A Computer Modeling Study of Water Radiolysis at High Dose Rates. Relevance to FLASH Radiotherapy

Alanazi, Ahmed; Meesungnoen, Jintana; Jay‐Gerin, Jean‐Paul

doi:10.1667/rade-20-00168.1

Cited by 34 publications

(56 citation statements)

References 60 publications

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“…33 This study aims precisely to explore this question in greater depth. For this, we extended our previous calculations 42,43 to study the influence of high dose rates on the transient yields and concentrations of hydronium ions, that are formed early during radiolysis of water by 300-MeV incident protons, which mimic the low LET of 60 Co  rays or fast electrons. Our objective here is to determine the corresponding pH values that prevail in the irradiated solution over time.…”

Section: The Early Transitory Acidic Ph Responsementioning

confidence: 99%

“…We recently developed an irradiation model to study the effects of high dose rates on the radiolysis of water by incident protons 42,43 at ambient and elevated temperatures.…”

Section: R a F Tmentioning

confidence: 99%

“…1 of ref. 42). This is the so-called "model of the instantaneous pulse", 51 in which the pulse duration is assumed to be zero.…”

Section: R a F Tmentioning

confidence: 99%

“…We used a modified version of our Monte Carlo track-chemistry computer code IONLYS-IRT 15 to simulate the radiolysis of deaerated or aerated water at ambient temperature by 300-MeV irradiating protons under conditions of high dose rates. This code has been described in detail elsewhere, 42,43,53 and only its most essential features are given below.…”

Section: Modeling the Multi-track Chemistry: Monte Carlo Simulationsmentioning

confidence: 99%

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Generation of ultrafast, transient, highly acidic pH spikes in the radiolysis of water at very high dose rates: relevance for FLASH radiotherapy

et al. 2022

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Monte Carlo multi-track chemistry simulations were carried out to study the effects of high dose rates on the transient yields of hydronium ions (H3O+) formed during low linear energy transfer (LET) radiolysis of both pure, deaerated and aerated liquid water at 25 °C, in the interval ~1 ps–10 μs. Our simulation model consisted of randomly irradiating water with N interactive tracks of 300-MeV incident protons (LET ~ 0.3 keV/μm), which simultaneously impact perpendicularly on the water within a circular surface. The effect of the dose rate was studied by varying N. Our calculations showed that the radiolytic formation of H3O+ causes the entire irradiated volume to temporarily become very acidic. The magnitude and duration of this abrupt “acid-spike” response depend on the value of N. It is most intense at times less than ~10–100 ns, equal to ~3.4 and 2.8 for N = 500 and 2000 (i.e., for dose rates of ~1.9 × 109 and 8.7 × 109 Gy/s, respectively). At longer times, the pH gradually increases for all N values and eventually returns to the neutral value of seven, which corresponds to the non-radiolytic, pre-irradiation concentration of H3O+. It is worth noting that these early acidic pH responses are very little dependent on the presence or absence of oxygen. Finally, given the importance of pH for many cellular functions, this study suggests that these acidic pH spikes may contribute to the normal tissue-sparing effect of FLASH radiotherapy.

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Section: The Early Transitory Acidic Ph Responsementioning

confidence: 99%

“…We recently developed an irradiation model to study the effects of high dose rates on the radiolysis of water by incident protons 42,43 at ambient and elevated temperatures.…”

Section: R a F Tmentioning

confidence: 99%

“…1 of ref. 42). This is the so-called "model of the instantaneous pulse", 51 in which the pulse duration is assumed to be zero.…”

Section: R a F Tmentioning

confidence: 99%

Section: Modeling the Multi-track Chemistry: Monte Carlo Simulationsmentioning

confidence: 99%

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Generation of ultrafast, transient, highly acidic pH spikes in the radiolysis of water at very high dose rates: relevance for FLASH radiotherapy

et al. 2022

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“…Chemical inter-track effects (in the heterogeneous stage), in contrast, are not likely to take place. Most prominently, they affect OH• radicals and their recombinations [48,49,50] but also reduce oxygen consumption due to the competition of reactions (1) with recombination among the primary radicals [51,52]. The impact starts to be noticeable e. g. for 10 Gy delivered instantaneously [48].…”

Section: Discussionmentioning

confidence: 99%

May oxygen depletion explain the FLASH effect? A chemical track structure analysis

Boscolo

Scifoni

Durante

et al. 2021

Radiotherapy and Oncology

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A potential revolution in cancer treatment: A topical review of FLASH radiotherapy

Gao

Liu

Chang

et al. 2022

J Applied Clin Med Phys

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FLASH radiotherapy (RT) is a novel technique in which the ultrahigh dose rate (UHDR) (≥40 Gy/s) is delivered to the entire treatment volume. Recent outcomes of in vivo studies show that the UHDR RT has the potential to spare normal tissue without sacrificing tumor control. There is a growing interest in the application of FLASH RT, and the ultrahigh dose irradiation delivery has been achieved by a few experimental and modified linear accelerators. The underlying mechanism of FLASH effect is yet to be fully understood, but the oxygen depletion in normal tissue providing extra protection during FLASH irradiation is a hypothesis that attracts most attention currently. Monte Carlo simulation is playing an important role in FLASH, enabling the understanding of its dosimetry calculations and hardware design. More advanced Monte Carlo simulation tools are under development to fulfill the challenge of reproducing the radiolysis and radiobiology processes in FLASH irradiation. FLASH RT may become one of standard treatment modalities for tumor treatment in the future. This paper presents the history and status of FLASH RT studies with a focus on FLASH irradiation delivery modalities, underlying mechanism of FLASH effect, in vivo and vitro experiments, and simulation studies. Existing challenges and prospects of this novel technique are discussed in this manuscript.

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A Computer Modeling Study of Water Radiolysis at High Dose Rates. Relevance to FLASH Radiotherapy

Cited by 34 publications

References 60 publications

Generation of ultrafast, transient, highly acidic pH spikes in the radiolysis of water at very high dose rates: relevance for FLASH radiotherapy

Generation of ultrafast, transient, highly acidic pH spikes in the radiolysis of water at very high dose rates: relevance for FLASH radiotherapy

May oxygen depletion explain the FLASH effect? A chemical track structure analysis

A potential revolution in cancer treatment: A topical review of FLASH radiotherapy

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