scholarly journals Generation of ultrafast, transient, highly acidic pH spikes in the radiolysis of water at very high dose rates. Relevance for FLASH radiotherapy.

2021 ◽  
Author(s):  
Abida Sultana ◽  
Ahmed Alanazi ◽  
Jintana Meesungnoen ◽  
Jean-Paul Jay-Gerin
Keyword(s):  
High Dose ◽  
Acidic Ph ◽  
Cellular Functions ◽  
Spike Response ◽  
Dose Rates ◽  
Hydronium Ions ◽  
Circular Surface ◽  
Sparing Effect ◽  
Tissue Sparing ◽  
Very High

Monte Carlo multi-track chemistry simulations were carried out to study the effects of high dose rates on the transient yields of hydronium ions (H<sub>3</sub>O<sup>+</sup>) 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 <i>N</i> 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 <i>N</i>. Our calculations showed that the radiolytic formation of H<sub>3</sub>O<sup>+</sup> 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 <i>N</i>. It is most intense at times less than ~10–100 ns, equal to ~3.4 and 2.8 for <i>N</i> = 500 and 2000 (<i>i.e.</i>, for dose rates of ~1.9 × 10<sup>9</sup> and 8.7 × 10<sup>9</sup> Gy/s, respectively). At longer times, the pH gradually increases for all <i>N</i> values and eventually returns to the neutral value of seven, which corresponds to the non-radiolytic, pre-irradiation concentration of H<sub>3</sub>O<sup>+</sup>. 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.

scholarly journals Back to the Future: Very High-Energy Electrons (VHEEs) and Their Potential Application in Radiation Therapy

Cancers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 4942
Author(s):  
Maria Grazia Ronga ◽  
Marco Cavallone ◽  
Annalisa Patriarca ◽  
Amelia Maia Leite ◽  
Pierre Loap ◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Current Knowledge ◽  
High Energy ◽  
High Dose Rate ◽  
Point Of View ◽  
High Dose ◽  
Dose Rates ◽  
High Energy Electrons ◽  
Very High Energy ◽  
Very High

The development of innovative approaches that would reduce the sensitivity of healthy tissues to irradiation while maintaining the efficacy of the treatment on the tumor is of crucial importance for the progress of the efficacy of radiotherapy. Recent methodological developments and innovations, such as scanned beams, ultra-high dose rates, and very high-energy electrons, which may be simultaneously available on new accelerators, would allow for possible radiobiological advantages of very short pulses of ultra-high dose rate (FLASH) therapy for radiation therapy to be considered. In particular, very high-energy electron (VHEE) radiotherapy, in the energy range of 100 to 250 MeV, first proposed in the 2000s, would be particularly interesting both from a ballistic and biological point of view for the establishment of this new type of irradiation technique. In this review, we examine and summarize the current knowledge on VHEE radiotherapy and provide a synthesis of the studies that have been published on various experimental and simulation works. We will also consider the potential for VHEE therapy to be translated into clinical contexts.

The radiation chemistry of carbon monoxide at very high dose rates

1970 ◽  
Vol 48 (19) ◽  
pp. 3029-3033 ◽  
Author(s):  
C. Willis ◽  
O. A. Miller
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Excited State ◽  
Oxygen Atom ◽  
Dose Rate ◽  
Electron Accelerator ◽  
Radiation Chemistry ◽  
High Dose ◽  
Dose Rates ◽  
Very High

Carbon monoxide has been irradiated with single intense pulses from an electron accelerator at a dose rate of ~ 2 × 1027 eV g−1 s−1. The yield of carbon dioxide obtained was G(CO2) = 0.7 ± 0.1 with a very small yield of carbon suboxide, G(C3O2) ≤ 0.02.Addition of propene reduces the carbon dioxide yield to almost zero while addition of propane has no effect. This suggests that propene is acting as an oxygen atom scavenger rather than as a quencher of an excited state of carbon monoxide. However, rate constant data do not support this suggestion and it is concluded that the residual yield of carbon dioxide observed at high dose rates arises from reaction 9[Formula: see text]where CO+ is in an A2Π or B2Σ+ state.

Absorbed dose-to-water protocol applied to synchrotron-generated x-rays at very high dose rates

2016 ◽  
Vol 61 (14) ◽  
pp. N349-N361 ◽  
Author(s):  
P Fournier ◽  
J C Crosbie ◽  
I Cornelius ◽  
P Berkvens ◽  
M Donzelli ◽  
...  
Keyword(s):  
Absorbed Dose ◽  
High Dose ◽  
X Rays ◽  
Dose Rates ◽  
Absorbed Dose To Water ◽  
Very High

scholarly journals Feasibility Study of a Prostate Cancer FLASH Therapy Treatment With Electrons of High Energy

2021 ◽  
Author(s):  
Alessio Sarti ◽  
Patrizia De Maria ◽  
Battistoni Giuseppe ◽  
Micol De Simoni ◽  
Cinzia Di Felice ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Technological Development ◽  
High Energy ◽  
Planning System ◽  
Treatment Planning System ◽  
High Dose ◽  
Dose Rates ◽  
Very High Energy ◽  
Almost All ◽  
Very High

Abstract Prostate cancer is among the most common cancers in men and one of the leading causes of death worldwide. Different therapies are adopted for its treatment and generally radiotherapy with photons (RT) is the preferred solution in almost all cases. Up to now, in addition to photons, only protons have been implemented as alternative radiotherapy. The use of Very High Energy Electron (VHEE) beams (100-200 MeV) has been suggested in literature but the needed accelerators are more demanding, as far as space and cost are concerned, with respect to standard photon devices, with only limited advantages when compared to protons or other heavy ions. In this contribution we investigate how recent developments in electron beam therapy could reshape the landscape of prostate treatments. The VHEE Treatment Planning System obtained combining an accurate Monte Carlo (MC) simulation with a simple modelling of the FLASH effect (healthy tissues sparing at very high dose rates) is compared with conventional RT. The results demonstrate that FLASH therapy with VHEE beams of 70-130 MeV could represent a valid alternative to standard RT allowing a better sparing of the healthy tissues surrounding the tumour, in the framework of an affordable technological development.

High Dose Rate Oxygen Implantation for Formation of Silicon-on-Insulator Structures

1990 ◽  
Vol 201 ◽  
Author(s):  
E. Cortesi ◽  
F. Namavar ◽  
R. F. Pinizzotto ◽  
H. Yang
Keyword(s):  
Dose Rate ◽  
Silicon Surface ◽  
High Dose Rate ◽  
Silicon On Insulator ◽  
High Dose ◽  
Surface Oxide Layer ◽  
Dose Rates ◽  
Pit Formation ◽  
Lower Dose Rate ◽  
Very High

AbstractWe have studied Separation by IMplantation of OXygen (SIMOX) processes using very high dose rates (40–60 μA/cm2). For a dose of 4 × 1017 O+/cm2 at 160 keV, the structure formed by implantation at 50 μA/cm2 is very similar to that associated with lower dose rates. The same dose implanted at a dose rate of 60 μA/cm2, however, results in the formation of pits in the silicon surface as well as a somewhat different oxide structure. Implantation through a surface oxide layer appears to result in a structure similar to that associated with lower dose rate implantation. These and higher dose samples suggest that the threshold for pit formation is related to both dose rate and dose.

Isotope effects in the gas phase radiolysis of H2S and D2S

1976 ◽  
Vol 54 (17) ◽  
pp. 2767-2772
Author(s):  
Robert D. McAlpine ◽  
O. A. Miller ◽  
A. W. Boyd
Keyword(s):  
Dose Rate ◽  
Gas Phase ◽  
Isotope Effects ◽  
High Dose ◽  
Dose Rates ◽  
Kinetic Isotope ◽  
A Value ◽  
Straight Line ◽  
Separation Factors ◽  
Very High

Gas phase radiolysis studies have been carried out on mixtures of H2S and D2S using as irradiation sources, either a Gammacell or a Febetron 705 pulsed electron accelerator. Separation factors (α = (H/D)prod ÷ (H/D)react) were obtained for various values of xD (the mole fraction of D2S), dose rate and temperature, as well as with the addition of SF6. All of the observed α values, for 0.2 ≤ xD ≤ 0.8, fall on the following empirical straight line.[Formula: see text]The addition of neon to a D2S/H2S mixture gives a value of α which decreases as the partial pressure of neon increases. For a 70% D2S/30% H2S mixture, &([a-z]+); = 1.9 ± 0.1 for the pure mixture and 1.28 ± 0.08 when 90 kPa of neon has been added to 10 kPa of the mixture. The &([a-z]+); values described by eq. 1 are interpreted as arising from kinetic isotope effects in the reactions of (translationally) hot H or D atoms with H2S, HDS, or D2S to form H2, HD or D2.Hydrogen yields from the gas phase radiolysis of pure H2S and pure D2S have been determined for dose rates from 4 × 1016 to 2 × 1028 eV g−1 s−1. Using dose rates of up to 2 × 1027 eV g−1 s−1, ΔG = G(H2) − G(D2) = 0.5. For the highest dose rate used (2 × 1028 eV g−1 s−1), ΔG = 1.5. The larger value of ΔG at very high dose rates is thought to arise from the dissociative neutralization processes. A possible mechanism is discussed.

scholarly journals Radiobiology Experiments With Ultra-high Dose Rate Laser-Driven Protons: Methodology and State-of-the-Art

2021 ◽  
Vol 9 ◽  
Author(s):  
Pankaj Chaudhary ◽  
Giuliana Milluzzo ◽  
Hamad Ahmed ◽  
Boris Odlozilik ◽  
Aaron McMurray ◽  
...  
Keyword(s):  
Dose Rate ◽  
Biological Effects ◽  
Therapeutic Index ◽  
High Dose Rate ◽  
High Dose ◽  
Particle Accelerators ◽  
Dose Rates ◽  
Normal Tissues ◽  
Multiple Pulses ◽  
Tissue Sparing

The use of particle accelerators in radiotherapy has significantly changed the therapeutic outcomes for many types of solid tumours. In particular, protons are well known for sparing normal tissues and increasing the overall therapeutic index. Recent studies show that normal tissue sparing can be further enhanced through proton delivery at 100 Gy/s and above, in the so-called FLASH regime. This has generated very significant interest in assessing the biological effects of proton pulses delivered at very high dose rates. Laser-accelerated proton beams have unique temporal emission properties, which can be exploited to deliver Gy level doses in single or multiple pulses at dose rates exceeding by many orders of magnitude those currently used in FLASH approaches. An extensive investigation of the radiobiology of laser-driven protons is therefore not only necessary for future clinical application, but also offers the opportunity of accessing yet untested regimes of radiobiology. This paper provides an updated review of the recent progress achieved in ultra-high dose rate radiobiology experiments employing laser-driven protons, including a brief discussion of the relevant methodology and dosimetry approaches.

The Radiolysis of Water Vapor at Very High Dose Rates. II. Isotope Effects in the Hydrogen Yield from H2O–D2O Mixtures

1973 ◽  
Vol 51 (24) ◽  
pp. 4056-4061 ◽  
Author(s):  
A. W. Boyd ◽  
C. Willis ◽  
O. A. Miller
Keyword(s):  
Water Vapor ◽  
Isotope Effect ◽  
Isotope Effects ◽  
High Dose ◽  
Hydrogen Yield ◽  
Hydrogen Atoms ◽  
Dose Rates ◽  
Very High

The isotope effect in the formation of hydrogen has been measured for H2O–D2O mixtures (10–90% H2O, 0.5–1.0 mg ml−1, 412–138 °C) with and without 1 mol% SF6 at 2 × 1027 eV g−1 s−1. The values of α ((H/D) radiolytic hydrogen/(H/D) H2O–D2O) for the reactions of hydrogen atoms are in the range 3–6 varying with H/D ratio of the substrate. Consideration of possible mechanisms for these large α values leads to the conclusions that reaction of the hydrogen atoms to form hydrogen involves the substrate and that the species H3O may be formed as an intermediate.

scholarly journals High National Rates of High-Dose Dopamine Agonist Prescribing for RLS

SLEEP ◽  
2021 ◽  
Author(s):  
John W Winkelman
Keyword(s):  
Dopamine Agonist ◽  
Daily Maximum ◽  
High Dose ◽  
Patient Age ◽  
Dose Rates ◽  
Patient Âgé ◽  
Related Symptom ◽  
Icd 10 ◽  
High Doses ◽  
Very High

Abstract Study Objectives Long-term dopamine agonist (DA) use in restless legs syndrome (RLS) is associated with augmentation, a dose-related symptom worsening leading to further dose escalation to manage RLS. This study investigated rates and factors of high-dose DA prescribing in US RLS patients. Methods This retrospective analysis examined data from a US longitudinal prescriptions database (October 2017–September 2018). Patients diagnosed with RLS (ICD-10 G255.81) without Parkinson’s disease who were prescribed ropinirole, pramipexole, and/or rotigotine were included. Daily DA dosage was categorized: LOW/MID (FDA-approved/guideline or slightly above FDA-approved [pramipexole]); HIGH (101%–149%); VERY HIGH (&gt;150%). Patient counts were converted to US national estimates. Logistic regression of patient counts evaluated factors associated with HIGH/VERY HIGH DA dosing. Results Of 670,404 RLS patients (131,289,331 therapy days), 58.8% were prescribed DA therapy. Overall, 19.1% of RLS patients were prescribed DAs above maximum FDA-approved/guideline daily doses—over half of these were &gt;150% maximum recommended doses; 67.6% of HIGH/VERY HIGH-dose prescriptions were pramipexole (OR [95% CI] pramipexole vs ropinirole, 5.8 [5.7–6.0]). The highest 1% of DA prescriptions were ≥10× the FDA-recommended maximum daily dose. Rates of HIGH/VERY HIGH DA dosing increased with patient age. Twice as many neurologists (31.1%) prescribed HIGH/VERY HIGH doses vs other specialties (OR [95%CI], 2.1 [1.2–2.0]). Conclusions Approximately 20% of DA-treated RLS patients were prescribed doses above the approved and guideline daily maximum. Pramipexole, Neurology as specialty, and patient age were independently associated with HIGH/VERY HIGH DA dosing. Increased education is warranted regarding risks of high-dose DA exposure in RLS.

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