High dose‐per‐pulse electron beam dosimetry — A model to correct for the ion recombination in the Advanced Markus ionization chamber

Petersson, Kristoffer; Jaccard, Maud; Germond, Jean‐François; Buchillier, Thierry; Bochud, François; Bourhis, Jean; Vozenin, Marie-Catherine; Bailat, Claude

doi:10.1002/mp.12111

Cited by 153 publications

(254 citation statements)

References 22 publications

(54 reference statements)

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“…Irradiation was performed using a prototype 6MeV electron beam linear accelerator (LINAC) of type Oriatron 6e (eRT6; PMB-Alcen), available at Lausanne University Hospital and described previously (43). Physical dosimetry has been extensively described and published to ensure reproducible and reliable biological studies (19,(43)(44)(45). This LINAC is able to produce pulsed electron beams at a mean dose rate ranging from 0.1 Gy·s −1 (i.e., comparable to conventional dose rates used in RT) up to 1,000 Gy·s −1 , corresponding to a dose, in each electron pulse, ranging from 0.01 up to 10 Gy.…”

Section: Methodsmentioning

confidence: 99%

Long-term neurocognitive benefits of FLASH radiotherapy driven by reduced reactive oxygen species

Montay‐Gruel

Acharya

Petersson

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Here, we highlight the potential translational benefits of delivering FLASH radiotherapy using ultra-high dose rates (>100 Gy·s −1 ). Compared with conventional dose-rate (CONV; 0.07-0.1 Gy·s −1 ) modalities, we showed that FLASH did not cause radiation-induced deficits in learning and memory in mice. Moreover, 6 months after exposure, CONV caused permanent alterations in neurocognitive end points, whereas FLASH did not induce behaviors characteristic of anxiety and depression and did not impair extinction memory. Mechanistic investigations showed that increasing the oxygen tension in the brain through carbogen breathing reversed the neuroprotective effects of FLASH, while radiochemical studies confirmed that FLASH produced lower levels of the toxic reactive oxygen species hydrogen peroxide. In addition, FLASH did not induce neuroinflammation, a process described as oxidative stress-dependent, and was also associated with a marked preservation of neuronal morphology and dendritic spine density. The remarkable normal tissue sparing afforded by FLASH may someday provide heretofore unrealized opportunities for dose escalation to the tumor bed, capabilities that promise to hasten the translation of this groundbreaking irradiation modality into clinical practice.ultra-high dose-rate irradiation | cognitive dysfunction | neuronal morphology | neuroinflammation | reactive oxygen species R adiation therapy (RT) remains an essential part of cancer treatment, and, today, the benefit of RT would increase dramatically if normal tissues surrounding the tumor could tolerate higher doses of radiation (1-3). In the last decade, major advances in high-precision treatment delivery and multimodal imaging have improved tolerance to RT (4), but the selective protection of normal tissue remains a significant clinical challenge and the radiation-induced toxicities still adversely impact the patient's quality of life. This latter fact largely remains an unmet medical need, and points to the urgency of developing improved RT modalities for combating those cancers refractory to treatment.This issue is especially critical for those afflicted with brain tumors, including glioblastoma multiforme (GBM), for which standard treatment consists of surgical resection followed by RT and concomitant chemotherapy (temozolomide). Typical radiotherapeutic protocols for GBM induce neurocognitive complications, including impairments in learning and memory, attention, and executive function and a variety of mood disorders (5-8). A breadth of past work from our laboratories has linked adverse neurocognitive outcomes following cranial irradiation to a range of neuropathologies, including reductions in dendritic complexity and spine density (9-12), reductions in microvascular density (13-15), reduced myelination and synapse density, and increased neuroinflammation (16,17). These changes are persistent and problematic in the conventionally irradiated brain and have prompted efforts to more fully develop a truly innovative approach to RT, where we have concept...

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Section: Methodsmentioning

confidence: 99%

Long-term neurocognitive benefits of FLASH radiotherapy driven by reduced reactive oxygen species

Montay‐Gruel

Acharya

Petersson

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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352

447

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“…When necessary, depths in solid water were scaled with the scaling factor c pl = 0.946 to give depths in water. The present study focuses mainly on relative measurements, we report on the use of EBT3 films and the Advanced Markus for absolute dose determination at high dose‐rate elsewhere …”

Section: Methodsmentioning

confidence: 99%

“…The present study focuses mainly on relative measurements, we report on the use of EBT3 films and the Advanced Markus for absolute dose determination at high dose-rate elsewhere. 16,17…”

Section: C Dosimetric Systemsmentioning

confidence: 99%

High dose‐per‐pulse electron beam dosimetry: Commissioning of the Oriatron eRT6 prototype linear accelerator for preclinical use

et al. 2018

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“…Several limitations of Boag's expression have been shown for air-filled chambers in high dose-per-pulse fields. [16][17][18] Boag himself extended his original expressions to include the effects of free electrons 7 acting as charge carriers. 16 Considering this fraction of charge collected as free electrons p, one such extended expression is…”

Section: A Theorymentioning

confidence: 99%

Correction for volume recombination in liquid ionization chambers at high dose‐per‐pulse

Götz

Tölli

et al. 2019

Medical Physics

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Purpose To determine the volume recombination at high dose‐per‐pulse in liquid ionization chambers (LIC) and to ascertain whether existing calculation methods verified in air‐filled chambers may be used to calculate a correction factor. Methods Two LICs, one filled with 2,2,4‐trimethylpentane (isooctane) the other with tetramethylsilane (TMS), were irradiated in a pulsed, 20 MeV electron beam. Via reference measurements with a Faraday cup, the saturation correction for volume recombination was determined for dose‐per‐pulse values ranging from about 5 mGy to 1 Gy for both chambers at a pulse duration of 693 ns. In addition, the isooctane chamber was irradiated with pulses of varying duration, ranging from 5 ps to 10 ms, at a dose‐per‐pulse of about 76.5 mGy. The dose‐per‐pulse‐dependent measurements were compared to calculations based on Boag's models (with and without a free electron fraction), the two‐dose‐rate method, and a numerical calculation. The pulse duration dependent measurements were compared only to a numerical calculation that iteratively calculates the charge transport and loss in a 1D model of an ionization chamber. Results In TMS only Boag's model with a free electron fraction and the numerical calculation are in good agreement with the experimental data. However, in isooctane, good agreement is observed between the experimental data, the numerical calculation as well as the two‐dose‐rate method, and Boag's model including a free electron fraction. Only Boag's model without a free electron fraction shows a good agreement with lesser extend. Furthermore, the pulse duration‐dependent data for isooctane are well described by the numerical model. Conclusion With isooctane as an active medium, a LIC could be directly used in a field with high dose‐per‐pulse utilizing the well‐established two‐dose‐rate method to correct the volume recombination. In addition, pulsed fields with variable pulse duration are easily modeled for this medium using a numerical calculation. Other media, as exemplified by the TMS‐filled chamber, might require additional considerations, such as including a fraction of free electrons in the consideration of volume recombination.

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High dose‐per‐pulse electron beam dosimetry — A model to correct for the ion recombination in the Advanced Markus ionization chamber

Cited by 153 publications

References 22 publications

Long-term neurocognitive benefits of FLASH radiotherapy driven by reduced reactive oxygen species

Long-term neurocognitive benefits of FLASH radiotherapy driven by reduced reactive oxygen species

High dose‐per‐pulse electron beam dosimetry: Commissioning of the Oriatron eRT6 prototype linear accelerator for preclinical use

Correction for volume recombination in liquid ionization chambers at high dose‐per‐pulse

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