Radiolysis of Hydrogen Sulfide at Very High Dose Rates. The Effect of SF61

1971 ◽  
Vol 49 (10) ◽  
pp. 1677-1682 ◽  
Author(s):  
C. Willis ◽  
A. W. Boyd ◽  
O. A. Miller
Keyword(s):  
Hydrogen Sulfide ◽  
Low Dose ◽  
Single Pulse ◽  
Ion Pair ◽  
High Dose ◽  
Hydrogen Yield ◽  
Dose Rates ◽  
Absorbed Doses ◽  
Electron Pulses ◽  
Very High

Gaseous H2S has been irradiated with electron pulses from a Febetron 705 at a dose rate of ~2 × 1027 eV g−1 s−1. For single pulse experiments, the yield of hydrogen is G(H2) = 12.0 ± 0.5, independent of pressure from at least 350 to 1600 Torr. Addition of SF6 reduces the yield to G(H2) = 7.9 ± 0.3 which is fairly close to that observed for pure H2S at low dose rates. The reduction, ΔG(H2) = 4.1 ± 0.3, agrees very well with the ion pair yield based on a W value of 25.3 eV.In multi-pulse irradiations, for pure H2S, the yield falls off with dose giving a limiting yield close to G(H2) = 8.0. No similar fall-off is observed for H2S–SF6 mixtures. It is proposed that at high absorbed doses and at low dose rates, there is no contribution to the hydrogen yield from neutralization processes; and that this is due to neutralization of H3S+ by an ion of the type Sn− rather than a free electron.

Gas phase radiolysis of hydrogen chloride, hydrogen bromide, and nitrous oxide with intense electron pulses

1969 ◽  
Vol 47 (20) ◽  
pp. 3783-3791 ◽  
Author(s):  
C. Willis ◽  
A. W. Boyd ◽  
D. A. Armstrong
Keyword(s):  
Nitrous Oxide ◽  
Dose Rate ◽  
Hydrogen Chloride ◽  
Low Dose ◽  
Hydrogen Bromide ◽  
Negative Ion ◽  
Dose Rates ◽  
Electron Pulses ◽  
Intense Electron ◽  
Very High

Hydrogen chloride and hydrogen bromide have been irradiated with single electron pulses at a very high intensity (1027 eV g−1 s−1) with a Febetron 705. At room temperature the yields of hydrogen from hydrogen chloride and hydrogen bromide, for pressures between 700 and 1200 Torr, are G(H2) = 8.1 ± 0.2 and G(H2) = 9.9 ± 0.3, respectively. These are the same as the yields observed at low dose rates. Detailed lifetime calculations, however, show that the mechanism is significantly different at the higher dose rate. Scavenger experiments with chlorine in hydrogen chloride show that the negative ion intermediates form thermal hydrogen atoms.The value of G(N2) = 12.4 ± 0.2 from nitrous oxide at a dose rate of 1027 eV g−1 s−1 is confirmed and the use of nitrous oxide as a dosimeter for pulsed electron beams is discussed. The higher nitrogen yield at Febetron dose rates appears to be due to changes in the reactions of electrons.

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.

THE EFFECT OF ELECTRIC FIELDS, AND A RELATED DEPENDENCE ON DOSE RATE, IN THE γ-RADIOLYSIS OF HYDROCARBON GASES

1963 ◽  
Vol 41 (6) ◽  
pp. 1463-1468 ◽  
Author(s):  
T. W. Woodward ◽  
R. A. Back
Keyword(s):  
Dose Rate ◽  
Gas Phase ◽  
Electric Fields ◽  
Low Dose ◽  
High Dose ◽  
Hydrogen Yield ◽  
Hydrocarbon Gases ◽  
Saturation Field ◽  
Dose Rates ◽  
And Diffusion

The effect of electric fields on the γ-radiolysis of ethane, propane, and the butanes has been investigated briefly at 800 mm pressure, with dose rates between 2 × 1010 and 400 × 1010 ev/cc sec. Yields of hydrogen were reduced when a saturation field was applied, except with ethane at low dose rate, where a slight increase in hydrogen yield was observed. With propane and n-butane, the yield of hydrogen in the presence of a saturation field was independent of dose rate, while with ethane, it decreased with decreasing dose rate. At the same time, a dose rate dependence was discovered in the simple radiolysis, in the absence of any field, of ethane, propane, and n-butane, a decrease in the yield of hydrogen at low dose rates being observed. An explanation of these observations is suggested in terms of a competition between neutralization of ions in the gas phase and diffusion of ions to the wall. High dose rates should favor the former process, and low dose rates the latter. At sufficiently high dose rates, all ions should be neutralized in the gas phase. At sufficiently low dose rates, all ions should diffuse to the wall before neutralization, and it is suggested that the radiolysis under these conditions should closely resemble that in the presence of a saturation field at higher dose rates.

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.

Linear energy transfer dependence of transient yields in water irradiated by 150 keV – 500 MeV protons in the limit of low dose rates

2020 ◽  
Vol 98 (8) ◽  
pp. 427-433
Author(s):  
Ahmed Alanazi ◽  
Jintana Meesungnoen ◽  
Jean-Paul Jay-Gerin
Keyword(s):  
Energy Transfer ◽  
Linear Energy Transfer ◽  
Low Dose ◽  
High Dose ◽  
Dose Rates ◽  
Normal Tissues ◽  
High Let ◽  
Proton Track ◽  
Electron And Photon ◽  
Anti Tumor Activity

FLASH radiotherapy is a new irradiation method in which large doses of ionizing radiation are delivered to tumors almost instantly (a few milliseconds), paradoxically sparing healthy tissue while preserving anti-tumor activity. Although this technique is primarily studied in the context of electron and photon therapies, proton delivery at high dose rates can also reduce the adverse side effects on normal cells. So far, no definitive mechanism has been proposed to explain the differences in the responses to radiation between tumor and normal tissues. Given that living cells and tissues consist mainly of water, we set out to study the effects of high dose rates on the radiolysis of water by protons in the energy range of 150 keV – 500 MeV (i.e., for linear energy transfer (LET) values between ∼72.2 and 0.23 keV/μm, respectively) using Monte Carlo simulations. To validate our methodology, however, we, first, report here the results of our calculations of the yields (G values) of the radiolytically produced species, namely the hydrated electron ([Formula: see text]), •OH, H•, H2, and H2O2, for low dose rates. Overall, our simulations agree very well with the experiment. In the presence of oxygen, [Formula: see text] and H• atoms are rapidly converted into superoxide anion or hydroperoxyl radicals, with a well-defined maximum of [Formula: see text] at ∼1 μs. This maximum decreases substantially when going from low-LET 500 MeV to high-LET 150 keV irradiating protons. Differences in the geometry of the proton track structure with increasing LET readily explain this diminution in [Formula: see text] radicals.

High-dose lidocaine does not affect defibrillation efficacy: implications for defibrillation mechanisms

1998 ◽  
Vol 274 (4) ◽  
pp. H1113-H1120 ◽  
Author(s):  
Michael R. Ujhelyi ◽  
J. Jason Sims ◽  
Allison Winecoff Miller
Keyword(s):  
Ventricular Fibrillation ◽  
Cycle Length ◽  
Low Dose ◽  
High Dose ◽  
Channel Blockade ◽  
Group 3 ◽  
Baseline Values ◽  
Group 2 ◽  
Very High ◽  
Group 1

This study assessed the effect of low (10 mg ⋅ kg−1 ⋅ h−1) and very high (18 mg ⋅ kg−1 ⋅ h−1) doses of lidocaine on defibrillation energy requirements (DER) to relate changes in indexes of sodium-channel blockade with changes in DER values using a dose-response study design. In group 1 (control; n = 6 pigs), DER values were determined at baseline and during treatment with 5% dextrose in water (D5W) and with D5W added to D5W. In group 2 ( n = 7), DER values were determined at baseline and during treatment with low-dose lidocaine followed by high-dose lidocaine. In group 3 ( n = 3), DER values were determined at baseline and high-dose lidocaine. Group 3 controlled for the order of lidocaine treatment with the addition of high-dose lidocaine after baseline. DER values in group 1 did not change during D5W. In group 2, low-dose lidocaine increased DER values by 51% ( P = 0.01), whereas high-dose lidocaine added to low-dose lidocaine reduced DER values back to within 6% of baseline values ( P = 0.02, low dose vs. high dose). DER values during high-dose lidocaine in group 3 also remained near baseline values (16.2 ± 2.7 to 12.9 ± 2.7 J), demonstrating that treatment order had no impact on group 2. Progressive sodium-channel blockade was evident as incremental reduction in ventricular conduction velocity as the lidocaine dose increased. Lidocaine also significantly increased ventricular fibrillation cycle length as the lidocaine dose increased. However, the greatest increase in DER occurred when ventricular fibrillation cycle length was minimally affected, demonstrating a negative correlation ( P = 0.04). In summary, lidocaine has an inverted U-shaped DER dose-response curve. At very high lidocaine doses, DER values are similar to baseline and tend to decrease rather than increase. Increased refractoriness during ventricular fibrillation may be the electrophysiological mechanism by which high-dose lidocaine limits the adverse effects that low-dose lidocaine has on DER values. However, there is a possibility that an unidentified action of lidocaine is responsible for these effects.

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.

Ionization of liquid argon by X-rays: -value

1969 ◽  
Vol 47 (22) ◽  
pp. 4286-4288 ◽  
Author(s):  
N. V. Klassen ◽  
Werner F. Schmidt
Keyword(s):  
Gas Phase ◽  
Low Dose ◽  
Liquid Argon ◽  
Ion Pair ◽  
X Rays ◽  
Dose Rates

Liquid argon at 87 °K was irradiated with 1.5 MeV X-rays. Saturation currents were achieved at low dose rates. The energy required to produce an ion pair [Formula: see text] was found to be 22.5 ± 3 eV, which is similar to the gas phase value.

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.

Sign in / Sign up

Export Citation Format

Share Document