, a uniform radiation response proximal to the Bragg peak is attributed to nuclear reaction products interacting with PVA-PFB nanodroplets, with the 50% drop in ultrasound contrast being 0.17 mm AE 0.20 mm 1983

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Comparison of the space bubble detector response to space-like neutron spectra and high energy protons

Cited by 4 publications

References 8 publications

Proton range verification with ultrasound imaging using injectable radiation sensitive nanodroplets: a feasibility study

Proton range verification with ultrasound imaging using injectable radiation sensitive nanodroplets: a feasibility study

Spatiotemporal Distribution of Nanodroplet Vaporization in a Proton Beam Using Real-Time Ultrasound Imaging for Range Verification

Modulating ultrasound contrast generation from injectable nanodroplets for proton range verification by varying the degree of superheat

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